論文 - 室町 実大
件数 52 件-
Sanehiro Muromachi, Satoshi Takeya, Kiyofumi Suzuki, Norio Tenma
Fluid Phase Equilibria 587 114213 2024年8月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 単著
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Discovery of the final primitive Frank-Kasper phase of clathrate hydrates
Muromachi, S; Takeya, S
SCIENCE ADVANCES 10 ( 30 ) 2024年7月 [査読有り]
担当区分：筆頭著者, 最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 共著
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Microstructural investigation of morphology and kinetics of methane hydrate in the presence of tetrabutylammonium bromide: Insights for preservation and inhibition
Satoshi Takeya, Sanehiro Muromachi, Michihiro Muraoka, Kiyofumi Suzuki, Norio Tenma, Keiichi Hirano … 全著者表示
Satoshi Takeya, Sanehiro Muromachi, Michihiro Muraoka, Kiyofumi Suzuki, Norio Tenma, Keiichi Hirano, Kazuyuki Hyodo, Masahide Kawamoto, Akio Yoneyama 閉じる
The Journal of Chemical Physics 2024年4月 [査読有り]
記述言語：英語 掲載種別：研究論文（学術雑誌） 共著
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Discovery of the final primitive Frank-Kasper phase of clathrate hydrates
Sanehiro Muromachi,Satoshi Takeya
ChemRxiv 2024年3月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（その他学術会議資料等） 共著
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Discovery of the final primitive Frank-Kasper phase of clathrate hydrates
Sanehiro Muromachi,Satoshi Takeya
ChemRxiv 2024年3月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（その他学術会議資料等） 共著
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Sanehiro Muromachi,Kosuke Ikeda,Kazuki Maesaka,Hiroyuki Miyamoto
Energy 290 130176 - 130176 2024年3月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Elsevier BV 共著
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Sanehiro Muromachi,Satoshi Takeya
Physical Chemistry Chemical Physics 26 ( 4 ) 3315 - 3321 2023年12月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 共著
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Sanehiro Muromachi,Kiyofumi Suzuki,Norio Tenma
FLUID PHASE EQUILIBRIA 568 2023年5月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER 共著
Subsea methane hydrates are expected as a potential natural gas resource. To develop gas production methods for the subsea methane hydrates, flow assurance technologies are necessary. Urea is one of the environmentally-friendly thermodynamic hydrate inhibitors (THIs) which is expected to be applicable for subsea methane hydrate systems. To evaluate its performance as a THI, a set of phase equilibrium data are necessary. In this study, we report phase equilibrium data for systems of urea + methane + water and urea + carbon dioxide + water in the range of aqueous compositions of urea up to its solubility limits. The present data for urea + methane + water ranged in pressures from 5 to 13 MPa and in urea mass fractions from 0.05 to 0.5. The comparison with the literature found that the inhibition effect of urea is a few kelvin weaker than that of methanol in the present measurement range. With the dense urea solutions, the system reached four phase equilibrium, i.e., solid urea-aqueous solution-gas-hydrate. At 13 MPa, approximately 13 K of inhibition temperature was obtained with 0.500 of feed mass fraction where solid urea was precipitated from the aqueous phase. In the urea + carbon dioxide + water systems, urea also worked as a THI. The maximum inhibition temperature was approximately 10 K with 0.400 of urea mass feed fraction at the four phase equilibrium. Based on the present equilibrium data and seafloor conditions of the subsea methane hydrates, it was found that urea can be used for the both systems of the methane gas production and the hydrate based carbon capture and storage.
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CO2ハイドレートの物理特性およびCCSへの応用
室町実大, 村岡道弘, 鈴木清史,天満則夫
高圧力の科学と技術 32 ( 4 ) 205 - 217 2022年12月 [査読有り] [招待有り]
担当区分：筆頭著者, 責任著者 記述言語：日本語 掲載種別：研究論文（学術雑誌） 単著
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Satoshi Takeya,Sanehiro Muromachi,Akio Yoneyama
Energy & Fuels 36 ( 18 ) 10659 - 10666 2022年9月 [査読有り]
記述言語：英語 掲載種別：研究論文（学術雑誌） 共著
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Sanehiro Muromachi,Masato Kida,Masato Morimoto,Shogo Yamane,Satoshi Takeya
PHYSICAL CHEMISTRY CHEMICAL PHYSICS 24 ( 30 ) 18198 - 18204 2022年7月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
Semiclathrate hydrates are host-guest materials that form from ionic guests and water. There are numerous options for ionic guests, such as quaternary ammonium salts, to tune the functional properties of these materials such as melting temperature, fusion heat, and gas capacity and selectivity. To design these materials, the stabilization mechanism of the side chains of quaternary ammonium salts must be understood based on both thermodynamic and crystallographic properties and relevant host-guest dynamics. In this paper, we studied semiclathrate hydrates formed from n-propyl, tri-n-butylammonium bromide (N3444Br) and tri-n-butyl, n-pentylammonium bromide (N4445Br). Their cation side chains are decremented or incremented from tetra-n-butylammonium (N-4444 or TBA), which is one of the best fits for semiclathrate hydrate structures. The use of the widely used tetra-n-butylammonium bromide (N4444Br or TBAB) as an ionic guest, an increment of the carbon chain, i.e., N4445Br, caused disorders in its hydrate structure due to the oversizing of the cation. This suitably oversized cation selectively stabilized the orthorhombic structure, whose hydration number is relatively high. As a result, the fusion heat at the congruent composition of the hydrate phase was higher than that of the widely used N4444Br (TBAB) hydrates. The N3444Br hydrate showed both significantly decreased melting temperature and fusion heat compared to the N4444Br (TBAB) hydrates. The phase behaviour of the N3444Br hydrate was found to be analogous to that of the N4444Br (TBAB) hydrates. It was demonstrated that the semiclathrate hydrate structures and relevant properties can be modified by adjusting the alkyl side chain length of quaternary ammonium salts.
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Sanehiro Muromachi,Satoshi Takeya,Saman Alavi,John A. Ripmeester
CRYSTENGCOMM 24 ( 24 ) 4366 - 4371 2022年6月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
The crystal structure of tetra-n-butylammonium chloride (TBAC) + CO2 semiclathrate hydrate that is known to have high CO2 selectivity was studied by single crystal X-ray diffraction. The presence of the CO2 gas leads to occupation of dodecahedral (D) cages by water, CO2 and chloride. This hydrate structure has three types of D cages, i.e., D-L, D-M and D-N, with the ratio for cage number D-L : D-M : D-N = 2 : 2 : 1. CO2 occupied D-M and D-N cages which were suitably distorted for the linear CO2 molecular shape. Chloride anions partly occupied the D-M cages, coordinating to water molecules. The lateral distortion of the D-M and D-N cage leads restricted spatial CO2 distribution in the cages. The D-L cages were highly distorted by the TBA cation. In D-L cages, partial occupancies with both water and chloride, which coordinated to cage water molecules, were found. Contrary to the water molecules which were placed at the cage center, chloride anions were off-centred at two distinct positions due to slightly longer coordination lengths with the cage water molecules. The present analysis showed a superior CO2 capture preference of TBAC hydrate in the structural aspect.
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Superheating of Structure I Gas Hydrates within the Structure II Cyclopentane Hydrate Shell
Satoshi Takeya,Sanehiro Muromachi,Akio Yoneyama,Keiichi Hirano,Kazuyuki Hyodo,John A. Ripmeester
JOURNAL OF PHYSICAL CHEMISTRY LETTERS 13 ( 9 ) 2130 - 2136 2022年3月 [査読有り]
DOI Web of Science Scopus PubMed
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：AMER CHEMICAL SOC 共著
The superheated state of methane (CH4) hydrate that exists under the surface ice layer can persist for considerable lengths of time, which showed promise as a method for storing and transporting natural gas. This study extends this further by coating sI CH4 hydrate with one of several sII hydrates, thus eliminating the need for a defect-free continuous interface between the sI and sII hydrates. Gas hydrate crystals were kept intact above their dissociation temperature by immersing them in liquid cyclopentane (CP), as observed with powder X-ray diffraction and X-ray CT methods. It was observed that placing the CH4 hydrate in CP converted the outer layer of CH4 hydrate to a thin layer of CP hydrate at around 270 K under atmospheric pressure, which is similar to 80 K higher than the usual dissociation temperature. It was also observed that sI CO2 hydrate and C2H6 hydrate could be preserved by CP hydrate.
