Reaction Calorimetry in Microreactor Environments-Measuring Heat of Reaction by Isothermal Heat Flux Calorimetry

摘要

A novel setup to analyze the heat of reaction of different single- and multiphase reactions carried out in continuous flow is presented. The measurement principle of the calorimetric system is based on true heat flow measurements and therefore ensures precise calorimetric data within 10 mW resolution. In addition to the investigation of simple mixing phenomena (ethylene glycol and water), a number of exothermic, industrially relevant chemical transformations including the nitration of phenol, the reduction of nitrobenzene, as well as several oxidation and reduction processes, were investigated as model systems. For these experiments a commercially available batch calorimeter (ChemiSens CPA202) was equipped with a glass static mixer (250 mu L) optionally connected to a tubular microreactor (PFA coil) allowing overall reaction volumes of up to ca. 5.5 mL. Experiments were performed by feeding individual streams with syringe pumps (alternatively substituting one liquid feed with a gaseous feed controlled by a mass flow controller) and mixing the feeds inside the glass static mixer contained in the thermostatted reactor zone of the calorimeter. By adjusting the residence time, volume, and flow rates, chemical transformations were driven to full conversion in order to obtain meaningful calorimetric data. A comparison with literature data indicates that the calorimetric flow system described herein provides comparable data to those obtained by standard batch calorimetry.