C:Corrosive;
64-18-6Relevant articles and documents
Synergistic activating effect of promoter and oxidant in single step conversion of methane into methanol over a tailored polymer-Ag coordination complex
Shavi, Raghavendra,Hiremath, Vishwanath,Sharma, Aditya,Won, Sung Ok,Seo, Jeong Gil
, p. 24168 - 24176 (2017)
Single-step conversion of methane to its oxygenated derivatives, such as methanol, is a challenging topic in C1 chemistry. The presence of Br?nsted-acidic sites, N- and O-type chelating ligands, and noble metals are demonstrated to be essential criteria for effective catalysis of this reaction. Considering these criteria, a catalytic complex was tailored herein. Poly-d-glucosamine (Ch) was used as chelating ligand for Ag, to incorporate the robust redox properties of Ag(i). The prepared AgCh complex was characterized by techniques including solid-state 1H-NMR, FE-TEM, XANES, and XPS. Besides highlighting the utility of chelate complexation for providing new materials, this study elucidates the effects of the oxidant and promoters on the methane oxidation. The catalytic activity was tested for different oxidant combinations, including hydrogen peroxide, oxygen, and carbon dioxide. Of all of them, a mixture of hydrogen peroxide and oxygen showed the highest selectivity for oxidation of methane to methanol. Further, it was observed that the addition of 1-butyl-3-methylimidazolium chloride [BMIM]+Cl- as a promoter to the hydrogen peroxide and oxygen-containing AgCh system could enhance methanol production. The methanol yield reached up to 3166 μmol, representing an 18-fold yield increase and an 8-fold methane conversion increase when compared to the results (175 μmol) without a promoter.
Mechanism of the Photooxidation of Formaldehyde Studied by Flash Photolysis of CH2O-O2-NO Mixtures
Veyret, Bernard,Rayez, Jean-Claude,Lesclaux, Robert
, p. 3424 - 3430 (1982)
The mechanism of the chain process leading to formic acid in the photooxidation of CH2O has been studied with the flash photolysis technique.Mixtures of CH2O, O2, and NO were photolyzed and the rate of appearance and yield of NO2 were monitored.Kinetic simulations of both sets of data allowed the determination of the rate constants for the main reactions HO2 + CH2O -> O2CH2OH (6), OCH2OH + O2 -> HO2 + HCO2H (8), OCH2OH + NO -> products (9) (k6=(7.5 +/-3.5)E-14; k8=(3.5 +/-1.6)E-14; k9=(4.0 +/-1.9)E-11 cm3molecule-1s-1).Quantum calculations provided estimates of the heats of formation for the radicals involved.The effect of temperature was investigated, suggesting the importance of the decomposition of the radical HOCH2O into H atom and formic acid.The validity of the global scheme is discussed along with its importance for the removal of CH2O and the production of formic acid in the athmosphere.
Photo-reduction of CO2 by vis light on polythiophene-ZSM-5 zeolite hybrid photo-catalyst
Kiani?ka, Jana,?ík, Gabriel,?er?eň, Franti?ek,?pánik, Ivan,Sokolík, Robert,Filo, Juraj
, (2019)
A new hybrid photo-catalyst based on ZSM-5 zeolite suitable for reduction of carbon dioxide was synthesized. The photo-catalyst was prepared by oxidative polymerization of thiophene with FeCl3 in the presence of ZSM-5 with participation of ultrasound. The synthesized photo-catalyst strongly absorbs light radiation up to approx. 650 nm, with the absorption edge in the NIR region. Reactive radicals were generated by VIS light irradiation in an aqueous suspension consisting of the photo-catalyst with CO2. Formic acid and acetic acid were generated as the main products of the CO2 reduction. EPR spin trapping technique was applied to identify the reactive radical intermediates. In this work, the mechanism of product formation is also discussed.
