Arsenic Impurity in Flue Gas Significantly Inhibiting N2O Byproduct Formation on the Chromium-Poisoned V2O5-WO3/TiO2 Catalyst in the NH3-SCR Reaction.

The chromium (Cr) impurity in flue gas often leads to the undesirable byproduct of the greenhouse gas N2O in the NH3-SCR reaction. Herein, an interesting phenomenon is first reported. Arsenic (As), as another impurity, markedly suppresses N2O generation over the Cr-poisoned V2O5-WO3/TiO2 (Cr/VWTi) catalyst, especially reducing by nearly 10 times at 300 °C in NH3-SCR. Characterizations show that the introduction of As induces the interaction between Cr and As, which inhibits the Cr incorporation into the TiO2 lattice and promotes the transformation of monomeric VOx species from VO5 (Cr/VWTi) to VO4 and VO5H (As-Cr/VWTi). In situ DRIFTS and calculations demonstrate that due to the structural changes in Cr/VWTi, As-Cr/VWTi exhibits reduced oxygen vacancies as well as increased VO4 species and Brønsted acid sites, which makes the dehydrogenation of the NH2NO* intermediate more difficult, resulting in lower N2O formation during the NH3-SCR reaction. This work provides new insights into N2O suppression from flue gas impurities.