In situ Raman Spectroscopic Study of the Dissociation of Methane Hydrate at High Pressure

• Published in: Applied Spectroscopy
• Main Authors: Sun, Q., Zheng, H. F.
• Format: Article in Journal/Newspaper
• Language: English
• Published: SAGE Publications 2006
• Subjects: Spectroscopy; Instrumentation; Methane hydrate
• Online Access: http://dx.doi.org/10.1366/000370206778397281; http://journals.sagepub.com/doi/pdf/10.1366/000370206778397281

The dissociation of methane hydrate at high pressure is studied by in situ Raman spectroscopy in a diamond-anvil cell. As for the Raman spectrum of sI methane hydrate, the v 1 band of CH 4 is split into two peaks v′ 1 and v′ 1 , indicating the partitioning of CH 4 between the large (5 12 6 2 ) and small (5 12 ) cavities, respectively. With increasing temperature, the intensity ratio of Iv′ 1 / Iv′ 1 decreases obviously, and the d( Iv′ 1 / Iv′ 1 )/d T is −0.079 K −1 . Additionally, the v 1 band of the dissolved CH 4 is close to v′ 1 of the CH 4 molecule engaged in the small 5 12 cavity. This implies that, in the initial stage of hydrate formation, the abundance of small 5 12 cavities is greater than that of large 5 12 6 2 cavities.