Effects of Alkali and Alkaline Earth Cocations on the Activity and Hydrothermal Stability of Cu/SSZ-13 NH3-SCR Catalysts
Effects of Alkali and Alkaline Earth Cocations on the Activity and Hydrothermal Stability of Cu/SSZ-13 NH3-SCR Catalysts
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DOI：
10.1021/acscatal.5b01621
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发表时间：
2015-11-01
期刊：
影响因子：
12.9
通讯作者：
Peden, Charles H. F.
中科院分区：
文献类型：
--
作者：
Gao, Feng;Wang, Yilin;Peden, Charles H. F.
采用三步水溶液离子交换法制备了阳离子改性Cu/SSZ-13 SCR催化剂。这些催化剂，在新鲜和水热老化的形式，其特征在于与几种方法，包括程序升温还原H-2（H-2-TPR），程序升温脱附NH3（NH3-TPD），和Al-27固态核磁共振（NMR）和漫反射红外傅立叶变换（DRIFT）光谱。使用稳态标准NH3-SCR来探测它们的催化性能。表征结果表明，cocations削弱铜离子和CHA框架之间的相互作用，使它们更容易还原。通过除去一部分布朗斯台德酸位点，共阳离子还有助于减轻沸石催化剂在水热老化期间的水解，如Al-27 NMR所证明的。反应测试表明，某些共阳离子，特别是Li+和Na+，促进低温SCR速率，而其他共阳离子显示出不太明显的效果。在应用方面，我们的研究结果表明，引入共阳离子可以是一个可行的策略，以改善低温和高温性能的Cu/SSZ-13 SCR催化剂。
Using a three-step aqueous solution ionexchange method, cocation modified Cu/SSZ-13 SCR catalysts were synthesized. These catalysts, in both fresh and hydrothermally aged forms, were characterized with several methods including temperature-programmed reduction by H-2 (H-2-TPR), temperature-programmed desorption of NH3 (NH3-TPD), and Al-27 solid-state nuclear magnetic resonance (NMR) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies. Their catalytic performance was probed using steady-state standard NH3-SCR. Characterization results indicate that cocations weaken interactions between Cu ions and the CHA framework making them more readily reducible. By removing a portion of Bronsted acid sites, cocations also help to mitigate hydrolysis of the zeolite catalysts during hydrothermal aging as evidenced from Al-27 NMR Reaction tests show that certain cocations, especially Li+ and Na+, promote low-temperature SCR rates while others show much less pronounced effects. In terms of applications, our results indicate that introducing cocations can be a viable strategy to improve both low- and high-temperature performance of Cu/SSZ-13 SCR catalysts.