- Synthesis of 6-Adamantyl-2-pyridone and Reversible Hydrogen Activation by the Corresponding Bis(perfluorophenyl)borane Complex
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We herein describe the two-step synthesis of 6-Adamantyl-2-pyridone from 1-Acetyladamantane. The borane complex derived from 6-Adamantyl-2-pyridone and the Piers borane liberates dihydrogen at 60 °C. The reverse reaction, hydrogen activation by the formed pyridonate borane is accomplished under mild conditions. The mechanism of the hydrogen activation is studied by DFT computations.
- Wech, Felix,Müller, Tizian,Becker, Jonathan,Gellrich, Urs
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Read Online
- Nickel Hydride Complexes Supported by a Pyrrole-Derived Phosphine Ligand
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The synthesis of two nickel hydride complexes bearing the pyrrole-derived phosphine ligand CyPNH (2-(dicyclohexylphosphino)methyl-1H-pyrrole) was developed, namely, (κP-CyPNH)(κP,κN-CyPN)NiH and the acid-stable trans-(κP-CyPNH)2Ni(OAc)H·HOAc. (κP-CyPNH)(κP,κN-CyPN)NiH stoichiometrically reduces benzaldehyde and acetophenone in a metal-ligand cooperative manner and catalytically dimerizes ethylene and cycloisomerizes 1,5-cyclooctadiene and 1,5-hexadiene. trans-(κP-CyPNH)2Ni(OAc)H·HOAc, available from the protonation of (κP-CyPNH)(κP,κN-CyPN)NiH with acetic acid, catalyzes the cycloisomerization of 1,5-cyclooctadiene more effectively and produces the less thermodynamically favored cycloisomers of 1,5-cyclooctadiene.
- Collett, Joel D.,Guan, Hairong,Krause, Jeanette A.
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p. 345 - 353
(2022/02/16)
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- Merging Halogen-Atom Transfer (XAT) and Cobalt Catalysis to Override E2-Selectivity in the Elimination of Alkyl Halides: A Mild Route towardcontra-Thermodynamic Olefins
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We report here a mechanistically distinct tactic to carry E2-type eliminations on alkyl halides. This strategy exploits the interplay of α-aminoalkyl radical-mediated halogen-atom transfer (XAT) with desaturative cobalt catalysis. The methodology is high-yielding, tolerates many functionalities, and was used to access industrially relevant materials. In contrast to thermal E2 eliminations where unsymmetrical substrates give regioisomeric mixtures, this approach enables, by fine-tuning of the electronic and steric properties of the cobalt catalyst, to obtain high olefin positional selectivity. This unprecedented mechanistic feature has allowed access tocontra-thermodynamic olefins, elusive by E2 eliminations.
- Zhao, Huaibo,McMillan, Alastair J.,Constantin, Timothée,Mykura, Rory C.,Juliá, Fabio,Leonori, Daniele
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supporting information
p. 14806 - 14813
(2021/09/18)
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- METHOD OF PRODUCING TERMINAL DOUBLE BOND-CONTAINING COMPOUND
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SOLUTION: A method of producing a terminal double bond-containing compound includes: reacting a compound represented by the following general formula (I) under a pressure of 0 MPa-G or lower in the presence of a metal oxide catalyst to produce a terminal double bond-containing compound represented by the following general formula (II). In formula (I) and formula (II), R1 and R2 represent hydrocarbon groups, and R1 and R2 may bond each other to form a ring together with carbon atoms by which R1 and R2 bond. EFFECT: According to the present invention, a terminal double bond-containing compound can be safely and easily produced with high selectivity. SELECTED DRAWING: None COPYRIGHT: (C)2020,JPOandINPIT
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Paragraph 0044-0048
(2020/10/09)
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- Olefin oligomerization via new and efficient Br?nsted acidic ionic liquid catalyst systems
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Olefin oligomerization reaction catalyzed by new catalyst systems (a Br?nsted-acidic ionic liquid as the main catalyst and tricaprylylmethylammonium chloride as the co-catalyst) has been investigated. The synthesized Br?nsted acidic ionic liquids were characterized by Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV), 1H nuclear magnetic resonance (NMR), and 13C NMR to analyze their structures and acidities. The influence of different ionic liquids, ionic liquid loading, different co-catalysts, catalyst ratios (mole ratio of ionic liquid to co-catalyst), reaction time, pressure, temperature, solvent, source of reactants, and the recycling of catalyst systems was studied. Among the synthesized ionic liquids, 1-(4-sulfonic acid)butyl-3-hexylimidazolium hydrogen sulfate ([HIMBs]HSO4) exhibited the best catalytic activity under the tested reaction conditions. The conversion of isobutene and selectivity of trimers were 83.21% and 35.80%, respectively, at the optimum reaction conditions. Furthermore, the catalyst system can be easily separated and reused; a feasible reaction mechanism is proposed on the basis of the distribution of experimental products.
