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Ruthenium Catalysts
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Ruthenium Catalysts

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

Deadline for manuscript submissions: closed (15 November 2016) | Viewed by 131623

Special Issue Editors

Prof. Dr. Albert Demonceau

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Guest Editor
Department of Chemistry, University of Liège, Sart-Tilman (B.6a), 4000 Liège, Belgium
Interests: macromolecular chemistry; organometallic synthesis; homogeneous catalysis; carbon-carbon bond formation; ruthenium-arene complexes
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Ileana Dragutan

E-Mail Website
Guest Editor
Institute of Organic Chemistry of the Romanian Academy, 202B Spl. Independentei, 060023 Bucharest, Romania
Interests: transition metals complexes and their chemistry and use in homogeneous catalysis and polymer synthesis; Ru-catalyzed olefin metathesis; metathesis driven syntheses of some bioactive compounds and metathesis-related processes; stable nitroxide free radicals and their preparation and multifarious applications using ESR
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Valerian Dragutan

E-Mail Website
Guest Editor
Institute of Organic Chemistry of the Romanian Academy, 202B Spl. Independentei, 060023 Bucharest, Romania
Interests: organic chemistry; organic synthesis; organometallic chemistry; coordination complexes; catalysis; free radicals; metathesis chemistry; polymerization chemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue of Catalysts highlights challenging aspects of the design and applications of the presently exceptionally broad array of ruthenium catalysts active in homogeneous and heterogeneous catalysis. Ruthenium-based catalysts are involved in a variety of organic reactions, such as alkylation, allylation, arylation, cyclization, cyclopropanation, hydrogenation, hydroformylation, hydrosilylation, hydroxylation, isomerization, olefin metathesis, oxidation, transfer hydrogenation, tandem reactions, water splitting, etc. Ru-catalysis is effectively exploited in the synthesis of natural and biologically active organic compounds, to access recognized chemotherapeutic agents, supramolecular assemblies, smart materials, specialty polymers, biopolymers, agrochemicals, and, increasingly, in valorization of renewable resources as platform chemicals for polymers. A particular attention is devoted to contemporary endeavors in C-H and C-X bond activation, olefin metathesis, and newest trends of green chemistry, such as water oxidation and hydrogen production, reduction of CO2 to CO, oleochemistry and reactions in eco-friendly media. Contents will encompass novel mono- and binuclear ruthenium catalysts bearing chiral and multidentate ligands. The editors hope that the topics covered in this issue will convey the expanding potential of ruthenium catalysts and will be of interest for those active in the field. Original research papers and reviews focusing on the synthesis and utilization of ruthenium catalysts are welcome for inclusion in this Special Issue of Catalysts.

Prof. Dr. Albert Demonceau
Prof. Dr. Ileana Dragutan
Prof. Dr. Valerian Dragutan
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 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

  • ADMET
  • Aqueous ruthenium systems
  • Asymmetric catalysis
  • ATRA (Kharasch addition)
  • ATRC
  • ATRP
  • CM
  • Domino reactions
  • Electrocatalysts
  • Homogeneous catalysis
  • Immobilized catalysts
  • Latent catalysts
  • Photoactive catalysts
  • RCM
  • ROMP
  • Tagged catalysts
  • Tandem catalysis
  • Z-selective catalysts

Published Papers (17 papers)

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Research

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4159 KiB  
Article
Exploring Promising Catalysts for Chemical Hydrogen Storage in Ammonia Borane: A Density Functional Theory Study
by Sateesh Bandaru, Niall J. English, Andrew D. Phillips and J. M. Don MacElroy
Catalysts 2017, 7(5), 140; https://doi.org/10.3390/catal7050140 - 05 May 2017
Cited by 11 | Viewed by 6185
Abstract
Density functional theory (DFT) has been applied to study potential ammonia borane (AB) dehydrogenation pathways via new bifunctional ruthenium-based catalysts, alongside their computationally-designed iron-based counterparts (i.e., four catalysts), using the wB97XD (dispersion-included) functional. The efficiency of each catalyst was under scrutiny based on [...] Read more.
