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1 2007

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Aktywacja cząsteczek organicznych przez jony Cu+ w zeolitach

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

Wiadomości Chemiczne

2007

[Z] 61, 11-12

839-890

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.