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Enhanced methane storage in clathrate hydrates induced by antifreezes
Byeonggwan Lee,Kyuchul Shin,Sanehiro Muromachi,Igor L. Moudrakovski,Christopher I. Ratcliffe,John A … 全著者表示
Byeonggwan Lee,Kyuchul Shin,Sanehiro Muromachi,Igor L. Moudrakovski,Christopher I. Ratcliffe,John A. Ripmeester 閉じる
CHEMICAL ENGINEERING JOURNAL 418 2021年8月 [査読有り]
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCIENCE SA 共著
Antifreezes are widely used in preventing hydrate formation in oil and gas flowlines. Recent studies have revealed that methanol and ammonia can be incorporated into clathrate hydrate phases along with a more hydrophobic guest such as THF or propane and that these antifreezes act as catalysts for methane hydrate formation from ice. In this work, we demonstrated that these antifreezes can enhance the methane storage content of binary clathrate hydrates, namely those of THF and TBAB. THF + methane and TBAB + methane binary hydrates with/without methanol or ammonia were synthesized and analyzed with 13C NMR spectroscopy and Xray diffraction (XRD) methods. In the THF hydrate system, 84% and 81% of the 512 small cages were occupied by methane in the presence of methanol and ammonia respectively, while only 44% of the small cages were occupied in the absence of these antifreezes. In the TBAB-H2O system, the powder XRD (PXRD) patterns of 1TBAB:38H2O samples without antifreeze both before and after methane introduction showed mostly tetragonal structures. On the other hand, it was confirmed that methanol can easily induce TBAB hydrates to form the orthorhombic structure which is more suitable for methane storage than the tetragonal structures of TBAB hydrates. The single crystal XRD analysis of a crystal grown from the 1TBAB:1CH3OH:38H2O solution at 277 K showed that methanol was present in the 512 cage of the orthorhombic TBAB hydrate phase. The 13C NMR spectra of TBAB + methane hydrates also showed an enhanced methane content in the presence of methanol. The present findings on the enhancement of methane storage induced by antifreezes suggest that methanol can be a key material for hydrate-based methane storage systems.
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Sanehiro Muromachi
ENERGY 223 2021年5月 [査読有り]
担当区分：筆頭著者, 最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD 単著
In this study, we investigate CO2 capture properties of semiclathrate hydrates formed with tetra-n- butylammonium (TBA) Br (TBAB), TBA Cl (TBAC), tetra-n-butylphosphonium (TBP) Br (TBPB) or TBP Cl (TBPC) from H-2 + CO2 mixed gas. Parametric tests found that all of these hydrates capture almost only CO2. Captured CO2 amounts basically increased with increase of aqueous concentration of ionic substances, while irregular CO2 capture was observed with a TBAB aqueous solution of which concentration was 0.3 in mass fraction. The data with this solution can be divided into two groups: CO2 capture amount of one group is three times higher than the other. It was found that this polymorphic phase behavior for TBAB hydrate was caused by a slight difference in subcooling temperature. TBAC hydrates captured the least CO2 among the presently used hydrates possibly due to its tetragonal hydrate structure which has relatively small gas capacity. Because TBPC hydrates showed unpredictable behavior of CO2 capture, it was suggested that unique hydrate phase formation with TBPC under H-2 + CO2 gas pressure. Among these four salts, TBPB was found to be suitable for H-2/CO2 gas separation due to their superior gas capture performance and simple phase behavior. (C) 2021 Elsevier Ltd. All rights reserved.
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Structural Characterization of Pyrrolidine-Including Structure II Clathrate Hydrates
Sanehiro Muromachi,Hassan Sharifi,Saman Alavi,John A. Ripmeester,Peter Englezos
CRYSTAL GROWTH & DESIGN 21 ( 5 ) 2828 - 2836 2021年5月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：AMER CHEMICAL SOC 共著
Clathrate hydrates are host-guest crystalline compounds which can capture both small gases such as H-2, CH4, and CO2 and larger guest molecules which are in the liquid state. Large guests (LGs) such as tetrahydrofuran (THF) can strongly stabilize the structure II clathrate hydrate under moderate conditions and provide a substantial number of small cages for the encapsulation of smaller guest gases. Most hydrocarbon LGs are volatile and immiscible in water, and even the water-miscible LGs such as THF are still volatile. The use of these LGs requires a recovery process in applications based on hydrates. Amines are one chemical group of alternative LGs which have low vapor pressure compared to hydrocarbon LGs. In this study, we report structural characterization for clathrate hydrates formed with the cyclic amine pyrrolidine (PL) and the structurally related THF. Crystal samples were formed from aqueous solutions of PL and THF with several ratios. Lattice constants determined by the single-crystal X-ray diffraction increased with the increase of PL content in the hydrate. Inspection of the cage size found that 5(12)6(4) cages expand due to PL inclusion, while the empty 5(12) cages do not expand to the same degree. The refined X-ray diffraction structure suggests that the PL is incorporated in the large cage without forming hydrogen bonds with the cage water molecules. Molecular dynamics simulations also support weak hydrogen bond interactions between PL and water molecules.
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Recovery of N2O: Energy-Efficient and Structure-Driven Clathrate-Based Greenhouse Gas Separation
Jiyeong Jang,Sol Geo Lim,Jae Hak Jeong,Appu Vengattoor Raghu,Jong-Won Lee,Minjun Cha,Sanehiro Murom … 全著者表示
Jiyeong Jang,Sol Geo Lim,Jae Hak Jeong,Appu Vengattoor Raghu,Jong-Won Lee,Minjun Cha,Sanehiro Muromachi,Yoshitaka Yamamoto,Ji-Ho Yoon 閉じる
ENVIRONMENTAL SCIENCE & TECHNOLOGY 55 ( 6 ) 3909 - 3917 2021年3月 [査読有り]
DOI Web of Science Scopus PubMed
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：AMER CHEMICAL SOC 共著
N2O has 300 times more global warming potential than CO2 and is also one of the main stratospheric ozone-depleting substances emitted by human activities such as agriculture, industry, and the combustion of fossil fuels and solid waste. We present here an energy-efficient clathrate-based greenhouse gas-separation (CBGS) technology that can operate at room temperature for selectively recovering N2O from gas mixtures. Clathrate formation between alpha-form/beta-form hydroquinone (alpha-HQ/beta-HQ) and gas mixtures reveals guest-specific and structuredriven selectivity, revealing the preferential capture of N2O in beta HQ and the molecular sieving characteristics of alpha-HQ. With a maximum gas storage capacity and cage occupancy of 54.1 cm(3) g(-1) and 0.86, respectively, HQ clathrate compounds including N2O are stable at room temperature and atmospheric pressure and thus can be easily synthesized, treated, and recycled via commercial CBGS processes. High selectivity for N2O recovery was observed during beta-HQ clathrate formation from N2O/N-2 gas mixtures with N2O concentrations exceeding 20%, whereas alpha-HQ traps only N-2 molecules from gas mixtures. Full characterization using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, solid-state nuclear magnetic resonance, and compositional analysis and the formation kinetics of HQ clathrates was conducted to verify the peculiar selectivity behavior and to design the conceptual CBGS process. These results provide a new playground on which to tailor host-guest materials and develop commercial processes for the recovery and/or sequestration of greenhouse gases.
