TiO2晶相对MnOx/TiO2催化剂催化NO氧化性能的影响

以浸渍在不同晶相TiO₂ （金红石型（R）、锐钛矿型（A）和P25型（P））上的锰基催化剂为对象，研究了TiO₂晶相对MnO_x/TiO₂催化剂催化NO氧化活性的影响。 结果表明，MnO_x/TiO₂（P）催化剂活性最高，NO转化率在300℃及GHSV = 20000 h^-1条件下可达83%。 各催化剂活性顺序为MnO_x/TiO₂（P）>MnO_x/TiO₂（A）>MnO_x/TiO₂（R）。采用X射线粉末衍射、场发射扫描电子显微镜、X射线光电子能谱、H₂程序升温还原和O₂程序升温脱附等手段研究了TiO₂晶相影响MnO_x/TiO₂催化剂催化活性的作用机理。结果表明，相比于A和R型TiO₂，P型TiO₂能够增加MnO_x在其表面的分散度并抑制催化剂颗粒的团聚和粘连，且更有利于Mn₂O₃的生成，而后者催化NO氧化活性比其它MnO_x更高；此外，P型TiO₂可以增加MnO_x尤其是Mn₂O₃的还原性，并可促进O₂^-从M³⁺-O键的脱附。

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%MnO_x/TiO₂(P) was the most active catalyst, giving 83% of NO conversion at 300℃ and a GHSV of 20000 h^-1. The catalyst activities were in the order MnO_x/TiO₂(P) > MnO_x/TiO₂(A) > MnO_x/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 MnO_x 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 MnO_x, especially for Mn₂O₃, and the formation of easily desorbed O₂^- generated from the Mn³⁺-O bond.