Kinetics and reactor modelling of fatty acid epoxidation in the presence of heterogeneous catalyst
Résumé
Epoxidized fatty acids and fatty acid esters are used as chemical intermediates and environmentally friendly bio-lubricants. The epoxidation is carried out by the Prileschajew reaction, which implies the use of hydrogen peroxide as oxidation agent and a percarboxylic acid as the oxygen carrier. The epoxidation process is slow in the two-phase system (aqueous phase and oil phase), but it can be considerably enhanced by incorporating a heterogeneous acid catalyst. The results for the epoxidation of a model compound, oleic acid were presented. A cation-exchange resin (Amberlite IR-120) was used as the heterogeneous catalyst and acetic acid was the reaction carrier. Experimental data on oleic acid epoxidation were obtained at 40–50 °C under conventional heating and microwave irradiation. The experimental set was focused on studying the catalytic effect of the solid resin. The kinetic results revealed that the presence of the heterogeneous catalyst completely masked the enhancing effect of microwave radiation. An extensive set of kinetic data obtained from a laboratory-scale loop reactor was modelled with a realistic heterogeneous model taking into account the co-existence of three phases in the chemically complex reaction system. Rate equations were presented for all the reaction steps involved: the perhydrolysis, epoxidation and ring-opening steps. The rate equations were included in the three-phase reactor model and the kinetic parameters of the system were determined by non-linear regression analysis.