笼状水合物拉曼光谱特征与结构水合数的耦合关系

为了探讨不同气体组分和环境介质对形成笼状结构类型水合物和水合数的影响, 开展了一元体系 (CH4、CO2、C3H8 )和二元体系(CH4 +CO2、CH4 +C3H8、CH4 +N2 )的水合物生成结晶充填过程、结晶构型和动力学特性分析, 并对生成的水合物进行了拉曼光谱分析。结果表明单组分甲烷充填小孔穴 512和大孔穴 512 62 形成Ⅰ型笼状结构水合物(SⅠ), 二氧化碳和丙烷只占据大孔穴 512 64 形成Ⅱ型笼状结构水合物 (SⅡ ); 而二元混合组分中小孔穴中只充填有甲烷, 而没有CO2、N2 和C3H8。应用反褶积的ν1 对称谱带测定了CH4 分子在Ⅰ型结构大孔穴和小孔穴中的相对占有率,并根据谱带的面积比(对应于小孔穴与大孔穴)计算了平衡条件下甲烷水合物孔穴占有率及其耦合的水合数, 认为气体分子的大小不仅影响它所充填的孔穴形态和类型, 而且影响水合物生成的结构类型和水合数。

Coupled Relationship among Hydrate Structure, Hydration Number,and Raman Spectrum

To discuss the affects of the different gas compositions and environment media on the forming of the different complicated clathrate hydrates with the different structure types,and hydration numbers, this study (analyzed) the crystal filling process of the hydrate, the crystal construction type,and the dynamics characteristics in the singleness system(CH_4, CO_2, and C_3H_8,respectively)and in the duality system(CH_4+CO_2, CH_4+C_3H_8, and CH_4+N_2,respectively), and proceeded to analyse the results using Raman spectra. The results show that the methane fills the small cavities of 5~(12) and the large cavities of 5~(12)6~2 forming structure Ⅰ clathrate hydrate((SⅠ)),CO_2 and C_3H_8 only occupy the large cavities of 5~(12)6~4 forming structure Ⅱ clathrate hydrate((SⅡ) )in the singleness system,and that in the duality system the small cavities are only filled by CH_4,neither CO_2 nor N_2 and C_3H_8 is found. Applying the deconvoluting v_1 symmetric bands to measure the relative (occupancy) factors of CH_4 in the large cavities and in the small cavities of SⅠ, and according to the area ratio (corresponding to the small cavities and to the large cavities) of the bands, and computing the cavity occupancy factors and the coupling hydration numbers of methane hydrate under a few equilibrium terms,it is shown that the size of the gas molecule not only affects the appearance and the type of the filling cavities , but also do the structure type and the hydration number of hydrates.