ABSTRACT

Catalyst poisoning can be reversible or irreversible, depending on the degree of affinity between impurity and active site. In fact, various degrees of reversibility can be associated with poisoning. Catalyst poisoning can also be selective or nonselective [ l ]. In the case of nonselective poisoning, the chemisorption of poison on the catalyst removes active sites in a uniform manner, and there is a linear relationship between catalyst activity and the amount of poison chemisorbed. In selective poisoning, only active sites with certain properties (e.g., strongly acidic sites) are neutralized by the poison, resulting in a nonuniform deactivation of the catalyst. In that case, there is an exponential or hyperbolic relationship between catalyst activity and the amount of poison chemisorbed (1,2].