Khalik M. Sabil and Cor J. Peters. DelftChemTech (PCMT), Delft University of Technology, Faculty of Applied Sciences, Julianalaan 136, Delft, 2628 BL, Netherlands
With growing interest in gas hydrate technology as a possible method for carbon dioxide separation and sequestration, there have been necessities for more experimental data of carbon dioxide hydrate-containing systems. In the present work, the three- and four-phase hydrate equilibria of the ternary system of carbon dioxide (CO2) + tetrahydrofuran (THF) + water are measured by using a Cailletet equipment. The experimental temperature ranged from 275 to 295K and pressure up 1 to 7.5 MPa has been applied. Measurements show that the addition of tetrahydrofuran cause the hydrate equilibrium pressure to be drastically lowered by 60-80% at a specified temperature and equivalently the hydrate equilibrium temperature to be raised with about 6-8K at a specified pressure depending on the concentration of tetrahydrofuran in water. Moreover, depending on the overall composition of the systems, a liquid-liquid phase split is observed creating a four-phase equilibrium in the system and it is bounded by the bubble (Lw-Lv-V → Lw-Lv) and dew (Lw-Lv-V → Lw + V) points lines of the ternary system. At higher overall concentration of carbon dioxide, experimental measurements show that a pseudo-retrograde phenomenon exists at pressure between 2.5 to 5 MPa at a temperature of 291K.