Measurements and modeling of CO2 solubility in 1,8-diazabicyclo-[5.4.0]-undec-7-ene—Glycerol solutions

The solubility of CO2 in pure 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) and pure glycerol were determined with the static total pressure method. Additionally, a switchable ionic liquid was formed by dissolving CO2 into DBU–glycerol mixtures. All measurements were conducted at temperatures from 302 to 353K. In addition, density of DBU was measured at temperatures from 293 to 358K. The solubility of CO2 into DBU–glycerol solutions was slightly temperature dependent at the measured temperature range. CO2 solubility was found to depend strongly on the composition of DBU–glycerol solution and the partial pressure of CO2. Highest loadings to DBU were achieved with glycerol rich mixtures. A model taking into account the effect of DBU:glycerol ratio was developed. A CO2 molecule bound to the glycerol hydroxyl group was assumed to hinder reactivity of the remaining hydroxyl groups in the glycerol molecule, therefore affecting CO2 solubility in the solution. In the model, the equilibrium reactions between CO2, DBU and the hydroxyl groups of glycerol were simplified to two reactions. In addition, the physical solubility of CO2 in pure DBU and glycerol was measured and modeled. The physical solubility model was used in modeling CO2 solubility in DBU–glycerol solutions.