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Catalysts
Special Issues
Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis
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Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis

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

Deadline for manuscript submissions: closed (31 December 2014) | Viewed by 63167

Special Issue Editors

Prof. Dr. Masahiko Arai

E-Mail Website
Guest Editor
Division of Chemical Process Engineering, Faculty of Engineering, Hokkaido University, Hokkaido 060-8628, Japan
Interests: multiphase catalytic reactions in the presence of dense phase carbon dioxide and/or water; Preparation and application of nitrogen-doped carbon materials as multifunctional metal-free catalysts; Catalytic and photocatalytic transformation of carbon dioxide and biomass-derived disused materials to value-added organic compounds; Preparation of mesoporous smectite-lke materials as acid/base catalysts
Prof. Dr. Fengyu Zhao

E-Mail Website
Guest Editor
Laboratory of Green Chemistry and Process, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China
Interests: Design and preparation of heterogeneous catalysts; Catalytic hydrogenation and oxidation in green solvents;Conversion and utilization of carbon dioxide; Catalytic conversion of biomass; Fabrication of nano materials, Supercritical fluids

Special Issue Information

Dear Colleagues,

Heterogeneous metal catalysts rather than homogeneous ones are recommended for industrial applications after considering their performance in activity, separation, and recycling. The recycling of metal catalysts is desirable from economical and environmental points of view. When supported and bulk metal catalysts are used in liquid-phase organic reactions, there is a possibility that active metal species leach away into the liquid phases and the dissolved metal species may also act as an active center. The leaching of metal species from heterogeneous catalysts makes it difficult to reuse the catalysts in batch reactors and maintain the desired initial performance in continuous reactors. It is required, therefore, to find novel methods to immobilize/stabilize metal species and to separate/collect/reuse the dissolved metal species. The leaching of metal species also complicates the heterogeneous/homogeneous nature of catalysis. Do the reactions occur heterogeneously on heterogeneous metal catalysts and/or homogeneously with the dissolved metal species? In the latter, what is a working active center in the liquid phases?

This Special Issue aims at covering recent progress in the preparation and application of recyclable metal catalysts and in the fundamental aspects of reaction mechanisms and heterogeneous/homogeneous nature of reactions using heterogeneous metal catalysts. Heterogeneous metal catalysts in any form are of interest.

Prof. Dr. Masahiko Arai
Prof. Dr. Fengyu Zhao
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

  • metal catalysts
  • immobilization
  • stabilization
  • leaching
  • catalyst separation
  • catalyst recycling
  • heterogeneous/homogeneous mechanisms

Published Papers (7 papers)

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Editorial

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175 KiB  
Editorial
Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis
by Masahiko Arai and Fengyu Zhao
Catalysts 2015, 5(2), 868-870; https://doi.org/10.3390/catal5020868 - 27 May 2015
Cited by 29 | Viewed by 6293
Abstract
Heterogeneous metal catalysts rather than homogeneous ones are recommended for industrial applications after considering their performance in activity, separation, and recycling [1]. The recycling of metal catalysts is important from economic and environmental points of view. When supported and bulk metal catalysts are [...] Read more.
Heterogeneous metal catalysts rather than homogeneous ones are recommended for industrial applications after considering their performance in activity, separation, and recycling [1]. The recycling of metal catalysts is important from economic and environmental points of view. When supported and bulk metal catalysts are used in liquid-phase organic reactions, there is a possibility that active metal species are leaching away into the liquid phases [2,3]. The metal leaching would make it difficult for the catalysts to maintain their desired initial performance for repeated batch reactions and during continuous ones. The metal leaching would also cause some undesired contamination of products by the metal species dissolved in the reaction mixture, and the separation of the metal contaminants would be required to purify the products. Therefore, various novel methods have been proposed so far to immobilize/stabilize the active metal species and to separate/collect/reuse the dissolved metal species [4]. In addition, knowledge on the heterogeneous and homogeneous natures of organic reactions using heterogeneous catalysts is important to discuss their reaction mechanisms and catalytically working active species. [...] Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)

