Hydrodeoxygenation Of Lignin Over Transition Metal Phosphide Catalysts

Lignin is a kind of lignocellulose,whoes regeneration rate is very fast,has the bright prospect of producing fossil fuels and high value-added chemicals instead of fossil fuels.Under the suitable catalysts,the high selectivity of high value-added target products for catalytic hydrodeoxygenation of lignin is an important means for its comprehensive utilization.As a new type of hydrogenation catalyst,transition metal phosphide has the incomparable advantage of traditional catalysts in hydrodeoxygenation and important research value in the comprehensive utilization of lignin.In this thesis,the HDO reactivity on phosphide catalysts and lignin model compounds with different C-C bonds and C-O bonds was investigated.Firstly,we designed and synthesized molybdenum-based phosphide catalysts with different metal promoters.By means of XRD,TEM and SEM,we know the composition and structure of the catalyst.Using guaiacol as reactant,the bimetallic synergistic effect was studied,and the effect of adding different additives on the structure and HDO performance of the catalyst was explored.The molybdenum-based bimetallic phosphide catalyst Fe Mo P/SiO₂ is the most suitable one for the Production of Phenolic Products.Under the conditions of the temperature of 325°C and the initial hydrogen pressure of 5.5MPa,the conversion rate of guaiacol reached 99.4% and the total yield of phenols reached 73.6%.Then by adjusting the molar ratio of Fe/Mo,six different ratios of iron molybdenum phosphide catalysts were prepared by the same method to explore the effect of different Fe/Mo ratio on the catalyst structure and HDO performance and found that the addition of excess Fe will lead to the decline of the catalyst activity.When the Fe/Mo 1:3,we can get the highest selectivity to the phenolic products with the stable conversion rate.The reaction path of the catalyst and the catalyst recycling were investigated.Meanwhile,the catalytic performance of the catalyst in the hydrodeoxygenation of other common lignin model compounds was also evaluated.Finally,a series of other types of supported transition metal phosphides catalysts were prepared by temperature-programmed reduction method.The guaiacol was used as a reactant to investigate its hydrodeoxygenation performance.The activity and product distribution of Ni2P/SiO₂ catalyst is explored from the temperature,pressure and reaction time.The product of the guaiacol HDO reaction on this catalyst system is relatively simple,with only cyclohexane,phenol and anisole.Under the condition of the initial hydrogen pressure of 4MPa at a temperature of 300°C for 2h,the conversion rate of guaiacol is 95.1% and cyclohexane yield is 86.4%,then with a prolonged reaction time to 6h,the yield of cyclohexane reached 98.8%.The research in this thesis provides a scientific basis and theoretical guidance for the development of a new type of high-efficiency catalytic conversion system of lignin.