Study On Catalytic Oxidation Of NO By Cerium Manganese Based Composite Metal Oxides

With the rapid development of the electronic industry,the removal of low concentration NO_x has put forward higher requirements in recent years,how to effectively remove NO_x in the electronic industry has become one of the research hotspots.In this paper,a series of Ce based and Mn based catalysts were prepared,and the catalytic oxidation performance of the catalysts was investigated.The structure of the catalysts was characterized by XRD,NO-TPD,BET,H₂-TPR and XPS,and the kinetics of the catalysts was analyzed.1.A series of Ce based catalysts were prepared by coprecipitation method,the results show that:（1）Ce-Mn catalyst has relatively high catalytic activity for oxidative denitration,the optimum mole ratio of Ce-Mn is 1:4,and the corresponding reaction temperature of C1-M4 catalyst is 62℃,118℃and 150℃when NO conversion is 30%,50%and 70%,respectively;（2）the optimum preparation conditions of C1-M4 catalyst were determined as follows:aging time of 1 h,pH value of precipitation of9.5 and precipitant of ammonia water,the optimum calcination temperature of the catalyst was 450℃,and the corresponding reaction temperature of NO conversion of 30%,50%and 70%at CMD-450 was 58℃,115℃and141℃,respectively.2.A series of Mn based catalysts were prepared by coprecipitation method,the results show that:（1）among the Mn based catalysts with different metal oxides,Mn-Zr and Mn-Ni catalysts have relatively high catalytic oxidation denitration activity,when NO conversion is 30%,50%and 70%,the corresponding reaction temperatures of Mn-Zr and Mn-Ni catalysts are 68℃,99℃,153℃and 73℃,107℃,137℃,respectively;（2）the optimum pH value of Mn-Zr catalyst was 10 for the effect of pH value on the catalytic activity;（3）the activity of M1-Z1 catalyst was the highest when the NO conversion was 30%,50%and 70%and the corresponding reaction temperature of M1-Z1 catalyst was 68℃,99℃and 153℃,respectively;（4）the activity of M2-N1 catalyst was the highest when the NO conversion was 30%,50%and 70%,and the corresponding reaction temperature of M2-N1 catalyst was 62℃,94℃and 122℃,respectively.3.The reaction kinetics of Ce based and Mn based catalysts were studied,the main results are as follows:（1）among the Ce based metal oxide catalysts,the activation energy of Ce-Mn catalyst is relatively low,which is 12.77 kJ/mol,and the activation energy of C1-M4 catalyst is the lowest,which is 8.86 kJ/mol,the results show that the minimum NO reaction order of C1-M4 catalyst is 0.786,and the increase of O₂ content（2-6%）is beneficial to the catalytic oxidation of NO;（3）the activation energies of Mn-Zr and Mn-Ni catalysts with better activity are 8.62 kJ/mol and 8.97kJ/mol,respectively,the activation energy of M1-Z1 catalyst is the lowest,which is 8.62 kJ/mol,the results showed that the reaction order of M1-Z1catalyst was small,the reaction order of NO was 0.830,and the reaction order of O₂ was 0.362,which indicated that the catalyst was less affected by the change of inlet concentration;（5）according to the prediction of reaction kinetics model,the NO adsorption E-R model was most suitable to describe the NO oxidation reaction mechanism of C1-M4 catalyst,and the O₂ adsorption E-R model was most suitable to describe the NO oxidation reaction mechanism of M1-Z1 catalyst.4.Comparing the catalytic performance of Ce based and Mn based catalysts for NO removal,M1-Z1 catalyst has the best catalytic activity,when the gas composition is 500 ppm NO+4%O₂+N₂（equilibrium gas）,the space velocity（GHSV）is 6000 h^-1,the gas flow rate is 100 mL/min,and the reaction temperature is 99℃,the NO conversion is 50%,the catalyst has good low temperature denitration activity.