Zeolite-like ion-exchanged Cu-attapulgite catalysts for promoted selective oxidation of ammonia†

The selective catalytic oxidation of ammonia (NH₃-SCO) to N₂ and H₂O is a highly efficient method for eliminating NH₃ pollution. However, it is still a challenge to develop low-cost and high-performance catalysts. Herein, zeolite-like ion-exchanged Cu-attapulgite (Cu-ATP) catalysts have been originally developed for NH₃-SCO, and the obtained Cu-ATP catalysts exhibit comparable NH₃-SCO performance to the conventional Cu-zeolite catalysts. The dominant Cu²⁺ active sites in Cu-ATP facilitate the adsorption and activation of NH₃ and O₂, leading to high activity (T₉₀ = 300 °C) and N₂ selectivity (100%) over a wide temperature range from 180 °C to 390 °C. Temperature-programmed surface reaction and in situ diffuse reflectance infrared Fourier transform spectroscopy studies reveal that the NH₃-SCO reaction at Cu²⁺ sites proceeds via the internal selective catalytic reaction (i-SCR) pathway, with NO₂ serving as the key intermediate. This work paves the way for developing natural clay-based zeolite-like catalysts, which are expected to replace zeolite catalysts in various reactions.