Clathrate Hydrates. Группа авторов

hydrate from single‐crystal X‐ray diffraction. 1999 Dyadin et al. reported that H₂ forms a clathrate hydrate at high pressure. 1999 Moudrakovski et al. reported the first magnetic resonance imaging (MRI) of hydrate formation on ice particles. 2000 Huang, Walker, and Ripmeester showed that antifreeze proteins (AFPs) inhibit hydrate formation and, in some cases, eliminate the freezing memory effect for hydrate reformation. 2000–2001 Loveday et al., Hirai et al., Chou et al., and Manakov et al. prepared and characterized high‐pressure phases of water, including a high‐pressure HS‐III clathrate phase. 2001 Moudrakovski et al. used hyperpolarized ¹²⁹Xe NMR to observe the nucleation, growth, and decomposition of Xe hydrate in real time. 2001 Udachin et al. determined a new structural type for dimethyl ether clathrate hydrate. 2001 Moudrakovski et al. observed a metastable CS‐II Xe hydrate phase. 2001 Loveday et al. discovered a high‐pressure structure of CH₄ hydrate using diamond anvil diffraction methods. 2002 Ballard and Sloan developed CSMGem software for hydrate equilibrium prediction. 2002 Mao et al. synthesized the CS‐II hydrogen hydrate under high‐pressure and low‐temperature conditions to observe high H₂:H₂O storage ratios. 2002 Servio and Englezos accurately measure the temperature dependence of the solubility of CH₄ and CO₂ gases in the aqueous phase in equilibrium with the corresponding clathrate hydrate phases. 2004 The mechanism of self‐preservation of methane hydrate was studied with scanning electron microscope (SEM) imaging by Stern and coworkers. Falenty and Kuhs used SEM to study self‐preservation of CO₂ hydrate in 2009. 2005 Lee et al. developed a method for tuning the H₂ content of the mixed CS‐II hydrate with THF. 2005 Clarke and Bishnoi developed a focused beam reflectance method for in situ, time‐dependent hydrate particle size analysis under conditions of hydrate nucleation and growth. 2007–2016 Bačić and coworkers performed quantum mechanical calculations to determine discrete translation‐rotational states of H₂ and CH₄ in different CS‐I and CS‐II cages with single and multiple occupancies. 2007 Celli, Ulivi, and coworkers initiated IINS studies on H₂/D₂/HD dynamics in CS‐I and CS‐II clathrate hydrates 2007 Linga, Kumar, and Englezos provided the thermodynamic and kinetic basis for CO₂ capture from post‐combustion flue gas and pre‐combustion fuel gas. 2009 Detailed characterization of hydrogen bonding of hydrates was determined using molecular dynamics simulations by two groups: Buch et al. and at the NRC. 2009 Simulation work initiated by Jordan and coworkers determined the stepwise (layer by layer) decomposition mechanism for methane hydrate. 2010 Walsh et al. carried out millisecond molecular dynamics simulations of CH₄ hydrate nucleation and growth. 2010 Following an early proposal by McTurk and Waller, Mori, and coworkers formed ozone hydrate in an apparatus incorporating in situ ozone generation. 2012–2014 Shin et al. characterized clathrate hydrates incorporating NH₃ and CH₃OH synthesized using vapor deposition. 2013 Udachin et al. performed single‐crystal X‐ray diffraction and molecular dynamics simulations on halogen hydrates which indicated the possibility of halogen bonding between these guests and water molecules of the cages. 2014 Falenty, Hanssen, and Kuhs prepared a metastable ice phase (Ice XVI) with the structure of the empty CS‐II lattice. 2015 NMR spectroscopy gave direct evidence of cage‐to‐cage transfer of hydrate guests CO₂ in THF‐CO₂ CS‐II hydrate and for CH₄ and CH₃F in double hydrates of THF and tert‐butylmethylether. 2015 Molecular dynamics simulations performed at the NRC and University of British Columbia showed the formation of nanobubbles of methane upon decomposition of methane hydrate.

1.3 Clathrate Hydrate Research at the NRC Canada

      For about 50 years, gas hydrate research was a supported project at the NRC in Ottawa. It had its start in the early 1960s when Don Davidson, working in the Colloid Section of the Division of Applied Chemistry (Figure 1.1), took the initiative to follow up on a fundamental question that arose during his investigation of the dielectric properties of liquids: in the dielectric properties of liquids, is it possible to separate the contributions from molecular reorientation and diffusion? This led to the first studies on clathrate hydrates where molecules are trapped in pseudo‐spherical molecule‐sized cages so that one may well expect that contributions from diffusion should be reduced or eliminated.

Clathrate hydrate science was at a stage of development where two hydrate structures were known, confirming their clathrate nature. Statistical thermodynamics had provided a model of clathrate hydrates based on weak guest–host interactions; however, many of the features of the model remained untested.

      Early work on guest dynamics in clathrates at the University of British Columbia (by Charles McDowell) convinced Don, Figure 1.2a, that NMR spectroscopy would be another useful technique for the study of guest motion, as it provided the means to study the effect of polar versus non‐polar guests. It was an opportune time to initiate an NMR capability, as a 12″ NMR electromagnet became available from William G. Schneider's lab. Dr. Schneider, FRS (Figure 1.2b), was an internationally known pioneer in NMR spectroscopy who had taken on the Directorship of the Division of Pure Chemistry in 1963 and the Presidency of NRC in 1967.

      Figure 1.1 National Research Council of Canada Building M‐12 on the NRC Montreal Road campus in Ottawa, home of the Colloid Chemistry (later Colloid and Clathrate Chemistry) group until 1990. Source: Reproduced with permission from the National Research Council.