- Wang, Guoqin,Song, Heyuan,Li, Ruiyun,Li, Zhen,Chen, Jing
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p. 1110 - 1120
(2018/05/28)
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- METHOD FOR PRODUCING 4-METHYL-1-PENTENE
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PROBLEM TO BE SOLVED: To provide a method for producing 4-methyl-1-pentene that can inhibit the by-production of olefins other than 4-methyl-1-pentene and is relatively safe. SOLUTION: A method for producing 4-methyl-1-pentene includes the step of dehydrating 4-methyl-1-pentanol in the presence of a solid acid catalyst. SELECTED DRAWING: None COPYRIGHT: (C)2018,JPOandINPIT
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Paragraph 0024
(2018/05/05)
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- Selective Dimerization of Propylene with Ni-MFU-4l
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We report the selective dimerization of propylene to branched hexenes using Ni-MFU-4l, a solid catalyst prepared by cation exchange. Analysis of the resulting product distribution demonstrates that the selectivity arises from 2,1-insertion and slow product reinsertion, mechanistic features reproduced by a molecular nickel tris-pyrazolylborate catalyst. Characterization of Ni-MFU-4l by X-ray absorption spectroscopy provides evidence for discrete, tris-pyrazolylborate-like coordination of nickel, underscoring the small-molecule analogy that can be made at metal-organic framework nodes.
- Comito, Robert J.,Metzger, Eric D.,Wu, Zhenwei,Zhang, Guanghui,Hendon, Christopher H.,Miller, Jeffrey T.,Dinc?, Mircea
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supporting information
p. 1681 - 1683
(2017/05/15)
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- Hydrogenation of ketones over bifunctional Pt-heteropoly acid catalyst in the gas phase
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Gas-phase hydrogenation of a wide range of ketones to alkanes, including hydrogenation of aliphatic ketones and acetophenone, was investigated using bifunctional metal-acid catalysis. The catalysts were comprised of a metal (Pt, Ru, Ni, and Cu) supported on acidic caesium salt of tungstophosphoric heteropoly acid Cs2.5H0.5PW12O40 (CsPW). The reaction occurred via a sequence of steps involving hydrogenation of ketone to alcohol on metal sites followed by dehydration of alcohol to alkene on acid sites and finally hydrogenation of alkene to alkane on metal sites. Catalyst activity decreased in the order: Pt > Ru >> Ni > Cu. Pt/CsPW showed the highest catalytic activity, giving almost 100% alkane yield at 100 °C and 1 bar pressure. Evidence is provided that the reaction with Pt/CsPW at 100 °C is limited by ketone-to-alcohol hydrogenation, whereas at lower temperatures (≤60 °C) by alcohol dehydration yielding alcohol as themain product. The catalyst comprised of a physical mixture of Pt/C + CsPW was found to be highly efficientas well, which indicates that the reaction is not limited by migration of intermediates between metal andacid sites in the bifunctional catalyst.
