Several factors can lead to catalyst termination, including: 1. Poisoning: Contaminants in the reaction mixture can bind to the catalyst surface, decreasing its activity. 2. Sintering: High temperatures can cause catalyst particles to agglomerate, reducing the surface area available for reactions. 3. Coking: The buildup of carbonaceous deposits on the catalyst surface can block active sites. 4. Leaching: Soluble catalysts can dissolve into the reaction medium, leading to loss of active material. 5. Structural Changes: Changes in the crystal structure of the catalyst due to prolonged use can alter its activity.