Effect of inhibitor methanol on the microscopic structure of aqueous solution

摘要

Several experimental investigation have been carried out to study the stability o f methane hydrates under various conditions.~(1-7) Methanol has been used as an inhibitor of gas hydrate formation for a long time. It is well known that the equilibrium temperature of gas hydrates is reduced by the addition of methanol.~1 The addition of some cyclic ethers, such as THF, also changes the equilibrium condition of gas hydrates~1 and they are added mainly to promote gas hydrate formation. Recently, stdudies were carried out to clarify the effect of methanol on hydrate formation on a molecular level.~(6,7) From a microscopic viewpoint, these compounds are expected to change the clustering structure of liquid phase from that of pure water, leading to the change of the crystallization properties of gas hydrates. Therefore, it is important to determine the correlation between the crystallization properties and the microscopic liquid structure of an aqueous solution in order to gain further understanding of the gas hydrate formation mechanism. We previously reported that the stable clusters that were formed from methanol-water and THF-water mixtures have rather different structures.~8 However, this measurement was carried out only for comparatively low concentration solutions.