Density functional theory (DFT) has been applied to study potential ammonia borane (AB) dehydrogenation pathways via new bifunctional ruthenium-based catalysts, alongside their computationally-designed iron-based counterparts (i.e., four catalysts), using the wB97XD (dispersion-included) functional. The efficiency of each catalyst was under scrutiny based on the addition of ammonia borane, with a focus on the associated activation-energy barriers, whilst hydrogen release from the catalyst was also studied in detail. Here, natural-population analysis charges were key quantities of interest. It was found that the iron-based catalysts display more promising dehydrogenation energy barriers vis- Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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3955 KiB  
Article
Unprecedented Multifunctionality of Grubbs and Hoveyda–Grubbs Catalysts: Competitive Isomerization, Hydrogenation, Silylation and Metathesis Occurring in Solution and on Solid Phase
by Maitena Martinez-Amezaga, Carina M. L. Delpiccolo, Luciana Méndez, Ileana Dragutan, Valerian Dragutan and Ernesto G. Mata
Catalysts 2017, 7(4), 111; https://doi.org/10.3390/catal7040111 - 09 Apr 2017
Cited by 7 | Viewed by 10215
Abstract
This contribution showcases the interplay of several non-metathetic reactions (isomerization, silylation and “hydrogen-free” reduction) with metathesis in systems comprising a functionalized olefin and a soluble or resin-immobilized silane. These competing, one-pot reactions occur under activation by second-generation Ru-alkylidene catalysts. Different olefinic substrates were [...] Read more.
This contribution showcases the interplay of several non-metathetic reactions (isomerization, silylation and “hydrogen-free” reduction) with metathesis in systems comprising a functionalized olefin and a soluble or resin-immobilized silane. These competing, one-pot reactions occur under activation by second-generation Ru-alkylidene catalysts. Different olefinic substrates were used to study the influence of the substitution pattern on the reaction outcome. Emphasis is placed upon the rarely reported yet important transformations implying a solid phase-supported silane reagent. Catalytic species involved in and reaction pathways accounting for these concurrent processes are evidenced. An unexpected result of this research was the clearly proved partial binding of the olefin to the resin, thereby removing it from the reacting ensemble. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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1486 KiB  
Article
Catalytic Transfer Hydrogenation of Biobased HMF to 2,5-Bis-(Hydroxymethyl)Furan over Ru/Co3O4
by Ting Wang, Junhua Zhang, Wenxing Xie, Yanjun Tang, Daliang Guo and Yonghao Ni
Catalysts 2017, 7(3), 92; https://doi.org/10.3390/catal7030092 - 21 Mar 2017
Cited by 45 | Viewed by 7120
Abstract
2,5-Bis-(hydroxymethyl)furan (BHMF) is an important biomass-based platform chemical that can be derived from the hydrogenation of biomass-based 5-hydroxymethylfurfural (HMF). In this paper, the formation of BHMF from HMF via the catalytic transfer hydrogenation (CTH) process, using isopropanol as the hydrogen source and Ru/Co [...] Read more.
2,5-Bis-(hydroxymethyl)furan (BHMF) is an important biomass-based platform chemical that can be derived from the hydrogenation of biomass-based 5-hydroxymethylfurfural (HMF). In this paper, the formation of BHMF from HMF via the catalytic transfer hydrogenation (CTH) process, using isopropanol as the hydrogen source and Ru/Co3O4 as the catalyst, was studied. The results revealed that the Ru/Co3O4 catalyst displayed a high catalytic efficiency, and that a BHMF yield of up to 82% was obtained at 190 °C in 6 h. Moreover, it was found that the recovered Ru/Co3O4 exhibited a similar catalytic activity to the pristine Ru/Co3O4 catalyst. These results supported the conclusion that the present CTH process is an attractive green route for the synthesis of BHMF from biomass-based HMF. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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3280 KiB  
Article
The Role of Ruthenium in CO2 Capture and Catalytic Conversion to Fuel by Dual Function Materials (DFM)
by Shuoxun Wang, Erik T. Schrunk, Harshit Mahajan and And Robert J. Farrauto
Catalysts 2017, 7(3), 88; https://doi.org/10.3390/catal7030088 - 17 Mar 2017
Cited by 76 | Viewed by 10350
Abstract
Development of sustainable energy technologies and reduction of carbon dioxide in the atmosphere are the two effective strategies in dealing with current environmental issues. Herein we report a Dual Function Material (DFM) consisting of supported sodium carbonate in intimate contact with dispersed Ru [...] Read more.