- Alharbi,Kozhevnikova,Kozhevnikov
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p. 457 - 462
(2015/10/05)
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- Ethylene-bridged C1-symmetric ansa-(3-R-indenyl)(fluorenyl) zirconocene complexes for propylene dimerization or polymerization: The effect of R group
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A series of ethylene-bridged C1-symmetric ansa-(3-R-indenyl) (fluorenyl) zirconocene complexes 3a-i (R = 2-[2-(4-methylphenyl)propyl], 3a; R = 2-[2-(3,5-dimethylphenyl)propyl], 3b; R = 2-(2-benzylpropyl), 3c; R = 2-methylbenzyl, 3d; R = 2-(2-cyclohexylpropyl), 3e; R = 2-[2-(1-cyclohexenyl) propyl], 3f; R = 2-(2-n-butylpropyl), 3g; R = cyclohexyl, 3h; R = iPr, 3i) were synthesized by a salt metathesis method and characterized by NMR spectroscopy, elemental analysis (or HRMS) and X-ray diffraction (3e and 3h). Upon activation with methylaluminoxane, most of these zirconocene complexes exhibited sufficient catalytic activities up to 2.5 × 105 g C6/(mol-Zr·h) and high selectivities up to 99% toward propylene dimerization, affording 2-methyl-1-pentene as the major isomer which was confirmed by gas chromatography. Remarkably, the selectivity and activity of complexes 3a-i were significantly influenced by the structural features of the substituent on the 3-position of indenyl ring: a pendant aryl or alkyl group linked by a quaternary carbon bridge provided the complex with high selectivities in the range of 89.9-99.0% for 2-methyl-1-pentene and low to moderate catalytic activities; the lack of a quaternary carbon bridge within the substituent would lead to mainly polypropylenes of low molecular weight. The steric hindrance around the active metal center induced by the pendant group might be responsible for the catalytic dimerization behavior, and the presumed mechanism was discussed. In addition, for complexes 3h and 3i, the selectivity for propylene dimerization could also be enhanced with the increase of reaction temperature. Noticeably, most of these ansa-zirconocene complexes exhibit excellent thermal stability at 100 °C, which is important with regard to industrial application. 2014 Elsevier Ltd. All rights reserved.
- Wang, Yan,Huang, Wenzhong,Ma, Haiyan,Huang, Jiling
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- SELECTIVE DEHYDRATION OF ALCOHOLS TO DIALKYLETHERS AND INTEGRATED ALCOHOL-TO-GASOLINE PROCESSES
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The invention involves an integrated process for converting a C1-C4 alcohol to gasoline and/or diesel boiling tinge product, said process comprising: contacting a C1-C4 alcohol feed under selectively dehydrating conditions with a catalyst comprising γ-alumina which is substantially free of terminal hydroxyl groups on tetrahedrally coordinated aluminum sites of the catalyst to form a dialkylether dehydration product; and contacting the dialkylether dehydration product with a zeolite conversion catalyst under conversion conditions to form the gasoline and/or diesel boiling range hydrocarbon product.
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Paragraph 0045
(2013/04/24)
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- Hydrogenation of methyl isobutyl ketone over bifunctional Pt-zeolite catalyst
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Methyl isobutyl ketone (MIBK) can be viewed as a key intermediate for the conversion of biomass-derived acetone - the by-product of biobutanol production - to transportation fuel. Zeolite H-ZSM-5 doped with Pt nanoparticles was found to be a highly efficient catalyst for gas-phase hydrogenation of MIBK to methylpentanes with >99% yield at 200 °C. The reaction proceeds via bifunctional metal-acid catalysed pathway involving MIBK hydrogenation to 4-methyl-2-pentanol (MP-ol) on metal sites followed by MP-ol dehydration on acid sites to form olefin and finally olefin hydrogenation to 2-methylpentane (2MP) on metal sites, with all three steps occurring on a single catalyst bed. 2MP thus obtained underwent isomerisation over bifunctional Pt/H-ZSM-5 catalyst to give a mixture of 2- and 3-methylpentanes in a ratio of 83:17. The catalyst did not show any deactivation for at least 16 h on stream.
