- Tert-amyl methyl ether (TAME). Thermodynamic analysis of reaction equilibria in the liquid phase
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Ethers obtained from C5 olefin streams provide a good mix of octane-enhancing and CO-reducing qualities. They are considered as a replacement for the more common isobutylene-derived fuel additives, e.g., MTBE. Data on the thermodynamic reaction equilibria for the synthesis of TAME, which is produced from the etherification reaction of 2-methyl-1-butylene and 2-methyl-2-butylene with methanol, were computed by studying TAME decomposition in a recirculating batch reactor at different temperatures with activity coefficients obtained using the UNIFAC method. A comparison of experimental data and theoretical predictions showed the possibility of erroneous values reported in the literature for the standard Gibbs free energy of TAME formation. Expressions for the thermodynamic equilibrium constants as a function of temperature were developed. A corrected value for the Gibbs free energy of formation for TAME was also provided.
- Datta,Egleston,Syed
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- Polysulfones: Catalysts for alkene isomerization
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A radical intermediate is generated when methylidenecyclopentane (1) is isomerized by SO2 into 1-methylcyclopentene (3) through the formation of a polysulfone polymer (PS), which first abstracts a hydrogen atom from the alkene. The allyl radical intermediate 2 abstracts a hydrogen atom from another alkene molecule 1, to yield the isomerized alkene and regenerating the allyl radical. Polysulfones are organic catalysts.
- Markovic, Dean,Vogel, Pierre
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- Reactions of Propene and Cyclopropane Radical Cations with Neutral Ethylene
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The gas-phase reactions of propene and cyclopropane radical cations with neutral ethylene were investigated by using Fourier transform, chemical ionization and tandem mass spectrometries.Both reactions form covalent C5H10 adduct ions.The adduct ions are hypothesized to form initially as distonic radical cations that isomerize via a substituted cyclopropane intermediate and are detected as the most stable C5H10 isomer, the 2-methylbut-2-ene radical cation.The rate constant for each reaction is approximately 20percent of the theoretically collision rate, indicating that product ions are formed in one out of every five collisions of the C3H6 radical cationcs with neutral C2H4.
- Vollmer, D. L.,Gross, M. L.
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- Novel synthesis of isoprene from 3-methylbutan-2-one using phosphate catalysts
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AlPO4 and BPO4 catalyse the conversion of 3-methylbutan-2-one to isoprene in high yields via 2-methylbut-2-en-1-ol as an intermediate.
- Hutchings, Graham J.,Hudson, Ian D.,Bethell, Donald,Timms, Don G.
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- Vapor-liquid and chemical reaction equilibria in the synthesis of 2-methoxy-2-methylbutane (TAME)
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The isobaric VLE data were measured for three binary mixtures, i.e., methanol/TAME, methanol/2-methyl-2-butene, and methanol/2-methylbutane at 101.3 kPa. Based on the experimental results, the binary parameters were adjusted for the Wilson method of activity coefficient estimation. Using the Wilson method, the reaction equilibrium constants were recalculated for the liquid-phase synthesis of TAME. All systems exhibited a positive deviation from ideality with a minimum-boiling-point azeotrope. The azeotropic boiling points and the mole fractions of the binary systems obtained in the experiments agreed well with the values found in the literature. The non-ideality was well described with the Wilson method, and the equilibrium constants remained more invariable than those calculated earlier with the UNIQUAC method. Based on the experimental reaction equilibrium, a value of -109.6 kJ/mole was presented for the Gibbs energy of formation for TAME in the gas phase at 298 K.
- Krause,Pavlov,Rihko-Struckmann,Linnekoski
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- Kinetics of the Thermal Isomerization of 1,1-Dimethylcyclopropane
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Rate constants for the unimolecular thermal isomerization of gaseous 1,1-dimethylcyclopropane to isomeric methylbutenes have been measured, and Arrhenius parameters determined, over a wide temperature range, 683 - 1132 K, using a single-pulse shock tube and a static reactor. For the overall reaction, Ea = 61.8 +/- 0.4 kcal/mol, and log10(A, s-1) = 15.04 +/- 0.10. These values are in good agreement with previously reported values obtained over a much narrower temperature range. Rate constants for formation of the two major products, 2-methylbut-2-ene and 3-methylbut-1-ene, are given by Ea = 61.9 kcal/mol, logA = 14.80 and Ea = 61.1 kcal/mol, logA = 14.54, respectively. A comparison of the activation parameters for structural isomerizations of cyclopropane, methylcyclopropane, and 1,1-dimethylcyclopropane confirms a trend toward lower activation energy values as hydrogen atoms in cyclopropane are replaced by CH3 groups.
- Kalra, Bansi L.,Lewis, David K.
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- Enthalpy of combustion and enthalpy of vaporization of 2-ethyl-2-methoxypropane and thermodynamics of its gas-phase synthesis from (methanol + a 2-methylbutene)
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Equilibrium constants the gas-phase synthesis reaction of 2-ethyl-2-methoxypropane (EMOP) from methanol and a 2-methylbutene have been found at the temperatures: 373 K, 399 K, and 413 K.The molar enthalpy of combustion was determined calorimetrically. ΔvapHmdeg(298.15 K) = (35.3 +/- 1.5) kJ * mol-1 and ΔfHmdeg(298.15 K, g) = -(305.4 +/- 1.8) kJ * mol-1 were found for EMOP both on the basis of the results obtained in the present work and literature values.
- Rozhnov, A. M.,Safronov, V. V.,Verevkin, S. P.,Sharonov, K. G.,Alenin, V. I.
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- Catalytic dehydrogenation of isopentane with iridium catalysts
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(Graph Presented) Activation by adding PPh3: The catalytic dehydrogenation of isopentane to give isopentene and hydrogen with iridium catalysts ona silica gel support at 450°C proceeds with impressive conversion whenthe support is impregnated w
- Alt, Helmut G.,Boehmer, Ingrid K.
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- Reaction Equilibria in the Synthesis of 2-Methoxy-2-methylbutane and 2-Ethoxy-2-methylbutane in the Liquid Phase
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Equilibrium constants for the liquid-phase synthesis of 2-methoxy-2-methylbutane (TAME) and 2-ethoxy-2-methylbutane (TAEE) were measured in the temperature range 323-363 K.The equilibria were studied using the alcohol/alkene mixture in various mole ratios and the respective ether as a reagent in a batch reactor.A commercial cation exchange resin (Amberlyst 16) was used as the catalyst.The system was strongly nonideal, and the UNIQUAC estimation method was used in the calculation of the liquid-phase activity coefficients.The experimental equilibrium constants are given as a function of temperature.At 333 K the equilibrium constants Ka for the synthesis of TAME were 39.6+/-2.5 from methanol and 2-methyl-1-butene (2M1B) and 4.1+/-0.3 from 2-methyl-2-butene (2M2B).The equilibrium constants for the synthesis of TAEE were 17.4+/-1.1 from ethanol and 2M1B and 1.7+/-0.1 from 2M2B.The experimental ΔrH values for the liquid-phase synthesis of TAME were -33.6+/-5.1 kJ*mol-1 (2M1B) and -26.8+/-2.3 kJ*mol-1 (2M2B), and those for the synthesis of TAEE were -35.2+/-5.8 kJ*mol-1 (2M1B) and -27.3+/-6.7 kJ*mol-1 (2M2B).The results were compared with the literature values.
- Rihko, Liisa K.,Linnekoski, Juha A.,Krause, A. Outi I.
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- Hexaruthenium carbido carbonyl methyl cluster as catalyst precursor for hydrogenation of olefins. Syntheses and structures of unsaturated and saturated hexaruthenium hydrido clusters and
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Cluster (2) has been found to be catalytic active for the hydrogenation and isomerization of olefins at 60 deg C after an induction period.Reaction of 2 or with dihydrogen at 130 deg C gives an unsaturated hydrido cluster (6), which behaves as the catalyst at ambient temperature.The structure of 6 has a carbon-centered octahedral geometry of ruthenium atoms which is surrounded by fifteen carbonyl ligands, two terminal ones for each ruthenium atom and three bridging ones, and a bridging hydrido ligand.Treatment of 6 with carbon monoxide yields a saturated hydrido cluster (5), which is also prepared by protonation of 2.X-ray analysis of 5 shows the cluster anion is disordered between two sites in the ratio of 8 to 2.The major one contains a carbon centered octahedron of six ruthenium atoms with two terminal carbonyl ligands for each ruthenium atom, with four bridging carbonyl ligands, and a terminal hydrido ligand. Key words: Ruthenium; Carbide; Carbonyl; Cluster; Catalyst precursor
- Chihara, T.,Yamazaki, H.
