Influence of the TiO2 crystalline phase of MnOx/TiO2 catalysts for NO oxidation

Mn-based catalysts impregnated on TiO2 with different crystalline phases (rutile (R), anatase (A), and P25 (P)) were studied for the oxidation of NO to NO2. 10%MnOx/TiO2(P) was the most active catalyst, giving 83% of NO conversion at 300 °C and a GHSV of 20000 h−1. The catalyst activities were in the order MnOx/TiO2(P) > MnOx/TiO2(A) > MnOx/TiO2(R). The catalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, and O2 temperature-programmed desorption. Compared to anatase and rutile, P25 gave better dispersion of MnOx on the support surface, suppressed the agglomeration of catalyst particles, and also produced more Mn2O3, which was more active for the oxidation of NO. In addition, P25 enhanced the reduction of MnOx, especially for Mn2O3, and the formation of easily desorbed O2− generated from the Mn3+–O bond.

Graphical AbstractMn-based catalyst supported on P25 TiO2 was more active for NO oxidation than those supported on anatase and rutile TiO2, achieving 83% of NO conversion at 300 °C and 20000 h−1 of GHSV.Figure optionsDownload as PowerPoint slide