Tailoring the local environment of silver in SSZ-13 zeolites for low-temperature catalytic oxidation of ammonia

Abstract

Supported Ag catalysts have shown great potential in selective catalytic oxidation of ammonia (NH3-SCO) for the depletion of harmful ammonia emissions. However, the lack of effective ways to control the proportional population of active Ag species in/on the support has been the major limitation to their catalytic performance. Herein, the electronic properties, stability, and dispersion of Ag species were rationally tuned by tailoring the micro-environment of SSZ-13 zeolite supports. The influence of the local environment of Ag species in SSZ-13 on their catalytic behavior during NH3-SCO reaction was extensively investigated by comprehensive characterizations. Results obtained have shown that SSZ-13 (31s) with moderate ion-exchange sites, a large external surface area and abundantly accessible defect sites are beneficial to the stabilization and dispersion of the Ag active sites which trigger the formation of plentiful active Ag0 species. The Ag0 species are immobilized on SSZ-13(31s) with high metal dispersion which facilitates the activation of oxygen and the dehydrogenation of adsorbed NH3, thus exhibiting excellent low-temperature activity and hydrothermal stability in the NH3-SCO reaction. This work deepens the understanding on the effect of support towards the engineering of active metal species and provides a facile strategy for the preparation of highly efficient metal-based catalysts.