Development of sustainable energy technologies and reduction of carbon dioxide in the atmosphere are the two effective strategies in dealing with current environmental issues. Herein we report a Dual Function Material (DFM) consisting of supported sodium carbonate in intimate contact with dispersed Ru as a promising catalytic solution for combining both approaches. The Ru-Na2CO3 DFM deposited on Al2O3 captures CO2 from a flue gas and catalytically converts it to synthetic natural gas (i.e., methane) using H2 generated from renewable sources. The Ru in the DFM, in combination with H2, catalytically hydrogenates both adsorbed CO2 and the bulk Na2CO3, forming methane. The depleted sites adsorb CO2 through a carbonate reformation process and in addition adsorb CO2 on its surface. This material functions well in O2- and H2O-containing flue gas where the favorable Ru redox property allows RuOx, formed during flue gas exposure, to be reduced during the hydrogenation cycle. As a combined CO2 capture and utilization scheme, this technology overcomes many of the limitations of the conventional liquid amine-based CO2 sorbent technology. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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4726 KiB  
Article
Dendrimer-Stabilized Ru Nanoparticles Immobilized in Organo-Silica Materials for Hydrogenation of Phenols
by Eduard Karakhanov, Anton Maximov, Anna Zolotukhina, Adila Mamadli, Anna Vutolkina and Andrey Ivanov
Catalysts 2017, 7(3), 86; https://doi.org/10.3390/catal7030086 - 14 Mar 2017
Cited by 31 | Viewed by 6900
Abstract
New hybrid catalysts based on Ru nanoparticles, encapsulated into poly(propylene imine dendrimers), immobilized into silica pores, were synthesized and examined for the hydrogenation of alkyl-substituted phenols. The corresponding alkyl-substituted cyclohexanols were presented as the major reaction products, while incomplete hydrogenation products appeared to [...] Read more.
New hybrid catalysts based on Ru nanoparticles, encapsulated into poly(propylene imine dendrimers), immobilized into silica pores, were synthesized and examined for the hydrogenation of alkyl-substituted phenols. The corresponding alkyl-substituted cyclohexanols were presented as the major reaction products, while incomplete hydrogenation products appeared to be minor. A competition between the sterical factors of dendrimer-containing carriers and the electronic factors of substrate substituents influenced the hydrogenation rate of the alkyl-substituted phenols. The carrier structure was found to have a significant influence on both the physical and chemical properties of the catalysts and their hydrogenation activity. The synthesized hybrid catalysts appeared to be stable after recycling and could be re-used several times without significant loss of activity. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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1602 KiB  
Article
Mechanistic Analysis of Water Oxidation Catalyst cis-[Ru(bpy)2(H2O)2]2+: Effect of Dimerization
by Darren Erdman, Yuliana Pineda-Galvan and Yulia Pushkar
Catalysts 2017, 7(2), 39; https://doi.org/10.3390/catal7020039 - 25 Jan 2017
Cited by 17 | Viewed by 6318
Abstract
While the catalytic activity of some Ru-based polypyridine complexes in water oxidation is well established, the relationship between their chemical structure and activity is less known. In this work, the single site Ru complex [Ru(bpy)2(H2O)2]2+ (bpy [...] Read more.
