Partial internal wetting of catalyst particles with a distribution of pore size

Abstract

The recent model of partial internal wetting of catalyst particles (Bhatia, 1988) is extended to allow for pore-size distribution, multicomponent diffusion, and nonlinear kinetics for spherical particles exposed to condensible vapor undergoing an exothermic reaction. Profiles of liqid filling of the pores are computed, and the influence on mass transfer and effectiveness factor is determined. Under certain circumstances, the effectiveness factor has a maximum with respect to the mole fraction of condensible component suggesting an optimum vapor-phase composition. As the bulk vapor approaches saturation the effectiveness factor and particle temperature can drop sharply because of precipitious increase in liquid filling. However, a significant fraction of the pore space is still dry in contradiction to prior models assuming complete internal wetting of catalyst particles. The new model is more realistic than earlier attempts and lays the framework for proper representation of the physical phenomena involved.