Physicochemical characteristics of non-ionic and ionic clathrate hydrates and their applications to energy devices

Abstract

Under low temperature and high pressure condition, various low molecular weight gas molecules like methane react with water, then clathrate hydrate is made. Clathrate hydrates called gas hydrates have some structures, sI, sII, sH etc. ‘Host’ water molecules make cage and then ‘guest’ gas molecules are entrapped. Gas hydrate is expected to replace petroleum energy. Because the amount of world gas hydrate is estimated more than twice as fossil fuel’s. Gas hydrates have infinite potential as the energy source of next generation. In this stud, at first, Hexamethyleneimine, 1-methylpiperidine, 2-methylpiperidine, 3-methylpiperidine and 4-methylpiperidine as isomers of C6H13N were revealed as new sH clathrate hydrate forming molecules. They show fully soluble characteristics to water whereas already known sH formers such as mechylcyclohexane and 2, 2-dimethylbutane (neohexane) are immiscible or very slightly soluble to water. The L-H-V equilibrium P-T behavior of these new sH clathrate hydrates shows a tendency to shift to much milder condition than already known ones. We particularly note that 1-methylpiperidine appears to be the best for promotion. To verify the distribution of CH4 molecules and crystal structure of clathrate hydrates, 600MHz solid-state NMR, Raman spectroscopy and XRD pattern analysis were conducted. These noticeable properties of new formers are expected to open new research fields to the hydrate community and contribute to hydrate-based technological applications with high energy efficiency. At second, two types of new amine-type sII formers were suggested: pyrrolidine and piperidine. These guest compounds fail to form clathrate hydrate structures with host water, but instead have to combine with light gaseous guest molecules (methane) for enclathration. Two binary clathrate hydrates of (pyrrolidine+methane) and (piperidine+methane) were synthesized at various amine concentrations. 13C NMR and Raman analysis were done to identify the clathrate ...