- One-pot dual catalysis for the hydrogenation of heteroarenes and arenes
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A simple dinuclear monohydrido bridged ruthenium complex [{(η6-p-cymene)RuCl}2(μ-H-μ-Cl)] acts as an efficient and selective catalyst for the hydrogenation of various heteroarenes and arenes. The nature of the catalytically active species was investigated using a combination of techniques including in situ reaction monitoring, kinetic studies, quantitative poisoning experiments and electron microscopy, evidencing a dual reactivity. The results suggest that the hydrogenation of heteroarenes proceeds via molecular catalysis. In particular, monitoring the reaction progress by NMR spectroscopy indicates that [{(η6-p-cymene)RuCl}2(μ-H-μ-Cl)] is transformed into monomeric ruthenium intermediates, which upon subsequent activation of dihydrogen and hydride transfer accomplish the hydrogenation of heteroarenes under homogeneous conditions. In contrast, carbocyclic aryl motifs are hydrogenated via a heterogeneous pathway, by in situ generated ruthenium nanoparticles. Remarkably, these hydrogenation reactions can be performed using molecular hydrogen under solvent-free conditions or with 1,4-dioxane, and thus give access to a broad range of saturated heterocycles and carbocycles while generating no waste.
- Chatterjee, Basujit,Kalsi, Deepti,Kaithal, Akash,Bordet, Alexis,Leitner, Walter,Gunanathan, Chidambaram
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p. 5163 - 5170
(2020/09/07)
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- Ru subnanoparticles on N-doped carbon layer coated SBA-15 as efficient Catalysts for arene hydrogenation
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The N-doped carbon layer coated SBA-15 support has been accomplished via a pyrolysis process. The ultra-low loading Ru nanoparticles (ca. 0.1 wt.%) was incorporated into the support by impregnation and the sequential reduction. The images of HAADF-STEM revealed that the Ru particles with sub-1-nm size (0.2-0.7 nm) were uniformly dispersed on the support. The ultrafine Ru particles displayed the excellent activity for the hydrogenation of olefins, arenes, phenol derivatives and heteroarenes in aqueous phase. The aliphatic or alicyclic compounds were produced selectively without the hydrogenolysis of C–O and C–N bonds. The high turnover frequency (TOF) values can reach up to 10,000 h?1. Notably, the activity of these catalysts improved dramatically with decreasing the sizes of Ru particles. Meanwhile, the N-doped carbon layer coating endowed the high stability of the Ru catalysts and prevented the leaching of the Ru species owning to the strong interaction between doped-N atoms and the ultrafine Ru particles. Overall, this work provides a highly attractive strategy to construct the supported sub-1-nm Ru particles utilized for the aqueous hydrogenation.
- Qian, Wei,Lin, Lina,Qiao, Yunxiang,Zhao,Xu, Zichen,Gong, Honghui,Li,Chen,Huang, Rong,Hou, Zhenshan
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-
- Polyoxometalates Comprising Noble Metals and Corresponding Metal Clusters
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The invention relates to poly oxometalates represented by the formula (An)m+{M′s[M″M15X10OyRzHq]}m? or solvates thereof, corresponding supported poly-oxometalates, and processes for their preparation, as well as corresponding metal-clusters, optionally in the form of a dispersion in a liquid carrier medium or immobilized on a solid support, and processes for their preparation, as well as their use in reductive conversion of organic substrate.
- -
-
Paragraph 0288-0292
(2019/02/13)
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- Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation
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Titania (TiO2) is widely used in the chemical industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying molecular mechanism is not understood due to the presence of multiple catalytic species on the TiO2 surface. This challenge can be addressed with metal-organic frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti8(μ2-O)8(μ2-OH)4 node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO2 support to enable CoII-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported CoII-hydride is strongly dependent on the reduction of the Ti-oxo cluster, definitively proving the pivotal role of TiIII in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understating the strong metal-support interaction of TiO2-supported heterogeneous catalysts.
