Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

The cyclopentane hydrate, formed by combination of cyclopentane (CP) and water, is frequently used as a model system for clathrate hydrate compounds as it can form at atmospheric pressure and at temperatures below about 280 K. However, due to the immiscibility of CP and water, the dissociation enthalpy is challenging to obtain experimentally because total conversion of water to hydrate is difficult to achieve in quiescent conditions. Only two dissociation enthalpy values are available in literature, and a difference of 25 kJ.mol-1 between them clearly indicates a discrepancy. In this study, a stirring calorimetric cell was used with a Tian-Calvet heat-flow calorimeter, to measure phase change properties. The technical system made it possible to form pure CP-hydrate with complete conversion of water to hydrate. The dissociation temperature and dissociation enthalpy of the CP-hydrate (with max 5 wt% of residual liquid CP) were measured at 280.2 +- 0.5 K and 115,400 +- 7600 J.mol-1 of CP (377 +- 27 J.g-1 of water; 307 +- 21 J.g-1 of hydrate), respectively. This high enthalpy value opens new ways for using CP-hydrates in cold storage and refrigeration applications.