KEIO RESEARCHERS INFORMATION SYSTEM

Career 【 Display / hide 】

Career 【 Display / hide 】

• 1999.04

  -

  2000.03

  JSPS Research Fellow (DC1)

• 2000.04

  -

  2002.03

  JSPS Research Fellow (PD)

• 2002.04

  -

  2006.03

  Research Scientist, AIST

• 2006.04

  -

  Present

  Assistant Professor

• 2009.04

  -

  Present

  慶應義塾大学准教授

Academic Background 【 Display / hide 】

Academic Background 【 Display / hide 】

• 1996.03

  Keio University, Faculty of Science and Technology, Dapartment of Mechanical Engineering

  University, Graduated

• 2000.03

  Keio University, －, 機械工学専攻

  Graduate School, Completed, Doctoral course

Academic Degrees 【 Display / hide 】

Academic Degrees 【 Display / hide 】

• Ph. D., Keio University, Coursework, 2000.03

Research Areas 【 Display / hide 】

Research Areas 【 Display / hide 】

• Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Thermal engineering (Thermal Engineering)

• Nanotechnology/Materials / Fundamental physical chemistry (Physical Chemistry)

Research Keywords 【 Display / hide 】

Research Keywords 【 Display / hide 】

• Energy

• Clathrate Hydrates

• Physical Chemistry

• Environment

• Crystal Growth

Research Themes 【 Display / hide 】

Research Themes 【 Display / hide 】

• Physical Chemistry in Clathrate Hydrate Forming Systems, 

  1996

  -

  Present

Papers 【 Display / hide 】

Papers 【 Display / hide 】

• Methane enrichment from CH4 + CO2 gas mixture via structure II clathrate hydrate: A continuous separation experiment for biogas upgrading

  Maruyama M., Takeya S., Schicks J.M., Ohmura R.

  Fuel 419 2026.09

  ISSN  00162361

  　View Summary

  Toward the widespread adoption of biomass energy for carbon neutral age, demand for biogas separation technologies that enables easier operation and maintenance is increasing. CH<inf>4</inf> enrichment in biogas in solid structure II clathrate hydrate has recently attracted attention, yet the knowledge is limited to the batch-type operation, which is far from engineering practice. In the present study, we have conducted hydrate-based CH<inf>4</inf> enrichment experiments with semi-batch and continuous separation methods in CH<inf>4</inf> + CO<inf>2</inf> + tetrahydropyran (THP) + water system, which are closer to applied-side operations. Semi-batch CH<inf>4</inf>/CO<inf>2</inf> separation experiment with powder X-ray diffraction (PXRD) measurement revealed that CH<inf>4</inf> is enriched in the hydrate phase with its mole fraction from 0.60 to 0.81 via the formation of structure II hydrate with THP. The continuous CH<inf>4</inf>/CO<inf>2</inf> separation experiment showed that CH<inf>4</inf> is concentrated in the hydrate slurry during the continuous formation process. The concentration of CH<inf>4</inf> in the hydrate slurry reached 0.65 in mole fraction at the steady state at t = 24 h from 0.45 at t = 1h. The experimental results of time-dependent changes in the compositions in the gas phase as well as in the hydrate slurry exhibited that the long-term operation of hydrate-based CH<inf>4</inf> enrichment was achieved and therefore could be implemented on a continuous industrial scale. The overall results demonstrated that the continuous CH<inf>4</inf> enrichment in biogas is an applicable scheme utilizing structure II hydrate.

  • Access to Document (DOI)

• Phase transition of cubic structure II to tetragonal structure in monofluoromethane + 2-propanol clathrate hydrate

  Kamiya L., Takeya S., Ohmura R.

  Journal of Molecular Structure 1361 2026.06

  ISSN  00222860

  　View Summary

  The thermal properties of clathrate hydrates are determined by the combination of water molecules and encapsulated types of guest molecules through the resulting crystal structure. Takaya et al. have reported that the 2-propanol + CH₄ hydrate possesses a tetragonal structure II’ (sII′) below 110 K. This finding shows that thermodynamic conditions (T, P) could change the crystal structural transition in the same chemical system. This study investigated crystallographic characteristics of the HFC-41 + 2-propanol hydrate and demonstrated that a single-atom fluorination stabilizes the sII’, replaced with methane in small cages. We have employed variable-temperature powder X-ray diffraction (PXRD) measurement, and the results show that the binary HFC-41 + 2-propanol hydrate exhibits canonical cubic sII hydrate with a lattice constant of a = 17.2259(5) Å at 168 K. Cooling down to 93 K, HFC-41 + 2-propanol hydrate transits to a tetragonal structure (sII’) from sII with lattice constants a<inf>t</inf>=12.304(1) Å and c<inf>t</inf>=16.925(2) Å. The transition temperature from sII′ to sII is near 153 K, 40 K higher than that of the methane + 2-propanol hydrate. This result demonstrated that a single-atom fluorination stabilizes the sII’, which was replaced with methane in the small cage.

