Kinetics and thermodynamics of oil extraction from sunflower seeds in the presence of aqueous acidic hexane solutions

Abstract

Oil extraction was performed in aqueous HCl, H2SO4 and H3PO4 solutions with n-hexane (C6H14) at 30, 40, 50 and 60° C using 10 gr of sunflower seeds over l 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°C were $Delta H^{neq}=1.43 kJmol^{-1}$,$Delta S^{neq}5^ =-309.3 Jmol^{-1}$ and $Delta G^{neq}=104.4 kJmol^{-1}$. The enthalpy value was $Delta H=11.2 kJmol^{-1}$, and the other thermodynamic parameters at 60°C were $Delta S=36.75 Jmol^{-1}K^{-1}$ and $Delta G=-1.07 kJmol^{-1}$