Seebeck Calorimeter for the Characterization of Highly Exothermic Reactions in a Microreactor Made From PVDF-Foils

Abstract

Reaction calorimetry is one of the most important steps in designing chemical reactors. This contribution describes a continuously operated micro calorimeter using Seebeck elements for microreactors made of PVDF-foils. Seebeck elements allow for local and temporal resolution of heat flux profiles. Various calibration methods for the Seebeck effect based heat flux sensors are presented. Here, the direct correlation between measured thermoelectric voltage and heat flux is found to be the most promising one. Commissioning of the calorimeter and validation of its performance are done by means of heat transfer measurement of warm water and an acid base reaction. Obtained reaction enthalpy values of the neutralization reaction of acetic acid and sodium hydroxide agree very well with literature data. The progression of the reaction can be followed optically using phenolphthalein as color indicator and can be compared to measured data. Heat profiles over the course of the microreactor were shown and checked for consistency. Consequently, this approach helps to characterize reactors and aids reactor development.

Mixing Time Scale Determination in Microchannels Using Reaction Calorimetry

“…A Joule heat source is placed on the upper side of the SEs, which themselves are placed on the base plate, and the resulting thermoelectric voltage is correlated to the heat flux passing through the respective element. Each SE has to be calibrated separately and the regarding method has been described in detail in previous works .…”

“…A locally resolved heat flux profile is recorded for the microreactor in steady state and the peak position gives the location of main reaction progress. The reaction calorimeter and its measurement technique have been introduced in previous works , . The calibration of heat flux sensors has been shown and reaction enthalpies were determined for acid‐base reactions.…”

Equipment and Separation Units for Flow Chemistry Applications and Process Development

“…A reaction calorimeter for plate reactors was designed, which uses an array of Seebeck elements as heat flow sensors on the underside of the reactor , (see Fig. ).…”

“…With this setup, neutralization reactions (single‐proton, HCl, and multi‐proton, H 2 SO 4 , H 3 PO 4 ) and the strongly exothermic oxidation of sodium thiosulfate with hydrogen peroxide were measured as test systems with regard to their neutralization and reaction enthalpy. Furthermore, studies on the thermal passage of thiosulfate oxidation could be safely carried out in the microreactor . The average accuracy of the measurements is ± 3 %.…”

Ultrasonic Fabrication of Polymer Plate Reactors with a Surface Coating

“…Each segment is linked to one Seebeck element. Thermodynamic and kinetic data of highly exothermic reactions can be obtained using the microcalorimeter in combination with the surface‐coated microreactor. In Fig.…”