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Sanehiro Muromachi,Satoshi Takeya,Daisuke Yuhara,Kenji Yasuoka
FLUID PHASE EQUILIBRIA 527 2021年1月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER 共著
In this communication, effective cage radii of dodecahedral (D) cages in semiclathrate hydrates are investigated based on van der Waals and Platteeuw model. According to recent findings in semiclathrate hydrate structures, D cages in semiclathrate hydrates have anisotropic shapes which provide unique gas capacity and selectivity under mild temperature and pressure conditions. Since applications of these materials for cool energy storage and gas capture and storage technologies are expected, thermodynamic modeling of the semiclathrate hydrates is an emerging issue. So far, the van der Waals and Platteeuw model which is based on Langmuir adsorption theory has been used for modeling of canonical gas hydrates and semiclathrate hydrates. The model applies spherical cell potential to predict guest gas inclusion in the cages, and each cage is characterized by its radius with sphere approximation. While sizes of D cages in semiclathrate hydrates are quite similar to those in gas hydrates, their shapes are found to be irregularly anisotropic dodecahedra that can provide unique gas capture and storage properties. Therefore, when the van der Waals and Platteeuw model is applied to semiclathrate hydrates, it is necessary to discriminate the D cages in the model from those in canonical gas hydrates. Adjusting D cage radius in spherical cell potential model is a simple and convenient way to describe differences in cage shape between semiclathrate hydrates and canonical gas hydrates. Here, we investigated effective cage radii of D cages in the semiclathrate hydrates based on the conventional cell potential model with sphere approximation. Effective radii of D cages in the semiclathrate hydrates were found to be different from those in canonical gas hydrates. With the presently suggested radii, the conventional cell potential model can predict experimental data for cage occupancy in the semiclathrate hydrates more precisely. (C) 2020 Elsevier B.V. All rights reserved.
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Satoshi Takeya,Sanehiro Muromachi,Akihiro Hachikubo,Ryo Ohmura,Kazuyuki Hyodo,Akio Yoneyama
Physical Chemistry Chemical Physics 22 ( 47 ) 27658 - 27665 2020年11月 [査読有り]
DOI Web of Science Scopus PubMed
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
In this study, X-ray imaging of inclusion compounds encapsulating various guest species was investigated based on the calculation of X-ray attenuation coefficients. The optimal photon energies of clathrate hydrates were simulated for high-contrast X-ray imaging based on the type of guest species. The proof of concept was provided by observations of Kr hydrate and tetra-n-butylammonium bromide (TBAB) semi-clathrate hydrate using absorption-contrast X-ray computed tomography (CT) and radiography with monochromated synchrotron X-rays. The radiographic image of the Kr hydrate also revealed a sudden change in its attenuation coefficient owing to the K-absorption edge of Kr as the guest element. With a photon energy of 35 keV, X-ray CT provided sufficient segmentation for the TBAB semi-clathrate hydrate coexisting with ice. In contrast, the simulation did not achieve the sufficient segmentation of the CH4 and CO2 hydrates coexisting with water or ice, but it revealed the capability of absorption-contrast X-ray CT to model the physical properties of clathrate hydrates, such as Ar and Cl2 hydrates. These results demonstrate that the proposed method can be used to investigate the spatial distribution of specific elements within inclusion compounds or porous materials.
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Satoshi Takeya,Michihiro Muraoka,Sanehiro Muromachi,Kazuyuki Hyodo,Akio Yoneyama
Physical Chemistry Chemical Physics 22 ( 25 ) 14377 - 14379 2020年7月 [査読有り]
DOI Web of Science Scopus PubMed
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
© the Owner Societies. The authors would like to update Fig. 5 and 7 to correct errors present in the published version of the article. On page 3451, the notations ‘‘PP’’ and ‘‘Nylon’’ in Fig. 5(a)–(d), and (f) are in the wrong place. On page, 3452, Fig. 7(d) and (e) mistakenly reproduce a portion of Fig. 7 from a paper by Kerkar et al.1 The relevant parts of the figure were correct in the original submission but were replaced in error upon submission of the revised manuscript when updating the figure in response to reviewer comments. The correct versions of Fig. 5 and 7 are shown here. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. (Figure Presented).
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Hidenori Hashimoto,Hiroyuki Ozeki,Yoshitaka Yamamoto,Sanehiro Muromachi
ACS Omega 5 ( 13 ) 7115 - 7123 2020年4月 [査読有り]
DOI Web of Science Scopus PubMed
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：AMER CHEMICAL SOC 共著
Copyright © 2020 American Chemical Society. Semiclathrate hydrates of tetra-n-butylammonium fluoride (TBAF) are potential CO2 capture media because they can capture CO2 at near ambient temperature under moderate pressure such as below 1 MPa. In addition to other semiclathrate hydrates, CO2 capture properties of TBAF hydrates may vary with formation conditions such as aqueous composition and pressure because of their complex hydrate structures. In this study, we investigated CO2 capture properties of TBAF hydrates for simulated flue gas, that is, CO2 + N2 gas, by the gas separation test with three different parameters for each pressure and aqueous composition of TBAF in mass fraction (wTBAF). The CO2 capture amount in TBAF hydrates with wTBAF = 0.10 was smaller than that obtained with wTBAF = 0.20 and 0.30. The results found that gas pressure greatly changed the CO2 capture amount in TBAF hydrates, and the aqueous composition highly affected CO2 selectivity. The crystal morphology and single-crystal structure analyses suggested that polymorphism of TBAF hydrates with congruent aqueous solution may lower both the CO2 capture amount and selectivity. Our present results proposed that an aqueous solution with wTBAF = 0.20 is advantageous for the CO2 capture from flue gas compared to near congruent solutions of TBAF hydrates (wTBAF = 0.30) and dilute solution (wTBAF = 0.10).
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Sanehiro Muromachi
Fluid Phase Equilibria 506 2020年2月 [査読有り]
担当区分：筆頭著者, 最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER 単著
© 2019 Elsevier B.V. Semiclathrate hydrates are host–guest materials that can be used for CO2 capture due to their unique gas selectivity. CO2 capture from H2 + CO2 mixed gas is possible by semiclathrate hydrates formed by tetra-n-butylammonium (TBA) and tetra-n-butylphosphonium (TBP) salts. TBA bromide (TBAB), TBA chloride (TBAC), TBP bromide (TBPB) and TBP chloride (TBPC) are widely available ionic substances for semiclathrate hydrate formation. In order to understand their gas capture properties, phase equilibrium data of these materials are necessary. Here we report experimental three phase (gas–hydrate–aqueous phase) equilibrium data measured in (TBAB, TBAC, TBPB or TBPC) + H2 + CO2 + H2O systems. The comparison with the literature data suggested that H2 can be incorporated in the TBAB and TBAC hydrates together with CO2, but TBPB and TBPC hydrates reject H2. The hydrate phases were identified by single crystal X-ray diffraction analyses. The TBAB, TBPB and TBPC form the same or similar hydrate phases, i.e., orthorhombic and hexagonal phases. The TBAC formed the tetragonal hydrate phase. The present results suggest that different CO2 capture properties are obtained by these semiclathrate hydrates.
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X-ray CT observation and characterization of water transformation in heavy objects
Satoshi Takeya,Michihiro Muraoka,Sanehiro Muromachi,Kazuyuki Hyodo,Akio Yoneyama
Physical Chemistry Chemical Physics 22 ( 6 ) 3446 - 3454 2020年2月 [査読有り]
DOI Web of Science Scopus PubMed
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Royal Society of Chemistry ({RSC}) 共著
This journal is © the Owner Societies. Nondestructive observations and characterization of low-density materials composed of low-Z elements, such as water or its related substances, are essential for materials and life sciences. However, visualizing these compounds and their phase changes is still challenging. In this study, an approach to X-ray imaging of water-related substances in heavy objects without the use of contrast agents is proposed. The implementation of the approach is based upon X-ray phase shift, in which the optimal photon energy is simulated for high-contrast X-ray imaging. Proof of concept is provided by observations of resins, water, and clathrate hydrates such as CO2 hydrate and tetrahydrofuran (THF) hydrate in an aluminum container by diffraction-enhanced X-ray imaging with synchrotron X-rays of 35 keV. These results suggest that the proposed approach is a unique method for visualizing the transformation of these clathrate hydrates and is also applicable to in situ observations of other objects composed of multiphase materials with small density differences.
