- Synthesis of a Highly Active Superacid of Platinum-supported Zirconia for Reaction of Butane
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A highly active superacid of 8 masspercent Pt-supported ZrO2 for the skeletal isomerization of butane to isobutane is obtained by impregnating zirconia gel with 0.5 mol dm-3 H2SO4 followed by drying, impregnating the sulfated gel with a solution of H2PtCl6, and finally calcining in air at 600 deg C.
- Hino, Makoto,Arata, Kazushi
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- Photoassisted Isomerisation of Olefins by Platinum Complexes
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Photoassisted isomerisation of carbon-carbon double bonds has been affected for the first time in the presence of platinum complexes; pent-2-ene, hex-2-ene, and 1,2-dichloroethene can be cis-trans interconverted with high efficiency.
- Courtot, Pierre,Pichon, Roger,Salauen, Jean-Yves
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- LE COMPLEXE 2> CATALYSEUR HOMOGENE D'HYDROGENATION ET D'HYDROSILYLATION D'OLEFINES ET D'ALDEHYDES ET CETONES α,β-INSATURES
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The chloro-bridged platinum(II) complex dichlorobis(2,4,6-trimethylpyridine)platinum was found to be an active catalyst for homogeneous hydrogenation and hydrosilylation of olefins and α,β-unsaturated aldehydes and ketones at room temperature and under atmospheric pressure.Hydrosilylation of terminal olefins can be achieved with dimethylphenylsilane and a catalyst/reactant ratio of 10-6/1.This complex is the first example of a platinum(II) compound containing pyridine ligands having good catalytic activity possibilities.
- Rumin, R.
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- The roles of carbide and hydride in oxide-supported palladium nanoparticles for alkyne hydrogenation
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Particle size affects the activity and selectivity to partial hydrogenation of 1-pentyne over oxide-supported palladium nanoparticles. Larger particles are intrinsically more selective because of the weaker bond strength of 1-pentene. In situ X-ray absorption near edge structure (XANES) at the Pd L3 edge revealed the formation of a carbide-like phase as soon as the catalyst is exposed to alkyne, irrespective of particle size. The newly formed phase prevented hydride formation. Surface poisoning of the palladium carbide by alkyne is responsible for the constantly high selectivity, up to almost complete conversion. At almost 100% conversion, all catalysts show low selectivity. The lack of significant pentyne adsorption on the surface causes pentene to undergo consecutive reactions, such as isomerization and complete hydrogenation. The structure of the catalyst was that of carbide-like phase and did not change. Palladium hydride did not form under any of the conditions. Exposure of a carbided catalyst to pure hydrogen leads to partial reversal of the structure. Hydride is not essential for complete hydrogenation to occur.
- Tew, Min Wei,Janousch, Markus,Huthwelker, Thomas,Van Bokhoven, Jeroen A.
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- Some Diels-Alder reactions of trimethoxysilylpropylcyclopentadiene and the synthesis of a silica-supported 4,5-dicyanonorbornenepalladium complex
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Trimethoxysilylpropylcyclopentadiene reacts with the electron-deficient acetylenes, RO2CC2CO2R (R=Me, Et) and olefins R1CH=CHR2 (R1=H, R2=SOPh; R1=R2=P(O)Ph2, R1=R2=CN) to give the corresponding Diels-Alder adducts.The compounds CHCl=CHCl and E-Ph2P(S)CH=CHP(S)Ph2 failed to react under similar conditions.The adduct from fumarodinitrile has been used to synthesise a silica-anchored bis-nitrile palladium chloride complex, which catalyses the isomerisation of pent-1-ene.
- Adeleke, J. A.,Booth, B. L.
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- Homologation of Small Alkanes on Pt, Pd and Ni Catalysts. Contribution of Intermediate Carbenes to Skeletal Isomerisation
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Chain lengthening homologation of propane, n-butane, 2-methylpropane, 2-methylbutane and 2,2-dimethylpropane has been investigated over Pt, Pd and Ni catalysts.With both Pd and Ni the chain lengthening selectivity was observed to be commensurable to the isomerisation one.Addition of CHx onto the β-carbon atom in n-butane and propane as well as chain lengthening of 2-methylpropane and 2-methylbutane were observed.The mechanism of the skeletal rearragement is discussed in terms of CHx addition.
- Sarkany, Antal
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- Understanding ketone hydrodeoxygenation for the production of fuels and feedstocks from biomass
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Although we can efficiently convert bioderived furans into linear alkanes, the most energy-intensive step in this approach is the hydrodeoxygenation of the intermediate polyketone. To fully understand this process, we have examined the hydrodeoxygenation of a model compound, 3-pentanone, which allows us to follow this process stepwise using Pd/C, H2 (200 psi), and La(OTf)3 in acetic acid to remove the oxygen atom at temperatures between 25 and 200 C. We have found that ketone reduction to an alcohol is followed by acetoxylation, which provides a more facile route to C-O bond cleavage relative to the parent alcohol. (Chemical Presented).
- King, Amanda E.,Brooks, Ty J.,Tian, Yong-Hui,Batista, Enrique R.,Sutton, Andrew D.
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- Oligomerisation of alkenes by radical initiation
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The use of di-tert-butyl peroxide (DTBP) as initiator for the radical oligomerisation of 1-octene and pentene, typical Fischer-Tropsch-derived products, was studied in the temperature range 100-200°C. Using this approach, the favourable product distributi
- Cowley, Michele
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- Selective hydrogenolysis of furfuryl alcohol to 1,5- and 1,2-pentanediol over Cu-LaCoO3 catalysts with balanced Cu0-CoO sites
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Selective hydrogenolysis of biomass-derived furfuryl alcohol (FFA) to 1,5- and 1,2-pentanediol (PeD) was conducted over Cu-LaCoO3 catalysts with different Cu loadings; the catalysts were derived from perovskite structures prepared by a one-step citrate complexing method. The catalytic performances of the Cu-LaCoO3 catalysts were found to depend on the Cu loading and pretreatment conditions. The catalyst with 10 wt% Cu loading exhibited the best catalytic performance after prereduction in 5%H2-95%N2, achieving a high FFA conversion of 100% and selectivity of 55.5% for 1,5-pentanediol (40.3%) and 1,2-pentanediol (15.2%) at 413 K and 6 MPa H2. This catalyst could be reused four times without a loss of FFA conversion but it resulted in a slight decrease in pentanediol selectivity. Correlation between the structural changes in the catalysts at different states and the simultaneous variation in the catalytic performance revealed that cooperative catalysis between Cu0 and CoO promoted the hydrogenolysis of FFA to PeDs, especially to 1,5-PeD, while Co0 promoted the hydrogenation of FFA to tetrahydrofurfuryl alcohol (THFA). Therefore, it is suggested that a synergetic effect between balanced Cu0 and CoO sites plays a critical role in achieving a high yield of PeDs with a high 1,5-/1,2-pentanediol selectivity ratio during FFA hydrogenolysis.
- Gao, Fangfang,Liu, Hailong,Hu, Xun,Chen, Jing,Huang, Zhiwei,Xia, Chungu
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- Rare-earth metal allyl and hydrido complexes supported by an (NNNN)-type macrocyclic ligand: Synthesis, structure, and reactivity toward biomass-derived furanics
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The preparation and characterization of a series of neutral rare-earth metal complexes [Ln(Me3TACD)(η3-C3H 5)2] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane anion (Me3TACD -) are reported. Upon treatment of the neutral allyl complexes [Ln(Me3TACD)(η3-C3H5) 2] with Bronsted acids, monocationic allyl complexes [Ln(Me3TACD)(η3-C3H5)(thf) 2][B(C6X5)4] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me3TACD)H2]n (Ln=Y, n=3; La, n=4; Sm). X-ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me3TACD)R2]n (R=η3-C3H5, n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring-opening conditions.
- Abinet, Elise,Martin, Daniel,Standfuss, Sabine,Kulinna, Heiko,Spaniol, Thomas P.,Okuda, Jun
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- HYDROGENATION OF PENTYNES WITH Rh4(CO)12 AND Rh2(CO)4Cl2 IN SOLUTION AND ANCHORED ON Al2O3
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The catalytic activities of Rh4(CO)12 and Rh2(CO)4Cl2 for the homogeneous hydrogenation of pentynes in toluene have been studied and compared with those of these complexes anchored on γ-Al2O3.Rh3(CO)12 and Rh2(CO)4Cl2 interact strongly with γ-Al2O3, and the resulting species give identical IR spectra in the C-O stretching region characterised by absorptions at 2080 cm-1 and 1997 cm-1, suggesting that the same carbonylrhodium active centres are formed upon binding of both metal carbonyls.However, Rh4(CO)12/Al2O3 and Rh2(CO)4Cl2/Al2O3 show completely different behaviour as catalysts in the hydrogenation of pentynes; Rh2(CO)4Cl2/Al2O3 is more active than Rh2(CO)4Cl2 in solution, while the activity of Rh4(CO)12 is not substantially altered upon going from the homogeneous to the heterogenised system.Complete hydrogenation to give pentane is favored when Rh2(CO)4Cl2 and Rh4(CO)12 are bound to Al2O3, and occurs much more slowly when the complexes are used as homogeneous catalysts.
- Lausarot, P. Michelin,Vaglio, G. A.,Valle, M.
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- Catalytic consequences of particle size and chloride promotion in the ring-opening of cyclopentane on Pt/Al2O3
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Ring-opening of cyclopentane on alumina-supported Pt particles was studied as a function of Pt particle size in the presence of different Cl contents. With catalysts prepared from a Cl-free precursor, measured turnover rates increased monotonically with increasing Pt particle size (1-15 nm). On catalysts derived from a Cl-containing precursor, the turnover rates fell into two separate trends with the change of Pt particle size, depending on the extent of Cl removal by increasing thermal treatment temperature. In both cases, catalytic activity increased with increasing particle size in the examined ranges of dispersions (D = 0.7-1.0 and 0-0.6) and for both series of catalysts, the apparent activation energies were higher on large Pt particles than on small ones, with only small differences in the reaction orders for H2 and cyclopentane on particles of widely varying average sizes. Therefore, the effect of particle size on the turnover rates stems mainly from intrinsic rate constants, rather than from coverage effects. The relative adsorption coefficients of toluene and benzene indicated lower electron densities at the surface Pt atoms in the catalysts prepared from the Cl-containing precursor than in those from the Cl-free precursor. This subtle electron deficiency, which seems not to stem from the local Cl enrichment near Pt, affects both the concentration of chemisorbed hydrogen under reaction conditions and the barrier for C-C bond cleavage. The Cl postintroduced to the catalyst, in contrast, does not induce a similarly positive effect.
