¹³C NMR spectra were obtained for pure CH₄, mixed CH₄+THF, and mixed CH₄+Neohexane hydrates in order to identify hydrate structure and cage occupancy of guest molecules. In contrast to the pure CH₄ hydrates, the NMR spectra of the mixed CH₄+THF hydrate verified that methane molecules could occupy only the small portion of 5¹² cages because the addition of THF, water-soluble guest component, to aqueous solution prevents the complete filling of methane molecules into small cages. Furthermore, from these NMR results one important conclusion can be made that methane molecules can’t be enclathrated at all in the large 5¹²6⁴ cages of structure II. In addition, gas uptake measurements were carried out to determine methane amount consumed during pure and mixed hydrate formation process. The moles of methane captured into pure CH₄ hydrate per mole of water were found to be similar to the full occupancy value, while the moles of methane captured into the mixed CH₄+THF hydrate per moles of water were much lower than the ideal value. The overall results drawn from this study can be usefully applied to storage and transportation of natural gas.

Hydrate ¹³C NMR Analysis Methane THF Neohexane

Adisasmito S, Frank RJ, Sloan ED, J. Chem. Eng. Data, 36, 68 (1991) 
Englezos P, Ind. Eng. Chem. Res., 31, 2232 (1992) 
Gudmundsson JS, Parlaktuna M, Khokhar AA, "Storing Natural Gas as Frozen Hydrate," SPE Production and Facilities, February, 69 (1994)
Gudmundsson JS, Mork M, Graff OF, "Hydrate Non-Pipeline Technology," Proceedings of the 4th International Conference on Gas Hydrates, Yokohama, 997 (2002)
Holder GD, Zeets SP, Pradhan N, Rev. Chem. Eng., 5, 1 (1988)
Kang SP, Seo YT, Lee H, Ryu BJ, J. Chem. Thermodyn., 31(6), 763 (1999) 
Khokhar AA, Gudmundsson JS, Sloan ED, Fluid Phase Equilib., 150-151, 383 (1998)
Lee JW, Chun MK, Lee KM, Kim YJ, Lee H, Korean J. Chem. Eng., 19(4), 673 (2002)
Lundgaard L, Mollerup JM, Fluid Phase Equilib., 70, 70 (1991)
Parrish WR, Prausnitz JM, AIChE J., 11, 26 (1972)
Reid RC, Prausnitz JM, Poling BE, "The Properties of Gases and Liquids," 4th edition, McGraw-Hill, New York (1987)
Ripmeester JA, Ratcliffe CI, J. Phys. Chem., 92, 337 (1988) 
Ripmeester JA, Ratcliffe CI, Energy Fuels, 12(2), 197 (1998) 
Seo Y, Lee H, Environ. Sci. Technol., 35, 3386 (2001) 
Seo YT, Kang SP, Lee H, Lee CS, Sung WM, Korean J. Chem. Eng., 17(6), 659 (2000)
Seo YT, Kang SP, Lee H, Fluid Phase Equilib., 189(1-2), 99 (2001) 
Seo YT, Lee H, J. Phys. Chem. B, 105(41), 10084 (2001) 
Sloan ED, "Clathrate Hydrates of Natural Gases 2nd Edition," Marcel Dekker, New York (1998)
Subramanian S, Sloan ED, Fluid Phase Equilib., 158-160, 813 (1999) 
Subramanian S, Kini RA, Dec SF, Sloan ED, Chem. Eng. Sci., 55(11), 1981 (2000) 
DeSwaanArons J, Diepen GA, Rec. Trav. Chim., 82, 249 (1963)
Udachin KA, Ripmeester JA, Nature, 397(6718), 420 (1999) 
vanderWaals JH, Platteeuw JC, Adv. Chem. Phys., 2, 1 (1959)
Zhong Y, Rogers RE, Chem. Eng. Sci., 55(19), 4175 (2000)