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Sol–Gel Chemistry: A Toolbox for Catalyst Preparation

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A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Environmental Catalysis".

Deadline for manuscript submissions: closed (15 September 2018) | Viewed by 50740

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Special Issue Editor

Dr. Damien P. Debecker

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Guest Editor

Institute of Condensed Matter and Nanosciences, Université catholique de Louvain, Place L. Pasteur 1, B-1348 Louvain-la-Neuve, Belgium
Interests: heterogeneous catalysis; porous materials; green chemistry; biocatalysis; biomass conversion; CO2 conversion; enzyme immobilization; flow chemistry

Special Issue Information

Dear Colleagues,

Sol–gel chemistry encompasses a wide range of chemical routes that allow producing tailored solid materials starting form molecular precursors. Specifically in the field of heterogeneous catalysts preparation, sol–gel methods permit the design of advanced catalytic formulations showing unique properties. Taking advantage of the controlled synthesis conditions in sol–gel methods, chemists develop catalytic materials which exhibit improved catalytic performance thanks to their advantageous textures, structures, compositions, homogeneity, surface functionality, etc. This field is evolving quickly as, for example, new processing modes, new molecular precursors or new templating agents are proposed.

In fact, our ability to modernise industrial chemistry, strongly relies on our aptitude to design and understand new types of catalysts with specific properties and exhibiting remarkable catalytic behaviour. The challenges are numerous. The transition from a petro-based chemical industry to a bio-based one requires multifunctional catalysts that can withstand polar working conditions. Embracing the huge potential of natural or genetically engineered enzymes requires effective immobilization strategies to obtain efficient heterogeneous biocatalysts. Turning batch chemical processes into continuous flow mode processes requires catalysts that can be moulded so as to allow optimal mass transfer. In all these examples, sol–gel chemistry can help shape innovative solutions.

This Special Issue aims to cover recent progress and trends in synthesizing advanced heterogeneous catalysts by sol–gel chemistry routes.

Dr. Damien P. Debecker
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. 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

Sol–gel chemistry
Evaporation-induced self-assembly
Hybrid catalysts
Enzyme immobilization
Mixed oxides
Flow chemistry with heterogeneous catalyst
Porous catalysts
Monoliths and shaped catalysts
Multifunctional catalysts
Hierarchical porosity
Immobilization of organometallic complexes
Xerogel
Aerogel
Aerosol
Non-hydrolytic sol–gel
Sacrificial templates and surfactants

Published Papers (5 papers)

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Research

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3094 KiB

Open AccessArticle

Sol-Gel-Assisted Microwave-Derived Synthesis of Anatase Ag/TiO₂/GO Nanohybrids toward Efficient Visible Light Phenol Degradation

by E. H. Alsharaeh, T. Bora, A. Soliman, Faheem Ahmed, G. Bharath, M. G. Ghoniem, Khalid M. Abu-Salah and J. Dutta

Catalysts 2017, 7(5), 133; https://doi.org/10.3390/catal7050133 - 01 May 2017

Cited by 96 | Viewed by 13101

Abstract

Abstract: A simple microwave-assisted (MWI) wet chemical route to synthesize pure anatase phase titanium dioxide (TiO₂) nanoparticles (NPs) is reported here using titanium tetrachloride (TiCl₄) as starting material. The as-prepared TiO₂ NPs were characterized by electron microscopy, X-ray diffraction, UV/visible absorption spectroscopy, and infrared and Raman spectroscopic techniques. Further modification of the anatase TiO₂ NPs was carried out by incorporating plasmonic silver (Ag) NPs and graphene oxide (GO) in order to enhance the visible light absorption. The photocatalytic activities of the anatase TiO₂, Ag/TiO₂, and Ag/TiO₂/GO nanocomposites were evaluated under both ultraviolet (UV) and visible light irradiation using phenol as a model contaminant. The presence of Ag NPs was found to play a significant role to define the photocatalytic activity of the Ag/TiO₂/GO nanocomposite. It was found that the Ag performed like a sink under UV excitation and stored photo-generated electrons from TiO₂, whereas, under visible light excitation, the Ag acted as a photosensitizer enhancing the photocatalytic activity of the nanocomposite. The detailed mechanism was studied based on photocatalytic activities of Ag/TiO₂/GO nanocomposites. Therefore, the as-prepared Ag/TiO₂/GO nanocomposite was used as photocatalytic materials under both UV and visible light irradiation toward degradation of organic molecules. Full article

(This article belongs to the Special Issue Sol–Gel Chemistry: A Toolbox for Catalyst Preparation)

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2927 KiB

Open AccessArticle

Enantioselective Transamination in Continuous Flow Mode with Transaminase Immobilized in a Macrocellular Silica Monolith

by Ludivine Van den Biggelaar, Patrice Soumillion and Damien P. Debecker

Catalysts 2017, 7(2), 54; https://doi.org/10.3390/catal7020054 - 10 Feb 2017

Cited by 42 | Viewed by 8272

Abstract

ω-Transaminases have been immobilized on macrocellular silica monoliths and used as heterogeneous biocatalysts in a continuous flow mode enantioselective transamination reaction. The support was prepared by a sol-gel method based on emulsion templating. The enzyme was immobilized on the structured silica monoliths both by adsorption, and by covalent grafting using amino-functionalized silica monoliths and glutaraldehyde as a coupling agent. A simple reactor set-up based on the use of a heat-shrinkable Teflon tube is presented and successfully used for the continuous flow kinetic resolution of a chiral amine, 4-bromo-α-methylbenzylamine. The porous structure of the supports ensures effective mass transfer and the reactor works in the plug flow regime without preferential flow paths. When immobilized in the monolith and used in the flow reactor, transaminases retain their activity and their enantioselectivity. The solid biocatalyst is also shown to be stable both on stream and during storage. These essential features pave the way to the successful development of an environmentally friendly process for chiral amines production. Full article

