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The reduction and oxidation of Co species in CoZSM-5 zeolites studied by IR spectroscopy
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dc.type
JournalArticle
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dc.description.physical
1023-1029
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dc.abstract.en
The process of reducing Co ions in zeolite CoZSM-5 by NO, $H_{2}$ and CO, as well as of oxidizing them by $O_{2}$ was studied by IR spectroscopy with CO as the probe molecule for $Co^{2+}$ and NO as the probe for $Co^{3+}$. Two zeolites of different Co status were used: in the first, $Co^{2+}$ ions were localized mostly in cation exchange positions, and in the second most of the $Co^{2+}$ occurred in the form of CoO and oxide-like clusters. IR studies evidenced that NO reduced some $Co^{3+}$ to $Co^{2+}$ already at room temperature, and also reduced some $Co^{2+}$ to lower oxidation states (probably $Co^{+}$) at 670 and 1070 K. Only $Co^{2+}$ in exchange positions could be reduced with NO. The treatment of zeolite CoZSM-5 with $H_{2}$ or with CO at 670 and 1070 K made the reduction of $Co^{3+}$ to $Co^{2+}$ (the contribution of $Co^{3+}$ decreased and the contribution of $Co^{2+}$ increased). IR studies illustrated that the most electron-acceptor $Co^{3+}$ (characterized by a high frequency $Co^{3+}$–NO band) were transformed, by reduction, into the most electron-acceptor $Co^{2+}$ (characterized by a high frequency $Co^{2+}$–CO band). The treatment of zeolite CoZSM-5 with oxygen at 670–1070 K resulted in the oxidation of $Co^{2+}$ to $Co^{3+}$ (the contribution of $Co^{2+}$ decreased while the contribution of $Co^{3+}$ increased).
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dc.subject.en
CoZSM-5 zeolite
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dc.subject.en
reduction
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dc.subject.en
oxidation
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dc.subject.en
IR spectroscopy
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dc.description.volume
52
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dc.description.number
8
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dc.identifier.doi
10.1007/s11244-009-9260-y
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dc.identifier.eissn
1572-9028
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dc.title.journal
Topics in Catalysis
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dc.title.volume
Catalysis for society
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dc.language.container
eng
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dc.affiliation
Wydział Chemii : Zakład Chemii Nieorganicznej
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dc.subtype
Article
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dc.rights.original
bez licencji
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