Liu Chang-Ling, Ye Yu-Guang, Meng Qing-Guo, Lü Wan-Jun, Wang Fei-Fei
Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao 266071, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2011 Jun;31(6):1524-8.
Micro laser Raman spectroscopic technique was used for in situ observation of the micro-processes of methane hydrate formed and decomposed in a high pressure transparent capillary. The changes in clathrate structure of methane hydrate were investigated during these processes. The results show that, during hydrate formation, the Raman peak (2 917 cm(-1)) of methane gas gradually splits into two peaks (2 905 and 2 915 cm(-1)) representing large and small cages, respectively, suggesting that the dissolved methane molecules go into two different chemical environments. In the meantime, the hydrogen bonds interaction is strengthened because water is changing from liquid to solid state gradually. As a result, the O-H stretching vibrations of water shift to lower wavenumber. During the decomposition process of methane hydrates, the Raman peaks of the methane molecules both in the large and small cages gradually clear up, and finally turn into a single peak of methane gas. The experimental results show that laser Raman spectroscopy can accurately demonstrate some relevant information of hydrate crystal structure changes during the formation and dissociation processes of methane hydrate.
采用显微激光拉曼光谱技术对高压透明毛细管内甲烷水合物生成和分解的微观过程进行原位观测，研究了这些过程中甲烷水合物笼形结构的变化。结果表明，在水合物生成过程中，甲烷气体的拉曼峰（2917cm⁻¹）逐渐分裂为分别代表大笼和小笼的两个峰（2905和2915cm⁻¹），这表明溶解的甲烷分子进入了两种不同的化学环境。同时，由于水逐渐从液态转变为固态，氢键相互作用增强，导致水的O-H伸缩振动向低波数移动。在甲烷水合物分解过程中，大笼和小笼中甲烷分子的拉曼峰逐渐消失，最终转变为甲烷气体的单峰。实验结果表明，激光拉曼光谱能够准确地展示甲烷水合物生成和解离过程中有关水合物晶体结构变化的一些相关信息。
