Thermodynamic modeling and measurement of CO2 clathrate equilibrium conditions with a hydrophobic surface – An application in dry water hydrate

[Display omitted] •CO2 hydrate formation condition was investigated in dry water with 5 and 10 wt% of SiO2.•A new mechanism is proposed for hydrate equilibrium in the vicinity of a hydrophobic surface.•A new thermodynamic framework was proposed based on the entropic effects of hydrophobic surfaces.•The Bridging-Cluster model was used for the hydrophobic attraction effect.•A single parameter has correlated equilibrium hydrate formation conditions for CO2 dry water hydrates. Dry water is a powdery liquid composed of tiny water droplets surrounded by super-hydrophobic nanosilica. We used a high-pressure cell to determine the equilibrium temperature and pressure of CO2 hydrate in the presence of dry water. The Bridging-Cluster model for the hydrophobic attraction force was used to evaluate the hydrophobic force effect on the excess properties of water in the liquid phase. We modified Ballard and Sloan's framework for the CO2 clathrate hydrates in the hydrate phase by introducing the Bridging-Cluster model. The distance of hydrate cells from the hydrophobic surface (δ) was calculated by optimizing the measured hydrate formation conditions. An absolute average relative deviation for pressure was 1.99% and 1.22% for silica 5 and 10 wt% dry water systems, respectively. The present model explains the promotion effect of the dry water hydrate system and the calculated equilibrium formation conditions with high accuracy.