Controlling the distribution of aluminum in a Cu–zeolite catalyst by seed-assisted synthesis to improve its NH3-SCR activity

Abstract

Modulating the Al sites in zeolites has been regarded as a promising but difficult strategy for designing high-performance catalysts for various reactions. To this end, a simple seed-assisted strategy was devised in this study to tune the Al distribution in a KFI-type zeolite for improving its activity for the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). The seed-assisted approach aided in modifying the Al distribution, which increased the proportion of paired Al sites in the KFI zeolite. The resulting distribution of Al sites led to different coordination environments of the Cu ions and enhanced proximity among the Cu ions in the KFI cage due to weaker interactions with the framework. Regulating the cation–framework interactions by altering the Al distribution promoted the redox cycle of the Cu ions in the seed-added Cu-KFI catalysts, which enabled their superior intrinsic NH₃-SCR activity compared to that of the Cu-KFI parent catalyst, especially at low temperatures (200–250 °C).