Four-phase equilibrium relations including clathrate hydrate phase in a ternary system of xenon, benzene, and water

Thermodynamic stability boundaries of xenon (Xe) + benzene mixed hydrate system were measured in a temperature range of (274.1 to 284.4) K and pressure range up to 0.5 MPa. The four-phase equilibrium curve of structure-II hydrate (HsII), aqueous (Lw), C6H6-rich liquid (LHC), and gas (G) phases in the Xe+benzene mixed hydrate system intersects with the three-phase equilibrium curve (HsI+Lw+G) in the structure-I simple Xe hydrate system. The slope of HsII+Lw+LHC+G in the Xe +benzene mixed hydrate system changes around (283.00 ± 0.05) K and (0.420 ± 0.005) MPa. At temperatures above 283.00 K, the structure-II Xe+benzene mixed hydrate collapses and instead, the structure-I simple Xe hydrate is formed.Takeshi Sugahara. Four-phase equilibrium relations including clathrate hydrate phase in a ternary system of xenon, benzene, and water. Journal of Chemical & Engineering Data, 61 (12), 4057–4060, December 8, © 2016 American Chemical Society. https://doi.org/10.1021/acs.jced.6b0054

Dissociation and Nucleation of Tetra-n-butyl Ammonium Bromide Semi-Clathrate Hydrates at High Pressures

The equilibrium pressure-temperature relations of the tetra-n-butyl ammonium bromide (TBAB) semiclathrate hydrate were measured at pressures of up to 80 MPa by high-pressure differential scanning calorimetry. As a pressurizing medium, tetrafluoromethane (CF4), which cannot occupy any hydrate cages in the TBAB semiclathrate hydrate at the present experimental pressures, was used. The dissociation temperature of tetragonal TBAB semiclathrate hydrate (TBAB·26H2O) increases with the increase in pressure, whereas the dissociation enthalpy is (192 ± 3) J·g-1 and almost constant at pressures of up to 80 MPa. The temperature difference between formation and dissociation at the same pressure, that is, the maximum allowable degree of supercooling, is (17.7 ± 0.7) K and independent of the pressure.Takeshi Sugahara and Hironobu Machida. Dissociation and Nucleation of Tetra-n-butyl Ammonium Bromide Semi-Clathrate Hydrates at High Pressures. Journal of Chemical & Engineering Data, 62 (9), 2721–2725, September 14, © 2017 American Chemical Society. https://doi.org/10.1021/acs.jced.7b0011

Phase behavior of ethane hydrate system in the presence of ammonium bromide

The three-phase equilibrium curves of hydrate, aqueous, and gas phases in the ternary system of ethane (C2H6), ammonium bromide (NH4Br), and water were measured at pressures up to 3 MPa and temperatures of 278.45-283.76 K. The phase equilibrium curves exhibit two trends; the curve paralleled with that of simple C2H6 hydrate and the one steeper than that of simple C2H6 hydrate. The latter implies the incorporation of NH4Br into C2H6 hydrate while the former indicates the thermodynamic inhibition effect of NH4Br. To investigate the incorporation of NH4Br, Raman spectra of the N-stretching vibration of NH4+ were analyzed. Raman spectra imply the existence of the motionally restricted NH4+ in the formed hydrate. Both results from the phase behavior and Raman spectra imply the formation of C2H6 + NH4Br semi-clathrate hydrates

Thermodynamic stability of H2 + tetrahydrofuran mixed gas hydrate in nonstoichiometric aqueous solutions

Phase equilibria (pressure - temperature relations) of the H2 + tetrahydrofuran mixed gas hydrate system have been measured for various concentrations of tetrahydrofuran aqueous solutions. The three-phase equilibrium lines obtained in the present study are shifted to the low-temperature or high-pressure side from that of the stoichiometric THF solution. Each three-phase equilibrium line of H2 + tetrahydrofuran hydrate converges at the three-phase equilibrium line of the pure tetrahydrofuran hydrate. At the cross point on the lines, the tetrahydrofuran concentration of mother aqueous solution agrees with each other. The Raman spectra of H 2 and tetrahydrofuran for the H2 + tetrahydrofuran mixed gas hydrate do not change with the variation of tetrahydrofuran mole fraction from 0.010 to 0.130 in the aqueous solution. © 2007 American Chemical Society.Shunsuke Hashimoto, Takeshi Sugahara, Hiroshi Sato et al. Thermodynamic Stability of H2 + Tetrahydrofuran Mixed Gas Hydrate in Nonstoichiometric Aqueous Solutions. Journal of Chemical & Engineering Data, 52 (1), 517-520, March 1, © 2007 American Chemical Society. https://doi.org/10.1021/je060436

Phase equilibria for H2 + CO2 + H2O system containing gas hydrates

Isothermal phase equilibrium (pressure-composition in the gas phase) for the ternary system of H2 + CO2 + H2O has been investigated in the presence of gas hydrate phase. Three-phase equilibrium pressure increases with the H2 composition of gas phase. The Raman spectra suggest that H2 is not enclathrated in the hydrate-cages and behaves only like the diluent gas toward the formation of CO2 hydrate. This fact is also supported by the thermodynamic analysis using Soave-Redlich-Kwong equation of state. © 2005 Elsevier B.V. All rights reserved