  • Access to Document (DOI)

• Crystal growth of CO2 hydrate formed in the system of CO2 + water + trehalose toward the development of solid carbonated foods

  Tokunaga R., Maruyama M., Shigehara S., Alavi S., Ohmura R.

  International Journal of Food Properties 29 ( 1 )  2026

  ISSN  10942912

  　View Summary

  Application of CO<inf>2</inf> clathrate hydrate as a constituent of solid carbonated foods is an emerging new idea to utilize the large gas-storage capacity of this material. The CO<inf>2</inf> gas concentration of CO<inf>2</inf> hydrate is 50 times higher than the CO<inf>2</inf> concentration in carbonated water. To design an industrial process for making CO<inf>2</inf> clathrate hydrates and to determine the texture of hydrate foodstuffs, understanding the crystal growth dynamics and crystal morphology is essential. This study reports the visual observations of crystal growth of CO<inf>2</inf> hydrate in the presence of trehalose under conditions relevant to potential food production. To classify the observation results, the subcooling temperature ΔT<inf>sub</inf> defined as the difference between equilibrium hydrate formation temperature, T<inf>eq</inf> and the experimental temperature, T<inf>ex</inf> was used as an index of the driving force for the crystal growth. The experiments were performed at the ∆T<inf>sub</inf> range of 0.8 K to 4.9 K. At any ΔT<inf>sub</inf>, the formation and growth of the crystals were observed at the interface between the CO<inf>2</inf> gas phase and the trehalose solution. The hydrate crystals covered the interface and grew into the liquid phase. The crystal morphology significantly depends on ΔT<inf>sub</inf>. The shape of crystals was polygonal at ΔT<inf>sub</inf> < 2.5 K, columnar at ΔT<inf>sub</inf> ≈ 3.5 K, and dendritic at ΔT<inf>sub</inf> > 3.8 K. The effects of CO<inf>2</inf> hydrate crystal morphology in the system with trehalose, on the dynamics of hydrate slurry and the texture of hydrate food are discussed.

  • Access to Document (DOI)

• Phase Equilibria of D2O Hydrates for Hydrate-Based Tritium Separation

  Kasai R., Ito H., Kiyokawa H., Kamiya L., Alavi S., Ohmura R.

  International Journal of Thermophysics 46 ( 12 )  2025.12

  ISSN  0195928X

  　View Summary

  Clathrate-hydrate-based tritium separation from isotope water is a promising process for removing tritium that is not effectively separated by conventional methods. Clathrate hydrates (hereafter hydrates) are crystalline compounds composed of water and guest molecules. Hydrate-based tritium separation utilizes the property that heavy water (D<inf>2</inf>O) forms hydrates under milder temperatures than light water (H<inf>2</inf>O). Efficient industrial operation requires a guest compound that forms hydrates at high temperatures and low pressures and has a large difference in phase equilibrium temperature between H<inf>2</inf>O and D<inf>2</inf>O hydrates (ΔT<inf>DH</inf>). In this study, we measured the phase equilibrium conditions of D<inf>2</inf>O hydrates formed with HFC-134a, HFC-32, and HFC-23. The formation of D<inf>2</inf>O hydrates with these guests can be a route to tritium separation through co-precipitation of T<inf>2</inf>O. HFC-134a formed hydrates under the mildest conditions, with ΔT<inf>DH</inf> values of 2.8 K, 1.8 K, and 2.4 K for HFC-134a, HFC-32, and HFC-23. In addition to the three investigated guests, the potentials of propane, cyclopentane, and cyclopentane + CO₂ hydrate systems for hydrogen isotope separations were also compared, suggesting that HFC-134a and cyclopentane may be suitable guests for tritium separation. Present and previous studies have also shown a strong positive correlation between the hydration number and ΔT<inf>DH</inf> (correlation coefficient = 0.76). This trend may be ascribed to the fact that a higher proportion of water molecules in the hydrate amplifies the effect of replacing H<inf>2</inf>O with D<inf>2</inf>O. These results indicate that the equilibrium conditions of D₂O hydrates may be approximately predicted to identify suitable guests for tritium separation.

