Bubble point pressure measurements and two models, ASOG theory and cubic equation of state, for sulfur dioxide – methanol and sulfur dioxide – polyethylene glycol binary systems

Bubble point pressures were measured for the SO₂ – methanol binary system at (298.15 to 313.15) K and SO₂ – polyethylene glycol (PEG) binary system at (288.14 to 323.16) K using a static apparatus. The molar mass of PEG was (190 to 210) g·mol^-1. Both binary systems were determined to be zeotropic. SO₂ – methanol system showed higher pressures and the SO₂ – PEG showed lower pressures than those of the ideal solution, respectively. Experimental data for SO₂ – PEG were analyzed with two models, analytical solution of groups (ASOG) theory and Peng-Robinson (PR) equation of state. Parameters in the ASOG model were determined for three group pairs, SO₂ – -CH₂OCH₂-, -CH₂OCH₂- – -CH₂OH and SO₂ – -CH₂OH, using literature data for SO₂ - dimethyl ether, dimethyl ether – 2-methoxyethanol and using experimental data measured in this work for SO₂ – methanol. A steric factor was employed for the -CH₂OCH₂- groups in PEG. Predicted pressures were lower than those of the experimental data for SO₂ – PEG making it necessary to redetermine the parameters for SO₂ – -CH₂OH group pairs by fitting SO₂ – PEG experimental data. For the PR equation, binary parameters in mixing rule were determined by SO₂ – PEG data. Average absolute relative deviations for SO₂ – PEG were 7.28 % and 4.05 % for the ASOG model and the PR equation, respectively. Isolated -CH₂OH groups in methanol have an interaction with SO₂ that is different from that of the -CH₂OH group binding with -CH₂OCH₂- in the ASOG model.