- Shi, Hui,Gutiérrez, Oliver Y.,Yang, Hao,Browning, Nigel D.,Haller, Gary L.,Lercher, Johannes A.
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- Conversion of furfural and 2-methylpentanal on Pd/SiO2 and Pd-Cu/SiO2 catalysts
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The conversion of furfural (FAL) and 2-methylpentanal (MPAL) under hydrogen has been studied over silica-supported monometallic Pd and bimetallic Pd-Cu catalysts. At low space times, the conversion of MPAL yields primarily pentane (decarbonylation), but at higher space times, di-methylpentyl ether (etherification) becomes the main product. Upon addition of Cu, both the overall activity and the decarbonylation selectivity decrease while the selectivity to hydrogenation and etherification increases. In contrast to MPAL, the conversion of FAL shows no etherification products at any space time in the temperature range 210-250 °C but only produces furan via decarbonylation. It is proposed that the presence of the aromatic ring in the furfural molecule has a marked effect in inhibiting the formation of the alkoxide surface intermediate, which is required in the etherification reaction. Density Functional Theory (DFT) calculations of furfural and 2-methyl pentanal have been conducted to gain a better understanding of the differences in the molecule-surface interactions between the aldehydes and the Pd and Pd-Cu surfaces. The reaction mechanisms and the resulting selectivity towards the possible reaction paths (hydrogenation/etherification/decarbonylation) are discussed in terms of the relative stability of the η2-(C,O) and acyl surface species occurring on the different metal surfaces.
- Sitthisa, Surapas,Pham, Trung,Prasomsri, Teerawit,Sooknoi, Tawan,Mallinson, Richard G.,Resasco, Daniel E.
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- Activation of alkyl C-F Bonds by B(C6F5)3: Stoichiometric and catalytic transformations
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The Lewis acid B(C6F5)3 is shown to activate a series of alkyl fluorides. In stoichiometric reactions, treatment of sterically demanding phosphines with B(C6F5) 3/alkyl fluorides gives phosphonium fluoroborate salts while treatment of B(C6F5)3/alkyl fluorides with the salts [tBu3PX][XB(C6F5)3] (X = H, PhS) gives the alkane and the salt byproduct [tBu3PX][FB(C 6F5)3]. These fluoroalkanes are also catalytically converted to the corresponding alkanes by reaction of the fluoroalkane and Et3SiH using B(C6F5)3 as the catalyst.
- Caputo, Christopher B.,Stephan, Douglas W.
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- Hydrogenation of Conjugated Dienes and Isomerization of Butenes on CdO, Co3O4 and Cr2O3
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Deuteration of buta-1,3-diene, 2-methylbuta-1,3-diene and penta-1,3-diene selectively yielded but-2-ene, 2-methylbut-2-ene and 1,4-2H2>pent-2-ene on CdO and Co3O4, and but-1-ene, 2-methylbut-1-ene and 4,5-2H2>pent-2-ene on Cr2O3, respectively.These results imply that the selectivity for 1,2- and 1,4-hydrogen addition is maintained in hydrogenation of conjugated dienes, i.e. 1,4-addition on CdO and Co3O4, and 1,2-addition on Cr2O3.The hydrogenation of buta-1,3-diene using a 1:1 mixture of H2 and D2 gave 2H2>but-1-ene in larger amounts than the 2H0>isomer on Cr2O3.An isotope effect smaller than unity was interpreted by prefential adsorption of D2 on the Cr2O3 surface.Formation of 2H1>butene was dominant in deuteration of buta-1,3-diene, indicating that residual hydrogen participates in the reaction; the amount corresponded to 7 times as much as that of chemisorbed hydrogen at room temperature.Co-isomerization of 2H0> and 2H8>but-1-ene yielded, selectively, 2H0>but-2-ene on CdO.Hydrogenation of buta-1,3-diene with a 1:1:1 mixture of H2, HD and D2 also gave 2H0>butene isomers selectively on CdO.These results infer that one intermediate species for hydrogenation of buta-1,3-diene is closely related to that for isomerization of butenes, and these reactions occur through a ?-allylic anion intermediate on CdO.
- Suzuki, Takashi,Tanaka, Katsumi,Toyoshima, Isamu,Okuhara, Toshio,Tanaka, Ken-ichi
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- Direct Observation of Ion-Pair Dynamics
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The intimate ion pair is spontaneously generated by the change-transfer excitation of the electron donor-acceptor complex of anthracene donors (A) and tetranitromethane (TNO2) with a 25-ps laser pulse.The kinetics of the subsequent ion-pair decay to the adduct (i.e., -> AT) is followed spectroscopically over the separate picosecond, nanosecond, and microsecond time domains, each with a different laser-flash system.Three distinctive rate profiles are observed: (a) the picosecond decay following first-order kinetics (kI), the nanosecond decay also following first-order but slower kinetics (kII), and the microsecond decay following second-order kinetics (kIII).The experimental rate constants kI, kII, and kIII are associated with the relaxation of the intimate or tight ion pair , the solvent-separated or loose ion pair , and the free ions , respectively, as originally formulated by Winstein and co-workers for solvolysis mechanisms.These kinetics data together with the measurements of the fractional partitioning of ion pairs allow all the microscopic rate constsnts relevant to ion pair dynamics to be separately evaluated.The Winstein ion-pair formulation is substantiated by the observation and quantitative treatment of the "common-ion" and "special" salt effects.The role of solvent is underscored by the unique kinetics responses of reactive and persistent cations derived from various 9-substituted and 9,10-disubstituted anthracenes, respectively, with changes in the polarity of the medium from benzene and dichloromethane to acetonitrile.The overall importance of charge annihilation and separation in the microdynamics of transient ion pairs is underscored by a comparison with the bimolecular kinetics of radical-radical interaction measured under comparable conditions.
- Masnovi, J. M.,Kochi, J. K.
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- The reaction mechanism of C6 hydrocarbons over acid-base Bifunctional catalysts, TiO2-ZrO2
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This study examined the relation between the acid-base properties of a binary oxide, TiO2-ZrO2, and the reaction behavior of various C6 hydrocarbons over this mixed oxide. Based on experimental results, both the strong acid sites and the strong base sites performed as cracking sites and could be poisoned by doping a small amount of K2O and B2O3, respectively. It was demonstrated that the paired acid-base sites played most important roles on dehydrogenation of cyclohexane and cyclization of n-hexane and hexene. Both the yield and selectivity of benzene increased with the relative paired acid-base amount. The results of isomerization of 1-hexene showed that the yield of the molecular isomerization increased at the expense of the double bond migration as the relative acid/base ratio increased. The results also showed that 2-hexene had a much higher aromatization rate than 1-hexene over TiO2-ZrO2 catalysts. A detailed reaction mechanism of the aromatization C6 hydrocarbons over an acid-base bifunctional catalyst is proposed, which was different from the mechanism of a conventional metal-acid bifunctional catalysts.
- Fung, Jingly,Wang, Ikai
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- Push-pull mechanism of hydrodenitrogenation over silica-supported MoP, WP, and MoS2 hydroprocessing catalysts
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The mechanism of liquid-phase catalytic hydrodenitrogenation at 3.1 MPa on silica-supported molybdenum phosphide, MoP/SiO2, and tungsten phosphide, WP/SiO2, was studied using a series of pentylamines of different structures. The reactivity pattern suggested that removal of nitrogen occurred primarily by an E2 elimination mechanism involving acidic and base sites on the catalyst surfaces in a push-pull process. Infrared spectroscopy and temperature-programmed reaction studies of ethylamine indicated that alkyl ammonium species formed on Bronsted acid sites were intermediates in the reaction. Similar results were obtained with a reference MoS2/SiO2 sample tested at the same conditions. This suggested that sulfur was probably present on the active surface and assisted in the removal of sulfur.
- Clark,Wang,Deck,Oyama
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- Activation of a Ruthenium Cluster by a Gold Centre
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Substitution of Au(PPh3) for hydrogen in increases the rate of catalytic pent-1-ene isomerisation.
- Evans, John,Jingxing, Gao
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- Correlating heat of adsorption of CO to reaction selectivity: Geometric effects vs electronic effects in neopentane isomerization over Pt and Pd catalysts
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Silica-supported Pt and Pd nanoparticles from 1 to 10 nm in diameter were evaluated for neopentane conversion (hydrogenolysis and isomerization). Characterization of the catalysts was conducted utilizing scanning transmission electron microscopy (STEM), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of adsorbed CO, X-ray absorption spectroscopy (XAS), and isothermal calorimetry of CO adsorption to determine how geometric or electronic structure effects can explain changes in reactivity. Isomerization selectivity of Pt was much higher than Pd for all particle sizes. There is a pronounced effect of particle size on selectivity, with the highest isomerization selectivity achieved over catalysts containing the largest particle size for both Pt (57%) and Pd (26%) catalysts. For both Pd and Pt catalysts, DRIFTS showed a decrease in the ratio of linear-to-bridge bonded CO with particle size, while isothermal calorimetry of CO adsorption shows that both Pt and Pd enthalpies of adsorption decrease with increasing particle size. The isomerization selectivity was found to correlate inversely with the strength of CO adsorption for all catalysts suggesting that the chemisorption energy and not the particle size, coordination geometry, or ensemble size is the most important factor for increasing the isomerization selectivity.
- Childers, David,Saha, Arindom,Schweitzer, Neil,Rioux, Robert M.,Miller, Jeffrey T.,Meyer, Randall J.
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- Selectively Weakened C-C ?-Bond in Cation Radicals of Linear and Branched Pentanes As Studied By Electron Spin Resonance
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Radical cations which have the fully extended structure (trans-trans conformation) but have lost the symmetry of the mother molecules were detected by electron spin resonance for n-pentane, 3-methylpentane, and 3,3-dimethylpentane in frozen matrices at 4 K.It was indicated, with the aid of an INDO calculation, that one of the two inner C-C bonds in the main chain is elongated and the unpaired electron tends to be confined in this bond.Selective bond elongation was also shown for the trans-gauche conformers of 3-methylpentane and 3,3-dimethylpentane cations.These facts suggest that selective elongation of a C-C bond is essential with alkane cations even if it is not Jahn-Teller active.This selective weakening of a skeletal bond should be related to the selectivity in the bond scission in alkane radiolysis.In addition, hole migration between the solute alkanes in the frozen matrices at 77 K was suggested from the radical conversion between the different conformers.
