Influence of Framework n(Si)/n(Al) Ratio on the Nature of Cu Species in Cu-ZSM-5 for NH3-SCR-DeNOx

Nanosized Cu-containing ZSM-5 catalysts with different n(Si)/n(Al) ratio of 18.9-50.5 were prepared by ion-exchange. The physico-chemical characterization clearly shows that the molar ratio of framework T atoms influences the nature and distribution of copper species. According to DR UV-Vis, TPR-H-2, EPR, or FT-IR spectroscopy analyses, the amount of aggregated copper species increases with increasing the framework n(Si)/n(Al) ratio. Thus, the activity of the Cu-containing ZSM-5 with n(Si)/n(Al) ratio of 47.0-50.5 in the selective catalytic NO reduction with NH3 (NH3-SCR-DeNO(x)) significantly decreases compared to the other materials (n(Si)/n(Al) ratio of 18.9-19.6). The reaction mechanism has been discussed in light of the results of 2D COS (two-dimensional correlation spectroscopy) analysis of IR spectra and catalytic properties of the zeolites. The results make evident that enhanced activity of Cu-containing ZSM-5 in NH3-SCR-DeNO(x) is correlated with the formation of different NOx- under the experimental conditions.

Automated summary

In this study, nanosized Cu-containing ZSM-5 catalysts with different n(Si)/n(Al) ratios ranging from 18.9 to 50.5 were prepared by ion-exchange. Physico-chemical characterization revealed that the nature and distribution of copper species are influenced by the molar ratio of framework T atoms. Spectroscopic analyses, including DR UV-Vis, TPR-H-2, EPR, and FT-IR, indicated that the amount of aggregated copper species increases with an increase in the framework n(Si)/n(Al) ratio. The activity of Cu-containing ZSM-5 in the NH3-SCR-DeNO(x) reaction significantly decreases when the n(Si)/n(Al) ratio is between 47.0 and 50.5 compared to other materials with n(Si)/n(Al) ratios of 18.9-19.6. The mechanism of the reaction was discussed based on 2D COS analysis of IR spectra and the catalytic properties of zeolites.