Boosting Water-Resistance Ability on a PTFE Modified Ti-OMS-2 Catalyst for Low-Temperature NH3-SCR Reaction

Abstract

Manganese-based catalysts are considered as ideal alternative catalysts for NH3 selective catalytic reduction of NOx due to their excellent denitrification performance, but their weak water resistance limits industrial applications. To improve the water resistance of low-temperature Mn-based catalysts in the NH3-SCR reaction, a Ti-OMS-2 (titanium-manganese oxide octahedral molecular sieve) catalyst was prepared by the hydrothermal method, and polytetrafluoroethylene (PTFE) powder was methodically introduced on the catalyst surface by the impregnation method. Importantly, the introduction of PTFE on the Ti-OMS-2 catalyst surface could effectively inhibit the adsorption of water molecules and reduce the probability of active species being consumed. Thus, it showed better catalytic activity and water resistance. The activity of the Ti-OMS-2-20%-PTFE catalyst could reach more than 80% when water vapor was introduced at 180 °C. More importantly, the Ti-OMS-2-20%-PTFE catalyst did not readily bind the active species (Mn4+ and Oads) and maintained the adsorption and activation of NH3 species. Moreover, it was easy for PTFE to form a weak surface hydrophobic layer on the Ti-OMS-2 catalyst surface that could effectively inhibit water toxicity. Therefore, this work provided a reasonable idea and experimental accumulation for the industrial application of Mn-based catalysts.