- Highly Efficient and 1,2-Regioselective Method for the Oligomerization of 1-Hexene Promoted by Zirconium Precatalysts with [OSSO]-Type Bis(phenolate) Ligands
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A mixture of zirconium complex 7, which carries a phenyl-substituted [OSSO]-type bis(phenolate) ligand, and dried modified methylaluminoxane (dMMAO) catalyzes the 1,2-regioselective oligomerization of 1-hexene at relatively low catalyst loadings (0.0056 mol %) to produce the corresponding vinylidene-terminated dimer, 5-methyleneundecane (74-80%), and trimer, 7-butyl-5-methylenetridecane (8-11%). The observed turnover frequencies (TOFs) are relatively high (up to 11a€?100 h-1). When a mixture of 2,6-dimethylphenyl-substituted precatalyst 8 and dMMAO was used, the oligomerization of 1-hexene proceeded effectively to afford predominantly the dimer (87-91%) together with a small amount of the trimer (8-11%) at remarkably high TOFs (up to 6640 h-1).
- Nakata, Norio,Nakamura, Kazuaki,Ishii, Akihiko
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p. 2640 - 2644
(2018/08/21)
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- Structurally uniform 1-hexene, 1-octene, and 1-decene oligomers: Zirconocene/MAO-catalyzed preparation, characterization, and prospects of their use as low-viscosity low-temperature oil base stocks
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An original approach to α-olefin oligomerization as well as novel thermally stable zirconocene catalysts for use in such reactions has been elaborated. The method reported allows the achievement of fractions of lightweight α-olefin oligomers up to 90% yields without considerable formation of byproducts like internal alkenes, alkanes, and higher oligomers. Trimers, tetramers, and pentamers of 1-hexene, 1-octene, and 1-decene were isolated as individual compounds and were hydrogenated. Viscosity characteristics of the isolated saturated and unsaturated hydrocarbons have been studied at various temperatures. The isolated saturated oligomers of 1-octene and 1-decene outperform the traditional electrophilic oligomerization products in terms of viscosity indexes, pour points, and low-temperature viscosity.
- Nifant'ev, Ilya E.,Vinogradov, Alexander A.,Vinogradov, Alexey A.,Sedov, Igor V.,Dorokhov, Viktor G.,Lyadov, Anton S.,Ivchenko, Pavel V.
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- Effect of Alcohol Structure on the Kinetics of Etherification and Dehydration over Tungstated Zirconia
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Linear and branched ether molecules have attracted recent interest as diesel additives and lubricants that can be produced from biomass-derived alcohols. In this study, tungstated zirconia was identified as a selective and green solid acid catalyst for the direct etherification of primary alcohols in the liquid phase, achieving ether selectivities of >94 % for C6–C12 linear alcohol coupling at 393 K. The length of linear primary alcohols (C6–C12) was shown to have a negligible effect on apparent activation energies for etherification and dehydration, demonstrating the possibility to produce both symmetrical and asymmetrical linear ethers. Reactions over a series of C6 alcohols with varying methyl branch positions indicated that substituted alcohols (2°, 3°) and alcohols with branches on the β-carbon readily undergo dehydration, but alcohols with branches at least three carbons away from the -OH group are highly selective to ether. A novel model compound, 4-hexyl-1dodecanol, was synthesized and tested to further demonstrate this structure–activity relationship. Trends in the effects of alcohol structure on selectivity were consistent with previously proposed mechanisms for etherification and dehydration, and help to define possible pathways to selectively form ethers from biomass-derived alcohols.
- Rorrer, Julie,Pindi, Suresh,Toste, F. Dean,Bell, Alexis T.
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p. 3104 - 3111
(2018/09/06)
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- Catalytic oligomerization of α-olefins in the presence of two-stage activated zirconocene catalyst based on 6,6-dimethylfulvene ‘dimer’
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Zirconocene obtained from 6,6-dimethylfulvene ‘dimer’, being activated subsequently with triisobutylaluminium and methylalumoxane, catalyzes transformation of α-olefins into a mixture of vinylidene oligomers with minimal losses to isomerization, which allows one to consider this catalyst perspective for the synthesis of branched hydrocarbons with uniform structure.
