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Letteratura scientifica selezionata sul tema "Ruthenium-based catalysts"

Autore: Grafiati

Pubblicato: 7 settembre 2024

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Articoli di riviste sul tema "Ruthenium-based catalysts"

1

Singh, Keisham. "Recent Advances in C–H Bond Functionalization with Ruthenium-Based Catalysts". Catalysts 9, n. 2 (12 febbraio 2019): 173. http://dx.doi.org/10.3390/catal9020173.

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The past decades have witnessed rapid development in organic synthesis via catalysis, particularly the reactions through C–H bond functionalization. Transition metals such as Pd, Rh and Ru constitute a crucial catalyst in these C–H bond functionalization reactions. This process is highly attractive not only because it saves reaction time and reduces waste,but also, more importantly, it allows the reaction to be performed in a highly region specific manner. Indeed, several organic compounds could be readily accessed via C–H bond functionalization with transition metals. In the recent past, tremendous progress has been made on C–H bond functionalization via ruthenium catalysis, including less expensive but more stable ruthenium(II) catalysts. The ruthenium-catalysed C–H bond functionalization, viz. arylation, alkenylation, annulation, oxygenation, and halogenation involving C–C, C–O, C–N, and C–X bond forming reactions, has been described and presented in numerous reviews. This review discusses the recent development of C–H bond functionalization with various ruthenium-based catalysts. The first section of the review presents arylation reactions covering arylation directed by N–Heteroaryl groups, oxidative arylation, dehydrative arylation and arylation involving decarboxylative and sp3-C–H bond functionalization. Subsequently, the ruthenium-catalysed alkenylation, alkylation, allylation including oxidative alkenylation and meta-selective C–H bond alkylation has been presented. Finally, the oxidative annulation of various arenes with alkynes involving C–H/O–H or C–H/N–H bond cleavage reactions has been discussed.

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2

Nahra, Fady, e Catherine S. J. Cazin. "Sustainability in Ru- and Pd-based catalytic systems using N-heterocyclic carbenes as ligands". Chemical Society Reviews 50, n. 5 (2021): 3094–142. http://dx.doi.org/10.1039/c8cs00836a.

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This review is a critical presentation of catalysts based on palladium and ruthenium bearing N-heterocyclic carbene ligands that have enabled a more sustainable approach to catalysis and to catalyst uses.

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3

Weissenberger, Tobias, Ralf Zapf, Helmut Pennemann e Gunther Kolb. "Catalyst Coatings for Ammonia Decomposition in Microchannels at High Temperature and Elevated Pressure for Use in Decentralized and Mobile Hydrogen Generation". Catalysts 14, n. 2 (26 gennaio 2024): 104. http://dx.doi.org/10.3390/catal14020104.

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We report an investigation of catalyst performance for the decomposition of ammonia under industrially relevant conditions (high temperatures of up to 800 °C and an elevated pressure of 5 bar) with further emphasis on their stability at high reaction temperatures. The catalysts were applied and tested as coatings in 500 µm wide channels of microreactors. Nickel-based catalysts were studied and compared to a ruthenium-based catalyst supported on SiO2. The effect of the support on the catalytic performance was investigated, and CeO2-supported nickel catalysts were found to exhibit the highest activity. Promoters were applied to increase the NH3 decomposition activity of the Ni/CeO2 catalysts. The addition of cesium led to a slight reduction in activity, while lanthanum, calcium, and barium doping resulted in increased activity. In particular, the barium-doped Ni/CeO2 catalyst showed very high ammonia conversion and closed the activity gap with respect to ruthenium catalysts at reactor temperatures of 650 °C and higher. The hydrogen production rates achieved in this work were compared to values in the literature and were shown to exceed values found earlier for both nickel- and ruthenium-based catalysts. Furthermore, the ruthenium-based catalysts under investigation were rapidly deactivated at 700 °C, while the nickel-based catalysts did not show deactivation after 220 h on time on stream at 700 °C.

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4

Podolean, Iunia, Mara Dogaru, Nicolae Cristian Guzo, Oana Adriana Petcuta, Elisabeth E. Jacobsen, Adela Nicolaev, Bogdan Cojocaru, Madalina Tudorache, Vasile I. Parvulescu e Simona M. Coman. "Highly Efficient Ru-Based Catalysts for Lactic Acid Conversion to Alanine". Nanomaterials 14, n. 3 (29 gennaio 2024): 277. http://dx.doi.org/10.3390/nano14030277.

