Kinetic and thermodynamic behaviour of CF4 clathrate hydrates

Abstract

This study presents experimental kinetic and thermodynamic data for CF4 clathrate hydrates. Experimental measurements were undertaken in a high pressure equilibrium cell with a 40cm3 inner volume. The measurements of experimental hydrate dissociation conditions were performed in the temperature range of (273.8 to 278.3)K and pressures ranging from (4.55 to 11.57)MPa. A thermodynamic model based on van der Waals and Platteeuw (vdW–P) solid solution theory was used for prediction and comparison of hydrate dissociation conditions and the Langmuir constant parameters for CF4 based on Parrish and Prausnitz equation are reported. For the kinetics, the effect of initial pressure and temperature on the induction time, CF4 hydrate formation rate, the apparent rate constant of reaction, storage capacity, and water to hydrate conversion during the hydrate formation were studied. Kinetic experiments were performed at initial temperatures of (275.3, 276.1 and 276.6)K and initial pressures of (7.08, 7.92, 9.11, 11.47 and 11.83)MPa. Results show that increasing the initial pressure at constant temperature decreases the induction time, while CF4 hydrate formation rate, the apparent rate constant of reaction, storage capacity, and water to hydrate conversion increase. The same trends are observed with a decrease in the initial temperature at constant pressure.