- Alotaibi, Mshari A.,Kozhevnikova, Elena F.,Kozhevnikov, Ivan V.
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scheme or table
p. 141 - 144
(2012/10/07)
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- Method for Producing a Compound with a Double Bond
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A method is provided for highly selectively producing a compound with a double bond represented by formula (III), including the following steps: (A): reacting a compound represented by a ketone of formula (I) and/or a compound represented by an aralkyl alcohol of formula (II) with hydrogen in the presence of 0.1 parts by weight or more of a hydrogenation catalyst, thereby obtaining a reaction liquid,(B): removing the hydrogenation catalyst until the amount of the hydrogenation catalyst contained in the reaction liquid obtained in step (A) becomes 0.0010 parts by weight or less, thereby obtaining a hydrogenation catalyst-removed liquid,(C): obtaining a compound with a double bond represented by formula (III) in the presence of a dehydration catalyst from the hydrogenation catalyst-removed liquid obtained in step (B).
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Page/Page column 4
(2012/07/13)
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- ZrO2-SiO2 mixed oxides xerogel and aerogel as solid acid catalysts for solvent free isomerization of α-pinene and dehydration of 4-methyl-2-pentanol
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Sulfated and non-sulfated ZrO2-SiO2 mixed oxide xerogel and aerogel samples having varied Zr/Si molar ratio were evaluated as solid acid catalysts for the isomerization of α-pinene and dehydration of 4-methyl-2-pentanol. Sulfation resulted into enhancement in the catalytic activity of both xerogel and aerogel samples towards the studied reactions. For example, sulfated catalysts showed 86-98% conversion of α-pinene and 8-35% conversion of 4-methyl-2-pentanol. The selectivity data for camphene and limonene indicated the requirement of moderate acidity. The correlation with cyclohexanol dehydration showed that isomerization of α-pinene is a Bronsted acid catalyzed reaction. The relationship of 4-methyl-2-pentanol conversion with acid site density and sulfur per unit area was found to be linear.
- Sidhpuria, Kalpesh B.,Tyagi, Beena,Jasra, Raksh V.
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experimental part
p. 1164 - 1170
(2012/06/30)
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- Propylene dimerization in the presence of nickel hydride complexes formed in situ
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We study the influence of nickel hydride complexes formed in situ by reaction nickel(0) complexes having phosphorus-containing ligands with Broensted acids in the presence of various modifiers on a catalyst turnover and selectivity in propylene dimerization. The activating action of boron trifluoride etherate is considered. Pleiades Publishing, Ltd., 2010.
- Shmidt,Titova,Belykh,Gomboogiin
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scheme or table
p. 205 - 213
(2011/04/24)
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- AROMATIC HYDROGENATION CATALYST AND PROCESS
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An MCM-41 catalyst having a crystalline framework containing SiO2 and a Group IV metal oxide, such as TiO2 or ZrO2 is provided. The catalyst is low in acidity and is suitable for use in processes involving aromatic saturation of hydrocarbon feedstocks.
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Page/Page column 30; 31; 32; 33
(2009/08/14)
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- Hydrodesulfurization of 4,6-dimethyldibenzothiophene over noble metals supported on mesoporous zeolites
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(Figure Presented) Pores for thought: Noble-metal catalysts supported on mesoporous zeolites have been found to be much more efficient than on microporous zeolites and γ-Al2O3 for the hydrodesulfurization of 4,6-dimethyldibenzothioph
- Sun, Yinyong,Prins, Roel
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supporting information; experimental part
p. 8478 - 8481
(2009/04/12)
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- Fast propene dimerization using upper rim-diphosphinated calix[4]arenes as chelators
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The complexes [NiBr2·1] and [NiBr2· 2], containing the upper rim-diphosphinated calixarenes 5,17-bis(diphenylphosphino)-25,26,27,28-tetrapropoxycalix[4]arene (1) and 5,17-dibromo-11,23-bis(diphe-nylphosphino)-25,26,27,28-tetrapropoxycalix[4] arene (2) were assessed as propene dimerization catalysts. Combined with methylaluminoxane, both complexes result in highly efficient dimerization catalysts displaying C6 selectivities in the range 80-97% and activities that compare with the best reported systems, the latter using PCy3 as ligand. The origin of the remarkable activities of the calixarene derivatives may be the ability of the diphosphine to undergo a periodic bite angle increase that incidentally favors the insertion step. Calixarenes such as 1 or 2, which each incorporate two "stable" Ph2PAr moieties, constitute interesting alternatives to the use PCy3 in propene dimerization.
