In-Situ 13C NMR studies of 1-butene reactions on acid catalystswithout magic angle spinning

Summary:A Magic Angle Spinning (MAS) NMR probe has been designed allowing the in-situ measurements of NMR spectra of working catalyst. The probe was built following the original design of M. Hunger [Hunger, 1995 #2]. It allows the magic angle spinning of powder samples up to 3.5 kHz, under gas flowing conditions, and at temperatures up to 573K.

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Lithium-7 NMR Studies of Li1−xCoO2 Battery Cathodes

MRS Proceedings ◽

10.1557/proc-369-59 ◽

1994 ◽

Vol 369 ◽

Cited By ~ 13

Author(s):

B. Ouyang ◽

X. Cao ◽

H.W. Lin ◽

S. Slane ◽

S. Kostov ◽

...

Keyword(s):

Chemical Shifts ◽

Parent Compound ◽

Magic Angle Spinning ◽

Magic Angle ◽

Line Broadening ◽

X Ray Diffraction ◽

Nmr Studies ◽

Relaxation Measurements ◽

Angle Spinning

AbstractLithium-deficient cathode materials Li1-xCoO2 where x = 0.1, 0.4 and 0.6 were prepared electrochemically from the stoichiometric parent compound (x = 0.0).The materials were observed to be air-stable, and x-ray diffraction characterization yielded good agreement with the in situ studies of Dahn and co-workers, regarding changes in lattice parameters. In addition to both static and magic angle spinning (MAS) 7Li NMR, measurements, the samples were investigated by EPR and cobalt K-edge NEXAFS. The removal of Li is accompanied by compensating electrons from the Co d-orbitals, asevidenced by both shifts in the NEXAFS peak and the observation of EPR signals due to spins localized on the Co ions. These spins, in turn, result in dramatic 7Li chemical shifts (89 ppm for x = 0.6) and line broadening. Whereas MAS analysis of Li0.9CoO2 indicates two magnetically inequivalent Li sites, the spectra becometoo broad to resolve different sites for higher values of x. Finally NMR linewidth and spinlattice relaxation measurements as a function of temperature suggest a modest increase in Li+ ion mobility for Li-deficient samples as compared to the parent compound.

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High-temperature in-situ magic angle spinning NMR studies of chemical reactions on catalysts

The Journal of Physical Chemistry ◽

10.1021/j100199a052 ◽

1992 ◽

Vol 96 (20) ◽

pp. 8106-8111 ◽

Cited By ~ 36

Author(s):

F. Gregory Oliver ◽

Eric J. Munson ◽

James F. Haw

Keyword(s):

High Temperature ◽

Chemical Reactions ◽

Magic Angle Spinning ◽

Magic Angle ◽

Nmr Studies ◽

Angle Spinning

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Magic Angle Spinning 13C NMR Studies of Filled Vulcanizates

Rubber Chemistry and Technology ◽

10.5254/1.3538175 ◽

1983 ◽

Vol 56 (5) ◽

pp. 959-970 ◽

Cited By ~ 13

Author(s):

Richard A. Komoroski

Keyword(s):

13C Nmr ◽

Direct Analysis ◽

Magic Angle Spinning ◽

Magic Angle ◽

Nmr Studies ◽

Absolute Deviation ◽

Standard Curve ◽

Peak Resolution ◽

Power Decoupling ◽

Angle Spinning

Abstract Magic angle spinning (MAS) 13C NMR is investigated as an alternative method to IR spectroscopy of solution state NMR for the characterization of the elastomeric conmponents of filled vulcanizates. Good high resolution spectra can be obtained from standard. Bloch decays (i.e., without cross polarization) using magic angle spinning and high power decoupling. Although the peak resolution is not as good as in 13C spectra of comparable solubilized or pyrolyzed materials, the MAS spectra are of sufficient quality for polymer identification in simple filled vulcanizates in most cases. The MAS spectra are usable for direct quantitative analysis of the polymeric components without priot sample workup. A known series of filled cis-BR/SBR vulcanizates ranging from 0 to 100% SBR was examined. Direct analysis yielded results with an average absolute deviation of 1.2% from the expected values. A known series of NR cis-BR-SBR compounds which had been characterized previously by IR was also studied. The direct NMR analysts gave results comparable to those of the IR method. Use of a cis-BR/SBR standard curve derived from the previous cis-BR/SBR analysis improved the results for the triblend analyses. The MAS 13C NMR method has the advantage that a potentially suspect solubilization or pyrolysis step is eliminated. In many cases, results can be obtained in several hours. Also, results should not depend on degree of cure. The NR cis-BR/SBR results show that low levels of NR (∼3 to 5%) are detectable.

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