While the catalytic activity of some Ru-based polypyridine complexes in water oxidation is well established, the relationship between their chemical structure and activity is less known. In this work, the single site Ru complex [Ru(bpy)2(H2O)2]2+ (bpy = 2,2′-bipyridine)—which can exist as either a cis isomer or a trans isomer—is investigated. While a difference in the catalytic activity of these two isomers is well established, with cis-[Ru(bpy)2(H2O)2]2+ being much more active, no mechanistic explanation of this fact has been presented. The oxygen evolving capability of both isomers at multiple concentrations has been investigated, with cis-[Ru(bpy)2(H2O)2]2+ showing a second-order dependence of O2 evolution activity with increased catalyst concentration. Measurement of the electron paramagnetic resonance (EPR) spectrum of cis-[Ru(bpy)2(H2O)2]2+, shortly after oxidation with CeIV, showed the presence of a signal matching that of cis,cis-[RuIII(bpy)2(H2O)ORuIV(bpy)2(OH)]4+, also known as “blue dimer”. The formation of dimers is a concentration-dependent process, which could serve to explain the greater than first order increase in catalytic activity. The trans isomer showed a first-order dependence of O2 evolution on catalyst concentration. Behavior of [Ru(bpy)2(H2O)2]2+ isomers is compared with other Ru-based catalysts, in particular [Ru(tpy)(bpy)(H2O)]2+ (tpy = 2,2′;6,2′′-terpyridine). Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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4869 KiB  
Article
Catalytic Ammonia Decomposition over High-Performance Ru/Graphene Nanocomposites for Efficient COx-Free Hydrogen Production
by Gang Li, Masakoto Kanezashi and Toshinori Tsuru
Catalysts 2017, 7(1), 23; https://doi.org/10.3390/catal7010023 - 11 Jan 2017
Cited by 33 | Viewed by 7023
Abstract
Highly-dispersed Ru nanoparticles were grown on graphene nanosheets by simultaneously reducing graphene oxide and Ru ions using ethylene glycol (EG), and the resultant Ru/graphene nanocomposites were applied as a catalyst to ammonia decomposition for COx-free hydrogen production. Tuning the microstructures of [...] Read more.
Highly-dispersed Ru nanoparticles were grown on graphene nanosheets by simultaneously reducing graphene oxide and Ru ions using ethylene glycol (EG), and the resultant Ru/graphene nanocomposites were applied as a catalyst to ammonia decomposition for COx-free hydrogen production. Tuning the microstructures of Ru/graphene nanocomposites was easily accomplished in terms of Ru particle size, morphology, and loading by adjusting the preparation conditions. This was the key to excellent catalytic activity, because ammonia decomposition over Ru catalysts is structure-sensitive. Our results demonstrated that Ru/graphene prepared using water as a co-solvent greatly enhanced the catalytic performance for ammonia decomposition, due to the significantly improved nano architectures of the composites. The long-term stability of Ru/graphene catalysts was evaluated for COx-free hydrogen production from ammonia at high temperatures, and the structural evolution of the catalysts was investigated during the catalytic reactions. Although there were no obvious changes in the catalytic activities at 450 °C over a duration of 80 h, an aggregation of the Ru nanoparticles was still observed in the nanocomposites, which was ascribed mainly to a sintering effect. However, the performance of the Ru/graphene catalyst was decreased gradually at 500 °C within 20 h, which was ascribed mainly to both the effect of the methanation of the graphene nanosheet under a H2 atmosphere and to enhanced sintering under high temperatures. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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9379 KiB  
Article
Synthesis and Application of Novel Ruthenium Catalysts for High Temperature Alkene Metathesis
by Tegene T. Tole, Jean I. Du Toit, Cornelia G. C. E. Van Sittert, Johan H. L. Jordaan and Hermanus C. M. Vosloo
Catalysts 2017, 7(1), 22; https://doi.org/10.3390/catal7010022 - 10 Jan 2017
Cited by 7 | Viewed by 5010
Abstract
Four pyridinyl alcohols and the corresponding hemilabile pyridinyl alcoholato ruthenium carbene complexes of the Grubbs second generation-type RuCl(H2IMes)(O^N)(=CHPh), where O^N = 1-(2′-pyridinyl)-1,1-diphenyl methanolato, 1-(2′-pyridinyl)-1-(2′-chlorophenyl),1-phenyl methanolato, 1-(2′-pyridinyl)-1-(4′-chlorophenyl),1-phenyl methanolato and 1-(2′-pyridinyl)-1-(2′-methoxyphenyl),1-phenyl methanolato, are synthesized in very good yields. At high temperatures, the precatalysts [...] Read more.