- Toriyama, Kazumi,Okazaki, Masaharu
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- Kinetic and FTIR studies of 2-methyltetrahydrofuran hydrodeoxygenation on Ni2P/SiO2
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The hydrodeoxygenation of 2-methyltetrahydrofuran (2-MTHF) at a medium pressure of 0.5 MPa is studied over a Ni2P/SiO2 catalyst. Contact time studies show the formation of n-pentanal, 1-pentanol, 2-pentanone, 2-pentanol, and 2-pentene, as reaction intermediates and the production of pentane and butane as major products. The results are consistent with adsorption of 2-MTHF followed by rate-determining ring-opening to form either 1-pentoxide or 2-pentoxide alkoxide intermediates. Subsequent hydrogen-transfer steps produce the various intermediates, a decarbonylation step of the pentanal forms n-butane and CO, and further hydrodeoxygenation steps result in n-pentane. Fitting of the results using a rake mechanism that considers adsorbed intermediates gives excellent agreement with experimental data, and agrees with a simulation with a simpler first-order model. The more detailed rake analysis indicates that the surface species from the 1-pentoxide intermediate are ten-fold more plentiful than those produced from the 2-pentoxide intermediate. In situ infrared measurements support this reaction mechanism.
- Cho, Ara,Kim, Hosoo,Iino, Ayako,Takagaki, Atsushi,Ted Oyama
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- Thermodynamic parameters of the single-stage dehydrogenation of isopentane to isoprene
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From the results of experiments with platinum-containing catalysts operating in the steady mode, adiabatic changes in temperature in the course of 2-metylbutane dehydrogenation to monoolefins and isoprene were calculated. Dehydrogenation of 2-methylbutane
- Romanova,Lamberov,Shaikhutdinova,Gil'Manov,Gil'Mullin
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- The hydrogenation of 1,3-pentadiene over an alumina-supported palladium catalyst: An FTIR study
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The hydrogenation of a mixture of cis- and trans-1,3-pentadiene over a 1% Pd/Al2O3 catalyst at 303 K has been studied using infrared spectroscopy to monitor the changes in the composition of the gas phase over the catalyst as a function of time. The reaction is seen to occur as a consecutive process, with the terminal double bond hydrogenated in advance of the internal double bond. Vibrational assignments have been confirmed through ancillary calculations for a number of C5 molecules. The reaction profile is consistent with the catalyst presenting two distinct reaction sites: hydrogenation of the terminal double bond occurs at Site α, whilst Site β is responsible for hydrogenation of the internal double bond. Trans-pent-2-ene is identified as the only reaction intermediate. From comparative studies of the hydrogenation of pentenes over the catalyst, the absence of any cis-pent-2-ene in the reaction mixture is tentatively attributed to cis-1,3-pentadiene isomerising at Site α to form trans-1,3-pentadiene. The effect of toluene-d8 to act as a chemical modifier was also investigated and shown to selectively poison Site β Site α being unperturbed.
- Opara, Elaine,Lundie, David T.,Lear, Timothy,Sutherland, Iain W.,Parker, Stewart F.,Lennon, David
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- Selective Catalytic Hydrogenolysis of Carbon-Carbon σ Bonds in Primary Aliphatic Alcohols over Supported Metals
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The selective scission of chemical bonds is always of great significance in organic chemistry. The cleavage of strong carbon-carbon σ bonds in the unstrained systems remains challenging. Here, we report the selective hydrogenolysis of carbon-carbon σ bonds in primary aliphatic alcohols catalyzed by supported metals under relatively mild conditions. In the case of 1-hexadecanol hydrogenolysis over Ru/TiO2 as a model reaction system, the selective scission of carbon-carbon bonds over carbon-oxygen bonds is observed, resulting in n-pentadecane as the dominant product with a small quantity of n-hexadecane. Theoretical calculations reveal that the 1-hexadecanol hydrogenolysis on flat Ru (0001) undergoes two parallel pathways: i.e. carbon-carbon bond scission to produce n-pentadecane and carbon-oxygen bond scission to produce n-hexadecane. The removal of adsorbed CO on a flat Ru (0001) surface is a crucial step for the 1-hexadecanol hydrogenolysis. It contributes to the largest energy barrier in n-pentadecane production and also retards the rate for n-hexadecane production by covering the active Ru (0001) surface. The knowledge presented in this work has significance not just for a fundamental understanding of strong carbon-carbon σ bond scission but also for practical biomass conversion to fuels and chemical feedstocks.
- Di, Lu,Yao, Sikai,Li, Mengru,Wu, Guangjun,Dai, Weili,Wang, Guichang,Li, Landong,Guan, Naijia
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- HYDROGENATION OF PENTYNES AND OF PENTADIENES CATALYSED BY Ru3(CO)12, Fe3(CO)12 AND MIXED METAL Ru-Fe DODECACARBONYLS SUPPORTED ON γ-Al2O3
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Hydrogenation under mild conditions of 1- and 2-pentyne and of 1,3-cis- and 1,3-trans-pentadiene catalysed by Ru3(CO)12, FeRu2(CO)12, Fe2Ru(CO)12 and Fe3(CO)12 in toluene solutions or anchored on γ-Al2O3 has been studied.For all the systems examined, catalytic activity was highest for Ru3(CO)12-containing catalysts and lowest for Fe3(CO)12-containing ones.For mixed metal catalysts, activity decreased with increasing number of Fe atoms in the dodecacarbonyls.Anchorage of the clusters to γ-Al2O3 produced catalysts which were less active towards hydrogenation of 1- and 2-pentyne and more active towards hydrogenation of 1,3-cis- and 1,3-trans-pentadiene, but had no effect on product distribution.
- Lausarot, P. Michelin,Vaglio, G. A.,Valle, M.
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- HOMOGENEOUS CATALYTIC HYDROGENATION AND ISOMERIZATION OF LINEAR AND CYCLIC MONOENES AND DIENES IN THE PRESENCE OF THE HETEROMETALLIC CLUSTER (η5-C5H5)NiRu3(μ-H)3(CO)9
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The complex (η5-C5H5)NiRu3(μ-H)3(CO)9 catalyses the selective hydrogenation of the therminal double bond of conjugated linear dienes in homogeneous conditions; isomerization of non-conjugated to conjugated dienes and of pent-1-ene to pent-2-ene also occurs.Selective hydrogenation and isomerization of cyclic hexenes and hexadienes takes place without opening of the ring; a reaction scheme is proposed, and the activity of the cluster itself relative to that of its decomposition products is discussed.Its behaviour is compared with the analogous complex (η5-C5H5)NiOs3(μ-H)3(CO)9.
- Castiglioni, Mario,Giordano, Roberto,Sappa, Enrico
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- Using modifiers to specify stereochemistry and enhance selectivity and activity in palladium-catalysed, liquid phase hydrogenation of alkynes
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Enhancing selectivity is a key parameter in green chemistry. In this study, we have examined the liquid phase hydrogenation of alkynes over a palladium catalyst and used modifiers to enhance selectivity and activity. The reactions studied were the hydrogenation of 1-pentyne and 2-pentyne. Five modifiers were used, pentane nitrile and its respective amine, pentyl amine, 3-phenyl propionitrile and its respective amine, 3-phenyl propylamine and trans-cinnamonitrile. These modifiers were not hydrogenated under reaction conditions. It was possible to obtain high (>90%) selectivities to 1-pentene and cis-2-pentene at high conversion. The effect on rate was dependent upon the modifier and the alkyne. The effect of the modifier was the same whether added with or before the reactants. Competitive reactions confirmed that terminal alkynes and internal alkynes are hydrogenated on separate sites and do not interfere and that the modifier influences each separately.
- Garcia, Paloma E.,Lynch, Ailsa S.,Monaghan, Andy,Jackson, S. David
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- Preparation of the Ru/HZSM-5 catalyst and its catalytic performance for the 2-pentanone hydrodeoxygenation reaction
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Levulinic acid is an ideal model compound for complex oxygenated components in bio-oil. To assist the understanding of its hydrodeoxygenation (HDO) performance, it is necessary to investigate separately the HDO property of the ketonic carbonyl group and carboxyl group. Herein, 2-pentanone was selected as a model to study the HDO property of the ketonic carbonyl group. The Ru/HZSM-5 catalyst was prepared by an excessive impregnation method and its structure and acidity were characterized by H2-TPR, NH3-TPD, HRTEM, SEAD, Py-IR, TG-DSC, and ICP analyses. The effect of preparation conditions on the catalytic performance of Ru/HZSM-5 was studied; the suitable preparation conditions were determined as follows: a calcination temperature of 450 °C, a calcination time of 3 h, a reduction temperature of 350 °C, and a reduction time of 4 h. The catalytic performance of Ru/HZSM-5 for the 2-pentanone HDO reaction was evaluated; pentane selectivity of 77.7% at a 2-pentanone conversion of 91.8% was achieved under the conditions of a reaction pressure of 5 MPa, a reaction temperature of 190 °C, a catalyst amount of 6 wt% and a reaction time of 6 h. 2-Pentanone HDO follows the reaction path of 2-pentanone hydrogenation to 2-pentanol and then 2-pentanol dehydration and hydrogenation to the target product pentane. The acidity of the catalyst plays a certain role in influencing its catalytic performance: Lewis acid sites show high activity for activating C-O bonds and Br?nsted acid sites are the key to accelerate the further dehydration of 2-pentanol and hydrogenation to alkanes.
- An, Hualiang,Wang, Yanji,Xi, Xi,Yang, Ye,Zhao, Xinqiang
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- EFFECT OF THERMODIFFUSION AND CHEMICAL TREATMENT OF THE SURFACE OF MEMBRANE CATALYSTS MADE FROM PALLADIUM ALLOYS WITH RUTHENIUM AND RHODIUM ON PENTA-1,3-DIENE HYDROGENATION
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It has been shown that the nature of the metal used for thermal diffusion treatment of the surface of membrane catalysts affects the selectivity toward penta-1,3-diene hydrogenation.The formation of cyclopentene and cyclopentane has been established for membrane catalysts made from Pd Alloys with Ru and Rh that have been subjected to thermal diffusion of Zn and Ga and chemical treatment.
- Mishchenko, A. P.,Gryaznov, V. M.,Sarylova, M. E.
