Preparation Of Nickel-based Catalyst And Catalytic Study Of Hydeogenation Of Fatty Acid Methyl Ester

Fatty acid methyl ester sulfonate is a renewable alternative product of petroleum derivative alkylbenzene sulfonate,which can be prepared by sulfonation of fatty acid methyl ester.Unsaturated components in fatty acid methyl ester will affect its sulfonate performance.The preparation of hydrogenation catalyst is of great significance for increasing the saturation of fatty acid methyl ester,which could meet the requirements of sulfonate performance.In this thesis,Ni which has high hydrogenation activity,is selected as the active component.A series of nickel-based catalysts are prepared with different technologies,such as employing different carriers and introducting citric acid as an additive,and were evaluated by the hydrogenation activity of the fatty acid methyl ester.The main research contents are as follows:（1）Al₂O₃,SiO₂ and TiO₂ were selected as carriers to prepare Ni/Al₂O₃,Ni/SiO₂,and Ni/TiO₂ catalysts.XRD,XPS,TEM,H₂-TPR and other characterizations methods were used to characterize the pore structure parameters of the carrier and catalyst,the dispersion of Ni species,and the redox performance of metal oxides.The research results showed that Al₂O₃ had a proper specific surface area and proper interaction between the Ni species and the carrier,resulting in better dispersion of Ni species and smaller particle size,and Ni/Al₂O₃ gave the best catalytic activity.Under the reaction conditions of 190℃,3 h,2wt%of catalyst and 2.5 MPa,Ni/Al₂O₃ catalyst reduced the iodine value from 61 to 0.68.（2）Through the impregnation process,citric acid was introduced to prepare Ni-CA/Al-1.XRD,FT-IR and TEM were used to characterize the influence of citric acid and its addition on the pore structure parameters of Ni-based catalysts,the redox performance and the particle size and dispersion of Ni species,and the catalytic study in the hydrogenation of fatty acid methyl esters was evaluated.The addition of citric acid in the catalyst preparation process increased the specific surface area,and had a positive impact on the porosity.In addition,the interaction force between the Ni species and the carrier was weakened,making the nickel oxide easier to be reduced.The Ni particle size is smaller and the distribution is more uniform.The Ni-CA/Al-1 catalyst had better hydrogenation performance.Ni-CA/Al-x catalysts with different addition ratios were prepared by changing the addition amount of citric acid to further investigate the relationship between the citric acid addition ratio and the structure.The catalysts were characterized by XRD,N₂ adsorption and desorption,and TEM.It was found that the specific surface area of Ni-CA/Al-x catalyst increases first and then decreases with the increase of citric acid addition,and the size and distribution of Ni crystallites also showed this trend.When Ni-CA/Al-1is used as catalyst,the iodine value of the product can be reduced from 61 to 0.2,under the conditions of a reaction temperature of 190℃,reaction time of 3 h,catalyst amount of 2 wt%,reaction pressure of 2.5 MPa.（3）The technologies of catalyst preparation process were studies,including different calcination temperatures and reduction temperatures,N₂ adsorption and desorption,XPS,elemental analysis and TEM were employed to study the structure and Ni species of the catalyst.in the catlaysts were evaluated with the hydrogenation reaction of fatty acid methyl esters.It was found that changes in the calcination temperature and reduction temperature affected the pore structure parameters of the catalyst,the redox performance of the Ni species in the catalyst precursor,the residual carbon content after the decomposition of citric acid,and the interaction force between the Ni species and the carriers.As the calcination temperature decreased,the specific surface area and residual carbon content of the catalyst showed an increasing trend,and the dispersion of Ni species was better.The hydrogenation activity showed a trend of increasing with the decrease of calcination temperature,and increased first and then decreased as the reduction temperature increases.The catalyst prepared with calcination temperature of 300°C and reduction temperature of 450°C exhibited the best hydrogenation performance.Under the reaction conditions of 190℃,3 h,2 wt%of catalyst and 2.5 MPa,the iodine value of the reactant can be reduced from 61 to 0.08.