Feasibility of coupling dehydrogenation of ethylbenzene with hydrogenation of nitrobenzene in an autothermal catalytic membrane reactor: Modeling study

The coupling of reactions in catalytic membrane reactors provides novel reactor configurations that allow shifting the thermodynamic equilibrium and yields of thermodynamically limited reactions and enhancing significantly the rate of production. An interesting pair to couple is the dehydrogenation of ethylbenzene to styrene and the hydrogenation of nitrobenzene to aniline. Hydrogen produced in the dehydrogenation side diffuses through the membrane and assists in shifting the equilibrium conversion of ethylbenzene and the yield of styrene while the large heat of reaction released from the hydrogenation side is utilized to provide the heat needed on the dehydrogenation side. The feasibility and performance of the co-current integrated catalytic membrane reactor configuration is investigated by means of models based on both homogeneous and heterogeneous fixed bed concepts. The ethylbenzene conversion and styrene yield obtained from the proposed reactor are then compared with those for simple fixed bed reactors without membranes. In the homogeneous modeling, the conversion of ethylbenzene is predicted to be ∼39% in the simple fixed bed (without any membrane) compared to ∼85% in the proposed catalytic membrane reactor. When intraparticle diffusion resistance is taken into consideration, the integrated reactor is predicted to have an ethylbenzene conversion of ∼72% when catalyst pellets are isothermal and ∼65% for non-isothermal catalyst pellets. The yields of styrene predicted by the homogeneous modeling are ∼35% and ∼80% for the simple fixed bed and the catalytic integrated reactor, respectively. The heterogeneous model of the integrated reactor, however, predicts less substantial, though still major gains, than the homogenous model, i.e. a styrene yield of ∼70% for the isothermal catalyst pellets compared to ∼65% for the non-isothermal catalyst pellets.