Thermodynamic Stability Conditions of Clathrate Hydrates in Methane/Carbon Dioxide + Tetrahydrofuran + Cyclopentane + Water Systems: Experimental Measurement and Modeling

Abstract

In this communication, experimental hydrate dissociation data for methane + tetrahydrofuran (THF) (0.03 and 0.0555 mole fractions in aqueous solution) + cyclopentane (CP) + water systems are reported in the temperature range from 294.8 to 301.3 K and pressure range from 1.91 to 4.95 MPa, which are measured using an isochoric pressure-search method. Other experimental data were collected from the literature. Then a thermodynamic model for four-phase equilibria, hydrate (H)–aqueous liquid (Lw)–organic liquid (La)–vapor/gas (V), systems composed of water, methane (CH4), carbon dioxide (CO2), and/or CP was developed. The thermodynamic model is based on the solid solution theory of van der Waals–Platteeuw (vdW-P) for the hydrate phase and Peng–Robinson equation of state (P-R EOS) for vapor/gas phase. For calculating the activity coefficient of water and THF in the aqueous phase, the universal quasichemical (UNIQUAC) functional-group activity coefficient (UNIFAC) model is also used. The Langmuir constants of TH...