Toluene Hydrodealkylation PFR Design Proposal Summary

TOLUENE HDA | Approval proposal | 29 September 2026 1
Toluene hydrodealkylation
One-page data-use summary
Approval proposal | 29 September 2026
C6H5CH3 + H2 → C6H6 + CH4
Proposed task: size an ideal, isothermal, gas-phase plug-flow reactor (PFR) for 75% toluene
conversion, including reversible benzene-to-biphenyl formation. Use Mathcad as the main
calculation sheet and Excel for an independent numerical check. The target conversion and
isothermal approximation are project choices.
Peer-reviewed paper / exact locator Data to extract and intended use
J1. Kristanto & Hermawan (2020)
Reaktor
Original pp. 130–131; packet pp. 10–11. Fig.
1; Tables 1–2; Eqs. (3)–(4).
Primary design kinetics. Pressure-based HDA and
reversible biphenyl rate laws, including Arrhenius constants
and units. Feed: 5000 lbmol/h; mole fractions H₂ 0.4169, CH₄
0.4922, benzene 0.0080, toluene 0.0829. Use 1150°F and
521 psia as the chosen constant reactor conditions.
J2. Lee et al. (2021)
Journal of Advanced Manufacturing and
Processing
Original p. 12, Eq. (12); p. 21, Table 3; p.
11, Fig. 3. Packet pp. 29, 38, 28.
Separate model/units benchmark. Simplified first-order
toluene rate: A = 6.3 × 10¹⁰ mol m⁻³ s⁻¹ Pa⁻¹; E = 217.6
kJ/mol. Table 3 gives inlet/outlet streams and a 0.147 m³
CSTR benchmark. Do not combine these constants with J1.
J3. Chang & Fedorov (2023)
ChemSusChem (online 2022)
Original p. 2; packet p. 49. Table 1, entry 9;
Table 2, entries 1–4; Fig. 1A–D.
Experimental comparison. KH/C-catalyzed liquid batch
HDM: temperature, H₂ pressure, time, conversion, selectivity
and apparent benzene production rates. Table 1 entry 9: X =
15.3%, S = 63%, apparent rate = 0.61 mol benzene/(mol
KH·h). These are not thermal PFR kinetics.
Analysis plan: enter J1 rate laws directly; no new regression is required by the course guide when the full
expression is available. Solve component balances and reactor volume in Mathcad; use Excel RK4 with
step-halving. Plot volume against conversion, composition against volume, and a local temperature
sensitivity. Use J3 Fig. 1 only to discuss experimental trends, not to fit a thermal Arrhenius law.
Feasibility: a preliminary numerical check gives approximately 263 m³ at 75% conversion under the
proposed isothermal assumptions. Allow 22–28 focused hours over 2–3 weeks for the final documented
calculation and report. J1’s printed 9.53-inch diameter is not used as a validated design dimension.
Packet: proposal pp. 2–8; complete J1 pp. 9–17; complete J2 pp. 18–47; complete J3 pp. 48–52. Three distinct
industrial patents are reviewed on p. 4 and linked on p. 8. All selected publications date from 2020–2024 and
are openly accessible.

TOLUENE HDA | Approval proposal | 29 September 2026 2
1. Introduction and background
Toluene hydrodealkylation (HDA), also called hydrodemethylation, converts
toluene and hydrogen into benzene and methane. Benzene is an important
intermediate for chemical manufacturing. The correct toluene formula is C₆H₅CH₃;
C₆H₅CH₂ is not the molecular formula of toluene. The main reaction is exothermic,
and benzene can also form biphenyl through a reversible side reaction.
Industrial approaches include thermal gas-phase conversion and catalytic
conversion. Recent industrial disclosures describe tubular thermal reactors and
fixed-bed catalytic units within larger aromatics-processing schemes. These
patents establish industrial relevance but concern mixed feeds and integrated
processes; their conditions are not independent measurements of pure-toluene
reaction kinetics (Koseoglu & Hodgkins, 2021a, 2021b; Al-Mana et al., 2024).
Recent academic work provides complementary evidence. Kristanto and
Hermawan (2020) give pressure-based kinetic expressions in a heater–PFR study.
Lee et al. (2021) provide a simpler kinetic model and a reproducible reactor
benchmark. Chang and Fedorov (2023) demonstrate lower-temperature
liquid-phase conversion using carbon-supported potassium hydride, with
measurable competing hydrogenation. This laboratory route should not be treated
as an established substitute for industrial thermal HDA.
The proposed project is a representative ideal-reactor design based on published
kinetics. Its central deliverables are a reusable Mathcad calculation sheet, an
Excel cross-check, a labeled reactor flowsheet and a concise discussion of the
assumptions that separate the ideal model from an industrial reactor.

