Increasingly stringent environmental regulations require significant quality improvements in both gasoline and diesel fuels. Specifications for diesel will likely include ultra low sulfur and reduced multiring aromatic contents. Such mandates can be met by a combination of deep hydrodesulfurization and aromatic saturation. Further diesel quality improvements are possible by lowering density and increasing cetane value by selective ring opening (SRO) single and multiring naphthenes present in mid-distillate streams into acyclic paraffins. Noble metal based hydrogenolysis catalysts such as platinum and iridium are quite effective for selectively ring opening five-membered ring naphthenes such as methylcyclopentane. Ring opening of six-membered-ring are, in contrast, much more difficult to open via a hydrogenolysis route [1]. Strongly acidic hydrocracking catalysts readily covert naphthenic molecules but the primary ring opened products undergo rapid secondary reactions to lighter molecules [2,3,4]. To achieve significant diesel quality improvements it will be necessary to selectively convert alkyl substituted molecules in mid-distillate feedstocks.
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