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

Abstract

Catalysts are severely poisoned by ammonium sulfate (AS) and ammonium bisulfate (ABS) during selective catalytic NOx 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 SOY2- to form M-1 (S) catalysts (Y = 3 or 4). The Mn-1 (S) could balance pre-factor and energy barrier required for the SCR, thereby exhibiting the highest NOx consumption rate (activity) among the M-1 (S) catalysts. The Mn-1 (S) also had desirable redox property, leading to the best SCR performance maximum-obtainable at low temperatures. Notably, the Mn-1 (S) substantially reduced the thermal energy needed to decompose AS/ABS poisons. Such unique feature of the Mn-1 (S) was pronounced when the Mn-1 (S) was promoted by Sb (Mn-1-Sb (S)). The resulting Mn-1-Sb (S) showed the best SCR performance among all catalysts tested. The Mn-1-Sb (S) could minimize the deposition of AS/ABS on the surface and unprecedentedly recovered its performance after regeneration even in the presence of NOx, NH3, SO2, and H2O at 260 - 280 degrees C. The temperatures required for the regeneration of the Mn-1-Sb (S) were reduced by 100 degrees C or more in comparison with those of SCR catalysts reported previously.