- Silica-immobilized ionic liquid Br?nsted acids as highly effective heterogeneous catalysts for the isomerization of: N -heptane and n -octane
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Metal-free imidazolium-based ionic liquid (IL) Br?nsted acids 1-methyl imidazolium hydrogen sulphate [HMIM]HSO4 and 1-methyl benzimidazolium hydrogen sulphate [HMBIM]HSO4 were synthesized. Their physicochemical properties were investigated using spectroscopic and thermal techniques, including UV-Vis, FT-IR, 1H NMR, 13C-NMR, mass spectrometry, and TGA. The ILs were immobilized on mesoporous silica gel and characterized by FT-IR spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller analysis, ammonia temperature-programmed desorption, and thermogravimetric analysis. [HMIM]HSO4?silica and [HMBIM]HSO4?silica have been successfully applied as promising replacements for conventional catalysts for alkane isomerization reactions at room temperature. Isomerization of n-heptane and n-octane was achieved with both catalysts. In addition to promoting the isomerization of n-heptane and n-octane (a quintessential reaction for petroleum refineries), these immobilized catalysts are non-hazardous and save energy.
- Al-Fatesh, Ahmed S.,Dhar, Abhishek,Fakeeha, Anis H.,Ibrahim, Ahmed A.,Khimani, Mehul,Patel, Hiren,Siva Kumar, Nadavala,Vekariya, Rohit L.
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p. 15282 - 15292
(2020/05/05)
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- Impact of the Spatial Organization of Bifunctional Metal–Zeolite Catalysts on the Hydroisomerization of Light Alkanes
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Improving product selectivity by controlling the spatial organization of functional sites at the nanoscale is a critical challenge in bifunctional catalysis. We present a series of composite bifunctional catalysts consisting of one-dimensional zeolites (ZSM-22 and mordenite) and a γ-alumina binder, with platinum particles controllably deposited either on the alumina binder or inside the zeolite crystals. The hydroisomerization of n-heptane demonstrates that the catalysts with platinum particles on the binder, which separates platinum and acid sites at the nanoscale, leads to a higher yield of desired isomers than catalysts with platinum particles inside the zeolite crystals. Platinum particles within the zeolite crystals impose pronounced diffusion limitations on reaction intermediates, which leads to secondary cracking reactions, especially for catalysts with narrow micropores or large zeolite crystals. These findings extend the understanding of the ??intimacy criterion” for the rational design of bifunctional catalysts for the conversion of low-molecular-weight reactants.
- Cheng, Kang,Harmel, Justine,Oenema, Jogchum,Sunley, Glenn,Yoshida, Hideto,Ze?evi?, Jovana,Zhang, Zhaorong,de Jong, Krijn P.,van der Wal, Lars I.
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supporting information
p. 3592 - 3600
(2020/02/05)
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- PROCESS FOR SELECTIVE RING OPENING OF CYCLIC HYDROCARBONS
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PURPOSE: A process for ring opening is provided to obtain improved conversion ratio and selectivity in comparison with the case of using hydrogen as a reducing agent. CONSTITUTION: A cyclic hydrocarbon and a reducing agent are provided as supplying materials. The supplying materials are transferred into a reactor (5) and reacted under the presence of a catalyst. A product is separated from the effusion of reaction zone. The catalyst is a heterogeneous catalyst having both acid site and metallic component. The product is obtained by evaporating and heating a mixture containing 100 parts by weight of porous molecular sieve and 0.01-20 parts by weight of water soluble metallic salt. The cyclic hydrocarbon is a naphthene group cyclic hydrocarbon which is pentagonal or hexagonal compound, or an alkyl derivative thereof selected from cyclopentane and cyclohexane. The alkyl derivative is methyl, ethyl, profile, butyl, isopropyl or an isobutyl derivative.
