Catalysts can fail due to several reasons, including:
1. Deactivation: This is the most common failure mode, where the catalyst loses its activity over time. Deactivation can occur due to poisoning, fouling, thermal degradation, or sintering. 2. Poisoning: Certain substances, known as poisons, can strongly adsorb onto the active sites of a catalyst, rendering them inactive. Common poisons include sulfur, phosphorus, and heavy metals. 3. Fouling: Fouling occurs when contaminants deposit on the catalyst surface, blocking active sites and hindering the reaction. This is often seen in heterogeneous catalysis. 4. Thermal Degradation: High temperatures can cause physical and chemical changes in the catalyst, such as phase transformations or loss of surface area. 5. Sintering: Sintering involves the aggregation of catalyst particles, leading to a reduction in surface area and active sites.
