Recycling of CO2: an alternative to

Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Recycling of CO2: an alternative to petrochemistry for the
synthesis of nitrogen compounds
Recyclage du CO2 : une alternative à la pétrochimie pour la synthèse
de composés azotés
E. Blondiaux1,2, X. Frogneux1, J. Pouessel1, T. Cantat*,1
1
CEA, 91191 Gif-sur-Yvette
2
ADEME, 49004 Angers
* Corresponding author: [email protected]
______________________________________________________________
Résumé : L'utilisation du CO2 pour la production de molécules contenant des atomes C1 est une voie attrayante
pour la synthèse de produits chimiques à valeur ajoutée. En particulier, la formation de composés azotés peut être
obtenue par fonctionnalisation réductrice du CO2 en présence d'amines. En utilisant des réducteurs doux tels que
des hydrosilanes et des hydroboranes, de nouvelles réactions ont été conçues pour faciliter la transformation du CO2
en dérivés formamides, formamidines, aminals et méthylamines, par voies organocatalytiques.
________________________________________________________________________
Summary: CO2 utilization for the production of C1-containing molecules is a desirable route to value-added
chemicals. In particular, formation of nitrogen compounds can be obtained by reductive functionalization of CO2 in the
presence of amines. Using mild reductants, such as hydrosilanes and hydroboranes, novel catalytic reactions have
been designed to facilitate the transformation of CO2 to formamide, formamidine, aminal and methylamine
derivatives, by organocatalysis.
Keywords: CO2; reduction; catalysis; sustainable chemistry; nitrogen compounds
While the CO2 concentration in the atmosphere continues to grow, the search for technologies to reduce CO2 emissions
is urgent. Among the solutions explored, CO2 transformation into fuels and chemicals has emerged as an alternative to
CO2 capture and storage for reducing the emissions of this greenhouse gas. CO2 conversion to chemicals might offer
niche applications in the short term, because the endproducts possess an added-value able to balance the cost of CO2
capture and transformation.
Alors que la concentration de CO2 dans l'atmosphère continue d’augmenter, la recherche de technologies pour réduire
les émissions de CO2 est urgente. Parmi les solutions explorées, la transformation du CO 2 en carburants et produits
chimiques a émergé comme une alternative à la capture et au stockage du CO2 pour réduire les émissions de ce gaz à
effet de serre. La conversion du CO2 en produits chimiques pourrait offrir des applications de niche à court terme, car les
produits finaux possèdent une valeur ajoutée en mesure d'équilibrer le coût du captage du CO2 et de sa transformation.
1
Introduction
CO2 conversion into chemicals is an attractive
opportunity for CO2 recycling and has therefore
received a wide attention over the last few years.[1]
Using amines as functionalizing reagents, synthesis
of nitrogen compounds have been developed.
These novel processes are able to transform CO2
into formamide, formamidine, aminal and
methylamine derivatives, which are important
moieties in synthetic chemistry (fig. 1.). For
example, formamidines derivatives are useful
chemicals because they are utilized as antifungal,
antibacterial, anticancer and anticonvulsant agents;
methylamines are valuable for the synthesis of a
broad range of products applicable in such diverse
fields as medicine, agriculture, rubber, plastics and
synthetic fibers. In particular, monomethylamine,
dimethylamine and trimethylamine are produced
each year at about 500 000 t.
Fig. 1. Nitrogen compounds available from CO2 and amines
under organocatalysis and hydrosilylation or hydroboration
conditions
2
Experimental/methodology
The thermodynamic stability of CO2 imposes an
input of energy to convert CO2 into chemicals. The
second challenge is kinetic in nature: catalysts are
required to ensure that the activation barriers
remain as low as possible along the chemical
transformation pathways so that the overall carbon
balance for CO2 utilization is not hampered by
thermal loading needed to overcome high energy
transition states.
Obviously, these energetic considerations are
associated with strong constraints on the resources
utilized for CO2 conversion as the energy input
must be carbon-free and rare or toxic metal
catalysts must be avoided.
In this regard, in order to convert CO2 into
chemicals, mild reductants have been employed
such as hydrosilanes (Si–H bonds) and
hydroboranes (B–H bonds). Among them, PMHS
(polymethylhydrosiloxane) is particularly attractive
because it is a cost-efficient, non-toxic and air
stable waste of the silicon industry.
Furthermore, organocatalysts like nitrogen or
phosphorus bases have been considered because
they usually combine low cost and low toxicity with
an enhanced stability to moisture and air, which can
circumvent classical drawbacks of many metallic
catalysts.
Fig. 1. Organocatalysts and reductants used in this contribution:
Verkade’s base (VB), TBD (1.5.7-triazabicyclo[4.4.0]des-5-ene),
PMHS (polymethylhydrosiloxane), 9-BBN (9-borabicyclo[3.3.1]
nonane)
3
Results and discussion
Under
organocatalysis
conditions,
five
processes for CO2 conversion are highlighted.
Using a Verkade base and PMHS, a 2–electron
reduction to formamides and formamidines has
been achieved.[2] Aminals have been also
synthesized with short reaction time (< 6 h).[3]
Finally, the 6–electron reduction of CO2 to
methylamines, a process unveiled in 2013, was
developed for the first time under metal-free
conditions.[4] Interestingly, the reaction under
hydroboration conditions exhibits better activities
than the precedent reported processes using Zn or
Ru based catalysts for this reaction.[5]
Table 1 Processes for CO2 conversion into nitrogen compounds
Nitrogen
Catalyst
Reductant
Conditions
compound
Formamides
VB
PMHS
24 h / 20 °C
Formamidines
VB
PMHS
24 h / 70 °C
Aminals
TBD
PhSiH3
6 h / 80 °C
Methylamines
VB
9-BBN
1 h / 90 °C
Methylamines
VB/B(C6F6)3
PMHS
24 h / 100 °C
4
Conclusions
In
conclusion,
we
have
developed
unprecedented methods for the creation of nitrogen
compounds with CO2. These transformations
enable the functionalization of a large scope of
substrates, including aliphatic and aromatic amines,
with a high chemoselectivity.
Acknowledgements
For financial support of this work, we
acknowledge the CEA, CNRS, ADEME, the
CHARMMMAT Laboratory of Excellence and the
European Research Council (ERC Starting Grant
Agreement n.336467). T.C. thanks the Foundation
Louis D. – Institut de France for its formidable
support.
References
[1] (a) A. Goeppert, M. Czaun, J.-P. Jones, G. K. Surya
Prakash, G. A. Olah, Chem. Soc. Rev. 43 (2014) 7995. (b)
F. J. Fernandez-Alvarez, A. M. Aitani, L. A. Oro, Catal. Sci.
Technol. 4 (2014) 611. (c) A. Tlili, E. Blondiaux, X.
Frogneux, T. Cantat, Green Chem. 17 (2015) 157. (d) A.
Tlili, X. Frogneux, E. Blondiaux, T. Cantat, Angew. Chem.
Int. Ed. 53 (2014) 2543.
[2] E. Blondiaux, T. Cantat, submitted, (2015).
[3] X. Frogneux, E. Blondiaux, P. Thuery, T. Cantat, submitted,
(2015).
[4] E. Blondiaux, J. Pouessel, T. Cantat, Angew. Chem. Int. Ed.
53 (2014) 12186.
[5] (a) O. Jacquet, X. Frogneux, C. Das Neves Gomes, T.
Cantat, Chem. Sci. 4 (2013) 2127. (b) Y. Li, I. Sorribes, T.
Yan, K. Junge, M. Beller, Angew. Chem. Int. Ed. 52 (2013)
12156. (c) K. Beydoun, T. vom Stein, J. Klankermayer, W.
Leitner, Angew. Chem. Int. Ed. 52 (2013) 9554.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
New Glycerol-derived Hydrotropes for Low Temperature
Cloud Point Extraction Processes.
Nouveaux Hydrotropes à base de Glycérol pour
d’Extractions à Points Troubles à Basse Température.
des
Procédés
R. Lebeuf1, E. Illous2, V. Nardello-Rataj2, J.-M. Aubry1*
1
ENSCL, Cité Scientifique, Avenue Mendeleïev, 59652 Villeneuve D’Ascq
2
Université de Lille, UCCS, équipe CISCO, bât C6, F-59655 Villeneuve d’Ascq CEDEX
* Corresponding author: [email protected]
______________________________________________________________
Résumé : des dialkyl-éthers de glycerols avec de courtes chaînes carbonées ont été synthétisés afin d’étudier leurs
propriétés hydrotropiques. En plus de leur bon pouvoir solubilisant envers les molécules hydrophobes, ils présentent
en solutions aqueuses des points de troubles à basses températures sur une large gamme de concentrations, ce qui
les rend potentiellement intéressants pour des procédés d’extractions moins énergivores. Ils peuvent ainsi être de
bons substituts aux hydrotropes pétrosourcés tels que le C4E1 et les sulfonates d’alkylbenzenes, comme démontré
avec l’extraction de la pipérine du poivre.
_______________________________________________________________________
Summary: Some glycerol dialkylethers with short alkyl chains have been synthesized to study their hydrotropic
properties. In addition to their good properties for the solubilization of hydrophobic molecules, they possess in
aqueous solutions low temperature cloud points on a large range of concentrations, making them potentially suitable
for lower energy demanding extraction processes. Hence, they could be good alternatives to petro-based
hydrotropes like C4E1 or alkyl-benzensulfonates, as demonstrated by the extraction of the piperine from pepper.
Keywords: hydrotrope, glycerol, extraction, cloud point, piperine.
Les produits naturels sont de plus en plus plébiscités, cependant leur extraction du milieu naturel peut être
problématique pour cause de dégradations lors de chauffages ou de purifications supplémentaires couteuses et
énergivores. Les procédés d’extractions à base d’hydrotropes sont des alternatives modernes plus respectueuses
envers ces critères. Néanmoins, pour cela, de nouvelles molécules si possibles agro-sourcées restent à être identifiées,
ce qui fait l’objet de ce travail illustré par l’extraction de la pipérine présente naturellement dans le poivre.
1
Introduction
Hydrotropes are small amphiphilic compounds
composed of a polar head and a short hydrophobic
tail that distinguish them from surfactants which
possess longer tails. They could be used for many
applications such solubilization of high value
hydrophobic compounds, for the formation of
microemulsions in presence of surfactants, and for
extraction processes like shown in a recent study
showing the separation of lignine from bagasse of
sugar cane, that may allow to get purer lignic and
cellulosic materials for bioenergetic conversions by
this way.[1]
Extraction processes are generally performed
using solvents, which have to be separated by
distillation. Selectivity of the extraction is also a
critical parameter to reduce waste and costly
purifications. In response to these problems,
hydrotropes allows using water as solvent and
could enhance extraction selectivity. The solubilized
product could be then separated by simple dilution,
however, the use of a large amount of water
impede the easy recovery of the hydrotrope. Cloud
Point Extraction (CPE) process could avoid such
problems. Indeed, when a homogeneous aqueous
solution of a hydrotrope having a cloud point is
heated above this temperature, the hydrotrope is
released from water. If a solute would also be
present, it will go in the organic layer formed by the
hydrotrope, which can be then more easily recover.
This concept was first applied for the extraction of
metals, but could be extended for organic
compounds.
2
Synthesis
and
properties
dialkylglycerol ether
of
a
A glycerol dialkylether could be easily obtained
from butyl glycidyl ether, a largely available product
due to its use in epoxy resins. Simple acidcatalyzed ring opening of the epoxide in methanol
give a mixture of the two regioisomers in 4:1 ratio.
Even if the regioisomers could be separated, the
present study was done on the mixture to proof its
scalability.
could be a good alternative for alkylbenzene
sulfonates used for such application. [3] The
extraction was monitored by HPLC at 340 nm (max
piperine) and 254 nm. A clean extraction is
observed, allowing quantifying the amount of
extracted piperine (Figure 3).
300000
200000
relative intensity
The resulting mixture of alcohols is miscible in
water in all proportions at room temperature. As
shown in figure 1, it present cloud points in water, a
rare phenomenon for non-ionic compounds other
than polyoxoethylenes. [2]
150000
100000
50000
0
100
non miscibility
domain
60
(C4E1)
40
miscibility domain
20
0
20
40
60
Hydrotrope in water (%wt)
80
100
Fig. 1. Cloud points of a dialkylglycerol mixture compared to
C4E1 in function of the weight fraction of the hydrotrope.
The solubilizing properties of a hydrotrope for
hydrophobic compounds are characterized by a
rapid increase of the amount of solubilized product
from a certain concentration of the hydrotrope
called Minimum Hydrotropic Concentration (MHC).
That is observed in our case using Disperse Red13,
dye and the solubilization was more pronounced
compared to the corresponding mono alkylglycerol
(Figure 2).
solubilized Disperse Red 13
(mmol.L-1)
12
10
6
4
MHC
2
0
0,5
10
20
30
40
Time / Min.
50
60
70
1
1,5
8
6
4
without hydrotrope
2
0
0
2
4
6
8
Extraction time (h)
Fig. 3. Extraction chromatogram (after 4 hours) and amount of
extracted piperine from black pepper at room temperature with a
2M solution of hydrotropes in water (mixture of isomers of butylmethyl glycerol diether)
Like for alkylbenzene sulfonates, [3] extraction
is not linear along the time. Presence of hydrotrope
increase the amount of solubilized piperine
compared to a blank experiment done with only
water. Hence, piperine could be extracted and
easily recovered along the hydrotrope by heating
the solution above the cloud point.
Acknowledgements
2
Hydrotrope (mol.L-1)
Fig. 2. Solubilization of hydrophic disperse red 13 at room
temperature by two hydrotropes in water. Comparison of mono
and dialkyl glycerol ether.
The authors thank the Université de Lille and the
Ecole Nationale Supérieure de Chimie de Lille for
financial supports.
References
3
80
10
4
Conclusions
Dialkyl glycerol ethers are good candidates for
Cloud Point Extraction processes (CPE) and
variation of the substituents could tune the thermal
and solubility properties of such compounds for
more specific applications.
8
0
0
12
Piperine in solution (mg/g)
Temperature ( C)
-50000
80
0
piperine
340 nm
254 nm
250000
Extraction of piperine from pepper
A solution (2M) of the synthesized hydrotropes
was stirred with black pepper to see whether they
[1]
[2]
[3]
K. B. Ansari, V. G. Gaikar Chem. Eng. Sci. 115 (2014) 157.
A. Lavergne, L. moity, V. Molinier, J.-M. Aubry RSC
Advances 3 (2013) 5997.
G. Raman, V. G. Gaikar Ind. Eng. Chem. Res. 41 (2002)
2966.
10
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Study of prompt NO formation during methyl
combustion in low pressure premixed flames
esters
Etude de la formation du NO précoce lors de la combustion des esters
méthyliques à basse préssion et en conditions de flammes plates
prémélangées
M.D. Sylla*, L. Gasnot, N. Lamoureux
Université de Lille, Laboratoire de PhysicoChimie des Processus de Combustion et de
l’Atmosphère PC2A UMR 8522, Bâtiment C11, 59655 Villeneuve d’Ascq Cedex France
* Corresponding author: [email protected]
______________________________________________________________
Résumé : Ce travail porte sur l'étude de l'impact environnemental des esters méthyliques utilisés comme biodiesel et
concerne plus particulièrement la cinétique de formation des oxydes d'azote (NOx) dans des conditions de flamme. Il
s’agit de tester et d'optimiser un mécanisme cinétique détaillé dédié à la prédiction de la formation des NOx lors de
l'oxydation du méthyle de butanoate, composé modèle représentatif du biodiesel. Pour cela, les profils d’un large
panel d’espèces chimiques ont été mesurés dans un brûleur de laboratoire, et comparés à ceux obtenus par les
mécanismes cinétiques détaillés disponibles dans la littérature. Les mesures sont réalisées par couplage des
techniques de spectroscopie laser et de techniques d'analyse classiques.
________________________________________________________________________
Summary: This work is focused on the study of the environmental impact of methyl esters used as biodiesel and
concerns more particularly the kinetic of nitrogen oxides formation in flame conditions. The aim of this study is to test
and optimize detailed kinetic mechanism for the prediction of NOx formation during the oxidation of methyl butanoate,
a compound chosen as model for biodiesel. For that, the profiles for a wide range of chemical species were
measured in a laboratory burner, and compared with those obtained by detailed kinetic mechanisms available in the
literature. Measurements are performed by coupling laser diagnostic techniques and classical analysis techniques.
Keywords: Prompt-NO; Methyl esters; Combustion; Premixed flame; kinetic chemistry;
Environmental concerns lead to the development of biofuels as renewable energy. Methyl esters issued from chemical
transformation from biomass are used as additives to fossile energy (diesel or gasoline). These additives allow limiting
greenhouse emissions. However, very few data are available concerning their oxidation impact on NOx emissions.
Les préoccupations liées à la pollution atmosphérique ont conduit à l’accroissement de l’utilisation d’agrocarburants. Les
esters méthyliques, issus de la transformation chimique de la biomasse, peuvent être utilisés comme additifs aux
carburants fossiles (diesel ou essence). Ces additifs présentent l’avantage de limiter les émissions de gaz à effet de
serre. Cependant, peu de données ont été réalisées pour caractériser l’impact de leur oxydation sur le plan des
émissions de NOx.
1
Introduction
Due to the increase of demand for energy,
concerns for the oxidation of fuels impact on
environment and healthy have been reviewed since
the late 90’s. Concerning the reduction of pollutant
emission due to transport, one option relies on the
use of biodiesels that are typically derived from oil
transesterification.
Because of the complexity of biodiesel, methyl
butanoate (MB) which is the simplest methyl ester
is a very good candidate to examine the chemical
kinetics aspect of the ester oxidation.
In the present work, NO formation was studied
during MB oxidation in premixed low pressure
flames. Experimental conditions were selected to
examine the prompt-NO formation exclusively. NO
species and temperature profiles were measured in
situ by using LIF (Laser-Induced Fluorescence)
techniques. Stable species profiles were measured
after gas probe sampling by using analytical
techniques such as GC (Gas Chromatography) and
FTIR (Fourier Tranform InfraRed) spectroscopy.
Experimental results have been compared to
species profiles calculated by using Premix code
with appropriated detailed kinetics mechanisms.
For that purpose, detailed mechanisms available in
the literature [1, 2] were updated with the NOx
chemistry extracted from Lamoureux et al. [3].
2
Experimental/methodology
Structure analysis in laminar low pressure
flames consists in measuring absolute species
profiles along the vertical axis above the burner.
Due to the flame configuration, the vertical axis is
representative of the chemical time scale
connected to the time scale of the reactions.
Five MB/CH4/O2/N2 premixed flames were
stabilized on a McKenna burner in low pressure
20
15
0.
25
0.
25
10
0.
32
0.
29
0.
25
3
Results and discussion
The first experimental results show that the
addition of MB in the CH4/O2/N2 flame leads to a
significant decrease of the NO in the burnt gases.
For the equivalence ratio Ф=1, the addition of 50%
MB yields a decrease of NO of 20%. On the other
side, when the C/O ratio is fixed to the constant
value of 0.25, the addition of 50 % MB leads to a
decrease of 60% of the initial amount of NO in the
burnt gases (fig.1).
