Identification of copper species present in Cu-ZSM-5 catalysts for NO{sub x} reduction

Journal Article · Sun Apr 25 04:00:00 EDT 1999 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1999.2391· OSTI ID:350254

Millar, G J; Canning, A; Rose, G; Wood, B; Trewartha, L; Mackinnon, I D.R. ^[1]

---

1. Univ. of Queensland, Brisbane, Queensland (Australia)

The structure of Cu-ZSM-5 catalysts that show activity for direct NO decomposition and selective catalytic reduction of NO{sub x} by hydrocarbons has been investigated by a multitude of modern surface analysis and spectroscopy techniques including X-ray photoelectron spectroscopy, thermogravimetric analysis, and in situ Fourier transform infrared spectroscopy. A series of four catalysts were prepared by exchange of Na-ZSM-5 with dilute copper acetate, and the copper loading was controlled by variation of the solution pH. Underexchanged catalysts contained isolated Cu{sup 2+}OH{sup {minus}}(H{sub 2}O) species and as the copper loading was increased Cu{sup 2+} ions incorporated into the zeolite lattice appeared. The sites at which the latter two copper species were located were fundamentally different. The Cu{sup 2+}OH{sup {minus}}(H{sub 2}O) moieties were bound to two lattice oxygen ions and associated with two framework aluminum ions. Once the Cu-ZSM-5 samples attained high levels of exchange, the development of [Cu({mu}-OH){sub 2}Cu]{sub n}{sup 2+}OH{sup {minus}}(H{sub 2}O) species along with a small concentration of Cu(OH){sub 2} was observed. On activation in helium to 500 C the Cu{sup 2+}OH{sup {minus}}(H{sub 2}O) species transformed into Cu{sup 2+}O{sup {minus}} and Cu{sup +} moieties, whereas the Cu{sup 2+} ions were apparently unaffected by this treatment (apart from the loss of ligated water molecules). Calcination of the precursors resulted in the formation of Cu{sup 2+}O{sub 2}{sup {minus}} and a one-dimensional CuO species. Temperature-programmed desorption studies revealed that oxygen was removed from the latter two species at 407 and 575 C, respectively.

• OSTI ID: 350254
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 183; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CATALYSTS
CHEMICAL PREPARATION
COPPER
NITROGEN OXIDES
PHASE STUDIES
SELECTIVE CATALYTIC REDUCTION
ZEOLITES