A novel kinetic study of H3PW12O40 - catalyzed oleic acid esterification with methanol via 1H NMR spectroscopy

Abstract

In this work, the H3PW12O40 heteropolyacid - catalyzed oleic acid esterification reaction with methanol was investigated via 1H NMR spectroscopy in situ. H3PW12O40 heteropolyacid has recently attracted significant attention due to its potential for application in the production of biodiesel, in either homogeneous or heterogeneous catalytic conditions. Although fatty acids esterification reaction has been known for some time, data is still scarce regarding kinetic and thermodynamic parameters, especially when catalyzed by non-conventional compounds such as H3PW12O40. Herein, a kinetic study utilizing 1H NMR spectroscopy in situ allows for evaluating the effects of temperature on reaction rate, and determining the activation energy along with thermodynamic constants including ΔG, ΔS and ΔH. Although used in homogeneous phase, the HPW catalyst was recovered and reutilized via a simple recycle protocol without activity loss. Additionally, the order of reaction in relation to both substrate and catalyst concentrations was also determined. NMR spectroscopy showed to be an efficient method of investigation and allows accurate measurement of the reaction rate and of thermodynamic parameters of the H3PW12O40 - catalyzed oleic acid esterification reactions.