Ethylbenzene dehydrogenation into styrene: kinetic modeling and reactor simulation
A fundamental kinetic model based upon the Hougen-Watson formalism was
derived as a basis not only for a better understanding of the reaction behavior but also
for the design and simulation of industrial reactors.
Kinetic experiments were carried out using a commercial potassium-promoted
iron catalyst in a tubular reactor under atmospheric pressure. Typical reaction conditions
were temperature = 620oC, steam to ethylbenzene mole ratio = 11, and partial pressure
of N2 diluent = 0.432 bar. Experimental data were obtained for different operating
conditions, i.e., temperature, feed molar ratio of steam to ethylbenzene, styrene to
ethylbenzene, and hydrogen to ethylbenzene and space time. The effluent of the reactor
was analyzed on-line using two GCs.
Kinetic experiments for the formation of minor by-products, i.e. phenylacetylene,
Ã?Â±-methylstyrene, Ã?Â²-methylstyrene, etc, were conducted as well. The reaction conditions
were: temperature = 600oC ~ 640oC, a molar ratio of steam to ethylbenzene = 6.5, and partial pressure of N2 diluent = 0.43 bar and 0.64 bar. The products were analyzed by
The mathematical model developed for the ethylbenzene dehydrogenation
consists of nonlinear simultaneous differential equations in multiple dependent variables.
The parameters were estimated from the minimization of the multiresponse objective
function which was performed by means of the Marquardt algorithm. All the estimated
parameters satisfied the statistical tests and physicochemical criteria. The kinetic model
yielded an excellent fit of the experimental data.
The intrinsic kinetic parameters were used with the heterogeneous fixed bed
reactor model which is explicitly accounting for the diffusional limitations inside the
porous catalyst. Multi-bed industrial adiabatic reactors with axial flow and radial flow
were simulated and the effect of the operating conditions on the reactor performance was
The dynamic equilibrium coke content was calculated using detailed kinetic
model for coke formation and gasification, which was coupled to the kinetic model for
the main reactions. The calculation of the dynamic equilibrium coke content provided a
crucial guideline for the selection of the steam to ethylbenzene ratio leading to optimum
Advisor:Anthony, Rayford G.; Froment, Gilbert F.; Rosynek, Michael P.; Shantz, Daniel F.
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:ethylbenzene dehydrogenation styrene kinetic modeling radial flow reactor simulation
Date of Publication:12/01/2005