Catalytic Reactions of NO over 0–7 mol% Ba/MgO Catalysts I. The Direct Decomposition of NO

Author： Xie S. Rosynek M.P. Lunsford J.H.

ISSN： 0021-9517

Source： Journal of Catalysis, Vol.188, Iss.1, 1999-11, pp. : 24-31

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Abstract

A series of catalysts composed of barium oxide supported on magnesium oxide with Ba loadings up to 7 mol% has been studied for NO and N₂O decomposition. Nitrous oxide is an intermediate in the decomposition of nitric oxide; however, the rate of N₂O decomposition is much greater than that of NO decomposition so that the selectivity for N₂ formation approaches 100% at T>700°C. Over 4 mol% Ba/MgO catalyst, the rate of N₂ formation at 800°C was 0.22 μmol g^-1 s^-1 for a gas stream containing 1% NO in He. When the inhibiting effect of O₂ is properly accounted for, the reaction order with respect to NO is two. This order is consistent with a mechanism in which gas-phase NO reacts with a surface NO_x species that is probably present in an ionic form, considering the temperatures at which the reaction occurs. In situ Raman spectroscopy has demonstrated the presence of nitrate and nitrite ions on the surface, but the exact nature of the surface intermediate is not known.