Thermolysis of 1,3-dioxin-4-ones: fast generation of kinetic data using in-line analysis under flow

• Thomas Durand^a
• Cyril Henry^a
• David Bolien^a
• David C. Harrowven^a
• Sally Bloodworth^a
• Xavier Franck^b
• Richard J. Whitby^{* a}

• ^a Chemistry, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton, UK
• ^b Normandie Université, COBRA, UMR 6014 & FR 3038, Université de Rouen, INSA Rouen, CNRS, 1 rue Tesnière, 76821 Mont-Saint-Aignan Cedex, France

Rapid acquisition of kinetic data is demonstrated with a commercial meso-scale flow reactor, using a step-change in flow rate or ‘push-out’ from the flow line. For thermolysis of 1,3-dioxin-4-ones (1), we obtain excellent reproducibility in the activation energies measured from spectroscopic data collected by in-line UV or transmission FT-IR monitoring of the output during the transitional period between two flow rates (±3 kJ mol−1, 0.7 kcal mol−1). Analysis of multi-component UV and IR data is conducted using an orthogonal projection approach (multivariate curve resolution by alternating least squares) for complex spectra, or by calibration-less integration of non-overlapping peak absorbance. All analysis methods were validated using off-line 1H NMR analysis, and kinetic parameters obtained using the method of a flow rate step-change were validated against conventional steady-state measurements in which time-series data were acquired across multiple experiments. Thermal transfer and dispersion effects are addressed. The experimental methods described herein are valuable for accelerated reaction study and in process development.

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