- 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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- GAS-TO-LIQUID REACTOR AND METHOD OF USING
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A device and a process to propagate molecular growth of hydrocarbons, either straight or branched chain structures, that naturally occur in the gas phase to a molecular size sufficient to shift the natural occurring phase to a liquid or solid state is provided. According to one embodiment, the device includes a grounded reactor vessel having a gas inlet, a liquid outlet, and an electrode within the vessel; a power supply coupled to the electrode for creating an elecirostatic field within the vessel for converting the gas to a liquid and or solid state.
- -
-
Paragraph 0140-0142
(2019/08/15)
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- Production of Gasoline Fuel from Alga-Derived Botryococcene by Hydrogenolysis over Ceria-Supported Ruthenium Catalyst
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Hydrogenolysis of hydrogenated botryococcene (Hy-Bot) was conducted over various supported Ru catalysts, Ir/SiO2, and Pt/SiO2–Al2O3. Ru/CeO2 with very high dispersion showed the highest yield (70 %) of gasoline-range (C5–C12) alkanes at 513 K. The main gasoline-range products were dimethylalkanes. This yield is comparable to or higher than the gasoline yields from botryococcene in the literature, which were obtained at much higher temperature. Ir/SiO2 also showed a high fuel yield, but the activity was much lower than that with the Ru catalysts. The reaction over Pt/SiO2–Al2O3 slowed down before total conversion of Hy-Bot was achieved. Ru/CeO2 was stable in the hydrogenolysis of Hy-Bot without loss of activity and selectivity during reuses. The carbon balance was low for the hydrogenolysis of Hy-Bot over all catalysts if the main products are heavy hydrocarbons, whereas for the hydrogenolysis of squalane the carbon balance was kept near 100 %. 1H NMR spectra of the product mixture and thermogravimetric analyses of the product mixture and the recovered catalyst revealed that the formation of aromatic compounds, polymeric products, and coke was negligible for the carbon balance. In a model reaction using substrate compounds with a substructure of Hy-Bot, only 2,5-dimethylhexane, which has a C6 chain with two Cprimary?Ctertiary bonds, produced a cyclic product, 1,4-dimethylcyclohexane, which has a higher boiling point than the substrate. This dehydrocyclization reaction makes the product distribution in the hydrogenolysis of Hy-Bot more complex.
- Nakaji, Yosuke,Oya, Shin-Ichi,Watanabe, Hideo,Watanabe, Makoto M.,Nakagawa, Yoshinao,Tamura, Masazumi,Tomishige, Keiichi
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p. 2701 - 2708
(2017/07/28)
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- PROCESS OF MAKING OLEFINS OR ALKYLATE BY REACTION OF METHANOL AND/OR DME OR BY REACTION OF METHANOL AND/OR DME AND BUTANE
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Methods of simultaneously converting butanes and methanol to olefins over Ti-containing zeolite catalysts are described. The exothermicity of the alcohols to olefins reaction is matched by endothermicity of dehydrogenation reaction of butane(s) to light olefins resulting in a thermo- neutral process. The Ti-containing zeolites provide excellent selectivity to light olefins as well as exceptionally high hydrothermal stability. The coupled reaction may advantageously be conducted in a staged reactor with methanol/DME conversion zones alternating with zones for butane(s) dehydrogenation. The resulting light olefins can then be reacted with iso-butane to produce high-octane alkylate. The net result is a highly efficient and low cost method for converting methanol and butanes to alkylate.
- -
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Page/Page column 15; 25; 26; 31; 32
(2017/05/10)
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- Influence of the Br?nsted acidity, SiO2/Al 2O3 ratio and Rh-Pd content on the ring opening. Part II. Selective ring opening of methylcyclohexane
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Monometallic and bimetallic Pd-Rh catalysts with various Rh/Pd atomic ratios (=0.5, 1 and 2) and a total metal charge of 1 wt% supported on SiO 2-Al2O3 (SIRAL 40, 20, 5) were studied for the ring opening of methylcyclohexane (MCH). The results were compared with those obtained previously for ring opening of decalin. It was found that the total acidity and the Br?nsted acidity of the support have a higher influence on the activity for ring opening of naphthenic bicycles than on the activity for opening single rings. The influence of the metal charge is more important on the reaction of MCH. All the catalysts display a high MCH conversion, which increases with the reaction temperature. The bimetallic catalyst with the Rh/Pd ratio equal to 2 and supported on SIRAL 40 has the highest yield to ring opening products.
- D'Ippolito, Silvana A.,Especel, Catherine,Vivier, Laurence,Epron, Florence,Pieck, Carlos L.
