甲烷水合物分解过程原位激光拉曼光谱观测

In situ Raman spectroscopic observation on methane hydrate dissociation

为了获取水合物分解过程中分子水平的信息,采用激光拉曼光谱法对冰—水转化及两种不同体系下甲烷水合物的分解过程进行了原位监测,研究了冰—水转化及甲烷水合物分解的微观动力学过程,探讨了水合物分解过程中笼型结构的变化。实验结果表明,在冰融化过程中,冰的四面体结构不断瓦解,氢键数目不断减少,O—H键的特征谱带中,带氢键的伸缩振动拉曼峰所占比例逐渐下降,不带氢键的伸缩振动拉曼峰的比例相应增大。两种不同体系下合成的甲烷水合物均为Ⅰ型水合物,大小笼中甲烷分子的拉曼峰分别为2905cm-1和2915cm-1,随着水合物的不断分解,拉曼双峰逐渐消解,并最终转化成甲烷气体单峰(2917cm-1);结构水峰的变化与冰融化的过程相类似,随着笼型结构的瓦解,氢键数目迅速减少,导致带氢键的O—H键伸缩振动峰减弱。

In situ laser Raman spectroscopic observation was carried out on the process of ice-melting and methane hydrate dissociation,during which the data of molecular level was to be obtained.The methane hydrate was synthesized in two different systems (SDS-CH4 and Dry Water-CH4).The micro-kinetics of ice-melting and methane hydrate dissociation were investigated,and the clathrate structure change of hydrate was also discussed.The results show that the tetrahedral structure of ice began to disintegrate as the ice melted,and the hydrogen bonds decreased.The proportion of the stretching vibration of hydrogen bonds gradually decreased in O-H bond characteristic bands,while the ratio of non-hydrogen bonds stretching vibration correspondingly increased.The synthesized methane hydrates under two kinds of different systems were both structure I and the Raman peak positions for methane molecules in the large and small cages were at 2905 cm-1 and 2915 cm-1 respectively.During the decomposition process of the methane hydrates,the twin Raman peaks for methane molecules both in the large and small cages gradually became reverse,and finally turned into a single peak for methane gas at 2917 cm-1;the changes of the spectrum of the structured water are similar to the process of ice melting.The disintegration of cage structure and the rapid decline in the number of hydrogen bonds resulted in the decline of the intensity of the O-H bond stretching vibration peaks with hydrogen bonds.