3031-73-0Relevant articles and documents
Fourier Transform Infrared Studies of the Self-Reaction of CH3O2 Radicals
Niki, H.,Maker, P. D.,Savage, C. M.,Breitenbach, L. P.
, p. 877 - 881 (1981)
Product studies were made with the FT IR method in the photooxidation of CH3N2CH3 and in the Cl-atom initiated oxidation of CH4 in O2-N2 mixtures at 700 torr and 297 K.The major products were CH2O, CH3OH, and CH3O2H in both systems.A weak, broad absorption band centered at 1030 cm-1 was assigned tentatively to CH3O2CH3.These results are consistent with the following primary and secondary reactions: (primary) 2CH3O2 ---> 2CH3O + O2 (1a); 2CH3O2 ---> CH3OH + CH2O + O2 (1b); 2CH3O2 ---> CH3O2CH3 + O2 (1c); (secondary) CH3O + O2 ---> CH2O + HO2 (5); CH3O2 + HO2 ---> CH3O2H + O2 (6).The relative rate costants for reactions 1a-c were determined to be k1a:k1b:k1c = 0.32 : 0.60 : 0. 08, respectively.
Catalytic oxidation of methane to methyl hydroperoxide and other oxygenates under mild conditions
Nizova, Galina V.,Suess-Fink, Georg,Shul'pin, Georgiy B.
, p. 397 - 398 (1997)
Methane is oxidized by air in acetonitrile solution to give methyl hydroperoxide (easily reduced to methanol), formaldehyde and formic acid in the presence of [NBu4]VO3-pyrazine-2-carboxylic acid as the catalyst and H2O2 as a promoter.
Insights into the direct selective oxidation of methane to methanol over ZSM-5 zeolytes in aqueous hydrogen peroxide
Al-Megren, Hamid,Al-Shihri, Saeed,Chadwick, David,Richard, Christian J.
, p. 269 - 278 (2020)
The direct selective oxidation of methane by aqueous hydrogen peroxide over ZSM-5(50) has been investigated. Methyl hydroperoxide was confirmed as the initial product of methane oxidation. The decomposition of methyl hydroperoxide to formaldehyde is established as a key intermediate in an oxidation pathway to formic acid and ultimately CO2. Hydrogen was detected during the oxidation of methane over ZSM-5 zeolites. The hydrogen was evaluated in terms of its origins and possible role in the production of MeOH. The addition of a copper salt to the ZSM-5(50) zeolite was found to decrease the overall productivity of all methane oxygenates. The use of copper also promoted the selectivity for methyl hydroperoxide whilst removing formic acid. The role of hydroxymethyl-methyl hydroperoxide is considered as an intermediate in the decomposition of methyl hydroperoxide to methanol. A tentative proposal into the nature of the iron species responsible for the catalytic species in ZSM-5(50) is made.
FTIR Study of the Kinetics and Mechanism for Cl-Atom-Initiated Reactions of Acetaldehyde
Niki, H.,Maker. P. D.,Savage, C. M.,Breitenbach, L. P.
, p. 588 - 591 (1985)
The rate constant for the reaction Cl + CH3CHO -> CH3CO + HCl was determined to be 7.6 X 10-11 cm3 molecule-1 s-1 at 298 +/- 2 K, using the competitive chlorination method with the reaction Cl + C2H6 as the refe
High-Pressure Falloff Curves and Specific Rate Constants for the Reaction CH3 + O2 CH3O2 CH3O + O
Cobos, C. J.,Hippler, H.,Luther, K.,Ravishankara, A. R.,Troe, J.
