Preface

Summary

Heterogeneous catalysis is used widely in chemical, refinery and pollution-control processes. Current worldwide catalyst usage is about 10 billion dollars annually, with ca. 3% annual growth rates. While these numbers are impressive, the economic importance of catalysis is far greater since about $200–$1,000 worth of products are manufactured for every $1 worth of catalyst consumed. Further, a vast majority of pollution-control devices, such as catalytic converters for automobiles, are based on catalysis. Thus, heterogeneous catalysis is critically important for the economic and environmental welfare of society.

In most applications, the catalyst is deposited on a high surface area support of pellet or monolith form. The reactants diffuse from the bulk fluid, within the porous network of the support, react at the active catalytic site, and the products diffuse out. The transport resistance of the porous support alters the concentrations of chemical species at the catalyst site, as compared to the bulk fluid. Similarly, owing to heat effects of reaction, temperature gradients also develop between the bulk fluid and the catalyst. The consequence of these concentration and temperature gradients is that reactions occur at different rates, depending on position of the catalyst site within the porous support. In this context, since the catalytic material is often the most expensive component of the catalyst-support structure, the question naturally arises as to how should it be distributed within the support so that the catalyst performance is optimized? This book addresses this question, both theoretically and experimentally, for supported catalysts used in pellets, reactors and membranes.