25
NO à 20 mm (ppm)
conditions (52.6 mbar). A stoichiometric CH4/O2/N2
flame (for which the C/O ratio is equal to 0.25) is
studied as reference flame. MB fuel is substituted to
CH4 (20 or 50%) with respect to either the
equivalence ratio or the C/O ratio.
5
expérience
simulation_Dooley
simulation_Gail
0
1
1
1
Richesse, 
0.85
0.77
Fig.2. Measured and modeled absolute NO mole fraction in the
burnt gases. Comparison between experimental data and
simulated by using DL and GL mechanisms. Labels (nearby red
symbols) refer to C/O ratio in the mixture.
Fig.1. Experimental
CH4/MB/O2/N2.
absolute
NO
profiles
measured
in
For the purpose of selecting the more
appropriate detailed kinetic mechanism, two
mechanisms previously developed and validated in
other experimental conditions [1,2] have been
completed with a well-suited NOx chemistry submechanism [3]. Figure 2 compares the NO mole
fraction measured and calculated in the burnt
gases. Both mechanisms predict a decrease of the
NO mole fraction in the burnt gases as the initial
amount of MB increases. Calculations issued from
combination of mechanisms [2] and [3] (GL
scheme) do not follow the trend experimentally
observed. On the contrary, calculations performed
with the mechanism combined from [1] and [3] (DL
scheme) are in quite good agreement with
experimental results.
4
Conclusions
In this work, NO profiles were obtained in
different MB/CH4/O2/N2 premixed flames stabilized
at low pressure. NO and temperature profiles were
measured by using LIF technique. Stable species
were measured by classical techniques such as
FTIR and GC.
Experimental NO profiles were compared to
simulated ones by using two detailed mechanisms
available in the literature [1, 2]. None of them were
validated for NO formation. N-species chemistry
extracted from a recent mechanism validated for
prompt-NO formation [3] was implemented to these
2 mechanisms. The simulated species profiles
issued from the mechanism previously proposed by
Dooley et al. [1] are in relative good agreement with
the experimental ones.
Acknowledgements
This work was supported by the Air Quality
Program of CPER-IRENI (Institut de Recherche en
ENvironnement Industriel). M.D. Sylla thanks
University Lille1 for its founding.
References
[1]
[2]
[3]
S. Dooley, H.J. Curran, J.M. Simmi. Combustion and
Flame.153 (2008) 2-32.
S. Gail, M.J. Thomson, S.M. Sarathy, S.A. Syed, P.
Dagaut, P. Diévart, A.J. Marchese, F.L Dryer. Proceedings
of the combustion Institute.31 (2007) 305-311.
N. Lamoureux, P. Desgroux, A. El Bakali, J.F. Pauwels.
Combustion and Flame. 157 (2010) 1929-1941.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
CO2 solubility and reactivity in molten carbonates
Réactivité et solubilité du CO2 dans les carbonates fondus
D. Corradini1,2, F.-X. Coudert3, R. Vuilleumier*,1,2
1
École Normale Supérieure - PSL Research University, Département de Chimie, 24 rue
Lhomond 75005 Paris
2
Sorbonne 14
Universités - UPMC Univ Paris 06, CNRS UMR 8640 PASTEUR
3
PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie Paris,
75005 Paris, France
* Corresponding author: [email protected]
______________________________________________________________
Résumé : La solubilité de CO2 dans les carbonates fondus est particulièrement élevée, près de deux ordres de
grandeur plus grand que les halogénures d’alcalin fondus, ce qui en fait un milieu potentiel pour développer des
approches originales aux problème du captage et de la valorisation de CO2. Nous avons mené des simulations ab
initio pour comprendre cette interaction spécifique de CO2 avec les carbonates fondus, qui montrent la formation
d’un dimère C2O52-. Cette espèce pyrocarbonate a été suggérée pour expliquer la forte solubilité de CO2, mais
jamais mise en évidence. Nous discuterons alors des implications de cette espèce vis à vis du problème de captage
et de la valorisation de CO2.
________________________________________________________________________
Summary: Molten carbonates exhibit a very high solubility of CO2, two orders of magnitude larger than alkali-halides,
and may then provide an original route for tackling the problem of CO2 re-use and sequestration. To understand this
exceptional behaviour of molten carbonates, we performed first-principle simulations, which showed that CO2 strongly
2interacts with the carbonate anions, forming for about a third of the time a dimer C2O5 . This pyrocarbonate species
has been suggested as an explanation of the high CO2 solubility in molten carbonates, but never evidenced before.
We will then discuss the implication of this species for CO2 sequestration or electro-reduction in molten carbonates.
Keywords: molten carbonates; CO2; solubility; transport; first-principle simulations
The ultimate goal of this work is CO2 sequestration and electro-reduction in molten carbonates. Reversely to the use of
molten-carbonates in fuel-cells it will then be potentially possible to reduce CO2 in CH4 as an original route for valorizing
CO2 and store energy chemically. Because of their use as electrolytes in the molten-carbonate fuel-cells, there already
exists an industrial network employing molten-carbonates.
Ce travail se place a pour but ultime l’emploi de carbonates fondus pour le captage et l’électro-réduction de CO2. Il serait
alors possible potentiellement de réduire CO2 en CH4 comme méthode de valorisation de CO2 et de stockage chimique
de l’énergie. Les carbonates fondus sont dores et déjà fortement utilisés comme électrolyte pour des piles à combustilbe
de sort qu’un tissu industriel existe dores et déjà.
Our theoretical study is carried on in the context
of an original route to tackle the challenging
problem of CO2 sequestration and re-use. The idea
is to employ molten carbonates, commonly used
electrolytes in fuel cells, due to their ability to
dissolve CO2 (see for example [1]). To this aim, the
nature and composition of the carbonate melt have
to be optimized for CO2 dissolution and reduction. A
crucial step in this direction is to gather new data on
the solvation and transport of CO2 in molten
carbonates and get a better understanding of these
processes at the molecular level. By DFT first
principles molecular dynamics simulations we study
the properties of the solvent melt Li2CO3-K2CO3 at
the eutectic ratio (62:38%) at three different
temperatures, T = 900, 1000, 1100 K. Then the
solvation of CO2 in the melt is investigated with
particular focus on the possible formation of the
2pyrocarbonate ion C2O5 . This species was
observed in the gas phase [2, 3] and, albeit shortlived, in the condensed phase of CaCO3 [4].
Furthermore, it has been observed that the
solubility of CO2 in the carbonates increases with
increasing temperature, a fact that seems to
contradict the exothermic nature of the formation
2reaction of C2O5 in the gas phase. It is then
necessary to ascertain what is effect of the
environment in the condensed phase. Preliminary
results indicate that the pyrocarbonate ion is quite
stable in the eutectic Li2CO3- K2CO3 melt, with
possible implications on the thermodynamics of
reactivity and on the transport of CO2 in this
particular melt.
References
[1]
D. Chery, V. Albin, V. Lair & M. Cassir, Thermodynamic
and experimental approach of electrochemical reduction of
[2]
[3]
[4]
CO2 in molten carbonates. Int. J. Hydrogen Energ. 39,
12330 (2014). [
D. Peeters, D. Moyaux & P. Claes, Solubility and Solvation
of Carbon Dioxide in the Molten Li2CO3/Na2CO3/K2CO3
(43.5:31.5:25.0 mol-%) Eutectic Mixture at 973 K. II.
Theoretical Part. Eur. J. Inorg. Chem. 1999, 589 (1999).
P. J. Bruna, F. Grein & J. Passmore, Density functional
theory (DFT) calculations on the structures and stabilities of
2–
and [CnO2n+1]X2 polycarbonates containing
[CnO2n+1]
chainlike (CO2)n units (n = 2–6; X = H or Li). Can. J. Chem.
89, 671 (2011).
R. Vuilleumier, A. Seitsonen, N. Sator & B. Guillot,
Structure, equation of state and transport properties of
molten calcium carbonate (CaCO3) by atomistic
simulations. Geochim. Cosmochim Ac. 141, 547 (2014).
EXTRACTION DE LA MATIÈRE ORGANIQUE DES
SCHISTES BITUMINEUX MAROCAINS
S. Mansouri1, M. Oumam1 A. Abourriche2, H. Hannache1,
1
Equipe des Matériaux Thermostructuraux et Polymères. LIMAT-FSB, UH2MC. BP. 7955
Casablanca, Maroc
2
Laboratoire Matériaux, Procédés, Environnement et Qualité, ENSA-Safi, UCAM. BP.
63,46000 Safi, Morocco
[email protected]
Le Maroc dispose de réserves importantes en schistes bitumineux, estimées à 50millions de barils,
lui
permettant
d’être
classé
au
6ème
rang
après
les
Etats-Unis,
la
Russie,
le
Brésil,
la
République Démocratique du Congo et l’Italie. La valorisation industrielle de cette richesse nationale
s’impose alors et constitue aujourd’hui une préoccupation majeure des décideurs politiques. Cette ressource
naturelle se présente comme source de pétrole non conventionnel, riche en matière organique intimement
liée à une matrice minérale ; ce qui confère à la roche brute des potentialités importantes qui lui permettent
d’être utilisée comme source d’énergie.
Dans le cadre de cette étude orientée vers la valorisation de cette richesse nationale, nous avons
étudié des schistes bitumineux issus du gisement de Timahdite, La roche brute est composée
essentiellement de carbonates (calcite et dolomites) et d’argile. Le présent travail a donc consisté à étudier
les différents paramètres qui ont une influence sur l'extraction de la matière organique des schistes
bitumineux dans des conditions sub- et supercritiques, dans le but d'établir les conditions optimales
susceptibles de donner un bon rendement d'extraction et une meilleure qualité d'huile.
Résultats et discussion :
L’ensemble des résultats expérimentaux que nous avons obtenus montre que :
- à température et durée du traitement fixée, nous avons montré que l’eau, le toluène et l’ammoniac ont une
influence très importante sur le rendement d’extraction de la matière organique des schistes bitumineux.
- à température et durée du traitement fixée, nous avons montré que le toluène permet de donner le meilleur
rendement d’extraction de la matière organique.
- à température et durée du traitement fixée nous avons montré que l’eau, le toluène et l’ammoniac ont une
influence sur la composition des huiles obtenues a partir des schistes bitumineux.
- Dans ce travail on a déterminé les conditions optimales pour l’obtention du meilleur rendement d’extraction
de la matière organique pour chaque solvant.
Mots clés : L'extraction supercritique / Le schiste bitumineux / toluène
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Investigations on the energetic conversion of magnesium
pretreated cypress sawdust through controlled pyrolysis and
valorisation of the biochars for phosphorus removal from
synthetic solutions
Etudes de la conversion énergétique de la sciure de bois de cyprès
prétraitée avec du magnésium par pyrolyse contrôlée et valorisation
des biochars pour l’élimination du phosphore présent dans des
solutions aqueuses
1
K. Haddad
1,*
, A. Ben Hassen Trabelsi2, M. Jeguirim3, L. Limousy3, S.Jellali1
Water Research and Technologies Centre (CERTE), Wastewater treatment Laboratory,
Echo park of Borj Cédria, BP273, 8020
Soliman Tunisia.
2
Research and Technology Centre of Energy (CRTEn), Laboratory of Wind Power Control and
Energy Valorization of Waste, Echo-park of Borj Cédria BP 95, 2050, Hammam Lif, Tunisia.
3
Institute of Materials Sciences of Mulhouse, 15, road of Jean Starcky, BP 2488, 68057
Mulhouse cedex, France.
* Corresponding author: [email protected]
Résumé : Ce travail vise à étudier l'influence de la température de pyrolyse et du prétraitement, réalisés sur de la sciure
de bois de cyprès avec des sels de magnésium, sur les rendements des produits générés ainsi que sur l’efficacité
d’adsorption des biochars vis à vis du phosphore en milieu aqueux. Les résultats expérimentaux montrent que
l'imprégnation de la sciure de bois par du MgCl2 conduit à une augmentation des rendements de production de biochar
et de gaz. A titre d’exemple, pour une température de pyrolyse de 600°C, ces rendements passent respectivement de
27,0% à 33.3% (biochar) et de 36,6% à 40,9% (biogaz) pour la sciure brute et la sciure prétraitée. L’augmentation de la
température de chauffe de 400 °C à 600°C fait diminuer le rendement de biochar d’environ 52,5% à 33,3% pour la sciure
prétraitée. Les quantités de phosphore adsorbées par les biochars augmentent avec le prétraitement ainsi qu’avec la
température de pyrolyse. En effet, cette quantité croit d'environ 19,2 mg/g pour le biochar produit à 400°C (après
prétraitement) à plus de 33,8 mg/g pour celui généré à 600 °C (idem).
Summary: The present work aimed to study the influence of pyrolysis temperature and magnesium salts impregnation of
cypress sawdust on the by- products yields as well as on the efficiency of the produced biochars in removing phosphorus
from synthetic solutions. The experimental results showed that for a pyrolysis temperature of 600°C, the addition of
MgCl2 to the raw material increased the solid products (biochar) and biogas yields from 27.0% to 33.3% and from 36.6%
to 40.9% respectively and decreased the bio-oil yields. Furthermore, the pyrolysis temperature increase significantly
decreases the bio-char production yields from 52.5% at 400°C to 33.3% at 600°C. The sorbed phosphorus amounts
increased from 19.2 mg/g to more than 33.8 mg/g when pyrolysis temperature increased from 400°C to 600°.
Keywords: Sawdust; pyrolysis; biochar; magnesium; removal; phosphorus
-Application de la technologie innovante de pyrolyse pour la valorisation de déchets (problème d’ordre sociétal) et la
production d’énergie (biocarburants de deuxième génération) à haute valeur ajoutée permettant ainsi de résoudre au
moins en partie certains problèmes économiques liés à la demande en énergie primaire.
- Avec l’introduction de ce procédé de la pyrolyse, il est possible de créer de l’emploi et de cycles de formation sur ce
procédé.
-the application of the pyrolysis of organic wastes, which is an innovative technology, will contribute to the
implementation of the concept of “sustainable wastes management” and consequently to resolve a real societal problem.
Furthermore, this technology will permit the production of new forms of energy (second generation biofuels) with high
added value. Moreover, with the introduction of this innovative process of pyrolysis, it is possible to create jobs and
ensure training courses on this process.
1 Introduction
The development of alternative energy processes
has become imperative due to concerns about the
depletion of petroleum resources [1]. Pyrolysis is
thermochemical technique that converts biomass
into solid (char), liquid and gaseous fractions at
moderate temperature in absence of oxygen [2].
Recent studies tried to quantify and to better
understand the effect of the impregnation of
biomass with inorganic additives on the pyrolytic
products yields and the pyrolysis process. Today,
biochar is receiving great research attention due to
its potential importance in agronomic and
environmental applications. During the last decade,
considerable attention has been paid to the study of
the use of biochar-based adsorbents for the
removal of mineral and organic compounds.
However, only very few studies have been
performed for the determination of the efficiency of
raw or treated biochars for nutrients removal and
recovery from aqueous solutions. Therefore, the
main aims of this study were: i) to study the
influence of MgCl2 addition to cypress sawdust and
temperature pyrolysis on the production yields of
the pyrolytic byproducts and ii) to assess the P
removal potentials of biochars derived from treated
cypress sawdust at different pyrolysis temperature.
2
Experimental
Biomass is constituted by raw cypress sawdust
(RCS) which is locally collected from a carpentry
manufactory located in the region of Menzel
Bouzelfa (North East of Tunisia). Only the fraction
with dimension lower than 2 mm is used in this
study. The RCS is chemically pretreated using
MgCl2 salt. The prepared cypress sawdust (600 g)
is pyrolyzed in fixed-bed reactor and then ramped
to the desired temperatures of 400°C, 500°C and
600°C. The batch experiments are conducted at
room temperature (20°C) in 100 mL capped flasks.
During these assays, a predetermined amount of
the adsorbent is shaken in a phosphorus solution
(50 mL), at 400 rpm using a Varimag-poly15
magnetic stirrer. The dissolved phosphorus
concentrations are determined by using an UVvisible spectrometer (UV1 Spectronic apparatus)
after filtration of the suspension.
3
Results and discussion
Fig.1 shows the yields production of gas, bio-char
and bio-oil from the pyrolysis of both raw and
treated cypress sawdust samples at 600°C.The
addition of MgCl2 led to an increase in the yields of
gas and biochar while a decrease in the liquid
phase yield was observed. The highest yield of biochar production (33%) was obtained for cypress
sawdust pretreated with MgCl2 (CS-Mg) while the
lowest yield (27%) was obtained for RCS at 600°C.
Furthermore, the yields of liquid oil decreased from
about 37% for RCS to almost 27% for CS-Mg. In
fact, magnesium appeared to strongly catalyze the
primary reactions of dehydration, leading to across
linking of the cellulose chain and consequently to a
significant increase in the yield of biochar.
highest at 400°C (about 26 %) and the lowest one
was obtained at 600 °C with a percentage of 21%.
This finding could be imputed to the formation of
secondary cracking reactions of the pyrolysis
vapors.
Fig.2.Effect of temperature on syngaz, bio-oil and biochar
production yields.
The pyrolysis temperatures as well as the contact
time have important effects on P removal from the
synthetic aqueous solutions (Fig. 3). Indeed, for all
the produced biochars the P removal was clearly
time dependent. Furthermore, as the pyrolysis
temperature increases, the P removal efficiency
increases: for an initial aqueous concentration of 75
mg/L, a solution pH of 5 and a biochar
concentration of 1 g/L, the phosphorus adsorption
increases from 19.2 to 26.5 and to 33.8 mg/g when
the pyrolysis temperature increased from 400°C to
500°C
and
600°C,
respectively.
The
thermochemical treatment has changed the
physicochemical characteristics of the RCS through
the increase of their specific surface area and the
formation of MgO nanoparticles.
Fig.3. Effect of contact time and pyrolysis temperature on
phosphorus removal from aqueous solutions
Fig.1. Effect of magnesium on syngaz, bio-oil and biochar
production yields from cypress sawdust pyrolysis.
Moreover, it appears that temperature is a key
parameter in the conversion of sawdust during
pyrolysis process (Fig. 2). Indeed, the yield of biochar production decreases from 52 to 33% when
temperature increases from 400°C to 600°C. This is
attributed to the greater primary decomposition of
the biomass or secondary decomposition of the
char residue. At the same time, gas yield
significantly increased. The bio-oil yield was the
4
Conclusions
This work demonstrates that the impregnation of
cypress sawdust with MgCl2 has a significant effect
on its thermochemical degradation process. This
chemical pre-treatment significantly increases the
production yields of biogas and biochar. As
pyrolysis temperature increased, bio-char yields
decreased from 52% to 33%. Moreover, biochars
originated from the slow pyrolysis at high
temperature of pretreated cypress sawdust with
MgCl2 exhibited relatively high adsorption
capacities of phosphorus from aqueous solutions.
