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CO2 methanation is the catalytic reduction of CO2 to methane, which is accompanied by side reactions that produce CO. Being an equilibrium-limited exothermic reaction, thermal management is essential for good reactor performance. We analyze efficient thermal coupling by transferring the heat of reaction from outlet to the inlet stream in a single thermally-integrated microreactor with counter-current flow. We use CFD simulations to compare two modes of heat removal, viz. external cooling and feed dilution, over a wide range of operating conditions. In one mode of operation, undiluted feed is processed with external cooling using air in counter flow (air-cooled reactor) and in the other, diluted reactant mixtures in alternate channels exchange heat counter-currently as the reaction proceeds (counter-current reactor). Depending on the inlet temperature, a favorable temperature profile that improves conversion to methane forms in each reactor. For the base case, 67 % CO2 conversion is obtained, with CH4 selectivity of 88 % and 91 % in air-cooled and counter-current reactors, respectively. Counter-current reactor shows autothermal operation with feed at ambient temperature while air-cooled reactor gives good performance at higher inlet temperatures. It is possible to attain high selectivity to methane through appropriate choice of operating conditions.

Reproducible and controllable incorporation and immobilization of catalysts and other active particles onto silicone microreactor channels is still challenging. In this work, we present an innovative fabrication protocol to attain affordable, custom-designed photocatalytic microreactors in a fast and simple manner. In this protocol, a 3D-printed ABS microreactor mold is first dip-coated with the photocatalyst, and subsequently, the catalytic layer is transferred onto the microchannel walls by indirect immobilization during the silicone casting and scaffold removal step. Serpentine-shaped microreactors have been satisfactorily fabricated with Au@POM-impregnated TiO2 nanoparticles (Au@POM/TiO2; Au 0.18 % w/w, POM: H3PW12O40) as the integrated photocatalytic layer. The suitability of our fabrication method has been validated on the basis of the excellent photocatalytic performance shown by the microreactors in a model test reaction such as the continuous-flow photoreduction of 4-nitrophenol to 4-aminophenol with NaBH4 and monitored by UV-Vis spectroscopy. Financial support from Gobierno de Navarra (grants PC025-26 and PI030) an Spanish Ministerio de Ciencia, Innovación y Universidades, and the European Regional Development Fund (ERDF/FEDER) (grant RTI2018-096294-B-C31) is gratefully acknowledged. I.P. and S.R. thank Obra Social la Caixa, Fundación Caja Navarra and Universidad Pública de Navarra (UPNA) for their research contracts in the framework of the programs 'Ayudas Postdoctorales' and 'Captación del Talento'. L.M.G. thanks Banco de Santander and UPNA for their financial support under 'Programa de Intensificación de la Investigación 2018' initiative. Centro Tecnológico Lurederra is gratefully acknowledged for its partnership in the project FOREST (PC025-026).

A quartz microreactor containing 28 microchannels of 500 µm width and 105 mm length has been used to photoproduce hydrogen from liquid water-ethanol using an Au/TiO2 photocatalyst and UV light. The photomicroreactor has been tested in two flow configurations: (i) as a catalytic wall photoreactor by coating the microchannels with the photocatalyst, and (ii) as a slurry photoreactor by dispersing the photocatalyst in the liquid mixture of water-ethanol. The catalytic wall photoreactor configuration shows superior performance, with hydrogen yields more than three times higher than those obtained with the best slurry configuration under the same operation conditions.

Conversion of syngas (CO + CO2 + H2) to dimethyl ether (DME) with in–situ steam separation is modeled in a membrane integrated, isothermal catalytic microchannel reactor. Reaction channel, involving washcoated form of physically mixed Cu–ZnO/Al2O3 and HZSM–5 catalysts, is separated from the permeate channel by a supported sodalite (SOD) membrane layer. Conservation of momentum and mass within the porous washcoat and the channels, and cross–membrane material transport are modeled in two dimensions at steady–state to elucidate the effects of temperature, pressure, syngas composition and permeate flow properties. Dosing syngas to both channels at 523 K, 50 bar, CO2/COx (COx: CO + CO2) = 0.5 and H2/COx = 2.0 gives CO and CO2 conversions, and DME yield of 33.2, 12.4 and 15.3 %, respectively, which are 29.9, 7.2 and 12.7 % without membrane. These findings are coherent with relaxed thermodynamic limitations on methanol synthesis and dehydration upon selective H2O removal. Higher permeate syngas flow rates promote steam efflux and H2 influx across the membrane and further elevate CO2 conversion and DME yield up to 15.8 and 17.4 %, respectively. These metrics can be improved up to 23.4 and 22.9 %, respectively upon dosing pure H2 as the permeate fluid. However, a positive pressure gradient from reaction to permeate channel does not improve reactor performance. Coherent with its higher dehydration activity, HZSM–5 responds to membrane assistance stronger than γ–Al2O3.

The paper compares conceptual designs of a microstructured reactor/heat-exchanger for the small-scale production of C8+ range hydrocarbons from methanol over H-ZSM-5 catalytic coatings. In these designs, air was used as a cooling fluid in the adjacent cooling channels. The heat transfer characteristics of a single-zone reactor (with channels 500 μm in diameter) and a two-zone reactor (with an additional coolant inlet) have been compared. A single reaction zone was not able to reduce the temperature gradient below 15 K, while a two-zone configuration, with a counter-current fluid flow in the upstream section and co-current flow in the downstream section, demonstrated a near-isothermal behaviour, with a mean temperature of 653 K.

The interplay of heat and mass transfer in a gas/liquid/solid or heterogeneous catalytic microreactor, in which bubbles grow on a surface, is highly complex. Specifically, distortion of the fluid due to the protrusion and the location of the bubbles can affect transport phenomena, and, in turn, the chemical conversion. Therefore, understanding nucleation and growth of bubbles within microreactors is desirable to optimize reactor performance. A promising approach to that end, and to ultimately control transport phenomena in multiphase catalytic microreactors, is to direct the nucleation of bubbles. For this purpose, we report here a microfluidic device that contains hydrophobic micropits along the smooth floor of a rectangular cross-section microchannel, which were patterned in a silicon substrate using deep reactive ion etching. The pits are intended to act as nucleation sites. Device performance was evaluated for the two cases of boiling of water and outgassing of dissolved carbon dioxide (CO2). As intended, bubbles were observed to form at the micropits, but also along the rough microchannel side walls. Confocal microscopy revealed that bubbles had spherical shapes, and formed a contact angle with the microchannel floor of >90°. The experimentally determined bubble geometry was used as the boundary condition for a 3D-numerical model. Numerical simulations indicated that the presence of bubbles had a large impact on the local flow distribution, concentration field and reaction conversion within the microreactor, and therefore on the overall conversion for a chosen model reaction.

