Selective Reduction of NO with Methane over Alumina-Supported Palladium Catalysts

Megumu INABA*, Yoshiaki KINTAICHI, Masaaki HANEDA and Hideaki HAMADA

National Institute of Materials and Chemical Research; 1-1 Higashi, Tsukuba-shi 305-8565 Japan

Selective reduction of NO with methane in the presence of oxygen using metal oxide-supported palladium catalysts was explored. Effect of various metal oxides and the conditions for catalysts preparation on the catalytic activity was investigated. Alumina-supported palladium exhibited especially highest catalytic activity for the selective reduction of NO among the other alumina-supported metal catalysts; alumina was found to be most effective as the support among several metal oxides. Although most of preparation conditions did not affect the activity of Pd/Al2O3, reduction at high temperature resulted in the decrease of deNOx activity. Result for catalyst characterization indicated that alumina support had strong solid-acidity and that the Pd dispersion for Pd/Al2O3 having high deNOx activity was high. The reduction at high temperature led to low dispersion of palladium supported on the same alumina. These results indicate that the solid acidity of the support and the dispersion of palladium are essential for the high catalytic activity. Concerning the reaction pathway, it was presumed that methane was first oxidized on palladium particles to partially oxidized compounds, which then reacted with NOx on alumina support to give N2, COx and H2O.

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