Green process for the preparation of phytosterol esters: Microwave-mediated noncatalytic synthesis

Phytosterol esters are compounds with health benefits and widespread industrial applications. In this work, the noncatalytic esterification of phytosterols and oleic acid was efficiently conducted using microwave irradiation for producing phytosterol esters. The influences of the reaction parameters on the phytosterol conversion were examined. The reaction conversion increased with increasing oleic acid:phytosterols molar ratio, microwave power, temperature, and reaction time. The phytosterol conversion of 95.42% was achieved at a temperature of 453 K, microwave power of 200 W, oleic acid:phytosterols molar ratio of 5:1, and reaction time of 50 min. Fourier transform infrared spectroscopy was employed to identify the molecular structure of the synthesized phytosterol esters. A second-order kinetic model was successfully developed for describing the esterification reaction. This study suggests that noncatalytic esterification through microwave irradiation is a reliable and eco-friendly approach for the production of high-quality phytosterol esters to prevent the contamination of the catalyst and side products.