The Rate Equation for Surface Kinetics

Although here we introduce all the phenomena which affect the rate, the real world is never so exciting that we have to concern ourselves with all five factors at any one time. In fact, in the majority of situations with porous catalyst particles we only have to consider factors and . 

Because of the great industrial importance of catalytic reactions, considerable effort has been spent in developing theories from which kinetic equations can rationally be developed. The most useful for our purposes supposes that the reaction takes place on an active site on the surface of the catalyst. Thus three steps are viewed to occur successively at the surface. 

Step 1. A molecule is adsorbed onto the surface and is attached to an active site. 

Step 2. It then reacts either with another molecule on an adjacent site (dualsite mechanism), with one coming from the main gas stream (single-site mechanism), or it simply decomposes while on the site (single-site mechanism). 

Step 3, Products are desorbed from the surface, which then frees the site. 

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