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Takeshi Sugahara,Hironobu Machida,Sanehiro Muromachi,N. Tenma
International Journal of Refrigeration 106 113 - 119 2019年10月 [査読有り]
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCI LTD 共著
© 2019 Elsevier Ltd and IIR The quaternary onium salt-based semiclathrate hydrates have been investigated in many kinds of fields such as latent heat storage materials and gas separation media. In the present study, equilibrium (temperature−composition) relations in the tetra-n-butylammonium 2-ethylbutyrate (TBA-2 EB) semiclathrate hydrate system have been measured. In addition, thermodynamic and spectroscopic properties of TBA-2 EB semiclathrate hydrate were analyzed. The maximal equilibrium temperature and stoichiometric concentration of TBA-2 EB semiclathrate hydrate was 283.22 ± 0.05 K and x1 = 0.0281 ± 0.0007, respectively. The crystal lattice of TBA-2 EB semiclathrate hydrate, determined by the single crystal X-ray diffraction, was tetragonal. Other properties, not only Raman spectrum but also the maximum allowable degree of supercooling, in the TBA-2 EB semiclathrate hydrate system were similar to those in the tetra-n-butylammonium bromide (TBAB) hydrate. The TBA-2 EB semiclathrate hydrate would be an alternative to TBAB hydrate as a halogen-free semiclathrate hydrate system.
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Anisotropy of dodecahedral water cages for guest gas occupancy in semiclathrate hydrates
Daisuke Yuhara,Kenji Yasuoka,Satoshi Takeya,Sanehiro Muromachi
Chemical Communications 55 ( 68 ) 10150 - 10153 2019年7月 [査読有り]
DOI Web of Science Scopus PubMed
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
© 2019 The Royal Society of Chemistry. Anisotropic dodecahedral (D) water cages found in semiclathrate hydrates have unique gas selectivity due to their varied shapes. Herein, the D cages incorporating ideally isotropic rare gases, i.e., Xe, Kr and Ar, were characterized by crystal structure analyses. Stabilization mechanisms of the semiclathrate hydrates by the D cages are discussed.
その他リンク： https://pubs.rsc.org/en/content/articlelanding/2019/CC/C9CC05009D#!divAbstract
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Sanehiro Muromachi
Fluid Phase Equilibria 485 234 - 238 2019年4月 [査読有り]
担当区分：筆頭著者, 最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCIENCE BV 単著
© 2018 Elsevier B.V. Methane hydrates are one of unconventional energy resources. There are vast depositions of methane hydrates on the sea floor and under permafrost. The methane hydrates are stable under high pressure and low temperature conditions. Depressurization method is being developed for methane gas production from deep sea methane hydrate layers. In this method, the methane hydrates are depressurized by a pump, and dissociated to be methane gas and water. There is a risk of plugging in the production well by reformed methane hydrates such as at stagnation points and during an operation stop. To manage the plugging risk, inhibitors for methane hydrate formation are necessary. Among several chemical inhibitors, thermodynamic hydrate inhibitors (THIs) are a unique technique that can dissociate methane hydrates. Ammonium salts are one of THIs which naturally occur in oceans and vastly available in the deep sea area. In this study, inhibition effects of ammonium chloride on gas hydrates of methane, carbon dioxide and ethane are investigated. Three phase (gas–hydrate–aqueous) equilibrium conditions are measured by a temperature search method. The equilibrium data show that ammonium chloride suppresses equilibrium temperatures of these gas hydrates until it reaches solubility limit in water. The comparison with molecular inhibitors showed that ammonium chloride inhibits methane hydrate formation more than urea, but less than methanol. The present data clarified the inhibition effect of ammonium chloride on subsea natural gas hydrates and CO2 injection and sequestration techniques.
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Sanehiro Muromachi,Satoshi Takeya
ACS Omega 4 ( 4 ) 7317 - 7322 2019年4月 [査読有り]
DOI Web of Science Scopus PubMed PMC
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：American Chemical Society 共著
© 2019 American Chemical Society. Semiclathrate hydrates are a crystalline host-guest material, which forms with water and ionic substances such as tetra-n-butylammonium (TBA) salts. Various anions can be used as a counter anion to the TBA cation, and they can modify thermodynamic properties of the semiclathrate hydrates, which are critical for applications, for example, cold energy storage and gas separation. In this study, the semiclathrate hydrates of the TBA glycolate were newly synthesized. Measurements for melting temperatures and a heat of fusion and a crystal structure analysis were performed. In comparison with the other similar materials, such as acetates, propionates, lactates, and hydroxybutyrates, the glycolate greatly changed the melting temperature and the heat of fusion. The preliminarily determined crystal structure showed that the glycolate anion builds a relatively porous structure compared to the previously reported hydrates formed with hydroxycarboxylates. The present study showed that substitution of a hydrophobic group by a hydrophilic group is an effective method to control the thermodynamic properties as well as to improve environmental, biological, and chemical properties.
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Sanehiro Muromachi,Satoshi Takeya
Industrial and Engineering Chemistry Research 57 ( 8 ) 3059 - 3064 2018年2月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：American Chemical Society 共著
© 2018 American Chemical Society. Semiclathrate hydrates form from aqueous solution of ionic guest substance such as tetra-n-butylammonium (TBA) and tetra-n-butylphosphonium (TBP) salts. Thermophysical properties of these materials are varied by the ionic guest cations and anions. Investigation of the modification of the semiclathrate hydrates by ionic guest substances is needed to design and improve properties of semiclathrate hydrates for applications such as cool energy storage and for gas separation and storage. Here we report synthesis of semiclathrate hydrates of tetra-n-butylammonium 3-hydroxybutyrate (TBA 3HB) and measurements for melting temperatures and a heat of fusion. We performed phase equilibrium measurements under optical observation for crystal morphology. A heat of fusion was measured by differential scanning calorimetry (DSC) measurements, and a crystal structure of TBA 3HB hydrate was identified to be tetragonal by single-crystal X-ray diffraction (XRD) measurements. The results showed that the highest melting temperature was 282.2 K and the heat of fusion was 172 kJ kg-1. We compared the presently obtained data with similar semiclathrate hydrates reported in the literature. The position of OH group in butyrate varied the melting temperature but had little influence on the heat of fusion. It was found that substitution of carboxylates by a hydrophilic OH group in TBA carboxylates can be used to design thermophysical properties of TBA carboxylate hydrates.
その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85042771151&origin=inward
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Structure-driven CO<inf>2</inf> selectivity and gas capacity of ionic clathrate hydrates
Hidenori Hashimoto,Tsutomu Yamaguchi,Hiroyuki Ozeki,Sanehiro Muromachi
Scientific Reports 7 ( 1 ) 2017年12月 [査読有り]
DOI Web of Science Scopus PubMed
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：NATURE PUBLISHING GROUP 共著
© 2017 The Author(s). Ionic clathrate hydrates can selectively capture small gas molecules such as CO2, N2, CH4 and H2. We investigated CO2 + N2 mixed gas separation properties of ionic clathrate hydrates formed with tetra-n-butylammonium bromide (TBAB), tetra-n-butylammonium chloride (TBAC), tetra-n-butylphosphonium bromide (TBPB) and tetra-n-butylphosphonium chloride (TBPC). The results showed that CO2 selectivity of TBAC hydrates was remarkably higher than those of the other hydrates despite less gas capacity of TBAC hydrates. The TBAB hydrates also showed irregularly high CO2 selectivity at a low pressure. X-ray diffraction and Raman spectroscopic analyses clarified that TBAC stably formed the tetragonal hydrate structure, and TBPB and TBPC formed the orthorhombic hydrate structure. The TBAB hydrates showed polymorphic phases which may consist of the both orthorhombic and tetragonal hydrate structures. These results showed that the tetragonal hydrate captured CO2 more efficiently than the orthorhombic hydrate, while the orthorhombic hydrate has the largest gas capacity among the basic four structures of ionic clathrate hydrates. The present study suggests new potential for improving gas capacity and selectivity of ionic clathrate hydrates by choosing suitable ionic guest substances for guest gas components.