- Nifant'ev, Ilya E.,Vinogradov, Alexey A.,Vinogradov, Alexander A.,Bezzubov, Stanislav I.,Ivchenko, Pavel V.
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- DIARYL AMINE ANTIOXIDANTS PREPARED FROM BRANCHED OLEFINS
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Diaryl amines are selectively alkylated by reaction with branched olefins, which olefins are capable of forming tertiary carbonium ions and can be conveniently prepared from readily available branched alcohols. The diaryl amine products are effective antioxidants and often comprise a high amount of di-alkylated diaryl amines and a low amount of tri- and tetra-alkylated diaryl amines.
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Paragraph 0058
(2017/02/09)
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- 1-Hexene: A renewable C6 platform for full-performance jet and diesel fuels
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A highly efficient and selective process has been developed for the conversion of 1-hexene to jet and diesel fuels. In combination with commercial processes for the dehydration of ethanol and trimerization of ethylene, this work provides a basis for the synthesis of full-performance hydrocarbon fuels from bio-ethanol. Selective oligomerization of 1-hexene with a Cp 2ZrCl2/MAO catalyst at ambient temperature and pressure resulted in 100% conversion of 1-hexene with >80% selectivity to a mixture of the dimer and trimer. The hydrogenated dimer had a -20 °C viscosity of only 3.5 mPa s, an exceptionally low freezing point of -77 °C, and a cetane number of 67 suggesting that it has performance characteristics suitable for both jet and diesel fuels. The hydrogenated trimer had a flash point of 128 °C, a cetane number of 92, a 40 °C viscosity of 3.1 mPa s, and a -20 °C viscosity of 24.5 mPa s. These properties suggest that the trimer has applications as a high-performance diesel fuel. In addition to the fuel-range hydrocarbons, heavier oligomers have potential as biolubricants which improves the carbon yield of useful products to near quantitative levels.
- Harvey, Benjamin G.,Meylemans, Heather A.
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p. 770 - 776
(2014/02/14)
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- Scope and mechanism of homogeneous tantalum/iridium tandem catalytic alkane/alkene upgrading using sacrificial hydrogen acceptors
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An in-depth investigation of a dual homogeneous catalyst system for the coupling of alkanes and alkenes based on an early-/late-transition-metal pairing is reported. The system is composed of Cp*TaCl2(alkene) for alkene dimerization and pincer-iridium hydrides for alkane/alkene transfer hydrogenation. Because there is no kinetically relevant interaction between the two catalysts, the tandem mechanism can be entirely described using the two independent catalytic cycles. The alkene dimerization mechanism is characterized by an entropically disfavored pre-equilibrium between Cp*TaCl 2(1-hexene) + 1-hexene and Cp*TaCl 2(metallacyclopentane) (ΔH° = -22(2) kcal/mol; ΔS° = -16(2) eu); thus, the overall rate of alkene dimerization is positive order in 1-hexene (exhibiting saturation kinetics), and increases only modestly with temperature. In contrast, the rate of 1-hexene/n-heptane transfer hydrogenation catalyzed by t-Bu[PCP]IrH4 is inverse order in 1-hexene and increases substantially with temperature. Styrene has been investigated as an alternate sacrificial hydrogen acceptor. Styrene dimerization catalyzed by Cp*TaCl2(alkene) is considerably slower than 1-hexene dimerization. The conversion of styrene/heptane mixtures by the Ta/Ir tandem system leads to three product types: styrene dimers, coupling of styrene and heptane, and heptene dimers (from heptane). Through careful control of reaction conditions, the production of heptene dimers can be favored, with up to 58% overall yield of heptane-derived products and cooperative TONs of up to 12 and 10 for Ta and Ir catalysts, respectively. There is only slight inhibition of Ir-catalyzed styrene/n-heptane transfer hydrogenation under the tandem catalysis conditions.
