Special Issue "Enabling Technologies toward Green Catalysis"

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

Deadline for manuscript submissions: closed (15 July 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Giancarlo Cravotto

Dipartimento di Scienza e Tecnologia del Farmaco, University of Turin, via P. Giuria 9, Turin, 10125, Italy
Website | E-Mail
Interests: enabling technologies from lab scale to industrial applications; green chemistry; sustainable processes; plant extraction; process intensification

Special Issue Information

Dear Colleagues,

Although, in the last two decades, the 12 principles of green chemistry have become extremely fashionable, the development of scalable protocols of green catalysis showed a certain inertia with a growing gap between academia and industry. Current organic synthesis requires both innovative catalysts and suitable technologies to address the rules of green chemistry and the goal of process intensification. Ultrasound, hydrodynamic cavitation, microwaves, ball milling, flow chemistry and other non-conventional technologies may dramatically enhance chemical conversions, cutting down reaction times and energy consumption. Green catalysis is a holistic concept that requires enabling technologies as irreplaceable tools for an efficient physical activation. This Special Issue aims to highlight how properly harness all the new technologies and better integrate all disciplines for a modern green catalysis.

Prof. Dr. Giancarlo Cravotto
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 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

  • green catalysis
  • physical activation
  • enabling technologies
  • process intensification
  • microwaves
  • ultrasound
  • hydrodynamic cavitation
  • ball milling
  • flow chemistry

Published Papers (9 papers)

