Integration of a fused silica capillary and in-situ Raman spectroscopy for investigating CO2 solubility in n-dodecane at near-critical and supercritical conditions of CO2

To determine the solubility of CO2 in n-dodecane at T = 303.15–353.15 K, P ≤ 11.00 MPa, an integrated fused silica capillary and in-situ Raman spectroscopy system was built. The Raman peak intensity ratio (ICO2/IC-H) between the upper band of CO2 Fermi diad (ICO2) and the C–H stretching band of n-dodecane (IC-H) was employed to determine the solubility of CO2 in n-dodecane based on the calibrated correlation equation between the known CO2 molality in n-dodecane and the ICO2/IC-H ratio with R2 = 0.9998. The results indicated that the solubility of CO2 decreased with increasing temperature and increased with increasing pressure. The maximum CO2 molality (30.7314 mol/kg) was obtained at 303.15 K and 7.00 MPa. Finally, a solubility prediction model (lnS=(P−A)/B) based on the relationship with temperature (T in K) and pressure (P in MPa) was developed, where S is CO2 molality, A=−8×10−6T2+0.0354T−8.1605, and B=0.0405T−10.756 . The results indicated that the solubilities of CO2 derived from this model were in good agreement with the experimental data.