Study On Thermal Stability Of Cerium Zirconium Aluminum Materials

Nowadays,increasingly strict regulations for the automobile exhaust control demands for higher catalytic conversion rate and better thermal stability,so researchers are concentered on how to improve the catalytic performance and the thermal stability of the TWCs.The researches have improved the thermal stability to a certain extent,but the comprehensive studies of the thermal stability are less.So,this dissertation is engaged in comprehensively studying the thermal stability of the TWCs.In this paper,we carried out the following work:(1)the sample of Zr0.4Ce0.6O2(CZ)support was synthesized by homogeneous precipitation method,and the precipitation agent was urea.Then,the obtained oxygen storage material was calcined at different temperatures to investigate thermal stability of the support.Last,the calcined supports were loaded Pd(0.5 wt%)by impregnation method.The thermal stability,catalytic performance and OSC of Pd/CZ catalysts were investigated in detail.(2)the alumina materials(LBA,lanthanum-barium-aluminum)were synthesized by co-precipitation method.Then,the obtained LBA samples were calcined at different temperature to investigate their thermal stability.Last,the calcined supports were loaded Pd(0.5 wt%)by impregnation method.The thermal stability and catalytic performance of Pd/LBA catalysts were investigated.(3)The supports of LBA and CZ were mixed by high-energy balling mixing at different ration of LBA/CZ,thus a new support CZA was obtained.In this part,the researches are focused on the interaction between LBA and CZ,especially the effect of the interactions on the thermal stability,OSC and catalytic performance.(4)The obtained support CZ,LBA and CZA,and the catalysts Pd/CZ,Pd/LBA and Pd/CZA were characterized by XRD,N2-absortption-desorption,CO-pulse,O2-pulse,H2-TPR,SEM and so on.The research results are as follows:(a)The crystal's growing of CZ solid solution isn't linear change with calcined temperature,but it is sintered when the temperature reach to1000-1200?.When the calcined temperature reaches 1100?,a phase separation occurs.The CZ's thermal stability is well.And the properties of Pd/CZ samples are time-dependent when calcined at 960?,and 4h is the best choice for catalytic performance.(b)Thermal stability of alumina was enhanced by doping in La and Ba,and the phase transition temperature of alumina increase to more than 1100?.The duration time at 960? has little influence on the structures of LB A.And the dispersity of Pd on the LBA is not only influenced by the properties of LBA support,but also associated with re-dispersing of Pd.The best catalytic performance and highest Pd dispersity were obtained on the catalyst of Pd/LAB-600-800.(c)Thermal stability of CZA,which was prepared' by high-energy ball mixing of CZ and LBA,wasn't significantly improved compared to the CZ and LBA.The catalytic performance of Pd/CZA wasn't improved.And the interaction between CZ and LBA is weak.