title: Dissociation behavior of methane--ethane mixed gas hydrate coexisting structures I and II.
abstract: Dissociation behavior of methane-ethane mixed gas hydrate coexisting structures I and II at constant temperatures less than 223 K was studied with use of powder X-ray diffraction and solid-state (13)C NMR techniques. The diffraction patterns at temperatures less than 203 K showed both structures I and II simultaneously convert to Ih during the dissociation, but the diffraction pattern at temperatures greater than 208 K showed different dissociation behavior between structures I and II. Although the diffraction peaks from structure II decreased during measurement at constant temperatures greater than 208 K, those from structure I increased at the initial step of dissociation and then disappeared. This anomalous behavior of the methane-ethane mixed gas hydrate coexisting structures I and II was examined by using the (13)C NMR technique. The (13)C NMR spectra revealed that the anomalous behavior results from the formation of ethane-rich structure I. The structure I hydrate formation was associated with the dissociation rate of the initial methane-ethane mixed gas hydrate.
authors: Methane Hydrate Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 2-17-2-1 Tsukisamu-Higashi, Toyohiraku, Sapporo, Hokkaido 062-8517, Japan.
authors: Masato
authors: M
authors: Kida
authors: Yusuke
authors: Y
authors: Jin
authors: Nobuo
authors: N
authors: Takahashi
authors: Jiro
authors: J
authors: Nagao
authors: Hideo
authors: H
authors: Narita
mesh_terms: D004980:Ethane / Q000737:chemistry*; D005740:Gases / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000737:chemistry*; D015394:Molecular Structure; D033362:Powder Diffraction; D013696:Temperature
chemical_list: D005740:Gases; D004980:Ethane; D008697:Methane