Who Uses Japanese Vocational Schools (&lt;i&gt;Senmon Gakko&lt;/i&gt;) and How?:

Nagao, Yukiko

doi:10.11151/eds.83.85

Cited by 11 publications

(11 citation statements)

References 1 publication

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“…The push of the larger gas molecules on the cages is dominated by van der Waals repulsion, increasing by the size of the cages and therefore the size of the lattice. The maximum van der Waals diameters of propane and THF molecules were estimated using the Winmostar program: 6.7 Å for C 3 H 8 and 6.5 Å for THF. Despite the larger guest-size of C 3 H 8 as compared to THF, Figure shows that C 3 H 8 hydrates has the smaller lattice parameters at the same temperature, which might be an evidence for the anomalous interaction between THF and host molecules in sII clathrate hydrates.…”

Section: Resultsmentioning

confidence: 99%

Modeling Thermodynamic Properties of Propane or Tetrahydrofuran Mixed with Carbon Dioxide or Methane in Structure-II Clathrate Hydrates

et al. 2017

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A sound knowledge of thermodynamic properties of sII hydrates is of great importance to understand the stability of sII gas hydrates in petroleum pipelines and in natural settings. Here, we report direct molecular dynamics (MD) simulations of the thermal expansion coefficient, the compressibility and the specific heat capacity of C3H8, or tetrahydrofuran (THF), in mixtures of CH4 or CO2, in sII hydrates under a wide, relevant range of pressure-and temperature conditions. The simulations were started with guest molecules positioned at the cage center of the hydrate. Annealing simulations were additionally performed for hydrates with THF. For the isobaric thermal expansion coefficient, an effective correction method was used to modify the lattice parameters, and the corrected lattice parameters were subsequently used to obtain thermal expansion coefficients in good agreement with experimental measurements. The simulations indicated that the isothermal expansion coefficient and the specific heat capacity of C3H8-pure hydrates were comparable, but slightly larger than those of THF-pure hydrates, which could form Bjerrum defects. The considerable variation in the compressibility between the two, appeared to be due to crystallographic defects. However, when a second guest molecule occupied the small cages of the THF hydrate, the deviation was smaller, because the subtle guest-guest interactions can offset an unfavorable configuration of unstable THF hydrates, caused by local defects in free energy. Unlike the methane molecule, the carbon dioxide molecule, when filling the small cage, can increase the expansion coefficient and compressibility as well as decrease the heat capacity of the binary hydrate, similar to the case of sI hydrates. The calculated bulk modulus for C3H8 pure and binary hydrates with CH4 or CO2 molecule varied between 8.7 and 10.6 GPa at 287.15K between 10 and 100MPa. The results for the specific heat capacities varied from 3155 to 3750.0 J kg-1 K-1 for C3H8 pure and binary hydrates with CH4 or CO2 at 287.15K. These results are the first of this kind reported so far. The simulations show that the thermodynamic properties of hydrates largely depend on the enclathrated compounds. This provides a much-needed atomistic characterization of the sII hydrate properties, and gives an essential input for large-scale discoveries of hydrates and processing as a potential energy source.

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Section: Resultsmentioning

confidence: 99%

Modeling Thermodynamic Properties of Propane or Tetrahydrofuran Mixed with Carbon Dioxide or Methane in Structure-II Clathrate Hydrates

et al. 2017

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“…The maximum van der Waals diameters (and volumes) of each guest molecule were then estimated using the program Winmoster: [23,24] Although n-C 4 H 10 is the longest molecule in the series of guest molecules, the unit-cell parameters of the n-C 4 H 10 +CH 4 hydrate are comparable to those of the iso-C 4 H 10 +CH 4 hydrate. The maximum van der Waals diameter of iso-C 4 H 10 is the same as C 3 H 8 , but the unit-cell parameter of the simple iso-C 4 H 10 hydrate is much larger than that of the C 3 H 8 hydrate (see Figure 3).…”

