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67-64-1Relevant articles and documents
Atomically precise silver clusters for efficient chlorocarbon degradation
Bootharaju,Deepesh,Udayabhaskararao,Pradeep
, p. 611 - 620 (2013)
We describe the degradation of chlorocarbons (CCl4, C 6H5CH2Cl and CHCl3) in solution at room temperature (27 ± 4 °C) by the monolayer-protected silver quantum cluster, Ag9MSA7 (MSA: mercaptosuccinic acid) in the presence of isopropyl alcohol (IPA). The main degradation products were silver chloride and amorphous carbon. Benzyl chloride was less reactive towards clusters than CCl4 and CHCl3. Materials used in the reactions and the reaction products were characterized using several spectroscopic and microscopic tools such as ultraviolet-visible (UV/Vis) absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), energy dispersive analysis of X-rays (EDAX) and scanning electron microscopy (SEM). We have shown that clusters are more efficient for the degradation of halocarbons than the corresponding monolayer-protected nanoparticles (Ag@MSA, particle diameter 15 ± 5 nm) at a given time and temperature. The higher reactivity of clusters is attributed to their small size and large surface area. Clusters and nanoparticles were used for reactions in supported (on neutral alumina) and unsupported forms. A possible mechanism for the reaction has been postulated on the basis of experimental results.
Transfer hydrogenation with abnormal dicarbene rhodium(iii) complexes containing ancillary and modular poly-pyridine ligands
Farrell, Kevin,Melle, Philipp,Gossage, Robert A.,Müller-Bunz, Helge,Albrecht, Martin
, p. 4570 - 4579 (2016)
Treatment of an abnormal dicarbene ligated rhodium(iii) dimer with 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen) or 2,2′:6′,2′′-terpyridine (terpy) results in coordination of the N-donor ligands and concomitant cleavage of the dimeric structure. Depending on the denticity of the pyridyl ligand, this situation retains one (L = terpy) or two (L = bipy, phen) flexible sites for substrate coordination. In the case of the bipy complexes, modification of the electron density at Rh, without directly affecting the steric environment about the metal centre, was achieved by the incorporation of electron-donating or electron-withdrawing substituents on the bipy backbone. The dicarbene pyridyl complexes were active in transfer hydrogenation catalysis of benzophenone at 0.15 mol% catalyst loading in a iPrOH/KOH mixture. The catalysts displayed a strong characteristic colour change (yellow to purple) after activation which allowed for visual monitoring of the status of the reaction. The colour probe and the robustness of the active catalysts proved useful for catalyst recycling. The catalytic activity sustained over five consecutive substrate batch additions and gave a maximum overall turnover number of 3100.
Conversion of ethanol over supported cobalt oxide catalysts
Rybak,Tomaszewska,MacHocki,Grzegorczyk,Denis
, p. 14 - 20 (2011)
Conversion of ethanol was investigated on supported (ceria, zirconia and ceria-zirconia) cobalt oxide catalysts. The catalysts were prepared by support impregnation with cobalt nitrate-citric acid solution and they were explored by comparing results from different characterization techniques: X-ray fluorescence, X-ray diffraction, Raman spectroscopy and nitrogen adsorption techniques. Their catalytic properties at 693 K were characterized in a fixed-bed reactor. The CoOx/CeO2 catalyst displayed the highest catalytic activity. The conversion of ethanol decreased with the increase of the ZrO2/CeO2 ratio in the support of catalyst. All catalysts exhibited high selectivity of ethanol conversion to hydrogen and acetone. The coking of catalysts under reaction conditions was also characterized by gravimetric method. The results indicated that the increase of the ZrO2/CeO2 ratio in the support exerts significant influence on the coke formation. The amount of carbon deposited on CoO x/ZrO2 at 693 K was higher than on any other catalyst. Raman studies of used catalysts proved that their surface was almost completely covered with carbonaceous deposit, which was probably the main reason of deactivation of catalysts under reaction conditions.
