Role of organic nitro compounds in selective reduction of NO_x with ethanol over different supported silver catalysts

The adsorption of organic nitro compounds such as nitromethane and nitroethane on different supported silver catalysts (Ag/Al₂O₃, Ag/TiO₂, Ag/SiO₂) has been studied using infrared spectroscopy. The adsorbed NCO species formation was strongly influenced by the catalyst support and therefore clearly detected on Ag/Al₂O₃ and Ag/TiO₂ catalysts by thermal decomposition of nitromethane and nitroethane at temperatures higher than 150°C. With the Ag/SiO₂ catalyst, very little NCO formation was observed at 350°C. On the other hand, the catalyst support was found to affect the N₂ formation in the selective reduction of NO_x on supported silver catalysts. On the basis of these findings, the role of adsorbed nitromethane, nitroethane and isocyanate species in the selective reduction of NO_x is discussed with respect to the catalyst support effect and the catalytic activity.