In the present study, due to various advantages of process miniaturization, the integrated design and operation of a mobile power generation system consisting of a microreactor reformer and a proton exchange membrane fuel cell (PEMFC) are investigated. The hydrogen fuel is supplied through autothermal steam-reforming of methanol in a microreactor leading to a safer, as well as more efficient, and economical operation. A high-temperature polymer membrane fuel cell with external accessories is applied for power generation. Then, simulation-optimization programming is applied for simultaneously optimizing the process design and operation at the same level. The result shows that the implemented procedure ensures the economic and flexible operation of the process while satisfying the safety constraints. The maximum gross power and net power generation are 109.3 and 91.9, respectively, while the cost of hydrogen production reduces from 13 to 20 $/kg to 7.7 $/kg. The fuel (methanol) consumption can be as low as 0.42 L/kWh.

Methanol steam reforming (MSR) is an attractive option for in-situ hydrogen production and to supply for transportation and industrial applications. This paper presents a novel thermally autonomous MSR microreactor that uses silicon carbide (SiC) honeycomb ceramic as a catalyst support to enhance energy conversion efficiency and hydrogen production. The structural design and working principle of the MSR microreactor are described along with the development of a 3D numerical model to study the heat transfer and fluid flow characteristics. The simulation results indicate that the proposed microreactor has a significantly low drop in pressure and more uniform temperature distribution in the SiC ceramic support. Further, the microreactor was developed and an experimental setup was conducted to test its hydrogen production performance. The experimental results show that the developed microreactor can be operated as thermally autonomous to reach its target working temperature within 9 min. The maximum energy efficiency of the microreactor is 67.85% and a hydrogen production of 316.37 ml/min can be achieved at an inlet methanol flow rate of 360 μl/min. The obtained results demonstrate that SiC honeycomb ceramic with high thermal conductivity can serve as an effective catalyst support for the development of MSR microreactors for high volume and efficient hydrogen production.

Objectives. The introduction of digital tools for the development of medicines, intelligent management systems, and quality control is stipulated not only by modern requirements for the chemical and pharmaceutical industry but also by strict regulatory requirements for manufactured products. This principle ensures the release of a quality product on the first attempt. The aim of this study is to develop information support for the intelligent quality management system for the production of active pharmaceutical substances (APSs) for medicines using a fundamentally new technology: continuous synthesis in flow microreactors. To develop the necessary information support, we developed appropriate systemic, informational, and mathematical models; algorithms for the online management of the experiment; and techniques and algorithms to qualitatively assess whether the product meets official regulatory documents.Methods. System analysis techniques, information and mathematical modeling techniques with multireference regression models, and online optimization using the Hook–Jeevs algorithm (a method of expert evaluation based on the concordance factor) were used to solve the problems formulated.Results. To manage the quality of the process of continuous APS synthesis in the flow microreactor, we developed theoretic multiple system models that were designed to build the digital information environment for the process of experimental research. We developed algorithms for mathematical modeling and optimization of the control process based on multiresponse regression models and an online optimization algorithm that allows the process to be managed step by step, taking into account the limitations. Our results show that the degree of conversion is higher in reactions that contain bromodiphenylmethan.Conclusions. Based on mathematical modeling method algorithms for the quality control of the process of continuous APS synthesis on a fundamentally new microreactor system, Qmix were developed. The applicability of the proposed methods and algorithms in the production of the drug diphenhydramine from chlorobenzohydrol and bromobenzohydrol as initial substances was proven by an experimental study. The built models were statistically adequate and valid.

It is usually necessary to first perform temperature reduction treatment to enable the catalyst to exert its catalytic activity in the subsequent process of preparing carbon nanotubes by chemical vapor deposition. In this experiment, Fe-Mo/Al2O3 catalyst was prepared based on microreactor, and the effect of reduction temperature on the microstructure of the catalyst and the morphology of carbon nanotubes was investigated. The results show that the reduction temperature has a significant effect on the microstructure of the catalyst, which in turn affects its catalytic activity and the yield and quality of carbon nanotubes. Moderately reducing the reduction temperature during the catalyst reduction process is beneficial to increase the catalytic activity of the catalyst. However, although its sintering degree could be weakened when the catalyst was reduced at an excessively low temperature of 350 °C, its catalytic efficiency was greatly reduced and the degree of defects of the catalyzed carbon nanotubes was increased. When the catalysts calcined at 450 °C and reduced at 600 °C, the catalysts show excellent catalytic activity, and catalytic efficiency can reach 74.76%. In addition, the reduction temperature also has a certain effect on carbon nanotubes. As the reduction temperature increases, the span of carbon nanotubes is relatively concentrated, but the specific gravity of the thicker outer diameter gradually increases. As for the defect degree of carbon nanotubes, the carbon nanotubes M600-600 is better and the defects are fewer when the reduction temperature is reduced from 670 °C to 600 °C.

In order to prepare carbon nanotubes with high specific surface area, small diameter, low resistivity, high purity and high catalytic activity, the Fe-Mo/Al2O3 catalyst was prepared based on the microreactor. The influence of different Fe/Al molar ratios on the catalyst and the carbon nanotubes prepared was studied through BET, SEM, TEM and other detection methods. Studies have shown that the pore structure of the catalyst is dominated by slit pores at a lower Fe/Al molar ratio. The catalytic activity is the highest when the Fe/Al molar ratio is 1:1, reaching 74.1%. When the Fe/Al molar ratio is 1:2, the catalyst has a higher specific surface area, the maximum pore size is 8.63 nm, and the four-probe resistivity and ash content of the corresponding carbon nanotubes are the lowest. The higher the proportion of aluminum, the higher the specific surface area of the catalyst and the carbon nanotubes, and the finer the diameter of the carbon nanotubes, which gradually tends to relax. The results show that when the Fe/Al molar ratio is 1:2, although the catalytic activity of the catalyst is not the highest, the carbon nanotubes prepared have the best performance.