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- ORGANOBORANES FOR SYNTHESIS. 1. PROTONOLYSIS OF TRIALKYLBORANES. A CONVENIENT NON-CATALYTIC CONVERSION OF ALKENES INTO SATURATED COMPOUNDS via HYDROBORATION-PROTONOLYSIS
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The protonolysis of trialkylboranes with carboxylic acids proceeds very rapidly for the first group, somewhat slower for the second, but requires elevated temperatures for removal of the third.A close examination of the protonolysis of representative symmetrical, as well as mixed trialkylboranes, reveals that the steric requirements of the alkyl groups attached to boron play an important role in the rate.Secondary alkyl groups protonolyze less readily than primary alkyl groups.More hindered alkyl groups are still more resistant.Since the hydroboration-protonolysis sequence involves relatively mild conditions, this procedure can be applied for hydrogenating olefinic derivatives containing labile groups, such as active sulfur, halogen and nitrogen functionalities.The stereochemistry of protonolysis has been established via deuteroboration of norbornene and deuterolysis of the product.It is evident that protonolysis proceeds with retention of configuration at the migrating carbon.Partially alkylated boranes can be used for hydroboration-protonolysis with improved regioselectivity.Subsequent protonolysis of the resulting mixed trialkylboranes provides the desired alkanes in good yields.Products sensitive to the action of hot acetic acid offer difficulties.For example, when this procedure was applied to the preparation of 1-menthene from d-limonene, the product was racemic.
- Brown, Herbert C.,Murray, Kenneth J.
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- Palladium metal nanoparticles stabilized by ionophilic ligands in ionic liquids: Synthesis and application in hydrogenation reactions
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The reduction of [Pd(acac)(COD)]BF4 (acac = acetylacetonate; COD = 1,5-cyclooctadiene), dissolved in BMI·BF4, in the presence of P- or N-containing ionophilic ligands by H2 yields "soluble" and stable [Pd(0)]n nanoparticles (NPs). These ionic liquid soluble NPs are active and selective catalysts for the hydrogenation of 1,3-dienes and alkynes under mild reaction conditions. Selectivities up to 87% to cis-2-pentene and 95% conversion were obtained using Pd NPs modified with 1-(3-(diphenylphosphino)propyl)-2,3-dimethyl-1H-imidazol-3-ium N-bis(trifluoromethylsulfonyl)imide in 1-n-butyl-3-methylimidazolium tetrafluoroborate.
- Leal, Brbara C.,Consorti, Crestina S.,Machado, Giovanna,Dupont, Jairton
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- Ring-Opening Hydrogenation Reactions of Monoalkyl-Substituted Cyclobutanes over Ni/SiO2 Catalyst
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The hydrogenative ring-opening reactions of methyl- and propylcyclobutane were studied over Ni/SiO2 catalyst in wide temperature and hydrogen pressure ranges, Firstly, the temperature dependence of ring opening was determined and maximum curves were observed for both reactants.On the basis of temperature dependence curves, various temperature were selected for hydrogen pressure studies.At both 523 and 573 K, only hydrogenative ring opening occurred, and the ring opened mostly in the sterically less hindered direction in the case of methylcyclobutane over clean as well as working catalysts.However, for propylcyclobutane the selectivity was close to statistical or opposite to that for methylcyclobutane, especially at lower hydrogen pressures over the initial catalyst.At the lowest temperature at which ring opening occurred at all, exclusive heptane formation (ring opening in the more hindered direction) was observed.The hydrogen pressure dependence curves over the initial and working catalysts were used to draw mechanistic inferences concerning the ring-opening reactions.
- Toeroek, Bela,Bartok, Mihaly
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- Hydrogen storage using heterocyclic compounds: The hydrogenation of 2-methylthiophene
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Alkyl substituted thiophenes are promising candidates for hydrogen carriers, as their dehydrogenation reactions are known to occur under mild conditions. Four types of catalysts, including supported noble metals, bimetallic noble metals, transition metal
- Zhao,Oyama,Naeemi
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- Photochemistry of Surface-Confined Organometallics. Photochemical Release of a Surface-Confined Cobalt Carbonyl Catalyst
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Inorganic oxide surfaces, SiO2 and Al2O3, bearing -OH functionality have been functionalized with -Co(CO)4 by first treating the solids with (EtO)3SiH, Me2ClSiH, or Cl3SiH to introduce SiH functionality followed by reaction with Co2(CO)8.Derivatized surfaces have been characterized by infrared spectroscopy and compared to solution analogues to confirm the presence of SiH and SiCo(CO)4 groups on the surface.The surface-confined SiCo(CO)4 undergoes photoreactions that begin with loss of CO subsequent to optical excitation in the near-ultraviolet.The photochemistry closely parallels the behavior of solution R3SiCo(CO)4 analogues; CO can be photosubstituted by P(OPh)3 and the surface-confined SiCo(CO)3(P(OPh)3) species is detectable by infrared spectroscopy.Irradiation of the oxide powders bearing SiCo(CO)4 suspended in Et3SiH solutions results in the release of the -Co(CO)4 into solution at Et3SiCo(CO)4 concurrent with the regeneration of surface SiH functionality.Irradiation of the powders (SiCo(CO)4) in the presence of 1-pentene yields Co4(CO)12 in solution and surface Si(pentenyl) groups.In the presence of Et3SiH/1-pentene photoactivated catalysis by the derivatized powders (SiCo(CO)4) occurs to give isomerization of the alkene, hydrosilation to Et3Si(n-pentyl), and small ammounts of pentane.Reaction under H2 improves the relative yield of pentane, while H2/CO mixtures yield no hydroformylation products and lower the observed rate due to CO competing for coordinatively unsaturated species.The surface SiH groups also add to 1-pentene to give powders bearing Si(n-pentyl) functianality.The use of powders functionalized with SiCo(CO)3(P(OPh)3) also gives catalysis upon photoexcitation, but the product distribution differs significantly and includes at least two isomers of Et3Si(pentenyl).In all cases the bulk of the catalysis appears to result from Co-carbonyl fragments photoreleased from the oxide support.The initial rate of catalysis appears to depend on the initial rate at which the fragments are released into homogeneous solution.The heterogeneous photocatalysts thus give the same product distribution as appropriate homogeneous precursors, but the oxide supported SiCo(CO)4 is more easily isolated and handled and more durable than R3SiCo(CO)4.
- Reichel, Carol L.,Wrighton, Mark S.
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- Radical reactions in the radiolysis of cyclopentane
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The end products produced in the γ-radiolysis of cyclopentane have been measured at very low total doses (25-50 krad). Iodine scavenging techniques in solutions of 0.1-30 mM were used to elucidate radical yields and reaction mechanisms. The yields of the main radical species were found to be as follows: cyclopentyl, 4.9; 1-pentyl, 0.2; 3-cyclopentenyl, 0.07; H atom, 1.3 radical/100 eV. The change in yields from neat cyclopentane to 0.1 mM iodine solution suggests that about 79% of the cyclopentyl radicals escape the spur and react in the bulk medium with a disproportionation to combination ratio of 0.97. Radical precursors account for about 50% of the total end product yield, which is much smaller than found in the radiolysis of cyclohexane or cyclooctane. The radiolysis mechanism for cyclopentane is discussed and compared to those for cyclohexane and cyclooctane.
- Wojnarovits,LaVerne
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- Mechanism of n-butane skeletal isomerization on H-mordenite and Pt/H-mordenite
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Kinetics and isotope labeling experiments were used to investigate the reaction pathways of n-butane on H-mordenite and Pt/H-mordenite at atmospheric pressure and temperatures of 543-583 K. Butenes, either formed on the catalyst or present in the feed, controlled the relative rates of mono- and bimolecular reaction pathways. The true activation energy for isobutane formation was found to be 120-134 kJ/mol. The reaction order for isobutane formation with respect to n-butene on Pt/H-mordenite was 1.0-1.2, consistent with a predominately monomolecular route of formation. An order close to 2 for disproportionation products indicated a bimolecular route of formation. An increase of the butene concentration from less than 20 ppm to about 120 ppm greatly increased the rate of bimolecular skeletal isomerization, as determined from conversion of 1,4-13C2-n-butane. The findings explain how reaction conditions affect product selectivity and clarify the controversy around butane isomerization on solid acids.
- Wulfers, Matthew J.,Jentoft, Friederike C.
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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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- Conversion of Phenol and Lignin as Components of Renewable Raw Materials on Pt and Ru-Supported Catalysts
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Hydrogenation of phenol in aqueous solutions on Pt-Ni/SiO2, Pt-Ni-Cr/Al2 O3, Pt/C, and Ru/C catalysts was studied at temperatures of 150–250? C and pressures of 40–80 bar. The possibility of hydrogenation of hydrolysis lignin in an aqueous medium in the presence of a Ru/C catalyst is shown. The conversion of hydrolysis lignin and water-soluble sodium lignosulfonate occurs with the formation of a complex mixture of monomeric products: a number of phenols, products of their catalytic hydrogenation (cyclohexanol and cyclohexanone), and hydrogenolysis products (cyclic and aliphatic C2 –C7 hydrocarbons).
- Bobrova, Nataliia A.,Bogdan, Tatiana V.,Bogdan, Viktor I.,Koklin, Aleksey E.,Mishanin, Igor I.
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- Mechanism change of (+)-nonlinear effect in a phase separation system in a CuII-catalyzed asymmetric friedel-crafts reaction using a C2-chiral dioxolane-containing-bisamidine ligand, Naph-diPIM-dioxo-iPr
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A CuII complex of bisamidine ligand LS, chirally modified naphtho[1,2-b:7,8-b′]dipyrroloimidazole (Naph-diPIM), catalyzes the enantioselective Friedel-Crafts (FC) reaction of indole (1a) with ethyl trifluoropyruvate (2) to give quantitatively the FC adduct 3a with a 98:2 S/R enantiomer ratio (er). The reaction shows no nonlinear effect (NLE) under the standard conditions of [1a] = [2] = 100mM; [Cu(OTf)2] = [LS + LR] = 0.10 mM; CPME; and 0 °C irrespective of the catalyst aging temperature. A five-fold increase in the catalyst concentration (0.50mM) changes the situation, leading to a strong (+)-NLE with phase separation of a white solid. The NLE is expressed by the Noyori-type mechanism: Aggregate of heterochiral dimer CuLSCuLR is separated from the reaction system (Khetero > 1 > Khomo). Furthermore, a strong (+)-NLE is observed via a purple solid liberation even with [CuII] = 0.10mM after the catalyst aging at 100 °C in the presence of an excess amount of chiral ligand. A mechanistic study has revealed i) that the sterically disfavored homochiral 1:2 complex CuLSLS is more stabilized by an intramolecular n-π? interaction than the sterically favored heterochiral 1:2 complex CuLSLR and ii) that the (+)-NLE originates from the phase separation of heterochirally interacted (CuLSLSCuLRLR).
