•Materials for microreactor fabrication, fabrication methods, and design principles are presented.•Challenges in microreactor commercialization and need for integrated process is ...highlighted.•Applications of microreactors in the field of nanoparticles, polymers, organic chemicals, and medicines are presented.
This review focuses on the latest trends and advancements in microstructured reactors. With the recent drive towards the production of miniaturized systems, microstructured reactors have gained significant prominence in the chemical and process industries. Herein, we describe the fabrication, commercial aspects, design principles, and cutting-edge applications of microreactors. An overview of the significant areas of application under broad categories such as biological and pharmaceutical applications, inorganic and noble metal nanoparticles, and organic chemicals and polymers is also included. Finally, the article discusses future research prospects and key issues on microstructured reactors.
Continuous‐flow photochemistry is used increasingly by researchers in academia and industry to facilitate photochemical processes and their subsequent scale‐up. However, without detailed knowledge ...concerning the engineering aspects of photochemistry, it can be quite challenging to develop a suitable photochemical microreactor for a given reaction. In this review, we provide an up‐to‐date overview of both technological and chemical aspects associated with photochemical processes in microreactors. Important design considerations, such as light sources, material selection, and solvent constraints are discussed. In addition, a detailed description of photon and mass‐transfer phenomena in microreactors is made and fundamental principles are deduced for making a judicious choice for a suitable photomicroreactor. The advantages of microreactor technology for photochemistry are described for UV and visible‐light driven photochemical processes and are compared with their batch counterparts. In addition, different scale‐up strategies and limitations of continuous‐flow microreactors are discussed.
Light up your chemistry! Continuous‐flow photochemistry is used increasingly by researchers in academia and industry to facilitate photochemical processes and their subsequent scale‐up. This Review provides an up‐to‐date overview of both technological and chemical aspects associated with photochemical processes in microreactors.
The simulation of heat pipe microreactors is an active area of research. In this paper, a thermal analysis of a heat pipe microreactor motivated by the eVinci™ design is performed. Thorough ...discussion on the modeling of heat pipes without a dedicated heat pipe modeling code, such as Sockeye, is also provided. The performance of two heat pipe modeling techniques is compared, one a more accurate approach which explicitly tracks heat pipe temperatures, and the other an approximation which simplifies the thermal hydraulic model development. One-way coupling is used where the Serpent neutronics code is used to generate a power distribution which is applied in an OpenFOAM model to calculate a temperature distribution. After a detailed convergence analysis, the core temperature distribution resulting from a core with control drums facing outward, or fully withdrawn, is compared with one having the control drums facing inward, or fully inserted. Finally, a parametric analysis was performed where the thermal resistances associated with the heat pipe model were varied and core temperatures were tracked. It was observed that the relationship between average and maximum core temperatures had a highly linear relationship to the thermal resistances used in the heat pipe model.
•OpenFOAM performs thermal simulations on an eVinci-like microreactor.•Serpent code generates power distribution; OpenFOAM calculates temperature.•A simplified heat pipe model based on a thermal resistance network is used.•Different iterative procedures for solving temperatures are explored.
The external quenching method based on flow microreactors allows the generation and use of short‐lived fluoro‐substituted methyllithium reagents, such as fluoromethyllithium, fluoroiodomethyllithium, ...and fluoroiodostannylmethyllithium. Highly chemoselective reactions have been developed, opening new opportunities in the synthesis of fluorinated molecules using fluorinated organometallics.
Quenched: An external quenching method based on flow microreactors allows the generation and use of short‐lived fluoro‐substituted methyllithium agents, such as fluoromethyllithium, fluoroiodomethyllithium, and fluoroiodostannylmethyllithium. Highly chemoselective reactions have been developed, opening new opportunities in the synthesis of fluorinated molecules using fluorinated organometallics. LDA=lithium diisopropylamide.
•Efficient glucose-to-FA conversion was achieved in a continuous flow microreactor.•Possible intermediates were extensively examined while DFT was used to calculate different C–C bond cleavage ...energies of glucose and fructose.•Plausible reaction pathways were proposed for the conversion of glucose to FA catalyzed by HPA-2.•Sources of CO2 influencing the FA yield were discovered for the conversion of glucose catalyzed by HPA-2.
