Precisely tuned mesoporous Mn-Ti-Al oxide catalysts for highly efficient and selective low-temperature NOx reduction

Ammonia selective catalytic reduction (NH 3 -SCR) of nitrogen oxides (NO x ) is a widely adopted method for controlling NO x emissions. However, achieving superior low-temperature activity while maintaining high N 2 selectivity over a broad temperature range remains a major challenge. In this study, a novel mesoporous manganese–titanium–aluminum (Mn-Ti-MA-S) composite oxide catalyst was synthesized by a modified evaporation-induced self-assembly method. The incorporation of Mn and Ti into mesoporous alumina (MA) framework significantly optimized the redox-acidic properties of the Mn-Ti-MA catalyst, with Mn in a highly dispersed state with fully exposed microcrystalline structures. Subsequent sulfur treatment further transformed the Lewis acid sites into Brønsted acid sites, shifting the reaction pathway from a Lewis acid site-dominated to Brønsted acid site-dominated mechanism. This strategy successfully overcame the conventional trade-off between low-temperature activity and high-temperature N 2 selectivity in NH 3 -SCR catalysts. Consequently, the optimized Mn-Ti-MA-S catalyst exhibited excellent catalytic performance, achieving both NO x conversion and N 2 selectivity above 90 % over a wide temperature range (104–400 °C). This work highlights a synergistic strategy that integrates redox and acid sites engineering with reaction pathway regulation, enabling the development of highly efficient NH 3 -SCR catalysts.