Sulfur Adsorption and Poisoning of Metallic Catalysts

The catalytic activity of most transition metals is drastically reduced by the presence of hydrogen sulfide or other sulfur-containing compounds at extremely low concentration in the reagents. This poisoning effect is a major problem in many catalytic reactions, especially hydrogen reaction such as methanation of coal synthesis gas or reforming of naphthas. On the other hand, beneficial effects on the selectivity can be obtained by a partial and well-controlled poisoning of catalysts by sulfur. For example, an enhancement of the selectivity for heavier hydrocarbons in the CO + H2 reaction has been reported [1–3]. Increases of the selectivity for partial hydrogenation of diolefins to the corresponding monoolefins were also observed [4, 5]. In the catalytic reforming of naphthas, partial poisoning by sulfur minimizes excessive hydrocracking.