Research

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917 KiB  
Article
Effect of Phosphine Doping and the Surface Metal State of Ni on the Catalytic Performance of Ni/Al2O3 Catalyst
by Xiaoru Li, Haiyang Cheng, Guanfeng Liang, Limin He, Weiwei Lin, Yancun Yu and Fengyu Zhao
Catalysts 2015, 5(2), 759-773; https://doi.org/10.3390/catal5020759 - 23 Apr 2015
Cited by 25 | Viewed by 7671
Abstract
Ni-based catalysts as replacement for noble metal catalysts are of particular interest in the catalytic conversion of biomass due to their cheap and satisfactory catalytic activity. The Ni/SiO2 catalyst has been studied for the hydrogenolysis of glycerol, and doping with phosphorus (P) [...] Read more.
Ni-based catalysts as replacement for noble metal catalysts are of particular interest in the catalytic conversion of biomass due to their cheap and satisfactory catalytic activity. The Ni/SiO2 catalyst has been studied for the hydrogenolysis of glycerol, and doping with phosphorus (P) found to improve the catalytic performance significantly because of the formation of Ni2P alloys. However, in the present work we disclose a different catalytic phenomenon for the P-doped Ni/Al2O3 catalyst. We found that doping with P has a significant effect on the state of the active Ni species, and thus improves the selectivity to 1,2-propanediol (1,2-PDO) significantly in the hydrogenolysis of glycerol, although Ni-P alloys were not observed in our catalytic system. The structure and selectivity correlations were determined from the experimental data, combining the results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR) and ammonia temperature-programmed desorption (NH3-TPD). The presence of NiO species, formed from P-doped Ni/Al2O3 catalyst, was shown to benefit the formation of 1,2-PDO. This was supported by the results of the Ni/Al2O3 catalyst containing NiO species with incomplete reduction. Furthermore, the role the NiO species played in the reaction and the potential reaction mechanism over the P-doped Ni/Al2O3 catalyst is discussed. The new findings in the present work open a new vision for Ni catalysis and will benefit researchers in designing Ni-based catalysts. Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)
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156 KiB  
Article
Guanidine Hydrochloride/ZnI2 as Heterogeneous Catalyst for Conversion of CO2 and Epoxides to Cyclic Carbonates under Mild Conditions
by Bo Liu, Mengshuai Liu, Lin Liang and Jianmin Sun
Catalysts 2015, 5(1), 119-130; https://doi.org/10.3390/catal5010119 - 11 Feb 2015
Cited by 15 | Viewed by 9769
Abstract
In this article, the combination of guanidine hydrochloride with co-catalyst ZnI2 proved to be a highly efficient heterogeneous catalyst for the environmentally benign, solvent-free synthesis of cyclic carbonates under mild reaction conditions. The effects of different co-catalysts as well as reaction parameters [...] Read more.
In this article, the combination of guanidine hydrochloride with co-catalyst ZnI2 proved to be a highly efficient heterogeneous catalyst for the environmentally benign, solvent-free synthesis of cyclic carbonates under mild reaction conditions. The effects of different co-catalysts as well as reaction parameters including catalyst loadings, CO2 pressure, reaction temperature, and reaction time on the coupling reaction of CO2 to propylene oxide were thoroughly investigated. With the molar ratio of guanidine hydrochloride to ZnI2 at 5:1, excellent yield (94%) and selectivity (≥99%) of propylene carbonate were obtained under 100 °C and at 1 MPa for 1.5 h. Additionally, ZnI2 could be recycled, but because of the washing loss of guanidine hydrochloride, there was a slight decrease in the yield of propylene carbonate. Gratifyingly, the activity of the catalytic system could be restored by adding additional 20 mol% of fresh guanidine hydrochloride, thus exhibiting excellent recyclability of the ZnI2 catalyst. Moreover, the binary catalysts were also versatile when using other epoxides for CO2 cycloaddition. A possible reaction mechanism was proposed wherein guanidine hydrochloride plays a dual role in activating CO2 and epoxide, and ZnI2 activated epoxide, simultaneously. The synergistic effect of guanidine hydrochloride and ZnI2 ensure the reaction proceeds effectively. Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)
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14316 KiB  
Article
Application of “Boomerang” Linear Polystyrene-Stabilized Pd Nanoparticles to a Series of C-C Coupling Reactions in Water
by Atsushi Ohtaka, Toshiyuki Okagaki, Go Hamasaka, Yasuhiro Uozumi, Tsutomu Shinagawa, Osamu Shimomura and Ryôki Nomura
Catalysts 2015, 5(1), 106-118; https://doi.org/10.3390/catal5010106 - 09 Feb 2015
Cited by 27 | Viewed by 7441
Abstract
The application of a catch-and-release system for soluble Pd species between water (reaction medium) and polystyrene (polymer support) was examined in the Suzuki coupling reaction with 2-bromothiophene and the Heck reaction with styrene or bromobenzene. Although a slight increase in particle size was [...] Read more.
The application of a catch-and-release system for soluble Pd species between water (reaction medium) and polystyrene (polymer support) was examined in the Suzuki coupling reaction with 2-bromothiophene and the Heck reaction with styrene or bromobenzene. Although a slight increase in particle size was observed by TEM after re-stabilization of the Pd species on linear polystyrene, no agglomeration was observed. Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)
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645 KiB  
Article
Polymer Supported Triphenylphosphine-Palladium Acetate Complex PS-TPP-Pd(OAc)2 as a Heterogeneous and Reusable Catalyst for Indirect Reductive Amination of Aldehydes
by Sunil S. Ekbote, Sandip T. Gadge and Bhalchandra M. Bhanage
Catalysts 2014, 4(3), 289-298; https://doi.org/10.3390/catal4030289 - 15 Jul 2014
Cited by 5 | Viewed by 6455
Abstract
Indirect reductive amination of aldehydes, catalyzed by polymer supported triphenylphosphine-palladium acetate complex PS-TPP-Pd(OAc)2 catalyst have been developed. The imine is prepared with molecular sieves in the first stage, followed by reduction with potassium formate catalyzed by PS-TPP-Pd(OAc)2. The recovered catalyst [...] Read more.
Indirect reductive amination of aldehydes, catalyzed by polymer supported triphenylphosphine-palladium acetate complex PS-TPP-Pd(OAc)2 catalyst have been developed. The imine is prepared with molecular sieves in the first stage, followed by reduction with potassium formate catalyzed by PS-TPP-Pd(OAc)2. The recovered catalyst could be reused for four consecutive cycles without loss in activity and provided an excellent yield of the desired products. Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)
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2525 KiB  
Article
Selective Hydrogenation of m-Dinitrobenzene to m-Nitroaniline over Ru-SnOx/Al2O3 Catalyst
by Haiyang Cheng, Weiwei Lin, Xiaoru Li, Chao Zhang and Fengyu Zhao
Catalysts 2014, 4(3), 276-288; https://doi.org/10.3390/catal4030276 - 14 Jul 2014
Cited by 16 | Viewed by 8946
Abstract
Series catalysts of Ru-SnOx/Al2O3 with varying SnOx loading of 0–3 wt% were prepared, and their catalytic activity and selectivity have been discussed and compared for the selective hydrogenation of m-dinitrobenzene (m-DNB) to m-nitroaniline [...] Read more.
Series catalysts of Ru-SnOx/Al2O3 with varying SnOx loading of 0–3 wt% were prepared, and their catalytic activity and selectivity have been discussed and compared for the selective hydrogenation of m-dinitrobenzene (m-DNB) to m-nitroaniline (m-NAN). The Ru-SnOx/Al2O3 catalysts were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and hydrogen temperature-programmed reduction (H2-TPR) and desorption (H2-TPD). Under the modification of SnOx, the reaction activity increased obviously, and the best selectivity to m-NAN reached above 97% at the complete conversion of m-DNB. With the increasing of the SnOx loading, the amount of active hydrogen adsorption on the surface of the catalyst increased according to the H2-TPD analysis, and the electron transferred from Ru to SnOx species, as determined by XPS, inducing an electron-deficient Ru, which is a benefit for the absorption of the nitro group. Therefore, the reaction rate and product selectivity were greatly enhanced. Moreover, the Ru-SnOx/Al2O3 catalyst presented high stability: it could be recycled four times without any loss in activity and selectivity. Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)
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Review

