Effects of Cr on the NO oxidation over the ceria–zirconia solid solution

Abstract

CrO_x, Ce_0.5Zr_0.5O₂ and 10Cr/Ce_0.5Zr_0.5O₂ catalysts were prepared to investigate the separate effect of Cr and Ce_0.5Zr_0.5O₂ for selective catalytic oxidation of NO. It was found that the co-actions of CrO_x and Ce_0.5Zr_0.5O₂ exhibited the higher catalytic activity than separate effect of CrO_x or Ce_0.5Zr_0.5O₂. The separate effects of Cr and Ce_0.5Zr_0.5O₂ on the structure of the catalysts were systematically examined by XRD, TEM, BET, XPS, NO-TPD and O₂-TPD. The XPS results showed that Cr species were enriched on the surface and the amount of Cr⁶⁺ increased after Cr was loaded on the Ce_0.5Zr_0.5O₂. TPD results showed that NO was adsorbed on the sites of Cr, and O₂ was adsorbed and activated on the ceria–zirconia solid solution. Finally, the adsorbed NO interacted with the adsorbed O₂ to generate NO₂ in the Langmuir–Hinshelwood mechanism.