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Micromachines
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Micromachines for Chemical Process Intensification
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Micromachines for Chemical Process Intensification

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "C：Chemistry".

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 11560

Special Issue Editor

Prof. Dr. Yangcheng Lu

E-Mail Website
Guest Editor
Department of Chemical Engineering, Tsinghua University, Beijing 100091, China
Interests: microreactor; process intensification; micromixing; microdispersion; nanoparticles; flow synthesis; microextraction
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

A sustainable society needs green, efficient, and precise chemical syntheses. To this end, a common and effective strategy is process intensification at various scales. In recent, micromachines as tools for process monitoring, regulation, and intensification have been drawing more and more attentions by scientists and engineers due to the concerns in recognition vision, manipulation capacity, and environmental footprint. For example, flow synthesis based on microtube opens new reaction windows to resolve challenges in low atoms and energy utilization and large intermediate materials hold-up. Accordingly, this special issue seeks to showcase research papers and review articles that focus on all kinds of micromachines towards chemical synthesis intensification. They could be fixed equipment like micromixer, microreactor, and micro-separator, or variable element like microdroplet, microbubbles and micelles, as long they have functions or potentials in the improvement of chemical synthesis. Besides, the angle of view could be a chemical process, a micromachine, or an integrated system.

Prof. Dr. Yangcheng Lu
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • chemical process intensification
  • microreactor
  • chemical synthesis
  • separation
  • microfluidics
  • microfabrication
  • microdevices

Related Special Issues

Published Papers (5 papers)