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The primary objective of this research was to develop efficient solid catalysts that can directly convert the lactic acid (LA) obtained from lignocellulosic biomass into alanine (AL) through a reductive amination process. To achieve this, various catalysts based on ruthenium were synthesized using different carriers such as multi-walled carbon nanotubes (MWCNTs), beta-zeolite, and magnetic nanoparticles (MNPs). Among these catalysts, Ru/MNP demonstrated a remarkable yield of 74.0% for alanine at a temperature of 200 °C. This yield was found to be superior not only to the Ru/CNT (55.7%) and Ru/BEA (6.6%) catalysts but also to most of the previously reported catalysts. The characterization of the catalysts and their catalytic results revealed that metallic ruthenium nanoparticles, which were highly dispersed on the external surface of the magnetic carrier, significantly enhanced the catalyst’s ability for dehydrogenation. Additionally, the -NH2 basic sites on the catalyst further facilitated the formation of alanine by promoting the adsorption of acidic reactants. Furthermore, the catalyst could be easily separated using an external magnetic field and exhibited the potential for multiple reuses without any significant loss in its catalytic performance. These practical advantages further enhance its appeal for applications in the reductive amination of lactic acid to alanine.

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5

Reany, Ofer, e N. Gabriel Lemcoff. "Light guided chemoselective olefin metathesis reactions". Pure and Applied Chemistry 89, n. 6 (27 giugno 2017): 829–40. http://dx.doi.org/10.1515/pac-2016-1221.

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AbstractAn appealing concept in synthetic chemistry is photo-induced catalysis; where dormant complexes become catalytically active upon activation with light. The ruthenium-based olefin metathesis complexes founded on the original Grubbs catalyst have probably been one of the most widely studied families of catalysts for the past 25 years. Greater stability and versatility of these olefin-metathesis catalysts has been achieved by careful design of the ligand sphere, including latent catalysts which are activated by external stimuli. This article describes our recent developments towards light-induced olefin metathesis reactions based on photoactive sulfur-chelated ruthenium benzylidene catalysts. Alternative chemical reactions, be it photo-induced olefin metathesis or other direct photochemical processes, by using light of different frequencies were studied in chemoselective chromatic orthogonal pathways. The lessons learned during the development of these reactions have given birth to selective photo-deprotection sequences and novel pathways for stereolithographic applications.

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6

Chen, Hui, Runxu Deng, Shixin Gao e Feng Liu. "Preparation of porous iridium-ruthenium-based acidic water oxidation catalyst by ascorbic acid reduction and evaporation". Journal of Physics: Conference Series 2566, n. 1 (1 agosto 2023): 012017. http://dx.doi.org/10.1088/1742-6596/2566/1/012017.

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Abstract Green hydrogen is the ultimate direction for energy development technology. Hereon, the porous materials of promoted iridium-ruthenium-based catalyst were prepared by ascorbic acid reduction and evaporation drying methods. The unsupported iridium ruthenium-based catalysts were porous structures, characterized by scanning electron microscopes (SEM). In 0.5 mol·L−1 H2SO4, the electrochemical oxygen precipitation reaction overpotential was only 251 mV at 10 mA·cm2, compared to commercial 303 mV. The polarization overpotential was not significantly reduced, after 20 000 cycles of accelerated cyclic aging experiments. The porous structure of the iridium-ruthenium-based catalysts showed higher catalytic activity for oxygen precipitation than the commercial IrO2(ZrO2) catalysts. Porous materials could improve the activity of catalysts, which provides a good research idea for the synthesis of electrocatalysts.

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7

Truszkiewicz, Elżbieta, Wioletta Raróg-Pilecka, Magdalena Zybert, Malwina Wasilewska-Stefańska, Ewa Topolska e Kamila Michalska. "Effect of the ruthenium loading and barium addition on the activity of ruthenium/carbon catalysts in carbon monoxide methanation". Polish Journal of Chemical Technology 16, n. 4 (1 dicembre 2014): 106–10. http://dx.doi.org/10.2478/pjct-2014-0079.