Rate constant for the reaction of CH3C(O)CH2 radical with HBr and its thermochemical implication
Farkas, Edit,Kovacs, Gergely,Szilagyi, Istvan,Dobe, Sandor,Berces, Tibor,Marta, Ferenc
, p. 32 - 37 (2006)
The fast flow method with laser induced fluorescence detection of CH 3C(O)CH2 was employed to obtain the rate constant of k1 (298 K) = (1.83 ± 0.12 (1σ)) × 1010 cm3 mol-1 s-1 for the reaction CH 3C(O)CH2 + HBr ? CH3C(O)CH3 + Br (1, -1). The observed reduced reactivity compared with n-alkyl or alkoxyl radicals can be attributed to the partial resonance stabilization of the acetonyl radical. An application of k1 in a third law estimation provides Δf H298O (CH 3C(O)CH2) values of -24 kJ mol-1 and -28 kJ mol-1 depending on the rate constants available for reaction (- 1) from the literature.
CHANGE IN THE RATE OF DECOMPOSITION OF DIOXETANES IN SULFOLANE SOLUTIONS IN THE TRANSITION FROM THE LIQUID TO THE SOLID PHASE
Sharipov, G. L.,Ostakhov, S. S.,Voloshin, A. I.,Lotnik, S. V.,Kazakov, V. P.,Tolstikov, G. A.
, p. 2012 - 2016 (1988)
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Cooley
, (1938)
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Ketonization of Acetophenone Enol in Aqueous Buffer Solutions. Rate-Equilibrium Relations and Mechanism of the "Uncatalyzed" Reaction
Chiang, Y.,Kresge, A. J.,Santaballa, J. A.,Wirz, J.
, p. 5506 - 5510 (1988)
Rates of ketonization of acetophenone enol, generated by photohydration of phenylacetylene and Norrish type II photoelimination of γ-hydroxybutyrophenone, were measured at 25 deg C in aqueous buffer solutions of six carboxylic acids, six phosphonic acid monoanions, phosphoric acid, and dihydrogen phosphate.Analysis of the carboxylic acid data produced catalytic coefficients from which linear Broensted correlations were constructed, with α = 0.50 for ketonization of the enol and α = 0.32 for the more rapid ketonization of the enolate ion.A more extended, curved Broensted correlation for ketonization of the enolate ion was constructed by combining the carboxylic acid results with catalytic coefficients for the phosphonic acid monoanions, and analysis of this by Marcus theory gave the intrinsic barrier ΔG0+ = 12 kcal mol-1 and the work terms wτ = 2 kcal mol-1 and wp = 4 kcal mol-1.These results differ from the much smaller intrinsic barrier and strongly disparate work terms obtained previously in a similar study of isobutyrophenone enol, and an explanation of the difference in terms of a looser transition state (Kreevoy τ = 0.30) for the isobutyrophenone system is offered.Evidence is also supplied which indicates that the so-called "uncatalyzed" ketonization reaction occurs by a stepwise route rather than by a cyclic single-step mechanism.
Gas-Phase Chemiluminescence Study of Chemically Activated Tetramethyl-1,2-dioxetane Formed from the Reaction of O2(1Δg) with 2,3-Dimethyl-2-butene
Bogan, Denis J.,Lee, Dong-Heon
, p. 9304 - 9310 (1992)
Chemically activated tetramethyl-1,2-dioxetane has been prepared by the reaction of O2(1Δg) with 2,3-dimethyl-2-butene at temperatures of 450 to 775 K and a pressure of 0.25 Torr.The observed product of the reaction was excited 1n?*(S1) acetone, which was identified by chemiluminescence spectra of the acetone (S1 -> S0) transition.Neither acetone (Ti) nor any other excited states were observed under the above conditions.The temperature dependence of the chemiluminescence gave an activation energy for the cycloaddition reaction of 8610 +/- 200 (1?) cal/mol.The quantum yield for acetone (S1) was 4 * 10-3 per reactive collision; its (1?) error is estimated as +/- a factor of 3.Chemiluminescence spectra taken at O2(3Σ1g) partial pressures greater than 2 Torr showed formaldehyde (S1 -> S0) bands.This is attributed to the well-known hydrocarbon "cool flame" mechanism, due to the presence of methyl radical formed by the thermal decomposition, in two steps, of 2,3-dimethyl-3-hydroperoxy-1-butene, another product path for the title reaction.This is the first report on the chemically activated decomposition of tetramethyl-1,2-dioxetane.
