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Title: Oxidation states of copper ions in ZSM-5 zeolites. A multitechnique investigation

Abstract

The redox behavior of Cu/ZSM-5 zeolites prepared by ion exchange from Cu{sup 2+} aqueous solutions has been followed by a variety of spectroscopic techniques to provide a thorough picture of the so-called self-reduction of cupric ions, which occurs upon dehydration of the hydrated system at various temperatures, and of the reverse process of reoxidation as well. Conflicting hypotheses on both these processes are, in fact, present in the literature. The experimental techniques employed in this work are electron paramagnetic resonance (EPR), IR, and optical spectroscopies, extended X-ray absorption fine structure, and X-ray absorption near-edge structure. The early stages of dehydration (from room temperature to about 470 K) involve cupric ion migration and formation of RPR silent moieties but no reduction to Cu{sup +}. The onset of this latter phenomenon starts at 470 K and, in the range 470--670 K, involves the majority of copper ions present in the system. Rehydration of Cu{sup +}-containing samples does not cause direct Cu{sup +} to Cu{sup 2+} by molecular oxygen, in fact, does not take place at room temperature if O{sub 2} is contacted with the dehydrated material but easily occurs when oxygen is adsorbed on rehydrated samples at the same temperature.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Univ. di Torino (IT)
OSTI Identifier:
20050842
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical
Additional Journal Information:
Journal Volume: 104; Journal Issue: 17; Other Information: PBD: 4 May 2000; Journal ID: ISSN 1089-5647
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COPPER; ZEOLITES; REDUCTION; SPECTROSCOPY; DEHYDRATION; REDOX POTENTIAL; CATALYSTS

Citation Formats

Palomino, G.T., Fisicaro, P., Bordiga, S., Zecchina, A., Giamello, E., and Lamberti, C. Oxidation states of copper ions in ZSM-5 zeolites. A multitechnique investigation. United States: N. p., 2000. Web. doi:10.1021/jp993893u.
Palomino, G.T., Fisicaro, P., Bordiga, S., Zecchina, A., Giamello, E., & Lamberti, C. Oxidation states of copper ions in ZSM-5 zeolites. A multitechnique investigation. United States. doi:10.1021/jp993893u.
Palomino, G.T., Fisicaro, P., Bordiga, S., Zecchina, A., Giamello, E., and Lamberti, C. Thu . "Oxidation states of copper ions in ZSM-5 zeolites. A multitechnique investigation". United States. doi:10.1021/jp993893u.
@article{osti_20050842,
title = {Oxidation states of copper ions in ZSM-5 zeolites. A multitechnique investigation},
author = {Palomino, G.T. and Fisicaro, P. and Bordiga, S. and Zecchina, A. and Giamello, E. and Lamberti, C.},
abstractNote = {The redox behavior of Cu/ZSM-5 zeolites prepared by ion exchange from Cu{sup 2+} aqueous solutions has been followed by a variety of spectroscopic techniques to provide a thorough picture of the so-called self-reduction of cupric ions, which occurs upon dehydration of the hydrated system at various temperatures, and of the reverse process of reoxidation as well. Conflicting hypotheses on both these processes are, in fact, present in the literature. The experimental techniques employed in this work are electron paramagnetic resonance (EPR), IR, and optical spectroscopies, extended X-ray absorption fine structure, and X-ray absorption near-edge structure. The early stages of dehydration (from room temperature to about 470 K) involve cupric ion migration and formation of RPR silent moieties but no reduction to Cu{sup +}. The onset of this latter phenomenon starts at 470 K and, in the range 470--670 K, involves the majority of copper ions present in the system. Rehydration of Cu{sup +}-containing samples does not cause direct Cu{sup +} to Cu{sup 2+} by molecular oxygen, in fact, does not take place at room temperature if O{sub 2} is contacted with the dehydrated material but easily occurs when oxygen is adsorbed on rehydrated samples at the same temperature.},
doi = {10.1021/jp993893u},
journal = {Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical},
issn = {1089-5647},
number = 17,
volume = 104,
place = {United States},
year = {2000},
month = {5}
}