  • Access to Document (DOI)

• Interactions between gas hydrate and hydrogen in nature: Laboratory evidence of hydrogen incorporation

  Maruyama M., Horsfield B., Spangenberg E., Ohmura R., Schicks J.M.

  International Journal of Hydrogen Energy 184 2025.11

  ISSN  03603199

  　View Summary

  Natural hydrogen is generated via serpentinization, radiolysis and organic metagenesis in geological settings. After expulsion from the source, and along its upward migration path, the free gas may encounter hydrate-bearing sediments. To simulate this natural scenario, CH<inf>4</inf> hydrate and CH<inf>4</inf> + C<inf>3</inf>H<inf>8</inf> hydrate were synthesized at 5.0 MPa and exposed to a hydrogen-containing gas mixture. In-situ Raman spectroscopic measurements demonstrated the incorporation of H<inf>2</inf> molecules into the hydrate phase even at a partial pressure of 0.5 MPa. Ex-situ Raman spectroscopic characterization of hydrates formed from a CH<inf>4</inf> + H<inf>2</inf> gas mixture at 5.0 MPa confirmed the H<inf>2</inf> inclusion within the large cavities of structure I. The results show that the interactions between H<inf>2</inf> and the natural gas hydrate phase range from the incorporation of H<inf>2</inf> molecules into the hydrate phase to the rapid dissociation of the gas hydrate, depending on thermodynamic conditions and H<inf>2</inf> concentration in the coexisting gas phase.

  • Access to Document (DOI)

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Papers, etc., Registered in KOARA 【 Display / hide 】

Papers, etc., Registered in KOARA 【 Display / hide 】

• Development of efficient, environment-friendly CO2 capture technology using clathrate hydrate

  Omura, Ryo

  科学研究費補助金研究成果報告書 2015

• Possibility of carbon dioxide hydrate as a extinguishing agent agait large scale fire

  Omura, Ryo

  科学研究費補助金研究成果報告書 2013

• Crystal growth of clathrate hydrates in systems with seawater : towards advancement of novel energy technologies

  Omura, Ryo

  科学研究費補助金研究成果報告書 2012

• Thermal engineering studies of double-hydrate formation : attempts toward establishing new energy-utilization technologies

  Omura, Ryo

  科学研究費補助金研究成果報告書 2010

• Investigation into variations in hydrate crystal morphology

  Omura, Ryo

  科学研究費補助金研究成果報告書 2009

Presentations 【 Display / hide 】

Presentations 【 Display / hide 】

• 二酸化炭素分離に適したクラスレートハイドレートの探索と物性測定

  Ohmura Ryo

  [Domestic presentation]  化学工学会第46回秋季大会, 

  2014.09

  , 

  Oral presentation (invited, special), 公益社団法人 化学工学会

• Crystallographic structure and thermodynamic stability of clathrate hydrates formed with halogen-containing guests

  Ryo Ohmura

  [International presentation]  2012 "Natural Gas Hydrate Systems" Gordon Research Conference (Ventura, CA) , 

  2012.03

  , 

  Oral presentation (invited, special)

• Crystal growth of clathrate hydrates in hydrophobic-guest fluid + liquid-water systems

  Ohmura Ryo

  [International presentation]  ACS 241st National Meeting (Anaheim, CA, USA) , 

  2011.03

  , 

  Oral presentation (invited, special), American Chemical Society

• Understanding thermodynamics of clathrate hydrates toward energy/environment technology innovations

  Ohmura Ryo

  [International presentation]  21st IUPAC International Conference on Chemical Thermodynamics Conference (ICCT-2010) (Tsukuba) , 

  2010.08

  , 

  Oral presentation (invited, special), IUPAC

• Combustion Characteristics of Methane Hydrate in a Laminar Boundary Layer

  Yuki Nakmura, Ryoji Katsuki, Takeshi Yokomori, Ryo Ohmura, Toshihisa Ueda, Masahiro Takahashi, Toru Iwasaki and Kazuo Uchida

  [International presentation]  6th International Conference on Gas Hydrates (ICGH 2008) (Vancouver) , 

