Study On Manganese Oxide Modificated By Cu/Bi For Catalytic Oxidation Of Soot

The bismuth(Bi),transition metal manganese(Mn)and copper(Cu)oxide have excellent redox properties and are widely used in the field of catalysis.In this paper,different synthesis methods were used to prepare Mn-Bi and Mn-Cu bimetallic oxide catalysts.Based on the soot combustion reaction,the physical and chemical properties of the catalyst were analyzed via a variety of characterization techniques.Firstly,a series of Mn-Bi binary composite metal oxides(MnxBiOy,X=1,3,6,9)were synthesized by hydrothermal,co-precipitation and hydrolysis-driven redox approaches.The performance of the catalysts produced by different synthesis methods was discussed.The Mn/Bi=3/1 is the optimal ratio of MnxBiOy.The catalytic property of soot was evaluated by programmed temperature oxidation tests.The r-Mn3BiOy sample prepared by the hydrolysis-driven redox method has the best soot catalytic activity,with the value of T10,T50 and T90 at 330,385 and 425℃,respectively.Combining the results of characterization,it is concluded that the strong metal interaction formed by the uniform distribution of Mn and Bi contributes to the formation of oxygen vacancies and active oxygen,while the presence of Bi helps to strengthen the mobility of lattice oxygen,thereby endowing the catalyst with excellent activity.Secondly,a series of MnxCuOy catalysts(X=2,4,6,8)were prepared by the abovementioned methods.The catalytic performance follows the order of Mn4CuOy>Mn6CuOy>Mn2CuOy>Mn8CuOy.The Mn/Cu=4/1 is the optimal ratio of MnxCuOy.The r-MnxCuOy samples prepared by hydrolysis-driven redox approach presented great advantages in improving the physical and chemical properties such as metal distribution,specific surface area,and lattice defects.The results of the TPO experiment show that the r-Mn4CuOy sample possesses the best soot catalytic activity,with the figure of T10,T50 and T90 reaching 303,355 and 386℃,respectively.Such results can be ascribed to the homodisperse of Mn and Cu,the increased specific surface area,the promotion of the content of Mn4+,as well as the improvement of the concentration of lattice defects and oxygen vacancies.Additionally,the cycling experiments show that r-Mn4CuOy also has excellent catalytic stability.In summary,the hydrolysis-driven redox method has certain advantages in the preparation of Mn-based binary metal oxide catalysts,which helps prevent a large amount of single metal oxides from agglomerating,and is beneficial to the formation of strong metal interactions.The introduction of Bi and Cu elements changes the crystal structure of Mn2O3,contributes to the generation of oxygen vacancies and active oxygen,improves the activity and stability of the catalyst,which facilitates the lowtemperature catalytic combustion of soot and achieves the purpose of efficient removal of soot particles in diesel exhaust.