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Abstract A group of supported ruthenium catalysts was prepared and tested in methanation of small CO amounts (7000 ppm) in hydrogen-rich streams. High surface area graphitized carbon (484 m2/g) was used as a support for ruthenium and RuCl3 was used as a Ru precursor. Some of the Ru/C systems were additionally doped with barium (Ba(NO3)2 was barium precursor). The catalysts were characterized by the chemisorption technique using CO as an adsorbate. To determine the resistance of the catalysts to undesired carbon support methanation, the TG-MS experiments were performed. They revealed that the barium addition inhibits support losses. The studies of CO methanation (fl ow reactor, atmospheric pressure) have shown that some of the supported ruthenium catalysts exhibit high activities referred to the metal mass. The catalytic properties of ruthenium proved to be dependent on metal dispersion. Some of the Ru/C and Ba-Ru/C systems exhibit higher activity in CO hydrogenation than the commercial nickel-based catalyst.

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8

Zhong, He Xiang, Hua Min Zhang e Mei Ri Wang. "Oxygen Reduction Reaction on Carbon Supported Ruthenium-Based Electrocatalysts in PEMFC". Materials Science Forum 675-677 (febbraio 2011): 97–100. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.97.

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The ruthenium-based electrocatalysts supported on carbon black were prepared by the decarbonylation of the transition metal carbonyl with the 1,6-hexanediol as the solvent. The catalysts were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The electrochemical behaviours of the catalysts were investigated by cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements in 0.5 M H2SO4 solution. The catalysts demonstrate attractive catalytic activity towards the ORR. The catalyst is expected to be promising alternative non-Pt electrocatalysts for PEMFC.

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9

Ma, Peng, Jiaren Zhang, Xiaqian Wu e Jianhui Wang. "Ruthenium Metathesis Catalysts with Imidazole Ligands". Catalysts 13, n. 2 (26 gennaio 2023): 276. http://dx.doi.org/10.3390/catal13020276.

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Phosphine-free ruthenium benzylidene complexes containing imidazole ligands are reported. These catalysts are effective for ring-closing metathesis (RCM) and cross-metathesis (CM) reactions at high temperatures, where the more widely used phosphine-containing N-heterocyclic carbene-based ruthenium catalysts show side reactions. This discovery opens up a pathway to develop more selective ruthenium metathesis catalysts for reactions requiring harsh conditions.

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10

Dunn, E., e J. Tunge. "Decarboxylative Allylation of Ketone Enolates with Rh, Ir, and Mo". Latvian Journal of Chemistry 51, n. 1-2 (1 gennaio 2012): 31–40. http://dx.doi.org/10.2478/v10161-012-0007-x.

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Decarboxylative Allylation of Ketone Enolates with Rh, Ir, and MoA variety of catalysts were investigated for their ability to impart branched regioselectivity in decarboxylative allylation reactions. While catalysts based on Mo, Rh, and Ir were active catalysts, their regio-selectivities were low and the reactions required an equivalent of base for efficient coupling. Alternatively, a ruthenium-based catalyst was identi-fied that operates under neutral conditions and gives high branched selectivity in decarboxylative allylations.

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Tesi sul tema "Ruthenium-based catalysts"

1

Robinson, Alan. "Novel catalysts and additives for ruthenium-based metathesis systems". Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508098.

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2

MOTOKI, YOSHIDA. "Synthesis of Ruthenium-based Water Oxidation Catalysts and Mechanistic Study". Thesis, KTH, Skolan för kemivetenskap (CHE), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173843.

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Two series of new mononuclear ruthenium complexes with hydrophobic or hydrophilic ligands [Ru(bda)L2] and [Ru(pdc)L3] (H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid; H2pdc = 2,6-pyridinedicarboxylic acid; L = pyridyl ligands) were synthesized and their electrochemical properties and catalytic activity toward water oxidation were examined. It was revealed that the hydrophobic ligands introduced to [Ru(bda)L2 ] improved the catalytic performance, ahnost twofold TON and TOF values were achieved compared to the [Ru(bda)] catalyst with hydrophilic ligands. The cyclic voltammogram of [Ru(bda)L2] exhibited marginal difference between the catalysts with hydrophobic ligands and hydrophilic ones, implying that the hydrophobic ligands promoted the catalytic activity by :lacilitating formation of a reaction intermediate dimer.

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3

Urbina-Blanco, César A. "Design and synthesis of ruthenium indenylidene-based catalysts for olefin metathesis". Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3737.

