Primary factors affecting denitrification efficiency of V-based catalysts in low-temperature selective catalytic reduction using NH_3

摘要

The denitrification efficiency of vanadium-based catalyst for low-temperature selective catalytic reduction (SCR) using NH3 (200 degrees C) highly depends on the structural species of vanadium oxide (VOx) and the physicochemical properties of the catalyst. In this study, we investigated the main factors affecting the denitrification efficiency of low-temperature NH3-SCR by adjusting synthetic factors such as calcination temperature and vanadium to oxalic acid (OA) ratio during the V/TiO2 synthesis. The main factors for enhancing the activity of low-temperature NH3-SCR with vanadium-based catalysts were identified to be (1) a high proportion of well dispersed monomeric VOx species (57.3%); (2) a large number of NH3-Lewis acid sites; and (3) a high oxygen mobility (surface adsorbed oxygen). In particular, the surface adsorbed oxygen species (O-alpha) of the catalyst was identified as a reactive factor in low-temperature NH3-SCR, which enhances the oxygen mobility of V/TiO2 in terms of turnover frequency (TOF). The NH3-Lewis acid sites significantly contribute to promoting the activity of low-temperature NH3-SCR at 180 degrees C owing to the strong adsorption strength of NH3 at a slow reaction rate.