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15014 KiB  
Review
Magnetically Separable and Sustainable Nanostructured Catalysts for Heterogeneous Reduction of Nitroaromatics
by Mohammadreza Shokouhimehr
Catalysts 2015, 5(2), 534-560; https://doi.org/10.3390/catal5020534 - 31 Mar 2015
Cited by 176 | Viewed by 15059
Abstract
This review is focused on the strategies and designs of magnetic nanostructured catalysts showing the enhanced and sustainable catalytic performances for the heterogeneous reduction of nitoaromatics. Magnetic catalysts have the benefits of easy recovery and reuse after the completion of the reactions and [...] Read more.
This review is focused on the strategies and designs of magnetic nanostructured catalysts showing the enhanced and sustainable catalytic performances for the heterogeneous reduction of nitoaromatics. Magnetic catalysts have the benefits of easy recovery and reuse after the completion of the reactions and green chemical processes. Magnetic separation, among the various procedures for removing catalysts, not only obviates the requirement of catalyst filtration or centrifugation after the completion of reactions, but also provides a practical technique for recycling the magnetized nanostructured catalysts. Consequently, discussions will address the methodologies and exemplars for the reusable magnetic composite catalysts. Because the synthesis of ideal magnetic nanostructured catalysts is of primary importance in the development of high-quality sustainable processes, the designs, preparation methods and recyclability of various recoverable magnetic nanostructured catalysts are emphasized. The representative methods and strategies for the synthesis of durable and reusable magnetic nanostructured catalysts are highlighted. The advantages, disadvantages, recyclability and the efficiency of the introduced heterogeneous systems have been explored in the reduction of nitrobenzene derivatives. Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)
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