Direct Decomposition of NO over Supported-alkaline Earth Metal Oxide Catalysts

Abstract

NO decomposition over supported alkaline earth metal oxide catalysts was strongly dependent on the type of metal oxide support. Y 2 O 3 was the most effective support. Ba/Y 2 O 3 showed the highest NO decomposition activity, which decreased in the order of Ba/Y 2 O 3 > Sr/Y 2 O 3 > Ca/Y 2 O 3 > Mg/Y 2 O 3 ∼Y 2 O 3 . The catalytic activity of Ba/Y 2 O 3 for NO decomposition at 900°C gradually increased with reaction time. The activity enhancement was due to the decomposition of barium carbonate into barium oxide during the reaction. Barium carbonate was completely decomposed by reduction with H 2 at 900°C, resulting in significant enhancement of NO decomposition activity. The activity of Ba/Y 2 O 3 increased with higher barium loading up to 5 wt%, and then became constant. There was a strong relationship between NO conversion and the amount of NO adsorption on Ba/Y 2 O 3 , suggesting that NO adsorption sites are the reaction sites for NO decomposition. The relationship between the activity for 1-butene isomerization, which is an indicator for the basicity of Ba/Y 2 O 3 catalysts, and the activity for NO decomposition suggests direct participation of basic sites in the NO decomposition reaction over supported alkaline earth metal oxide catalysts.