Section: 6 | Properties of Gas Clathrate Hydrates |
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One or more tables in this document differ to those in the book. This is due to space restrictions in the book.
Summary of table differences
The table 'TABLE 4a. Ternary CH4+C3H8+Water Hydrate Phase Equilibria' has one or more different columns to those in the book version.
The table 'TABLE 2b. Ethane Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 2c. Propane Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 2d. Carbon Dioxide Hydrate (Ref. 1)' has one or more different columns to those in the book version.
The table 'TABLE 2e. Nitrogen (N2) Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 2f. Xenon Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 2g. Hydrogen Sulfide Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 3. Ternary Methane+MCH (Methylcyclohexane)+Water Structure H Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 4b. Ternary CH4+CO2+Water Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 4c. Ternary CH4+H2S+Water Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 4d. Ternary CH4+C2H6+Water Hydrate' has one or more different columns to those in the book version.
The table 'TABLE 5a. Methane Hydrate Phase Equilibria in the Presence of Sodium Chloride' has one or more different columns to those in the book version.
The table 'TABLE 5b. Methane Hydrate Phase Equilibria in the Presence of Methanol (MeOH)' has one or more different columns to those in the book version.
The table 'TABLE 5c. Methane Hydrate Phase Equilibria in the Presence of 1,2-Ethanediol (MEG)' has one or more different columns to those in the book version.
How to Cite this Reference
The recommended form of citation is:
John R. Rumble, ed., CRC Handbook of Chemistry and Physics, 102nd Edition (Internet Version 2021), CRC Press/Taylor & Francis, Boca Raton, FL.
If a specific table is cited, use the format: "Physical Constants of Organic Compounds," in CRC Handbook of Chemistry and Physics, 102nd Edition (Internet Version 2021), John R. Rumble, ed., CRC Press/Taylor & Francis, Boca Raton, FL.

PROPERTIES OF GAS CLATHRATE HYDRATES

Carolyn A. Koh, M. Naveed Khan, and E. Dendy Sloan

Gas clathrate hydrates (also known as gas hydrates) are crystalline inclusion compounds composed of hydrogen-bonded water cavities (host) that encage small gas (guest) molecules in cavities. Generally, a maximum of one guest molecule occupies each water cavity. Typical guest molecules that form gas hydrates are methane, ethane, carbon dioxide, and propane (see gas hydrate phase equilibria data in Table 2). The three important structures of gas hydrates are: cubic structure I (sI) with two small and six large cavities (cages); cubic structure II (sII) with sixteen small and eight large cavities; and hexagonal structure (sH) with three small. two medium, and one large cavities in the unit cell. The structural and physical properties of each type are given in Tables 1a and 1b. Data have been taken from the references indicated.

TABLE 1a. Gas Hydrate Structural Properties (All values are from Ref. 1 unless noted otherwise)



StructuresI SmallsI LargesII SmallsII LargesH SmallsH MediumsH Large
Crystal systemCubicCubicCubicCubicHexagonalHexagonalHexagonal
Space groupPm3n (No. 223)bPm3n (No. 223)bFd3m (No. 227)bFd3m (No. 227)bP6/mmm (No. 191)bP6/mmm (No. 191)bP6/mmm (No. 191)b
Lattice descriptionPrimitivePrimitiveFace centeredFace centeredHexagonalHexagonalHexagonal
Lattice parametersaa = 12 Å
α = β = γ = 90o
a = 12 Å
α = β = γ = 90o
a = 17.3 Å
α = β = γ = 90o
a = 17.3 Å
α = β = γ = 90o
a = 12.2 Å, c = 10.1 Å
α = β = 90ο, γ = 120o
a = 12.2 Å, c = 10.1 Å
α = β = 90ο, γ = 120o
a = 12.2 Å, c = 10.1 Å
α = β = 90ο, γ = 120o
Ideal unit cell formula6(51262)·2(512).46H2O6(51262)·2(512).46H2O8(51264)·16(512)·136H2O8(51264)·16(512)·136H2O1(51268)·3(512)·2(435663)·34H2O1(51268)·3(512)·2(435663)·34H2O1(51268)·3(512)·2(435663)·34H2O
CavitySmallLargeSmallLargeSmallMediumLarge
Description512512625125126451243566351268
Number of cavities/unit cell26168321
Average cavity radius (Å)c3.954.333.914.733.94d4.04d5.79d
H2O molecules/cavitye20242028202036
  • a Lattice parameters are a function of temperature, pressure, and guest composition. Typical average values given.
  • b Space group reference numbers from the International Tables of Crystallography.
  • c The average cavity radius will vary with temperature, pressure, and guest composition.
  • d From the atomic coordinates measured using single crystal x-ray diffraction on 2,2-dimethylpentane·5(Xe,H2S)·34H2O at 173 K (Ref. 2). The Rietveld refinement package, GSAS was used to determine the atomic distances for each cage oxygen to the cage center.
  • e Number of oxygen atoms at the periphery of each cavity.


