The nature of active sites on catalytic alumina: Information from site poisoning by sulfur-containing molecules Academic Article uri icon

abstract

  • The natures of low-temperature (<100 C) catalytic sites on activated alumina have been examined by selective poisoning studies, using various sulfur-containing molecules. Hydrogen sulfide and methyl mercaptan are effective poisons, at 25 C, for sites on alumina that catalyze double-bond migration and cis/trans rotation in olefins, but have virtually no effect on sites that promote deuterium exchange reactions of olefins and aromatics. Sulfur dioxide, on the other hand, affects neither type of site at 25 C, but is "lethal" to both types when absorded at 400 C. The results have been correlated with those of previous infrared, EPR, and selective poisoning studies. Olefin isomerization sites on alumina have a surface density of 5 1013/cm2 and consist of certain exposed Al3+ ions at the surface, but may require the presence of adjacent O2- ions. Deuterium exchange sites are much less numerous (0.3-0.8 1013/cm2) and are associated with a very small fraction of highly energetic surface O2- ions. At 25 C, the two types of sites apparently operate simultaneously but independently of each other. 1976.

published proceedings

  • Journal of Catalysis

author list (cited authors)

  • ROSYNEK, M.

citation count

  • 21

complete list of authors

  • ROSYNEK, M

publication date

  • February 1976