References
[1]
[2]
M. Zabeti , T.S. Nguyen, L. Lefferts , H.J. Heeres , K.
Seshan , Bioresour Technol 118 (2012) 374–381
H. Hwang, S. Oh, T.-S. Cho, I.-G. Choi, J.W. Choi,.
Bioresour. Technol. 150(2013) pp. 359-366
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Fossil and bio carbon chemistry in FCC co-refining of bio-oils
mixed with crude oil distillates
Chimie du carbone fossile et renouvelable dans le processus de coraffinage FCC de bio-huiles et de distillats du pétrole
Laurent Gueudré, Claude Mirodatos*, Yves Schuurman
Ircelyon, CNRS-UCBL, 2 Avenue Albert Einstein, 69626 Villeurbanne, France.
* Corresponding author: [email protected]
______________________________________________________________
Résumé : Cette étude concerne la chimie du carbone et plus spécifiquement du coke formé lors du craquage
catalytique de bio-huiles issues de la pyrolyse de la biomasse et de distillats pétroliers de type VGO. Il est montré
que la formation de coke provient (i) du craquage conventionnel des hydrocarbures fossiles dans les micropores de
la zéolithe USY, principale composante des catalyseurs de FCC, sous forme de coke graphitique bien structuré et (ii)
de la conversion de fragments de lignine et d’autres composés oxygénés de type phénolique, en hydrocarbures et en
"bio-coke" moins structuré, dans les zones mésoporeuses des catalyseurs. Ces deux voies sont contrôlées par la
structure, texture at acidité des catalyseurs zéolithiques et interagissent par les transferts d’hydrogène qui
caractérisent le craquage catalytique.
________________________________________________________________________
Summary: Carbon chemistry occurring in FCC catalysts during co-processing of fossil feeds blended with upgraded
bio-oils produced by fast pyrolysis of lignocellulosic bio-mass is investigated, focussing on coke formation. The latter
would result from (i) the conventional catalytic cracking for the fossil hydrocarbons leading to well-structured graphitic
coke in the USY zeolite micropores, and (ii) the conversion of lignin fragments and other lighter oxygenated
compounds (phenolic type) into hydrocarbons, residual oxygenates and finally "bio-coke" which accumulates
reversibly in mesopores as less structured coke. These two routes are monitored by the catalysts structure, texture
and acidity and are strongly interacting via hydrogen transfer between light hydrocarbons and phenolic type
fragments.
Keywords: FCC, co-processing, coke chemistry, bio-oils, vacuum gas oil cracking, ultra-stabilized Y zeolite
This work contributes to the understanding of an advanced industrial strategy to meet international renewable energy
targets by 2020 (up to 10% share in all forms of transportation fuels). Adding renewable feedstock’s to conventional fossil
ones in a crude oil refinery would provide a realistic answer to meet this greener and greener composition of
transportation fuels. However severe drawbacks as the increase of coke formation under co-refining conditions have to
be accounted for in the existing processes for reaching a high technology readiness level in a near future.
1
Introduction
In order to meet the international renewable
energy targets by 2020 (up to 10% share in all
forms of transportation fuels) [1], a realistic
alternative to the first generation bio-fuels is to
produce hybrid bio- and fossil fuels by co-refining
biomass pyrolysis oil with crude oil fractions in a
conventional oil refinery [2]. However, for the case
of the FCC process, co-refining leads to significant
changes in products quality, such as a higher
aromaticity and residual oxygenates of phenolic
type in the hybrid gasoline and higher coke
deposits in the FCC catalysts during the cracking
step [2]. A detailed understanding is required on
how the oxygenated moieties introduced in the
added bio-oils affect the cracking mechanism and
how both fossil and renewable carbon are
distributed among the FCC products. From this
understanding, solutions can be proposed to keep
the FCC products quality within the standard
specifications. In this study carried on a micro
activity test (MAT) reactor, up-graded pyrolysis biooils are added to crude oil distillates (VGO type) to
undergo the FCC cracking/regeneration cycle by
using model (USY and ZSM-5 zeolite) or industrial
FCC catalysts. The quality of the produced "hybrid"
FCC fuels is analyzed and compared, focusing on
coke generation and nature as a signature of the
cracking process, in tight relationship with catalysts
structure and active sites accessibility.
2
Experimental/methodology
The used crude oil distillates as vacuum gas oil
(VGO) and upgraded bio-oils as hydrotreated
thermal pyrolysis oil (HDO) or catalytic pyrolysis oil
(CPO) as well as the micro activity test (MAT)
reactor and on- and off-line reactants and products
analyses are described in [2,3].
Basically, mixtures of VGO and HDO (90/10)
were tested in the fixed bed MAT reactor at various
catalyst/oil ratios in order to follow the impact of
these feed combinations on the distribution of the
cracking products among which gasoline, light
gases, LPG and coke formation.
The catalysts used were either FCC e-catalysts
or USY catalysts, the latter being as being the main
active compound of an industrial FCC catalyst.
3
Results and discussion
From pore volume changes and coke analysis,
the rate of coke deposition was found about two
fold higher in the presence of oxygenates in the
feed (leading to >100°C exotherm in the
regenerator) (Fig. 1)
Fig. 1. Impact of co-processing on coke formation (◊: pure VGO
cracking, 10% hydrotreated bio-oil with 90% VGO)
Coke formed in the presence of bio-oils is
shown to affect more Lewis acid sites than
Brønsted ones.
These results lead to a tentative mechanistic
scheme for coke formation (Fig. 2) where the lignin
polymeric fragments are cracked into smaller
oxygenates (e.g., methoxy phenols) in the extraframework mesoporous space (Lewis acid sites),
leading to a specific amorphous coke deposition,
including thermal condensation into polyaromatic
coke precursors. In turn, the graphitic coke
deposition arising from the hydrocarbons cracking
essentially in the zeolite micropores (Brønsted acid
sites) is not significantly affected by the presence of
oxygenated molecules [3].
Table 1. Changes in surface area and porous volume of the
reference fresh or regenerated USY zeolite according the
cracking conditions. The values in parenthesis correspond to the
percentage of loss as compared to the fresh sample data.
Fresh
USY
VGO coked
USY
CPO coked
USY
VGO90/CPO10 coked
USY
BET (m2/g)
810
470 (42%)
510 (37%)
510 (37%)
Vmicro from t-plot analysis
(cm3/g)
0,32
0,16 (49%)
0,18 (44%)
0,20 (38%)
Vmeso from BJH analysis
(cm3/g)
0,23
0,17 (26%)
0,17 (24%)
0.21 (7%)
Textural data/samples
From TEM and BET-BJH analyses (Table 1),
the coke deposits from the VGO cracking are found
essentially graphitic and located inside or close to
the Y zeolite microstructures, while extra framework
deposits, essentially amorphous, are formed in the
meso/macroporous
structure
after
bio-oil
degradation/condensation.
From NMR and DRIFT analysis, the coke
formed from the oxygen containing bio-molecules is
found to present more highly condensed aromatic
rings than the coke formed from the feed
hydrocarbons.
From the radio carbon analysis (14C), it comes
that the bio-carbon contained in the HDO-oil is
concentrated mainly in the gas fraction (11%) and
in the coke fraction (16%) while the targeted liquid
product, gasoline, contains only around 7% of biocarbon [3].
Fig. 2. Schematic mechanism of catalytic cracking under FCC
co-processing conditions
4
Conclusions
From an in-depth analysis of the nature,
location, structure and texture of the deposited coke
under FCC co-refining conditions, a mechanistic
scheme is proposed based on two strongly
interacting pathways related to the coke chemistry
dealing with fossil and oxygenated molecules,
respectively. By pointing out the relationships
between this fossil/bio carbon fate and catalysts
structure, texture, acidity and cracking properties,
this work is deemed to provide strong guide-lines to
adapt the FCC catalysts design to demanding corefining operating conditions. Strategies such as
creating a hierarchical mesoporosity (via e.g.,
dealumination + desilication) to enhance bio-oil
diffusion and conversion to fuel will be discussed to
conclude that presentation.
Acknowledgements
Part of the present study was initiated during
previous EU projects BIOCOUP (FP6) and
HECABIO (ACENET).
References
[1]
[2]
Fig. 2 Strong acidity distribution from pyridinium ions FTIR
bands intensity after desorption at 300°C for the fresh reference
USY catalyst, then, after VGO processing, CPO processing and
VGO90-CPO10 co-processing.
[3]
http://ec.europa.eu/energy/renewables/targets_eu.htm
Y. Schuurman, G. Fogassy, C. Mirodatos. Tomorrow's
biofuels: hybrid bio-gasoline by co-processing in FCC units
in "The Role of Catalysis for the Sustainable Production of
Bio-fuels and Bio-chemicals", Eds Triantafyllidis, Stöcker
and Lappas, Elsevier, 2013, 321–349.
L. Gueudré, N. Thegarid, L. Burel, B. Jouguet, F. Meunier,
Y. Schuurman, C. Mirodatos, Catal. Today (2014),
http://dx.doi.org/10.1016/j.cattod.2014.09.00
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Bio-oil hydrodeoxygenation: Effect of water and phenol
compounds on the stability of sulfided (Co)Mo catalysts
Hydrodésoxygenation des bio-huiles: effet de l’eau et des composés
phenoliques sur la stabilité des catalyseurs (Co)Mo sulfurés
F. Maugé*1, E. Kondratieva1, J.P. Gilson1, L. Mariey1, A. Popov1, A. Travert1,
M. Badawi2, S. Cristol2, E. Payen2, J.F. Paul2, S. Brunet3, F. Richard3, Y.
Romero3
1
Laboratoire Catalyse et Spectrochimie, ENSICAEN, Université de Caen, CNRS, 6, Bd du
Maréchal Juin, 14050 Caen, France ;
2
- Unité de Catalyse et Chimie du Solide – Université de Sciences et Technologie de Lille –
CNRS – 59650 Villeneuve d’Ascq, France
3
Institut de Chimie des Milieux et Matériaux de Poitiers, Université de Poitiers – CNRS,
86022 Poitiers, France
* Corresponding author: [email protected]
______________________________________________________________
Résumé :
Cette étude concerne la compréhension de l'origine de la désactivation des catalyseurs
d’hydrodésoxygénation (HDO). La modification des catalyseurs sulfurés (Co)Mo/Al2O3 en presence d'eau
(un produit de la réaction de HDO) et de molécules de type phénolique (représentant les fonctions
oxygénées les plus réfractaires en HDO) a été étudiée. Les catalyseurs les plus actifs (i.e. CoMo) sont
faiblement sensibles à l'eau. Les molécules phénoliques conduisent à la formation d'espèces phénate sur
le support d'alumine qui diminuent fortement l'accessibilité aux sites actifs. Les propriétés de surface du
support du catalyseur sont déterminantes dans l'étendue de l’empoisonnement des catalyseurs d’HDO.
________________________________________________________________________
Summary:
This paper deals with the origin of hydrodeoxygenation (HDO) catalyst deactivation. It reports the
interaction of water (a product of the HDO reaction) and phenolic representative of refractive oxygenated
functions of pyrolysis bio-oils, with sulfided (Co)Mo/ Al2O3 catalyst. The most active catalysts are weakly
sensitive to water. Phenolic molecules leads to the formation of phenate-type species anchored on the
alumina support that hinder the accessibility of the sulfide edge sites i.e. active sites. Hence, the nature of
the oxygenated compound as well as the surface properties of the catalyst support are determining in the
extent of HDO active sites poisoning
Keywords: hydrodeoxygenation, sulfide catalyst, water, phenol, desactivation
1
Introduction
The environmental concerns in limiting carbon
dioxide emissions imply the substitution of
conventional fuels by new products issued of
renewable sources. In European Union, 20% of the
conventional fuels should be replaced by alternative
fuels in the road transport sector by 2020. A
sustainable route is the use of lignocellulosic
biomass issued from agricultural and wood
residues. To produce liquids from solid
lignocellulosic materials, fast pyrolysis seems the
most promising route. However, lignocellulosicderived bio-oils resulting from this thermochemical
process contain very important amounts of
oxygenated compounds (up to 45 wt% O) [1].
Consequently, the main challenges for production
of bio-fuel from pyrolytic bio-oils are the elimination
of oxygen. The typical hydrodesulfurization catalyst
i.e. sulfided CoMo supported on Al2O3 is also a very
interesting candidate for hydrodeoxygenation
(HDO). However, deactivation of HDO catalyst is a
key problem, and deactivation mechanisms are still
unclear. Deactivation can be related to water effect
(that can modify active phase or support), sintering
of the active phase, or coking.
The aim of this work is to clarify the origin of
HDO catalyst deactivation in order to propose
rational solutions based on understanding. In this
paper, we investigated the influence of water
(produced by the HDO reaction) and phenolic type
molecules (the most refractory oxygenated
molecules for HDO [3]) on the active sites of
sulfided (Co)Mo/Al2O3 catalyst. The objective is to
determine the mode of interaction and the toxicity of
these various compounds in model and in real
conditions in order to propose solutions based on
these findings for preserving HDO catalyst activity.
2
Experimental/methodology
Materials. The (Co)Mo/Al2O3 catalysts were
prepared by conventional incipient wetness
impregnation.
Activity measurements. All the catalysts were
sulfided in situ into a high-pressure dynamic flow
reactor using a mixture of DMDS diluted in toluene
under 4.0 MPa, at 623 K for 14 hours. The catalytic
test was carried out at 613 K under 7 MPa using
the oxygenated model compound (phenol or 2ethylphenol) diluted in toluene. Their partial
pressure was fixed to 49 kPa. DMDS was added to
the feed and the partial pressure of hydrogen was
kept constant.
IR spectroscopy. The catalyst was sulfided in
situ under a flow of H2S/H2 (10/90) at 623 K during
2 hours and followed by an evacuation during one
hour at the same temperature. Calibrated doses of
phenol or 2-ethylphenol were introduced at room
temperature. The impact of phenol and 2ethylphenol on the accessibility of the sites of the
sulfide phase was assessed using CO as a probe
molecule.
Computational methods. The density-functional
theory calculations were performed with the Vienna
Ab initio Simulation Package (VASP) using the
PAW method. Throughout this work, we used a
large super cell, which contains four elementary
MoS2 units in the x and z direction, and two layers
along the y-axis. The promoted catalyst is model by
substituting of the Mo atoms on the S edge and half
of the atoms on the metallic edge. The adsorption
energy is computed following the next equation:
Eads = E(surface) + E(molecule) + E(molecule +
surface). Positive adsorption energy corresponds to
an exothermic adsorption.
3
Results and discussion
The different techniques were used to
understand the impact of water and nature of
phenolic compounds on the stability of Mo and
CoMo sulfide catalysts supported on alumina. The
main findings can be summarized as follows:
Effect of water
- Water addition during the hydrodeoxygenation
of 2-ethylphenol decreases slightly the catalyst
activity. This is fully reversible on the CoMo
catalyst, but partly irreversible on the unpromoted
Mo catalyst.
- IR characterization highlights that a water
treatment at reaction temperature leads to a strong
and irreversible decrease in the number of
unpromoted Mo sites, while the poisoning of the
Co-promoted sites occurs to a lower extent and is
fully reversible.
- DFT calculations show that incorporation of
cobalt at the edge of the MoS2 sulfide phase
increases its stability toward water.
All these findings indicate that the presence of
large amounts of water at reaction temperature can
lead to sulfur–oxygen exchanges of the edges sites
of sulfide slabs, hence changing the nature of
(Co)MoS2 edge sites. The extent of water poisoning
is much lower for Co-promoted catalyst than for Mo
catalyst.
Effect of phenolic compounds
The study of the interaction of oxygenated
aromatic compounds (as phenol, ethylphenols and
guaiacol) with sulfided (Co)Mo/Al2O3 catalyst shows
that basicity of the phenolic molecules as well as
the nature of the substituent are the key parameters
which determine the adsorption mechanisms.
All the phenolic compounds anchor on the
alumina support as phenate-type species whereas
only the most basic phenolic molecules (as 2 and 4
ethylphenol) and guaiacol interact also with the
sulfide phase. At temperature typical of the HDO
operating conditions, only phenate species on the
support are detected.
As expected, oxygenated compounds adsorbed
on the sulfide phase poison the sulfide sites. But,
phenate-type species anchor on the alumina also
hinder the accessibility to the sulfide edge sites.
Modeling of the catalyst surface quantitatively
confirms the screening effect of these phenate
species.
Characterization
of
catalysts
tested
in
ethylphenol HDO confirms the role of poison of the
ethylphenate species that was suspected from the
model condition study.
4
Conclusions
This paper points out that the extent of water
poisoning is much lower and reversible on CoMo
than on Mo catalysts. Co atoms prevent sulfur–
oxygen exchanges. Hence, in HDO, Co does not
only increase the intrinsic activity of the catalyst
(promotion effect) but also stabilizes active phase in
the presence of water (passivation effect).
The nature of the oxygenated aromatic
compound as well as the surface properties of the
catalyst support are determining in the mode and
extent of HDO active sites poisoning. A decrease of
the strength of the acid-base paired sites of the
support should be a way to improve HDO catalyst
stability.
Acknowledgements
This work was performed within ECOHDOC, a
project funded by ANR and Programme National de
Recherche sur les Bioénergies
References
[1]
[2]
[3]
E. Furimski, Applied Catalysis, A: General (2000) 199, 147190.
E. Laurent, A. Centeno, B. Delmon, Studies in Surface
Science and Catalysis, (1994) 88, 573-578.
G. W. Huber, S. Iborra, and A. Corma, Chem. Rev., 2006,
106, 4044-4098.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Understanding the deactivation of metal catalysts related to
the use of more sustainable feedstocks
Comprehension de la désactivation de catalyseurs de reactions liées à
la transition fossile-biomasse
F.C. Meunier*, Y. Schuurman
Institut de Recherches sur la Catalyse et l’Environnement de Lyon, Université Lyon 1, CNRS. 2, Av.
Albert Einstein F-69626 Villeurbanne
* Corresponding author: [email protected]
______________________________________________________________
Résumé : L’utilisation accrue de charges issues de la biomasse présentera de nouveaux défis pour l’industrie
chimique car les catalyseurs utilisés pour la conversion des matières premières fossiles peuvent être désactivés par
les impuretés dérivées des biomasses. La spectroscopie operando infra-rouge a été utilisée pour étudier la
désactivation de catalyseurs sous flux. Des exemples seront présentés basés sur l’effet du CO2 et du chlore, tous
deux souvent présents dans des dérivées de biomasses, sur des réactions d’hydrogénations. La stabilité de
nanoparticles bimétalliques Pt-Sn et Pt-Co, matériaux envisagés aussi pour des électrodes de piles à combustibles,
sera aussi discutée.
________________________________________________________________________
Summary: The transition from fossil to biomass-derived feedstocks creates new challenges for the chemical industry
because the catalysts used in feedstock conversion may deactivate due to biomass-derived impurities. Operando FTIR spectroscopy was used to investigate catalyst deactivation under relevant operating conditions. Examples will be
discussed dealing with the poisoning of hydrogenation catalysts by CO2 and chlorine, both being typical biomassderived compounds found in biogas. The stability of Pt-Sn and Pt-Co nanoparticles, which are envisaged in a range
of applications from catalysis to fuel cell electrodes, was also shown to depend on operating conditions.
