The catalytic properties of Cu modified attapulgite in NH3–SCO and NH3–SCR reactions

Abstract

The cheap and readily available attapulgite (ATP) was doped with different Cu content by using an improved wet impregnation method and their NH3 oxidation and NOx reduction properties were analyzed at 150–500 °C. Results suggested that all these Cu-ATP catalysts possessed superior NH3 oxidation activity, which was further promoted in the presence of NO. However, higher Cu loading led to lower N2 selectivity and NO conversion at high temperatures. 1%Cu-ATP catalyst exhibited good performance in both selective catalytic oxidation of NH3 (NH3-SCO) and selective catalytic reduction of NO by NH3 (NH3-SCR) at 350 °C. And it showed relatively good SO2 and H2O tolerance in the presence of NO. Characterization results proved that Cu2+ ion increased the strong acid sites and redox properties of 1%Cu-ATP, and should be responsible for the outstanding NH3-SCO and NH3-SCR activity. While CuO species, which introduced abundant moderate acid sites and significantly improved redox capability, enriched on the catalysts as the copper loading increased. It dramatically promoted NH3 oxidation and inhibited NO conversion and N2 formation. Therefore, 1%Cu-ATP was more suitable to simultaneously remove slip ammonia and residual NOx in the flue gas, which would facilitate the efficient operation of SCR system and reduce the maintenance costs.