Studies on Cu/CeO2: A New NO Reduction Catalyst

Abstract

Fine particle and large surface area Cu/CeO2 catalysts of crystallite sizes in the range of 100–200 Å synthesized by the solution combustion method have been investigated for NO reduction. Five percent Cu/CeO2 catalyst shows nearly 100% conversion of NO by NH3 below 300°C, whereas pure ceria and Zr, Y, and Ca doped ceria show 85–95% NO conversion above 600°C. Similarly NO reduction by CO has been observed over 5% Cu/CeO2 with nearly 100% conversion below 300°C. Hydrocarbon (n-butane) oxidation by NO to CO2, N2, and H2O has also been demonstrated over this catalyst below 350°C making Cu/CeO2 a new NO reduction catalyst in the low temperature window of 150–350°C. Kinetics of NO reduction over 5% Cu/CeO2 have also been investigated. The rate constants are in the range of 1.4×104 to 2.3×104 cm3 g−1 s−1 between 170 and 300°C. Cu/CeO2 catalysts are characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy where Cu2+ ions are shown to be dispersed on the CeO2 surface.