Catalytic activity of Cu–SSZ-13 prepared with different methods for NH3-SCR reaction

Abstract

A series of Cu–SSZ-13 catalysts with the same Cu loading were prepared by different methods of incipient wetness impregnation [Cu–SSZ-13 (IWI)], ion exchange [Cu–SSZ-13 (IE)] and hydro-thermal synthesis [Cu–SSZ-13 (HTS)]. Their activity for selective catalytic reduction of nitrogen oxides (NOx) with NH3 was determined. The results show that the Cu–SSZ-13(HTS) catalyst exhibits a better ammonia selective catalytic reduction (NH3-SCR) activity compared with the other two catalysts, over which more than 90% NO conversion is obtained at 215–600 °C under the space velocity of 180,000 h−1. The characterization results reveal that the Cu–SSZ-13(HTS) catalyst possesses more amount of stable Cu2+ in the six-membered ring and high ability for NH3 and NO adsorption, leading to its high NH3-SCR activity, although this catalyst has low surface area. On the other hand, the activity of Cu–SSZ-13(IE) catalyst is almost the same as that of Cu–SSZ-13 (IWI) catalyst at the temperature lower than 400 °C, but the activity of the former is much higher than that of the latter at > 400 °C due to the high activity of Cu–SSZ-13(IWI) catalyst for NH3 oxidation. Three kinds of Cu–SSZ-13 with the same amount of Cu loading were prepared by different methods. The catalyst prepared by hydrothermal synthesis displayed the better NH3-SCR activity due to more isolated Cu2+ in six-membered ring of the CHA structure.