Mass Transfer and Equilibrium Parameters on High-Pressure CO2 Extraction of Plant Essential Oils

摘要

The production of plant extracts is currently limited by safety and regulatory constraints on the concentration of toxic residues of organic solvents such as n-hexane or methanol (Sanders 1993). Carbon dioxide (CO2) is an excellent alternative to these organic solvents due to its inertness, non-toxicity, non-flammability, and low cost (Brunner 1994; del Valle and Aguilera 1999). The recommended temperature in so-called supercritical fluid (SCF) extraction (SCFE) processes is slightly above the critical temperature (Tc) of the solvent so that a near-environmental temperature is applied when using CO2 (Tc = 304.2 K) in SCFE, thus reducing the requirement of energy for separation as well as the thermal damage of labile bioactive compounds (Brunner 1994). Furthermore, objectionable solvent traces are eliminated from the treated substrate and the extract because, being a gas under normal environmental conditions, CO2 is easily and fully removed following SCFE.