DYNAMIC PROCESSES IN ACTIVE PHASE SUPPORT INTERACTIONS

This paper constitutes an attempt to discern the main dynamic interactions between active phase and support in catalytic reactions. The focus is on the structural or textural changes and mobility phenomena that take place during the reaction, and which as a consequence, have a direct bearing on the real nature of the active catalyst centers, as well as on ageing and deactivation processes. We begin with an inventory of the various types of interactions, distinguishing between those which bring about changes in the active phase and those exhibiting, as a consequence, a modification of the catalytic reaction. Three groups of processes, the dynamic nature of which has important consequences, will be examined: (i) those dealing with the changes in texture (in particular, dispersion) of the active phase; (ii) those originating from reactions in the solid state and (iii) those linked to movements of mobile surface species (spillover) between the active phase and support. Catalysis-driven processes, as opposed to those simply developing along with catalysis, without interaction between both phenomena will be particularly discussed. © 1990.