Abstract
Styrene is mainly produced by dehydrogenating ethylbenzene over an iron oxide-based catalyst. The reaction is endothermic and thermodynamically limited when operated in conventional catalytic fixed-bed reactors. This makes the styrene production process a conversion-selectivity trade-off, where different objectives must be compromised. In this work, a one-dimensional reactor model accounting for changes in molar flowrate, temperature, and pressure is used to predict the performance of a membrane reactor. Three main hydrogen flux profiles were assumed along the reactor axial direction: constant, linearly increasing, and linearly decreasing. It is found that the styrene yield and selectivity in a membrane reactor operated with a linearly decreasing hydrogen flux profile are higher than those with constant or linearly increasing hydrogen flux profiles in both isothermal and nonisothermal cases. It is also observed that the styrene yield and selectivity of the membrane reactor operated with a linearly decreasing hydrogen flux can be enhanced by improving the membrane's average hydrogen permeability. The influence of nonlinearity in the hydrogen flux equation is marginal and observed mainly at the reactor inlet. The improvement is due to enhanced hydrogen permeation, which is observed to be better for the linearly decreasing hydrogen profile than for the constant, linearly increasing hydrogen flux profile. When a permeation section is included in the reactor at the point where maximum hydrogen production is observed, the styrene yield is better than that of the completely permeated catalytic reactor.