Preparation Of Cu,Co,Ni-based Catalyst By MOCVD And Its Application In GVL Synthesis

As a clean and renewable substance,biomass energy has become a research hotspot forthe catalytic conversion of biomass into liquid fuels and high value-added chemicals.Among them,?-valerolactone(GVL),which is widely used,is one of the important platform compounds.There are many ways to synthesize GVL.In this thesis,ethyl levulinate(EL)was used as a substrate to prepare target product GVL by catalytic hydrogenation under the action of supported transition metal catalysts.The supported transition metal catalysts were used Ni(acac)2,Co(acac)2,and Cu(acac)2 as metal organic precursors and activated carbon as a carrier.The different loadings of Ni/AC,Co/AC,and Cu/AC catalysts were prepared by MOCVD method,and the reaction conditions for EL hydrogenation were optimized.Firstly,Ni(acac)2 was used as an organic nickel metal precursor,and the precursor was loaded onto activated carbon at a temperature of 200 °C.The Ni/AC catalysts were prepared by a simple MOCVD method with different amounts.From the results of XRD,TEM and other characterizations,it could be seen that the size of nickel particles reached nanoscale(average particle size was 5.8 nm)and uniformly dispersed on the carrier.The prepared Ni/AC catalyst was used for the EL hydrogenation reaction.Compared with Ni/AC prepared by the traditional impregnation method,the catalytic activity of that synthesized by MOCVD method was obviously higher.The optimal reaction conditions were: 10 wt% Ni/AC as a catalyst,isopropanol as a solvent,the reaction at 250 °C,1 MPa H2 for 4.5 h.After optimization,EL conversion rate was 100%,and the yield of GVL was 95.2%.Afterward,Co(acac)2 was used as the precursor of cobalt metal to prepare the different amounts of Co/AC catalysts by the same preparation method.The results of XRD,TEM and other characterization methods showed that cobalt nanoparticles uniformly dispersed on activated carbon led to the exposure of more active sites,which was conducive to the EL hydrogenation reaction.Compared with the impregnation method,the catalytic effect is outstanding.After optimization of the reaction conditions,the conversion of EL could reach100% with a 2 wt% Co/AC catalyst,isopropanol as a solvent,250 °C,and atmospheric H2 for4.5 h.The yield of GVL was 97.4% under this reaction condition.Based on the previous experiments,Cu/AC catalysts with different loadings were prepared by the same preparation method,using Cu(acac)2 as an organic copper metalprecursor and activated carbon as a carrier,and applied to EL hydrogenation to prepare GVL.Compared with Cu/AC catalyst prepared by the impregnation method,the catalytic hydrogenation activity of the catalyst prepared by MOCVD method had obvious advantages.It could be known from the results of XRD,TEM and other characterizations that in the catalyst prepared by MOCVD,the copper nanoparticles were uniformly dispersed on the surface of the carrier,and the particle size was small.In addition,the contact area between the metal active sites and the substrate was increased.All the reasons above were favorable for the hydrogenation reaction.In order to improve the conversion of EL and the yield of GVL,the reaction conditions were optimized.The results showed that when 2 wt% Cu/AC was used as a catalyst,isopropanol was used as a solvent,and the reaction was completed at 240 °C and1 MPa H2 for 3.5 h,complete conversion of EL was achieved.The yield of target product GVL was up to 99.7%.