Deactivation of Cu-SSZ-13 in the presence of SO2 during hydrothermal aging
Deactivation of Cu-SSZ-13 in the presence of SO2 during hydrothermal aging
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DOI：
10.1016/j.cattod.2017.11.006
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发表时间：
2017-11
期刊：
影响因子：
5.3
通讯作者：
Yulong Shan;Xiaoyan Shi;Zidi Yan;Jingjing Liu;Yunbo Yu;Hong He
中科院分区：
文献类型：
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作者：
Yulong Shan;Xiaoyan Shi;Zidi Yan;Jingjing Liu;Yunbo Yu;Hong He
具有菱沸石 (CHA) 结构的 Cu2+ 交换沸石催化剂被认为是用 NH3 选择性催化还原 NOx 的最佳候选者。然而在实际应用中，SCR催化剂很容易发生水热老化和硫中毒。在这项工作中，研究了 SO2 和高温水热老化的共同影响。与低温下发生的SO2中毒的可逆抑制不同，高温下的硫中毒由于沸石结构的破坏而是永久性的，并且没有观察到硫酸盐的沉积。通过固态 27Al 核磁共振 (27Al-NMR)、X 射线衍射 (XRD)、NH3 和 NO 程序升温解吸 (NH3/NO-TPD)、电子顺磁共振 (EPR)、H2 程序升温还原 (H2-TPR)、原位 DRIFTS 和质谱检测热重分析 (TG-Mass) 对 Cu-SSZ-13 催化剂进行表征，以了解降解情况高温水热老化和硫化过程中的机制。结果表明，SO2 去除了水热老化过程中脱铝过程产生的骨架外铝原子。与仅进行水热老化处理的Cu-SSZ-13相比，在高温硫化后，更多的Cu2+物质以CuOx的形式积累。 Cu2+物质的脱铝和积累导致Cu-SSZ-13催化剂酸位和活性位点的损失，并导致NH3-SCR性能下降。
Cu2+-exchanged zeolite catalysts with the chabazite (CHA) structure have been thought to be optimal candidates for selective catalytic reduction of NOx with NH3. In real applications, however, SCR catalysts readily undergo hydrothermal aging and sulfur poisoning. In this work, the co-effect of SO2and hydrothermal aging at high temperature was investigated. Different from the reversible inhibition of SO2poisoning that occurs at low temperatures, the sulfur poisoning at high temperature is permanent due to the destruction of the zeolite structure, and no deposit of sulfate is observed. Cu-SSZ-13 catalysts were characterized through solid state27Al nuclear magnetic resonance (27Al-NMR), X-ray diffraction (XRD), temperature-programmed desorption of NH3and NO (NH3/NO-TPD), electron paramagnetic resonance (EPR), temperature-programmed reduction by H2(H2-TPR), in situ DRIFTS, and thermogravimetric analysis with mass spectrometric detection (TG-Mass) to develop an understanding of the degradation mechanisms during hydrothermal aging and sulfurization at high temperature. The results indicated that SO2dislodged the extra-framework Al atoms that resulted from the dealumination process that occurs during hydrothermal aging. More Cu2+species were accumulated as CuOx for Cu-SSZ-13 after sulfurization at high temperature compared to that treated by hydrothermal aging only. The dealumination and accumulation of Cu2+species caused a loss of acid and active sites for the Cu-SSZ-13 catalyst, and resulted in degradation of NH3-SCR performance.