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As part of a European wide effort to develop metathesis catalysts for use in fine chemical and pharmaceutical compound synthesis, this study focuses on the design and synthesis of ruthenium based catalysts for olefin metathesis. The aim, of this work was simple: to develop new, more active, more stable, easy to synthesise and commercially viable Ruthenium based catalysts, as well trying to rationalize the effect of structural changes on reactivity. Two different approaches were explored in order to develop more active catalysts bearing N-heterocyclic carbene (NHC) ligands: changing the leaving group and the effect of the NHC moiety in indenylidene type complexes. Over 12 new catalysts were developed and their activity compared to that of commercially available catalysts. Overall, the new complexes exhibited superior reactivity compared to previously reported catalysts in several benchmark transformations. However, olefin metathesis is a very substrate specific reaction, and rather than finding one catalyst that is superior to all, a catalogue of catalysts suitable for specific transformations was developed. In addition, the effect of structural changes on substrate activity was investigated in the ring closing metathesis of 1,8-nonadienes. The reaction profiling showcased the presence of a gem-difluoro group as an accelerating group in this incarnation of the olefin metathesis reaction and leads to ring formation over polymerization. In order to rationalize the effect of structural changes on catalyst activity, kinetic studies dealing with the initiation mechanism of ruthenium-indenylidene complexes were examined and compared with that of benzylidene counterparts. It was discovered that not all indenylidene complexes followed the same mechanism, highlighting the importance of steric and electronic properties of so-called spectator ligands, and that there is no single mechanism for the ruthenium-based olefin metathesis reaction. These results highlight the importance of systematic development of catalysts and that as scientists we should not take for granted.

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4

Gowda, Anitha Shankaralinge. "HYDROGENATION AND HYDROGENOLYSIS OF FURAN DERIVATIVES USING BIPYRIDINE-BASED ELECTROPHILIC RUTHENIUM(II) CATALYSTS". UKnowledge, 2013. http://uknowledge.uky.edu/chemistry_etds/29.

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The catalytic activity of ruthenium(II) bis(diimine) complexes cis-[Ru(6,6′-Cl2bpy)2(OH2)2](Z)2 (2, Z = CF3SO3; 3, Z = (3,5-(CF3)2C6H3)4B ,i.e. BArF), cis-[Ru(4,4′-Cl2bpy)2(OH2)2](Z)2 (4, Z = CF3SO3; 5, Z = BArF) and cis-[Ru(bpy)2(PR3)(OH2)](CF3SO3)2 (7, bpy = 2,2’-bipyridine, PR3 = P(C6H4F)3; 8, bpy = 2,2-bipyridine, PR3 = PPh3; 9, bpy = 4,4’-dichloro-2,2’-bipyridine, PR3 = PPh3; 10, bpy = 4,4’-dimethyl-2,2’-bipyridine, PR3 = P(C6H4F)3) for the hydrogenation and hydrogenolysis of furfural (FFR), furfuryl alcohol (FFA) and 5-hydroxymethylfurfural (HMF) was investigated. The compounds 2-5 are active and highly selective catalysts for the hydrogenation of FFR to FFA. Using 2 as catalyst at 100 °C, hydrogenation of FFR proceeded to high conversion (≥98%) and with 100% selectivity to FFA in 2 h. The catalyst cis-[Ru(6,6′-Cl2bpy)2(OH2)2](CF3SO3)2 (2) also showed some activity for hydrogenolysis of FFR and FFA at 130 °C in ethanol, giving up to 25% of 2-methylfuran (MF) yield. The catalyst 3 alsodisplayed high catalytic activity for the hydrogenation of FFA to tetrahydrofurfuryl alcohol. Catalysts 7-10 are also active towards the hydrogenation of furfural (FFR) in NMP giving >90% FFR conversion with 100% selectivity for furfuryl alcohol (FFA) in 12 h. Compounds 7-10 are active C-O bond hydrogenolysis catalysts in presence of bismuth halide Lewis acids. For example, hydrogenolysis of FFA in the presence of 1 mol% of catalyst cis-[Ru(4,4’-Cl2bpy)2(PPh3)(OH2)](CF3SO3)2 (9) and 20 mol% bismuth bromide at 180 °C/51 atm H2 pressure gave >96% conversion of FFA and 55% MF yield. Compounds 7-10 in the presence of bismuth halides, showed almost 100% conversion of HMF with a very high selectivity (65-72%) for 2,5-DMF, along with 10-12% of MF, and trace amount of 5-methylfurfural (MeFFR). In order to test the activity of ruthenium hydrides towards the C-O bond hydrogenation and hydrogenolysis of HMF, series of monocationic ruthenium complexes cis-[Ru(bpy)2(PR3)(H)](CF3SO3) (12, bpy = 2,2’-bipyridine, PR3 = P(C6H4F)3; 13, bpy = 2,2-bipyridine, PR3= PPh3; 14, bpy = 4,4’-dimethyl-2,2’-bipyridine, PR3= P(C6H4F)3) were prepared. The hydrogenation of HMF using catalysts 12-14, produced 70-72% of 2,5-DMF and 11% MF, suggesting that ruthenium hydrides are active and efficient catalysts for HMF hydrogenation.

