Journal of Flow Chemistry最新文献

Due to the miniaturization of equipment for flow chemistry and microprocess engineering, low-cost sensors and analytical devices are becoming increasingly important for automated inline process control and monitoring. The combination of 3D printing technology and open-source lab automation facilitates the creation of a microfluidic toolbox containing tailored actuators and sensors for flow chemistry, enabling a flexible and adaptable design and efficient processing and control based on the measured data. This contribution presents a set of 3D-printed microfluidic sensor flow cells for inline measurement of temperature, electrical conductivity (EC), and pH value, while compensating for the temperature dependence of EC and pH. The tailored sensor flow cells were tested using model reactions in a single-phase capillary flow system. They have an accuracy comparable to reference sensors in batch measurements. The sensor data can be used to monitor the reaction progress (conversion), determine the kinetic data (activation energy, pre-exponential factors) of saponification reactions, and identify titration characteristics (equivalence and isoelectric points) of neutralization reactions. Hence, the 3D-printed microfluidic sensor flow cells offer an attractive alternative to commercial analytical flow devices for open-source and low-cost lab automation.

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Microbubble reactors play an important role in the development of gas-liquid reaction process enhancement. However, the urgent demand for high efficiency and low energy consumption in gas-liquid reaction processes, as well as the trend towards large-scale production, have put forward higher requirements for the design and optimization of microbubble reactors. In this study, a self-priming microbubble reactor was designed and its structure parameters were optimized by (computational fluid dynamics) CFD simulations. Based on the grid division method combining structured and unstructured grids, the most suitable mesh number is selected, and the simulation calculation time is saved on the premise of ensuring the accuracy. The effects of five structural parameters on the gas content and energy loss was discussed and the optimal structural parameters of the microbubble reactor were determined as follows: the diffusion section length is 75 mm, the contraction angle is 22°, the diffusion angle is 10.5°, the inlet diameter of the gas phase is 6 mm, the inlet diameter of the liquid phase flowing into the gas chamber is 3 mm, the diffusion section inlet diameter is 5 mm. Under the condition of the same inlet flow rate, the outlet gas content of the optimized gas-liquid reactor is increased by 42.9% compared with the initial structure. In the wastewater treatment experiment, the microbubble reactor reduced the chemical oxygen demand of wastewater by 61% within three hours. This study provides significant references for the design of the self-priming microbubble reactor.

In the realm of flow chemistry, Do-It-Yourself (DIY) flow setups represent a versatile and cost-effective alternative to expensive commercially available reactors. Not only they are budget friendly, but also unlock a world of possibilities for researchers to explore and create customized setups tailored to their specific needs. This minireview serves as a short compendium of DIY flow systems to assist flow researchers in the challenging task of finding a suitable setup for their experiments and facilitate the transition from batch to flow chemistry. Our goal is to demonstrate that flow chemistry can be affordable, easy-to-build, and reproducible at the same time. Therefore, herein we review and describe selected illustrative examples of easily assembled/constructed DIY flow setups, with a particular emphasis on how to select the most suitable one based on the specific chemistry of interest, ranging from simple homogeneous monophasic reactions to more complex systems for photo-, electrochemistry, and so on. In addition, we briefly comment on the significance of DIY approach on education, particularly its integration into the standard undergraduate curriculum as a key educational tool for young chemists. Ultimately, we hope this mini review will help and encourage the reader to go with the flow and get started with the fine art of flow chemistry.

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Hundred-gram scale of highly selective catalytic hydrogenation of folic acid has been developed, which is adopted continuous-flow technology with Raney Ni as a catalyst. Through optimization of the reaction condition, a high conversion rate of folic acid (> 99%) and a high selectivity (99%) of tetrahydrofolate have been achieved. Additionally, a high-purity calcium-6S-5-methyltetrahydrofolate (6S-5-MTHF.Ca) has been synthesized from tetrahydrofolate obtained by continuous hydrogenation through chiral resolution, methylation, salting and recrystallization (purity: 99.5%, de: 97.6%). Compared to known methods, this method provides a feasible procedure using simple, inexpensive, and readily available reagents, making it a step-economical and cost-effective alternative strategy for production of tetrahydrofolate and its active derivatives.

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For Table of Contents Only

Flow chemistry is the future of chemical processing. It represents a significant advance in energy consumption and waste generation regarding operations in batch and continuous flow macroscopic equipment since the transport rate (of mass, heat, photons, electrons, etc.) is tremendously intensified. In parallel, computational fluid dynamics (CFD) is part of engineering’s future. Digitalization of transport processes (involving fluid flow and scalar transport, e.g., species, energy, etc.) is the state-of-the-art for designing, optimizing, and scaling chemical reactors, separation and purification units, heat exchangers, etc. This perspective initially presents relevant fundamental CFD concepts applicable to any field. In the sequence, an overview of applications of CFD in flow chemistry reported in the literature over the last two decades is presented, highlighting the evolution of complexity and variety of topics investigated (ranging from single-phase flow optimization to multiphysics cases involving coupling of multiphase flow and external forces—e.g., ultrasound and electric field). Next, the contributions of our research group in CFD in flow chemistry are presented—with a focus on photocatalytic and electrocatalytic systems—and accompanied by highlights about our personal experience. Further discussion about strengths, limitations, and opportunities for CFD in flow chemistry is presented, highlighting to the reader the gaps that should be in the spotlight over the next few years, followed by our final remarks. After reading this perspective, the reader (either a starter in this field or an expert) will be able to identify how CFD has evolved in flow chemistry over the years and what are the next directions from the authors’ point of view.