The synthesis of α-amino acids was carried out in a continuous flow system. In this system, aldimines were efficiently generated in situ via the dehydration-condensation of aldehydes with anilines in a desiccant bed column filled with 4 A molecular sieves desiccant, followed by reaction with CO2 in an electrochemical flow microreactor to afford the α-amino acids in high to moderate yields. The present system can provide α-amino acids without using stoichiometric amounts of metal reagents or highly toxic cyanide reagents.

This work integrates the advantages of microfluidic devices, nanoparticle synthesis, and on-chip sensing of biomolecules. The concept of microreactors brings new opportunities in chemical synthesis, especially for metallic nanoparticles favorable in surface-enhanced Raman spectroscopy (SERS) for high-resolution and low-limit detection of biomolecules. However, still missing is our understanding of reactions at the microscale and how microsystems can be exploited in biosensing applications via precise control of nanomaterial synthesis. We investigate how microfluidic geometry affects nanoparticle patterning for high-resolution SERS-based sensing and propose a spiral-shaped microchannel that can achieve enhanced mixing, rapid reaction at room temperature, and uniform in situ patterning. The roles of channel geometry as the key parameter on patterning have been studied systematically to provide insight into the rational design of continuous microfluidic systems for SERS applications. We also demonstrate potential applications of this integrated system in label-free on-chip detection of 1 pM rhodamine B (enhancement factor, ∼4.3 × 1011) and a 1 nM 41-base single-stranded deoxyribonucleic acid (DNA) sequence (enhancement factor, ∼1.5 × 108). Our ready-to-use multifunctional system provides an alternative strategy for the facile fabrication of SERS-active substrates and promotes system integration, miniaturization, and on-site biological applications.

In this study, a steady-state analytical model for heat and mass transfer in a 2D micro-reactor coated with a Nickel-based catalyst is developed to investigate microscale hydrogen production. Appropriate correlations for each species’ net rate of production or consumption, mass diffusivity, and the heat of reactions are developed using a detailed reaction mechanism of methane steam reforming. The energy and species conservation equations are then solved for the reactive mixture coupled with the wall energy equation. Finally, the response surface methodology (RSM) is employed to study the effects of channel height, inlet velocity and temperature, wall thickness and conductivity, and external heat flux on CH4 conversion. It is found that the inlet gas temperature, among different parameters, has the most influence on the overall performance of the microchannel hydrogen production. Also, the maximum necessary heat of reforming reaction increases by 84% and 26% if the CH4 conversion changes from 50% to 60% and 60% to 70%, respectively. The developed analytical simulation can be a useful tool for designing experiments in micro-scale hydrogen production.

The liquid phase catalytic exchange of hydrogen isotopes is a promising process for upgrading recycle water in nuclear power station. To facilitate the isotope catalytic reaction, a series of two-dimensional hydrophobic catalysts of Pt/modified carbon nitride (Pt/s-C3N4) with different Pt loadings were fabricated and applied in microchannel reactor. Their excellent catalytic performances were found in our experiments by comparing with purchased Pt/activated carbon (Pt/AC), the Turn-Over-Frequency (TOF) of Pt/s-C3N4 is 3 times higher than Pt/AC. Because the Pt clusters of 0.82 ± 0.08 nm were uniformly distributed on the support of two-dimensional carbon nitride (C3N4) to improve availability of the Pt catalyst by exposing more active sites and decreasing effect of the internal diffusion. The catalytic activity of Pt/s-C3N4 catalysts remained stable after 1800 min reaction, whereas Pt/AC displayed a 20% drop. Hydrophobicity of the catalyst maintained its high activity and stability in the liquid phase catalytic exchange reaction.

A special type of reactor with a high active surface-to-volume ratio was used for investigation of organic pollutants degradation from a gasfield produced water by photoelectrocatalysis process. The GC–MS analysis showed that there were more than 50 organic substances in this wastewater; therefore, COD was considered as the target parameter for studying. A simple evaporation process used for decreasing high TDS of the wastewater reduced its electrical conductivity from 6300 μS/cm to 1100 μS/cm and also initial COD decreased simultaneously from 9500 mg/L to 750 mg/L. Distilled wastewater from the evaporation process was treated again by the photoelectrocatalysis process using a coil type microreactor, and its COD dropped off to 143 mg/L. Instead of usual semiconductors in photoelectrocatalysis like TiO2, boron carbon nitride (BCN) nanosheets are used as a photocatalyst in this study. Investigating the impact of different parameters on COD removal efficiency showed that the greatest COD removal efficiency (81%) was obtained at residence time 15 min, pH = 3, applied cell voltage 20 V, electrical conductivity = 2500 μS/cm and H2O2 concentration of 8 mM.

Lithium-sulfur battery is desirable for the future potential electrochemical energy storage device with advantages of high theoretical energy density, low cost and environmental friendliness. However, some natural hindrances, particularly fast capacity degradation resulting from the migration of dissolved polysulfide intermediates, remain to be significant challenges prior to the practical applications. In this work, a composite interlayer of carbon nanofibers (CNFs) which are enriched by Co-based metal organic frameworks (ZIF-67) growth in-situ is exploited. Notably, physical blocking and chemical trapping abilities are obtained synergistically from the ZIF/CNFs interlayer, which enables to restrain the dissolution of polysulfides and alleviate shuttle effect. Moreover, the three-dimensional fiber networks provide an interconnected conductive framework between each ZIF microreactor to promote fast electron transfer during cycling, thus contributing to excellent rate and cycling performance. As a result, Li-S cells with ZIF/CNFs interlayer show a high specific capacity of 1334 mAh g−1 at 1 C with an excellent cycling stability over 300 cycles. Besides, this scalable and affordable electrospinning fabrication method provides a promising approach for the design of MOFs-derived carbon materials for high performance Li-S batteries.

