Design of bifunctional TiO2-SSZ-13 mixed supports for potassium-resistant vanadia catalysts for NH3-SCR

Abstract

In this paper, a novel catalyst, SSZ-13 doped V2O5-WO3/TiO2, was designed and synthesized, which owns excellent resistance to potassium poisoning in the selective catalytic reduction of NO by NH3 (NH3-SCR). V2O5-WO3/TiO2-SSZ-13 (30 wt% and 50 wt% SSZ-13 addition) catalysts show more than 80 % NOx conversion at 260–550 °C after K-poisoning. The modified catalyst effectively shields V2O5 as the main active species from K poisoning by preferential reaction of K+ with H+ from Brønsted acid sites (Si-O(H)-Al) of SSZ-13 via ion exchange. Furthermore, SSZ-13 modification also enhances the low-temperature denitrification activity of V2O5-WO3/TiO2 catalyst by producing more polymeric VOx and low-valent VOx. In situ DRIFTS and kinetic studies indicate that the addition of SSZ-13 does not change the reaction mechanism of the vanadia catalyst for NH3-SCR. Physicochemical characterizations coupled with theoretical calculations demonstrate the difference in formation energies of V and K adsorption on TiO2 and SSZ-13, which is the driving force in realizing the directional enrichment of V and K on different supports.