Desulfurization Of 2-phenylcyclohexanethiol Over Mo-based Catalysts

The removal of fused ring sulfur compounds is an important process for the production of clean oil products,and revealing the hydrodesulfurization reaction mechanism is of great significance for the development of catalysts.In this thesis,six catalysts,inclulding MoS₂,Ni-MoS₂ and Co-MoS₂ with Al₂O₃ and SiO₂ as support,were prepared by impregnation method.2-Phenylcyclohexanethiol?2-PCHT?with alkyl C-S bond was synthesized.Desulfurization reaction of 2-PCHT over the aforementioned catalysts and the effect of the nitrogen-containing compound piperidine on the desulfurization reaction were studied in the presence and absence of H₂.in a fixed bed reactor.The reaction network of 2-PCHT and its reaction kinetics over the catalysts under H₂ were studied.By comparing the catalytic characteristics of the six catalysts,the effects of the support,active metal components,reaction atmosphere,and nitrogen-containing compounds on the desulfurization performance were investigated.At 240? and 5.0 MPa H₂,2-PCHT desulfurized through three parallel pathways:hydrogenolysis,?-elimination and dehydrogenation.Hydrogenolysis and?-elimination were the two major pathways,and dehydrogenation pathway contributed slightly.Under Ar,2-PCHT was mainly converted via three parallel pathways:?-elimination,homolytic C-S cleavage or hydrogenolysis,and dehydrogenation,with?-elimination was the major pathway,and the proportion of homolytic C-S cleavage or hydrogenolysis pathway contributed slightly.In the presence of H₂ and Ar,the active center of the?-elimination path or the reaction pathway determined the products of the?-elimination path.The products of the?-elimination pathway included phenyl cyclohexene?PCHEs:1-PCHE,3-PCHE,and 4-PCHE?,and cyclopentylmethylbenzene?CPMB?and cyclopentenylmethylbenzene?CPEMB?which were produced by isomerization of PCHEs.The product of the homolytic C-S cleavage or hydrogenolysis pathway is cyclohexylbenzene?CHB?,whereas the dehydrogenation pathway may lead to ring closure to generate 1,2,3,4-Tetrahydro-dibenzothiophene?TH-DBT?or to desulfurization to yield biphenyl?BP?.The addition of Ni or Co improved the desulfurization activity of 2-PCHT,and the promotion effect of Ni was stronger than that of Co.In the desulfurization reaction,Ni-MoS₂showed the highest intrinsic activity.A pseudo-first-order kinetic model was used to calculate the rate constants of each reaction pathway in H₂.It was found that Ni and Co on both supports promote the?-elimination pathway,and Ni has a stronger promotion than Co.Both Ni and Co had no significant effect on the dehydrogenation pathway.In general,the introduction of Co suppressed the hydrogenolysis pathway.In Ar,according to the total concentration of the products in each pathways,it can be seen that the introduction of Ni and Co also promoted the?-elimination pathway.Both Ni and Co suppressed the homolytic C-S cleavage pathway,and Ni has a stronger inhibitory effect than Co.The dehydrogenation pathway was hardly affected by the instruction of Ni or Co.Research found that piperidine mainly inhibited the?-elimination pathway and the dehydrogenation pathway,and had little effect on the hydrogenolysis or homolytic C-S cleavage pathways.The activity and the nitrogen resistance of Al₂O₃ supported catalysts were higher than those of SiO₂ supported in H₂.In H₂,the hydrogenolysis and?-elimination activities of Al₂O₃ supported catalysts were higher than those of SiO₂ supported ones.In Ar,Al₂O₃ supported catalysts have higher?-elimination activity.Ni and Co reduced the nitrogen resistance of SiO₂,Co enhanced the nitrogen resistance of Al₂O₃,Ni enhanced the nitrogen resistance of Al₂O₃ under H₂,and reduced the nitrogen resistance of Al₂O₃ under Ar.