Simultaneous determination of enthalpy of mixing and reaction using milli-scale continuous flow calorimetry

Abstract

A simultaneous determination of the enthalpy of mixing and reaction in a scalable continuous milli-scale flow calorimeter is investigated. As obtained calorimetric data is pivotal for the safety assessment of chemical reactions and processes. The acid-catalysed selective, homogeneous hydrolysis of acetic anhydride with half-lives from a few seconds to a few minutes is investigated as a model reaction. For the enthalpy of mixing 7.2 ± 2.8 kJ/mol and for the enthalpy of reaction −60.8 ± 2.5 kJ/mol were determined. For reactions that show complete conversion in the continuous reactor, a technique is introduced to further improve the accuracy of the reaction enthalpy determination. Thereby, the resolution of the observed temperature profile is increased by measuring the profile at different flow rates. Applying this procedure, the reaction enthalpy of −62.5 kJ/mol was determined which is in good agreement with literature values for this model reaction. Graphical abstract

Design and characterization of a flow reaction calorimeter based on FlowPlate® Lab and Peltier elements

“…The reaction follows a pseudo first-order kinetics when a large excess of water is used and features a reaction enthalpy of approximately −62 kJ mol −1 . 25,28 Experimental procedure. Prior to the calorimetric measurements, the setup is preheated for about one hour to ensure a constant temperature inside the enclosure.…”

“…In literature, an endothermic mixing enthalpy is reported, 25,28,57 which has to be considered as well. The reaction and mixing enthalpy reported from Ładosz et al 25 and Steinemann et al 28 was also determined using flow calorimetry, which is why they are used as a reference. If the heat of mixing, reported by Ładosz et al 25 of approx.…”

“…For this purpose, FTIR has been used in the literature as an example. 25,28 Conclusions A microfluidic flow calorimeter was developed based on FlowPlate® Lab from Ehrfeld Mikrotechnik and PEs for determination of reaction enthalpy in both isoperibolic and isothermal operation mode. Therefore, the existing microreactor system was expanded to include a sensor array consisting of 14 PEs enabling isothermal and isoperibolic operation mode.…”

“…27 In their setup, a jacketed tubular reactor is equipped with ten temperature probes, enabling temperature profile measurements along the reaction channel. 9,16,28 The microcalorimeter developed by the Fraunhofer ICT, Pfinztal, Germany, is also commercially available and is based on heat flux measurement through Seebeck elements. 29 It is also to be seen as a model for the other calorimeters developed by Reichmann et al, 20,21 Maier et al, 24 Ładosz et al, 25 and Frede et al 30 In this work, a commercially available hastelloy C-22 microreactor from Ehrfeld Mikrotechnik GmbH, Wendelsheim, Germany, is equipped with a sensor array consisting of 14 Peltier elements (PEs) and five temperature sensors to develop a microscale flow platform for parameter determination of highly exothermic reactions.…”

Thermal characterization of highly exothermic flash chemistry in a continuous flow calorimeter

“…Furthermore, they presented a procedure to simultaneously decouple the heat of reaction and heat of mixing. 32 However, to measure the temperature these sensors have to be embedded into the channel and may influence the flow behavior, and a number of sensors are needed to obtain the temperature profile. Determination of the heat transfer coefficient is usually needed for this type of flow calorimetry.…”