- Enhanced activity and selectivity in n-octane isomerization using a bifunctional SCILL catalyst
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Bifunctional Solid Catalyst with Ionic Liquid Layer (SCILL) systems are presented and applied in the skeleton isomerization of n-octane in a slurry-phase reaction mode. It is demonstrated that Pt on silica, coated with a thin film of acidic chloroaluminate ionic liquid exhibits remarkable catalytic performance under mild conditions in the presence of hydrogen. Interestingly, both selectivity and activity of n-octane isomerization increase in these systems as a function of hydrogen pressure. This does not only suggest a hydrogenation activity of the catalytic Pt-centers embedded in the strongly Lewis acidic ionic liquid but also a significant increase in the proton acidity in this system as a function of the hydrogen pressure.
- Meyer,Hager,Schwieger,Wasserscheid
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Read Online
- Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
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Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
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supporting information
p. 9029 - 9039
(2021/06/28)
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- Highly selective aromatization and isomerization of N-alkanes from bimetallic Pt-Zn nanoparticles supported on a uniform aluminosilicate
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A bimetallic-support interaction through Pt-Zn nanoparticles and uniform compact cylindrical ZSM-5 particles shows selectivity over 90% towards BTX and i-octane at controlled 60% conversion with negligible coke formation when reforming n-octane. This is a significant improvement compared to alternative Pt-Zn on conventional ZSM-5, with a selectivity of less than 40%.
- Jarvis, Jack S.,Harrhy, Jonathan H.,He, Peng,Wang, Aiguo,Liu, Lijia,Song, Hua
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supporting information
p. 3355 - 3358
(2019/04/03)
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- A Heterogeneous Metal-Free Catalyst for Hydrogenation: Lewis Acid–Base Pairs Integrated into a Carbon Lattice
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Designing heterogeneous metal-free catalysts for hydrogenation is a long-standing challenge in catalysis. Nanodiamond-based carbon materials were prepared that are surface-doped with electron-rich nitrogen and electron-deficient boron. The two heteroatoms are directly bonded to each other to form unquenched Lewis pairs with infinite π-electron donation from the surrounding graphitic structure. Remarkably, these Lewis pairs can split H2 to form H+/H? pairs, which subsequently serve as the active species for hydrogenation of different substrates. This unprecedented finding sheds light on the uptake of H2 across carbon-based materials and suggests that dual Lewis acidity–basicity on the carbon surface may be used to heterogeneously activate a variety of small molecules.
- Ding, Yuxiao,Huang, Xing,Yi, Xianfeng,Qiao, Yunxiang,Sun, Xiaoyan,Zheng, Anmin,Su, Dang Sheng
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supporting information
p. 13800 - 13804
(2018/10/20)
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- One-step hydroprocessing of fatty acids into renewable aromatic hydrocarbons over Ni/HZSM-5: Insights into the major reaction pathways
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For high caloricity and stability in bio-aviation fuels, a certain content of aromatic hydrocarbons (AHCs, 8-25 wt%) is crucial. Fatty acids, obtained from waste or inedible oils, are a renewable and economic feedstock for AHC production. Considerable amounts of AHCs, up to 64.61 wt%, were produced through the one-step hydroprocessing of fatty acids over Ni/HZSM-5 catalysts. Hydrogenation, hydrocracking, and aromatization constituted the principal AHC formation processes. At a lower temperature, fatty acids were first hydrosaturated and then hydrodeoxygenated at metal sites to form long-chain hydrocarbons. Alternatively, the unsaturated fatty acids could be directly deoxygenated at acid sites without first being saturated. The long-chain hydrocarbons were cracked into gases such as ethane, propane, and C6-C8 olefins over the catalysts' Br?nsted acid sites; these underwent Diels-Alder reactions on the catalysts' Lewis acid sites to form AHCs. C6-C8 olefins were determined as critical intermediates for AHC formation. As the Ni content in the catalyst increased, the Br?nsted-acid site density was reduced due to coverage by the metal nanoparticles. Good performance was achieved with a loading of 10 wt% Ni, where the Ni nanoparticles exhibited a polyhedral morphology which exposed more active sites for aromatization.
