Isomerization of Oleic Acid over Acid Zeolites: Design of Experiments and Proposal of a Novel Kinetic Mechanism

Three acid zeolites (H-ZSM-5, H-Beta, and H-FER) were evaluated in the oleic acid isomerization to branched-chain fatty acids (bc-FA). Understanding its kinetic behavior is essential to develop new technologies regarding biofuels, lubricants, and cosmetics. The catalysts were characterized through XRD, N-2 physisorption, and NH3-TPD. Preliminary reactions demonstrated that Ferrierite shows better yields in the reaction, which is associated with its higher Bronsted acidity. Optimal reaction pressure and time were 10 bar and 10 h, respectively. A full factorial design of experiments was used to evaluate the reaction temperature and the use of the cocatalysts, water and triphenylphosphine (TPP). The maximum yield (59%) was achieved using 8% of water and 10% of TPP at 300 degrees C. A reaction mechanism in which the oleic acid turns into its trans isomer before bc-FA formation was proposed, and the kinetic modeling of the process was carried out with reproducible results.

Automated summary

The study evaluated three acid zeolites in oleic acid isomerization reaction and characterized their kinetic behavior, finding that Ferrierite showed better yields. The optimal reaction conditions were determined as 10 bar pressure, 10 hours reaction time, and using 8% water and 10% TPP at 300 degrees Celsius to achieve a maximum yield of 59%. A proposed reaction mechanism and kinetic modeling showed reproducible results.