Polymerization Reactor Monitoring by In-line Raman Spectrometry

Abstract

This paper explores the feasibility of using in-line Raman spectrometry to monitor different monomer-solvent-polymer systems by different techniques: in-line, by an immersion probe; in-line, but externally aiming the spectrometer through the glass of the reactor wall; and off-line, taking the samples in small vials. The monitoring of chemical systems was done in the absence of polymer in order to simplify and facilitate the initial studies as well as in polymerization reactors operated with different processes: coordination polymerization of styrene-myrcene, anionic polymerization of myrcene, styrene emulsion polymerization, and methyl methacrylate-butyl acrylate mini-emulsion copolymerization. In all of these systems, it is of interest having an online monitoring technique for feedback control which would increase the productivity of the process, the quality of the product and the safety of the operation. Results show that Raman spectrometry was always capable to reproduce the trend of the process, with reasonable deviation with respect to gravimetric analysis.

Some Applications of Vibrational Spectroscopy for the Analysis of Polymers and Polymer Composites

“…The usefulness of Raman spectroscopy for monitoring polymerization reactions in academic and industrial environments has been demonstrated by several authors [25,26,27,28]. One major advantage of the Raman technique over infrared absorption spectroscopy is that it allows the study of aqueous heterogeneous systems such as emulsions.…”

“…The industrial application of Raman spectroscopy for the control and optimization of vinyl acetate resin polymerization has been discussed by Frauendorfer and Hergth [27]. Martinez et al [28] explore the feasibility of Raman spectroscopy for polymerization reactor monitoring by using different techniques: in-line, by an immersion probe, through a site glass window or off-line by collecting samples in vials.…”

Raman Spectroscopy of Glass Beads in Ammonium Nitrate Solution and Compensation of Signal Losses

“…A more practical solution is provided by online measurement methods, including Raman spectroscopy. The Raman probe can follow the reaction process non-invasively and, as no sample has to be taken (as with offline methods), also provides a non-destructive alternative [ 27 , 28 ]. The problem with spectroscopy, as described above, is that, in multiphase systems, the detected signal can drop significantly, and new dependencies arise due to the interfaces between the individual phases.…”

Raman Spectroscopy of Disperse Systems with Varying Particle Sizes and Correction of Signal Losses

“…In addition, the strength of the resulting signal is linearly dependent on the concentration, which allows for a quantitative evaluation of the target. The use of this measurement technique in homogeneous mixtures is now widespread and much researched [4,6,[13][14][15][16]. However, the analysis of heterogeneous mixtures represents a special application.…”