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- 2015
Ag改性Mn/H-beta催化剂的甲烷低温催化燃烧
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Abstract:
为提高Mn基催化剂的甲烷低温催化燃烧活性,以H？？beta分子筛作为催化剂载体,采用浸渍法通过Ag改性制备了Mn？？Ag/H？？beta催化剂;在固定床反应器中研究了Mn？？Ag/H？？beta催化剂在低温(523～823 K)时的甲烷低温催化燃烧活性和抗水耐硫性;通过X射线衍射和X射线光电子能谱等表征手段研究了Mn？？Ag/H？？beta催化剂中Ag和Mn的相互作用。研究表明:在温度低于823 K时,Ag改性显著提高了Mn/H？？beta催化剂的低温催化活性;当催化剂中Ag和Mn的质量分数均为6％时,Mn？？Ag/H？？beta催化剂的催化活性较好;SO2和H2O会抑制Mn？？Ag/H？？beta催化剂的活性;H2O对于催化剂的硫酸化无明显的促进作用;Mn？？Ag/H？？beta催化剂中Mn主要以Mn3+和Mn4+的氧化态形式存在,Ag的添加可促进部分Mn3+向Mn4+的转变;催化剂中Mn具有稳定Ag+活性位的作用。研究结果可为甲烷低温催化燃烧催化剂的优化设计提供参考。
To improve the catalytic activity of Mn？？based catalysts for CH4 combustion at low temperature, the H？？beta zeolites were employed as the support for Mn, and Ag was used as the cooperating agent for Mn/H？？beta catalyst. Mn？？Ag/H？？beta catalysts were prepared by impregnation method. The combustion activity, H2O resistance and SO2 tolerance of Mn？？Ag/H？？beta catalysts were studied in a fixed？？bed reactor at low temperatures between 523 K and 823 K. The interaction of Mn and Ag was investigated by X？？ray diffraction (XRD) and X？？ray photoelectron spectroscopy (XPS). Ag addition significantly promotes the catalytic performance of Mn/H？？beta catalysts below 823 K. A Mn？？Ag/H？？beta catalyst with equal metal mass fraction of 6％ has the highest activity for CH4 oxidation. However, the activity of Mn？？Ag/H？？beta catalyst is inhibited in the presence of SO2 and H2O. No obvious promotion of H2O for the formation of sulfate species is observed in the catalyst. Mn is mainly present in both the 3+and 4+oxidation states in Mn？？Ag/H？？beta catalysts. The presence of Ag enforces the transformation of certain amount of Mn3+ ions to Mn4+ ions. The major contribution of Mn suggested by the data in this paper is to stabilize Ag in a dispersed Ag+ state. This work is of considerable referential importance in the optimization design of catalysts for CH4 combustion at low temperature
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