A Cu-containing CHA-type zeolite was prepared via aqueous ion exchange of the CHA zeolite from organic template-free synthesis. The thus-obtained template-free Cu-CHA showed the best catalytic performance (i.e., high low- and high-temperature reactivity, wide temperature-window, and high hydrothermal stability) in ammonia selective catalytic reduction (NH₃-SCR) of NO_x among three investigated Cu-CHA zeolites. Different Cu ion distributions of these Cu-CHA catalysts were confirmed by deconvolution of NO adsorbed Fourier transform infrared spectra; the Cu-containing template-free CHA catalyst has a high amount of isolated Cu²⁺ in a six-membered ring (6MR). Furthermore, the framework Al distribution is investigated by ²⁹Si MAS NMR analysis, indicating that the catalyst has a high fraction of paired Al sites, which stabilize Cu²⁺ ions in the 6MR, leading to a high ability to resist the harsh hydrothermal aging.

中文翻译：

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无模板合成的铜交换CHA型沸石：NH ₃ -SCR的有效催化剂

通过无有机模板合成中的CHA沸石的水离子交换来制备含Cu的CHA型沸石。如此获得的不含模板的Cu-CHA在NO的氨选择性催化还原（NH ₃ -SCR）中表现出最佳的催化性能（即高低温和高温反应性，宽温度范围和高水热稳定性）。_x在三个调查的Cu-CHA沸石中。通过NO吸附傅里叶变换红外光谱的反卷积，证实了这些Cu-CHA催化剂的不同Cu离子分布。含铜的无模板CHA催化剂在六元环（6MR）中具有大量的分离出的Cu ²⁺。此外，框架Al分布由²⁹Si MAS NMR分析表明，该催化剂具有很高比例的成对的Al位，可稳定6MR中的Cu ²⁺离子，从而具有很高的抵抗苛刻水热老化的能力。