論文 - 大村　亮

Solubility of Nitrogen Gas in Aqueous Solution of Tetra-n-Butylammonium Bromide

大村 亮

INTERNATIONAL JOURNAL OF THERMOPHYSICS 38 （ 12 ） 20 - 25 2017年12月

研究論文（学術雑誌）,  ISSN  0195-928X

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Preservation of carbon dioxide clathrate hydrate in the presence of fructose or glucose and absence of sugars under freezer conditions

大村 亮

JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY 54   332 - 340 2017年10月

研究論文（学術雑誌）,  ISSN  1226-086X

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Thermodynamic Properties of Ionic Semiclathrate Hydrate Formed with Tetrabutylammonium Propionate

大村 亮

CHEMICAL ENGINEERING & TECHNOLOGY 40 （ 10 ） 1810 - 1816 2017年10月

研究論文（学術雑誌）,  ISSN  0930-7516

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Formation, growth and sintering of CO2 hydrate crystals in liquid water with continuous CO2 supply: Implication for subsurface CO2 sequestration

大村 亮

INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL 63   386 - 391 2017年08月

研究論文（学術雑誌）,  ISSN  1750-5836

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Interfacial tension between (methane + ethane + propane) gas mixture and water from 283.2 K to 298.2 K under up to 10 MPa

Hayama Hiroaki, Fukuzawa Kazuki, Yasuda Keita, Ohmura Ryo

Journal of Chemical Thermodynamics 108   71 - 75 2017年05月

ISSN  0021-9614

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<p>This paper reports a study of the interfacial tension between natural gas (methane + ethane + propane gas mixture) and water. The composition of the (methane + ethane + propane) gas mixture was 89.95:7.05:3.00 and 95.0:3.5:1.5, in mole ratio. These measurements were performed using the pendant drop method at pressure and temperature conditions of up to 10 MPa and between 283.2 K and 298.2 K, respectively. These conditions were chosen to eliminate the possibility of clathrate hydrate formation. Interfacial tension in the (natural gas + water) system decreased with increasing pressure, but no temperature dependence was found for any of the at all conditions. The interfacial tension gradient with respect to pressure was found to depend on the composition of gas phase. The interfacial tension in a (natural gas + water) system was found to be smaller than that of a (methane + water) system.</p>

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Phase equilibrium condition measurements in the clathrate hydrate forming system of (propan-2-ol + carbon dioxide + water) at temperatures between 250.8 K and 265.7 K

Fukushima Naruki, Shiratori Satoshi, Makiya Takeshi, Murakami Takashi, Ohmura Ryo

Journal of Chemical Thermodynamics 115   114 - 118 2017年

ISSN  0021-9614

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<p>The phase equilibrium conditions in the (propan-2-ol + carbon dioxide + water) system were measured. The measurements were performed using the batch, isochoric method at the temperatures between 250.8 K and 265.7 K. The equilibrium pressures were measured between 0.275 MPa and 0.995 MPa, and increased with increasing temperatures. Propan-2-ol is known as thermodynamic inhibitor for hydrate formation. However at the temperatures below 262 K, the equilibrium pressures in the (propan-2-ol + carbon dioxide + water) system are lower than those without propan-2-ol (carbon dioxide + water system). The measurements indicate the formation of the hydrates containing propan-2-ol and carbon dioxide in this system.</p>

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Phase equilibria for Kr hydrate formed with 2,2-dimethylbutane, methylcyclohexane and 1-methylpiperidine

Ohfuka Yugo, Fukushima Naruki, Chen Zheguang, Fukuda Masao, Takeya Satoshi, Ohmura Ryo

Journal of Chemical Thermodynamics 2017年

ISSN  0021-9614

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<p>This paper reports the thermophysical properties of hydrates in the (krypton + 1-methylpiperidine, 2,2-dimethylbutane or methylcyclohexane + water) system. Phase equilibrium conditions were measured in the temperature ranges from 274.6. K to 297.3. K at the corresponding equilibrium pressures between 0.532. MPa and 6.246. MPa in the (krypton + 1-methylpiperidine + water) system. In the temperature ranges from 291.2. K to 297.0. K and 290.6. K to 296.8. K, the equilibrium pressure was between 4.035. MPa to 8.936. MPa and 3.993. MPa to 9.128. MPa, in the (krypton + 2,2-dimethylbutane + water) system and (krypton + methylcyclohexane + water) system, respectively. These results indicate that hydrates can be formed under the condition of lower temperature and pressure in the (krypton + 1-methylpiperidine + water) system than in the other two systems. The crystallographic structure of (krypton + 1-methylpiperidine) hydrate was thereby identified to be structure H at 183. K based on the Powder X-ray diffraction (PXRD) measurements. Dissociation heat of (krypton + 1-methylpiperidine) hydrate was estimated to be 73.5. kJ/mol, that is smaller than that of structure II hydrates containing krypton. These results support the potential for (krypton + 1-methylpiperidine) structure H hydrate to be utilized in hydrate-based technologies.</p>