Drastically enhanced visible-light photocatalytic degradation of colorless aromatic pollutants over TiO2 via a charge-transfer-complex path: A correlation between chemical structure and degradation rate of the pollutants
Wang, Nan,Zhu, Lihua,Huang, Yingping,She, Yuanbin,Yu, Yanmin,Tang, Heqing
, p. 199 - 206 (2009)
Photocatalytic degradation of colorless aniline and phenolic pollutants was investigated over TiO2 under visible-light irradiation, which was confirmed to proceed via a charge-transfer-complex (CTC)-mediated pathway. The correlation between the chemical structure and the degradation rate of these pollutants was established experimentally and theoretically. It was found that an electron-donating substituent in benzene ring, which raises the highest occupied molecular orbital and lowers the ionization potential of the organic compound, is favorable to the CTC-mediated photodegradation of the pollutant, but an electron- withdrawing substituent has a reversed effect. The addition of sacrificial electron acceptors was adopted to enhance the degradation and mineralization of the aromatic pollutants. The increased degradation rate by 3 to 10 times suggests that the CTC-mediated photocatalytic technique has promising applications in the removal of colorless organic pollutants in the presence of sacrificial electron acceptors.
MnO2 Electrocatalysts Coordinating Alcohol Oxidation for Ultra-Durable Hydrogen and Chemical Productions in Acidic Solutions
Chen, Lisong,Han, Shuhe,Li, Yan,Shi, Jianlin,Wei, Xinfa
, p. 21464 - 21472 (2021)
Electrocatalytic hydrogen production under acidic conditions is of great importance for industrialization in comparison to that in alkaline media, which, unfortunately, still remains challenging due to the lack of earth-abundant, cost-effective and highly active anodic electrocatalysts that can be used durably under strongly acidic conditions. Here we report an unexpected finding that manganese oxide, a kind of common non-noble catalysts easily soluble in acidic solutions, can be applied as a highly efficient and extremely durable anodic electrocatalyst for hydrogen production from an acidic aqueous solution of alcohols. Particularly in a glycerol solution, a potential of as low as 1.36 V (vs. RHE) is needed at 10 mA cm?2, which is 270 mV lower than that of oxygen evolution reaction (OER), to oxidize glycerol into value-added chemicals such as formic acid, without oxygen production. To our surprise, the manganese oxide exhibits extremely high stability for electrocatalytic hydrogen production in coupling with glycerol oxidation for longer than 865 hours compared to shorter than 10 h for OER. Moreover, the effect of the addition of glycerol on the electrochemical durability has been probed via in situ Raman spectroscopic analysis and density functional theory (DFT) calculations. This work demonstrates that acid-unstable metal oxide electrocatalysts can be used robustly in acidic media under the presence of certain substances for electrochemical purposes, such as hydrogen production.
Use of Bifurcation Diagrams as Fingerprints of Chemical Mechanisms
Noszticzius, Zoltan,McCormick, William D.,Swinney, Harry L.
, p. 2796 - 2800 (1989)
Various chemical reagents were fed continuously into a continuously stirred tank reactor to perturb the Belousov-Zhabotinskii system.The resulting bifurcation diagrams each contain multiple curves separating regions with different types of dynamical behav
SYNTHESIS OF D-RIBO-C-NUCLEOSIDE ANALOGUES BY DEHYDRATION OF NEW D-ALLO-PENTITOL-1-YL HETEROCYCLES
Perez, Juan A. Galbis,Caballero, Reyes Babiano,Ventula, Arturo Cert
, p. 129 - 142 (1985)
The reaction of 2-amino-2-deoxy-D-glycero-D-altro-heptose hydrochloride with acyclic and cyclic 1,3-dicarbonyl compounds gives, respectively, (D-allo-pentitol-1-yl)-pyrroles and -tetrahydroindoles that can be dehydrated to yield D-ribo-C-glycosyl heterocycles having furanoid or pyranoid structures, depending on the reaction conditions.Thus, when the reactions were kinetically controlled, α- and β-D-ribofuranosyl heterocycles were obtained, but α- and β-D-ribopyranosyl heterocycles were formed under conditions of thermodynamic control.A criterion is proposed to differentiate between both structures on the basis of the mass spectra of their triacetates.
Formate ester Norrish Type II elimination: Diode laser probing of gas-phase yields
Niu, Yuping,Christophy, Elizabeth,Pisano, Patrick J.,Zhang, Ying,Hossenlopp, Jeanne M.