  2008.07

  , 

  Poster presentation

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

Research Projects of Competitive Funds, etc. 【 Display / hide 】

• 海水と炭酸ガスの炭酸塩晶析反応に関する基礎研究

  2007.07

  -

  2008.03

  受託研究費, Commissioned ｒesearch, No Setting

• クラスレート水和物の結晶モルフォロジー多様性の解明

  2007.04

  -

  2008.03

  Grant-in-Aid for Scientific Research, Research grant, No Setting

• シクロペンタンハイドレートの生成特性の解明

  2006.10

  -

  2007.03

  東京電力株式会社, 共同研究費, Joint research, No Setting

• クラスレート水和物の結晶構造多様性を利用した省エネルギー天然ガス貯蔵・輸送技術に関する研究

  2005.10

  -

  2006.09

  NEDO, -, Research grant, No Setting

Intellectual Property Rights, etc. 【 Display / hide 】

Intellectual Property Rights, etc. 【 Display / hide 】

• 構造Hクラスレート水和物の生成方法

  Date announced： 特開2003-3181   

  Patent, Single

• 気体の分離剤及び気体を分離濃縮するための方法と装置

  Date announced： 特開2003-138281   

  Patent, Single

• 不凍タンパク質を用いた包接化合物の生成制御法

  Date announced： 特開2005-89353   

  Patent, Single

• トレハロースを用いた包接化合物の生成制御法

  Date announced： 特開2005-89331   

  Patent, Single

• 新規構造H水和物

  Date announced： 特願2004-355852   

  Patent, Joint

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Awards 【 Display / hide 】

Awards 【 Display / hide 】

• 日本機械学会奨励賞（研究）

  大村　亮, 2004.04, 日本機械学会, クラスレートハイドレートに関する熱工学的研究

• 日本機械学会奨励賞（研究）

  Ohmura Ryo, 2004.04, クラスレートハイドレートに関する熱工学的研究

  Type of Award： Award from Japanese society, conference, symposium, etc.

Courses Taught 【 Display / hide 】

Courses Taught 【 Display / hide 】

• PHYSICAL CHEMISTRY OF MOLECULAR CRYSTALS

  2026

• ADVANCED COURSE IN APPLIED AND COMPUTATIONAL MECHANICS 1

  2026

• FACTORY VISITING

  2026

• MECHANICAL ENGINEERING SEMINAR 1

  2026

• GRADUATE RESEARCH ON ENGINEERING AND DESIGN 2

  2026

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Social Activities 【 Display / hide 】

Social Activities 【 Display / hide 】

• ガスハイドレート産業創出イノベーション

  2006.09

  -

  Present

  　View Summary

  産業技術総合研究所が主催する研究会の会員．産総研，民間企業，大学から会員を集め，ハイドレート利用技術の事業化へ向けた取り組みを進める．

• 天然ガスハイドレート製造利用システム実証特別委員会

  2006.08

  -

  2008.03

  　View Summary

  上記委員会はNEDOから三井造船（株）と中国電力（株）への委託事業におけるプロジェクトリーダーの諮問機関という位置づけ

• NEDO平成17年度「天然ガスハイドレート技術の国内市場への適用可能性調査」検討委員会

  2005.04

  -

  2005.07

  　View Summary

  NEDOから（財）エネルギー総合工学研究所への委託研究の検討委員会委員

Memberships in Academic Societies 【 Display / hide 】

Memberships in Academic Societies 【 Display / hide 】

• 日本機械学会, 

  2011.04

  -

  Present

• 日本機械学会　メカライフ編集委員会, 

  2007.04

  -

  2008.03

• 日本機械学会熱工学部門 広報委員, 

  2005.04

  -

  2006.03

Committee Experiences 【 Display / hide 】

Committee Experiences 【 Display / hide 】

• 2011.04

  -

  Present

  Committee Member, 日本機械学会

• 2007.04

  -

  2008.03

  Committee Member, 日本機械学会　メカライフ編集委員会

• 2006.09

  -

  Present

  Member, ガスハイドレート産業創出イノベーション

  　View Remarks

  産業技術総合研究所が主催する研究会の会員．産総研，民間企業，大学から会員を集め，ハイドレート利用技術の事業化へ向けた取り組みを進める．

• 2006.08

  -

  2008.03

  Committee Member, 天然ガスハイドレート製造利用システム実証特別委員会

  　View Remarks

  上記委員会はNEDOから三井造船（株）と中国電力（株）への委託事業におけるプロジェクトリーダーの諮問機関という位置づけ

• 2005.04

  -

  2006.03

  Committee Member, 日本機械学会熱工学部門 広報委員

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