2005 Fiscal Year Final Research Report Summary
Development of multinuclear, high-temperature, and diffusion NMR probe and dynamics of supercritical aqueous solutions
| Project/Area Number |
15205004
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NAKAHARA Masaru Kyoto University, Institute for Chemical Research, Professor, 化学研究所, 教授 (20025480)
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| Co-Investigator(Kenkyū-buntansha) |
MATUBAYASI Nobuyuki Kyoto University, Institute for Chemical Research, Associate Professor, 化学研究所, 助教授 (20281107)
OKAMURA Emiko Kyoto University, Institute for Chemical Research, Assistant Professor, 化学研究所, 助手 (00160705)
WAKAI Chihiro Kyoto University, Institute for Chemical Research, Assistant Professor, 化学研究所, 助手 (40293948)
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| Project Period (FY) |
2003 – 2005
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| Keywords | diffusion / high-resolution NMR / supercritical water / ion / transport phenomena / ceramic / high-temperature and high-pressure / electric conductivity |
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| Research Abstract |
In order to elucidate the dynamics of hot water including supercritical, a high-resolution nuclear magnetic resonance (NMR) probe (500 MHz for ^1H) has been developed for multinuclear pulsed field gradient spin-echo (PGSE) diffusion measurements at high temperatures up to 400℃. The convection effect on the self-diffusion measurement is minimized by achieving the homogeneous temperature distributions of±1 and ±2℃, respectively, at 250 and 400℃. The high temperature homogeneity is attained by using the solid-state heating system composed of a ceramic (AlN) with high thermal conductivity comparable with that of metal aluminium. The self-diffusion coefficients D for light (^1H_2O) and heavy (^2H_2O) water are distinguishably measured at subcritical temperatures of 30-350℃ with intervals of 10-25℃ on the liquid-vapor coexisting curve and at a supercritical temperature of 400℃ as a function of water density between 0.071 and 0.251 g/cm^3. The D value obtained for ^1H_2O is 10%-20% smaller than those previously reported because of the absence of the convection effect. At 400℃, the D value for ^1H_2O is increased by a factor of 3.7 as the water density is reduced from 0.251 to 0.071 g/cm^3. Roughly speaking, the observed self-diffusion coefficient of supercritical water appears, although not exactly, inversely proportional to the density or the number of hydrogen bonds in the low-density region covered in this study. The isotope ratio D(^1H_2O)/D(^2H_2O) decreases from 1.23 to 〜1.0 as the temperature increases from 30 to 400℃. Since ^2H_2O is considered to be more structured than ^1H_2O, the isotope effect is interesting to discuss in terms of intermolecular interaction, typically hydrogen bonding, apart from the density and the temperature dependences.
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[Journal Article] Effect of Concentration, Acid, Temperature, and Metal on Competitive Reaction Pathways for Decarbonylation and Decarboxylation of Formic Acid in Hot Water2004
Author(s)
Wakai, C., Yoshida, K., Tsujino, Y., Matubayasi, N., Nakahara, M.
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Journal Title
Chem. Lett. 33
Pages: 572-573
Description
「研究成果報告書概要(和文)」より
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[Journal Article] Effect of Concentration, Acid, Temperature, and Metal on Competitive Reaction Pathways for Decarbonylation and Decarboxylation of Formic Acid in Hot Water2004
Author(s)
Wakai, C., Yoshida, K., Tsujino, Y., Matubayasi, N., Nakahara, M.
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Journal Title
Chemistry Letters 33
Pages: 572-573
Description
「研究成果報告書概要(欧文)」より
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