Investigation Of Synthesization,And Denitrification Characterization Of Core-shell Structure ZSM-5 Molecular Sieve

Nitrogen oxide （NOX） is one of the main sources of air pollution.ZSM-5 zeolite has excellent SCR catalytic performance due to its favorable thermal stability and more active center introduced by doping metal ions.This paper synthesize two kinds of core-shell structure molecular sieve, Fe-ZSM-5@meso-SiO2 and hollow CeO₂@Fe-ZSM-5 and study structure and properties of samples. This paper firstly synthesize Fe-ZSM-5 by hydrothermal preparation,and Fe-ZSM-5@meso-SiO2 with micro-and mesoporous structure synthesized by coating mesoporous silica on the external surface of modified Fe-ZSM-5 by PDDA. The core-shell structure molecular sieve was doped different metal （Ce、Ni）by hyrothermal method and impregnation method. The morphology of samples were characterized by x-ray diffraction spectra （XRD）,High Resolution Transmission Electron Microscopy （HRTEM）, hydrogen temperature-programmed desorption （H2-TPR）, X-ray photoelectron spectroscopy （XPS）. The catalytic activity of catalyst in NH3-SCR reaction were characterized in a fixed bed reactor,and the reaction mechanism was studied by in situ DRIFRS. The results show that the conversion rate of sample ynthesized by hyrothermal method is higher than that of sample ynthesized by impregnation method, and Ce（Ni） is more conduciveto SCR reaction compared to Ni（La）. In the process of Ce impregnated, different solvent affect the activity of the sample. Solvent have a certain influence on the size of CeO₂, the content of Ce4+ and the reduction temperature, thus affect the adsorption capacity of the NO and NH3.In the sample FeZ@Ce/MS-H2O, the CeO₂ particles is smallest than other samples, which is highly dispersed in MS channel and easy to restore. Besides the content of Ce4+which is conducive to the adsorption of NO is also the most. All these characters are of benefit to raise the activity of NH3-SCR reaction which show FeZ@Ce/MS-H2O exhibit higher catalytic activity.The preparation conditions of hollow core-shell structure CeO₂@Fe-ZSM-5 were studied.The results show that the mixing time of precursor liquid, crystallization time, seed has a certain impact on the structure and morphology of sample. The results of denitration activity experiments show that the catalytic activity of CeO₂@Fe-ZSM-5 in NH3-SCR is higher than Ce/FeZ due to Ce4+concentration which is conducive to the adsorption of NO is more than that of Ce/Fe-ZSM-5.