Promotional effects of ascorbic acid on the low-temperature catalytic activity of selective catalytic oxidation of ammonia over Pt/SA: effect of Pt0 content

Abstract

Low-temperature selective catalytic oxidation (SCO) is one of the important strategies used to remove the NH₃ slip upstream of NH₃ selective catalytic reduction (NH₃-SCR). We have systematically studied the influence of the dispersity of active species, particle size and Pt⁰ content on the catalytic activity of ammonia oxidation with a Pt-based catalyst. Ascorbic acid was added to the modified Pt/SiO₂–Al₂O₃ catalyst by the co-impregnation method for selective catalytic oxidation of ammonia (NH₃-SCO), to explore the influence of different properties of the active components on the catalytic activity. It was found that addition of ascorbic acid changed the Pt⁰ content in the catalyst. Further studies found that increase in the Pt⁰ content could effectively promote activation of oxygen and facilitate more rapid conversion of O₂ molecules to oxygen atoms. Thus, the dehydrogenation reaction of ammonia and oxygen atoms was promoted and proceeded at a lower temperature, improving the low-temperature activity of the NH₃-SCO reaction. At the same time, it was shown that the Pt⁰ content in the system was the key factor affecting the NH₃-SCO reaction, and this was confirmed by X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, H₂ temperature-programmed reduction and in situ diffuse-reflectance infrared Fourier transform spectroscopy.