Department of Chemistry, University of Glasgow, Glasgow G12 8QQ.

A large number of industrial scale reactions make use of solid acid catalysts. In order to understand the manner in which the catalyst aids formation of the desired products at an economically desirable rate, it is necessary to understand the nature and distribution of the acid sites. This information is commonly obtained by examining the vibrational spectrum of a suitable base chemisorbed on the high surface area catalyst. Pyridine is the base most commonly used, as the vibrational spectrum can distinguish Lewis and Brönstead acid sites.

This presentation will illustrate how infrared spectroscopy has been used to determine the acid site distribution for a series of alumina catalysts that are active for the formation of methyl chloride. Correlation between the adsorbed pyridine modes and perturbations in hydroxyl groups present on the catalyst surface have been used to define the catalyst surface structure and identify the active sites.