Experimental Investigation on Tuning Patterns of Isoxazole Clathrate Hydrates

ABSTRACT

Here, tuning patterns of methane (CH₄) inclusion in isoxazole (C₃H₃NO) clathrate hydrates were experimentally investigated through spectroscopic observations. Powder X-ray diffraction (PXRD) was used to analyze the crystal structure of binary (isoxazole + CH₄) clathrate hydrates having two different hydration numbers (C₃H₃NO with 17H₂O and C₃H₃NO with 34H₂O systems). Raman spectroscopy was used to reveal the possible tuning patterns of CH₄ inclusion in isoxazole clathrate hydrates. Both spectroscopic results showed that both clathrate hydrate samples exhibits same cubic Fd3m structure II hydrate as expected, and CH₄ can be captured in both small and large cavities of structure II hydrate in C₃H₃NO with 34H₂O system while CH₄ can be entrapped in only small cavities of structure II hydrate in C₃H₃NO with 17H₂O system. The phase equilibrium conditions of binary (isoxazole + CH₄) clathrate hydrate were also measured through high-pressure micro differential scanning calorimetry and the equilibrium temperatures of binary (isoxazole + CH₄) clathrate hydrate at given pressures are higher than those of pure CH₄ hydrate. The present findings are expected to provide the useful information for better understanding of novel tuning reaction pathways in isoxazole clathrate hydrates that might be significantly affected by the hydration numbers.