, p. 4181 - 4187 (1996)
Time-resolved infrared absorption spectroscopy was utilized to monitor the production of HCOOH, CO2, and CO following ultraviolet laser excitation of gas-phase formate esters. Excitation of ethyl formate at 227.5 nm resulted in formation of HCOOH and CO2. The CO2 quantum yield was estimated to be 0.5 ± 0.1. No evidence for CO formation was obtained at this wavelength. Relative quantum yields for the Norrish Type II elimination of HCOOH from ethyl, n-propyl, n-butyl, isopropyl, isobutyl, and tert-butyl formate were obtained at 227.5 and 222 nm. Normalization of the observed HCOOH yields with respect to the number of γ-hydrogen atoms resulted in reactivity trends at 227.5 nm of 1:3:9 for the abstraction of primary, secondary, and tertiary hydrogen atoms, respectively. At 222 nm, a similar reactivity trend was observed with yields per available γ-hydrogen of 1:3:7 for abstraction of primary, secondary, and tertiary hydrogen atoms. Yields were found to be independent of ester pressure over the range 100-550 mTorr. Semiempirical and ab initio calculations of the excited state hydrogen abstraction step were performed and enthalpies of activation of 8-12 kcal/mol were obtained using AM1 with configuration interaction.
Radical-initiated oxidative conversion of methane to methanol over metallic iron and copper catalysts
Shavi, Raghavendra,Hiremath, Vishwanath,Seo, Jeong Gil
, p. 232 - 239 (2018)
Oxidative conversion of methane gas into value-added chemicals such as methanol is of great interest due to high economic feasibility of liquid fuel molecules for storage and transportation purpose. Activation and conversion of methane occur at very high temperatures due to its strong C–H bonding and hence the process is highly energy intensive. Therefore, homolytic cleavage of methane to produce CH3 and H radicals and subsequent conversion to methanol could be an alternative way to catalyze the reaction through a less energy-intensive process. In this work, radical-based conversion of methane to methanol was conducted in water-diluted 1-butyl-3-methylimidazolium chloride ionic liquid (IL) using metallic iron and copper as catalysts. The acidic IL, besides producing the high oxidation potential radicals from K2S2O8, enhanced their longevity. ZV Cu was found to be highly active in the reaction catalyzing with steady rate at a lower activation energy (Ea = 31.5 kJ/mol) and retains its oxidation state even after the reaction. On the other hand, ZV Fe, catalyzed the reaction with slightly slow initial rate ultimately resulting in moderate activation energy (40.77 kJ/mol). However, it was observed that ZV Fe fails to retain its oxidation state after reaction.
Cerium Doped Pt/TiO2 for Catalytic Oxidation of Low Concentration Formaldehyde at Room Temperature
Shi, Yuanyuan,Qiao, Zhiwei,Liu, Zili,Zuo, Jianliang
, p. 1319 - 1325 (2019)
Abstract: Formaldehyde is a carcinogenic and teratogenic toxic gas. With the extensive use of a variety of building materials, indoor formaldehyde has seriously threatened human health and environment. The catalytic oxidation is considered the most promising method for the removal of formaldehyde from air. In this work, we report a Pt/TiO2 catalyst with Ce modification, and investigate its activity of catalytic oxidation of low concentration formaldehyde at room temperature. The experimental results show that the trace formaldehyde (20?mg/m3) could be completely degraded at 55?min by using Pt–Ce/TiO2 catalyst. In view of multiple characterizations, such as BET, XRD, TEM, STEM, XPS and CO adsorption, it is indicated that the modification of Ce can effectively improve the dispersion of Pt particles in the surface and reduction of Pt particle size from 2.9 to 2.2?nm. Moreover, XPS results show that the Ce in the catalyst could enhance the binding energies of Pt, provide abundant oxygen vacancies, and could increase the ratio of adsorbed oxygen atoms to lattice oxygen atoms, which is conducive to the adsorption of oxygen, leading to the improvement of catalytic activity. Graphical Abstract: [Figure not available: see fulltext.].
