Hydrogen molecules are known to occupy the small cages of structure I (sI) and II (sII) hydrates with the aid of coguests, leading to the highly stable state of their crystalline framework. For the first time, we synthesized the double hydrogen hydrates incorporated with ethane and propane that play a special role as the hydrate promoters or stabilizers. The resulting hydrate structures cage occupancy was identified by the spectroscopic methods of the PXRD and solid-state NMR. In addition, direct GC analysis confirmed that the encaged hydrogen amounts are 0.127 for sI ethane and 0.370 for sII propane at 120 bar and 270 K. The proper hydrate thermodynamics particularly focusing on the cage occupancy estimated that 0.17 and 0.33 wt% of hydrogen are observed in small cages of sI and sII hydrates. The overall spectroscopic and physicochemical analysis strongly imply that the sII cages act as much more favorable sites than sI cages in storing hydrogen.

Clathrate Hydrate Hydrogen Ethane Propane NMR

Berry GD, Aceves SM, Energy Fuels, 12, 49 (1998)
Lee H, Lee JW, Kim DY, Park J, Seo YT, Zeng H, Moudrakovski IL, Ratcliffe CI, Ripmeester JA, Nature, 434, 743 (2005)
Mao WL, Mao H, Goncharov AF, Struzhkin VV, Guo Q, Hu J, Shu J, Hemley RJ, Somayazulu M, Zhao Y, Science, 297, 2247 (2002)
Kim DY, Lee H, J. Am. Chem. Soc., 127(28), 9996 (2005)
Service RF, Science, 285, 682 (1999)
Steele BCH, Nature, 400, 620 (1999)
Park SD, Vohs JM, Gorte RJ, Nature, 404(6775), 265 (2000)
Kirchner MT, Boese R, Billups WE, Norman LR, J. Am. Chem. Soc., 126(30), 9407 (2004)
Mak TCW, McMullan RK, J. Chem. Phys., 42, 2732 (1965)
Subramanian S, Kini RA, Dec SF, Sloan ED, Chem. Eng. Sci., 55(11), 1981 (2000)