Several factors can lead to decreased catalyst activity, including:
1. Poisoning: This occurs when impurities in the reactants bind to the active sites of the catalyst, rendering them inactive. Common poisons include sulfur, lead, and arsenic.
2. Sintering: High temperatures can cause the active metal particles to agglomerate, decreasing the surface area available for the reaction. This phenomenon is particularly problematic for metal catalysts like platinum and palladium.
3. Coking: During hydrocarbon cracking, carbonaceous deposits can form on the catalyst surface, blocking active sites and reducing activity.
4. Leaching: In liquid-phase reactions, the active components of a catalyst can dissolve into the reaction medium, especially in acidic or basic environments.
5. Structural Changes: Physical alterations in the catalyst, such as phase transformations or loss of surface area, can also lead to decreased activity.
