Fatty Acid Epoxidation on Enzymes: Experimental Study and Modeling of Batch and Semibatch Operation

Biolubricants, plasticizers, bio-based rigid foams, andnon-isocyanatepolyurethanes can be made in a green way from epoxidized fatty acids.The classical technology for fatty acid epoxidation requires a reactioncarrier, which acts as the real epoxidation agent. The process iscomplicated and involves a safety risk because of the appearance ofpercarboxylic acids. Therefore, the direct epoxidation of fatty acidsin the presence of an immobilized enzyme is an attractive pathwayto epoxidized fatty acids. Oleic acid was used as the model compoundis this work, and commercial immobilized lipase Novozym 435 was usedas the catalyst and hydrogen peroxide as the epoxidation agent. Batchand semibatch operation modes were tested in a laboratory-scale stirredtank reactor. The experimental results showed that almost completeconversions of the double bonds in oleic acid were achievable underisothermal batch and semibatch operation, with low concentrationsof ring-opening byproducts. Semibatch operation gave an improvementof the product yield. Mathematical modeling of the experimental datawas based on the reaction stoichiometry OA + HP -> POA + W andOA + POA -> EOA + OA, where OA = oleic acid, HP = hydrogen peroxide,POA = peroleic acid, W = water, and EOA = epoxized OA. Rate equationsfor the formation of peroleic acid and epoxide were derived, and thenumerical values of the kinetic and adsorption parameters were estimatedwith nonlinear regression analysis. The reactor models consisted ofordinary differential equations, which were solved numerically duringthe parameter estimation until the optimal parameter values were reached.The model gave a very good description of the experimental data.