A New Insight into Active Cu2+ Species Properties in One-Pot Synthesized Cu-SSZ-13 Catalysts for NOx Reduction by NH3

The Cu-SSZ-13 catalysts with different copper content are prepared by one-pot method and changing the mole ratio of Cu-tetraethylenepentamine/Al2O3. Cu-SSZ-13 catalyst with 3.25 wt.% Cu exhibits excellent catalytic activity (operation temperature window of 145-490 degrees C), adaptability to high GHSV (gas hourly space velocity) and hydrothermal stability in NH3-SCR reaction. The results of XRD Rietveld refinement coupled with H-2-TPR and EPR show that three active Cu2+ species (Cu1, Cu2 and Cu3) locate in various sites in the CHA (chabazite) structure and play different action in NH3-SCR reaction. Cu1 species situated close to an eight-membered-ring play a crucial role in the low temperature activity for its optimum reduction ability. While Cu3 species located in the center of the hexagonal prism are the most stable and its content basically remains unchanged after SO2 pretreatment, which contributes to the excellent SO2 resistance.