F+:Highly flammable;
74-85-1Relevant articles and documents
Stable and selective electrochemical reduction of carbon dioxide to ethylene on copper mesocrystals
Chen, Chung Shou,Handoko, Albertus D.,Wan, Jane Hui,Ma, Liang,Ren, Dan,Yeo, Boon Siang
, p. 161 - 168 (2015)
Stable and selective electrochemical reduction of carbon dioxide to ethylene was achieved using copper mesocrystal catalysts in 0.1 M KHCO3. The Cu mesocrystal catalysts were facilely derived by the in situ reduction of a thin CuCl film during the first 200 seconds of the CO2 electroreduction process. At -0.99 V vs. RHE, the Faradaic efficiency of ethylene formation using these Cu mesocrystals was ～18× larger than that of methane and forms up to 81% of the total carbonaceous products. Control CO2 reduction experiments show that this selectivity towards C2H4 formation could not be replicated by using regular copper nanoparticles formed by pulse electrodeposition. High resolution transmission electron microscopy reveals the presence of both (100)Cu facets and atomic steps in the Cu mesocrystals which we assign as active sites in catalyzing the reduction of CO2 to C2H4. CO adsorption measurements suggest that the remarkable C2H4 selectivity could be attributed to the greater propensity of CO adsorption on Cu mesocrystals than on other types of Cu surfaces. The Cu mesocrystals remained active and selective towards C2H4 formation for longer than six hours. This is an important and industrially relevant feature missing from many reported Cu-based CO2 reduction catalysts.
Effects of thickness extension mode resonance oscillation of acoustic waves on catalytic and surface properties. IV. Activation of a Ag catalyst for ethanol decomposition by overtone resonance frequencies
Saito,Inoue
, p. 2040 - 2045 (2003)
The effects of resonance frequencies of acoustic waves on catalytic and surface properties were studied. The overtone resonance frequencies of 3.5, 10.8, and 17.9 MHz were applied to a 100 nm thick Ag catalyst deposited on a ferroelectric z-cut LiNbO3 crystal which generated thickness extension mode resonance oscillation (TERO). For ethanol decomposition, the TERO enhanced ethylene production without significant changes in acetaldehyde production for all the frequencies. The extent of catalyst activation strongly depended on the resonance frequency. In a low power region (1.0 W), it increased in the order 3.5 > 10.8 > 17.9 MHz. The activation energy for ethylene production decreased remarkably in the presence of TERO, the extent of which strongly depended on the frequency. Laser Doppler measurements showed that with increasing resonance frequency, the number of standing waves increased markedly, whereas the amplitudes of the wave decreased considerably. The specific catalytic activity, defined as the activity enhancement per the density of wave, increased in a nonlinear manner with lattice displacement. The resonance frequency effects of TERO on catalyst activation are discussed.
Role of Exposed Surfaces on Zinc Oxide Nanostructures in the Catalytic Ethanol Transformation
Morales, María V.,Asedegbega-Nieto, Esther,Iglesias-Juez, Ana,Rodríguez-Ramos, Inmaculada,Guerrero-Ruiz, Antonio
, p. 2223 - 2230 (2015)
For a series of nanometric ZnO materials, the relationship between their morphological and surface functionalities and their catalytic properties in the selective decomposition of ethanol to yield acetaldehyde was explored. Six ZnO solids were prepared by a microemulsion-precipitation method and the thermal decomposition of different precursors and compared with a commercial sample. All these materials were characterized intensively by XRD and SEM to obtain their morphological specificities. Additionally, surface area determinations and IR spectroscopy were used to detect differences in the surface properties. The density of acid surface sites was determined quantitatively using an isopropanol dehydration test. Based on these characterization studies and on the results of the catalytic tests, it has been established that ZnO basal surfaces seem to be responsible for the production of ethylene as a minor product as well as for secondary reactions that yield acetyl acetate. Furthermore, one specific type of exposed hydroxyl groups appears to govern the surface catalytic properties.
Reaction of the ethyl radical with oxygen at millitorr pressures at 243-368 K and a study of the Cl + HO2, ethyl + HO2, and HO2 + HO2 reactions
Dobis, Otto,Benson, Sidney W.
