Chapter 4 Catalytic and Non-Catalytic Heterogeneous Reactions

Abstract

On an industrial scale, chemical reactions involving reactants in the gaseous or vaporized state that come into contact with a solid, which is either a catalyst or another reactant, necessarily involve several physical and chemical steps. Some of these physical and chemical steps are coupled and it is this complexity, together with the problem of efficient gas–solid contact, which dictates that gas–solid catalytic and noncatalytic reactions should be considered as a particular class of problem. This chapter discusses principles relating to the mechanistic events with focus on (a) an analysis of the effect that mass and heat transfer has on heterogeneous chemical reactions, (b) evolving satisfactory models to account for these events, and (c) the industrial equipment that is utilized to effect these reactions. Surface area is not the only physical property that determines the extent of adsorption and catalytic reaction. Equally important is the catalyst pore structure, which, although contributing to the total surface area, is more conveniently regarded as a separate factor. The models of porous solids, such as wheeler's semi-empirical pore model, and the mathematical models of porous structures (dusty gas model and random pore model), are discussed.