Interaction between NO and CO on the surface of CuCo 2O 4 spinel

Abstract

The interaction between NO and CO on the surface of CuCo 2O 4 spinel was investigated at 293–700 K. IR studies were carried out on a γ-Al 2O 3-supported spinel using a flow-cell reactor and a gradientless cell reactor. TPD experiments were performed on supported and unsupported spinels. Exposure of the support to NO+CO at 293 K produced bands at 1330–1350 and 1420 cm −1, which gradually disappeared at 323–400 K. Within the same temperature range, the evolution of CO 2, NO and CO were observed, accompanied by a TD max in the TPD spectra, and NO was registered in the gas flow in experiments with a gradientless cell reactor. This was attributed to the formation of (CO.NO) x complexes of a carbonate, nitro or nitrate type, respectively, which determines the low-temperature interaction mechanism. At temperatures above 470 K the catalyst at first consumed CO, after which neutralization of NO began. A mechanism is proposed based on the interaction between NO from the gas phase and pre-adsorbed CO. No formation of isocyanate complexes was observed irrespective of the high CO:NO ratio (5:1).