- Ji, Pengfei,Song, Yang,Drake, Tasha,Veroneau, Samuel S.,Lin, Zekai,Pan, Xiandao,Lin, Wenbin
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p. 433 - 440
(2018/01/17)
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- Effect of the Crystallographic Phase of Ruthenium Nanosponges on Arene and Substituted-Arene Hydrogenation Activity
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Identifying crystal structure sensitivity of a catalyst for a particular reaction is an important issue in heterogeneous catalysis. In this context, the activity of different phases of ruthenium catalysts for benzene hydrogenation has not yet been investigated. The synthesis of hcp and fcc phases of ruthenium nanosponges by chemical reduction method has been described. Reduction of ruthenium chloride using ammonia borane (AB) and tert-butylamine borane (TBAB) as reducing agents gave ruthenium nanosponge in its hcp phase. On the other hand, reduction using sodium borohydride (SB) afforded ruthenium nanosponge in its fcc phase. The as prepared hcp ruthenium nanosponge was found to be catalytically more active compared to the as prepared fcc ruthenium nanosponge for hydrogenation of benzene. The hcp ruthenium nanosponge was found to be thermally stable and recyclable over several cycles. This self-supported hcp ruthenium nanosponge shows excellent catalytic activity towards hydrogenation of various substituted benzenes. Moreover, the ruthenium nanosponge catalyst was found to bring about selective hydrogenation of aromatic cores of phenols and aryl ethers to the respective alicyclic products without hydrogenolysis of the C?O bond.
- Ghosh, Sourav,Jagirdar, Balaji R.
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p. 3086 - 3095
(2018/05/29)
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- A stable and practical nickel catalyst for the hydrogenolysis of C-O bonds
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The selective hydrogenolysis of C-O bonds constitutes a key step for the valorization of biomass including lignin fragments. Moreover, this defunctionalization process offers the possibility of producing interesting organic building blocks in a straightforward manner from oxygenated compounds. Herein, we demonstrate the reductive hydrogenolysis of a wide variety of ethers including diaryl, aryl-alkyl and aryl-benzyl derivatives catalyzed by a stable heterogeneous NiAlOx catalyst in the presence of a Lewis acid (LA). The special feature of this catalyst system is the formation of substituted cyclohexanols from the corresponding aryl ether.
- Cui, Xinjiang,Yuan, Hangkong,Junge, Kathrin,Topf, Christoph,Beller, Matthias,Shi, Feng
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p. 305 - 310
(2017/01/24)
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- Nanoscale Ziegler catalysts based on bis(acetylacetonate)nickel in the arene hydrogenation reactions
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The turnover frequencies of catalytic systems based on Ni(acac)2–AlEt3 or AlEt2(OEt) in the hydrogenation of benzene and its methyl-substituted homologs (toluene, three isomers of xylene, and 1,3,5-trimethylbenzene) have been determined at temperatures of 80–120 °C, initial PH2 = 15 bar, and different ratios of Al/Ni. The size and nature of the nanoparticles forming in the systems based on Ni(acac)2–AlEt3 or AlEt2(OEt) under the benzene hydrogenation condition shave been resolved by high-resolution electron microscopy and X-ray microanalysis. This study included the performance of competitive hydrogenation reactions of benzene with toluene or three xylene isomers. The relative adsorption constants of toluene and three xylene isomers have been determined and the stereochemistry of the hydrogen addition to the arene ring has also been elucidated.
- Titova, Yuliya Yu.,Schmidt, Fedor K.
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p. 105 - 114
(2017/09/05)
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- Upgrading of aromatic compounds in bio-oil over ultrathin graphene encapsulated Ru nanoparticles
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Fast pyrolysis of biomass for bio-oil production is a direct route to renewable liquid fuels, but raw bio-oil must be upgraded in order to remove easily polymerized compounds (such as phenols and furfurals). Herein, a synthesis strategy for graphene encapsulated Ru nanoparticles (NPs) on carbon sheets (denoted as Ru@G-CS) and their excellent performance for the upgrading of raw bio-oil were reported. Ru@G-CS composites were prepared via the direct pyrolysis of mixed glucose, melamine and RuCl3 at varied temperatures (500-800 °C). Characterization indicated that very fine Ru NPs (2.5 ± 1.0 nm) that were encapsulated within 1-2 layered N-doped graphene were fabricated on N-doped carbon sheets (CS) in Ru@G-CS-700 (pyrolysis at 700 °C). And the Ru@G-CS-700 composite was highly active and stable for hydrogenation of unstable components in bio-oil (31 samples including phenols, furfurals and aromatics) even in aqueous media under mild conditions. This work provides a new protocol to the utilization of biomass, especially for the upgrading of bio-oil.
