High-Pressure Phase Behavior of Methyl Lactate and Ethyl Lactate in Supercritical Carbon Dioxide

Lactates obtained from biological sources are used as solvents in various industries from fine chemicals to pharmaceuticals. However, chemicals dissolved in lactates are typically degenerated during distillation due to the high boiling point of lactates. This problem can be solved by supercritical fluid extraction (SCFE) at lower temperatures instead of distillation. SCFE requires high-pressure phase behavior data on CO2 and lactates for its design and operation. The high-pressure phase behavior of methyl lactate and ethyl 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 (PR EOS) using the Wong–Sandler mixing rules and the nonrandom two-liquid (NRTL) model. The critical constants were estimated by the Nannoolal–Rarey method, and the acentric factor was estimated by the Lee–Kesler method.