Keywords: catalysis; metal; alloy; operando; spectroscopy; hydrogenation.
Renewable fuels and base chemicals can be obtained from biomasses, which come yet with impurities that will require
the development of new technological solutions to be able to process those into added-value products. This work
illustrates some related new challenges facing catalysis, a crucial science that enables enormous feedstock and energy
savings by directing chemical conversion into desirable products and making possible the use of much lower reaction
temperatures.
Des combustibles renouvelables et des produits chimiques de base peuvent être obtenus à partir de biomasses.
Cependant, celles-ci contiennent des impuretés qui nécessitent d’adapter les procédés industriels. Cet exposé décrit
quelques nouveaux défis dérivant de l’utilisation de biomasse en catalyse, qui est une science permettant de convertir de
façon sélective et économique des produits de base en dérivés à forte valeur ajoutée.
1
Introduction
Catalytic hydrogenation is an ubiquitous reaction
and is used for instance in the synthesis of fine
chemicals and fuel upgrading. Environmental
legislation is driving down the aromatic content of
gasoline and arene hydrogenation is thus of
significant interest. Concomitantly, using “green” H2
derived from biomass conversion is desirable and
might even become economically viable in time. H2
can be produced from organic waste fermentation
and CO2 can be formed alongside in large
concentrations. Therefore, there is an interest in
understanding any effects that CO2 could have on a
catalytic reaction in which biomass-derived H2
could be used. Toluene hydrogenation was used
here as a model reaction. Such knowledge would
help determining the purification limits to reach,
defining thus the associated technology and cost, if
required. The same question arises for chlorine,
widely present in biomass and its effect was
followed here in the case of CO hydrogenation to
hydrocarbons on a cobalt-based catalyst (FischerTropsch reaction).
2
Experimental/methodology
The ambient pressure experimental setup and
the DRIFTS cells are described elsewhere [1-3].
The toluene and trichloroethylene were introduced
via a saturator. The reaction products were
quantified using a 2m-pathlength FT-IR gas cell and
mass spectrometry.
3
Results and discussion
Rhodium highly dispersed on alumina becomes
partly poisoned by strongly bound CO when used
for toluene hydrogenation at 348 K in the presence
of CO2 [3]. Operando FT-IR analysis enabled to
observed CO(ads) build up over the sample, while
no CO(gas) could be measured in the reactor
effluent. Analyses carried out by complementary
operando and in situ infrared spectroscopy studies
unraveled the nature of the deactivating sites, i.e.
low coordination number Rh sites located at the
interface with the alumina support basic sites on
which CO2 strongly adsorbs [3]. Rh supported on
silica with a lower dispersion remained free of
adsorbed carbon monoxide even under higher CO2
pressures, stressing the relevance of infrared
studies in catalyst rational design (Fig. 1).
Carbonates,
Hydrogenocarbonates,
Formates
Log (1/R)
O
C
0.2
O
C
Rh Rh
Rh
Rh/Al2O3
suggesting that those were associated with the
-1
most active sites. The 1911 cm species only led to
a minor dipole-dipole coupling and were thus most
likely forming a mono-dimensional, or even
punctual, network of CO(ads). These species were
likely bridged CO adsorbed on step sites, where
chlorine
could
preferentially
adsorb.
The
corresponding C-O bond strength increased by
about 7 kJ/mol in the presence of chlorine.
Assuming that the rate-determining step of
CO hydrogenation was C-O bond dissociation,
these observations are consistent with chlorine
main poisoning effects being both site blocking (i.e.
competitive adsorption) and an electronic effect
through the strengthening of the C-O bond that
made CO(ads) less likely to dissociate (i.e.
modification of the activation energy barrier).
Rh/SiO2
2200
2000
1800
Wavenumbers
1600
1400
/cm-1
Fig. 1. Operando DRIFTS spectra recorded over Rh supported
on alumina (top) and silica (bottom). Feed: 0.8 % toluene + 66 %
H2 + 10 % CO2 in the case of the silica-supported sample and
0.8 % toluene + 66 % H2 + 1.7 % CO2 in the case of the
alumina-supported sample. Ar balance. T = 75°C.
The use of alloys may also enable to reduce the
poisoning effect of CO. Pt-Sn and Pt-Co alloys
have been often reported for their improved
properties as compared to the plain metal catalysts
or electrodes. We have recently measured by
Adsorption Equilibrium IR (AEIR), for the first time,
the heat of adsorption of CO on a Pt-Sn alloy and
shown that is was about half the value measured
on a Pt sample [2]. The alloy was yet shown to
segregate at temperatures lower than 175°C [2].
The effect of chlorine, introduced as
trichloroethylene (TCE), on the CO hydrogenation
activity of an alumina-supported cobalt was studied
at atmospheric pressure [4]. The surface of metallic
cobalt was covered with CO(ads) under reaction
conditions and the corresponding IR signal could be
exactly decomposed into three bands, whether
chlorine was present or not (data not shown).
Chlorine induced a strong and partly reversible
poisoning (Fig. 2).
A major effect of chlorine on the electronic
structure of the cobalt particles was evidenced, in
addition to the previously reported site blocking.
The carbonyl band position remained unchanged,
while its intensity decreased significantly in the
presence of TCE. This is in contrast to typical
surface coverage effects. This difference was
related to the electronic density removed by
chlorine from the metallic cobalt that limited the
weakening of the C-O bonds, which occurred
through electronic back-donation from cobalt to the
CO π* anti-bonding orbital.
The CO(ads) exhibiting a wavenumber at
-1
ca. 1911 cm were most affected by chlorine,
Fig. 2. Rates of formation of (+) methane, (x) ethene, (∆)
propene and (o) methanol measured at the exit of the DRIFTS
cell loaded with a 15% Co/Al2O3. T = 220 °C. Feed: 30 % CO +
60 % H2 (+ 50 ppm TCE if present) in Ar.
4
Conclusions
In many instances the deactivation of metal
catalysts can be understood using operando IR
spectroscopy. This provides a crucial tool in the
design of future catalysts and electrodes associated
with renewable feedstocks.
Acknowledgements
Part of this work was partly supported by the
ANR, (BioSyngOp, reference ANR-11-BS07-026).
References
[1]
[2]
[3]
[4]
A. Paredes-Nunez, D. Lorito, N. Guilhaume, C. Mirodatos,
Y. Schuurman, F.C. Meunier, Catal. Today 242 (2015)
178–183.
A. Moscu, Y. Schuurman, L. Veyre, C. Thieuleux, F.C.
Meunier, Chem. Commun. 50 (2014) 8590-8592.
J. Scalbert, C. Daniel, Y. Schuurman, C. Thomas, F.C.
Meunier, J. Catal. 318 (2014) 61-66.
Anaëlle Paredes-Nunez, Davide Lorito, Yves Schuurman,
Nolven Guilhaume, Frederic C. Meunier, submitted for
publication.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Lanthanum promotion of cobalt supported Fischer-Tropsch
Catalysts
Promotion par le lanthane des catalyseurs Fischer-Tropsch à base de
cobalt
C. Brabant1, A.Y. Khodakov1, A. Griboval-Constant*,1
1
Université de Lille,UCCS,UMR 8181, Bât C3, 59655 Villeneuve d’Ascq
* Corresponding author: [email protected]
______________________________________________________________
Résumé :
Au cours de la préparation classique des catalyseurs Fischer-Tropsch, la réaction chimique entre l'oxyde de cobalt et
le support alumine produit des oxydes mixtes tels que les aluminates de cobalt, qui sont à peine réductibles et donc
inactifs pour cette réaction. L’objectif du travail présenté a été d’affaiblir l’interaction entre l’oxyde de cobalt et le
support, grâce à un couche mince d’oxyde de lanthane. Des catalyseurs mixtes ont été synthétisés et l'effet du
rapport La/Co sur la structure des catalyseurs est présenté. Différentes techniques ont été utilisées pour la
caractérisation des catalyseurs à chaque étape de la préparation et les résultats ont montré un impact fort du rapport
La/Co sur la structure et la réductibilité des phases. Il a été trouvé qu’une teneur de 10% de lanthane permet de
réduire la formation d’aluminate de cobalt et d'améliorer les performances catalytiques.
________________________________________________________________________
Summary: text in english
During the conventional Fischer-Tropsch catalyst preparation, the chemical reaction between cobalt oxide and
alumina support leads to mixed oxides such as cobalt aluminates, which are barely reducible and inactive for the
reaction. The objective of the present work has been to weaken the interaction between cobalt oxide and support,
through a thin layer of lanthanum oxyde. Mixed catalysts were synthesized and the effect of the La/Co ratio on the
structure of catalysts is presented. Different techniques have been used for the characterization of catalysts at each
stage of the preparation and the results showed a strong impact of the La/Co report on the structure and the
contractility of the phases. It was found that 10% of lanthanum can reduce the formation of cobalt aluminate and
increase catalytic performance.
Keywords: Fischer-Tropsch, catalyst, lanthanum, cobalt
La synthèse Fischer-Tropsch permet de produire des carburants propres à partir du gaz de synthèse (mélange CO, H2)
qui peut être obtenu par transformation du méthane, du charbon ou de la biomasse. La production de carburants à partir
de la synthèse Fischer-Tropsch apparaît comme une voie très prometteuse dans la stratégie mondiale énergétique de
demain. Ces carburants représentent en effet une vraie alternative aux carburants traditionnels issus du pétrole brut. Ils
présentent l’avantage d’une teneur nulle en soufre et très faible en composés aromatiques.
Le procédé restant coûteux, une optimisation de la synthèse du catalyseur permettrait de le rendre encore plus attractif.
Ce travail présente l’intérêt d’une promotion par le lanthane des catalyseurs classiques. Une synthèse contrôlée du
catalyseur et une compréhension des relations existant entre les propriétés de ce catalyseur et l’activité catalytique
représentent un challenge pour les années à venir.
1
Introduction
Fischer-Tropsch (FT) synthesis is an essential
part of the GTL, CTL and BTL technologies which
manufacture valuable hydrocarbons exempt of
sulfur and aromatics from natural gas, coal or
biomass. Cobalt catalysts supported by refractory
oxides are preferentially used for the production of
middle distillates and waxes. These catalysts are
typically prepared by impregnation with cobalt
nitrate followed by oxidative or/and reductive
pretreatments. High cobalt dispersion, good
reducibility and catalyst stability are key parameters
to attain high and enduring yields of hydrocarbons.
Because of a high surface area, porosity, alumina
has been especially convenient for the design of
cobalt FT catalysts for fixed-bed reactors. On the
other hand, the metal–support interaction in
alumina-supported catalysts can also result in
mixed oxide (cobalt aluminate) [1-2], which should
be avoided, since it does not catalyze FT synthesis.
Minimization of the concentration of barely
reducible cobalt aluminate and maximization of
cobalt metal dispersion would therefore result in a
better catalytic performance. Previous reports [3-4]
have shown that promotion with lanthanum could
improve the performance of cobalt FT catalysts.
The mechanism of the modification of catalyst
structure by using lanthanum promoter and his
2
Experimental/methodology
the profile obtained for the catalyst prepared
without lanthanum. This result shows that 10wt%
seems to be the best value for the preparation, in
agreement with the limit of good dispersion. It
seems that high quantity of lanthanum deposited
(>15%) doesn’t allow to obtain good dispersion of
lanthanum and also protection of the support.
Catalysts are prepared by wetness impregnation
of Puralox alumina followed by calcination in air.
Typically, the catalysts contain 10wt% of cobalt and
between 0 to 20 wt% of La (0, 2, 5, 10, 15, 20).
Cobalt was introduced on the lanthanum calcined
catalyst. The effect of calcination temperature
(400°C or 800°C) for lanthanum catalysts was also
studied. The catalysts were activated by reduction
in hydrogen at 673 K. A wide range of techniques
(TPR, XRD, XPS, SEM…) were used for catalyst
characterization at each preparation step. The
catalytic performance was evaluated in fixed bed
reactor at 20 bars, 493K, H2/CO =2.
X(CO), selectivity for CO2 and CH4
60%
100%
50%
96%
40%
92%
30%
88%
20%
84%
10%
0%
80%
0
3
Results and discussion
20
30
40
Time-on-stream (h)
S(CH4)
S(CO2)
50
60
S(C5+)
Fig. 2. : Catalytic performances of 10La10Co/Al2O3 with
time-on-stream (GHSV=5.6NL.h-1.g-1).
No increase in conversion is observed (Fig. 2)
for this catalyst but the coverage of the support with
lanthanum layer allows to obtain a very low
selectivity in methane, which improves catalytic
performances. Moreover a higher selectivity of C5+
is obtained and no CO2 was observed.
20La10Co/Al2O3
15La10Co/Al2O3
H2 consumption (u.a.)
50
10
X(CO)
The results show strong impact of La/Co ratio on
the structure, and reducibility of supported cobalt
phases. Co3O4 phase is predominant in all
catalysts, but differences appear in the size of
Co3O4 crystallites depending on the La/Al ratio.
Fig. 1 compares TPR profiles obtained by varying
percent of lanthanum. The TPR profile of
10Co10La/Al2O3 catalyst shows that the reduction
of Co3O4 to CoO appears at higher temperature
Selectivity for C5+
influence on the catalytic performance remain
however rather erratic. In this paper we present the
effect of La/Co ratio on the structure of alumina
cobalt supported catalysts.
10La10Co/Al2O3
4
10Co/Al2O3
Conclusions
10La/Al2O3
250
450
650
850
1050
Temperature ( C)
The results have shown that impregnation of the
support with 10wt% of lanthanum leads to minimize
the concentration of barely reducible cobalt
aluminate which is present in conventional cobalt
catalysts used for FT reaction and also to maximize
the cobalt metal dispersion. For similar conversion,
lower selectivity in methane, and at the same time
higher selectivity of heavy hydrocarbons are
obtained.
compared with 10Co/Al2O3 but no cobalt aluminates
are observed after 1073 K.
Fig. 1. : H2-TPR profiles of high lanthanum
calcined catalysts (3K/min, 5%H2/Ar)
This result shows that promotion with 10%wt of
lanthanum allows to prevent the formation of the
most refractory cobalt aluminate which is
responsible of activity loss. TPR profiles of
10Co15La/Al2O3 and 10Co20La/Al2O3 are similar to
References
[1] G. Jacobs, T.K. Das, Y.Q. Zhang, J.L. Li, G. Racoillet, B.H.
Davis, Appl. Catal. A 233 (2002) 263.
[2] E. Iglesia, S.L. Soled, R.A. Fiato, G.H. Via, J. Catal. 143
(1993), 345.
[3] S. Vada, B. Chen, J.G. Goodwin, J. Catal. 153 (1995), 224.
[4] J.S. Ledford, M. Houalls, A. Proctor, D.M. Hercules, J.
Phys. Chem. 93 (1989), 6770.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Rhodium-catalyzed hydroformylation of triglycerides
aqueous media using supramolecular emulsifiers
in
Hydroformylation des triglycérides en milieu aqueux par utilisation
d’émulsifiants supramoleculaires
Théodore Vanbésien1, Frédéric Hapiot1, Eric Monflier1
1
Université d’Artois, Unité de Catalyse et de Chimie du Solide - UCCS Artois, Faculté Jean Perrin, rue Jean
Souvraz, SP18, 62307 Lens Cedex, France.
eric.monflier@univ-artois.
______________________________________________________________
Résumé :
Les considérations environnementales sur l’impact des procédés chimiques ont poussé les chimistes à développer de
nouveaux systèmes propres utilisant l’eau comme solvant. Bien que ces systèmes soient appropriés pour les petites
molécules partiellement solubles dans l’eau, ces procédés ne le sont pas pour les substrats très hydrophobes en raison
des limitations de transfert de matière entre phases aqueuse et organique.
Dans ce contexte, nous avons développé un procédé capable de convertir les insaturations de triglycérides naturels
dans l’eau par utilisation de complexes supramoléculaires en présence de cyclodextrines (CDs) (oligomères cycliques
composés d’unités glucopyranoses). Durant la réaction d’hydroformylation, un complexe supramoléculaire éphémère est
formé entre l’une des chaines alkyle du triglycéride et une CD appropriée dans des conditions de concentration bien
définie. Ce complexe tensioactif CD/triglyceride permet d’aider à la conversion des doubles liaisons C=C dans des
conditions biphasiques au moyen d’un catalyseur organométallique rhodié hydrosoluble. Par inclusion du triglycéride et
formation du complexe émulsifiant, le triglycéride est le moteur de sa propre transformation. Une fois la transformation
achevée, l’émulsion instable est rapidement décantée. Les produits hydroformylés peuvent être facilement récupérés
dans la phase organique surnageante et la phase aqueuse contenant le catalyseur peut être recyclée. Ce procédé
« propre » est applicable à une large gamme d’huiles d’origine végétale.
A travers cette présentation, les paramètres clés influençant ce nouveau système innovant seront décrits et commentés.
________________________________________________________________________
Summary:
Concerns about the environmental impact of chemical transformations prompted chemists to develop clean chemical
processes using water as a solvent. Although appropriate for small partially water-soluble molecules, these processes
are not suitable for the transformation of hydrophobic substrates due to the mass transfer limitation between the aqueous
and the organic phase.
In this context, we have developed a process capable of converting naturally occurring triglycerides in water through
supramolecular means in the presence of cyclodextrins (CDs) (cyclic oligomers consisting of glucopyranose units).
During the course of the hydroformylation reaction, a transient supramolecular complex is formed between triglyceride
alkyl chains and appropriate CDs in a well-defined range of concentrations. The resulting CD/triglyceride supramolecular
emulsifiers help converting the triglyceride C=C double bonds in biphasic conditions using a water soluble organometallic
Rh-catalyst. Thus, through inclusion of their alkyl chains within the CD cavity and the subsequent formation of
supramolecular emulsifiers, the triglycerides drive their own transformation into hydroformylated products. Once the
reaction is complete, the unstable emulsion is broken rapidly. The hydroformylated products are recovered in the upper
organic phase while the catalyst-containing aqueous phase can be recycled. Thus, this biphasic process can truly be
considered as a clean process. Moreover it is applicable to a wide range of vegetable oils.
Through the presentation, the key parameters influencing this novel catalytic process will be described and
commented.
Keywords: Triglycerides, Cyclodextrins, Supramolecular Emulsifier, Rh-catalyzed hydroformylation.
Currently, most industrial polymers are derived from fossil resources. However, it was recently showed that they can also
be produced from renewable resources as a means of addressing environmental and economic concerns. To access
such green polymers, we recently demonstrated that unsaturated triglycerides can be used as potential monomers. They
are of major interest as they can be derived from abundant feedstock such as vegetable oils and animal fats. As such,
they constitute an eco-friendly alternative to fossil feedstock. To convert unsaturated triglycerides into monomers, we
made use of a catalyst retained in water (the “ultimate green solvent”) and cyclodextrins (biosourced cyclic sugar) to
overcome the mass transfer limitation between the hydrophobic substrate and the water-soluble catalyst by
supramolecular means. Thus, the Rh-catalyzed hydroformylation (atom economic reaction) of unsaturated triglycerides
led to poly-aldehydes. The latter can readily react to form polyols, polyacids or polyamines which are promising
monomers for polycondensation reaction leading to new biosourced polymers. The studied catalytic system is applicable
to a wide range of natural occurring unsaturated triglycerides.
