Selective catalytic oxidations of alkylaromatic compounds

Energy Technology Data Exchange (ETDEWEB)

Fischer, R.W. [Celanese GmbH, Oberhausen (Germany); Roehrscheid, F. [Hoechst AG, Frankfurt am Main (Germany). Zentralforschung und Technologie

1998-12-31

Focused to the guidelines of `Sustainable Development` `Responsible Care` and `Customer Satisfaction`, modern production processes are critically assessed on their balance between their ecological benefits and their economical parameters as well as their value to the community. Also in the area of fine chemicals, it is obvious that more and more processes are devolved which save feedstock, reduce emissions and minimize the potential for safety hazards: Less additive but more integrated protection of the environment yielding ecologically highly valuable processes. The described production of aromatic carboxylic acids is an ideal example for such a modern process. Nowadays the synthesis of derivatives of benzoic acid utilizes air as Ideal oxidant and acetic acid as environmental unquestionable solvent. The major byproduct of the oxidation reaction is water in some cases, dependend on the substrate also carbon dioxide. (orig.)

Atmospheric oxidation of selected alcohols and esters

Energy Technology Data Exchange (ETDEWEB)

Becker, K H; Cavalli, F

2001-03-01

The decision whether it is appropriate and beneficial for the environment to deploy specific oxygenated organic compounds as replacements for traditional solvent types requires a quantitative assessment of their potential atmospheric impacts including tropospheric ozone and other photooxidant formation. This involves developing chemical mechanisms for the gasphase atmospheric oxidation of the compounds which can be reliably used in models to predict their atmospheric reactivity under a variety of environmental conditions. Until this study, there was very little information available concerning the atmospheric fate of alcohols and esters. The objectives of this study were to measure the atmospheric reaction rates and to define atmospheric reaction mechanisms for the following selected oxygenated volatile organic compounds: the alcohols, 1-butanol and 1-pentanol, and the esters, methyl propionate and dimethyl succinate. The study has successfully addressed these objectives. (orig.)

Compound 13, an α1-selective small molecule activator of AMPK, inhibits Helicobacter pylori-induced oxidative stresses and gastric epithelial cell apoptosis

International Nuclear Information System (INIS)

Zhao, Hangyong; Zhu, Huanghuang; Lin, Zhou; Lin, Gang; Lv, Guoqiang

2015-01-01

Half of the world's population experiences Helicobacter pylori (H. pylori) infection, which is a main cause of gastritis, duodenal and gastric ulcer, and gastric cancers. In the current study, we investigated the potential role of compound 13 (C13), a novel α1-selective small molecule activator of AMP-activated protein kinase (AMPK), against H. pylori-induced cytotoxicity in cultured gastric epithelial cells (GECs). We found that C13 induced significant AMPK activation, evidenced by phosphorylation of AMPKα1 and ACC (acetyl-CoA carboxylase), in both primary and transformed GECs. Treatment of C13 inhibited H. pylori-induced GEC apoptosis. AMPK activation was required for C13-mediated GEC protection. Inhibition of AMPK kinase activity by the AMPK inhibitor Compound C, or silencing AMPKα1 expression by targeted-shRNAs, alleviated C13-induced GEC protective activities against H. pylori. Significantly, C13 inhibited H. pylori-induced reactive oxygen species (ROS) production in GECs. C13 induced AMPK-dependent expression of anti-oxidant gene heme oxygenase (HO-1) in GECs. Zinc protoporphyrin (ZnPP) and tin protoporphyrin (SnPP), two HO-1 inhibitors, not only suppressed C13-mediated ROS scavenging activity, but also alleviated its activity in GECs against H. pylori. Together, these results indicate that C13 inhibits H. pylori-induced ROS production and GEC apoptosis through activating AMPK–HO–1 signaling. - Highlights: • We synthesized compound 13 (C13), a α1-selective small molecule AMPK activator. • C13-induced AMPK activation requires α1 subunit in gastric epithelial cells (GECs). • C13 enhances Helicobacter pylori-induced pro-survival AMPK activation to inhibit GEC apoptosis. • C13 inhibits H. pylori-induced reactive oxygen species (ROS) production in GECs. • AMPK-heme oxygenase (HO-1) activation is required for C13-mediated anti-oxidant activity

Compound 13, an α1-selective small molecule activator of AMPK, inhibits Helicobacter pylori-induced oxidative stresses and gastric epithelial cell apoptosis

Energy Technology Data Exchange (ETDEWEB)

Zhao, Hangyong; Zhu, Huanghuang; Lin, Zhou; Lin, Gang; Lv, Guoqiang, E-mail: lvguoqiangwuxivip@163.com

2015-08-07

Half of the world's population experiences Helicobacter pylori (H. pylori) infection, which is a main cause of gastritis, duodenal and gastric ulcer, and gastric cancers. In the current study, we investigated the potential role of compound 13 (C13), a novel α1-selective small molecule activator of AMP-activated protein kinase (AMPK), against H. pylori-induced cytotoxicity in cultured gastric epithelial cells (GECs). We found that C13 induced significant AMPK activation, evidenced by phosphorylation of AMPKα1 and ACC (acetyl-CoA carboxylase), in both primary and transformed GECs. Treatment of C13 inhibited H. pylori-induced GEC apoptosis. AMPK activation was required for C13-mediated GEC protection. Inhibition of AMPK kinase activity by the AMPK inhibitor Compound C, or silencing AMPKα1 expression by targeted-shRNAs, alleviated C13-induced GEC protective activities against H. pylori. Significantly, C13 inhibited H. pylori-induced reactive oxygen species (ROS) production in GECs. C13 induced AMPK-dependent expression of anti-oxidant gene heme oxygenase (HO-1) in GECs. Zinc protoporphyrin (ZnPP) and tin protoporphyrin (SnPP), two HO-1 inhibitors, not only suppressed C13-mediated ROS scavenging activity, but also alleviated its activity in GECs against H. pylori. Together, these results indicate that C13 inhibits H. pylori-induced ROS production and GEC apoptosis through activating AMPK–HO–1 signaling. - Highlights: • We synthesized compound 13 (C13), a α1-selective small molecule AMPK activator. • C13-induced AMPK activation requires α1 subunit in gastric epithelial cells (GECs). • C13 enhances Helicobacter pylori-induced pro-survival AMPK activation to inhibit GEC apoptosis. • C13 inhibits H. pylori-induced reactive oxygen species (ROS) production in GECs. • AMPK-heme oxygenase (HO-1) activation is required for C13-mediated anti-oxidant activity.

Catalytic oxidant scavenging by selenium-containing compounds

DEFF Research Database (Denmark)

Carroll, Luke; Pattison, David I; Fu, Shanlin

2017-01-01

Myeloperoxidase produces strong oxidants during the immune response to destroy invading pathogens. However, these oxidants can also cause tissue damage, which contributes to the development of numerous inflammatory diseases. Selenium containing compounds, including selenomethionine (SeMet) and 1,...

Solidification of aqueous radioactive waste using insoluble compounds of magnesium oxide

International Nuclear Information System (INIS)

Carlson, J.E.

1986-01-01

A process is described for the treatment of radioactive waste which comprises: (a) first adding, under continuous agitation, a sufficient amount of a powdered magnesium oxide or magnesium hydroxide to an aqueous radioactive waste solution containing boric acid, the temperature of the water solution being 55-95 degrees C. to produce a magnesium borate derivative; (b) adding cement, under continuous agitation, to the magnesium borate derivative; and (c) then adding, under continuous agitation, after the cement has been dispersed, a sufficient amount of a compound selected from the group consisting of calcium oxide and calcium hydroxide to (b) to produce a gel matrix structure

Tunable catalytic properties of bi-functional mixed oxides in ethanol conversion to high value compounds

Energy Technology Data Exchange (ETDEWEB)

Ramasamy, Karthikeyan K.; Gray, Michel J.; Job, Heather M.; Smith, Colin D.; Wang, Yong

2016-04-10

tA highly versatile ethanol conversion process to selectively generate high value compounds is pre-sented here. By changing the reaction temperature, ethanol can be selectively converted to >C2alcohols/oxygenates or phenolic compounds over hydrotalcite derived bi-functional MgO–Al2O3cata-lyst via complex cascade mechanism. Reaction temperature plays a role in whether aldol condensationor the acetone formation is the path taken in changing the product composition. This article containsthe catalytic activity comparison between the mono-functional and physical mixture counterpart to thehydrotalcite derived mixed oxides and the detailed discussion on the reaction mechanisms.

Kinetics of biological methane oxidation in the presence of non-methane organic compounds in landfill bio-covers

International Nuclear Information System (INIS)

Albanna, Muna; Warith, Mostafa; Fernandes, Leta

2010-01-01

In this experimental program, the effects of non-methane organic compounds (NMOCs) on the biological methane (CH 4 ) oxidation process were examined. The investigation was performed on compost experiments incubated with CH 4 and selected NMOCs under different environmental conditions. The selected NMOCs had different concentrations and their effects were tested as single compounds and mixtures of compounds. The results from all experimental sets showed a decrease in CH 4 oxidation capacity of the landfill bio-cover with the increase in NMOCs concentrations. For example, in the experiment using compost with 100% moisture content at 35 deg. C without any NMOCs the V max value was 35.0 μg CH 4 h -1 g wetwt -1 . This value was reduced to 19.1 μg CH 4 h -1 g wetwt -1 when mixed NMOCs were present in the batch reactors under the same environmental conditions. The experimental oxidation rates of CH 4 in the presence of single and mixed NMOCs were modeled using the uncompetitive inhibition model and kinetic parameters, including the dissociation constants, were obtained. Additionally, the degradation rates of the NMOCs and co-metabolic abilities of methanotrophic bacteria were estimated.

Insertion compounds of transition-metal and uranium oxides

International Nuclear Information System (INIS)

Chippindale, A.M.; Dickens, P.G.; Powell, A.V.

1991-01-01

Several transition-metal and actinide oxides, in which the metal occurs in a high oxidation state, have open covalent structures and are capable of incorporating alkali and other electropositive metals under mild conditions to form insertion compounds A x MO n . These are solids which have several features in common: Over a range of compositions, A x MO n exists as one or more stable or metastable phases in which the structure of the parent oxide MO n is largely retained and the insertion element A is accommodated interstitially. Insertion is accompanied by a redox process A=A i . + e - M in which M is reduced and the electronic properties of the parent oxide change to those typical of a mixed-valence compound. The insertion process xA + MO n = A x MO n can be reversed, at least to some extent, by chemical or electrochemical reaction, with retention of structure (topotactic reaction). This review concentrates on methods of synthesis, characterisation, crystal structure and thermochemistry of these insertion compounds. It updates and extends previous work. (author)

Thermal oxidation of III-V compounds

International Nuclear Information System (INIS)

Monteiro, O.R.; Evans, J.W.

1988-01-01

The thermal oxidation of two important III-V compound semiconductor materials, namely GaAs and InP, has been studied between 300 and 600 0 C. In-situ TEM, cross-sectional TEM (XTEM) and SIMS analyses were used to characterize the reaction products. The first technique allows us to access the reactions at the very moment they are occurring. XTEM provides a clearer picture of the distribution of phases in the oxidized samples. SIMS gives us information on the dopant redistribution after oxidation as well as enrichment of group V element at the oxide semiconductor interface. Based on those results, the reaction products were characterized and reaction mechanisms proposed

An eco-friendly oxidation of sulfide compounds

Indian Academy of Sciences (India)

An improved green route has been developed for the oxidation of sulfide compounds. Albendazole is converted to ricobendazole or albendazole sulfone using H₂O₂ as an oxidant and H₂O as the solvent. High yields of the corresponding products were obtained by carrying out the reaction at room temperature.

The Impact and Oxidation Survival of Selected Meteoritic Compounds: Signatures of Asteroid Organic Material on Planetary Surfaces

Science.gov (United States)

Cooper, George; Horz, Fred; Oleary, Alanna; Chang, Sherwood

2013-01-01

Polar, non-volatile organic compounds may be present on the surfaces (or near surfaces) of multiple Solar System bodies. If found, by current or future missions, it would be desirable to determine the origin(s) of such compounds, e.g., asteroidal or in situ. To test the possible survival of meteoritic compounds both during impacts with planetary surfaces and under subsequent (possibly) harsh ambient conditions, we subjected known meteoritic compounds to relatively high impact-shock pressures and/or to varying oxidizing/corrosive conditions. Tested compounds include sulfonic and phosphonic acids (S&P), polyaromatic hydrocarbons (PAHs) amino acids, keto acids, dicarboxylic acids, deoxy sugar acids, and hydroxy tricarboxylic acids (Table 1). Meteoritic sulfonic acids were found to be relatively abundant in the Murchison meteorite and to possess unusual S-33 isotope anomalies (non mass-dependent isotope fractionations). Combined with distinctive C-S and C-P bonds, the S&P are potential signatures of asteroidal organic material.

Selective oxidation

International Nuclear Information System (INIS)

Cortes Henao, Luis F.; Castro F, Carlos A.

2000-01-01

It is presented a revision and discussion about the characteristics and factors that relate activity and selectivity in the catalytic and not catalytic partial oxidation of methane and the effect of variables as the temperature, pressure and others in the methane conversion to methanol. It thinks about the zeolites use modified for the catalytic oxidation of natural gas

Atmospheric oxidation of selected hydrocarbons

Energy Technology Data Exchange (ETDEWEB)

Benter, T.; Olariu, R.I.

2002-02-01

This work presents investigations on the gas-phase chemistry of phenol and the cresol isomers performed in a 1080 l quartz glass reactor in Wuppertal and in a large-volume outdoor photoreactor EUPHORE in Valencia, Spain. The studies aimed at clarifying the oxidation mechanisms of the reactions of these compounds with OH and NO{sub 3} radicals. Product investigations on the oxidation of phenol and the cresol isomers initiated by OH radicals were performed in the 1080 l quartz glass reactor with analyses by in situ FT-IR absorption spectroscopy. The primary focus of the investigations was on the determination of product yields. This work represents the first determination and quantification of 1,2-dihydroxybenzenes in the OH oxidation of phenolic compounds. Possible reaction pathways leading to the observed products have been elucidated. (orig.)

Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

Science.gov (United States)

Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

2015-12-30

This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

Advances in Base-Free Oxidation of Bio-Based Compounds on Supported Gold Catalysts

Directory of Open Access Journals (Sweden)

Robert Wojcieszak

2017-11-01

Full Text Available The oxidation of bio-based molecules in general, and of carbohydrates and furanics in particular, is a highly attractive process. The catalytic conversion of renewable compounds is of high importance. Acids and other chemical intermediates issued from oxidation processes have many applications related, especially, to food and detergents, as well as to pharmaceutics, cosmetics, and the chemical industry. Until now, the oxidation of sugars, furfural, or 5-hydroxymethylfurfural has been mainly conducted through biochemical processes or with strong inorganic oxidants. The use of these processes very often presents many disadvantages, especially regarding products separation and selectivity control. Generally, the oxidation is performed in batch conditions using an appropriate catalyst and a basic aqueous solution (pH 7–9, while bubbling oxygen or air through the slurry. However, there is a renewed interest in working in base-free conditions to avoid the production of salts. Actually, this gives direct access to different acids or diacids without laborious product purification steps. This review focuses on processes applying gold-based catalysts, and on the catalytic properties of these systems in the base-free oxidation of important compounds: C5–C6 sugars, furfural, and 5-hydroxymethylfurfural. A better understanding of the chemical and physical properties of the catalysts and of the operating conditions applied in the oxidation reactions is essential. For this reason, in this review we put emphasis on these most impacting factors.

Kinetics of aerobic oxidation of volatile sulfur compounds in wastewater and biofilm from sewers

DEFF Research Database (Denmark)

Rudelle, Elise Alice; Vollertsen, Jes; Hvitved-Jacobsen, Thorkild

2013-01-01

Laboratory experiments were conducted to investigate the kinetics of aerobic chemical and biological oxidation of selected odorous volatile sulfur compounds (VSCs) by wastewater and biofilm from sewers. The VSCs included methyl mercaptan (MeSH), ethyl mercaptan (EtSH), dimethyl sulfide (DMS......-spot downstream of a force main and the other was a gravity sewer transporting young aerobic wastewater. The kinetics of VSC oxidation for both wastewater and suspended biofilm samples followed a first-order rate equation. The average values of the reaction rate constants demonstrated the following order...... in the aerobic wastewater....

Computerized infrared spectroscopic study of surface reactions on selected lanthanide oxides

International Nuclear Information System (INIS)

Dellisante, G.N.

1982-01-01

The natures of adsorption sites on La 2 O 3 , Nd 2 O 3 , and selected praseodymium oxides were investigated by examining surface reactions of probe molecules using computerized transmission ir spectroscopy on unsupported samples. Additionally, the rehydration/dehydration behavior and crystallographic phase transitions of these oxides were examined in pretreatment temperature experiments involving rehydration of the sesquioxides to hydroxides by water exposure. Following rehydration of La 2 O 3 to La(OH) 3 , the effect of increasing vacuum pretreatment temperature (350 to 1000 0 C) is to gradually remove surface hydroxyl and carbonate entities (up to 650 0 C), and increase the degree of A-type crystallinity. Increasing crystallinity causes a concomitant decrease in surface oxide basicity. The removal of hydroxyl and carbonate species, as well as increases in oxide basicity, strongly correlated to increases in certain catalytic activities. The adsorption of NH 3 , CO 2 , mixtures of NH 3 and CO 2 , formic acid, acetic acid, acetaldehyde, and ethanol on the oxides was determined to weakly coordinate in Ln 3 + sites, and the surface reactions are discussed. Heating was found to desorb the adsorbed compounds and/or causes changes of the originally adsorbed form into other compounds. The effects of temperature on both adsorption and desorption are reported

Reactivity of selenium-containing compounds with myeloperoxidase-derived chlorinating oxidants

DEFF Research Database (Denmark)

Carroll, Luke; Pattison, David I.; Fu, Shanlin

2015-01-01

and N-chloramines, causes damage to host tissue. Low molecular mass thiol compounds, including glutathione (GSH) and methionine (Met), have demonstrated efficacy in scavenging MPO-derived oxidants, which prevents oxidative damage in vitro and ex vivo. Selenium species typically have greater reactivity...... compounds (selenomethionine, methylselenocysteine, 1,4-anhydro-4-seleno-L-talitol, 1,5-anhydro-5-selenogulitol) studied. In general, selenomethionine was the most reactive with N-chloramines (k2 0.8-3.4×10(3)M(-1) s(-1)) with 1,5-anhydro-5-selenogulitol and 1,4-anhydro-4-seleno-L-talitol (k2 1.1-6.8×10(2)M......(-1) s(-1)) showing lower reactivity. This resulted in the formation of the respective selenoxides as the primary oxidation products. The selenium compounds demonstrated greater ability to remove protein N-chloramines compared to the analogous sulfur compounds. These reactions may have implications...

Selectivity and Activity of Iron Molybdate Catalysts in Oxidation of Methanol

Directory of Open Access Journals (Sweden)

Khalid Khazzal Hummadi

2009-06-01

Full Text Available The selectivity and activity of iron molybdate catalysts prepared by different methods are compared with those of a commercial catalyst in the oxidation of methanol to formaldehyde in a continuous tubular bed reactor at 200-350 oC (473-623 oK, 10 atm (1013 kPa, with a methanol-oxygen mixture fixed at 5.5% by volume methanol: air ratio. The iron(III molybdate catalyst prepared by co-precipitation and filtration had a selectivity towards formaldehyde in methanol oxidation comparable with a commercial catalyst; maximum selectivity (82.3% was obtained at 573oK when the conversion was 59.7%. Catalysts prepared by reacting iron (III and molybdate by kneading or precipitation followed by evaporation, omitting a filtration stage, were less active and less selective. The selectivity-activity relationships of these catalysts as a function of temperature were discussed in relation to the method of preparation, surface areas and composition. By combing this catalytic data with data from the patent literature we demonstrate a synergy between iron and molybdenum in regard to methanol oxidation to formaldehyde; the optimum composition corresponded to an iron mole fraction 0.2-0.3. The selectivity to formaldehyde was practically constant up to an iron mole fraction 0.3 and then decreased at higher iron concentrations. The iron component can be regarded as the activity promoter. The iron molybdate catalysts can thus be related to other two-component MoO3-based selective oxidation catalysts, e.g. bismuth and cobalt molybdates. The iron oxide functions as a relatively basic oxide abstracting, in the rate-controlling step, a proton from the methyl of a bound methoxy group of chemisorbed methanol. It was proposed that a crucial feature of the sought after iron(III molybdate catalyst is the presence of -O-Mo-O-Fe-O-Mo-O- groups as found in the compound Fe2(MoO43 and for Fe3+ well dispersed in MoO3 generally. At the higher iron(III concentrations the loss of

Magnetic and structural properties of yellow europium oxide compound and Eu(OH)3

International Nuclear Information System (INIS)

Lee, Dongwook; Seo, Jiwon; Valladares, Luis de los Santos; Avalos Quispe, O.; Barnes, Crispin H.W.

2015-01-01

A new material based on a yellow europium oxide compound was prepared from europium oxide in a high vacuum environment. The structural and magnetic properties of the material were investigated. Owing to the absence of a crystal structure, the material exhibited a disordered magnetic behavior. In a reaction with deionized (DI) water without applied heat, the compound assumed a white color as soon as the DI water reached the powder, and the structure became polycrystalline Eu(OH) 3 . The magnetic properties, such as the thermal hysteresis, disappeared after the reaction with DI water, and the magnetic susceptibility of the yellow oxide compound weakened. The magnetic properties of Eu(OH) 3 were also examined. Although Eu 3+ is present in Eu(OH) 3 , a high magnetic moment due to the crystal field effect was observed. - Graphical abstract: (top left) Optical image of the yellow europium oxide compound. (top right) Optical image of the product of DI water and yellow europium oxide. (bottom) Magnetization curves as a function of temperature measured in various magnetic field. - Highlights: • We prepared a new material based on a yellow europium oxide compound from europium oxide. • We characterized the magnetic properties of the material which exhibits a disordered magnetic behavior such as thermal hysteresis. • The compound turned white (Eu(OH) 3 ) as soon as the DI water reached the powder. • The thermal hysteresis disappeared after the reaction with DI water and the magnetic susceptibility of the yellow oxide compound weakened

Pressure effect on magnetic and magnetotransport properties of intermetallic and colossal magnetoresistance oxide compounds

International Nuclear Information System (INIS)

Arnold, Z; Ibarra, M R; Algarabel, P A; Marquina, C; Teresa, Jose MarIa de; Morellon, L; Blasco, J; Magen, C; Prokhnenko, O; Kamarad, J; Ritter, C

2005-01-01

The joint power of neutron diffraction and pressure techniques allows us to characterize under unique conditions the nature and different role of basic interactions in solids. We have covered a broad phenomenology in archetypical compounds: intermetallics and magnetic oxides. We have selected compounds in which the effect of moderate pressure is able to modify the electronic structure and bond angles that in turn are in the bases of magnetic and structural transitions. Complex magnetic and structural phase diagrams are reported for compounds with magnetic (Tb 1-X Y X Mn 2 ) and structural (RE 5 Si 4-X Ge X ) instabilities. Pressure-induced change of the magnetic structure in (R 2 Fe 17 ) intermetallics and the effect on the colossal magnetoresistance manganites are described

Electrochemical reduction of nitroaromatic compounds by single sheet iron oxide coated electrodes

Energy Technology Data Exchange (ETDEWEB)

Huang, Li-Zhi, E-mail: lizhi@plen.ku.dk [Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK–1871 Frederiksberg C (Denmark); Hansen, Hans Christian B. [Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK–1871 Frederiksberg C (Denmark); Bjerrum, Morten Jannik [Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK–2100 København Ø (Denmark)

2016-04-05

Highlights: • Composite layers of single sheet iron oxides were coated on indium tin oxide electrodes. • Single sheet iron oxide is an electro-catalyst for reduction of nitroaromatic compounds in aqueous solution. • The reduction is well explained by a diffusion layer model. • The charge properties of the nitrophenols have an important influence on reduction. • Low-cost iron oxide based materials are promising electro-catalyst for water treatment. - Abstract: Nitroaromatic compounds are substantial hazard to the environment and to the supply of clean drinking water. We report here the successful reduction of nitroaromatic compounds by use of iron oxide coated electrodes, and demonstrate that single sheet iron oxides formed from layered iron(II)-iron(III) hydroxides have unusual electrocatalytic reactivity. Electrodes were produced by coating of single sheet iron oxides on indium tin oxide electrodes. A reduction current density of 10 to 30 μA cm{sup −2} was observed in stirred aqueous solution at pH 7 with concentrations of 25 to 400 μM of the nitroaromatic compound at a potential of −0.7 V vs. SHE. Fast mass transfer favors the initial reduction of the nitroaromatic compound which is well explained by a diffusion layer model. Reduction was found to comprise two consecutive reactions: a fast four-electron first-order reduction of the nitro-group to the hydroxylamine-intermediate (rate constant = 0.28 h{sup −1}) followed by a slower two-electron zero-order reduction resulting in the final amino product (rate constant = 6.9 μM h{sup −1}). The zero-order of the latter reduction was attributed to saturation of the electrode surface with hydroxylamine-intermediates which have a more negative half-wave potential than the parent compound. For reduction of nitroaromatic compounds, the SSI electrode is found superior to metal electrodes due to low cost and high stability, and superior to carbon-based electrodes in terms of high coulombic efficiency and

Dual passivation of intrinsic defects at the compound semiconductor/oxide interface using an oxidant and a reductant.

Science.gov (United States)

Kent, Tyler; Chagarov, Evgeniy; Edmonds, Mary; Droopad, Ravi; Kummel, Andrew C

2015-05-26

Studies have shown that metal oxide semiconductor field-effect transistors fabricated utilizing compound semiconductors as the channel are limited in their electrical performance. This is attributed to imperfections at the semiconductor/oxide interface which cause electronic trap states, resulting in inefficient modulation of the Fermi level. The physical origin of these states is still debated mainly because of the difficulty in assigning a particular electronic state to a specific physical defect. To gain insight into the exact source of the electronic trap states, density functional theory was employed to model the intrinsic physical defects on the InGaAs (2 × 4) surface and to model the effective passivation of these defects by utilizing both an oxidant and a reductant to eliminate metallic bonds and dangling-bond-induced strain at the interface. Scanning tunneling microscopy and spectroscopy were employed to experimentally determine the physical and electronic defects and to verify the effectiveness of dual passivation with an oxidant and a reductant. While subsurface chemisorption of oxidants on compound semiconductor substrates can be detrimental, it has been shown theoretically and experimentally that oxidants are critical to removing metallic defects at oxide/compound semiconductor interfaces present in nanoscale channels, oxides, and other nanostructures.

Screening and identification of phytotoxic volatile compounds in medicinal plants and characterizations of a selected compound, eucarvone.

Science.gov (United States)

Sunohara, Yukari; Baba, Yohei; Matsuyama, Shigeru; Fujimura, Kaori; Matsumoto, Hiroshi

2015-07-01

Screening and identification of phytotoxic volatile compounds were performed using 71 medicinal plant species to find new natural compounds, and the characterization of the promising compound was investigated to understand the mode of action. The volatile compounds from Asarum sieboldii Miq. showed the strongest inhibitory effect on the hypocotyl growth of lettuce seedlings (Lactuca sativa L.cv. Great Lakes 366), followed by those from Schizonepeta tenuifolia Briquet and Zanthoxylum piperitum (L.) DC.. Gas chromatography-mass spectrometry (GC/MS) identified four volatile compounds, α-pinene (2,6,6-trimethylbicyclo[3.1.1]hept-2-ene), β-pinene (6,6-dimethyl-2-methylenebicyclo[3.1.1]heptane), 3-carene (3,7,7-trimethylbicyclo[4.1.0]hept-3-ene), and eucarvone (2,6,6-trimethy-2,4-cycloheptadien-1-one), from A. sieboldii, and three volatile compounds, limonene (1-methyl-4-(1-methylethenyl)-cyclohexene), menthone (5-methyl-2-(propan-2-yl)cyclohexan-1-one), and pulegone (5-methyl-2-propan-2-ylidenecyclohexan-1-one), from S. tenuifolia. Among these volatile compounds, eucarvone, menthone, and pulegone exhibited strong inhibitory effects on both the root and shoot growth of lettuce seedlings. Eucarvone-induced growth inhibition was species-selective. Cell death, the generation of reactive oxygen species (ROS), and lipid peroxidation were induced in susceptible finger millet seedlings by eucarvone treatment, whereas this compound (≤158 μM) did not cause the increase of lipid peroxidation and ROS production in tolerant maize. The results of the present study show that eucarvone can have strong phytotoxic activity, which may be due to ROS overproduction and subsequent oxidative damage in finger millet seedlings.