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Research

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Open AccessArticle Co-Production of Ethanol and 1,2-Propanediol via Glycerol Hydrogenolysis Using Ni/Ce–Mg Catalysts: Effects of Catalyst Preparation and Reaction Conditions
Catalysts 2017, 7(10), 290; doi:10.3390/catal7100290
Received: 17 August 2017 / Revised: 12 September 2017 / Accepted: 25 September 2017 / Published: 29 September 2017
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Abstract
Crude glycerol from biodiesel production is a biobased material capable of co-producing biofuels and chemicals. This study aimed to develop a line of Ni catalysts supported on cerium–magnesium (Ce–Mg) to improve the process efficiency of glycerol hydrogenolysis for ethanol and 1,2-propanediol (1,2-PDO). Results
[...] Read more.
Crude glycerol from biodiesel production is a biobased material capable of co-producing biofuels and chemicals. This study aimed to develop a line of Ni catalysts supported on cerium–magnesium (Ce–Mg) to improve the process efficiency of glycerol hydrogenolysis for ethanol and 1,2-propanediol (1,2-PDO). Results showed that catalytic activity was greatly improved by changing the preparation method from impregnation to deposition precipitation (DP), and by adjusting calcination temperatures. Prepared via DP, the catalysts of 25 wt % Ni supported on Ce–Mg (9:1 mol/mol) greatly improved the effectiveness in glycerol conversion while maintaining the selectivities to ethanol and 1,2-PDO. Calcination at 350 °C provided the catalysts better selectivities of 15.61% to ethanol and 67.93% to 1,2-PDO. Increases in reaction temperature and time improved the conversion of glycerol and the selectivity to ethanol, but reduced the selectivity to 1,2-PDO. A lower initial water content led to a higher conversion of glycerol, but lower selectivities to ethanol and 1,2-PDO. Higher hydrogen application affected the glycerol conversion rate positively, but the selectivities to ethanol and 1,2-PDO negatively. A comparison to the commercial Raney® Ni catalyst showed that the Ni/Ce–Mg catalyst developed in this study showed a better potential for the selective co-production of ethanol and 1,2-PDO from glycerol hydrogenolysis. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessArticle Efficient Catalytic Upgrading of Levulinic Acid into Alkyl Levulinates by Resin-Supported Acids and Flow Reactors
Catalysts 2017, 7(8), 235; doi:10.3390/catal7080235
Received: 24 July 2017 / Revised: 7 August 2017 / Accepted: 9 August 2017 / Published: 15 August 2017
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Abstract
Biomass-derived levulinic acid (LA) is an excellent substrate to obtain high-value esters that can be used as second-generation biofuels and biofuel additives. The present study focuses on the identification and definition of the key parameters crucial for the development of chemically and environmentally
[...] Read more.
Biomass-derived levulinic acid (LA) is an excellent substrate to obtain high-value esters that can be used as second-generation biofuels and biofuel additives. The present study focuses on the identification and definition of the key parameters crucial for the development of chemically and environmentally efficient protocols operating in continuous-flow for the preparation of structurally diverse alkyl levulinates via the esterification of LA. We have focused on the use of solid acid catalysts consisting of sulfonated cation exchange resins and considered different aliphatic alcohols to prepare levulinates 3 and 11–17 regioselectively, and in good to high yields (50–92%). Direct correlations between several reaction parameters and catalyst activity have been investigated and discussed to set proper flow reactors that allow minimal waste production during the workup procedure, enabling Environmental factor (E-factor) values as low as ca. 0.3, full recoverability and reusability of the catalysts, and the production of levulinates up to ca. 5 gxh−1 scale. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessFeature PaperArticle Is Selective Heating of the Sulfonic Acid Catalyst AC-SO3H by Microwave Radiation Crucial in the Acid Hydrolysis of Cellulose to Glucose in Aqueous Media?
Catalysts 2017, 7(8), 231; doi:10.3390/catal7080231
Received: 1 July 2017 / Revised: 23 July 2017 / Accepted: 1 August 2017 / Published: 8 August 2017
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Abstract
Selective heating of microwave-absorbing solid catalysts in a heterogeneous medium may affect a chemical reaction; such selectivity cannot be achieved by conventional oil-bath or steam heating methods. Moreover, microwave methods are often misunderstood with respect to equipment and temperature measurements, so that additional
[...] Read more.
Selective heating of microwave-absorbing solid catalysts in a heterogeneous medium may affect a chemical reaction; such selectivity cannot be achieved by conventional oil-bath or steam heating methods. Moreover, microwave methods are often misunderstood with respect to equipment and temperature measurements, so that additional experimentation is necessary. In this regard, the present study intended to clarify the effect of microwave selective heating on acid hydrolytic processes using a sulfonated activated carbon catalyst (AC-SO3H). The model reaction chosen was the acid hydrolysis of cellulose carried out in a Pyrex glass microwave reactor, with the process being monitored by examining the quantity of total sugar, reducing sugar, and glucose produced. Heat transfer from the catalyst to the aqueous solution through absorption of microwaves by the catalyst occurred as predicted from a simulation of heat transfer processes. The resulting experimental consequences are compared with those from the more uniform microwave conduction heating method by also performing the reaction in a SiC microwave reactor wherein microwaves are absorbed by SiC. Some inferences of the influence of microwave selective heating of carbon-based catalyst particles are reported. Under selective heating conditions (Pyrex glass reactor), the yield of glucose from the acid hydrolysis of cellulose was 56% upon microwave heating at 200 °C, nearly identical with the yield (55%) when the hydrolytic process was performed under mainly conventional heating conditions in the SiC reactor. Although the beneficial effect of catalyst selective heating was not reflected in the reaction efficiency, there were substantial changes in the state of adsorption of cellulose on the catalyst surface. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessArticle Microwave-Assisted Synthesis of Co3(PO4)2 Nanospheres for Electrocatalytic Oxidation of Methanol in Alkaline Media
Catalysts 2017, 7(4), 119; doi:10.3390/catal7040119
Received: 16 January 2017 / Revised: 11 April 2017 / Accepted: 12 April 2017 / Published: 17 April 2017
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Abstract
Low-cost and high-performance advanced electrocatalysts for direct methanol fuel cells are of key significance for the improvement of environmentally-pleasant energy technologies. Herein, we report the facile synthesis of cobalt phosphate (Co3(PO4)2) nanospheres by a microwave-assisted process and
[...] Read more.
Low-cost and high-performance advanced electrocatalysts for direct methanol fuel cells are of key significance for the improvement of environmentally-pleasant energy technologies. Herein, we report the facile synthesis of cobalt phosphate (Co3(PO4)2) nanospheres by a microwave-assisted process and utilized as an electrocatalyst for methanol oxidation. The phase formation, morphological surface structure, elemental composition, and textural properties of the synthesized (Co3(PO4)2) nanospheres have been examined by powder X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), field emission-scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption isotherm investigations. The performance of an electrocatalytic oxidation of methanol over a Co3(PO4)2 nanosphere-modified electrode was evaluated in an alkaline solution using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Detailed studies were made for the methanol oxidation by varying the experimental parameters, such as catalyst loading, methanol concentration, and long-term stability for the electro-oxidation of methanol. The good electrocatalytic performances of Co3(PO4)2 should be related to its good surface morphological structure and high number of active surface sites. The present investigation illustrates the promising application of Co3(PO4)2 nanospheres as a low-cost and more abundant electrocatalyst for direct methanol fuel cells. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessArticle Solvent-Free Biginelli Reactions Catalyzed by Hierarchical Zeolite Utilizing a Ball Mill Technique: A Green Sustainable Process
Catalysts 2017, 7(3), 84; doi:10.3390/catal7030084
Received: 3 February 2017 / Revised: 27 February 2017 / Accepted: 6 March 2017 / Published: 13 March 2017
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Abstract
A sustainable, green one-pot process for the synthesis of dihydropyrimidinones (DHPMs) derivatives by a three-component reaction of β-ketoester derivatives, aldehyde and urea or thiourea over the alkali-treated H-ZSM-5 zeolite under ball-milling was developed. Isolation of the product with ethyl acetate shadowed by vanishing
[...] Read more.
A sustainable, green one-pot process for the synthesis of dihydropyrimidinones (DHPMs) derivatives by a three-component reaction of β-ketoester derivatives, aldehyde and urea or thiourea over the alkali-treated H-ZSM-5 zeolite under ball-milling was developed. Isolation of the product with ethyl acetate shadowed by vanishing of solvent was applied. The hierachical zeolite catalyst (MFI27_6) showed high yield (86%–96%) of DHPMs in a very short time (10–30 min). The recyclability of the catalyst for the subsequent reactions was examined in four subsequent runs. The catalyst was shown to be robust without a detectable reduction in catalytic activity, and high yields of products showed the efficient protocol of the Biginelli reactions. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessArticle Synthesis of Ti4O7 Nanoparticles by Carbothermal Reduction Using Microwave Rapid Heating
Catalysts 2017, 7(2), 65; doi:10.3390/catal7020065
Received: 14 December 2016 / Accepted: 13 February 2017 / Published: 16 February 2017
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Abstract
The polymer electrolyte fuel cell (PEFC) is an attractive power generation method from the perspective of environmental protection. Carbon is usually used as a catalyst support in PEFC, but it is oxidized under high electrical potential conditions. Ti4O7 is expected
[...] Read more.
The polymer electrolyte fuel cell (PEFC) is an attractive power generation method from the perspective of environmental protection. Carbon is usually used as a catalyst support in PEFC, but it is oxidized under high electrical potential conditions. Ti4O7 is expected as a new catalyst support because of its high electrical conductivity and chemical resistivity. Though Ti4O7 as a catalyst support must have a high specific surface area for a high performance, it is difficult to synthesize nanostructured Ti4O7. In this research, Ti4O7 nanoparticles with a size of about 60 nm were synthesized by carbothermal reduction of TiO2 nanoparticles with polyvinylpyrrolidone (carbon source) using 2.45 GHz microwave irradiation. The experiment condition was at 950 °C for 30 min and the samples synthesized by conventional heating showed a grain growth. The findings of this study suggest that microwave processing can drastically reduce the total processing time for the synthesis of nanostructured Ti4O7. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Review

