Mixing time scales are derived from heat flux profiles for an instantaneous and exothermic reaction in a commercially available microreactor. A continuous reaction calorimeter, based on numerous heat flux sensors, is used to record spatially resolved heat flux profiles in steady state. Total volumetric flow rate is varied at constant flow rate ratio and the region of main reaction progress is shifted within the microreactor according to the advancement of the mixing process. Secondary flow patterns, induced by Dean mixing elements within the microchannel at higher flow rates, enhance the mixing. Results display a decrease in mixing time at increased flow rates and energy dissipation rate. Additionally, the passive micromixer is evaluated regarding its efficiency.
Continuous flow calorimeters are a promising tool in process development and safety engineering, particularly for flow chemistry applications. An isoperibolic flow calorimeter is presented for the characterization of exothermic reactions. The calorimeter is adapted to commercially available plate microreactors made of glass and uses Seebeck elements to quantify the heat of reaction. For automation of calibration procedures and calorimetric measurements, the device is connected to a lab automation system. Reaction enthalpy of exothermic reactions is determined via an energy balance of the entire calorimeter. Characterization of reaction kinetics is carried out via a local balancing of the individual Seebeck elements without changing the experimental setup, while using the previous measurements and additional ones at higher flow rates. The calorimeter and the associated measurement procedures were tested with the oxidation of sodium thiosulfate using hydrogen peroxide. Reaction enthalpy was determined to be 594.3 ± 0.7 kJ mol−1, which is within the range of literature values.
Fast chemical process development is inevitably linked to an optimized determination of thermokinetic data of chemical reactions. A miniaturized flow calorimeter enables increased sensitivity when examining small amounts of reactants in a short time compared to traditional batch equipment. Therefore, a methodology to determine optimal reaction conditions for calorimetric measurement experiments was developed and is presented in this contribution. Within the methodology, short-cut calculations are supplemented by computational fluid dynamics (CFD) simulations for a better representation of the hydrodynamics within the microreactor. This approach leads to the effective design of experiments. Unfavourable experimental conditions for kinetics experiments are determined in advance and therefore, need not to be considered during design of experiments. The methodology is tested for an instantaneous acid-base reaction. Good agreement of simulations was obtained with experimental data. Thus, the prediction of the hydrodynamics is enabled and the first steps towards a digital twin of the calorimeter are performed. The flow rates proposed by the methodology are tested for the determination of reaction enthalpy and showed that reasonable experimental settings resulted. Graphical abstract A methodology is suggested to evaluate optimal reaction conditions for efficientacquisition of kinetic data. The experimental design space is limited by thestepwise determination of important time scales based on specified input data.
A software‐guided, continuous reaction calorimeter based on thermoelectric modules for direct heat flux measurements is presented. Sensors and actuators of the calorimeter's setup are implemented within a lab automation system, which enables the automated calibration of the heat flux sensors and investigations of chemical reactions through sequential function charts. Functionality of the calibration is shown by heat transfer experiments. Additionally, the calorimeter's performance is demonstrated by good agreement of conducted neutralization experiments with literature data.
Calorimetric data from chemical reactions such as reaction enthalpy, adiabatic temperature rise, and activation energy are essential for reaction safety and scale-up from laboratory investigations to reactor design and operation. Typically, these data are gained from batch calorimeters with sophisticated setups and elaborate measurement procedures. Continuous flow calorimeters, compared with batch setups, have different mixing and heat transfer characteristics and enable harsh reaction conditions, particularly within microstructured reactors with their enhanced heat transfer capability. This review provides an overview of currently investigated and applied flow calorimeters in research and development in relation to existing concepts. Novel approaches for heat flux measurements as well as integrated sensors are presented. Safety aspects of flow chemistry are a main driver, but additionally, low material consumption is important in early process development. Limitations of the concepts are presented with a comprehensive literature overview of flow calorimetry to show that continuous flow calorimeters form a new tool in process development and safety engineering, particularly with microstructured devices and novel sensing techniques.
Recent studies showed the superior separation performance of stirred‐pulsed columns of different diameters in liquid‐liquid extraction processes. Here, an efficient shortcut method will be presented, which is time and resource‐efficient as well as cost‐effective to determine the operational window of these columns for industrial separation tasks. Savings in time of less experiments and costs of materials consumption can be estimated with up to 30 %. The presented method is particularly suitable before the application of new chemical systems, which are particularly cost‐intensive and scarce in material supply.
Continuous manurfacturing and development of flow processes depend significantly on an optimized and adapted determination of thermokinetic data of chemical reations. Reaction calorimetry represents a prominent technique to quantify the...
Unifying research data collection methods and capturing data streams in an organized and standardized manner are becoming increasingly important in laboratories as digital processes and automation progressively shape the laboratory workflows. In this context, the Internet of Things (IoT) not only offers the opportunity to minimize time-consuming and repetitive tasks by delegating them to machines, but it also supports scientists in curating data. As a contribution to the establishment of IoT tools in academic research laboratories, a microscale reaction calorimeter is exemplarily connected to a modular open-source IoT-platform. The microcalorimeter’s process data is streamed to the data platform for data repository and analysis. Advantages of the platform from academia’s point of view are presented. Finally, the application of the platform was successfully tested with the hydrolysis of acetic anhydride. The data were accessed and analyzed exclusively via the IoT-platform, which provided important advantages for the operator in terms of standardized evaluation in just a few steps.
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