Heterogeneous hydrogenation catalyses over recyclable Pd(0) nanoparticle catalysts stabilized by PAMAM-SBA-15 organic-inorganic hybrid composites
Jiang, Yijun,Gao, Qiuming
, p. 716 - 717 (2006)
Pd(0) nanoparticle catalysts stabilized by Gn-PAMAM-SBA-15 (n = 1-4) organic-inorganic hybrid composites were successfully prepared. Heterogeneous hydrogenation reaction of allyl alcohol over the Pd(0)-Gn-PAMAM-SBA-15 catalysts showed their high activities with TOFs of 2185, 2266, 711, and 739 and selectivities of 79.0, 82.0, 93.4, and 91.4%, respectively. The activity over the Pd(0)-G4-PAMAM-SBA-15 catalyst was 1.5 times that over the fourth generation PAMAM encapsulated Pd(0) homogeneous catalyst. These catalysts can be easily recovered, reused multiple times, and preserved for one month in the air, maintaining high catalytic efficiencies. Copyright
Cleavage of the carbon-carbon bond in α-glycols under the action of bismuth(v) derivatives
Dolganova,Dodonov,Zinov'eva,Prezhbog
, p. 1164 - 1166 (1997)
Di(tert-butylperoxy)triphenylbismuth and the triphenylbismuth - tert-butyl hydroperoxide system react with 2,3-dimethylbutane-2,3-diol, benzopinacol, butane-2,3-diol, and ethane-1,2-diol with the cleavage of the C - C bond of α-glycol to form carbonyl compounds. Both heterolytic (through formation of cyclic triphenylbismuth glycolate) and homolytic cleavage occur.
Aerobic oxidation of pinacol by vanadium(V) dipicolinate complexes: Evidence for reduction to vanadium(III)
Hanson, Susan K.,Tom Baker, R.,Gordon, John C.,Sutton, Andrew D.,Thorn, David L.,Scott, Brian L.
, p. 428 - 429 (2009)
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Acetic Acid Ketonization over Fe3O4/SiO2 for Pyrolysis Bio-Oil Upgrading
Bennett, James A.,Parlett, Christopher M. A.,Isaacs, Mark A.,Durndell, Lee J.,Olivi, Luca,Lee, Adam F.,Wilson, Karen
, p. 1648 - 1654 (2017)
A family of silica-supported, magnetite nanoparticle catalysts was synthesised and investigated for continuous-flow acetic acid ketonisation as a model pyrolysis bio-oil upgrading reaction. The physico-chemical properties of Fe3O4/SiO2 catalysts were characterised by using high-resolution transmission electron microscopy, X-ray absorption spectroscopy, X-ray photo-electron spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, thermogravimetric analysis and porosimetry. The acid site densities were inversely proportional to the Fe3O4 particle size, although the acid strength and Lewis character were size-invariant, and correlated with the specific activity for the vapour-phase acetic ketonisation to acetone. A constant activation energy (～110 kJ mol?1), turnover frequency (～13 h?1) and selectivity to acetone of 60 % were observed for ketonisation across the catalyst series, which implies that Fe3O4 is the principal active component of Red Mud waste.
Kinetics and mechanism of the sonolytic destruction of methyl tert- butyl ether by ultrasonic irradiation in the presence of ozone
Kang, Joon-Wun,Hoffmann, Michael R.
, p. 3194 - 3199 (1998)
The kinetics and mechanism of the sonolytic degradation of methyl tert- butyl ether (MTBE) have been investigated at an ultrasonic frequency of 205 kHz and power of 200 W L-1. The observed first-order degradation rate constant for the loss of MTBE increased from 4.1 x 10-4 s-1 to 8.5 x 10- 4 s-1 as the concentration of MTBE decreased from 1.0 to 0.01 mM. In the presence of O3, the sonolytic rate of destruction of MTBE was accelerated substantially. The rate of MTBE sonolysis with ozone was enhanced by a factor of 1.5-3.9 depending on the initial concentration of MTBE. tert-Butyl formate, tert-butyl alcohol, methyl acetate, and acetone were found to be the primary intermediates and byproducts of the degradation reaction with yields of 8, 5, 3, and 12%, respectively. A reaction mechanism involving three parallel pathways that include the direct pyrolytic decomposition of MTBE, the direct reaction of MTBE with ozone, and the reaction of MTBE with hydroxyl radical is proposed. The kinetics and mechanism of the sonolytic degradation of methyl tert-butyl ether (MTBE) have been investigated at an ultrasonic frequency of 205 kHz and power of 200 W L-1. The observed first-order degradation rate constant for the loss of MTBE increased from 4.1 × 10-4 s-1 to 8.5 × 10-4 s-1 as the concentration of MTBE decreased from 1.0 to 0.01 mM. In the presence of O3, the sonolytic rate of destruction of MTBE was accelerated substantially. The rate of MTBE sonolysis with ozone was enhanced by a factor of 1.5-3.9 depending on the initial concentration of MTBE. tert-Butyl formate, tert-butyl alcohol, methyl acetate, and acetone were found to be the primary intermediates and byproducts of the degradation reaction with yields of 8, 5, 3, and 12%, respectively. A reaction mechanism involving three parallel pathways that include the direct pyrolytic decomposition of MTBE, the direct reaction of MTBE with ozone, and the reaction of MTBE with hydroxyl radical is proposed.