- Lejeune, Manuel,Semeril, David,Jeunesse, Catherine,Matt, Dominique,Lutz, Pierre,Toupet, Loic
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p. 881 - 886
(2007/10/03)
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- Method for producing of 2,3-dimethylbutene-1 and 2,3-dimethylbutene-2
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There is disclosed a method for producing 2,3-dimethylbutene-1 and 2,3-dimethylbutene-2, which is characterized by the steps of (a) dimerizing propylene in a propylene-dimerization step using a nickel complex catalyst as described below as a propylene-dimerization catalyst having propylene-dimerization activity and DMB-1 selectivity, (b) rectifying the resulting reaction solution to obtain 2,3-dimethylbutene-1 as a distillate and a distillation residue containing 2,3-dimethylbutene-1 in a 2,3-dimethylbutene-1 distillation step, (c) allowing the distillation residue to contact with sulfuric acid, sulfonic acid or hetetopolyacid to isomerize 2,3-dimethylbutene-1 in said distillation residue into 2,3-dimethylbutene-2 in an isomerization step, and (d) rectifying the resulting isomerization reaction solution to obtain 2,3-dimethylbutene-2 in a 2,3-dimethylbutene-2 distillation step, wherein said nickel complex catalyst containing (A) at least one nickel compound and the like, (B) a trialkylaluminum, (C) a trivalent phosphorus compound, (D) a fluorinated isopropanol or a halogenated phenol (E) at least one sulfur compound selected from a sulfonic acid and a dialkylsulfuric acid.
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Page column 5-6
(2008/06/13)
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- CeO2-La2O3 catalytic system part II. Acid-base properties and catalytic activity for 4-methylpentan-2-ol dehydration
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CeO2-La2O3 mixed oxides, formerly prepared via a sol-gel procedure and characterised by several techniques, have been further investigated as to their acid-base properties and catalytic activity. Surface acidity and basicity have been assessed by adsorption microcalorimetry, using ammonia and carbon dioxide as probe molecules. Catalytic activity for 4-methylpentan-2-ol dehydration has been tested at atmospheric pressure in a fixed-bed flow microreactor. The acid and base features of the catalysts markedly depend on the relative amounts of the two component oxides. For pure ceria, cerium and oxygen ions are the source for acidity and basicity, respectively. Some contribution of OH groups to the acid-base character is probable for the mixed oxides. Most of the acid sites of each catalyst are weak, whereas most of its base sites are strong. The concentration of the base sites tends to prevail over that of the acid sites as the lanthanum content increases. 4-Methylpent-1-ene is by far the most abundant product of 4-methylpentan-2-ol conversion for all the catalysts, which are quite stable, even after repeated operation cycles. Subtle differences in the relative extents of dehydration and dehydrogenation activity seem to be due to a shift in the reaction mechanism, originated by changes in the relative amounts of acid and base sites.