The process of converting glucose into formic acid (FA) has been explored as a promising route for using biomass as a renewable feedstock for green chemical manufacturing. However, the most commonly used batch-tank reactor systems currently suffer from several drawbacks, including extended processing time, limited product selectivity, and high energy consumption, while the underlying reaction paths have been poorly understood. In this work, a continuous flow microchannel reactor was employed for the glucose conversion catalyzed by H5PV2Mo10O40 with O2 as an oxidant. The influence of various parameters on the conversion rate of glucose and the FA yield was characterized. Experimental results indicated that with a residence time of less than 3 min, the glucose was completely converted, and the highest FA yield reached 82.40 %. Extensive examination on the apparent by-products revealed that most of them acted as intermediates to produce FA through various pathways, including glyoxal, glyceraldehyde and glycolaldehyde as key intermediates for the oxidation of glucose to FA. Furthermore, the density functional theory (DFT) method was used to determine the bond energies of different C–C bond cleavage modes of substrate glucose and fructose produced by the isomerization of glucose. Experimentally, the conversion of three main intermediates and some other possible intermediates and their FA yield were measured with different residence time. It was also found that the CO2 was produced through the decarboxylation of α-hydroxy and α-carbonyl carboxylic acid compounds, while the aldehyde groups in the compounds were more likely converted to FA by the α-carbon bond cleavage. Finally, plausible reaction pathways were proposed for the process of glucose-to-FA catalyzed by HPA-2, providing useful guidance for the identification of side reaction pathways and further improvement of FA yield.
Photochemical activation routes are gaining the attention of the scientific community since they can offer an alternative to the traditional chemical industry that mainly utilizes thermochemical ...activation of molecules. Photoreactions are fast and selective, which would potentially reduce the downstream costs significantly if the process is optimized properly. With the transition towards green chemistry, the traditional batch photoreactor operation is becoming abundant in this field. Process intensification efforts led to micro- and mesostructured flow photoreactors. In this work, we are reviewing structured photoreactors by elaborating on the bottleneck of this field: the development of an efficient scale-up strategy. In line with this, micro- and mesostructured bench-scale photoreactors were evaluated based on a new benchmark called photochemical space time yield (mol·day
·kW
), which takes into account the energy efficiency of the photoreactors. It was manifested that along with the selection of the photoreactor dimensions and an appropriate light source, optimization of the process conditions, such as the residence time and the concentration of the photoactive molecule is also crucial for an efficient photoreactor operation. In this paper, we are aiming to give a comprehensive understanding for scale-up strategies by benchmarking selected photoreactors and by discussing transport phenomena in several other photoreactors.
•The hydrodynamics, mixing and mass transfer of two-phase processes are reviewed.•Bubble/droplet formation mechanism and scaling models are summarized.•The dynamic behavior during formation stage is ...highlighted.•The circulation topology and mixing inside both droplets and slugs are discussed.•The interfacial mass transfer regimes and simulative models are presented.
Microreaction technology is preferential in process intensification and chemical synthesis, especially in multiphase applications. A thorough understanding of the hydrodynamics and mass transfer is the pre-requisite for implementing such applications. This review discusses the recent progress on the flow and mass transfer of two-phase systems in microchannels, in a multi-scale view from local mechanism to global behavior. The flow patterns, the formation of bubbles/droplets, and the manipulation of bubbles/droplets are presented and discussed in detail. The mass transfer aspects include the velocity profile and mixing inside droplets/slugs, as well as the interfacial mass transfer mechanism and simulative models. The aim of the review is to show directly the physical ingredients which determine the transport phenomena, help explain the observed behavior, and guide reactor design. To simplify the physical ingredients, the attention is focused on straight channels while phenomena in other channels (e.g., meandering channel) are neglected.
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•H2SO4-catalyzed selective dehydration of fructose over glucose to HMF was studied.•Direct sugar/HMF degradation to formic acid was confirmed by ESI-MS spectroscopy.•Phase volume ...change was included in the kinetic modelling of biphasic systems.•Microreactors were used to address process intensification and scale-up aspects.•81% HMF yield was obtained from 10 wt% high fructose corn syrup in a microreactor.
