Thermodynamic modeling of pressure-temperature phase diagrams of binary clathrate hydrates of methane, carbon dioxide or nitrogen plus tetrahydrofuran, 1,4-dioxane or acetone

In this communication, we report a thermodynamic model for predicting pressure-temperature phase diagrams of binary clathrate hydrates of methane, carbon dioxide or nitrogen + tetrahydrofuran (THF), 1.4-dioxane or acetone for various concentrations of the latter water-soluble chemicals in aqueous solution. The model is based on equality of water fugacity in the aqueous and hydrate phases. The solid solution theory of van der Waals-Platteeuw is used for calculating the fugacity of water in the hydrate phase. The UNIFAC group contribution model is used to calculate the water and THF, 1,4-dioxane or acetone fugacities in the aqueous phase. The Peng-Robinson equation of state is employed to calculate the gas phase fugacity. It is assumed that the gas phase is pure. The results of this model are compared with some selected experimental data from the literature. Acceptable agreement between the model predictions and experimental data demonstrates its reliability. (C) 2012 Published by Elsevier B.V.