Preparation And Viscosity Reduction Performance Of Coated Magnetic Hydrocracking Catalysts

The high content of asphaltene and colloid in heavy oil leads to high viscosity and poor fluidity.The key to realize efficient processing and utilization of heavy oil is to reduce viscosity and improve oil quality.Hydrocracking upgrading and viscosity reduction technology can achieve the dual benefits of permanent viscosity reduction and quality improvement,so it has great potential for development.The hydrocracking catalyst suitable for heavy oil is the core of hydrocracking upgrading and viscosity reduction technology.In this study,the coated hydrocracking catalyst with magnetic function was prepared and used to evaluate the viscosity reduction of heavy oil.Using Fe₃O₄magnetic nanoparticles and Fe-Fe₂O₃ magnetic nano-chain as magnetic cores,the Si O₂modified layer and Al₂O₃ carrier layer were coated respectively,and the active components of Co and Ni were loaded to obtain the supported magnetic hydrocracking catalyst.By increasing the nucleation growth time of alumina precipitation and ultrasound-assisted dispersion,alumina gel suspension with uniform magnetic core dispersion was obtained,and the alumina coating rate of almost 100%was achieved by centrifugal separation and calcination molding.According to the characterization and analysis of SEM,the sample of Fe₃O₄@Si O₂@Al₂O₃@Co Ni is irregular,the surface is honeycomb,and the particle size is micron（1.5～30μm）.In addition,VSM tests showed that the catalyst sample has a high saturation magnetization,which can reach 24.91 emu/g.Because of the special chain structure,the Fe-Fe₂O₃@Si O₂@Al₂O₃@Co Ni series catalysts improve the dispersion of the samples during the coating process,so that the catalysts have more significant honeycomb surface structure and smaller particle size（1.5μm）.However,the iron element is unstable,which is easy to be oxidized to iron oxide and lose its high magnetic advantage during the calcination process.VSM tests showed that the saturation magnetization of Fe-Fe₂O₃ and its catalyst sample are 110 emu/g and 14.63 emu/g,respectively.A dispersed magnetic catalyst Fe-Fe₂O₃@PDA@Mo S₂ without calcination was prepared by using Fe-Fe₂O₃ nanochain as magnetic core and polydopamine（PDA）as modified layer.PDA can realize the functionalization of hydroxyl on the surface of nano-chain,and make use of the reducibility of hydroxyl to realize the effective grafting between magnetic core and Mo S₂.In addition,the thickness of PDA coating can be effectively regulated by controlling the concentration of dopamine solution,and PDA films of about 5 nm and 10 nm were prepared respectively.Compared with the metal supported catalyst,the active component loading of Mo S₂ dispersed catalyst is higher,up to 20 wt%.SEM micro-morphology analysis showed that Mo S₂ nanoflakes,like petals,can be almost completely exposed on the surface of magnetic nano-chain,increasing the hydrogenation active site of the catalyst.In addition,the XRD test showed that there is still obvious crystal structure of Fe in the magnetic Mo S₂,indicating that the preparation method makes the magnetic nanochain stable,so the magnetism of the catalyst can be high,and VSM test showed that the saturation magnetization of the sample is 36.3 emu/g.The prepared magnetic hydrocracking catalyst was used to evaluate the viscosity reduction of residue of Canadian oil sands asphalt and Venezuelan crude oil.The viscosity reduction performance of metal supported catalyst is closely related to its surface structure.The calcination and chain structure of Al₂O₃ contribute to the formation of honeycomb surface morphology of the catalyst,thus increasing the specific surface area and improving the hydrogenation activity.Among them,the viscosity reduction rate of Fe-Fe₂O₃@Si O₂@Al₂O₃@Co Ni with active metal loading of 2.6 wt%was the highest,which was 97.70%.In addition,because of the high magnetism of iron and high content of active components,the viscosity reduction of Mo S₂ dispersed catalyst is better than that of supported catalyst,and the viscosity reduction rate of heavy oil is up to 99.92%,which is higher than the reported viscosity reduction rate of 75%～99.8%.There are 40 figures,16 tables and 111 references in this paper.