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- Isomerization of neopentyl chloride and neopentyl bromide by a 1,2-Interchange of a halogen atom and a methyl group
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The recombination of chloromethyl and t-butyl radicals at room temperature was used to generate neopentyl chloride molecules with 89 kcal mol-1 of internal energy. The observed unimolecular reactions, which give 2-methyl-2-butene and 2-methyl-1-butene plus HCl, as products, are explained by a mechanism that involves the interchange of a methyl group and the chlorine atom to yield 2-chloro-2-methylbutane, which subsequently eliminates hydrogen chloride by the usual four-centered mechanism to give the observed products. The interchange isomerization process is the rate-limiting step. Similar experiments were done with CD2Cl and C(CH3)3 radicals to measure the kinetic-isotope effect to help corroborate the proposed mechanism. Density functional theory was employed at the B3PW91/6-31G(d',p') level to verify the Cl/CH3 interchange mechanism and to characterize the interchange transition state. These calculations, which provide vibrational frequencies and moments of inertia of the molecule and transition state, were used to evaluate the statistical unimolecular rate constants. Matching the calculated and experimental rate constants, gave 62 ± 2 kcal mol -1 as the threshold energy for interchange of the Cl atom and a methyl group. The calculated models also were used to reinterpret the thermal unimolecular reactions of neopentyl chloride and neopentyl bromide. The previously assumed Wagner-Meerwein rearrangement mechanism for these reactions can be replaced by a mechanism that involves the interchange of the halogen atom and a methyl group followed by HCl or HBr elimination from 2-chloro- 2-methylbutane and 2-bromo-2-methylbutane. Electronic structure calculations also were done to find threshold energies for several related molecules, including 2-chloro-3,3-dimethylbutane, 1-chloro-2-methyl-2-phenylpropane, and 1-chloro-2-methyl-2-vinylpropane, to demonstrate the generality of the interchange reaction involving a methyl, or other hydrocarbon groups, and a chlorine atom. The interchange of a halogen atom and a methyl group located on adjacent carbon atoms can be viewed as an extension of the halogen atom interchange mechanisms that is common in 1,2-dihaloalkanes.
- Lisowski, Carmen E.,Duncan, Juliana R.,Ranieri, Anthony J.,Heard, George L.,Setser,Holmes, Bert E.
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- Sorption, acid, and catalytic properties of a sulfonic cation exchanger supported on the carbon fiber
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Distribution in strength of the acid centers in sulfonic cation in the form of exchanger granules and fibers was studied by the novel modification of the thermal desorption method.
- Egiazarov,Shachenkova,Radkevich,Cherches,Gorbatsevich,Ermolenko
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- Characterization of phenylene-bridged hybrid mesoporous materials incorporating arenetricarbonyl complexes (-C6H4Me(CO) 3-; Me = Cr, Mo) and their catalytic activities
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The successful construction of arenetricarbonyl complexes (-C 6H4Me(CO)3-; Me = Cr, Mo) was achieved through the direct modification of phenylene (-C6H4-) moieties of phenylene-bridged hybrid mesoporous materials (HMM-ph) by the simple chemical vapor deposition (CVD) of corresponding metal hexacarbonyls. The pore structure as well as high surface area of HMM-ph were retained even after CVD treatment. It was found that HMM-ph incorporating an arenetricarbonyl molybdenum complex (HMM-phMo(CO)3) exhibited higher catalytic performance for the polymerization of phenylacetylene and dehydrochlorination of 2-chloro-2-methylbutane than HMM-phCr(CO)3. Various spectroscopic investigations revealed that the strength of the chemical bond between the phenylene ligand and metal center of the arenetricarbonyl complexes affects the catalytic performance of HMM-phMe(CO)3 (Me = Cr, Mo).
- Kamegawa, Takashi,Saito, Masakazu,Sakai, Takahiro,Matsuoka, Masaya,Anpo, Masakazu
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- Homogeneous Unimolecular Gas-Phase Elimination Kinetics of 2-Chloro-2-alkylpropanes. The Electronic Effect of Alkyl Substituents on the α-Carbon of Tertiary Chlorides
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The pyrolysis kinetics of 2-chloro-2-methylbutane and 2-chloro-2,3-dimethylbutane have been investigated, in a static system and seasoned vessel, over the pressure range of 50-280 torr and the temperature range of 260-320 deg C.The reactions are homogeneous and unimolecular, follow a first-order law, and are invariable to the presence of a cyclohexene inhibitor.The temperature dependence of the rate coefficients is given by the following Arrhenius equations: for 2-chloro-2-methylbutane, logk1 (s-1)=(13.77 +/- 0.25)-(184.1 +/- 2.6) kJ mol-1 (2.303RT)-1; for 2-chloro-2,3-dimethylbutane, logk1(s-1)=(13.33 +/- 0.18)-(175.3 +/- 1.9) kJ mol-1 (2.303RT)-1.The distribution of the olefin products from these reactions has been quantitatively determined and reported in details.The alkyl series ((CH3)3C, (CH3)2CH, CH3CH2, CH3, and H) in the tertiary halides, 2-chloro-2-alkylpropanes, influence the rate of elimination by electronic effect.This is similar to those obtained with α- and β-alkyl-substituted ethyl chlorides.The plot of log k/k0 vs. ?*(R) gives a very good straight line with ρ*=-4.75, r=0.994, and intercept=0.048 at 300 deg C.The previous and present results reveal that, if a reaction center at the transition state of an organic molecule is markedly polar, the +I inductive electron release of alkyl substituents may affect gas-phase elimination processes.
- Chuchani, Gabriel,Martin, Ignacio
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- Investigations of the magnitude of steric and α deuterium kinetic isotope effects in a carbon-carbon bond-forming reaction of a permethylscandocene complex
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No measurable isotope effect is observed in the reaction of (Cp*-d15)2Sc-CH3 (1a, Cp* = η5-C5(CH3)5) with CD3CCCH3 to yield a mixture of (Cp*-d15)2Sc-C(CD3)C=C(CH3)2 (2a) and (Cp*-d15)2Sc-C(CH3)C=C(CH3)(CD3) (2b) (2b:2a = 1.01 +/- 0.02:1).Thus steric repulsions between the 2-butyne methyl group and the scandium-bound methyl group are not sufficiently severe to give rise to a measurable steric deuterium kinetic isotope effect.Similarly, 1a reacts with CH3CCCH3 at approximately the same rate as does (Cp*-d15)2Sc-CD3 (1b), producing a mixture of (Cp*-d15)2Sc-C(CH3)C=C(CH3)2 (2c) and (Cp*-d15)2Sc-C(CH3)C=C(CD3)(CH3) (2d) (k2c/k2d=1.02+/-0.07).The implication from the latter finding is that a 2-CH2-H)> α agostic interaction is likely not present in the transition state for 2-butyne insertion into the scandium methyl bond of 1.
- Cotter, W. Donald,Bercaw, John E.
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- Selectivity patterns in heterogeneously catalyzed hydrogenation of conjugated ene-yne and diene compounds
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Selectivity control in heterogeneously catalyzed hydrogenation of conjugated hydrocarbons (ene-yne and diene compounds) is a challenging task. Available studies on the topic mainly encircle 1,3-butadiene as the substrate and palladium as the catalyst, while more elaborated playground molecules and other metals remain largely unexplored. This study investigates the gas-phase hydrogenation of valylene (2-methyl-1-butene-3-yne) and isoprene (2-methyl-1,3-butadiene) over Pd, Pb-poisoned Pd, CO-modified Pd, Cu, Ni, and bimetallic CuNi catalysts. Chemoselectivity, regioselectivity, full hydrogenation, and CC bond formation/scission footprints of the catalytic systems at different inlet hydrogen-to-hydrocarbon ratios and conversion degrees have been rationalized. Complementary studies of 3-methylbutyne and 1-penten-4-yne hydrogenation were carried out in order to analyze (i) the impact of isomerization on the observed mono-olefin distribution in valylene/isoprene hydrogenation and (ii) the conjugation issue in partial ene-yne hydrogenation. Our results lead to an improved understanding of hydrogenation of polyunsaturated hydrocarbons and open doors to design more selective heterogeneous catalysts and related processes for this practically important class of reactions.