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Phase equilibrium condition measurements in methane clathrate hydrate forming system from 197.3 K to 238.7 K

Nagashima Hironori D., Ohmura Ryo

Journal of Chemical Thermodynamics 102   252 - 256 2016年11月

ISSN  0021-9614

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<p>This paper reports three-phase (ice + vapor + clathrate hydrate) equilibrium conditions in methane + water system at temperatures between 197.3 K and 238.7 K. These equilibrium condition data could be applied for utilization of methane clathrate hydrate as a natural gas transportation medium, a working medium for heat pump/power generation cycles, and to further our understanding of the environments of planets and satellites. The equilibrium conditions were measured using the isochoric procedure. The measured equilibrium pressures are from 111.7 kPa at 197.3 K to 794.1 kPa at 238.7 K and increase with an increase in temperature. The internal consistency of the measured equilibrium data are examined by applying the Clausius-Clapeyron equation. Discussion is given on the comparison of the equilibrium data measured in this study to those reported in the literature.</p>

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Phase equilibrium temperature and dissociation heat of ionic semiclathrate hydrate formed with tetrabutylammonium butyrate

Yamauchi Yuji, Arai Yuta, Yamasaki Tatsuro, Endo Fuyuaki, Hotta Atsushi, Ohmura Ryo

Fluid Phase Equilibria 2016年10月

ISSN  0378-3812

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<p>This paper reports the phase equilibrium temperature and dissociation heat of ionic semiclathrate hydrate formed with tetrabutylammonium butyrate (TBABu). The temperature - composition phase diagram of the TBABu hydrate was determined in the mass fraction from 0.10 to 0.44. The highest equilibrium temperature of TBABu hydrate was 15.4 °C in the mass fraction range from 0.35 to 0.37. On the dissociation heat of DSC measurements, a single heat flow peak of TBABu hydrate excluding ice melting peak was observed at all the mass fraction systems. The largest dissociation heat was 184.9 ± 3.1 kJ/kg at the mass fraction 0.36. TBABu hydrate could potentially be used as a thermal energy storage material.</p>

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Understanding decomposition and encapsulation energies of structure I and II clathrate hydrates

Alavi Saman, Ohmura Ryo

Journal of Chemical Physics 145 （ 15 ）  2016年10月

ISSN  0021-9606

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<p>When compressed with water or ice under high pressure and low temperature conditions, some gases form solid gas hydrate inclusion compounds which have higher melting points than ice under those pressures. In this work, we study the balance of the guest-water and water-water interaction energies that lead to the formation of the clathrate hydrate phases. In particular, molecular dynamics simulations with accurate water potentials are used to study the energetics of the formation of structure I (sI) and II (sII) clathrate hydrates of methane, ethane, and propane. The dissociation enthalpy of the clathrate hydrate phases, the encapsulation enthalpy of methane, ethane, and propane guests in the corresponding phases, and the average bonding enthalpy of water molecules are calculated and compared with accurate calorimetric measurements and previous classical and quantum mechanical calculations, when available. The encapsulation energies of methane, ethane, and propane guests stabilize the small and large sI and sII hydrate cages, with the larger molecules giving larger encapsulation energies. The average water-water interactions are weakened in the sI and sII phases compared to ice. The relative magnitudes of the van der Waals potential energy in ice and the hydrate phases are similar, but in the ice phase, the electrostatic interactions are stronger. The stabilizing guest-water “hydrophobic” interactions compensate for the weaker water-water interactions and stabilize the hydrate phases. A number of common assumptions regarding the guest-cage water interactions are used in the van der Waals-Platteeuw statistical mechanical theory to predict the clathrate hydrate phase stability under different pressure-temperature conditions. The present calculations show that some of these assumptions may not accurately reflect the physical nature of the interactions between guest molecules and the lattice waters.</p>