TOLUENE HDA | Approval proposal | 29 September 2026 3
2. Literature review
J1. Kristanto and Hermawan (2020). This peer-reviewed, open-access study
evaluates temperature control for a heater and HDA PFR. Equations (3) and (4), on
printed p. 131, specify reaction orders, pre-exponential factors, activation
energies and the pressure/rate unit basis. Tables 1 and 2 supply feed and
operating conditions. These reused literature kinetics will form the design basis;
the project will not reproduce the paper’s dynamic control simulation.
J2. Lee et al. (2021). This peer-reviewed, open-access framework paper
includes an HDA case study. Equation (12) supplies a complete, simplified rate
expression, and Table 3 gives a CSTR benchmark. It is useful for checking
rate-unit handling and the mole-balance calculation. Its zero explicit hydrogen
order and omitted biphenyl reaction make it a different model from J1; constants
cannot be exchanged between the two.
J3. Chang and Fedorov (2023). This peer-reviewed, open-access experimental
article reports KH/C-assisted liquid-batch toluene conversion. Tables 1 and 2 give
conversions, selectivities and apparent rates; Figure 1 shows temperature,
pressure, time and loading effects. The apparent rate is normalized to potassium
hydride and is averaged over a batch interval. It cannot be inserted into a
gas-volume-based PFR balance without a separately validated kinetic model.
The three papers are recent publications, but the rate laws in J1 and J2 derive from
older literature. The selection meets the guide’s requirement for at least one
complete rate expression; it does not represent three newly measured industrial
kinetic datasets.

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2. Industrial patent review
P1. US11066609B2 (20 July 2021). Koseoglu and Hodgkins disclose an
integrated hydrodearylation/HDA process assigned to Saudi Arabian Oil Company.
The HDA description covers broad temperature and residence-time ranges; the
comparative example uses a tubular thermal reactor. Use the process figures and
HDA conditions to discuss industrial integration. The heavy-aromatics feed differs
from the project feed, and no complete pure-toluene Arrhenius law is supplied.
P2. US11939538B2 (26 March 2024). Al-Mana and co-inventors disclose pygas
upgrading to BTX, also assigned to Saudi Arabian Oil Company. The
HDA–transalkylation section describes a fixed-bed option at 300–500°C and 1.5–6
MPa. Use the process description to compare catalytic integration with thermal
HDA. These operating limits are not rate constants or evidence that the project’s
thermal model applies to that catalyst.
P3. US11110428B2 (7 September 2021). Koseoglu and Hodgkins describe a
coiled tubular reactor, assigned to Saudi Arabian Oil Company. Although titled
“Hydrodearylation reactor,” claims 5, 8 and 10 explicitly include
hydrodealkylation. Use those claims and the two-reactor description to support
the tubular-reactor discussion. The broader reaction network is outside the
proposed calculation.
These are three granted publications from distinct patent families, not
application/grant duplicates counted twice. Their full texts are free to read.
Patents provide industrial disclosures, rather than peer review or proof of
commercial operation. None is used as a substitute for the journal kinetic
equations.

TOLUENE HDA | Approval proposal | 29 September 2026 5
3. Reactor design basis
Design question: determine ideal PFR volume for 75% toluene conversion at constant 1150°F
(894.261 K) and 521 psia (35.922 bar absolute), using the feed of J1 Table 1. Include benzene
loss to biphenyl. This is an isothermal adaptation of J1’s adiabatic example, not a reproduction of
its reported geometry.
Labeled process boundary
S1: vapor feed → H-101: preheater → S2: 1150°F, 521 psia → R-101: ideal PFR, T and P
held constant → S3: 75% toluene conversion → downstream separation (outside calculation
boundary). Heat exchange at R-101 maintains the specified temperature.
Quantity Value / provenance
Total flow and composition 5000 lbmol/h = 83.3333 lbmol/min. J1 Table 1: yT = 0.0829; yH = 0.4169; yB
= 0.0080; yM = 0.4922; yD = 0.
Unit convention Partial pressures in psia; temperature in °R. T = °F + 459.67. R = 1.9858775
Btu/(lbmol·°R). Rates in lbmol/(ft³·min).
Shared activation energy E = 90,800 Btu/lbmol, as printed in J1 Eqs. (3)–(4). Pre-exponential factors
below must retain this unit system.
Model assumptions Steady ideal gas; perfect radial mixing and no axial mixing; no pressure drop;
imposed isothermal operation; no catalyst/deactivation or coke model; only
the two published reactions.
Published rate equations: J1, p. 131
T + H → B + M; 2B ⇌ D + H
r₁ = 3.686 × 10⁶ exp[−90,800/(RT)] pT pH0.5
r₂ = exp[−90,800/(RT)] [9.000 × 10⁴ pB² − 2.553 × 10⁵ pD pH]
T = toluene, H = hydrogen, B = benzene, M = methane, D = biphenyl (called diphenyl in J1). Here r₂ is the net
reaction extent rate; benzene consumption is 2r₂. The A₁ units are lbmol ft⁻³ min⁻¹ psia⁻¹·⁵; A₂f and A₂r units
are lbmol ft⁻³ min⁻¹ psia⁻². These units follow dimensionally from the paper’s stated rate basis.
Balances to solve in Mathcad
dFT/dV = −r₁; dFH/dV = −r₁ + r₂; dFB/dV = r₁ − 2r₂;
dFM/dV = r₁; dFD/dV = r₂; pᵢ = P Fᵢ/FΣ.
Both reactions preserve total molar flow, so FΣ = FΣ,0. Stop when FT = 0.25 FT,0.
Scope boundary: this first design fixes temperature by assumption. An adiabatic extension would require
consistent species enthalpies, heat capacities and reaction heats. Do not import the IDAES heat-of-reaction
parameter into J1 without reconciling thermodynamic reference states.