Catalyst particle effectiveness with unsymmetrical boundary conditions

Abstract

In trickle-bed reactors part of the surface of the catalyst particles may be covered by liquid and part by gas. Under such conditions conventional expressions for effectiveness factors are not applicable because the surface concentration is not uniform. In this paper more general equations for both particle and overall effectiveness factors are derived. The first development is for slab geometry where the two plane surfaces of equal areas have different reactant concentrations. This is followed by treatment of a cubic particle where one or more faces are covered by liquid. Approximate methods are then presented for evaluating the effectiveness factor for any fractional liquid coverage, f. Comparison of the results at permissible values of f indicates that a simple weighting-factor method gives good results. The method is illustrated by comparing predicted and experimental reaction rates for a case where experimental results are available—the hydrogenation of α-methyl styrene.