Four pyridinyl alcohols and the corresponding hemilabile pyridinyl alcoholato ruthenium carbene complexes of the Grubbs second generation-type RuCl(H2IMes)(O^N)(=CHPh), where O^N = 1-(2′-pyridinyl)-1,1-diphenyl methanolato, 1-(2′-pyridinyl)-1-(2′-chlorophenyl),1-phenyl methanolato, 1-(2′-pyridinyl)-1-(4′-chlorophenyl),1-phenyl methanolato and 1-(2′-pyridinyl)-1-(2′-methoxyphenyl),1-phenyl methanolato, are synthesized in very good yields. At high temperatures, the precatalysts showed high stability, selectivity and activity in 1-octene metathesis compared to the Grubbs first and second generation precatalysts. The 2-/4-chloro- and 4-methoxy-substituted pyridinyl alcoholato ligand-containing ruthenium precatalysts showed high performance in the 1-octene metathesis reaction in the range 80–110 °C. The hemilabile 4-methoxy-substituted pyridinyl alcoholato ligand improved the catalyst stability, activity and selectivity for 1-octene metathesis significantly at 110 °C. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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2312 KiB  
Article
Hydrochlorination of Acetylene Catalyzed by an Activated Carbon-Supported Ammonium Hexachlororuthenate Complex
by Junjie Gu, Yumiao Gao, Jinli Zhang, Wei Li, Yanzhao Dong and You Han
Catalysts 2017, 7(1), 17; https://doi.org/10.3390/catal7010017 - 10 Jan 2017
Cited by 17 | Viewed by 5434
Abstract
Ammonium hexachlororuthenate ((NH4)2RuCl6) complex was used as a catalyst precursor and coconut activated carbon (AC) was used as the support in the preparation process of the Ru-based catalyst. (NH4)2RuCl6/AC catalyst was [...] Read more.
Ammonium hexachlororuthenate ((NH4)2RuCl6) complex was used as a catalyst precursor and coconut activated carbon (AC) was used as the support in the preparation process of the Ru-based catalyst. (NH4)2RuCl6/AC catalyst was prepared via an incipient wetness impregnation method and assessed in an acetylene hydrochlorination reaction. Meanwhile, the (NH4)2RuCl6/AC catalyst was analyzed with low-temperature N2 adsorption/desorption, thermogravimetry (TG), transmission electron microscopy (TEM), temperature programmed reduction (TPR), X-ray photoelectron spectra (XPS), and temperature programmed desorption (TPD) techniques. Catalytic performance test results show that the (NH4)2RuCl6/AC catalyst exhibits a superior catalytic activity with the highest acetylene conversion of 90.5% under the conditions of 170 °C and an acetylene gas hourly space velocity of 180 h−1. The characterization results illustrate that the presence of the NH4+ cation can inhibit coke deposition as well as the agglomeration of ruthenium particles, and it can also enhance the adsorption ability for reactant HCl, hence improving the catalytic activity and stability. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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7403 KiB  
Article
Dehydrogenative Oxidation of Alcohols Catalyzed by Highly Dispersed Ruthenium Incorporated Titanium Oxide
by Youngyong Kim, Seokhoon Ahn, Jun Yeon Hwang, Doo-Hyun Ko and Ki-Young Kwon
Catalysts 2017, 7(1), 7; https://doi.org/10.3390/catal7010007 - 28 Dec 2016
Cited by 14 | Viewed by 5408
Abstract
Ruthenium incorporated titanium oxides (RuxTiO2) were prepared by a one-step hydrothermal method using Ti(SO4)2 and RuCl3 as the precursor of Ti and Ru, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), [...] Read more.
