ABSTRACT
A . HDS Catalysts. Hydrodesulfurization (HDS) of fossil fuels continues to attract a great deal of research attention [1]. The HDS reaction, eq. 1 , is arguably one of the largest scale catalytic reactions practiced world wide in the p e tro leu m industry [2]. During HDS, C-S bonds in organic sulfur compounds are cleaved and die sulfur is then removed from the catalyst surface as H2S. In addition to C-S bond hydrogenolysis, hydrogenation of unsaturated molecules and hydrocracking of larger molecules into smaller ones can also occur. The catalyst normally used in an industrial setting consists of a sulfided mixture of Mo and Co on a high surface area support, usually γ-alumina, although other combinations, e.g. W/Ni, are also used. The late transition metal (TM), Co or Ni, is referred to as the "promoter", although Mo can "promote" Co as well [1]. The nature of die sulfided catalyst has been the subject of research and controversy for over 30 years.
