Reduction of NO over TiO2-supported Cu catalysts

TiO2-supported Cu catalyst pretreated with H-2 at 473 K exhibits higher activity for the conversion of NO at low temperatures than Cu on other supports. The NO is converted to N-2 via N2O as an intermediate. In the reaction at 303 K, NO is reduced to N2O. For the reaction above 323 K, the conversion of N2O to N-2 is accelerated. The samples were characterized by X-ray absorption near-edge structure (XANES), UV-VIS and EPR spectroscopies. Treatment of the sample with hydrogen at 473 K leads to formation of Cu metal particles and promotes the reduction of Ti ions. The extent of the reduction of TiO2 supporting Cu is much higher than that of TiO2 itself. NO has a role in the oxidation of both Cu and Ti ion, even at room temperature and H-2 reduces both ions. The active Cu-species is a CuO particle with a Cu metal core.