Measurement of clathrate hydrates via Raman spectroscopy
Measurement of clathrate hydrates via Raman spectroscopy
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DOI：
10.1021/jp970768e
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发表时间：
1997-09-18
影响因子：
3.3
通讯作者：
Sloan, ED
中科院分区：
文献类型：
--
作者：
Sum, AK;Burruss, RC;Sloan, ED
给出了以下体系中三种已知结构（I (sI)、II (sII) 和 H (sH)）的笼形水合物客体分子的拉曼光谱：CH4 (sI)、CO2 (sI)、C3H8 (sII)、CH4 + CO2 (sI)、CD4 + C3H8 (sII)、CH4 + N-2 (sI)、CH4 + THF-d(8) (sII) 和 CH4 + C7D14 (sH)。通过对 nu(1) 对称带进行解卷积来确定 sI 的大空腔和小空腔中 CH4 的相对占据量，从而得到 6.04 +/- 0.03 的水合数。结构 I、II 和 H 中 CH4 的 nu(1) 谱带频率存在统计差异，因此拉曼光谱是识别水合物晶体结构的潜在工具。还测量了 CH4 + CO2 系统的两种蒸气成分的水合物客体成分，结果与预测相比较。据测量，大空腔几乎完全被 CH4 和 CO2 占据，而小空腔中只有一小部分被 CH4 占据。在小空腔中没有发现二氧化碳。计算出混合水合物的水合数为 7.27 至 7.45。
Raman spectra of clathrate hydrate guest molecules are presented for three known structures (I (sI), II (sII), and H (sH)) in the following systems: CH4 (sI), CO2 (sI), C3H8 (sII), CH4 + CO2 (sI), CD4 + C3H8 (sII), CH4 + N-2 (sI), CH4 + THF-d(8) (sII), and CH4 + C7D14 (sH). Relative occupancy of CH4 in the large and small cavities of sI were determined by deconvoluting the nu(1) symmetric bands, resulting in hydration numbers of 6.04 +/- 0.03. The frequency of the nu(1) bands for CH4 in structures I, II, and H differ statistically, so that Raman spectroscopy is a potential tool to identify hydrate crystal structure. Hydrate guest compositions were also measured for two vapor compositions of the CH4 + CO2 system, and they compared favorably with predictions. The large cavities were measured to be almost fully occupied by CH4 and CO2, whereas only a small fraction of the small cavities are occupied by CH4. No CO2 was found in the small cavities. Hydration numbers from 7.27 to 7.45 were calculated for the mixed hydrate.