A two-step process combining the (equilibrium) glucose isomerization to fructose with selective dehydration of fructose in the obtained sugar mixture to 5-hydroxymethylfurfural (HMF), where glucose is largely unconverted and recycled, represents an attractive concept to increase the overall efficiency for HMF synthesis. This work presents experimental and modelling studies on the conversion of such fructose-glucose mixture to HMF using the sulfuric acid catalyst in a water-methyl isobutyl ketone biphasic system under a wide range of conditions (e.g., temperature, catalyst and sugar concentrations). Through detailed product analyses and ESI-MS spectroscopy, the excess formation of formic acid (together with humins) by the direct sugar/HMF degradation was confirmed and included in the reaction network (neglected in most literatures). The kinetic modelling based on batch experiments in monophasic water well describes the measurements thereof, whereas distinct deviations were found in the prediction of typical literature kinetic models. The incorporation of HMF equilibrium extraction into the developed kinetic model, with consideration of phase volume change as a function of temperature and partial phase miscibility, enables to predict reaction results in the biphasic system in batch. This kinetic model allows to optimize conditions for HMF synthesis that are favored in continuous reactors with minimized back mixing. Based on the model implications, the biphasic system was optimized with slug flow microreactors to better address process intensification and scale-up aspects. Using a simulated fructose-glucose mixture feedstock to represent commercially available high fructose corn syrups, a maximum HMF yield of 81% was obtained at 155 °C over 0.05 M H2SO4 at a residence time of 16 min in the microreactor, with 96% fructose conversion and over 95% of glucose remaining unconverted.
•Decomposition of co-precipitation process into unit operations allowed to distinguish four dedicated elements of reactors.•Microreactors were shown as most appropriate devices for nanoparticles ...synthesis by co-precipitation.•Co-precipitation in microreactors allows to produce nanoparticles with improved characteristics.•The temperature growth in microreactor with free impinging jets is negligible.•Smaller size of nanoparticles correlates with better micromixing conditions in microreactors compared to usual reactors.
The aim of the paper was to formulate the concept of controlled solution synthesis (a version of co-precipitation method) and to demonstrate its realization on several types of reactors, with a special focus on microreactors with free impinging jets (MRFIJ). The objects of this work are (i) co-precipitation method for synthesis of nanoparticles and (ii) various types of microreactors as a structured system consisting from dedicated elements. The procedure consisted on the decomposition of the total process into unit operations with further analysis of their spatial and temporal characteristics. It was shown that the elements for following unit operations should be presented in the microreactor: premixing; converging clusters (intense mixing in a thin layer/channel); ripening of nuclei; particle separation. Microreactors were shown as most appropriate devices for nanoparticles synthesis by co-precipitation method. Particularly, three case studies of co-precipitation synthesis in MRFIJ demonstrated possibility to produce nanoparticles having narrow particle size distribution (dmean: BiFeO3 – 20 nm, CoFe2O4 – 12 nm, GdFeO3 – 30 nm), without impurities of other phases and improved characteristics (e.g. low coercivity for GdFeO3 which makes it possible to use them as MRI-contrast agents) with high performance (4.3 m3/day). Besides, the temperature increase due to the energy dissipation in the liquid sheet in MRFIJ was analysed: it does not exceed 0.001 K and 0.2 K for characteristic jet velocities of 3.35 m/s and 40 m/s, correspondingly.
•Peroxidation and oxidation reactions are carried out simultaneously.•Safety is ensured by in situ generation and consumption of peroxyacetic acid.•Three-stream micromixing process has advantages in ...residence time and instantaneous volume.•Saves reaction time in 90% and increase productivity by 12 times.
2,3-dimethyl-4-methylsulfonylbromobenzene(BDSO) is an important intermediate of topramezone, a highly effective corn herbicide. However, its synthesis requires peroxyacetic acid as oxidant and poses a safety risk. In this work, a continuous flow to in situ generations of peroxyacetic acid and thioether oxidation for the preparation of BDSO was developed using a three-stream micromixing process. By in-situ generation and consumption of peroxyacetic acid, the safety hazard of peroxyacetic acid was eliminated, and a green and efficient preparation of BDSO was also achieved. Compared to the batch reactor, the three-stream micromixing process has a shorter residence time(6 min), and higher space-time yield(8.56 mol L−1 h−1). This method has great potential in industrial applications.
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