过渡金属改性锰金属有机骨架催化剂低温NH3 -SCR 脱硝活性研究

Study on low⁃temperature NH3 -SCR activity of manganese metal organic framework catalyst modified by transition metal

  • 摘要: 采用过渡金属硝酸盐溶液浸渍 Mn-MOF(金属有机骨架)前驱体材料,经过煅烧后获得了 3种掺杂型锰基催化剂:MnFeOx,MnNiOx和MnCeOx。 对MnMeOx催化剂进行低温氨气选择性催化还 原(NH3-SCR)活性及抗硫性能测试。 结果表明,在空速(GHSV)为 30 000 h-1 下,MnFeOx 和 MnNiOx催化剂表现出最佳的低温 NH3-SCR 脱硝性能和抗硫性能,脱硝效率大于 90%的工作窗口 范围分别为100~250 °C和125~275 °C。 铈元素的掺杂未能显著提高催化剂的脱硝性能。 不同空 速测试结果表明,空速对催化剂性能有显著影响,空速越大催化剂脱硝效率越低,但对 N2 O 的生成 量影响较小。 通过 X-射线粉末衍射 (XRD)、扫描电子显微镜(SEM)、N2 吸附-脱附、X 射线光电 子能谱(XPS)、氢气程序升温还原性能测试(H2 -TPR)、氨气程序升温脱附测试(NH3 -TPD)等对掺 杂催化剂的理化性质进行研究。 结果表明,铁或镍的掺杂增大了催化剂的比表面积,改变了 Mn-MOF 烧结过程中 MnOx 晶体的成型过程,增加了催化剂表面 Mn4+ 和表面氧( Oα ) 含量,改善了 催化剂的氧化还原性能,增加了催化剂的活性位点。 相比之下,铈元素的掺杂降低了催化剂的比表 面积和表面氧含量,抑制了催化剂的氧化还原性能和表面活性位点的形成,导致其脱硝活性较差。 研究表明,适当的硝酸盐浸渍 Mn-MOF 能够制备高效的低温 NH3 -SCR 脱硝催化剂。

     

    Abstract: MnFeOx , MnNiOx and MnCeOx were synthesized by impregnating the precursor material of Mn - MOF (metal⁃organic framework) with transition metal nitrate solution. Low temperature selective catalytic reduction (SCR) activity and sulfur resistance of MnMeOx catalyst were investigated. The results showed that the MnFeOx and Mn⁃ NiOx catalysts had the best low⁃temperature NH3 -SCR denitration performance and sulfur resistance when the space velocity was 30 000 h-1. The working window ranges of their denitration efficiency greater than 90% were 100-250 °C and 125 - 275 °C respectively. The doping of cerium did not significantly improve the denitration performance of the catalyst. The results of different space velocity tests showed that the space velocity had a significant effect on the performance of the catalysts. The larger the space velocity the lower the denitration efficiency of the catalysts,but the variation of space velocity had less effect on the amount of N2 O production. The physicochemical properties of the doped catalysts were studied by X-ray powder diffraction (XRD),scanning electron microscope (SEM),N2 ad⁃ sorption⁃desorption,X-ray photoelectron spectroscopy (XPS),Hydrogen temperature⁃programmed reduction perform⁃ ance test (H2 -TPR),and Ammonia temperature⁃programmed desorption test (NH3 -TPD). The results showed that the doping of Fe or Ni increased the specific surface area of the catalyst,changed the formation process of MnOx crystal during Mn-MOF sintering,and increased Mn4+ and surface oxygen on the catalyst surface. Doping metal ions improved the redox performance of the catalyst and increased the active center of the catalyst. In contrast,the do⁃ ping of cerium element reduced the specific surface area and surface oxygen content of the catalyst,inhibited the redox performance and the formation of surface active sites,resulting in poor denitration activity. The results showed that ap⁃ propriate nitrate impregnation Mn-MOF could prepare an efficient low⁃temperature NH3 -SCR denitration catalyst.

     

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