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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 (31 July 2019) | Viewed by 16880

Special Issue Editors

Dr. Pilar Salagre

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Guest Editor
Universitat Rovira i Virgili, Departament de Química Física i Inorgànica, C/Marcel lí Domingo 1, 43007 Tarragona, Spain
Interests: heterogeneous catalysis; green chemistry; microwaves; ultrasounds; biomass valorization; glycerol revalorization; catalyst preparation and characterization
Prof. Dr. Yolanda Cesteros

E-Mail Website
Guest Editor
Universitat Rovira i Virgili, Departament de Química Física i Inorgànica, C/Marcel lí Domingo 1, 43007 Tarragona, Spain
Interests: heterogeneous catalysis; green chemistry; microwaves; ultrasounds; biomass valorization; glycerol revalorization; catalysts preparation and characterization

Special Issue Information

Dear Colleagues,

The use of microwaves applied to catalysis has received considerable attention in the last years as an alternative to conventional heating. The benefits of microwave heating for catalysis mainly lie in the fact that it accelerates the reaction rates, can be used at milder reaction conditions than conventional heating (lower temperature and time) with subsequent energy saving, and can lead to higher chemical yields. Additionally, considering that molecules or solid surfaces have a different ability to transform electromagnetic energy into heat, a different reaction selectivity could be obtained by controlling the catalyst properties. On the other hand, the main drawbacks reported until now are related to the non-uniform microwave fields generated in most microwave ovens, which can involve the formation of superheating spots, or the arcing phenomena basically linked to the use of large metal particles.

This Special Issue on “Microwave-Assisted Catalysis” will collect original research papers and short reviews focused on the recent research on this topic in order to highlight its importance. Hence, studies of the application of microwaves for acid-base, (de)-hydrogenation, oxidation reactions or in non-polar reaction media, but also related to the improvements achieved in the design of microwave ovens and reactors employed for catalysis or the scale-up of microwave-assisted reactions, are welcome.

Dr. Pilar Salagre
Prof. Dr. Yolanda Cesteros
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 acid/base-catalysed reactions
  • microwave-assisted (de)-hydrogenation reactions
  • microwave-assisted oxidation reactions
  • microwaves in non-polar reaction media
  • microwave reactors and equipment
  • scale-up microwave-assisted reactions
  • microwave effect on catalyst deactivation
  • nanomaterials in microwave-assisted reactions

Published Papers (5 papers)

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Editorial

Jump to: Research

4 pages, 176 KiB  
Editorial
Editorial Catalysts: Special Issue on “Microwave-Assisted Catalysis”
by Pilar Salagre and Yolanda Cesteros
Catalysts 2020, 10(8), 842; https://doi.org/10.3390/catal10080842 - 26 Jul 2020
Viewed by 1898
Abstract
The concept of circular economy is based on several principles, such as the use of renewable energy resources, including those obtained from the sun, wind, or water; the use of natural raw materials; the manufacturing of products avoiding the generation of wastes and [...] Read more.
The concept of circular economy is based on several principles, such as the use of renewable energy resources, including those obtained from the sun, wind, or water; the use of natural raw materials; the manufacturing of products avoiding the generation of wastes and pollution; keeping products and materials in use for a longer time; or giving new applications to waste [...] Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)