- Shi, Juanjuan,Zhao, Mengsi,Wang, Yingyu,Fu, Jie,Lu, Xiuyang,Hou, Zhaoyin
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supporting information
p. 5842 - 5848
(2016/05/24)
-
- Aromatic ring hydrogenation catalysed by nanoporous montmorillonite supported Ir(0)-nanoparticle composites under solvent free conditions
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Ir(0)-nanoparticles (Ir-NPs) were synthesized into the nanopores of modified montmorillonite clay by incipient wetness impregnation of IrCl3 followed by reduction with ethylene glycol. The activation of the montmorillonite clay was carried out by treatment with HCl under controlled conditions to increase the surface area by generating nanopores which act as host for the metal nanoparticles. The synthesized Ir-NP-montmorillonite composites were characterized by N2-sorption, powder XRD, SEM, EDS, TEM, XPS, etc. The composites exhibit high surface area of 327 m2 g-1 and the Ir-NPs with size around 4 nm are uniformly distributed on the support. The Ir-NPs show efficient catalytic activity in aromatic ring hydrogenation under solvent free conditions with maximum conversion up to 100% and Turn Over Frequency (TOF) up to 79 h-1. The catalyst can be easily separated by simple filtration and remained active for several runs without significant loss of catalytic efficiency.
- Das, Prabin,Sarmah, Podma Pollov,Borah, Bibek Jyoti,Saikia, Lakshi,Dutta, Dipak Kumar
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p. 2850 - 2855
(2016/03/22)
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- Enhancing the catalytic activity of Ru NPs deposited with carbon species in yolk-shell nanostructures
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The synthesis of metal NPs with a well-defined size, shape and composition provides opportunities for tuning the catalytic performance of metal NPs. However, the presence of a stabilizer on the metal surface always blocks the active sites of metal NPs. Herein, we report an efficient method to remove the stabilizer on the metal surface via H2 pyrolysis with Ru-poly(amindoamine) encapsulated in silica-based yolk-shell nanostructures as an example. The CO uptake amount of Ru NPs increases sharply after H2 pyrolysis, indicating that the exposure degree of Ru NPs is increased. No aggregation of the colloidal Ru NPs occurs after H2 pyrolysis, which could be mainly assigned to the protection effect of C and N species formed on Ru NPs. The overall activity of Ru NPs in the yolk-shell nanostructure after the pyrolysis could reach as high as 20 300 mmol per mmol Ru per h in the hydrogenation of toluene, which is much higher than that of most reported Ru-based solid catalysts. It was found that the yolk-shell nanostructure could efficiently prevent the leaching of Ru NPs during the catalytic process. Ru NPs in the yolk-shell nanostructure could also catalyze the hydrogenation of benzoic acid and Levulinic acid with high activity and selectivity.
- Guo, Miao,Lan, Guojun,Peng, Juan,Li, Mingrun,Yang, Qihua,Li, Can
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p. 10956 - 10963
(2016/07/21)
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- Preparation of silicalite-1@Pt/alumina core-shell catalyst for shape-selective hydrogenation of xylene isomers
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A silicalite-1@Pt/alumina core-shell catalyst that combined molecular sieving and hydrogenation was synthesized by coating silicalite-1 onto the surface of Pt/alumina pellet. While a Pt/alumina catalyst had no selectivity in the hydrogenation of xylene isomers, the silicalite-1@Pt/alumina core-shell catalyst showed much higher efficiency for the hydrogenation of p-xylene than for that of m- and o-xylene. The shape-selective hydrogenation catalyst has great potential for application in xylene separation.
- Wu, Yilan,Chai, Yongming,Li, Jiangchuan,Guo, Hailing,Wen, Ling,Liu, Chenguang
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p. 110 - 113
(2015/03/04)
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- Catalytic hydrogenation of aromatic rings catalyzed by Pd/NiO
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A simple and efficient heterogeneous palladium catalyst was prepared for aromatic ring hydrogenation. The catalyst was prepared by a reduction-deposition method and exhibited high activity and selectivity for the hydrogenation of a variety of substituted aromatic compounds to the corresponding cyclohexane and cyclohexanol derivatives with up to 99% yields. The catalyst was characterized by BET, TEM, XRD, XPS and ICP. Meanwhile the reusability of the catalyst was investigated, and it can be reused for several runs without significant deactivation.
