Monitoring of the acid catalysed esterification of ethanol by acetic acid using Raman spectroscopy

Abstract

The acid catalysed esterification of ethanol by acetic acid has been monitored using Raman spectroscopy. It was found that noise and baseline shift due to fluorescence spectra and process dynamics obscured the essential chemical information in the data. Principal components analysis and regression analyses have been applied progressively to de-noise the data and to extract the Raman signal. It was found that the first principal component (PC1) contained the fluorescence, while the second principal component (PC2) contained the pure Raman spectra. It was then possible to reconstruct the original data using only the second principal component, and then use this reconstructed data to follow the progress of the reaction. To be sure that the data in PC2 represented the real chemical process, the kinetics of the reaction were calculated using selected wavelength profiles in PC2. It was shown that the reaction follows theoretical second order kinetics, which is expected of this esterification.