Studies On Novel Ru-Mn Catalytic Materials With Multi-center Structure For Green Selective Oxidation Of Alcohols

The dissertation aimed at molecular oxygen activation and product selectivity, which were consideredto be the most concerned problems in the green selective oxidation of alcohols with molecular oxygen. Wefocused on Ru-Mn mixed oxide with multi-center structure to synthesize new catalytic materials with highefficiency for the selective oxidation of alcohols under mild conditions, and to optimize the reaction systemby associating synthetic method with catalytic performances. The results obtained in this study couldprovide theoretic and technological foundation for designing efficient catalysts and catalytic systems. It iscomposed of three parts:In the first part, a series of MnO（OH）/γ-Al₂O₃were synthesized by a precipitation method and used assupport of2.5%Ru/MnO（OH）/γ-Al₂O₃catalyst for the oxidation of alcohols was prepared by precipitation.XRD, N2adsorption, XAS, FI-IR and H2-TPR were used to characterize the synthesizedMnO（OH）/γ-Al₂O₃. Effects of Mn content, Mn source, calcination temperature on the catalyticperformances of2.5%Ru/MnO（OH）/γ-Al₂O₃were also studied. When10%MnO（OH）/γ-Al₂O₃withMn（NO3）2as the Mn source and calcined at773K was used as the support, the catalyst showed highercatalytic activity.58.2%of benzaldehyde yield was achieved at333K in1h with catalyst0.1g and benzylalcohol4mmol. The catalyst could be reused for several times without appreciable loss of its activity.In the second part, Mn_xCe_1-xO₂/γ-Al₂O₃were prepared by the impregnation method and used assupport of2.5%Ru/Mn_xCe_1-xO₂/Al₂O₃catalyst which was prepared by precipitation. The synthesizedcatalysts was investigated for the oxidation of benzyl alcohol with the molecular oxygen as oxidant.2.5%Ru/Mn_xCe_1-xO₂/Al₂O₃with the support prepared by the co-impregnation method showed highercatalytic activity. XRD, N2adsorption, FI-IR and H2-TPR suggested that the support by co-impregnationprocess leaded to Mn species mainly existed as amorphous state and easier to form Mn-Ce-O compositeoxide. Mn source, calcination temperature, Mn/Ce molar ratio as well as loading of Mn_xCe_1-xO₂exertedgreat impacts on the structure of Mn_xCe_1-xO₂/γ-Al₂O₃and the catalytic activity of2.5％Ru/Mn_xCe_1-xO₂/γ-Al₂O₃. When n（Mn）/n（Ce）=1/1, n（Mn+Ce）/n（Al）=1/10, Mn（NO3）2as the Mn source,calcination temperature773K were used to synthesize, the catalyst showed higher catalytic activity. Upto90%of benzyl alcohol conversion with99%of benzaldehyde selectivity was achieved at333K in0.7h. In the third part, Mn_xCe_1-xO₂were prepared by sol-gel, precipitation and mechanical mixing methods,and used as support of2.5%Ru/Mn_xCe_1-xO₂catalyst which was prepared by precipitation. The oxidation ofbenzyl alcohol with molecular oxygen was carried out on the catalyst, in which Ru mass fraction is2.5%.Effects of different preparation methods for the support, calcination temperature of the support andMn/（Mn+Ce） molar ratio in the support on the catalytic activity of2.5%Ru/Mn_xCe_1-xO₂were investigated.The catalyst showed high catalytic activity when the support with n（Mn）/n（Mn+Ce）=0.5was prepared bysol-gel method and calcined at773K for6h. Up to68.1％of benzaldehyde yield was achieved at333k in1h. XRD, SEM, N2adsorption and FI-IR suggested that the Mn_xCe_1-xO₂support possessed perfect porestructure, large surface area and high containing of Mn-Ce-O composite oxide.