Enhancement of low-temperature activity of γ-Fe2O3-modified V2O5-MoO3/TiO2 catalysts for selective catalytic reduction of NOx with NH3

In this study, a series of γ-Fe 2 O 3 -modified V 2 O 5 -MoO 3 /TiO 2 (VMT) catalysts was prepared by wet impregnation method. The γ-Fe 2 O 3 -modified catalysts exhibited excellent catalytic performance, and 1.25 wt% γ-Fe 2 O 3 content improved the deNO x efficiency at 150 °C from 54% (unmodified VMT catalyst) to 84% (modified catalyst). BET, XRD, XPS, NH 3 -TPD, H 2 -TPR, and in situ DRIFTs were employed to characterize the physicochemical properties and reaction mechanisms of the catalysts. The introduction of γ-Fe 2 O 3 increased the V 5+ /V 4+ ratio, surface chemisorbed oxygen content, redox ability, and a number of acid sites in the prepared catalysts. XPS confirmed the addition of γ-Fe 2 O 3 introduced new charge transfer pathways (Fe 3+ /Fe 2+ ↔ V 5+ /V 4+ ). In situ DRIFTs suggested that the addition of γ-Fe 2 O 3 to the catalyst significantly increased the adsorption capacity of catalyst for NH 3 and NO x , while also exerting a strong activating effect on the adsorbed NH 3 . Furthermore, selective catalytic reduction over the VMT and 5PEG@1.25Fe-VMT catalysts followed the Eley-Rideal (E-R) mechanism. At temperatures above 200 °C, the 5PEG@1.25Fe-VMT catalyst also followed the Langmuir-Hinshelwood (L-H) mechanism.