Molybdenum Carbide-based Catalysts Are Used In The Hydrogenation Reaction Of Ethyl Levulinate

As a renewable resource,Biomass can be converted into liquid fuels and carbon-based chemicals.Hydrogenation of levulinic acid and its esters to produceγ-valerolactone is one of the effective routes for biomass conversion.In this dissertation,a series of metal-doped molybdenum carbide catalysts were prepared and characterized by XRD,XPS,HRTEM,H₂-TPR,etc.,and its catalytic performance was investigated in the hydrogenation of ethyl levulinate toγ-valerolactone.A series of Fe-doped Mo₂C catalysts were prepared by using ionic liquid synthesized by citric acid and N-methylimidazole,and a solution of Fe Cl₃ and ammonium molybdate as precursors.And the effects of the kind of precursors and the molar ratio of metal to carbon in the precursors on Fe-doped Mo₂C were investigated.Under the condition reaction temperature of 260℃,H₂ pressure 1.5 MPa and catalyst dosage 0.13 g,Fe-Mo₂C-1:18,which was prepared from the precursor with 1:18 of n（M）/n（C）,is used as a catalyst for the hydrogenation of ethyl levulinate,and the complete conversion of ethyl levulinate and the 95.9%selectivity ofγ-valerolactone were obtained when the reaction was carried in water for 8 h.It was because the interaction between oxygen and the catalyst surface is enhanced when the Fe species was introduced in the Mo₂C catalyst and it is beneficial to the activation of the reaction substrate.After the catalyst was used 4 times in succession,its catalytic performance decreased slightly due to the loss of active components and the carbon deposition on the catalyst surface.A series of cobalt-doped molybdenum carbide catalyst Co-Mo₂C were prepared by using ionic liquid synthesized by citric acid and N-methylimidazole,and a solution of cobalt acetate and ammonium molybdate as the precursors.And the effects of the molar ratio of metal to carbon in the precursor and preparation temperature on Co-Mo₂C were investigated.In the presence of Co-Mo₂C-1:8-700,which was prepared by using the precursor with 1:8 of n（M）/n（C）at 700℃,ethyl levulinate was completely converted and the 95.4%selectivity ofγ-valerolactone was achieved when the hydrogenation of ethyl levulinate was performed in water for 6 h under 220 ^oC and 1.5 MPa with 0.07 g catalyst.It was because,during the reaction,there is the synergy between Co and Mo₂C in the catalyst and the water phase system is also helpful to reduce the energy barrier required for the reaction.After the catalyst was cycled 4 times,the catalytic performance of Co-Mo₂C-1:8-700 was decreased.Using a mixed solution of glucose,nickel chloride and ammonium molybdate as the precursor,a series of Ni-doped Mo₂C catalysts were prepared.Employing Ni-Mo₂C-1:8 as a catalyst,The hydrogenation of ethyl levulinate was carried out under the conditions of reaction temperature 200℃,H₂ pressure 1.5 MPa,catalyst dosage 0.07 g in H₂O for 3 h,ethyl levulinate was completely converted and the selectivity ofγ-valerolactone was 95.8%.The reusing ability of Ni-Mo₂C-1:8-700 was evaluated under the optimal reaction conditions,and the catalyst was deactivated after 3 cycles.