Zirconia catalysed acetic acid ketonisation for pre-treatment of biomass fast pyrolysis vapours
Jahangiri, Hessam,Osatiashtiani, Amin,Bennett, James A.,Isaacs, Mark A.,Gu, Sai,Lee, Adam F.,Wilson, Karen
, p. 1134 - 1141 (2018)
Crude pyrolysis bio-oil contains significant quantities of carboxylic acids which limit its utility as a biofuel. Vapour phase ketonisation of organic acids contained within biomass fast-pyrolysis vapours offers a potential pre-treatment to improve the stability and energy content of resulting bio-oils formed upon condensation. Zirconia is a promising catalyst for such reactions, however little is known regarding the impact of thermal processing on the physicochemical properties of zirconia in the context of it's corresponding reactivity for the vapour phase ketonisation of acetic acid. Here we show that calcination progressively transforms amorphous Zr(OH)4 into small tetragonal ZrO2 crystallites at 400 °C, and subsequently larger monoclinic crystallites >600 °C. These phase transitions are accompanied by an increase in the density of Lewis acid sites, and concomitant decrease in their acid strength, attributed to surface dehydroxylation and anion vacancy formation. Weak Lewis acid sites (and/or resulting acid-base pairs) are identified as the active species responsible for acetic acid ketonisation to acetone at 350 °C and 400 °C, with stronger Lewis acid sites favouring competing unselective reactions and carbon laydown. Acetone selectivity is independent of acid strength.
Aldol condensation of acetic acid and formaldehyde to acrylic acid over a hydrothermally treated silica gel-supported B-P-V-W oxide
Khalameida, S.,Khyzhun, O.,Kubitska, I.,Nebesnyi, R.,Pavliuk, A.,Pikh, Z.,Sydorchuk, V.,Voronchak, T.
, (2020)
Supported on silica B-P-V-W-Ox catalysts of the aldol condensation process, subjected to hydrothermal treatment (HTT), were synthesized and characterized. It was found that HTT of silica has a significant effect on catalyst texture, namely specific surface area, pore size. These properties affect the distribution of the active phase on the support surface. It was suggested that this is the reason of change in acid-base characteristics of the catalysts. It was observed that HTT at 100?150 °C leads to increase in surface, available for the reagents, ability to sorb acetic acid, decrease of acidity, improving catalytic activity and selectivity. It had been demonstrated that HTT allows to increase acrylic acid yield up to 67.6 % which is 10 % higher compared to that for catalyst supported on initial silica. The HTT of silica support before the active phase deposition is suggested as a cheap and efficient way to improve catalytic performance of B-P-V-W-Ox/SiO2 catalysts.
Reaction Mechanism of 2-Propanol Dehydrogenation with a Carbon-Supported Ru-Pt Composite Catalyst in the Liquid Phase
Ando, Yuji,Yamashita, Masaru,Saito, Yasukazu
, p. 2045 - 2049 (2003)
The reaction mechanism of dehydrogenation of 2-propanol substrates with and without deuterium-substitution with the Ru-Pt/carbon catalyst was studied to obtain strategies for catalyst designing suitable to direct 2-propanol fuel cells (D2PFC) and the catalyst-assisted chemical heat pump system. The Ru-Pt/carbon composite catalyst gave kinetic isotope effects of 1.54 and 1.96 for dehydrogenation at 82.4°C from (CH3)2CHOD and (CH3)2CDOH, respectively, which were contrasted to the corresponding magnitudes of 1.69 and 1.57 with a Ru/carbon catalyst and those of 1.13 and 1.81 with a Pt/carbon catalyst. The rate constants of dehydrogenation as a function of the H/D ratio in molecular hydrogen suggested that the step to form molecular hydrogen from surface hydrogen species was slow on the Ru catalyst, whereas the step to split the methine C-H bond was rather difficult for the Pt and Ru-Pt catalysts. Reflecting the facile dissociation at the hydroxy group on the catalyst surface, deuterium transfer from the hydroxy to the methyl groups of both acetone and 2-propanol proceeded tremendously for (CH3)2CHOD.
