Effect of Mass-Transport Limitations on the Performance of a Packed Bed Membrane Reactor for Partial Oxidations. Transport from the Membrane to the Packed Bed

With a packed bed membrane reactor, the product yield can be significantly enhanced for partial oxidation systems, via distributive addition of oxygen to the reaction mixture along the axial coordinate of the reactor, provided that the reaction order in oxygen of the formation rate of the target product is smaller than the reaction order in oxygen of the consecutive reaction toward the waste product. In Part 1, the intrinsic and integral effects of intraparticle diffusion limitations on the performance of the packed bed membrane reactor have been investigated. In this paper, the study is extended by studying the effects of mass-transfer limitations from the membrane wall to the center of the packed bed. Again, first the intrinsic effects are examined, followed by a study of the integral effects over the entire reactor using a two-dimensional reactor model. A modified Thiele modulus Φ‘‘ was defined and it was found that only for Φ‘‘> 1 radial concentration profiles inside the packed bed does the integral reactor performance deteriorate and that for values <1, a one-dimensional reactor model suffices. Asymptotic solutions for high values of the modified Thiele modulus for the relative conversion rate of the main reaction and the relative product selectivity have been derived, which allows a quick (conservative) estimate of the influence of the mass-transfer limitations from the membrane wall to the center of the packed bed.