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Open AccessFeature PaperReview The Beneficial Sinergy of MW Irradiation and Ionic Liquids in Catalysis of Organic Reactions
Catalysts 2017, 7(9), 261; doi:10.3390/catal7090261
Received: 26 July 2017 / Revised: 17 August 2017 / Accepted: 23 August 2017 / Published: 1 September 2017
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Abstract
The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source,
[...] Read more.
The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source, with ionic liquids, as both solvents and catalysts, offered interesting solutions in recent years. The literature data of the last 15 years concerning selected reactions are presented, highlighting the importance of microwave (MW) technology coupled with ionic liquids. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessFeature PaperReview Merging Metallic Catalysts and Sonication: A Periodic Table Overview
Catalysts 2017, 7(4), 121; doi:10.3390/catal7040121
Received: 8 March 2017 / Revised: 7 April 2017 / Accepted: 14 April 2017 / Published: 19 April 2017
Cited by 1 | PDF Full-text (8874 KB) | HTML Full-text | XML Full-text
Abstract
This account summarizes and discusses recent examples in which the combination of ultrasonic waves and metal-based reagents, including metal nanoparticles, has proven to be a useful choice in synthetic planning. Not only does sonication often enhance the activity of the metal catalyst/reagent, but
[...] Read more.
This account summarizes and discusses recent examples in which the combination of ultrasonic waves and metal-based reagents, including metal nanoparticles, has proven to be a useful choice in synthetic planning. Not only does sonication often enhance the activity of the metal catalyst/reagent, but it also greatly enhances the synthetic transformation that can be conducted under milder conditions relative to conventional protocols. For the sake of clarity, we have adopted a structure according to the periodic-table elements or families, distinguishing between bulk metal reagents and nanoparticles, as well as the supported variations, thus illustrating the characteristics of the method under consideration in target synthesis. The coverage focuses essentially on the last decade, although the discussion also strikes a comparative balance between the more recent advancements and past literature. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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Open AccessReview Pd/C Catalysis under Microwave Dielectric Heating
Catalysts 2017, 7(3), 89; doi:10.3390/catal7030089
Received: 16 December 2016 / Revised: 10 March 2017 / Accepted: 16 March 2017 / Published: 20 March 2017
Cited by 1 | PDF Full-text (7214 KB) | HTML Full-text | XML Full-text
Abstract
Microwave-assisted organic synthesis (MAOS) provides a novel and efficient means of achieving heat organic reactions. Nevertheless, the potential arcing phenomena via microwave (MW) interaction with solid metal catalysts has limited its use by organic chemists. As arcing phenomena are now better understood, new
[...] Read more.
Microwave-assisted organic synthesis (MAOS) provides a novel and efficient means of achieving heat organic reactions. Nevertheless, the potential arcing phenomena via microwave (MW) interaction with solid metal catalysts has limited its use by organic chemists. As arcing phenomena are now better understood, new applications of Pd/C-catalyzed reactions under MW dielectric heating are now possible. In this review, the state of the art, benefits, and challenges of coupling MW heating with heterogeneous Pd/C catalysis are discussed to inform organic chemists about their use with one of the most popular heterogeneous catalysts. Full article
(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)
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