Deactivation of the Catalyst: Catalysts can lose activity over time due to phenomena such as
sintering,
poisoning, or
coking. Sintering refers to the agglomeration of catalyst particles, reducing surface area, while poisoning involves the adsorption of impurities that block active sites.
Mass Transfer Limitations: In heterogeneous catalysis, the transport of reactants to and products away from the catalyst surface can limit the reaction rate. This is especially significant in reactions where the reactants or products are in different phases.
Temperature Effects: While increasing temperature generally increases reaction rates, it can also lead to the deactivation of certain catalysts. For example, high temperatures might cause structural changes in the catalyst, reducing its activity.
Concentration Effects: The rate of reaction is also dependent on the concentration of reactants. In some cases, a high concentration of products or by-products can inhibit the reaction by blocking active sites on the catalyst.
pH and Solvent Effects: The pH and choice of solvent can significantly affect catalytic efficiency. In
enzymatic catalysis, for example, pH changes can alter the enzyme's active site and reduce its activity.