- Bridier, Blaise,Perez-Ramirez, Javier
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- A Novel Cationic Optically Active Complex of Platinum(II) Containing 2-Methyl-2-butene and o-Benzenediamine. The Circular Dichroism Spectrum and Kinetics of Olefin Exchange
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An optically active cationic olefin complex, B(C6H5)4 was obtained for the first time as crystal stable in air at room temperature.It deteriorates slightly in solution, but is still stable enough to be characterized.Comparison of its CD spectrum with that of related complexes disclosed that the coordinating atoms at the cis sites to the olefin have a dominant influence upon the CD pattern in the region 20000-35000 cm-1, as compared with those at the trans site.Substitution of cis-1,2-dichloroethylene for the coordinated (S)-2-methyl-2-butene (S-mbn) proceeds in accordance with the second order rate law; there is no contribution of the solvent path.The second order rate constant is smaller than that of trans-.The steric effect of the o-benzenediamine at the transition state seems responsible for the small rate rather than the basicity of the ligand at the trans site to mbn.
- Miya, Shin'ya,Kashiwabara, Kazuo,Saito, Kazuo
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- Participation of Surface Radical Species with Base Catalytic Activity of Na Metal Doped MgO
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Participation of F+ centers with the formation of superbase sites was studied.Two kinds of ESR signals were observed with Na metal doped MgO, which was thermally activated at 773, 873, and 973 K.A relationship was found between double bond migration activity of 3-methyl-1-butene and ESR signal intensity which was observed at low magnetic field.This radical species was assigned to an F+ center formed on an unstable MgO surface.The maximum activity was obtained when two electrons were trapped in an anion vacancy.It was concluded that the F+ and F centers played the most important role for the formation of superbase sites.
- Matsuhashi, Hiromi,Arata, Kazushi
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- The study of alkene isomerization catalyzed by the system: Rhodium dimeric complex-tertiary phosphine-tin dichloride
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Rhodium(I) dimeric complexes, [(Ph3P)4Rh2Cl2] and [(C2H4)4Rh2Cl2], form active catalysts for alkenes isomerization on interaction with tertiary phosphine and tin dichloride in CH2Cl2. Besides 2-methylbut-2-ene, which is the normal product of 1,2-double bond migration, 3-methylbut-1-ene gives the product of unusual 1,3-double bond migration, 2-methylbut-1-ene, which is formed at early stages of the reaction under kinetic control in over-equilibrium quantities. The proposed mechanism for 1,3-double bond migration includes the methyl C-H bond activation, followed by intramolecular transfer hydrogenation.
- Permin,Petrosyan
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- Non-electrophilic Behaviour of Alkyl-substituted Metaphosphates in the Gas Phase: Formation of Alkenes by an Unusual 1,2-Methyl Shift induced by Hydrogen Abstraction-A Methyl Analogue of the Neophyl Ester Rearrangement
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Pyrolytic expulsion of ethylene from 2-neopentoxy-1,3,2-dioxaphospholane in the gas phase yields a virtually quantitative mixture of 2-methylbut-1-ene and its more stable isomer, 2-methylbut-2-ene in the ratio 2:1; this can be rationalised, using deuterium-labelling studies, as being formed from a thermally generated metaphosphate by a cyclic, concerted elimination reaction involving, as the key step, an unusual 1,2-methyl shift induced by competing α- and γ-hydrogen abstraction reactions with loss of metaphosphoric acid.
- Banks, Malcolm R.,Cadogan, J. I. G.,Gosney, Ian,Hodgson, Philip K. G.,Jack, Audrey G. C.,Rodger, David R.
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- Mechanochemical activation of MoS2-Surface properties and catalytic activities in hydrogenation and isomerization of alkenes and in H2/D2 exchange
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High-energy ball milling has been employed to convert a microcrystalline, stoichiometric (S/Mo = 2), catalytically completely inactive MoS2 (prepared by high-temperature decomposition of ammonium tetrathiomolybdate, ATM) into an active catalyst, the activity profile of which was studied with test reactions (ethylene hydrogenation, H2/D2 scrambling, cis-trans isomerization of cis-but-2-ene, double-bond isomerization of 2-methyl-1-butene). Structural and surface properties of the materials were studied by XRD, SEM, TEM, XPS, nitrogen physisorption, oxygen chemisorption, and isotope exchange with D2 (quantity of exchangeable surface hydrogen). The reaction rates obtained after mechanochemical activation were compared with data from a reference MoS2 made by low-temperature decomposition of ATM. Ball-milled MoS2 became active for most of the test reactions (except double-bond isomerization) only after reductive treatments that were effective also with the reference MoS2. After identical treatments, the ball-milled MoS2 was much more active in hydrogenation than the reference MoS2, whereas H2/D2 scrambling proceeded more slowly, and cis-trans isomerization not at all. On the basis of earlier conclusions about the site selectivity of these reactions, the activity pattern indicates that mechanochemical activation led to a site structure dominated by sites with multiple vacancies whereas single-vacancy sites were not present at all, which is in agreement with TEM results showing highly defective bent nanoslab structures after ball milling. The results confirm that ethylene hydrogenation, H2/D2 scrambling and cis-trans isomerization of cis-but-2-ene may be employed as test reactions for sites on MoS2 surfaces whereas data for the double-bond shift in 2-methyl-1-butene suggest that the Bronsted sites catalyzing this reaction are related to structural defects rather than to the regular MoS2 structure.
- Polyakov, Mykola,Indris, Sylvio,Schwamborn, Stefanie,Mazheika, Aliaksei,Poisot, Martha,Kienle, Lorenz,Bensch, Wolfgang,Muhler, Martin,Gruenert, Wolfgang
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- Catalysis by coke deposits: Synthesis of isoprene over solid catalysts
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A help rather than a hindrance: Carbonaceous deposits have been found to play a key role in the selective synthesis of isoprene from formaldehyde and isobutene over solid catalysts. They accumulate on the catalyst surface during the induction period and promote the interaction of the substrates at the steady state. The proposed mechanism (see scheme) shows the way forward for the design of efficient solid catalysts for the synthesis of isoprene. Copyright
- Ivanova, Irina,Sushkevich, Vitaly L.,Kolyagin, Yury G.,Ordomsky, Vitaly V.
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- Etherification of tert-amyl alcohol with methanol over ion-exchange resin
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tert-Amyl methyl ether (TAME) is a proven high octane additive. The synthesis of tert-amyl methyl ether from tert-amyl alcohol and methanol has been carried out in the presence of a variety of solid acid catalysts. Amberlyst-36 was found to be very effective in comparison with other solid acids. A complete theoretical and experimental analysis is presented for the model studies of tert-amyl alcohol with methanol. The parallel reactions of tert-amyl alcohol adsorbed on the sites were found to control the overall rate of reaction, which led to the formation of TAME, 2-methyl-1-butene (2MB1), and 2-methyl-2-butene (2MB2). The reaction follows pseudo-first-order kinetics at a fixed catalyst loading. The individual rate constants for the formation of TAME, 2MB1, and 2MB2 were also evaluated from the same data.
- Yadav,Joshi
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- Mechanisms of Methylenecyclobutane Hydrogenation over Supported Metal Catalysts Studied by Parahydrogen-Induced Polarization Technique
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In this work the mechanism of methylenecyclobutane hydrogenation over titania-supported Rh, Pt and Pd catalysts was investigated using parahydrogen-induced polarization (PHIP) technique. It was found that methylenecyclobutane hydrogenation leads to formation of a mixture of reaction products including cyclic (1-methylcyclobutene, methylcyclobutane), linear (1-pentene, cis-2-pentene, trans-2-pentene, pentane) and branched (isoprene, 2-methyl-1-butene, 2-methyl-2-butene, isopentane) compounds. Generally, at lower temperatures (150–350 °C) the major reaction product was methylcyclobutane while higher temperature of 450 °C favors the formation of branched products isoprene, 2-methyl-1-butene and 2-methyl-2-butene. PHIP effects were detected for all reaction products except methylenecyclobutane isomers 1-methylcyclobutene and isoprene implying that the corresponding compounds can incorporate two atoms from the same parahydrogen molecule in a pairwise manner in the course of the reaction in particular positions. The mechanisms were proposed for the formation of these products based on PHIP results.
