A calorimetric and Raman spectroscopy study on the phase behavior of DIOX + CO2 hydrate

This work presents a calorimetric and Raman spectroscopy investigation on the phase behavior of DIOX (1,3-Dioxolane) + CO2 hydrate. A high-pressure micro-differential scanning calorimeter (HP μ-DSC) was used to determine the phase equilibrium data of DIOX + CO2 hydrate formed at 1 mol% and 5.56 mol% DIOX. A high-pressure in situ Raman spectroscopy apparatus was used to record the transient CO2 Raman spectra. The spectra were employed to study CO2 incorporation into the hydrate cages during the DIOX hydrate formation process. The results indicate that the DIOX + CO2 hydrate formed at 5.56 mol% DIOX is more stable than that formed at 1 mol% DIOX. The amount of DIOX + CO2 hydrate is increased when increasing the pressure from 3.0 MPa to 4.8 MPa, and more CO2 molecules are captured in the hydrate. Through the in situ Raman spectroscopy experiments, it is found that DIOX hydrate formed quickly at the beginning of the experiment and CO2 molecules were trapped in the small cages more slowly than the incorporation of DIOX into the hydrate. The results reported in this work have confirmed the feasibility of using DIOX as a thermodynamic additive to promote the hydrate-based CO2 capture.