A new set of gas-structure-dependent parameters to improve gas hydrate equilibrium calculations and structure descriptions by van der Waals-Platteeuw model

The traditional Kihara potential parameters employed in the van der Waals-Platteeuw (vdW-P) model were only related to the species of hydrate-forming gases. Although our previous study (Chemical Engineering Science 248, 117213) proposed a framework for optimizing the gas-dependent Kihara potential parameters in vdW-P model to improve the hydrate equilibrium calculations, the predictions for hydrate structures are barely satisfactory. Thus, this study provides a new set of Kihara potential parameters which are dependent on not only the gas species but also the hydrate structures. With the constraints on hydrate structure changes, a novel procedure for fitting the gas-structure-dependent parameters is developed. The calculation results show that the newly obtained parameters improve the performances of vdW-P model in predicting the hydrate equilibria for the pure-gas and gasmixture systems. Besides, the vdW-P model coupled with gas-structure-dependent parameters can provide reliable temperature-composition phase diagrams and properly identify the crystalline structures for various gas hydrates.