On the effect of flow restrictions on the nucleation behavior of molecules in tubular flow NucleatorsJournal of Flow Chemistry - Tập 10 - Trang 241-249 - 2020
Bart Rimez, Robin Debuysschère, Benoit Scheid
This paper discusses theoretical and experimental considerations of organic molecules nucleating inside tubular reactors or nucleators. Temperature evolution of these liquid systems is experimentally shown for different flow rates as a function of distance when these nucleators are immersed into a water bath set at spontaneous nucleating conditions. When different restrictions in the flow path are introduced before the cooling phase of the liquid; important differences on the nucleation rates are observed. For this study, Aspirin was dissolved in a blend of water and ethanol in a 50/50 vol%. At a concentration of 200 mg/mL and a nucleation temperature of 10 °C, demonstrated to be close to the metastable zonewidth, these flow restrictions show an antagonistic effect on the nucleation rate. One restriction, placed right before the nucleator enters the cooling bath, induces a reduction in nucleation rate. Putting more restrictions into the flow path with an equal separation of 5 cm in between, the nucleation recovers back to its initial value when a second restriction of an expansion ratio 2 is applied. Restrictions with an expansion ratio of 4 exceed this nucleation rate up to an order of magnitude when more than 2 restrictions are put in place. At a higher kinetic driving force defined KDF, at a concentration of 300 mg/mL of Aspirin, the influence of the restriction becomes invariant as a function of the expansion ratio. For all experiments, the nucleation rates is highly increased with the number of restrictions introduced into the flow path. A thermal gradient difference by using the restrictions on the cooling rate of the liquid flowing inside the tubing was not observed experimentally. Therefore only hydrodynamic changes of the flow seems a plausible cause for this nucleation rate - restriction dependence as it is expected that finite amplitude perturbations, amplified by the use of restrictions, cause vortex shedding in current experimental setup.
Continuous preparation for rifampicinJournal of Flow Chemistry - Tập 8 - Trang 129-138 - 2018
Xin Li, Zhuang Liu, Hao Qi, Zheng Fang, Siyu Huang, Shanshan Miao, Kai Guo
To reduce the cost and improve the efficiency for rifampicin preparation, a continuous flow synthesis of rifampicin starting from rifamycin S and tert-butylamine was studied in a microreactor. Two reaction steps and one purification step were coupled in a microreactor, and rifampicin was obtained with 67% overall yield. This method used 25% less 1-amino-4-methyl piperazine and got 16% higher overall yield without changing solvent and purification process between steps. This method has a good potential for further industrial application.
Flow chemistry experiments in the undergraduate teaching laboratory: synthesis of diazo dyes and disulfidesJournal of Flow Chemistry - Tập 11 - Trang 7-12 - 2020
Koen P. L. Kuijpers, Wilko M. A. Weggemans, C. Jan A. Verwijlen, Timothy Noël
By embedding flow technology in the early phases of academic education, students are exposed to both the theoretical and practical aspects of this modern and widely-used technology. Herein, two laboratory flow experiments are described which have been carried out by first year undergraduate students at Eindhoven University of Technology. The experiments are designed to be relatively risk-free and they exploit widely available equipment and cheap capillary flow reactors. The experiments allow students to develop a hands-on understanding of continuous processing and gives them insights in both organic chemistry and chemical engineering. Furthermore, they learn about the benefits of microreactors, continuous processing, multistep reaction sequences and multiphase chemistry. Undoubtedly, such skills are highly valued in both academia and the chemical industry.
Continuous synthesis of copper nanoparticles using a polyol process in a milli-channel reactorJournal of Flow Chemistry - Tập 11 - Trang 661-674 - 2021
Vamsi Vikram Gande, S. Pushpavanam
The physio-chemical properties of metallic nanoparticles are different from their corresponding bulk material. Synthesizing stable zero valent copper nanoparticles is a challenge since they get oxidized easily. This paper discusses both the batch and continuous synthesis of copper nanoparticles using a polyol process in the absence of an inert atmosphere. The nanoparticles were synthesized using copper amine complex as a precursor, ascorbic acid as a reducing agent, and polyvinyl pyrrolidone as a capping agent. UV-Vis spectra confirmed that particles from a continuous synthesis had better Localized Surface Plasmon Resonance (LSPR) peak than those from batch synthesis. At 120 °C, nanoparticles in the continuous process could be synthesized at a residence time of 1 min in contrast to the batch reactor, which needed a reaction time of 4 min. The nanoparticles synthesized were of size 1.5–6 nm. Those synthesized in continuous mode were stable for 10 days as compared to those synthesized in batch mode.
