Quantum Chemistry Study Of NO Oxidation Catalyzed By Transitional Metal Supported ZSM-5

The environment pollution of China is more and more serious.NO_x is a very important pollutant which cause haze.The most developed technologies in denitration are SCR?Selective Catalytic Reduction?and SCO?Selective Catalytic Oxidation?.The efficiency of SCR only reacted with NO was not quite good as that of with NO and NO₂,so fast-SCR technology was developed.To both of fast-SCR and SCO,the technology of NO oxidation was very important.But at present,the research of NO catalytic oxidation is more experimental but theoretical.So,based on the importance of NO catalytic oxidation in denitration field,the catalytic mechanism of NO oxidation was studied in this paper.First of all,on the basis of quantum chemistry's DFT?Density Functional Theory?,different methods and bases were used in this paper to optimize molecule's configuration and calculate the scf energy of the NO oxidation reaction without catalyst.As a result,a possible pathway was gained.Meanwhile,the effect of different optimization and energy calculation methods was analyzed,which made it reliable to compare with the results of catalytic oxidation.Then the reactants,transition states,intermediates and products along all the relevant reactions of NO oxidation catalyzed by ZSM-5 supported transitional metal?Mn or Co?with different attachment site atom?Si,Al,Ce?were calculated and optimized by UB3LYP//SDD method.Possible pathway and activation energy were obtained.Finally,by analyzing and summarizing,the mechanism of these reactions were studied in detail.The result shows that the activation energy of NO oxidation catalyzed by Mn-ZSM5 or Co-ZSM5 was 40 to 80 kJ/mol,which lower than that?>130kJ/mol?of reaction without catalyst by using UB3LYP//SDD method,so Mn-ZSM5 and Co-ZSM5 show good catalytic effect.In the mean time,different activation energy was obtained when the attachment site atom was different.Result showed that the activation energy when Ce or Al as the attachment site atom was about 40 kJ/mol,which lower than that?>70kJ/mol?when it was Si.As to Mn-ZSM5 and Co-ZSM5,result showed that the efficiency of both was quite near but Mn-ZSM5 may better.comparing with the experimental result,it is hard to judge witch one is more effective,because it maybe related to the temperature or air speed etc.The catalytic mechanism of NO oxidation catalyzed by Mn-ZSM5 or Co-ZSM5 was revealed in this paper by using quantum chemistry theory,which could supply a theoretical reference for the further research of catalytic oxidation of nitric oxide.Meanwhile,the promoting effect of Al or Ce oxide in catalytic reaction was proved in this paper,which coincide with the experimental conclusion.Finally,the comparison of effect of Mn-ZSM5 and Co-ZSM5 can be a reference for further study of different factors which affect the NO catalytic oxidation.