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

Abstract

CrOx, Ce0.5Zr0.5O2 and 10Cr/Ce0.5Zr0.5O2 catalysts were prepared to investigate the separate effect of Cr and Ce0.5Zr0.5O2 for selective catalytic oxidation of NO. It was found that the co-actions of CrOx and Ce0.5Zr0.5O2 exhibited the higher catalytic activity than separate effect of CrOx or Ce0.5Zr0.5O2. The separate effects of Cr and Ce0.5Zr0.5O2 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 Ce0.5Zr0.5O2. 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.