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Solubility of Nitrogen Gas in Aqueous Solution of Tetra-n-Butylammonium Bromide
Sanehiro Muromachi,Hiroyuki Miyamoto,Ryo Ohmura
International Journal of Thermophysics 38 ( 12 ) 2017年12月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：SPRINGER/PLENUM PUBLISHERS 共著
© 2017, Springer Science+Business Media, LLC. Semiclathrate hydrates are water-based host-guest compounds formed from aqueous solutions of ionic guest substances. These materials can greatly moderate formation pressures and temperatures from canonical gas hydrates. This is a significant advantage for industrial applications such as gas separation and storage. N 2 gas is a major component contained in various flue gases and is usually mixed with CO 2. Semiclathrate hydrates can separate these gases under moderate thermodynamic conditions. Tetra-n-butylammonium bromide (TBAB) is a widely used ionic guest substance. To develop the application technologies and their theoretical models, solubility data of N 2 gas in TBAB aqueous solutions are required. In this study, we report N 2 gas solubility measured by an absolute gravimetric method for the semiclathrate hydrate formation system of TBAB + H 2O + N 2. The measurement pressures, temperatures and TBAB mass fractions were 3 MPa, 5 MPa and 7 MPa, 292.15 K, 302.15 K and 307.15 K, and 0 (pure water), 0.10, 0.20, 0.32 and 0.40, respectively. The uncertainties were 0.056 MPa, 0.44 K and 0.00012 in mole fraction. Although the technical difficulty lays on measurements of small N 2 gas solubility by the absolute gravimetric method, our data implied the unique gas dissolution property of aqueous TBAB solution depending on the TBAB concentration. The aqueous TBAB solutions with mass fractions of 0.10 and 0.20 had similar N 2 gas solubility as that in pure water. With higher mass fractions, 0.32 and 0.40, the N 2 gas solubility slightly increased from that in pure water, which implies the salting-in effect of TBAB.
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Sanehiro Muromachi,Satoshi Takeya
Fluid Phase Equilibria 441 59 - 63 2017年6月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCIENCE BV 共著
© 2017 Elsevier B.V. Semiclathrate hydrates are water-based host-guest materials that consist of water and ionic guest substances such as quaternary ammonium salts. Widely-used tetra-n-butylammonium (TBA) salts are designed for gas selectivity and capacity with respect to the industrial application of these materials. This study reported on the formation of semiclathrate hydrates of TBA carboxylates with guest gas characterized by phase equilibrium measurements and single crystal X-ray diffraction. Specifically, TBA acrylate and TBA butyrate are used for ionic guest substances, and this may induce a tetragonal P42/mmm semiclathrate hydrate structure. In the four systems of (TBA acrylate or TBA butyrate) + (CH4 or CO2) + H2O, the measured three (gas–hydrate–aqueous) phase equilibrium data exhibited better promotion effects due to the TBA acrylate and TBA butyrate when compared with that of the widely-used TBA bromide. The slopes on pressure–temperature plane suggest differences in the incorporation of CH4 and CO2 in these hydrates. Characterization of the hydrate phases by X-ray diffraction analyses supports this mechanism. However, it is necessary to further understand the complicated gas incorporation in semiclathrate hydrate structures that are handled by ionic guest substances and the guest gas itself.
その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85009783370&origin=inward
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Hidenori Hashimoto,Tsutomu Yamaguchi,Takahiro Kinoshita,Sanehiro Muromachi
Energy 129 292 - 298 2017年 [査読有り]
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD 共著
© 2017 Elsevier Ltd Ionic clathrate hydrates are composed of water and ionic guest substance, which can selectively capture gas under moderate conditions. We performed gas separation experiments with tetra-n-butylammonium bromide (TBAB) widely-used for an ionic guest substance. The experiments in a closed system showed good CO2 gas selectivity of the TBAB hydrates even under the mild conditions: 1 MPa and 282 K. We also performed the gas separation with tetrahydrofuran (THF) which is a guest substance forming the structure II clathrate hydrate. Comparison with THF clearly revealed the better CO2 selectivity of TBAB than that of the structure II clathrate hydrate. We further compared our data with the literature, and found that the condition of low pressure and dense TBAB concentration provided superior CO2 selectivity. Gas separation with continuous gas flow was demonstrated. The hydrate formation behavior was similar to the cases without gas flow. The results showed that controlling the crystal growth temperature is important to capture gases by the TBAB hydrates.
その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85018879680&origin=inward
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Satoshi Takeya,Sanehiro Muromachi,Tatsuo Maekawa,Yoshitaka Yamamoto,Hiroko Mimachi,Takahiro Kinoshi … 全著者表示
Satoshi Takeya,Sanehiro Muromachi,Tatsuo Maekawa,Yoshitaka Yamamoto,Hiroko Mimachi,Takahiro Kinoshita,Tetsuro Murayama,Hiroki Umeda,Dong Hyuk Ahn,Yasunaga Iwasaki,Hidenori Hashimoto,Tsutomu Yamaguchi,Katsunori Okaya,Seiji Matsuo 閉じる
Energies 10 ( 7 ) 2017年 [査読有り]
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：MDPI AG 共著
© 2017 by the authors. This paper proposes an innovative CO2 enrichment system for crop production under a controlled greenhouse environment by means of tetra-n-butylammonium bromide (TBAB) + CO2 semi-clathrate hydrate (SC). In this system, CO2 is captured directly from exhaust gas from a combustion heater at night, which can be used for stimulating photosynthesis of crops in greenhouses during daytime. Although the gas capacity of TBAB + CO2 SC is less than that of CO2 gas hydrate, it is shown that TBAB + CO2 SC can store CO2 for CO2 enrichment in crop production even under moderate pressure conditions (<1.0 MPa) at 283 K.
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Thermodynamic stabilization of semiclathrate hydrates by hydrophilic group
S. Muromachi,R. Kamo,T. Abe,T. Hiaki,S. Takeya
RSC Advances 7 ( 22 ) 13590 - 13594 2017年 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
© The Royal Society of Chemistry. Introducing hydrophilic groups into carboxylates is a way to modify semiclathrate hydrate frameworks and change the properties of the hydrates. In this study, we report the characterization of semiclathrate hydrates formed by tetra-n-butylammonium (TBA) 2-hydroxybutyrate (2HB). In addition, TBA lactate and the TBA 2HB salt formed stable hydrate crystals, which basically had rectangular columnar shapes. We performed equilibrium measurements and calorimetry. The melting temperature and fusion heat of the TBA 2HB hydrate crystals were 285.3 K and 177 kJ kg−1, respectively. A comparison with other carboxylate anions showed that the substitution of hydrogen atom at the 2-position in the carbon chain by a hydrophilic hydroxy group stabilizes the hydrates more than that by hydrophobic methyl group, which is the case for alcohols in clathrate hydrates. The phase equilibrium data for a number of semiclathrate hydrates were compared. A rough trend of temperature depending on type of guest anions was observed, but it is unclear if there are other correlating factors.
