Effects of H2S on bifunctional catalysts

Poisoning of noble metal catalysts by sulfur-containing organic compounds is a well-known phenomenon. These compounds are frequently present in hydrotreating feedstocks and cause a selective decrease in the metal hydrogenation function of noblemetal-based hydrotreating catalysts. The effects of H 2 S, considered as a model sulfiding compound, were studied on a supported platinum catalyst. Low coverages of H 2 S are found to cause a selective poisoning of noble metal particles, which with increasing coverage becomes unable to chemisorb H 2 at room temperature. At higher coverages H 2 S spills over to the support, modifying its acidic properties. Eventually new weak acid sites are formed.