Combustion in catalytic microreactors has applications in portable power generation and process intensification. In this work, catalytic microcombustion of propane in two geometries – U-bend and Spiral, which have heat recirculation in counter-current and co-current configurations respectively – is investigated computationally. 2D CFD simulations are performed to analyze the performance characteristics of both the reactors and a comparative study is presented. Heat recirculation due to transverse heat transfer occurs in both the geometries. U-bend reactor is more stable than spiral over a wider range of operating conditions due to effective counter-current heat exchange. Spiral reactor has higher peak temperatures due to better internal heat recirculation and lower heat loss to the ambient. Excess enthalpy combustion in both the reactors allows combustion at lean conditions, resulting in lower temperatures and fairly uniform temperature profile, useful for coupling thermoelectrics.

In the present work, silica nanoparticles were synthesized, adapting the conventional sol-gel method in both bench and microflow systems for comparison purposes. A custom-made polydimethylsiloxane microreactor, consisting of a T-junction as droplet generator, was first designed and fabricated using the direct writing lithography method. The process involved tetraethyl orthosilicate as a precursor, acetic acid as a catalyst, and water as a hydrolyzing agent. The produced silica nanoparticles were characterized using transmission electron microscopy (TEM), Energy-dispersive X-ray (EDX), and X-ray diffraction (XRD) analysis. The silica nanoparticles produced from the bench-scaled sol-gel method showed poor monodispersity with irregular configuration and a mean particle size of 95 ± 4 nm. Meanwhile, the microflow system’s silica nanoparticles showed high monodispersity, perfectly spherical shapes, and a narrower particle size distribution with an average of 5.76 ± 1.27 nm. A reduction of particle size by about 93.94% was achieved using a microflow system. The effect of residence time on the size of silica nanoparticles was conducted by varying the operating pressure that affect the flow rate. Reducing the residence time from 95.65 s to 38.72 s reduces the size from 5.76 nm to 4.89 nm. The shorter residence time also reduces the size distribution to 1.11 nm. However, aggregation of silica nanoparticles was observed, indicating particle growth stage took place. Increasing the aging time for silica nanoparticle synthesis showed a negative effect where large silica up to 1 μm was produced hence lowering the dispersity. EDX and XRD analysis confirmed that silica nanoparticles with high purity were obtained from a droplet-based microreactor.

Lactams are cyclic amides that are indispensable as drugs and as drug candidates. Conventional lactamization includes acid-mediated approaches and coupling agent-mediated approaches that suffer from a narrow substrate scope, much waste, and/or high cost. Inexpensive, less wasteful and highly electrophilic reagent-mediated approaches are attractive, but there is an imminent risk of side reactions. Herein, we describe methods using highly electrophilic triphosgene in a micro-flow reactor that accomplish lactamization that are rapid (0.5-10 sec), mild, inexpensive, and less wasteful. We developed two methods, referred to here as A and B, using NMM and NMI, respectively. Various lactams as well as a cyclic peptide containing acid- and/or heat-labile functional groups were synthesized in good to high yields without the need for tedious purifications. Undesired reactions were successfully suppressed and the risk in handling triphosgene was minimized by the use of micro-flow technology.

Here we developed a continuous flow microreactor system to synthesis N-benzoylpiperazine, which is an important intermediate of novel nootropic Sunifiram. And the kinetics of the condensation amidation of piperazine and benzoic acid using HATU as coupling reagent was revealed in microreactor. A kinetic model was established, all the reactions kinetics parameters, including the reaction order of each reactant, rate constants, pre-exponential factors and activation energies were acquired. With this model the selectivity vs. reaction temperature/molar flow ratio were obtained to help understand this kind of reaction and further optimize operating conditions. Under the condition of using equivalent piperazine, 95.6% of selectivity and 91.2% of yield were obtained in microreactor with 50 s. To further expand the scope of carboxylic acid, cyclopropanecarboxylic acid was tried as acylating agent, and 92.8% of selectivity and 86.1% of yield were obtained in microreactor.

We present a novel multi-emitter electrospray ionization (ESI) interface for the coupling of microfluidic free-flow electrophoresis (μFFE) with mass spectrometry (MS). The effluents of the μFFE outlets are analyzed in near real-time, allowing a direct optimization of the electrophoretic separation and an online monitoring of qualitative sample compositions. The short measurement time of just a few seconds for all outlets even enables a reasonable time-dependent monitoring. As a proof of concept, we employ the multi-emitter ESI interface for the continuous identification of analytes at 15 μFFE outlets via MS to optimize the μFFE separation of important players of cellular respiration in operando. The results indicate great potential of the presented system in downstream processing control, for example, for the monitoring and purification of products in continuous-flow microreactors.

Hypothesis A binary mixture was used during injection with one water-miscible component and the other water-immiscible, which can help particles to migrate toward and then self-assemble at the interface. Experiments The ethanol-tetrachloromethane binary mixture was used to verify the self-assembly method, with the diameter of droplets being about 1 mm. As the ethanol diffused into the colloidal solution, the colloidal particles efficiently moved towards and self-assembled on the oil/water interface, while a colloidal particle film with high-coverage was able to rapidly form on the droplet surface even in an ultra-low concentration colloidal solution. The effects of ethanol concentration and particle concentration on self-assembly were investigated. Findings The driving force for self-assembly originated from the tension gradient generated by ethanol's concentration gradient at the particle/liquid interfaces, where the concentrations of ethanol and the colloidal solution had significant effects on self-assembly. The simulation and calculations results aligned well with experiments, providing the theoretical basis for this self-assembly method. Further, as-prepared magnetic particle-coated droplets transformed into a non-wetting soft solid, which had long lifetimes and could be precisely moved, coalesced, and transferred in various two-dimensional and three-dimensional liquid environments. Thus, wider applications are facilitated, such as droplet transfer, microreactor and other potential fields.

