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

Abstract Mn-based catalysts impregnated on TiO 2 with different crystalline phases (rutile (R), anatase (A), and P25 (P)) were studied for the oxidation of NO to NO 2 . 10%MnO x /TiO 2 (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 MnO x /TiO 2 (P) > MnO x /TiO 2 (A) > MnO x /TiO 2 (R). The catalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, H 2 temperature-programmed reduction, and O 2 temperature-programmed desorption. Compared to anatase and rutile, P25 gave better dispersion of MnO x on the support surface, suppressed the agglomeration of catalyst particles, and also produced more Mn 2 O 3 , which was more active for the oxidation of NO. In addition, P25 enhanced the reduction of MnO x , especially for Mn 2 O 3 , and the formation of easily desorbed O 2 − generated from the Mn 3+ –O bond.