Highly ordered mesoporous MnOx catalyst for the NH3-SCR of NOx at low temperatures

Abstract

MnOx catalysts with 3D structure (Mn-HT) were prepared by the hard-template method using KIT-6 as a template, and the catalytic performance for the selective catalytic reduction of NOx by NH3 (NH3-SCR) at low temperatures was investigated. The template KIT-6 prepared by the different hydrothermal temperatures can exert significant effect on the catalytic performance of Mn-HT catalysts. Among the Mn-HT catalyst, the catalyst prepared using the template obtained at the hydrothermal temperature of 140 °C (Mn-140) exhibited the highest catalytic performance. Characterizations showed that Mn-140 catalyst possesses high reducibility with abundant surface oxygen species and Mn4+ species. NH3-TPD and in situ DRIFTS demonstrated that there are more Lewis acid sites and Brønsted acid sites on the surface of Mn-140 catalyst, both of which would promote the adsorption and activation of NH3, leading to the reduction of NOx efficiently to proceed mainly by the Eley-Rideal(E-R) mechanism, accompanied by the Langmuir-Hinshelwood (L-H) mechanism.