, p. 8798 - 8809 (1993)
Ethyl radicals formed in the reaction of C2H6 + Cl are allowed to react with molecular oxygen in a very low pressure reactor (VLPR) experimental flow system over the temperature range of 243-368 K. Mass spectrometric analysis of reactants and products made possible the determination of rate constants (cm3/(molecule·-s)) of all major reaction steps. Mass balances for C, H, and Cl are good to ±4% on average. The elementary steps are the following: C2H5 + O2 → HO2 + C2H4, k6 = (1.42 ± 0.38) × 10-17 exp[(5064 ± 154)/RT], measured independently from recording C2H5 consumption or C2H4 formation rates; 2HO2 → H2O2, k7 = (4.50 ± 0.56) × 10-13 exp[(1064 ± 77)/RT]; C2H5 + HO2 → H2O2 + C2H4, k8a = (2.98 ± 0.11) × 10-12; Cl + HO2 → HCl + O2, k9 = (4.45 ± 0.06) × 10-11. Activation energies are given in cal/mol. Reactions 8a and 9 show no change in the temperature range of measurements, while reactions 6 and 7 both have negative temperature dependence. The radical oxidation reaction 6 is suggested to occur via excited ethylperoxy and 2-hydroperoxyethyl radical formations as consecutive reversible steps.
NEW PATHWAYS IN LASER INDUCED THERMAL GAS-PHASE CHEMISTRY
Pola, J.
, p. 607 - 616 (1990)
Various cw CO2 laser-induced reactions in the presence of energy conveying SF6 are shown to proceed in a specific way due to the absence of heterogeneous stages that are very difficult to avoid in normal hot wall reactors.Truly homogeneous courses are reported for some dehydrochlorinations, oxidations of perhaloalkenes with molecular oxygen, and decomposition of representatives of amines, nitroalkanes and perfluorinated, bridged and unsaturated derivatives of carboxylic acids.
High selectivity for ethylene from carbon dioxide reduction over copper nanocube electrocatalysts
Roberts, F. Sloan,Kuhl, Kendra P.,Nilsson, Anders
, p. 5179 - 5182 (2015)
Nanostructured surfaces have been shown to greatly enhance the activity and selectivity of many different catalysts. Here we report a nanostructured copper surface that gives high selectivity for ethylene formation from electrocatalytic CO2 reduction. The nanostructured copper is easily formed in situ during the CO2 reduction reaction, and scanning electron microscopy (SEM) shows the surface to be dominated by cubic structures. Using online electrochemical mass spectrometry (OLEMS), the onset potentials and relative selectivity toward the volatile products (ethylene and methane) were measured for several different copper surfaces and single crystals, relating the cubic shape of the copper surface to the greatly enhanced ethylene selectivity. The ability of the cubic nanostructure to so strongly favor multicarbon product formation from CO2 reduction, and in particular ethylene over methane, is unique to this surface and is an important step toward developing a catalyst that has exclusive selectivity for multicarbon products. Cubic nanostructures formed on a polycrystalline copper surface give high selectivity for ethylene formation from carbon dioxide electroreduction. The nanocubes are easily synthesized in situ, and online electrochemical mass spectrometry is used to compare the reactivity to other copper single-crystal surfaces.
Cross-metathesis vs. silylative coupling of vinyl alkyl ethers with vinylsilanes catalyzed by a ruthenium-carbene complex (Grubbs catalyst)
Marciniec,Kujawa,Pietraszuk
, p. 671 - 675 (2000)
Grubbs complex, (PCy3)2Cl2Ru=CHPh (I) is a very effective catalyst of the cross-disproportionation of vinyl-trisubstituted silanes H2C=CHSiR3 [where R3 = Me3, PhMe2, (OEt)3] with vinyl alkyl ethers H2C=CHOR' [where R' = ethyl, propyl, butyl, t-butyl, t-pentyl, 2-(ethyl)hexyl, cyclohexyl, trimethylsilyl] to yield a mixture of (E + Z) 1-silyl-2-alkoxyethenes. The reaction occurs quantitatively under milder conditions (60 °C) than the analogous one catalyzed by Ru-H and/or Ru-Si complexes reported previously (80 °C). The stoichiometric reaction of (I) and (PCy3)2Cl2Ru=CH2 (III) with vinyl ethyl ether leads to the formation of (PCy3)2Cl2Ru=CH(OEt) (II), inactive in the stoichiometric reaction with vinylsilanes but very active in the catalytic process. Experiments with the use of deuterated vinylsilanes indicate the non-metallacarbene mechanism of the reaction and provide evidence for the initiation of Ru-H bond formation via the hydrovinylation with vinylsilanes.
