| Light oil products mainly contain some organic sulfur compounds such as mercaptan-type, sulfides-type and thiophenes-type. It is the basis of developing new desulfurization method to discuss the reaction of these organic sulfides. At present, there are far from enough to investigate the catalytic reaction especially catalytic reaction course of organic sulfides at the point of molecular level.The thermal conversion and catalytic desulfurization conversion and mechanism of thiophene as probe molecules over acidic HZSM-5 and Cu modified HZSM-5 zeolites have been studied in a fixed-bed micro-reactor.The transformation mechanism of thiophene over acidic catalysts were all carbenium ion mechanism. thiophene over HZSM-5 zeolite catalysts were to transforming to yield hydrogen sulfide. The transformation of thiophene were more easily with more strong acidity of catalysts. Thiophene may be transformed while the reaction temperature got up to 300℃; cracked and converted into H2 S over HZSM-5 zeolite catalyst while the reaction temperature exceeds 350 ℃.As a main product, THT is formed in the course of the cracking-desulfurization of thiophene; The cracking reaction of thiophene could be carried out only at high temperature over HZSM-5 zeolite, and coke was formed with a small part hydrogen sulfide in the absence of hydride donor.Alcohol-type substances especially methanol have not only certain polarity, but also better reaction activity, they are usually as reaction assist to accelerate the reaction. The transformation reaction of organic sulfur compounds in the presence of methanol have been discussed in the paper. It is found that their thermal conversion pathway of thiophene can change after the addition of few methanol. The transformation of isobutyl mercaptan was favorable if the volume ratio of methanol and benzene was 0.2.The addition of methanol assume certain effect on the catalytic cracking of thiophene in solvent benzene but without changing the cracking reaction mechanism of thiophene. The reaction mechanism of thiophene is investigated, and the key step of cracking reaction is the rupture of C-S bond. Formation mechanism of THT can be that carbenism ion attack primary carbon hydrogen and cyclize in the cooperation course of primary carbon and sulfur.Thiophene conversion is increased and the cracking temperature of thiophene is remarkably decreased when methanol is added to the feed. At the same time, thiophene converted into main product of hydrogen sulfide other than evolving alkyl-benzothiophenes in the presence of hydrogen donor methanol. The yield of hydrogen sulfide is favored at high temperature and in the presence of much methanol and low space velocity. In addition, the conversion of thiophene increases while sulfur content in stocks decreases, but the thiophene is more inclined to form alkyl-benzothiophenes to give large amounts of coke.There were facilitation for the catalytic transformation of isobutyl mercaptan over Cu modified HZSM-5 zeolites catalysts and there was better effect while the content of 1.0% Cu was dipped. The Cu modified HZSM-5 zeolites catalysts by impregnant show higher cracking conversion of sulfide than parent HZSM-5 zeolite, and the yield of THT increases. |
