Raman spectroscopy of a hydrated CO 2/water composite

Abstract

Formation of a sinking carbon dioxide (CO 2) hydrate composite has been investigated as an alternative to direct liquid CO 2 injection and pure CO 2 hydrate formation for ocean carbon sequestration. Raman spectroscopy of the CO 2 hydrate composite was also performed to determine the presence of various components in the composite produced by the co-injection of liquid CO 2 and water. This work is focused on the formation and spectroscopy of a semi-solid sinking CO 2 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 CO 2 and water molecules as well as shifts in Raman peak positions due to different CO 2 phases were obtained. The Raman spectra of the composite showed that both liquid and hydrate phases of CO 2 are present. The dissolution rate of CO 2 hydrate composite in water was also studied. An attempt was made to calculate the hydration number for the CO 2 hydrate composite and also the percentage of liquid CO 2 and water loss during formation.