Studies On Selective Oxidation Of Alcohols Catalyzed By Co-based Bimetallic Oxides

Selective oxidation of alcohols to carbonyl compounds is one of the most important reactions in synthetic chemistry.The development of heterogeneous catalytic system in which molecular oxygen replaces highly toxic and strong oxidizing oxidants such as dichromate and permanganate.It enables high-efficiency selective oxidation of alcohols to carbonyl compounds under mild conditions and provides theoretical support for establishing an eco-friendly green synthesis process.In this thesis,the synthesis of cobalt-based bimetal oxides for selective oxidation of alcohols to carbonyl compounds had been studied.The catalysts were characterized by XRD,SEM,TEM,BET,XPS,O2-TPD,H2-TPR and EXAFs.The relationship between the structure and catalytic properties of cobalt-based bimetal oxides is obtained by experimental research and theoretical calculation.The main research results are listed as follows:(1)A series of cobalt-based bimetal oxides were prepared by co-precipitation method,such as CoFe2O4,CuCO2O4,Co2AlO4,NiCo2O4,MnCo2O4,and a series of cobalt-manganese composite oxides with different Co/Mn ratios(CMO-n,n represents the Co/Mn molar ratio)were also synthesized.(2)The results of XRD,SEM,TEM,XPS and BET show that:cobalt-based composite oxide are spinel structures;CMO-n are mesoporous materials composed of micron rod structure,which has specific surface areas(51.9-71.4 m2/g)and mesoporous pore volumes(0.24-0.29 cm3/g);With the increasing of Co/Mn ratios,the oxygen defects of CMO-n increase continuously.(3)The catalytic activities of cobalt-based bimetal oxides for the selective oxidation of alcohols to aldehydes/ketones show that CMO-n have excellent catalytic performance under molecular oxygen as an oxidant and mild reaction conditions.And the best catalytic performance was obtained when the Co/Mn is 5～7.Eight recycling cycles based on n=5 show that CMO-5 has excellent catalytic activity,strong stability and good recycling capacity for different types of alcohols.(4)Combining the results of catalytic performance,theory calculation and characterizations of XPS,O2-TPD,H2-TPR and in-situ IR,it is concluded as follows:Mn is the adsorption site for catalytic oxidation of p-methyl benzyl alcohol to p-methyl benzaldehyde by CMO-n;The oxygen defects of CMO-n can significantly increase its adsorption energy to the reactants;The high catalytic performance of CMO-n is derived from the synergistic catalytic effect of oxygen defects and redox pairs of cobalt-manganese composite oxides.