MODELING OF TRANSFER PHENOMENA ON HETEROGENEOUS ZIEGLER CATALYSTS .2.EXPERIMENTAL INVESTIGATION OF INTRAPARTICLE MASS-TRANSFER RESISTANCE DURING THE POLYMERIZATION OF ETHYLENE IN SLURRY

An experimental investigation of mass transfer limitations on a single batch of high activity, heterogeneous catalysts used in the slurry po lymerization of ethylene is presented. The viscosity of the continuous phase was varied, using trace amounts of inert copolymer in order to reduce the monomer diffusivity, and the activity levels were varied us ing hexene as an activator. These changes were intended to clearly ide ntify situations in which the polymerization becomes mass-transfer-lim ited due to diffusion resistance in the pores of the catalyst. Increas ing the observed activity of the catalyst from approximately 9000 to 4 0,000 grams of polymer per gram of catalyst per hour (g/g/h) revealed no evidence of mass transfer resistance, even when the diffusivity of the monomer in solution was reduced by a factor of six. Analysis of th e molecular weight as a function of particle size supported this concl usion but did suggest that there might be slight chemical differences between large and small particles. (C) 1996 John Wiley & Sons, Inc.