Investigation of the Nature and Number of Surface Active Sites of Supported and Bulk Metal Oxide Catalysts Through Methanol Chemisorption

Abstract

The present Chapter presents a chronological summary of the application (advantages and disadvantages) of probe molecules both in the liquid and gas media to investigate the surface of oxide based materials and heteropoly compounds. In view of that previous knowledge, the reader is guided through a comprehensive discussion of the sequence that must be followed in order to develop a tailored probe molecule methodology. Such a method requires the use of the reactant itself as a probe molecule along with the investigation of the surface reaction mechanism of the adsorption-reaction processes in order to identify the reactive surface intermediate species. The formation of a monolayer of surface reactive species on the oxide surface allows to quantitatively determining the density of surface active sites (sites per unit surface area). The investigations that led to the development of a “custom made” method based on methanol chemisorption to investigate the nature and number of surface active sites of transition metal oxide based catalysts during methanol oxidation are discussed in detail. Additionally, the investigation of the number and strength of the super-acid sites of heteropolyoxo-metallates through alcohol chemisorption and temperature programmed surface reaction is presented for the first time in the literature.