- Salnikov, Oleg G.,Burueva, Dudari B.,Kovtunova, Larisa M.,Bukhtiyarov, Valerii I.,Kovtunov, Kirill V.,Koptyug, Igor V.
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- METHOD FOR THE PREPARATION OF A COMPOSITION ENRICHED IN 2-METHYL-BUT-2-ENE AND USE FOR MAKING A POLYMER
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Method for the preparation of a composition enriched in 2-methyl-but-2-ene and use for making a polymer.
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Page/Page column 7-8
(2021/04/01)
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- CATALYTIC HYDROCARBON DEHYDROGENATION
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A catalyst for dehydrogenation of hydrocarbons includes a support including zirconium oxide and Linde type L zeolite (L-zeolite). A concentration of the zirconium oxide in the catalyst is in a range of from 0.1 weight percent (wt. %) to 20 wt. %. The catalyst includes from 5 wt. % to 15 wt. % of an alkali metal or alkaline earth metal. The catalyst includes from 0.1 wt. % to 10 wt. % of tin. The catalyst includes from 0.1 wt. % to 8 wt. % of a platinum group metal. The alkali metal or alkaline earth metal, tin, and platinum group metal are disposed on the support.
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Paragraph 0056; 0122; 0123
(2021/03/13)
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- A Series of Crystallographically Characterized Linear and Branched σ-Alkane Complexes of Rhodium: From Propane to 3-Methylpentane
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Using solid-state molecular organometallic (SMOM) techniques, in particular solid/gas single-crystal to single-crystal reactivity, a series of σ-alkane complexes of the general formula [Rh(Cy2PCH2CH2PCy2)(ηn:ηm-alkane)][BArF4] have been prepared (alkane = propane, 2-methylbutane, hexane, 3-methylpentane; ArF = 3,5-(CF3)2C6H3). These new complexes have been characterized using single crystal X-ray diffraction, solid-state NMR spectroscopy and DFT computational techniques and present a variety of Rh(I)···H-C binding motifs at the metal coordination site: 1,2-η2:η2 (2-methylbutane), 1,3-η2:η2 (propane), 2,4-η2:η2 (hexane), and 1,4-η1:η2 (3-methylpentane). For the linear alkanes propane and hexane, some additional Rh(I)···H-C interactions with the geminal C-H bonds are also evident. The stability of these complexes with respect to alkane loss in the solid state varies with the identity of the alkane: from propane that decomposes rapidly at 295 K to 2-methylbutane that is stable and instead undergoes an acceptorless dehydrogenation to form a bound alkene complex. In each case the alkane sits in a binding pocket defined by the {Rh(Cy2PCH2CH2PCy2)}+ fragment and the surrounding array of [BArF4]- anions. For the propane complex, a small alkane binding energy, driven in part by a lack of stabilizing short contacts with the surrounding anions, correlates with the fleeting stability of this species. 2-Methylbutane forms more short contacts within the binding pocket, and as a result the complex is considerably more stable. However, the complex of the larger 3-methylpentane ligand shows lower stability. Empirically, there therefore appears to be an optimal fit between the size and shape of the alkane and overall stability. Such observations are related to guest/host interactions in solution supramolecular chemistry and the holistic role of 1°, 2°, and 3° environments in metalloenzymes.
- Bukvic, Alexander J.,Burnage, Arron L.,Tizzard, Graham J.,Martínez-Martínez, Antonio J.,Mckay, Alasdair I.,Rees, Nicholas H.,Tegner, Bengt E.,Kr?mer, Tobias,Fish, Heather,Warren, Mark R.,Coles, Simon J.,Macgregor, Stuart A.,Weller, Andrew S.
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supporting information
p. 5106 - 5120
(2021/05/04)
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- Deoxygenation of Epoxides with Carbon Monoxide
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The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO2 from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate-dependent change in the mechanism for the epoxide C?O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration.
- Maulbetsch, Theo,Jürgens, Eva,Kunz, Doris
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p. 10634 - 10640
(2020/07/30)
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- Upgrading 1-butanol to unsaturated, carbonyl and aromatic compounds: A new synthesis approach to produce important organic building blocks
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Unsaturated, carbonyl and aromatic products were obtained by reacting 1-butanol or a 1-butanol:methanol mixture with a copper mixed metal oxide catalyst in a fixed bed reactor. The selectivities observed, mostly for the unsaturated and carbonyl products, can represent a new alternative and greener pathway for the production of fine-chemicals and organic building blocks.
- Boscolo, Mauricio,Metzker, Gustavo,Mora Vargas, Jorge,Orduna Ortega, Julieth,Tofaneli Morelato, Luiz Henrique
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supporting information
p. 2365 - 2369
(2020/05/13)
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- PREPARATION OF OLEFIN BY ALCOHOL DEHYDRATION, AND USES THEREOF FOR MAKING POLYMER, FUEL OR FUEL ADDITIVE.
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A process for the preparation of olefin by alcohol dehydration, for making polymer, fuel or fuel additive and use of olefin obtainable by said process for making polymer, fuel or fuel additive. Preferred olefin is C5 olefin obtained from dehydration of an alcohol or alcohol mixture, preferably from fusel oil.
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Page/Page column 10; 11
(2019/10/04)
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- Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in Silica Pores, as Catalysts for Selective Hydrogenation of Unsaturated Compounds
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Heterogeneous Pd-containing nanocatalysts, based on poly (propylene imine) dendrimers immobilized in silica pores and networks, obtained by co-hydrolysis in situ, have been synthesized and examined in the hydrogenation of various unsaturated compounds. The catalyst activity and selectivity were found to strongly depend on the carrier structure as well as on the substrate electron and geometric features. Thus, mesoporous catalyst, synthesized in presence of both polymeric template and tetraethoxysilane, revealed the maximum activity in the hydrogenation of various styrenes, including bulky and rigid stilbene and its isomers, reaching TOF values of about 230000 h?1. Other mesoporous catalyst, synthesized in the presence of polymeric template, but without addition of Si(OEt)4, provided the trans-cyclooctene formation with the selectivity of 90–95 %, appearing as similar to homogeneous dendrimer-based catalysts. Microporous catalyst, obtained only on the presence of Si(OEt)4, while dendrimer molecules acting as both anchored ligands and template, demonstrated the maximum activity in the hydrogenation of terminal linear alkynes and conjugated dienes, reaching TOF values up to 400000 h?1. Herein the total selectivity on alkene in the case of terminal alkynes and conjugated dienes reached 95–99 % even at hydrogen pressure of 30 atm. The catalysts synthesized can be easily isolated from reaction products and recycled without significant loss of activity.
- Karakanov, Edward A.,Zolotukhina, Anna V.,Ivanov, Andrey O.,Maximov, Anton L.
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p. 358 - 381
(2019/04/04)
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- Oligomerization of Light Olefins Catalyzed by Br?nsted-Acidic Metal-Organic Framework-808
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Sulfated metal-organic framework-808 (S-MOF-808) exhibits strong Br?nsted-acidic character which makes it a potential candidate for the heterogeneous acid catalysis. Here, we report the isomerization and oligomerization reactions of light olefins (C3-C6) over S-MOF-808 at relatively low temperatures and ambient pressure. Different products (dimers, isomers, and heavier oligomers) were obtained for different olefins, and effective C-C coupling was observed between isobutene and isopentene. Among the substrates investigated, facile oligomerization occurred very specifically for the structures with an α-double bond and two substituents at the second carbon atom of the main carbon chain. The possible oligomerization mechanism of light olefins was discussed based on the reactivity and selectivity trends. Moreover, the deactivation and regeneration of S-MOF-808 were investigated. The catalyst deactivates via two mechanisms which predominance depends on the substrate and reaction conditions. Above 110 °C, a loss of acidic sites was observed due to water desorption, and the deactivated catalyst could be regenerated by a simple treatment with water vapor. For C5 substrates and unsaturated ethers, the oligomers with increased molecular weight caused deactivation via blocking of the active sites, which could not be readily reversed. These findings offer the first systematic report on carbocation-mediated olefin coupling within MOFs in which the Br?nsted acidity is associated with the secondary building units of the MOF itself and is not related to any guest substance hosted within its pore system.
- Liu, Ping,Redekop, Evgeniy,Gao, Xiang,Liu, Wen-Chi,Olsbye, Unni,Somorjai, Gabor A.