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Research

9 pages, 2327 KiB  
Article
Using High-Power UV-LED to Accelerate a Decatungstate-Anion-Catalyzed Reaction: A Model Study for the Quick Oxidation of Benzyl Alcohol to Benzoic Acid Using Molecular Oxygen
by Mamoru Hyodo, Hitomi Iwano, Takayoshi Kasakado, Takahide Fukuyama and Ilhyong Ryu
Micromachines 2021, 12(11), 1307; https://doi.org/10.3390/mi12111307 - 25 Oct 2021
Cited by 8 | Viewed by 2509
Abstract
High-power UV-LED irradiation (365 nm) effectively accelerated the decatungstate-anion-catalyzed oxidation of benzyl alcohol 1 to benzoic acid 3 via benzaldehyde 2. As the power of the UV-LED light increased, both the selectivity and yield of benzoic acid also increased. The reaction was [...] Read more.
High-power UV-LED irradiation (365 nm) effectively accelerated the decatungstate-anion-catalyzed oxidation of benzyl alcohol 1 to benzoic acid 3 via benzaldehyde 2. As the power of the UV-LED light increased, both the selectivity and yield of benzoic acid also increased. The reaction was finished within 1 h to give 3 in a 93% yield using 2 mol% of decatungstate anion catalyst. The combination of a flow photoreactor and high-power irradiation accelerated the oxidation reaction to an interval of only a few minutes. Full article
(This article belongs to the Special Issue Micromachines for Chemical Process Intensification)
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23 pages, 7193 KiB  
Article
Numerical Analysis of the Heterogeneity Effect on Electroosmotic Micromixers Based on the Standard Deviation of Concentration and Mixing Entropy Index
by Alireza Farahinia, Jafar Jamaati, Hamid Niazmand and Wenjun Zhang
Micromachines 2021, 12(9), 1055; https://doi.org/10.3390/mi12091055 - 31 Aug 2021
Cited by 5 | Viewed by 1575
Abstract
One approach to achieve a homogeneous mixture in microfluidic systems in the quickest time and shortest possible length is to employ electroosmotic flow characteristics with heterogeneous surface properties. Mixing using electroosmotic flow inside microchannels with homogeneous walls is done primarily under the influence [...] Read more.
One approach to achieve a homogeneous mixture in microfluidic systems in the quickest time and shortest possible length is to employ electroosmotic flow characteristics with heterogeneous surface properties. Mixing using electroosmotic flow inside microchannels with homogeneous walls is done primarily under the influence of molecular diffusion, which is not strong enough to mix the fluids thoroughly. However, surface chemistry technology can help create desired patterns on microchannel walls to generate significant rotational currents and improve mixing efficiency remarkably. This study analyzes the function of a heterogeneous zeta-potential patch located on a microchannel wall in creating mixing inside a microchannel affected by electroosmotic flow and determines the optimal length to achieve the desired mixing rate. The approximate Helmholtz–Smoluchowski model is suggested to reduce computational costs and simplify the solving process. The results show that the heterogeneity length and location of the zeta-potential patch affect the final mixing proficiency. It was also observed that the slip coefficient on the wall has a more significant effect than the Reynolds number change on improving the mixing efficiency of electroosmotic micromixers, benefiting the heterogeneous distribution of zeta-potential. In addition, using a channel with a heterogeneous zeta-potential patch covered by a slip surface did not lead to an adequate mixing in low Reynolds numbers. Therefore, a homogeneous channel without any heterogeneity would be a priority in such a range of Reynolds numbers. However, increasing the Reynolds number and the presence of a slip coefficient on the heterogeneous channel wall enhances the mixing efficiency relative to the homogeneous one. It should be noted, though, that increasing the slip coefficient will make the mixing efficiency decrease sharply in any situation, especially in high Reynolds numbers. Full article
(This article belongs to the Special Issue Micromachines for Chemical Process Intensification)
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10 pages, 25824 KiB  
Article
Metal-Free Fabrication of Fused Silica Extended Nanofluidic Channel to Remove Artifacts in Chemical Analysis
by Kyojiro Morikawa, Ryoichi Ohta, Kazuma Mawatari and Takehiko Kitamori
Micromachines 2021, 12(8), 917; https://doi.org/10.3390/mi12080917 - 31 Jul 2021
Cited by 8 | Viewed by 2342
Abstract
In microfluidics, especially in nanofluidics, nanochannels with functionalized surfaces have recently attracted attention for use as a new tool for the investigation of chemical reaction fields. Molecules handled in the reaction field can reach the single–molecule level due to the small size of [...] Read more.
In microfluidics, especially in nanofluidics, nanochannels with functionalized surfaces have recently attracted attention for use as a new tool for the investigation of chemical reaction fields. Molecules handled in the reaction field can reach the single–molecule level due to the small size of the nanochannel. In such surroundings, contamination of the channel surface should be removed at the single–molecule level. In this study, it was assumed that metal materials could contaminate the nanochannels during the fabrication processes; therefore, we aimed to develop metal-free fabrication processes. Fused silica channels 1000 nm-deep were conventionally fabricated using a chromium mask. Instead of chromium, electron beam resists more than 1000 nm thick were used and the lithography conditions were optimized. From the results of optimization, channels with 1000 nm scale width and depth were fabricated on fused silica substrates without the use of a chromium mask. In nanofluidic experiments, an oxidation reaction was observed in a device fabricated by conventional fabrication processes using a chromium mask. It was found that Cr6+ remained on the channel surfaces and reacted with chemicals in the liquid phase in the extended nanochannels; this effect occurred at least to the micromolar level. In contrast, the device fabricated with metal-free processes was free of artifacts induced by the presence of chromium. The developed fabrication processes and results of this study will be a significant contribution to the fundamental technologies employed in the fields of microfluidics and nanofluidics. Full article
(This article belongs to the Special Issue Micromachines for Chemical Process Intensification)
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16 pages, 3146 KiB  
Article
Liquid Flow and Mass Transfer Behaviors in a Butterfly-Shaped Microreactor
by Haicheng Lv, Zhirong Yang, Jing Zhang, Gang Qian, Xuezhi Duan, Zhongming Shu and Xinggui Zhou
Micromachines 2021, 12(8), 883; https://doi.org/10.3390/mi12080883 - 27 Jul 2021
Cited by 12 | Viewed by 2071
Abstract
Based on the split-and-recombine principle, a millimeter-scale butterfly-shaped microreactor was designed and fabricated through femtosecond laser micromachining. The velocity fields, streamlines and pressure fields of the single-phase flow in the microreactor were obtained by a computational fluid dynamics simulation, and the influence of [...] Read more.
Based on the split-and-recombine principle, a millimeter-scale butterfly-shaped microreactor was designed and fabricated through femtosecond laser micromachining. The velocity fields, streamlines and pressure fields of the single-phase flow in the microreactor were obtained by a computational fluid dynamics simulation, and the influence of flow rates on the homogeneous mixing efficiency was quantified by the mixing index. The flow behaviors in the microreactor were investigated using water and n-butanol, from which schematic diagrams of various flow patterns were given and a flow pattern map was established for regulating the flow behavior via controlling the flow rates of the two-phase flow. Furthermore, effects of the two-phase flow rates on the droplet flow behavior (droplet number, droplet size and standard deviation) in the microreactor were investigated. In addition, the interfacial mass transfer behaviors of liquid–liquid flow were evaluated using the standard low interfacial tension system of “n-butanol/succinic acid/water”, where the dependence between the flow pattern and mass transfer was discussed. The empirical relationship between the volumetric mass transfer coefficient and Reynold number was established with prediction error less than 20%. Full article
(This article belongs to the Special Issue Micromachines for Chemical Process Intensification)
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16 pages, 3870 KiB  
Article
Process Intensification of 2,2′-(4-Nitrophenyl) Dipyrromethane Synthesis with a SO3H-Functionalized Ionic Liquid Catalyst in Pickering-Emulsion-Based Packed-Bed Microreactors
by Hong Zhang, Minjing Shang, Yuchao Zhao and Yuanhai Su
Micromachines 2021, 12(7), 796; https://doi.org/10.3390/mi12070796 - 05 Jul 2021
Cited by 2 | Viewed by 2256
Abstract
A stable water-in-oil Pickering emulsion was fabricated with SO3H-functionalized ionic liquid and surface-modified silica nanoparticles and used for 2,2′-(4-nitrophenyl) dipyrromethane synthesis in a packed-bed microreactor, exhibiting high reaction activity and product selectivity. The compartmentalized water droplets of the Pickering emulsion had [...] Read more.
A stable water-in-oil Pickering emulsion was fabricated with SO3H-functionalized ionic liquid and surface-modified silica nanoparticles and used for 2,2′-(4-nitrophenyl) dipyrromethane synthesis in a packed-bed microreactor, exhibiting high reaction activity and product selectivity. The compartmentalized water droplets of the Pickering emulsion had an excellent ability to confine the ionic liquid against loss under continuous-flow conditions, and the excellent durability of the catalytic system without a significant decrease in the reaction efficiency and selectivity was achieved. Compared with the reaction performance of a liquid–liquid slug-flow microreactor and batch reactor, the Pickering-emulsion-based catalytic system showed a higher specific interfacial area between the catalytic and reactant phases, benefiting the synthesis of 2,2′-(4-nitrophenyl) dipyrromethane and resulting in a higher yield (90%). This work indicated that an increase in the contact of reactants with catalytic aqueous solution in a Pickering-emulsion-based packed-bed microreactor can greatly enhance the synthetic process of dipyrromethane, giving an excellent yield of products and a short reaction time. It was revealed that Pickering-emulsion-based packed-bed microreactors with the use of ionic liquids as catalysts for interfacial catalysis have great application potential in the process of intensification of organic synthesis. Full article
(This article belongs to the Special Issue Micromachines for Chemical Process Intensification)
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