Formation Kinetics of Cyclopentane + Methane Hydrates in Brine Water Systems and Raman Spectroscopic Analysis

Abstract

The kinetics of the formation of cyclopentane (CP) + methane (CH4) hydrates are studied to find the optimum condition for the rapid hydrate formation under the submarine condition (NaCl mass fraction of 0.035, around 277.15 K and 12 MPa). The influences of the CP/liquid phase volume ratio and the volume of the liquid phase on the amount of gas uptake and CH4 consumption rate are determined. The results show that the high volume ratio of CP/liquid phase is favorable for the rapid formation of CP + CH4 hydrates. There is an optimal ratio of the liquid phase volume for obtaining the highest gas consumption. Raman spectrum analyses for CP + CH4 hydrates are carried out to examine the hydrate structure and guest molecule occupation. The results show that CP mainly occupies the large cavities (51264) and CH4 is encapsulated in the small cavities (512) of the structure II hydrates. When the volume ratio of the CP/liquid phase is 0.05, CP with CH4 also occupies the large cavities (51264).