Integration of a fused silica capillary and in-situ Raman spectroscopy for investigating CO_(2) solubility in n-dodecane at near-critical and supercritical conditions of CO_(2)

To determine the solubility of CO_(2)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(I_(CO_(2))/IC-H)between the upper band of CO_(2)Fermi diad(I_(CO_(2)))and the C-H stretching band of n-dodecane(IC-H)was employed to determine the solubility of CO_(2)in n-dodecane based on the calibrated correlation equation between the known CO_(2)molality in n-dodecane and the I_(CO_(2))/IC-Hratio with R^(2)=0.9998.The results indicated that the solubility of CO_(2)decreased with increasing temperature and increased with increasing pressure.The maximum CO_(2)molality(30.7314 mol/kg)was obtained at 303.15 K and7.00 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 CO_(2)molality,A=-8×10^(-6)T^(2)+0.0354T-8.1605,and B=0.0405T-10.756.The results indicated that the solubilities of CO_(2)derived from this model were in good agreement with the experimental data.