52026-74-1Relevant articles and documents
NMR Study of Species Formed during Ethylene Oxidation over Supported Silver
Fernandes, E.F.,Benesi, A. J.,Vannice, M. A.
, p. 8498 - 8506 (1994)
13C solid-state NMR spectroscopy has been used to study the various species formed during the oxidation of ethylene on Ag catalysts.The NMR spectra obtained after heat treatments of sealed catalyst samples provide direct observation of surface species which can be identified by their chemical shift values.This study also reports 13C shifts for standard compounds dispersed on Ag/η-Al2O3 and Ag/SiO2 which provide groups that can be present under reaction conditions, and the decomposition of 13C-labeled ethylene oxide on Ag/SiO2 in the absence of O2 was investigated.On the basis of these experiments, 13C assignments have been made for the following absorbed species: ethylene oxide, formic acid, formate, oxalic acid, oxalate, acetic anhydride, acetaldehyde, and carbonate.In the absence of O2, ethylene oxide decomposed to acetic acid, acetaldehyde, and formaldehyde, and broad peaks indicative of polymers on the SiO2 surface were also observed.The observation of ethylene oxide adsorbed on Ag/SiO2 after reaction between 13C2H4 and O2 was consistent with a previous study showing this catalyst was much more selective than a Ag/η-Al2O3 catalyst; CO2, adsorbed 13C2H4, and a deprotonated oxalate or formate species were also identified.The formation of CO2 in the absence of aldehyde or acetate species but in the presence of oxalate species suggests an alternative route may exist for complete oxidation that does involve isomerization of ethylene oxide.
Coupling conversion of methane with carbon monoxideviacarbonylation over Zn/HZSM-5 catalysts
Wen, Fuli,Zhang, Jin,Chen, Zhiyang,Zhou, Ziqiao,Liu, Hongchao,Zhu, Wenliang,Liu, Zhongmin
, p. 1358 - 1364 (2021/03/14)
Efficient direct transformation of methane into value-added chemicals has great significance for long-term sustainability of fuels and chemicals, but remains a major challenge due to its high inertness. Reported here is that methane can be activated effectivelyviacarbonylation with CO over Zn/HZSM-5 catalysts under mild conditions. The selectivity to aromatics alone reaches 80% among all hydrocarbon products at 823 K, whereas as high as 92% ethane selectivity is achieved at a lower temperature of 673 K.13CO isotope labelling experiments demonstrate that approximately 50% of the carbon atoms in all the products originate from carbon monoxide, whereas another half of the carbons come from methane, indicating that the precursors of hydrocarbon products are acyl compounds and/or acetic acid formed by carbonylation of methane with carbon monoxide. This provides potential for transformation of methane into value-added chemicals under mild reaction conditions.
Mechanistic Insights into Catalytic Ethanol Steam Reforming Using Isotope-Labeled Reactants
Crowley, Stephen,Castaldi, Marco J.
supporting information, p. 10650 - 10655 (2016/09/03)
The low-temperature ethanol steam reforming (ESR) reaction mechanism over a supported Rh/Pt catalyst has been investigated using isotope-labeled EtOH and H2O. Through strategic isotope labeling, all nonhydrogen atoms were distinct from one another, and allowed an unprecedented level of understanding of the dominant reaction pathways. All combinations of isotope- and non-isotope-labeled atoms were detected in the products, thus there are multiple pathways involved in H2, CO, CO2, CH4, C2H4, and C2H6product formation. Both the recombination of C species on the surface of the catalyst and preservation of the C?C bond within ethanol are responsible for C2product formation. Ethylene is not detected until conversion drops below 100 % at t=1.25 h. Also, quantitatively, 57 % of the observed ethylene is formed directly through ethanol dehydration. Finally there is clear evidence to show that oxygen in the SiO2-ZrO2support constitutes 10 % of the CO formed during the reaction.
ATP-independent formation of hydrocarbons catalyzed by isolated nitrogenase cofactors
Lee, Chi Chung,Hu, Yilin,Ribbe, Markus W.
experimental part, p. 1947 - 1949 (2012/04/04)
Reduce to produce: Molybdenum- and vanadium-nitrogenase cofactors have been isolated and shown to reduce carbon monoxide and cyanide ions to a mixture of alkanes and alkenes in the presence of a strong reductant, europium(II) diethylenetriaminepentaacetate (see scheme). Various hydrocarbons of up to seven carbon atoms in length are detected as products in these ATP-free reactions.