Effects of Post-Pyrolysis Air Oxidation of Biomass Chars on Adsorption of Neutral and Ionizable Compounds.

Science.gov (United States)

Xiao, Feng; Pignatello, Joseph J

2016-06-21

This study was conducted to understand the effects of thermal air oxidation of biomass chars experienced during formation or production on their adsorptive properties toward various compounds, including five neutral nonpolar and polar compounds and seven weak acids and bases (pKa = 3-5.2) selected from among industrial chemicals and the triazine and phenoxyacetic acid herbicide classes. Post-pyrolysis air oxidation (PPAO) at 400 °C of anoxically prepared wood and pecan shell chars for up to 40 min enhanced the mass-normalized adsorption at pH ∼ 7.4 of all test compounds, especially the weak acids and bases, by up to 100-fold. Both general and specific effects were identified. The general effect results from "reaming" of pores by the oxidative removal of pore wall matter and/or tarry deposits generated during the pyrolysis step. Reaming creates new surface area and enlarges nanopores, which helps relieve steric hindrance to adsorption. The specific effect results from creation of new acidic functionality that provides sites for the formation of very strong, charge-assisted hydrogen bonds (CAHB) with solutes having comparable pKa. The CAHB hypothesis was supported by competition experiments and the finding that weak acid anion adsorption increased with surface carboxyl content, despite electrostatic repulsion from the growing negative charge. The results provide insight into the effects of air oxidation on pollutant retention.

Magnetic and structural properties of yellow europium oxide compound and Eu(OH){sub 3}

Energy Technology Data Exchange (ETDEWEB)

Lee, Dongwook, E-mail: dongwookleedl324@gmail.com [Cavendish Laboratory, University of Cambridge, J. J Thomson Av., Cambridge CB3 0HE (United Kingdom); Seo, Jiwon, E-mail: jiwonseo@yonsei.ac.kr [Department of Physics and IPAP, Yonsei University, Seoul 120-749 (Korea, Republic of); Valladares, Luis de los Santos [Cavendish Laboratory, University of Cambridge, J. J Thomson Av., Cambridge CB3 0HE (United Kingdom); Avalos Quispe, O. [Laboratorio de Cerámicos y Nanomateriales, Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima, Perú (Peru); Barnes, Crispin H.W. [Cavendish Laboratory, University of Cambridge, J. J Thomson Av., Cambridge CB3 0HE (United Kingdom)

2015-08-15

A new material based on a yellow europium oxide compound was prepared from europium oxide in a high vacuum environment. The structural and magnetic properties of the material were investigated. Owing to the absence of a crystal structure, the material exhibited a disordered magnetic behavior. In a reaction with deionized (DI) water without applied heat, the compound assumed a white color as soon as the DI water reached the powder, and the structure became polycrystalline Eu(OH){sub 3}. The magnetic properties, such as the thermal hysteresis, disappeared after the reaction with DI water, and the magnetic susceptibility of the yellow oxide compound weakened. The magnetic properties of Eu(OH){sub 3} were also examined. Although Eu{sup 3+} is present in Eu(OH){sub 3}, a high magnetic moment due to the crystal field effect was observed. - Graphical abstract: (top left) Optical image of the yellow europium oxide compound. (top right) Optical image of the product of DI water and yellow europium oxide. (bottom) Magnetization curves as a function of temperature measured in various magnetic field. - Highlights: • We prepared a new material based on a yellow europium oxide compound from europium oxide. • We characterized the magnetic properties of the material which exhibits a disordered magnetic behavior such as thermal hysteresis. • The compound turned white (Eu(OH){sub 3}) as soon as the DI water reached the powder. • The thermal hysteresis disappeared after the reaction with DI water and the magnetic susceptibility of the yellow oxide compound weakened.

Selectivity in the oxidative dehydrogenation of butene on zinc-iron oxide catalyst

Energy Technology Data Exchange (ETDEWEB)

Kung, H.H.; Kundalkar, B.; Kung, M.C.; Cheng, W.H.

1980-02-21

Adsorption, temperature-programed desorption, and pulse reaction studies of cis-2-butene and butadiene on spinel zinc ferrite by previously described methods provided evidence that the selectivity for oxidative dehydrogenation of butenes increases when zinc is added to the iron oxide catalyst because selective oxidation and complete oxidation proceed on separate sites, as they do on pure iron; because the density of sites for selective oxidation is higher and the density of sites for complete combustion is lower than on pure iron oxide; and because the activity of the combustion sites is lower.

Oxidation of refractory sulfur compounds over Ti-containing mesoporous molecular sieves prepared by using a fluorosilicon compound.

Science.gov (United States)

Jeong, Kwang-Eun; Cho, Chin-Soo; Chae, Ho-Jeong; Kim, Chul-Ung; Jeong, Soon-Yong

2010-05-01

Titanium containing mesoporous molecular sieve (Ti-MMS) catalysts were studied for the oxidative desulfurization of refractory sulfur compounds. Ti-MMS catalysts were synthesized from fluorosilicon compounds and Ti with the hydrolysis reaction of H2SiF6 in an ammonia-surfactant mixed solution. The solid products were characterized by XRD, XRF, nitrogen adsorption, and diffuse reflectance UV-vis spectroscopy. Effects of Ti loading and oxidant/sulfur mole ratio, and sulfur species on ODS activity were investigated.

Selective propene oxidation on mixed metal oxide catalysts

International Nuclear Information System (INIS)

James, David William

2002-01-01

Selective catalytic oxidation processes represent a large segment of the modern chemical industry and a major application of these is the selective partial oxidation of propene to produce acrolein. Mixed metal oxide catalysts are particularly effective in promoting this reaction, and the two primary candidates for the industrial process are based on iron antimonate and bismuth molybdate. Some debate exists in the literature regarding the operation of these materials and the roles of their catalytic components. In particular, iron antimonate catalysts containing excess antimony are known to be highly selective towards acrolein, and a variety of proposals for the enhanced selectivity of such materials have been given. The aim of this work was to provide a direct comparison between the behaviour of bismuth molybdate and iron antimonate catalysts, with additional emphasis being placed on the component single oxide phases of the latter. Studies were also extended to other antimonate-based catalysts, including cobalt antimonate and vanadium antimonate. Reactivity measurements were made using a continuous flow microreactor, which was used in conjunction with a variety of characterisation techniques to determine relationships between the catalytic behaviour and the properties of the materials. The ratio of Fe/Sb in the iron antimonate catalyst affects the reactivity of the system under steady state conditions, with additional iron beyond the stoichiometric value being detrimental to the acrolein selectivity, while extra antimony provides a means of enhancing the selectivity by decreasing acrolein combustion. Studies on the single antimony oxides of iron antimonate have shown a similarity between the reactivity of 'Sb 2 O 5 ' and FeSbO 4 , and a significant difference between these and the Sb 2 O 3 and Sb 2 O 4 phases, implying that the mixed oxide catalyst has a surface mainly comprised of Sb 5+ . The lack of reactivity of Sb 2 O 4 implies a similarity of the surface with

Selected heterocyclic compounds as antioxidants. Synthesis and biological evaluation.

Science.gov (United States)

Tsolaki, E; Nobelos, P; Geronikaki, A; Rekka, E A

2014-01-01

Reactive oxygen species, oxidative stress, and oxidative damage are increasingly assigned important roles as harmful factors in pathological conditions and ageing. ROS are potentially reactive molecules derived from the reduction of molecular oxygen in the course of aerobic metabolism. ROS can also be produced through a variety of enzymes. Under normal circumstances, ROS concentrations are tightly controlled by physiological antioxidants. When excessively produced, or when antioxidants are depleted, ROS can impose oxidative damage to lipids, proteins, sugars and DNA. This reduction-oxidation imbalance, called oxidative stress, can subsequently contribute to the development and progression of tissue damage and play a role in the pathology of various diseases. An antioxidant is defined as "any substance that, when present at low concentrations compared with those of a substrate, significantly delays, prevents or removes oxidative damage to this target molecule". Despite evidence that oxidative damage contributes to a wide range of clinically important conditions, few antioxidants act as effective drugs in vivo. Inter alia, the difficulty of measuring antioxidant efficacy in vivo makes the interpretation of results from clinical trials difficult. A large number of synthetic compounds have been reported to possess antioxidant activity. Several of them derive from natural antioxidants, others have various structures. In this review, some of the most often reported classes of heterocyclic antioxidant compounds, as well as methods for evaluation of their antioxidant activity are discussed.

Catalytic oxidation of chlorinated volatile organic compounds, dichloromethane and perchloroethylene. New knowledge for the industrial CVOC emission abatement

Energy Technology Data Exchange (ETDEWEB)

Pitkaeaho, S.

2013-09-01

The releases of chlorinated volatile organic compounds (CVOCs) are controlled by strict regulations setting high demands for the abatement systems. Low temperature catalytic oxidation is a viable technology to economically destroy these often refractory emissions. Catalysts applied in the oxidation of CVOCs should be highly active and selective but also maintain a high resistance towards deactivation. In this study, a total of 33 different {gamma}-Al{sub 2}O{sub 3} containing metallic monoliths were studied in dichloromethane (DCM) and 25 of them in perchloroethylene (PCE) oxidation. The active compounds used were Pt, Pd, Rh or V{sub 2}O{sub 5} alone or as mixtures. The catalysts were divided into three different testing sets: industrial, CVOC and research catalysts. ICP-OES, physisorption, chemisorption, XRD, UV-vis DRS, isotopic oxygen exchange, IC, NH{sub 3}-TPD, H{sub 2}-TPR and FESEM-EDS were used to characterise the catalysts. Screening of the industrial catalysts revealed that the addition of V{sub 2}O{sub 5} improved the performance of the catalyst. DCM abatement was easily affected by the addition of VOC or water, but the effect on the PCE oxidation was only minor. Based on these screening tests, a set of CVOC catalysts were developed and installed into an industrial incinerator. The comparison between the laboratory and industrial scale studies showed that DCM oxidation in an industrial incinerator could be predicted relatively well. Instead, PCE was always seen to be oxidised far better in an industrial unit indicating that the transient oxidation conditions are beneficial for the PCE oxidation. Before starting the experiments with research catalysts, the water feed was optimised to 1.5 wt.%. Besides enhancing the HCl yields, water improved the DCM and PCE conversions. In the absence of oxygen, i.e. during destructive adsorption, the presence of water was seen to have an even more pronounced effect on the HCl formation and on the catalysts

A New Approach to Deep Desulfurization of Light Cycle Oil over Ni2P Catalysts: Combined Selective Oxidation and Hydrotreating

Directory of Open Access Journals (Sweden)

Gwang-Nam Yun

2018-03-01

Full Text Available Amphiphilic phosphotungstic acid (A-PTA and Ni2P/SBA-15 catalysts were prepared to apply for selective oxidation of refractory sulfur compounds in light cycle oils and hydrotreating of the oxidized S compounds, respectively. Physical properties of the catalyst samples were analyzed by BET, CO uptake chemisorption, and TEM. Structural properties for the supported Ni2P catalysts were analyzed by X-ray diffraction (XRD and extended X-ray absorption fine structure (XAFS spectroscopy. The selective oxidation of S compounds in the LCO feed was conducted in a batch reactor at H2O2/S ratio of 10, atmospheric pressure and 353 K and then the products were fed to a continuous flow fixed-bed reactor for hydrotreating at 623 K, 3.0 MPa, and LHSV’s of 0.5–2.0 h−1. A-PTA catalyst showed a high oxidation conversion of 95% for a real LCO feed. The following hydrotreating led to a hydrodesulfurization (HDS conversion of 99.6% and a hydrodenitrogenation (HDN conversion of 94.7% over Ni2P/SBA-15, which were much higher than those of direct hydrotreating results which gave an HDS conversion of 63.5% and an HDN conversion of 17.5% based on the same LHSV of 2.0 h−1. It was revealed that the reduction in refractory nitrogen compounds after oxidative treatment contributed to the increase of the following HDS activity.

Mechanism of the oxidation of diphenylamine compounds

International Nuclear Information System (INIS)

Pankratov, A.N.; Shmakov, S.L.; Mushtakova, S.P.; Gribov, L.A.

1986-01-01

A spectrophotometric, radiospectroscopic, and quantum chemical study of the oxidation of compounds of the diphenylamine series in acid medium has made it possible to establish a common reaction scheme for amines with different types of substituents and to determine certain details of the reaction mechanism: the participation of protonated amine molecules in the interaction with the oxidizing agent; intermediate formation of radical cations of the type of diphenylamine and N,N'-diarylbenzidine; the concrete directions of the dimerization of radical cations of diarylamines with the participation of the para-carbon atoms of the aromatic rings

Selective adsorption of thiophenic compounds from fuel over TiO{sub 2}/SiO{sub 2} under UV-irradiation

Energy Technology Data Exchange (ETDEWEB)

Miao, Guang [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 (China); Ye, Feiyan [Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education South China University of Technology, Guangzhou 510640 (China); Wu, Luoming; Ren, Xiaoling [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 (China); Xiao, Jing, E-mail: cejingxiao@scut.edu.cn [School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 (China); Li, Zhong, E-mail: cezhli@scut.edu.cn [Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education South China University of Technology, Guangzhou 510640 (China); Wang, Haihui [Key Laboratory of Enhanced Heat Transfer and Energy Conservation of the Ministry of Education South China University of Technology, Guangzhou 510640 (China)

2015-12-30

Highlights: • TiO{sub 2}/SiO{sub 2} was developed for selective adsorption of DBTs under UV irradiation. • Remarkable adsorption uptake and selectivity were achieved for deep desulfurization. • Introduction of TiO{sub 2} into SiO{sub 2} enhanced its adsorption for DBTO{sub 2}. • Adsorption mechanism using TiO{sub 2}/SiO{sub 2} under UV irradiation was elucidated. - Abstract: This study investigates selective adsorption of thiophenic compounds from fuel over TiO{sub 2}/SiO{sub 2} under UV-irradiation. The TiO{sub 2}/SiO{sub 2} adsorbents were prepared and then characterized by N{sub 2} adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO{sub 2}/SiO{sub 2} were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO{sub 2}/0.7SiO{sub 2} adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO{sub 2} served as the photocatalytic sites for DBT oxidation, while SiO{sub 2} acted as the selective adsorption sites for the corresponding oxidized DBT using TiO{sub 2} as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO{sub 2}/SiO{sub 2}; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO{sub 2}/SiO{sub 2} was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO{sub 2}/0.7SiO{sub 2} adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions.

