Abstract:
Nitrogen oxides is one of the major pollutants in diesel exhaust, which has caused serious environmental pollution. The selective catalytic reduction (SCR) is the most efficient way to control NO
x emission, and the key is the catalysts with high activity. Recently, zeolites-based catalysts have been attracted more attention because of their special pore structure and catalytic performance. In this paper, impregnation, liquid-state ion exchange, and liquid-state ion exchange followed by impregnation methods were employed to prepare Fe-Cu-ZSM-5 catalyst. Over 80% of NO conversion can be achieved at the temperature region of 188-530℃, 200-520℃, and 240-530℃ for catalyst Fe
0.7-Cu
0.97-ZSM-5(IWI), Fe
0.59-Cu
1.0-ZSM-5(IE) and Fe
0.65(IWI)-Cu
0.95(IE)-ZSM-5, respectively. It was found that the catalyst Fe
0.7-Cu
0.97-ZSM-5 prepared with impregnation method exhibited the best catalytic performance for SCR reaction. However, the Fe
0.65-Cu
0.95-ZSM-5 catalyst prepared with liquid-state ion exchange followed by impregnation exhibited the lowest catalytic performance. The catalysts were characterized by XRD, UV-vis, H
2-TPR, XPS, NH
3-TPD, and NO oxidation. It was revealed that the catalyst Fe
0.7-Cu
0.97-ZSM-5(IWI) had more isolated Cu
2+ and Fe
3+ species at the exchange site, which are the active species for NH
3-SCR reaction at the low-temperature region. In addition, the catalyst Fe
0.7-Cu
0.97-ZSM-5(IWI) had the stronger redox ability and NO oxidation ability, as well as more acid sites on catalyst surface compared with catalyst Fe
0.59-Cu
1.0-ZSM-5(IE) and Fe
0.65 (IWI)-Cu
0.95 (IE)-ZSM-5. Above all, the states of active Cu and Fe species, reducibility of the catalyst and acidic properties on the catalyst surface are the critical factors for the catalytic performance of the Fe-Cu-ZSM-5 catalysts.