Energetic Aspects of Catalytic Activity

If a molecule is to enter a reactive state, it must undergo activated adsorption on the catalyst surface. Hence the catalyst must chemisorb at least one of the reaction partners, as we have already seen. 

The strength of adsorption of the molecules is decisive for effective catalysis neither too strong nor too weak binding of the reactants can induce the required reactivity a certain medium binding strength is optimum. 

Sometimes the product or transition state being formed may be so strongly bound on the surface that its desorption or further reaction is hindered. In this case the catalyst is poisoned by the product and becomes inactive. 

For a deeper understanding of the catal5hic reaction mechanism, knowledge regarding the structure and stability of the adsorbed intermediates is particularly important. In many cases a simple qualitative view of the chemisorption is sufficient. 

The chemisorption of gases on metals has been the subject of particularly intensive investigations, and the available data allow the catal5hic properties of metals to be explained well. Experimentally determined, quahtative orders of catalytic effectiveness are often found in the literature. For example, for the adsorption of hydrocarbons  

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