General Introduction

Abstract

Schematically, two principal objectives may be distinguished in the application of physical techniques in the study of catalysis: (1) The characterization of the catalysts; and (2) the acquisition of information relevant to understanding the catalytic phenomenon. The first objective consists of establishing an “identity card” for the catalyst, indicating its structure, morphology, and other fundamental physicochemical data. This information is essential for a meaningful comparison of catalysts prepared in different laboratories. The situation in this area has improved greatly during the last 20 years, but is still not entirely satisfactory. The second objective concerns the catalytic process. Schematically heterogeneous catalytic reactions involve five steps:

• 1. Transportation of the reagents to the active surface.

• 2. Chemisorption of at least one reagent when there is more than one.

• 3. Formation of the reaction intermediate (activated complex).

• 4. Desorption of the products and regeneration of the catalyst.

• 5. Transportation of the reaction products.