The process characteristics of two main steps in the preparation of 4-nitrobiphenyl (4-NBP) from 4-nitroaniline (PNA) were clearly revealed by applying two continuous-flow microreactors. The first step was the synthesis of 4-nitrobenzene diazonium tetrafluoroborate (4-NBDT) through the diazotization reaction. The reaction temperature, the residence time, and the molar ratio of different reactants were investigated to achieve optimal reaction conditions with the highest yield of 4-NBDT. Notably, the yield of 4-NBDT reached 97% at 25 °C only in 2.3 s with the optimal molar ratio of HBF4, NaNO2 and PNA (i.e., 2.72:1.05:1). The second step was the Suzuki-Miyaura cross-coupling reaction, in which HNO3 was used to transform the reaction system into a homogeneous state. The effects of mixing performance, the molar percentage of Pd(OAc)2 to 4-NBDT, the reaction temperature and the residence time on the Suzuki-Miyaura cross-coupling reaction were investigated systematically. With the molar percentage of Pd(OAc)2 to 4-NBDT of 1 mol%, the yield of 4-nitrobiphenyl (4-NBP) was optimized to 99% in just 13 min at 25 °C. This study demonstrated the excellent potential of utilizing the continuous-flow microreactor for the diazotization and the following Suzuki-Miyaura cross-coupling reaction.

A low-cost, simple, and one-step synthesis of cellulose acetate nanoparticles (CANPs) has been invented using a continuous-flow advanced microfluidic reactor. For this purpose, the CANPs are self-organized inside a cross-junction microchannel by flowing cellulose acetate (CA) dissolved in N,N-dimethylformamide (DMF) through the axial inlet and the antisolvent water through the pair of side inlets. The preferential solubility (insolubility) of DMF (CA) to antisolvent water stimulates the in situ synthesis of CANPs at the DMF/water miscible interface following a phase-inversion process. Subsequently, nanofiltration, ultrafiltration, and microfiltration membranes of different porosities and permeabilities have been prepared from freshly synthesized CANPs. The porosity, thickness, transparency, and wettability of the membranes are tuned by varying the thickness of the membranes, size of the nanoparticles, and the porosity of the membranes. The as-synthesized CANPs show enhanced bactericidal properties with and without loading an external drug, curcumin, which has been validated against the Gram-negative Pseudomonas aeruginosa species. Importantly, enabling a pulsatile flow during the synthesis, the CANPs are embedded as nanofiltration membranes inside the microfluidic channel. Such microfluidic devices have been used to separate a corrosive dye from water. Concisely, the proposed in situ synthesis of CANPs in the continuous-flow microfluidic reactors, their usage for fabricating membranes with tunable wettability and transparency, and their subsequent integration into the microfluidic channel show the potential of the invention for a host of applications related to health care and environmental remediation.

The rapid cis-trans isomerization of α-anionic stilbene was regioselectively controlled by using flow microreactors, and its reaction with various electrophiles was conducted. The reaction time was precisely controlled within milliseconds to seconds at -50 °C to selectively give the cis- or trans-isomer in high yields. This synthetic method in flow was well-applied to synthesize precursors of commercial drug compound, (E)- and (Z)-tamoxifen with high regioselectivity and productivity.

The development of miniaturized flow platforms would enable efficient and selective synthesis of drug and lead molecules by rapidly exploring synthetic methodologies and screening for optimal conditions, progress in which could be transformative for the field. In spite of tremendous advances made in continuous flow technology, these reported flow platforms are not devised to conduct many different reactions simultaneously. Herein, we report a metal-based flow parallel synthesizer that enables multiplex synthesis of libraries of compounds and efficient screening of parameters. This miniaturized synthesizer, equipped with a unique built-in flow distributor and n number of microreactors, can execute multiple types of reactions in parallel under diverse conditions, including photochemistry. Diazonium-based reactions are explored as a test case by distributing the reagent to 16 (n = 16) capillaries to which various building blocks are supplied for the chemistry library synthesis at the optimal conditions obtained by multiplex screening of 96 different reaction variables in reaction time, concentration, and product type. The proficiency of the flow parallel synthesizer is showcased by multiplex formation of various C–C, C–N, C–X, and C–S bonds, leading to optimization of 24 different aryl diazonium chemistries. Flow reactors have applications in reaction screening and optimisation, but typically operate in linear or radial configurations. Here a bench-top parallel flow synthesiser which distributes reagents between sixteen microreactors allows for rapid optimisation of chemical libraries, with uniform flow distribution even when clogging occurs.

Photocatalysis and Fenton process are two primary and promising advanced oxidation processes to degrade organic pollutants. However, the practical applications of single photocatalysis and Fenton process are still limited. Introducing one of them into another to form a combined photocatalytic Fenton-like system has shown great potential but still faces challenges in designing a well-tailored catalyst. Herein, a confined photocatalytic Fenton-like micro-reactor catalyst with a movable Fe3O4 core and a mesoporous TiO2 shell has been constructed via a successive Stober coating strategy, followed by an ultrasound assisted etching method. The resulting micro-reactor possesses well-defined yolk-shell structures with uniform mesopores (∼4 nm), a large Brunauer-Emmett-Teller (BET) surface area (∼166.7 m2/g), a high pore volume (∼0.56 cm3/g) and a strong magnetization (∼51 emu/g), as well as tunable reactor sizes (20−90 nm). When evaluated for degrading bisphenol A under solar light in the presence of peroxymonosulfate, the micro-reactor exhibits a superior catalytic degradation performance with a high magnetic separation efficiency and an excellent recycle ability. The outstanding performance can be attributed to its unique textual structure, which leads to a great synergistic effect from the photocatalytic and Fenton-like process. This study gives an important insight into the design and synthesis of an advanced micro-reactor for a combined advanced oxidation processes (AOPs).

Electrosynthesis and microflow synthesis have become essential tools in their own rights in modern organic synthesis. In this personal account, we summarize our works on the integrated use of these techniques, i. e., electrosynthesis in a flow microreactor. Our group has developed an electrochemical microflow system composed of a pair of electrodes that face each other to form a micrometer-scale gap for the flow path, through which solution passes in laminar flow. By the aid of laminar flow, unprecedented chemo- and electrochemical selectivity has been observed, which is not achievable with conventional batch-type electrochemical cells. In addition, we showcase various unique electrochemical systems and reactions achieved with the flow microreactor, including self-supported electrolysis, efficient paired electrolysis, in situ generation of active species and its flash use, the spaciotemporal control of electropolymerization, and combinatorial screening of the reaction conditions.