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supporting information
p. 11557 - 11564
(2019/08/20)
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- Competitive adsorptions between thiophenic compounds over a CoMoS/Al2O3 catalyst under deep HDS of FCC gasoline
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The transformation of various model sulfur compounds (2-methylthiophene: 2MT, 3-methylthiophene: 3MT and benzothiophene: BT) representative of sulfur compounds in FCC gasoline was investigated over a CoMoS/Al2O3 catalyst. More specifically, a quantitative reactivity scale was established with BT being more reactive than 3MT and 2MT. In mixture, their reactivity was reduced due to the presence of the other sulfur compound, the scale of reactivity being preserved. BT strongly inhibits the transformation of 2MT. With a single kinetic model based on a Langmuir Hinshelwood formalism, kinetic and adsorption parameters were calculated and the results explained by mutual competitive adsorption between 2MT and BT with a higher adsorption constant for BT compared to that of 2MT.
- dos Santos, Alan Silva,Girard, Etienne,Leflaive, Philibert,Brunet, Sylvette
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p. 292 - 298
(2018/12/11)
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- Effect of ketene additive and Si/Al ratio on the reaction of methanol over HZSM-5 catalysts
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The influence of ketene as possible intermediate for the reaction of methanol to aromatics was investigated over HZSM-5 catalysts (Si/Al ratio of 15 and 9) using diketene-acetone (2,2,6-trimethyl-4H-1,3-dioxin-4-one) as ketene precursor under atmospheric
- Hassanpour, Javad,Zamani, Mehdi,Dabbagh, Hossein A.
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- Cobalt-Iron-Manganese Catalysts for the Conversion of End-of-Life-Tire-Derived Syngas into Light Terminal Olefins
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Co-Fe-Mn/γ-Al2O3 Fischer–Tropsch synthesis (FTS) catalysts were synthesized, characterized and tested for CO hydrogenation, mimicking end-of-life-tire (ELT)-derived syngas. It was found that an increase of C2-C4 olefin selectivities to 49 % could be reached for 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn/γ-Al2O3 with Na at ambient pressure. Furthermore, by using a 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al2O3 catalyst the selectivity towards the fractions of C5+ and CH4 could be reduced, whereas the selectivity towards the fraction of C4 olefins could be improved to 12.6 % at 10 bar. Moreover, the Na/S ratio influences the ratio of terminal to internal olefins observed as products, that is, a high Na loading prevents the isomerization of primary olefins, which is unwanted if 1,3-butadiene is the target product. Thus, by fine-tuning the addition of promoter elements the volume of waste streams that need to be recycled, treated or upgraded during ELT syngas processing could be reduced. The most promising catalyst (5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al2O3) has been investigated using operando transmission X-ray microscopy (TXM) and X-ray diffraction (XRD). It was found that a cobalt-iron alloy was formed, whereas manganese remained in its oxidic phase.
- Falkenhagen, Jan P.,Maisonneuve, Lise,Paalanen, Pasi P.,Coste, Nathalie,Malicki, Nicolas,Weckhuysen, Bert M.
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supporting information
p. 4597 - 4606
(2018/03/06)
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- Synthesis of Densely Packaged, Ultrasmall Pt02 Clusters within a Thioether-Functionalized MOF: Catalytic Activity in Industrial Reactions at Low Temperature
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The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt02 clusters, homogenously distributed and densely packaged within the channels of a metal–organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO2 methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal clusters in solids for technically easier, cheaper, and dramatically less-dangerous industrial reactions.
- Mon, Marta,Rivero-Crespo, Miguel A.,Ferrando-Soria, Jesús,Vidal-Moya, Alejandro,Boronat, Mercedes,Leyva-Pérez, Antonio,Corma, Avelino,Hernández-Garrido, Juan C.,López-Haro, Miguel,Calvino, José J.,Ragazzon, Giulio,Credi, Alberto,Armentano, Donatella,Pardo, Emilio
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supporting information
p. 6186 - 6191
(2018/05/30)
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- Metal-Free Dehydrogenative Diels-Alder Reactions of Prenyl Derivatives with Dienophiles via a Thermal Reversible Process
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An efficient dehydrogenative Diels-Alder reaction of prenyl derivatives with dienophiles has been developed. The reaction exhibits broad substrate scope and provides efficient access to cyclohexene derivatives with good to excellent yields. A reasonable mechanism involving a metal-free thermal reversible process is proposed.
- Xu, Wen-Lei,Zhang, Heng,Hu, Yu-Long,Yang, Hui,Chen, Jie,Zhou, Ling
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supporting information
p. 5774 - 5778
(2018/09/21)
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- Alkanethiolate-capped palladium nanoparticles for selective catalytic hydrogenation of dienes and trienes
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Selective hydrogenation of dienes and trienes is an important process in the pharmaceutical and chemical industries. Our group previously reported that the thiosulfate protocol using a sodium S-alkylthiosulfate ligand could generate catalytically active Pd nanoparticles (PdNP) capped with a lower density of alkanethiolate ligands. This homogeneously soluble PdNP catalyst offers several advantages such as little contamination via Pd leaching and easy separation and recycling. In addition, the high activity of PdNP allows the reactions to be completed under mild conditions, at room temperature and atmospheric pressure. Herein, a PdNP catalyst capped with octanethiolate ligands (C8 PdNP) is investigated for the selective hydrogenation of conjugated dienes into monoenes. The strong influence of the thiolate ligands on the chemical and electronic properties of the Pd surface is confirmed by mechanistic studies and highly selective catalysis results. The studies also suggest two major routes for the conjugated diene hydrogenation: the 1,2-addition and 1,4-addition of hydrogen. The selectivity between two mono-hydrogenation products is controlled by the steric interaction of substrates and the thermodynamic stability of products. The catalytic hydrogenation of trienes also results in the almost quantitative formation of mono-hydrogenation products, the isolated dienes, from both ocimene and myrcene.
- Chen, Ting-An,Shon, Young-Seok
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p. 4823 - 4829
(2017/10/19)
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- Revealing Hydrogenation Reaction Pathways on Naked Gold Nanoparticles
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Gold nanoparticles (AuNPs) display distinct characteristics as hydrogenation catalysts, with higher selectivity and lower catalytic activity than group 8-10 metals. The ability of AuNPs to chemisorb/activate simple molecules is limited by the low coordination number of the surface sites. Understanding the distinct pathways involved in the hydrogenation reactions promoted by supported AuNPs is crucial for broadening their potential catalytic applications. In this study, we demonstrate that the mechanism of the hydrogenation reactions catalyzed by AuNPs with "clean" surfaces may proceed via homolytic or heterolytic hydrogen activation depending on the nature of the support. The synthesis of naked AuNPs employing γ-Al2O3 and ionic liquid (IL)-hybrid γ-Al2O3 supports was accomplished by sputtering deposition using ultrapure gold foils. This highly reproducible and straightforward procedure furnishes small (~6.6 nm) and well-distributed metallic gold nanoparticles (Au(0)NPs) that are found to be active catalysts for the partial and selective hydrogenation of substituted conjugated dienes, alkynes, and α,β-unsaturated carbonyl compounds (aldehydes and ketones). Kinetic and deuterium labeling studies indicate that heterolytic hydrogen activation is the primary pathway occurring on the AuNPs imprinted directly on γ-Al2O3. In contrast, AuNPs supported on IL-hybrid γ-Al2O3 materials cause the reaction to proceed via a homolytic hydrogen activation pathway. The IL layer surrounds the AuNPs and acts as a cage, influencing the frequency of the interaction of the catalytically active species and the metal surface and, consequently, the catalytic performance of the AuNPs. The IL layer is shown to improve the product selectivity by the enhancement of the substrate/product discrimination, and to decrease the catalytic activity by shifting the rate-determining step to the H2 and substrate competitive adsorption/activation on the same active sites. A series of kinetic experiments suggest that AuNPs imprinted on an IL-hybrid γ-Al2O3 support are more efficient (lower activation energy, Ea) than group 8-10 metal based catalysts for hydrogenation reactions at moderate to high temperatures (75-150 °C).
