Abstract

Various types of catalysis are named and categorized by the reagents involved. Enzymatic catalysis, phase transfer catalysis, homogeneous catalysis, and heterogeneous catalysis are a few of the more well-known branches of study. This review focuses on heterogeneous catalysis and, in particular, on three-phase catalysis in which gas and liquid reagents react with each other on the surface of a solid catalyst. The evaluation of reaction rate data and how it is affected by bulk diffusion in liquids, pore diffusion, adsorption, desorption, and chemical reaction. Summaries are provided of various analytical techniques commonly used as well as an overview of ideal reactors (CSTR and PFR) and how they relate to one another. Examples of well know real reactors are given, such as ebulating bed, fluid bed, trickle-flow and multi-tube reactors.

Catalysis can be grouped into categories: Heterogeneous catalysis, Homogeneous catalysis, Phase Transfer catalysis, Enzymatic catalysis, and some others. There is, unfortunately, no clean division between the categories, but some generalizations allow us to define the gross differences between various types of catalysis.

The term "Heterogeneous Catalysis" is generally reserved for reactions of gases and/or liquids which occur at a solid interface. It is this category to which the bulk of this paper will deal. Heterogeneous catalysis represents over 90% of all commercially practiced chemistry today Trillions of dollars’ worth of products can be traced to catalytic chemistry. Catalyst manufacturing itself is a 5 Billion (US) dollar annual business. (1)

"Homogeneous Catalysis" is the term given to catalysis in which the reactants and catalysts are in the same phase. Most often it is the liquid phase which is important. The catalyst and, perhaps, gaseous co-reactants are dissolved in the liquid reactant. Homogeneous catalysts are known for their high activity and, particularly, their superb selectivity.

"Phase Transfer Catalysis" is the term used to refer t ...