- Xing, Shiyou,Lv, Pengmei,Wang, Jiayan,Fu, Junying,Fan, Pei,Yang, Lingmei,Yang, Gaixiu,Yuan, Zhenhong,Chen, Yong
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p. 2961 - 2973
(2017/02/05)
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- The use of ultrasmall iron(0) nanoparticles as catalysts for the selective hydrogenation of unsaturated C-C bonds
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The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and CX bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2) 2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for CO bond hydrogenation.
- Kelsen, Vinciane,Wendt, Bianca,Werkmeister, Svenja,Junge, Kathrin,Beller, Matthias,Chaudret, Bruno
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p. 3416 - 3418
(2013/05/22)
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- PdAu alloy nanoparticles encapsulated by PPI-g-MWCNTs as a novel catalyst for chemoselective hydrogenation of alkenes under mild conditions
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The synthesis, characterization and catalytic applications of bimetallic PdAu encapsulated on polypropylene imine grafted multi-wall carbon nanotubes hybrid materials have been reported. The results show that the catalyst induces a highly activity and chemoselective hydrogenation of less hindered alkenes to the corresponding alkanes using hydrogen gas in environmentally friendly solvents H2O/EtOH at 50 °C with high yields. The characterization of catalyst was confirmed by FT-IR, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray powder diffraction.
- Shaabani, Ahmad,Mahyari, Mojtaba
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p. 1277 - 1284
(2014/01/06)
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- PROCESS FOR PREPARING JET FUEL FROM MOLECULES DERIVED FROM BIOMASS
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The invention relates to a process for preparing jet fuel or jet fuel precursors which comprises the treatment of a charge derived from biomass, the said charge comprising at least one compound chosen from terpenes of formula [CH2=C(CH3)CH=CH2]n, in which n is an integer of from 2 to 12, the carbon chain of which is linear, cyclic or branched, or cyclic or branched terpenes as defined previously, which have been chemically modified by oxidation and/or rearrangement of the carbon backbone, the said process comprising a cycloaddition step (i) followed by a cracking and hydrogenation step (ii).
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Page/Page column 16; 17
(2013/04/25)
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- Impact of cationic surfactant chain length during SAPO-11 molecular sieve synthesis on structure, acidity, and n-octane isomerization to di-methyl hexanes
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The structure, acidity, and n-octane di-branched isomerization of SAPO-11 synthesized with surfactants of different chain lengths in water-propanol system were investigated. The results showed that with the increasing chain length of surfactants, the crys
- Guo, Lin,Bao, Xiaojun,Fan, Yu,Shi, Gang,Liu, Haiyan,Bai, Danjiang
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p. 161 - 170
(2012/11/07)
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- Ring opening of decalin via hydrogenolysis on Ir/- and Pt/silica catalysts
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The catalytic conversion of cis-decalin was studied at a hydrogen pressure of 5.2 MPa and temperatures of 250-410 °C on iridium and platinum supported on non-acidic silica. The absence of catalytically active Br?nsted acid sites was indicated by both FT-IR spectroscopy with pyridine as a probe and the selectivities in a catalytic test reaction, viz. the hydroconversion of n-octane. On iridium/silica, decalin hydroconversion starts at ca. 250-300 °C, and no skeletal isomerization occurs. The first step is rather hydrogenolytic opening of one six-membered ring to form the direct ring-opening products butylcyclohexane, 1-methyl-2-propylcyclohexane and 1,2- diethylcyclohexane. These show a consecutive hydrogenolysis, either of an endocyclic carboncarbon bond into open-chain decanes or of an exocyclic carboncarbon bond resulting primarily in methane and C9 naphthenes. The latter can undergo a further endocyclic hydrogenolysis leading to open-chain nonanes. All individual C10 and C9 hydrocarbons predicted by this direct ring-opening mechanism were identified in the products generated on the iridium/silica catalysts. The carbon-number distributions of the hydrocracked products C9- show a peculiar shape resembling a hammock and could be readily predicted by simulation of the direct ring-opening mechanism. Platinum on silica was found to require temperatures around 350-400 °C at which relatively large amounts of tetralin and naphthalene are formed. The most abundant primary products on Pt/silica are spiro[4.5]decane and butylcyclohexane which can be readily accounted for by the well known platinum-induced mechanisms described in the literature for smaller model hydrocarbons, namely the bond-shift isomerization mechanism and hydrogenolysis of a secondary-tertiary carboncarbon bond in decalin.
