Oxidation activity and 18O-isotope exchange behavior of nickel oxide-stabilized cubic zirconia

Dongare, Mohan K. ; Malshe, Kusum ; Gopinath, Chinnakonda S. ; Murwani, Irmina Kris ; Kemnitz, Erhard (2004) Oxidation activity and 18O-isotope exchange behavior of nickel oxide-stabilized cubic zirconia Journal of Catalysis, 222 (1). pp. 80-86. ISSN 0021-9517

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/j.jcat.2003.11.009


A series of NiO-ZrO2 samples with 2 to 40 mol% of NiO were prepared using a sol-gel synthesis technique and calcined at 873 K. XRD characterization of the samples revealed the stabilization of a cubic zirconia- (fluorite) phase containing nickel oxide up to 20 mol%. Bulk NiO characteristics were observed above 20 mol% loading of NiO. The linear decrease in lattice parameter up to 20 mol% of NiO indicates the probable incorporation of Ni2+ into the lattice position of Zr4+ ions. The NiO-ZrO2 sample with 20% NiO retained its cubic phase even after prolonged heating at 1273 K, indicating 20 mol% as an optimum content of NiO for a thermally stable cubic zirconia phase. The BET surface areas of these samples were in the range of 40 to 70 m2 g−1. XPS spectra along with XRD data indicated that at low (5 mol%) concentrations of NiO, Ni2+ enters ZrO2 lattice substitutionally creating oxygen vacancies. TPR of NiO-ZrO2 showed the reduction of nickel oxide at 533 and 633 K, indicating nickel in two different environments, at a substitutional position and at a surface/interstitial position. 18O-isotope exchange studies of these samples showed a partial heterogeneous exchange and the Tonset was found to be lowest for the sample containing 20 mol% NiO. The activity for CH4 and CO oxidation was investigated by 18O-isotope exchange as well as catalytic studies in complete oxidation of CH4 and CO. The activity for CH4 oxidation was highest for the NiO-ZrO2 sample with 20 mol% NiO. CH4 and CO oxidation with 18O isotope over NiO-ZrO2 catalysts showed the formation of CO2 with 16O (amu 44), suggesting that the bulk oxygen is acting as an active species for methane oxidation. The structure of NiO-ZrO2 samples with varying NiO content and its correlation with catalytic activity mechanism is discussed.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:NiO-stabilized Zirconia; Methane Oxidation; CO Oxidation; 18O-isotope Exchange; Sol-gel Synthesis
ID Code:61841
Deposited On:15 Sep 2011 12:11
Last Modified:15 Sep 2011 12:11

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