Use of FTIR for preliminary analysis of the Conversion rate of oleic acid to ethyl oleate

Abstract

In the work here reported, an efficient and preliminary method to calculate the conversion rate of esterification reactions is presented, through a simple, fast and cost-effective technique, the Fourier-transform infrared spectroscopy, given that conversion rate is the percentage of ester formation when compared to the initial amount of carboxylic acid. From referential samples containing mixtures of oleic acid and ethyl oleate in different proportions, both substances purchased commercially and with a high degree of purity, a calibration curve was elaborated through linear regression, providing an equation for calculating conversion rates based on the integration of carbonyl peaks in Fourier-transform infrared spectroscopy spectra of reactants and products. The esterification of oleic acid with ethanol was verified under influence of two different solid-acid catalyst nanoparticles, niobium pentoxide and zirconium dioxide, in which the calculated conversion rates were, respectively, 38.1% and 10.4%. At the end of the work, it was possible to verify that the reported method provided a fast, simple and cheap way of obtaining esterification conversion rates, using exclusively infrared spectroscopy spectra of reaction products, which has the potential to avoid extra steps in sample preparation, consequently, reducing costs.