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Quadruple point determination in carbon dioxide hydrate forming system

Nema Yuki, Ohmura Ryo, Senaha Izuru, Yasuda Keita

Fluid Phase Equilibria 2016年10月

ISSN  0378-3812

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<p>The quadruple point in carbon dioxide hydrate forming system, ice + water-rich liquid + hydrate + carbon dioxide-rich gas four-phase equilibrium condition, has been determined based on supercooled water-rich liquid + hydrate + carbon dioxide-rich gas and water-rich liquid + hydrate + carbon dioxide-rich gas three-phase equilibrium conditions measured in this study combined with ice + hydrate + carbon dioxide-rich gas three-phase equilibrium conditions reported in the literature (K. Yasuda, R. Ohmura, J. Chem. Eng. Data 53 (2008) 2182-2188). The intersection of the three types of the three-phase equilibrium conditions was used to determine the quadruple point. The three-phase equilibrium condition experiments were performed at temperatures between 269.45 K and 275.75 K, and at pressures between 0.825 MPa and 1.708 MPa. The determined . p-T condition at quadruple point was . T = 271.6 ± 0.2 K and . p = 1.04 ± 0.02 MPa. It was also observed that the freezing of supercooled water during some experimental runs performed below the quadruple point temperature, which causes sudden increase in both pressure and temperature.</p>

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Surfactant Effects on Crystal Growth Dynamics and Crystal Morphology of Methane Hydrate Formed at Gas/Liquid Interface

Hayama Hiroaki, Mitarai Makoto, Mori Hiroyuki, Verrett Jonathan, Servio Phillip, Ohmura Ryo

Crystal Growth and Design 16 （ 10 ） 6084 - 6088 2016年10月

ISSN  1528-7483

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<p>This paper presents visual observations aiming to clarify the underlying physics of surfactant effects on clathrate hydrate crystal growth at the interface between methane gas and water with surfactant. Sodium dodecyl sulfate (SDS), which is commonly used in industrial processes, was used in this study. Various SDS mass fractions from 0 to w_SDS = 100 ppm with a step of size 10 ppm were examined, where w_SDS represents the mass fraction of SDS aqueous solution. The crystal growth behavior and the crystal morphology of the methane hydrate at the interface varied depending on surfactant concentration and ΔT_sub. In systems with w_SDS ≤ 20 ppm, the nucleation occurred on the droplet surface (gas/liquid interface), then grew laterally, and finally covered the whole droplet surface. On the contrary, at w_SDS ≥ 30 ppm, the droplet shape was not maintained and enhanced hydrate crystal growth was observed compared to those systems with w_SDS ≤ 20 ppm. Individual hydrate crystals at w_SDS = 20 ppm were observed to be smaller than those in a pure water system at a given ΔT_sub, which is ascribed to the enhanced hydrate nucleation by the addition of SDS.</p>

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Interfacial tension between (CO₂ + N₂) gas and tetrabutylammonium bromide aqueous solution

Akiba Hotaka, Ohmura Ryo

Journal of Chemical Thermodynamics 97   83 - 87 2016年06月

ISSN  0021-9614

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<p>This paper reports experimental values of the interfacial tension between (CO₂ + N₂) gas and tetrabutylammonium bromide aqueous solution (TBAB_aq). The experiments were performed by the pendant drop method in conditions from P = (1.00 to 4.00) MPa, from T = (288.15 to 303.15) K and from w_TBAB = (0.10 to 0.40), where w_TBAB denotes the mass fraction of TBAB in the aqueous solution. The interfacial tension decreased with increasing w_TBAB and pressure. The depletion of the interfacial tension with increasing w_TBAB in the (CO₂ + N₂ + TBAB_aq) system was consistent with that in (CO₂ + TBAB_aq) system. The depletion ratio of the pressure gradient of the interfacial tension caused by the addition of TBAB in (CO₂ + N₂ + water) system was almost the same as that in (CO₂ + water) system. There might be little effect on the interfacial tension caused by the interaction between gases and tetrabutylammonium ions. The temperature dependence of γ was not observed as well as in the (CO₂ + TBAB_aq) system.</p>

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Disorder of Hydrofluorocarbon Molecules Entrapped in the Water Cages of Structure i Clathrate Hydrate

Takeya Satoshi, Udachin Konstantin A., Moudrakovski Igor L., Ohmura Ryo, Ripmeester John A.