1
Introduction
Environmental
considerations
regarding
chemical processes lead chemical industries to
seek for new environmental-friendly processes
based of renewable resources. In this context, we
developed a new process based on supramolecular
means permitting the functionalization of natural
occurring insaturations of triglyceride in water using
water-soluble Rh-based catalyst. This clean,
recyclable and simply implemented process leads
to polyaldehydic compounds from naturals
resources that can be easily transform into polyols.
Those polyols have a great interest in polymer
industry.
nature of the formed supramolecular surfactant
leading to fast decantation in time and temperature.
2
Experimental/methodology
Due to the transient nature of CD/Triglyceride
complex, different methodologies have been
performed to highlight the presence of those
complexes and their stability, such as tensiometry
and phase diagrams. This also permitted to
determine the range of CDs concentration for
optimal emulsification.
[1]
This process was then applied to aqueous
biphasic hydroformylation using Rh-TPPTS (sodium
salt of the trisulfonated triphenylphosphane) of
triolein,
a
model
triglyceride
containing
monounsaturated chains as a first model
coumpound.
Fig. 2: formation of supramolecular surfactant complex
between CDs and Triglyceride
Fig. 1: triolein hydroformylation in presence of CDs
Table 1
Hydroformylation of triolein using different modified CDs
Aldehyde
Rank
CDs
Conversion
selectivity
1
2
3
RAME-β-CD(34wt%)[a]
[a]
HP-β-CD(34wt%)
CRYSMEB(20wt%)
[b]
51
80
91
85
100
91
Conditions [a]: Rh(CO)2acac ( 0.015mmol), TPPTS
(0.075mmol), triolein (1mmol, 3mmol C=C), water ( 3.4
mL), CO/H2 (1:1, 80 bars) T (80°C), 18h.
[b] : water (8.2mL), 6h.
3
Results and discussion
The tensiometry data show that supramolecular
complexes are formed at oil/water interface in
presence of chemically modified CDs, leading to an
important decrease of interfacial tension. The more
stable complexes are formed with low methylated
or hydroxypropylated-substituted CDs, whereas the
use of higher methylated CDs leads to lesser stable
complexes.
Phase diagrams show an unstable behavior of
the resulting emulsion composed of CDs aqueous
solution and triglyceride-containing oil. The
instability of those emulsions reflects the transient
Application of this self-emulsifying system to
aqueous catalysis led to very good conversions and
aldehyde selectivities in reasonable time and
catalytic conditions, especially using CRYSMEB.
The aqueous catalyst-containing phase is also
easily recovered and recyclable without obvious
loss neither in activity nor selectivity. The use of
natural occurring oil is also possible through such a
system.
4
Conclusions
We show that the use of different chemically
modified
CDs
in
biphasic
Rh-catalyzed
hydroformylation can lead to very good conversions
and aldehyde selectivity. This system is promoted
by a transient supramolecular CD/triglyceride
complex stabilizing oil/water interface and
permitting the self-emulsification. Thanks to its
transient properties, the biphasic system decants
rapidly and allows for an easy recovery of the
products and a recycling of the catalyst-containing
aqueous phase.
Acknowledgements
This work was performed, in partnership with the
SAS PIVERT, within the frame of the French
Institute for the Energy Transition (Institut pour la
Transition
Energétique
(ITE)
P.I.V.E.R.T.
(www.institut-pivert.com) selected as an Investment
for the Future (“Investissements d’Avenir”). This
work was supported, as part of the Investments for
the Future, by the French Government under the
reference ANR-001.
References
[1]
T. Vanbesien, F. Hapiot, E. Monflier: Patent application
PCT/FR2014/052860 deposited on November 7th, 2014 :
« procédé d’hydroformylation de triglycérides en milieu
auto-émulsifiant »
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Starch based biopolymers : from molecular structure to
material properties
Biopolymères à base d’amidon : de la structure moléculaire aux
propriétés du matéraux
Chloé Volant1, Fatima Beddiaf1, Yoann Guillotin4, Agnès Sabaté2, Nicolas Descamp3,
Philippe Looten3, Caroline Tokarski4, Christian Rolando4
1
Institut Français des Matériaux AgroSourcés (IFMAS), Parc de la Haute Borne, 11A avenue
de l'Harmonie, 59650 Villeneuve d'Ascq Cedex
2
Institut National de la Recherche Agronomique, Unité de recherche Biopolymères
Interactions Assemblages, Rue de la Géraudière BP 71627, 44 316 Nantes Cedex 3, France
3
ROQUETTE Rue de la Haute Loge, 62136 Lestrem
4
Université de Lille 1, Sciences et technologies, Miniaturisation pour la Synthèse, l’Analyse
et la Protéomique, Rue Paul Langevin, bâtiment C4, 59655 Villeneuve d’Ascq Cedex
* Corresponding author: [email protected]
______________________________________________________________
Résumé :
Notre projet de recherche a pour but de déterminer les liens existants entre la structure microscopique
d’un grain d’amidon et les fonctions des matériaux obtenus à partir de cet amidon. Un grain d’amidon est
composé de deux types de polymères de glucose dont les caractéristiques influencent les propriétés
macroscopiques. Nous avons développé des méthodes permettant de caractériser les structures
moléculaires d’amidons natifs et modifiés, provenant de plusieurs bases végétales (maïs, blé, pomme de
terre, pois). Les paramètres ciblés ont été la distribution de longueur de chaînes, les points de
branchements et l’identification des modifications (type et localisation). Pour atteindre cet objectif, les
techniques utilisées ont été la spectrométrie de masse, la chromatographie et l’électrophorèse.
_______________________________________________________________________
Summary:
Our research project aims at determining the existing links between the microscopic structure of a starch
granule and the functions of materials obtained from this starch. Starch granule consists of two types of
polymers of glucose, the characteristics of which influence the macroscopic properties. We developed
methods allowing to characterize the molecular structures of native and modified starches, coming from
several vegetable bases (corn, wheat, potato, pea). The targeted parameters were the chain-length
distribution, the branching points and the identification of the modifications (type and location). To reach
this goal, the used techniques were mass spectrometry, chromatography and electrophoresis.
Keywords: starch; chemical modifications; mass spectrometry; chromatography, electrophoresis
Current plastics consist of synthetic polymers based on monomers stemming from oil. In a context of energy transition, to
decrease the recourse of oil for the production of plastics is a major stake. A solution is the production of plastics
stemming from vegetable raw materials. Our project which aims at characterizing the structures of starches stemming
from several vegetable bases and containing chemical modifications would later allow to plan the development of new
materials with starch in a rational way.
Les plastiques actuels sont composés de polymères synthétiques basés sur des monomères issus du pétrole. Dans un
contexte de transition énergétique, diminuer le recours à ce type de plastiques est un enjeu majeur. Une solution est la
production de plastiques issus de matières premières végétales. Notre projet qui vise à caractériser les structures
d’amidons issus de plusieurs bases végétales et comportant des modifications chimiques permettrait à terme de prévoir
le développement de nouveaux matériaux à base d’amidon de façon rationnelle.
1
Introduction
Current plastics are composed of synthetic
polymers based on monomers stemming from oil.
Decreasing the carbon footprint of plastics is a
major challenge of energy transition. One solution
is the production of plastics based on bio-sourced
materials. Starch is a biopolymer from plants which
appears a very promising starting material for bioplastics due to its availability, cost and
degradability. Development of new starch-based
materials needs to characterize microscopic
structures in order to understand and to forecast
the product functionalities.
Starch granule is composed of two polymers of
glucose: amylose (linear chain, little branching
point) and amylopectin (large and more frequently
branched chain). Botanical origin, granule size and
shape, amylose and amylopectin ratio induce
differences between two starches. In addition,
physical and chemical modification can be made on
the granule to reach some properties or during
transformation processes. Chemical modifications
like oxidation, chain scission, hydrolysis or addition
of a functional group can be realized on the granule
surface or inside the granule. Chain organization
will be different and then properties of the starchbased material also. We will present here methods
for measuring key parameters to describe the
structure-function
relationship:
chain-length
distribution, branching position, type and position of
modifications.
modification can be identified and the average
number of modification per glucose units.
2
Experimental/methodology
The amount of material available during
botanical screening or during early development is
limited and thus it is important to develop sensitive
methods. New protocols have been developed from
preparation to analysis for natives and modified
starches, with an emphasis on reducing the amount
of sample requested. The general methodology for
our samples was: dispersion of starch, purification
by filtering, enzymatic digestion, derivatization by
reductive amination and then analysis by MatrixAssisted Laser-Desorption Ionization-Time of Flight
(MALDI-TOF), ElectroSpray Ionization Mass
Spectrometry (ESI-MS) or Fluorophore - Assisted
Carbohydrate Electrophoresis (FACE) [1, 2].
3
Results and discussion
Step of preparation was optimized for natives
and modified starches. A method inspired by the eFASP (Filter Aided Sample Preparation) protocol
used in proteomics was adapted to starch [3].
Starch is dispersed in dimethyl sulfoxide at 60 °C
and then diluted in water. Sample is then purified
and concentrate by centrifugation before enzymatic
digestion with a buffer ammonium formiate 1 M and
isoamylase (2000 Units). Digested starch was then
purified and fractionated by Solid Phase Extraction,
with a porous graphitic carbon stationary phase.
Elution was performed with a gradient of
acetonitrile, water and trifluoroacetic acid. Labeling
of samples was performed by reductive amination,
as described by the Figure 1. Reducing end of
glucose chain is labeled either with a fluorophore
molecule
or
mass
spectrometry
signal
enhancement tag (8-aminopyrene-1,3,6-trisulfonate
reciprocally anthranilamide) in presence of a
reducing agent (2-picoline-borane or sodium
cyanoborohydride) [4].
Protocols for analysis by MALDI-TOF were
optimized for chemically modified starches. Spot
preparation had been optimized: matrix (2,5dihydroxybenzoic acid or 3-aminoquinoline),
proportions of sample and matrix (1:1 or 1:2), and
air flow drying [5]. Figure 1 shows two spectra
obtained during the project. The first one is a
MALDI-TOF spectrum from a chemically modified
starch, we can notice three populations of peaks
which each correspond to a type of modification.
From this spectrum the chemical nature of
Fig. 1. MALDI-TOF MS spectrum of debranched starch (a:
native starch; b: chemically modified starch with hydroxypropyl
groups)
4
Conclusions
Characterization methods have been developed
on some starches with various botanical origins
(potato, maize) and with chemical modifications
(hydroxypropyl group, cationic group; granule
surface or inside the granule). Set of informations
allowed to determine molecular composition of
native and chemically modified starches. Structural
information on chain modifications will be linked to
the macroscopic properties of the starch-based
material.
Acknowledgements
This project has been granted by the French
State under the “Programme d’Investissements
d’Avenir” Program (reference number: ANR-10IEED-0004-01).
References
[1]
[2]
[3]
[4]
[5]
O’Shea M.G., Samuel M.S., Konik C.M., Morell M.K.
Carbohydrate Research 307 (1998) 1-12.
Morell M.K., Samuel M.S., O’Shea M.G. Electrophoresis 19
(1998) 2603-2611.
Wisniewski J., Zielinska D., Mann M. Analytical
Biochemistry 410 (2011) 307-309.
Ruhaak L.R., Steenvoorden E., Koeleman C.A.M., Deelder
A.M. Proteomics 10 (2010) 2330-2336.
Rohmer M., Meyer B., Mank M., Stahl B., Bahr U., Karas
M. Analytical Chemistry 82 (2010) 3719-3726.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Lignin as powerfull renewable flame retardant for bio-based
plastics
Les lignines, un ignifugeant biosourcé efficace pour les bioplastiques
B. Prieur1,3, M. Wittemann2,3, R. Klein2,3, G. Fontaine1,3, S. Bourbigot*1,3
R2Fire group/UMET – UMR CNRS 8207, Ecole Nationale Supérieure de Chimie de Lille
(ENSCL), Avenue Dimitri Mendeleïev – Bât. C7a, CS 90108, 59652 Villeneuve d’Ascq Cedex,
France
1
Group of Design Interfaces, Fraunhofer Institute for Structural Durability and System
Reliability LBF – Schlossgartenstrasse 6, 64289 Darmstadt, Germany
2
3
Members of the FP7 European project PHOENIX – www.phoenix-eu-project.eu/
*[email protected]
______________________________________________________________
Résumé : Dans le contexte de valorisation de la biomasse, les lignines présentent un intérêt car elles ne sont
présentent dans aucune application majeure. De par leur structure chimique, ces macromolécules présentent un
potentiel en tant que retardateur de flamme pour les polymères. Dans cette optique, plusieurs types de lignines ont
été étudiés. Des composites «vert » à 92% à base d’acide polylactique (PLA) et de lignines ont été développés.
Leurs propriétés thermiques et retard au feu ont été évaluées. Ces composites verts présentent des performances
feu très intéressantes dans une simulation d’incendie. Un mode d’action des lignines comme retardateur de flamme a
été proposé.
_______________________________________________________________________________
Summary: In the context of development of biomass, lignins are of interest because they are not present in major
application. According to its chemical structure, these macromolecules could be used as flame retardant in polymers.
In this context, several types of lignin were studied. "Green" composite, up to 92%, based on polylactic acid (PLA)
and lignin have been developed. Their thermal properties and fire retardancy were evaluated. These green
composites exhibit very interesting performances in a simulated fire. The mode of action of lignin as a flame retardant
has been proposed.
Keywords: lignin, polylactic acid (PLA), biomass, flame retardancy, thermal stability, lignin modification
This work is done in the context of a FP7 European Project called PHOENIX. Some papers are intended to be published
and if the consortium is interested in, some part of the work could be patented. The motivation of this work is based on
the efforts make to replace halogenated compounds from the European flame retardant market (REACH) by renewable
and bio-based products.
Ces travaux sont issus des recherches d’un projet européen FP7 appelé PHOENIX. Des articles sont susceptibles d’être
publiés et si le consortium est intéressé, certains aspects des travaux pourraient être brevetés. Ces travaux s’appuient
sur la nécessité de remplacer les retardateurs de flamme halogénés du marché européen (REACH) par des matériaux
renouvelables et biosourcés.
1
Introduction
Lignin is one of the three components along with
cellulose and hemicellulose responsible for the
strength and rigidity of plants. Because of its
complex structure, this byproduct of wood pulping
or ethanol production industries is generally burnt
for energy recovery. Although many researches
were undertaken aiming the valorization of lignin,
there is no major application [1].
Due to its aromatic structure, lignin produces a
significant carbonaceous residue called “char”
under heating and therefore should be considered
as potential flame retardant (FR) for plastics.
Indeed, char formation is a mode of action to flame
retard polymers. Thus, the char formed from lignin
can act as a physical barrier preventing the polymer
burning [2].
In the context of the valorization of the biomass,
the bio-based plastic polylactic acid (PLA) has been
chosen for this study. PLA is a very well-known
renewable polymer with interesting properties,
which makes it useful in many applications but
some of them require fire standards. Thus, PLA
needs to be flame retarded (FR). In order to
develop green products, FR composites made of
PLA and lignin were developed.
Since the extraction process of lignin changes
their chemical structure, lignins from different
extraction process have been considered. Chemical
modifications of lignin have also been done in order
to increase their fire performances and compatibility
in PLA [3]. The first part of talk will be focused on
the characterization of the neat lignins and of the
modified lignins. Then, the green PLA/lignin
composites will be analyzed and their FR
performances investigated. Finally, a mode of
action of the lignin as FR will be proposed.
2
Experimental/methodology
Lignin produced by different extraction
processes were used: Kraft (KL), Organosolv (OL),
Alkali (AL) and Soda (SL). In order to improve their
final properties, lignins were chemically modified
and fully characterized. Chemical structure and
thermal stability were particularly analyzed.
Green composites were prepared by mixing the
lignin with the PLA together. In several
formulations, coadditives were added. The testing
specimens were then shaped by thermoforming.
Advanced characterizations of the composites
were undertaken. FR performances were deeply
investigated. Other properties, like the morphology,
were also taken into account.
3
Results and discussion
Since the lignin should be modified, a
characterization protocol was developed to assess
the efficiency of the modifications. Then, the
influence of the extraction process and of the
modifications on the final properties of the lignin
were studied. For example, the thermal stability of
kraft lignin was significantly improved after a
phosphorylation as it is shown in the figure 1.
Indeed the modified lignin is degrading slower than
the KL, and it presents a more stable residue at
high temperature.
Fig. 1. Thermal stability of KL and phosphorylated KL (TGA,
10°C/min heating rate, N2 and Air atmospheres)
Selected from the first step of the study, the
most promising lignin were incorporated as FR
additives in the PLA. The composites were then
analyzed. The dispersion of the lignin in the matrix
was investigated. Indeed it is known that the
additive is more efficient as it is well dispersed in
the polymer [4]. Thermal stability, thermal
decomposition as well as FR performances were
studied. Influences on the FR properties of the
lignin’s
extraction
process,
the
chemical
modifications as well as the coadditives were
investigated and will be discussed in the talk. In the
figure 2, heat release rates under heating of three
different formulations are compared. On such
testing, an effective FR permits to significantly
decrease the peak of heat release rate (pHRR) as
well as the total energy released (curve area). In
this case, a PLA-composite with kraft lignin and
ammonium polyphosphate (APP) led to higher than
50% pHRR’s reduction. These interesting results
were obtained with a green composite made of
92% of bio-based and renewable materials.
Fig. 2. Mass Loss Calorimeter (35kW/m², 35mm) results for
different PLA/KL/APP formulations (3:1 and 1:3 is the ratio of
APP vs. KL in the 30% of loading)
Finally, thanks to advanced characterization
techniques, a mode of action of the lignin as FR
was proposed and will be discussed in the talk.
4
Conclusion
In order to valorize the biomass, this work
presents the first use of lignin as flame retardant
additive in a bio-based PLA. Several lignins were
evaluated with or without chemically modifications,
in order to improve their thermal properties. They
were then incorporated into PLA, and the produced
green composites exhibits significant improved FR
performances. As a conclusion, green composites
made of 92% PLA/lignin were successfully flame
retarded, and the mode of action of the lignins as
FR additive was elucidated.
Acknowledgements
The Phoenix project has received funding from
the European Union’s Seventh Framework Program
for research, technological development and
demonstration (Grant Agreement n°310187). The
authors thank all the Phoenix partners.
References
[1]
[2]
[3]
[4]
S. Laurichesse, L. Avérous, Prog. In Polym. Science, 39
(2014) 1266-1290
C. Reti, M. Casetta, S. Duquesne, R. Delobel, J. Soulestin,
S. Bourbigot, J. of Eng. Fiber Fabr, 4 (2) (2009) 33-39
Y. Yu, S. Fu, P. Song, X. Luo, Y. Jin, F. Lu, Q. Wu, J. Ye,
Polym. Deg. And Stab., 97 (2012) 541-546
A.V. Maldhure, A.R. Chaudhari, J. Therm. Anal. Calorim.