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Paragraph 0078-0085
(2020/04/29)
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- Bis(imino)pyridine cobalt-catalyzed dehydrogenative silylation of alkenes: Scope, mechanism, and origins of selective allylsilane formation
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The aryl-substituted bis(imino)pyridine cobalt methyl complex, ( MesPDI)CoCH3 (MesPDI = 2,6-(2,4,6-Me 3C6H2-N=CMe)2C5H 3N), promotes the catalytic dehydrogenative silylation of linear α-olefins to selectively form the corresponding allylsilanes with commercially relevant tertiary silanes such as (Me3SiO) 2MeSiH and (EtO)3SiH. Dehydrogenative silylation of internal olefins such as cis- and trans-4-octene also exclusively produces the allylsilane with the silicon located at the terminus of the hydrocarbon chain, resulting in a highly selective base-metal-catalyzed method for the remote functionalization of C-H bonds with retention of unsaturation. The cobalt-catalyzed reactions also enable inexpensive α-olefins to serve as functional equivalents of the more valuable α, ω-dienes and offer a unique method for the cross-linking of silicone fluids with well-defined carbon spacers. Stoichiometric experiments and deuterium labeling studies support activation of the cobalt alkyl precursor to form a putative cobalt silyl, which undergoes 2,1-insertion of the alkene followed by selective β-hydrogen elimination from the carbon distal from the large tertiary silyl group and accounts for the observed selectivity for allylsilane formation.
- Atienza, Crisita Carmen Hojilla,Diao, Tianning,Weller, Keith J.,Nye, Susan A.,Lewis, Kenrick M.,Delis, Johannes G. P.,Boyer, Julie L.,Roy, Aroop K.,Chirik, Paul J.
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supporting information
p. 12108 - 12118
(2014/10/16)
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- Influence of chlorine on the catalytic properties of supported rhodium, iridium and platinum in ring opening of naphthenes
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Pt, Ir and Rh were deposited on SiO2 or Al2O 3 using chlorinated precursors and various amounts of HCl in the impregnation medium. The Br?nsted and Lewis acidities increased with the chlorine content of the alumina supported catalysts. The silica-supported catalysts only presented Lewis acid sites. The catalysts were evaluated in methylcyclopentane (MCP) and methylcyclohexane (MCH) ring-opening (RO) under pressure (2.85 and 3.95 MPa, respectively), from 200 to 425 C. For MCP conversion, the acidity of the alumina support had no sensitive effect on the activity and selectivity to RO products, and few effects on the distribution of RO products. No isomerization or hydrocracking products were observed, confirming that these reactions occurred mainly on the metal function, which was not modified by the presence of chlorine. The nature of the support, SiO 2 or Al2O3, had a strong effect on both the activity (1.9 against 0.5 mol h-1 g-1metal for Ir/Al2O3 and Ir/SiO2, respectively at 225 C) and selectivity to RO products (99.6% against 97.5% for Ir/Al2O 3 and Ir/SiO2, respectively, at 80% of MCP conversion) for Ir catalysts only. Interestingly, the Rh/SiO2 exhibited a high selectivity for converting MCP to RO products, similar to Ir/Al 2O3, i.e. 99.6% at 80% of conversion. Depending on the metal and the supports, three types of behavior were observed for MCH ring-opening: (i) a direct ring-opening on the metal function whatever the support for Ir, (ii) a first step of isomerization, and then a need of a sufficiently acidic support, for Pt and (iii) an intermediate behavior for Rh, which was able to either directly convert MCH in absence of acidic support or favor a bifunctional mechanism on chlorinated alumina.
- Samoila,Epron,Marécot,Especel
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p. 207 - 219
(2013/07/26)
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- Hydrocarbon separation
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Process for the separation of close boiling compounds comprising distilling a hydrocarbon mixture of said compounds in the presence of a high boiling diluent liquid and a solid adsorbent. The high boiling diluent is withdrawn from the bottom of the distillation column and recycled to the column. The process is particularly suitable for the separation of straight-chain isomers from isomerate mixtures, the separation of benzene from hydrocarbon mixtures and the separation of paraffins from olefins.
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Page/Page column 11
(2008/12/06)
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- Process for the preparation of a paraffin isomerization catalyst
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A process for preparation of a paraffin isomerization catalyst comprising a mixture of a Group IVB metal oxide, a Group VIB metal oxide, a Group IIIA metal oxide and a Group VIII metal. The process includes the steps of: a) contacting a hydroxide of the Group IVB metal with an aqueous solution of an oxyanion of the Group VIB metal to provide a mixture, (b) drying the mixture to provide a dry powder, (c) kneading the powder with a Group IIIA hydroxide gel and a polymeric cellulose ether compound to form a paste, (d) shaping the paste to form a shaped material, (e) calcining the shaped material to form a calcined material, (f) impregnating the calcined material with an aqueous solution of a Group VIII metal salt to provide the catalyst, and (g) calcining the catalyst.
