Mass transfer in polymerization of olefins on solid catalysts. The double-grain model

Abstract

Inadequacy of the description of catalyst particles by the single-grain model has been shown by analysing mass transfer effects in polymerization of olefins on highly active solid catalysts. Evidence is presented which speaks in favour of the double-grain model. The latter was used to describe mass transfer in polymerization of ethylene of a highly active supported catalyst. In this model the lowering of diffusion coefficient depends on the size of macro- and microparticles of the catylyst. A generalized relationship between the extent of catalyst utilization and the value of modified Tilé criterion has been derived, which enables one to estimate the effect of both the size of catalyst particles or subparticles on the diffusion coefficient and of restricted diffusion for catalysts differing in texture and activity.