Catalysts, influenced by various factors during use, may lose their activity rapidly or slowly. The reasons for catalyst deactivation are complex and can be summarized into the following categories:

1. Permanent inactivation

The active components of catalysts lose their activity due to the influence (poisoning) of certain external components, often resulting in permanent deactivation. These external components often cause changes in the active components through chemical reactions or ion exchange with the active components of the catalyst. For example, acidic catalysts are neutralized by alkalis, and precious metal catalysts are poisoned by sulfides or nitrides. The deactivation of catalysts due to poisoning often manifests as a rapid decline in activity. The loss of active components through wear or sublimation during use also leads to permanent deactivation, which is often difficult to recover simply

2. The gradual deactivation of active components due to their being covered is a non-permanent deactivation. For example, carbon deposits generated during the reaction process may cover the active components or block the pores of the catalyst, preventing the reactants from coming into contact with the active components. These coverings can be removed through certain methods. For instance, deactivation caused by carbon deposits can be reversed through carbon regeneration by burning coke.

3. Incorrect operations can lead to catalyst deactivation, such as excessively high reaction temperatures or drastic pressure fluctuations that cause disarray or crushing of the catalyst bed. Such deactivation is irreversible.