Optimal Distribution of Catalyst in Pellets

Abstract

A large fraction of the chemical and refinery processes are catalytic in nature. While the worldwide sales of catalysts are only about $4 billion annually, the economic impact of catalysis comes from the fact that approximately $200 worth of products are manufactured for every $1 worth of catalyst consumed [1]. The active materials used as catalysts are often expensive metals, and in order to be utilized effectively, they are deposited on high surface area supports. This approach in many cases introduces intrapellet activity gradients during the preparation process, which were traditionally thought to be detrimental to catalyst performance. However, the effects of deliberate nonuniform distribution of the catalytic material within the support on the performance of a catalyst pellet started receiving attention in the late 1960's (see Refs. 2–6). These, as well as later studies, both experimental and theoretical, demonstrated that nonuniformly distributed catalysts can offer superior conversion, selectivity, durability, and thermal sensitivity characteristics over those wherein the activity is uniform.