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p. 541 - 549
(2014/01/06)
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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
-
p. 207 - 219
(2013/07/26)
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- Ring opening of decalin and methylcyclohexane over alumina-based monofunctional WO3/Al2O3 and Ir/Al 2O3 catalysts
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Ring-opening reactions of decalin and MCH were studied over monofunctional acid (WO3/Al2O3) and metal (Ir/Al 2O3) catalysts containing, respectively, up to 5.3 at. W/nm2 and 1.8 wt% Ir. The catalysts were characterized by X-ray diffraction, Raman spectroscopy, low-temperature CO adsorption followed by infrared spectroscopy, and H2 chemisorption. A reaction network was proposed for both molecules and used to determine the kinetic parameters. Kinetic modeling allowed relating characterization results and catalytic performance. For WO3/Al2O3 catalysts, ring contraction precedes ring opening of both molecules. The evolution of ring contraction activity was consistent with the development of relatively strong Bronsted acid sites. Ring opening occurs according to a classic acid mechanism. For Ir/Al2O3 catalysts, only direct ring opening was observed. Ring opening proceeds mostly via dicarbene mechanism. Analysis of products indicated that monofunctional metal catalysts are better suited than acid solids for upgrading LCO.
- Moraes, Rodrigo,Thomas, Karine,Thomas, Sebastien,Van Donk, Sander,Grasso, Giacomo,Gilson, Jean-Pierre,Houalla, Marwan
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scheme or table
p. 62 - 77
(2012/03/11)
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- PROCESS FOR THE PRODUCTION OF A HYDROCARBON
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A method of alkane homologation is provided, comprising contacting: a reactive alkane; a methylating agent; an optional diamondoid modifier; and an activating catalyst, thereby generating a hydrocarbon product having a greater number of carbon atoms than the reactive alkane.
- -
-
Page/Page column 27-28
(2009/06/27)
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- Activation and isomerization of hydrocarbons over WO3/ZrO2 catalysts. II. Influence of tungsten loading on catalytic activity: Mechanistic studies and correlation with surface reducibility and tungsten surface species
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We studied the correlation among the catalytic behavior of WO3/ZrO2 samples toward unsaturated and saturated hydrocarbons transformation, tungsten surface species oxidation states, and the crystallographic structure of the zirconia support. Different tungsten-loaded catalysts were studied, from 9 wt% (near-monolayer coverage) to 30 wt%. The resulting WO3/ZrO2 materials were obtained by impregnation of a tungsten salt on either a commercially available monoclinic zirconia or an amorphous hydroxide, ZrOx(OH)4-2x, followed by a calcination step (according to the Hino and Arata procedure), leading to a tetragonal structure. In contrast to previous works, here we demonstrate that the crystallographic structure of zirconia has no influence on catalytic properties. Correlations with XPS analyses revealed two aspects of catalytic behavior that depend strongly on the catalyst reducibility and thus on the W surface species oxidation states. First, on hardly reducible (tungsten loadings a purely acidic monomolecular mechanism for both isomerization (largely predominant) and cracking reactions, associated with W6+ and W5+ surface species, was demonstrated. Second, on easily reducible (tungsten loadings >15 wt%) or deeply reduced (over 723 K) surfaces, a bifunctional mechanism associating dehydrogenating/hydrogenating properties occurring on metallic tungsten and acidic isomerization and cracking on W5+ and W6+ surface species was observed. However, in this last case, we could not exclude the participation of a purely metallic isomerization mechanism occurring through σ-alkyl adsorbed species on the β-W metallic phase. A more pronounced reduction then led to an increase in the extensive hydrogenolysis mechanism, causing catalyst deactivation.
- Di Gregorio, Francois,Keller, Nicolas,Keller, Valerie
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p. 159 - 171
(2008/09/21)
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- PROCESS FOR THE PRODUCTION OF A HYDROCARBON
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A process for the production of a hydrocarbon which comprises contacting, in a reactor, methanol and/or dimethyl ether with a catalyst comprising a metal halide, such as a zinc halide, in which the methanol and/or dimethyl ether is contacted with the catalyst in the presence of at least one phosphorus compound having at least one P-H bond.
