Physical chemistry and technological applications of gas hydrates: topical aspects

The review considers the research and engineering works in selected fields of the physical chemistry of gas hydrates and gas hydrate technologies, mainly performed over the last 10–15 years. Data on the hydrate structures are given, including the structures formed during phase transitions at low temperatures, and on new hydrate structures that are formed under ultrahigh pressures. The dynamics of guest and host subsystems is considered in brief. Phase diagrams of systems involving hydrate formation (in particular, in some porous media) and methods for calculating phase equilibria and compositions of hydrates in these systems are analyzed. Data on the hydrates formed by ‘non-classical’ hydrate formers (alcohols, amines, ammonia, etc.) studied in the last decade and on some of their properties are presented. The Section devoted to hydrate formation kinetics addresses the effect of compounds dissolved in water (surfactants, low-dosage inhibitors) and catalysts on this process. The hydrate growth dynamics on the water surface and hydrate decomposition-formation processes in disperse systems are discussed. Among technological applications, the attention is focused on gas storage and transportation in the hydrate form. Methods for the preparation of hydrates are considered. The bibliography includes 618 references.