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• Visual Observation of Tetra-n-butylammonium Bromide Ionic Semiclathrate Hydrate Formation: A Laboratory Experiment

  Keita Yasuda

  Journal of Chemical Education ( American Chemical Society )  98   3587 - 3592   2021年11月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  　概要を見る

  A laboratory experiment was performed using tetra-n-butylammonium bromide (TBAB) ionic semiclathrate hydrate, a crystalline compound. Ionic semiclathrate hydrates have unique properties, and hence, novel technologies utilizing the ionic semiclathrate hydrates have been proposed to date. Thus, students could learn fundamentals of functional materials through ionic semiclathrate hydrates from chemical and engineering points of view. In the experiment, formation of the TBAB hydrate was observed at fixed temperature and under atmospheric pressure by using TBAB aqueous solutions having TBAB mass fractions of wTBAB = 0.10, 0.20, 0.30, 0.40, and 0.50. There are no serious safety hazards. In addition, the experiment can be performed using inexpensive equipment and materials. The amount of the formed TBAB hydrate and its crystal morphology depended on the concentration of the aqueous solution. The students needed to submit a laboratory report describing fundamentals of the ionic semiclathrate hydrates, a relationship between equilibrium conditions and the amount of the formed TBAB hydrate, and an adequate crystal morphology of the TBAB hydrate crystals as a thermal storage material. Most students understood the experiment well, and the average score of the reports was approximately 80%.

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• Simultaneous Crystallization of Cyclopentane Hydrate and Sodium Chloride for Desalination and Salt Manufacture

  Mikihiro Tanaka, Keita Tsugane, Daiki Suga, Shigeo Tomura, Ryo Ohmura, Keita Yasuda

  ACS Sustainable Chemistry & Engineering ( American Chemical Society )  9   9078 - 9084   2021年07月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  関連する研究費コード: 19K14911

  　概要を見る

  Simultaneous crystallization of cyclopentane hydrate and sodium chloride dihydrate was implemented to demonstrate a dual-functional system for hydrate-based seawater desalination and salt manufacture that could be performed with zero emission. A sodium chloride aqueous solution having an initial mass fraction of sodium chloride of 0.235 or 0.264 was used for the experiments as an alternative to seawater. When using the aqueous solution having a sodium chloride concentration of 0.264 in mass fraction, the precipitation of polyhedral sodium chloride dihydrate crystals was first observed, followed by the formation of particulate cyclopentane hydrate crystals. In contrast, when using the aqueous solution having a sodium chloride concentration of 0.235 in mass fraction, the formation of particulate cyclopentane hydrate was first observed and then the particulate sodium chloride dihydrate precipitated. The formed cyclopentane hydrate and the precipitated sodium chloride dihydrate were separated by the remaining sodium chloride aqueous solution due to the density difference even after the agitation of the system. The eutectic temperature and concentration were determined to be 259.75 K and 0.238 in mass fraction of sodium chloride, respectively.

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• Phase Equilibrium Condition Measurements in Carbon Dioxide Hydrate Forming System Coexisting with Seawater

  Rihito Nakane, Yusuke Shimosato, Eito Gima, Ryo Ohmura, Izuru Senaha, Keita Yasuda

  The Journal of Chemical Thermodynamics ( Elsevier )  152   106276   2021年01月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  関連する研究費コード: 17K14604

  　概要を見る

  Three phase equilibrium conditions of synthetic standard (seawater + carbon dioxide hydrate + carbon dioxide gas) were experimentally determined based on the batch, isochoric procedure. The total mass fraction of the electrolytes in the synthetic standard seawater, wss, was 0.0351, 0.0700, or 0.1036 that was composed of pure water and seven salts. The equilibrium pressure–temperature conditions were as follows: 271.95 K < T < 279.05 K and 1.298 MPa < p < 3.144 MPa in the system having wss = 0.0351, 272.25 K < T < 278.15 K and 1.530 MPa < p < 3.361 MPa in the wss = 0.0700 system and 271.15 K < T < 275.65 K and 1.643 MPa < p < 2.909 MPa in the wss = 0.1036 system. The quantitative evaluation of the changes in the equilibrium temperature at a fixed pressure was performed by applying the equilibrium conditions to the Clausius–Clapeyron equation. The results are essential to design the thermodynamic conditions for the clathrate hydrate-based seawater desalination technology.

