Special Issue "Continuous-Flow Catalysis"

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

Deadline for manuscript submissions: closed (28 February 2021).

Special Issue Editors

Dr. Sándor B. Ötvös
E-Mail Website
Guest Editor
Institute of Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
Interests: asymmetric catalysis; continuous flow chemistry; heterocyclic chemistry; heterogeneous catalysis; microreactor technology; photocatalysis; sustainable syntheses
Prof. Dr. Christophe Len
E-Mail Website
Co-Guest Editor
1. Chimie ParisTech - CNRS, Institute of Chem. For Life & Health Sciences, 11 rue P&M Curie, F-75231 Paris Cedex 05, France
2. Centre de Recherche Royallieu, Université de Technologie de Compiègne – UTC, F-60200 Compiègne, France
Interests: fine chemistry from natural substances: carbohydrates, cyclodextrins, nucleosides, lipids; chemistry and processes for the sustainable development; organic chemistry in green solvents; homogeneous, heterogeneous, and micellar catalysis; continuous flow applied to organic chemistry; organic chemistry under microwave activation
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Special Issue Information

Dear Colleagues,

Advances toward increased sustainability require novel approaches and developments that involve enhanced performance and value in association with a reduced environmental impact. These demands provoked the launch of novel synthetic methodologies, and continuous-flow chemistry has emerged as an enabling tool to accelerate, integrate, simplify, scale up, and automatize chemical reactions, in combination with an inherently safer and ‘greener’ nature over conventional batch-based protocols. Over the past few years, it has been repeatedly demonstrated that flow chemistry and catalysis constitute an ideal match for the sustainable synthesis of a variety of valuable products. Either homogeneous or heterogeneous catalytic reactions can greatly be facilitated by virtue of the technical advances of continuous flow reaction technology, and this is especially true for reactions involving gases, hazardous substances, and reactive intermediates, as well as for photo- and electrocatalytic transformations.

This Special Issue will focus on recent research on ‘Continuous-Flow Catalysis’ and welcome original research papers, reviews, and commentaries from the field. The potential topics include organo-, organometallic- and biocatalysis, various metal-catalyzed reactions, photo- and electrocatalysis, and catalytic reactions involving gases, by applying either homogenous or heterogeneous catalysts in flow systems.

Dr. Sándor B. Ötvös
Prof. Dr. Christophe Len
Guest Editors

Manuscript Submission Information

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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 2000 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

  • Biocatalysis
  • Continuous-flow chemistry
  • Homogeneous catalysts
  • Heterogeneous catalysts
  • Metal-catalyzed reactions
  • Microreactors
  • Organocatalysis
  • Photocatalysis
  • Sustainable synthesis

Published Papers (6 papers)