Quasi-elastic neutron scattering studies on fast dynamics of water molecules in tetra-n-butylammonium bromide semiclathrate hydrate

The dynamics of the water molecules in tetra-n-butyl-d36-ammonium bromide semiclathrate hydrate were investigated by quasi-elastic neutron scattering (QENS). The QENS results clearly revealed afast reorientation motion of water molecules in the temperature range of 212–278 K. The mean jumpdistance of hydrogen atoms was within 1.5‒2.0 Å. The relaxation time of water reorientation wasestimated to be 100‒410 ps with activation energy of 10.2±5.8 kJ·mol-1. The activation energy wasin good agreement with the cleavage energy of hydrogen bonds. Such a short relaxation time ofwater reorientation is possibly due to strong interaction between a bromide anion and its surroundingwater molecules (similar to so-called negative hydration), which suggests a unique strategy fordesigning efficient, safe, and inexpensive proton conductors having the framework of semiclathratehydrates.Shimada Jin, Tani Atsushi, Yamada Takeshi, et al. "Quasi-elastic neutron scattering studies on fast dynamics of water molecules in tetra-n-butylammonium bromide semiclathrate hydrate", Applied Physics Letters 123, 50 (2023) https://doi.org/10.1063/5.0157560

Phase equilibrium relations of tetra-n-butylphosphonium propionate and butyrate semiclathrate hydrates

This paper reports phase equilibrium (temperature–composition) relations of semiclathrate hydrates formed from tetra-n-butylphosphonium propionate (TBP-Pro) and butyrate (TBP-But) + water systems. Their maximum solid–liquid phase equilibrium temperatures at atmospheric pressure were located at (288.75 ± 0.06) K and the mole fraction x1 = 0.035 ± 0.001 and (287.01 ± 0.06) K and x1 = 0.028 ± 0.001, respectively. They showed equilibrium temperatures higher than those of tetra-n-butylphosphonium formate, acetate, and lactate semiclathrate hydrates. The dissociation enthalpies of TBP-Pro and TBP-But semiclathrate hydrates were (190 ± 5) J·g−1 and (204 ± 5) J·g−1, respectively. The temperature difference between formation and dissociation, that is, the maximum allowable degree of supercooling, was (17.7 ± 1.5) K for TBP-Pro semiclathrate hydrate and (15.4 ± 1.4) K for TBP-But one

Phase equilibrium relations for tetra-n-butylphosphonium acetate semiclathrate hydrate systems in the presence of methane, carbon dioxide, nitrogen, or ethane

Thermodynamic stabilities of tetra-n-butylphosphonium acetate (TBP-Ace) semiclathrate hydrates in the presence of methane (CH 4 ), carbon dioxide (CO 2 ), nitrogen (N 2 ), or ethane (C 2 H 6 ) were measured in a pressure range up to approximately 5 MPa. The dissociation temperature of TBP-Ace + CH 4 , TBP-Ace + CO 2 , and TBP-Ace + N 2 semiclathrate hydrates increased drastically with an increase in pressure, which means that CH 4 , CO 2 , and N 2 molecules occupy the vacant cages of the TBP-Ace semiclathrate hydrate. On the other hand, the C 2 H 6 molecules hardly occupied the cages, resulting in small pressure dependence of the dissociation temperature. Raman spectra and powder X-ray diffraction patterns of TBP-Ace + CO 2 semiclathrate hydrate reveal that the phase transition occurs at 1.04 ± 0.04 MPa and 285.88 ± 0.05 K. One of the possible reasons why the phase transition occurs is that the carbonate and/or hydrogen carbonate anions derived from the CO 2 molecules are replaced with some of acetate anions in the TBP-Ace + CO 2 semiclathrate hydrate

Long-term survivor of relapsed MFH on the thigh treated with autologous formalin-fixed tumor vaccine (AFTV) combined with limb-sparing surgery and radiotherapy

Malignant fibrous histiocytoma (MFH) is an aggressive spindle cell cancer of soft-tissue sarcoma type in the elderly, mostly affecting the extremities. Lesions > 5 cm, positive margins, and local recurrence are significant poor prognostic indicators. The strongest predictor for distant metastasis was tumor size (> 5 cm), and for overall survival, presence of local recurrence. Limb-sparing extensive tumor resection is preferred to achieve negative surgical margins. However, in some circumstances, amputation is inevitable. Recent studies demonstrated that adjuvant radiotherapy for microscopically positive surgical margins significantly improved local control and disease-free survival rates. Therefore, effective therapeutic strategies against locally relapsed high grade MFH are required to prevent distant metastasis and to achieve long-term disease-free survival. Here, we report local relapse of high grade MFH treated by successive application of autologous formalin-fixed tumor vaccination (AFTV) with limb-sparing surgery and postoperative radiotherapy. The patient is alive and well, disease-free and with no functional impairment, more than five years after treatment