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Page/Page column 4-5
(2008/06/13)
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- Isomerization of N-heptane in naphtha cuts
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A process for the isomerization of normal heptane contained within a naphtha stream, such as a C6-C8 naphtha, in which the naphtha stream is fractionated into a fraction substantially free of normal heptane and a fraction containing normal heptane. The fraction containing normal heptane is contacted with an isomerization catalyst in an isomerization zone operated as a singe pass fixed bed reactor having a single effluent to isomerize a portion of said normal heptane to branched heptane. The effluent is recovered from said isomerization zone and the effluent is fractionated to recover said branched heptane. The unconverted normal heptane is recovered and returned to the isomerization since it can be separated from the branded heptanes by fractionation.
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Page/Page column 4
(2008/06/13)
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- Alkane metathesis catalyzed by a well-defined silica-supported Mo imido alkylidene complex: [(≡SiO)Mo(=NAr)(=CHtBu)(CH2tBu)]
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A two-functions-in-one catalyst precursor allows an olefin metathesis catalyst to be turned into an alkane metathesis catalyst. A silica-supported alkyl alkylidene molybdenum complex containing an ancillary imido ligand is a highly active olefin metathesis catalyst and also acts as a catalyst precursor for alkane metathesis. This system involves a single metal with dual properties and shows that ancillary ligands are compatible with alkane metathesis reactions. (Chemical Equation Presented).
- Blanc, Frederic,Coperet, Christophe,Thivolle-Cazat, Jean,Basset, Jean-Marie
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p. 6201 - 6203
(2007/10/03)
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- C7+ paraffin isomerisation process and catalyst therefore
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There is provided a process for selective isomerisation of C4+ paraffins using a catalyst comprising mixed aluminium, tungsten and zirconium oxides, and a hydrogenation/dehydrogenation component, such as palladium or other Group VIII metals. The feed may optionally also include shorter paraffins, aromatics or cycloparaffins.
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- Process of paraffin hydrocarbon isomerisation catalysed by an ionic liquid in the presence of a cyclic hydrocarbon addditive
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A process for the conversion of linear and/or branched paraffins hydrocarbons, catalysed by an ionic liquid catalyst, in the presence of a cyclic hydrocarbon additive containing a tertiary carbon atom. The presence of the specific hydrocarbon additives influences the reaction mechanism by increasing the selectivity towards the formation of paraffin hydrocarbons with a higher degree of branching.
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- Isomerization catalyst and processes
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A catalyst and process is disclosed to selectively upgrade a paraffinic feedstock to obtain an isoparaffin-rich product for blending into gasoline. The catalyst comprises a support of a tungstated oxide or hydroxide of a Group IVB (IUPAC 4) metal, a first component of at least one lanthanide element, yttrium or mixtures thereof, which is preferably ytterbium or holmium, and at least one platinum-group metal component which is preferably platinum.
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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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- Gas to liquid conversion process
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A process is disclosed for the conversion of lower molecular weight hydrocarbons, such as methane, into higher molecular weight hydrocarbon products, such as hydrocarbons having between 4 and 29 carbons. The process includes forming hydrated electrons, such as by mixing the lower molecular weight hydrocarbons with water and contacting the mixture with an energy source to form hydrated electrons. The hydrated electrons react with the methane to form hydrogen and higher molecular weight hydrocarbon products. Also disclosed is a related process for converting higher molecular weight hydrocarbons to lower molecular weight hydrocarbons by forming a mixture of higher molecular weight hydrocarbons and water and contacting the mixture with an energy source to form hydrated electrons that react with the higher molecular weight hydrocarbons to form hydrogen and lower molecular weight hydrocarbon products.
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Page column 3-4
(2008/06/13)
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- Isomerization of n-Heptane over Pd-Loaded Silico-Alumino-Phosphate Molecular Sieves
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Isomerization of n-heptane was studied on a series of bifunctional SAPO-based catalysts with contents of 0.1 wtpercent Pd.From results on temperature programmed desorption of NH3 it is deduced that the different molecular sieve structures contain nearly identical amounts of silicon substituting for phosphorus in the framework (0.3 to 0.5 silicon atoms per unit cell).Best activities and selectivities for branched heptane isomers are achieved with SAPO-11 and SAPO-31.SAPO-17 and SAPO-5 show substantially lower activities.With SAPO-5, there is a high cracking selectivity which is assumed to be caused by the reduced accessibility of parts of the bridged hydroxyl groups within the molecular sieve framework.Different locations of these acid sites are evidenced by infrared OH vibration spectra recorded after adsorption of n-heptane.
