Preparation Of Hydrotalcite-like NiCu-Al₂O₃ Catalyst And Catalyic Hydrogenation Of Levulinic Acid To ?-Valerolactone

With the rapid development of the global economy,human dependence on fossil resources has become increasingly serious.Due to the non-renewable nature of fossil resources,people have begun to pay attention to and develop renewable energy.Among the many renewable energy sources,biomass has attracted widespread attention as the only carbon-containing resource.Levulinic acid(CSH8O3,LevuIinic acid,LA)can be prepared from the widely existing lignocellulose through acid-catalyzed hydrolysis.It is a basic raw material for the synthesis of various light chemical products and an important biomass-based chemical.Using levulinic acid and its esters as raw materials,a series of high value-added chemicals such as y-valerolactone,1,4-pentanediol,2-methylfuran,and valerate can be synthesized by hydrogenation.Among them,y-valerolactone is widely used in the fields of food additives,fuel additives,solvents,gasoline,diesel,and the synthesis of various chemical intermediates.It is considered to be the most promising biological platform molecule for the production of renewable fuels and chemical products one.Hydrogenation of levulinic acid as a raw material to produce valerolactone has attracted much attentionIn this thesis,a series of hydrotalcite-like Ni-Al2O3 and NiCu-Al2O3 catalysts were prepared,and various characterization methods were used,such as XRD,TG-DTG,FT-IR,in situ FT-IR,HRTEM,and H2-TPR/TPD and other systems have studied the hydrotalcite-like intercalation anion,the formation of Cu-Ni alloys,and the Ni/Cu molar ratio on the texture,structure,and surface properties of hydrotalcite-based catalysts and the direct hydrogenation of levulinic acid/levulinate Of hydrogen/hydrogen transfer hydrogenation to y-valerolactone properties.The main research contents and conclusions are as follows:1.The effects of hydrotalcite-like intercalation anions on the texture,structure and catalytic performance of levulinic acid hydrogenation over Ni-Al2O3 catalysts were studied.The results show that intercalation anions have important effects on the active metal-support interaction,active metal dispersion,surface acid properties,and catalytic performance of levulinic acid hydrogenation in the catalyst.Compared with the catalyst prepared with NO3-intercalated hydrotalcite as precursor,there is a strong interaction between CO32-and Laminate hydroxyl in the precursor of CO32-intercalated hydrotalcite.Laminate hydroxyl is removed quickly,and the obtained catalyst exhibits strong metal-support interaction,high metal dispersion,and abundant L acid acid centers Under the synergistic effect of active metal and L acid,the catalyst It exhibits high C=O hydrogenation activity,high ?-valerolactone yield,and high cycle stability.The yield of?-valerolactone reached 71.82%when reacted with methanol as a solvent at 160 0 C and 4 MPa hydrogen pressure for 1 h.When the catalyst was used 6 times,the activity remained almost constant2.NiCu-Al catalyst was prepared with hydrotalcite-like precursor,and isopropanol was used as the hydrogen source.The performance of the catalyst for hydrogen transfer hydrogenation of ethyl levulinate to valerolactone was studied.The prepared NiCu-Al catalyst and the hydrotalcite-like Ni-Al and Cu-Al catalysts were compared.The results show that the formation of Ni-Cu alloy in the catalyst significantly improves the conversion of ethyl levulinate and the selectivity to ?-valerolactone,and the catalytic performance of bimetal catalysts is significantly better than that of single metal catalysts NiCu-Al prepared with hydrotalcite-like precursor formed a uniform Ni-Cu alloy structure,and the catalyst showed high active metal dispersion and rich acidic center.The reaction temperature was 160? and the reaction time was 4 At h,the yield of the target product ?-valerolactone was 96.64%The effects of the molar ratio of Ni/Cu on the texture,structure,surface properties and catalytic performance of levulinic acid/levulinate hydrogenation hydrogenation of NiCu-Al catalysts were studied.The results show that when Cu species are introduced into the Ni3Al catalyst,with the increase of Cu content,the conversion rate of acetopropene/ethyl levulinate and the yield of ?-valerolactone increase first and then decrease.At 2:1,the yield of ?-valerolactone was the highest.