Effect of catalyst poisoning on the overall selectivity and activity

A mathematical model describing the pore-mouth poisoning of porous catalysts by a strongly adsorbed poison is presented. The effect of poisoning on catalyst selectivity and activity are examined for various pellet geometries; namely, an infinite slab, an infinite cylinder and a sphere. Three types of multiple reactions; independent, parallel and consecutive reactions are considered. For each type of multiple reaction, poisonings of the desired reaction, the undesired reaction and both the desired and the undesired reactions are treated separately.The variations in catalyst selectivity are discussed in terms of the reaction rate constants, the effective diffusities of reacting species, and the extent of catalyst poisoning.A criterion is given for selection of a catalyst that offers a high selectivity for the desired reaction.