On-line conversion monitoring of the solution polymerization of methyl methacrylate using near-infrared spectroscopy

Abstract

Fiber-optic near-infrared (NIR) spectroscopy was successfully used to monitor the conversion of monomer during the solution polymerization of methyl methacrylate (MMA) carried out in a lab-scale reactor. NIR spectra were recorded during 18 batch and semi-continuous reactions using an in-situ transmission probe. An empirical model was generated using partial least-squares regression (PLS) to relate the NIR spectral data to the conversion measured off line by gravimetry. The obtained calibration was characterized by a correlation coefficient of 99.45% and a standard error of calibration (SEC) equal to 1.95%. The measurements were then validated for various operating conditions and for both batch and semi-continuous modes. The conversion was measured with a standard error below 2.6%, in the worst case scenario. The on-line NIR measurement of conversion was demonstrated to be accurate, robust, and suitable for versatile use in the polymerization plant. Validation of the on-line measurement of MMA conversion during the semi-continuous Runs V2 and V3.