74-84-0Relevant articles and documents
Catalytic hydrosilylation of oxalic acid: Chemoselective formation of functionalized C2-products
Feghali, Elias,Jacquet, Olivier,Thuery, Pierre,Cantat, Thibault
, p. 2230 - 2234 (2014)
Oxalic acid is an attractive entry to functionalized C2-products because it can be formed by C-C coupling of two CO2 molecules under electrocatalytic reduction. Herein, we describe the first attempts to reduce oxalic acid by catalytic hydrosilylation. Using B(C6F 5)3 as a Lewis acidic catalyst, oxalic acid can be converted to reduced C2-molecules, with high chemoselectivity, under mild reaction conditions.
Oxidative Condensation of Methane on Sr2 –xLaxTiO4 Catalysts: Effect of the Degree of Substitution of Sr and La
Petrov,Ivanova, Yu. A.,Reshetnikov,Isupova
, p. 862 - 867 (2019)
Abstract: The Sr2 –xLaxTiO4 (x = 0–2.0) catalysts were synthesized based on strontium titanate with a layered perovskite structure. The effect of the degree of substitution of La for Sr on the physicochemical (phase composition and textural characteristics) and catalytic properties of oxides in the oxidative condensation of methane at temperatures of 700–800°C were studied. It was found that multiphase Sr2?–?xLaxTiO4 samples with the degree of substitution x = 0.8–1.8 were most active and selective in the test reaction; this was likely related to the presence of lanthanum oxide and strontium oxide impurities in them, their optimum distribution over the surface, and the specific surface area.
New mechanism of photodissociation of gaseous acetone
Skorobogatov,Meilakhs,Pogosyan,Khripun
, p. 1271 - 1275 (2002)
It is found for the first time that photolysis of gaseous acetone under UV irradiation produces ethane not only via recombination of methyl radicals, but also by the mechanism of induced predissociation.
Mechanisms of 1,1-Reductive Elimination from Palladium: Elimination of Ethane from Dimethylpalladium(II) and Trimethylpalladium(IV)
Moravskiy, A.,Stille, J. K.
, p. 4182 - 4186 (1981)
The energies and entropies of activation for the 1,1-reductive elimination of ethane from cis-bis(diphenylmethylphosphine)dimethylpalladium(II) (2a) in polar and nonpolar solvents were determined.The rates of elimination are slower in polar solvents such as Me2SO, acetone, and acetonitrile than in nonpolar solvents such as benzene.The energies of activation in nonpolar solvents are very close (25 kcal/mol) to the calculated values (extended HMO).Lower energies of activation (6-10 kcal/mol) but high negative entropies of activation (ca.45 eu) in polar solvents are consistent with an elimination that produced a coordinatively unsaturated palladium(0) complex and a late transition state having the characteristics of the product, such that solvent coordinates during the transition state.Reaction of 2a or the corresponding bis(triphenylphosphine)dimetnylpalladium(II) complex 2b with methyl iodide yields ethane and the trans-bis(phosphine)iodomethylpalladium(II) complexes (10a,b).The second-order reaction proceeds through a rate-determining oxidative addition of methyl iodide to 2a,b, yielding the bis(phosphine)iodotrimethylpalladium(IV) intermediate, followed by a rapid elimination.In polar solvents, the rates of these reactions are faster than the 1,1-reductive eliminations from 2a,b mostly because of the lower entropies of activation in the oxidative addition step.In nonpolar solvents, the rates are comparable.The reaction of 2a,b with CD3I gave both C2H6 and C2H3D3, the ratios of these isomers in the reaction of 2a being most consistent with the trans oxidative addition reaction followed by statistical reductive elimination from adjacent methyls.
Gold-doping of carbon-supported palladium improves reduction catalysis
Fang, Yu-Lun,Heck, Kimberly N.,Zhao, Zhun,Pretzer, Lori A.,Guo, Neng,Wu, Tianpin,Miller, Jeffrey T.,Wong, Michael S.
, p. 1776 - 1786 (2016)
Bimetallic palladium-gold (PdAu) catalysts have better catalytic performance than monometallic catalysts for many applications. PdAu catalysts with controlled nanostructures and enhanced activities have been extensively studied but their syntheses require multiple and occasionally complicated steps. In this work, we demonstrated that supported PdAu catalysts could be simply prepared by doping a supported Pd catalyst with gold through wet impregnation and calcination. Resulting PdAu-on-carbon (PdAu/C) catalysts were tested for the room-temperature, aqueous-phase hydrodechlorination of trichloroethene. The most active PdAu/C catalyst (Pd 1.0 wt%, Au 1.1 wt%, dried/air/H2 process) had an initial turnover frequency (TOF) of 34.0 × 10?2 molTCE molPd?1 s?1, which was >15 times higher than monometallic Pd/C (Pd 1.0 wt%, initial TOF of 2.2 × 10?2 molTCE molPd?1 s?1). Through X-ray absorption spectroscopy, the gold kept Pd from oxidizing under calcination at 400 °C. Probable nanostructure evolution pathways are proposed to explain the observed catalysis.
Arrhenius Parameter Determination for the Reaction of Methyl Radicals with Iodine Species in Aqueous Solution
Mezyk, Stephen P.,Madden, Keith P.
