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Catalysts
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Microwave-Assisted Catalysis
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Microwave-Assisted Catalysis

A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (30 June 2021) | Viewed by 13328

Special Issue Editors

Dr. Dawid Mikulski

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Guest Editor
Department of Biotechnology, Faculty of Biological Sciences, Kazimierz Wielki University, 85-671 Bydgoszcz, Poland
Interests: bioethanol; biomass pretreatment; fermentation technology; yeast; cellulose hydrolysis; microwave-assisted pretreatment; biosynthesis; biotransformation; biofuels production; biocatalysis
Special Issues, Collections and Topics in MDPI journals
Dr. Grzegorz Kłosowski

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Guest Editor
Department of Biotechnology, Faculty of Biological Sciences, Kazimierz Wielki University, 85-671 Bydgoszcz, Poland
Interests: optimization of bioethanol production technology from lignocellulosic biomass and starchy raw materials (improvement of the ethanol productivity, costs reduction, energy saving); improvement of the technological methods used for the enzymatic degradation of polysaccharides; impact of raw materials contamination and quality on fermentation yield and formation of alcoholic fermentation volatile by-products (quality of raw spirit and alcoholic beverages); screening and selection strategies of filamentous fungi degrading cellulosic biomass
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Microwave radiation intensifies the synthesis of organic compounds and supports the decomposition of complex structures (such as lignocellulose) in an acidic environment or when metallic catalysts are used. The absorption of microwaves by the reaction medium is accompanied by so-called dielectric loss, mainly due to dipole polarization and dielectric constant phenomenon, which is related to the material's ability to absorb and preserve energy. If the material-absorbing microwaves contain molecules with an electrical dipole moment, then the energy of the electromagnetic waves is transmitted to the material and dissipated in the form of heat. Thanks to these specific interactions, microwave radiation is an alternative to the conventional heating method. However, compared to conventional heating, microwave radiation: (I) has a better energy balance, (II) provides a possibility of heating the material itself, not the tank in which it is located, (III) reaches the desired temperature faster, (IV) increases reaction rate and improves its efficiency, (V) ensures even temperature distribution in biomass, (VI) provides a better control of reaction temperature, as the heating process can be stopped immediately. Effective microwave heating is the main reason for using this technique in the thermochemical conversion of biomass to biofuels. Due to its properties, microwave radiation is increasingly used in catalytic processes and organic compound conversions.

The Catalysts Special Issue entitled "Microwave-Assisted Catalysis" includes original research papers and reviews that cover the latest developments in the use of microwave radiation in lignocellulosic biomass decomposition, the conversion of organic compounds, and catalysis using acid/basic and metallic catalysts. The Special Issue also features articles on the industrial use of microwave generators and the construction of microwave catalysis reactors.

Dr. Dawid Mikulski
Prof. Grzegorz Kłosowski
Guest Editors

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. Catalysts 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 2700 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

  • microwave-assisted biomass pretreatment
  • microwave-assisted organic compounds conversion
  • microwave-assisted acid/base and metal-catalysed reactions
  • industrial microwave generators
  • microwave reactors and equipment.

Published Papers (4 papers)

