Halogenation of organic compounds using continuous flow and microreactor technology

Cantillo, David; Kappe, C. Oliver

doi:10.1039/c6re00186f

Cited by 114 publications

(52 citation statements)

References 66 publications

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“…Microflow chemistry represents a better alternative to these methods, as it avoids headspace and high amounts of gas in each section of the reactor. Moreover, microflow reactors can be easily pressurized in a safe manner, providing good mass transfer and large, well-defined interfacial areas without compromising safety or irradiation [20][21][22]. Several methods for gas-liquid reactions in flow have been developed [23], generally suitable for photochemical conditions.…”

Section: Multiphasic Systems In Continuous-flow Photochemistrymentioning

confidence: 99%

Flow Photochemistry: Shine Some Light on Those Tubes!

Sambiagio

Noël

2020

Trends in Chemistry

316

223

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Continuous-flow chemistry has recently attracted significant interest from chemists in both academia and industry working in different disciplines and from different backgrounds. Flow methods are now being used in reaction discovery/methodology, in scale-up and production, and for rapid screening and optimization. Photochemical processes are currently an important research field in the scientific community and the recent exploitation of flow methods for these methodologies has made clear the advantages of flow chemistry and its importance in modern chemistry and technology worldwide. This review highlights the most important features of continuous-flow technology applied to photochemical processes and provides a general perspective on this rapidly evolving research field. Microflow Technology and Photochemistry: A Perfect MatchThe use of light to promote chemical reactions has been exploited since the 18th century, but only recently a resurgence has been observed in synthetic organic chemistry, in particular due to the development of visible-light photoredox catalysis [1-5]. All transformations involving light (e.g., Figure 1A-D) must consider, besides classical chemical parameters (i.e., reaction conditions), the photophysical aspects of the sensitizer (see Glossary)/photocatalyst (when used), and the reactor design. The latter, although often neglected by chemists, is a critical aspect for the outcome of the studied chemical transformation. This includes, for example, the size, shape, and material of the reaction vessel, the characteristics and positioning of the light source(s), and heat-transfer properties, particularly when high-intensity lamps are used [6,7]. The engineering and technological aspects of photochemical processes are often at the basis of the irreproducibility and non-scalability of such transformations.According to the Beer-Lambert law, light transmittance decreases exponentially with the distance from the light source ( Figure 1F). For a standard batch reactor (diameter at least in the centimeter range), light intensity decreases considerably from the flask walls to the middle of the reaction mixture, resulting in slow reactions and nonhomogeneous irradiation of the reaction mixture. Performing photochemical reactions in microchannels (ID < 1 mm) allows a higher and more homogeneous photon flux, resulting in shorter reaction times and consequently less side-product formation due to over-irradiation, often observed in batch [8,9]. Another advantage of microflow chemistry, correlated with the large surface:volume ratio, is improved heat and mass transfer, with the possibility to perform mass-transfer-limited multiphasic reactions efficiently [10]. Reactive chemicals and intermediates can be handled more safely in flow than in batch, as no accumulation of dangerous components occurs within the confined reactor volume due to the continuous nature of the process. Together, these result in often faster, safer, and higher-yielding reactions, with the possibility to perform reactions under condition...

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Section: Multiphasic Systems In Continuous-flow Photochemistrymentioning

confidence: 99%

Flow Photochemistry: Shine Some Light on Those Tubes!

Sambiagio

Noël

2020

Trends in Chemistry

316

223

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“…Gas-liquid chemical reactions include a broad range of highly relevant chemistries such as halogenation, oxidation, and hydrogenation, which are of great importance for fine chemical and pharmaceutical industries [1][2][3][4][5][6][7]. Gaseous reagents are prone to be atom economic [8]; however, they are often used in large stoichiometric excess because of insufficient interfacial mixing [9].…”

Section: Introductionmentioning

confidence: 99%

Energy Optimization of Gas–Liquid Dispersion in Micronozzles Assisted by Design of Experiment

2017

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Abstract:In recent years gas-liquid flow in microchannels has drawn much attention in the research fields of analytics and applications, such as in oxidations or hydrogenations. Since surface forces are increasingly important on the small scale, bubble coalescence is detrimental and leads to Taylor bubble flow in microchannels with low surface-to-volume ratio. To overcome this limitation, we have investigated the gas-liquid flow through micronozzles and, specifically, the bubble breakup behind the nozzle. Two different regimes of bubble breakup are identified, laminar and turbulent. Turbulent bubble breakup is characterized by small daughter bubbles and narrow daughter bubble size distribution. Thus, high interfacial area is generated for increased mass and heat transfer. However, turbulent breakup mechanism is observed at high flow rates and increased pressure drops; hence, large energy input into the system is essential. In this work Design of Experiment assisted evaluation of turbulent bubbly flow redispersion is carried out to investigate the effect and significance of the nozzle's geometrical parameters regarding bubble breakup and pressure drop. Here, the hydraulic diameter and length of the nozzle show the largest impacts. Finally, factor optimization leads to an optimized nozzle geometry for bubble redispersion via a micronozzle regarding energy efficacy to attain a high interfacial area and surface-to-volume ratio with rather low energy input.

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“…For the first purpose, microreactor‐based flow chemistry systems have been demonstrated to have strong abilities in controlling reaction environments, such as temperature, pressure, and concentration distribution; therefore, microreaction system provided more desirable results in contrast to hard‐to‐control batch reaction processes . The much smaller sized microreactor also enhanced the safety of experiments with toxic and highly reactive chemicals . Microreactors can also be equipped with automated feeding and sampling machines, programmed heating and cooling elements, and online detectors; thus, flow synthesis of nanocrystals have the advantages of implementing high‐throughput screening experiments in evaluating material preparation method, optimizing of synthesis condition, and determining nucleation/growth kinetics …”

Section: Introductionmentioning

confidence: 99%

Continuous Synthesis of Nanocrystals via Flow Chemistry Technology

Sui

Yan

Liu

et al. 2019

Small

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Modern nanotechnologies bring humanity to a new age, and advanced methods for preparing functional nanocrystals are cornerstones. A considerable variety of nanomaterials has been created over the past decades, but few were prepared on the macro scale, even fewer making it to the stage of industrial production. The gap between academic research and engineering production is expected to be filled by flow chemistry technology, which relies on microreactors. Microreaction devices and technologies for synthesizing different kinds of nanocrystals are discussed from an engineering point of view. The advantages of microreactors, the important features of flow chemistry systems, and methods to apply them in the syntheses of salt, oxide, metal, alloy, and quantum dot nanomaterials are summarized. To further exhibit the scaling‐up of nanocrystal synthesis, recent reports on using microreactors with gram per hour and larger production rates are highlighted. Finally, an industrial example for preparing 10 tons of CaCO3 nanoparticles per day is introduced, which shows the great potential for flow chemistry processes to transfer lab research to industry.

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Halogenation of organic compounds using continuous flow and microreactor technology

Abstract: Halogenation reactions involving highly reactive halogenating agents can be performed safely and with improved efficiency and selectivity under continuous flow conditions.

Cited by 114 publications

References 66 publications

Flow Photochemistry: Shine Some Light on Those Tubes!

Flow Photochemistry: Shine Some Light on Those Tubes!

Energy Optimization of Gas–Liquid Dispersion in Micronozzles Assisted by Design of Experiment

Continuous Synthesis of Nanocrystals via Flow Chemistry Technology

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