- Wang, Yanan,Cui, Xinjiang,Deng, Youquan,Shi, Feng
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p. 2729 - 2732
(2014/01/06)
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- Rhodium nanoparticles stabilized with phosphine functionalized imidazolium ionic liquids as recyclable arene hydrogenation catalysts
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Rhodium nanoparticles (Rh NPs) stabilized by phosphine functionalized ionic liquids (FILs) were prepared in [BDMI]NTf2 (BDMI = 1-butyl-2,3-dimethylimidazolium, NTf2 = bis(trifluoromethanesulfonyl) imide) using H2(g) (4 bar) as a reducer. Rh(allyl)3 was used as a "salt-free" Rh NP precursor and allowed to enhance the stability of the Rh NPs compared to the usual RhCl3 precursor. The synthesized FIL stabilized Rh NPs proved to be active biphasic catalysts for the hydrogenation of toluene, styrene and xylenes under mild conditions (75°C, 40 bar H2(g), 3 h). The impact on activity of the length of the spacer between the phosphine function and the ionic liquid moiety in the FIL was studied. The Rh NPs stabilized by FILs showed higher catalytic activity and recyclability than NPs synthesized in the absence of a stabilizer and more stable than the system employing triphenylphosphine (PPh3) as a stabilizer. The size of the stabilized Rh NPs was measured to be around 2 nm by TEM, while those produced in the absence of a FIL stabilizer formed only aggregates.
- Stratton, Samantha A.,Luska, Kylie L.,Moores, Audrey
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experimental part
p. 96 - 100
(2012/06/18)
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- Catalytic dehydroaromatization of n-alkanes by pincer-ligated iridium complexes
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Aromatic hydrocarbons are among the most important building blocks in the chemical industry. Benzene, toluene and xylenes are obtained from the high temperature thermolysis of alkanes. Higher alkylaromatics are generally derived from arene-olefin coupling, which gives branched products-that is, secondary alkyl arenes-with olefins higher than ethylene. The dehydrogenation of acyclic alkanes to give alkylaromatics can be achieved using heterogeneous catalysts at high temperatures, but with low yields and low selectivity. We present here the first catalytic conversion of n-alkanes to alkylaromatics using homogeneous or molecular catalysts-specifically 'pincerg'-ligated iridium complexes-and olefinic hydrogen acceptors. For example, the reaction of n-octane affords up to 86% yield of aromatic product, primarily o-xylene and secondarily ethylbenzene. In the case of n-decane and n-dodecane, the resulting alkylarenes are exclusively unbranched (that is, n-alkyl-substituted), with selectivity for the corresponding o-(n-alkyl)toluene.
- Ahuja, Ritu,Punji, Benudhar,Findlater, Michael,Supplee, Carolyn,Schinski, William,Brookhart, Maurice,Goldman, Alan S.
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experimental part
p. 167 - 171
(2012/03/27)
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- Hydrogenation of arenes and N-heteroaromatic compounds over ruthenium nanoparticles on poly(4-vinylpyridine): A versatile catalyst operating by a substrate-dependent dual site mechanism
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A nanostructured catalyst composed of Ru nanoparticles immobilized on poly(4-vinylpyridine) (PVPy) has been synthesized by NaBH4 reduction of RuCl3·3H2O in the presence of the polymer in methanol at room temperature. TEM measurements show well-dispersed Ru nanoparticles with an average diameter of 3.1 nm. Both powder XRD patterns and XPS data indicate that the Ru particles are predominantly in the zerovalent state. The new catalyst is efficient for the hydrogenation of a wide variety of aromatic hydrocarbons and N-heteroaromatic compounds representative of components of petroleum-derived fuels. The experimental data indicate the existence of two distinct active sites in the nanostructure that lead to two parallel hydrogenation pathways, one for simple aromatics involving conventional homolytic hydrogen splitting on Ru and a second one for N-heteroaromatics taking place via a novel heterolytic hydrogen activation on the catalyst surface, assisted by the basic pyridine groups of the support.
- Fang, Minfeng,MacHalaba, Nataliya,Sanchez-Delgado, Roberto A.