- Kitamura, Masato,Le, Thien Phuc,Tanaka, Shinji,Yoshimura, Masahiro
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supporting information
p. 1319 - 1333
(2020/11/30)
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- Tungsten Catalyst Incorporating a Well-Defined Tetracoordinated Aluminum Surface Ligand for Selective Metathesis of Propane, [(≡Si?O?Si≡)(≡Si?O?)2Al?O?W(≡CtBu) (H)2]
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A well-defined aluminium-bound hydroxyl group on the surface of mesoporous SBA-15, [(≡Si?O?Si≡) (≡Si?O)2 Al?OH], 3 was obtained by reacting di-isopropyl aluminium hydride with SBA-15 treated at 700 °C. The resulting surface [(≡Si?O?Si≡) (≡Si?O) 2 Al (isobutyl) fragment undergoes β-H elimination at 400 °C leading to [(≡Si?O?Si≡)(≡Si?O?)2Al?O) Al?H]. Further oxidation of this Al-hydride with N2O leads to 3. This acidic support was used to create a well-defined surface organo-tungsten fragment [(≡Si?O?Si≡)(≡Si?O?)2Al?O?W(≡CtBu)(CH2tBu)2] by reacting 3 with W(≡C-tBu)(CH2-tBu)3. A further reaction with hydrogen under mild conditions afforded the tungsten carbyne bis-hydride [(≡Si?O?Si≡)(≡Si?O?)2Al?O?W(H)2(≡C-tBu)]. The performance of each of the W-supported catalysts was assessed for propane metathesis in a flow reactor at 150 °C. [(≡Si?O?Si≡)(≡Si?O?)2 Al?O?W(≡CtBu)(H)2] was found to be a single-site catalyst, giving the highest turnover number (TON=800) and the highest reported selectivity for butane (45 %) vs. ethane (32 %) known for oxide-supported tungsten complex catalysts (with the supports being silica, silica-alumina, and alumina). The results demonstrate that modification of the oxide ligands on silica via the creation of Al Lewis acid center as an anchoring site for organometallic complexes opens up new catalytic properties, markedly enhancing the catalytic performance of supported organo-tungsten species.
- Werghi, Baraa,Bendjeriou-Sedjerari, Anissa,Jedidi, Abdesslem,Morlanes, Natalia,Abou-Hamad, Edy,Bhatte, Kushal,Guan, Erjia,Ma, Tao,Aguilar-Tapia, Antonio,Ould-Chikh, Samy,Cavallo, Luigi,Gates, Bruce C.,Basset, Jean-Marie
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p. 614 - 620
(2019/01/04)
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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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- Deacylative transformations of ketones via aromatization-promoted C–C bond activation
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Carbon–hydrogen (C–H) and carbon–carbon (C–C) bonds are the main constituents of organic matter. Recent advances in C–H functionalization technology have vastly expanded our toolbox for organic synthesis1. By contrast, C–C activation methods that enable editing of the molecular skeleton remain limited2–7. Several methods have been proposed for catalytic C–C activation, particularly with ketone substrates, that are typically promoted by using either ring-strain release as a thermodynamic driving force4,6 or directing groups5,7 to control the reaction outcome. Although effective, these strategies require substrates that contain highly strained ketones or a preinstalled directing group, or are limited to more specialist substrate classes5. Here we report a general C–C activation mode driven by aromatization of a pre-aromatic intermediate formed in situ. This reaction is suitable for various ketone substrates, is catalysed by an iridium/phosphine combination and is promoted by a hydrazine reagent and 1,3-dienes. Specifically, the acyl group is removed from the ketone and transformed to a pyrazole, and the resulting alkyl fragment undergoes various transformations. These include the deacetylation of methyl ketones, carbenoid-free formal homologation of aliphatic linear ketones and deconstructive pyrazole synthesis from cyclic ketones. Given that ketones are prevalent in feedstock chemicals, natural products and pharmaceuticals, these transformations could offer strategic bond disconnections in the synthesis of complex bioactive molecules.
- Xu, Yan,Qi, Xiaotian,Zheng, Pengfei,Berti, Carlo C.,Liu, Peng,Dong, Guangbin
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p. 373 - 378
(2019/05/22)
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- Hydrocarbon Synthesis via Photoenzymatic Decarboxylation of Carboxylic Acids
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A recently discovered photodecarboxylase from Chlorella variabilis NC64A (CvFAP) bears the promise for the efficient and selective synthesis of hydrocarbons from carboxylic acids. CvFAP, however, exhibits a clear preference for long-chain fatty acids thereby limiting its broad applicability. In this contribution, we demonstrate that the decoy molecule approach enables conversion of a broad range of carboxylic acids by filling up the vacant substrate access channel of the photodecarboxylase. These results not only demonstrate a practical application of a unique, photoactivated enzyme but also pave the way to selective production of short-chain alkanes from waste carboxylic acids under mild reaction conditions.
- Zhang, Wuyuan,Ma, Ming,Huijbers, Mieke M. E.,Filonenko, Georgy A.,Pidko, Evgeny A.,Van Schie, Morten,De Boer, Sabrina,Burek, Bastien O.,Bloh, Jonathan Z.,Van Berkel, Willem J. H.,Smith, Wilson A.,Hollmann, Frank
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supporting information
p. 3116 - 3120
(2019/03/06)
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- High-Quality Gasoline Directly from Syngas by Dual Metal Oxide–Zeolite (OX-ZEO) Catalysis
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Despite significant efforts towards the direct conversion of syngas into liquid fuels, the selectivity remains a challenge, particularly with regard to high-quality gasoline with a high octane number and a low content of aromatic compounds. Herein, we show that zeolites with 1D ten-membered-ring (10-MR) channel structures such as SAPO-11 and ZSM-22 in combination with zinc- and manganese-based metal oxides (ZnaMnbOx) enable the selective synthesis of gasoline-range hydrocarbons C5–C11 directly from syngas. The gasoline selectivity reached 76.7 % among hydrocarbons, with only 2.3 % CH4 at 20.3 % CO conversion. The ratio of isoparaffins to n-paraffins was as high as 15, and the research octane number was estimated to be 92. Furthermore, the content of aromatic compounds in the gasoline was as low as 16 %. The composition and structure of ZnaMnbOx play an important role in determining the overall activity. This process constitutes a potential technology for the one-step synthesis of environmentally friendly gasoline with a high octane number from a variety of carbon resources via syngas.
- Li, Na,Jiao, Feng,Pan, Xiulian,Chen, Yuxiang,Feng, Jingyao,Li, Gen,Bao, Xinhe
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supporting information
p. 7400 - 7404
(2019/05/10)
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- Study of the Structure of Cobalt-Containing Catalysts Synthesized under Subcritical Conditions
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Abstract: A physicochemical study of cobalt-containing (10 wt %) silica-supported Fischer–Tropsch catalysts was carried out. The catalysts were obtained under subcritical conditions (T = 200°C, P = 8 MPa) using water (Tc = 374.1°C, Pc = 22.1 MPa) and propanol-2 (Tc = 235.6°C, Pc = 5.8 MPa). The obtained samples were compared with a 10 wt % Co/SiO2 catalyst prepared by incipient-wetness impregnation. Comparison of the properties of catalysts in the liquid-phase Fischer–Tropsch synthesis showed that the sample prepared in subcritical water was the most active and selective to aliphatic C6–C7 hydrocarbons. This sample is characterized by a high surface area (131.7 m2/g), a uniform distribution of particles in the active phase with an average size of 5 nm and higher accessibility of cobalt species for reagents. According to XPS data, the composition of catalyst active phase is mainly represented by two compounds: Co(OH)2 and Co3O4.
- Markova,Gavrilenko,Stepacheva,Molchanov,Matveeva,Sulman,Sulman
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p. 618 - 626
(2019/10/19)
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- Enzymatic Electrosynthesis of Alkanes by Bioelectrocatalytic Decarbonylation of Fatty Aldehydes
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An enzymatic electrosynthesis system was created by combining an aldehyde deformylating oxygenase (ADO) from cyanobacteria that catalyzes the decarbonylation of fatty aldehydes to alkanes and formic acid with an electrochemical interface. This system is able to produce a range of alkanes (octane to propane) from aldehydes and alcohols. The combination of this bioelectrochemical system with a hydrogenase bioanode yields a H2/heptanal enzymatic fuel cell (EFC) able to simultaneously generate electrical energy with a maximum current density of 25 μA cm?2 at 0.6 V and produce hexane with a faradaic efficiency of 24 %.
- Abdellaoui, Sofiene,Macazo, Florika C.,Cai, Rong,De Lacey, Antonio L.,Pita, Marcos,Minteer, Shelley D.
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p. 2404 - 2408
(2018/01/27)
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- Synthesis, Characterization, and Reactivity of a High-Spin Iron(II) Hydrido Complex Supported by a PNP Pincer Ligand and Its Application as a Homogenous Catalyst for the Hydrogenation of Alkenes
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This study focused on the synthesis and characterization of a range of low-valent, high-spin iron(II) complexes supported by a carbazole-based PNP pincer-type ligand. The addition of the lithiated ligand (PNP)Li to FeCl2(THF)1.5 yielded the chlorido complex (PNP)FeCl (1), which could be readily converted to the four-coordinate iron(II) alkyl complexes (PNP)FeR [R = CH2SiMe3 (3a), Me (3b), CH2Ph (3c)]. These iron(II) complexes were fully characterized by X-ray analysis and a comprehensive, density-functional-theory-assisted study with complete assignment of their paramagnetic 1H and 13C NMR spectra. Treatment of 1 with KHBEt3 or the addition of molecular hydrogen to (PNP)FeR afforded a high-spin iron(II) PNP hydrido complex, which was identified as the dimer [(PNP)Fe(μ-H)]2 (4) with two bridging hydrido ligands between the iron centers. Exposing complexes 1 and 4 to carbon monoxide led to the corresponding six-coordinate, diamagnetic complexes (PNP)Fe(CO)2Cl (2) and (PNP)Fe(CO)2H (5), of which 2 was present as cis/trans isomers. Furthermore, 4 was found to be an active catalyst for the hydrogenation of alkenes.
