Dimensional changes in catalysts can be caused by several factors:
1. Thermal Expansion: Variations in temperature can cause catalysts to expand or contract. This is particularly important in reactions requiring high temperatures.
2. Phase Transformations: Some catalysts undergo phase changes during reactions. For example, a metal catalyst might transition from a solid to a molten state, altering its dimensions.
3. Mechanical Stress: Repeated use of catalysts can lead to wear and tear, causing changes in their structure and dimensions.
4. Chemical Reactions: Reactions can lead to the formation or removal of atoms or molecules from the catalyst surface, impacting its dimensions.
