School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, 100083, People's Republic of China.
Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, University of Science and Technology Beijing, Beijing, 100083, People's Republic of China.
Environ Sci Pollut Res Int. 2022 Mar;29(14):21210-21220. doi: 10.1007/s11356-021-14644-5. Epub 2021 Nov 9.
In this research, one-step synthesis of redox co-precipitation method (using sodium lauryl sulfate, KMnO, and metal precursor) was well applicable in universally preparing low-dimensional Me-MnOx nanosheet catalysts with different metal doping (Me=Co, Ni, or Sn). NH-SCR activity was explored to the relationship with structure morphology and physio-chemical properties via the characterization techniques of SEM, XRD, XPS, H-TPR, and NH-TPD. It was found that Ni-MnOx has a relatively poor activity at low-down temperature but was improved as the reaction temperature rising. Co-MnOx presented a relatively stable catalytic activity of which the NOx conversion rate can be maintained 80~90% in a wide temperature window of 100-250 °C with relatively better N selectivity. Compared with Co- or Ni-modified MnOx, Sn-MnOx catalyst has an excellent low-temperature catalytic activity (93% NOx conversion at 100 °C) that was maintained > 80% before 200 °C but with poor selectivity to N. Due to its nanosheet-structured solid solution structure, Sn-MnOx promoted the interaction between MnOx and SnO with the increased contents of adsorbed oxygen and also the numbers of surface Lewis acid sites, which integrally promoted the NH-SCR reaction at low temperature and also contributed to an acceptable resistances to water and sulfur. High content of adsorbed oxygen was beneficial to improve the catalytic activity at lower temperatures, while the electron cycle interaction of different metal valence ions will play a more important role with the increase of reaction temperature.
在这项研究中，一步合成的氧化还原共沉淀法（使用十二烷基硫酸钠、KMnO4 和金属前体）可普遍适用于制备不同金属掺杂（Me=Co、Ni 或 Sn）的低维 Me-MnOx 纳米片催化剂。通过 SEM、XRD、XPS、H-TPR 和 NH-TPD 等表征技术，研究了 NH-SCR 活性与结构形态和物理化学性质的关系。结果表明，Ni-MnOx 在低温下活性较差，但随着反应温度的升高而提高。Co-MnOx 表现出相对稳定的催化活性，在 100-250°C 的较宽温度窗口内，NOx 转化率可保持在 80-90%，具有较好的 N 选择性。与 Co 或 Ni 改性的 MnOx 相比，Sn-MnOx 催化剂具有优异的低温催化活性（100°C 时 NOx 转化率为 93%），在 200°C 之前保持>80%，但对 N 的选择性较差。由于其纳米片结构的固溶体结构，Sn-MnOx 促进了 MnOx 和 SnO 之间的相互作用，增加了吸附氧的含量和表面路易斯酸位的数量，这整体上促进了低温下的 NH-SCR 反应，并有助于对水和硫的可接受的阻力。高含量的吸附氧有利于提高低温下的催化活性，而不同金属价态离子的电子循环相互作用将随着反应温度的升高而发挥更重要的作用。
