Preparation Of Catalysts And Their Alkylation Desulfurization Technology In FCC Gasoline

The technique for low sulfur gasoline has become an important research work in petrochemical industry since the environmental protection is more strictly. Thiophene sulfides account for above eighty percent of the fluid catalytic cracking gasoline(FCC). Enhancement of thiophene sulfides transform ratio during the process of FCC gasoline alkylation is a key to reduce sulfur content. Alkylation in FCC gasoline by solid acid catalyst is an important way to realize environmentally friendly catalysis.Mixed solid acid catalyst and heteropoly acid catalyst were synthesized by MCM-41, silicon, Al₂O₃ and kieselguhr, and employed to desulfurize components of FCC gasoline. After that, we chose catalysts with strongger activities than others and investigated the preparation process of the catalysts. The catalytic activities of alkylation were discussed by characterization.The reaction condition was discussed in terms of sulfides removal rate, such as reaction temperature, reaction time and catalysts/gasoline ratio. Hydrocarbons and sulfides species were investigated before and after alkylation reaction by GC-FID and GC-SCD, it was indicated that olefin and sulphur content was declined, meanwhile some new sulfides are produced.Light and heavy fraction was separated from gasoline by distillation. Sulphur content in light fraction was tested and could be used as the fuel directly. Heavy fraction could be used as the composition of diesel oil.For the mixed solid acid catalyst, the activity of alkylation achieved optimization in the conditions of Mpoly-phosphoric/Mphosphoric-acid=2, Mmixed-acid/MAl₂O₃=6, calcination time=3 h, and calcination temperature=500℃. For the Silica-supported H₃PW₁₂O₄₀.nH₂O, the activity of alkylation achieved optimization in the condition of loading weight 60%, calcination temperature=200℃. For fraction of gasoline with boiling point less than 100℃, the suitable alkylation reaction condition on the solid mixed acid catalyst were Mcatalyst/Mgasoline=1:12, reaction time=80 min, reaction temperature=140℃, sulfides removal rate achieved 86.7%, the sulphur content decreased from 82.38 mg/L to 10.95 mg/L. As the same, the suitable alkylation reaction condition on the Silica-supported H₃PW₁₂O₄₀.nH₂O were Mcatalyst/Mgasoline=1:8, reaction time=110 min, reaction temperature=110℃, the sulphur content decreased from 82.38 mg/L to 10.38 mg/L, sulfides removal rate achieved 87.4%,. After alkylation reaction, in order to separate light and heavy fraction from gasoline by distillation, the distillation temperature was chose on 170℃. The sulphur content is 31.01 mg/L (42.4μg/g).