Substrate impurities can affect catalyst performance in various ways:
- Catalyst Poisoning: Certain impurities bind strongly to the active sites of the catalyst, preventing the desired reaction from occurring. For example, sulfur-containing compounds can poison platinum-based catalysts in hydrogenation reactions.
- Active Site Blocking: Impurities can physically block the active sites of the catalyst, reducing the number of available sites for the catalytic reaction. This is often seen with particulate impurities.
- Change in Reaction Pathways: Some impurities can alter the mechanism of the reaction, leading to the formation of unwanted by-products. For instance, the presence of halides can change the selectivity in oxidation reactions.
- Catalyst Deactivation: Over time, impurities can accumulate on the catalyst surface, leading to gradual deactivation. This can necessitate frequent regeneration or replacement of the catalyst, increasing operational costs.
