1. Adsorption of Impurities: Impurities present in the reactants or the catalyst support can adsorb onto active sites. 2. Formation of By-products: Some catalytic reactions produce by-products that can adsorb onto the catalyst surface. 3. Reaction Intermediates: In some cases, reaction intermediates can strongly bind to active sites, preventing further reactions. 4. Coking: The deposition of carbonaceous materials, often referred to as coking, is a common cause of site blockage, particularly in hydrocarbon processing.
