Contaminants such as sulfur, chlorine, or heavy metals can poison catalysts, leading to a drastic reduction in activity and selectivity. These substances may bind irreversibly to the active sites, blocking them from participating in the desired reactions. The presence of organic compounds or particulates can also lead to fouling, where the catalyst surface becomes covered with unwanted materials, further impairing its function. Regular monitoring and purification of reactants are essential to mitigate these effects.
