Heterogeneous modeling of an autothermal membrane reactor coupling dehydrogenation of ethylbenzene to styrene with hydrogenation of nitrobenzene to aniline: Fickian diffusion model

Coupling of reactions in catalytic membrane reactors provides a route to process intensification. Dehydrogenation of ethylbenzene and hydrogenation of nitrobenzene form a promising pair of processes to be coupled in a membrane reactor. The heat released from the hydrogenation side is utilized to break the endothermality on the dehydrogenation side, while hydrogen produced on the dehydrogenation side permeates through the hydrogen-selective membranes, enhances the equilibrium conversion of ethylbenzene and reacts with nitrobenzene on the permeate side to produce aniline. Mathematical reactor models are excellent tools to evaluate the extent of improvement before experiments are set up. However, a careful selection of phenomena considered by the reactor model is needed in order to obtain accurate model predictions.To investigate the effect of the intraparticle resistances on the performance of the cocurrent configuration of the coupling reactor, a heterogeneous fixed bed reactor model is developed with Fickian diffusion inside the catalyst pellets. For the condition of interest, the styrene yield is found to be 82% by the homogenous model, 73% by the heterogeneous model for isothermal pellets, and 69% by the heterogeneous model with non-isothermal pellets. Hence, the homogeneous model overestimates the yield by 5-15% of their actual values.