- Cutrufello,Ferino,Monaci,Rombi,Colon,Navio
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p. 2928 - 2934
(2007/10/03)
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- 4-Methylpentan-2-ol dehydration over zirconia catalysts prepared by sol- gel
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Zirconia samples have been prepared from xerogels and aerogels obtained using zirconium n-propoxide as precursor. Structure and texture have been investigated by X-ray diffraction, thermal analysis, transmission electron microscopy, nitrogen adsorption/desorption. Surface acidity and basicity have been assessed by adsorption microcalorimetry, using ammonia and carbon dioxide as probe molecules. 4-Methylpentan-2-ol dehydration has been tested at atmospheric pressure in a fixed-bed flow microreactor. The xerogel gives tetragonal zirconia upon calcination, during which a mesoporous system is formed. The crystal phase depends on the presence of oxygen during the cooling step in the case of the aerogel, whose texture is partially retained upon calcination. Both kinds of catalysts have well-balanced concentrations of acid and base sites, but the acid sites are weaker in comparison with the basic ones. At 603 K the initial conversion of 4-methylpentan-2-ol over the calcined xerogel and aerogel is 45 and 63%, respectively; the selectivity to 4-methylpent-1-ene is 77% for both. The occurrence of an E2-like mechanism with the activated complex having a marked carbanionic character seems probable. The aerogel catalyst is quite stable during operation, whereas changes in activity and selectivity are observed for the xerogel catalyst.
- Ferino,Casula,Corrias,Cutrufello,Monaci,Paschina
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p. 1847 - 1854
(2007/10/03)
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- Acid-base properties and catalytic activity of nanophase ceria-zirconia catalysts for 4-methylpentan-2-ol dehydration
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The room-temperature high energy ball-milling technique was used to prepare nanophase Ce(1-x)Zr(x)O2 (x = 0; 0.2; 0.5; 0.8; 1) catalysts. The acid-base properties of these catalysts were investigated by means of adsorption microcalorimetry, using NH3 and CO2 as probe molecules. The catalytic activity for 4-methylpentan-2-ol dehydration was tested at atmospheric pressure in a fixed-bed flow microreactor. The inclusion of increasingly high contents of zirconium into the ceria lattice has a complex influence on the acidity and basicity of the pure parent oxide, in terms of both number and strength of the sites. A maximum in 1-alkene selectivity is observed for the ceria-rich catalyst and a minimum for the zirconia-rich sample. Catalytic results are correlated with the acid-base properties and can be interpreted in the light of the mechanism formerly proposed for zirconia, ceria and lanthania. Surface conditioning of the zirconia-rich catalyst occurs during the run, resulting in a remarkable variation of selectivity.
- Cutrufello,Ferino,Solinas,Primavera,Trovarelli,Auroux,Picciau
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p. 3369 - 3375
(2007/10/03)
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- Nickel(II) Naphthenate Complexes with Phosphorous Amides in Dimerization of Propylene
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Dimerization of propylene in the presence of diethylaluminum chloride and nickel(II) naphthenate complexes with phosphorous amides of the general formulas (RO)2P-NR'2 and (R'2N)3P (where R = C6H5, AlkC6H4; R' = C2H5, C4H9) was studied.The catalytic activity of the systems was examined in relation to the donor properties of these ligands.The procedure for recovery of 2-methyl-2-pentene and 2,3-dimethyl-2-butene from the dimerization products was developed.
- Munshieva, M. K.
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p. 1779 - 1782
(2007/10/03)
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- Dehydration of 4-methylpentan-2-ol over lanthanum and cerium oxides
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Lanthanum and cerium oxides have been tested for the title reaction at 623 K and atmospheric pressure in a flow reactor. Lanthanum oxide (prepared from the corresponding nitrate) gives mainly 4-methylpent-1-ene (80% of the products). Similar results are observed with cerium oxide obtained from the corresponding hydroxide, whereas cerium oxide prepared from nitrate is less selective towards alk-1-enes. In addition to dehydration, dehydrogenation to 4-methylpentan-2-one is also observed to a limited extent for all the catalysts. Information on the acid-base properties of the samples was obtained by adsorption microcalorimetry of ammonia and carbon dioxide and correlated to reaction selectivities. Possible changes in the oxidation state of cerium ions due to the reaction atmosphere are considered. The present results are compared with former data for zirconia catalysts. Modification of cerium oxide via immersion in NaOH solution does not appear to be useful for improving alk-1-ene selectivity.