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Bashal, Ali Habib. "Aqueous phase hydrogenation of succinic acid using mono-and bi-metallic ruthenium-based catalysts". Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3021601/.

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6

Morgan, John Philip Stoltz Brian M. Grubbs Robert H. "Ruthenium-based olefin metathesis catalysts coordinated with n-heterocyclic carbene ligands : synthesis and applications /". Diss., Pasadena, Calif. : California Institute of Technology, 2003. http://resolver.caltech.edu/CaltechETD:etd-10222002-204928.

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7

Fraser, Ian. "The feasibility of high synthesis gas conversion over ruthenium promoted iron-based Fischer Tropsch catalyst". Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2588.

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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.
One of the very promising synthetic fuel production strategies is the Fischer-Tropsch process, founded on the Fischer-Tropsch Synthesis, which owes its discovery to the namesake researchers Franz Fischer and Hans Tropsch. The Fischer-Tropsch Synthesis (FTS) converts via complex polymerisation reaction a mixture of CO and H2 over transition metal catalysts to a complex mixture of hydrocarbons and oxygen containing compounds with water as major by-product. The mixture of CO and H2 (termed syngas) may be obtained by partial oxidation of carbon containing base feedstocks such as coal, biomass or natural gas via gasification or reforming. The Fischer-Tropsch (FT) process thus presents the opportunity to convert carbon containing feedstocks to liquid fuels, chemicals or hydrocarbon waxes, which makes, for instance, the monetisation of stranded gas or associated gas a possibility. The FT-process is typically carried out in two modes of operation: low temperature Fischer-Tropsch (LTFT) and high temperature Fischer-Tropsch (HTFT). LTFT is normally operated at temperatures of 200 – 250 °C and pressures of 10 – 45 bar to target production of high molecular weight hydrocarbons, while HTFT is operated at 300 – 350 °C and 25 bar to target gasoline production. The catalytically active metals currently used commercially are iron and cobalt, since product selectivity over nickel is almost exclusively to methane and ruthenium is highly expensive in addition to requiring very high pressures to perform optimally. Fe is much cheaper, but tends to deactivate more rapidly than Co due to oxidation in the presence of high H2O partial pressures. One of the major drawbacks to using Fe as FT catalyst is the requirement of lower per pass conversion which necessitates tail gas recycle to extend catalyst life and attain acceptable overall conversions. A more active or similarly active but more stable Fe-catalyst would thus be advantageous. For this reason promotion of a self-prepared typical LTFT Fe-catalyst with Ru was investigated. A precipitated K-promoted Fe-catalyst was prepared by combination of co-precipitation and incipient wetness impregnation and a ruthenium containing catalyst prepared from this by impregnation with Ru3(CO)12. The catalysts, which had a target composition of 100 Fe/30 Al2O3/5 K and 100 Fe/30 Al2O3/5 K/3 Ru, were characterised using XRD, SEMEDX, ICP-OES, TPR and BET N2-physisorption, before testing at LTFT conditions of 250 °C and 20 bar in a continuously stirred slurry phase reactor.

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Zhang, Hui-Jun. "Novel syntheses from building blocks based on 1,3-butadienyl skeleton and new polysubstitued ruthenium based catalysts for regioselective allylation". Rennes 1, 2010. http://www.theses.fr/2010REN1S011.

