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

doi:10.1007/s11244-009-9260-y

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tytuł	The reduction and oxidation of Co species in CoZSM-5 zeolites studied by IR spectroscopy
autor	Góra-Marek Kinga
tytuł czasopisma	Topics in Catalysis
tom	52
numer	8
data wydania	2009
strony	1023-1029
ISSN	1022-5528
eISSN	1572-9028
DOI	10.1007/s11244-009-9260-y
język	angielski
język czasopisma	angielski
abstrakt w j. angielskim	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).
słowa kluczowe w j. angielskim	CoZSM-5 zeolite, reduction, oxidation, IR spectroscopy
wydział:instytut/zakład/katedra	Wydział Chemii : Zakład Chemii Nieorganicznej
typ	artykuł w czasopiśmie
podtyp	artykuł