103 (2011) 625-632
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Recovery of platform molecules from black liquor throught
hydrothermal treatment
Production d’intermédiaires pour la chimie verte à partir de liqueur
noire par traitement hydrothermal
Marion Huet1, Anne Roubaud1*, Dominique Lachenal2
1 CEA Grenoble, LITEN, Laboratoire de Thermo-Conversion des Bio-ressources, 17 rue des
martyrs, 38054 Grenoble - France
2 LGP2 - Grenoble INP - Pagora, 461, rue de la Papeterie, CS 10065, 38402 Saint-Martind'Hères - France
* Corresponding author: [email protected]
______________________________________________________________
Résumé :
La liqueur noire est un effluent des usines papetières qui contient la fraction résiduelle du bois, principalement de la
lignine et des fragments de lignine. Dans ce travail, un procédé de valorisation de ces molécules est étudié. Il s’agit
de les convertir par un traitement hydrothermal, c’est-à-dire en portant la liqueur noire entre 250 et 310°C à une
pression légèrement supérieure à la pression de vapeur saturante correspondante (i.e .en restant en phase liquide).
Ce traitement permet d’obtenir dans la phase aqueuse de nombreux composés phénoliques ainsi qu’un biocrude
combustible permettant de garder l’efficacité énergétique de l’usine ainsi que de recycler le sodium nécessaire à la
cuisson du bois. La production de composés phénoliques pourrait représenter un revenu complémentaire intéressant
pour l’industrie papetière.
________________________________________________________________________
Summary:
Black liquor is a side stream of the paper production from wood cooking by the pulp&paper industry. It contains the
residual fraction of wood, mainly lignin and lignin fragments. In this work, a process is studied for valorization of those
molecules through an hydrothermal treatment. It means bringing black liquor at a temperature between 250°C and
310°C with a pressure lightly above the vapor pressure (i.e remaining in liquid phase). This treatment produces
numerous phenolic compounds in the aqueous phase and a kind of biocrude. Combustion of this biocrude allows to
maintain the energetic efficiency of the plant and the sodium can be recycled for the wood cooking. This production of
phenolic compounds can be an interesting complementary income for the pulp&paper industry.
Keywords: black liquor, hydrothermal, phenolic compound, platform molecules
This work is a proposition to improve and increase the economic viability of the pulp and paper industry by diversifying
its products and on the other hand, it will provide the chemical industry with biosourced aromatic intermediates.
140 Mt of fibers are produced every year for the paper industry which necessitates the use of around 300 Mt of biomass
It has been estimated that 10-15%% of the residual lignin could be used for more valuable purposes than combustion
without compromising the energy balance of the kraft mill. TRL of this process is estimated at 4.
Ce travail se propose d’améliorer et d’augmenter la viabilité économique de l’industrie papetière en diversifiant ses
produits. Il s’agit aussi de fournir à l’industrie chimique des intermédiaires de synthèse aromatiques biosourcés. 140 Mt
de fibres sont produites chaque année par l’industrie papetière ce qui nécessite environ 300Mt de biomasse. Il a été
estimé que 10 à 15% de la lignine résiduelle pourrait être utilisée pour produire des composés à plus forte valeur ajoutée
que la traditionnelle combustion sans pour autant mettre en péril l’équilibre énergétique des usines. Le TRL du procédé
proposé est estimé à 4.
1
Introduction
Numerous studies deal with the conversion of
chemical pulp mills into wood-based biorefineries.
In particular, the extraction of the hemicelluloses of
wood by an autohydrolysis allows the recovery of
sugars for the chemical industry and the use of a
soda cooking instead of a kraft cooking to produce
cellulosic pulp. Lignin of wood ends up in an
aqueous effluent called black liquor which is usually
burned in a Thomlison boiler. This process allows
to recover 96.6 % of introduced Na and between
56.5 and 65.4% of the energy of black liquor [1].
An alternative process of black liquor
valorization should allow to recover at least as
much energy and as much of introduced Na than
the classical one. In this work, an hydrothermal
treatment is proposed. Under hydrothermal
conditions (250-315 °C, 8-15MPa) water behaves
both as a solvent and as a reactant and hydrolysis
is enhanced. Conversion of black liquor through
hydrothermal conversion will be compared to the
Thomlinson recovery in term of energetic efficiency.
The sodium recovery and the production of
phenolic compounds will be studied.
2
Experimental methodology
Experiments were performed in a 600 mL batch
reactor. Temperature set points were between 250
and 310 °C with a holding time between 5 and 120
minutes. The black liquor used is resulting from a
sulfur free cooking after pre-hydrolysis performed
by our colleagues from Pagora [2]. It contains 19%
of dry matter content. Black liquor is directly poured
in the reactor without prior any dilution or
concentration in order to be close to industrial
conditions. HHV is measured in the lab with a
calorimetric bomb and the carbon content is
determined with a Shimadzu VCSH TOC meter for
aqueous phases and SSM module for the biocrude.
3
Those results demonstrate that with an
hydrothermal treatment the recovery of phenolic
compounds from black liquor is feasible. This
process is thus producing chemical plateform
molecules valuable for a green chemistry
application. This could be an interesting income for
the pulp&paper industry. Moreover, the sodium
recovery is efficient and the energetic efficiency is
better. Under hydrothermal conditions water is able
to deconstruct natural organic polymers like lignin.
Acknowledgements
The authors would like to thank Carnot
“Energies du Futur” for funding and also the INPGPagora LGP2 team for its fruitful collaboration.
References (font style: Arial bold 10pt)
[1]
Results and discussion
[2]
After the experiments an aqueous phase and a
“biocrude” phase is recovered. The viscous
biocrude contains up to 59% of the initial carbon.
Up to 70% of the Higher Heating Value of black
liquor can be then recovered. In the aqueous phase
some organic carbon are remaining and 97% of the
initial Na of black liquor. A global analysis of the
medium molecular weight for the organics in the
aqueous phase indicates that it is devided by 6
compared to the initial black liquor. I.e. the medium
molecular weight of organic is below 600 g/mol
whereas it is at 3100 g/mol for black liquor (see fig.
1).
Fig 1 Average molecular weight in black liquor and after
hydrothermal treatment
It means that the initial lignins molecules or
lignins fragments are cut in smaller molecules by
the hydrolysis reactions. Fragmentation occurs till
mainly phenolic compounds remains.
Phenolic
compounds
(phenol,
catechol,
guaiacol, syringol ect.) were identified by GCMS
analysis and quantified by HPLC. Up to 0.7% of
the carbon of black liquor can be recovered in
guaiacol, precursor of vanillin. This represents
approximately 3000t/y of guaiacol in an average
pulpmill of 1000t/d per day.
4
Conclusions
Adams, T.N., Technical Association of the Pulp and Paper
Industry, American Forest & Paper Association, 1997. Kraft
recovery boilers. Tappi press ; AF&PA.Pagora
Roubaud, A., Chirat, C., Huet, M., Monot, C., Lachenal, D.
Development of a new pulp production process and black
liquor gasification. Récents progress en genie des
procédés. 2013, 104.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
New La3Fe(MoO4)6 catalyst for ethanol oxidation
Un nouveau catalyseur La3Fe(MoO4)6 pour l'oxydation de l'éthanol
Anita Borowiec*1, Georgiana Bucataru1, Mickaël Capron1, Marie Colmont1,
Pascal Roussel1, Franck Dumeignil1, 2
1
Université Lille 1 Sciences et Technologies, UCCS UMR CNRS 8181, 59655 Villeneuve
d’Ascq, France
2
Institut Universitaire de France, Maison des Universités, 106 Boulevard Saint-Michel,
75005 Paris, France
* Corresponding author: [email protected]
Résumé : Cette étude concerne un nouveau catalyseur pouvant être utilisé pour la réaction d’oxydation de l’éthanol.
Des monocristaux de La3Fe(MoO4)6 ont été préparés via les précurseurs oxydes FeO6 et MoO4. La combinaison de
ces éléments donne un catalyseur avec le caractère redox désiré pour la réaction susmentionnée. Le matériau a été
obtenu par réaction solide-solide et ses performances catalytiques ont été mesurées et ont mis en évidence une
importante sélectivité en acétaldéhyde.
Summary: This study concerns a new catalyst which can be used for ethanol oxidation. Single crystals of
La3Fe(MoO4)6 were prepared from fluxes of FeO6 and MoO4. A combination of these atoms gives a catalyst with
redox character desired in the ethanol oxidation reaction. Within the research the catalyst was synthetized by
standard solid state reaction and catalytic tests were performed which confirmed possible utility of La 3Fe(MoO4)6 in
the industry.
Keywords: ethanol, oxidation, acetaldehyde
Presented project shows alternative way of acetaldehyde production from bioethanol as a raw material. That production
method is interesting for several reasons. The most important is environmental aspect. Green chemistry is becoming a
good substitute for many traditional chemical processes. It is needed then to find efficient catalysts for these particular
reactions. Presented La3Fe(MoO4)6 catalyst could be successfully used in industrial applications what gives to a project
a potential for the future.
Le projet présenté montre une méthode de production d’acétaldéhyde à partir d’éthanol qui pourrait être extrapolé à du
bioéthanol. Ce procédés est intéressant pour plusieurs raisons, le plus important étant l’aspect environnemental. La
chimie est en train de devenir un bon substitut pour de nombreux processus chimiques traditionnels. Il est nécessaire
alors de trouver des catalyseurs efficaces pour ces réactions particulières. Le catalyseur La 3Fe(MoO4)6 présenté
pourrait être utilisé avec succès dans les applications industrielles ce qui donne à ce projet un potentiel pour l’avenir.
1. Introduction
Nowadays because of decreasing amount of
fuel, alternative ways of several compounds
production are actively researched. Therefore
products obtained from biomass became more
popular and their valorization is now examined.
Bioethanol is one of the most largely produced
biosourced compound which found many industrial
applications with being converted to high value
products. In this study redox properties of new
La3Fe(MoO4)6 catalyst were examined. As a main
product acetaldehyde was obtained which gives a
perspective of future industrial utilization.
2. Experimental/methodology
The La3Fe(MoO4)6 catalyst was synthetized by
flux growth technique which permits to obtain single
crystals. Its corresponding powder was prepared
from the stoichiometric mixture of La(OH)3 and
oxides Fe2O3 and MoO3. The mixture was heated at
900°C followed by attrition treatments. Then a
single phase was obtained after sudden remove
from oven. The catalyst was characterized by XRD,
HT-XRD and BET tests. Catalytic properties of
La3Fe(MoO4)6 were studied in the simple fixed bed
reactor connected online with gas chromatograph.
Sample quantity in the reactor was defined of
200mg and mixed with 200mg of SiC with the
diameter of particles chosen from the range 100125µm. Reaction temperature was controlled by
two thermocouples and chosen from the range 325
and 375°C. Total gas flow rate was constant
-1
(GHSV=2256 h ) and had a composition of 13,2%
of ethanol, 7% of oxygen and 40,8% of helium as a
carrier gas.
3. Results and discussion
In catalysis field, BET surface area is often very
important for increase the reaction. It has been
measured for the as-synthesized sample and is
equal to 0.4 m²/g. This low value, for an oxidation
catalysts, is due to the way of synthesizes (i.e. solid
state chemistry). As it can be seen in the figure 1 A,
this synthesis method leads to big particles which
do not develop SSA. In order to increase this
important factor, before the catalytic tests the
sample was grinded in a planetary mortar during
different times. The SSA evolution is linear function
2
of grinding time from 0.4 m /g for the native solid up
2
to 5.6 m /g after 4 h. This phenomenon has been
characterized by MEB (Figure 1B). The particle size
of the sample attrited for 4 hours is much more little
compare to the native one explaining the increase
of SSA between these two samples. The figure 1c
presents the evolution of the ethanol conversion
function of the temperature for the samples with
and without attrition treatment. As it was expected
increasing catalyst surface measured by BET
induced improvement of ethanol conversion. The
highest value of conversion was reached for the
highest temperature of 375°C – up to 97%. This
increase of activity does not affect the selectivity, as
it can be seen in the figure 1d. For the best catalyst
(i.e. the one treated with attrition) the acetaldehyde
selectivity (target molecule) is rather constant with
the temperature. The by-products are formaldehyde
and CO2.The formation of formaldehyde is explain
by an aldolisation of two acetaldehyde molecules
follow by a C-C cleavage to produce the
aforementioned molecule and acetone. Traces of
this very reactive compound are also detected. In
the same reaction conditions, we have tested a
[2]
traditional FeMo based catalyst generally used for
the synthesis of formaldehyde from methanol in
industry. The performances of this material for the
aforementioned reaction are very good (i.e. around
90% of formaldehyde yield). We have tested, this
FeMo based catalyst, to the target reaction. At low
ethanol conversion (i.e. under 50%), the catalyst
produces mainly acetaldehyde but around 290300°C, a hot point appears in the reactor and the
conversion increases up to 100% producing mainly
CO2. This hot point, not detected with the
La3Fe(MoO4)6 material, is due to the combustion of
ethanol which is an exothermic reaction. Adding La
atoms in the structure permits to avoid this
combustion phenomenon.
Fig. 1. SEM micrographs of La3Fe(MoO4)6 sample prepared by
solid state reaction a) before and b) after 4 hours attrition with
precision of specific surface area (SSA), c) comparison of
ethanol conversion for La3Fe(MoO4)6 prepared with and without
attritor and b) selectivity to different products for La3Fe(MoO4)6
prepared with attritor.
4. Conclusion
The new La3Fe(MoO4)6 catalyst can be
successfully used in industrial process of ethanol
oxidation because of high selectivity to
acetaldehyde. Obtained results were compared
with traditional FeMo catalyst used for this reaction.
In this case selectivity of acetaldehyde is lower
where the selectivity to carbon dioxide is higher.
That confirms a potential of new La3Fe(MoO4)6
catalyst.
Observation of formaldehyde as a byproduct could be explained by production of enol
which is then a substratum for formaldehyde and
[1]
acetone production .
5. Acknowledgment
This project is supported by ADEME (The
French Environment and Energy Management
Agency)
within
the
framework
of
the
Investissements d'Avenir program ("Investment for
the Futur").
6. References
[1]
[2]
Bussi, J.; Parodi, S.; Irigaray, B.; Kieffer, R. Appl. Catal.
Gen. 1998, 172, 117–129.
J. Gornay, X. Sécordel, B. de Ménorval, S. Cristol, P.
Fongarland, M. Capron, E. Payen, J-L Dubois, and F.
Dumeignil “Direct conversion of methanol to 1,1dimethoxymethane: Remarkably high productivity over a
FeMo catalyst placed under unusual conditions”, Green
Chem., 12 (2010) 1722–1725.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
An alternative route to synthesize acrylic acid: dehydration
of lactic acid and lactates over alkaline earth phosphates
Une voie alternative d'accès à l'acide acrylique: la déshydratation de
l'acide lactique et de lactates sur phosphates alcalino-terreux
E. Blanco1, C. Lorentz1, P. Delichere1, J.M.M. Millet1, S. Loridant
*,1
1
IRCELYON, CNRS-Université Claude Bernard Lyon 1, Villeurbanne France
* Corresponding author: [email protected]
_________________________________________________________________________
Résumé : L’acide acrylique constitue un des plus grands intermédiaires pétrochimiques. A terme, il devra être
produit à partir de ressources renouvelables par un procédé propre. Sa synthèse par déshydratation de l’acide
lactique constitue une des voies alternatives à explorer. Dans ce travail, différents phosphates alcalino-terreux ont
été préparés et évalués pour cette réaction mais également la déshydratation du lactate d’éthyle qui s’est avéré être
une alternative intéressante. En outre, les mécanismes réactionnels ont été déterminés en s’attachant à l’effet de
l’eau. De plus, une corrélation entre les propriétés catalytiques et acido-basiques a été établie. Enfin, les sites actifs,
sélectifs ou non, ont été identifiés à partir de nombreuses techniques notamment la spectroscopie DRIFT in situ.
_____________________________________________________________________________________________
Summary: Acrylic acid is one of the major petrochemical intermediates. In near future, its production from renewable
resources is required by clean process. Dehydration of lactic acid to acrylic acid corresponds to one of the alternative
routes to investigate. In the present work, alkaline earth phosphates have been prepared and evaluated for this
reaction and also dehydration of ethyl lactate to acrylic acid and ethyl acrylate that appeared as more interesting.
Moreover, the reaction mechanisms were determined focusing the effect of water. Furthermore, a correlation
between catalytic and acido-base properties was established. Finally, the active sites, selective or not, were identified
from numerous techniques including in situ DRIFT spectroscopy.
Keywords: Lactic acid, Acrylic acid, Gas phase dehydration, Alkaline earth phosphates, Acid-base properties, Active
selective sites.
Acrylic acid is a key platform molecule whose main applications are superabsorbent polymers (diapers), paints, coatings,
adhesives and flocculating agents for water treatment. It is produced at 4.5 Mt/year by selective oxidation of propene,
whose price is growing quickly because of increasing demand and rarefaction of petroleum. Several alternative
sustainable routes are investigated at the present time. Among them, dehydration of lactic acid and lactates are
interesting since these reactants can be yielded both by dehydrogenation of glycerol, a by-product of bio-diesel
production and directly by fermentation of sugars.
1
Introduction
In spite of first study in 1958 [1], dehydration of
lactic acid (LA) and derivatives have been mostly
investigated since recent years with the rise of
biomass valorization. High yields to acrylic acid
(AA) and derivatives were obtained using modified
zeolites [2] or calcium phosphates [3-4]. However,
zeolites suffer from hydrothermal instability.
In this work, different alkaline earth phosphates
were prepared and evaluated for dehydration of
lactic acid to acrylic acid. Because of high LA
reactivity, the ethyl lactate (EL) conversion was also
investigated. The origin of catalytic efficiency was
explained from acido-base properties and the
nature of the active sites present in such catalysts.
2
Experimental
Alkaline earth ortho, pyrophosphates and
hydroxyapatites were prepared by co-precipitation
method. Their labeling was described elsewhere
[5]. The solids were characterized by XRD, FTIR
spectroscopy, BET measurements and ICP
analysis. Furthermore, surface characterization was
1
31
obtained crossing XPS, H- P CP-MAS NMR, TEM
and IR techniques. Acid-Base properties were
measured by NH3/CO2-TPD respectively and
adsorption of probe molecules followed by FTIR.
Gas phase dehydration of ethyl lactate or lactic acid
was conducted in a fixed bed reactor at
atmospheric pressure. Solutions of reactant were
vaporized at 160-170°C and diluted with N2 before
sending to the top of the reactor. After trapping, the
condensed molecules were analyzed off-line with a
GC chromatograph while gas products were
analyzed on line.
3
Results and discussion
In first step, the influence of reaction parameters
was investigated: selectivity to acrylic acid strongly
depends on the reaction temperature but not on the
contact time. At optimized temperature of 380°C,
values ranging from 19 to 49% were measured for
the different prepared phosphates catalysts that are
stable for at least 24 h. The best yield (43%) was
obtained from barium orthophosphate [5].