- Haas, Andreas,Rabl, Sandra,Ferrari, Marco,Calemma, Vincenzo,Weitkamp, Jens
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experimental part
p. 97 - 109
(2012/07/13)
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- Conversion of biomass-derived butanal into gasoline-range branched hydrocarbon over Pd-supported catalysts
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For production of gasoline-range branched hydrocarbon from butanal, Pd catalysts supported on different metal oxides were applied. Among the prepared catalysts, Pd/ZrO2 showed the complete butanal conversion with the formation of C7-to-C9 branched hydrocarbon (75% yield). Additionally, the ratios of O/C and straight-chain to branched hydrocarbon (n-C/br-C) were found to be 0.005 and 0.17, respectively. This indicates that an adequate combination of Pd dispersion and amphoteric ZrO2 character promoted hydrodeoxygenation, C-C coupling and isomerization reactions. Consequently, both Pd dispersion and acid-base properties of supports are suggested to play a pivotal role in producing gasoline-range hydrocarbon at a high yield.
- Kim, Sung Min,Lee, Mi Eun,Choi, Jae-Wook,Suh, Dong Jin,Suh, Young-Woong
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scheme or table
p. 108 - 113
(2012/03/10)
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- Hydroisomerization of n-octane on molybdenum based catalyst
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Balanced metal-acid bifunctional MoO2-x(OH)y catalytic system has been prepared. 2-3 monolayers of this phase on the sample surface were obtained following controlled reduction by hydrogen of equivalent 5 monolayers of MoO3/sub
- Al-Kandari,Al-Kharafi,Katrib
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scheme or table
p. 141 - 148
(2010/11/03)
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- The reaction of biphenyl radical anion and dianion with alkyl fluorides. From ET to SN2 reaction pathways and synthetic applications
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The reaction of dilithium biphenyl (Li2C12H10) with alkyl fluorides has been studied from the point of view of the distribution of products. Two main reaction pathways, the nucleophilic substitution (SN2) and the electron transfer (ET), can compete to yield the same alkylation products in what is known as the SN2-ET dichotomy. SN2 seems to be the main mechanism operating with primary alkyl fluorides (n-RF). Alkylation proceeds in good yields, and the resulting alkylated dihydrobiphenyl anion (n-RC12H10Li) can be trapped with a second conventional electrophile (E+) affording synthetically interesting dearomatized biphenyl derivatives (n-RC12H10E). The reaction gives a higher amount of ET products as we move to secondary (s-RF) and to tertiary alkyl fluorides (t-RF), in which case the mechanism seems to be dominated by ET. In this case, alkylation by radical coupling is still feasible, giving access to the synthesis of t-RC12H10E, although in lower yields. A rational interpretation of this SN2-ET dichotomy is given on the basis of the full distribution of products observed when 5-hexenyl fluoride and 1,1-dimethyl-5-hexenyl fluoride were are used as radical probes in their reaction with Li2C12H10 and LiC12H10.
