Gas Hydrate Single-Crystal Structure Analyses

• Published in: Journal of the American Chemical Society Vol. 126; no. 30; pp. 9407 - 9412
• Main Authors: Kirchner, Michael T, Boese, Roland, Billups, W. Edward, Norman, Lewis R
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 04.08.2004
• Subjects: Aliphatic, non-condensed and condensed benzenic, and alicyclic compounds; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Organic compounds; Physics; Single-crystal and powder diffraction; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; X-ray diffraction and scattering; Geometrical structure; Molecular packing; Electronic structure; Molecular structure; Electron density map; Hydrocarbons; Cocrystallization; Gas hydrates; XRD; Experimental study; Crystal structure
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja049247c

The first single-crystal diffraction studies on methane, propane, methane/propane, and adamantane gas hydrates SI, SII, and SH have been performed. To circumvent the problem of very slow crystal growth, a novel technique of in situ cocrystallization of gases and liquids resulting in oligocrystalline material in a capillary has been developed. With special data treatment, termed oligo diffractometry, structural data of the gas hydrates of methane, acetylene, propane, a propane/ethanol/methane-mixture and an adamantane/methane-mixture were obtained. Cell parameters are in accord with reported values. Host network and guest are subject to extensive disorder, reducing the reliability of structural information. It was found that most cages are fully occupied by a guest molecule with the exception of the dodecahedral cage in the acetylene hydrate which is only filled to 60%. For adamantane in the icosahedral cage a disordered model is proposed.