- -
-
Page/Page column 19-20; 25-26
(2008/06/13)
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- Selective methylative homologation: An alternate route to alkane upgrading
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InI3 catalyzes the reaction of branched alkanes with methanol to produce heavier and more highly branched alkanes, which are more valuable fuels. The reaction of 2,3-dimethylbutane with methanol in the presence of InI3 at 180-200°C affords the maximally branched C7 alkane, 2,2,3-trimethylbutane (triptane). With the addition of catalytic amounts of adamantane the selectivity of this transformation can be increased up to 60%. The lighter branched alkanes isobutane and isopentane also react with methanol to generate triptane, while 2-methylpentane is converted into 2,3-dimethylpentane and other more highly branched species. Observations implicate a chain mechanism in which InI3 activates branched alkanes to produce tertiary carbocations which are in equilibrium with olefins. The latter react with a methylating species generated from methanol and InI 3 to give the next-higher carbocation, which accepts a hydride from the starting alkane to form the homologated alkane and regenerate the original carbocation. Adamantane functions as a hydride transfer agent and thus helps to minimize competing side reactions, such as isomerization and cracking, that are detrimental to selectivity.
- Bercaw, John E.,Hazari, Nilay,Labinger, Jay A.,Scott, Valerie J.,Sunley, Glenn J.
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scheme or table
p. 11988 - 11995
(2009/02/05)
-
- Hydrocarbon separation
-
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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- 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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- Paraffin alkylation
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A liquid acid process is disclosed in which a hydrocarbon component containing an olefin, an olefin precursor or mixture and an isoalkane and a liquid acid catalyst is fed to a downflow reaction zone containing a disperser, under conditions to induce pulse flow at or near the outlet to react the isoalkane and olefin to produce a reaction product and feeding the reaction product to a vaporization zone containing a disperser under conditions to induce pulse flow at or near the outlet of the vaporization zone. A pressure drop across the disperser in the vaporization zone causes partial vaporization of the hydrocarbon which quench es the heat reaction and cooling the unvaporized portion of said reaction product, which is recovered and allowed to separate into an acid phase and hydrocarbon phase containing the alkylate. The acid catalyst and hydrocarbons may be fractally fed to the reaction zone.
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Page/Page column 7
(2008/06/13)
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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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- ESTER SYNTHESIS
-
Process for making lower aliphatic ester, especially ethyl acetate, by reacting a lower olefin with a saturated lower aliphatic mono-carboxylic acid in the vapor phase using a heteropolyacid catalyst, wherein the reaction pressure is 11 to 20 barg (1100 to 2000 KPa), more preferably 12 to 15 barg (1200 to 1500 KPa). The reaction temperature is 140 to 250°C, more preferably 160 to 195°C. The process reduces the level of by-products, for example methyl ethyl ketone and/or acetaldehyde.
- -
-
Page/Page column 8-11
(2008/06/13)
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- SYSTEM AND METHOD FOR PURIFYING HEPTANE
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Removing impurities from a heptane stream by contacting the heptane stream with an acidic catalyst, wherein the contacting reduces a concentration of one or more close boiling impurities, one or more olefins, or both. The impurities are isomerized via contact with the acidic catalyst into species that possess lower octane levels or that do not possess boiling points as near to the boiling point of n-heptane, which promotes separation of the impurities via distillation. Close boiling impurities may include such compounds as cis-1,2-dimethylcyclopentane and methylcyclohexane or may be compounds having boiling points at a standard pressure of 760 Torr in the range of about 96.5 to about 100.5 degrees Celsius including such compounds as cis-1,2-dimethylcyclopentane and methylcyclohexane. The concentration of cis-1,2-dimethylcyclopentane and methylcyclohexane may be reduced by at least about 25 and 10 percent by weight, respectively. The concentration of olefins, as measured by the Bromine Index, may be reduced by at least about 25 percent by weight.
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Page/Page column 26-31
(2008/06/13)
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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.
- -
-
-
- Process of paraffin hydrocarbon isomerisation catalysed by an ionic liquid in the presence of a cyclic hydrocarbon addditive
-
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.
- -
-
-
- 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.
- -
-
-
- Catalyst and process for contacting a hydrocarbon and ethylene
-
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.
- -
-
-
- Process of paraffin hydrocarbon isomerisation catalysed by an ionic liquid in the presence of a cyclic hydrocarbon additive
-
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.
- -
-
-
- 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.
-
-
- 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.
-
p. 141 - 147
(2007/10/03)
-
- HYDROCONVERSION OF HEPTANE CATALYZED BY SULFIDED NiMo/HY ZEOLITES
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A series of catalysts made of Ni, Mo and NiMo sulfide encaged in HY zeolites (Si/Al = 3 to 17) were tested for the hydroconversion of heptane.The reaction was carried out at P(H2) = 8 MPa and with a constant supply of H2S.Propane and isobutane were the main products, but bimolecular cracking processes occurred to some extent.The yield of heptane isomers was low, showing a deficient hydrogenation function.The influence of the Si/Al ratio upon catalytic activity and selectivity was examined.
