Activation of NO with microwave irradiation for low temperature direct decomposition

Direct decomposition of nitric oxide (NO) on metal oxides under microwave (MW) irradiation was investigated and it was found that the most metal oxides show higher NO decomposition activity than that in the conventional electric furnace heating at low temperature. Among the examined oxides, it was found that TiO 2 , CeO 2 , ZrO 2 , and Y 2 O 3 show about 95 % or higher NO conversion at 573 K, and both N 2 and O 2 are formed with almost equimolar amount. In particular, ZrO 2 exhibited high and stable NO decomposition activity more than 25 h. In this study, the influence of coexisting gases on NO decomposition activity on ZrO 2 under microwave heating was further investigated and the direct decomposition of NO can be proceeded even in the presence of 5 % O 2 , 5 % CO 2, or humidified condition. Mechanism of high NO decomposition activity under MW irradiation was also studied and it was found that removal of oxygen from the catalyst was much increased under MW irradiation because of direct activation of oxygen and also direct activation of NO which is also suggested by pulse reaction. • ZrO 2 shows high activity to NO direct decomposition under micro wave irradiation. • Complete NO direct activation to N 2 and O 2 was achieved on ZrO 2 at 573 K under micro wave irradiation. • High activity of NO decomposition was sustained for 24 h and even under O 2 , CO 2 , and steam coexisted. • Micro wave irradiation effects can be assigned to removal of oxygen strongly adsorbed on ZrO 2 .