Acid–base properties determined from NH3 and
CO2 TPD measurements revealed that such
phosphates contain high proportion of acidic and
basic sites with same weak strength. Furthermore,
correlation between selectivity to acrylic acid and
the acid–base balance was clearly established: it
was 50% for balance close to 1 and decreased
increasing this parameter [5].
Fig. 1. Correlations between the acrylic acid selectivity of
catalysts at 380°C and contact time of 2.1 s and the acid-base
balance determined by TPD measurements.
Dehydration of ethyl lactate appeared as
promising reaction in spite of lower conversions.
Indeed, selectivity values in dehydration products
(AA and ethyl acrylate (EA)) were much higher with
maxima of 87%. The evolution of selectivity sets
with the conversion revealed that AA is mainly
formed by simultaneous dehydration/hydrolysis
reaction. However, the catalysts were unstable
vaporizing pure EL solution because of
polymerization of EA leading to coke formation.
Interestingly, it was shown that deactivation can be
inhibited adding water to the gas phase [6].
XPS characterization of the catalysts evidenced
the presence at the surface of P-rich phase that
corresponds to amorphous overlayer of few
1
nanometers as evidenced by TEM. From XPS, H31
P CPMAS and DRIFT spectra, it was concluded
that such phase contains high quantity of POH
species and could correspond to a mixture of mono
and dihydrogenophosphates or polyphosphates. In
situ DRIFT spectra have revealed that POH species
are formed under water vapor whereas they are
consumed or modified under reaction mixture for
both reactants suggesting that they involved in one
step of the reaction mechanism. Finally, NH3 and
CO2-TPD measurements followed by in situ DRIFT
spectroscopy revealed that acid base pairs (M2+;
P=O) and P=O basic sites are respectively probed
by these techniques. The acid-base balance of 1
obtained for the most selective catalysts was
explained by the involvement of (M2+; P=O) pairs in
the rate-determining step of the reaction
mechanism. Finally, the monitoring of POH isotopic
labeling under reaction feed revealed proton
transfer to the methyl group of lactic acid. From all
these results, it was proposed that (M2+; P=O) pairs
would constitute the adsorption site of lactic acid
which then dehydrate in acrylic acid by an E2
mechanism involving POH species.
Fig. 2. In situ DRIFT spectra of Ba3(PO4)2 after treatment at
380°C under flow of a) He, b) 50%H2O-He, c)
AL/H2O/He:3/50/47, d) 7%EL-He, e) 5%D2O-He and f) 5%D2OHe followed by AL/H2O/He:3/50/47.
4
Conclusions
Selectivity to acrylic acid is limited for
dehydration of lactic acid over alkaline earth
phosphates. Very high selectivity to dehydration
products can be obtained using ethyl lactate as
reactant but high specific surface area is required to
reach high yield. Water vapor has to be added to
the reaction feed in good proportion to avoid
catalyst deactivation and reactant hydrolysis
leading to lower selectivity. Finally, crossing
different techniques and from in situ experiments, it
was proposed that (M2+; P=O) pairs are the active
and selective sites in such catalysts. These findings
will allow designing more efficient catalysts.
Acknowledgements
This work was supported by French ANR
Program Chimie Durable – Industries – Innovation
(CD2I) GALAC, a joint project between IRCELYON,
UCCS, LC/ENS-Lyon and Novance company.
References
[1]
[2]
[3]
[4]
[5]
[6]
R.E. Holmen, US Patent 2859240, 1958.
J.Zhang, Y.Zhao, M. Pan, X. Feng, W. Ji, C. Au, ASC
Catal., 1 (2011) 32.
J. H. Hong, J.-M. Lee, H. Kim, Y. Kyu Hwang, J.-S. Chang,
S. B. Halligudi, Y.-H. Han, App. Catal A, 396 (2011) 194.
V.C. Ghantani, S.T. Lomate, M.K. Dongare and S.B.
Umbarkar, Green Chemistry, 15 (2013) 1211.
E. Blanco, P. Delichere, J.M.M. Millet, S. Loridant, Catal.
Tod. 226(2014)185–191.
E. Blanco, P. Delichere, C. Lorentz, L. Burel, C. Pinel, M.
Vrinat, J.M.M. Millet, S. Loridant, Appl. Catal. B :
Environm., Submitted.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Cross-metathesis of biosourced fatty acid derivatives
Valorisation d’oléfines bio-sourcées par métathèse croisée
T. Vancompernolle1, P.Vignon1, R.M. Gauvin1*, A. Mortreux1
T. Vancompernolle, Dr. P. Vignon Prof. A. Mortreux, Dr. R.M. Gauvin, UCCS (CNRSUMR8181), Université Lille Nord de France, USTL-ENSCL 59652 Villeneuve d’Ascq (France)
* Corresponding author: [email protected]
1
______________________________________________________________
Résumé : L’amélioration de l’efficacité de la valorisation catalytique d’oléfines agro-sourcées, plus précisément des
esters méthyliques à longues chaines est présentée. La réaction étudiée, la métathèse croisée fonctionnalisante,
permet d’obtenir des diesters plus courts utilisables comme (pré)monomères de polyesters. Le passage d’une oléfine
terminale (acrylate de méthyle) à une oléfine interne (crotonate de méthyle) comme partenaire de métathèse croisée
permet l’emploi de charge catalytique de l’ordre du ppm, avec de hautes productivités et sélectivités. Cette réaction a
été réalisée avec succès à plus grande échelle (50g) sur un substrat biosourcé commercial.
________________________________________________________________________
Summary: The improved catalytic conversion of bioresources, namely unsaturated fatty acid derivatives is
presented. The targeted reaction is ruthenium-catalyzed cross-metathesis with functionalized olefins that affords
shorter diesters. These can be used as biosourced (pre)monomers for the production of polyesters. Switch to internal
cross-metathesis partners (from methyl acrylate to methyl crotonate) allows use of ppm-level catalyst loadings, while
retaining high productivity and selectivity. This was exemplified with success on a 50g scale of a commercial
biosourced fatty acid methyl esters mixture.
Keywords: ruthenium catalyst, cross-metathesis, methyl oleate, FAME, methyl crotonate
These studies were carried out in the framework of a European project, Eurobioref. Its main purpose was the upgrading
of bioresources order to obtain value chains from the crop to the end products. One of the selected value chains involves
olefin cross-metathesis with fatty acid derivatives. The end products are monomers for polyester synthesis.
Ces recherches s’inscrivent dans un projet européen Eurobioref, qui a pour but de développer des chaines de valeur
allant de la culture agricole jusqu’au produits chimiques. Une des chaines de valeurs sélectionnées implique une étape
de métathèse croisée avec des dérivés d’acides gras. Les produits finaux sont des monomères utilisés en synthèse de
polyesters.
1
Introduction
The use of renewable raw materials by the
chemical industry is nowadays increasingly important,
as exemplified by the emerging concept of biorefinery
[1].
Due to the need for improved biomass
transformation, constant efforts have been devoted to
functionalization of the fatty acid methyl ester (FAME)
derivatives. In this context, olefin metathesis plays a
key role as a powerful, versatile reaction, thanks
mostly to the spectacular development of ruthenium
catalysts.[2] These combine high activity and selectivity
along with tolerance toward impurities, a most crucial
feature when considering their use in biomass-derived
chemicals, the purity of which being occasionally
problematic.
Following on seminal work,[3] further improvement in
catalytic systems design triggered use of electrondeficient cross-metathesis partners such as acrylates
or acrylonitrile: when applied to fatty acid derivatives,
this affords an efficient entry into α,ω-bifunctional
molecules, such as diesters, ester-nitrile or esteramine that have found application as monomers for
polyesters or polyamides production.[4] With these
terminal olefins as cross-partners, ruthenium-
methylidene fragments are formed during metathesis.
Most often, the formation of such fragments leads to
the degradation of the catalyst. It may thus be of
interest to overcome such a problem through the use
of internal olefin derivatives (scheme 1, R= alkyl).
Indeed, this strategy was successfully followed by
Patel and coworkers for non-functionalized alkenes:
switching from ethylene to internal olefin such as 2butene has a most beneficial influence on productivity
toward cross-metathesis of bio-sourced fatty acid
derivatives.[5] We demonstrate here that such
approach can be efficiently applied to the crossmetathesis reaction using functionalized, electron-poor
olefins.[6]
2
Experimental/methodology
All the experiments are carried out under argon
(glove box and Schlenk techniques). The solvents
were freshly distilled, and substrates and reagents
were degased then percolated over activated alumina.
Conversion and selectivity was determined by GC
analysis using a SP-2380 from Supleco. Identity and
purity of products was checked by GC, GC-MS and 1H
and 13C NMR. Catalysts were provided by Umicore,
and Lubrirob was kindly donated by Novance.
3
Results and discussion
The cross-metathesis of methyl oleate 1 with an
excess of methyl acrylate (4 equiv.) was performed in
toluene at 60°C with Umicore catalysts M51 (Figure 1)
to give four products as a mixture of E (major) and Z
isomers. Among these four products, two originate
from the cross-metathesis reaction (CM, 2 and 3,
Figure 1), and two from self-metathesis (SM) of methyl
oleate. As previously reported, vinylidene-terminated
products 4-H and 5-H are not detected, due to
methylenic fragments’ depletion from the reaction
mixture through ethylene formation and release from
the reaction mixture.
Figure 1. Cross-metathesis of methyl oleate (1) with terminal and
internal functionalized olefin.
Table 1.
Cross-metathesis between 1 and methyl acrylate/methyl
Entry
Catalyst
Loading
(ppm)
R:
C
CM
SM
[b]
[c]
[d]
(%)
(%)
(%)
Y
(%)
Productive
TON[e]
1
260
96
92
8
88
3380
2
26
69
52
48
36
13700
3
260
95
99
1
93
3590
4
26
96
96
4
93
35600
were observed with other second generation Grubbs
catalysts.
Having demonstrated the interest of crossmetathesis with an internal functionalized olefin, we
moved on to a bio-sourced substrate, namely Lubrirob
201.01, provided by Novance. This fatty methyl esters
mixture is composed of saturated compounds (8.6%),
along with methyl linoleate (7.3%) and methyl oleate
as the major unsaturated species (83.6%). In the
presence of 4 equivalents of methyl acrylate and using
M51 at a loading of 260 ppm, Lubrirob is as efficiently
converted as 1, with about 1800 productive TON.
Switching to methyl crotonate for the cross-metathesis
cleavage proved there again beneficial: 260 ppm of
M51 afford excellent conversion and selectivity of
Lubrirob (3400 productive TON, 97% of selectivity). On
these grounds, we demonstrated the efficiency of our
approach to a large scale synthesis using 50 g of
Lubrirob, with 100 ppm of M51 (11 mg), under similar
reaction conditions (4 equivalents of methyl crotonate,
60°C, 4h). The substrate was converted up to 96% (1
and methyl linoleate), with high selectivity toward
cross-metathesis products (97%). Separation of
diester 2 was achieved by automated chromatography,
affording the compound with 84 % isolated yield based
on the initial content in 1 and methyl-linoleate.
4
Conclusions
In conclusion, we have shown that crossmetathesis of methyl oleate with a functionalized olefin
can be improved by a switch from terminal to internal
alkene cross-partner. Thus, a valuable diester
compound can be accessed with high purity in high
yield, using low catalyst loading, using solvent freeconditions, from a commercial bio-sourced FAME
mixture.
Acknowledgements
The research leading to these results has received funding from the
European Union Seventh Framework Programme (FP7/2007-2013)
under grant agreement n° 241718 EuroBioRef. We also thank the
CNRS and the French Ministry of Higher Education for their financial
support.
References
In the first place, we observed that switching to an
internal olefin has no detrimental effect on reactivity
(Entries 1 and 3). The beneficial effect appears at
lower catalyst loading. At 26 ppm loading, more than
35000 productive TON are reached with methyl
crotonate (Table 1, Entry 4), which is significantly
better than with methyl acrylate (13700 TON, Table 1,
Entry 2). Regarding the underlying mechanistic issues,
these results indicate a better tolerance of the
ruthenium ethylidene vs. the methylidene derivative
towards decomposition, whether intrinsic to these
species or due to traces of impurities within the
substrates and reagents. [7] Similar reactivity patterns
[1] Biorefinery: From Biomass to Chemicals and Fuels, M. Aresta, A.
Dibenedetto, F. Dumeignil Eds, De Gruyter Pub. (Berlin), 2012.
[2] S. Chikkali, S. Mecking, Angew. Chem. Int. Ed. 51 (2012) 5802
[3] a) S.J. Connon, S. Blechert, Angew. Chem. Int. Ed. 42 (2003)
1900; b) L. Ferrié, D. Amans, S. Reymond, V. Bellosta, P.
Capdevielle, J. Cossy, J. Organomet. Chem. 691 (2006) 5456; c) S.
J. Langford, M. J. Latter, C. P. Woodward, Org. Lett. 8 (2006) 2595.
[4] a) A. Rybak, M.A.R. Meier, Green Chem. 9 (2007) 1356.; b)
R.Malacea, C. Fischmeister, C.Bruneau, P. H. Dixneuf, Green
Chem. 11 (2009) 152 c) X.Miao, C. Fischmeister, C. Bruneau, P. H.
Dixneuf, J. –L. Couturier, ChemSusChem. 5 (2012) 1410.
[5] J. Patel, J. Elaridi, W. R. Jackson, A. J. Robinson, A. K. Serelis,
C. Such, Chem. Commun., (2005) 5546;
[6] ChemSusChem (2015) DOI: 10.1002/cssc.201403170
[7] M.Ulman, R. H. Grubbs, J.Org.Chem. 64 (1999) 7202
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Efficient and economical-atom synthesis of butenyl ethers
from bio-sourced alcohols via the nickel catalyzed
hydroalkoxylation reaction of butadiene.
Synthèse d’éthers de butényl à partir d’alcools bio-sourcés par
réaction d’hydroalcoxylation du butadiène catalysée au nickel.
A. Mifleur1, I. Suisse1, A. Mortreux1, M. Sauthier*,1
1
UCCS (Unité de Catalyse et de Chimie du Solide), Université Lille Nord de France – ENSCL,
BP 90108 - 59652 Villeneuve d’Ascq Cedex (France)
* Corresponding author: [email protected]
______________________________________________________________
Résumé : Les composés agro-sourcés constituent une source renouvelable et variée de matière carbonée qui après
transformation offre un large panel de produits chimiques utilisables en synthèse organique. Très répandus dans la
biomasse, les alcools tels que les dérivés de sucre ou de glycérol sont des produits de premier ordre pour servir de
base à ces transformations. Notre laboratoire a développé une expertise dans le domaine de l’éthérification
catalytique à partir de butadiène avec les réactions de télomerisation et hydroalcoxylation. La présente
communication se propose de montrer l’application de cette méthodologie sur des substrats d’origine renouvelable.
________________________________________________________________________
Summary: Bio-sourced molecules are renewable and diversified starting materials for the production of added
valuevalue-added chemicals. Common in biomass, alcohols such as sugars or glycerol are largely accessible and
thus interesting compounds. The expertise developed by our laboratory in the field of catalytic etherification by mean
of the telomerization and more recently the hydroalkoxylation reactions lead us to apply these methodologies to the
conversion of polyols into higher values products of the specialty chemical range.
Keywords: Hydroalkoxylation; renewable alcohols; butadiene; nickel catalyst.
The nickel catalyzed hydroalkoxylation reaction of butadiene with polyols allows an access to the corresponding butenyl
ethers. The grafted polyols are amphiphilic with a polar polyhydroxylated part and a short lipophilic C4 tail. Owing to this
property, these compounds can be used as hydrotropes or solvents for paints. The clean transformation used doesn’t
necessitate heavy purification steps related to salts separation and fulfills many of the green chemistry principles.
La réaction d’éthérification proposée permet d’accéder à des éthers de polyols possédant une courte chaine de type
butényle. Ces composés possèdent un caractère amphiphile qui provient de la présence d’une partie polaire hydrophile
et d’une partie apolaire. Cette caractéristique permet d’envisager des applications de ces molécules en tant
qu’hydrotropes ou solvants de peinture. La réaction utilisée a pour qualité d’être à haute économie d’atome et respecte
les principes de la chimie verte.
1
Introduction
Allyl ethers or derivatives such as but-2-enyl
ethers are found in many naturally occurring and
biologically active molecules and are frequently
involved in organic synthesis. Allyl ethers are for
example classically used as protecting groups for
alcohols [1] especially in carbohydrates chemistry
due to their stability under the conditions required
for glycoside formation [2] or electrophiles in allylic
alkylation reactions.[3]
The oldest and undoubtedly most used is the
Williamson reaction that involves an alcohol and an
alkyl halide in the presence of a base. Nevertheless
this synthetic pathway is not ideal for several
reasons. Side reactions such as halide eliminations
are occurring and excesses of alkylating reagent
are thus often needed and formation of
stoichiometric amount of salts as waste that needs
to be removed according to costly processes. This
reaction thus doesn’t fill at all the criteria of the
green chemistry concepts with regard to the lack of
atom economy. [4] Consequently, new convenient
methods oriented toward the synthesis of ethers
according to atom economical and more generally
salt free reactions are needed.
Regarding dienes, studies were mainly focused
towards the telomerization reaction which
corresponds to the metal catalyzed linear
dimerization of butadiene with simultaneous
addition of an alcohol that provides octadienyl
ethers. [5] Classically palladium catalysts provided
very efficient systems and this reaction is now at
the base of an industrial process for the production
of 1-octene.[6] Amphiphiles were also obtained by
grafting hydrocarbon C8 chains on agro-based
polyol substrates.[7]
On the other hand, the simple addition of an
alcohol on one unsaturation of a butadiene unit
(c.a. hydroalkoxylation reaction) has received only
little attention, due to the lack of efficient catalytic
process in terms of activity and selectivity. In our
group,
we
recently
disclosed
the
Nihydroalkoxylation of butadiene with primary
alcohols to form selectively OC4 ethers in the
presence of diphosphine ligand based nickel
catalysts.[7] Application of this methodology on
various biosourced alcohols provides new building
blocks according to the green chemistry concepts.
2
Results and discussion
According to nickel based hydroalkoxylation of
butadiene methodology developed in our laboratory
[9] we focused our attention on bio-sourced
alcohols. Furfuryl and tetrahydrofurfuryl alcohols
are issuing from the reduction of furfural which is
produced itself from the hydrolysis and dehydration
of agricultural wastes. Hydrogenolysis of sorbitol or
xylitol, originating from glucose, affords the
production of 1,2-ethanediol or 1,3-propanediol. On
the other hand, 1,4-butanediol could be obtained by
fermentation of biomass sugars. Carbonate glycerol
and solketal were synthesized according to
described procedures from glycerol which is
available in large amounts as by-product of
biodiesel production.[8] We performed catalytic
reactions in the presence of dppb (1) or dppmb (2)
based nickel catalysts. Only the best results for
each alcohol in terms of activity and
chemoselectivity into OC4 ethers are reported in
Table 1.
Table 1
Hydroalkoxylation of butadiene with biosourced alcohols.