- Pérez, Henoc,Melero, Cristóbal,Guijarro, Albert,Yus, Miguel
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experimental part
p. 10769 - 10783
(2010/02/28)
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- Reactivity of mixed organozinc and mixed organocopper reagents. Part 4: A kinetic study of group transfer selectivity in C-C coupling of mixed diorganocuprates
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The competitive rate data and Taft relationships for the coupling of bromomagnesium n-butyl (substituted phenyl) cuprates with alkyl bromides show that selective n-butyl transfer can be explained by an oxidative addition mechanism. Taft reaction constants
- Erdik, Ender,Oezkan, Duygu
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experimental part
p. 1148 - 1154
(2010/07/13)
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- Preparation of highly active and dispersed platinum nanoparticles on mesoporous Al-MCM-48 and their activity in the hydroisomerisation of n-octane
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Platinum nanoparticles supported on Al-MCM-48 materials have been prepared. The resultant catalysts have been characterized by means of XRD, N2 physisorption experiments, scanning electron microscopy (SEM), transmission electron microscopy (TEM
- Campelo, Juan M.,Lee, Adam F.,Luque, Rafael,Luna, Diego,Marinas, Jose M.,Romero, Antonio A.
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scheme or table
p. 5988 - 5995
(2009/06/05)
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- CATALYTIC PROCESS FOR CONVERTING RENEWABLE RESOURCES INTO PARAFFINS FOR USE AS DIESEL BLENDING STOCKS
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A process for converting renewable resources such as vegetable oil and animal fat into paraffins in a single step which comprises contacting a feed which is a renewable resources with hydrogen and a catalyst which comprises molybdenum, a non-precious metal and an oxide to produce a hydrocarbon product having a ratio of even-numbered hydrocarbons to odd-numbered hydrocarbons of at least 2:1.
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Page/Page column 7
(2009/01/24)
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- Palladium nanoparticles stabilized by alkylated polyethyleneimine as aqueous biphasic catalysts for the chemoselective stereocontrolled hydrogenation of alkenes
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Palladium nanoparticles were prepared, stabilized, and dispersed in water by alkylated branched polyethyleneimine. The palladium nanoparticles were effective aqueous biphasic catalysts for the chemoselective hydrogenation of alkenes with preferential reduction of less hindered double bonds, such as reduction of 3-methylcyclohexene in the presence of 1-methylcyclohexene and 1-octene in the presence of 2-methyl-2-heptene.
- Vasylyev, Maxym V.,Maayan, Galia,Hovav, Yonathan,Haimov, Adina,Neumann, Ronny
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p. 5445 - 5448
(2007/10/03)
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- Alkylation process with recontacting in settler
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A system and/or process for decreasing the level of at least one organic fluoride present in a hydrocarbon phase contained in an alkylation settler by contacting the hydrocarbon phase with an HF containing stream, containing greater than about 80 wt. % and less than about 94 wt. % HF, in the intermediate portion of the settler which contains at least one tray system, with each tray system comprising a perforated tray defining a plurality of perforations and a layer of packing below the perforated tray, are disclosed.
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Page/Page column 3-5
(2008/06/13)
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- Process for the manufacture of a gasoline blending component
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The present invention relates to a process for the manufacture of paraffinic hydrocarbons, which can be used as gasoline blending components. The obtained gasoline blending component is substantially free of sulphur compounds. The process comprises simultaneous hydrogenation of olefins and degradation of sulphur compounds by hydrogenolysis. In the process a feed-stock containing as impurities sulphur compounds is hydrogenated in two steps in the presence of a noble metal catalyst on aluminium oxide support, and in the first step the major part of olefins are converted and in the secondary step the remaining olefins and sulphur compounds react.