その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85014421053&origin=inward
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Sanehiro Muromachi,Yoshitaka Yamamoto,Satoshi Takeya
Korean Journal of Chemical Engineering 33 ( 6 ) 1917 - 1921 2016年6月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：KOREAN INSTITUTE CHEMICAL ENGINEERS 共著
© 2016, Korean Institute of Chemical Engineers, Seoul, Korea. We report the bulk phase behavior of ionic clathrate hydrates of tetra-n-butylammonium bromide (TBAB) formed with a common guest substance: CO2 or CH4. We formed the bulk samples by a classical mixing reactor for gas hydrates, and measured them by the powder X-ray diffraction (PXRD). PXRD patterns of the TBAB+(CO2 or CH4) hydrates formed with 0.32 of TBAB mass fraction in the aqueous phase were obtained. They are consistent with the orthorhombic hydrate (Shimada et al., Acta Crystallogr. 2005; Muromachi et al., Chem. Commun. 2014), but not identical with the other stable phase, i.e., the tetragonal TBAB hydrate (Rodionova et al., J. Phys. Chem. B 2013). When the aqueous solutions are under the substantial pressure of CO2 or CH4 gas, TBAB is likely to form the orthorhombic Pmma and/or Imma phases. A question for the bulk orthorhombic TBAB hydrate phase about the scarce gas incorporation is newly proposed.
その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84961199780&origin=inward
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Sanehiro Muromachi,Hidenori Hashimoto,Tatsuo Maekawa,Satoshi Takeya,Yoshitaka Yamamoto
Fluid Phase Equilibria 413 249 - 253 2016年4月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCIENCE BV 共著
© 2015 Elsevier B.V. We report the three-phase (gas-hydrate-aqueous) equilibrium measurements and phase characterization of ionic clathrate hydrates formed in a nitrogen + tetra-n-butylammonium bromide (TBAB) + water system. The measurement conditions used were 0.0029 ≤ xTBAB ≤ 0.0257 (0.05 ≤ wTBAB ≤ 0.32), 280 K < T < 291 K, and 1 MPa < P < 12 MPa, where xTBAB, wTBAB, T, and P denote the mole fraction of TBAB in the aqueous phase, mass fraction of TBAB in the aqueous phase, temperature, and pressure, respectively. We also performed single-crystal structure analyses of the crystals formed at 2.1 and 5.8 MPa, which indicated that they possessed the same orthorhombic Pmma hydrate phase but significantly different gas capacities. We also showed that the low nitrogen gas pressure supply extends the melting point of the simple TBAB hydrate formed in the absence of gas. CO2 may be efficiently captured from flue gas when the partial pressure of N2 is maintained below 4 MPa.
その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84957851243&origin=inward
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Selective occupancy of methane by cage symmetry in TBAB ionic clathrate hydrate
Sanehiro Muromachi,Konstantin A. Udachin,Saman Alavi,Ryo Ohmura,John A. Ripmeester
Chemical Communications 52 ( 32 ) 5621 - 5624 2016年4月 [査読有り]
DOI Web of Science Scopus PubMed
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
© The Royal Society of Chemistry 2016. 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.
その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84964665868&origin=inward
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Preservation of CO<inf>2</inf> hydrate under different atmospheric conditions
Satoshi Takeya,Sanehiro Muromachi,Yoshitaka Yamamoto,Hiroki Umeda,Seiji Matsuo
Fluid Phase Equilibria 413 137 - 141 2016年4月 [査読有り]
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCIENCE BV 共著
© 2015 Elsevier B.V... A comprehensive understanding of the preservation of gas hydrates is important from a physicochemical point of view, and for practical applications such as gaseous CO2 storage and transport in the form of solid hydrate. We measured dissociation rates of CO2 hydrate under different gases, such as CO2, N2 and Xe, at 0.1 MPa and studied the effects of ambient gas pressure on CO2 hydrate-dissociation rate by powder X-ray diffraction method. The crystallographic structure of CO2 hydrate was refined to estimate the amount of CO2 gas in the hydrate. CO2 hydrates showed a self-preservation phenomenon, even in CO2 + N2 mixed gases such as flue gas, and it is estimated that the self-preserved CO2 hydrate holds more than 150 times the volume of hydrate crystal at 0.1 MPa and temperatures just below the melting point of ice. Small amounts of gas molecules, such as Xe, disturb the onset of CO2 hydrate self-preservation.
その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84957865151&origin=inward
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Takayuki Kobori,Sanehiro Muromachi,Tatsuro Yamasaki,Satoshi Takeya,Yoshitaka Yamamoto,Saman Alavi,R … 全著者表示
Takayuki Kobori,Sanehiro Muromachi,Tatsuro Yamasaki,Satoshi Takeya,Yoshitaka Yamamoto,Saman Alavi,Ryo Ohmura 閉じる
Crystal Growth and Design 15 ( 8 ) 3862 - 3867 2015年8月 [査読有り]
担当区分：責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：AMER CHEMICAL SOC 共著
© 2015 American Chemical Society. This paper reports phase equilibrium measurements and crystal structure analysis on the ionic clathrate hydrate formed from tetra-n-butylphosphonium hydroxide (TBPOH). Phase equilibrium temperatures were measured in the mole fraction range of TBPOH in aqueous solution from 0.0072 to 0.0416. The highest ionic clathrate hydrate-solution equilibrium temperature was determined to be 290.2 K at a TBPOH mole fraction of 0.0340, which corresponds to the congruent composition. Single-crystal X-ray diffraction measurements were performed on the crystal formed at 288.7 K, and the chemical composition of the TBPOH hydrate crystal was determined to be TBPOH·29.6H<inf>2</inf>O, which is consistent with the congruent composition obtained by the phase equilibrium measurement. The crystal structure of the TBPOH hydrate has a superstructure identical with Jeffrey's type I cubic structure, with an I43d space group with a lattice constant of 24.5191(13) Å. The TBPOH hydrate structure is compared with the same hydrate structure formed by the tetra-n-butylammonium fluoride. We provide a comprehensive overview of the dissociation temperature, the counteranion, and the hydrate structure regarding TBP and TBA salt hydrates. The dissociation temperatures decrease linearly with the increase in the partial molal volume of anions for TBA and TBP salt hydrates, changing the hydrate structures from the primitive cubic one that has the minimum hydration number.
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Phase equilibrium for clathrate hydrate formed in methane+water+urea system
Sanehiro Muromachi,Toru Abe,Tatsuo Maekawa,Yoshitaka Yamamoto
Fluid Phase Equilibria 398 1 - 4 2015年7月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCIENCE BV 共著
© 2015 Elsevier B.V. We performed phase equilibrium measurements in a methane. +. urea. +. water system for three phases (gas-hydrate-liquid) and four phases (gas-hydrate-liquid-solid urea). The data ranged from 262. K to 277. K for temperature, 2 to 4.5. MPa for pressure, and 0.05 to 0.50 for mass fraction (0.0159 to 0.231 for mole fraction) for aqueous urea composition. Urea, even in small dosages, shifted the methane hydrate formation conditions to lower temperature. The equilibrium state achieved a four-phase equilibrium, i.e., gas-hydrate-liquid-solid urea, when the aqueous feed composition was above a mass fraction of 0.40. The difference in equilibrium temperature between the urea. +. methane. +. water and methane. +. water systems expanded to approximately 10. K. The effect of urea on methane hydrate formation conditions was compared with that of alcoholic substances.
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Sanehiro Muromachi,Atsushi Shijima,Hiroyuki Miyamoto,Ryo Ohmura
Journal of Chemical Thermodynamics 85 94 - 100 2015年6月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD 共著
© 2015 Elsevier Ltd. All rights reserved. In this paper, we report the absolute measurements of CO2 solubility in aqueous tetra-n-butylammonium bromide (TBAB) solution. The measurement range was 0.2 MPa < P < 4 MPa, 286.15 K < T < 298.15 K, with 0 (pure water) < wTBAB < 0.4, where P, T, and wTBAB denote the pressure, temperature, and mass fraction of TBAB in the aqueous feed solutions, respectively. These thermodynamic conditions are outside the hydrate formation region. We evaluated salting-in and -out effects based on the experimental data, and confirmed that the CO2 salting-out effect of TBAB clearly appeared at T = 292 K with wTBAB < 0.32 and the salting-in effect may exist for P > 3 MPa and T > 292 K with wTBAB ≤ 0.4 mass fraction of TBAB.
