CO_2—CH_4—N_2瓦斯混合气水合分离产物Raman光谱特征

Raman Spectroscopic Studies on CO_2—CH_4—N_2 Mixed-Gas Hydrate System

抽采瓦斯气分离产物特性精确获取是水合分离新技术应用关键。针对两种浓度构成的瓦斯混合气(CO2—CH4—N2),利用瓦斯水合分离产物Raman测试装置,原位合成两种水合物样品并观测Raman光谱。基于客体分子振动模式、"松笼-紧笼"模型及Raman谱带面积比,结合van der Waals-Platteeuw模型,确定出水合物晶体结构,计算出晶体孔穴占有率、水合指数等结构参数。结果表明,两种瓦斯水合物样品均为Ⅰ型结构,其大孔穴占有率分别为98.57%和98.52%,小孔穴占有率分别为29.93%和33.87%,小孔穴不易被客体分子填充;两种分离产物水合指数比较接近,分别为7.14和6.98,均大于Ⅰ型水合物水合指数理论值。

Accurate determination of coal mine gas separation product characteristics is the key for gas separation application based on hydrate technology.Gas hydrate was synthesized from two types of gas compositions （CO2-CH4-N2 ）.The separa-tion products were measured by in situ Raman spectroscopy.The crystal structure of mixed-gas hydrate was determined,and the cavity occupancy and hydration index were calculated,based on the object molecular various vibrational mode,“loose cage-tight cage”model and the Raman bands area ratio,combined with the model of van der Waals-Platteeuw.The results show that the mixed-gas hydrates are both structureⅠ for the two gas samples;Large cages of mixed-gas hydrate are nearly occupied by guest molecules,and the large cavity occupancies are 98. 57% and 98. 52%,respectively;but small cages are not easy to be occupied, and the small cavity occupancies are 29. 93% and 33. 87%,respectively;hydration index of the two gas samples hydrate is 7. 14 and 6. 98,respectively,which is greater than the theoretical value of structure Ⅰ.