As two hydroxyl functions are present, diethers
were also found in the reaction mixture. In the case
of propane-1,2-diol, the secondary hydroxyl moiety
was almost unreactive as we already observed in
the
case
of
isopropanol
or
ter-butanol
hydroalkoxylation.[9] The monoether issuing from
the etherification of the primary hydroxyl group was
the sole product of reaction.
Fig. 1. Ligand dppb (1) and dppmb (2)
3
Conclusions
Agro-based alcohols and diols were efficiently
converted according to the reaction oh
hydroalkoxylation by nickel based catalyst thus
showing the interest of the synthetic methodology in
a context of polyols valorization.
Acknowledgements
We are grateful to the Région Nord Pas de
Calais for A. Mifleur’s fellowship. We acknowledge
the Ministry of Research and Technology, the
CNRS and the Institut Universitaire de France for
their financial support.
Rank
alcohols
Conv. (%)
Sel. (%)
1
Furfuryl alcohol
100
98
[1]
2
Tetrahydrofurfuryl
alcohol
92
46
[2]
[b]
3
Solketal
4
Glycerol carbonate
0[a,b]
-
5
Ethylene glycol
81
83
6
1,3-propanediol
90
83
7
1,4-butanediol
93
85
8
Propylene glycol
54
52
100
References
98
In the first set of experiments, we used the
catalytic conditions: Ni(cod)2/ligand in toluene as
solvent. It appeared that furfuryl alcohol,
tetrahydrofurfuryl alcohol and solketal could be
converted into the corresponding OC4 ethers with
satisfying selectivities (81 to 100% conversions,
Entries 1-3, Table 1) whereas in the case of
glycerol carbonate, no reaction occurred (Entry 4).
In the case of the diols that are more hydrophilic,
conversions were always very limited whatever the
ligand (48% conversion for 1,3-butanediol and
<10% for ethane-1,2-diol and 1,2- or 1,3propanediol). While we performed these catalytic
reactions, we observed that these diols were not
entirely soluble into toluene then we used THF as
solvent in which diols were much more soluble.
With these conditions, the alcohols could be
converted into OC4 ethers with average to high
conversions and selectivities (conversions = 54-93
%, selectivities OC4 = 52-83 %, Entries 5-8).
[3]
[4]
[5]
[6]
[7]
[8]
[9]
T. W. Greene, P. G. M. Wuts, Protective Groups in Organic
Synthesis, John Wiley & Sons, Inc., 3rd Ed., 1999, p. 67-74
J. P. Kamerling, Comprehensive Glycoscience: From
Chemistry to Systems Biology, Ed.: A. Liptak et al., Elsevier
Ltd., 2007, chap. 6, p. 222-225.
A. Commerçon, M. Bourgain, M. Delaumeny, J. F.
Normant, J. Villieras, Tetrahedron Lett. 1975, 16, 38373840
P. T. Anastas, J. C. Warner, Green Chemistry - Theory and
Practice, Oxford Univ. Press, Oxford, 1998.
A) S. Takahashi, T. Shibano, N. Hagihara, Tetrahedron
Lett. 1967, 8, 2451-2453.
a) R. Mülhaupt, Macromol. Chem. Phys. 2003, 204, 289327; b) M. Zintl, B. Rieger, Angew. Chem., Int. Ed. 2007,
46, 333-335; c) C. L. Edwards, 2005, US 20050038305; d)
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652-656.
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Synthesis of polyols esters through catalytic carbonylation
reactions
Synthèse d’esters de polyols par carbonylation catalytique
M. Sauthier, A. Mortreux, R. Pruvost
Université de Lille, UCCS, ENSCL Bâtiment C7, 59652 Villeneuve D’Ascq
* [email protected]
______________________________________________________________________
Résumé : Les esters de polyols sont accessibles via la réaction d’hydroestérification qui implique l’utilisation
d’oléfines et de monoxyde de carbone comme co-réactifs. La réaction a notamment permis de synthétiser des
diesters de dianhydrohexitols, dont l’isosorbide, avec de bons rendements. La réaction a également été mise à profit
pour la préparation de monoesters de polyols. Des phosphines ioniques solubles en phase polyols ont notamment
été utilisées afin de permettre d’atteindre de hautes sélectivités en monoesters ainsi que de séparer le catalyseur des
produits de réaction par simple séparation de phase.
_____________________________________________________________________________________________
Summary: Polyol derived esters are readily accessible through the palladium catalyzed hydroesterification reaction
with carbon monoxide and an olefin. According to this reaction, diesters derived from isosorbide and more generally
dianhydrohexitols have been readily synthesized in high yield. The study was also orientated toward the selective
synthesis of monoesters derived from polyols. In this context, the use of highly polar phosphines allowed to perform
the reaction in a polyol phase. The catalyst is in that case advantageously separated from the products of reaction
through simple phase decantation.
Keywords: homogeneous catalysis; esters; carbon monoxide, polyol, isosorbide
Cette communication présente des résultats par lesquels des esters d’isosorbide analogues au produit ISOSORB-ID37,
commercialisé par la société Roquette Frères et utilisé comme plastifiants du PVC, sont obtenus en une étape par une
voie catalytique impliquant l’isosorbide, CO et un alcène. Cette méthodologie de synthèse a de plus été mise à profit
pour la réparation de monoesters de polyols d’intérêt dans la chimie des cosmétiques via une approche permettant la
séparation du métal des produits de réaction.
This communication shows that isosorbide diesters can be synthesized using isosorbide, carbon monoxide and an
alkene. The compounds are analogs of the commercially available Polysorb ID 37 (Roquette Frères) used as plasticizer
of PVC. This synthetic methodology has also been efficiently applied to the selective synthesis of polyol monoesters with
potent applicative properties in the field of cosmetics according to a protocol that additionally allows separation of the
metal from the products of reaction.
1
Introduction
The metal catalyzed hydroesterification reaction
of a α-olefin with carbon monoxide and an alcohol
yields linear and branched esters depending on the
position of the carboalkoxy group on the aliphatic
chain (regioisomers). This transformation is
therefore a one step, straightforward synthetic
process for the synthesis of esters from readily
available and low cost derivatives (olefin, carbon
monoxide and alcohol).[1] It is thus not surprising
that the reaction is now involved for the synthesis of
methylpropionate, a key intermediate for the
production of methylmethacrylate. [2] In most of
reported works, the reaction has been used to
synthesize esters from a quite large variety of
olefins but mainly simple primary alcools like
methanol or ethanol. The reaction has been indeed
only rarely applied for the conversion of elaborated
alcohols or polyols issuing from agro resources. [3]
Scheme 1 : The hydroestérification reaction
The aim of our work was to achieve through the
hydroesterification reaction 1) the synthesis of
diesters from isosorbide 2) the selective synthesis
of polyol derived monoesters through a biphasic
process that allows metal separation from the
products. [4]
2
Experimental/methodology
Synthesis of isosorbide diesters : This part of
the work targeted a full conversion of isosorbide in
the corresponding diester. As isosorbide and 1octene are not miscible, catalytic experiments
performed for optimization of the reaction were
carried out with a solubilizing solvent, 1,4-dioxane.
Catalysts was typically in situ generated from the
association Pd(OAc)2 , PPh3 (ligand L1 of Scheme
2) and p-toluenesulfonic acid.
Synthesis of polyol monoesters: The reaction
has been optimized in order to synthesize
selectively monoesters of polyols. In that case, the
reaction has been performed with an apolar solvent
and a large excess of polyol. Moreover, ionic
ligands have been chosen so as the catalyst is
highly soluble in the polyol phase (ligands L2 and
L3 of the scheme 1).
Scheme 2 : Ligands used for the hydroesterification
reaction
3
Results and discussion
Homogeneous conditions with PPh3 as ligand
and dioxane as solvent are suitable to efficiently
afford the isosorbide diesters in high yield with 0.2
% of palladium. Noteworthy is the fact that the
reaction has been also succesfully processed with
solvent free conditions: neat melted isosorbide and
the olefin.
hydroxyl groups. Comparative experiments showed
that isosorbide has a reactivity toward the
hydroesterification of 1-octene similar to the one of
methanol (see Fig. 1).
Finally, the use of the ionic ligands L2 and L3
allows the reaction to proceed under biphasic
conditions. With these catalytic systems, ethylene
glycol was for example reacted with 1-octene and
converted in the corresponding monoester with 95
% selectivity whereas lower selectivities and no
metal separation were obtained with PPh3 (see Fig.
2).
Fig. 2. : comparison of the crude of reaction obtained
with PPh3 and L2 – hydroesterification with ethyleneglycol
and 1-octene. Crude of reaction obtained with ligand L2 (left)
and PPh3 (right). For more clarity, the crude with PPh3 was
diluted with toluene and ethylene glycol.
Conclusions
4
The hydroesterification of olefins is suitable to
convert isosorbide in diesters that are potent PVC
plasticizers. Monoesters of polyols can also be
efficiently accessed under biphasic conditions.
Acknowledgements
We are grateful to the ANR for the financial
support dedicated to the project ISOSORB-CO
(2010-006-01). Roquette Frères is gratefully
acknowledged for providing pure samples of
isosorbide. Isosorbide is part of the BIOHUB
program (http://www.biohub.fr).
References
[1]
[2]
[3]
[4]
Fig. 1. : Compared reactivity of isosorbide - methanol –
isopropanol. Experimental conditions: Pd(OAc)2 (0.02 mmol) ;
PPh3 (0.16 mmol); PTSA (0.51mmol) and Isosorbide (10.26
mmol) or methanol (20.52 mmol) or isopropanol (20.52 mmol) ;
1-octene (25.66 mmol); 40 bar CO; 110°C.
A complementary study showed that other dianhydrohexitols can be converted according to this
procedure albeit with different reaction rates
depending on the endo or exo position of the
a) M. Beller (editor), Topics In Organometallic Chemistry, Catalytic
carbonylation reactions 2006, vol 18, p97 (chapter title : Hydroxyand Alkoxycarbonylations of akenes and alkynes; Authors : P.
Kalck, M. Urrutigoïti, O. Dechy-Cabaret); b) G. Kiss, Chem. Rev.
2001, 3435; c) B. R. Sarkar, R. V. Chaudhari Catalysis Surveys
from Asia, 2005, 9, 3, 193
a) T. Fanjul, G. Eastham, N. Fey, A. Hamilton, A. G. Orpen, P. G.
Pringle, M. Waugh, Organometallics 2010, 29, 2292.
a) D. Foster, H. Van Rensburg, R. P. Tooze WO 2008/023338 A1
and references herein; b) H. Isa, K. Karube, J. Nakayama US
4,244,882; 1981 and references herein; c) A. Osichow; S. Mecking
Chem. Commun. 2010, 4980
a) R. Pruvost, J. Boulanger, B. Léger, A. Ponchel, E.
Monflier, M. Ibert, A. Mortreux, T. Chenal, M. Sauthier
ChemSusChem
2014, vol.
7
(11),
3157;
DOI
10.1002/cssc.20140258 ; b) Submitted for publication
Congrès de la Société Chimique de France – 2015
SCF Congress - 2015
Multi-Scale Modeling and kinetic study of
Dehydration over γ-Alumina for Biomass Upgrading
Alcohol
Modélisation Multi-Échelle et Etude Cinétique de la Déshydratation
d'Alcool sur Alumine Gamma pour la Valorisation de la Biomasse
K. Larmier1*, C. Chizallet2, S. Maury2, N. Cadran2, A. Nicolle2, A.-F. LamicHumblot1, E. Marceau1, H. Lauron-Pernot1
1
Sorbonne Universités, UPMC Univ Paris 06, UMR CNRS 7197, Laboratoire de Réactivité de
Surface, 4 place Jussieu, F-75005 Paris, France
2
IFP Energies nouvelles, 69360 Solaize and 92852 Rueil-Malmaison, France
* Corresponding author: [email protected]
______________________________________________________________
Résumé : Les alcools sont des molécules plateforme obtenues à partir de la biomasse lignocellulosique, qui peuvent
être converties en alcènes pour l’industrie des polymères. La conception d'un procédé sélectif nécessite une bonne
connaissance du site actif à l’échelle moléculaire sur le catalyseur, mais aussi du réseau cinétique de réactions
impliquant le réactif. La déshydratation de l’isopropanol sur alumine γ est ici étudiée en comparant une étude
cinétique expérimentale aux résultats de modélisation multi-échelle incluant des calculs ab initio et une modélisation
cinétique. La sélectivité en propène et diisopropyléther peut être expliquée sur toute la gamme de conversion en
considérant les réactions directes de déshydratation, la décomposition de l'éther et l’inhibition de la réaction par l’eau
formée, se déroulant toutes sur un site actif unique situé sur les facettes (100) de l’alumine. La sélectivité est donc
uniquement gouvernée par les conditions de réaction expérimentales, et non par l'action de sites distincts sur le
catalyseur dont la proportion pourrait être variée.
________________________________________________________________________
Summary: Alcohols are platform molecules resulting from lignocellulosic biomass conversion. They can be
catalytically converted into alkenes for the polymer industry. Designing a selective process requires a good
knowledge of the active site on the catalyst at the molecular scale, as well as of the kinetic network of reactions
involving the reactant. Here, isopropanol dehydration on γ-alumina is examined by combining experimental kinetic
studies and multi-scale modeling including ab initio calculations and kinetic modeling. Selectivity in propene and
diisopropylether is explained on the whole conversion range by considering direct dehydration routes, ether
decomposition and inhibition by water, all taking place on a unique site located on the (100) terminations of alumina.
Selectivity is thus only governed by experimental reaction conditions, and not by the action of distinct sites on the
catalyst whose proportions could be varied.
Keywords: γ-alumina, alcohol dehydration, isopropanol, DFT, kinetics, kinetic modeling
The catalytic dehydration of alcohols is a key-step in the production of fuels and chemicals from renewable resources.
Comparing experimental results with multi-scale modeling is necessary to develop selective processes and identify the
key parameters governing the reaction.
La déshydratation catalytique des alcools est une étape majeure dans la production de carburants et de produits
chimiques de base à partir de ressources renouvelables. La confrontation de résultats expérimentaux et de modélisation
à plusieurs échelles est indispensable pour développer des procédés sélectifs en identifiant les paramètres clés
gouvernant la réaction
1
Introduction
Alcohols are important platform molecules
obtained from the conversion of lignocellulosic
biomass [1]. It is well known that dehydration
reactions of alcohols toward both olefins and ethers
are successfully catalyzed by common and costeffective acidic oxides such as γ-alumina. Both
types of products, currently supplied by the
petrochemicals industry, are industrially significant,
as monomers for polymer production (olefins) or as
fuel additives (ethers).
However, the key parameters governing each
dehydration reaction, in terms of active sites and
mechanisms, are still under debate, as shown by
several experimental [2,3] or computational [4-6]
studies dealing with ethanol dehydration. We wish
to address here the selectivity issue stemming from
the two competing dehydration paths offered to
isopropanol on γ-Al2O3 and related solids, and to
rationalize the evolution of the olefin-to-ether ratio
over the whole conversion range of the alcohol. To
this end, we have set up a combined experimental
and theoretical approach, in which experimental
measurements are compared with the results of
DFT calculations (modeling at the molecular scale)
and microkinetic simulations (modeling at the
macroscopic scale).
2
Experimental/methodology
3
Results and discussion
Isopropanol conversion was measured at
200 °C over three related aluminas. While the
specific activity varied with the catalyst (γ-Al2O3
being the most active one), the selectivity towards
diisopropylether was found to be identical at a given
conversion (Fig. 1, marks), with an increase to a
maximum for an isopropanol conversion of 35%,
and a subsequent decrease to the benefit of
propene. This leads to the conclusion that the
reaction paths giving propene and diisopropylether
should not be treated as parallel and independent
reactions in modeling, and that the active sites
should be similar regardless of alumina, though
more or less abundant.
In order to identify plausible active sites, the
reaction pathways leading to the formation of
propene or diisopropylether from isopropanol have
been calculated by DFT on the most abundant
surfaces of γ-alumina, taken in their relevant
hydration state under reaction conditions: (100)
facets are dehydrated while (110) terminations are
-2
partially hydrated (around 9.0 OH.nm ). The most
favorable pathways for both reactions have been
found on the (100) surface, with an identical
intermediate, an isopropanol molecule adsorbed on
a pentacoordinated AlV Lewis site (Fig. 2).
Computed activation enthalpies for the formation of
propene and diisopropylether are close (125 kJ.mol
1
-1
/E2
mechanism,
and
112
kJ.mol /SN2
mechanism, respectively); they match the
-1
experimental values (128 ± 5 and 118 ± 5 kJ.mol ,
respectively) and the former computational results
from the literature obtained for ethanol [5,6].
Calculations show that the selectivity toward one
product or the other is thus more entropy- than
‡
-1
-1
enthalpy- driven (ΔrS = –8 and –36 J.K .mol ,
respectively).
A microkinetic model was established according
to the molecular modeling results, which also
included the ether decomposition back to propene
and isopropanol, occurring at higher temperatures
and also favored on the same active site, as well as
water inhibition as proposed by DeWilde et al.[3].
The simulated evolution of partial pressures with
contact time and of selectivity with conversion (Fig.
1, solid line) successfully reproduces the
experimental data.
40
Selectivity ether (%)
Experimental measurements were carried out
on a gas-phase catalytic test using a plug-flow
reactor. Before reaction, aluminas (γ-alumina,
Sasol; Na-poisoned γ- alumina; δ-alumina) were
-1
activated at 450 °C (5 °C.min ) under nitrogen flow
for 3 h. Isopropanol (Sigma-Aldrich, 99%) was
introduced with a partial pressure of 1.5 kPa in a N2
-1
flow (5 to 60 cc.min ). The composition of the
effluent was determined by gas chromatography
(Carbowax column). Ab initio calculations
(DFT+D2) were performed using the VASP
software (PBE+D2, PAW, Ecutoff = 400 eV), and
transition state determinations were performed
using the NEB method. We employed the models
for the γ-alumina surface proposed by Digne et al.
[7]. Kinetic modeling was performed with the
Chemkin® software, by implementing the
elementary steps calculated ab initio.
γ-alumina
δ-alumina
Na/γ-alumina
Simulation
35
30
25
20
15
10
5
0
0
20
40
60
80
100
Conversion (%)
Fig. 1. Selectivity to ether vs. conversion plot at 200 °C for 3
aluminas (marks) and simulated by kinetic modeling (solid line).
(b)
(a)
H3C
HC
CH2
HO
H
Al
O
H3C CH3
HO
Al
C
O
H
H
CH
CH3
CH3
O
Fig. 2. Activation complexes: formation of (a) propene (b)
diisopropylether.
4
Conclusions
Comparison between experimental data and
multi-scale modeling shows that dehydration
reactions to olefin and ether may involve the same
active site, an AlV Lewis acid site located on the
lateral (100) surface of the alumina grains. As a
consequence, the various paths leading to olefin
and ether during alcohol dehydration cannot be
treated as independent and parallel reactions, but
interact following a complex interplay on a unique
site. Selectivity is thus only governed by
experimental reaction conditions, and not by the
action of distinct sites on the catalyst whose
proportions could be varied.
Acknowledgements
The authors acknowledge the GENCI for
allowing access to the computational facilities
IDRIS and CINES.
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