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 N 2 O in the NH 3 –SCR reaction. Herein, an interesting phenomenon is first reported. Arsenic (As), as another impurity, markedly suppresses N 2 O generation over the Cr-poisoned V 2 O 5 –WO 3 /TiO 2 (Cr/VWTi) catalyst, especially reducing by nearly 10 times at 300 °C in NH 3 –SCR. Characterizations show that the introduction of As induces the interaction between Cr and As, which inhibits the Cr incorporation into the TiO 2 lattice and promotes the transformation of monomeric VO x species from VO 5 (Cr/VWTi) to VO 4 and VO 5 H (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 VO 4 species and Brønsted acid sites, which makes the dehydrogenation of the NH 2 NO* intermediate more difficult, resulting in lower N 2 O formation during the NH 3 –SCR reaction. This work provides new insights into N 2 O suppression from flue gas impurities.