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Cu+, Ag+ and Na+ Cationic Sites in ZSM-5 Interacting with Benzene: DFT Modeling

Załucka J., Kozyra P., Mitoraj M., Brocławik E., Datka J.

Polish Journal of Chemistry

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2008

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Vol. 82, nr 9

1801-1808

EN

Synthesis and characterization of new multimodal porous systems containing thin MFI zeolitic films is reported. These films cover the internal surface of the meso- and macroporous silica-alumina monoliths. They are easily accessible through the open porous structure retained in the partially recrystallized, originally amorphous monolith. When the mesoporous Al-SBA-15 sieves are used in stead of monoliths, a controlled hydrothermal process results in the formation of the MFI nanodomains dispersed in the walls that separate mesopores hexagonally arranged. These do mains possess strong acidic sites of the zeolitic type, but the original ordering of mesopores in the parent material is very well retained. A simple method for the synthesis of the MFI crystals containing both meso- and macrovoids is also proposed. It makes use of the suspended mono- and polydispersed carbon particles that serve as porogens. Thus, the porous MFI crystals obtained can be used for the preparation of effective bifunctional catalysts by the de position of a highly dispersed metallic (Pd) phase.

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Aktywacja cząsteczek organicznych przez jony Cu+ w zeolitach

Kukulska-Zając E., Kozyra P., Datka J.

Wiadomości Chemiczne

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2007

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[Z] 61, 11-12

839-890

EN

The present paper describes the activation of organic molecules containing multiple bonds by donation of electrons to ?* antibonding orbitals of the molecules. The data concerning the adsorption of alkenes (ethene, propene, cis-but-2-ene, trans--but-2-ene), acetylene, benzene, acetone, and formaldehyde on Cu+ sites in zeolites CuX, CuY, and CuZSM-5 will be presented. The spectroscopic IR data, as well as the results of quantum chemical DFT calculations will be considered. Both IR studies and DFT calculations evidenced a weakening of C=C and C-C bonds. IR red shift reaches 78-115 cm-1 for C=C band and 168 cm-1 for acetylene. Moreover, in the case of ethene and acetylene the stretching modes of the C=C and C-C bonds which were IR inactive in free molecules became IR active when interacting with Cu+, indicating the loss of symmetry. On the contrary, the C=C stretching in trans-but-2-ene was still IR inactive when trans-but-2-ene interacted with Cu+. At high loading some Cu+ ions were able to bond two alkene molecules. Although the activation is small, it occurs also for aromatic C-C bond in benzene adsorbed on Cu+ site; the red band shift was 13 cm-1 i.e. much less than in the case of alkenes and acetylene. Similarly, the activation of C=O bond in acetone and formaldehyde inter-acting with Cu+ also results in the red band shift of 38 and 56 cm-1.

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Formation of Brönsted acid sites in the reaction of cyclohexanol on NaCeY zeolites

Vogt O., Nattich M., Datka J., Gil B.

Bulletin of the Polish Academy of Sciences. Chemistry

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2002

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Vol. 50, No. 2

281-288

EN

This study was undertaken to elucidate why the catalytic activity of NaCeY in cyclohexanol reactions carried out in a pulse reactor increases with the pulse number. We studied therefore the effect of cyclohexanol and also of ethanol and water on catalytic activity of NaCeY (of exchange degrees 36 and 72%) in cyclohexanol reactions: isomer-ization and disproportionation. We also studied the reaction of cyclohexanol and water with NaCeY zeolite by IR spectroscopy. Our results evidenced that new Bronsted acid sites were formed by the reaction of cyclohexanol, and water. This was shown by IR spectroscopy: the increase of Si-O(1)H-Al band 3638 cm (-1) and in increase of ammonium ions band (upon ammonia adsorption), The new sites were formed by hydrolysis of Ce(3+) ions with water introduced in a pulse, or produced by dehydration of cyclohexanol catalyzed by acid sites. Formation of new Bronsted acid sites resulted in an increase of catalytic activity of NaCeY in cyclohexene reaction as observed in this study and also in cyclohexanol reactions.

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Acid Properties of HY Zeolite Dealuminated by Steaming and EDTA Treatment - NMR, XPS and IR Studies

Datka J., Gil B., Złamaniec J., Batamack P., Fraissard J., Massiani P.

Polish Journal of Chemistry

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1999

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Vol. 73, nr 9

1535-1548

EN

Steaming of zeolite is known to remove some Al atoms from the framework, which results in the formation of extraframework Al species and in the increase of the framework Si/Al ratio (Si/Al fram). The effects of these factors on the nature, concentration, strength, homogeneity and accessibility of the acid sites in Y zeolite were followed by an IR study of the adsorption/desorption of ammonia and pyridine.