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Page/Page column 3
(2008/06/13)
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- Chemical transformations of isopentane and isooctane in trifluoromethanesulfonic acid
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The process of isopentane and isooctane activation in trifluoromethanesulfonic acid (H0 = -14) has been studied by GC/MS and NMR. The results show evidence for a high reactivity of isopentane. Various mechanisms constructed using the experimental data and the results of nonempirical quantum-mechanical calculations are compared, and it is concluded that a key role in the reaction under consideration is played by the direct electrophilic attack of CF3SO3H at the C2-C3 bond of isooctane. Copyright
- Gekhman,Smurnyi,Ustynyuk
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p. 1766 - 1770
(2007/10/03)
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- Alkene oligomerization process
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A process for oligomerising alkenes having from 3 to 6 carbon atoms which comprises contacting a feedstock comprising a) one or several alkenes having x carbon atoms, and, b) optionally, one or several alkenes having y carbon atoms, x and y being different, with a catalyst containing a zeolite of the MFS structure type, under conditions to obtain selectively oligomeric product containing predominant amounts of certain oligomers. The process is carried out at a temperature comprised between 125 and 175° C. when the feedstock contains only alkenes with 3 carbon atoms and between 140 and 240° C., preferably between 140 and 200° C. when the feedstock contains comprises at least one alkene with 4 or more carbon atoms.
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- Catalyst and process for contacting a hydrocarbon and ethylene
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A process of contacting at least one feed hydrocarbon, containing three to about seven carbon atoms per molecule, and ethylene in a hydrocarbon-containing fluid in the presence of a catalyst composition to provide at least one product hydrocarbon isomer containing about four to about nine carbon atoms per molecule is provided. The at least one feed hydrocarbon can be selected from paraffins, isoparaffins, and the like and combinations thereof. The catalyst composition contains a hydrogen halide component, a sulfone component, and a metal halide component.
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- Disproportionation of hydrocarbons
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A novel hydrocarbon disproportionation process is provided and includes contacting a hydrocarbon feed comprising at least one paraffin with a disproportionation catalyst comprising a support component, a metal, and a halogen in a disproportionation reaction zone under disproportionation reaction conditions.
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- Pillared trioctahedral micas and/or vermiculites
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Pillared trioctahedral micas and/or vermiculites are prepared. The process includes a conditioning operation for the partial reduction of the layer charge through an accelerated weathering process, and also includes a pillaring operation.
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Page/Page column 13-14
(2008/06/13)
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- Effect of zeolite structure and acidity on the product selectivity and reaction mechanism for n-octane hydroisomerization and hydrocracking
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The activity, product selectivity, and stability of a series of bifunctional zeolite catalysts, primary ZSM-12, USY, and β-zeolite, with different Si/Al ratios were compared for the hydroisomerization and hydrocracking of n-octane. The performance of L-zeolite and mordenite was examined to a lesser extent as well. It was found that the activity per acidic site decreases at the initial stage (1 h on stream) in the following order: ZSM-12 > β-zeolite > mordenite > USY > L-zeolite. For extended periods of operation, the activity of ZSM-12 remains unchanged. The superior stability of ZSM-12 even under accelerating coking conditions results from its unique pore structure, which does not favor coke formation. Its one-dimensional noninterpenetrating puckered channels (5.5 × 6.1 A) act as perfect tubes, which do not trap coke precursors. The branched product selectivity increases with the increase in Bronsted acid site strength of the zeolite catalysts, and thus hydroisomerization is favored at the expense of cracking at a higher Bronsted acid strength. USY-5.8 (CBV-712) showed relatively high initial activity with respect to other USYs. This is probably related to its high surface Al content. The Bronsted acid strength of the USY zeolites decreases in the order USY-2.6 > USY-28 > USY-5.8. The 2,2-DMC6 and 3,3-DMC6 isomers are not favored as final products due to their bulky molecular size even in USY. In addition, the 2,2-DMC6 species is more abundant than 3,3-DMC6 because the rate of isomerization by PCP intermediates decreases in the following order: 2-MC7 > 3-MC7 > 4-MC7. The 2,3-DMC6 concentration is much higher than that predicted by equilibrium, which indicates that the interconversion of 2,3-DMC6 to other dibranched isomers is not preferred. The i-C4/n-C4 ratio detected depends on both the reaction temperature and zeolite pore structure/acidity. Aluminium content determines the type of β-scission. For zeolites with a high concentration of acid sites (Si/Ai about 30), type A β-scission dominates at low temperature, while at lower Al content, type A, B, and C β-scissions are equally important.
