The reduction and oxidation of Co species in CoZSM-5 zeolites  studied by IR spectroscopy

doi:10.1007/s11244-009-9260-y

The reduction and oxidation of Co species in CoZSM-5 ...

Bibliographic description

title:	The reduction and oxidation of Co species in CoZSM-5 zeolites studied by IR spectroscopy
author:	Góra-Marek Kinga
Journal title:	Topics in Catalysis
volume:	52
issue:	8
date of publication:	2009
pages:	1023-1029
ISSN:	1022-5528
eISSN:	1572-9028
DOI:	10.1007/s11244-009-9260-y
language:	English
Journal language:	English
abstract in english:	The process of reducing Co ions in zeolite CoZSM-5 by NO, H2 and CO, as well as of oxidizing them by O2 was studied by IR spectroscopy with CO as the probe molecule for Co2+ and NO as the probe for Co3+. Two zeolites of different Co status were used: in the first, Co2+ ions were localized mostly in cation exchange positions, and in the second most of the Co2+ occurred in the form of CoO and oxide-like clusters. IR studies evidenced that NO reduced some Co3+ to Co2+ already at room temperature, and also reduced some Co2+ to lower oxidation states (probably Co+) at 670 and 1070 K. Only Co2+ in exchange positions could be reduced with NO. The treatment of zeolite CoZSM-5 with H2 or with CO at 670 and 1070 K made the reduction of Co3+ to Co2+ (the contribution of Co3+ decreased and the contribution of Co2+ increased). IR studies illustrated that the most electron-acceptor Co3+ (characterized by a high frequency Co3+–NO band) were transformed, by reduction, into the most electron-acceptor Co2+ (characterized by a high frequency Co2+–CO band). The treatment of zeolite CoZSM-5 with oxygen at 670–1070 K resulted in the oxidation of Co2+ to Co3+ (the contribution of Co2+ decreased while the contribution of Co3+ increased).
keywords in english:	CoZSM-5 zeolite, reduction, oxidation, IR spectroscopy
affiliation:	Wydział Chemii : Zakład Chemii Nieorganicznej
type:	journal article
subtype:	academic paper