Selective carbon monoxide oxidation over Ag-based composite oxides

Energy Technology Data Exchange (ETDEWEB)

Guldur, C. [Gazi University, Ankara (Turkey). Chemical Engineering Department; Balikci, F. [Gazi University, Ankara (Turkey). Institute of Science and Technology, Environmental Science Department

2002-02-01

We report our results of the synthesis of 1 : 1 molar ratio of the silver cobalt and silver manganese composite oxide catalysts to remove carbon monoxide from hydrogen-rich fuels by the catalytic oxidation reaction. Catalysts were synthesized by the co-precipitation method. XRD, BET, TGA, catalytic activity and catalyst deactivation studies were used to identify active catalysts. Both CO oxidation and selective CO oxidation were carried out in a microreactor using a reaction gas mixture of 1 vol% CO in air and another gas mixture was prepared by mixing 1 vol% CO, 2 vol% O{sub 2}, 84 vol% H{sub 2}, the balance being He. 15 vol% CO{sub 2} was added to the reactant gas mixture in order to determine the effect of CO{sub 2}, reaction gases were passed through the humidifier to determine the effect of the water vapor on the oxidation reaction. It was demonstrated that metal oxide base was decomposed to the metallic phase and surface areas of the catalysts were decreased when the calcination temperature increased from 200{sup o}C to 500{sup o}C. Ag/Co composite oxide catalyst calcined at 200{sup o}C gave good activity at low temperatures and 90% of CO conversion at 180{sup o}C was obtained for the selective CO oxidation reaction. The addition of the impurities (CO{sub 2} or H{sub 2}O) decreased the activity of catalyst for selective CO oxidation in order to get highly rich hydrogen fuels. (author)

Volatile organic compounds and oxides of nitrogen. Further emission reductions

Energy Technology Data Exchange (ETDEWEB)

Froste, H [comp.

1997-12-31

This report presents the current status in relation to achievement of the Swedish Environmental target set by Parliament to reduce emission of volatile organic compounds by 50 per cent between 1988 and 2000. It also instructed the Agency to formulate proposed measures to achieve a 50 per cent reduction of emission of nitrogen oxides between 1985 and 2005. The report presents an overall account of emission trends for volatile organic compounds (from all sectors) and nitrogen oxides (from the industry sector) and steps proposed to achieve further emission reductions. 43 refs

Volatile organic compounds and oxides of nitrogen. Further emission reductions

Energy Technology Data Exchange (ETDEWEB)

Froste, H. [comp.

1996-12-31

This report presents the current status in relation to achievement of the Swedish Environmental target set by Parliament to reduce emission of volatile organic compounds by 50 per cent between 1988 and 2000. It also instructed the Agency to formulate proposed measures to achieve a 50 per cent reduction of emission of nitrogen oxides between 1985 and 2005. The report presents an overall account of emission trends for volatile organic compounds (from all sectors) and nitrogen oxides (from the industry sector) and steps proposed to achieve further emission reductions. 43 refs

Selective oxidation of alkanes and/or alkenes to valuable oxygenates

Science.gov (United States)

Lin, Manhua [Maple Glen, PA; Pillai, Krishnan S [North Brunwick, NJ

2011-02-15

A catalyst, its method of preparation and its use for producing at least one of methacrolein and methacrylic acid, for example, by subjecting isobutane or isobutylene or a mixture thereof to a vapor phase catalytic oxidation in the presence of air or oxygen. In the case where isobutane alone is subjected to a vapor phase catalytic oxidation in the presence of air or oxygen, the product is at least one of isobutylene, methacrolein and methacrylic acid. The catalyst comprises a compound having the formula A.sub.aB.sub.bX.sub.xY.sub.yZ.sub.zO.sub.o wherein A is one or more elements selected from the group of Mo, W and Zr, B is one or more elements selected from the group of Bi, Sb, Se, and Te, X is one or more elements selected from the group of Al, Bi, Ca, Ce, Co, Fe, Ga, Mg, Ni, Nb, Sn, W and Zn, Y is one or more elements selected from the group of Ag, Au, B, Cr, Cs, Cu, K, La, Li, Mg, Mn, Na, Nb, Ni, P, Pb, Rb, Re, Ru, Sn, Te, Ti, V and Zr, and Z is one or more element from the X or Y groups or from the following: As, Ba, Pd, Pt, Sr, or mixtures thereof, and wherein a=1, 0.05oxidation state of the other elements.

p-p Heterojunction of Nickel Oxide-Decorated Cobalt Oxide Nanorods for Enhanced Sensitivity and Selectivity toward Volatile Organic Compounds.

Science.gov (United States)

Suh, Jun Min; Sohn, Woonbae; Shim, Young-Seok; Choi, Jang-Sik; Song, Young Geun; Kim, Taemin L; Jeon, Jong-Myeong; Kwon, Ki Chang; Choi, Kyung Soon; Kang, Chong-Yun; Byun, Hyung-Gi; Jang, Ho Won

2018-01-10

The utilization of p-p isotype heterojunctions is an effective strategy to enhance the gas sensing properties of metal-oxide semiconductors, but most previous studies focused on p-n heterojunctions owing to their simple mechanism of formation of depletion layers. However, a proper choice of isotype semiconductors with appropriate energy bands can also contribute to the enhancement of the gas sensing performance. Herein, we report nickel oxide (NiO)-decorated cobalt oxide (Co 3 O 4 ) nanorods (NRs) fabricated using the multiple-step glancing angle deposition method. The effective decoration of NiO on the entire surface of Co 3 O 4 NRs enabled the formation of numerous p-p heterojunctions, and they exhibited a 16.78 times higher gas response to 50 ppm of C 6 H 6 at 350 °C compared to that of bare Co 3 O 4 NRs with the calculated detection limit of approximately 13.91 ppb. Apart from the p-p heterojunctions, increased active sites owing to the changes in the orientation of the exposed lattice surface and the catalytic effects of NiO also contributed to the enhanced gas sensing properties. The advantages of p-p heterojunctions for gas sensing applications demonstrated in this work will provide a new perspective of heterostructured metal-oxide nanostructures for sensitive and selective gas sensing.

Simulation of uranium and plutonium oxides compounds obtained in plasma

Science.gov (United States)

Novoselov, Ivan Yu.; Karengin, Alexander G.; Babaev, Renat G.

2018-03-01

The aim of this paper is to carry out thermodynamic simulation of mixed plutonium and uranium oxides compounds obtained after plasma treatment of plutonium and uranium nitrates and to determine optimal water-salt-organic mixture composition as well as conditions for their plasma treatment (temperature, air mass fraction). Authors conclude that it needs to complete the treatment of nitric solutions in form of water-salt-organic mixtures to guarantee energy saving obtainment of oxide compounds for mixed-oxide fuel and explain the choice of chemical composition of water-salt-organic mixture. It has been confirmed that temperature of 1200 °C is optimal to practice the process. Authors have demonstrated that condensed products after plasma treatment of water-salt-organic mixture contains targeted products (uranium and plutonium oxides) and gaseous products are environmental friendly. In conclusion basic operational modes for practicing the process are showed.

Study of compounds emitted during thermo-oxidative decomposition of polyester fabrics

Directory of Open Access Journals (Sweden)

Dzięcioł Małgorzata

2016-03-01

Full Text Available Compounds emitted during thermo-oxidative decomposition of three commercial polyester fabrics for indoor outfit and decorations (upholstery, curtains were studied. The experiments were carried out in a flow tubular furnace at 600°C in an air atmosphere. During decomposition process the complex mixtures of volatile and solid compounds were emitted. The main volatile products were carbon oxides, benzene, acetaldehyde, vinyl benzoate and acetophe-none. The emitted solid compounds consisted mainly of aromatic carboxylic acids and its derivatives, among which the greatest part took terephthalic acid, monovinyl terephthalate and benzoic acid. The small amounts of polycyclic aromatic hydrocarbons were also emitted. The emission profiles of the tested polyester fabrics were similar. The presence of toxic compounds indicates the possibility of serious hazard for people during fire.

Rapid Deposition of Oxidized Biogenic Compounds to a Temperate Forest

Science.gov (United States)

Nguyen, Tran B.; Crounse, John D.; Teng, Alex P.; St. Clair, Jason M.; Paulot, Fabien; Wolfe, Glenn M.; Wennberg, Paul O.

2015-01-01

We report fluxes and dry deposition velocities for 16 atmospheric compounds above a southeastern United States forest, including: hydrogen peroxide (H2O2), nitric acid (HNO3), hydrogen cyanide (HCN), hydroxymethyl hydroperoxide, peroxyacetic acid, organic hydroxy nitrates, and other multifunctional species derived from the oxidation of isoprene and monoterpenes. The data suggest that dry deposition is the dominant daytime sink for small, saturated oxygenates. Greater than 6 wt %C emitted as isoprene by the forest was returned by dry deposition of its oxidized products. Peroxides account for a large fraction of the oxidant flux, possibly eclipsing ozone in more pristine regions. The measured organic nitrates comprise a sizable portion (15%) of the oxidized nitrogen input into the canopy, with HNO3 making up the balance. We observe that water-soluble compounds (e.g., strong acids and hydroperoxides) deposit with low surface resistance whereas compounds with moderate solubility (e.g., organic nitrates and hydroxycarbonyls) or poor solubility (e.g., HCN) exhibited reduced uptake at the surface of plants. To first order, the relative deposition velocities of water-soluble compounds are constrained by their molecular diffusivity. From resistance modeling, we infer a substantial emission flux of formic acid at the canopy level (approx. 1 nmol m(exp.-2)·s(exp.-1)). GEOS-Chem, awidely used atmospheric chemical transport model, currently underestimates dry deposition for most molecules studied in this work. Reconciling GEOS-Chem deposition velocities with observations resulted in up to a 45% decrease in the simulated surface concentration of trace gases.

Pseudoliquid behavior of heteropoly compound catalysts. Unusual pressure dependencies of the rate and selectivity for ethanol dehydration

International Nuclear Information System (INIS)

Misono, M.; Okuhara, T.; Ichiki, T.; Arai, T.; Kanda, Y.

1987-01-01

Heteropoly compounds arenow utilized as industrial catalysts for olefin hydration and aldehyde oxidation and as interesting cluster models of mixed oxide catalysts. Certain heteropoly acids, like H 3 PW 12 O 40 and H 3 PMo 12 O 40 , easily absorb a large amount of water, alchols, and ethers in the solid state, although their surface areas are very low. This is not adsorption in micropores; rather molecules are absorbed between the lattice polyanions, sometimes expanding the lattice. The expansion can be seen visually as well as by x-ray diffraction. The authors showed that in some cases catalytic reactions take place in this novel bulk phase. Presumably due to this behavior, very high catalytic activity and unique selectivity as well as unusual reactivity order have been observed. They called this state the pseudoliquid phase. However, in only one case was the amount of absorbed reactant measured under the working conditions. They report here unusual pressure dependencies of the rate and selectivity of ethanol dehydration over heteropoly compounds. The dependency can only be explained by the formation of a pseudoliquid phase, i.e., a phase where the amount of absorbed ethanol has changed as a function of ethanol pressure

"Nanorust"-catalyzed benign oxidation of amines for selective synthesis of nitriles.

Science.gov (United States)

Jagadeesh, Rajenahally V; Junge, Henrik; Beller, Matthias

2015-01-01

Organic nitriles constitute key precursors and central intermediates in organic synthesis. In addition, nitriles represent a versatile motif found in numerous medicinally and biologically important compounds. Generally, these nitriles are synthesized by traditional cyanation procedures using toxic cyanides. Herein, we report the selective and environmentally benign oxidative conversion of primary amines for the synthesis of structurally diverse aromatic, aliphatic and heterocyclic nitriles using a reusable "nanorust" (nanoscale Fe2 O3 )-based catalysts applying molecular oxygen. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of Volatile Compounds with HS-SPME from Oxidized n-3 PUFA Rich Oils via Rancimat Tests.

Science.gov (United States)

Yang, Kai-Min; Cheng, Ming-Ching; Chen, Chih-Wei; Tseng, Chin-Yin; Lin, Li-Yun; Chiang, Po-Yuan

2017-02-01

Algae oil and fish oil are n-3 PUFA mainstream commercial products. The various sources for the stability of n-3 PUFA oxidation are influenced by the fatty acid composition, extraction and refined processing. In this study, the oil stability index (OSI) occurs within 2.3 to 7.6 hours with three different n-3 PUFA rich oil. To set the OSI in the Rancimat test as the oil stability limit and observed various degrees of oxidation (0, 25, 50, 75, 100 and 125%). The volatile oxidation compounds were analyzed via headspace-solid phase microextraction (HS-SPME) and GC/MS. We detected 51 volatile compound variations during the oxidation, which were composed of aldehydes, hydrocarbons, cyclic compounds, alcohols, benzene compounds, ketones, furans, ester and pyrrolidine. The off-flavor characteristics can be strongly influenced by the synergy effects of volatile oxidation compounds. Chemometric analysis (PCA and AHC) was applied to identify the sensitive oxidation marker compounds, which included a (E,E)-2,4-heptadienal appropriate marker, via lipid oxidation in the n-3 PUFA rich oil.