- Ott, Jonas C.,Blasius, Clemens K.,Wadepohl, Hubert,Gade, Lutz H.
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supporting information
p. 3183 - 3191
(2018/03/26)
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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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- Selective Hydrogenolysis of Furfural Derivative 2-Methyltetrahydrofuran into Pentanediol Acetate and Pentanol Acetate over Pd/C and Sc(OTf)3 Cocatalytic System
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It is of great significance to convert platform molecules and their derivatives into high value-added alcohols, which have multitudinous applications. This study concerns systematic conversion of 2-methyltetrahydrofuran (MTHF), which is obtained from furfural, into 1-pentanol acetate (PA) and 1,4-pentanediol acetate (PDA). Reaction parameters, such as the Lewis acid species, reaction temperature, and hydrogen pressure, were investigated in detail. 1H NMR spectroscopy and reaction dynamics study were also conducted to help clarify the reaction mechanism. Results suggested that cleavage of the primary alcohol acetate was less facile than that of the secondary alcohol acetate, with the main product being PA. A PA yield of 91.8 % (150 °C, 3 MPa H2, 30 min) was achieved by using Pd/C and Sc(OTf)3 as a cocatalytic system and an 82 % yield of PDA was achieved (150 °C, 30 min) by using Sc(OTf)3 catalyst. Simultaneously, the efficient conversion of acetic esters into alcohols by simple saponification was carried out and led to a good yield.
- Zhang, Kun,Li, Xing-Long,Chen, Shi-Yan,Xu, Hua-Jian,Deng, Jin,Fu, Yao
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p. 726 - 734
(2018/02/06)
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- Catalytic Hydrodefluorination of C?F Bonds by an Air-Stable PIII Lewis Acid
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Catalytic hydrodefluorination (HDF) of unactivated fluoroalkanes or CF3-substituted aryl species is performed using the PIII Lewis acids, [(bipy)PPh]2+ (12+) and [(terpy)PPh]2+ (22+) under
- Chitnis, Saurabh S.,Krischer, Felix,Stephan, Douglas W.
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p. 6543 - 6546
(2018/04/26)
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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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- Continuous-Flow Alkane Dehydrogenation by Supported Pincer-Ligated Iridium Catalysts at Elevated Temperatures
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Pincer-ligated iridium complexes of the form [Ir(R4PCP)L] (R4PCP = κ3-C6H3-2,6-(XPR2)2; X = CH2, O; R = tBu, iPr) are efficient homogeneous alkane dehydrogenation catalysts that have been reported to be highly active at temperatures of 240 °C or below. In this work, silica-supported [Ir(C2H4)(p-tBu2PO-tBu4POCOP)] (1/SiO2) was used to study a model continuous-flow gas-phase acceptorless alkane dehydrogenation system. This particular supported framework is thermally stable at temperatures up to 340 °C, 100 °C above the highest temperature at which analogous homogeneous complexes have been reported to show stable activity, with observed butane dehydrogenation rates of ca. 80 molbutenes molcat.-1 h-1. Solid-state 31P MAS NMR and ATR IR are used to demonstrate that the backbone pincer ligand remains intact and coordinated at 340 °C. The complex is fully converted to [Ir(CO)(p-tBu2PO-tBu4POCOP)] (3/SiO2) above 300 °C. 3/SiO2 is observed to be catalytically active at the higher temperatures tested, and reaction rates are comparable to those of 1/SiO2. 3/SiO2 and 1/SiO2 act as resting states for the active 14-electron fragment, through dissociation of the CO or olefin ligand, respectively. Given that 3/SiO2 is air resistant at ambient temperature and is structurally stable and catalytically active at elevated temperatures, it is a suitable candidate as a catalyst for the highly endothermic acceptorless dehydrogenation of alkanes.
- Sheludko, Boris,Cunningham, Molly T.,Goldman, Alan S.,Celik, Fuat E.
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p. 7828 - 7841
(2018/07/25)
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- Interactions of C?F Bonds with Hydridoboranes: Reduction, Borylation and Friedel–Crafts Alkylation
-
The stoichiometric reactions of the alkylfluorides 1-fluoroadamantane (Ad-F), fluorocyclohexane (Cy-F), 1-fluoropentane (Pent-F) and benzyl fluorides with secondary boranes pinacolborane (HBpin), catecholborane (HBcat), 9-borabicyclo(3.3.1)nonane (9-BBN)
- Bamford, Karlee L.,Chitnis, Saurabh S.,Qu, Zheng-wang,Stephan, Douglas W.
-
supporting information
p. 16014 - 16018
(2018/10/15)
-
- Alkanethiolate-capped palladium nanoparticles for selective catalytic hydrogenation of dienes and trienes
-
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)
-
- Catalytic double hydroarylation of alkynes to 9,9-disubstituted 9,10-dihydroacridine derivatives by an electrophilic phenoxyphosphonium dication
-
The electrophilic pyridinium-substituted phenoxy-phosphonium dicationic salt [(PhO)P(2-(N-Mepy))Ph2][B(C6F5)4]2, is shown to be an effective catalyst for the double hydroarylation of alkynes with diarylamines to afford a series of 9-methyl-9-aryl-9,10-dihydroacridine and 9,10-dimethyl-9-aryl-9,10-dihydroacridine derivatives.
- LaFortune, James H. W.,Bayne, Julia M.,Johnstone, Timothy C.,Fan, Louie,Stephan, Douglas W.
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supporting information
p. 13312 - 13315
(2017/12/26)
-
- Flexible gasoline process using multiple feedstocks
-
A flexible process for gasoline refineries is described. The process can vary depending on the available feedstock and the desired products. At one time, the process can involve disproportionating pentanes to a product mixture including isobutane and isohexane. At other times, by switching the feedstock and operating conditions, the process can convert a mixture of C4 and C7 paraffins to a low aromatic blendstock with suitable octane and a vapor pressure lower than butanes. The process can be performed in separate stand-alone units operated at different times, or a single unit can be operated according to one process at one time and according to the other process at another time.
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Page/Page column 14
(2017/03/08)
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- Rhodium-Complex-Catalyzed Hydroformylation of Olefins with CO2and Hydrosilane
-
A rhodium-catalyzed one-pot hydroformylation of olefins with CO2, hydrosilane, and H2has been developed that affords the aldehydes in good chemoselectivities at low catalyst loading. Mechanistic studies indicate that the transformation is likely to proceed through a tandem sequence of poly(methylhydrosiloxane) (PMHS) mediated CO2reduction to CO and a conventional rhodium-catalyzed hydroformylation with CO/H2. The hydrosilylane-mediated reduction of CO2in preference to aldehydes was found to be crucial for the selective formation of aldehydes under the reaction conditions.
- Ren, Xinyi,Zheng, Zhiyao,Zhang, Lei,Wang, Zheng,Xia, Chungu,Ding, Kuiling
-
supporting information
p. 310 - 313
(2016/12/30)
-
- COMPOSITIONS AND METHODS FOR CO2 ADSORPTION AND CONVERSION TO LONG-CHAIN HYDROCARBONS
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The invention provides novel, low-cost catalysts and methods for their preparation and application in CO2 adsorption and conversion to long-chain hydrocarbons via photosynthesis with ambient CO2 and solar energy.
- -
-
Paragraph 0059-0065
(2017/03/21)
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- Selective Hydrogenation of 2-Methylfuran and 2,5-Dimethylfuran over Atomic Layer Deposited Platinum Catalysts on Multiwalled Carbon Nanotube and Alumina Supports
-
2-Methylfuran (2MF) and 2,5-dimethylfuran (DMF) were hydrogenated in the vapor phase to the corresponding tetrahydrofurans, linear 2-ketones, and alcohols over Pt nanoparticles supported on multiwalled carbon nanotubes (MWCNTs) and alumina by atomic layer deposition. The hydrogenation behavior of sub-nanometer Pt deposited on alumina was influenced by the acidity of the support. Relative to a commercial Pt/C catalyst, the Pt/MWCNT catalyst was found to contain similarly sized Pt nanoparticles that display a broader size distribution and significantly more n-alkanes than oxygenates during hydrogenation of these alkyl-substituted furans.
- Kang, Jungshik,Liang, Xinhua,Guliants, Vadim V.
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p. 282 - 286
(2017/02/05)
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- Evidence of Structure Sensitivity in the Fischer–Tropsch Reaction on Model Cobalt Nanoparticles by Time-Resolved Chemical Transient Kinetics
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The Fischer–Tropsch process, or the catalytic hydrogenation of carbon monoxide (CO), produces long chain hydrocarbons and offers an alternative to the use of crude oil for chemical feedstocks. The observed size dependence of cobalt (Co) catalysts for the Fischer–Tropsch reaction was studied with colloidally prepared Co nanoparticles and a chemical transient kinetics reactor capable of measurements under non-steady-state conditions. Co nanoparticles of 4.3 nm and 9.5 nm diameters were synthesized and tested under atmospheric pressure conditions and H2/CO=2. Large differences in carbon coverage (ΘC) were observed for the two catalysts: the 4.3 nm Co catalyst has a ΘC less than one while the 9.5 nm Co catalyst supports a ΘC greater than two. The monomer units present on the surface during reaction are identified as single carbon species for both sizes of Co nanoparticles, and the major CO dissociation site is identified as the B5-B geometry. The difference in activity of Co nanoparticles was found to be a result of the structure sensitivity caused by the loss of these specific types of sites at smaller nanoparticle sizes.
- Ralston, Walter T.,Melaet, Gér?me,Saephan, Tommy,Somorjai, Gabor A.
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p. 7415 - 7419
(2017/06/13)
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- Deep hydrodenitrification of pyridine by solid catalyst coupling with ionic liquids under mild conditions
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A new route for deep hydrodenitrification (HDN) by solid catalyst coupling with ionic liquids (ILs) under mild conditions was proposed. Ni2P/SBA-15 activated at different temperatures were characterized with XRD, XPS, TG/DTA, and TEM and studied for further improvement. The deep HDN catalyzed by Ni2P/SBA-15 coupling with different ILs was evaluated. [Bmim]BF4 was selected as the best one compared with [Emim]BF4, [Bmim]Cl and [Bmim]Br. The effect of reaction temperature, hydrogen pressure and the amount of IL on denitrification efficiency was investigated with parallel experiments using Ni2P/SBA-15 coupling with [Bmim]BF4. The N-removal efficiency increased from 27.09% to 73.48% after optimization. The IL system could be recycled for three times without a significant decrease in HDN activity. The coupled catalyzed HDN process and mechanism were also proposed and evaluated preliminarily through molecular simulation.
