Study On FCC Gasoline Alkylation Desulfurization Over Solid Phosphoric Acid Catalyst

The technique for low sulfur gasoline has become an important research duty in petrochemical industry since the legislation of environmental protection is more and more strict. Thiophene sulfides accounted for above eighty percent of the fluid catalytic cracking gasoline (FCC). So how to promote thiophene sulfides transform during the process of FCC gasoline desulfurization was the key of reducing sulfur content. While solid phosphoric acid catalyst prepared by kieselguhr and phosphoric acid was an important way of realizing environmental friendly catalysis craft.A series of solid phosphoric acid catalysts were prepared by impregnation method using orthophosphoric acid, pyrophosphoric acid as materials, with kieselguhr and MCM-41 mesoporous molecular sieve as support. The effects of different preparation factors, such as weight ratio of pyrophosphoric acid to orthophosphoric acid, weight ratio of total acid to kieselguhr, calcination temperature and calcination time, and reaction conditions, such as weight ratio of catalyst to gasoline, reaction temperature and reaction time, on FCC gasoline alkylation desulfurization were investigated. The stability of the best catalyst was also preliminary studied.The results indicated that the main factors of influence on the catalytic performance of SPAC were the weight ratio of total acid to support, the influence of the weight ratio of pyrophosphoric acid to orthophosphoric acid and calcination time was smaller. While the reaction temperature was 150℃and reaction time was 1h, the sulfur content in oil fraction under 100℃was reduced from 160.43mg?L-1 to 35.86 mg?L-1, between 100℃and 120℃from305.74 mg?L-1 to80.76 mg?L-1 and above 120℃from 421.49mg?L-1 to 533.19mg?L-1. The stability results showed that when FCC gasoline material was pretreated after resin adsorption, the activity of the catalyst after used five times in sequence in catalyzing alkylation reaction was stable; when FCC gasoline material was not pretreated, the activity of the catalyst was still very stable. Comparison with the performance of the two catalysts prepared with different supports, the results indicated that surface area of supports has not influence on the performance of the catalyst, the main factor of influence on the activity of catalyst was the relatively proportion of orthophosphoric acid silicon and pyrophosphoric acid silicon. The results have shown that the optimum preparation conditions of SPAC by the support of kieselguhr or MCM-41 mesoporous molecular with entire silicon are the weight ratio of pyrophosphoric acid to orthophosphoric acid as 2, the weight ratio of total acid to support as 6, calcination temperature as 500℃and calcination time as 4 h.