Understanding the Catalytic Deactivation upon Hydrothermal Aging at 850 °C of WO[sub.3]/Fe-Cu-ZSM-5 Catalyst for Selective Catalytic Reduction of NO by NH[sub.3]

A WO[sub.3] /Fe-Cu-ZSM-5 catalyst was prepared using the solid state ion exchange method (SSIE) and its performance for the Selective Catalytic Reduction of NO with NH[sub.3] (NH[sub.3] -SCR of NO) was investigated. The study shows that the tungsten addition can slightly improve the high temperature catalytic activity of Fe-Cu-ZSM-5. The influence of hydrothermal aging at 850 °C for 5 h on the structural and textural properties of WO[sub.3] /Fe-Cu-ZSM-5 was also studied in this paper. The XRD and FE-SEM measurements did not indicate a breakdown of the zeolite structure upon steam treatment for both aged catalysts. The aged W-base catalyst demonstrates a lower deactivation and better catalytic activity for NO reduction than the bimetallic catalyst after hydrothermal aging despite the lower acidic properties as shown by FTIR-Pyr spectroscopy owing to the presence of tungsten oxide crystallites. The “severe” stage of aging occurring in the absence of W led to the formation of copper oxide agglomerates detected using STEM and H[sub.2] -TPR techniques being responsible for the deterioration of SCR activity of the aged Fe-Cu-ZSM-5.