Study of Na/Cu/TiO ₂ catalysts for the storage and reduction of NO

A Pt-free system based on Na/Cu/TiO 2 catalysts was used to study the adsorption of NO under lean conditions. The results show that the NO adsorption activity dramatically increased when both sodium and copper are in intimate contact. Although copper is the active phase in the oxidation of NO to NO 2, it was found that the addition of sodium species is of vital importance on the subsequent adsorption of NO 2, which mainly occurs on the surface of the alkali in the form of nitrates and nitrites. It was found that a loading increase of the alkali led to an increase in the reduction temperature of the copper phase, which is ascribed to a close interaction between the copper and the sodium phases. Among the Na loadings that were studied, the addition of 5% Na gave the optimum adsorption of NO. After successive cycles of adsorption, the catalysts were fully regenerated at temperatures higher than 250°C using either CO or H 2 as a reducing agent. © 2012 Elsevier B.V.