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In this thesis the author concentrates on the preparation of several novel building blocks based on butadienyl skeleton and their synthetic application for organic synthesis. Stereo-defined 1,1,4,4-tetrahalo-1,3-butadienes could be readily synthesized. The reactions of these butadienes with butyllithium and its Suzuki coupling reactions with aryl boronic acid are unprecedented. Moreover, bis(pinacolato)diboron could react with 1,4,4-trihalo-1-lithiodienes which were obtained in situ by lithiation of our new bis(gem-dihalo)dienes, to afford corresponding novel gem-diboryldienes which serve as good substrates for the Miyaura-Suzuki coupling reaction. Upon treatment with LiAlH₄, 1,4-dicyano-1,4-bis(trimethylsilyl)-1,3-dienes could undergo a novel hydride-induced cyclization to afford multiply functionalized cyclopentadienes in high isolated yields. In a second objective, novel [Ru(C₅Me₄R)(2-quinolinecarboxylato)(CH₂CHCHR')][PF6] and [Ru(C₅Me₅)(2-quinolinecarboxylato)(CH₂CHCHn-Pr)][BF₄], allyl ruthenium(IV) complexes were synthesized. These complexes were used as catalysts in allylation reactions, and it is the first time that high regioselectivity in favor of the branched product was obtained from purely aliphatic allylic substrates and functional vinylsilanes
Un objectif de cette thèse était la préparation de nouveaux fragments organique à partir du squelette butadiényle et leurs applications en synthèse organique. Des 1,1,4,4-tétrahalo-1,3-butadiènes ont été préparés de façon stéréosélective. La réaction de ces butadiènes avec le butyllithium et leur couplage de Suzuki avec des acides arylboroniques constituent des transformations nouvelles et originales. De nouveaux gem-diboryldiènes, également d��excellents agents de couplage de Suzuki, ont été obtenus à partir des gem-dihalodiènes correspondants. Le traitement avec LiAlH₄ de 1,4-dicyano-1,4-bis(triméthylsilyl)-1,3-diènes a conduit à une nouvelle réaction de cyclisation induite par des hydrures pour former des cyclopentadiènes multi-fonctionnalisés avec de très bons rendements. Dans un deuxième objectif, une série de complexes inédits du ruthénium porteurs de nouveaux ligands Cp et N-O chelatants ont été conçus et préparés avec l’objectif d’obtenir de bonnes propriétés catalytiques en allylation de nucléophiles. Ces complexes ont été utilisés comme catalyseurs d’allylation et ont conduit pour la première fois à d’excellentes régiosélectivités en faveur des produits branchés à partir de substrats allyliques purement aliphatiques et à la préparation de dérivés vinylsilanes fonctionnels

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Delgado, Jaime Mario Ulises. "Electronic structure studies of ruthenium-based catalysts for olefin metathesis : an x-ray absoprtion spectroscopy perspective". Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/17434.

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Interest in olefin metathesis has increased over the years with the development of ruthenium-based catalysts. Their unique properties have allowed their use in numerous industrial and laboratory processes in relatively mild conditions and in combination with a wide range of solvents. Several studies have provided insights into how these catalysts work, but very little has been done in order to understand why they work that way; an important aspect that has the potential of benefiting chemists while designing new catalysts. The research introduced here has focused on the fundamental understanding of their reactivity by exploring their electronic structure, using a combination of synchrotron-based X-ray-absorption (XAS) techniques in combination with DFT calculations and multiplet simulations. As part of the experimental work, samples from various ruthenium-based catalysts classified as first-generation (whenever the ancillary ligand is a phosphine) or as second-generation analogues (whenever this ligand is an N-heterocyclic carbene, NHC) were used. The Ru K-edge XAS data have revealed that the ruthenium centre in second-generation analogues is more positively charged than the corresponding first-generation counterparts. This offers a rationale for previously observed kinetic results, which have shown a slower initial step for the second-generation Grubbs catalyst. At the same time, they raise questions in a more fundamental level on whether or not NHCs are truly better charge donors than phosphine ligands. DFT results are consistent and the ongoing analyses of the Cl K- and C K-edge XAS data indicate similar overall bonding structures between first- and second- generation analogues. In addition, from preliminary results on these edges, two possible identities of substantially different nature have emerged for the LUMO orbital. In this regard, the final conclusion should provide important insights on through which orbital the metathesis reaction gets started. As a side product, the analyses of the challenging Cl K-edge XAS data have inspired the development of a new methodology and a Matlab-based computer program for fitting. Ultimately, the methods and techniques detailed here can serve as the foundation for the comprehensive study of other related systems relevant to olefin metathesis, or in general, to the field of homogeneous catalysis.

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10

Bernardi, Andrea. "Synthesis, characterization and catalytic performances of ruthenium-based catalysts for the acceptorless dehydrogenative coupling of butanol". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8521/.

