Intermediate product yield enhancement with a catalytic inorganic membrane: I. Analytical model for the case of isothermal and differential operation

M.P. Harold, V.T. Zaspalis, K. Keizer, A.J. Burggraaf

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Abstract

A simple model is developed to examine the performance of a supported catalytic membrane within which occurs the consecutive-parallel reaction system given by A + B → R, with rate = k1pαA1ApαBB, and A + R → P, with rate = k2pαA2ApαRR. Closed-form solutions reveal that segregation of reactants A and B to opposite sides of the membrane is an effective strategy for increasing the desired product (R) point yield. However, increases in the component R yield come at the expense of the point catalyst utilization, due, in part, to depletion of reacting components B and R. The membrane performance is sensitive to the relative reaction orders with respect to component A for the special case in which the rates are zeroth-order with respect to B and R (αB = αR = 0). The segregation strategy is shown to be most beneficial if three requirements are met: (i) αA1 < αA2, (ii) k1, k2 sufficiently large and (iii) active layer sufficiently thin compared to support. Under favorable conditions [requirements (i)-(iii) met], component R is selectively produced near the active layer surface, and diffuses out of the membrane before further reaction to undesired product (P). The simulations indicate that the fractional increases in the R yield attained, as the degree of segregation is increased, exceed the fractional decreases in catalyst utilization. A secondary benefit of the membrane design is the confinement of reaction products in the bulk stream on the active layer side, thus reducing the downstream separation needs.
Original languageEnglish
Pages (from-to)2705-2725
Number of pages21
JournalChemical engineering science
Volume48
Issue number15
DOIs
Publication statusPublished - 1993

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