Preparation Of La-Mn Perovskite By Soft Template And Catalytic Activity For CO+NO

The hollow structure LaMnO₃ perovskite catalysts were fabricated by P123 soft template.A series of template-P123 concentration(0-6.12mmol?L^-1)were employed to optimize the reaction conditions,and the possible formation mechanism was explored.The morphologies of catalyst were adjusted by changing the temperature,the amount of ethanol and citric acid,the pH and the templating agent,In addition,the catalytic activity of catalyst for NO+CO was experimented with catalyst evaluation device.By comparing the morphology and activity,the highly activity perovskite catalysts were synthesized by doping Sr,Ce,Eu and Cu elements under the optimal experimental conditions.In the first part,the core-shell structure perovskite microspheres were prepared with the concentration of P123 is 3.0mmol?L^-1.The possible formation mechanism was revealed via XRD,SEM,TEM,EDS and HRTEM.Molecules of P123 were suitably mixed with solvents for double-shelled vesicles through self-assembly,which interacted with metal complexes to form P123-metal vesicles.After the removal of P123 and citric acid by calcination at 700°C,the yolk-shell LaMnO₃microspheres with through-channels were obtained.Through channels on the surface were due to citric acid and the solid core was attributed to the shrink of inner vesicles.At the same time,citric acid promoted the formation of cubic phase crystal structure and through-channels.In the second part,based on the first part,serious of catalysts were synthesized by changing the condition of temperature,stirring,the amount of ethanol and citric acid,the pH and the templating agent.The catalysts were characterized by XRD,SEM,TEM,BET methods and catalytic activity for harmful gas?NO+CO?.The parameters above were effected the morphology of the catalyst and promoted the formation of a variety of morphologies such as hollow spheres,core-shell structures,porous structures and solid spherical structures.In addition,the core-shell structure LaMnO₃ microsphere possessed the highest CO activity(T_90%=364°C)and NO activity(T_90%=346°C)at the conditions of 25°C stirring 10 h,adding 13.34 ml ethanol,1:1 ratio of metal to citric acid,PH=2 and P123+AEO-3 soft-template.In the end,based on the optimal experimental conditions,the catalyst were prepared by P123+AEO-3/AEO-3 soft-template,dropping Sr,Ce,Eu and Cu.The prepared catalysts were characterized by XRD,SEM,TEM,BET and catalytic activity for harmful gas?NO+CO?.The results shown that Sr,Ce,Eu and Cu have great effect on the morphologies.After dropping,the catalyst prepared by P123+AEO-3 soft-template formed special branch structures,and the catalyst prepared by AEO-3 soft-template formed nanoparticle.At the same time,the activity of the doped catalysts were greatly improved.The catalyst dropping Sr,Ce and Cu prepared by AEO-3 soft-template has the highest CO activity?about 90%at 264°C?and NO activity?about 90%at 262°C?.