- Zhang, Wenmin,Smirniotis, Panagiotis G.
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p. 400 - 416
(2007/10/03)
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- Reactions of Saturated and Unsaturated Tertiary Alkyl Halides and Saturated Secondary Alkyl Iodides with Lithium Aluminum Deuteride. Convincing Evidence for a Single-Electron-Transfer Pathway
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Reactions of saturated secondary and tertiary alkyl halides with LiAlH4 (LAH) and LiAlD4 (LAD) have been carried out, and convincing evidence for a single-electron-transfer (SET) pathway has been obtained. Reactions involving saturated alkyl halides with LAD provide a model system in which a halogen-atom radical chain process is not possible, and therefore, the observation of large quantities (in some cases >90 percent) of protium in the reduction product provides strong evidence for a radical intermediate and a SET pathway. Specifically, the reaction of 2-iodooctane (10) with LAD produced octane with a deuterium content as low as 21 percent. Also, the reaction of the tertiary halide 2-iodo-2-methylheptane (15) with LAD produced 2-methylheptane (16) with a deuterium content as low as 8 percent. The effect of stoichiometry, halogen type, and reaction vessel surface on these reactions was studied. Reaction of the unsaturated tertiary halide 6-iodo-6-methyl-1-heptene (25) with LAD was also studied and was found to proceed predominantly by a SET process involving a halogen-atom radical chain process. The possibility of a carbocation intermediate in all of these reactions is discussed.
- Ashby, E. C.,Welder, Catherine O.
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p. 7707 - 7714
(2007/10/03)
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- Pt/SAPO-5 and Pt/SAPO-11 as Catalysts for the Hydroisomerization and Hydrocracking of n-Octane
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n-Octane hydroisomerization and hydrocracking on SAPO-5 and SAPO-11 catalysts containing 0.5 wt.percent Pt have been investigated in a flow reactor over a wide range of temperatures (573-708 K) and pressures (atmospheric, 3 and 5 bar).These studies have shown that hydroisomerization is a function of the total conversion.The primary products obtained with n-octane were the monobranched isomers.Multibranched feed isomers and cracked products were formed in subsequent reactions.In all cases, hydrogen pressure had a strong influence on the activity and time-on-stream deactivation.Hydroisomerization can be considered to be the primary reaction, with hydrocracking occurring to a significant extent only at higher conversions (>40percent for Pt/SAPO-5 and >65percent for Pt/SAPO-11).The selectivity patterns found in these molecular-sieve catalysts are interpreted in terms of a series of reaction pathways incorporating both confinement effects and shape selectivity factors.
- Campelo, J. M.,Lafont, F.,Marinas, J. M.
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p. 1551 - 1556
(2007/10/02)
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- A Novel Family of Aprotic Organic Superacids for Low-temperature Alkane and Cycloalkane Transformations
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The CBr4*nAlBr3, CHBr3*nAlBr3, CCl4*2AlBr3, CHCl3*2AlBr3 and CH2Br2*nAlBr3 (n=1, 2) systems have been found to catalyse various transformations of alkanes and cycloalkanes under mild conditions.
- Akhrem, Irena,Orlinkov, Alexander,Vol'pin, Mark
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p. 671 - 672
(2007/10/02)
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- ALKANE DEHYDROCYCLIZATION AND ALKYLCYCLOPENTANE CONVERSIONS AT 13.8 bar (200 psi) WITH Pt-Al2O3 CATALYSTS
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The selectivity, defined as aromatics/isoalkanes, for the formation of aromatics is greater for the conversion of n-alkanes than for the conversion of alkylcyclopentanes with a platinum nonacidic alumina catalyst.Alkylcyclopentanes undergo hydrogenolysis to isoalkanes with the same carbon number at least ten to twenty times faster than they react to form aromatics over this catalyst.The results do not support an aromatization mechanism that includes the formation of five carbon ring intermediates.
