Probing catalytic reactions at surfaces

A review of the major contributions from modern surface science to the understanding of the chemistry of heterogeneous catalysis is provided. A number of basic concepts. including the nature of surface bonds, the dynamics of surface reactions, find the identification of the intermediates and elemental steps that comprise the catalytic processes, are surveyed. The localized nature of the surface chemical bond, the drastic changes that varying surface coverages introduce on surface energetics and kinetics, and the key role that subtle energy barrier differences among competing reactions play in defining the overall selectivity of catalytic processes are particularly noted. A discussion on the implications of these microscopic concepts to catalysis is then provided. A critical analysis of the limitations encountered when extrapolating results from well-defined model systems to more realistic reaction conditions using supported catalysts and on the ways those problems have been addressed is also presented. A more comprehensive summary of the knowledge acquired to date on the surface chemistry or hydrocarbon conversion reactions on transition metals is provided. Finally, some ideas on the future directions of surface science in connection with catalysis are advanced. (C) 2001 Elsevier Science Ltd. All rights reserved.