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Characterization of the ionic clathrate hydrate of tetra- n -butylammonium acrylate
Sanehiro Muromachi,Masato Kida,Satoshi Takeya,Yoshitaka Yamamoto,Ryo Ohmura
Canadian Journal of Chemistry 93 ( 9 ) 954 - 959 2015年4月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS 共著
© 2015 Published by NRC Research Press. The ionic clathrate hydrate of tetra-n-butylammonium (TBA) acrylate was characterized using single-crystal X-ray diffraction, elemental analysis, and nuclear magnetic resonance (NMR) spectroscopy. The crystal structure of TBA acrylate was Jeffrey's type III and tetragonal P42/n, with a 33.076(7) × 33.076(7) × 12.170(2) Å3 unit cell. The volume of the unit cell was 13315(5) Å3, which is almost twice that of the ideal structure. The TBA cation was disordered and located in two types of fused cages. Although the acrylate anion was located in a pentagonal dodecahedral cage neighboring the TBA cation, there is a residual acrylate anion that could be around the other TBA cation in the unit cell. Solid-state 13C NMR spectra showed that the TBA cation was clearly disordered at 173 K, but not at 239 K. NMR peaks from the acrylate anion were not observed at either temperature. This is probably because of the strong restriction on the acrylate anion by hydrogen bonding with the lattice water. Some of the characteristics of the anion and cation of the ionic guest incorporated in the hydrate structure have yet to be defined. Further research is needed to clarify complexation of the ionic clathrate hydrate and the ionic guest, and the resulting structure.
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Takayuki Kobori,Sanehiro Muromachi,Ryo Ohmura
Journal of Chemical and Engineering Data 60 ( 2 ) 299 - 303 2015年2月 [査読有り]
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：AMER CHEMICAL SOC 共著
© 2014 American Chemical Society. This paper reports the vapor-liquid-hydrate three phase equilibrium conditions of ionic semiclathrate hydrates formed in the system of water + tetra-n-butylammonium bromide pressurized with carbon dioxide. The three phase equilibrium temperatures were measured in the ranges from 278.8 to 287.4 K of temperature and from 0.05 to 0.45 of mass fraction of tetra-n-butylammonium bromide (wTBAB). Measurements were performed at the system pressures of 0.3 MPa, 0.6 MPa, and 1 MPa. For the three system pressures, the equilibrium temperatures increased with the increase in wTBAB for wTBAB < 0.35 and decreased for wTBAB > 0.40. The highest equilibrium temperatures were obtained at wTBAB = 0.35 and 0.40. The equilibrium temperatures of the tetra-n-butylammonium bromide + carbon dioxide hydrates were higher than those of the simple tetra-n-butylammonium bromide hydrates formed under atmospheric pressure. The improvement of the thermodynamic stability of the tetra-n-butylammonium bromide + carbon dioxide hydrates is ascribed to the incorporation of carbon dioxide molecules into the hydrate cages. The data obtained in the present study may be utilized to specify the thermodynamic conditions to form the tetra-n-butylammonium bromide + carbon dioxide hydrates without forming the simple tetra-n-butylammonium hydrates.
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Sanehiro Muromachi,Toru Abe,Yoshitaka Yamamoto,Satoshi Takeya
Physical Chemistry Chemical Physics 16 ( 39 ) 21467 - 21472 2014年9月 [査読有り]
DOI Web of Science Scopus PubMed
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
Ionic clathrate hydrates are water-based materials that have unique properties, such as a wide range of melting temperatures and high gas capacities. In their structure, water molecules coordinate around ionic substances, which is regarded as the actual hydration structure and also linking of the hydrate clusters, giving insight into the dynamics of the water molecules and ions. This paper reports the synthesis and characterization of the ionic clathrate hydrate of tetra-n-butylammonium lactate (TBAL), the anion of which is a biological organic material. Phase equilibrium measurements and optical observations of the crystal morphology and crystal structure analysis were performed. The TBAL hydrate has a melting temperature of 284.8 K suitable for cool energy storage applications. The actual hydration patterns around a lactate anion are shown in the form of ionic clathrate hydrate structure. © the Partner Organisations 2014.
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Guest-induced symmetry lowering of an ionic clathrate material for carbon capture
S. Muromachi,K. A. Udachin,K. Shin,S. Alavi,I. L. Moudrakovski,R. Ohmura,J. A. Ripmeester
Chemical Communications 50 ( 78 ) 11476 - 11479 2014年9月 [査読有り]
DOI Web of Science Scopus PubMed
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
We report a new lattice structure of the ionic clathrate hydrate of tetra-n-butylammonium bromide induced by guest CO2 molecules, which is found to provide high CO2 storage capacity. The structure was characterized by a set of methods, including single crystal X-ray diffraction, NMR, and MD simulations. © Partner Organisations 2014.
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Increasing molecular O<inf>3</inf> storage capacity in a clathrate hydrate
Kazutoshi Shishido,Sanehiro Muromachi,Ryo Nakamura,Satoshi Takeya,Ryo Ohmura
New Journal of Chemistry 38 ( 7 ) 3160 - 3165 2014年7月 [査読有り]
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
This paper reports an experimental study to further increase the ozone storage capacity in a clathrate hydrate and to better understand the relationship between the gas phase O3 concentration and the O 3 storage capacity in the hydrate. We performed experiments with the O3 + O2 + CO2 feed gas with an increased O 3 fraction in the gas phase exceeding that covered by a preceding study. To accurately specify the thermodynamic conditions to form the hydrate, we first measured the three-phase (gas + liquid + hydrate) equilibrium conditions for the (O3 + O2 + CO2 + H 2O) and (O2 + CO2 + H2O) systems. The phase equilibrium data cover the temperature range from 272 to 277 K, corresponding to pressures from 1.6 to 3.1 MPa, for each of the two different (O3 + O2)-to-CO2 or O2-to-CO 2 molar ratios in the feed gas, which are approximately 4:6 and 5:5, respectively. The O3 fraction in the gas phase was ∼0.025. Based on the equilibrium data, we prepared crystal samples of the O3 + O2 + CO2 hydrates at a system pressure of 3.0 MPa and a temperature of 272 K. The highest O3 storage capacity in the hydrates was measured to be 2.15 mass% which is 2.36 times higher than the highest past record of 0.91 mass%. The results also show that the dominant factor to control the O3 storage capacity in the hydrates is the O3 mole fraction in the gas phase in contact with the hydrates. © the Partner Organisations 2014.
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Sanehiro Muromachi,Satoshi Takeya,Yoshitaka Yamamoto,Ryo Ohmura
CrystEngComm 16 ( 10 ) 2056 - 2060 2014年3月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ROYAL SOC CHEMISTRY 共著
We report the crystal structure analysis of the semiclathrate hydrate of tetra-n-butylphosphonium bromide (TBPB), which is a candidate material for refrigeration and gas-capture technologies. Refinement of the single crystal X-ray diffraction measurements revealed that the found structure of the TBPB hydrate has an orthorhombic structure, with the space group Pmma, and unit cell parameters a = 21.065(5), b = 12.657(3) and c = 11.992(3) Å. The chemical formula is TBPB·38H2O. The TBP ion is accommodated in a combined cage that consists of two tetrakaidecahedra and two pentakaidecahedra. The structure features three dodecahedral cages for each TBPB molecule that may accommodate small gas molecules (e.g., CH4, CO2 and N 2). The structure determined in this work is compared in detail with that of a similar hydrate, tetra-n-butylammonium bromide (TBAB) hydrate. In contrast to the TBAB hydrates, the most stable structure of the TBPB hydrate is not tetragonal but orthorhombic. Since C-P has a longer bond length than C-N, the TBP ion was packed tightly by the combined cage, having complex disorder. The relative comparison of the atom positions showed that the difference in the bond lengths of the two cations is counteracted by the displacement of water molecules in the TBPB hydrate lattice. © The Royal Society of Chemistry 2014.