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experimental part
p. 10621 - 10632
(2011/11/29)
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- Enhanced rate of arene hydrogenation with imidazolium functionalized bipyridine stabilized rhodium nanoparticle catalysts
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The imidazolium functionalized bipyridine compounds, {4,4'-bis-[7-(2,3- dimethylimidazolium)heptyl]-2,2'-bipyridine}2+ ([BIHB]2+) and {4,4'-bis[(1,2-dimethylimidazolium)methyl]-2,2'-bipyridine}2+ ([BIMB]2+), were prepared and used as Rh nanoparticle stabilizers. The dispersed Rh nanoparticles were used as catalysts in the biphasic hydrogenation of various arene substrates. The catalytic activity was strongly influenced by the stabilizer employed and followed the trend [BIHB] > bipy > [BIMB]2+. The steric and electronic characteristics of the imidazolium functionalized bipyridine ligands were assessed via the synthesis of rhenium carbonyl complexes, which facilitated the rationalization of the catalytic properties of the nanoparticles.
- Dykeman, Ryan R.,Yan, Ning,Scopelliti, Rosario,Dyson, Paul J.
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scheme or table
p. 717 - 719
(2011/04/23)
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- Ruthenium(0) nanoclusters supported on hydroxyapatite: Highly active, reusable and green catalyst in the hydrogenation of aromatics under mild conditions with an unprecedented catalytic lifetime
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The preparation of ruthenium(0) nanoclusters supported on hydroxyapatite and their characterization by a combination of complementary techniques are described. The resultant ruthenium(0) nanoclusters provide high activity and reusability in the complete hydrogenation of aromatics under mild conditions (at 25 °C and with 42 psi initial H2 pressure).
- Zahmakiran, Mehmet,Tonbul, Yalcin,Oezkar, Saim
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supporting information; experimental part
p. 4788 - 4790
(2010/09/10)
-
- Avoiding olefin isomerization during decyanation of alkylcyano α,ω-dienes: A deuterium labeling and structural study of mechanism
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(Chemical Equation Presented) A two-step synthetic pathway involving decyanation chemistry for the synthesis of pure alkyl α,ω-dienes in quantitative yields is presented. Prior methodologies for the preparation of such compounds required 6-9 steps, sometimes leading to product mixtures resulting from olefin isomerization chemistry. This isomerization chemistry has been eliminated. Deuteration labeling and structural mechanistic investigations were completed to decipher this chemistry. Deuterium labeling experiments reveal the precise nature of this radical decyanation chemistry, where an alcohol plays the role of hydrogen donor. The correct molecular design to avoid competing intramolecular cyclization, and the necessary reaction conditions to avoid olefin isomerization during the decyanation process are reported herein.
- Rojas, Giovanni,Wagener, Kenneth B.
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p. 4962 - 4970
(2008/12/20)
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- Rhodium and iridium nanoparticles entrapped in aluminum oxyhydroxide nanofibers: Catalysts for hydrogenations of arenes and ketones at room temperature with hydrogen balloon
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The recyclable metal nanoparticle catalysts, rhodium in aluminum oxyhydroxide [Rh/ AlO(OH)] and iridium in aluminum oxyhydroxide [Ir/A1O(OH)], were simply prepared from readily available reagents. The catalysts showed high activities in the hydrogenation of various arenes and ketones under mild conditions. Selective hydrogenation was possible for bicyclic and tricyclic arenes in high yields. The catalysts were active at room temperature even with a hydrogen balloon. Also, the catalysts showed high turnover frequency (TOF) values under solventless conditions at 75 °C under 4 atm hydrogen pressure: ca. 1700h 1 in the hydrogenation of benzene. Furthermore, Rh/A1O(OH) can be reused forat least 10 times without activity loss. The catalysts were characterized by the transmission electron microscopy (TEM), powder X-ray diffraction (XRD), inductively coupled plasma (ICP), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption and hydrogen chemisorption experiments. The sizes of rhodium and iridium particles were estimated to be 3-4 nm and 2-3 nm, respectively. Aluminum oxyhydroxide nanofibers of these catalysts have surface areas of 500-600 m2 g -1.