, p. 9360 - 9364 (1996)
The techniques of electron pulse radiolysis and direct ESR detection have been used to determine Arrhenius parameters for the recombination reaction of methyl radicals and methyl radical reaction with iodine in aqueous solution.At 22.8 deg C, rate constants of 2k7=(1.77+/-0.16)E9 dm3 mol-1 s-1 and k1=(2.75+/-0.43)E9 dm3 mol-1 s-1, with corresponding activation energies of 14.89+/-0.87 and 13.10+/-0.71 kJ mol-1 (5.7-39.6 deg C), were obtained respectively for these two reactions.The analogous reaction of methyl radicals with iodide or iodate was found to be much slower, with the room temperature rate constant for both reactions estimated as k3 mol-1 s-1.
Kinetic limit of the ethane and ethylene yield in the gas phase condensation of methane
Vedeneev, V. I.,Arutyunov, V. S.,Basevich, V. Ya.
, p. 372 - 373 (1995)
A kinetic simulation of the initiated condensation of methane in the gas phase showed that the additional generation of methyl radicals via the reaction CH4 + I2 -> CH3 + HO2 causes a nearly tenfold increase in the C2 hydrocarbon yield.However, a kinetic limit of the yield exist that is close to that determined in experiments on the catalytic oxidative condensation of methane. - Key words: kinetic simulation; oxidative condensation of methane.
Variability of particle configurations achievable by 2-nozzle flame syntheses of the Au-Pd-TiO2 system and their catalytic behaviors in the selective hydrogenation of acetylene
Pongthawornsakun, Boontida,Mekasuwandumrong, Okorn,Santos Aires, Francisco J.Cadete,Büchel, Robert,Baiker, Alfons,Pratsinis, Sotiris E.,Panpranot, Joongjai
, p. 1 - 7 (2018)
Catalysts with Au and Pd supported on TiO2 (Au:Pd 1:1 wt/wt%) were prepared by 1- and 2-nozzle flame spray pyrolysis (FSP). The 2-nozzle configuration allowed to synthesize various particle configurations by separate or co-feeding of the metal precursor solutions to the two nozzles. For the Au-Pd/TiO2 system, four different catalyst particle configurations were investigated: “TiO2 + AuPd”, “Pd/TiO2 +Au”, “Au/TiO2 +Pd”, and “Pd/TiO2 + Au/TiO2”, where + separates the corresponding precursor solutions fed to the two nozzles. There were no significant differences in the specific surface areas and the average TiO2 crystallite sizes of the catalysts (100 m2/g and 16–17 nm, respectively) with the exception of “Pd/TiO2 +Au/TiO2”, which exhibited larger surface area and smaller crystallite size (152 m2/g, 12 nm) due to halving of the Ti precursor concentration in each nozzle. As revealed by CO chemisorption, XPS, and STEM-EDX results, the catalyst properties varied largely in terms of bimetallic AuPd particle compositions, the interaction between metal–metal and metal-support, and the location of Pd (or AuPd) on the TiO2. Among the catalysts studied, “TiO2 + AuPd” prepared with the 2-nozzle system exhibited the highest conversion of acetylene (～50%) at 40 °C with high selectivity to ethylene ( > 95%). Co-feeding the noble metal precursors together with the Ti precursor afforded less active catalysts due to the formation of Ti-O species partially covering the most active bimetallic AuPd particles. Compared to the commercially available acetylene hydrogenation catalyst and the AuPd/TiO2 prepared by conventional co-impregnation and deposition-precipitation, all the FSP-AuPd/TiO2 catalysts showed superior performances under the reaction conditions used.
Oxidative Coupling of Methane over Na2WO4/CeO2 and Related Catalysts
Yu, Zhenqiang,Yang, Xueming,Lunsford, Jack H.,Rosynek, Michael P.
, p. 163 - 173 (1995)
Na2WO4/CeO2 is an active and selective catalyst for the oxidative coupling of methane (OCM).At 780 deg C and using a reactant feed of CH4:O2:He=4.8:1.0:5.6, a C2 selectivity in excess of 70percent can be achieved over a 9.4 molpercent Na2WO4/CeO2 catalyst at a CH4 conversion of 22percent.By contrast, the C2 selectivity exhibited by pure CeO2 under the same reaction conditions, in the absence of Na2WO4 promoter, is 2- on the calcined catalysts and reveal no evidence for additional surface oxygen species, such as O22- or O-, that might serve as sites for CH4 activation.Pulse reaction experiments show that bulk lattice oxygen species do not participate directly in the OCM reaction, and that the active oxygen species involved in the activation of methane exist only in the presence of gas phase oxygen.Ion scattering spectroscopy and in situ Raman spectroscopy indicate that the initial CeO2 surface of the calcined catalyst is completely covered by one or more layers of Na2WO4, which exists in the molten state under reaction conditions.
Novel catalysts for carbon dioxide-induced selective conversion of methane to C2 hydrocarbons
Cai, Yingchun,Chou, Lingjun,Li, Shuben,Zhang, Bing,Zhao, Jun
, p. 828 - 829 (2002)
The combination of Mn with BaCO3 leads to active catalysts for carbon dioxide-induced selective conversion of methane to ethane and ethylene in the absence of oxygen.
