posted on 2020-03-31, 15:34authored byYong 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
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.