GAS HYDRATE PHASE EQUILIBRIUM PREDICTIONS FOR CYCLOPENTANE CONTAINING GAS MIXTURES WITH OPTIMIZED KIHARA PARAMETERS

摘要

Clathrate hydrates (also known as gas hydrates) are non- stoichiometric inclusion compounds comprised of appropriately sized gas (guest) molecules which are trapped inside hydrogen-bonded water cages typically at elevated pressures (e.g. 2-10 MPa) and seafloor temperatures (e.g. 4 °C). The three common gas hydrate structures are sI, sII and sH, which have different sized cavities and crystallographic structures (Figure 1). Structure I (sI) is a primitive cubic structure with two pentagonal dodecahedral (small, 5~(12)) cages, where 5 represents the number of sides per face and 12 is the number of faces per cage, and six tetrakaidecahedral (large, 5~(12)6~2) cages per unit cell. Structure II (sII) is a diamond cubic structure with sixteen 512 (small) cages and eight hexakaidecahedral (large, 5~(12)6~4) cages per unit cell. Structure H comprises three 5~(12) small cages, two irregular dodecahedral (mid-sized, 4~3 5~6 6~3 ) cages, and one icosahedral (large, 5~(12)6~8) cage per unit cell.