Bubble point pressures for dimethyl ether – methanol, dimethyl ether – 2-methoxyethanol and dimethyl ether - 2-ethoxyethanol at (293.15–313.15) K, and their predictions considering pair interactions for three functional groups, -CH2OCH2-, -CH2OH and -CH2CH2CH2-

Abstract

2-Alkoxyethanols enhance the miscibility for aqueous solvents with a propellant, dimethyl ether, in spray cans. Therefore, the bubble point pressures (BPs) were measured for dimethyl ether – methanol, dimethyl ether - 2-methoxyethanol and dimethyl ether – 2-ethoxyethanol by using static apparatuses at (293.15–313.15) K. The experimental BPs were compared with the previous data of dimethyl ether – 2-butoxyethanol. The BPs were larger than those of ideal solution. The order was dimethyl ether – methanol > dimethyl ether - 2-methoxyethanol > dimethyl ether – 2-ethoxyethanol > dimethyl ether – 2-butoxyethanol. Analytical solution of groups (ASOG) model was modified for the predictions. The original model provides the activity coefficients by combining Flory-Huggins and Wilson equations, and the parameters have been determined for 43 functional groups. Only three groups, -CH₂OCH₂-, -CH₂OH and -CH₂CH₂CH₂-, were newly considered in this study. Then, 2-ethoxyethanol was assumed to be composed of -CH₂OCH₂-, -CH₂OH and one-third of -CH₂CH₂CH₂-. The group pair interaction parameters, for (-CH₂CH₂CH₂- and -CH₂OCH₂-) and (-CH₂CH₂CH₂- and -CH₂OH), were determined from the literature data of vapor-liquid equilibria for propane - dimethyl ether and propane - methanol. Two different methods were employed to determine the parameters for (-CH₂CH₂CH₂- and -CH₂OH). One was from the BPs of dimethyl ether – methanol. The other was from those of dimethyl ether - 2-methoxyethanol. The better reproducibilities were obtained by the latter method. The average values of relative deviation for BP were 4.14, 3.62 and 4.37 % for dimethyl ether - 2-methoxyethanol, dimethyl ether - 2-ethoxyethanol and dimethyl ether - 2-butoxyethanol, respectively.