Simulation of the Selective Hydrogenation of C3-Cut in the Liquid Phase

Gaetan Mary; Amin Esmaeili; Jamal Chaouki

doi:10.1515/ijcre-2015-0095

Published by De Gruyter March 12, 2016

Simulation of the Selective Hydrogenation of C₃-Cut in the Liquid Phase

Gaetan Mary , Amin Esmaeili and Jamal Chaouki

From the journal International Journal of Chemical Reactor Engineering

https://doi.org/10.1515/ijcre-2015-0095

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Abstract

In this work, the selective hydrogenation of C₃-cut in the liquid phase has been investigated. A realistic model has been developed to simulate the selective transformation of methylacetylene (MA) and propadiene (PD) into propylene in an industrial-scale reactor. The reaction rates have been determined for the gas phase hydrogenation process and adapted for the liquid phase by considering several changes including the catalyst activity and the concentration of reactive components. In the last part of this work, a three-phase hydrodynamic model was developed and the kinetic and hydrodynamic models were then combined in order to achieve the global reactor model. In addition, the results obtained from the model were compared to those from an industrial reactor. It was found that there is a good agreement between the simulation predictions and the output of the real industrial reactor.

Keywords: C3-cut; selective hydrogenation; hydrodynamic model; reaction rates; simulation; three-phase reactor

Acknowledgments

The authors are grateful to Dr. G. Vulpescu and Dr. D. Mertens for the productive discussions on simulations and for providing the authors with valuable advices and data series. Financial support from Total Petrochemicals made this work possible and is greatly appreciated.

Nomenclature

a: interfacial area per unit volume of the reactor (m⁻¹)
a_j: specific surface area at the interface j (m⁻¹)
a_L: gas-liquid interfacial area per unit volume of the bed (m².m⁻³)
a_p: specific area of catalyst particle (surface of particle/volume of particle), SP/VP (m⁻¹)
a_s: surface area of the catalyst per volume of the bed, aP(1−εB) (m⁻¹)
A_i: pre-exponential factor i for the reaction constant k_i
Ai': pre-exponential factor i for the reaction constant k_i
B_i: pre-exponential factor i for the constant K_j
Bj': pre-exponential factor i for the constant K_j
C_p,i: specific heat capacity of the phase j (liquid or solid) (kJ. kg⁻¹.K⁻¹)
Cc: deactivating agent concentration (kgC. kgcat⁻¹)
C_i: concentration of compound i (kmol.m⁻³)
CiJ: concentration of compound i in the phase j (liquid or solid) (kmol.m⁻³)
(CiL): concentration of the component i in the liquid phase at the entrance of reactor (kmol.m⁻³)
d_p: particle diameter (m)
d_T: diameter of the reactor (m)
D_g: diffusion coefficient in the gas phase (m².s⁻¹)
D_L: diffusion coefficient in the liquid phase (m².s⁻¹)
E_i: activation energy of reaction i for the constant k_i (kJ.kmol⁻¹)
F_j: activation energy of reaction i for the constant K_j (kJ.kmol⁻¹)
G: gas mass flow rate (kg.m⁻².s⁻¹)
h_LS: heat transfer coefficient for the liquid film surrounding the catalyst particle (kJ.m⁻². s⁻¹.K⁻¹)
H_i: Henry constant (Pa. mol.m⁻³)
K_J: reaction rate coefficient for component j (where j represents C₆, C₉ or C₁₂) for the formation of the deactivating agent (kgC. kgcat⁻¹.s⁻¹)
ki0: reaction rate coefficient for the reaction i (kmol. kgcat⁻¹.s⁻¹)
kiL: gas-liquid mass transfer coefficient of species i (m.s⁻¹)
kiS: liquid-solid mass transfer coefficient of species i (m.s⁻¹)
Ki: adsorption equilibrium constant for the compound i (bar⁻¹)
L: liquid mass flow rate (kg.m⁻².s⁻¹)
[L]: concentration of active sites on the catalyst
P_i: partial pressure of the compound i (bar)
(PiG)0: partial pressure of the component i in the gas phase at the entrance of reactor (bar)
r_c: rate of formation of the deactivating agent (kgC. kgcat⁻¹.s⁻¹)
r_i: rate of reaction for the reaction i (kmol. kgcat⁻¹.s⁻¹)
ri0: rate of reaction in absence of deactivation for the reaction i (kmol. kgcat⁻¹.s⁻¹)
ri,g: rate of reaction i in the gas phase (kmol. kgcat⁻¹.s⁻¹)
ri,1: rate of reaction i in the liquid phase (kmol. kgcat⁻¹.s⁻¹)
R: gas constant (kJ.kmol⁻¹.K⁻¹)
R_i: global reaction rate for the compound i (kmol. kgcat⁻¹.s⁻¹)
ReG: Reynolds number for the gas phase, dPugρg/μL(−)
Re_L: Reynolds number for the liquid phase, dPulρL/μL(−)
Scat: pre-exponential corrective term for the reaction rate coefficient
SM,tr,2D0: standard entropy of the active complex (kJ.kmol⁻¹.K⁻¹)
Sc: Schmit number, μL/ρLDL(−)
Sh: Sherwood number, Ksdp/DL(−)
t: time (s)
T: temperature (K)
T₀: temperature of the fluid at the entrance of the reactor (K)
T_G: temperature in the gas phase (K)
T_m: mean temperature (K)
T_s: temperature in the solid phase (K)
u_g: superficial velocity of the gas phase (m.s⁻¹)
u_i: superficial velocity of the liquid phase (m.s⁻¹)
x_i: conversion (-)
_Z: reactor length (m)

Greek letters

αC: deactivation factor (by C) for the formation of the deactivation agent C (kgcat. kgC⁻¹)
αi: deactivation factor (by C) for the main reaction i (kgcat. kgC⁻¹)
γi: deactivation factor for the main reaction i (bar⁻¹)
γi,cor: correcting factor for the ideal gas law (-)
Δ: common denominator for the reaction rates on metal sites
Δ′: common denominator for the reaction rates on acid sites
ΔSr,i: heat of reaction for the reaction i (kJ.kmol⁻¹)
ΔSint†: variation of standard entropy occurring during the formation of the active complex (formation occurring during the chemical elementary step) (kJ.kmol⁻¹.K⁻¹)
εB: bed void fraction (-)
εi: liquid holdup per unit volume of the reactor (-)
λi: solubility coefficient (m^3.kg⁻¹.Pa⁻¹)
μg: viscosity of the gas (kg.m⁻¹.s⁻¹)
μL: viscosity of the liquid (kg.m⁻¹.s⁻¹)
VN: molar gas volume at standard condition (m³.mol⁻¹)
ρB: bulk density of solid (kg.m⁻³)
ρG: gas density (kg.m⁻³)
ρL: liquid density (kg.m^–3)
ρ20: gas density at 20 °C (gr. cm⁻³)
σL: surface tension of liquid (N.m⁻¹)
ϕC: deactivation function for the formation of deactivation agent C
ϕi: deactivation function for the main reaction i
ϕP: surface shape factor of the catalyst particle, as/dp2
ϕW: fractional particle wetted with active liquid, a/as(−)

Acronyms

C: Coke (typically C₁₂)
EOR: End of the run
GO: Green oil
ind: industrial data
MA: Methylacetylene
MAPD: Methylacetylene-Propadiene
MID: Middle of the run
ppm: Parts per million
PD: Propadiene
PN: Propane
PP: Propylene
R1: Reactor1
R2: Reactor 2
sim: Simulation results
SOR: Start of the run

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Published Online: 2016-3-12

Published in Print: 2016-8-1