- Auroux,Artizzu,Ferino,Monaci,Rombi,Solinas,Petrini
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p. 2619 - 2624
(2007/10/03)
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- High-temperature oxidation of LnCu2 intermetallics and their catalytic behavior in 4-methyl-2-pentanol decomposition
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The air-oxidation of the intermetallic compounds LaCu2, CeCu2, PrCu2, and NdCu2 was followed by thermogravimetry. The mass uptake occurred over a wide range of temperature (423-1100 K), leading to two stoichiometrics according to the lanthanide; CeCu2O4 and LnCu2O3.5 (Ln = La, Pr, Nd). The characterization by powder X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis, and surface area measurements showed that segregation took place with the formation of CuO along with CeO2 or Ln2CuO4 (Ln = La, Pr, Nd). Therefore, the oxidized intermetallics are better described by the formulas CeO2·2CuO and Ln2CuO4·3CuO. The oxidation process noticeably increased the surface areas and promoted CuO migration to the surface. These systems exhibited selectivities in 4-methyl-2-pentanol decomposition, which are associated with the lanthanide.
- Ballivet-Tkatchenko,Branco,de Matos
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p. 5481 - 5484
(2007/10/02)
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- Dehydration of 4-Methylpentan-2-ol over Zirconia Catalysts
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Several zirconia catalysts, differing in their preparative procedures and/or in the addition of dopants, have been tested for the title reaction.The catalysts were characterized by means of calorimetric techniques.The heats of adsorption of the probe molecules, ammonia and carbon dioxide, were measured to obtain information on the acid-base properties of the samples.Both flow and pulse reactors were used to investigate the behaviour of the catalysts. 4-Methylpentan-1-ol undergoes dehydration to give 4-methylpent-1-ene, which is the desired product, and 4-methylpent-2-ene, in variable amounts; skeletal isomers of C6-alkenes can also form.Simultaneous dehydrogenation of the reactant to 4-methylpent-2-one can also occur.The acid-base properties of the catalyst appear to play a key role in governing the reaction mechanism, a well balanced number of acid and base sites being needed to obtain a good selectivity to the alk-1-ene isomer.
- Auroux, A.,Artizzu, P.,Ferino, I.,Solinas, V.,Leofanti, G.,et al.
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p. 3263 - 3268
(2007/10/03)
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- Regioselective dehydration in cyclic system with triphenylphosphine-azodicarboxylate
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The regioselective dehydration of cyclohexanol derivatives was achieved by using the Mitsunobu reagent system. The reaction undergoes under mild and neutral conditions. The observed regioselectivity was explained by considering the importance of the orientation of the leaving group at the elimination stage.
- Iimori,Ohtsuka,Oishi
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p. 1209 - 1212
(2007/10/02)
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- La photochimie du cis-penta-1,3-diene, en phase gazeuse a 184,9 et 147,0 nm
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We have studied the 184,9 and 147.0 nm photochemistry of gaseous cis-1,3-pentadiene: the main products observed at 184.9 nm are trans-1,3-pentadiene and 1,3-cyclopentadiene.The formation of radicals also occurs as shown through the use of DI as a radical scavenger.Cyclopentadiene is the likely product of successive eliminations of two hydrogen atoms from the photoexcited molecule after rearrangement of the pentadienyl radical to the cyclopentenyl structure: Φ0(cyclo-C5H6) ca.0.25.Elimination of a methyl radical (Φ0 ca. 0.50) also occurs, with formation of CH2=CHCH=CH* and, in a lower yield, CH2=C=CHCH2*.However, it is not possible to identify properly the mechanism of the formation of the latter radical.It may be the result of the isomerization of either the first photoexcited molecule or the excited 1,3-butadienyl radicals.A small amount of 1,4-pentadiene formation is also observed (Φ0 ca 0.035 +/- 0.015).At 147.0 nm, the same characteristics are observed, together with higher fragmentation due to the higher energy content of the photoexcited molecules.It appears that the photofragmentation at both wavelengths is more in line with that of acyclic alkenes than with that of 1,3-butadiene, which tends to undergo isomerization of the photoexcited molecules to the 1,2-butadiene structure. Key words: 1,3-pentadiene, far UV, vacuum UV, photolysis, monomolecular, fragmentation, stabilization.