The study deals with the synthesis of nitrous oxide via selective oxidation of ammonia in a microreactor (MCR), which is a metal disk with cylindrical channels filled with the manganese-bismuth oxide catalyst. The proposed 3D mathematical model of MCR takes into account axial and radial heat and mass transfer, catalytic reactions and related changes of the reaction mixture volume, heat exchange between the disk and channels, and thermal conductivity of the disk. Parameters providing the maximum output of nitrous oxide were determined with allowance for restrictions on the temperature in MCR channels. The highest efficiency of the nitrous oxide synthesis is achieved at a temperature of the outer edge of reactor 370 °С and an inlet concentration of ammonia 20 vol.%. The output per unit catalyst volume in MCR is approximately 1.5 times higher as compared to a tubular reactor; the maximum temperature corresponds to the optimal one, which provides the best selectivity of the process with respect to nitrous oxide.

Droplet manipulation plays a significant role in the fields of biomedical detection, microfluidics, and chemical engineering. However, it still remains a great challenge to simultaneously achieve remote, selective, and in situ droplet manipulation on the same surface. Here, Fe3O4 nanoparticles were doped in a shape-memory polymer (SMP) to prepare a photothermal-responsive Fe3O4-SMP composite which showed remarkable near-infrared (NIR) light-triggered shape-memory property. Superhydrophobic micropillar array was constructed on such Fe3O4-SMP composite through femtosecond laser microfabrication and fluoroalkylsilane modification. The surface wettability of the as-prepared surface can transform from a low-adhesive sliding state to a high-adhesive pinning state as the micropillars are deformed by pressing. Interestingly, the deformed micropillars can stand up and restore to their original morphology under remote NIR light irradiation, resulting in the reversible and repeatable recovery of the ultralow-adhesive superhydrophobicity. With such light-triggered wettability switching, the droplets pinning on the sample surface can be remotely, selectively, and in situ released. Furthermore, the superhydrophobic Fe3O4-SMP surface is successfully applied in lossless liquid transfer, selective droplet release, and droplet-based microreactor. The as-fabricated superhydrophobic surfaces with NIR light-controlled reversible wettability will hold great promise in the fields of liquid manipulation, lab-on-a-chip, and microfluidics.

Hypothesis Manipulating droplet transportation without inputting work is desired and important in microfluidic systems. Although the creation of wettability gradient on surfaces has been employed to achieve this goal, the transport distance is very limited, hindering its applications in long-term operations. Experiments Here, we show that programming long-ranged transport of droplets on surfaces can be achieved by the addition of trisiloxane surfactants and the creation of deep grooves. The former provides Marangoni stress to actuate the droplet motion and also reduces the inherent contact line pinning. The latter acts as a railing to guide the motion of surfactant-laden droplets to follow various layouts with geometric features of roads. Findings It is found that the droplets with microliters can move over 20 cm. This work-free method is applicable to a variety of substrate materials and liquids. By using self-running shuttles, a convenient platform for liquid cargos transport is developed and demonstrated. Moreover, the coalescence of cargos carried by different shuttles is accomplished in a three-branch layout, revealing new droplet microreactors.

The oxidation of rabeprazole sulfide is a key step in the synthesis of rabeprazole, a drug for the treatment of stomach acid-related disorders. The current rabeprazole production process adopts one pot batch process, which has low reaction efficiency and poor stability. A continuous process can greatly improve the production efficiency and solve the above problems. Therefore, the reaction parameters of rabeprazole in microreactor were explored through laboratory experiments to explore the possibility of continuous production of rabeprazole. Rabeprazole sodium was synthesized by using rabeprazole thioether as a raw material and sodium hypochlorite solution as the oxidant. Oxidation, quenching, acid-base regulation and extraction were completed continuously in the microreactor. Rabeprazole solution with a purity of 98.78% (±0.13%) can be obtained continuously in 56 s, whereas intermittent production lasted for at least 2 h. Thus, the microreactor can effectively improve the oxidation synthesis efficiency of rabeprazole, and provide reference for the realization of other reactions in the microreactor.

The demand for transportation diesel fuels has been increasing in most countries for the last decade. As is one of the primary sources for diesel distillates, light cycle oil (LCO), having the advantages of inheriting similar density and boiling point range to diesel fuels, but high contents of aromatics, sulfur, and nitrogen, needs to be upgraded before being utilized. This work reports a trinary porous SiO2–Al2O3–TiO2 (SAT) synthesized by sol–gel method and used as the NiMo catalyst support for the LCO hydro-upgrading. NiMo/Al2O3-zeolite (AZ) was used as a reference to evaluate the performances of the NiMo/SAT. The catalysts were characterized by XRD, BET, Pyridine-FTIR, and TEM; and evaluated in a 20-mL fixed-bed microreactor using a Fluid Catalytic Cracking LCO as feedstock. It was found that the SAT support possessed a high surface area, high pore volume, and good acid properties. The NiMo/SAT catalyst exhibited even better hydrodesulfurization, hydrodenitrogenation, and hydrodearomatization performances than NiMo/AZ when the reaction was performed at 375 °C and 1100 psi. Compared with the zeolite addition catalyst, the SAT catalyst has the advantages of simple synthesis procedures and low input cost.

A novel fluorinated soft thermoplastic elastomer (sTPE) for microfluidics is presented. It allows the rapid fabrication of microfluidic devices through a 30‐second hot embossing cycle at 220°C followed by self‐sealing through simple conformal contact at room temperature, or with baking. The material shows high chemical resistance, particularly in comparison to polydimethylsiloxane (PDMS), to many common organic solvents and can be rapidly micropatterned with high fidelity using a variety of microfluidic master molds thanks to its low mechanical stiffness. Self‐sealing of the material is reversible and withstands pressures of up to 2.8 bar with room temperature sealing and four bar with baking at 185°C for 2 hours. The elastomeric, transparent sTPE exhibits material characteristics that make it suited for use as a microreactor, such as low absorption, surface roughness and oxygen permeability, while also allowing a facile and scalable fabrication process. Modular microfluidic devices, leveraging the fast and reversible room temperature self‐sealing, are demonstrated for the generation of water droplets in a toluene continuous phase using T‐junctions of variable size. The sTPE offers an alternative to common microfluidic materials, overcoming some of their key drawbacks, and giving scope for low‐cost and high‐throughput devices for flow chemistry applications.