Organocatalyzed Asymmetric α-Oxidation, α-Aminoxylation and α-Amination of Carbonyl Compounds

Directory of Open Access Journals (Sweden)

Worawan Bhanthumnavin

2010-02-01

Full Text Available Organocatalytic asymmetric α-oxidation and amination reactions of carbonyl compounds are highly useful synthetic methodologies, especially in generating chiral building blocks that previously have not been easily accessible by traditional methods. The concept is relatively new and therefore the list of new catalysts, oxidizing and aminating reagents, as well as new substrates, are expanding at an amazing rate. The scope of this review includes new reactions and catalysts, mechanistic aspects and synthetic applications of α-oxidation, hydroxylation, aminoxylation, amination, hydrazination, hydroxyamination and related α-heteroatom functionalization of aldehydes, ketones and related active methylene compounds published during 2005–2009.

Electrochemical oxidation of nitrogen-heterocyclic compounds at boron-doped diamond electrode.

Science.gov (United States)

Xing, Xuan; Zhu, Xiuping; Li, Hongna; Jiang, Yi; Ni, Jinren

2012-01-01

Nitrogen-heterocyclic compounds (NHCs) are toxic and bio-refractory contaminants widely spread in environment. This study investigated electrochemical degradation of NHCs at boron-doped diamond (BDD) anode with particular attention to the effect of different number and position of nitrogen atoms in molecular structure. Five classical NHCs with similar structures including indole (ID), quinoline (QL), isoquinoline (IQL), benzotriazole (BT) and benzimidazole (BM) were selected as the target compounds. Results of bulk electrolysis showed that degradation of all NHCs was fit to a pseudo first-order equation. The five compounds were degraded with the following sequence: ID>QL>IQL>BT>BM in terms of their rates of oxidation. Quantum chemical calculation was combined with experimental results to describe the degradation character of NHCs at BDD anode. A linear relationship between degradation rate and delocalization energy was observed, which demonstrated that electronic charge was redistributed through the conjugation system and accumulated at the active sites under the attack of hydroxyl radicals produced at BDD anode. Moreover, atom charge was calculated by semi empirical PM3 method and active sites of NHCs were identified respectively. Analysis of intermediates by GC-MS showed agreement with calculation results. Copyright © 2011 Elsevier Ltd. All rights reserved.

Kinetic studies of electrochemical generation of Ag(II) ion and catalytic oxidation of selected organics

International Nuclear Information System (INIS)

Zawodzinski, C.; Smith, W.H.; Martinez, K.R.

1993-01-01

The goal of this research is to develop a method to treat mixed hazardous wastes containing selected organic compounds and heavy metals, including actinide elements. One approach is to destroy the organic via electrochemical oxidation to carbon dioxide, then recover the metal contaminants through normally accepted procedures such as ion exchange, precipitation, etc. The authors have chosen to study the electrochemical oxidation of a simple alcohol, iso-propanol. Much of the recent work reported involved the use of an electron transfer mediator, usually the silver(I)/(II) redox couple. This involved direct electrochemical generation of the mediator at the anode of a divided cell followed by homogeneous reaction of the mediator with the organic compound. In this study the authors have sought to compare the mediated reaction with direct electrochemical oxidation of the organic. In addition to silver(I)/(II) they also looked at the cobalt(II)/(III) redox coupled. In the higher oxidation state both of these metal ions readily hydrolyze in aqueous solution to ultimately form insoluble oxide. The study concluded that in a 6M nitric acid solution at room temperature iso-propanol can be oxidized to carbon dioxide and acetic acid. Acetic acid is a stable intermediate and resists further oxidation. The presence of Co(III) enhances the rate or efficiency of the reaction

Catalytic properties of niobium compounds

International Nuclear Information System (INIS)

Tanabe, K.; Iizuka, T.

1983-04-01

The catalytic activity and selectivity of niobium compounds including oxides, salts, organometallic compounds and others are outlined. The application of these compounds as catalysts to diversified reactions is reported. The nature and action of niobium catalysts are characteristic and sometimes anomalous, suggesting the necessity of basic research and the potential use as catalysts for important processes in the chemical industry. (Author) [pt

Aerobic Oxidation of Alcohols to Carbonyl Compounds Catalyzed by ...

Indian Academy of Sciences (India)

Hydrotalcite-like compounds; cobalt porphyrin; alcohol oxidation; ... cient catalytic method for the low temperature oxy- ... nitrate,8 acetaldehyde,9 ammonium salts10 and NO2,11 ..... N, Sakurai H and Tsukuda T 2009 Effect of electronic.

Internal Displacement Reactions in Multicomponent Oxides: Part I. Line Compounds with Narrow Homogeneity Range

OpenAIRE

Reddy, SNS; Leonard, DN; Wiggins, LB; Jacob, KT

2005-01-01

As a model of an internal displacement reaction involving a ternary oxide line compound, the following reaction was studied at 1273 K as a function of time, t: $Fe+NiTiO_3 = Ni + FeTiO_3$ Both polycrystalline and single-crystal materials were used as the starting $NiTiO_3$ oxide. During the reaction, the Ni in the oxide compound is displaced by Fe and it precipitates as a \\gamma -(Ni-Fe) alloy. The reaction preserves the starting ilmenite structure. The product oxide has a consta...

Copper-catalyzed oxidative desulfurization-oxygenation of thiocarbonyl compounds using molecular oxygen: an efficient method for the preparation of oxygen isotopically labeled carbonyl compounds.

Science.gov (United States)

Shibahara, Fumitoshi; Suenami, Aiko; Yoshida, Atsunori; Murai, Toshiaki

2007-06-21

A novel copper-catalyzed oxidative desulfurization reaction of thiocarbonyl compounds, using molecular oxygen as an oxidant and leading to formation of carbonyl compounds, has been developed, and the utility of the process is demonstrated by its application to the preparation of a carbonyl-18O labeled sialic acid derivative.

Heterogeneous inhibition of the liquid phase oxidation of hydrocarbons by molybdenum compounds

Energy Technology Data Exchange (ETDEWEB)

Tavadyan, L.A.; Karapetyan, A.P.; Madatovyan, V.M.

1988-05-01

The heterogeneous action of molybdenum compounds: MoB, MoSe/sub 2/, MoSi/sub 2/, Mo/sub 2/C, MoO/sub 3/, Mo on the oxidation of n-decane, ethylbenzene, and nonene-1 has been investigated. A parameter representing the inhibiting effect of the heterogeneous catalyst was calculated theoretically. It was found that NoB, MoSe/sub 2/, and MoSi/sub 2/ inhibited the oxidation of n-decane at 408 K while the remaining heterogeneous contacts catalyzed it. A critical phenomenon was detected in the inhibition by MoSi/sub 2/. All the molybdenum compounds investigated inhibited the oxidation of ethylbenzene at 393 K owing to the formation of phenol by catalytic decomposition of the hydroperoxide. The liquid phase oxidation autoinhibited by phenol is described theoretically.

Theoretical study of ionization and one-electron oxidation potentials of N-heterocyclic compounds.

Science.gov (United States)

Sviatenko, Liudmyla K; Gorb, Leonid; Hill, Frances C; Leszczynski, Jerzy

2013-05-15

A number of density functionals was utilized to predict gas-phase adiabatic ionization potentials (IPs) for nitrogen-rich heterocyclic compounds. Various solvation models were applied to the calculation of difference in free energies of solvation of oxidized and reduced forms of heterocyclic compounds in acetonitrile (AN) for correct reproduction of their standard oxidation potentials. We developed generally applicable protocols that could successfully predict the gas-phase adiabatic ionization potentials of nitrogen-rich heterocyclic compounds and their standard oxidation potentials in AN. This approach is supported by a MPW1K/6-31+G(d) level of theory which uses SMD(UA0) approximation for estimation of solvation energy of neutral molecules and PCM(UA0) model for ionized ones. The mean absolute derivation (MAD) and root mean square error (RMSE) of the current theoretical models for IP are equal to 0.22 V and 0.26, respectively, and for oxidation potentials MAD = 0.13 V and RMSE = 0.17. Copyright © 2013 Wiley Periodicals, Inc.

Characterization of selected volatile organic compounds, polycyclic aromatic hydrocarbons and carbonyl compounds at a roadside monitoring station

Science.gov (United States)

Ho, K. F.; Lee, S. C.; Chiu, Gloria M. Y.

Volatile organic compounds (VOCs), PAHs and carbonyl compounds are the major toxic components in Hong Kong. Emissions from motor vehicles have been one of the primary pollution sources in the metropolitan areas throughout Hong Kong for a long time. A 1-yr monitoring program for VOCs, PAHs and carbonyl compounds had been performed at a roadside urban station at Hong Kong Polytechnic University in order to determine the variations and correlations of each selected species (VOCs, PAHs and carbonyl compounds). This study is aimed to analyze toxic volatile organic compounds (benzene, toluene, ethylbenzene and xylene), two carbonyl compounds (formaldehyde, acetaldehyde), and selective polycyclic aromatic hydrocarbons. The monitoring program started from 16 April 1999 to 30 March 2000. Ambient VOC concentrations, many of which originate from the same sources as particulate PAHs and carbonyls compounds, show significant quantities of benzene, toluene and xylenes. Correlations and multivariate analysis of selected gaseous and particulate phase organic pollutants were performed. Source identification by principle component analysis and hierarchical cluster analysis allowed the identification of four sources (factors) for the roadside monitoring station. Factor 1 represents the effect of diesel vehicle exhaust. Factor 2 shows the contribution of aromatic compounds. Factor 3 explains photochemical products—formaldehyde and acetaldehyde. Factor 4 explains the effect of gasoline vehicle exhaust.

Antioxidant and Antiradical Properties of Selected Flavonoids and Phenolic Compounds

Directory of Open Access Journals (Sweden)

Zübeyir Huyut

2017-01-01

Full Text Available Phenolic compounds and flavonoids are known by their antioxidant properties and one of the most important sources for humans is the diet. Due to the harmful effects of synthetic antioxidants such as BHA and BHT, natural novel antioxidants have become the focus of attention for protecting foods and beverages and reducing oxidative stress in vivo. In the current study, we investigated the total antioxidant, metal chelating, Fe3+ and Cu2+ reduction, and free radical scavenging activities of some phenolic and flavonoid compounds including malvin, oenin, ID-8, silychristin, callistephin, pelargonin, 3,4-dihydroxy-5-methoxybenzoic acid, 2,4,6-trihydroxybenzaldehyde, and arachidonoyl dopamine. The antioxidant properties of these compounds at different concentrations (10–30 μg/mL were compared with those of reference antioxidants such as BHA, BHT, α-tocopherol, and trolox. Each substance showed dose-dependent antioxidant activity. Furthermore, oenin, malvin, arachidonoyl dopamine, callistephin, silychristin, and 3,4-dihydroxy-5-methoxybenzoic acid exhibited more effective antioxidant activity than that observed for the reference antioxidants. These results suggest that these novel compounds may function to protect foods and medicines and to reduce oxidative stress in vivo.

Selective Oxidation of Biomass-Derived Chemicals

DEFF Research Database (Denmark)

Modvig, Amalie Elise

. These processes should be able to compete with the established processes based on fossil resources. Glycolaldehyde is an often-observed by-product formed from degradation of larger sugars. Due to competing ecological and economical aspects of the well-established processes for extraction and conversion....... The objective of this dissertation was to develop new, alternative and sustainable methods for oxidative catalytic upgrading of biomass-derived compounds, with focus on oxidation of glycolaldehyde and simple alcohols as model substrates for larger sugars. Supported gold nanoparticle were studied...

Selective chloroform sensor using thiol functionalized reduced graphene oxide at room temperature

Science.gov (United States)

Midya, Anupam; Mukherjee, Subhrajit; Roy, Shreyasee; Santra, Sumita; Manna, Nilotpal; Ray, Samit K.

2018-02-01

This paper presents a highly selective chloroform sensor using functionalised reduced graphene oxide (RGO) as a sensing layer. Thiol group is covalently attached on the basal plan of RGO film by a simple one-step aryl diazonium chemistry to improve its selectivity. Several spectroscopic techniques like X-ray photoelectron, Raman and Fourier transform infrared spectroscopy confirm successful thiol functionalization of RGO. Finally, the fabricated chemiresistor type sensor is exposed to chloroform in the concentration range 200-800 ppm (parts per million). The sensor shows a 4.3% of response towards 800 ppm chloroform. The selectivity of the sensor is analyzed using various volatile organic compounds as well. The devices show enhanced response and faster recovery attributed to the physiosorption of chloroform onto thiol functionalized graphene making them attractive for 2D materials based sensing applications.

Effects of trace volatile organic compounds on methane oxidation

Directory of Open Access Journals (Sweden)

Chiemchaisri Wilai

2001-01-01

Full Text Available The effects of volatile organic compounds (VOCs on methane oxidation in landfill cover soils were examined. The batch experiments were conducted using single and mixed VOCs, such as, dichloromethane (DCM, trichloroethylene (TCE, tetrachloroethylene (PCE, and benzene. The results from all combinations showed a decrease in methane oxidation rate with increase in VOC concentrations. Moreover, inhibition effects of TCE and DCM were found higher than benzene and PCE. The reduction of methane oxidation by benzene and PCE could be attributed to the toxicity effect, whereas TCE and DCM were found to exhibit the competitive-inhibition effect. When the soil was mixed with DCM, no methane oxidation was found. Damage to the cell's internal membrane was found in a methanotrophic culture exposed to VOC gases which is the attachment site of a key enzyme needed for methane oxidation

Developments in Synthetic Application of Selenium(IV Oxide and Organoselenium Compounds as Oxygen Donors and Oxygen-Transfer Agents

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Jacek Młochowski

2015-06-01

Full Text Available A variety of selenium compounds were proven to be useful reagents and catalysts for organic synthesis over the past several decades. The most interesting aspect, which emerged in recent years, concerns application of hydroperoxide/selenium(IV oxide and hydroperoxide/organoselenium catalyst systems, as “green reagents” for the oxidation of different organic functional groups. The topic of oxidations catalyzed by organoselenium derivatives has rapidly expanded in the last fifteen years This paper is devoted to the synthetic applications of the oxidation reactions mediated by selenium compounds such as selenium(IV oxide, areneseleninic acids, their anhydrides, selenides, diselenides, benzisoselenazol-3(2H-ones and other less often used other organoselenium compounds. All these compounds have been successfully applied for various oxidations useful in practical organic syntheses such as epoxidation, 1,2-dihydroxylation, and α-oxyfunctionalization of alkenes, as well as for ring contraction of cycloalkanones, conversion of halomethyl, hydroxymethyl or active methylene groups into formyl groups, oxidation of carbonyl compounds into carboxylic acids and/or lactones, sulfides into sulfoxides, and secondary amines into nitrones and regeneration of parent carbonyl compounds from their azomethine derivatives. Other reactions such as dehydrogenation and aromatization, active carbon-carbon bond cleavage, oxidative amidation, bromolactonization and oxidation of bromide for subsequent reactions with alkenes are also successfully mediated by selenium (IV oxide or organoselenium compounds. The oxidation mechanisms of ionic or free radical character depending on the substrate and oxidant are discussed. Coverage of the literature up to early 2015 is provided. Links have been made to reviews that summarize earlier literature and to the methods of preparation of organoselenium reagents and catalysts.

