Methane hydrate formation from swollen gel particles based on cross-linked copolymers of acrylamide and acrylic acid
M. E. SEMENOV1, U. ZH. MIRZAKIMOV1, A. YU. MANAKOV1,2, A. K. SAGIDULLIN1,2, R. S. PAVELYEV1, M. A. VARFOLOMEEV1
1Kazan (Volga Region) Federal University, Kazan, Russia
2Nikolaev Institute of Inorganic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: methane hydrate, gels, copolymers, promoter, gas storage
Abstract
The results of studying methane hydrate formation processes using swollen gel particles synthesised from the copolymers of acrylamide and acrylic acid with varying degrees of cross-linking are presented. The effect of chemical composition of gel particles and their structural-morphological characteristics on the hydrate formation kinetics and efficiency of water conversion to methane hydrate is investigated. Experimental studies were conducted in specialised autoclave installations under strictly controlled thermobaric conditions: initial pressure at 20 °C was 9.5 MPa with subsequent temperature reduction to 1 °C to ensure thermodynamic conditions for hydrate stability. It has been established that gel particles containing predominantly acrylamide fragments exhibit low activity in initiating hydrate formation and do not contribute to the formation of significant amounts of hydrate. In contrast, particles with reduced cross-linking degree and increased content of acrylic acid functional groups demonstrate intense hydrate formation with almost no induction period. The quantitative analysis of hydrate formation products in the case of samples with a high content of acrylic acid fragments has demonstrated high efficiency of water conversion into methane hydrate reaching 42-67 %. Introduction of a kinetic promoter based on castor oil (COS-3MS) into the mixture of gel-forming agents allowed for an additional increase in the degree of water conversion to hydrate up to 58 %. Visual observations revealed a characteristic hydrate growth mechanism: the process is initiated on the surface of gel particles, and then the crystals propagate into the gel volume through diffusive and capillary transport of the aqueous phase. The obtained results convincingly demonstrate the high potential for the practical application of gel systems for intensifying hydrate formation processes and creating innovative technologies for efficient storage and transportation of natural gas in the hydrate form.
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