The cost-effective gas storage/transportation technologies should be based on one type of material which can be available in large quantities, does not have any environmental hazard and health effects. From these points of view, the possibility of water form a three-dimensional host structure where the atoms or molecules (guests) accumulated in the empty voids under favorable thermodynamic conditions allow us to consider the water in the solid state as functional separation adsorbents or/and delivery systems. There are significant difficulties in the experimental investigation of the phase diagrams of multi-component clathrate hydrates that could result in a loss of important information related to the guest content in storage media [1]. The theoretical predictions of phase diagrams of clathrate hydrates could intensify the development of storage media based on hydrates significantly. Here, we have demonstrated the combined approach that allows us to construct the p-T phase diagrams of clathrate hydrates with complex gas compositions without resorting to any empirical parameter fittings. First, the parameters of weak interactions are evaluated using a time-dependent density-functional formalism and after that the thermodynamic properties of gas clathrate hydrates can be calculated [2, 3]. Moreover, the present method allow to modeling the structural transition depending on composition and type of the guests in agreement with experimental data [4]. Recently, the formation of CO2/CH4, CO2/N2 and CO2/N2/CH4 hydrates were studied. It was found that at high nitrogen concentration in CO2/N2 gas mixture, carbon dioxide can replace methane in the hydrate phase at temperatures and pressures of the permafrost regions or below the seafloor, since the phase stability of binary CO2/N2 hydrate is similar to pure CH4 hydrate [5]. We have also studied the phase diagram of He-H2O system in a wide range of p-T regions. The calculated results show that helium can form a hydrate with cubic structure II and transform to ice II-based helium hydrate at higher pressures.

Atomistic-level description of stability and composition of multicomponent clathrate hydrates

2019 Fall National Meeting

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