Experimental study and thermodynamic modeling of clathrate hydrate stability conditions in carbon dioxide + cyclopentane + water system: Retrograde region

In this study, hydrate dissociation conditions for the carbon dioxide + cyclopentane + water system were measured. The pressure-search method at constant volume was employed to measure equilibrium conditions in the temperature range from 287.4–293.1 K and pressure range from 0.99–4.78 MPa. The results exhibit a retrograde behavior at pressures above 4 MPa for this system. Also, the experiments show that cyclopentane would significantly promote carbon dioxide hydrate stability conditions. In addition, based on the minimization of Gibbs free energy, a multiphase flash calculation was performed using the van der Waals and Platteeuw (vdW-P) solid solution theory along with the cubic plus association (CPA) equation of state to predict gas hydrate stability conditions. Modeling results are found in good agreement with the experimental data even in the retrograde region.