Cu-Exchanged CHA-Type Zeolite from Organic Template-Free Synthesis: An Effective Catalyst for NH<sub>3</sub>-SCR
Yong Wang, Toshiki Nishitoba, Yunan Wang, Xiangju Meng, Feng‐Shou Xiao, Weiping Zhang, Bernd Marler, Hermann Gies, Dirk De Vos, Ute Kolb, Mathias Feyen, Robert McGuire, Andrei‐Nicolae Parvulescu, Ulrich Müller, Toshiyuki Yokoi
Abstract
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 NOx 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.