- Leitch, David C.,Labinger, Jay A.,Bercaw, John E.
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supporting information
p. 3353 - 3365
(2014/08/05)
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- TANDEM TRANSFER HYDROGENATION AND OLIGOMERIZATION FOR HYDROCARBON PRODUCTION
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The disclosure provides for hydrocarbon production by hydrogenation and oligomerizaton and, more particularly, to catalysis of alkanes and alkenes by a tandem transfer hydrogenation and oligomerization.
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Paragraph 0112-0114
(2014/07/23)
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- Upgrading light hydrocarbons via tandem catalysis: A dual homogeneous Ta/Ir system for alkane/alkene coupling
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Light alkanes and alkenes are abundant but are underutilized as energy carriers because of their high volatility and low energy density. A tandem catalytic approach for the coupling of alkanes and alkenes has been developed in order to upgrade these light hydrocarbons into heavier fuel molecules. This process involves alkane dehydrogenation by a pincer-ligated iridium complex and alkene dimerization by a Cp*TaCl2(alkene) catalyst. These two homogeneous catalysts operate with up to 60/30 cooperative turnovers (Ir/Ta) in the dimerization of 1-hexene/n-heptane, giving C13/C14 products in 40% yield. This dual system can also effect the catalytic dimerization of n-heptane (neohexene as the H2 acceptor) with cooperative turnover numbers of 22/3 (Ir/Ta).
- Leitch, David C.,Lam, Yan Choi,Labinger, Jay A.,Bercaw, John E.
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supporting information
p. 10302 - 10305
(2013/08/23)
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- Enantioselectivity of chiral zirconocenes as catalysts in alkene hydro-, carbo- and cycloalumination reactions
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The enantioselectivity of chiral Zr catalysts L1L2ZrCl2 [L1 = L2 = 1-neomenthylindenyl (Ind*), 1; L1 = Cp, L2 = Ind* 2; L1 = Cp, L2 = 1-neomenthylindenyl-4,5,6,7-tetrahydroindenyl (Cp*) 3] in the hydro-, carbo- and cycloalumination of alkenes by organoaluminium compounds (OAC) (AlMe3, AlEt3, HAlBu2i) has been studied. It was found that OAC exhibit the most effect on the reaction chemo- and enantioselectivity. The reaction chemo- and enantioselectivity depend on the catalyst structure and reaction conditions (solvent type, catalyst concentration, temperature) as well. It is shown that the lack of asymmetric induction in the reaction of α-methylstyrene hydroalumination by HAlBu2i, catalyzed with complexes 1 or 3, is the result of the formation of Zr hydride complexes of different structures as reaction intermediates. MTPA was used as a derivatization reagent for the enantiomeric excess estimation and absolute configuration assignment of β-chiral alcohols obtained after the oxidation and hydrolysis of the reaction products. The applicability of MTPA for the assignment of the absolute configuration of the stereogenic centre in β-ethyl substituted primary alcohols and β-alkyl-1,4-butanediols is shown.
- Parfenova, Lyudmila V.,Berestova, Tatyana V.,Tyumkina, Tatyana V.,Kovyazin, Pavel V.,Khalilov, Leonard M.,Whitby, Richard J.,Dzhemilev, Usein M.
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experimental part
p. 299 - 310
(2010/06/14)
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- Cobalt-catalyzed dimerization of α-olefins to give linear α-olefin products
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[Cp*P(OMe)3CoCH2CH3]+ [BarF]-, generated by the addition of HBArF to Cp*P(OMe)3Co(ethene), catalyzes the oligomerization of 1-hexene to give dimers and trimers. When a deficit of the acid is used, linear α-olefin dimers are produced at the expense of trimeric products: e.g., 1-butene, 1-hexene, and 1-octene give 1-octene, 1-dodecene, and 1-hexadecene, respectively. Copyright
- Broene, Richard D.,Brookhart, Maurice,Lamanna, William M.,Volpe Jr., Anthony F.
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p. 17194 - 17195
(2007/10/03)
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