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Research

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19 pages, 3048 KiB  
Article
Environmentally Friendly Nafion-Catalyzed Synthesis of Substituted 2-Ethyl-3-Methylquinolines from Aniline and Propionaldehyde under Microwave Irradiation
by Chieh-Kai Chan, Chien-Yu Lai and Cheng-Chung Wang
Catalysts 2021, 11(8), 877; https://doi.org/10.3390/catal11080877 - 21 Jul 2021
Cited by 3 | Viewed by 2400
Abstract
Herein, we report a facile synthetic methodology for the preparation of 2,3-dialkylquinolines from anilines and propionaldehydes. This cyclization involved environmentally friendly Nafion® NR50 as an acidic catalyst with microwave irradiation as the heating source. A series of substituted 2-ethyl-3-methylquinolines were prepared from [...] Read more.
Herein, we report a facile synthetic methodology for the preparation of 2,3-dialkylquinolines from anilines and propionaldehydes. This cyclization involved environmentally friendly Nafion® NR50 as an acidic catalyst with microwave irradiation as the heating source. A series of substituted 2-ethyl-3-methylquinolines were prepared from various anilines and propionaldehyde derivatives through this protocol with good to excellent yields. Some new chemical structures were confirmed by X-ray single-crystal diffraction analysis and the related data were provided. The plausible reaction mechanism studies are also discussed. Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)
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14 pages, 18445 KiB  
Article
Search for the Microwave Nonthermal Effect in Microwave Chemistry: Synthesis of the Heptyl Butanoate Ester with Microwave Selective Heating of a Sulfonated Activated Carbon Catalyst
by Daisuke Sakemi, Nick Serpone and Satoshi Horikoshi
Catalysts 2021, 11(4), 466; https://doi.org/10.3390/catal11040466 - 2 Apr 2021
Cited by 3 | Viewed by 1760
Abstract
The heptyl butanoate ester was synthesized from butanoic acid and heptanol in a heterogeneous medium in the presence of sulfonated activated carbon (AC-SO3H) catalyst particles subjected to microwave irradiation, which led to higher conversion yields (greater product yields) than conventional heating [...] Read more.
The heptyl butanoate ester was synthesized from butanoic acid and heptanol in a heterogeneous medium in the presence of sulfonated activated carbon (AC-SO3H) catalyst particles subjected to microwave irradiation, which led to higher conversion yields (greater product yields) than conventional heating with an oil bath. The advantage of the microwaves appeared only when the moisture content in the butanoic acid batch(es) was high, suggesting that, unlike conventional heating, the reverse reaction caused by the moisture content and/or by the byproduct water was suppressed by the microwaves. This contrasted with the results that were found when carrying out the reaction in a homogeneous medium in the presence of the 2,4,6-trimethylpyridinium-p-toluene sulfonate (TMP-PTS) catalyst, as product yields were not improved by microwave heating relative to conventional heating. The removal of moisture/water content in the reaction solution was more pronounced when the reactor was cooled, as the reaction yields were enhanced via selective heating of the heterogeneous catalyst. A coupled electromagnetic field/heat transfer analysis gave credence to the selective heating of the AC-SO3H catalyst, which was further enhanced by cooling the reactor. It was deduced that unforeseen impurities and local high-temperature fields generated on the surface of small fine catalyst particles may have had an effect on the microwave chemistry such that the associated phenomena could be mistaken as originating from a nonthermal effect of the microwaves. Accordingly, it is highly recommended that impurities and selective heating be taken into consideration when examining and concluding the occurrence of a microwave nonthermal effect. Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)
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14 pages, 4695 KiB  
Article
Application of Variable Frequency Microwaves in Microwave-Assisted Chemistry: Relevance and Suppression of Arc Discharges on Conductive Catalysts
by Satoshi Horikoshi, Yuuhei Arai, Iftikhar Ahmad, Clayton DeCamillis, Keith Hicks, Bob Schauer and Nick Serpone
Catalysts 2020, 10(7), 777; https://doi.org/10.3390/catal10070777 - 11 Jul 2020
Cited by 10 | Viewed by 2896
Abstract
The application and advantages of variable frequency microwaves (VFM; range, 5.85–6.65 GHz) are reported for the first time in microwave chemistry, particularly when carrying out reactions catalyzed by metallic conductive catalysts so as to avoid the formation of arc discharges, and especially when [...] Read more.
The application and advantages of variable frequency microwaves (VFM; range, 5.85–6.65 GHz) are reported for the first time in microwave chemistry, particularly when carrying out reactions catalyzed by metallic conductive catalysts so as to avoid the formation of arc discharges, and especially when using a strong microwave absorber such as activated carbon (AC) particulates as supports of metal-based catalysts. Two model reactions performed in low boiling point nonpolar solvents are described wherein arc discharges easily occur under the more conventional fixed frequency microwave (FFM) approach: (i) the synthesis of 4-methylbiphenyl (4MBP) by the Suzuki-Miyaura cross-coupling process catalyzed by Pd particles supported on AC particulates (Pd/AC), and (ii) the synthesis of toluene via the dehydrogenation of methylcyclohexane (MCH) catalyzed by Pt particles dispersed on AC particulates (Pt/AC). Contrary to the usage of fixed frequency microwaves (5.85 GHz and 6.65 GHz), the use of VFM microwaves increased the chemical yields of 4MBP {49% versus 5–8% after 60 min} and toluene {89% versus 24% after 10 min} by suppressing the formation of discharges that otherwise occur on the catalyst/AC surface with FFM microwaves. Consequently, relative to the latter approach, the VFM technology is significantly advantageous, especially in reactions with solid conductive catalysts, not least of which are the reduction in power consumption, thus energy savings, and the prevention of potential mishaps. Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)
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Review

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35 pages, 12552 KiB  
Review
Recent Advances in Microwave-Assisted Copper-Catalyzed Cross-Coupling Reactions
by Younis Baqi
Catalysts 2021, 11(1), 46; https://doi.org/10.3390/catal11010046 - 31 Dec 2020
Cited by 23 | Viewed by 5528
Abstract
Cross-coupling reactions furnishing carbon–carbon (C–C) and carbon–heteroatom (C–X) bond is one of the most challenging tasks in organic syntheses. The early developed reaction protocols by Ullmann, Ullman–Goldberg, Cadiot–Chodkiewicz, Castro–Stephens, and Corey–House, utilizing elemental copper or its salts as catalyst have, for decades, attracted [...] Read more.
Cross-coupling reactions furnishing carbon–carbon (C–C) and carbon–heteroatom (C–X) bond is one of the most challenging tasks in organic syntheses. The early developed reaction protocols by Ullmann, Ullman–Goldberg, Cadiot–Chodkiewicz, Castro–Stephens, and Corey–House, utilizing elemental copper or its salts as catalyst have, for decades, attracted and inspired scientists. However, these reactions were suffering from the range of functional groups tolerated as well as severely restricted by the harsh reaction conditions often required high temperatures (150–200 °C) for extended reaction time. Enormous efforts have been paid to develop and achieve more sustainable reaction conditions by applying the microwave irradiation. The use of controlled microwave heating dramatically reduces the time required and therefore resulting in increase in the yield as well as the efficiency of the reaction. This review is mainly focuses on the recent advances and applications of copper catalyzed cross-coupling generation of carbon–carbon and carbon–heteroatom bond under microwave technology. Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)
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