Ruthenium incorporated titanium oxides (RuxTiO2) were prepared by a one-step hydrothermal method using Ti(SO4)2 and RuCl3 as the precursor of Ti and Ru, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), Energy-dispersive X-ray spectroscopy (EDS) mapping, and BET were applied for the analyses of catalysts. Ruthenium atoms are well dispersed in the anatase phase of TiO2 and the crystallite size of RuxTiO2 (≈17 nm) is smaller than that of pure TiO2 (≈45 nm). In particular, we found that our homemade pure TiO2 exhibits a strong Lewis acid property. Therefore, the cooperation of ruthenium atoms playing a role in the hydride elimination and the Lewis acid site of TiO2 can efficiently transfer primary alcohols into corresponding aldehydes in an oxidant-free condition. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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2512 KiB  
Article
Hydrothermal Stability of Ru/SiO2–C: A Promising Catalyst for Biomass Processing through Liquid-Phase Reactions
by Martín N. Gatti, Bárbara Lombardi, Delia Gazzoli, Gerardo F. Santori, Francisco Pompeo and Nora N. Nichio
Catalysts 2017, 7(1), 6; https://doi.org/10.3390/catal7010006 - 27 Dec 2016
Cited by 5 | Viewed by 5434
Abstract
In this work, structural and morphological properties of SiO2–C composite material to be used as support for catalysts in the conversion of biomass-derived oxygenated hydrocarbons, such as glycerol, were investigated in liquid water under various temperatures conditions. The results show that [...] Read more.
In this work, structural and morphological properties of SiO2–C composite material to be used as support for catalysts in the conversion of biomass-derived oxygenated hydrocarbons, such as glycerol, were investigated in liquid water under various temperatures conditions. The results show that this material does not lose surface area, and the hot liquid water does not generate changes in the structure. Neither change in relative concentrations of oxygen functional groups nor in Si/C ratio due to hydrothermal treatment was revealed by X-ray photoelectron spectroscopy (XPS) analysis. Raman analysis showed that the material is made of a disordered graphitic structure in an amorphous silica matrix, which remains stable after hydrothermal treatment. Results of the hydrogenolysis of glycerol using a Ru/SiO2–C catalyst indicate that the support gives more stability to the active phase than a Ru/SiO2 consisting of commercial silica. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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2543 KiB  
Article
Reaction Mechanisms of CO2 Reduction to Formaldehyde Catalyzed by Hourglass Ru, Fe, and Os Complexes: A Density Functional Theory Study
by Chunhua Dong, Mingsong Ji, Xinzheng Yang, Jiannian Yao and Hui Chen
Catalysts 2017, 7(1), 5; https://doi.org/10.3390/catal7010005 - 27 Dec 2016
Cited by 15 | Viewed by 8102
Abstract
The reaction mechanisms for the reduction of carbon dioxide to formaldehyde catalyzed by bis(tricyclopentylphosphine) metal complexes, [RuH2(H2)(PCyp3)2] (1Ru), [FeH2(H2)(PCyp3)2] (1Fe) and [...] Read more.
The reaction mechanisms for the reduction of carbon dioxide to formaldehyde catalyzed by bis(tricyclopentylphosphine) metal complexes, [RuH2(H2)(PCyp3)2] (1Ru), [FeH2(H2)(PCyp3)2] (1Fe) and [OsH4(PCyp3)2] (1Os), were studied computationally by using the density functional theory (DFT). 1Ru is a recently reported highly efficient catalyst for this reaction. 1Fe and 1Os are two analogues of 1Ru with the Ru atom replaced by Fe and Os, respectively. The total free energy barriers of the reactions catalyzed by 1Ru, 1Fe and 1Os are 24.2, 24.0 and 29.0 kcal/mol, respectively. With a barrier close to the experimentally observed Ru complex, the newly proposed iron complex is a potential low-cost catalyst for the reduction of carbon dioxide to formaldehyde under mild conditions. The electronic structures of intermediates and transition states in these reactions were analyzed by using the natural bond orbital theory. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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4189 KiB  
Article
Effect of Ru Species on N2O Decomposition over Ru/Al2O3 Catalysts
by Chao Sui, Fulong Yuan, Zhiping Zhang, Chi Zhang, Xiaoyu Niu and Yujun Zhu
Catalysts 2016, 6(11), 173; https://doi.org/10.3390/catal6110173 - 05 Nov 2016
Cited by 23 | Viewed by 6781
Abstract
Ru is considered as an effective active species for N2O decomposition; however, there is disagreement about which ruthenium species is key for catalytic activity. In order to understand the role of Ru species in N2O decomposition, Ru/Al2O [...] Read more.
