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"The toroid cavity autoclave for high-pressure and
variable-temperature
in situ nuclear magnetic resonance studies"
H. G. Niessen, P. Trautner, S. Wiemann, J. Bargon, and K.
Woelk, Rev. Sci. Instrum. 73, 1259-1266 (2002).
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The toroid cavity autoclave (TCA) is a coaxial NMR resonator and high-pressure
autoclave for in situ NMR studies, which combines the advantages
of a toroid NMR detector (TCD) with the
features of a cylindrical metal pressure vessel. It is designed to fit
within the limited space of a standard NMR narrow-bore cryomagnet and allows
for recording high resolution NMR spectra during chemical reactions under
high pressure.
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The following features are introduced:
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Compounds that, for example, initiate a reaction can be injected into the
reactor through a non-return valve even if the TCA is already pressurized.
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The TCA is heated by a resistive, coaxial heating arrangement that does
not generate any stray magnetic field in the sample volume.
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Current pressure and temperature capabilities are 0 - 300 bar and room
temperature to 150 °C, respectively.
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With standard 200 MHz 1H NMR experiments, signal resolution
of 0.55 Hz and signal-to-noise ratios comparable to those of standard NMR
probes were achieved.
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In a further development, the TCA is optimized for gas/liquid reactions
in which gaseous components are vigorously mixed with the liquid to obtain
maximum reaction rates.
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Applications to parahydrogen induced polarization (PHIP) are shown, in
which the nuclear spin polarization patterns show pairwise addition of
hydrogen in both liquid organic solvents and in supercritical CO2.
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K. Woelk, March 11,
2002