High-pressure Optical Cell for in Situ Raman Spectroscopy

Raman spectroscopy has been linked to a high-pressure optical cell for the in situ study of supercritical carbon dioxide (SC-CO2)-solute interactions. The body of the cell is made of a stainless steel cylinder enclosing a volumetric capacity of 24 mL, allowing optical access through sapphire windows on both ends. An argon ion laser was used for the excitation and Raman spectra were collected in the back-scattering geometry. This new set-up allows in situ studies of SC-CO2 adsorption by materials under pressures up to 300 bars and temperatures up to 100 °C, where only a minimal sample preparation is required. The set-up was tested in the system SC-CO2/alkyl ketene dimer (AKD), giving adsorption values up to 7 g of CO2 per g of AKD, as well as information about AKD solubility in SC-CO2. As a proof of concept, a possibility to study solubility and adsorption phenomena in SC-CO2 by the technique of Raman spectroscopy has been demonstrated.