- Yao, Haoyu,Wang, Gang,Zuo, Cuncun,Li, Chunshan,Wang, Erqiang,Zhang, Suojiang
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p. 1692 - 1700
(2017/05/29)
-
- Comparison of phosphide catalysts prepared by temperature-programmed reduction and liquid-phase methods in the hydrodeoxygenation of 2-methylfuran
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Two types of Ni2P/SiO2 were prepared by different methods, a conventional method involving temperature-programmed reduction (TPR) and a liquid-phase synthesis (LP). Both methods resulted in phase-pure materials with the Ni2P hexagonal phase, but the sample prepared by TPR had lower particle size (7 nm) than the sample prepared by LP synthesis (25 nm). The samples were tested in the gas-phase hydrodeoxygenation of 2-methylfuran (2-MF) in H2 at 0.5 MPa and 250–450 °C, and it was found that the Ni2P/SiO2-TPR gave higher conversions and turnover frequencies than the Ni2P/SiO2-LP. It was conjectured that the difference in activity was due to the higher phosphorus content of the sample prepared by TPR, and this was confirmed by measurements of the P/Ni ratio by x-ray photoelectron spectroscopy. The main products formed by the two catalysts were 2-pentanone and n-pentane and small amounts of 1-pentanol and 2-pentanol. Contact time measurements on the Ni2P/SiO2-TPR sample indicated that 2-pentanone was a primary product, the pentanols were intermediary compounds, and the n-pentane was a final product. Kinetic measurements on the Ni2P/SiO2-LP revealed orders of 0.6 for the 2-MF and 0.5 for H2, consistent with adsorption of both reactants on the catalyst and a surface reaction between the adsorbed species. TPR was also employed to prepare a Cu3P/SiO2 sample. Although a phase-pure material was formed, the substance showed very low activity for the HDO of 2-MF.
- Zhang, Jianwen,Matsubara, Kazuki,Yun, Gwang-Nam,Zheng, Huidong,Takagaki, Atsushi,Kikuchi, Ryuji,Oyama, S. Ted
-
-
- Effects of Co/Ce molar ratio and operating temperature on nanocatalyst performance in the Fischer-Tropsch synthesis
-
Iron-cobalt-cerium three-metal nanoparticles have been obtained by a solvothermal method for converting synthesis gas into light olefins. The effect of various fabrication molar ratios of Co/Ce and the effect of the operating temperature (270-400 °C) on the activity and selectivity were demonstrated. The nanocatalyst with a 1:1/4 Co/Ce molar ratio at an operating temperature of 300 °C performed optimally in selectivity converting synthesis gas into light olefin. The nanocatalysts prepared with different Co/Ce molar ratios were characterized. The morphology, structure and magnetic behavior were established by SEM, EDX, FTIR, XRD and VSM ?techniques.
- Taherzadeh Lari, Tahereh,Mirzaei, Ali Akbar,Atashi, Hossein
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p. 34497 - 34507
(2017/07/22)
-
- SYSTEM AND PROCESS FOR PRODUCTION OF MAGNESIUM METAL AND MAGNESIUM HYDRIDE FROM MAGNESIUM-CONTAINING SALTS AND BRINES
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A system and process are disclosed for production of consolidated magnesium metal products and alloys with selected densities from magnesium-containing salts and feedstocks. The system and process employ a dialkyl magnesium compound that decomposes to produce the Mg metal product. Energy requirements and production costs are lower than for conventional processing.
- -
-
Paragraph 00108; 00109
(2016/09/26)
-
- Cooperative Lewis acidity in borane-substituted fluorophosphonium cations
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A series of aryl-difluorophosphoranes are converted to give fluorophosphonium salts [Ph2PF(o-C6X4BR2)]+ (X = H, F; R = Cy, Mes). The proximity of the two weakly Lewis acidic fluorophosphonium and borane moieties results in enhanced Lewis acid catalytic reactivity.
- M?bus, Juri,Vom Stein, Thorsten,Stephan, Douglas W.
-
supporting information
p. 6387 - 6390
(2016/05/24)
-
- Pyridinium-phosphonium dications: Highly electrophilic phosphorus-based Lewis acid catalysts
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Using commercially available 2-pyridyldiphenylphosphine (o-NC5H4)PPh2, a family of electrophilic phosphonium cations [(o-NC5H4)PFPh2]+ (2) and dications [(o-MeNC5H4)PRPh2]2+ (R = F (4); Me (5)) were prepared. The Lewis acidity of these pyridinium-phosphonium dications was probed in Friedel-Crafts dimerization, hydrodefluorination, hydrosilylation, dehydrocoupling and hydrodeoxygenation reactions. The influence of the counterion on the catalytic activity of the electrophilic phosphonium cations is also discussed.
- Bayne, Julia M.,Holthausen, Michael H.,Stephan, Douglas W.
-
p. 5949 - 5957
(2016/04/26)
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- Ferrocenyl-derived electrophilic phosphonium cations (EPCs) as Lewis acid catalysts
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Oxidation of diphenylphosphinoferrocene and 1,1′-bis(diphenylphosphino)ferrocene with XeF2, resulted in the formation of CpFe(η5-C5H4PF2Ph2) 1 and Fe(η5-C5H4PF2Ph2)22 respectively. Subsequent reactions with [SiEt3][B(C6F5)4] yielded [CpFe(η5-C5H4PFPh2)][B(C6F5)4] 3 and [Fe(η5-C5H4PFPh2)2] [B(C6F5)4]24. PhP(η5-C5H4)2Fe 5 was prepared, converted to [PhMeP(η5-C5H4)2Fe][O3SCF3] 6 and then to [PhMeP(η5-C5H4)2Fe][B(C6F5)4] 7. The ability of the salts 3, 4 and 7 to catalyze Friedel-Crafts dimerization of 1,1-diphenylethylene, dehydrocoupling of phenol and triethylsilane, deoxygenation of acetophenone and hydrodefluorination of 1-fluoropentane were probed. While compound 7 proved to be ineffective, compounds 3 and 4 were useful Lewis acid catalysts. Compounds 3 and 4 were shown to catalyze the deoxygenation of a series of ketones.
- Mallov, Ian,Stephan, Douglas W.
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p. 5568 - 5574
(2016/04/09)
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- Understanding reaction processes for n-heptane over 10Mo2C/SZ catalyst
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Supported carbided molybdena catalysts was prepared by treating MoO3/sulfated zirconia in methane/hydrogen (1:4 volumetric ratio) at 923?K. Characterisation shows the oxide to be different from the carbide phase. Carburisation did not induce phase change of the support with the tetragonal phase remaining dominant but did results in some changes to the textural properties. Lewis acid site density was constant in transforming from oxide to carbide forms while Br?nsted acidity site densities was diminished by ca 10% to give a Br?nsted/Lewis density ratio 2.46 in the carbide form. The ratio of hydrogenation sites to (Br?nsted) acid sites on the carbidic form of the catalyst was 0.12. Increasing temperature and decreasing WHSV augmented heptane conversion but leads to multiple cracking. Analysis of the product distribution as a function of conversion or as a function of temperature implied that the reaction did not simply proceed via a single consecutive reaction pathway Conversion increased the research octane number (RON) due to of the increased fraction of pentane isomers.
- Oloye,McCue,Anderson
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p. 246 - 256
(2016/10/05)
-
- An investigation on the influence of support type for Ni catalysed vapour phase hydrogenation of aqueous levulinic acid to γ-valerolactone
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Ni (20 wt%) supported on SiO2, γ-Al2O3 and ZrO2 catalysts was examined for hydrogenation of aqueous levulinic acid (LA) to γ-valerolactone (GVL) at 270°C and ambient pressure. The band intensities of Br?nsted (BAS: 1540 cm-1) and Lewis acid sites (LAS: 1450 cm-1) estimated by pyridine adsorbed DRIFT spectra revealed a lower ratio of BAS/LAS over the Ni/SiO2 catalyst than over the Ni/ZrO2 and Ni/γ-Al2O3 catalysts. The rate of angelica lactone (AL) formation was lower than the rate of AL hydrogenation over the Ni/SiO2 catalyst. The poisoning and regeneration of the Ni/SiO2 catalyst using pyridine and 2,6-dimethylpyridine demonstrated that Lewis acid sites influenced the conversion of LA to AL and subsequent hydrogenation of AL to GVL occurred on surface Ni sites. In contrast, Br?nsted acid sites were responsible for the ring opening of GVL to valeric acid (VA). Kinetic data emphasized that the hydrogenation activity and product distribution were dependent on the type of acid site, and the Ni sites in close proximity to Br?nsted acid sites are prone to hydrogenolysis of GVL to valeric acid and hydrocarbons.
- Kumar, Velisoju Vijay,Naresh, Gutta,Sudhakar, Medak,Anjaneyulu, Chatla,Bhargava, Suresh Kumar,Tardio, James,Reddy, Vanga Karnakar,Padmasri, Aytam Hari,Venugopal, Akula
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p. 9872 - 9879
(2016/02/05)
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- PROCESS FOR PRODUCING ALKANES USING MICROORGANISMS COMBINED WITH KOLBE SYNTHESIS
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The present invention relatesto a method of producing at least one alkane, the method comprising, -producing at least one carboxylic acid from a carbon source using a genetically modified microorganism, and -performing Kolbe electrolysis on the carboxylic acid to produce the alkane, wherein the alkane comprises at least 6 carbon atoms and the carboxylic acid comprises at least 4 carbon atomsand wherein the carbon source is selected from the group consisting of ethanol, acetate, propionate, butyrate, isobutyrate, valerate, hexanoate and combinations thereof and the microorganism is capable of producing the carboxylic acid using ethanol-carboxylate fermentation.
