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Special Issue "Heterogeneous Acid Catalysts"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: closed (30 April 2014).

Special Issue Editors

Guest Editor
Prof. Dr. Detlef W. Bahnemann Website E-Mail
Gottfried Wilhelm Leibniz Universitat, Institute of Technical Chemistry, Hannover, Germany and Head of Laboratory ”Photoactive Nanocomposite Materials”, Saint-Petersburg State University, St.-Petersburg, Russia
Interests: photo catalysis; self-cleaning; superhydrophilic; antibacterial surfaces; metal and semiconductor particles; nanocristalyne transparent coatings; functional test according to DIN; CEN and ISO
Guest Editor
Dr. Amer Hakki E-Mail
Institut fuer Technische Chemie, Gottfried Wilhelm Leibniz Universitaet Hannover Callinstrasse 3, D-30167 Hannover, Germany
Interests: photocatalysis; nanotechnology

Special Issue Information

Dear Colleagues,

Acid-catalyzed reactions are by far the most numerous and best-studied reaction types in which organic functional groups undergo an array of different transformations. These include various electrophilic aromatic substitutions, e.g. nitration, halogenations, and Friedel-crafts alkylation and acylation. In addition, numerous rearrangement reactions, such as Beckmann and Fries rearrangements, are also catalyzed by acids, as well as a variety of cyclization reactions such as Diels-Alder reactions and the synthesis of heterocyclic compounds.

Moreover, esterification and transesterification reactions which enhance the use of high acid value oil to be used as feedstock for synthesis of biodiesel, which is thought to be one suitable solution to meet the future demand of energy sources, are also examples of important reactions that are catalyzed by acids.

However, the waste drives from the use of mineral and Lewis acids which cannot be readily recovered and recycled are the main drawbacks of these conventional homogeneous acid-catalysts.

In contrast, heterogeneous acid catalysts have the advantages of easy recovery and reusability and are readily amenable to continuous processing. Moreover, these acids are less corrosive and safer in handling than the known homogeneous acids.

Various solid acid catalysts, such as resins, tungstated and sulfated metal oxides, such as zirconia, polyaniline sulfate, heteropolyacid, metal complexes, zeolites, acidic ionic liquid, and others have been explored as potential heterogeneous acid catalysts. Beside the activity of these catalysts—resulting in moderate to high conversions and yields, their deactivation, poisoning, and ability of leaching in the reaction medium—are important aspects.

The objective of this Special Issue of Molecules is to focus attention on the latest developments in heterogeneous acid catalysts and their applicability for different syntheses along with all other aspects.

Prof. Dr. Detlef W. Bahnemann
Dr. Amer Hakki
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 papers will be 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. Molecules is an international peer-reviewed open access semimonthly 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 1800 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

  • solid acids
  • acid catalysts
  • cyclization
  • heterogeneous catalysts
  • biodiesel
  • heterocyclic compounds
  • rearrangement reactions

Published Papers (3 papers)

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Research

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Open AccessArticle
Montmorillonite Clay-Promoted, Solvent-Free Cross-Aldol Condensations under Focused Microwave Irradiation
Molecules 2014, 19(6), 7317-7326; https://doi.org/10.3390/molecules19067317 - 04 Jun 2014
Cited by 15
Abstract
An environmentally benign, clean and general protocol was developed for the synthesis of aryl and heteroaryl trans-chalcones. This method involved solvent-free reaction conditions under microwave irradiation in the presence of a clay-based catalyst, and afforded the target compounds in good yields and [...] Read more.
An environmentally benign, clean and general protocol was developed for the synthesis of aryl and heteroaryl trans-chalcones. This method involved solvent-free reaction conditions under microwave irradiation in the presence of a clay-based catalyst, and afforded the target compounds in good yields and short reaction times. Furthermore, the same conditions allowed the synthesis of symmetrical, diarylmethylene-α,β-unsaturated ketones from aromatic aldehydes and ketones. Full article
(This article belongs to the Special Issue Heterogeneous Acid Catalysts)
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Review

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Open AccessReview
Graphene-Based Nanomaterials as Heterogeneous Acid Catalysts: A Comprehensive Perspective
Molecules 2014, 19(9), 14582-14614; https://doi.org/10.3390/molecules190914582 - 15 Sep 2014
Cited by 75
Abstract
Acid catalysis is quite prevalent and probably one of the most routine operations in both industrial processes and research laboratories worldwide. Recently, “graphene”, a two dimensional single-layer carbon sheet with hexagonal packed lattice structure, imitative of nanomaterials, has shown great potential as alternative [...] Read more.
Acid catalysis is quite prevalent and probably one of the most routine operations in both industrial processes and research laboratories worldwide. Recently, “graphene”, a two dimensional single-layer carbon sheet with hexagonal packed lattice structure, imitative of nanomaterials, has shown great potential as alternative and eco-friendly solid carbocatalyst for a variety of acid-catalyzed reactions. Owing to their exceptional physical, chemical, and mechanical properties, graphene-based nanomaterials (G-NMs) offer highly stable Brønsted acidic sites, high mass transfer, relatively large surface areas, water tolerant character, and convenient recoverability as well as recyclability, whilst retaining high activity in acid-catalyzed chemical reactions. This comprehensive review focuses on the chemistry of G-NMs, including their synthesis, characterization, properties, functionalization, and up-to-date applications in heterogeneous acid catalysis. In line with this, in certain instances readers may find herein some criticisms that should be taken as constructive and would be of value in understanding the scope and limitations of current approaches utilizing graphene and its derivatives for the same. Full article
(This article belongs to the Special Issue Heterogeneous Acid Catalysts)
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Open AccessReview
The Use of Supported Acidic Ionic Liquids in Organic Synthesis
Molecules 2014, 19(7), 8840-8884; https://doi.org/10.3390/molecules19078840 - 26 Jun 2014
Cited by 60
Abstract
Catalysts obtained by the immobilisation of acidic ionic liquids (ILs) on solid supports offer several advantages compared to the use of catalytically active ILs themselves. Immobilisation may result in an increase in the number of accessible active sites of the catalyst and a [...] Read more.
Catalysts obtained by the immobilisation of acidic ionic liquids (ILs) on solid supports offer several advantages compared to the use of catalytically active ILs themselves. Immobilisation may result in an increase in the number of accessible active sites of the catalyst and a reduction of the amount of the IL required. The ionic liquid films on the carrier surfaces provide a homogeneous environment for catalytic reactions but the catalyst appears macroscopically as a dry solid, so it can simply be separated from the reaction mixture. As another advantage, it can easily be applied in a continuous fixed bed reactor. In the present review the main synthetic strategies towards the preparation of supported Lewis acidic and Brønsted acidic ILs are summarised. The most important characterisation methods and structural features of the supported ionic liquids are presented. Their efficiency in catalytic reactions is discussed with special emphasis on their recyclability. Full article
(This article belongs to the Special Issue Heterogeneous Acid Catalysts)
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