Maximizing the hydrothermal stability of Cu-LTA for NH3-SCR by control of Cu content and location

Abstract

Hydrothermal stability is crucial for the application of NOx emission control catalysts on diesel vehicles. In this study, the influences of Cu content and Cu species on the catalytic performance and hydrothermal stability of copper-exchanged LTA (Cu-LTA) zeolite catalysts for the selective catalytic reduction of NOx with NH3 (NH3-SCR) have been systematically investigated. The Cu-LTA(n)−0.41 catalyst with the maximum amount and ratio of Cu2+-2Z species in Cu-LTA, with Cu/Al = 0.41 and Si/Al = 16, was produced by full occupation of Al pairs in the single 6-rings (s6rs) with Cu2+ ions. This catalyst showed higher deNOx activity after hydrothermal aging under extremely harsh conditions of 920 °C for 24 h than any of the other catalysts. The results suggest that maximizing the amount of Cu2+-2Z species and diminishing the formation of comparatively vulnerable [Cu(OH)]+-Z species in the high-silica LTA zeolite is an effective strategy for developing hydrothermally stable NH3-SCR catalysts.