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A growing interest towards new sources of energy has led in recent years to the development of a new generation of catalysts for alcohol dehydrogenative coupling (ADC). This green, atom-efficient reaction is capable of turning alcohol derivatives into higher value and chemically more attractive ester molecules, and it finds interesting applications in the transformation of the large variety of products deriving from biomass. In the present work, a new series of ruthenium-PNP pincer complexes are investigated for the transformation of 1-butanol, one of the most challenging substrates for this type of reactions, into butyl butyrate, a short-chain symmetrical ester widely used in flavor industries. Since the reaction kinetics depends on hydrogen diffusion, the study aimed at identifying proper reactor type and right catalyst concentration to avoid mass transfer interferences and to get dependable data. A comparison between catalytic activities and productivities has been made to establish the role of the different ligands bonded both to the PNP binder and to the ruthenium metal center, and hence to find the best catalyst for this type of reaction.

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Capitoli di libri sul tema "Ruthenium-based catalysts"

1

Grubbs, R. H., e M. Sanford. "Mechanism of Ruthenium Based Olefin Metathesis Catalysts". In Ring Opening Metathesis Polymerisation and Related Chemistry, 17–21. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0373-5_2.

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2

Ilker, M. Firat, Habib Skaff, Todd Emrick e E. Bryan Coughlin. "Metathesis and Polyolefin Growth on Cadmium Selenide Surfaces Using Ruthenium-Based Catalysts". In Novel Metathesis Chemistry: Well-Defined Initiator Systems for Specialty Chemical Synthesis, Tailored Polymers and Advanced Material Applications, 263–70. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-010-0066-6_22.

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3

Quigley, Brendan L., e Robert H. Grubbs. "Catalyst Structure andCis-TransSelectivity in Ruthenium-based Olefin Metathesis". In Ligand Design in Metal Chemistry, 15–45. Chichester, UK: John Wiley & Sons, Ltd, 2016. http://dx.doi.org/10.1002/9781118839621.ch2.

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4

Pettinari, Claudio, Riccardo Pettinari, Corrado Di Nicola e Fabio Marchetti. "Half-Sandwich Rhodium(III), Iridium(III), and Ruthenium(II) Complexes with Ancillary Pyrazole-Based Ligands". In Advances in Organometallic Chemistry and Catalysis, 269–84. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118742952.ch21.

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5

Noels, A. F., e A. Demonceau. "Metathesis of Low-Strain Olefins and Functionalized Olefins with New Ruthenium-Based Catalyst Systems". In Metathesis Polymerization of Olefins and Polymerization of Alkynes, 29–46. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5188-7_2.

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6

Karabulut, Solmaz, e Francis Verpoort. "Ring-Opening Metathesis Activity of Ruthenium-Based Olefin Metathesis Catalyst Coordinated with 1,3-Bis(2,6-Diisopropylphenyl)-4,5-Dihydroimidazoline". In Metathesis Chemistry, 185–92. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-6091-5_11.

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7

Ernst Müller, Thomas. "Catalysis with Ruthenium for Sustainable Carbon Cycles". In Ruthenium - Materials Properties, Device Characterizations, and Advanced Applications [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.112101.

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Abstract (sommario):

Nestled between the noble and non-noble metals in the periodic table, ruthenium, one of the transition metals, offers a combination of intriguing properties. Due to its variable oxidation states and its ability to form complexes with various Lewis base compounds, ruthenium, has been widely used in the field of catalysis. Its application has led to groundbreaking breakthroughs in a variety of chemical transformations and has attracted considerable attention in both academic research and industrial applications. Ruthenium catalysis is a dynamic and rapidly evolving field, with ongoing efforts to further advance the efficiency and selectivity of these catalysts. Importantly, in the context of sustainability, ruthenium-based catalysts play an important role in promoting green chemistry practices. Because ruthenium catalysts are highly efficient, only small amounts of the element need to be used. Recovery rates at the end of catalyst life are typically very high, minimizing the need to mine fresh ore. The use of ruthenium catalysts promotes the utilization of renewable resources in various chemical transformations, is at the heart of the realization of new energy-related processes, and by enabling efficient and highly selective chemical transformations reduces waste and harmful emissions. These aspects reinforce the metal’s importance in the quest for a more sustainable future.

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"Ruthenium Sulfide Based Catalysts". In Hydrotreating Technology for Pollution Control, 191–204. CRC Press, 1996. http://dx.doi.org/10.1201/9781482273540-13.

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von Angerer, S. "With Ruthenium-Based Catalysts". In Ketones, 1. Georg Thieme Verlag KG, 2005. http://dx.doi.org/10.1055/sos-sd-026-00033.

