1 - Fundamentals of heterogeneous catalysis

Abstract

This chapter deals with the basic principles of catalytic reactions and focuses on gas-solid heterogeneous catalysis. It includes historical aspects of catalysis in general and heterogeneous catalysis in particular, and the main principles and main parameters of catalytic reactions. In particular, a description of metal oxide catalyst features, of active sites and of catalytic activity and selectivity is given and discussed. Kinetics and main reaction mechanisms involved in catalytic reactions are described, while main industrial processes using metal oxide catalysts in the past and present are summarized. A brief description of metal oxide materials is given with special emphasis on the importance of crystalline structure, structure sensitivity of catalytic reactions, lattice defects, ions and electrons mobility, doping, and use of promoters on their catalytic properties. At last, characterization of heterogeneous catalysts and of catalytic reaction intermediates and a description of the main physical techniques, frequently, even routinely used, are given. Special emphasis is brought about in-situ characterization, i.e. in real working conditions with mass spectrometry and/or gas chromatography analyses on line. Possible relationships between catalytic properties and physical/chemical characteristics of the catalysts and reaction intermediates are discussed, and shown to be rarely reliable.