The Preparation And Application Of Monolithic Molecular Sieve Catalyst For De-NO_x

Nitrogen oxide?NO_X?is one of the primary atmospheric pollutants,which has caused worldwide attention due to its damage to environment.Selective catalytic reduction?SCR?technology is the most promising way to control emission of NO_X in diesel exhaust,which also is the technology roadmap for diesel vehicle aftertreatment in China.In this paper,the molecular sieve SCR powder catalyst and the whole catalyst prepared by the surface coating method were systematically studied,then the SCR catalyst with good activity was screened.In this paper,Cu-beta,Cu-SAPO-34 and Cu-ZSM-5 catalysts were prepared and their denitrification properties were evaluated.It was found that the Cu-SAPO-34 catalyst had good denitrification activity,better sulfur resistance and hydrothermal stability.Then the effects of Cu loading and space velocity on the denitration performance of Cu-SAPO-34catalyst were investigated.It was found that the de-NO_X efficiency of 2.5%Cu-SAPO-34catalysts is the highest.The properties of the catalysts were characterized by XRD?BET?TPD?TPR?SEM?DRIFT.The results showed that the introduction of Cu species increased many new Lewis acid sites and increased NH₃ attachment sites.The SCR reaction is mainly carried out on L acid,and the coordinated NH₃ and NH₂ species are active species.The Cu-SAPO-34 doped with different transition metal of Ce,Zr,Ag was prepared with the methed of equal volume impregnation to improve the activity of the catalyst.The experimental results showed that the active temperature window of copper-based catalyst was greatly broadened by doped cerium and zirconium and silver,that also improved the de-NO_X efficiency in low temperature and sulfur resistance ability.The properties of the modified catalysts were characterized by XRD?BET?TPD?TPR?SEM?DRIFT.Results showed that the addition of second metals increased the density of medium and weak acid,enhanced the Lewis acid of the catalyst and increased the Cu dispersion.In this paper,cordierite honeycomb ceramics were used as carriers to monolithic catalyst,and the the influence of the monolithic catalyst preparation parameters was investigated.Then the single metal monolithic catalysts and bimetallic monolithic catalysts were prepared and their denitrification performances were evaluated.It was found that the monolithic catalysts also maintained good denitrification activity and sulfur resistance.The effects of space velocity and coating rate on the activity of monolithic catalyst were also investigated.The experiment showed that the amount of coating is positively correlated with the activity,and space velocity is related to the SCR reaction,which affect the denitrification activity of the monolithic catalyst.