Time-Resolved in Situ Infrared and Two-Dimensional Correlation Spectroscopy of V2o5/Tio2: Effects of Wo3 and Moo3 Loadings for Nh3-Scr

Abstract

Vanadia-based catalysts are widely applied in NOx reduction, while the promoting effect of WO3 and MoO3 is still under debate. Herein, we prepared V2O5/TiO2, V2O5-WO3/TiO2, and V2O5-MoO3/TiO2 catalysts and revealed that WO3 and MoO3 enhanced the activity of V2O5/TiO2, particularly under wet conditions. In situ DRIFTS, two-dimensional correlation spectroscopy (2D COS), and DFT calculations demonstrated that NH3 adsorption on Lewis acid sites of V2O5/TiO2 resulted in the formation of NH3ads-L1 (1284 cm-1, Ti sites of O=V-O-Ti) and NH3ads-L2 (1604 cm-1, V=O sites). By using 2D COS, we firstly found that the NH3ads-L1 exhibited higher reactivity towards NO to produce NH2NO* via NH2*, which was promoted by WO3. Moreover, WO3 and MoO3 doping inhibited H2O adsorption, and promoted its desorption at elevated temperature, thus protecting the V=O sites on V2O5/TiO2. Also, 2D COS analysis provides a new perspective for in-depth understanding of the active sites and intermediates in NH3-SCR reaction.

Keywords: NOx reduction, vanadia-based catalysts, in situ DRIFTS, in situ Raman spectroscopy, two-dimensional correlation spectroscopy