High pressure vapour–liquid equilibria of the binary and some of the ternary and multicomponent mixtures of the carbon dioxide + acetic anhydride + α-methylbenzyl alcohol + acetic acid + α-methylbenzyl acetate system: Experimental and modelling results

Bubble-point pressures of the binary systems CO2 + acetic anhydride, CO2 + α-methylbenzyl alcohol, and CO2 + α-methylbenzyl acetate were measured in the temperature range of 283–363 K up to 15 MPa in a high pressure capillary glass tube apparatus, using the synthetic method. The binary mixture CO2 + acetic acid was measured for x = 0.4962 and compared with previously published results. For the system CO2 + α-methylbenzyl alcohol, data of the three-phase line L2L1V are given in the temperature range of 283–308 K. UCEP (L2L1 = V) was found at P = 7.78 MPa and T = 308.42 K. Bubble-point pressures of the ternary systems CO2 + acetic anhydride + α-methylbenzyl alcohol, and CO2 + acetic acid + α-methylbenzyl acetate were also measured at selected compositions. These mixtures corresponded to the reactant and product mixtures in the enzyme-catalyzed esterification of α-methylbenzyl alcohol with acetic anhydride to produce α-methylbenzyl acetate and acetic acid using supercritical carbon dioxide as solvent. The five component mixture occurring at intermediate conversion was measured at xCO2=0.4041xCO2=0.4041 at a fixed equimolar ratio of the organic heavy components. Modelling of the VLE of the binary systems was performed using the Stryjek–Vera modification of the Peng Robinson EOS with the Wong–Sandier mixing rules. The fitted parameters of the binary subsystems were used to predict the phase behaviour of multicomponent mixtures. Validation of the predictions was achieved by comparison with the experimental results.