Preparation Of Cu/MgO Catalysts By MOCVD And Catalytic Performance

With the development of society,the fossil fuel reserves dwindling,while the demand for energy is increasing.It is imperative to study catalytic conversion of renewable energy into polyols.Supported copper catalysts have the advantages of low cost and high activity,which make them wide applications in catalytic conversion of biomass derivates and the treatment of organic pollutants,etc.In the thesis,MgO supported copper-based catalysts have been successfully synthesized by MOCVD using（hfac）Cu（COD）,Cu（hfac）₂ and Cu（acac）₂ as precursors,respectively,which are used for hydrogenolysis of glucose and hydrogenation of γ-valerolactone.The petaloid Mg（OH）₂ was synthesized from magnesium acetate,ethanol and deionized water by solvothermal method.Porous MgO with 210 m2g-1 was obtained by calcining Mg（OH）₂.The Cu precursor of（hfac）Cu（Ⅰ）（COD）and Cu（Ⅱ）（hfac）₂ were synthesized from cuprous oxide,1,5-cyclooctadiene and hexafluoroacetylacetonate under inert atmosphere.The structure and composition of copper organometallic precursors were confirmed by ¹H NMR and FT-IR.These precursors have strong volatile for the presence of CF₃ group.Based on the data of TG,the two metal-organic precursors could be supported on the Mg O through MOCVD method under 100 ℃ or 60 ℃.Cu/MgO（Ⅰ）and Cu/MgO（Ⅱ）materials with different loading were synthesized successfully.Characterization results of XRD and TEM indicate that Cu nanoparticles in Cu/MgO（Ⅰ）and Cu/MgO（Ⅱ）were uniformly dispersed on the Mg O.The catalytic performance of Cu/MgO（Ⅰ）and Cu/Mg O（Ⅱ）for the hydrogenolysis of glucose（5 wt%）have been evaluated,and all of them exhibited good activity and about 70 % selectivity for 1,2-PD（1,2-propanediol）.The one-pot conversion of glucose led to the formation of coke at high concentration（10 wt%）and high temperature,and further covered the surface of catalysts.Cu/MgO catalysts with different loadings（5.6 wt%,9.0 wt%,11.3 wt%,17.0 wt%）were also prepared by MOCVD method using the organometallic precursor Cu（acac）₂ and MgO at 180 ℃.Characterization results of FT-IR,XRD and TEM shown that there were not small molecule by-product on the catalyst,and Cu particle size was about 20 nm.The catalytic performance of Cu/MgO for the hydrogenation of γ-valerolactone has been tested.With increasing the loadings of copper,the catalytic activity was gradually increased.Compared to reaction H₂ pressure,the effect of reaction temperature on the selectivity of 1,4-PDO（1,4-pentanediol）was much more significant.Under the optimum reaction conditions,the Cu/MgO showed excellent activity and selectivity（>90 %）for 1,4-PDO in the hydrogenation of γ-GVL.The catalytic activity of Cu/Mg O didn’t diminish significantly after cycling for three times.Compared with（hfac）Cu（Ⅰ）（COD）and Cu（Ⅱ）（hfac）₂,Cu（acac）₂ possessed low volatility,but its stability is higher and price is cheaper.Green catalysts with high loadings could be prepared by MOCVD method using Cu（acac）₂ as precursor,which could efficiently reduced the environmental pollution.