超声辅助合成纳米氧化锰及其低浓度NO去除性能研究

通过超声辅助的工艺, 利用氧化还原法制备出多价态纳米MnO_x。通过调节超声时间、KMnO₄浓度、烘干温度、反应溶液pH, 探索MnO_x的最佳合成条件。结果表明: 超声时间20 min, 高锰酸钾浓度0.5 mol/L, 烘干温度80 ℃, 反应溶液pH=7的条件下, 合成的样品MnO_x表现出最佳的催化性能, 对100%的NO去除率可持续15 h。采用X射线衍射分析(XRD)、N₂-吸脱附测试、扫描电镜(SEM)、透射电镜(TEM)等技术考察最优催化剂MnO_x的结构和形貌, 借助X射线光电子能谱(XPS)和傅里叶红外分析(FT-IR)研究最优催化剂MnO_x对NO去除的催化氧化机理以及催化剂的失活机制。结果表明, 三维贯穿的多级孔结构, 花瓣状的形貌和弱晶化的晶体结构有利于气体吸附和传输。多价态Mn和氧空位的存在促进了NO和O₂的吸附和激活, 因此最优样品MnO_x表现出优异的NO的常温催化氧化。

Synthesis of Nano Manganese Oxide with Assistance of Ultrasonic for Removal of Low Concentration NO

The varied-valence nanocatalyst MnO_x was prepared using the oxidation-reduction method under ultrasonic. The optimal synthetic conditions of MnO_x were explored by adjusting the ultrasonic time, concentration of reaction precursor, drying temperature, and pH of reaction solution. The results indicated that the optimal sample MnO_x was synthesized under the condition of ultrasonic time of 20 min, 0.5 mol/L KMnO₄, drying temperature of 80 ℃ and pH=7, which showed the super catalytic performance and the time of 100% NO removal rate was as high as 15 h at room temperature. The structure and morphology of the optimal catalyst MnO_x were investigated by XRD, N₂-adsorption-desorption analysis, SEM and TEM. Besides, XPS and FT-IR were also applied to explore the catalytic oxidation process of NO removal and the deactivation mechanism of the optimal sample MnO_x. It is believed that the interpenetrating and hierarchal pore, the petaloid morphology and weak crystallization structure contribute to the gas adsorption and transmission. The presence of varied-valence Mn and oxygen vacancy can improve the adsorption and activation of NO and O₂, thus, enhancing the NO catalytic removal on the optimal catalyst MnO_x at room temperature.