(220u) New Applications of FTIR Spectroscopy for Process Control and Process Development

Abstract

  Infrared spectroscopy is a powerful method for qualitative and quantitative determination of substances. Infrared radiation causes molecular vibrations, the resulting absorption spectra give information on molecular structure and concentration.

 In the mid infrared range (4000 ‑ 400 cm^‑1), absorption bands are more intense and less broad in contrast to near-infrared (12000 – 4000 cm^-1), therefore an assignment of characteristic functional groups to single bands is possible. The information content is higher, making multivariate regression methods such as Partial Least Squares (PLS) regression more powerful¹.

  In process analytics, the optical setup of Attenuated Total Reflectance (ATR) in combination with PLS chemometrics allows quantitative inline determination of all reactants simultaneously. Moreover, even high viscous multiphase systems on industrial scale can be monitored with a single probe in presence of up to 4 phases, as shown by the biocatalytic synthesis of myristyl myristate in a bubble column².

  In process development, local determination of characteristic key parameters is possible, e.g. mass transport coefficients of CO₂in bubble columns or residence time distributions by means of IR-active tracers.* Here, first results from measurements with multiple ATR-probes will be presented. The local determination of parameters adds a layer of space resolution to the measurements, creating new possibilities for the development and validation of scale independent models.

  In case of transmission measurements, due to the relatively high absorbance of samples in the mid-infrared, a layer thickness of a few micrometers is required, hampering sample preparation. The limited applicability was overcome by the development of IR-transparent microreactors and microtiter plates, which are presented here. These devices open new possibilities for the screening of enzymatically catalyzed reactions.

*This project is supported by the Bundesministerium für Bildung und Forschung within the scope of the interdisciplinary project "Chemical Processing: Multiscale Modeling of Multiphase Reactors (Multi-Phase)", which arose from a pilot project out of the network „Campus Blasensäulen“.