Task 4.7 -- Diesel fuel desulfurization. Semi-annual report, January 1--June 30, 1995

Reductions in the maximum permissible sulfur content of diesel fuel to less than 0.05 wt% will require deep desulfurization technologies to meet these standards. In some refineries, a new hydrogenation catalyst may be required for diesel fuel production. Some of the major components of diesel fuel are dibenzothiophenes and its alkyl derivatives. These components are desulfurized by the Rhodococcus rhodocrous IGTS8 enzymes. But when they are highly diluted with other hydrocarbons in the diesel fuel, will there be enough specificity for their absorption and degradation by the enzyme systems? The extent to which a diesel fuel or middle distillate feed can be desulfurized by desulfurization enzymes will be determined. In addition, the effectiveness of molybdenum sulfide catalysts in removing sulfur from the middle distillate cut will be determined. The catalyst preparation involves creation of the molybdenum sulfide in a highly dispersed form essentially between the layers of a hydrotalcite material, which is then dissolved away to expose the active sites.