Specific Poisoning and Characterization of Catalytically Active Oxide Surfaces

Abstract

This chapter discusses the specific poisoning of a catalyst surface. A probe molecule other than the reactant is preadsorbed as a poison and its effect on the catalytic activity studied. From the nature of interaction of this probe molecule with the surface sites one may obtain information regarding the chemical nature of these sites and from the number of poisoning molecules necessary to bring the activity to zero one may estimate an upper limit of the active site density. Besides the obvious difficulty to discriminate between surface sites that purely absorb the probe molecule and those that are involved in the catalytic process as active sites, there are a number of other limitations making it difficult to obtain clear-cut information on the nature of active sites. The chapter describes the proposals that are indispensable for a proper application of this method and the precautions that have to be kept in mind while drawing conclusions from specific poisoning experiments. The chapter illustrates two examples—namely, the dehydration of alcohols and the isomerization of olefins on alumina.