Ryo Ohmura

This paper describes an experimental study on the statistical nature of clathrate-hydrate nucleation in a quiescent hydrochlorofluorocarbon-in-water system in which a hydrate was once formed and then dissociated. The primary objective of the study is to investigate how hydrate nucleation in the system depends on its thermal history (i.e., the time evolution of system temperature), through which the preceding hydrate dissociation was carried out, and thereby better characterize the nature of the

This paper reports confirmation of structure II hydrate formation in a methane−2-propanol−water system, which was previously suggested by Østergaard et al. (Ind. Eng. Chem. Res. 2002, 41, 2064−2068) based on a comparison of the phase-equilibrium data with corresponding statistical-thermodynamics predictions. A hydrate crystal sample was prepared with a 16.4 mass % aqueous solution of 2-propanol pressurized with methane and then subjected to a powder X-ray diffraction analysis. The X-ray diffract

An attempt has been made to form continuously either a structure-I or a structure-H hydrate using methane as the common guest substance and methylcyclohexane as the second guest for the structure-H hydrate. The experimental technique we tested was to spray water into a high-pressure chamber charged with methane gas. In the experiments to form the structure-I hydrate, water droplets sprayed from a single nozzle at the top of the chamber coalesced into a water pool underlying the methane gas phase

This paper reports on a visual study of formation and growth of clathrate hydrate crystals in liquid water saturated (prior to hydrate formation) and in contact with methane gas under the pressure of 6−10 MPa at a temperature of 273.5 K. Irrespective of the pressure set in the experimental system, in most of the experimental runs we observed that a hydrate film first formed to intervene between methane gas and liquid water, and then hydrate crystals grew in liquid water from the hydrate film. Di

Abstract This paper reports on our interpretation of our visual observations of the variations in macroscopic morphology of hydrate crystals growing in liquid water saturated with a guest substance prior to the hydrate formation. The observations were made in a high-pressure cell charged with liquid water and gaseous CO2. They revealed distinct variations in the morphology of hydrate crystals depending on the system subcooling ΔT sub, the temperature deficiency inside the cell from the triple CO

An experimental study was performed to visually observe the driving force dependence of hydrate growth in a porous medium filled with either liquid water and dissolved CO2 or liquid water and gaseous CO2. The given system subcooling, ΔT sub, i.e. the deficiency of the system temperature from the triple CO2−hydrate−water equilibrium temperature under a given pressure, ranged from 1.7 K to 7.3 K. The fine dendrites initially formed at ΔT sub = 7.3 K changed quickly into particulate crystals. For Δ

This paper reports an experimental study on the formation of the two new semi-clathrate hydrates with tetrabutylphosphonium chloride (TBPC) and tetrabutylammonium acrylate (TBAAc). The hydrate formation was demonstrated by the measurements of temperature-composition phase diagrams and dissociation heat of the hydrates, visual observations of the hydrate crystals, and single-crystal X-ray diffraction analyses. The highest equilibrium temperature for the TBPC system was 10.3 °C at wTBPC = 0.36, wh

The pressure and temperature conditions for the four-phase equilibrium in systems that include structure-H hydrate, methane gas, liquid water, and either 3,3-dimethyl-2-butanone (pinacolone) or 3,3-dimethyl-2-butanol (pinacolyl alcohol) liquid have been measured over the temperature range T = 273 K to T = 281 K. At a given temperature, the equilibrium pressures of the systems with pinacolone and pinacolyl alcohol are lower by 1.8 MPa and 1.3 MPa, respectively, than those of the structure-I hydra