Thermodynamic modeling for clathrate hydrates of ozone

• We present a phase-equilibrium model for ozone-containing clathrate hydrates.
• We determine intermolecular potential parameters for O3.
• There is good agreement between the developed model and the experimental data.
• The results show the capability of O3 as a guest substance for clathrate hydrates.
• We perform parametric studies for O3 storage capacity with various thermodynamic conditions.

We report a theoretical study to predict the phase-equilibrium properties of ozone-containing clathrate hydrates based on the statistical thermodynamics model developed by van der Waals and Platteeuw. The Patel–Teja–Valderrama equation of state is employed for an accurate estimation of the properties of gas phase ozone. We determined the three parameters of the Kihara intermolecular potential for ozone as a = 6.815 · 10−2 nm, σ = 2.9909 · 10−1 nm, and ε · kB−1 = 184.00 K. An infinite set of ε–σ parameters for ozone were determined, reproducing the experimental phase equilibrium pressure–temperature data of the (O3 + O2 + CO2) clathrate hydrate. A unique parameter pair was chosen based on the experimental ozone storage capacity data for the (O3 + O2 + CCl4) hydrate that we reported previously. The prediction with the developed model showed good agreement with the experimental phase equilibrium data within ±2% of the average deviation of the pressure. The Kihara parameters of ozone showed slightly better suitability for the structure-I hydrate than CO2, which was used as a help guest. Our model suggests the possibility of increasing the ozone storage capacity of clathrate hydrates (∼7% on a mass basis) from the previously reported experimental capacity (∼1%).