TABLE 1b. Physical Properties of sI, sII Hydrates Compared to Ice Ih (All values are from Refs. 1, 3, 4, and 5 unless noted otherwise)



PropertyIce IhsIsII
Dielectric constant at 273 K94~58~58
H2O reorientation time at 273 K (µs)21~10~10
H2O diffusion jump time (µs)2.7>200>200
Isothermal Young’s modulus at 268 K (109 Pa)9.58.4est8.2est
Poisson's ratio0.3301f0.31403f0.31119f
Bulk modulus (GPa)9.097f8.762f8.482f
Shear modulus (GPa)3.488f3.574f3.6663f
Compressional velocity, Vp (m/s)3870.1f3778f3821.8f
Shear velocity, Vs (m/s)1949f1963.62001.14g
Linear thermal expansion at 200 K (K–1)56 x 10–677 x 10–652 x 10–6
Thermal conductivity (W m–1 K–1) at 263 K2.18±0.01h0.51±0.01h0.50±0.01h
Adiabatic bulk compression at 273 K (GPa)1214est14est
Heat capacity (J kg–1 K–1)1700±200h20802130±40h
Refractive index (632.8 nm, –3 °C)1.3082 (Ref. 9)1.346 (Ref. 9)1.350 (Ref. 9)
Density (g/cm3)0.91j0.941.291k
  • f At 253–268 K, 22.4–32.8 MPa (ice, Ih), 258–288 K, 27.1–62.1 MPa (CH4, sI), 258–288 K, 30.5–91.6 MPa (CH4–C2H6, sII), Ref. 6.
  • g At 258–288 K, 26.6–62.1 MPa, Ref. 7.
  • h At 248–268 K (ice, Ih), 253–288 K (CH4, sI), 248–265.5 K (THF, sII), Ref. 8.
  • j Fractional occupancy (calculated from a theoretical model) in small (S) and large (L) cavities: sI = CH4: 0.87 (S) and CH4: 0.973 (L); sII = CH4: 0.672 (S), 0.057 (L); C2H6: 0.096 (L) only; C3H8: 0.84 (L) only.
  • k Calculated for 2,2-dimethylpentane.5(Xe,H2S).34H2O, Ref. 2; est = estimated.


References for Table 1

  1. Sloan, E .D. and Koh, C. A., Clathrate Hydrates of Natural Gases, Third Edition, CRC Press, 2008.
  2. Udachin, K. A., Ratcliffe, C. I., Enright, G. D., and Ripmeester, J. A., Supramol. Chem., 8, 173, 1997. [https://doi.org/10.1080/10610279708034933]
  3. Davidson, D. W., Natural Gas Hydrates (Cox, J. L., Ed.) Butterworths, Boston, 1, 1983.
  4. Davidson, D. W., Handa, Y. P., and Ripmeester, J. A., J. Phys. Chem., 90, 6549, 1986. [https://doi.org/10.1021/j100282a026]
  5. Ripmeester, J. A., Ratcliffe, C. I., Klug, D. D., and Tse, J. S., in Proc. First International Conference on Natural Gas Hydrates, (Sloan, E.D., Happel, J., and Hnatow, M.A., Eds.) Annals of the New York Academy of Sciences, 715, 161, 1994. [https://doi.org/10.1111/j.1749-6632.1994.tb38832.x]
  6. Helgerud, M. B., Circone, S., Stern, L., Kirby, S., and Lorenson, T. D., in Proc. Fourth International Conference on Gas Hydrates, p. 716, Yokohama, May 19–23, 2002.
  7. Helgerud, M .B., Waite, W. F., Kirby, S. H., and Nur, A., Can. J. Phys., 81, 47, 2003. [https://doi.org/10.1139/p03-016]
  8. Waite, W. F., Gilbert, L. Y., Winters, W. J., and Mason, D. H., in Proc. Fifth International Conference on Gas Hydrates, Trondheim, Norway, June 13–16, Paper 5042, 2005.
  9. Bylov, M. and Rasmussen, P., Chem. Eng. Sci., 52, 3295, 1997. [https://doi.org/10.1016/S0009-2509(97)00144-9]

Table 2: Phase Equilibria Data of Gas Clathrate Hydrates

This table gives measured phase equilibria data of pure sI and sII gas clathrate hydrates (see Table 1 for gas hydrate structure and physical property data). The temperature and pressure conditions at which gas hydrates are stable are listed here for typical guest molecules (Tables 2a–2g). For example, data for methane hydrate (Table 2a) show that at 277.1 K, methane hydrate will dissociate at pressures below 3.81 MPa. In addition to small hydrocarbons (methane, ethane, and propane) and carbon dioxide, the nitrogen (N2), xenon, and hydrogen sulfide hydrate systems have been measured extensively, and the hydrate phase equilibria data are available at temperatures and pressures as low as about 211.2 K and 6.5 kPa to as high as about 340.15 K and 1500 kPa.

TABLE 2a. Methane Hydrate (Ref. 1)



T/KP/MPa
Continued on next page...
Ice-Hydrate-Vapor (Ref. 2)
262.41.79
264.21.9
266.52.08
268.62.22
270.92.39
Liquid Water-Hydrate-Vapor (Ref. 2)
273.72.77
274.32.9
275.43.24
275.93.42
275.93.43
277.13.81
279.34.77
280.45.35
280.95.71
281.56.06
282.66.77
284.38.12
285.99.78
Liquid Water-Hydrate-Vapor (Ref. 3)
295.733.99


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