Two Catalysts for Selective Oxidation of Contaminant Gases

Science.gov (United States)

Wright, John D.

2011-01-01

Two catalysts for the selective oxidation of trace amounts of contaminant gases in air have been developed for use aboard the International Space Station. These catalysts might also be useful for reducing concentrations of fumes in terrestrial industrial facilities especially facilities that use halocarbons as solvents, refrigerant liquids, and foaming agents, as well as facilities that generate or utilize ammonia. The first catalyst is of the supported-precious-metal type. This catalyst is highly active for the oxidation of halocarbons, hydrocarbons, and oxygenates at low concentrations in air. This catalyst is more active for the oxidation of hydrocarbons and halocarbons than are competing catalysts developed in recent years. This catalyst completely converts these airborne contaminant gases to carbon dioxide, water, and mineral acids that can be easily removed from the air, and does not make any chlorine gas in the process. The catalyst is thermally stable and is not poisoned by chlorine or fluorine atoms produced on its surface during the destruction of a halocarbon. In addition, the catalyst can selectively oxidize ammonia to nitrogen at a temperature between 200 and 260 C, without making nitrogen oxides, which are toxic. The temperature of 260 C is higher than the operational temperature of any other precious-metal catalyst that can selectively oxidize ammonia. The purpose of the platinum in this catalyst is to oxidize hydrocarbons and to ensure that the oxidation of halocarbons goes to completion. However, the platinum exhibits little or no activity for initiating the destruction of halocarbons. Instead, the attack on the halocarbons is initiated by the support. The support also provides a high surface area for exposure of the platinum. Moreover, the support resists deactivation or destruction by halogens released during the destruction of halocarbons. The second catalyst is of the supported- metal-oxide type. This catalyst can selectively oxidize ammonia to

Determination of an Effective Perfluorinated Compounds (PFCs) Oxidation Method

Science.gov (United States)

Siriwardena, D. P.; Crimi, M.; Holsen, T.; Bellona, C.

2014-12-01

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a stable synthetic class of chemicals ubiquitously spread in environmental media (i.e. air, soil, biota, surface water and groundwater). The substances' strong polar carbon-fluorine bonds and their high thermal and chemical stability make them resistant to biological, chemical, and physical degradation. The purpose of this research is to identify the most effective oxidation method to treat perfluorinated compounds (PFCs) and their by-products that is suitable for in situ application. The laboratory oxidation study focuses on the more commonly detected and studied long-chain (C-8) PFAS; perfluorooctanoic acids (PFOA) and perfluorooctane sulfonic acid (PFOS). Existing research evaluating oxidizing treatment effectiveness on perfluoroalkyl sulfoinoic acids (PFSAs) is limited. A review of the literature and results from preliminary studies indicate that activated persulfate and catalyzed hydrogen peroxide propagation (CHP) reactions appear to be promising oxidants for PFOA. It has been demonstrated that the reactivity of superoxide in water increases in the presence of hydrogen peroxide (H2O2) and solids. Superoxide generated in CHP reactions degrades PFOA seemingly similar to superoxide-mediated destruction of the perhalogenated compounds.The goal of this study is to look at conditions that promote generation of superoxide and look at PFASs treatment effectiveness and byproduct generation. CHP reactions are conducted with varying amount of H2O2 and Fe(III) to determine the optimum conditions for PFC degradation. Results will be compared to those of another experiment using manganese dioxide as a CHP catalyst with varied H2O2 concentration to generate superoxide to degrade PFASs. Activated persulfate conditions to be compared include alkaline pH activation, heat activation, and dual oxidation (combined H2O2 and persulfate ). This presentation will focus on a comparison of oxidation effectiveness under the

Various ways to reduce zinc oxide levels in S-SBR rubber compounds

NARCIS (Netherlands)

Heideman, G.; Noordermeer, Jacobus W.M.; Datta, Rabin; van Baarle, Ben

2007-01-01

Because of environmental concerns, the zinc content in rubber compounds has come under scrutiny. The research described in this article encompasses zinc-oxide, various zinc-complexes and alternative metal oxides as activators for sulphur vulcanisation. Regarding zinc complexes, it can be concluded

Chemical Reductive Transformations of Synthetic Organic Compounds. Probe Compound Studies and Mechanistic Modeling

National Research Council Canada - National Science Library

Peyton, Gary

2001-01-01

Advanced Oxidation Processes (AOPs) can be used to selectively remove DNT (2,4-dinitrotoluene) from a complex waste stream by adding a precursor compound such as ethanol, which forms a reducing radical upon reaction with hydroxyl radical...

A chromatographic method to analyze products from photo-oxidation of anthropogenic and biogenic mixtures of volatile organic compounds in smog chambers.

Science.gov (United States)

Pindado Jiménez, Oscar; Pérez Pastor, Rosa M; Vivanco, Marta G; Santiago Aladro, Manuel

2013-03-15

A method for quantifying secondary organic aerosol compounds (SOA) and water soluble secondary organic aerosol compounds (WSOA) produced from photo-oxidation of complex mixtures of volatile organic compounds (VOCs) in smog chambers by gas chromatography/mass spectrometry (GC/MS) has been developed. This method employs a double extraction with water and methanol jointly to a double derivatization with N,O-bis (trimethylsilil) trifluoroacetamide (BSTFA) and O-(2,3,4,5,6)-pentafluorobenzyl-hydroxylamine hydrochloride (PFBHA) followed by an analysis performed by GC/MS. The analytical procedure complements other methodologies because it can analyze SOA and WSOA compounds simultaneously at trace levels. As application, the methodology was employed to quantify the organic composition of aerosols formed in a smog chamber as a result of photo-oxidation of two different mixtures of volatile organic compounds: an anthropogenic mixture and a biogenic mixture. The analytical method allowed us to quantify up to 17 SOA compounds at levels higher than 20 ng m(-3) with reasonable recovery and a precision below 11%. Values found for applicability, selectivity, linearity, precision, recovery, detection limit, quantification limit and sensitivity demonstrated that the methodology can be satisfactorily applied to quantify SOA and WSOA. Copyright © 2012 Elsevier B.V. All rights reserved.

Oxidative stress protection by newly synthesized nitrogen compounds with pharmacological potential.

Science.gov (United States)

Silva, João P; Areias, Filipe M; Proença, Fernanda M; Coutinho, Olga P

2006-02-09

In this study we used new nitrogen compounds obtained by organic synthesis whose structure predicted an antioxidant potential and then an eventual development as molecules of pharmacological interest in diseases involving oxidative stress. The compounds, identified as FMA4, FMA5, FMA7 and FMA8 differ in the presence of hydroxyl groups located in the C-3 and/or C-4 position of a phenolic unit, which is possibly responsible for their free radicals' buffering capacity. Data from the DPPH discoloration method confirm the high antiradical efficiency of the compounds. The results obtained with cellular models (L929 and PC12) show that they are not toxic and really protect from membrane lipid peroxidation induced by the ascorbate-iron oxidant pair. The level of protection correlates with the drug's lipophilic profile and is sometimes superior to trolox and equivalent to that observed for alpha-tocopherol. The compounds FMA4 and FMA7 present also a high protection from cell death evaluated in the presence of a staurosporine apoptotic stimulus. That protection results in a significant reduction of caspase-3 activity induced by staurosporine which by its turn seems to result from a protection observed in the membrane receptor pathway (caspase-8) together with a protection observed in the mitochondrial pathway (caspase-9). Taken together the results obtained with the new compounds, with linear chains, open up perspectives for their use as therapeutical agents, namely as antioxidants and protectors of apoptotic pathways. On the other hand the slight pro-oxidant profile obtained with the cyclic structures suggests a different therapeutic potential that is under current investigation.

Electrolytic photodissociation of chemical compounds by iron oxide electrodes

Science.gov (United States)

Somorjai, Gabor A.; Leygraf, Christofer H.

1984-01-01

Chemical compounds can be dissociated by contacting the same with a p/n type semi-conductor diode having visible light as its sole source of energy. The diode consists of low cost, readily available materials, specifically polycrystalline iron oxide doped with silicon in the case of the n-type semi-conductor electrode, and polycrystalline iron oxide doped with magnesium in the case of the p-type electrode. So long as the light source has an energy greater than 2.2 electron volts, no added energy source is needed to achieve dissociation.

Phenolic compounds of Triplaris gardneriana can protect cells against oxidative stress and restore oxidative balance.

Science.gov (United States)

de Almeida, Thiago Silva; Neto, José Joaquim Lopes; de Sousa, Nathanna Mateus; Pessoa, Igor Parra; Vieira, Leonardo Rogério; de Medeiros, Jackeline Lima; Boligon, Aline Augusti; Hamers, Astrid R M; Farias, Davi Felipe; Peijnenburg, Ad; Carvalho, Ana Fontenele Urano

2017-09-01

This work aimed to add value to an underexploited plant species from Brazil, Triplaris gardneriana. To that, the phenolic compounds profile of its seed ethanolic extract and fractions was examined by HPLC and the antioxidant capacity assessed using chemical assays as well as in vitro cell imaging. Twelve compounds were quantified and classified as either phenolic acids or flavonoids. The fractionation process did not generate fractions with different compositions except for chloroformic fraction, which showed only 6 out of 12 standard compounds used. DPPH assay revealed samples with a concentration-dependent radical scavenging activity, being methanolic fraction the one with the largest activity (SC 50 11.45±0.02μg/mL). Lipid peroxidation assessment, in the presence and absence of stress inducer, showed that particularly the ethanol extract (IC 50 26.75±0.08μg/mL) and the ethyl acetate fraction (IC 50 6.14±0.03μg/mL) could inhibit lipid peroxidation. The ethyl acetate fraction performed best in chelating iron (48% complexation at 1000μg/mL). Cell imaging experiments showed that the ethanolic extract could protect cells against oxidative stress as well as restore the oxidative balance upon stress induction. In conclusion, T. gardneriana seeds showed a promising phenolic compounds profile and antioxidant activity that may be further exploited. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Role of Oxidative Stress in Male Reproductive Dysfunctions with Reference to Phthalate Compounds.

Science.gov (United States)

Sedha, Sapna; Kumar, Sunil; Shukla, Shruti

2015-11-14

A wide variety of environmental chemicals/xenobiotics including phthalates have been shown to cause oxidative stress targeting the endocrine system and cause reproductive anomalies. The present review describes various issues by oxidative stress causing male reproductive dysfunctions. Here in this review, the importance and role of phthalate compounds in male reproductive dysfunction has been well documented. One class of environmental endocrine disruptors is phthalates. Phthalate compounds are mostly used as plasticizers, which increase the flexibility, durability, longevity, and etc. of the plastics. Large-scale use of plastic products in our daily life as well as thousands of workers engaged in the manufacture of plastic and plastic products and recycling plastic industry are potentially exposed to these chemicals. Further, general population as well as vulnerable groups i.e. children and pregnant women are also exposed to these chemicals. Phthalates are among wide variety of environmental toxicants capable of compromising male fertility by inducing a state of oxidative stress in the testes. They may also generate reactive oxygen species (ROS) that may affect various physiological and reproductive functions. The available data points out that phthalate compounds may also induce oxidative stress in the male reproductive organs mainly testis and epididymis. They impair spermatogenic process by inducing oxidative stress and apoptosis in germ cells or target sertoli cells and thereby hamper spermatogenesis. They also impair the Leydig cell function by inducing ROS, thereby decreasing the levels of steroidogenic enzymes. Thus in utero and postnatal exposure to phthalate compounds might lead to decreased sperm count and various other reproductive anomalies in the young male.

Palladium-catalysed anti-Markovnikov selective oxidative amination

Science.gov (United States)

Kohler, Daniel G.; Gockel, Samuel N.; Kennemur, Jennifer L.; Waller, Peter J.; Hull, Kami L.

2018-03-01

In recent years, the synthesis of amines and other nitrogen-containing motifs has been a major area of research in organic chemistry because they are widely represented in biologically active molecules. Current strategies rely on a multistep approach and require one reactant to be activated prior to the carbon-nitrogen bond formation. This leads to a reaction inefficiency and functional group intolerance. As such, a general approach to the synthesis of nitrogen-containing compounds from readily available and benign starting materials is highly desirable. Here we present a palladium-catalysed oxidative amination reaction in which the addition of the nitrogen occurs at the less-substituted carbon of a double bond, in what is known as anti-Markovnikov selectivity. Alkenes are shown to react with imides in the presence of a palladate catalyst to generate the terminal imide through trans-aminopalladation. Subsequently, olefin isomerization occurs to afford the thermodynamically favoured products. Both the scope of the transformation and mechanistic investigations are reported.

