The Exploration Of Highly Efficient Oxide Catalysts For Oxidative Coupling Of Alcohols And Amines To Imines

Imines are important intermediate,which were widely applied in the area of biology,agriculture,pharmacy and fine chemicals.There are many methods for the synthesis of imines,including the condensation of carbonyl compounds and amines,the self-condensation of amines,and the oxidation coupling of alcohol and amines.Alcohols are important chemical materials,which have the characteristics of abundant reserves,low prices and low toxicity.Under the conditions of air or oxygen as oxygen sources,oxidation of alcohols and amines to imines has attracted much attention.Nanosize metal/metal oxide catalysts have shown some unique physical and chemical properties during the catalytic process.The reduction of particle size greatly increased the effective surface area and the number of atoms on the surface of the catalyst,and promoted its excellent catalytic performance in the catalytic reaction.In this work,the effect of the structure and surface properties of the nanosize catalyst on the catalytic performance of the catalyst was further carried out based on our previous work.A series of supported lanthanum oxide catalysts(LaO_x/MC)were prepared with a wet impregnation method using mesoporous carbon(MC)as a support.The effects of particle size,interaction between support and active components on the performance of catalysts were investigated.The results showed that the catalyst of LaO_x/MC calcined by 500oC exhibits the highest catalytic performance,imine yield can reached 98.5%after 2 h.The catalyst has high cycle stability at the same time,and it can be used for many times.The characterization results show that the active components in the supported lanthanum oxide have smaller particle size.Compared with bulk lanthanum oxide,the increase of oxygen defects and unsaturated species on the catalyst surface may be more active for the activation of molecular oxygen in the reaction process.Additionally,a series of magnesium aluminum composite oxide catalysts were prepared by coprecipitation method.The effects of acid base properties of the catalysts on the oxidation of alcohol and amine on the synthesis of imide were investigated by regulating the Mg/Al ratio and the calcination temperature.The reaction results show that the catalytic performance of magnesium aluminum composite oxide is obviously higher than that of magnesium oxide and alumina.The system characterization results show that lots of weak acidic sites and basic sites on the surface of magnesium aluminum composite oxides.These weak acid and base centers play an important synergistic role in the catalytic reaction.Among them,weak basic sites can provide adsorption sites for benzyl alcohol with weak acid property and help it to be oxidized to benzyl alcohol.Weak acid sites can adsorb aniline and provide assistance for condensation reaction.In summary,two kinds of oxide catalysts with excellent properties were prepared by adjusting particle size and surface acid-base properties respectively.These explorations will provide references for further development of catalysts for the coupling oxidation of alcohols and amines.