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Thermodynamic modeling for clathrate hydrates of ozone
S. Muromachi,H. D. Nagashima,J. M. Herri,R. Ohmura
Journal of Chemical Thermodynamics 64 193 - 197 2013年 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 共著
We report a theoretical study to predict the phase-equilibrium properties of ozone-containing clathrate hydrates based on the statistical thermodynamics model developed by van der Waals and Platteeuw. The Patel-Teja-Valderrama equation of state is employed for an accurate estimation of the properties of gas phase ozone. We determined the three parameters of the Kihara intermolecular potential for ozone as a = 6.815 · 10-2 nm, σ = 2.9909 · 10-1 nm, and ε · kB-1 = 184.00 K. An infinite set of ε-σ parameters for ozone were determined, reproducing the experimental phase equilibrium pressure-temperature data of the (O3 + O2 + CO2) clathrate hydrate. A unique parameter pair was chosen based on the experimental ozone storage capacity data for the (O3 + O2 + CCl4) hydrate that we reported previously. The prediction with the developed model showed good agreement with the experimental phase equilibrium data within ±2% of the average deviation of the pressure. The Kihara parameters of ozone showed slightly better suitability for the structure-I hydrate than CO2, which was used as a help guest. Our model suggests the possibility of increasing the ozone storage capacity of clathrate hydrates (∼7% on a mass basis) from the previously reported experimental capacity (∼1%). © 2013 Elsevier Ltd. All rights reserved.
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Sanehiro Muromachi,Ryo Ohmura,Yasuhiko H. Mori
Journal of Chemical Thermodynamics 49 1 - 6 2012年6月 [査読有り]
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD 共著
The paper reports the three-phase (gas + aqueous liquid + hydrate) equilibrium pressure (p) versus temperature (T) data for a (O 3 + O 2 + CO 2 + H 2O) system and, for comparison, corresponding data for a (O 2 + CO 2 + H 2O) system for the first time. These data cover the temperature range from (272 to 279) K, corresponding to pressures up to 4 MPa, for each of the three different (O 3 + O 2)-to-CO 2 or O 2-to-CO 2 mole ratios in the gas phase, which are approximately 1:9, 2:8, and 3:7, respectively. The mole fraction of ozone in the gas phase of the (O 3 + O 2 + CO 2 + H 2O) system was from ∼0.004 to ∼0.02. The modified pressure-search method, developed in our previous study [S. Muromachi, T. Nakajima, R. Ohmura, Y.H. Mori, Fluid Phase Equilib. 305 (2011) 145-151] for p-T measurements in the presence of chemically unstable ozone, was applied, having been further modified for dealing with highly water-soluble CO 2, for the (O 3 + O 2 + CO 2 + H 2O) system, while the conventional temperature-search method was used for the (O 2 + CO 2 + H 2O) system. The measurement uncertainties (with 95% coverage) were ±0.11 K for T, ±6.0 kPa for p, and ±0.0015 for the mole fraction of each species in the gas phase. It was confirmed that, at a given CO 2 fraction in the gas phase, p for the (O 3 + O 2 + CO 2 + H 2O) system was consistently lower than that for the (O 2 + CO 2 + H 2O) system over the entire T range of the present measurements, indicating a preference of O 3 to O 2 in the uptake of guest-gas molecules into the cages of a structure I hydrate. © 2012 Elsevier Ltd. All rights reserved.
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Sanehiro Muromachi,Takahiro Nakajima,Ryo Ohmura,Yasuhiko H. Mori
Fluid Phase Equilibria 305 ( 2 ) 145 - 151 2011年6月 [査読有り]
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCIENCE BV 共著
This paper reports an attempt at acquiring phase-equilibrium pressure (p) versus temperature (T) data for ozone-containing clathrate hydrates formed from an ozone+oxygen gas mixture, a hydrophobic hydrate-forming liquid, and water in the liquid state. For dealing with ozone (O3), a chemically unstable material continuously decaying to oxygen (O2) in the gas phase, we devised a new method, i.e., a modified pressure-search method, to determine the equilibrium p-T conditions while maintaining the ozone concentration in the gas phase nearly constant by repeatedly replacing the contents of the gas phase with a freshly generated O3+O2 mixture. Using carbon tetrachloride (CCl4) as the hydrophobic hydrate-forming liquid, we obtained equilibrium p-T data in the range of 0.167MPa≤p≤0.361MPa and 275.6K≤T≤277.3K in the presence of a gas phase containing O3 at the molar concentration of 6.9±0.8%. We also obtained, for comparison, the corresponding p-T data, using pure O2 gas, instead of the O3+O2 mixture, and the conventional pressure-search method. The two data groups obtained from the O3-containing and O3-free systems, respectively, show simple, mutually consistent p-T relations each well fitted by the Clausius-Clapeyron equation assuming a constant enthalpy of hydrate dissociation. The paper also describes our additional attempt at obtaining equilibrium p-T data using 1,1-dichloro-1-fluoroethane (R141b) as a substitute for CCl4. Because of the partial decomposition of R141b due to the coexistence of O3 and water, however, we obtained only limited data which are tentative in nature. © 2011 Elsevier B.V.
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Clathrate hydrates for ozone preservation
Sanehiro Muromachi,Ryo Ohmura,Satoshi Takeya,Yasuhiko H. Mori
Journal of Physical Chemistry B 114 ( 35 ) 11430 - 11435 2010年9月 [査読有り]
DOI Web of Science Scopus PubMed
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：AMER CHEMICAL SOC 共著
We report the experimental evidence for the preservation of ozone (O 3) encaged in a clathrate hydrate. Although ozone is an unstable substance and is apt to decay to oxygen (O2), it may be preserved for a prolonged time if it is encaged in hydrate cavities in the form of isolated molecules. This possibility was assessed using a hydrate formed from an ozone + oxygen gas mixture coexisting with carbon tetrachloride or xenon. Each hydrate sample was stored in an air-filled container at atmospheric pressure and a constant temperature in the range between -20 and 2 °C and was continually subjected to iodometric measurements of its fractional ozone content. Such chronological measurements and structure analysis using powder X-ray diffraction have revealed that ozone can be preserved in a hydrate-lattice structure for more than 20 days at a concentration on the order of 0.1% (hydrate-mass basis). © 2010 American Chemical Society.
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S. Muromachi,H. Miyamoto,M. Uematsu
Journal of Chemical Thermodynamics 40 ( 11 ) 1594 - 1599 2008年11月 [査読有り]
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD 共著
The (p, ρ, T, x) properties for {xNH3 + (1 - x)H2O} with x = (0.1048, 0.2046, 0.3807, 0.5565, 0.7008, 0.8010, 0.9102, and 1.0000) in the compressed liquid phase were measured by means of a metal-bellows variable volumometer at temperatures of (450 and 500) K and pressures from (10 to 200) MPa. The volume fraction purities of the ammonia used in the measurements were 0.99999. The water employed was deionised, distilled, and degassed to 3.0 ≅ 10-4 Pa by freeze-thaw cycling with liquid nitrogen before use. In order to carry out these measurements at higher ranges of temperature (above T = 450 K) and pressure (up to p = 200 MPa), we have implemented several reconstructions to the apparatus, including the replacement of the sample cell containing the metal-bellows, and the development of a thermostatted air bath, in which the temperature of the air and sample cell can be raised up to 600 K. The expanded uncertainties (k = 2) in temperature, pressure, density, and composition measurements have been estimated to be less than 5 mK; 1.3 × 10-2%; 0.48%; and 8.2 × 10-4, respectively. Comparisons of the available equations of state (EoS) with the present measurements are reported. On the basis of the present results, moreover, the excess molar volume vmE of the mixtures was calculated and illustrated as a function of temperature and pressure. © 2008 Elsevier Ltd. All rights reserved.
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