Catalytic oxidative desulfurization of liquid hydrocarbon fuels using air

Science.gov (United States)

Sundararaman, Ramanathan

Conventional approaches to oxidative desulfurization of liquid hydrocarbons involve use of high-purity, expensive water soluble peroxide for oxidation of sulfur compounds followed by post-treatment for removal of oxidized sulfones by extraction. Both are associated with higher cost due to handling, storage of oxidants and yield loss with extraction and water separation, making the whole process more expensive. This thesis explores an oxidative desulfurization process using air as an oxidant followed by catalytic decomposition of sulfones thereby eliminating the aforementioned issues. Oxidation of sulfur compounds was realized by a two step process in which peroxides were first generated in-situ by catalytic air oxidation, followed by catalytic oxidation of S compounds using the peroxides generated in-situ completing the two step approach. By this technique it was feasible to oxidize over 90% of sulfur compounds present in real jet (520 ppmw S) and diesel (41 ppmw S) fuels. Screening of bulk and supported CuO based catalysts for peroxide generation using model aromatic compound representing diesel fuel showed that bulk CuO catalyst was more effective in producing peroxides with high yield and selectivity. Testing of three real diesel fuels obtained from different sources for air oxidation over bulk CuO catalyst showed different level of effectiveness for generating peroxides in-situ which was consistent with air oxidation of representative model aromatic compounds. Peroxides generated in-situ was then used as an oxidant to oxidize sulfur compounds present in the fuel over MoO3/SiO2 catalyst. 81% selectivity of peroxides for oxidation of sulfur compounds was observed on MoO3/SiO2 catalyst at 40 °C and under similar conditions MoO3/Al2O3 gave only 41% selectivity. This difference in selectivity might be related to the difference in the nature of active sites of MoO3 on SiO2 and Al2O 3 supports as suggested by H2-TPR and XRD analyses. Testing of supported and bulk Mg

Synthesis of thermally stable metal substituted hydroxy apatites for the selective oxidation of light paraffins

Directory of Open Access Journals (Sweden)

S. Singh

2013-04-01

Full Text Available Hydroxyapatite and a series of hydroxyapatite-type compounds containing Co, Fe or Sr were synthesized by co-precipitation and characterized by ICP-OES, BET, IR, Raman spectroscopy, powder and in-situ XRD, SEM, TEM, TPR, TPD and TGA. In-situ XRD and TGA studies indicate that the materials are able to maintain their structure at temperatures reaching 900 °C. The TPD data indicated that acidic sites of varying strengths were present in all the three hydroxyapatites. From SEM, the surface of the materials consisted of an agglomeration of irregular plate-like particles. The catalytic activity of the compounds was investigated in the oxidation of n-pentane and n-hexane. The conversion of the feed and composition of the products were largely influenced by changes in the temperature and flow rates. For n-pentane, the products consisted of lower hydrocarbons and oxygenated compounds, carbon oxides and very small amounts 1,3-pentadiene, furan and furfural. Low conversions of n-hexane were obtained for all the tested catalysts and selective products were the hexene isomers and some aromatics.DOI: http://dx.doi.org/10.4314/bcse.v27i1.6

Selective Oxidation of Soft Grade Carbon

Directory of Open Access Journals (Sweden)

Zecevic, N.

2007-12-01

Full Text Available Oil-furnace carbon black is produced by pyrolysis of gaseous or liquid hydrocarbons or their mixtures. The oil feedstock for the production of oil-furnace carbon black is mainly composed of high-boiling aromatic hydrocarbons, which are residues of petroleum cracking, while the gaseous raw material is commonly natural gas. Most of the oil-furnace carbon black production (> 99 % is used as a reinforcing agent in rubber compounds. Occasionally, oil-furnace carbon blacks are used in contact with other rubber compounds and fillers that have different pigments, particularly with the color white. It has been observed that frequently a migrating rubber soluble colorant would enter the white or light colored rubber composition from the adjacent carbon black filled rubber, resulting in a highly undesirable staining effect. Methods for determining non-oxidized residue on the surface of the oil-furnace carbon black include extraction of carbon black with the appropriate organic solvent, and measuring the color of the organic solvent by means of a colorimeter on 425 nm (ASTM D 1618-99. Transmittance values of 85 % or more are indicative of a practically non-staining carbon black, while transmittance values below 50 % generally lead to a carbon black with pronounced staining characteristics. Many oil-furnace carbon blacks, particularly those with a larger particle size (dp > 50 nm which are produced by pyrolysis, have strongly adsorbed non-reacted oil on their surfaces. Upon incorporation in a rubber compound, the colored materials are gradually dissolved by the rubber matrix and migrate freely into adjacent light colored rubber compounds, causing a highly objectionable staining effect. Adjusting furnace parameters in the industrial process of producing specific soft grades of carbon black cannot obtain minimal values of toluene discoloration. The minimal value of toluene discoloration is very important in special applications. Therefore, after-treatment of

Influence of iron solubility and charged surface-active compounds on lipid oxidation in fatty acid ethyl esters containing association colloids.

Science.gov (United States)

Homma, Rika; Johnson, David R; McClements, D Julian; Decker, Eric A

2016-05-15

The impact of iron compounds with different solubilities on lipid oxidation was studied in the presence and absence of association colloids. Iron (III) sulfate only accelerated lipid oxidation in the presence of association colloids while iron (III) oleate accelerated oxidation in the presence and absence of association colloids. Further, iron (III) oxide retarded lipid oxidation both with and without association colloids. The impact of charged association colloids on lipid oxidation in ethyl oleate was also investigated. Association colloids consisting of the anionic surface-active compound dodecyl sulphosuccinate sodium salt (AOT), cationic surface-active compound hexadecyltrimethylammonium bromide (CTAB), and nonionic surface-active compound 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton X-100) retarded, promoted, and had no effect on lipid oxidation rates, respectively. These results indicate that the polarity of metal compounds and the charge of association colloids play a big role in lipid oxidation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Selective oxidation of propane over cation exchanged zeolites

NARCIS (Netherlands)

Xu, J.

2005-01-01

This thesis focuses on investigation of the fundamental knowledge on a new method for selective oxidation of propane with O2 at low temperature (< 100°C). The relation between propane catalytic selective oxidation and physicochemical properties of cation exchanged Y zeolite has been studied. An

The catalytic activity of several tungsten oxides for the oxidation of propene

International Nuclear Information System (INIS)

De Rossi, S.; Schiavello, M.; Rome Univ.; Iguchi, E.; Tilley, R.J.D.

1976-01-01

A study has been made of the catalytic oxidation of propene over the oxides WO 3 , WOsub(2,95), WOsub(2,90), WOsub(2,72) and Wo 2 , which were selected because they possess specific features of chemical and structural interest rather than for their catalytic ability. It was found that the oxides WOsub(2,95), WOsub(2,90) and WOsub(2,72) all selectively produce acrolein in small amounts. The oxides WO 3 and WO 2 were non-selective and rather inactive. The results are discussed in terms of a mechanism involving both variable valence in the crystal and the specific structural geometry of these compounds. (orig.) [de

Protective Effects of Alkaloid Compounds from Nelumbinis Plumula on tert-Butyl Hydroperoxide-Induced Oxidative Stress

Directory of Open Access Journals (Sweden)

Ze-Bin Guo

2013-08-01

Full Text Available This study was conducted to investigate the effect of Nelumbinis Plumula total alkaloid (NPA and its main alkaloid components on oxidative stress induced by tert-butyl hydroperoxide (t-BHP in the human hepatocellular HepG2 cell line. According to HPLC analysis, several major alkaloid compounds such as liensinine, isoliensinine and neferine were present in NPA. The cytotoxic effects in 0.55 mM t-BHP-induced HepG2 cells were significantly inhibited by NPA and the major compound in NPA, neferine, showed the strongest activities. The protective effect of neferine against oxidative stress induced by t-BHP may be associated with decreased ROS formation, TBARS generation, LDH release and increased GSH levels, suggesting their involvement of the cytoprotective on oxidative stress. The effects were comparable with quercetin, which was used as positive control. Overall, total alkaloid and alkaloid compounds from Nelumbinis Plumula displayed a significant cytoprotective effect against oxidative stress. Further study is needed to elucidate the relationship between the chemical structures of the components in NPA and their protective effect on oxidative stress.

Copper oxide as efficient catalyst for oxidative dehydrogenation of alcohols with air

DEFF Research Database (Denmark)

Poreddy, Raju; Engelbrekt, Christian; Riisager, Anders

2015-01-01

The oxidative dehydrogenation of alcohols to carbonyl compounds was studied using CuO nanoparticle catalysts prepared by solution synthesis in buffered media. CuO nanoparticles synthesized in N-cyclohexyl- 3-aminopropanesulfonic acid buffer showed high catalytic activity for the oxidation...... of benzylic, alicyclic and unsaturated alcohols to their corresponding carbonyl compounds with excellent selectivities. The observed trend in activity for conversion of substituted alcohols suggested a β-H elimination step to be involved, thus enabling a possible reaction mechanism for oxidative...... dehydrogenation of benzyl alcohols to be proposed. The use of CuO as an inexpensive and efficient heterogeneous catalyst under aerobic conditions provides a new noble metal-free and green reaction protocol for carbonyl compound synthesis....

Plasmachemical synthesis and evaluation of the thermal conductivity of metal-oxide compounds "Molybdenum-uranium dioxide"

Science.gov (United States)

Kotelnikova, Alexandra A.; Karengin, Alexander G.; Mendoza, Orlando

2018-03-01

The article represents possibility to apply oxidative and reducing plasma for plasma-chemical synthesis of metal-oxide compounds «Mo‒UO2» from water-salt mixtures «molybdic acid‒uranyl nitrate» and «molybdic acid‒ uranyl acetate». The composition of water-salt mixture was calculated and the conditions ensuring plasma-chemical synthesis of «Mo‒UO2» compounds were determined. Calculations were carried out at atmospheric pressure over a wide range of temperatures (300-4000 K), with the use of various plasma coolants (air, hydrogen). The heat conductivity coefficients of metal-oxide compounds «Mo‒UO2» consisting of continuous component (molybdenum matrix) are calculated. Inclusions from ceramics in the form of uranium dioxide were ordered in the matrix. Particular attention is paid to methods for calculating the coefficients of thermal conductivity of these compounds with the use of different models. Calculated results were compared with the experimental data.

Escherichia coli as a potential hydrocarbon conversion microorganism. Oxidation of aliphatic and aromatic compounds by recombinant E. coli in two-liquid phase (aqueous-organic) systems

NARCIS (Netherlands)

Favre-Bulle, Olivier

1992-01-01

The increased interest in the study of hydrocarbon utilizing microorganisms in recent years has been stimulated by the possibility of using their monooxygenases in the selective oxidation of aliphatic and aromatic compounds. As an example, long chain (>C16) n-alkanes are converted to dicarboxylic

Natural thioallyl compounds increase oxidative stress resistance and lifespan in Caenorhabditis elegans by modulating SKN-1/Nrf.

Science.gov (United States)

Ogawa, Takahiro; Kodera, Yukihiro; Hirata, Dai; Blackwell, T Keith; Mizunuma, Masaki

2016-02-22

Identification of biologically active natural compounds that promote health and longevity, and understanding how they act, will provide insights into aging and metabolism, and strategies for developing agents that prevent chronic disease. The garlic-derived thioallyl compounds S-allylcysteine (SAC) and S-allylmercaptocysteine (SAMC) have been shown to have multiple biological activities. Here we show that SAC and SAMC increase lifespan and stress resistance in Caenorhabditis elegans and reduce accumulation of reactive oxygen species (ROS). These compounds do not appear to activate DAF-16 (FOXO orthologue) or mimic dietary restriction (DR) effects, but selectively induce SKN-1 (Nrf1/2/3 orthologue) targets involved in oxidative stress defense. Interestingly, their treatments do not facilitate SKN-1 nuclear accumulation, but slightly increased intracellular SKN-1 levels. Our data also indicate that thioallyl structure and the number of sulfur atoms are important for SKN-1 target induction. Our results indicate that SAC and SAMC may serve as potential agents that slow aging.

Data-Driven Derivation of an "Informer Compound Set" for Improved Selection of Active Compounds in High-Throughput Screening.

Science.gov (United States)

Paricharak, Shardul; IJzerman, Adriaan P; Jenkins, Jeremy L; Bender, Andreas; Nigsch, Florian

2016-09-26

Despite the usefulness of high-throughput screening (HTS) in drug discovery, for some systems, low assay throughput or high screening cost can prohibit the screening of large numbers of compounds. In such cases, iterative cycles of screening involving active learning (AL) are employed, creating the need for smaller "informer sets" that can be routinely screened to build predictive models for selecting compounds from the screening collection for follow-up screens. Here, we present a data-driven derivation of an informer compound set with improved predictivity of active compounds in HTS, and we validate its benefit over randomly selected training sets on 46 PubChem assays comprising at least 300,000 compounds and covering a wide range of assay biology. The informer compound set showed improvement in BEDROC(α = 100), PRAUC, and ROCAUC values averaged over all assays of 0.024, 0.014, and 0.016, respectively, compared to randomly selected training sets, all with paired t-test p-values agnostic fashion. This approach led to a consistent improvement in hit rates in follow-up screens without compromising scaffold retrieval. The informer set is adjustable in size depending on the number of compounds one intends to screen, as performance gains are realized for sets with more than 3,000 compounds, and this set is therefore applicable to a variety of situations. Finally, our results indicate that random sampling may not adequately cover descriptor space, drawing attention to the importance of the composition of the training set for predicting actives.

Oxidation of inorganic sulfur compounds in acidophilic prokaryotes

Energy Technology Data Exchange (ETDEWEB)

Rohwerder, T.; Sand, W. [Universitaet Duisburg-Essen, Biofilm Centre, Aquatic Biotechnology, Duisburg (Germany)

2007-07-15

The oxidation of reduced inorganic sulfur compounds to sulfuric acid is of great importance for biohydrometallurgical technologies as well as the formation of acidic (below pH 3) and often heavy metal-contaminated environments. The use of elemental sulfur as an electron donor is the predominant energy-yielding process in acidic natural sulfur-rich biotopes but also at mining sites containing sulfidic ores. Contrary to its significant role in the global sulfur cycle and its biotechnological importance, the microbial fundamentals of acidophilic sulfur oxidation are only incompletely understood. Besides giving an overview of sulfur-oxidizing acidophiles, this review describes the so far known enzymatic reactions related to elemental sulfur oxidation in acidophilic bacteria and archaea. Although generally similar reactions are employed in both prokaryotic groups, the stoichiometry of the key enzymes is different. Bacteria oxidize elemental sulfur by a sulfur dioxygenase to sulfite whereas in archaea, a sulfur oxygenase reductase is used forming equal amounts of sulfide and sulfite. In both cases, the activation mechanism of elemental sulfur is not known but highly reactive linear sulfur forms are assumed to be the actual substrate. Inhibition as well as promotion of these biochemical steps is highly relevant in bioleaching operations. An efficient oxidation can prevent the formation of passivating sulfur layers. In other cases, a specific inhibition of sulfur biooxidation may be beneficial for reducing cooling and neutralization costs. In conclusion, the demand for a better knowledge of the biochemistry of sulfur-oxidizing acidophiles is underlined. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

Selective Electrochemical Generation of Hydrogen Peroxide from Water Oxidation

DEFF Research Database (Denmark)

Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Nørskov, Jens K.

