Abstract
The activity of 0.25–5% Ag/Al2O3 catalysts in the selective catalytic reduction of nitrogen oxides with n-hexane under the conditions of promotion with a small amount of H2 was studied. It was found that, upon the introduction of ∼1000 ppm of H2 into the reaction mixture, the Ag/Al2O3 samples containing 1–2% Ag exhibited optimum activity and selectivity. It was established that, in the presence of 1000 ppm of H2, the rate of the selective catalytic reduction of NO x was higher by a factor of 10–13, and the onset temperature of the reaction was lower by approximately 100°C. It was found by X-ray photoelectron spectroscopy, temperature-programmed reduction, and UV spectroscopy that the high activity of 1–2% Ag/Al2O3 catalysts was due to the presence of small Ag δ+ n and Ag 0 m clusters on their surface. A decrease in the concentration of Ag below the optimum value resulted in the predominance of an inactive ionic form on the catalyst surfaces. As the concentration of Ag was increased (>2%), large particles of Ag2O and Ag0, which facilitate the oxidation of n-C6H14, were formed to lead to a decrease in selectivity and in the degree of reduction of nitrogen oxides.
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Original Russian Text © N.A. Sadokhina, A.F. Prokhorova, R.I. Kvon, I.S. Mashkovskii, G.O. Bragina, G.N. Baeva, V.I. Bukhtiyarov, A.Yu. Stakheev, 2012, published in Kinetika i Kataliz, 2012, Vol. 53, No. 1, pp. 110–119.
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Sadokhina, N.A., Prokhorova, A.F., Kvon, R.I. et al. Dependence of the catalytic activity of Ag/Al2O3 on the silver concentration in the selective reduction of NO x with n-hexane in the presence of H2 . Kinet Catal 53, 107–116 (2012). https://doi.org/10.1134/S0023158412010090
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DOI: https://doi.org/10.1134/S0023158412010090