Preparation Of Cerium And Lanthanum Based Composite Metal Oxide Composite Metal Oxides Catalyst For Highly Selective Catalytic Oxidation Of Toluene To Benzyl Alcohol And Benzaldehyde

Benzoaldehyde and benzyl alcohol are widely used in pharmaceutical,food,spices,dyes,cosmetics and other industrial field,which are important organic intermediates with high added value and benzoic acid also has some industrial value.Benzoaldehyde and benzyl alcohol are mainly produced by the hydrolysis of chlorination in China.Chlorine contained product of this method limits its application in the pharmaceutical and food industry.Direct oxidation of toluene molecular oxygen is a green and low cost route for the production of benzaldehyde and benzyl alcohol.But toluene oxidation is carried out under high temperature and pressure in industry,and the main product is benzoic acid with only a small by-product of benzaldehyde and benzyl alcohol.Under solvent-free conditions,benzoaldehyde and benzyl alcohol were produced by selective catalyzed oxidation of toluene as raw material with molecular oxygen used as green oxidant.This process is an new eco-friendly process with the advantage of simple operation,high atomic utilization rate and easy product separation.It.The main research conclusions are as follows:First,the cerium-cobalt metal oxide composite catalyst（Ce O₂-Co₃O₄）was prepared by co-precipitation method and its physical and chemical properties was characterized by various characterization methods（XRD,BET,FT-IR,UV-vis,H₂-TPR）.The catalytic performance of the solution-free oxidation of toluene to benzoaldehyde and benzyl alcohol was investigated in this work.The result showed4.8%toluene conversion,62.9%total selectivity of benzoaldehyde and benzyl alcohol,and 97.4%total selectivity of benzoaldehyde,benzyl alcohol and benzoic acid were obtained under optimal reaction conditions（temprature 190°C,time 2 h,O₂ 1.0 MPa,catalyst dosage 0.1g）.After five cycles,the catalyst still has good catalytic activity and high stability.Furthermore,Cerium-Manganese composite metal oxides were prepared by sol-gel method and used for the catalytic selective oxidation of toluene to benzaldehyde and benzyl alcohol.The Cerium-Manganese composite metal oxide（Ce O₂-Mn₂O₃）exhibited good catalytic performance with 6.9%toluene conversion,64.4%total selectivity of benzoaldehyde and benzyl alcohol,and 96.8%total selectivity of benzoaldehyde,benzyl alcohol and benzoic acid under optimal reaction conditions（temprature 180°C,time 2 h,O₂ 1.0 MPa,catalyst dosage 0.1g）.At the same time,the stability of the Cerium-Manganese compound metal oxide catalyst was also investigated and the catalyst activity had no significantly decline after repeated for five times.Moreover,the microstructure of catalyst was characterized by analysis methods（such as XRD,BET,FT-IR,UV-Vis,H₂-TPR,XPS and HRTEM）and the possible reaction mechanism was proposed.Finally,a cheaper metal compound oxide（La O_x-Fe O_x）was prepared and its catalytic reaction performance was investigated.under optimal reaction conditions（temprature 180°C,time 2 h,O₂ 1.0 MPa,catalyst dosage 0.1g）,6.3%toluene conversion,65.6%total selectivity of benzoaldehyde and benzyl alcohol,and 93.2%total selectivity of benzoaldehyde,benzyl alcohol and benzoic acid were achieved.In summary,the composite metal oxide catalysts prepared by co-precipitation method and sol-gel method have good catalytic performance,high stability and potential industrial application prospect.Maybe it can provide theoretical reference and technical basis for the preparation of high added value products by liquid phase selective catalytic oxidation of toluene.