Study On Selective Hydrodeoxygenation Of Levulinic Acid From Biomass Platform To Preparation Of Alcohol-ether Fuels

The conversion and utilization of biomass resources can not only realize the resource utilization of a large number of agricultural and forestry wastes in China,but also effectively reduce carbon dioxide emissions and alleviate the severe situation of energy shortage.However,the catalysts currently used for the catalytic conversion and utilization of biomass present precious metals with good activity but high price,non-precious metals with low price but poor activity,which is not conducive to large-scale industrial application.Based on this,two nano-metal catalysts,Ni-Co and Ni-Mn,were synthesized by the impregnation method using nano-alumina as the carrier,which was used for the hydrodeoxygenation reaction of levulinic acid on the biomass platform molecule.The structure properties and selection of the catalyst were studied.The relationship between the deoxidation and the optimization of the catalyst and the optimization of the reaction conditions have resulted in higher product yields.At the same time,the hydrodeoxygenation reaction path of levulinic acid has been studied.The Ni-Co/Al₂O₃ catalyst prepared with nano-alumina as the carrier and nickel nitrate and cobalt nitrate as the metal source showed high hydrogenation of levulinic acid to?-valerolactone in the temperature range of 100?-150?.After optimizing the metal ratio,it was found that the 15%Ni-15%Co/Al₂O₃ catalyst had the highest catalytic activity.Using this catalyst to optimize the reaction conditions,the reaction was performed at 110?and 3 MPa H₂ pressure for 2 h,The yield of?-valerolactone could reach 99.5%.The XRD characterization results of the catalyst showed that Ni and Co formed a mixed oxide during the calcination process,and this mixed oxide played an important role in the catalytic hydrogenation of levulinic acid after reduction.After five cycles of the catalyst,the conversion rate of levulinic acid was 90.5%,and the selectivity of?-valerolactone was 97.8%,which indicating that the catalyst has good cycle stability.After multiple cycles of reaction,due to the oxidation and loss of metal on the catalyst surface,the conversion of levulinic acid will continue to decrease.In an aqueous reaction system of 15%Ni-15%Co/Al₂O₃ catalyzed hydrodeoxygenation of levulinic acid,2-methyltetrahydrofuran appeared in the product when the temperature increased to 200?.Considering the effect of water solvents on the yield of 2-methyltetrahydrofuran,through solvent screening,it was found that under the same reaction conditions,the yield of 2-methyltetrahydrofuran was greatly improved by using isopropanol as a solvent.After optimizing the metal ratio,it was found that the yield of 2-methyltetrahydrofuran catalyzed by 5%Ni-25%Co/Al₂O₃ was the highest.At 240?and 5 MPa H₂ pressure for 5 h,the yield of 2-methyltetrahydrofuran reached 73.4%.Because the temperature and pressure of the reaction system are relatively high,the active metal on the catalyst surface is more easily lost,which affects its cycle stability,but its low cost makes it still have industrial application prospects.The Ni-Mn bimetal catalyst prepared with nano-alumina as the support and nickel nitrate and manganese carbonate as the metal source catalyzes the hydrodeoxygenation of levulinic acid in isopropanol solvent,showing high selectivity to 2-butanol.15%Ni-15%Mn/Al₂O₃ catalyzes the hydrodeoxygenation reaction of levulinic acid at 250?and 5MPa H₂ pressure for 4h,the yield of 2-butanol can reach 84.7%.In the XRD characterization results of the catalyst,we know that the presence of Mn increases the dispersibility of Ni on the catalyst surface,and Ni and Mn play a synergistic role in the reaction.In the gas phase after the reaction,CO and CH₄was detected.Based on this,a possible reaction path was proposed through analysis.The catalyst does not have good cycle stability under high temperature and pressure,but its low cost is a great advantage.