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 re-action under various NOx conditions is still challenging. To solve this problem, we explored the reaction char-acteristics 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 com-posite 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.