Xu Feng, Zhu Li-hua, Wu Qiang, Xu Long-jun
College of Resource & Environment Science, Chongqing University, Chongqing 400030, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2009 Sep;29(9):2457-61.
Complex thermodynamics and kinetics problems are involved in the methane hydrate formation and decomposition, and these problems are crucial to understanding the mechanisms of hydrate formation and hydrate decomposition. However, it was difficult to accurately obtain such information due to the difficulty of measurement since methane hydrate is only stable under low temperature and high pressure condition, and until recent years, methane hydrate has been measured in situ using Raman spectroscopy. Raman spectroscopy, a non-destructive and non-invasive technique, is used to study vibrational modes of molecules. Studies of methane hydrate using Raman spectroscopy have been developed over the last decade. The Raman spectra of CH4 in vapor phase and in hydrate phase are presented in this paper. The progress in the research on methane hydrate formation thermodynamics, formation kinetics, decomposition kinetics and decomposition mechanism based on Raman spectroscopic measurements in the laboratory and deep sea are reviewed. Formation thermodynamic studies, including in situ observation of formation condition of methane hydrate, analysis of structure, and determination of hydrate cage occupancy and hydration numbers by using Raman spectroscopy, are emphasized. In the aspect of formation kinetics, research on variation in hydrate cage amount and methane concentration in water during the growth of hydrate using Raman spectroscopy is also introduced. For the methane hydrate decomposition, the investigation associated with decomposition mechanism, the mutative law of cage occupancy ratio and the formulation of decomposition rate in porous media are described. The important aspects for future hydrate research based on Raman spectroscopy are discussed.
甲烷水合物的形成和分解涉及复杂的热力学和动力学问题，这些问题对于理解水合物形成和分解的机制至关重要。然而，由于甲烷水合物仅在低温高压条件下稳定，测量困难，因此难以准确获取此类信息。直到近年来，才开始使用拉曼光谱对甲烷水合物进行原位测量。拉曼光谱是一种无损且非侵入性的技术，用于研究分子的振动模式。在过去十年中，利用拉曼光谱对甲烷水合物的研究不断发展。本文展示了气相和水合物相中CH4的拉曼光谱。综述了基于实验室和深海拉曼光谱测量的甲烷水合物形成热力学、形成动力学、分解动力学及分解机制的研究进展。重点介绍了形成热力学研究，包括利用拉曼光谱对甲烷水合物形成条件的原位观测、结构分析以及水合物笼占有率和水合数的测定。在形成动力学方面，还介绍了利用拉曼光谱研究水合物生长过程中水中水合物笼数量和甲烷浓度变化的研究。对于甲烷水合物分解，描述了与分解机制、笼占有率比的变化规律以及多孔介质中分解速率公式相关的研究。讨论了基于拉曼光谱的未来水合物研究的重要方面。
