Formation of CO₂ Hydrate in Pure and Sea Waters

Abstract

The formation of CO₂ hydrates in both pure and sea waters along the three-phase coexistence of CO₂, H₂O, and hydrate is measured by use of a convenient temperature-cycle method proposed in the present study. Four kinds of three-phase coexisting curves are investigated in the temperature range from 270 to 283 K and pressures up to 9 MPa. By applying the Langmuir adsorption model based on statistical thermodynamics, the three-phase coexisting pressures obtained are correlated satisfactorily. The enthalpy changes of hydration in both systems are calculated from the Clapeyron equation of the three-phase coexisting curve. The apparent rate constant of hydration is estimated under the assumption of pseudo-first order reaction with respect to CO₂ concentration.