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(1) Diesel deep hydrodesulfurization and dearomatization technology. (a) Low-pressure hydrogenation technology-Synsat from ABB Lummus Crest and Standard Catalysts. The Synsat process can be used to produce diesel with a sulfur content of less than 500, as well as diesel with a sulfur content of less than 10 μg/g and aromatics of less than 5%. The aromatic hydrocarbon removal rate can reach 10% to 90%. Reaction pressure is 2.76~6.20MPa ； (b) The "Nipper Second Stage Hydrodesulfurization" process developed by the Japan Petroleum Corporation's Central Institute of Technology. A 1 million t/year diesel deep hydrodesulfurization unit has been built at Japan Petroleum Technology Co., Ltd. The raw oil is straight-run diesel with a sulfur content of 1.5% and FCC diesel with a sulfur content of 0.3%. The sulfur content of the desulfurized product is less than 500. The first and second stages adopt high temperature (360℃) and low temperature (260℃) reactions respectively. ； (c) Development of new catalysts for deep desulfurization. Danish Halder-Topsoe Company has developed TK-574 and TK-573. Using the highly active molybdenum-cobalt catalyst TK-574 can produce diesel with sulfur content of 500 μg/g or 350 μg/g. The Dutch company Akzo-Nobel has developed the diesel ultra-deep hydrodesulfurization catalyst KF-757. In addition to desulfurization activity, it also has hydrodenitrification and aromatic hydrocarbon saturation activities. It has been used in 4 industrial units. The French Petroleum Institute (1FP) has developed deep and ultra-deep desulfurization catalysts HR-416 and HR-448. Using HR-416 for ultra-deep desulfurization to produce ultra-low sulfur diesel ； Using HR-448, in addition to ultra-deep desulfurization, it can also reduce aromatic hydrocarbon content and increase cetane number. The German Southern Chemical Company and the American United Catalyst Company cooperated to develop a three-function (hydrodearomatization, hydrodesulfurization, hydrodenitrification) catalyst (called ASAT catalyst). The total aromatic hydrocarbon content of catalytic diesel can be reduced to less than 10%, and the condensed ring aromatic hydrocarbon content can be reduced to less than 1%. (2) Diesel biological desulfurization. Compared with hydrodesulfurization, diesel biological desulfurization can save 50% in investment costs and 20% in operating costs. Dibenzothiophene (DBT) compounds in catalytically cracked light diesel oil are difficult to remove by hydrogenation, but biological desulfurization is not only easy to remove, but also does not consume hydrogen. Three options can be used for diesel biodesulfurization: First, straight-run diesel plus catalytic diesel is hydrodesulfurized to 500 μg/g, and regenerated diesel is desulfurized to 50 μg/g. ； Second, direct biological desulfurization of direct sulfur diesel to 0.05% to 0.2% ； The third is to catalyze diesel bio-desulfurization to remove 80% of sulfur, and then mix it with direct sulfur diesel for hydrodesulfurization to 50 μg/g. In 2001, a 250,000 t/year industrial device for diesel bio-desulfurization was put into production.