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

Abstract

AbstractNanosized 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‐H2, 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‐DeNOx) 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‐DeNOx is correlated with the formation of different NOx− under the experimental conditions.