Products of the Gas-Phase OH Radical-Initiated Reactions of 4-Methyl-2-Pentanone and 2,6-Dimethyl-4-Heptanone
Atkinson, Roger,Aschmann, Sara M.
, p. 261 - 276 (1995)
The gas-phase reactions of OH radical with 4-methyl-2-pentanone and 2,6-dimethyl-4-heptanone have been investigated in the presence of NOx.Acetone and 2-methylpropanal were identified and quantified as products of both reactions.The acetone yield from 2,6-dimethyl-4-heptanone increased after addition of NO to reacted mixtures, indicating that acetone is formed through the intermediary of an acyl radical.The acetone and 2-methylpropanal formation yields were determined to be 0.78 +/- 0.06 and 0.071 +/- 0.011, respectively, from 4-methyl-2-pentanone and 0,68 +/- 0.11 and 0.385 +/- 0.034, respectively, from 2,6-dimethyl-4-heptanone.The possible reaction mechanisms are discussed and compared with these product data, and it is concluded that the experimental data provide direct evidence for isomerization of the (CH3)2CHCH2C(O)CH2C(O.)(CH3)2 alkoxy radical formed from 2,6-dimethyl-4-heptanone.However, the isomerization rates of the alkoxy radicals formed from the ketones depend on whether the H-atom abstracted is on a carbon atom α or β to the >C=O group, with H-atom abstraction from C-H bonds on the β carbon atoms being significantly faster than from C-H bonds on the α carbon atoms.
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Williams et al.
, p. 1190 (1956)
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Kinetics of one-stage Wacker-type oxidation of C2-C4 olefins catalysed by an aqueous PdCl2-heteropoly-anion system
Kozhevnikov,Lambert,Derouane
, p. 445 - 450 (2002)
The steady-state kinetics of the one-stage Wacker oxidation of gaseous olefins, e.g., ethylene, propylene, and 1-butene by oxygen catalyzed by the Pd(II)/heteropoly anions-3 redox system to form, respectively, acetaldehyde, acetone, and methyl ethyl ketone in aqueous solution was studied. The catalytic system involved an aqueous solution of Pd(II) chloride (0.05-2 mM Pd(II), [Pd(II)]/[Cl-] = l: 50) and Keggin-type heteropoly anions [PMo9V3O40]6-(50 mM), at 20°-50°C. The reactivity of olefins increases in the following order: ethylene ≤ 1-butene propylene; but the total range was only a factor of 3. The oxidation of ethylene and propylene occurred without any complication. The oxidation of 1-butene was accompanied by double-bond migration to form 2-butene, apparently proceeding through relatively stable π-allyl Pd(II) complexes. Use of a flow reactor with continuous removal of the products from the catalyst solution could reduce their overoxidation.
EFFECT OF PRESSURE ON THE DECOMPOSITION OF 2-TERT-BUTYL PEROXIDE IN SOLUTION
Zhulin, V. M.,Khueidzha, I.,Kabotyanskaya, E. B.,Koreshkov, Yu. D.
, p. 1739 - 1742 (1990)
A study was carried out on the effect of pressure up to 1400 MPa on the homolytic decomposition of di-tert-butyl peroxide (DTBP) at 403 K in 2-methoxy- (I) and 2-ethoxytetrahydropyran (II) as well as in a mixture of 30 mole percent (I) and 70 mole percent benzene.Spline approximation of the experimental pressure dependence of the logarithm of the decomposition rate constant (kd) gave the continuous dependence of the volumetric activation effect (ΔV excit.) on pressure.The value of ΔV excit. at atmospheric pressure (ΔV excit.0) and the nature of the change of ΔV excit. with increasing pressure were found to depend on the nature of the solvent.This dependence is difficult to explain in the framework of the accepted transition state theory.