- Luza, Leandro,Rambor, Camila P.,Gual, Aitor,Alves Fernandes, Jesum,Eberhardt, Dario,Dupont, Jairton
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p. 2791 - 2799
(2017/05/31)
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- Visible-light-mediated anti-regioselective nitrone 1, 3-dipolar cycloaddition reaction and synthesis of bisindolylmethanes
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The development of photoredox reactions of 1, 3- dipolar cycloaddition of nitrones with alkenes is reported. It offers an efficient synthetic method to obtain isoxazolidine derivatives under mild conditions in synthetically useful yields. The nitrones are cyclized with oxidizable styrenes and aliphatic alkenes via a polar radical crossover cycloaddition reaction through photocatalytic reaction without additives. In addition, bis(indole)methanes can also be prepared through this method.
- Zheng, Lewei,Gao, Fei,Yang, Chao,Gao, Guo-Lin,Zhao, Yating,Gao, Yuan,Xia, Wujiong
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supporting information
p. 5086 - 5089
(2017/11/07)
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- Kinetics of the gas-phase elimination reaction of benzyl chloroformate and neopentyl chloroformate
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The gas-phase eliminations of benzyl chloroformate (475-523 K, 31-103 Torr) and neopentyl chloroformate (563-622 K, 37-70 Torr), in a deactivated static reaction vessel, and in the presence of a free radical suppressor, are homogeneous, unimolecular, and follow a first-order rate law. The rate coefficients are expressed by the following Arrhenius equations: Benzyl chloroformate log κI = (13.30 ± 0.38) - (152.9 ± 3.6) kJ mol-1(2.303RT)-1; r = 0.9989 Neopentyl chloroformate Formation of neopentyl chloride: log κI = (14.29 ± 0.48) - (196.3 ± 5.5) kJ mol-1(2.303RT)-1; r = 0.9986 Formation of 2-methylbutenes: log κII = (12.12 ± 0.73) - (178.2 ± 8.3) kJ mol-1(2.303RT)-1; r = 0.9960 The derived kinetic and thermodynamic parameters for benzyl chloroformate decomposition indicate the reaction proceeds through a concerted four-membered cyclic transition state to give benzyl chloride and CO2 gas. Neopentyl chloroformate undergoes a parallel reaction, where neopentyl chloride formation may arise from a polar-concerted four-membered cyclic transition state, whereas the mixture of olefins, 2-methyl-2-butene, and 2-methyl-1-butene appears to be produced from a carbene intermediate. This intermediate seems to be originated from a concerted five-membered cyclic transition state of the neopentyl substrate.
- Lezama, Jesus,Domnguez, Rosa M.,Chuchani, Gabriel
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p. 104 - 112
(2015/04/22)
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- CATALYTIC CONVERSION OF ALCOHOLS HAVING AT LEAST THREE CARBON ATOMS TO HYDROCARBON BLENDSTOCK
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A method for producing a hydrocarbon blendstock, the method comprising contacting at least one saturated acyclic alcohol having at least three and up to ten carbon atoms with a metal-loaded zeolite catalyst at a temperature of at least 100°C and up to 550°C, wherein the metal is a positively-charged metal ion, and the metal-loaded zeolite catalyst is catalytically active for converting the alcohol to the hydrocarbon blendstock, wherein the method directly produces a hydrocarbon blendstock having less than 1 vol% ethylene and at least 35 vol% of hydrocarbon compounds containing at least eight carbon atoms.
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Paragraph 0062; 0063
(2015/01/16)
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- CATALYST AND PROCESS FOR THE CO-DIMERIZATION OF ETHYLENE AND PROPYLENE
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Disclosed are novel catalyst solutions comprising an organic complex of nickel, an alkyl aluminum compound, a solvent, and a phosphine compound, that are useful for the preparation of butenes, pentenes and hexenes by the co-dimerization or cross-dimerization of ethylene and propylene. Also disclosed are processes for the dimerization of ethylene and propylene that utilize these catalyst solutions. The catalyst systems described herein demonstrate that, depending on the choice of phosphine compound used with the catalytically active nickel, it is indeed possible to lower the concentration of hexene olefins relative to butenes and pentenes, even in the presence of excess propylene. The selectivity to the linear or branched pentene product can also be controlled by the selection of the phosphine compound. The catalyst solutions may be used with mixtures of olefins.
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Paragraph 0088
(2015/03/28)
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- Monomolecular Skeletal Isomerization of 1-Butene over Selective Zeolite Catalysts
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The mechanism of the 1-butene skeletal isomerization catalyzed by zeolites has remained elusive. We present direct evidence that even the initial isobutene formation over H-ferrierite, the best-known isomerization catalyst, is monomolecular in nature, whereas a bimolecular pathway is significant over the unselective H-ZSM-5. We also report that medium-pore high-silica H-HPM-1 outperforms H-ferrierite in selectively forming isobutene. This new catalyst displays a high activity and selectivity from the onset of the reaction, as well as an excellent resistance to deactivation, thanks to its anomalously weak acidity and low acid site density, together with an ability to effectively isolate reactant molecules from one another. (Chemical Equation Presented).
- Jo, Donghui,Hong, Suk Bong,Camblor, Miguel A.
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p. 2270 - 2274
(2015/04/14)
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- Mesoporous organic Pd-containing catalysts for the selective hydrogenation of conjugated hydrocarbons
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Palladium catalysts supported on ordered organic mesoporous polymers were synthesized. The catalysts are characterized by the narrow size distribution of palladium nanoparticles with an average particle size of 2.2-5.2 nm. They demonstrate high catalytic activity and selectivity in phenylacetylene hydrogenation (896-2590 min-1, selectivity 89-98%). High activity and selectivity for alkenes are observed in the hydrogenation of conjugated dienes (for isoprene, TOF = 1850-5000 min-1, selectivity 99%; for 2,5-dimethyl-2,4-hexadiene, TOF = = 1294-2400 min-1, selectivity 100%; for 1,4-diphenyl-1,3-butadiene, TOF = 14-22 min-1, selectivity 7-16%). A dependence of the selectivity on the nature of the support and substrate was found for the hydrogenation of 1,4-diphenyl-1,3-butadiene.
- Karakhanov,Maksimov,Aksenov,Kuznetsov,Filippova,Kardashev,Volkov
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p. 1710 - 1716
(2015/05/20)
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- Experimental investigation of the low temperature oxidation of the five isomers of hexane
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The low-temperature oxidation of the five hexane isomers (n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethylbutane, and 2,3-dimethylbutane) was studied in a jet-stirred reactor (JSR) at atmospheric pressure under stoichiometric conditions between 550 and 1000 K. The evolution of reactant and product mole fraction profiles were recorded as a function of the temperature using two analytical methods: gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Experimental data obtained with both methods were in good agreement for the five fuels. These data were used to compare the reactivity and the nature of the reaction products and their distribution. At low temperature (below 800 K), n-hexane was the most reactive isomer. The two methyl-pentane isomers have about the same reactivity, which was lower than that of n-hexane. 2,2-Dimethylbutane was less reactive than the two methyl-pentane isomers, and 2,3-dimethylbutane was the least reactive isomer. These observations are in good agreement with research octane numbers given in the literature. Cyclic ethers with rings including 3, 4, 5, and 6 atoms have been identified and quantified for the five fuels. While the cyclic ether distribution was notably more detailed than in other literature of JSR studies of branched alkane oxidation, some oxiranes were missing among the cyclic ethers expected from methyl-pentanes. Using SVUV-PIMS, the formation of C 2-C3 monocarboxylic acids, ketohydroperoxides, and species with two carbonyl groups have also been observed, supporting their possible formation from branched reactants. This is in line with what was previously experimentally demonstrated from linear fuels. Possible structures and ways of decomposition of the most probable ketohydroperoxides were discussed. Above 800 K, all five isomers have about the same reactivity, with a larger formation from branched alkanes of some unsaturated species, such as allene and propyne, which are known to be soot precursors.
