sup 13 C NMR identification of intermediates formed by 2-methyl-2-propanol adsorption in H-ZSM-5

Journal Article · Wed Feb 01 00:00:00 EST 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00185a009· OSTI ID:5092779

Aronson, M T; Gorte, R J; White, D ^[1]; Farneth, W E ^[2]

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1. Univ. of Pennsylvania, Philadelphia (USA)
2. E. I. du Pont de Nemours and Co., Wilmington, DE (USA)

{sup 13}C NMR spectroscopy has been used to characterize intermediates formed by the adsorption of 2-methyl-2-propanol, (CH{sub 3}){sub 3} {sup 13}COH, on a H-ZSM-5 zeolite. Previous adsorption studies had shown that, upon exposure of H-ZSM-5 to this alcohol and subsequent evacuation at 295 K, an adsorption complex could be formed, which had a coverage of 1 alcohol molecule/Al atom in the zeolite and had carbenium-ion-like properties. In the present NMR studies, it is shown that the adsorbed species can best be described as a silyl ether, with the alkyl group covalently bonded to the zeolite framework oxygen. Furthermore, the adsorption and evacuation conditions used for preparing the samples are found to be very important since these silyl ether intermediates are highly reactive. The {sup 13}C NMR spectrum obtained following adsorption shows two prominent features, one at 77 ppm from TMS, which is assigned to carbon that is bonded to the oxygen, and a second at 29 ppm, which is due to aliphatic carbons formed in secondary reactions. {sup 13}C NMR spectra were taken of samples at 10 K and after heating to 373 K to verify these assignments, as well as search for additional features that could be masked by dynamics at room temperature. No spectral features were observed in the region expected for carbenium ions, even though the chemistry observed for the adsorption intermediate was consistent with this chemistry and similar to that observed following olefin adsorption on H-ZSM-5. This implies that the steady-state concentration of carbenium ions in H-ZSM-5 is low or that the lifetime of these species is short. 32 refs., 8 figs.

• OSTI ID: 5092779
• Journal Information: Journal of the American Chemical Society; (USA), Vol. 111:3; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
PROPANOLS
ADSORPTION
ZEOLITES
SORPTIVE PROPERTIES
CARBON 13
EXPERIMENTAL DATA
NMR SPECTRA
ALCOHOLS
CARBON ISOTOPES
DATA
EVEN-ODD NUCLEI
HYDROXY COMPOUNDS
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
ISOTOPES
LIGHT NUCLEI
MATERIALS
MINERALS
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
SORPTION
SPECTRA
STABLE ISOTOPES
SURFACE PROPERTIES
400201* - Chemical & Physicochemical Properties
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation