Introduction to Catalysis

Nitrogen and hydrogen will sit happily together in a sealed vessel without reacting to form ammonia, with the equilibrium for the reaction being completely over to the left hand side of the equation under ambient conditions. 

By increasing the rate of attainment of equilibrium through lowering the activation energy, catalysts reduce the energy requirement of a process and 

Today it is estimated that some 90% of the chemicals used have, at some stage in their manufacture, come into contact with a catalyst. The range is truly broad from bulk chemicals such as acetic acid and ammonia to consumer products such as detergents and vitamins. Virtually all major bulk chemical and refining processes employ catalysts. The number of fine, speciality and pharmaceutical processes currently using catalysts is still relatively small by comparison, but a combination of economic and environmental factors is focusing much research on this area. The great 

Selectivity - the amount of substrate converted to the desired product as a percentage of total consumed substrate (a catalyst will be of limited benefit if it also enhances the rate of by-product formation). 

Turnover frequency - the number of moles of product produced per mole of catalyst per second (low turnover frequencies will mean large amounts of catalyst are required, resulting in higher cost and potentially more waste). 

It was noted earlier that enzymes are proteins that function as catalysts for biological reactions. When it is remembered that body temperature is 3TC and that many organic reactions occur at temperatures well above this, the need for these catalysts becomes apparent. It becomes of interest to understand how these proteins perform their catalytic function. The exact mechanism of enzyme action is a fundamental problem for the bioorganic chemist. Most of the action occurs on the surface of the protein catalyst at an area designated as the active site where chemical transformations follow the basic 

By definition, a catalyst is any substance that alters the speed of a chemical reaction without itself undergoing change. This is true of the enzymes, for they are of the same form (i.e., conformation and chemical integrity) before and after the catalytic reaction. This is mandatory for catalytic efficiency. If the enzyme were altered after the chemical reaction with a first molecule of substrate, then it would not be able to interact with a second substrate molecule. Of course, as catalysts, enzymes need only be present in small amounts. 

A catalyst may either increase or decrease the velocity of a chemical reaction. However, in current usage, a catalyst is a substance that increases the reaction velocity a substance that decreases the rate of a reaction is called an inhibitor. This definition also implies that a catalyst is not consumed during the course of the reaction, but serves repeatedly to assist molecules to react. In biochemistry many enzyme-catalyzed reactions require other substances which may also properly be called a catalyst, but which are consumed (or modified) in the course of the reaction they catalyze. They are the coenzymes and are often restored to their original form by a subsequent reaction, so that in the larger context the coenzymes are unchanged. The detailed chemistry of these substances will appear in Chapter 7. 

According to transition state theory, the processes by which the reagents collide are ignored. The only physical entities considered are the reagents, or 

The importance of transition state theory is that it relates the rate of a reaction to the difference in Gibbs free energy AG ) between the transition state and the ground state. This theory may be used quantitatively in enzymatic reactions to analyze structure reactivity and specificity relationships involving discrete changes in the structure of the substrate. 

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This book is based on courses, which the authors have taught at Lyngby and Eindhoven for many years. For example. Chapters 1-3 form the basis for a mandatory course Kinetics and Catalysis presented in the second year of the Bachelor s curriculum at Eindhoven, while Chapters 4,5 and 8-10 formed the basis for an optional course Introduction to Catalysis. In Lyngby, Chapters 1-7 have been used for an optional course in Chemical Reaction Kinetics and Catalysis in the Master s curriculum. At the end of the book we have added a list of questions for every chapter. 

Richardson, J. T., Principles of Catalyst Development, Plenum Press, New York, 1989. (Undergraduate level. An introduction to catalysis and catalyst development from an engineering perspective. The emphasis throughout is on the practical aspect of the subject, rather than on theory.)... 

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