- Wang, Zhandong,Herbinet, Olivier,Cheng, Zhanjun,Husson, Benoit,Fournet, Rene,Qi, Fei,Battin-Leclerc, Frederique
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p. 5573 - 5594
(2014/08/18)
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- Z -selective alkene isomerization by high-spin cobalt(II) complexes
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The isomerization of simple terminal alkenes to internal isomers with Z-stereochemistry is rare, because the more stable E-isomers are typically formed. We show here that cobalt(II) catalysts supported by bulky β-diketiminate ligands have the appropriate kinetic selectivity to catalyze the isomerization of some simple 1-alkenes specifically to the 2-alkene as the less stable Z-isomer. The catalysis proceeds via an "alkyl" mechanism, with a three-coordinate cobalt(II) alkyl complex as the resting state. β-Hydride elimination and [1,2]-insertion steps are both rapid, as shown by isotopic labeling experiments. A steric model explains the selectivity through a square-planar geometry at cobalt(II) in the transition state for β-hydride elimination. The catalyst works not only with simple alkenes, but also with homoallyl silanes, ketals, and silyl ethers. Isolation of cobalt(I) or cobalt(II) products from reactions with poor substrates suggests that the key catalyst decomposition pathways are bimolecular, and lowering the catalyst concentration often improves the selectivity. In addition to a potentially useful, selective transformation, these studies provide a mechanistic understanding for catalytic alkene isomerization by high-spin cobalt complexes, and demonstrate the effectiveness of steric bulk in controlling the stereoselectivity of alkene formation.
- Chen, Chi,Dugan, Thomas R.,Brennessel, William W.,Weix, Daniel J.,Holland, Patrick L.
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supporting information
p. 945 - 955
(2014/02/14)
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- METHOD OF FORMING C5 DI-OLEFINS
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A process is disclosed that includes reacting a C1 source with n-butene to form a C-5 diolefin.
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Paragraph 0086; 0087
(2014/09/30)
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- Phosphate-modified carbon nanotubes in the oxidative dehydrogenation of isopentanes
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Ketonic/quinonic C=O groups on the surface of a carbon matrix are capable of abstracting hydrogen in C-H bonds from hydrocarbons and enable them to selectively convert into corresponding unsaturated hydrocarbons; this process is the oxidative dehydrogenation (ODH) reaction. However, a variety of inevitable defects or graphene edges and other oxygen-containing groups on the carbon matrix are detrimental to the selective production of alkenes due to their high activity towards overoxidation. Herein, we show that phosphate can not only impede the total oxidation but also cover the selective C=O groups, hence allowing its use as a modulator to defects and oxygen-containing functional groups on the multiwalled carbon nanotubes, regulating the distribution of active sites and related catalytic targets.
- Huang, Rui,Liu, Hong Yang,Zhang, Bing Sen,Sun, Xiao Yan,Liang, Chang Hai,Su, Dang Sheng,Zong, Bao Ning,Rong, Jun Feng
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p. 3476 - 3482
(2015/03/13)
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- CATALYTIC DEHYDRATION OF ALCOHOLS AND ETHERS OVER A TERNARY MIXED OXIDE
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A ternary V—Ti—P mixed oxide is shown to catalytically dehydrate 2-methyl-tetrahydrofuran in high conversion to give piperylene, in good yield. Volatile products collected from this reaction contain piperylene in concentrations as high as 80 percent by weight. Dehydration of glycerol to acrolein in high conversion and moderate selectivity is also demonstrated. The catalyst is also shown to dehydrate other alcohols and ether substrates. The catalyst is resistant to deactivation and maintains activity between runs.
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Paragraph 0038; 0046
(2013/03/28)
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- A descriptor for the relative propagation of the aromatic- and olefin-based cycles in methanol-to-hydrocarbons conversion on H-ZSM-5
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The observed product distribution in methanol-to-hydrocarbons (MTH) catalysis can be rationalized based on the relative rates of propagation of the aromatic- and olefin-based cycles that operate on the zeolite catalyst. We report that the ratio of ethene to 2-methylbutane + 2-methyl-2-butene (ethene/2MB) yield can be used to describe the propagation of aromatic and olefin methylation/cracking cycles. The co-reaction of 12C-ethene with 13C-dimethyl ether (DME) shows that the rate of DME conversion (1.62 mol C (mol Al s)-1) is ~20 times faster than ethene conversion (0.08 mol C (mol Al s)-1), suggesting that ethene can be considered as terminal product for MTH at 623 K. At iso-conversion conditions at 548 K, propene is co-fed with DME to increase propagation of the olefin-based cycle and correspondingly a 1.7-fold decrease in the ethene/2MB yield is observed. Similarly, the co-reaction of toluene with DME increases propagation of the aromatic-based cycle and a 2.1-fold increase in the ethene/2MB yield is observed. The ethene/2MB yield also increased by a factor of 2 as DME conversion increased from 5% to 62%, which is consistent with the observed concurrent increase in selectivity to ethene and methylbenzenes. For the reaction of DME alone, increasing the temperature from 548 K to 723 K increases the propagation of the olefin-based cycle and a corresponding decrease in the ethene/2MB yield from 4.7 to 1.3 is also observed. The ethene/2MB yield varies systematically with feed composition, conversion, and temperature, showing that this ratio describes the relative propagation of the aromatic to olefin methylation/cracking cycles in MTH conversion on H-ZSM-5.
- Ilias, Samia,Khare, Rachit,Malek, Andre,Bhan, Aditya
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p. 135 - 140
(2013/07/05)
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- A novel monolith catalyst of plate-type anodic alumina for the hydrolysis of dimethyl ether
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A novel monolith catalyst of plate-type anodic alumina was applied in the dimethyl ether (DME) hydrolysis reaction system. The reactivity of the anodic alumina with hydration treatments in DME hydrolysis reaction was investigated. The preferred hydration-treated temperature was found to be 80 C and the anodic Al2O3/Al monolith exhibited higher activity than the commercial Al2O3 in DME hydrolysis reaction. Meanwhile, the anodic Al2O3/Al monolith was proven to have higher MeOH effluent mole percentage with less unfavorable side reactions than the ZSM-5 catalyst. The anodic γ-Al2O3/Al monolith had just 0.85% coking while the ZSM-5 catalyst had 8.81% after 100 h of continuous experiments.
- Zhang, Qi,Sun, Dongmei,Fan, Feiyue,Zhang, Qinghui,Zhu, Zibin
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- H-SAPO-5 as methanol-to-olefins (MTO) model catalyst: Towards elucidating the effects of acid strength
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The methanol-to-hydrocarbons (MTH) reaction was studied over a moderately acidic zeotype material, H-SAPO-5, at 350-450°C and with WHSV = 0.3-5 h -1. C3-C5 alkenes were the main products of reaction, followed by C6+ aliphatics. Conversion-selectivity plots from experiments conducted at various contact times revealed that coking did not influence product selectivity significantly. Steady-state isotope transient experiments (12CH3OH//13CH3OH) were performed at 450°C. 13C incorporation was more rapid in the alkene products than in the polymethylated benzene molecules that were retained inside the catalyst after testing, suggesting that polymethylbenzenes contribute only to a minor extent to alkene formation in H-SAPO-5. Co-feed studies of methanol and benzene at 350°C revealed that benzene shifts the product selectivity towards ethene and aromatic products. Co-feeding 13CH3OH and benzene at 250°C, giving 4+ alkene, formation. Furthermore, the isotopic labelling pattern of ethene provided the first direct experimental evidence for ethene formation by a paring-type reaction from polymethylated benzene intermediates. Overall, the results obtained in this study suggest that a lower acid strength promotes an alkene-mediated MTH reaction mechanism, and that acid strength is therefore an important design parameter for selectivity optimisation in zeotype catalysis.
- Westgard Erichsen, Marius,Svelle, Stian,Olsbye, Unni
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- PRODUCTION OF 3-METHYLBUT-1-EN BY MEANS OF DEHYDRATION OF 3-METHYLBUTANE-1-OL
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The invention relates to a process for preparing 3-methyl-1-butene by dehydration of 3-methyl-1-butanol over an aluminium-containing oxide in the temperature range from 200 to 450° C. in the gas phase or mixed liquid/gas phase, characterized in that an aluminium-containing oxide having a predominantly mesoporous pore structure whose: a) relative proportion of macropores is less than 15%; b) distribution of the pore diameter has a monomodal maximum in the range of mesopores from 3.6 to 50 nm; c) average pore diameter of all pores is in the range of mesopores and macropores from 5 to 20 nm; d) composition comprises more than 80% of gamma-aluminium oxide, is used.
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Page/Page column 4
(2012/06/16)
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- Titration of nonstabilized diazoalkane solutions by fluorine NMR
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A new protocol for titrating nonstabilized diazoalkane solutions by quantitative 19F NMR is reported. An excess of 2-fluorobenzoic acid dissolved in CDCl3 is treated with the diazoalkane solution at a low temperature, immediately forming the corresponding 2-fluorobenzoate ester upon warming. A significant difference in the 19F chemical shift between the ester and acid is seen, allowing facile and accurate integration to determine titer. The procedure is safe, rapid, and indicates the active diazoalkane concentration with high precision.