- Parlitz, B.,Schreier, E.,Zubowa, H. -L.,Eckelt, R.,Lieske, E.,et al.
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- Reaction Mechanisms of Isomerization and Cracking of Heptane on Pd/H-Beta Zeolite
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Tha vapor-phase isomerization and cracking of heptane on H-Beta zeolites loaded with various amounts of Pd metal has been studied at a temperature of 505 K and at a total pressure of 0,3 MPa.The cracking of heptane is interpreted as a combination of classic bifunctional hydrocracking and dimerization cracking.The isomerization of heptane proceeds through the classic-bifunctional mechanism and a second mechanism involving dimerization cracking.The contribution of the different mechanisms to the izomerization and cracking is derived from the formation of specific reaction products.The contribution of the different mechanisms is dependent on the Pd content of the zeolite.
- Blomsma, E.,Martens, J. A.,Jacobs, P. A.
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p. 141 - 147
(2007/10/03)
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- Hydrogenolysis and Homologation of 3,3-Dimethyl-1-butene on Ru/SiO2 Catalyst: Implications for the Mechanism of Carbon-Carbon Bond Formation and Cleavage on Metal Surfaces
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The reactions of 3,3-dimethyl-1-butene (neohexene) with hydrogen in the presence of zero-valent ruthenium metal particles supported on silica are reported.The predominant reaction is the hydrogenation of neohexene to neohexane.Simultaneous but slower homologation and hydrogenolysis reactions are reported.The homologation and hydrogenolysis reactions run at approximately equal rates, suggesting a mechanistic link between the two processes.The relative quantities of C1-C5 and C7 products and the variation of these quantities with respect to varying temperature, neohexene/ hydrogen ratio, and contact time are reported.The distribution of the primary products, neopentane, isobutene, and methane for hydrogenolysis and 2,2-dimethyl pentane, 2,2,3-trimethyl butane, and 4,4-dimethyl-1-pentene for homologation is discussed in terms of current thought on the mechanism of homologation and hydrogenolysis of alkanes.The most likely and strongly indicated mechanism for the hydrogenolysis of neohexene involves the deinsertion of a methylidene fragment from a ruthenium-neohexyl intermediate which is also an intermediate in the hydrogenation of neohexene.The distribution of C7 homologation products does not allow one to distinguish between a simple insertion mechanism and a mechanism passing through a metallacyclic intermediate.
- Toyir, Jamil,Leconte, Michel,Niccolai, Gerald P.,Basset, Jean-Marie
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p. 306 - 312
(2007/10/02)
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- Reactions of 1,1,3,3-Tetramethylcyclobutane on Evaporated Metal Films
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Reactions of 1,1,3,3-tetramethylcyclobutane (TMCB)-hydrogen mixtures on evaporated metal films have shown that both ring scission to 2,2,4-trimethylpentane (TMP) and ring enlargement to 1,1,3-trimethylcyclopentane (TMCP) are dominant on sintered platinum films, while ring scission to TMP predominates on sintered palladium and on unsintered molybdenum films.Unsintered tantalum and molybdenum films gave a large production of iC4 hydrocarbon, particularly above ca. 500 K: ring enlargement was a minor reaction found particularly with tantalum.The homogeneous reaction of TMCB giving a large iC4 production sets in at 600 K.The possibility, suggested by the product distribution, that the reaction of TMCB on Mo and Ta is a metal-assisted free-radical reaction is examined.While it may not be completely excluded that the catalysed ring enlargement on Pt and Pd is a free-radical reaction it is argued that only the previously proposed Rooney-Samman bond-shift mechanism accommodates without added qualifications published facts on bond shifts, including those at quaternary carbon atoms, and also ring enlargements.
- Clarke, John K. A.,Hegarty, Bernard F.,Rooney, John J.
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p. 2511 - 2518
(2007/10/02)
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- IONIC METHYLATION OF DICHLORO- AND DIBROMOALKANES
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The dichloro and dibromo derivatives of hydrocarbons are methylated by the action of tetramethylsilane in the presence of aluminum bromide with the formation of hydrocarbons containing a quaternary carbon atom irrespective of whether the halogen atoms are at one or at different carbon atoms.
- Parnes, Z. N.,Romanova, V. S.,Vol'pin, M. E.
