Study on the in situ desulfurization and viscosity reduction of heavy oil over MoO_(3)–ZrO_(2)/HZSM-5 catalyst

Heavy oil is characterized by high viscosity.High viscosity makes it challenging to recover and transport.HZSM-5,MoO_(3)/HZSM-5,ZrO_(2)/HZSM-5 and MoO_(3)–ZrO_(2)/HZSM-5 catalysts were developed to promote in situ desulfurization and viscosity reduction of heavy oil.The physical and chemical properties of catalysts were characterized by XPS,XRD,TEM,NH3-TPD,etc.The effects of temperature,catalyst type and addition amount on viscosity and composition of heavy oil were evaluated.The results showed that the presence of MoO_(3)–ZrO_(2)/HZSM-5 nanoparticles during aquathermolysis could improve the oil quality by reducing the heavy fractions.It reduced viscosity by 82.56%after the reaction at 280℃ and catalyst addition of 1 wt%.The contents of resins and asphaltic in the oil samples were 5.69%lower than that in the crude oil.Sulfur content decreased from 1.45%to 1.03%.The concentration of H2S produced by the reaction was 2225 ppm.The contents of sulfur-containing functional groups sulfoxide and sulfone sulfur in the oil samples decreased by 19.92%after the catalytic reaction.The content of stable thiophene sulfur increased by 5.71%.This study provided a basis for understanding the mechanism of heavy oil desulfurization and viscosity reduction.

Study on the mechanism of hydrodesulfurization of tetrahydrothiophene catalyzed by nickel phosphide

Hydrodesulfurization(HDS)reaction can significantly reduce the viscosity and sulfur content of heavy oil,while the HDS reaction mechanism of tetrahydrothiophene as the main sulfide in heavy oil is still unclear.The HDS experiment of tetrahydrothiophene catalyzed by nickel phosphide(Ni_(2)P)is carried out at 200-300°C.The results indicate that the H_(2)S production under the catalysis of Ni_(2)P increases obviously within 200-250°C.The main gas products of HDS reaction are butane,butene and H_(2)S.Meanwhile,the mechanism of tetrahydrothiophene catalyzed by Ni_(2)P is analyzed based on Density Functional Theory(DFT).It is revealed that the adsorption model is most stable when tetrahydrothiophene is vertically adsorbed on the V-Ni-Hcp1 site of Ni_(2)P(001).The C-S bond is elongated and the C-C bond is shortened after adsorption.Hydrogenation(HYD)is the most possible reaction route of tetrahydrothiophene on Ni_(2)P(001)surface.There are two routes with the lowest activation energy,which are C_(4)H_(8)S→C_(4)H_(8)SH^(*)→C_(4)H_(9)SH^(*)→C_(4)H_(10)+H_(2)S and C_(4)H_(8)S→C_(4)H9S^(*)→C_(4)H_(9)^(*)+SH^(*)→C_(4)H_(10)+H_(2)S.Butane and H_(2)S are produced in the reaction,corresponding to the experimental results.This study provides a basis for understanding of the HDS mechanism of tetrahydrothiophene catalyzed by Ni_(2)P.