Kinetics of Soybean Oil Epoxidation with in situ Formed Peracetic Acid in the Presence of Acidic Ion Exchange Resin
Janković M., Govedarica O., Sinadinović-Fišer S., Faculty of Technology, University of Novi Sad, 21000 Novi Sad, R. Serbia
Knez Ž., Faculty of Chemistry and Chemical Engineering, University of Maribor, 2000 Maribor, R. Slovenia

Soybean oil is industrially epoxidized with peracetic acid formed in situ from acetic acid and hydrogen peroxide in the presence of a mineral acid as a catalyst. A ‘green’ alternative to this catalyst is an acidic ion exchange resin. Besides heterogeneously catalyzed reaction of peracetic acid formation and homogenous uncatalyzed epoxy ring formation, in this liquid-liquid-solid system an epoxy ring opening reaction with acetic acid as the most likely side-reaction proceeds. To simplify mathematical modelling, in the present work this multireaction three-phase system was considered as pseudo-two phase liquid-solid system. Kinetics of peracetic acid formation is described by applying Langmuir-Hinshelwood-Hougen-Watson or Eley-Rideal postulates. By varying chemisorption mechanism of peracetic acid formation and order of ring opening reaction, fourteen models were established in which all kinetic parameters are presented as functions of temperature. Values of the model parameters were determined by fitting the experimentally determined changes of iodine number and epoxy oxygen content with time for soybean oil epoxidations run under different reaction conditions using Marquardt method. After discrimination, among viable models, the best-fit model was adopted. It is based on assumptions that peracetic acid formation is dual site reaction with acetic acid adsorption as rate-determining step. Adsorptions of all reactants and products are considered associative and all steps of chemisorption are considered reversible. The model correctly interprets experimental data in whole investigated ranges of temperature, reactants` ratio and catalyst concentration.

Acknowledgment: Authors are thankful to the Ministry of Education, Science and Technological Development of the R. Serbia (Project #III 45022) for financial support as well as to DAAD and INFU, FR Germany for instrument donation.