Journal of Flow Chemistry最新文献

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.

Myristyl-γ-picolinium chloride (MGPC) is an alkyl pyridine quaternary ammonium salt and a popular preservative in injectables such as Depo-Medrol (Methylprednisolone acetate). Herein we describe a successful high-p,T,c chemical intensification of MGPC synthesis from neat myristyl chloride and γ-picoline in continuous flow. The process is atom economical, scalable with low reactor footprint and under optimized conditions, consistently affords MGPC in 45 min (instead of 8–12 h reported in literature for a conventional batch process) with excellent yield (> 90%) and purity (> 99%).

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Synthesis of bio-based monomers via continuous flow ozonolysis of cardanol using a simple tubular reactor is demonstrated. The direct ozonolysis of cardanol produces unique monomer 8-(3-hydroxyphenyl) octanal (HPOA) and heptanal along with several other oxidation products. Maximum 47% yield of HPOA with 54.3% conversion of cardanol was obtained at 0 °C in 9 s. The complete conversion of cardanol was obtained at the ozone to cardanol molar flow ratios greater than 2 at all temperatures varied in the range of -10 °C to 20 °C. Owing to large gas–liquid ratios, the mass transfer limitation for transfer of ozone from gas to liquid was negligible; however, the extent of axial dispersion in the liquid phase was significant at lower liquid flow rates. The non-ideal behavior was incorporated in the axial dispersion model to predict the conversion of cardanol. Examination of kinetic rates by both ideal plug-flow model and plug-flow with axial dispersion model revealed that the reaction is fast and is least influenced by the axial-dispersion in the reactor at prevailing operating conditions. The findings of the current study show that continuous flow technique enables a simple and safer synthesis of high-value bio-based monomers via ozonolysis of cardanol compared to traditional batch methods.

Photochemistry and continuous flow chemistry are synthetic technology platforms that have witnessed an increasing uptake by chemical industries interested in complex organic molecule synthesis. Simultaneously, automation and data science are prominent targets in organic synthesis and in chemical industries for streamlined workflows, meaning hardware-software interaction between operators and devices is crucial. Since undergraduate teaching labs at public-funded research Universities typically (i) lack budget for commercial, user-friendly continuous flow reactors and (ii) do not teach synthetic chemists how to program or interact with reactors, there is a disparity between the skills undergraduates are equipped with and the skills that future industries need. We report a teaching lab project where undergraduates assemble, program and execute a continuous flow photoreactor to realize a multigram-scale photoredox catalyzed oxidation reaction. A palladium-free synthetic access to the starting material was described to further cut costs. Not only does this exercise introduce useful skills in reactor design, programming and wet chemistry (both photochemical and thermal, both batch and flow), it also accommodates both the typical budget and afternoon timeslot (2-3 h) of a teaching lab and can be followed by thin-layer chromatography/color changes without necessarily requiring access to NMR facilities.

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Porphyrin derivatives have found diverse applications due to their attractive photophysical and catalytic properties, but remain challenging to synthesize, particularly at scale. Porphyrin synthesis thus stands to benefit from the more controlled environment, opportunities for efficient optimization, and potential for scale-up available in flow. Here, we have transferred Lindsey porphyrin synthesis into flow, enabling controlled timing for oxidation and neutralization steps and real time monitoring of the reaction mixture with inline UV–Vis analysis. For tetraphenyl porphyrin (TPP), inline UV–Vis showed the presence of protonated TPP, formed due to residual acid. Thus, inline monitoring allowed optimization of the neutralization step to improve yield. Three further porphyrin substrates were produced in flow; in two cases, the yield from inline UV was significantly higher than the yield from post-purification, identifying further yield losses that could be recovered by modifying the purification step. The workflow presented here can be adapted to multiple substrates to systematically optimise porphyrin yield, reducing the time needed to develop scalable routes to these valuable compounds.