(624b) Reaction Calorimetry in Continuous Flow: Recent Advances and Applications in Flow Chemistry

In order to obtain crucial information regarding risk, scalability and criticality of chemical reactions and processes, reaction calorimetry is a key method to quantify the relevant data, such as reaction enthalpy, adiabatic temperature rise, or activation energy. Traditionally, calorimetric measurements are carried out in commercially available reaction calorimeters that are largely based on stirred batch reactors, with reaction vessels between 15 mL and 2 L capacity, displaying for certain transformations rather large laboratory equipment.¹ Although batch calorimetry is still state-of-the-art, it has several limitations for reaction conditions typically carried out in continuously operated microreactors. The small reactor dimensions of these reactors allow for rapid mixing and enhanced mass and heat transfer rates due to very high surface-to-volume ratios. Moreover, micro reaction technology also makes it possible to manage difficult process conditions precisely and is therefore particularly suitable for calorimetry under continuous flow conditions. A major driver are safety aspects of flow chemistry, but early process development also places an emphasis on minimal material use. Hence, reaction calorimetry in continuous flow is an effective method that strongly supports initiatives to enhance yield, conversion and selectivity and facilitates process automation.

This presentation will provide a general overview on continuous flow calorimetry with a specific focus on a device developed in our group.² The isothermal heat flow calorimeter consists mainly of 3D printed parts, which can be adapted and reassembled easily to meet user‑defined applications. The calorimeter segments are temperature-regulated independently of each other by a microcontroller, allowing isothermal operation conditions and locally resolved measurements. The usefulness and applicability of the designed calorimeter will be shown for important reactions, such as neutralizations, nitrations and flash chemistry³, as well as for heat capacity and mixing enthalpy measurements with good agreement of the obtained values with literature data.

(1) Frede, T. A.; Maier, M. C.; Kockmann, N.; Gruber-Woelfler, H. Advances in Continuous Flow Calorimetry. Organic Process Research and Development. 2022, pp 267–277. https://doi.org/10.1021/acs.oprd.1c00437.

(2) Maier, M. C.; Leitner, M.; Kappe, C. O.; Gruber-Woelfler, H. A Modular 3D Printed Isothermal Heat Flow Calorimeter for Reaction Calorimetry in Continuous Flow. React. Chem. Eng. 2020, 5 (8), 1410–1420. https://doi.org/10.1039/d0re00122h.

(3) Fu, G.; Jiang, J.; Hone, C. A.; Kappe, C. O. Thermal Characterization of Highly Exothermic Flash Chemistry in a Continuous Flow Calorimeter. React. Chem. Eng. 2022, 8 (3), 577–591. https://doi.org/10.1039/d2re00439a.