Reactivities in deep catalytic hydrodesulfurization: Challenges, opportunities, and the importance of 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene

The organosulfur compounds present in fossil fuels vary widely in their reactivities in catalytic hydrodesulfurization. In naphtha, thiophene is so much less reactive than the thiols, sulfides, and disulfides that the latter can be considered to be virtually infinitely reactive in practical high-conversion processes. Similarly, in gas oils and petroleum residua, the reactivities of (alkyl-substituted) 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene are much less than those of other sulfur-containing compounds. Consequently, in deep hydrodesulfurization, the conversion of these key substituted dibenzothiophenes largely determines the required conditions. Because of the growing technological importance of deep desulfurization of heavy feedstocks, we infer that 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene are the most appropriate compounds for investigations of candidate catalysts and reaction mechanisms. (C) 1997 Elsevier Science Ltd.