Intermediate product yield enhancement with a catalytic inorganic membrane .2. Nonisothermal and integral operation in a back-mixed reactor

The catalytic membrane reactor (CMR) offers added flexibility over its conventional reactor counterparts. In this study a model is developed to examine the performance of a completely back-mixed CMR for the consecutive-parallel reaction system given by 1 A + B --> R 2 A + R --> P + Q where the desired product is the intermediate R. The effect of segregating reactants to opposite sides of the nonpermselective membrane is examined with regard to the conversion of the main reactants A and B and the integral yield of R. The conversions and yield are shown to be sensitive functions of the degree of segregation. Several factors are identified which contribute to: the intrinsic kinetics and catalytic activity (e.e. apparent reaction orders), the degree of mixing of the reactants A and B between the characteristic flow, transmembrane diffusion, and reaction time), the proximity of the active layer to both of the reactants, and the relative extents and stoichiometries of the two reactions. For a fixed conversion of B and fixed overall B/A feed ratio, and for the case in which the rate of reaction 2 has a higher apparent reaction order with respect to A than reaction 1, the integral yield of R exceeds that for a mixed feed if A is concentrated on the support side and B is concentrated on the active layer side. The membrane in this case serves as a diffusional barrier to reactant A, thereby controlling the effective B/A ratio at the catalytic layer. The yield increase is achieved at the expense of contact time (or reactor volume). The analysis shows that it is possible to realize the same yield increase with a mixed feed by adjusting the B/A feed ratio. (C) 1997 Elsevier Science Ltd.