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

Effect of Impeller Agitation on Preparation of Tetra- n

The slurries-containing tetra-n-butyl ammonium bromide (TBAB) solution and its semiclathrate hydrate have attracted a lot of interest as latent heat transport media. These hydrate slurries contain some microparticles of crystal, and the size and shape of these hydrate particles could affect the mobility of slurries. Hence, it is essential to investigate the efficient hydrate-slurry preparation methods and the effect of hydrate particles on the fluid property of slurries for the application to latent heat transport media. In the present study, the effect of agitation on particle size distribution and aggregation of particles was studied to prepare easily flowing TBAB hydrate slurries that were suitable for fluid transport. First of all, the effects of impeller rotational speed and impeller type on the particle size and frequency of aggregation were investigated. The results suggested that the particle size distribution and the frequency of particle aggregation are strongly affected by the intensity of shear rate and its uniformity, which was controllable with impeller type and its rotation speed

High-pressure phase equilibria of tertiary-butylamine hydrates with and without hydrogen

Thermodynamic stability boundaries of the simple tertiary-butylamine (t-BA) hydrate and t-BA+hydrogen (H2) mixed hydrate were investigated at a pressure up to approximately 100 MPa. All experimental results from the phase equilibrium measurement, in situ Raman spectroscopy, and powder X-ray diffraction analysis arrive at the single conclusion that the t-BA hydrates, under pressurization with H2, are transformed from the structure VI simple t-BA hydrate into the structure II t-BA+H2 mixed hydrate. The phase transition point on the hydrate stability boundary in the mother aqueous solutions with the t-BA mole fractions (xt-BA) of 0.056 and 0.093 is located at (2.35 MPa, 267.39 K) and (25.3 MPa, 274.19 K), respectively. On the other hand, in the case of the pressurization by decreasing the sample volume instead of supplying H2, the simple t-BA hydrate retains the structure VI at pressures up to 112 MPa on the thermodynamic stability boundary.Tomohiro Tanabe, Takeshi Sugahara, Kazuma Kitamura et al. High-Pressure Phase Equilibria of Tertiary-Butylamine Hydrates with and without Hydrogen, Journal of Chemical & Engineering Data, 60 (2), 222–227, February 12, © 2015 American Chemical Society. https://doi.org/10.1021/je500301

Thermodynamic Properties of Hydrogen + Tetra-n-Butyl Ammonium Bromide Semi-Clathrate Hydrate

Thermodynamic stability and hydrogen occupancy on the hydrogen + tetra-n-butyl ammonium bromide semi-clathrate hydrate were investigated by means of Raman spectroscopic and phase equilibrium measurements under the three-phase equilibrium condition. The structure of mixed gas hydrates changes from tetragonal to another structure around 95 MPa and 292 K depending on surrounding hydrogen fugacity. The occupied amount of hydrogen in the semi-clathrate hydrate increases significantly associated with the structural transition. Tetra-n-butyl ammonium bromide semi-clathrate hydrates can absorb hydrogen molecules by a pressure-swing without destroying the hydrogen bonds of hydrate cages at 15 MPa or over

Intermolecular Hydrogen Transfer in Isobutane Hydrate

Electron spin resonance (ESR) spectra of butyl radicals induced with γ-ray irradiation in the simple isobutane (2-methylpropane) hydrate (prepared with deuterated water) were investigated. Isothermal annealing results of the γ-ray-irradiated isobutane hydrate reveal that the isobutyl radical in a large cage withdraws a hydrogen atom from the isobutane molecule through shared hexagonal-faces of adjacent large cages. During this “hydrogen picking” process, the isobutyl radical is apparently transformed into a <em>tert</em>-butyl radical, while the sum of isobutyl and <em>tert</em>-butyl radicals remains constant. The apparent transformation from isobutyl to <em>tert</em>-butyl radicals is an irreversible first-order reaction and the activation energy was estimated to be 35 ± 3 kJ/mol, which was in agreement with the activation energy (39 ± 5 kJ/mol) of hydrogen picking in the γ-ray-irradiated propane hydrate with deuterated water