Stabilization of gas hydrate by addition of anti-freeze protein like peptide-modified polymer particles

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Gas hydrate is one of the inclusion compounds, which consist of water and gas molecules. Usual procedure for preparation of gas hydrate is compressing and cooling of the system with gas and water. Stabilization and controlled formation of methane hydrate is a key technology for its utilization. However, growth inhibitor of methane hydrate has been investigated mainly. We proposed polymeric additives for stabilization of methane hydrate. Merits of polymeric additives are (1) low volatility, (2) recyclability, and (3) chemical stability of them. We proposed that the equilibrium temperature-equilibrium pressure curve (T-P curve) of gas hydrate formation will be shift to higher temperature and lower pressure side by addition of surface modified polymer particles into the gas-water system. This means that stabilization of gas hydrate by addition of the polymer particles.First, we added the poly(styrene-co-divinylbenzene), (PSt) particles to the system with methane and water. Addition of PSt … More particles shifted the T-P curve of methane hydrate to lower temperature and higher pressure. We also prepared surface-modified PSt particles. For example, p-alkoxybenzylalcohol-unit modified PSt particles (c-PSOH) were examined under similar condition. However, addition of c-PSOH particles did not shift the T-P curve of methane hydrate. It is known that anti-freeze protein(AFP) interacts with water molecules and inhibits the growth of ice.AFP has alanine (Ala)-rich peptide sequence. We modified c-PSOH particles with alanine-rich sequence, -(Ala)_<10>-, -(Ala)_5-, and -(Ala)-. The particles with Ala-rich sequence could not stabilize methane hydrate. However, storage ratio of methane in the formed hydrate was higher than that of the additive-free hydrate. This suggests that alanine-rich sequence modified PSt particles inhibit ice formation, i.e., methane-free solid.Similar experiments were performed in the system with water and carbon dioxide. Carbon dioxide hydrate is also stabilized by addition of PSt particles into the carbon dioxide and water system. Less