High-pressure phase behavior of propyl lactate and butyl lactate in supercritical carbon dioxide

Lactate esters synthesized with lactic acid and ester are used as solvents and reactants in various industries, including agricultural chemistry, pharmaceuticals, electronics, and fine chemicals. Among lactate esters, high purity propyl lactate and butyl lactate are used to produce fine chemicals and in the synthesis of chiral intermediates for use in pesticides and drugs. However, distillation for the removal of propyl lactate and butyl lactate alters or degenerates products due the high boiling points of these two lactate esters. This problem can be solved by supercritical fluid extraction (SCFE) at lower temperatures. SCFE process requires high-pressure phase behavior data on CO2 and lactates for its design and operation. In this study, high-pressure phase behavior of propyl lactate and butyl lactate in CO2 was measured from (323.2 to 363.2) K using a variable-volume view cell apparatus. Experimental data were well correlated by the Peng–Robinson equation of state using the van der Waals one-fluid mixing rules. The critical constants were estimated by the Joback method, the Constantinou–Gani method, and the Nannoolal–Rarey method. Acentric factor was estimated by the Lee–Kesler method.

► The phase behavior of propyl lactate and butyl lactate in scCO2 was measured.
► Experimental data were correlated by the PR-EOS.
► The critical constants were estimated by the three group contribution methods.
► Acentric factor was estimated by the Lee–Kesler method.
► The Nannoolal–Rarey and Lee–Kesler method shows the best correlation results.