The support effect of CuO catalyst for the reduction of nitric oxide with hydrogen or ammonia
Abstract
The reduction of nitric oxide (NO) with H2 or NH3 over CuOx catalysts supported on ZrO2 or TiO2 has been investigated. The activity and selectivity of NO reduction were very sensitive to the types of support oxide. A gradual increase in activity of CuO/ZrO2 for the reduction of NO with NH3 was observed in the course of the reaction, while the activity of CuO/TiO2 was rapidly reduced as the reaction proceeded under the same reaction conditions. For the reaction of NO + NH3 in the presence of oxygen, however, CuO/ZrO2 was less active than CuO/TiO2. Several states of Cu2+ on the surfaces of ZrO2 or TiO2 were detected by means of e.s.r. spectroscopy. Cu2+ ions on ZrO2 were reduced more easily than those on TiO2 and hence this catalyst was concluded to show a high activity in NO + NH3 or NO + H2 reactions.