Research

Jump to: Editorial

14 pages, 2199 KiB  
Article
Overcoming Stability Problems in Microwave-Assisted Heterogeneous Catalytic Processes Affected by Catalyst Coking
by Ignacio Julian, Christoffer M. Pedersen, Kostiantyn Achkasov, Jose L. Hueso, Henrik L. Hellstern, Hugo Silva, Reyes Mallada, Zachary J. Davis and Jesus Santamaria
Catalysts 2019, 9(10), 867; https://doi.org/10.3390/catal9100867 - 19 Oct 2019
Cited by 31 | Viewed by 4669
Abstract
Microwave-assisted heterogeneous catalysis (MHC) is gaining attention due to its exciting prospects related to selective catalyst heating, enhanced energy-efficiency, and partial inhibition of detrimental side gas-phase reactions. The induced temperature difference between the catalyst and the comparatively colder surrounding reactive atmosphere is pointed [...] Read more.
Microwave-assisted heterogeneous catalysis (MHC) is gaining attention due to its exciting prospects related to selective catalyst heating, enhanced energy-efficiency, and partial inhibition of detrimental side gas-phase reactions. The induced temperature difference between the catalyst and the comparatively colder surrounding reactive atmosphere is pointed as the main factor of the process selectivity enhancement towards the products of interest in a number of hydrocarbon conversion processes. However, MHC is traditionally restricted to catalytic reactions in the absence of catalyst coking. As excellent MW-susceptors, carbon deposits represent an enormous drawback of the MHC technology, being main responsible of long-term process malfunctions. This work addresses the potentials and limitations of MHC for such processes affected by coking (MHCC). It also intends to evaluate the use of different catalyst and reactor configurations to overcome heating stability problems derived from the undesired coke deposits. The concept of long-term MHCC operation has been experimentally tested/applied to for the methane non-oxidative coupling reaction at 700 °C on Mo/ZSM-5@SiC structured catalysts. Preliminary process scalability tests suggest that a 6-fold power input increases the processing of methane flow by 150 times under the same controlled temperature and spatial velocity conditions. This finding paves the way for the implementation of high-capacity MHCC processes at up-scaled facilities. Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)
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16 pages, 3536 KiB  
Article
Rapid Microwave-Assisted Polyol Synthesis of TiO2-Supported Ruthenium Catalysts for Levulinic Acid Hydrogenation
by Alexander G. R. Howe, Rhodri Maunder, David J. Morgan and Jennifer K. Edwards
Catalysts 2019, 9(9), 748; https://doi.org/10.3390/catal9090748 - 05 Sep 2019
Cited by 7 | Viewed by 3290
Abstract
One wt% Ru/TiO2 catalysts prepared by a one-pot microwave-assisted polyol method have been shown to be highly active for Levulinic acid hydrogenation to γ-Valerolactone. Preparation temperature, microwave irradiation time and choice of Ru precursor were found to have a significant effect on [...] Read more.
One wt% Ru/TiO2 catalysts prepared by a one-pot microwave-assisted polyol method have been shown to be highly active for Levulinic acid hydrogenation to γ-Valerolactone. Preparation temperature, microwave irradiation time and choice of Ru precursor were found to have a significant effect on catalyst activity. In the case of Ru(acac)3-derived catalysts, increasing temperature and longer irradiation times increased catalyst activity to a maximum LA conversion of 69%. Conversely, for catalysts prepared using RuCl3, shorter preparation times and lower temperatures yielded more active catalysts, with a maximum LA conversion of 67%. Catalysts prepared using either precursor were found to contain highly dispersed nanoparticles <3 nm in diameter. XPS analysis of the most and least active catalysts shows that the catalyst surface is covered in a layer of insoluble carbon with surface concentrations exceeding 40% in some cases. This can be attributed to the formation of large condensation oligomers from the reaction between the solvent, ethylene glycol and its oxidation products, as evidenced by the presence of C-O and C = O functionality on the catalyst surface. Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)
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15 pages, 3820 KiB  
Article
Microwave-Assisted Furfural Production Using Hectorites and Fluorohectorites as Catalysts
by Vladimir Sánchez, Anton Dafinov, Pilar Salagre, Jordi Llorca and Yolanda Cesteros
Catalysts 2019, 9(9), 706; https://doi.org/10.3390/catal9090706 - 23 Aug 2019
Cited by 5 | Viewed by 2794
Abstract
It has previously been reported that the use of microwave heating, together with the presence of co-solvents, improves the efficiency of furfural production from biomass. Solid acid catalysts can be a good alternative to mineral acids, since they can prevent corrosion and can [...] Read more.
It has previously been reported that the use of microwave heating, together with the presence of co-solvents, improves the efficiency of furfural production from biomass. Solid acid catalysts can be a good alternative to mineral acids, since they can prevent corrosion and can be reused. However, the formation of humines should be minimized. Several delaminated and fluorinated hectorites, with different types and strengths of acid sites, were synthesized and tested as catalysts for the production of furfural from commercial xylose and from an acid biomass extract of almond shells. A new methodology was developed to prepare crystalline fluorohectorite at 800 °C in just 3 h. The presence of F significantly increased the acidity strength in the protonated fluorohectorite (H-FH) taking into account its high ammonia desorption temperature (721 °C). Additionally, this sample had fourteen times higher total acidity by m2 than the reference H-βeta acid catalyst. H-FH was the most efficient catalyst at short reaction times (1 h) for the transformation of xylose to furfural under microwaves using toluene as co-solvent, regardless of whether the xylose was commercial (20% furfural yield) or an extract of almond shells (60% furfural yield). However, the acidity of the extract affected the fluorohectorite structure and composition. Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)
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11 pages, 2849 KiB  
Article
Microwave-Mediated Continuous Hydrogen Abstraction Reaction from 2-PrOH Catalyzed by Platinum on Carbon Bead
by Tomohiro Ichikawa, Tomohiro Matsuo, Takumu Tachikawa, Wataru Teranishi, Tsuyoshi Yamada, Yoshinari Sawama, Yasunari Monguchi and Hironao Sajiki
Catalysts 2019, 9(8), 655; https://doi.org/10.3390/catal9080655 - 31 Jul 2019
Cited by 6 | Viewed by 3197
Abstract
We developed a microwave-mediated continuous hydrogen production method from 2-PrOH using platinum on a spherical carbon-bead catalyst. The catalyst cartridge consisted of helical glass part, and straight glass part (helix−straight cartridge) was newly developed for the effective microwave heating of 2-PrOH in the [...] Read more.
We developed a microwave-mediated continuous hydrogen production method from 2-PrOH using platinum on a spherical carbon-bead catalyst. The catalyst cartridge consisted of helical glass part, and straight glass part (helix−straight cartridge) was newly developed for the effective microwave heating of 2-PrOH in the presence of 5% Pt/CB. The microwave resonance was properly adjusted within 2.4−2.5 GHz using the helix−straight cartridge with the glass resonance-adjuster tube. The reaction was conducted by the irradiation of only 10 W of single-frequency microwaves and the catalyst was used continuously for at least 13 h without any loss of catalyst activity. Full article
(This article belongs to the Special Issue Microwave-Assisted Catalysis)
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