Preparation Of Au-Pd/AC Catalysts And Catalytic Transfer Hydrogenation Performance For Levulinic Acid-Formic Acid

As the economy booms and the population continues to grow,global energy consumption is increasing day by day.Currently,most of the energy needs and raw materials for chemical synthesis are still derived from non-renewable fossil resources.The non-renewable nature of fossil resources and the series of negative impacts on the environment during the utilization of fossil resources have urged people to look for alternatives to fossil resources.Lignocellulose,as the sole carbon source,produces equimolar formic acid（FA）as a by-product when hydrolyzed to prepare levulinic acid（LA）.Theoretically,equimolar FA and LA can synthesize equimolarγ-valerolactone（GVL）.GVL can be widely used as food additives,high boiling point solvents and fuel additives.Especially,GVL can be used as an organic synthesis intermediate to further synthesize aromatic fuel additives,short-chain olefin jet fuel and long-chain olefin diesel fuel.The synthesis of GVL from equimolar LA and FA in aqueous solution has attracted a lot of attention because of the advantages of atomic economy and low energy consumption due to the reduction of LA distillation.In this thesis,the effects of Au/Pd molar ratio and nitrogen doping in the carrier on the formation of the alloy in Au-Pd/AC catalyst,the dispersion of the active metal and the performance of catalytic LA-FA hydrogen transfer hydrogenation for GVL synthesis in aqueous solution were systematically investigated using various characterization tools.The main studies includes:1.The Au-Pd/AC catalysts with activated carbon（AC）as the carrier were prepared by in situ reduction method to investigate the effect of Au/Pd molar ratio on the catalytic LA-FA hydrogen transfer hydrogenation performance of Au-Pd/AC catalysts and to compare them with those prepared by impregnation and deposition-precipitation methods.The Au₄Pd₁/AC catalyst with Au/Pd molar ratio of 4:1 prepared by in situ reduction method has high active metal dispersion and the presence of high content of Au-Pd alloy,and no single metal Pd is present,and the selectivity of catalytic FA decomposition to H₂ reaches 100%,showing excellent LA-FA hydrogen transfer hydrogenation performance,and the LA conversion&GVL at 240℃reaction for 5 h yield reached 58.68%..2.N-doped carbon carriers were prepared by urea-impregnated AC method and roasted urea-mixed glucose method,respectively,and further Au₁Pd₁ catalysts were prepared by in situ reduction method and compared with the AC-loaded Au₁Pd₁ catalysts.The results showed that the introduction of N in the carrier promoted the formation of Au-Pd alloy in the catalyst and also improved the dispersion of the active metal and the electron transfer from the carrier to the metal,which effectively improved the catalytic LA-FA hydrogen transfer hydrogenation activity.Under the same reaction conditions,the GVL yield increased from 19.97%for Au₁Pd₁/AC to 39.25%for Au₁Pd₁/n-CNS.