Compositions, enthalpies of dissociation, and heat capacities in the range 85 to 270 K for clathrate hydrates of methane, ethane, and propane, and enthalpy of dissociation of isobutane hydrate, as determined by a heat-flow calorimeter

Abstract Compositions, enthalpies of dissociation, and heat capacities in the range 85 to 270 K were determined for the first time for clathrate hydrates of methane, ethane, and propane using a Tian-Calvet heat-flow calorimeter. The enthalpy of dissociation was also measured for isobutane hydrate. The enthalpy of dissociation for the process (hydrate = ice + gas) at 273.15 K and 101.325 kPa is (18.13±0.27) kJ·mol −1 for CH 4 ·6.00H 2 O, (25.70±0.37) kJ·mol −1 for C 2 H 6 ·7.67H 2 O, and (27.00±0.33) kJ·mol −1 for C 3 H 8 ·17.0H 2 O. The enthalpy of dissociation of isobutane hydrate at 245 K is (31.07±0.20) kJ·mol −1 . Molar heat-capacity contributions from the guests to their hydrates were found to be comparable with the ideal-gas heat capacity for methane and somewhat higher for ethane and propane.

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