, p. 4332 - 4338 (1985)
The recombination reaction CH3 + O2 -> CH3O2 was studied at room temperature by laser flash photolysis over the pressure range 0.25-150 bar in the bath gases Ar and N2.Falloff curves are onstructed, leading to a limiting high-pressure rate constant of krec,infinite = (2.2 +/- 0.3) E-12 cm3 molecule-1s-1.By use of a simplified adiabatic channel model, on the basis of the measured krec,infinite a set of specific rate constants k(E,J) is calculated for the unimolecular dissociation CH3O2 -> CH3 + O2 and compared with the reaction CH3O2 -> CH3O + O.With the derived specific rate constants, thermal rate constants for the reaction CH3 + O2 ->/- CH 3O + O are calculated and compared with experiments.
Oxidation of a Monomethylpalladium(II) Complex with O2 in Water: Tuning Reaction Selectivity to Form Ethane, Methanol, or Methylhydroperoxide
Sberegaeva, Anna V.,Zavalij, Peter Y.,Vedernikov, Andrei N.
, p. 1446 - 1455 (2016)
Photochemical aerobic oxidation of n-Pr4N[(dpms)PdIIMe(OH)] (5) and (dpms)PdIIMe(OH2) (8) (dpms = di(2-pyridyl)methanesulfonate) in water in the pH range of 6-14 at 21 °C was studied and found to produce, in combined high yield, a mixture of MeOH, C2H6, and MeOOH along with water-soluble n-Pr4N[(dpms)PdII(OH)2] (9). By changing the reaction pH and concentration of the substrate, the oxidation reaction can be directed toward selective production of ethane (up to 94% selectivity) or methanol (up to 54% selective); the yield of MeOOH can be varied in the range of 0-40%. The source of ethane was found to be an unstable dimethyl PdIV complex (dpms)PdIVMe2(OH) (7), which could be generated from 5 and MeI. For shedding light on the role of MeOOH in the aerobic reaction, oxidation of 5 and 8 with a range of hydroperoxo compounds, including MeOOH, t-BuOOH, and H2O2, was carried out. The proposed mechanism of aerobic oxidation of 5 or 8 involves predominant direct reaction of excited methylpalladium(II) species with O2 to produce a highly electrophilic monomethyl PdIV transient that is involved in subsequent transfer of its methyl group to 5 or 8, H2O, and other nucleophilic components of the reaction mixture.
Oxygenation of methane with atmospheric oxygen in aqueous solution promoted by H2O2 and catalyzed by a vanadate ion-pyrazine-2-carboxylic acid system
Suess-Fink,Yan', Hong,Nizova,Stanislas,Shul'pin
, p. 1801 - 1803 (1997)
Methane is oxidized in aqueous solution with atmospheric oxygen and hydrogen peroxide in a reaction catalyzed by a NaVO3 - pyrazine-2-carboxylic acid system. Methyl hydroperoxide is selectively formed at 50°C. The turnover number of the catalyst after 24 h amounts to 480, and the yield of methyl hydroperoxide is 24% with respect to H2O2. Formaldehyde and formic acid are mainly formed at 120°C.
Unprecedentedly high efficiency for photocatalytic conversion of methane to methanol over Au-Pd/TiO2-what is the role of each component in the system?
