Stabilization of Gas Hydrate by Addition of Gel and its Application to Gas Storage

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Utilization of methane for energy sources is one of the best approaches for reducing production of CO_2. Methane is buried as methane hydrate form under the deep sea. Stabilization and controlled formation of methane hydrate is a key technology of its utilization. However, growth inhibitor of methane hydrate has been investigated mainly. For example, one class of growth inhibitors are polymers with pendant groups such as a lactam ring, containing an amide group (-N-C=O) at the top of each ring adjacent to the polymer backbone. We proposed the polymeric additives for stabilization of methane hydrate. Merits of polymeric additives are (1) low volatility, (2) recyclability, and (3) chemical stability of them. We prepared two-type additives, (1) water-soluble polymeric additives and (2) water-insoluble ones. Poly (acrylic acid) (PA) and poly (aryl amine) hydrochloride salt (PAAm/HCI) did not act as a stabilizer of methane hydrate. PA inhibited formation of methane hydrate. PAAm/HCI did not inhibit formation of methane hydrate. We added cross-linked poly (styrene) particle (c-PSt) as a water-insoluble additive. Temperature-pressure equilibrium curve of the methane-water system with c-PSt shifted to lower pressure and higher temperature side. This suggests that the c-PSt stabilized methane hydrate. Poly (tetrahydrofurfuryl methacrylate) (PTHFMA) also stabilized methane hydrate. Stabilization mechanism of the water-insoluble polymeric additives, c-PSt and PTHFMA is not clear in our investigation. However, these results suggest that interaction between the polymeric additives and the methane hydrate surface is important factor for the stabilization and crystal growth of the methane hydrate.