Electrical Properties of Solid Catalysts

Abstract

Widely different kinds of solid materials, ranging from the noble metals to activated earths, have been used to catalyse a variety of chemical reactions. Thus, the use of nickel for hydrogenation, of iron for ammonia synthesis, of vanadium pentoxide for oxidation reactions, of chemically processed clay and synthetic silica-alumina matrix for cracking of petroleum, is well known. Specificity of catalytic action is one of the most outstanding properties of a catalyst, particularly a contact catalyst. For each reaction or reaction-type, there is a restricted group of substances which can catalyse it. As a result, catalysts came to be classified application-wise1 as hydrogenation catalysts, oxidation catalysts, dehydration catalysts, cracking catalysts and so on. Within each group of catalysts, the activity (as defined by the accelerating effect on a given reaction) varied from substance to substance, so that the choice of the optimum catalyst for a given reaction still rested on empirical trial and error methods. Many attempts have been made, particularly during the last three decades, to rationalise the method of catalyst selection.