Highlights from the Flow Chemistry Literature 2013 (Part 2)Journal of Flow Chemistry - Tập 3 - Trang 103-107 - 2013
Toma N. Glasnov
In this section of the journal, the continuous-flow chemistry literature of the preceding months is presented. Included are articles published in the period April–June 2013. Some key examples are highlighted in the form of graphical abstracts. The remaining publications in the field are then listed, ordered by journal name, with review articles grouped at the end.
Continuous-flow photochemical carbene transfer reactionsJournal of Flow Chemistry - Tập 10 - Trang 157-160 - 2019
Claire Empel, Rene M. Koenigs
Photochemistry constitutes an important tool to conduct environmentally benign and efficient transformations in organic synthesis. Conventional batch transformations are limited in productivity and scale due to Beer’s law, which can be easily overcome using flow chemistry approaches. Herein, we report on the continuous-flow photolysis of aryl diazoacetates using a glass microreactor and blue LEDs. Following this methodology, we were able to demonstrate the application of continuous-flow chemistry in photochemical cyclopropanation and rearrangement reactions and demonstrate the scalability of photochemical carbene transfer reactions.
Continuous flow palladium-catalyzed trifluoromethylthiolation of C-H bondsJournal of Flow Chemistry - Tập 9 - Trang 9-12 - 2018
Alexanne Bouchard, Vanessa Kairouz, Maxime Manneveau, Heng-Ying Xiong, Tatiana Besset, Xavier Pannecoucke, Hélène Lebel
A continuous flow process for the synthesis of trifluoromethylthioethers is reported. The palladium-catalyzed C-H trifluoromethylthiolation of amides derived from the 8-aminoquinoline using N-[(trifluoromethyl)thio]phthalimide produced the desired products in moderate to good yields with a residence time of 20 min. In comparison with the batch process, the reaction time was decreased by a factor of 100 to 200, demonstrating the positive effect of continuous flow processes for this type of reaction.
Rapid prototyping of a modular optical flow cell for image-based droplet size measurements in emulsification processesJournal of Flow Chemistry - - 2024
Inga Burke, Christina Assies, Norbert Kockmann
Emulsification processes are often found in the process industry and their evaluation is crucial for product quality and safety. Numerous methods exist to analyze critical quality attributes (CQA) such as the droplet sizes and droplet size distribution (DSD) of an emulsification process. During the emulsification process, the optical process accessibility may be limited due to high disperse phase content of liquid-liquid systems. To overcome this challenge, a modular, optical measurement flow cell is presented to widen the application window of optical methods in emulsification processes. In this contribution, the channel geometry is subject of optimization to modify the flow characteristics and produce high optical quality. In terms of rapid prototyping, an iterative optimization procedure via SLA-3D printing was used to increase operability. The results demonstrated that the flow cell resulting from the optimization procedure provides a broad observation window for droplet detection.
“Impossible” Chemistries Based on Flow and MicroJournal of Flow Chemistry - Tập 7 - Trang 60-64 - 2017
Jun-ichi Yoshida, Heejin Kim, Aiichiro Nagaki
This perspective article discusses the basic concept of time control by space based on flow and micro, some examples that realized extremely fast reactions which were difficult to achieve by conventional flask chemistry, and the future of this fascinating chemistry.
A practical experiment to teach students continuous flow and physico-chemical methods: acetylation of ethylene diamine in liquid bi-phaseJournal of Flow Chemistry - Tập 11 Số 1 - Trang 31-36 - 2021
Mary E. Bayana, A. John Blacker, Adam D. Clayton, Katherine E. Jolley, Ricardo Labes, Connor J. Taylor, William R. Reynolds
AbstractDespite growing applications being reported both in academia and industry, continuous flow chemistry remains a relatively untaught field across most chemistry undergraduate courses. This is particularly true in laboratory practical classes, where it is often deemed simpler to carry out synthetic reactions in traditional batch mode using round-bottomed flasks. Herein, we report the development of an undergraduate project that utilises cheap and readily available materials to construct continuous flow reactors. The students compare the performance of different types of reactors and conditions in a biphasic selective acetylation of a symmetrical diamine. Throughout the investigation, the students can vary multiple parameters as they optimise the reaction, thus actively learning and readjusting them based on their improved understanding. The experiments give the students an appreciation of continuous flow techniques in comparison to batch.