Adsorption of trichloro- and trifluoromethane in Y-zeolites as studied by IR spectroscopy and multinuclear solid-state NMR
- 1 January 1999
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Physical Chemistry Chemical Physics
- Vol. 1 (4) , 579-584
- https://doi.org/10.1039/a808296k
Abstract
The adsorption of CH(D)Cl3 and CHF3 on a series of alkali-exchanged Y-zeolites was studied by 1H- and 23Na-NMR and by FTIR spectroscopy. Several adsorption structures were detected which involve H-bonding C–H(D)···OZ between the acidic C–H(D) group and basic OZ-framework atoms and between the exchangeable cations and halogen atoms of the probe molecules. 1H-NMR demonstrated rapid exchange between several adsorption species and IR spectroscopy permitted detection of at least two different species, namely purely H-bonded species I and species II and/or III involving cation–halogen interactions. It is inferred that these species can undergo facile interconversion and that such processes may be involved in the rapid exchange as detected by NMR. Based on 23Na-NMR results it is concluded that adsorption of CHCl3 on NaY modifies the negative charge distribution in the zeolite framework. The adsorption-induced C–H(D)-stretching frequency shift of trichloromethane is considered to be a measure of the base strength of the framework OZ-atoms.Keywords
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