Abundant Oxygen Vacancies Induced by the Mechanochemical Process Boost the Low-Temperature Catalytic Performance of MnO2 in NH3-SCR
Yuanyuan Dong, Baofang Jin, Shaomian Liu, Jiajian Gao, Kangjun Wang, Fabing Su
Abstract
Manganese oxides (MnOx) have attracted particular attention in the selective catalytic reduction of NOx with NH3 (NH3-SCR) because of their excellent low-temperature activity. Herein, we prepared a highly efficient MnO2 (MnO2-M) catalyst through a facile ball milling-assisted redox strategy. MnO2-M shows a 90% NOx conversion in a wide operating temperature window of 75–200 °C under a gas hourly space velocity of 40,000 h−1, which is much more active than the MnO2 catalyst prepared by the redox method without the ball-milling process. Moreover, MnO2-M exhibits better H2O and SO2 resistance. The enhanced catalytic properties of MnO2-M originated from the high surface area, abundant oxygen vacancies, more acid sites, and higher Mn4+ content induced by the ball-milling process. In situ DRIFTS studies probed the reaction intermediates, and the SCR reaction was deduced to proceed via the typical Eley–Rideal mechanism. This work provides a facile method to enhance the catalytic performance of Mn-based catalysts for low-temperature denitrification and deep insights into the NH3-SCR reaction process.