Ru is considered as an effective active species for N2O decomposition; however, there is disagreement about which ruthenium species is key for catalytic activity. In order to understand the role of Ru species in N2O decomposition, Ru/Al2O3 (Ru/Al2O3-H2, Ru/Al2O3-NaBH4, Ru/Al2O3-air) catalysts with different ratios of metallic Ru were prepared and evaluated for their catalytic activities. Various characterizations, especially in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), were applied to investigate the relationship between activity and different Ru species. The results indicate that the N2O conversion displayed a linear relationship with the amount of metallic Ru. The DRIFTS results of adsorption for N2O show that metallic Ru was the active site. The catalytic processes are put forward based on metallic Ru species. The deactivation with increasing times used is due to the decrease in the amount of metallic Ru and agglomerates of Ru particles on the surface of catalysts. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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2920 KiB  
Article
Support Screening Studies on the Hydrogenation of Levulinic Acid to γ-Valerolactone in Water Using Ru Catalysts
by Anna Piskun, Jozef G. M. Winkelman, Zhenchen Tang and Hero Jan Heeres
Catalysts 2016, 6(9), 131; https://doi.org/10.3390/catal6090131 - 30 Aug 2016
Cited by 34 | Viewed by 8202
Abstract
γ-Valerolactone (GVL) has been identified as a sustainable platform chemical for the production of carbon-based chemicals. Here we report a screening study on the hydrogenation of levulinic acid (LA) to GVL in water using a wide range of ruthenium supported catalysts in a [...] Read more.
γ-Valerolactone (GVL) has been identified as a sustainable platform chemical for the production of carbon-based chemicals. Here we report a screening study on the hydrogenation of levulinic acid (LA) to GVL in water using a wide range of ruthenium supported catalysts in a batch set-up (1 wt. % Ru, 90 °C, 45 bar of H2, 2 wt. % catalyst on LA). Eight monometallic catalysts were tested on carbon based(C, carbon nanotubes (CNT)) and inorganic supports (Al2O3, SiO2, TiO2, ZrO2, Nb2O5 and Beta-12.5). The best result was found for Ru/Beta-12.5 with almost quantitative LA conversion (94%) and 66% of GVL yield after 2 h reaction. The remaining product was 4-hydroxypentanoic acid (4-HPA). Catalytic activity for a bimetallic RuPd/TiO2 catalyst was by far lower than for the monometallic Ru catalyst (9% conversion after 2 h). The effects of relevant catalyst properties (average Ru nanoparticle size, Brunauer-Emmett-Teller (BET) surface area, micropore area and total acidity) on catalyst activity were assessed. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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Review

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13877 KiB  
Review
Recent Advancements in Stereoselective Olefin Metathesis Using Ruthenium Catalysts
by T. Patrick Montgomery, Adam M. Johns and Robert H. Grubbs
Catalysts 2017, 7(3), 87; https://doi.org/10.3390/catal7030087 - 14 Mar 2017
Cited by 98 | Viewed by 12530
Abstract
Olefin metathesis is a prevailing method for the construction of organic molecules. Recent advancements in olefin metathesis have focused on stereoselective transformations. Ruthenium olefin metathesis catalysts have had a particularly pronounced impact in the area of stereoselective olefin metathesis. The development of three [...] Read more.
