1999 Fiscal Year Final Research Report Summary
Reaction and Transport Process of Charged Species in Supercritical Fluids
| Project/Area Number |
10044097
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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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 | Kanagawa Institute of Technology |
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Principal Investigator |
NISHIKAWA Masaru Kanagawa Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (10012329)
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| Co-Investigator(Kenkyū-buntansha) |
ITOH Kengo University of Tokyo Graduate School, Assistant, 大学院・総合文化研究科, 助手 (40221080)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Supercritical fluids / Electron mobility / Electron attachment reaction / Attachment / detachment equilibria / Reaction volume change / Electrostriction / ion mobility / Cluster size |
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| Research Abstract |
Electron mobility μ in supercritical fluids
μ-values were measured in upercritical ethane as a function of temperature and pressure over the range 33-47℃ and 40-120 bar. At all temperatures measured, μ decreases exponentially with increasing pressure, but passes through a minimum in the pressure region where x goes through a maximum. Since excess electrons are quasifree in the region of μ minima (μ=50-100 cmィイD12ィエD1/Vs), it is obvious that the scattering of electrons by the maxima in the deformation potential due to density fluctuations are the cause for the minima. Measurement of μ in SC Xe was initiated.
Rate of electron attachment and attachment/detachment equilibria
Electron attachment rate to COィイD22ィエD2 pyrimidine, pyrazine, styrene and NO, was measured in supercritical ethane. By using 10 psec pulse from the laser-electron-accelerator, both attachment and detachment rate were measured for COィイD22ィエD2, pyrimidine and pyrazine. Styrene even at high concentrations are unreactive towa
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rds electrons. For NO, however, only attachment was observed even with 10 psec pulse. Attachment-detachment equilibrium constants KィイD2eqィエD2 were determined for COィイD22ィエD2, pyrimidine and pyrazine as a function of temperature and pressure. The Gibbs energy change △GィイD2rィエD2 and the reaction volume change △VィイD2rィエD2 were estimated from KィイD2eqィエD2. The comparison of △VィイD2rィエD2 with a compressible continum model led to the conclusion that these volume changes were essentially due to the electrostriction of media by negative ions. The model also shows that the trend in △ィイD2rィエD2 with respect to pressure or additives are largely accounted for by the magnitude of polarization energy due to irons.
Ion mobility in supercritical fluids
The mobility of positive ions in ethane and of both positive and negative ions in COィイD22ィエD2 were measured. Cluster radii were estimated by means of (1) Stokes' equation and by (2) a compressible continuum model. Radii go through a maximum at the pressure where compressibility reached its peak. For ethane, both methods give largest values 15-16 nm at 33℃ and ρ/ρィイD2cィエD2-0.8. In COィイD22ィエD2 the radius for the slower ion was 12 nm at 33℃ and ρ/ρィイD2cィエD2=0.8. Preliminary measurements of positive ion mobility μ in Sc Xe indicated that μ is lower that in SC ethane and the cluster radius at the maximum is ca. 1.2nm(293K). Less
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