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Research

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Open AccessFeature PaperArticle
Microwave-Assisted Continuous Flow for the Selective Oligomerization of Glycerol
Catalysts 2021, 11(2), 166; https://doi.org/10.3390/catal11020166 - 25 Jan 2021
Viewed by 424
Abstract
The continuous oligomerization of glycerol for the formation of polyglycerol was carried out for the first time under microwave activation. In the presence of potassium carbonate, we studied the ease of handling, effects of temperature, flow rate and residence time of an inexpensive [...] Read more.
The continuous oligomerization of glycerol for the formation of polyglycerol was carried out for the first time under microwave activation. In the presence of potassium carbonate, we studied the ease of handling, effects of temperature, flow rate and residence time of an inexpensive homogeneous commercial catalyst. The main linear and branched-chain diglycerol and triglycerol regioisomers were characterized and the quantification of the different isomers was realized. Successive cyclic mode processes followed by short distance distillation allowed the mixture to be enriched with glycerol ethers and thus to obtain a mixture of diglycerol (50.2 wt%), triglycerol (22.1 wt%), tetraglycerol (9.5 wt%), and pentaglycerol (4.3 wt%). Full article
(This article belongs to the Special Issue Continuous-Flow Catalysis)
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Open AccessFeature PaperArticle
Concatenated Batch and Continuous Flow Procedures for the Upgrading of Glycerol-Derived Aminodiols via N-Acetylation and Acetalization Reactions
Catalysts 2021, 11(1), 21; https://doi.org/10.3390/catal11010021 - 27 Dec 2020
Viewed by 456
Abstract
An unprecedented two-step sequence was designed by combining batch and continuous flow (CF) protocols for the upgrading of two aminodiol regioisomers derived from glycerol, i.e., 3-amino-1,2-propanediol and 2-amino-1,3-propanediol (serinol). Under batch conditions, at 80–90 °C, both substrates were quantitatively converted into the corresponding [...] Read more.
An unprecedented two-step sequence was designed by combining batch and continuous flow (CF) protocols for the upgrading of two aminodiol regioisomers derived from glycerol, i.e., 3-amino-1,2-propanediol and 2-amino-1,3-propanediol (serinol). Under batch conditions, at 80–90 °C, both substrates were quantitatively converted into the corresponding amides through a catalyst-free N-acetylation reaction mediated by an innocuous enol ester as isopropenyl acetate (iPAc). Thereafter, at 30–100 °C and 1–10 atm, the amide derivatives underwent a selective CF-acetalisation in the presence of acetone and a solid acid catalyst, to afford the double-functionalized (amide-acetal) products. Full article
(This article belongs to the Special Issue Continuous-Flow Catalysis)
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Open AccessArticle
Optimization of a Catalytic Chemoenzymatic Tandem Reaction for the Synthesis of Natural Stilbenes in Continuous Flow
Catalysts 2020, 10(12), 1404; https://doi.org/10.3390/catal10121404 - 01 Dec 2020
Cited by 1 | Viewed by 521
Abstract
In view of the development of efficient processes for the synthesis of high-value compounds, the combination of bio- and chemocatalysis is highly promising. In addition, implementation of immobilized catalysts into continuous setups allows a straightforward separation of the target compound from the reaction [...] Read more.
In view of the development of efficient processes for the synthesis of high-value compounds, the combination of bio- and chemocatalysis is highly promising. In addition, implementation of immobilized catalysts into continuous setups allows a straightforward separation of the target compound from the reaction mixture and ensures uniform product quality. In this work, we report the optimization of a chemoenzymatic tandem reaction in continuous flow and its extended application for the synthesis of pharmacologically active resveratrol and pterostilbene. The tandem reaction involves enzymatic decarboxylation of coumaric acid employing encapsulated phenolic acid decarboxylase from B. subtilis and a Heck coupling of the obtained vinylphenol with an aryl iodide using heterogeneous Pd-Ce-Sn oxides implemented in a packed bed reactor. By optimization of the reaction conditions for the limiting cross-coupling step, the yield of (E)-4-hydroxystilbene using the fully continuous setup could be more than doubled compared to previous work. Furthermore, the improved chemoenzymatic cascade could also be applied to the synthesis of resveratrol and pterostilbene in a continuous fashion. Leaching of the metal catalyst at high temperatures limited the process in many perspectives. Therefore, the feasibility of a reactor setup with reversed flow was experimentally evaluated and approved. Full article
(This article belongs to the Special Issue Continuous-Flow Catalysis)
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Open AccessArticle
Boosting the Performance of Nano-Ni Catalysts by Palladium Doping in Flow Hydrogenation of Sulcatone
Catalysts 2020, 10(11), 1267; https://doi.org/10.3390/catal10111267 - 02 Nov 2020
Viewed by 580
Abstract
The effect of Pd doping on nano-Ni catalyst hydrogenation aptitude in sulcatone (6-methyl-5-hepten-2-one) hydrogenation was investigated. Obtained results demonstrated that the addition of non-catalytic amounts of Pd to the surface of parent Ni catalyst improves the activity to the extent that it surpassed [...] Read more.
The effect of Pd doping on nano-Ni catalyst hydrogenation aptitude in sulcatone (6-methyl-5-hepten-2-one) hydrogenation was investigated. Obtained results demonstrated that the addition of non-catalytic amounts of Pd to the surface of parent Ni catalyst improves the activity to the extent that it surpassed the activity of 2.16 wt% Pd catalyst (model catalyst) at optimal reaction conditions in the flow hydrogenation of an unsaturated ketone. Pd doping improves hydrogen activation on the catalyst, which was found to be a rate-limiting step using kinetic isotopic measurements and theoretical calculations. Full article
(This article belongs to the Special Issue Continuous-Flow Catalysis)
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Open AccessArticle
Efficient Chemo-Enzymatic Flow Synthesis of High Value Amides and Esters
Catalysts 2020, 10(8), 939; https://doi.org/10.3390/catal10080939 - 16 Aug 2020
Cited by 4 | Viewed by 825
Abstract
A flow-based chemo-enzymatic synthesis of selected APIs (i.e., butacaine, procaine and procainamide) has been developed. A bioreactor made of MsAcT, a versatile acyltransferase from Mycobacterium smegmatis, immobilised on glyoxyl–garose, was exploited to efficiently prepare amide and ester intermediates in gram scale. Immobilised [...] Read more.
A flow-based chemo-enzymatic synthesis of selected APIs (i.e., butacaine, procaine and procainamide) has been developed. A bioreactor made of MsAcT, a versatile acyltransferase from Mycobacterium smegmatis, immobilised on glyoxyl–garose, was exploited to efficiently prepare amide and ester intermediates in gram scale. Immobilised MsAcT was employed in pure organic solvent, demonstrating high stability and reusability. In-line purification of the key intermediates using polymer-bound sulphonyl chloride was added after the bioreactor, enhancing the automation of the process. A final hydrogenation step using the H-Cube reactor was further carried out to obtain the selected APIs in excellent yields (>99%), making the process fast, safe and easily handled. Full article
(This article belongs to the Special Issue Continuous-Flow Catalysis)
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Review

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Open AccessReview
Recent Advances in Continuous-Flow Reactions Using Metal-Free Homogeneous Catalysts
Catalysts 2020, 10(11), 1321; https://doi.org/10.3390/catal10111321 - 13 Nov 2020
Viewed by 707
Abstract
Developments that result in high-yielding, low-cost, safe, scalable, and less-wasteful processes are the most important goals in synthetic organic chemistry. Continuous-flow reactions have garnered much attention due to many advantages over conventional batch reactions that include precise control of short reaction times and [...] Read more.
Developments that result in high-yielding, low-cost, safe, scalable, and less-wasteful processes are the most important goals in synthetic organic chemistry. Continuous-flow reactions have garnered much attention due to many advantages over conventional batch reactions that include precise control of short reaction times and temperatures, low risk in handling dangerous compounds, and ease in scaling up synthesis. Combinations of continuous-flow reactions with homogeneous, metal-free catalysts further enhances advantages that include low-cost and ready availability, low toxicity, higher stability in air and water, and increased synthetic efficiency due to the avoidance of the time-consuming removal of toxic metal traces. This review summarizes recently reported continuous-flow reactions using metal-free homogeneous catalysts and classifies them either as acidic catalysts, basic catalysts, or miscellaneous catalysts. In addition, we compare the results between continuous-flow conditions and conventional batch conditions to reveal the advantages of using flow reactions with metal-free homogeneous catalysts. Full article
(This article belongs to the Special Issue Continuous-Flow Catalysis)
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