CeO₂/ZrO₂-modified Mesoporous Ni/C-SiO₂ Catalysts For Hydrodeoxygenation Reaction

Bio-oil resulting from the fast pyrolysis of biomass is a renewable carbon-neutral source of energy. It is considered to be one of the most potential alternatives of the fossil fuel, which is being gradually depleted. However, the fact that bio-oil has high oxygen and water content, high corrosive and unstability, makes that bio-oils must be upgraded before using in motor vehicle. Catalytic hydrodeoxygenation(HDO) has been demonstrated to be a promising upgrading technology. Through HDO the oxygenated compounds in bio-oil can be converted into hydrocarbons. After separating the oil and aqueous phase, the product which is similar to crude oil are obtained. In the HDO process, catalysts are crucially important. In this thesis, we prepared a series of nickel based catalyst and investigated their catalytic activity in the oil-aqueous biphasic system.Amphiphilic carbon-silica nanocomposites were synthesized via a solvent evaporation induced self-assembly(EISA) method. After co- impregnation of N i and CeO2, ceria-doped Ni/carbon-silica nanocomposites catalysts were obtained. The structural analysis indicates that all the catalysts have highly ordered mesostructure with different CeO2 loading, and the size of nickel particle is 5.4 nm, and the pore size is about 6.4 nm. We selected a mixed solution of 30 mL decalin and 10 mL deionized water to simulate bio-oil and phenol as model compound, after reaction at 250℃, 5 MPa hydrogen pressure for 2 h, the conversion of phenol is only 16.6% on 5Ni/CS, while the value on 5N i-14.7Ce/CS is 96.7% and the selectivity of cyclohexanol is 85.0%.We chose C-SiO2 as support and zirconia as additives. By impregnating N i and ZrO2 step by step on the amphiphilic mesoporous C-SiO2 composites, zirconia-doped Ni/carbon-silica catalysts were prepared. The structural analysis indicates that all the catalysts have highly ordered mesostructure, the pore size is about 6.4 nm. The size of nickel and zirconia particle is 5.0 nm 20 nm. After catalytic hydrotreatme nt of phenol in oil/water system at 280℃, 5 MPa hydrogen pressure for 4 h, the phenol conversion is over 90.0% on different catalysts. With increasing the zirconia loading, the content of cyclohexanol gradually reduced in products, and the content of cyclohexene gradually increased. When the zirconia loading increased to 15%, the selectivity of cyclohexene reached to 55.0%. Furthermore, we found that the product selectivity can be varied if changing the reaction system. In a pure water system, phenol is mainly translated into cyclohexanol and cyclohexanone, with the selectivity of 67.8% and 32.2% respectively. In pure oil system, phenol is primarily converted into cyclohexane, with the selectivity of 97.6%. So we can selectively control the product selectivity by changing the reaction system.