Study On Catalytic Performance Of Oxide Composite Cobalt-Based Double Perovskite-Type Compound Catalyst For Ventilation Air Methane Combustion

In this paper,pure phase rare-earth double perovskite-type La2CoFeO6 and La2CoNiO6 oxide were prepared by sol-gel method,and a series of compound catalysts La2CoFeO6-CeO2,La2CoFeO6-MgO,La2CoFeO6-TiO2 and La2CoNiO6-CeO2,La2CoNiO6-MgO,La2CoNiO6-TiO2 were formed by sol-gel impregnation method composited with several simple oxides CeO2,MgO and TiO2.And the catalytic performance of the above catalysts for ventilation air methane combustion were studied.Then,the structure,redox performance,thermal decomposition properties and valence state of iron elements etc.of the catalysts were comparative study by various characterization methods such as XRD,SEM,XPS,H2-TPR,O2-TPD,TG-DTG-DSC,VSM(Vibrating sample magnetometry),Mossbauer and so on.The experimental conclusions were as follows:(1)A series of compound rare earth double perovskite-type catalysts La2CoFeO6-BOx(B=Ce,Mg,Ti)were prepared by sol-gel impregnation,and the effects of different oxides on the catalytic performance of ventilation air methane combustion of this series of catalysts were investigated.Among them,when the oxide was CeO2 and the content is 70%,the formed compound catalyst La2CoFeO6-CeO2 showed the optimal catalytic activity of ventilation air methane combustion(T10=396.7℃,T90=603.7℃).The T10 and T90 of La2CoFeO6-CeO2 decreased respectively by 27.0℃ and 44.8℃ compared with the pure phase catalyst La2CoFeO6,The catalytic performance of ventilation air methane combustion of La2CoFeO6-MgO was second.And then the characterization results showed that the good mutual dispersion of the catalyst La2CoFeO6-CeO2,the interaction between La2CoFeO6 and CeO2 and its good redox property were the key factors affecting the catalytic activity of the catalyst.(2)A series of compound catalysts La2CoFeO6-xMgO(x-10%,30%,50%,70%,90%)were prepared by sol-gel impregnation method,and the catalytic performance of ventilation air methane combustion of the series of catalysts La2CoFeO6-xMgO was further optimized.When x-30%,the compound catalyst La2CoFeO6-30%MgO had best catalytic activity of ventilation air methane combustion(T10=397.7℃,T90=613.0℃).The T10 and T90 of La2CoFeO6-30%MgO decreased respectively by 9.7℃ and 10.5℃ compared with the catalyst La2CoFeO6-70%MgO.And then the characterization results showed that the good resistance to sintering of the catalyst La2CoFeO6-30%MgO,which made the catalyst produce more active sites,and its good redox property,which made the oxidation activity of surface oxygen of the catalyst increase,affected activity of the catalyst.(3)A series of compound catalysts La2CoFeO6-xCeO2(x-10%,30%,50%,70%,90%)were prepared by sol-gel impregnation method,and the catalytic performance of ventilation air methane combustion of the series of catalysts La2CoFeO6-xCeO2 was further optimized.When x=70%,the compoundcatalyst La2CoFeO6-30%CeO2 had best catalytic activity of ventilation air methane combustion(T10=391.9℃,T90=580.7℃).The T10 and T90 of La2CoFeO6-30%CeO2 decreased respectively by 4.8℃ and 23.0℃ compared with the catalyst La2CoFeO6-7 0%CeO2.And then the characterization results showed that content of reactive oxygen species of La2CoFeO6-30%CeO2 was 23 times of La2CoFeO6-70%CeO2.And the strong interaction between La2CoFeO6 and CeO2 in the catalyst and smallest electron charge density of Fe nucleus also made the catalyst La2CoFeO6-30%CeO2 exhibited the most excellent catalytic activity.(4)On the basis of the above research on La2CoFeO6 compound catalysts,another type of compound rare-earth double perovskite-type compound catalysts La2CoNiO6-CeO2,La2CoNiO6-MgO and La2CoNiO6-TiO2 were prepared by sol-gel impregnation method,and the catalytic performance of ventilation air methane combustion was studied.And simply compared with the corresponding La2CoFeO6-CeO2,La2CoFeO6-MgO,La2CoFeO6-TiO2.In this series of catalysts,when the oxide is CeO2 and the content is 70%,The catalytic activity of the formed compound catalyst La2CONiO6-Ce02 was best(T10=414.3℃,T96=591.3℃).The T10 and T90 of La2CoNi06-Ce02 decreased respectively by 108.0℃ and 219.9℃ compared with the pure phase catalyst La2CoNiO6.And then the characterization results showed that the better redox performance of the catalyst and the stronger interaction between La2CoNiO6 and CeO2 in the catalyst and the higher lattice oxygen content were important reasons why the catalyst had good activity.