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 to remove the NH3 slip from the upstream of the NH3 selective catalytic reduction (NH3-SCR). We have systematically studied the influence of dispersity of active species, particle size and content of Pt0 on the catalytic activity of ammonia oxidation in Pt–based catalyst. Ascorbic acid (AA) was added to modified Pt/SiO2-Al2O3 catalyst by co-impregnation method for selective catalytic oxidation of ammonia (NH3-SCO), which for the purpose of exploring the influence of different properties of active components on catalytic activity. It was found that the addition of AA changed the content of Pt0 in the catalyst. Further studies have found that the increase of Pt0 content could effectively promote the activation of oxygen and facilitate O2 molecule to be activated into oxygen atoms more rapidly, thus promoting the dehydrogenation reaction of ammonia and oxygen atoms to proceed at a lower temperature and improving the low-temperature activity of NH3-SCO reaction. At the same time, it was also proved that the content of Pt0 in the system was the key factor affecting the NH3-SCO reaction and could be confirmed by XPS, HRTEM, H2-TPR and In situ DRIFT.