Preparation Of Metal Catalysts And Their Performance For Selective Oxidation Reaction Of Glycerol

Against the backdrop of global warming and resource constraints,sustainable new energy sources have received widespread attention.As an important biomass resource,the production of biodiesel is accompanied by the generation of a large amount of glycerol by-products,and the disposal of excess glycerol also causes great pressure on the environment.Therefore,the conversion of glycerol（GLY）into high value-added chemicals is an effective way to improve the comprehensive economic benefits of the diesel production industry.Selective oxidation reaction of glycerol is an environmentally friendly and economically efficient catalytic route that has received a lot of attention in recent years.Glyceric acid（GLYA）and lactic acid（LA）,the typical oxidation products,are the most promising bio-based polyester monomer feedstocks in the 21st century,which are favored by researchers.The use of traditional biological enzyme fermentation process to produce glyceric acid and lactic acid is inefficient and expensive,so the catalytic conversion of glycerol has stronger practical significance.In view of the above issues,based on the high thermal stability and chemical stability of Zr O₂ materials,which are also the only metal oxides with acid-base,reducing and oxidizing ability,supported noble metal catalysts（Pt/Zr O₂-T）and composite metal oxide catalysts（Cu Zr-MMO）were prepared towards glycerol selective oxidation to glyceric acid and lactic acid,respectively.The performance enhancement of the glycerol oxidation reactions has achieved under mild reaction conditions through fine tuning of the catalyst geometry/electronic structure.The structure-property relationship has been investigated through performance control experiments and in situ characterization techniques to further reveal the catalytic reaction pathways.The specific research and results of this thesis are as follows:1.Preparation of Pt-based catalysts and their catalytic performance for selective oxidation of glycerolPt clusters catalysts supported on zirconium dioxide were prepared based on a two-step preparation procedure:monoclinic Zr O₂ precursors（m-Zr O₂）were synthesized via a hydrothermal method and then calcined at 500°C,followed by a wet impregnation with Pt loading and a reduction treatment at different temperatures（250,350 and 450°C）.The catalyst Pt/Zr O₂-T was then used towards selective oxidation of glycerol.The optimized catalyst Pt/Zr O₂-350 shows high catalytic performance（conversion:92.9%;GLYA selectivity:64.9%）,with a formation rate of 277.1 mmol _GLYA g _Pt^-1 h^-1.which is preponderant to previous catalysts performed under identical reaction conditions.Experimental methods（HR-TEM,XAFS,XPS and Raman）confirms the formation of Pt^δ+-O_v-Zr³⁺structure at the metal-support interface,which serves as the intrinsic active site.A synergistic catalysis mechanism is demonstrated based on in situ FT-IR spectroscopy:the primary C-O bond of glycerol experiences bridge adsorption at Pt^δ+and Zr³⁺sites whilst O_v acts as active center for the formation of active oxygen species.This work demonstrates a valid paradigm for the development of heterogeneous catalysts via adjusting the metal-support synergistic effect towards selective oxidation reactions.2.Preparation of Cu Zr composite metal oxides and the catalytic properties for glycerol conversionA series of Cu Zr composite metal oxide catalysts were prepared and used in the production of lactic acid via anaerobic oxidation of glycerol.The activity of glycerol and the selectivity of lactic acid could be improved by Cu Zr-MMO（30 h）under relatively mild conditions（200°C,1.5 MPa N₂,8 h）,and the highest yield of lactic acid is more than 80%.Through the combination of XRD and SEM characterizations,the successful synthesis of Cu Zr composite metal oxides is confirmed.XPS results show that the significant differences in the Cu⁺/Cu²⁺ratios of the three catalysts（Cu Zr₂-MMO,Cu Zr-MMO,Cu₂Zr-MMO）.Control experiments demonstrate that the electronic structure of the catalysts Cu⁺/Cu²⁺makes an impact on the catalytic performance.This thesis work provides some theoretical guidance for the rational design and preparation of catalysts for the catalytic conversion reactions of glycerol.