Arsenic Impurity in Flue Gas Significantly Inhibiting N ₂ O Byproduct Formation on the Chromium-Poisoned V ₂ O ₅ –WO ₃ /TiO ₂ Catalyst in the NH ₃ –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 VO_<i>x</i> species from VO₅ (Cr/VWTi) to VO₄ and VO₅H (As-Cr/VWTi). <i>In situ</i> 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.