The influence of reaction variables on the epoxidation of castor oil (CO) in benzene with peracetic acid (P) generated in situ from acetic acid (A) and hydrogen peroxide (H) in the presence of an ion exchange resin as catalyst was examined. The highest relative epoxy yield (REY) of 78.32% was achieved at 323 K after 8 h when 0.5 mol of acetic acid and 1.5 mol of 30 wt% aqueous hydrogen peroxide per mol of double bond in oil were used in the presence of 15 wt% of Amberlite IR-120. The experimental data were fitted by proposed pseudo-homogeneous kinetic model which considers the side reaction of epoxy ring cleavage involving the formation of hydroxy acetate in addition to reactions of the peracetic acid and epoxy compound formation. Temperature dependency of the kinetic parameters is expressed by a reparameterized Arrhenius equation. The constants of the Arrhenius equation were determined by fitting experimental data using the Marquardt method. An increase of all rate coefficients for considered reactions with temperature and good agreement of the calculated reactant and product concentrations with experimental data, indicate the correctness of the proposed kinetic model. The model was compared with pseudo-homogeneous models reported in the literature. (C) 2012 Elsevier B.V. All rights reserved.