- Park, In Soo,Kwon, Min Serk,Kang, Kyung Yeon,Lee, Jae Sung,Park, Jaiwook
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p. 2039 - 2047
(2008/09/17)
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- Nanoheterogeneous catalytic hydrogenation of arenes: Evaluation of the surfactant-stabilized aqueous ruthenium(O) colloidal suspension
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The hydrogenation of various aromatic compounds by a surfactant-stabilized aqueous ruthenium(O) colloidal suspension was investigated. The nanocatalysts in the size range of 2.5-3.5 nm were synthesized by reducing ruthenium trichloride salt with sodium borohydride and were stabilized by the highly water soluble N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride salt according to our classical approach. The efficient catalytic reactions were performed at room temperature and under hydrogen pressure. The effect of the stirring, namely magnetic stir bar or gas projection impeller, was also studied. A comparison with an analogous rhodium nanocatalyst is described.
- Nowicki, Audrey,Boulaire, Virginie Le,Roucoux, Alain
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p. 2326 - 2330
(2008/09/18)
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- Ionic-liquid-like copolymer stabilized nanocatalysts in ionic liquids: II. Rhodium-catalyzed hydrogenation of arenes
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Rhodium nanoparticles stabilized by the ionic-liquid-like copolymer poly[(N-vinyl-2-pyrrolidone)-co-(1-vinyl-3-butylimidazolium chloride)] were used to catalyze the hydrogenation of benzene and other arenes in ILs. The nanoparticle catalysts can endure forcing conditions (75 °C, 40 bar H2), resulting in high reaction rates and high conversions compared with other nanoparticles that operate in ILs. The hydrogenation of benzene attained record total turnovers of 20,000, and the products were easily separated without being contaminated by the catalysts. Other substrates, including alkyl-substituted arenes, phenol, 4-n-propylphenol, 4-methoxylphenol, and phenyl-methanol, were studied and in most cases were found to afford partially hydrogenated products in addition to cyclohexanes. In-depth investigations on reaction optimization, including characterization of copolymers, transmission electron microscopy, and an infrared spectroscopic study of nanocatalysts, were also undertaken.
- Zhao, Chen,Wang, Han-zhi,Yan, Ning,Xiao, Chao-xian,Mu, Xin-dong,Dyson, Paul J.,Kou, Yuan
-
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- A simple and reproducible method for the synthesis of silica-supported rhodium nanoparticles and their investigation in the hydrogenation of aromatic compounds
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Colloidal suspensions of rhodium nanoparticles have been easily prepared in aqueous solution by chemical reduction of the precursor RhCl 3·3H2O in the presence of the surfactant N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride (HEA16Cl) and further used to immobilize rhodium nanoparticles on silica by simple impregnation. The obtained silica-supported rhodium nanoparticles have been investigated by adapted characterization methods such as transmission electron microscopy and X-ray photoelectron spectroscopy. A particle size increase from 2.4 to 5 nm after the silica immobilization step and total elimination of the surfactant has been observed. This "heterogeneous" catalyst displayed good activities for the hydrogenation of mono-, di- alkylsubstituted and/or functionalized aromatic derivatives in water under atmospheric hydrogen pressure and at room temperature. In all cases, the catalyst could be recovered several times after a simple decantation or filtration and reused without any significant loss in catalytic activity. This supported catalyst has also been tested under higher hydrogen pressure giving rise to TOFs reaching 6430 h -1 at 30 bar and in terms of catalytic lifetime 30 000 TTO in 8.5 h for pure anisole hydrogenation at 40 bar. the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
- Mevellec, Vincent,Nowicki, Audrey,Roucoux, Alain,Dujardin, Christophe,Granger, Pascal,Payen, Edmond,Philippot, Karine
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p. 1214 - 1219
(2007/10/03)
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- METHOD FOR THE PRODUCTION OF NON-AROMATIC HYDROCARBONS
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The invention relates to a method for the production of long-chain, branched-chain and/or cyclic hydrocarbons. A low molecular weight alkyl halide and a fused salt are firstly prepared. The fused salt contains an electrophilic compound and a reducing agent and is free from oxygen and oxygen compounds. The alkyl halide is then brought into contact with the fused salt such that long-chain, branched-chain and/or cyclic hydrocarbons are formed in the fused salt. The hydrocarbons formed in the fused salt are drawn off and can subsequently be separated from unreacted starting materials. By means of the above method, hydrogen can be produced during the reaction of the low molecular weight alkyl halide. The risk of oxidation of the alkane produced to give carbon monoxide or carbon dioxide is avoided by means of the reducing conditions in the fused salt. The product distribution can be controlled by means of suitable selection of the composition of the fused salt. Highly-branched hydrocarbons are produced with the preferred application of a sodium chloroaluminate fused salt.