Chemistry - A European Journal 22 （ 22 ） 7567 - 7573 2016年05月

ISSN  0947-6539

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<p>Water versus fluorine: Clathrate hydrates encaging hydrofluorocarbons as guests show both isotropic and anisotropic distributions within host water cages, depending on the number of fluorine atoms in the guest molecule; this is caused by changes in intermolecular interactions to host water molecules in the hydrates (see figure).</p>

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Selective occupancy of methane by cage symmetry in TBAB ionic clathrate hydrate

Muromachi Sanehiro, Udachin Konstantin A., Alavi Saman, Ohmura Ryo, Ripmeester John A.

Chemical Communications 52 （ 32 ） 5621 - 5624 2016年04月

ISSN  1359-7345

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<p>Methane trapped in the two distinct dodecahedral cages of the ionic clathrate hydrate of TBAB was studied by single crystal XRD and MD simulation. The relative CH₄ occupancies over the cage types were opposite to those of CO₂, which illustrates the interplay between the cage symmetry and guest shape and dynamics, and thus the gas selectivity.</p>

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Interfacial tension measurements in water-methane system at temperatures from 278.15 K to 298.15 K and pressures up to 10 MPa

Yasuda Keita, Mori Yasuhiko H., Ohmura Ryo

Fluid Phase Equilibria 413   170 - 175 2016年04月

ISSN  0378-3812

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<p>This paper reports the measurements of the interfacial tension in a water-methane system at temperatures from 278.15 K to 298.15 K and pressures up to 10 MPa. The measurements using the pendant-drop method were performed at various pressures lower than or, at the highest, nearly equal to the hydrate/liquid/gas equilibrium pressure corresponding to each of the following prescribed temperatures: 278.15 K, 283.15 K, 288.15 K, 293.15 K and 298.15 K. The obtained data show that at each temperature the interfacial tension decreases almost linearly with the increasing pressure, indicating that the observed decrease in the interfacial tension results from the promotion of methane adsorption onto the interface with the increasing pressure.</p>

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Preface to special issue on gas hydrates and semiclathrate hydrates

Sum Amadeu K., Ohmura Ryo, de Loos Theo

Fluid Phase Equilibria 413   1 2016年04月

ISSN  0378-3812

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Crystal growth of ionic semiclathrate hydrate formed at interface between CO₂+N₂ gas mixture and tetrabutylammonium bromide aqueous solution

Hayama Hiroaki, Akiba Hotaka, Asami Yuki, Ohmura Ryo

Korean Journal of Chemical Engineering    1 - 6 2016年04月

ISSN  0256-1115

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<p>This study reports a visual observation of the formation and growth of ionic semiclathrate hydrate on the surface of a Tetrabutylammonium bromide (TBAB) aqueous solution and CO₂+N₂ gas mixture. The composition of CO₂+N₂ gas mixture was 20: 80. The experimental temperature range was from 280 K to 290 K, under the pressures of 2.3MPa and 4.7MPa, at w_TBAB=0.10 and w_TBAB=0.40, where wTBAB denotes the mass fraction of TBAB in the aqueous solution. At w_TBAB=0.40, the hydrate crystals were initially observed to grow within the droplet, and followed by lateral growth at the droplet surface; but at w_TBAB=0.10, the hydrate crystals grew exclusively in the liquid phase and did not cover the droplet surface. Two types of different crystals with different sizes were clearly observed.</p>

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Crystal growth of ionic semiclathrate hydrate formed at interface between CO2+N2 gas mixture and tetrabutylammonium bromide aqueous solution

Hiroaki Hayama , Hotaka Akiba , Yuki Asami , Ryo Ohmura Affiliated with Department of Mechanical Engineering, Keio University Email author Hiroaki Hayama , Hotaka Akiba , Yuki Asami , Ryo Ohmura Affiliated with Department of Mechanical Engineering, Keio University Email author Hiroaki Hayama, Hotaka Akiba, Yuki Asami, Ryo Ohmura

Korean Journal of Chemical Engineering （Springer）  2016年04月

研究論文（学術雑誌）, 共著, 査読有り

Influence of hydrate structure on continuous separation of coal bed methane gas: A thermodynamic simulation study

Thaneer Malai Narayanan, Ryo Ohmura

Journal of Natural Gas Science & Engineering 2016年03月

研究論文（学術雑誌）, 共著, 査読有り

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