The influence of support composition on the activity of Cu:Ce catalysts for selective catalytic reduction of NO by CO in the presence of excess oxygen

Abstract

The catalytic activity of a series of Cu1:Ce3 catalysts supported on different supports (CNTs, AC, TiO₂, γ-Al₂O₃, and SiC) was studied for NO reduction by CO in the presence of excess oxygen. The effects of the support on the physicochemical properties of the Cu1:Ce3 catalysts were characterized by using SEM, TEM, N₂ adsorption–desorption, FTIR spectroscopy, XRD, XPS, CO-TPD, and NO-TPD techniques. The highest activity in the presence of oxygen was observed for the Cu1:Ce3/Al₂O₃ catalyst, and the NO conversion of 71.8% was obtained at 420 °C in the presence of 5% oxygen. The catalytic activity of the catalysts was significantly related to the synergistic interactions between surface oxygen vacancies and Cu⁺ species in the catalysts, as well as the electron transfer and metal/support interface. The high activity of the Al₂O₃ supported catalyst in the presence of oxygen is attributed to the presence of catalytically active centers on the support as well as on the surface of the supported crystallites. The NO conversion slightly increased after increasing the O₂ concentration from 2% to 5%, due to the adsorption of more O₂ on the surface, thus providing more adsorbed O, which reacted with adsorbed CO to form CO₂ and provide oxygen vacancy for NO adsorption and dissociation. The adsorbed O can react with NO and form NO₂, which quickly reacts with CO to form N₂ and CO₂. A possible reaction mechanism was proposed for the reaction in the presence of excess oxygen.