- Hardy, Rita H.,Davis, Burtron H.
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p. 269 - 278
(2007/10/02)
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- The Synthetic Potential of the Isocyanide-Cyanide Rearrangement
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Excellent chemical and optical yields (>96percent retention) of cyanides are achieved by vapor phase thermolysis or short contact flow thermolysis of isocyanides. trans-2-Butenyl isocyanide rearranges without concomitant allylic isomerization to trans-2-butenyl cyanide.Optically active 1-(formyloxymethyl)-2-phenylethyl cyanide is obtained from optically active L-phenylalanine as a new type of chiral pool synthon.
- Meier, Michael,Ruechardt, Christoph
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- HOMOLOGATION OF HEXANE ISOMERS CATALYZED BY PLATINUM
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The homologation of n-hexane, 3-methylpentane, hexadienes and n-heptane were studied over Pt-black (and some supported Pt) and compared to the reactions of C8 hydrocarbons.The composition of C8-aromatics was used to evaluate the possible pathways.The ratio of internal to terminal addition was about 0.25; this way, the C8-composition from n-hexane could be explained.The appearence of branched chain saturated buildup products from 3-methylpentane and methylcyclopentane complicates their homologation and confirms the possibility of addition of C1 units to internal C-atoms, too.The mechanism of O'Donohoe et al. was found to be valid.
- Dobrovolszky, Maria A.,Paal, Zoltan,Tetenyi, Pal
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-
- Photochemistry of Alkenes. 6. Direct Irradiation of 1,5-Hexadienes: and Sigmatropic Allyl Shifts
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The photochemical behavior of a series of alkyl-substituted 1,5-hexadienes has been studied.Competing allylcyclopropane formation and rearrangement to an isomeric 1,5-hexadiene via competing and sigmatropic allyl shifts, respectively, were observed.In one case a product (30 from 27) and in another a product (35 from 31) was obtained, but only in low yield.Extensive cis trans isomerization competed with the allyl shifts, and, in addition, other products were obtained which are characteristic of the photochemical behavior of isolated double bonds.At low conversion diene 10t underwent stereoselective rearrangement to 8t and 11t, whereas the cis isomer 10c afforded mixtures of the cis and trans isomers of 8 and 11.Attempts to induce the allyl migrations by sensitization with p-xylene or by irradiation at 254 nm afforded only cis trans isomerization.It is concluded that the allyl migrations occur via an excited state involving interaction between the double bonds and requiring a conformation in which the central C3-C4 bond is in a plane orthogonal to both double bonds, as proposed previously.In contrast with the acyclic dienes, 1,5-cyclooctadiene (50) afforded products 51-53 from competing , , and allyl shifts, respectively.The divergent behavior in this case apparently arises because appropriate interaction between the two double bonds can occur only in the boat conformation.
- Manning, T. D. R.,Kropp, Paul J.
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p. 889 - 897
(2007/10/02)
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- TETRAMETHYLSILANE AS ALKYLATING AGENT IN REACTIONS WITH ALKYL HALIDES IN THE PRESENCE OF ALUMINIUM CHLORIDE AND ALUMINIUM BROMIDE
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A systematic investigation was undertaken into the electrophilic substitution of halogen atoms by a methyl group in alkyl halides by the action of tetramethylsilane and aluminium halides.It was established that the structure of the substrate has an effect on the reaction path.The methylation of primary alkyl halides is accompanied by isomerization of the carbon skeleton and leads to the production of saturated branched hydrocarbons.In the case of alkyl halides with a branched hydrocarbon chain difficultly obtainable hydrocarbons with a quarternary carbon atom are formed with high yields.The reaction takes place at room temperature in l0-l5 min.
- Bolestova, G. I.,Parnes, Z. N.,Latypova, F. M.,Kursanov, D. N.
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p. 1203 - 1208
(2007/10/02)
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