CuO/ZnO/CeO2/ZrO2 nanoflowers catalyst was grown on an Al2O3 foam ceramic by a one-step hydrothermal process, while a naked Al2O3 foam ceramic and an Al2O3 foam ceramic grown with ZnO nanorods that directly impregnated into the catalyst precursor solution were also fabricated simultaneously. The morphology, composition, redox property and specific surface area of catalysts on the three ceramics were investigated in detail. The catalyst-loaded ceramics were used as catalyst supports in a microreactor to study the catalytic performance for methanol steam reforming. Results showed that the microreactor with Al2O3 support grown with nanoflowers catalyst achieved 99.8% methanol conversion rate, 0.16 mol/h H2 flow rate at 310 °C, and an inlet methanol flow rate of 0.048 mol/h. Moreover, the microreactor exhibited 92% methanol conversion rate after 30 h continuous reaction.

Methanol steam reforming microreactors can be used for hydrogen production in industry applications. This paper presents a novel thermally autonomous methanol steam reforming microreactor that uses porous copper foam as catalyst support to enhance the performance of hydrogen production. The proposed microreactor mainly consists of a vaporizer, a catalytic combustor, and a methanol steam reformer. It uses a Pt/Al2O3 catalyst with 0.15% Pt for methanol combustion and a CuO/ZnO/Al2O3 catalyst-coated copper foam for methanol steam reforming. A numerical model was developed to study the fluid flow and heat transfer characteristics in the porous copper foam and a thin-layer of coated catalyst. Simulation results revealed that the pressure drop and velocity gradient of the microreactor increased when the weight of the catalyst increased. Experimental tests were conducted to study the effects of catalyst loading on the methanol conversion, hydrogen production, and overall efficiency of the microreactor. The results indicate that the developed microreactor can be successfully startup within 13 min and its overall efficiency is approximately 35–45%. The results obtained in this research can be used to develop a highly efficient methanol steam reforming microreactor for hydrogen production.

Determining local concentrations of the analytes in state-of-the-art microreactors is essential for the development of optimized and safe processes. However, the selective, parallel monitoring of a...

The conventional sol-gel method used to synthesize monodispersed spherical silica nanoparticles produces particles with irregular shapes and low monodispersity. Microreactors show a promising new platform to synthesize nanomaterials due to their unique flow and mixing characteristics. In most known shear-based droplet generation microreactors, the effect of the flowing liquid’s physical properties on the reactor performance and product characteristics are not well investigated. Scaling-down the flow system was proven to change the flow behavior which will be dominated by the liquid apparent physical properties that are highly controllable. A new method to synthesize silica nanoparticles adapting the sol-gel approach in a microfluidic chip is proposed and experimentally tested in the present work. This work also analyzes changing the flowing reactants’ physical properties using nonionic surfactants with different concentrations on the reaction performance and nanoparticle size and properties. A custom-made microreactor, made from polydimethylsiloxane, was designed and then fabricated using a direct writing technique. The investigated surfactant concentration was within the range of 1 to 5 vol/vol%, respective to tetraethyl orthosilicate. A traditional bench-scale sole-gel method was also performed with the same reaction properties for comparison purposes. The obtained nanoparticles were characterized using transmission electron microscopy and EDX. The silica nanoparticles synthesized from a bench-scale system showed poor monodispersity and an irregular shape compared to the perfect spherical particles produced from the microflow system. The addition of surfactant reduced the coalescence of the droplet besides reducing the size of the droplets. Increasing the surfactant concentration reduces the silica nanoparticle size. The results showed that highly monodispersed silica nanoparticles with an average size of 5.76 ± 1.27 nm were synthesized using the microflow system comparing to silica nanoparticles with a mean size of 95 ± 4 nm produced from the bench-scale.

A green and efficient reaction route for the synthesis of pyrrolidin-2-ones via photoinduced organocatalyzed three-component cyclization of styrene, tertiary α-bromoalkyl esters and primary amines in a microchannel reactor under visible light conditions has been developed. Moreover, the overall process can be carried out under mild conditions without using a metal. In addition, a reasonable reaction mechanism was proposed based on control experiments.

The analysis and detection of ultra-trace biomarkers are often carried out in microliter droplets. Common stirring approaches have some difficulties in precise and contactless mixing and dispersion in microdroplets. In this work, an open mini-pillar-based platform that integrates with ultrasound units is developed to achieve contactless mixing and dispersion in microliter samples. On such a platform, mini-pillars can anchor microdroplets as individual microreactors, and each ultrasound unit can be remotely controlled to achieve on-demand contactless micro-stirring, which is also confirmed by mixing and dispersing of Fe3O4 nanoparticles (1 μm) in microdroplets (10 μL). Such on-demand high-throughput mixing and dispersion that integrates ultrasound mixing with microdroplet technology provides a potential robot-based platform for achieving high-throughput and ultra-trace biosensing in microliter droplets.

Polyether polyols as a crucial chemical for the synthesis of polyurethanes have attracted much attention, especially for propylene oxide-based polyether polyols due to their ready availability and good structural diversity. In the present work, microreactors configured with a SIMM-V2 micromixer and stainless steel capillary were developed for the continuous and efficient synthesis of propylene oxide-based polyether polyols. For the conversion of propylene oxide higher than 95%, the reaction time was less than 60 s that was significantly shorter than that in a batch reactor. Also, the reaction temperature can be controlled precisely, thereby obtaining high purity polyether polyol products. To identify the maximum performance of the microreactors, while keeping the conversion of PO higher than 95%, the novel process windows of the reactors were determined by investigating the relations of reaction temperature and pressure, reaction temperature and residence time, and feed flow rate and residence time. The results showed that high quality polyether polyols could be easily prepared in the microreactors under flexible operating conditions. In addition, polyether polyols with higher molecular weights could also be prepared by using a two SIMM-V2 configured microreactor. This work showed that the microreactors are promising candidates for the synthesis of polyether polyols in the industry.

Solvent-free continuous flow epoxidation of the alkene bonds of a range of biorenewable terpene substrates have been carried out using a recyclable tungsten-based polyoxometalate phase transfer catalyst and aqueous H2O2 as a benign oxidant. These sustainable flow epoxidation reactions are carried out in commercial microreactors containing static mixing channels that enable common monoterpenes (e.g. untreated crude sulfate turpentine, limonene, etc.) to be safely epoxidized in short reaction times and in good yields. These flow procedures are applicable for the flow epoxidation of trisubstituted and disubstituted alkenes for the safe production of multigram quantities of a wide range of epoxides.

