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Title: Inter-cage dynamics in structure I, II, and H fluoromethane hydrates as studied by NMR and molecular dynamics simulations

Prospective industrial applications of clathrate hydrates as materials for gas separation require further knowledge of cavity distortion, cavity selectivity, and defects induction by guest-host interactions. The results presented in this contribution show that under certain temperature conditions the guest combination of CH{sub 3}F and a large polar molecule induces defects on the clathrate hydrate framework that allow intercage guest dynamics. {sup 13}C NMR chemical shifts of a CH{sub 3}F/CH{sub 4}/TBME sH hydrate and a temperature analysis of the {sup 2}H NMR powder lineshapes of a CD{sub 3}F/THF sII and CD{sub 3}F/TBME sH hydrate, displayed evidence that the populations of CH{sub 4} and CH{sub 3}F in the D and D{sup ′} cages were in a state of rapid exchange. A hydrogen bonding analysis using molecular dynamics simulations on the TBME/CH{sub 3}F and TBME/CH{sub 4} sH hydrates showed that the presence of CH{sub 3}F enhances the hydrogen bonding probability of the TBME molecule with the water molecules of the cavity. Similar results were obtained for THF/CH{sub 3}F and THF/CH{sub 4} sII hydrates. The enhanced hydrogen bond formation leads to the formation of defects in the water hydrogen bonding lattice and this can enhance the migration of CH{sub 3}F molecules between adjacent smallmore » cages.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [4] ; ; ;  [1] ;  [1] ;  [5]
  1. Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, Ontario, K1A 0R6 (Canada)
  2. (Netherlands)
  3. Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, Separation Technology Group, Den Dolech 2, 5612 AZ Eindhoven (Netherlands)
  4. (United Arab Emirates)
  5. (Canada)
Publication Date:
OSTI Identifier:
22304270
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 21; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CARBON 13; CHEMICAL SHIFT; CLATHRATES; HYDRATES; HYDROGEN; INTERACTIONS; METHANE; METHYL FLUORIDE; MOLECULAR DYNAMICS METHOD; MOLECULES; NUCLEAR MAGNETIC RESONANCE; SIMULATION; WATER