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Page/Page column 29
(2016/02/26)
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- Selective hydrogenolysis of biomass-derived furfuryl alcohol into 1,2- and 1,5-pentanediol over highly dispersed Cu-Al2O3 catalysts
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Cu nanoparticles supported on a variety of oxide supports, including SiO2, TiO2, ZrO2, Al2O3, MgO and ZnO, were investigated for the hydrogenolysis of biomass-derived furfuryl alcohol to 1,2-pentanediol and 1,5-pentanediol. A Cu-Al2O3 catalyst with 10 wt% Cu loading prepared by a co-precipitation method exhibited the best performance in terms of producing pentanediols compared with the other materials. This catalyst generated an 85.8% conversion and a 70.3% combined selectivity for the target pentanediols at 413 K and 8 MPa H2 over an 8-h reaction. The catalyst could also be recycled over repeated reaction trials without any significant decrease in productivity. Characterizations with X-ray diffraction, NH3/CO2-temperature programmed desorption, N2 adsorption, transmission electron microscopy and N2O chemisorption demonstrated that intimate and effective interactions between Cu particles and the acidic Al2O3 support in this material greatly enhanced its activity and selectivity. The promotion of the hydrogenolysis reaction was found to be especially sensitive to the Cu particle size, and the catalyst with Cu particles 1.9 to 2.4 nm in size showed the highest turnover frequency during the synthesis of pentanediols.
- Liu, Hailong,Huang, Zhiwei,Kang, Haixiao,Xia, Chungu,Chen, Jing
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p. 700 - 710
(2016/05/19)
-
- Fischer–Tropsch synthesis with cobalt catalyst and zeolite multibed arrangement
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The role of zeolite in transformations of hydrocarbons produced from CO and H2 over a Fischer–Tropsch cobalt catalyst under the conditions of multibed arrangement of the cobalt catalyst and the zeolite has been determined. Hydrocarbon conversion over the HBeta zeolite occurs via the bimolecular mechanism, as evidenced by a low methane yield and a high yield of unsaturated gaseous and liquid hydrocarbons. The conversion over the CaA zeolite obeys the unimolecular mechanism, as evidenced by the formation of increased amounts of methane and saturated gaseous C2–C4 hydrocarbons.
- Asalieva, E. Yu.,Kul’chakovskaya,Sineva,Mordkovich,Bulychev
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p. 275 - 280
(2016/06/09)
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- INTEGRATED PROCESS FOR GASOLINE PRODUCTION
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An integrated process for gasoline production is described. The process includes introducing a feed comprising n-C5 hydrocarbons into a disproportionation reaction zone in the presence of a disproportionation catalyst to form a disproportionation mixture comprising iso-C4 and C6+ disproportionation products and unreacted n-C5 hydrocarbons. An iso-C4 hydrocarbon stream and an olefin feed are introduced into an alkylation reaction zone in the presence of an alkylation catalyst to produce an alkylation mixture comprising alkylate and unreacted iso-C4 paraffins. The disproportionation mixture and the alkylation mixture are combined, and the combined mixture is separated into at least a stream comprising the alkylate product, an iso-C4 stream, and an unreacted n-C5 hydrocarbon stream. The iso-C4 stream is recycled to the alkylation reaction zone, and the unreacted n-C5 hydrocarbon stream is recycled to the disproportionation reaction zone. The stream comprising the alkylate product is recovered.
- -
-
Paragraph 0081
(2016/07/05)
-
- Synthesis, structure and thermolysis of cis-dialkylplatinum(II) complexes - Experimental and theoretical perceptions
-
The formation of new C-C bonds by metal complexes always stimulates great interest because these fundamental reaction types possess numerous potential applications in organic synthesis. These reactions are well documented for a variety of transition metal complexes. Herein we report synthesis and characterization of a series of platinum-dialkyl complexes (1-10) of the type [Pt(L2)R2], (where L2 = dppp (1,3-bis(diphenylphosphino)propane or L = PPh3; R = n-butyl to n-nonyl) with a view to understand the organic product distribution patterns on thermolysis. The single crystal X-ray structures of the complexes [Pt(dppp){CH2(CH2)3CH3}2] (1) and [Pt(dppp){CH2(CH2)6CH3}2] (7) are reported. Thermal decomposition studies of these complexes show interesting behaviour; the longer chain dialkyls i.e. C7-C9 complexes undergo reductive elimination whereas the shorter chain dialkyl complexes and C3-C6 prefer only the β-hydride elimination reaction. Possible mechanistic aspects are discussed. Theoretical calculations reveal the strongest delocalizations in both complexes involve the interaction of Pt-C bond pair electron density with the trans positioned Pt-P antibonding orbital and vice-versa.
- Venkatesh, Sadhana,Sravani, Chinduluri,Janardan, Sannapaneni,Suman, Pothini,Goud, E. Veerashekhara,Pavankumar,Leninkumar, Vardi,Bhat, Haamid R.,Sivaramakrishna, Akella,Vijayakrishna, Kari,Jha, Prakash C.,Smith, Gregory S.
-
-
- Palladium-gold catalyst for the electrochemical reduction of CO2 to C1-C5 hydrocarbons
-
Copper is a unique electrocatalyst for CO2 reduction, since it is one of the few catalysts able to produce methane, ethylene and ethane from CO2 with decent faradaic efficiencies. Here we report on the design and synthesis of a new non-copper-containing catalyst able to reduce CO2 to C1 to C5 hydrocarbons. This catalyst was designed by combining a metal that binds CO strongly, Pd, with a metal that binds CO weakly, Au, in an attempt to tune the binding energy of CO. We show that a mixture of C1-C5 hydrocarbons and soluble products are produced from an onset potential of -0.8 VRHE. We propose that the higher hydrocarbons are formed via a polymerization of -CH2 groups adsorbed on the catalyst surface.
- Kortlever,Peters,Balemans,Kas,Kwon,Mul,Koper
-
supporting information
p. 10229 - 10232
(2016/08/23)
-
- Reactions of 2-Methyltetrahydropyran on Silica-Supported Nickel Phosphide in Comparison with 2-Methyltetrahydrofuran
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The reactions of 2-methyltetrahydropyran (2-MTHP, C6H12O) on Ni2P/SiO2 provide insights on the interactions between a cyclic ether, an abundant component of biomass feedstock, with a transition-metal phosphide, an effective hydrotreating catalyst. At atmospheric pressure and a low contact time, conditions similar to those of a fast pyrolysis process, 70% of products formed from the reaction of 2-MTHP on Ni2P/SiO2 were deoxygenated products, 2-hexene and 2-pentenes, indicating a good oxygen removal capacity. Deprotonation, hydrogenolysis, dehydration, and decarbonylation were the main reaction routes. The reaction sequence started with the adsorption of 2-MTHP, followed by ring-opening steps on either the methyl substituted side (Path I) or the unsubstituted side (Path II) to produce adsorbed alkoxide species. In Path I, a primary alkoxide was oxidized at the α-carbon to produce an aldehyde, which subsequently underwent decarbonylation to 2-pentenes. The primary alkoxide could also be protonated to give a primary alcohol which could desorb or form the final product 2-hexene. In Path II, a secondary alkoxide was oxidized to produce a ketone or was protonated to a secondary alcohol that was dehydrated to give 2-hexene. The active sites for the adsorption of 2-MTHP and O-intermediates were likely to be Ni sites.
- Bui, Phuong P.,Oyama, S. Ted,Takagaki, Atsushi,Carrow, Brad P.,Nozaki, Kyoko
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p. 4549 - 4558
(2016/07/12)
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- Deep hydrodesulfurization of FCC gasoline and gas oil cuts: Comparison of CO effect, a by-product from biomass
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Regarding the composition of the various feedstocks which should be hydrotreated in order to obtain fuels with amount of sulfur less than 10 wt ppm, we have shown that the presence of traces of CO, a by-product from lignocellulosic biomass feedstock conversion, inhibited the transformation of model compounds representative of FCC gasolines and gas oils over CoMo-based sulfide catalysts. Thus, this effect is more significant in the presence of 2-methylthiophene and 2,3-dimethylbut-2-ene representative of a FCC gasoline than in the presence of dibenzothiophene and 4,6-dimethyldibenzothiophene representative of a straight run gas oil, even if the operating conditions are not the same. This effect is attributed to phenomena of competitive adsorption between sulfur compounds, alkenes and CO on the catalyst surface.
- Pelardy, Florian,Philippe, Maxime,Richard, Frédéric,Daudin, Antoine,Devers, élodie,Hudebine, Damien,Brunet, Sylvette
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p. 1266 - 1275
(2016/10/13)
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- Tungsten and rhenium as hydrogenation agents in the hydrodenitrogenation of pyridine using stacked bed catalyst systems
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This study analyses the hydrodenitrogenation (HDN) of pyridine using a stacked bed catalyst system, composed of a first hydrogenating bed of Re/γ-Al2O3 or W/γ-Al2O3, over a second bed of Ni-Re/γ-Al2O3 (HDN bed). Using potentiometric methods, it can be seen that the Re/γ-Al2O3 shows higher acidic strength than the W/γ-Al2O3. The results show that higher activity levels are obtained working with stacked bed systems compared to the separate catalysts. These results suggest that the incorporation of the catalyst Re/γ-Al2O3 or W/γ-Al2O3 beds would favour the formation of hydrogenated intermediary products, facilitating the removal of N-containing molecules via HDN on the Ni-Re/γ-Al2O3 catalyst.
- Bassi,Villarroel,Llambías, F.J. Gil,Camú,Baeza
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p. 2931 - 2934
(2015/11/03)
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- Electrophilic bis-fluorophosphonium dications: Lewis acid catalysts from diphosphines
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Stepwise oxidation of 1,8-bis(diphenylphosphino)naphthalene and a series of (oligo)methylene-linked diphosphines with XeF2 followed by fluoride abstraction yields a family of compounds featuring phosphine, phosphonium and phosphorane moieties in close proximity. The bisphosphonium ions [(C10H6)(Ph2PF)2]2+ (5) and [CH2(Ph2PF)2]2+ (9a) exhibit remarkable Lewis acidity arising from the proximity of the phosphonium centers. The effectiveness of bisphosphonium dications (5, 9a-e) is examined in a series of Lewis acid catalysed transformations.
- Holthausen, Michael H.,Hiranandani, Rashi R.,Stephan, Douglas W.
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p. 2016 - 2021
(2015/08/18)
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- CATALYTIC DISPROPORTIONATION OF PARAFFINS USING IONIC LIQUIDS
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Processes for the disproportionation and isomerization of a hydrocarbon feed using a liquid catalyst comprising an ionic liquid and a carbocation promoter are described. The ionic liquid is unsupported, and the reactions occur at temperatures below about 200° C.
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Paragraph 0099
(2015/02/05)
-