Catalytic reactions of NO over 0-7 mol% Ba/MgO catalysts - II. Reduction with CH4 and CO
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The more general properties of Ba/MgO catalysts containing up to 7 mole % Ba were determined, emphasizing on the kinetics of the reaction. The SCR reaction with CH4 and the reaction with CH4 and CO in the absence of O2 were studied. Ba/MgO was an effective catalyst at elevated temperatures. The rate of the SCR reaction was greater than either the rate of reduction with CH4, in the absence of O2, or the rate of decomposition of NO. At 650C, the rate of the SCR reaction over 1 mole % Ba/MgO was 0.19 mol/g-sec with 1% NO, 0.25% CH4, and 0.5% O2. The SCR reaction occurred via gas-phase CH3- radicals that were formed at the surface. The SCR reaction was partially poisoned by CO2, which would be present as a product of combustion. This poisoning effect was less on the catalyst containing 1 mole % Ba than on the one containing 4 mole % Ba because at low loadings the basicity of the barium oxide was moderated by the less basic MgO support.