Study On Microwave Catalytic Degradation Of Toluene By Cobalt Manganese Lanthanum Composite Metal Oxides

Volatile organic compounds（VOCs）are a class of organic pollutants with a boiling point below 260°C at room temperature.Most VOCs have an unpleasant odor,and some VOCs have teratogenic and carcinogenic effects on humans and animals.Therefore,how to prevent VOCs pollution is one of the important topics in the field of ecological environmental protection.As a widely used method in the field of VOCs treatment,catalytic oxidation technology has the advantages of high efficiency and environmental protection.The key is to screen a high-performance catalyst or use external field enhancement to improve the reaction performance.In this paper,cobalt-manganese composite metal oxides and cobalt-manganese-lanthanum composite metal oxide catalysts were prepared by gel sol method for the catalytic oxidative degradation of VOCs,and the microwave field was introduced to enhance the reaction performance.Taking toluene as the pollutant to be investigated,the comparative experiments of catalytic oxidation performance were carried out in microwave reactor and conventional thermal reactor,and the effects of space velocity,catalyst ratio,initial toluene concentration and microwave power on the degradation performance of toluene were investigated.On this basis,the kinetics of toluene degradation was studied,and the reaction rate and apparent activation energy were calculated.The specific research contents and conclusions are as follows:（1）Cobalt-manganese composite metal oxides were prepared by gel sol method.FTIR,XRD and SEM characterization analysis showed that Mn1Co2 has a spinel structure,which has a smaller particle size and more Pores and Mn-O,Co-O functional groups;XPS and H₂-TPR detection results show that the surface of Mn1Co2 is dominated by Olatt,Mn^3+/4+and Co³⁺,and has better redox properties than single cobalt and manganese oxides.Mn1Co2 shows the best adsorption,heating performance and catalytic activity.The microwave catalytic oxidation of toluene has a T₅₀of 89°C and a T₉₀of 188°C.Its microwave catalytic activity at low temperature is much higher than that of the conventional thermal field,and its T₅₀is 48°C lower than that of the conventional thermal field.（2）On the basis of Mn1Co2,lanthanum was added to partially replace manganese to prepare cobalt manganese lanthanum composite metal oxides.XRD,N₂adsorption-desorption,SEM,FTIR,XPS and H₂-TPR characterization analysis show that the material has larger specific surface area,pore size,pore volume,smaller particle size,more pore channels,and more than Mn1Co2.Oads and Mn^3+/4+.The catalytic reaction results show that La0.8Mn0.2Co2 has the best microwave heating performance at 125～300℃,and exhibits better adsorption performance and microwave catalytic activity.The reaction kinetics analysis showed that the apparent activation energy of La0.8Mn0.2Co2 at the initial concentration of 1000 ppm toluene in the microwave field was 19.216 k J/mol,which was 6.914 k J/mol lower than that of the conventional thermal field（26.13 kJ/mol）.