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p. 258 - 260
(2007/10/02)
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- Activite catalytique du superacide SbF5-HF lors de l'isomerisation de l'heptane
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The isomerization of n-heptane in the presence of the superacid SbF5-HF can be carried out by control of operating conditions.The rate-determining step of the isomerization of n-heptane is the intramolecular hydride-ion transfer, whereas it is the carbocation rearrangement in the case of the formation of the dimethyl-2,2-pentyle ion which is the forerunner of the cracking products.The rate constant of n-heptane isomerization is used to determine the influence of temperature, SbF5 concentration, hydrogen pressure, presence of benzene, on catalytic activity.This depends directly on the carbocations concentrations, especially high because of cracking, and on the nature, secondary or tertiary of these carbocations.
- Bassir, Mahbod,Torck, Bernard,Hellin, Michel
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p. 760 - 766
(2007/10/02)
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- Two-stage Reduction of Carbon Dioxide by Hydrogen in a Discharge and in the Presence of a Cobalt-Zirconium Catalyst Deposited on Kieselguhr
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The reduction of carbon dioxide by hydrogen has been investigated in a circulation system at a pressure of 1066 GPa, for discharge parameters of 1.9 kV and 150 mA, and at a temperature of 190 to 195 deg C in the catalytic reactor.The overall rate of the reaction was determined by the rate of its catalytic stage; for a contact time between the gas and the catalyst shorter than 3 s, the reaction is displaced towards the formation of paraffinic hydrocarbons.The qualitative and quantitative compositions of the liquid phase depended on its condensation conditions.At positive condensation temperatures, a condensate with relatively heavy components was obtained, up to 60-80percent of which consisted of C9H20-C12 H26 hydrocarbons.Their predominance in the condensate can be explained by secondary reactions on the catalyst involving relatively light saturated hydrocarbons.
- Eremin, E. N.,Rubstsova, E. A.,Ivanter, V. I.,Belova, V. M.
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p. 1722 - 1724
(2007/10/02)
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- Hydrogenolysis of Alkanes with Quaternary Carbon Atoms over Pt and Ni Black Catalysts
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Hydrogenolysis of hydrocarbons with quaternary C atoms (neopentane, neohexane, 2,2,3-trimethylbutane, 2,2- and 3,3-dimethylpentanes and 2,2,3,3-tetramethylbutane) has been studied over Pt and Ni black catalysts.The reactivities of different types of C-C bond have been determined.The probability of C-C bond rupture where one of the carbon atoms is quaternary is inversely proportional to the bond dissociation energy.On Pt, two essential types of hydrogenolysis can be distinguished.One reaction is responsible for the breaking of internal C-C bonds attached to the quaternary carbon atom and the other for demethylation.With larger molecules, the former reaction is preferred and the surface intermediate should be 1,4-diadsorbed, while that for the latter reaction is 1,3-diadsorbed.Nickel, as previously suggested, causes terminal C-C rupture, although with branched hydrocarbon reactants internal C-C bond rupture is also possible, presumably via 1,4-adsorption.
- Zimmer, Helga,Tetenyi, Pal,Paal, Zoltan
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p. 3573 - 3586
(2007/10/02)
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- CYCLIZATION OF C7-ALKANES OVER Pt BLACK CATALYST
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C6-and C5-cyclization of heptane isomers (and also, olefin formation as a related process) over Pt-black have been studied in pulse and circulation systems.Hydrogendeficient conditions favour aromatization, via presumably terminal olefins.C5-Cyclization in the presence of more hydrogen is accompanied by internal olefin formation.Relative reactivities of all heptane isomers have been measured; this shows that cyclization is easier between terminal methyl groups.Optimum hydrogen pressures for both types of cyclization have been determined (and compared with hydrogenolysis, too).Earlier mechanism suggestion for aromatization and cyclopentane formation have been confirmed; the distinction between two types of bond shift mechanisms producing aromatics (from substituted pentanes) and saturated isomers, respectively, has recieved additional support facilitating the identification of these two reactions with mechanisms proposed in the literature.
- Zimmer, H.,Paal, Z.,Tetenyi, P.
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p. 513 - 532
(2007/10/02)
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- Direct Geminal Dimethylation of Ketones using Dimethyltitanium Dichloride
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Ketones are readily converted into the corresponding geminal dimethyl derivatives on reaction with dimethyltitanium dichloride under mild conditions; tertiary alcohols react similarly.
- Reetz, Manfred T.,Westermann, Juergen,Steinbach, Rainer
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p. 237 - 239
(2007/10/02)
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