Section: Resultsmentioning

confidence: 99%

Distribution of Butane in the Host Water Cage of Structure II Clathrate Hydrates

Takeya

Fujihisa

Hachikubo

et al. 2014

Chemistry A European J

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To understand host-guest interactions of hydrocarbon clathrate hydrates, we investigated the crystal structure of simple and binary clathrate hydrates including butane (n-C4 H10 or iso-C4 H10 ) as the guest. Powder X-ray diffraction (PXRD) analysis using the information on the conformation of C4 H10 molecules obtained by molecular dynamics (MD) simulations was performed. It was shown that the guest n-C4 H10 molecule tends to change to the gauche conformation within host water cages. Any distortion of the large 5(12) 6(4) cage and empty 5(12) cage for the simple iso-C4 H10 hydrate was not detected, and it was revealed that dynamic disorder of iso-C4 H10 and gauche-nC4 H10 were spherically extended within the large 5(12) 6(4) cages. It was indicated that structural isomers of hydrocarbon molecules with different van der Waals diameters are enclathrated within water cages in the same way owing to conformational change and dynamic disorder of the molecules. Furthermore, these results show that the method reported herein is applicable to structure analysis of other host-guest materials including guest molecules that could change molecular conformations.

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“…Therefore, this property should be one of the important factors for the solvent effects of the present reaction. The molecular volumes were calculated to be 19.4, 72.2, and 45.8 Å 3 for H 2 O, DMSO, and CH 3 CN, respectively 34…”

Section: Resultsmentioning

confidence: 99%

A free‐energy perturbation method based on Monte Carlo simulations using quantum mechanical calculations (QM/MC/FEP method): Application to highly solvent‐dependent reactions

et al. 2010

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This study describes the framework of the quantum mechanical (QM)/Monte Carlo (MC)/free-energy perturbation (FEP) method, a FEP method based on MC simulations using quantum chemical calculations. Because a series of structures generated by interpolating internal coordinates between transition state and reactant did not produce smooth free-energy profiles, we used structures from the intrinsic reaction coordinate calculations. This method was first applied to the Diels-Alder reaction between methyl vinyl ketone and cyclopentadiene and produced ΔG( sol)‡ values of 20.1 and 21.4 kcal mol(-1) in aqueous and methanol solutions, respectively. They are very consistent with the experimentally observed values. The other two applications were the free-energy surfaces for the Cope elimination of N,N-dimethyl-3-phenylbutan-2-amine oxide in aqueous, dimethyl sulfoxide, and tetrahydrofuran solutions, and the Kemp decarboxylation of 6-hydroxybenzo-isoxazole-3-carboxylic acid in aqueous, dimethyl sulfoxide, and CH(3) CN solutions. The calculated activation free energies differed by less than 1.8 kcal mol(-1) from the experimental values for these reactions. Although we used droplet models for the QM/MC/FEP simulations, the calculated results for three reactions are very close to the experimental data. It was confirmed that most of the interactions between the solute and solvents can be described using small numbers of solvent molecules. This is because a few solvent molecules can produce large portions of the solute-solvent interaction energies at the reaction centers. When we confirmed the dependency on the droplet sizes of solvents, the QM/MC/FEP for a large droplet with 106 water molecules produced a ΔG (sol)‡ value similar to the experimental values, as well as that for a small droplet with 34 molecules.

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Who Uses Japanese Vocational Schools (<i>Senmon Gakko</i>) and How?:

Cited by 11 publications

References 1 publication

Modeling Thermodynamic Properties of Propane or Tetrahydrofuran Mixed with Carbon Dioxide or Methane in Structure-II Clathrate Hydrates

Modeling Thermodynamic Properties of Propane or Tetrahydrofuran Mixed with Carbon Dioxide or Methane in Structure-II Clathrate Hydrates

Distribution of Butane in the Host Water Cage of Structure II Clathrate Hydrates

A free‐energy perturbation method based on Monte Carlo simulations using quantum mechanical calculations (QM/MC/FEP method): Application to highly solvent‐dependent reactions

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