High-pressure phase equilibrium data for the l-lactic acid + (propane + ethanol) and the l-lactic acid + (carbon dioxide + ethanol) systems

Biodegradable polymers have received increased attention due to their potential applications in the medicine and food industries; in particular, poly(l-lactic acid) (PLA) is of primary importance because of its biocompatibility and resorbable features. Recently, the synthesis of this biopolymer through the enzyme-catalyzed ring-opening polymerization of l-lactic acid in a compressed fluid has been considered promising. The aim of this work was to report the phase equilibrium data (cloud points) of the l-lactic acid + (propane + ethanol) and the l-lactic acid + (carbon dioxide + ethanol) systems. The phase equilibrium experiments were conducted in a variable-volume view cell employing the static synthetic method. These experiments were conducted in the temperature range of 323.15–353.15 K and at pressures up to 25 MPa; the mass ratio of ethanol to either CO2 or propane was maintained at 1:9. The l-lactic acid + (propane + ethanol) system exhibited vapor–liquid, liquid–liquid and vapor–liquid–liquid transitions, whereas the l-lactic acid + (carbon dioxide + ethanol) system only exhibited liquid–liquid type transitions.

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► Phase equilibrium of l-lactic acid + solvent and co-solvent was measured.
► System containing carbon dioxide + ethanol presented LCST behavior.
► System containing propane + ethanol presented UCST behavior.