- Leglise, Jacques,Qotbi, Mohammed El,Cornet, Daniel
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p. 882 - 895
(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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- 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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- L'isomerisation de radicaux insatures. II. Les radicaux α-ethallyles et α,γ-dimethallyles formes dans la photolyse de l'hexene-3 et du methyl-4-pentene-2 a 147,0 et 184,9 nm
-
The photolysis of cis-3-hexene and 4-methyl-cis-2-pentene has been studied at 147.0 and 184.9 nm.The fragmentation pattern of the photoexcited molecule is normal: it requires, mainly , the split of a C-C bond located in the β position relative to the double bond (ca. 80percent).Some α(C-C), β(C-H), and α(C-H) primary splits complete this mechanism.The formation of α-ethallyl and α,γ-dimethallyl radicals is improtant in 3-hexene and 4-methyl-2-pentene, respectively.An isomerization process, involving these two radicals, is necessary to explaine the formation of part of the 1,3-pentadiene in the 3-hexene system and of all the 1,3-butadiene in the 4-methyl-2-pentene system.This process involves a 1,4-hydrogen atom transfer.
- Collin, Guy J.,Deslauriers, Helene
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p. 944 - 950
(2007/10/02)
-
- Mecanisme de l'alkylation de l'isobutane par le propene sur zeolithe. I. Etudes preliminaires de la selectivite de la reaction
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Alkylation of isobutane by propylene has been studied at 70 and 80 deg C and 10 atm. of pressure over a cerium exchanged Y zeolite.Under these conditions large amounts of olefin are converted into adsorbed residues and C5-C9 isoalkanes (alkylate) are formed.Maximum alkylate yields are observed after 12 hours and become negligible after 24 hours.The main products result from alkylation, dimerization, self-alkylation and cracking reactions followed by hydride transfer.Catalyst poisonning is explained by the decrease of the zeolite cracking activity and dehydrogenation of the adsorbed species.
- Daage, Michel,Fajula, Francois
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p. 153 - 159
(2007/10/02)
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- Mecanisme de l'alkylation de l'isobutane par le propene sur zeolithe II. Etude des etapes elementaires de la reaction a l'aide de molecules marquees au carbone-13
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The mechanisms involved during the alkylation of isobutane by propene have been studied using carbon-13 labelled molecules.Several parallel reactions can lead to a same hydrocarbon.The carbon-13 distributions and structures of all the products can be explained by bimolecular processes between a limited number of species.These species are C3 and C4 olefins and ions and strongly adsorbed residues in which the tracer atoms lie in definite positions.
- Daage, Michel,Fajula, Francois
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p. 160 - 168
(2007/10/02)
-
- Thermolabile Hydrocarbons, XXI. Relationships between Thermal Stability and Strain of Non-Symmetrical Highly Branched Hydrocarbons
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The pyrolysis reaction of 20 hydrocarbons 3 into radicals 4 and tert-butyl radicals was investigated by product analysis and kinetics.It is shown that the same relationships between the free enthalpies of activation and the strain energies observed earlier for the cleavage of symmetrically substituted CC bonds are valid for the cleavage of unsymmetrical substituted bonds.The introduction of the new concept "strain energy of dissociation" (difference in strain between the ground state 3 and the residual strain in the radical fragments 4 and 5) has proven to be particularly useful.It is now possible to predict the rate of homolytic cleavage of almost all simple CC bonds by force field calculations.
- Hellmann, Siegried,Beckhaus, Hans-Dieter,Ruechardt, Christoph
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p. 2238 - 2249
(2007/10/02)
-
- 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)
-
- Mechanism of Isomerization of Hydrocarbons on Metals. Part 11.-Isomerization and Dehydrocyclization of (13)C-labelled 3-Methylhexanes on Pt-Al2O3 Catalysts
-
The isomerization, dehydrocyclization and hydrogenolysis of 3-methylhexane have been studied at 320-380 deg C over a series of Pt-Al2O3 catalysts with a metal dispersion extending from 0.05 to 1.The use of five labelled compounds, 3-methyl(1-(13)C), (2-(13)C), (3-(13)C), (6-(13)C)hexanes and 3-methyl((13)C)hexane, alloved distinction between the various parallel pathways.On all catalysts the predominant reaction was the isomerization according to a cyclic mechanism involving either 1,3-dimethyl-, 1,2-dimethyl- or ethyl-cyclopentane intermediates with a relative contribution of 60, 40 and 20 percent, respectively.These results are consistent wiith a dehydrocyclization scheme involving a metallocarbene as precursor and dicarbene or dicarbyne recombination as the rate-determining step.
- Amir-Ebrahimi, Valia,Gault, Francois G.
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p. 1735 - 1756
(2007/10/02)
-