Propane selective oxidation on alkaline earth exchanged zeolite Y: Room temperature in situ IR study
Xu, Jiang,Mojet, Barbara L.,Van Ommen, Jan G.,Lefferts, Leon
, p. 4407 - 4413 (2003)
The effect of zeolite Y ion-exchanged with a series of alkaline-earth cations on selective propane oxidation at room temperature was studied with in situ IR spectroscopy. Isopropylhydroperoxide was a reaction intermediate and could be decomposed into acetone and water. BaY was active at room temperature. The reaction rate increased in the order BaY MgY SrY CaY based on the rate of formation of adsorbed acetone. The acetone/water ratio increased with cation size, while no other products could be detected. The acetone/isopropylhydroperoxide ratio decreased with decreasing number of Bronsted acid sites. A two-step mechanism with two different active sites was proposed. Propane conversion into isopropylhydroperoxide took place on cations, while acetone decomposition occurred by Bronsted acid sites.
Electron-Transfer Conversion of Isopropylideneadamantane to its Dioxetane
Nelsen, Stephen F.,Kapp, Daniel L.,Teasley, Mark F.
, p. 579 - 580 (1984)
Adamantylideneadamantane (1) yields its dioxetane 2 by reaction with 3O2 and catalytic tris(o,p-dibromophenyl)aminium hexachloroantiminate (4) at -78 deg C in CH2Cl2 with a chain length of over 800.Isopropylideneadamantane (5) produces its dioxetane 6 under the same conditions with a chain length of greater than 60.
A common feature of H2-assisted HC-SCR over Ag/Al 2O3
Yu, Yunbo,He, Hong,Zhang, Xiuli,Deng, Hua
, p. 1239 - 1245 (2014)
CH4, C2H2, C2H4, C3H6, and C3H8 were selected as reductants for selective catalytic reduction (SCR) of NOx over Ag/Al2O3. Activity measurement showed that NOx reduction by hydrocarbons containing two- or three-carbon atoms was clearly promoted by H2 over Ag/Al2O3 at low temperatures, while such enhancement did not occur in the case of CH 4-SCR. Gas chromatography and gas chromatography coupled to a mass spectrometer analysis showed that the partial oxidation of hydrocarbons with more than one carbon atom was triggered at low temperatures by H2 addition over Ag/Al2O3. On the surface of Ag/Al 2O3, in situ diffuse reflectance infrared Fourier transform spectra indicated that this enhancement mainly originated from the formation of reactive enolic species, which is a common feature of H 2-assisted HC-SCR. the Partner Organisations 2014.
Effect of Pressure on the Thermolysis of Nitroalkanes in Solution
Wang, Jiang,Brower, Kay R.,Naud, Darren L.
, p. 9048 - 9054 (1997)
The effect of pressure up to 1.1 GPa on the rates of decomposition of two acidic nitroalkanes, nitromethane and 2-nitropropane, was measured. The mechanisms of thermolysis are inferred from kinetic studies and product analysis. The rate-controlling step for nitromethane decomposition in toluene at 230°C at low pressures is homolysis of the C-N bond. Beyond 20% conversion, the decomposition is autocatalytic. At high pressure, nitromethane has another reaction path which supplants homolysis. It is proposed that nitromethane forms an intermediate by cyclization of its aci-form. The high-pressure process is characterized by a first-order rate law without primary kinetic isotope effect, a low activation energy (28.5 kcal/mol), a negative activation volume (-5.5 mL/mol), and formation of products which cannot be attributed to radical intermediates. At high conversion, the reaction becomes autocatalytic as a result of accumulation of water leading to formation of products explainable by the Nef reaction. 2-Nitropropane is less stable than nitromethane. Pressure powerfully accelerates its decomposition owing to its activation volume averaging -11.2 mL/mol from 0.1 to 1.1 GPa. It is believed to cyclize via the aci-form like nitromethane. 2,2-Dinitropropane does not have a hydrogen and cannot tautomerize. In earlier work it was found to have a homolytic mechanism at high pressure. Therefore, the decomposition pathways of nitroalkanes in aprotic solvents are determined not only by the conditions but also by the availability of a hydrogen.
