The role of clathrate hydrates for solving the ecological and energetical problems. V.R.Belosludov (IRSAMC, 18 septembre 2017)

Nikolaev Institute of Inorganic Chemistry
Russian Academy of Sciences Siberian Division, Novosibirsk, Russia

PLACE : seminar’s room - Bat. IIIr1-B4 - third floor
DATE : 18 september, 14 H.
SUMMARY : In these last decades, a renewed interest in clathrate hydrates grew up for various reasons. From the applied point of view, methane hydrates can represent a possible source of energy in the future, since these clathrates are accumulated in the permafrost regions and in sediments on the deep ocean floor. Hydrogen clathrates represent promising systems as hydrogen storage materials, and carbon dioxide clathrates could be a possible method to sequestrate greenhouse gases. Wide use of hydrogen as the next generation clean energy carrier is connected with the solution of the major technical problems of storage and transportation of hydrogen. Search is intensively carried out for an efficient material and method for storing hydrogen. Among representative potential hydrogen storage materials, hydrogen clathrate hydrate and hydrogen filled-ices Ih and Ic are considered recently. Storage of hydrogen as hydrogen hydrate is a promising alternative technology to liquefied hydrogen at cryogenic temperatures or compressed hydrogen at high pressures One of possible means to diminish anthropogenic emissions of carbon dioxide with simultaneous controlled recovery of methane from gas hydrate deposits in permafrost regions and at continental shelf can be replacement of methane by carbon dioxide in gas hydrates. The possibility of such replacement was demonstrated previously in experimental studies. Recent experimental works have shown also high rate of the replacement process and its completeness when instead of pure carbon dioxide its mixture with nitrogen is used. The combination of both methods enables one to calculate thermodynamic properties of clathrate hydrates without resorting to any empirical parameter fittings. In order to evaluate the parameters of weak interactions, a time-dependent density-functional formalism and local density (TDLDA) technique entirely in real space have been implemented for the calculations of frequency-dependent polarizabilities and van der Waals dispersion coefficients for atoms within the all-electron mixed-basis approach (TOMBO code) developed at the Institute for Materials Research, Tohoku University. In this report, a method based on the solid solution theory of clathrate hydrate has been presented to investigated the effects of influence of nitrogen the equilibrium pressure as well as the hydrate composition of clathrate hydrates established from methane +carbon dioxide and nitrogen +carbon dioxide binary gas and methane +carbon dioxide+ nitrogen ternary gas mixtures. In all considered systems with and without 2N, at high and medium content of 2CO in the gas phase we have found that 2CO is more favorable to occupy clathrate hydrate cavities than 4CH or 2N. Addition of 2N to the gas phase increases ratio concentration 2CO in compressing with concentration 4CH in clathrate hydrates and makes gas replacement more effective. The phase P-T diagram of hydrogen hydrates at pressure (0–800 MPa) and temperature (200–290 K) range has been calculated. The obtained results are in a good agreement with known experimental data, calculated points are within experimental error. Moreover, we have calculated the monovariant equilibrium line “gas phase – sII hydrate – Ice II based hydrate” that complicated to study experimentally. Here, an original approach has been demonstrated that allows us to construct a p - T phase diagrams of various hydrates with complex gas compositions.

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