SOLUBILITY OF TRANS-CINNAMIC ACID IN SUPERCRITICAL CO_2 + ETHANOL MODIFIER: MEASUREMENTS AND CORRELATION

摘要

2-propenoic acid (cinnamic acid; trans-cinnamic acid) is widely used in food (as flavouring), cosmetics (perfumes, decorative cosmetics, fine fragrances, shampoos, toilet soaps, etc) and pharmaceuticals (because of its functional properties). Recent studies related to the use of trans-cinnamic acid in cosmetics revealed also its importance as a non-photosynthetic pigment in photoprotection. Furthermore, there is a growing interest in the use of cinnamic acid as a food supplement because of its reported antimicrobial, antifungal and antioxidant properties. Supercritical Fluid Extraction (SFE) is a viable technique for extraction of a great variety of compounds from their natural vegetable matrixes. The design of SFE processes requires knowledge of the solute solubility in the supercritical phase and the ability to efficiently model and predict it. This paper is devoted to the experimental measurement and correlation of the solubility of trans-cinnamic acid in pure supercritical CO_2 and with ethanol as a modifier, which, to our knowledge, has not been reported in the literature till present. Measurements were carried out at temperatures in the range of 313.15 K to 343.15 K and at pressures ranging from 100 to 400 bar. Two thermodynamic models were used and compared in the correlation of the experimental solubility data for trans-cinnamic acid - a cubic type equation of state, the Soave-Redlich-Kwong SRK-EoS, and the Group Contribution Associating EoS (GCA-EoS). In addition, values for the thermophysical properties of trans-cinnamic acid are also advocated.