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• Clathrate Hydrates at Temperatures below the Freezing Point of Water: A Review

  Hironori D Nagashima, Takuto Miyagi, Keita Yasuda, Ryo Ohmura

  Fluid Phase Equilibria ( Elsevier )  517   112610   2020年08月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  関連する研究費コード: 17K14604

  　概要を見る

  This paper provides the review focusing on the clathrate hydrates at the temperatures below the freezing point of water. The three main topics of the review are the chemical thermodynamics, naturally-occurring hydrates and novel industrial applications utilizing hydrates. Fundamental phase equilibria in the hydrate forming systems at the temperatures below the freezing point of water are first reviewed. The effects of water-soluble compound on the hydrate phase equilibria are extensively discussed based on the experimental data reported in the literature and the newly obtained experimental data on the solid ice + sodium chloride aqueous solution + carbon dioxide hydrate + carbon dioxide gas four-phase equilibria that were measured in the present study. Natural occurrence of hydrates is discussed by comparing the thermodynamic conditions in the planets and satellites with the relevant hydrate phase equilibrium data. The naturally-occurring hydrates would exist in the following planets and satellites; Mars and Titan. The storage of natural gas in the form of the hydrate has been well investigated in the past two decades. CO2 hydrate can be used as the fire-fighting agent and the solid carbonated foods. The refrigeration and engine utilizing hydrates as the working media may be the challenging technologies having the prospects in terms of the efficiency, environment friendliness and the safety.

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• Phase Equilibrium Condition Measurements in Carbon Dioxide Hydrate Forming System Coexisting with Sodium Chloride Aqueous Solutions

  Rihito Nakane, Eito Gima, Ryo Ohmura, Izuru Senaha, and Keita Yasuda

  The Journal of Chemical Thermodynamics ( Elsevier )  130   192 - 197   2019年01月 [ 査読有り ]

  掲載種別: 研究論文（学術雑誌）

  関連する研究費コード: 17K14604

  　概要を見る

  Three phase equilibrium conditions of (sodium chloride aqueous solution + carbon dioxide hydrate + vapour carbon dioxide) were measured to establish seawater desalination technology using clathrate hydrates. The three phase equilibrium condition measurements were performed at temperatures between 271.85 K and 279.05 K, and at pressures between 1.283 MPa and 3.617 MPa. The concentrations of sodium chloride aqueous solution were 0.0350, 0.0700, 0.1000, and 0.1050 in mass fraction. It was found that the equilibrium temperature difference between pure water system and each sodium chloride concentration system at the same pressure was hardly influenced by the pressure level. In addition, it was found that the equilibrium temperature depression of carbon dioxide hydrate by the addition of sodium chloride is smaller than that of ice and cyclopentane hydrate especially at the high concentration of sodium chloride.

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• クラスレートハイドレート法による海水淡水化/製塩ハイブリッドシステムの開発

  若手研究

  課題番号: 19K14911

  研究期間: 2019年04月  -  2021年03月 

  代表者: 安田　啓太 

  直接経費: 3,300,000（円）  間接経費: 990,000（円）  金額合計: 4,290,000（円）

• クラスレートハイドレート法による海水淡水化技術の開発

  若手研究(B)

  課題番号: 17K14604

  研究期間: 2017年04月  -  2019年03月 

  代表者: 安田　啓太 

  直接経費: 3,300,000（円）  間接経費: 990,000（円）  金額合計: 4,290,000（円）

• 氷点下温度域におけるクラスレート水和物　－相平衡条件測定と結晶構造解析ー

  特別研究員奨励費

  課題番号: 10J03623

  研究期間: 2010年04月  -  2012年03月 

  代表者: 安田　啓太 

  直接経費: 1,400,000（円）  間接経費: 0（円）  金額合計: 1,400,000（円）

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