The Study Of Oxidative Transformation Of Xylose And1,3-Propylene Glycol Catalyzed By Supported Noble Metal Catal Ysts

With the depletion of non-renewable petroleum-based resources,Bio-based productshavebeendeveloped as potential alternativesof petroleum-based products because of theircompetitivecost,worldwide availability,and renewable.The examples are xylose acid andmethyl3-hydroxypropionate respectively fromxylose and1,3-propanediol,whichcansubstitute the petroleum-based chemicals for the sustainable development of chemicalindustry.However,the conventional methods to produce chemical products have muchdefects,like complex production process,erode equipment,complicated separation process andharm to environment and so on. So developing a synthetic route that realizesenvironment-friendly industrial production is necessary.Recently,supported metalcatalysts,with its unique catalytic activity attract more and more attention.Among them,Pdand Au,noble metal nanometer catalyst with its stable chemical activity and high catalyticactivity is attractinggreat interest. Westudied thereaction conditions of xylose acid preparedfrom xylose catalyzed by Pd/C, which uses air as oxidant and water as solvent. Au/CeO2andAu/Al2O3catalysts with CeO2and Al2O3respectively as support were prepared by adeposition-precipitation method and tested for the1,3-propanediol oxidativetransformation.Three aspects of our research work were summarized.1.Wedid a research on reaction conditions of preparing xylose acid catalyzed by Pd/C, whichuses air as oxidant and water as solvent.Different parameters which may affect catalyticperformance,such as pH,temperature,substrate concentration,the dosage of catalystwereresearched.On conditions of pH=9,Vair=0.4L/min,nxylose:nPd=170:1of the system for4hours at50℃,the substrate conversion and the product selectivity can be up to99.2%and99.1%,respectively.Besides,under the optimum condition,the Pd/C catalyst can be recovered and usedmany times,and the frequency of use of the recovered catalyst has no effect on selectivity.2.Au/CeO2catalysts with CeO2Nano-cube as support were prepared by adeposition-precipitation method and tested for the oxidative transformation of1,3-propanediol.We studied the different parameters which may affect catalytic performance,such as mass ratio (urea:ceria),the loading temperature,the calcination temperatureAu/CeO2,the reactiontemperature.The1.5wt%Au/CeO2on conditions of murea:mceria=3:1,the loading temperature80℃,the Au/CeO2calcination temperature350℃,the reaction temperature111℃of thesystem for4hours,the substrate1,3-propanediol conversion and the selectivity of main productmethyl3-hydroxypropionatecan be up to96.4%and63%,respectively.3.Au/Al2O3catalysts with γ-Al2O3as support were prepared by a deposition-precipitationmethod and tested for the oxidative transformation of1,3-propanediol.We also studied thedifferent parameters which may affect catalytic performance,such as the gold loading, thedosage of1.5wt%Au/Al2O3catalyst,the catalyst calcination temperature,the reactiontemperature.The characterization of catalyst was measured by XRD,TEM,H2-TPR,NH3-TPDand CO2-TPD,and the results were related to the catalytic performance. The1.5wt%Au/Al2O3on conditions of the gold loading1.5%,0.24g1.5wt%Au/Al2O3catalyst, theAu/Al2O3calcination temperature350℃, the reaction temperature97℃of the system for4hours,the substrate1,3-propanediol conversion and the selectivity of main product methyl3-hydroxypropionatecan be up to94.8%and77.5%respectively.