High pressure phase equilibria for poly(ethylene glycol)s + CO2: experimental results and modelling

Phase equilibrium results for mixtures of three poly(ethylene glycol)s (PEG s) of molar mass 200, 400 and 600 g mol(-1) with carbon dioxide over the te mperature range 313.15-348.15 K and pressures up to 26 MPa are presented. A new static analytical apparatus was built to carry out these measurements. The precision of the method is better than 3% and the accuracy is estimate d to be better than 5% of the mass fraction. The results are well correlate d with the Sanchez-Lacombe equation of state, using a non-temperature depen dent interaction parameter zeta. Negative hydroxy end-group effects on the CO2 solubility in the polymer are highlighted in the case of PEG 200. Data from other workers for CO2 + heavier PEG (1500-8000 g mol(-1)) are also suc cessfully included in the correlation. However, previously published values for PEG 400 to PEG 1000 differ substantially from our results and could no t be simultaneously correlated by this model.