Oxidation and Deoxidation

Abstract

Surfaces of oxides used as catalysts at low temperatures (below about ¼ of the melting point in K) contain various defects (steps, vacancies, interstitials, etc.) which may be privileged sites for the catalytic reaction (Gravelle and Teichner, 1969). Satisfactory correlations may be then obtained between a defect surface structure of the catalyst and the catalytic activity. Indeed, the surface ionic mobility being restricted at such temperatures the defects are often frozen in. But when the catalytic reaction is studied at temperatures at which surface or bulk ionic mobility exists, the previous localized properties are smeared out by collective properties of the surface. The whole of the oxide surface takes part in the reaction at these temperatures, there being no localized areas (immobile areas) of high activity. It is for such conditions that the present Chapter attempts a search for correlations between the catalytic activity and some properties of oxide catalysts.