Turkish Journal of Chemistry

Abstract: Oil extraction was performed in aqueous HCl, H₂SO₄ and H₃PO₄ solutions with n-hexane (C₆H₁₄) at 30, 40, 50 and 60 ^oC using 10 gr of sunflower seeds over 1 h with 10-min. sampling intervals. The optimum acid concentration was wt. 10% for each acid, and the highest oil yield was obtained in the extraction procedure with n-hexane containing H₂SO₄. The extraction process was observed with regard to the percent oil yield versus time, and the reaction order was found to be first-order kinetics by the differential method. The activation energy for the oil extraction kinetics of sunflower seeds with 10% H₂SO₄ was found to be E_a=4.2 kJmol^-1, and the activation thermodynamic parameters at 60 ^oC were DH ^\neq =1.43 kJmol^-1, DS ^\neq=-309.3 Jmol^-1K^-1 and DG ^\neq =104.4 kJmol^-1. The enthalpy value was DH=11.2 kJmol^-1, and the other thermodynamic parameters at 60 ^oC were DS=36.75 Jmol^-1K^-1 and DG= -1.07 kJ mol^-1.

Key Words: Hexane, kinetics, oil extraction, sulfuric acid, sunflower seed, thermodynamics.