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10

"Ruthenium Based Ammonia Synthesis Catalysts". In Ammonia Synthesis Catalysts, 425–542. WORLD SCIENTIFIC / CHEMICAL INDUSTRY PRESS, CHINA, 2013. http://dx.doi.org/10.1142/9789814355780_0006.

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Atti di convegni sul tema "Ruthenium-based catalysts"

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Sudiyarmanto, Sudiyarmanto, Fauzan Aulia, Fauzul Adzim, Hendri Setiyanto e Adid Adep Dwiatmoko. "Catalytic conversion of furfural to furfuryl alcohol over ruthenium based catalysts". In SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems. Author(s), 2018. http://dx.doi.org/10.1063/1.5064313.

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2

Bartley, Gordon J., Zachary Tonzetich e Ryan Hartley. "Ruthenium-Based Catalyst in EGR Leg of a D-EGR Engine Offers Combustion Improvements Through Selective NOX Removal". In SAE 2016 World Congress and Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2016. http://dx.doi.org/10.4271/2016-01-0952.

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3

Yang, Lijun, e Wallace Woon-Fong Leung. "Improvement of Dye Sensitized Solar Cells With Nanofiber-Based Anode". In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64710.

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Abstract (sommario):

Dye Sensitized Solar Cell (DSSC) has great advantages over conventional silicon-based photovoltaics as it is inexpensive, flexible, and transparent. Sun energy is used to excite the electron of the organic (ruthenium-polypyridine) dye from which the electron from the dye is injected into the anode made of titanium dioxide (TiO2). The excited electron enters the conduction band of the TiO2 and gets transmitted across the TiO2 nanoparticles (anode) to the FTO (Fluorine-doped tin-oxide) glass/electrode, which in turn go to the external circuit powering the electrical load. The electron returns to the device via the counter electrode coated with a platinum catalyst to the electrolyte, typically iodide/tri-iodide, wherein the iodide ions carry the electron back to regenerate the dye attached to the TiO2 nanofibers. Improvement can be made by using 60–120 nm diameter TiO2 nanofibers produced in our lab, for which electrons can be directly transferred to the FTO reducing the recombination rate. Also, the large surface-to-volume ratio of the nanofibers allows numerous sites for attachment of the organic dye molecules, thereby increasing the capture of sunlight. In order to achieve high conversion efficiency, several critical parameters need to be optimized with the nanofiber-based DSSC. In this study, we investigate the thickness of the anode (TiO2 nanofiber) on the conversion efficiency. The conversion efficiency of the DSSC in our laboratory can reach more than 7%. Other improvements are believed to further boost this efficiency.

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Basu, Sumit, Yuan Zheng e Jay P. Gore. "Chemical Kinetics Parameter Estimation for Ammonia Borane Hydrolysis". In ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56139.

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Onboard hydrogen storage is an enabling factor in the development of fuel cell powered passenger cars. Ammonia borane (AB) hydrolysis is one of the potential technologies for onboard hydrogen storage. In this study, kinetics of catalyzed ammonia borane hydrolysis using ruthenium-supported-on-carbon has been measured. For reacting flows, chemical kinetics determines the rates of heat generation and species production or consumption in the overall energy and mass balances respectively. Kinetic measurements under isothermal conditions provide critical data for the design of hydrolysis reactors. It is, however, not always possible to eliminate the effects of internal diffusion in a heterogeneous chemical reaction. In such cases, the reaction efficiency (η), which depends on the effective liquid phase diffusivity (Deff) in the catalyst medium, should be determined. Determination of intrinsic kinetic parameters using apparent kinetics data is, thus, a challenge. In this study, the change in AB concentration (CAB) with reaction time (t) has been directly measured. It was observed that the AB hydrolysis reaction had orders between zero and one in a temperature range of 26°C to 55°C. A unified Langmuir-Hinshelwood (LH) model has been adopted to describe the reaction kinetics. The intrinsic kinetic parameters (A, Ea, ΔHads, K0) as well as Deff need to be estimated by inverse analysis of the measured CAB vs t data. Conventionally, kinetic parameters are determined using linear fitting. Sometimes, however, it is impossible to converge to a unique value by using the linear fitting approach as there are several values providing regression coefficients greater than 0.99. In this study, the multiple-variable inverse problem has been solved using a nonlinear fitting algorithm based on Powell’s conjugate-gradient error minimization. This algorithm minimizes errors without using derivatives. As a result, the uncertainties in the kinetic parameter estimation have been significantly reduced by the new approach.

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