Investigating multi-functional traits of metal-substituted vanadate catalysts in expediting NO_X reduction and poison degradation at low temperatures

Catalysts are severely poisoned by ammonium sulfate (AS) and ammonium bisulfate (ABS) during selective catalytic NO_X reduction (SCR) at low temperatures. To circumvent this issue, metal-substituted vanadates (MV₂O₆, M = Mn, Co, Ni, or Cu) supported on TiO₂ were synthesized and functionalized with SO_Y²⁻ to form M₁ (S) catalysts (Y = 3 or 4). The Mn₁ (S) could balance pre-factor and energy barrier required for the SCR, thereby exhibiting the highest NO_X consumption rate (activity) among the M₁ (S) catalysts. The Mn₁ (S) also had desirable redox property, leading to the best SCR performance maximum-obtainable at low temperatures. Notably, the Mn₁ (S) substantially reduced the thermal energy needed to decompose AS/ABS poisons. Such unique feature of the Mn₁ (S) was pronounced when the Mn₁ (S) was promoted by Sb (Mn₁-Sb (S)). The resulting Mn₁-Sb (S) showed the best SCR performance among all catalysts tested. The Mn₁-Sb (S) could minimize the deposition of AS/ABS on the surface and unprecedentedly recovered its performance after regeneration even in the presence of NO_X, NH₃, SO₂, and H₂O at 260−280 °C. The temperatures required for the regeneration of the Mn₁-Sb (S) were reduced by 100 °C or more in comparison with those of SCR catalysts reported previously.