Low temperatures and/or high pressures can result in the self-assembly of water molecules into three-dimensional stable, solid structures of particular geometry that have cages/cavities that can enclathrate guest molecules of certain size (e.g., methane, hydrogen, carbon dioxide, nitrogen, etc.) which are known as clathrate hydrates. The characteristic properties of clathrate hydrates have been under consideration for a number of industrial applications. Of particular interest are the following two properties: (i) the incorporation of large amounts of gas molecules into the solid structure has resulted in considering hydrates as possible material for the storage/transportation of energy or environmental gases, and (ii) the selective incorporation of guest molecules into the solid structure has resulted in considering hydrates for gas-mixture separations.
For the proper design of such industrial applications, it is essential to know accurately a number of thermodynamic and transport properties (i.e., three-phase equilibrium conditions, gas storage capacities, kinetic rates of hydrate formation/dissociation, diffusion coefficients). Such properties can either be measured experimentally or calculated at different scales that include the molecular scale up to the continuum scale. We report an overview of our recent computational and experimental multi-scale studies of pure and mixed hydrates. At the molecular scale we have used: (i) molecular dynamics simulations in order to calculate the three-phase equilibrium conditions (using the phase coexistence methodology) of pure methane [1], pure carbon dioxide [2], and binary methane – carbon dioxide [3] hydrates, as well as the kinetics rates for methane hydrate formation, and the diffusion coefficients of hydrate-forming alkanes in water [4]. (ii) Monte Carlo simulations to calculate the storage capacities of methane [5] and hydrogen hydrates [6] and the gas-mixture separation efficiencies for various hydrate structures. The obtained results are compared against experimental measurements from a newly-designed experimental set-up [7], as well as continuum-scale calculations [8] using models that couple an Equation of State (i.e., PC-SAFT, Peng–Robinson) with the van der Waals–Platteeuw statistical theory.
REFERENCES
1. Michalis, V.K., Costandy, J., Tsimpanogiannis, I.N., Stubos, A.K., and I.G. Economou, J. Chem. Phys., 2015, 142, 044501.
2. Costandy, J., Michalis, V.K., Tsimpanogiannis, I.N., Stubos, A.K., and I.G. Economou, J. Chem. Phys., 2015, 143, 094506.
3. Michalis, V.K., Tsimpanogiannis, I.N., Stubos A.K., and I.G. Economou, Phys. Chem. Chem. Phys., 2016, 18, 23538–23548.
4. Michalis, V.K., Moultos, O.A., Tsimpanogiannis, I.N., and I.G. Economou, Fluid Phase Equilib., 2016, 407, 236–242.
5. Papadimitriou, N.I., Tsimpanogiannis, I.N., Economou, I.G., and A.K. Stubos, J. Chem. Eng. Data, 2016, 61, 2886–2996.
6. Papadimitriou, N.I., Tsimpanogiannis, I.N., Economou, I.G., and A.K. Stubos, Mol. Phys., 2016, 114, 2664–2671.
7. Kastanidis, P., Romanos, G.E., Michalis, V.K., Economou, I.G., Stubos, A.K., and I.N. Tsimpanogiannis, Fluid Phase Equilib., 2016, 424, 152–161.
8. El Meragawi, S., Diamantonis, N.I., Tsimpanogiannis, I.N., and I.G. Economou, Fluid Phase Equilib., 2016, 413, 209–219.
Advances in molecular simulation , Carbon capture and other industrial applications , Challenges and advances in fluid phase equilibria
