Insight into micro-mechanism of hydrate-based methane recovery and carbon dioxide capture from methane-carbon dioxide gas mixtures with thermal characterization

Highlights: • A combination of DSC and PXRD, Raman, FTIR and Cryo-SEM is used for investigating CH₄-CO₂ hydrate formation. • Mechanism of hydrate formation from CH₄-CO₂ gas mixture is identified. • A way of ultrasonic dispersion for improving gas consumption is proposed. -- Abstract: Energy shortage and carbon emission reduction are the two big problems in the development of human society. The technologies involving CH₄-CO₂ binary hydrate is considered to be promising for CH₄ recovery and carbon emission reduction. The DSC, Raman, FTIR, Cryo-SEM and PXRD are employed to investigate the thermal process, the micro structure and compositions of the CH₄-CO₂ hydrate formation and decomposition. The investigations reveal that there are not one kind of hydrate but rather multi-kinds of hydrates coexistence during the hydrate formation. The mechanism of gas hydrate formation could be considered as, under a certain condition, the component with lower enthalpy prior to entrap the cavities to stabilize the hydrate cages in the process of constructing hydrate cages by water molecules, and once the relevant cages are stabilized, the hydrates thereby exist. To fully disperse the oil additive (e.g. CP) into water can effectively improve the gas consumption and enhance CO₂ separation efficiency in the process of CH₄-CO₂ binary hydrate formation. The methods presented here can also be employed for other fields such as hydrate-based sea-water desalination, CO₂ separation and H₂ purification from IGCC syngas, gas transportation, and other fields.