The merging of biocatalysis with continuous-flow chemistry opens up new opportunities for sustainable and efficient chemical synthesis. Cofactor-dependent enzymes are essential for various industrially attractive biocatalytic reactions. However, implementing these enzymes and biocatalytic reactions in industry remains challenging due to the inherent cost of cofactors and the requirement for their external supply in significant quantities. The development of efficient, low cost, simple and versatile methods for cofactor immobilization can address this important obstacle for biocatalysis in flow. This review explores recent progress in cofactor immobilization for biocatalysis by analyzing advantages and current limitations of the available methods that comprise covalent tethering, ionic adsorption, physical entrapment, and hybrid variations thereof. Moreover, this review analyzes all these immobilization techniques specifically for their utilization in continuous-flow chemistry and provides a perspective for future work in this area. This review will serve as a guide for steering the field towards more sustainable and economically viable continuous-flow biocatalysis.

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Accurate control of core–shell lipopolyplex nanoparticles (LPP NPs) size is crucial for finely adjusting their biomedical performance. However, the synthesis of LPP NPs encounters challenges as two mixing-sensitive processes are involved in the synthesis, rendering precise control over particle size difficult using conventional batch methods. In this study, the formation of the nucleic acid/cationic polymer cores through electrostatic complexation and the subsequent encapsulation by lipid shells via self-assembly were conducted in microreactors, with polyadenylic acid (poly A) and branched polyethylenimine (bPEI) employed as the model system. By assessing the micromixing performance of the microreactors using the Villermaux-Dushman method, the characteristic time scale for electrostatic complexation between poly A and bPEI, as well as the self-assembly of lipids, was determined to be below 1 ms. The Reynolds number, governing micromixing performance, emerged as a crucial factor influencing the sizes of poly A/bPEI cores and LPP NPs. In the kinetic control region, characterized by rapid mixing, the size of poly A/bPEI remained slightly influenced by the N/P molar ratio and volumetric flow rate ratio, irrespective of concentration. The zeta potential, however, was primarily affected by the N/P molar ratio. In the case of LPP NPs, under optimized conditions of anionic lipid molar ratio, the size of LPP NPs was significantly influenced by the composition of lipid shells. This study establishes the foundation for elucidating the structure–activity relationship of LPP NPs.

Herein we report the automation and scale-up of a photofluorination process key to the production of branched-chain aliphatic radiotracers such as (S)-5-[¹⁸F]fluorohomoleucine ((S)-5-[¹⁸F]]FHL). (S)-5-[¹⁸F]FHL is a leucine analogue that is primarily taken up by the L-type amino acid transporter (LAT or System L). LAT1 expression levels correlate closely with tumor proliferation, angiogenesis, and treatment outcomes, making it an attractive target for molecular imaging of cancer. We have previously synthesized (S)-5-[¹⁸F]FHL and tested this tracer in mice bearing PC3 (prostate) or U87 (glioma) xenografts in order to establish its feasibility for detecting and monitoring treatment for a broad range of cancers. In this study, the radiosynthesis of 5-[¹⁸F]FHL is demonstrated on an automated DT-PhotoFluor module with a radiochemical yield of 20.1 ± 4.8% (n = 3), radiochemical purity of 94.5 ± 4.9% (n = 3), and a synthesis time of ~ 75 min. The reported DT-PhotoFluor module will allow for higher molar activity, better reproducibility, and reduced radiation exposure for upcoming first-in-human studies.

A fully continuous-flow nitration and post-processing protocol has been introduced into the preparation of 4-nitropyrazole. The process started from the nitration reaction of pyrazole with mixed acid, followed by continuous quenching, neutralization, extraction and separation. After the collected organic phase was rotationally evaporated to recover the solvent, the final product 4-nitropyrazole was obtained with 96.9% yield, 99.3% purity and 381 g/h productivity. By establishing a kinetics model and MATLAB simulation calculation, it worked out to achieve the preferable selectivity conditions of mono-nitration product 4-nitropyrazole. The process of post-processing solved the problems of solid precipitation and extractant hydrolysis. The extraction process was determined by the distribution coefficient and twice extraction was used to reduce the amount of organic solvent.

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Azo compounds find use in many areas of science, displaying crucial properties for important applications as photoconductive organic pigments, fluorescent quenchers, paints, cosmetics, inks, and in the large and valuable dye industry. Due to the unstable intermediates, and the exothermic and fast reactions used in their synthesis, high value azo compounds are excellent candidates for continuous flow manufacturing. This comprehensive review covers the progress made to date on developing continuous flow systems for azo synthesis and reflects on the main challenges still to be addressed, including scale up, conversion, product purity, and environmental impact. The further development of integrated continuous flow processes has the potential to help tackle these challenges and deliver improved methods for azo compound generation.