汞在MnO_x-CeO_2/γ-Al_2O_3催化剂表面的赋存形态分析

为了高效经济地控制燃煤电站汞的排放,探索新型SCR催化剂上汞的催化氧化具有重要的学术价值和广阔的应用前景。Hg0在Mn Ox-Ce O2/γ-Al2O3(Mn Ce15)催化剂上被氧化后会以多种形态存在于催化剂表面,为确定Mn Ce15催化剂上汞的化合物的赋存形态,使用程序升温热分解方法研究了纯汞化合物的分解曲线,并与在不同烟气条件下处理过的Mn Ce15催化剂的分解脱附曲线进行了对比。研究确认了反应中Hg O、Hg Cl2、Hg(NO3)2和Hg SO4的生成,并根据实验结果分析了相应的汞化合物生成的反应路径。结果表明,在模拟烟气条件下Hg Cl2是主要的异相催化反应产物,同时可以在催化剂表面检测到少量Hg O和Hg SO4的生成。这一结论可为研究SCR催化剂上Hg0的催化氧化机理提供基础。

Speciation of mercury formed on MnOx-CeO2/γ-Al2O3 catalyst surface

Hg⁰ oxidation over selective catalytic reduction (SCR) catalysts would be of great scientific and practical value to control mercury emission in coal-fired power stations. To elucidate the mercury species existing on the MnO_x-CeO₂/γ-Al₂O₃(MnCe15) catalyst surface, a temperature programmed thermal decomposition (TPTD) method was used in this study to analyze the characteristics of the mercury species formed on the MnCe15 catalysts. A series of pure mercury compounds mixed with fresh MnCe15 were first studied for qualitative calibration. Then, the TPTD method was used to identify the Hg species on used MnCe15 catalysts pretreated under different operation conditions. The formation of HgO, HgCl₂, Hg(NO₃)₂ and HgSO₄ during the oxidation process was confirmed and the reaction pathways were proposed. The mercury species present were mainly HgCl₂ after MnCe15 catalysts were used to oxidize Hg⁰ under simulated flue gas conditions. HgO and HgSO₄ were found to exist in very low concentrations. This study provided the basis for the study on catalytic oxidation mechanism of Hg⁰ on SCR catalyst.