Catalyst deactivation mechanism

Solid acid and solid base catalysts, like other solid catalysts, undergo deactivation during the catalytic reaction process, and their mechanisms may involve the following possible pathways.

1. Toxic substances or inhibitors that adsorb alkaline molecular acid centers, while acidic molecules can inactivate the alkaline centers. These molecules may exist in the form of impurities in the raw materials or may form during the reaction process. The deposition of metal ions in raw materials can cause serious deactivation phenomena, and such deposits can directly cover the active centers or block the entrance of catalyst micropores.

2. After the formation of carbonaceous substances during the reaction process, coke deposits and masks the active centers, or narrows or blocks the catalyst pore openings, which can also be included in the adsorption of toxins.

3. The mechanism of chemical changes in the catalyst itself includes the following processes: (1) melting, which can lead to a decrease in the surface area and pore volume of the solid catalyst, (2) interconversion of catalyst components, (3) sublimation or melting of active components in the catalyst, and (4) chemical reactions between various components of the catalyst or between the catalyst and reactants, resulting in the active catalyst becoming a more stable and less active substance.