- Collin, Guy J.,Deslauriers, Helene,Mare, George R. De
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p. 1245 - 1251
(2007/10/02)
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- The E2C Mechanism in Elimination Reactions. IX. Re-Examination of the Olefin-Like Transition-State
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The kinetics and product olefins arising from E2C-like elimination reactions of secondary bromides and tosylates having various alkyl and conjugating substituents at Cα and Cβ are re-examined in the light of the theoretical Pross-Shaik valence-bond model and the apparent lack of a β-phenyl effect.Comparison of the effect of substituents at Cα and Cβ shows that whilst there are differences in reactivity and products of E2C reactions there is also a large degree of double-bond character in the transition state.There is a good correlation between the kinetics of E2C reactions and the double-bond stabilization energy arising from both alkyl and conjugating substituents.Contributing valence-bond structures, giving asymmetry and partial charge at Cα and Cβ, appear to vary in importance according to leaving group and substituent type.
- Muir, David M.,Parker, Alan J.
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p. 1667 - 1673
(2007/10/02)
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- PHOTO-DEHALOGANATION OF VICINAL DIHALIDE TO OLEFIN
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Irradiation of vicinal dihalides in the presence of methanol or triethylamine resulted in an efficient dehalogenation to regenerate olefins.
- Izawa, Yasuji,Takeuchi, Masaki,Tomioka, Hideo
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p. 1297 - 1300
(2007/10/02)
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- DIMERIZATION OF PROPYLENE IN THE PRESENCE OF NICKEL-CONTAINING COMPLEX CATALYSTS FIXED ON PHOSPHORYLATED POLYSTYRENE
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The effect of a series of factors (the type of nickel compound, the nature of the phosphorus-containing group, the nature of the solvent, the temperature, etc.) on the dimerization of propylene and on the activity of the nickel-containing complex catalysts fixed to phosphorylated polystyrene was investigated.The activity of the catalysts amounts to 1300-1700 g of the dimers per 1 g of nickel per hour.The main product in the dimeric fraction is 4-methyl-2-pentene.If the reaction is carried out in an alkane medium, the catalysts retain high activity for more than 1000 h.
- Aliev, V. S.,Khanmetov, A. A.,Mamedov, R. Kh.,Kerimov, R. K.,Akhmedov, V. M.
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p. 232 - 235
(2007/10/02)
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- ETUDE CINETIQUE DE LA DIMERISATION DU PROPYLENE CATALYSEE PAR L'HYDRIDO DIAZOTE TRIS(TRIPHENYLPHOSPHINE) COBALT(I)
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The dimerization of propylene catalyzed by CoHN2(PPh3)3 at room temperature in benzene, leads to a mixture of methylpentenes.The kinetic study of this condensation shows that it is governed by the following equation rate: with f=K'+ K/; k= ca. 3*10-2 min-1.The complex Co(C3H7)(PPh3)3 is proposed as the catalytic active species.
- Petit, F.,Arzouyan, C.,Peiffer, G.,Gaydou, E.
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p. 319 - 328
(2007/10/02)
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- Catalylic Conversion of Alcohols. Part 10.-Influence of Pretreatment on the Selectivity of MgO and CaO
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With both CaO and MgO catalysts, the hydrogen pretreated material is a selective dehydrogenation catalyst while the oxygen pretreated material has about the same activity for both dehydrogenation and dehydration.Initially the air (or oxygen) pretreated MgO sample produces an alkene distribution from 2-ols that resembles that obtained with alumina; as the reaction temperature is increased a similar alkene distribution, different from the equilibrium value, is obtained with both pretreatments.The three temperatures used with CaO yield an alkene distribution, with either pretreatment, that resembles the highest temperature run with MgO.Pure cis-2- or trans-2-methylcyclohexanol undergoes extensive cis-trans isomerisation; the different alkene distributions from the two alcohols suggest that a trans elimination pathway contributes to the dehydration mechanism.
- Davis, Burtron H.
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