Flow microcalorimetry for kinetic measurements in microreactors

Microstructured reactors have seen remarkable research activity over the last decade. The incentive for applying microreactors often lies in the possibility to operate under conditions which cannot safely be reached in conventional equipment; e. g. elevated temperatures and pressures. While some microreactor processes are already applied on technical scale, online monitoring and in situ measurement techniques for reaction variables in microreactors, such as the local reaction temperature, are decidedly less developed. In this work, a micro flow calorimeter (by Fraunhofer ICT, Pfinztal) is used to investigate the reaction kinetics of a highly exothermic reaction in a microreactor. The calorimeter design allows measuring the local heat fluxes generated by the reaction. The kinetics can then be obtained by comparing the experimental results to a numerical reactor model and fitting the kinetic parameters. Results: It could be shown that the conventional reaction scheme is valid for temperatures of up to 180 °C, but is incomplete as it does not allow for side product generation at higher temperatures. A more accurate model is proposed. The micro flow calorimeter proved to be a valuable tool for in situ kinetic measurements in microreactors.