- Rendina, Victor L.,Kingsbury, Jason S.
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experimental part
p. 1181 - 1185
(2012/03/12)
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- ZEOLITIC CATALYTIC CONVERSION OF ALCOHOLS TO HYDROCARBONS
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A method for converting an alcohol to a hydrocarbon, the method comprising contacting said alcohol with a metal-loaded zeolite catalyst at a temperature of at least 100°C and up to 550°C, wherein said alcohol can be produced by a fermentation process, said metal is a positively-charged metal ion, and said metal-loaded zeolite catalyst is catalytically active for converting said alcohol to said hydrocarbon.
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Page/Page column 19
(2013/02/28)
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- FUEL COMPOSITIONS COMPRISING ISOPRENE DERIVATIVES
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The invention provides for methods, compositions and systems using isoprene from a bioisoprene composition derived from renewable carbon for production of a variety of hydrocarbon fuels, fuel additives, and additives for fine chemistry and other uses.
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Page/Page column 70
(2012/01/06)
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- Process and system for the production of isoprene
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Disclosed herein is a process for producing isoprene that includes reacting a mixed C4 metathesis feed stream comprising isobutylene and at least one of 1-butene and 2-pentene in a first metathesis reactor in the presence of a first metathesis catalyst under conditions sufficient to produce an intermediate product stream comprising at least 30 wt. % 2-methyl-2-pentene based upon the olefin content of fresh feed in the mixed C4 feed stream, and at least one of ethylene and propylene, separating the 2-methyl-2-pentene, subjecting the separated 2-methyl-2-pentene to pyrolysis to produce a reaction product stream comprising isoprene, and separating the isoprene into an isoprene product stream using fractionation. A system used in producing isoprene is also disclosed.
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Page/Page column 6-7
(2011/02/26)
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- Thermal decomposition of t-amyl methyl ether (TAME) studied by flash pyrolysis/supersonic expansion/vacuum ultraviolet photoionization time-of-flight mass spectrometry
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Thermal decomposition of the oxygenated fuel component tert-amyl methyl ether (TAME) has been studied by flash pyrolysis up to 1250 K in a 20-100 μs time scale. Pyrolysis was followed by supersonic expansion to isolate intermediates and products, which are monitored by vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). The species detected, such as CH3, C2H4, C 2H5, C4H8, C5H 10, C3H6O, and C4H8O, show competition between molecular elimination and bond fission pathways. The alkenes 2-methyl-1-butene (1) and 2-methyl-2-butene (2), the primary molecular elimination products of TAME, were separately pyrolyzed to evaluate the extent of secondary decompositions, as were the ketones (acetone and 2-butanone) produced by losses of two alkyl radicals. While vicinal elimination of methanol from TAME to form 1 and 2 in an approximate 3:1 ratio begins around 600 K and continues to dominate at higher temperatures, homolysis of TAME to form radicals onsets >825 K, yielding more acetone than 2-butanone. Contributions from secondary dissociations of the ketone and alkene products are evaluated.
- Morton, Thomas Hellman,Weber, Kevin H.,Zhang, Jingsong
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experimental part
p. 210 - 218
(2012/07/17)
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- Kinetics of 2-methylbutene-2 epoxidation with 2-methylbutane hydroperoxide
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The kinetics of 2-methylbutene-2 epoxidation with 2-methylbutane hydroperoxide was studied in the presence of a molybdenum catalyst. The mathematical description of the hydroperoxide consumption and 2-methyl-butene-2 oxide formation was derived, and the most probable scheme of the process was suggested. The main kinetic constants were calculated.
- Petukhova,Sapunov,Kharlampidi,Petukhov
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experimental part
p. 381 - 387
(2011/04/23)
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- Polymers as novel modifiers for supported metal catalyst in hydrogenation of benzaldehydes
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Polyethylene glycol (PEG) was impregnated on a palladium metal supported on silica gel and used in a catalyst for hydrogenation of benzaldehydes. In the vapor-phase flow reaction, the PEG modification improved catalytic activity and selectivity for a partially hydrogenated product, benzyl alcohol. In isoprene hydrogenation, selectivity for partially hydrogenated products, monoenes, was also enhanced. X-ray photoelectron spectroscopy (XPS) analysis of the modified catalysts revealed that the modification with PEG makes the palladium surface negatively charged, possibly leading to an increase in the selectivity for the partially hydrogenated product caused by enhancement of its desorption from the surface. In the liquid-phase hydrogenation of benzaldehyde, the PEG modification also increased the selectivity for benzyl alcohol.
- Okamoto, Masaki,Hirao, Tomoyuki,Yamaai, Tatsuya
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experimental part
p. 423 - 428
(2011/02/27)
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- Selective hydrogenation process employing a catalyst having a controlled porosity
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A process for jointly carrying out selective hydrogenation of polyunsaturated compounds into monounsaturated compounds contained in gasolines, and for transforming light sulphur-containing compounds into heavier compounds by reaction with unsaturated compounds employing a supported catalyst, comprising at least one metal from group VIB and at least one non-noble metal from group VIII used in the sulphurized form deposited on a support and having a controlled porosity, and comprising bringing the feed into contact with the catalyst at a temperature in the range of 80° C. to 220° C. at a liquid hourly space velocity in the range of 1 h?1 to 10 h?1 and at a pressure in the range of 0.5 to 5 MPa.
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Page/Page column 9-10
(2010/06/11)
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- Propylene and isoprene production
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A process for producing propylene and isoprene from a feed stream comprising 1-butene and isobutene is disclosed. The feed stream is reacted in a catalytic distillation reactor containing an olefin isomerization catalyst to produce an overhead stream comprising 2-butene and isobutene and a bottoms stream comprising 2-butene. The overhead stream is reacted in the presence of a metathesis catalyst to produce propylene and isoamylenes. Isoprene is produced by dehydrogenation of isoamylenes.
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Page/Page column 3-4
(2009/03/07)
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- PROCESS FOR CRACKING TERT-ALKYL ETHERS THAT USE A MESOSTRUCTURED HYBRID ORGANIC-INORGANIC MATERIAL
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A process for cracking tert-alkyl ether(s) selected from among tert-amyl methyl ether (TAME) and ethyl tert-amyl ether (ETAE) for the production of tertiary olefins comprising bringing said tert-alkyl ether(s) into contact with at least one catalyst that is formed by at least one mesostructured hybrid organic-inorganic material that consists of at least two spherical elementary particles, whereby each of said spherical particles consists of a mesostructured matrix with a silicon oxide base to which are linked organic groups with acid terminal reactive functions, said groups representing less than 20 mol % of said matrix that is present in each of said spherical elementary particles, which have a maximum diameter of between 50 nm and 200 μm.
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Page/Page column 10-11
(2010/01/31)
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- High yield of liquid range olefins obtained by converting i-propanol over zeolite H-ZSM-5
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Methanol, ethanol, and i-propanol were converted under methanol-to-gasoline (MTH)-like conditions (400°C, 1-20 bar) over zeolite H-ZSM-5. For methanol and ethanol, the catalyst lifetimes and conversion capacities are comparable, but when i-propanol is use
- Mentzel, Uffe V.,Shunmugavel, Saravanamurugan,Hruby, Sarah L.,Christensen, Claus H.,Holm, Martin S.
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experimental part
p. 17009 - 17013
(2010/03/23)
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- Method of selectively hydrogenating conjugated diene by using supported ionic liquid nano-pd catalyst
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A method of selectively hydrogenating a conjugated diene by using a supported ionic liquid nano-palladium catalyst. The supported ionic liquid nano-palladium catalyst, hydrogen and a reactant having the conjugated diene react at a temperature ranging from 40 to 120° C. and a pressure ranging from 100 to 400 psig. A ratio of the catalyst to the reactant ranges from 1/20 to 1/250 (g/ml).
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Page/Page column 3-4
(2008/12/04)
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- Process for the production of hydrocarbons
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A process for the production of a hydrocarbon comprises reacting methanol, dimethyl ether, methyl acetate or mixtures thereof, with an olefin in the presence of methyl halide and/or hydrogen halide and at least one compound selected from the group consisting of ruthenium carbonyl halides, osmium carbonyl halides and mixtures thereof.
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Page/Page column 4-6
(2008/06/13)
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