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.