Tailoring the catalytic properties of Mn-V metal oxide composites for NOx abatement with NH3 under NO– or NO2-rich conditions

Abstract

Both V2O5 and MnOx on TiO2 are metal oxides widely used for selective catalytic reduction (SCR) with NH3. However, each has a different temperature window for optimal performance, and interpreting the catalytic reaction under various NOx conditions is still challenging. To solve this problem, we explored the reaction characteristics by varying the composition of Mn/V. Under NO-rich conditions, the number of active oxygen and oxygen vacancies at the optimal Mn/V ratio resulted in improved performance. Interestingly, under NO2-rich conditions, an increase in the amount of Mn compared to V led to an increase in the NOx consumption rate with a decrease in activation energy. Importantly, the catalysts synthesized according to the Mn/V ratio resulted in changes in the reaction rate and the type of species adsorbed. Meanwhile, the SCR reactions of all Mn-V composite catalysts follow the Langmuir-Hinshelwood (LH) mechanism type in which NH3 and NOx are adsorbed on the catalyst surface. In addition, durability of the optimal Mn/V is improved by suppressing the adsorption of K+ ions to the acidic site compared to the commercial modified catalyst. As a result, it was suggested that it follows the Eley-Rideal (ER) due to the changed adsorption characteristics.