Identification and active site analysis of the 1-aminocyclopropane-1- carboxylic acid oxidase catalysing the synthesis of ethylene in Agaricus bisporus
Meng, Demei,Shen, Lin,Yang, Rui,Zhang, Xinhua,Sheng, Jiping
, p. 120 - 128 (2014)
Background 1-Aminocyclopropane-1-carboxylate oxidase (ACO) is a key enzyme that catalyses the final step in the biosynthesis of the plant hormone ethylene. Recently, the first ACO homologue gene was isolated in Agaricus bisporus, whereas information concerning the nature of the ethylene-forming activity of this mushroom ACO is currently lacking. Methods Recombinant ACO from A. bisporus (Ab-ACO) was purified and characterised for the first time. Molecular modelling combined with site-directed mutagenesis and kinetic and spectral analysis were used to investigate the property of Ab-ACO. Results Ab-ACO has eight amino acid residues that are conserved in the Fe (II) ascorbate family of dioxygenases, including four catalytic residues in the active site, but Ab-ACO lacks a key residue, S289. In comparison to plant ACOs, Ab-ACO requires ACC and Fe (II) but does not require ascorbate. In addition, Ab-ACO had relatively low activity and was completely dependent on bicarbonate, which could be ascribed to the replacement of S289 by G289. Moreover, the ferrous ion could induce a change in the tertiary, but not the secondary, structure of Ab-ACO. Conclusions These results provide crucial experimental support for the ability of Ab-ACO to catalyse ethylene formation in a similar manner to that of plant ACOs, but there are differences between the biochemical and catalytic characteristics of Ab-ACO and plant ACOs. General significance This work enhances the understanding of the ethylene biosynthesis pathways in fungi and could promote profound physiological research of the role of ethylene in the regulation of mushroom growth and development.
Methane conversion to ethylene over GaN catalysts. Effect of catalyst nitridation
Dutta, Kanchan,Chaudhari, Vishnu,Li, Chao-Jun,Kopyscinski, Jan
, (2020)
Vast availability of natural and shale gases makes methane a reliable source for synthesizing valuable chemical building blocks such as ethylene. A new stable supported GaN/SBA15 catalyst from an emerging class of nitride catalysts was reported for the direct non-oxidative methane coupling to ethylene. The effect of nitridation on the catalyst properties and activity was investigated. The optimum nitridation temperatures were 700 °C and 750 °C for the GaN/SBA15 and the unsupported GaN catalyst, respectively. Supported catalysts were more stable and had 5–10 times higher product (ethylene) formation rates per gram of gallium than the unsupported catalysts due to the higher surface area (>320 vs. 2 g?1) and Ga-dispersion inside the pores. Compared to the oxide precursors, the nitrides exhibited a higher atom conversion efficiency for the CH4 carbon leading to higher ethylene selectivity (71 % for GaN/SBA15, 2O3/SBA15) and lower coke selectivity (27 % for GaN/SBA15, 40 % for Ga2O3/SBA15).
Calorimetric Study of Vanadium Pentoxide Catalysts Used in the Reaction of Ethane Oxidative Dehydrogenation
Le Bars, J.,Vedrine, J. C.,Auroux, A.,Pommier, B.,Pajonk, G. M.
, p. 2217 - 2221 (1992)
Vanadium pentoxide catalysts have been studied in the partial oxidation reaction of ethane in the 723-843 K temperature range.The relationship between the acid-base properties and the catalytic behavior was investigated.The number and character of acidic sites of V2O5 catalysts were determined by studying the adsorption of a basic molecule using microcalorimetry.The reducibility level and the evolution of the surface state, as well as the heat evolved, were studied by using a pulse method with pure ethane only.The reaction of ethane oxidative dehydrogenation was studied by a continuous flow method and the activation energies for the formation of C2H4 and CO were calculated.The selectivity of the catalyst was interpreted in connection with the acid-base properties.The strong sites were observed to decrease rapidly with time on stream, although the catalysts were still active.Temperature-programmed reduction of V2O5 using a TG-DSC coupling was also investigated with hydrogen, ethylene, or ethane as reducers.The different heats of reduction are given.It was observed that C2H4 is a much more efficient reducing agent than H2 and C2H6.Following each reduction, reoxidation studies by oxygen were performed in the same equipment showing clearly different steps in the reoxidation process.
