Raman spectroscopy of a hydrated CO2/water composite

Formation of a sinking carbon dioxide (CO2) hydrate composite has been investigated as an alternative to direct liquid CO2 injection and pure CO2 hydrate formation for ocean carbon sequestration. Raman spectroscopy of the CO2 hydrate composite was also performed to determine the presence of various components in the composite produced by the co-injection of liquid CO2 and water. This work is focused on the formation and spectroscopy of a semi-solid sinking CO2 hydrate composite formed using a co-flow injector in 72-liter and 0.45-liter pressurized vessels at pressure and temperature conditions equivalent to approximately 1.3-km depth in the ocean. The Raman wavenumber shifts (Δcm− 1) corresponding to CO2 and water molecules as well as shifts in Raman peak positions due to different CO2 phases were obtained. The Raman spectra of the composite showed that both liquid and hydrate phases of CO2 are present. The dissolution rate of CO2 hydrate composite in water was also studied. An attempt was made to calculate the hydration number for the CO2 hydrate composite and also the percentage of liquid CO2 and water loss during formation.