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-
- Supramolecular cluster catalysis: Facts and problems
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By checking the chemistry underlying the concept of "supramolecular cluster catalysis" we identified two major errors in our publications related to this topic, which are essentially due to contamination problems. (1) The conversion of the "closed" cluster cation [H3Ru3(C6H6) (C6Me6)2(O)]+ (1) into the "open" cluster cation [H2Ru3 (C6H6)(C6Me6)2 (O)(OH)]+ (2), which we had ascribed to a reaction with water in the presence of ethylbenzene is simply an oxidation reaction which occurs in the presence of air. (2) The higher catalytic activity observed with ethylbenzene, which we had erroneously attributed to the "open" cluster cation [H2Ru3 (C6H6)(C6Me6)2 (O)(OH)]+ (2), was due to the formation of RuO2·nH2O, caused by a hydroperoxide contamination present in ethylbenzene.
- Süss-Fink, Georg,Therrien, Bruno,Vieille-Petit, Ludovic,Tschan, Mathieu,Romakh, Vladimir B.,Ward, Thomas R.,Dadras, Massoud,Laurenczy, Gabor
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p. 1362 - 1369
(2007/10/03)
-
- Cyclization of methyl-substituted 6-heptenyl radicals
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(Matrix presented) The behavior of a series of methyl-substituted 6-heptenyl radicals, generated from the corresponding iodides ((Me3Si)3SiH, AIBN in benzene at 80°C), has been investigated. The stereoselectivity of the 6-exo cyclizations, affording dimethylcyclohexanes, is low, and sizable quantities of methylcycloheptane, generated via 7-endo cyclization, are also produced.
- Bailey, William F.,Longstaff, Sarah C.
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p. 2217 - 2219
(2007/10/03)
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- Rhodium complexes HRh[P(NC4H4)3]4 and HRh(CO)[P(NC4H4)3]3 as active catalysts of olefins and arenes hydrogenation : X-ray structure of HRh(CO)[P(NC4H4)3]3
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The rhodium hydrido complexes HRh[PPhx(NC4H4)3-x]4 (x=0-2) and HRh(CO)[PPhx(NC4H4)3-x]3 have been obtained in reactions of Rh(acac)(CO)2+PPhx(NC4H4) 3-x with H2 or H2/CO (0.1 MPa, room temperature) respectively. The crystal structure of HRh(CO)[P(NC4H4)3]3 has been determined. The complex is slightly distorted trigonal bipyramidal with H and CO ligands occupying the axial positions. The Rh atom is located 0.336 A out of plane of the three equatorial P atoms. The Rh-H distance in two crystallographically independent molecules is 1.51(5) and 1.69(6) A respectively. The complexes HRh[P(NC4H4)3]4 and HRh(CO)[P(NC4H4)3]3 are active catalysts of hydrogenation reaction of olefins and arenes (cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, propenylbenzene, styrene, toluene) at 353 K and 0.5 MPa H2. The TOF up to 836 mol/mol Rh per h have been obtained.
- Trzeciak, Anna M.,Glowiak, Tadeusz,Ziolkowski, Jozef J.
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p. 159 - 164
(2007/10/03)
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- EFFECTIVE GAS-PHASE DEOXYGENATION OF ALCOHOLS AND KETONES ON IRON CATALYST
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A method of gas-phase deoxygenation of alcohols and ketones into hydrocarbons on iron catalyst at 600 K and 1-2E5 Pa is dicussed.
- Glebov, L. S.,Mikaya, A. I.,Yatsenko, A. E.,Zaikin, V. G.,Kliger, G. A.,Loktev, S. M.
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p. 3373 - 3376
(2007/10/02)
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- Biphasic hydrogenation of olefins, dienes, and α,β-unsaturated carbonyl compounds catalyzed by the dimer of chloro(1,5-hexadiene)rhodium
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Olefins, dienes, and trienes can be hydrogenated in an aqueous-organic two-phase medium using the dimer of chloro(1,5-hexadiene)rhodium as the catalyst.Selective reduction of the double bond of α,β-unsaturated carbonyls occurs in high yields.These reactions occur at room temperatures and atmospheric pressure, and are simple to work up.