Cai, Xiaojiao,Fang, Siyuan,Hu, Yun Hang
, p. 10796 - 10802 (2021)
Direct and highly efficient conversion of methane to methanol under mild conditions still remains a great challenge. Here, we report that Au-Pd/TiO2 could directly catalyze the conversion of methane to methanol with an unprecedentedly high methanol yield of 12.6 mmol gcat-1 in a one-hour photocatalytic reaction in the presence of oxygen and water. Such an impressive efficiency is contributed by several factors, including the affinity between Au-Pd nanoparticles and intermediate species, the photothermal effect induced by visible light absorption of Au-Pd nanoparticles, the employment of O2 as a mild oxidant, and the effective dissolution of methanol in water. More importantly, for the first time, thermo-photo catalysis is demonstrated by the distinct roles of light. Namely, UV light is absorbed by TiO2 to excite charge carriers, while visible light is absorbed by Au-Pd nanoparticles to increase the temperature of the catalyst, which further enhances the driving force of corresponding redox reactions. These results not only provide a valuable guide for designing a photocatalytic system to realize highly efficient production of methanol, but also, highlight the great promise of thermo-photo catalysis. This journal is
A Supported Nickel Catalyst Stabilized by a Surface Digging Effect for Efficient Methane Oxidation
Zhou, Huang,Liu, Tianyang,Zhao, Xuyan,Zhao, Yafei,Lv, Hongwei,Fang, Shi,Wang, Xiaoqian,Zhou, Fangyao,Xu, Qian,Xu, Jie,Xiong, Can,Xue, Zhenggang,Wang, Kai,Cheong, Weng-Chon,Xi, Wei,Gu, Lin,Yao, Tao,Wei, Shiqiang,Hong, Xun,Luo, Jun,Li, Yafei,Wu, Yuen
, p. 18388 - 18393 (2019)
A surface digging effect of supported Ni NPs on an amorphous N-doped carbon is described, during which the surface-loaded Ni NPs would etch and sink into the underneath carbon support to prevent sintering. This process is driven by the strong coordination interaction between the surface Ni atoms and N-rich defects. In the aim of activation of C?H bonds for methane oxidation, those sinking Ni NPs could be further transformed into thermodynamically stable and active metal-defect sites within the as-generated surface holes by simply elevating the temperature. In situ transmission electron microscopy images reveal the sunk Ni NPs dig themselves adaptive surface holes, which would largely prevent the migration of Ni NPs without weakening their accessibility. The reported two-step strategy opens up a new route to manufacture sintering-resistant supported metal catalysts without degrading their catalytic efficiency.
Low-temperature direct conversion of methane to methanol over carbon materials supported Pd-Au nanoparticles
He, Yingluo,Luan, Chunhui,Fang, Yuan,Feng, Xiaobo,Peng, Xiaobo,Yang, Guohui,Tsubaki, Noritatsu
, p. 48 - 53 (2020)
Direct conversion of methane to methanol under mild conditions remains a great challenge. Here, we report a class of carbon material catalysts for this direct synthesis. The carbon materials such as carbon nanotubes (CNTs), activated carbon (AC), and reduced graphene oxide (rGO) are employed as catalyst support, and the palladium-gold (Pd-Au) nanoparticles are used as active center. By using oxygen/hydrogen as oxidant in the direct synthesis, the catalyst of Pd-Au/CNTs shows outstanding methanol productivity and selectivity. Compared with the Pd-Au/CNTs, the Pd-Au/CNTs-n with a treatment of nitric acid for the support enhances the methanol selectivity, but decreases the methanol productivity. In addition, our characterization results reveal that a weak interaction between Pd-Au nanoparticles and CNTs support is in favor of methanol productivity and selectivity. In contrast, a strong interaction between Pd-Au and AC or rGO catalysts inhibits the reaction activity. This work offers a simple and effective strategy to directly synthesize methanol from methane under the mild conditions.
Efficient Synthesis of Monomeric Fe Species in Zeolite ZSM-5 for the Low-Temperature Oxidation of Methane
Yu, Tao,Su, Yang,Wang, Aiqin,Weckhuysen, Bert M.,Luo, Wenhao
, p. 2766 - 2770 (2021/05/07)
Direct oxidation of methane into value-added C1 oxygenated products, such as methanol, is essential and remains a significant challenge in the field of catalysis. In this work, we have prepared Fe/ZSM-5 materials via three different methods and investigated the influence of various preparation methods on the composition and catalytic performance of Fe/ZSM-5 for the low-temperature oxidation of methane. Through a combination of scanning transmission electron microscopy, ultraviolet-visible diffuse reflectance and 57Fe M?ssbauer spectroscopy, we have found that the highest proportion of monomeric Fe species of 71 % could be achieved in the ZSM-5 zeolite by the solid-state ion-exchange method, affording an excellent C1 oxygenates yield of 120 mol/molFe with a C1 oxygenates selectivity of 96 % at 50 °C for 30 min in the aqueous solution of H2O2.
