(262t) Spectroscopic Identification of Hydroxyl Group Positioning in Butanol Hydrates

In this study, the inclusion of large alcohol guest molecules in hydrate structure are investigated through spectroscopic identifications and equilibrium condition measurements. Four clathrate hydrates formed by structural butanol isomers are identified with powder X-ray diffraction (PXRD). The PXRD results showed that 1-butanol, isobutanol, and tert-butanol can act as structure II hydrate formers, but 2-butanol cannot be enclathrated in hydrate cages. Raman spectroscopy was used to analyze the guest distributions and inclusion behaviors of large alcohol molecules in these hydrate systems. The existence of a free OH indicates that guest molecules (isobutanol and tert-butanol) can be captured in the large cages of structure II hydrates without any hydrogen bonding interaction between the hydroxyl group of the guests and the water-host framework. However, Raman spectra of the binary (1-butanol + CH₄) hydrate did not show the free OH signal, indicating that there could be possible hydrogen bonding interactions between the guests and hosts. We also measured the four-phase equilibrium conditions of the butanols + CH₄ + H₂O systems. The results of this study could provide a better understanding of the complex host â?? guest behaviors occurring in clathrate hydrate systems.