Correlating and estimating the solubilities of solid organic compounds in supercritical CO2 based on the modified expanded liquid model and the group contribution method

The expanded liquid model was investigated and a modified solution model was proposed in this paper. The results showed that in the expanded liquid model the accuracy of the solubility parameters of supercritical CO2 (sc-CO2) can affect the change of the variables. If the solubility parameters of sc-CO2 are accurate, the variables in the expanded liquid model are nearly temperature-independent. If the inaccurate solubility parameters of sc-CO2 were used, the variables in the model would be slightly temperature-dependent. When using the solubility parameter of the solute as variable and calculating the solubility parameters of sc-CO2 with accurate method in the expanded liquid model, it is found that the solubility parameter of the solute is the linear function of the ratio of the solubility parameter and molar volume of sc-CO2 (δ1/v1). Based on this linear function, the expanded liquid model was modified. In the modified model, the slope and the intercept of the linear function were used as the fitting parameters. The modified model was compared with the other two-parameter expanded liquid models and the results showed the modified model can provide better correlation results with the average absolute relative deviation (AARD) being 13.31%. A group contribution method was developed to estimate the parameters in the modified model. Based on the modified model and the group contribution method, the solubilitis of most of the solutes in sc-CO2 can be estimated in the order of magnitude.