Olefin metathesis is a prevailing method for the construction of organic molecules. Recent advancements in olefin metathesis have focused on stereoselective transformations. Ruthenium olefin metathesis catalysts have had a particularly pronounced impact in the area of stereoselective olefin metathesis. The development of three categories of Z-selective olefin metathesis catalysts has made Z-olefins easily accessible to both laboratory and industrial chemists. Further design enhancements to asymmetric olefin metathesis catalysts have streamlined the construction of complex molecules. The understanding gained in these areas has extended to the employment of ruthenium catalysts to stereoretentive olefin metathesis, the first example of a kinetically E-selective process. These advancements, as well as synthetic applications of the newly developed catalysts, are discussed. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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3274 KiB  
Review
Ruthenium–Platinum Catalysts and Direct Methanol Fuel Cells (DMFC): A Review of Theoretical and Experimental Breakthroughs
by Ana S. Moura, José L. C. Fajín, Marcos Mandado and Maria Natália D. S. Cordeiro
Catalysts 2017, 7(2), 47; https://doi.org/10.3390/catal7020047 - 05 Feb 2017
Cited by 55 | Viewed by 11413
Abstract
The increasing miniaturization of devices creates the need for adequate power sources and direct methanol fuel cells (DMFC) are a strong option in the various possibilities under current development. DMFC catalysts are mostly based on platinum, for its outperformance in three key areas [...] Read more.
The increasing miniaturization of devices creates the need for adequate power sources and direct methanol fuel cells (DMFC) are a strong option in the various possibilities under current development. DMFC catalysts are mostly based on platinum, for its outperformance in three key areas (activity, selectivity and stability) within methanol oxidation framework. However, platinum poisoning with products of methanol oxidation led to the use of alloys. Ruthenium–platinum alloys are preferred catalysts active phases for methanol oxidation from an industrial point of view and, indeed, ruthenium itself is a viable catalyst for this reaction. In addition, the route of methanol decomposition is crucial in the goal of producing H2 from water reaction with methanol. However, the reaction pathway remains elusive and new approaches, namely in computational methods, have been ensued to determine it. This article reviews the various recent theoretical approaches for determining the pathway of methanol decomposition, and systematizes their validation with experimental data, within methodological context. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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Letter
Olefin Metathesis with Ru-Based Catalysts Exchanging the Typical N-Heterocyclic Carbenes by a Phosphine–Phosphonium Ylide
by Laia Arnedo, Remi Chauvin and Albert Poater
Catalysts 2017, 7(3), 85; https://doi.org/10.3390/catal7030085 - 14 Mar 2017
Cited by 6 | Viewed by 5397
Abstract
Density functional theory (DFT) calculations have been used to describe the first turnover of an olefin metathesis reaction calling for a new in silico family of homogenous Ru-based catalysts bearing a phosphine–phosphonium ylide ligand, with ethylene as a substrate. Equal to conventional Ru-based [...] Read more.
Density functional theory (DFT) calculations have been used to describe the first turnover of an olefin metathesis reaction calling for a new in silico family of homogenous Ru-based catalysts bearing a phosphine–phosphonium ylide ligand, with ethylene as a substrate. Equal to conventional Ru-based catalysts bearing an N-heterocyclic carbene (NHC) ligand, the activation of these congeners occurs through a dissociative mechanism, with a more exothermic first phosphine dissociation step. In spite of a stronger electron-donating ability of a phosphonium ylide C-ligand with respect to a diaminocarbene analogue, upper energy barriers were calculated to be on average ca. 5 kcal/mol higher than those of Ru–NHC standards. Overall, the study also highlights advantages of bidentate ligands over classical monodentate NHC and phosphine ligands, with a particular preference for the cis attack of the olefin. The new generation of catalysts is constituted by cationic complexes potentially soluble in water, to be compared with the typical neutral Ru–NHC ones. Full article
(This article belongs to the Special Issue Ruthenium Catalysts)
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