日本語 | ENGLISH

pdf-fileLeaflet of
Chemistry Dept.

Dept. of Chemistry
OKAYAMA UNIVERSITY
Okayama-shi, Kita-ku
Tsushimanaka 3-1-1
JAPAN 700-8530
FAX: 086-251-7853

Featured Research

Home » Featured Research » Revisions to standard theory provide clues to understanding phase behavior of clathrate hydrates

Revisions to standard theory provide clues to understanding phase behavior of clathrate hydrates

Posted on : August 22, 2018

A research by Prof. Hideki Tanaka, Assoc. Prof. Masakazu Matsumoto and Assist. Prof. Takuma Yagasaki developed the new theory that estimates the conditions where various gas hydrates can exist, and elucidated the phase diagram of gas hydrates for the first time. The research article was featured by AIP (American Institute of Physics).

Clathrate hydrate represented by methane hydrate is a solid solution in which gas molecules and water are crystallized together. Usually, for crystals consisting of two or more components, the component ratio is a simple integer ratio. On the other hand, hydrates are called non-stoichiometric compounds, and composition ratios vary depending on temperature, pressure and the surrounding environment. For this reason, it is difficult to specify the composition ratio accurately and evaluate its stability in both experiments and simulations.

In this research, we have described a method to accurately estimate the range of possible composition ratios at arbitrary temperature pressure, without simulation, based on statistical mechanics theory. In Mars, or satellites of the outer planets, water and gas are present, but both pressure and temperature are low. Under such circumstances, it became possible to know under what conditions hydrates will be formed.

Figure 1. Phase diagram of methane hydrate (red) and ethane hydrate (blue), which is elucidated for the first time by this research. The axes are water-gas composition (horizontal), pressure (depth), and temperature (height). Gas hydrates are stable only within the filled regions

Figure 2. Coexistence of a hydrate (left) and liquif water (right). Only water molecules and the hydrogen bonds are drawn.

Research Article

Tanaka, H., Yagasaki, T. & Matsumoto, M. On the phase behaviors of hydrocarbon and noble gas clathrate hydrates: Dissociation pressures, phase diagram, occupancies, and equilibrium with aqueous solution. J. Chem. Phys. 149, 074502 (2018).

DOI: 10.1063/1.5044568

AIP Featured Articles list

https://aip.scitation.org/topic/collections/featured?SeriesKey=jcp

Highlight article (AIP Press Release "Scilight")

"Revisions to standard theory provide clues to understanding phase behavior of clathrate hydrates" by Adam Liebendorfer

DOI: 10.1063/1.5051832

 

[BACK] Back to list

[TOP]Return to top