Products and mechanism of the reaction of OH radicals with 2,2,4-trimethylpentane in the presence of NO
Arey,Atkinson,Atkinson,Aschmann
, p. 625 - 632 (2002)
Alkanes are important constituents of gasoline fuel and vehicle exhaust, with branched alkanes comprising a significant fraction of the total alkanes observed in urban areas. The products and mechanism of the OH radical-initiated reaction products and mec
Ethanol Steam Reforming by Ni Catalysts for H2 Production: Evaluation of Gd Effect in CeO2 Support
Assaf, Elisabete M.,Ferreira, Gabriella R.,Lucrédio, Alessandra F.,Nogueira, Francisco G. E.
, (2022/01/19)
Abstract: Ni-based catalysts supported on CeO2 doped with Gd were prepared in this work to investigate the role of gadolinium on ethanol conversion, H2 selectivity, and carbon formation on ethanol steam reforming reaction. For this, catalysts containing 5 wt% of Ni impregnated on supports of ceria modified with different amounts of Gd (1, 5, and 10 wt%) were used. Ex-situ studies of XRPD suggest an increase of the lattice parameters, indicating a solid solution formation between Gd and Ce. Results of TPR showed an increase in metal-support interactions as the content of Gd increased. In situ XRPD studies indicated the formation of a GdNiO ternary phase for the catalysts containing Gd, which is in agreement with the results obtained by XANES. The catalysts were tested at three temperatures: 400?°C, 500?°C, and 600?°C. The conversion and productivity showed dependence with the Gd content and also with the temperature of the reaction. After the catalytic tests, catalysts containing Gd presented filamentous carbon possible due to a change in the reaction pathway. The highest ethanol conversion and H2 productivity were obtained at 600?°C for all catalysts and the best catalyst at this temperature was 5Ni_5GdCeO2. The promising performance of this catalyst may be associate with the lowest formation of GdNiO ternary phase, among the catalysts containing Gd, which means more Ni0 active species available to convert ethanol. Graphical Abstract: [Figure not available: see fulltext.]
A 3D MOF based on Adamantoid Tetracopper(II) and Aminophosphine Oxide Cages: Structural Features and Magnetic and Catalytic Properties
?liwa, Ewelina I.,Nesterov, Dmytro S.,Kirillova, Marina V.,K?ak, Julia,Kirillov, Alexander M.,Smoleński, Piotr
supporting information, p. 9631 - 9644 (2021/06/30)
This work describes an unexpected generation of a new 3D metal-organic framework (MOF), [Cu4(μ-Cl)6(μ4-O)Cu(OH)2(μ-PTAO)4]n·2nCl-EtOH·2.5nH2O, from copper(II) chloride and 1,3,5-triaza-7-phosphaadamantane 7-oxide (PTAO). The obtained product is composed of diamandoid tetracopper(II) [Cu4(μ-Cl)6(μ4-O)] cages and monocopper(II) [Cu(OH)2] units that are assembled, via the diamandoid μ-PTAO linkers, into an intricate 3D net with an nbo topology. Magnetic susceptibility measurements on this MOF in the temperature range of 1.8-300 K reveal a ferromagnetic interaction (J = +20 cm-1) between the neighboring copper(II) ions. Single-point DFT calculations disclose a strong delocalization of the spin density over the tetranuclear unit. The magnitude of exchange coupling, predicted from the broken-symmetry DFT studies, is in good agreement with the experimental data. This copper(II) compound also acts as an active catalyst for the mild oxidation and carboxylation of alkanes. The present study provides a unique example of an MOF that is assembled from two different types of adamantoid Cu4 and PTAO cages, thus contributing to widening a diversity of functional metal-organic frameworks.
Selective Functionalization of Hydrocarbons Using a ppm Bioinspired Molecular Tweezer via Proton-Coupled Electron Transfer
Chen, Hongyu,Wang, Lingling,Xu, Sheng,Liu, Xiaohui,He, Qian,Song, Lijuan,Ji, Hongbing
, p. 6810 - 6815 (2021/06/28)
An expanded porphyrin-biscopper hexaphyrin was introduced as a bioinspired molecular tweezer to co-catalyze functionalization of C(sp3)-H bonds. Theoretical and experimental investigations suggested that the biscopper hexaphyrin served as a molecular tweezer to mimic the enzymatic orientation/proximity effect, efficiently activating the N-hydroxyphthalimide (NHPI) via light-free proton-coupled electron transfer (PCET), at an exceptionally low catalyst loading of 10 mol ppm. The resulting N-oxyl radical (PINO) was versatile for chemoselective C-H oxidation and amination of hydrocarbons.