Study On Denitrification Mechanism Of Iron-Based Catalysts Based On Density Functional Theory

Nitrogen oxides?NO_X?are one of the major pollutants in the atmosphere.NO_X composed of nitric oxide and nitrogen dioxide are harmful to human life.To effectively control the discharge of pollutants,our country has successively introduced a series of reward and punishment policies.Controlling NO_X emissions has become a hot topic of current research.Selective catalytic reduction?SCR?technology is currently the mainstream technology for controlling NO_X emissions,and its core is the denitrification catalyst.Iron-based catalysts have good denitrification efficiency,but their denitrification mechanisms are not yet clear.In this study,the SCR denitrification mechanism of iron-based catalysts was studied using density functional theory.In the first part,an iron oxide model was established.The second part was the adsorption calculation of?-Fe₂O₃?001?surface.And the third part is the calculation of surface denitrification reaction.The conclusions obtained from the study are as follows:?1?The bulk model test results modified by the addition of antiferromagnetic AFM1 and the Hubbard method are the best.The optimized parameters are a=b=5.065?,c=13.843?,and the magnetic moment is 4.160?B.The energy gap value is2.174eV.?2?It was determined through testing that the 2×2 surface was large enough.The adsorption site test results show that the three gases tend to adsorb to the Fe atom,ie,the top position of the?-Fe₂O₃?001?surface.The results of the multi-molecule gas adsorption test show that the co-adsorption does not occur on the surface.The results of adsorption state analysis show that the three gas molecules should be sorted according to their charge capacity which is O₂>NO>NH₃.The presence of O₂contributes to the multiple adsorption of NH₃ and NO.?3?In the three reaction pathways,a large energy barrier is required for the reaction involving the H bond breaking,indicating that the N-H or O-H bond is relatively difficult to break and needs to absorb more energy.In the reaction of NO and NH₃,the dissociation of NH₃ to NH₂ before the addition of NO is the decisive step,and the dissociation of M-NH₂NO into M-NHNO?1?after the addition of NO is the decisive step.In the reaction of NO and O₂,after the addition of NO,the reaction is divided into two reaction pathways that generate M-NO₃ and M-NO₂,and it is easier to generate M-NO₂ through the energy barrier comparison for the discovery of M-ONO₂.In the reaction of NO,O₂ and NH₃,the step of desorption of H₂O is a decisive step.The desorption of H₂O determines the reaction rate.Combining the reactions of the two generated waters,it can be seen that the desorption of generated water or water requires a large amount of energy,which may be an important factor affecting the completion of the reaction on the?-Fe₂O₃?001?surface.