Owing to its photonic band gap (PBG) and slow light effects, aniline black (AB)-poly(vinylidene fluoride) (PVDF) inverse opal (IO) photonic crystal (PC) was constructed to promote the utility of light and realize photothermal synergetic catalysis. As a highly efficient reaction platform with the capability of restricting heat, a microreactor was introduced to further amplify the photothermal effects of near infrared (NIR) radiation. The photocatalytic efficiency of ZnO/0.5AB-PVDF IO (Z0.5A) increases 1.63-fold compared to that of pure ZnO film under a full solar spectrum, indicating the effectiveness of synergetic promotion by slow light and photothermal effects. Moreover, a 5.85-fold increase is achieved by combining Z0.5A with a microreactor compared to the film in a beaker. The photon localization effect of PVDF IO was further exemplified by finite-difference time-domain (FDTD) calculations. In conclusion, photonic crystal-microreactor enhanced photothermal catalysis has immense potential for alleviating the deteriorating water environment.

Management of CO2 has been attracting great attention in this century. Reaction of CO2 with 2-haloanilines and isocyanides is an attractive way for both converting CO2 and producing quinazolinones, which are key intermediates for the synthesis of various biologically active products. However, the heterogeneous and relatively inert nature of CO2 with 2-haloaniline and isocyanide reactants limits the types of suitable catalysts. Herein, we use metal–organic frameworks (MOFs) as a “microreactor”, in which Pd(PPh3)2Cl2 is well-dispersed as a single-molecular catalyst, and the reactants react in the molecular level through a “quasi-homogeneous” way to convert CO2 into quinazolinones under mild conditions with both promising yields over homogeneous catalysts and good recyclability as a heterogeneous reaction. The MOF-assisted single-molecular catalysis strategy should contribute to CO2 conversion, production of quinazolinone-type bioactive intermediates, and the epochal development of “homo-and-heterogeneous” catalysis.

Comprehensive investigation of the synergistic effect of incorporating Fe and Ga into ZSM-5 in cracking of hexane.

A merger of organocatalysis and visible light photoredox catalysis performed in flow allowed access to a wide range of functionalizedN-aryl-substituted tetrahydroisoquinolines (THIQs) in a formal C-H oxidation/Mannich reaction. Strecker type functionalization and copper-catalyzed alkynylation of severalN-aryl-substituted THIQs were also successfully performed in flow, giving valuable products with high efficiencies. The use of custom-made porous polymeric type microreactors proved to be crucial regarding the C-H oxidation step and overall reaction performance. Supplementary material: [https://cer.ihtm.bg.ac.rs/handle/123456789/4495]

The kinetics of the synthesis of tert-butyl peroxy-2-ethylhexanoate were investigated in a capillary microreactor. TBPEH was synthesized from 2-ethylhexanoyl chloride and tert-butyl hydroperoxide in the presence of a strong base, using the Schotten-Baumann method. The peroxyesterification reaction is always in competition with the unwanted acid chloride hydrolysis. The synthesis was carried out with and without a phase-Transfer catalyst. The non-catalyzed reaction showed a low rate, which could be incremented by increasing the temperature and the liquid-liquid interfacial area or by using KOH instead of NaOH as base. The peroxyesterification and hydrolysis rates increased with temperature. However, the use of KOH or the increase in interfacial area accelerated only the peroxyester formation, increasing the selectivity towards the desired product. The addition of a PTC enhanced the peroxyesterification rate without changing the hydrolysis rate. Among the screened PTCs, quaternary ammonium salts with longer alkyl chains gave the best performance, up to 25 times faster peroxyesterification. The rate increase was proportional to the PTC amount. The interfacial area had the same effect as in the non-catalyzed reaction. Because of the tremendous increase in the reaction speed due to the PTC, the rate increased with slug velocity. At low slug velocity the reactants in the thin liquid film surrounding the droplets in the capillary are depleted and the peroxyesterification rate decreases. A reaction mechanism is proposed that explains the experimental observation. The corresponding kinetic model predicts the observed reaction rate with 10% accuracy.

Electrochemical methods are environmentally friendly and have unique advantages in the synthesis of organic chemicals. However, their implementation is limited due to the complex transport problems posed by traditional electrochemical reactors. Recently, the application of microreaction technology in electrosynthesis studies has reduced the transport distance of ions and increased the specific surface area of electrodes, leading to efficient, successive, and easily scaled-up electrosynthesis technologies. In this review article, engineering advantages of using microchannels in electrosynthesis are discussed from process enhancement perspective. Flow patterns and mass transfer behaviors in recently reported electrochemical microreactors are analyzed, and prototypes for the reactor scale-up are reviewed. As a relatively new research area, many scientific rules and engineering features of electrosynthesis in microreactors require elucidation. Potential research foci, considered crucial for the development of novel electrosynthesis technology, are therefore proposed.

The current demand for sustainable processes is increasing day by day. The considerable growth in biotechnological industries is attributed to enhanced enzyme production and their stability, and development in technologies for process intensification, which can pave the way towards large scale production and economical formulation. White biotechnology deals with the implementation of biotechnology at the industrial level. It is considered as one of the key tools, which can be utilized to boost the bio-economy. With the increasing research in the field of biocatalysis, it is proved to be a green tool in the synthesis of fine chemicals. It is quite evident that biocatalysis has numerous advantages over chemical catalysis. Immobilization of enzymes is the key towards practical and commercial viability of the processes, which improves the activity, stability, and reusability of enzymes, thereby making the biocatalytic reactions more sustainable and economical. The amalgamation of biocatalysis with process intensification techniques such as microwaves, ultrasound, hydrodynamic cavitation, and the combination of chemical and biological catalysis can be an effective way to enhance the yield and productivity of these processes. The use of microreactor technologies and continuous modes of operation, the co-called flow chemistry, has been exploited for different biocatalytic reactions. The current review summarizes and discusses the applications of immobilized enzymes used in different process intensification techniques. The techniques utilized can help in achieving better productivity and enhanced yields as compared to those with conventional techniques. These advances in bioprocesses will lead to rapid application at the industrial level for strengthening the bio-based economy.