In Situ Attenuated Total Reflectance Fourier Transform Infrared (ATR FT-IR) Spectroscopy Monitoring of 1,2-Butylene Oxide Polymerization Reaction by Using Iterative Concentration-Guided Classical Least Squares

Abstract

There has been rapid growth in the application of in situ optical spectroscopy techniques for reaction and process monitoring recently in both academia and industry. Vibrational spectroscopies such as mid-infrared, near-infrared spectroscopy, and Raman spectroscopy have proven to be versatile and informative. Accurate determination of concentrations, based on highly overlapped spectra, remains a challenge. As an example, 1,2-butylene oxide (BO) polymerization, an important industrial reaction, initiated by propylene glycol (PG) and catalyzed by KOH, is studied in this work in a semi-batch fashion by using in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) monitoring. The weak BO absorbance, the constantly changing interference from the product oligomers throughout the course of the reaction, and the change in BO spectral features with system polarity posed challenges for quantitative spectral analysis based on conventional methods. An iterative concentration-guided classical least-squares (ICG-CLS) method was developed to overcome these challenges. Taking advantage of the concentration-domain information, ICG-CLS enabled the estimation of the pure oligomer product spectra at different stages of the semi-batch process, which in turn was used to construct valid CLS models. The ICG-CLS algorithm provides an in situ calibration method that can be broadly applied to reactions of known order. Caveats in its applications are also discussed.

Kinetic Model Building through Simultaneous Optimization with Spectral Data: 1,2-Butylene Oxide Polymerization Case Study

“…In this section, we present the results from applying the methodology outlined in Section 3 to the population balance kinetic model. This problem is formulated using both Pyomo 21 and KIPET 25,29 and solved with IPOPT 30 with linear solver MA57. KIPET was used to build the individual models for each time period.…”

“…In this work, we use a simultaneous solution strategy to investigate the industrially relevant polymerization reaction of 1,2-butylene oxide (BO), with initiator propylene glycol (PG) and catalyst KOH. The experimental data, reference spectra, and an iterative method to obtain concentration information were originally published by Chen and coauthors . We briefly review the iterative method in ref which incorporates a single mechanistic constraint assuming a first-order reaction in BO.…”

Monitor Polyimide Production from Diamine and Dianhydride Reactions Using a Combination of In Situ Infrared and Raman Spectroscopy

“…Classical least squares (CLS) has been successfully utilized to overcome such spectral overlapping. 8,11–15 In order to overcome the abnormal peak profiles observed in Fig. 5, a CLS model was developed which included the following components: NBP solvent, PAA which was obtained by subtracting the solvent contribution form the starting solution, polyimide product (end spectrum after solvent subtraction), and the intermediate (spectrum (c) in Fig.…”

Process analytical chemistry and chemometrics, Bruce Kowalski's legacy at The Dow Chemical Company

“…Another example of a laboratory analysis concerns the elucidation of reaction kinetics . In this paper, the polymerization reaction kinetics of 1,2‐butylene oxide are studied using a new method called iterative concentration‐guided CLS.…”