- Januszkiewicz, Krzysztof R.,Alper, Howard
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p. 1031 - 1033
(2007/10/02)
-
- Ionization Energies and Entropies of Cycloalkanes. Kinetics of Free Energy Controlled Charge-Transfer Reactions.
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Enthalpies and entropies of ionization (ΔH0ion and ΔS0ion) of alkylcyclohexanes, as well as cycloheptane, cyclooctane, and trans-Decalin, have been determined by charge-transfer equilibrium measurements.Values of ΔHion, in units of kcal mol-1 (or eV), range from 229.6 (9.96) for cycloheptane to 210.7 (9.14) for trans-Decalin.A major effect of alkyl substitution is observed following substitution at a site α to a tertiary hydrogen atom (as from methylcyclohexane to 1,2-dimethylcyclohexane), or following replacement of a tertiary hydrogen atom (as from methylcyclohexane to 1,1-dimethylcyclohexane).In both cases, ΔH0 ion decreases by ca. 5 kcal mol-1.Entropies of ionization are near zero for alkylcyclohexanes but range up to 5 cal deg-1 mol-1 for nonsubstituted cycloalkanes (cyclooctane).The charge-transfer reactions involving the cycloalkanes are shown to be fast processes; i.e., the sum of the reaction efficiencies (r=k/kcollision) of the forward and reverse processes is near unity.The efficiencies of these processes appear to be determined uniquely by the overall free energy change (or equilibrium constant K).Specifically, the reaction efficiencies are defined, within a factor of 2 by the relation r=K/(1+K), which can be justified by using transition-state theory applied to the decomposition of a collision complex over surfaces lacking energy barriers.These reactions are defined as intrinsically fast processes in that they are slowed only by the overall reaction thermochemistry and not by any properties or reactions of the intermediate complex.
- Sieck, L. Wayne,Mautner, Michael
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p. 3646 - 3650
(2007/10/02)
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- VERSATILE POLYMER-BOUND RHODIUM CATALYSTS. FACILE HYDROGENATION OF AROMATIC COMPOUNDS IN THE LIQUID PHASE
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Immobilized complexes prepared from 2 (nbd=norbornadiene) and phosphinated polydiacetylene or silica are efficient catalysts for the hydrogenation of arenes under mild conditions.However, the homologous catalyst supported on a phosphinated polystyrene is not active.
- Okano, Tamon,Tsukiyama, Katsunori,Konishi, Hisatoshi,Kiji, Jitsuo
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p. 603 - 606
(2007/10/02)
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- Catalytic Hydrogenation of Aromatic Hydrocarbons. Stereochemical Definition of the Catalytic Cycle for η3-C3H5Co(P(OCH3)3)3
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The η3-C3H5Co(P(OCH3)3)3-catalyzed hydrogenations with D2of a series of unsaturated organic molecules, including cyclohexenes, cyclohexadienes, and arenes, have been investigated.Complete cis stereoselectivity was observed in the addition of deuterium to the unsaturated ring systems.When alkyl-substituted arenes were reduced with D2, the hydrogen atoms in the alkyl chains underwent H-D exchange as long as each successive carbon atom in the chain possessed at least one hydrogen atom.Hence, extensive H-D exchange occured in n-alkyl side chains while the tert-butyl side chain was deuterium free.When alkyl-substituted arenes were hydrogenated in the presence of olefins such as 1-hexene, a variety of isomeric alkylcyclohexenes and alkenylcyclohexanes were observed.The relative concentrations of these isomeric species provided information about the relative stabilities of the (olefin)cobalt species in the catalytic cycle.Further mechanistic information was obtained from other competitive reactions, i.e., hydrogenation reactions involving equimolar quantities of two different unsaturated molecules.The proposed initiation steps of the catalytic cycle have been revised on the basis of a study of η3-C8H13Co(P(OCH3)3)3 as a catalyst precursor.The cyclooctenyl-cobalt bond was cleaved by hydrogen early in the reaction, leaving the highly coordinately unsaturated hydride, HCo(P(OCH3)3)2, which is probably the true catalytic species.
- Bleeke, J. R.,Muetterties, E. L.
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p. 556 - 564
(2007/10/02)
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