Influence of Mn/(Mn+Ce) Ratio of MnOx-CeO2/WO3-ZrO2 Monolith Catalyst on Selective Catalytic Reduction of NOx with Ammonia

A series of monolith MnOx-CeO2/WO3-ZrO2 catalysts with different mass ratios of Mn/(Mn+Ce) were prepared and used for the selective catalytic reduction (SCR) of NOx with NH3 in the presence of excess O2. The catalysts were characterized by N2 adsorption, oxygen storage capacity, X-ray diffraction, X-ray photoelectron spectroscopy, NH3/NO temperature-programmed desorption, and H2 temperature-programmed reduction. The best catalyst had the mass ratio of Mn/(Mn+Ce) = 0.5. It gave 90% NOx conversion in the range of 173-355 °C at the gas hourly space velocity of 10000 h−1, and characterization results showed that a higher oxidation activity of NO to NO2, more surface Ce and Mn with a larger Ce3+/Ce4+ ratio, lower NH3 and NO desorption temperatures, and excellent redox ability were together responsible for its best NH3-SCR performance.

摘要制备了一系列不同 Mn/(Mn+Ce) 质量比的 MnOx-CeO2/WO3-ZrO2 整体式催化剂用于富氧条件下的 NH3 选择性催化还原 NOx (NH3-SCR), 并采用 N2 吸脱附、储氧量、X 射线衍射、X 光电子能谱、NH3/NO 程序升温脱附以及 H2 程序升温还原等手段对催化剂进行表征. 结果表明, 当 Mn/(Mn+Ce) 质量比为 0.5 时, 整体式催化剂具有较好的 NH3-SCR 性能, 在空速 10000 h−1 和 173–355 ºC 条件反应下, NOx 转化率达 90% 以上. 这是由于该 MnOx-CeO2/WO3-ZrO2 催化剂具有更高的 NO 氧化活性、更高的表面 Ce 和 Mn 原子浓度以及 Ce3+/Ce 值较低的 NH3 和 NO 脱附温度以及优异的氧化还原性能所致.

A monolithic 10%MnOx–10%CeO2/WO3-ZrO2 catalyst was active at low temperature and gave over 90% NO conversions at 173–355 °C.Figure optionsDownload as PowerPoint slide