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 CuO_x 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.