Preparation Of Modified Lanthanum Cobalt-based Perovskite Catalyst And Its Catalytic Performance For Toluene Combustion

In recent years,wide attention has been attracted by the problem of volatile organic compounds（VOCs）pollution,while catalytic combustion is acknowledged as an environmentally friendly and efficiently technology to treat VOCs pollutants.The key point of this technology is the development of catalysts with low cost,high activity and high stability.Consequently,the novel perovskite type catalysts,who have the required characteristics,have been widely noticed,although there is still much potential for improvement.In this paper,the catalytic combustion performance of LaCoO₃based perovskite catalysts were studied by structural adjustment and morphology optimization,during which the effects of calcination atmosphere,A-site doping and acid treatment of the catalyst were studied,with toluene as a typical VOCs pollutant.The changes of physical and chemical properties of modified perovskite,such as micro-morphology,surface element valence and oxidation reducibility,etc.,were analyzed by various characterization techniques,and the relationships between the structural characteristics and the catalytic activity of the catalyst were also established.The main research results are as follows:（1）LaCoO₃catalyst with three-dimensional ordered macroporous（3DOM）structure was prepared by polymethyl methacrylate（PMMA）crystal template method.The effects of calcination atmosphere on macroporous structure and catalytic activity of toluene were studied.The results showed that the La Co O₃-NA catalyst,synthesized by nitrogen solidification together with air calcination,could not only maintain the crystal structure of lanthanum cobalate,but also had high quality 3DOM structure.The T_50%and T_90%of La Co O₃-NA decreased by 40℃ and 42℃ compared with the bulk La Co O₃catalyst,which suggested improved catalytic activity and thermal stability.（2）3DOM La_1-xCe_xCoO₃catalysts,doped with Ce at site A,were prepared by PMMA crystal template method.The effect of Ce doping on the catalytic oxidation performance of La Co O₃perovskite was studied.The results showed that an appropriate Ce doping could enrich the concentration of surface adsorption oxygen on the catalyst,which was beneficail for the formation of surface oxygen vacancy,and effectively improved the catalytic activity for toluene.Among the catalysts,La_0.7Ce_0.3Co O₃catalyst showed the best catalytic activity for toluene(T_50%=218℃,T_90%=280℃).（3）The effects of acetic acid treatment on the structure and catalytic performance of3DOM La_0.7Ce_0.3Co O₃catalyst were also studied.The results showed that acetic acid etching could effectively improve the activity of La_0.7Ce_0.3Co O₃catalyst.The etching of the catalyst with 5 mol/L acetic acid did not destroy their 3DOM structure,but significantly increased the specific surface area of the catalyst（84.2 m²/g）.After the acid treatment,Ce O_1.675and Co₃O₄nanoparticles,who had been dissolved in situ from the skeleton,had a positive effect on the catalytic effect.In sum,the La_0.7Ce_0.3Co O₃catalyst with 5 mol/L acetic acid treatment showed the best toluene catalytic activity(T_50%=189℃,T_90%=249℃)and excellent thermal stability.