title: Highly selective encaging of carbon dioxide molecules in the mixed carbon dioxide and nitrogen hydrate at low temperatures.
abstract: The structural identification and guest compositions of the mixed CO(2) and N(2) hydrates at low temperature conditions were investigated by both theoretical predictions and experimental measurements. From the model calculations, at very low temperatures, the highly CO(2)-concentrated hydrates over 95 mol % CO(2) on the basis of water-free concentration could coexist with the gas mixtures of low CO(2) concentrations in equilibrium. X-ray diffraction measurements of the hydrates formed with the gas mixture of 3.16 mol % CO(2) and balanced N(2) indicate that the formed hydrates at all conditions considered in this study were identified as structure I, whereas the model predicts a structural transition to structure II around 220 K. However, it was also found that the formed hydrate samples contain a considerable amount of hexagonal ice resulting from incomplete conversion of ice to the hydrates. The compositional analysis suggests that a favorable encaging of CO(2) in the mixed hydrate can be obtained by the hydrate formation at low temperatures and relative amount of CO(2) molecules in the mixed hydrates increases with a decrease of temperature.
authors.affiliation: Department of Energy & Resource Engineering, Korea Maritime University, Busan 606-791, Korea. jhyoon@bada.hhu.ac.kr
authors.forename: Ji-Ho
authors.initials: JH
authors.lastname: Yoon
authors.forename: Taro
authors.initials: T
authors.lastname: Kawamura
authors.forename: Michica
authors.initials: M
authors.lastname: Ohtake
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takeya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Komai
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Emi
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kohara
authors.forename: Susumu
authors.initials: S
authors.lastname: Tanaka
authors.forename: Osamu
authors.initials: O
authors.lastname: Takano
authors.forename: Kazuo
authors.initials: K
authors.lastname: Uchida