(This article belongs to the Special Issue Sol–Gel Chemistry: A Toolbox for Catalyst Preparation)

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6488 KiB

Open AccessArticle

Cobalt-Doped Carbon Gels as Electro-Catalysts for the Reduction of CO₂ to Hydrocarbons

by Abdalla Abdelwahab, Jesica Castelo-Quibén, María Pérez-Cadenas, Abdelhakim Elmouwahidi, Francisco J. Maldonado-Hódar, Francisco Carrasco-Marín and Agustín F. Pérez-Cadenas

Catalysts 2017, 7(1), 25; https://doi.org/10.3390/catal7010025 - 12 Jan 2017

Cited by 24 | Viewed by 6136

Abstract

Two original series of carbon gels doped with different cobalt loadings and well-developed mesoporosity, aerogels and xerogels, have been prepared, exhaustively characterized, and tested as cathodes for the electro-catalytic reduction of CO₂ to hydrocarbons at atmospheric pressure. Commercial cobalt and graphite sheets have also been tested as cathodes for comparison. All of the doped carbon gels catalyzed the formation of hydrocarbons, at least from type C1 to C4. The catalytic activity depends mainly on the metal loading, nevertheless, the adsorption of a part of the products in the porous structure of the carbon gel cannot be ruled out. Apparent faradaic efficiencies calculated with these developed materials were better that those obtained with a commercial cobalt sheet as a cathode, especially considering the much lower amount of cobalt contained in the Co-doped carbon gels. The cobalt-carbon phases formed in these types of doped carbon gels improve the selectivity to C3-C4 hydrocarbons formation, obtaining even more C3 hydrocarbons than CH₄ in some cases. Full article

(This article belongs to the Special Issue Sol–Gel Chemistry: A Toolbox for Catalyst Preparation)

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Review

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28 pages, 4631 KiB

Open AccessReview

Nanostructured Oxides Synthesised via scCO₂-Assisted Sol-Gel Methods and Their Application in Catalysis

by Yehan Tao and Paolo P. Pescarmona

Catalysts 2018, 8(5), 212; https://doi.org/10.3390/catal8050212 - 17 May 2018

Cited by 17 | Viewed by 9389

Abstract

Nanostructured metal oxides and silicates are increasingly applied in catalysis, either as supports or as active species in heterogeneous catalysts, owing to the physicochemical properties that typically distinguish them from bulk oxides, such as higher surface area and a larger fraction of coordinatively unsaturated sites at their surface. Among the different synthetic routes for preparing these oxides, sol-gel is a relatively facile and efficient method. The use of supercritical CO₂ (scCO₂) in the sol-gel process can be functional to the formation of nanostructured materials. The physical properties of the scCO₂ medium can be controlled by adjusting the processing temperature and the pressure of CO₂, thus enabling the synthesis conditions to be tuned. This paper provides a review of the studies on the synthesis of oxide nanomaterials via scCO₂-assisted sol-gel methods and their catalytic applications. The advantages brought about by scCO₂ in the synthesis of oxides are described, and the performance of oxide-based catalysts prepared by scCO₂ routes is compared to their counterparts prepared via non-scCO₂-assisted methods. Full article

(This article belongs to the Special Issue Sol–Gel Chemistry: A Toolbox for Catalyst Preparation)

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5598 KiB

Open AccessFeature PaperReview

The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

by Ales Styskalik, David Skoda, Craig E. Barnes and Jiri Pinkas

Catalysts 2017, 7(6), 168; https://doi.org/10.3390/catal7060168 - 25 May 2017

Cited by 81 | Viewed by 12395

Abstract

This review is devoted to non-hydrolytic sol-gel chemistry. During the last 25 years, non-hydrolytic sol-gel (NHSG) techniques were found to be attractive and versatile methods for the preparation of oxide materials. Compared to conventional hydrolytic approaches, the NHSG route allows reaction control at the atomic scale resulting in homogeneous and well defined products. Due to these features and the ability to design specific materials, the products of NHSG reactions have been used in many fields of application. The aim of this review is to present an overview of NHSG research in recent years with an emphasis on the syntheses of mixed oxides, silicates and phosphates. The first part of the review highlights well known condensation reactions with some deeper insights into their mechanism and also presents novel condensation reactions established in NHSG chemistry in recent years. In the second section we discuss porosity control and novel compositions of selected materials. In the last part, the applications of NHSG derived materials as heterogeneous catalysts and supports, luminescent materials and electrode materials in Li-ion batteries are described. Full article

(This article belongs to the Special Issue Sol–Gel Chemistry: A Toolbox for Catalyst Preparation)

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