Raman Spectroscopic Study on Hydrate-based Carbon Dioxide Separation from Fuel Gas in the Presence of THF

Carbon dioxide (CO2) capture via clathrate hydrate is a promising method for reducing carbon emission. In this work, the water-solubility (tetrahydrofuran (THF)) was adopted to capture CO2 and recover hydrogen (H2) from fuel gas via clathrate hydrate at 274.15 K and 4.00 MPa. In order to understand hydrate nucleation and crystallization well from view of macroscopic morphology and microscopic structure, the CO2 concentration in the gaseous phase was measured by GC, the morphology of the hydrate formation was filmed by camera, and the structure changes of compounds in and around the gas/liquid interface was monitored by in-situ Raman spectrometer. The experimental results shows that the hydrate formation is completed in 5 hours in view of CO2 separation and macroscopic morphology, however, the compounds transition and hydrate formation are still in process from view of microscopic structure. The hydrate initially occurs in the gas/liquid interface due to the enough contact between CO2 and THF solution. With the hydrate formation, the hydrate nucleation interface is moving from the gas/liquid interface towards the THF aqueous solution. Finally, the THF-CO2 binary hydrate are subsided into the bulk solution in the form of hydrate layer. The aggregate state of water molecules around the gas/liquid interface is beneficial to construct the framework of the hydrate. It might be related to the original structures in the initial hydrate nucleation process.