MnOx/TiO2 composite nanoxides synthesized by deposition-precipitation method as a superior catalyst for NO oxidation

A series of MnOx/TiO2 composite nanoxides were prepared by deposition-precipitation (DP) method, and the sample with the Mn/Ti ratio of 0.3 showed a superior activity for NO catalytic oxidation to NO2. The maximum NO conversion over MnOx(0.3)/TiO2(DP) could reach 89% at 250 °C with a GHSV of 25,000 h−1, which was much higher than that over the catalyst prepared by conventional wet-impregnation (WI) method (69% at 330 °C). Characterization results including XRD, HRTEM, FTIR, XPS, H2-TPR, NO-TPD and Nitrogen adsorption–desorption implied that the higher activity of MnOx(0.3)/TiO2(DP) could be attributed to the enrichment of well-dispersed MnOx on the surface and the abundance of Mn3+ species. Furthermore, DRIFT investigations and long-time running test indicated that NO2 came from the decomposition of adsorbed nitrogen-containing species.

Graphical abstractMnOx/TiO2 composite nanoxides prepared by deposition-precipitation method showed much higher activity for NO catalytic oxidation than that prepared by wet-impregnation method due to well-dispersion of MnOx and abundant Mn3+ species.Figure optionsDownload full-size imageDownload high-quality image (92 K)Download as PowerPoint slideResearch highlights► MnOx(0.3)/TiO2(DP) showed much higher activity than MnOx(0.3)/TiO2(WI) for NO catalytic oxidation to NO2. ► DP method made MnOx better dispersed on the support surface and produced more trivalent Mn species with respect to WI method. ► Trivalent Mn species was more favorable than tetravalent Mn species for NO catalytic oxidation. ► NO2 comes from the decomposition of nitrogen-containing species generated during the co-adsorption NO and O2.