Study Of Core-shell Fe-ZSM-5 For DeNO_x

Fe-ZSM-5 with particle size of 200 nm was coated with a tiny silicalite-1 shell via secondary hydrothermal crystallization in order to improve the hydrophobicity of Fe-ZSM-5 on NH3-SCR. The formation mechanism, adsorption performance and SCR activity of the core-shell zeolites were investigated in this paper. During the secondary hydrothermal crystallization procedure, the different content of silicon source (TEOS) led to the different morphologies of the shell. Comparing to Fe-ZSM-5, the core-shell zeolites have higher activities on NH3-SCR and hardly impacted with H2O. For a further study, UV-Vis DRS, TPD, in situ DRIFTS and TG were combined and suggested that the differences between Fe-ZSM-5 and core-shell zeolites on NH3-SCR performance can be attributed to the adsorption of NOx on silicalite-1, Fe species transformation during secondary hydrothermal crystallization and the hydrophobicity of silicalite-1.Core-shell zeolite Fe-ZSM-5@Ce/mesosilica was prepared via self-assembling. The shell thickness and Ce content were controlled by adjusting the dosage of TEOS and Ce(NO3)3·6H2O in synthesis reaction mixtures. To investigate the textural properties of core-shell zeolites, a series of characterizations were conducted. It is confirmed that mesoporous silica shell was finely covered around the Fe-ZSM-5, the shell thickness was determined by the dosage of TEOS, moreover, Ge species mostly resided in the channels of shell. The NH3-SCR (selective catalytic reduction with ammonia) activity of different core-shell samples also had been studied. For a further study, the results of TPD and in situ DRIFTS were combined to illustrate the sequential reaction mechanism on core-shell samples For the sake of comparison, same runs had been conducted on Ce-loaded Fe-ZSM-5 without mesoporous silica shell. The results convincingly demonstrated the significant role of Ce loaded mesoporous silica shell in NH3-SCR.