Electron paramagnetic resonance studies of copper ion-exchanged ZSM-5

Journal Article · Thu Nov 03 04:00:00 EST 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100095a039· OSTI ID:7079731

Larsen, S C; Aylor, A; Bell, A T; Reimer, J A ^[1]

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1. Lawrence Berkeley Lab., CA (United States)

Electron paramagnetic resonance (EPR) spectroscopy was utilized to probe the oxidation state and coordination environment of copper in ion-exchanged CuZSM-5. EPR spectra of hydrated samples were consistent with octahedral coordination. Square pyramidal and square-planar sites were identified in pretreated CuZSM-5 samples, and the relative concentration of square-pyramidal sites in these samples was linearly correlated with the copper-exchange level. The extent of autoreduction was monitored by EPR and it was determined that a substantial fraction (approximately 40-60%) of the copper was reduced and the reduction process was reversible in the presence of water. A mechanism for the autoreduction of copper is proposed that is consistent with the EPR results. Further, the reactivity of the proposed copper species was probed in reducing and oxidizing environments and in the presence of nitric oxide. The increase in EPR signal intensity that was observed after room-temperature NO exposure of pretreated and oxidized CuZSM-5 is attributed to the formation of copper nitrite and nitrate species. High-temperature in situ EPR experiments revealed that on the time scale of the EPR experiment, the paramagnetic copper environment did not change at elevated temperatures in the presence of nitric oxide. 39 refs., 13 figs., 3 tabs.

• OSTI ID: 7079731
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:44; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
661300 -- Other Aspects of Physical Science-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CATALYSTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COPPER COMPOUNDS
COPPER NITRATES
DECOMPOSITION
ELECTRON SPIN RESONANCE
HYDRATION
INORGANIC ION EXCHANGERS
ION EXCHANGE
ION EXCHANGE MATERIALS
KINETICS
MAGNETIC RESONANCE
MATERIALS
MINERALS
NITRATES
NITRIC OXIDE
NITRITES
NITROGEN COMPOUNDS
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
REDUCTION
RESONANCE
SILICATE MINERALS
SOLVATION
TRANSITION ELEMENT COMPOUNDS
VALENCE
ZEOLITES