Effect of copper precursors on the catalytic performance of Cu-ZSM-5 catalysts in N2O decomposition

Five Cu-ZSM-5 catalysts were obtained by treating Na-ZSM-5 (Si/Al ratio = 15) with aqueous solutions of different Cu precursors (CuCl2, Cu(NO3)2, CuSO4, Cu(CH3COO)2, and ammoniacal copper (II) complex ion). After being pretreated in flowing He at 500 °C to form active Cu+, these catalysts exhibited quite different activities in catalytic decomposition of N2O. CZM-AC(II) (prepared by ammoniacal copper (II) complex ion) with 9.4 wt% Cu content was the most active among these Cu-ZSM-5 catalysts, achieving almost complete N2O conversion at 400 °C. CZM-CA (prepared using Cu(CH3COO)2 as the Cu precursor) with 2.8 wt% Cu content was the second most active catalyst among these Cu-ZSM-5 catalysts, achieving almost complete N2O conversion at 425 °C. CZM-CC, CZM-CN, and CZM-CS prepared by using CuCl2, Cu(NO3)2, or CuSO4 as the Cu precursor with similar Cu contents (≈ 1.7 wt%) were the least active among these Cu-ZSM-5 catalysts, achieving ca. 90% N2O conversion at 500 °C. XRD, ICP, SEM, TEM, EDX-mapping, and CO-IR experiments were conducted to characterize relevant samples. The superior activity of CZM-AC(II) can be attributed to the high contents of total Cu+ and dimeric Cu+ among these samples. The influence of co-fed O2 or H2O on the catalytic performance of typical samples was also studied.