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Selective Catalytic Reduction of NO by Methane over Pd Loaded on Heteropolyacids/SiO 2 at Low Temperature

2005; Oxford University Press; Volume: 78; Issue: 2 Linguagem: Inglês

10.1246/bcsj.78.361

1348-0634

Kazu Okumura, Ryosuke Yoshimoto, Katsuki Suzuki, Miki Niwa,

Catalysis and Oxidation Reactions

Abstract Pd was loaded on heteropolyacids/SiO2, and used for the selective reduction of NO with methane in the presence of oxygen and moisture. The catalyst exhibited activity in the selective reduction of NO in the temperature range between 473 and 573 K. The temperature was significantly lower than that in the conventional catalysts, such as Pd-loaded zeolites or monolayer-type oxides. Among tested heteropolyacids, H3PW12O40 gave rise to the highest activity in the reaction. The catalytic performance was improved by the addition of water vapor. The generation of highly dispersed PdO species was observed in the Pd K-edge EXAFS spectra, whose structure was similar to those found in the conventional Pd-loaded zeolites catalyst. The reason for the evolution of NO reduction activity over Pd/H3PW12O40/SiO2 was attributed to the formation of NOH+, as measured by IR, in addition to the generation of highly dispersed PdO species at low temperature on the Brønsted acid sites of heteropolyacid.