In-line monitoring of the transesterification reactions for biodiesel production using NIR spectroscopy

In this work, methods for in-line monitoring of the transesterification reactions of soybean oil with methanol using NIR spectroscopy are developed. Gas chromatography was employed for determining the contents of methyl ester (ME), monoglycerides (MG), diglycerides (DG) and triglycerides (DG) during the transesterification reaction and used as reference to build partial least squares regression (PLS) and multiple linear regression (MLR) calibration models employing NIR spectra. Some pre-processing and variable selection strategies of the spectral data were evaluated. Satisfactory RMSEP values were obtained for the external prediction subset. In addition, a multivariate control chart based on latent variables to monitor the progress of the reactions is also presented.