2015-01-01

evolution and form hydrogen peroxide. Using density functional theory calculations, we show that the free energy of adsorbed OH* can be used to determine selectivity trends between the 2e(-) water oxidation to H2O2 and the 4e(-) oxidation to O2. We show that materials which bind oxygen intermediates...... sufficiently weakly, such as SnO2, can activate hydrogen peroxide evolution. We present a rational design principle for the selectivity in electrochemical water oxidation and identify new material candidates that could perform H2O2 evolution selectively....

Evolution of Near-Surface Internal and External Oxide Morphology During High-Temperature Selective Oxidation of Steels

Science.gov (United States)

Story, Mary E.; Webler, Bryan A.

2018-05-01

In this work we examine some observations made using high-temperature confocal scanning laser microscopy (HT-CSLM) during selective oxidation experiments. A plain carbon steel and advanced high-strength steel (AHSS) were selectively oxidized at high temperature (850-900°C) in either low oxygen or water vapor atmospheres. Surface evolution, including thermal grooving along grain boundaries and oxide growth, was viewed in situ during heating. Experiments investigated the influence of the microstructure and oxidizing atmosphere on selective oxidation behavior. Sequences of CSLM still frames collected during the experiment were processed with ImageJ to obtain histograms that showed a general darkening trend indicative of oxidation over time with all samples. Additional ex situ scanning electron microscopy and energy dispersive spectroscopy analysis supported in situ observations. Distinct oxidation behavior was observed for each case. Segregation, grain orientation, and extent of internal oxidation were all found to strongly influence surface evolution.

Anti-trypanosomal activities and structural chemical properties of selected compound classes.

Science.gov (United States)

Ponte-Sucre, Alicia; Bruhn, Heike; Schirmeister, Tanja; Cecil, Alexander; Albert, Christian R; Buechold, Christian; Tischer, Maximilian; Schlesinger, Susanne; Goebel, Tim; Fuß, Antje; Mathein, Daniela; Merget, Benjamin; Sotriffer, Christoph A; Stich, August; Krohne, Georg; Engstler, Markus; Bringmann, Gerhard; Holzgrabe, Ulrike

2015-02-01

Potent compounds do not necessarily make the best drugs in the market. Consequently, with the aim to describe tools that may be fundamental for refining the screening of candidates for animal and preclinical studies and further development, molecules of different structural classes synthesized within the frame of a broad screening platform were evaluated for their trypanocidal activities, cytotoxicities against murine macrophages J774.1 and selectivity indices, as well as for their ligand efficiencies and structural chemical properties. To advance into their modes of action, we also describe the morphological and ultrastructural changes exerted by selected members of each compound class on the parasite Trypanosoma brucei. Our data suggest that the potential organelles targeted are either the flagellar pocket (compound 77, N-Arylpyridinium salt; 15, amino acid derivative with piperazine moieties), the endoplasmic reticulum membrane systems (37, bisquaternary bisnaphthalimide; 77, N-Arylpyridinium salt; 68, piperidine derivative), or mitochondria and kinetoplasts (88, N-Arylpyridinium salt; 68, piperidine derivative). Amino acid derivatives with fumaric acid and piperazine moieties (4, 15) weakly inhibiting cysteine proteases seem to preferentially target acidic compartments. Our results suggest that ligand efficiency indices may be helpful to learn about the relationship between potency and chemical characteristics of the compounds. Interestingly, the correlations found between the physico-chemical parameters of the selected compounds and those of commercial molecules that target specific organelles indicate that our rationale might be helpful to drive compound design toward high activities and acceptable pharmacokinetic properties for all compound families.

Highly effective degradation of selected groups of organic compounds by cavitation based AOPs under basic pH conditions.

Science.gov (United States)

Gągol, Michał; Przyjazny, Andrzej; Boczkaj, Grzegorz

2018-07-01

Cavitation has become on the most often applied methods in a number of industrial technologies. In the case of oxidation of organic pollutants occurring in the aqueous medium, cavitation forms the basis of numerous advanced oxidation processes (AOPs). This paper presents the results of investigations on the efficiency of oxidation of the following groups of organic compounds: organosulfur, nitro derivatives of benzene, BTEX, and phenol and its derivatives in a basic model effluent using hydrodynamic and acoustic cavitation combined with external oxidants, i.e., hydrogen peroxide, ozone and peroxone. The studies revealed that the combination of cavitation with additional oxidants allows 100% oxidation of the investigated model compounds. However, individual treatments differed with respect to the rate of degradation. Hydrodynamic cavitation aided by peroxone was found to be the most effective treatment (100% oxidation of all the investigated compounds in 60 min). When using hydrodynamic and acoustic cavitation alone, the effectiveness of oxidation was diversified. Under these conditions, nitro derivatives of benzene and phenol and its derivatives were found to be resistant to oxidation. In addition, hydrodynamic cavitation was found to be more effective in degradation of model compounds than acoustic cavitation. The results of investigations presented in this paper compare favorably with the investigations on degradation of organic contaminants using AOPs under conditions of basic pH published thus far. Copyright © 2018 Elsevier B.V. All rights reserved.

Simulation of the selective oxidation process of semiconductors

International Nuclear Information System (INIS)

Chahoud, M.

2012-01-01

A new approach to simulate the selective oxidation of semiconductors is presented. This approach is based on the so-called b lack box simulation method . This method is usually used to simulate complex processes. The chemical and physical details within the process are not considered. Only the input and output data of the process are relevant for the simulation. A virtual function linking the input and output data has to be found. In the case of selective oxidation the input data are the mask geometry and the oxidation duration whereas the output data are the oxidation thickness distribution. The virtual function is determined as four virtual diffusion processes between the masked und non-masked areas. Each process delivers one part of the oxidation profile. The method is applied successfully on the oxidation system silicon-silicon nitride (Si-Si 3 N 4 ). The fitting parameters are determined through comparison of experimental and simulation results two-dimensionally.(author)

The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

International Nuclear Information System (INIS)

Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D.

2004-01-01

X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca 2 Ge 0.8 Cr 0.2 O 4 , Ba 2 Ge 0.1 Cr 0.9 O 4 , Sr 2 CrO 4 , Ca 2 (PO 4 ) x (CrO 4 ) 1-x Cl (x=0.25,0.5), Ca 5 (CrO 4 ) 3 Cl, CrO 3 , the octahedrally coordinated compounds Cr(II)-acetate, CrCl 3 , CrF 3 , Cr 2 O 3 , KCr(SO 4 ) 2 · 12H 2 O, CrO 2 and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code

The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

Science.gov (United States)

Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D.

2004-05-01

X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca 2Ge 0.8Cr 0.2O 4, Ba 2Ge 0.1Cr 0.9O 4, Sr 2CrO 4, Ca 2(PO 4) x(CrO 4) 1- xCl ( x=0.25,0.5), Ca 5(CrO 4) 3Cl, CrO 3, the octahedrally coordinated compounds Cr(II)-acetate, CrCl 3, CrF 3, Cr 2O 3, KCr(SO 4) 2 · 12H 2O, CrO 2 and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code.

Oxidation behavior of U-Si compounds in air from 25 to 1000 C

Science.gov (United States)

Sooby Wood, E.; White, J. T.; Nelson, A. T.

2017-02-01

The air oxidation behavior of U3Si2, USi, and U3Si5 is studied from room temperature to 1000 C. The onsets of breakaway oxidation for each compound are identified during synthetic air ramps to 1000 C using thermogravimetric analysis. Isothermal air oxidation tests are performed below and above the breakaway oxidation onset to discern the oxidation kinetic behavior of these candidate accident tolerant fuel forms. Uranium metal is tested in the same manner to provide a reference for the oxidation behavior. Thermogravimetric, x-ray diffraction, and scanning electron microscopy analysis are presented here along with a discussion of the oxidation behavior of these materials and the impact of the lack of oxidation resistance to their deployment as accident tolerant nuclear fuels.

Nitroxide-catalyzed selective oxidation of alcohols and polysaccharides

International Nuclear Information System (INIS)

Ponedel'kina, I Yu; Khaibrakhmanova, E A; Odinokov, Viktor N

2010-01-01

The use of nitroxide radicals in the selective oxidation of alcohols is considered. Attention is focused on the oxidation of polysaccharides as a method of preparation of polyuronic acids, aldehydes and hemiacetals.

Studies On An Aerobic Oxidation Of Dibenzothiophene And Related Compounds Using Ruthenium Catalyst

Directory of Open Access Journals (Sweden)

Morishita Y.

2015-06-01

Full Text Available An aerobic oxidation of dibenzothiophene and related compounds using a catalytic amount of ruthenium chloride in hydrocarbon solvents at 80°C for 20 h gave the corresponding sulfones in almost quantitative yields. The reaction might proceed via autoxidation of solvents to hydroperoxides and the reaction of sulfur compounds with the resulting hydroperoxides.

Selective Electrocatalytic Activity of Ligand Stabilized Copper Oxide Nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Kauffman, Douglas R; Ohodnicki, Paul R; Kail, Brian W; Matranga, Christopher

2011-01-01

Ligand stabilization can influence the surface chemistry of Cu oxide nanoparticles (NPs) and provide unique product distributions for electrocatalytic methanol (MeOH) oxidation and CO{sub 2} reduction reactions. Oleic acid (OA) stabilized Cu{sub 2}O and CuO NPs promote the MeOH oxidation reaction with 88% and 99.97% selective HCOH formation, respectively. Alternatively, CO{sub 2} is the only reaction product detected for bulk Cu oxides and Cu oxide NPs with no ligands or weakly interacting ligands. We also demonstrate that OA stabilized Cu oxide NPs can reduce CO{sub 2} into CO with a {approx}1.7-fold increase in CO/H{sub 2} production ratios compared to bulk Cu oxides. The OA stabilized Cu oxide NPs also show 7.6 and 9.1-fold increases in CO/H{sub 2} production ratios compared to weakly stabilized and non-stabilized Cu oxide NPs, respectively. Our data illustrates that the presence and type of surface ligand can substantially influence the catalytic product selectivity of Cu oxide NPs.

Organocatalyzed Asymmetric α-Oxidation, α-Aminoxylation and α-Amination of Carbonyl Compounds

OpenAIRE

Worawan Bhanthumnavin; Tirayut Vilaivan

2010-01-01

Organocatalytic asymmetric α-oxidation and amination reactions of carbonyl compounds are highly useful synthetic methodologies, especially in generating chiral building blocks that previously have not been easily accessible by traditional methods. The concept is relatively new and therefore the list of new catalysts, oxidizing and aminating reagents, as well as new substrates, are expanding at an amazing rate. The scope of this review includes new reactions and catalysts, mechanistic aspects ...

Oxidation of organic compounds in wastewater from the humid processing of coffee berries

International Nuclear Information System (INIS)

Goncalves, Maraisa; Guerreiro, Mario Cesar; Oliveira, Luiz Carlos Alves; Rocha, Cristian Luciana da

2008-01-01

Materials based on pure iron oxide and impregnated with niobia (Nb 2 O 5 ) were prepared. Their catalytic activities were tested on the oxidation of compounds present in the wastewater from the processing of coffee berries. Particularly caffeine and catechol were tested. The oxidation reactions were carried out with the following systems: UV/H 2 O 2 ; photo-Fenton and heterogeneous Fenton. All materials were characterized with X-ray diffraction, Moessbauer and infrared spectroscopy. Iron was mainly in the forms of goethite and maghemite. The oxidation kinetics were monitored by UV-vis and the oxidation products were monitored by mass spectrometry. The photo-Fenton reaction presented highest oxidation efficiency, removing 98% of all caffeine and catechol contents. (author)

Deuterium enrichment by selective photo-induced dissociation of an organic carbonyl compound

International Nuclear Information System (INIS)

Marling, J.B.

1981-01-01

A deuterium-enriched material is produced by selective photoinduced dissociation of a gas phase organic carbonyl compound containing at least one hydrogen atom bonded to an atom adjacent to a carbonyl group. Alkyl carbonyl compounds such as acetone, acetaldehyde, trifluoroacetic acid, cyclobutanone, cyclopentanone, methyl acetate, 3,3-dimethyl-2-butanone, 2,4-pentanedione, and 4-methyl-2-pentanone are preferred. The carbonyl compound is subjected to intense infrared radiation from one laser, or two lasers operating at different frequencies, to selectively dissociate the deuterated molecules into stable products. The undissociated compound may be redeuterated by direct aqueous liquid phase H/D exchange, or by indirect liquid phase exchange using an alkanol in an intermediate step

Oxidation behavior of U-Si compounds in air from 25 to 1000 C

Energy Technology Data Exchange (ETDEWEB)

Sooby Wood, E., E-mail: sooby@lanl.gov; White, J.T.; Nelson, A.T.

2017-02-15

The air oxidation behavior of U{sub 3}Si{sub 2}, USi, and U{sub 3}Si{sub 5} is studied from room temperature to 1000 C. The onsets of breakaway oxidation for each compound are identified during synthetic air ramps to 1000 C using thermogravimetric analysis. Isothermal air oxidation tests are performed below and above the breakaway oxidation onset to discern the oxidation kinetic behavior of these candidate accident tolerant fuel forms. Uranium metal is tested in the same manner to provide a reference for the oxidation behavior. Thermogravimetric, x-ray diffraction, and scanning electron microscopy analysis are presented here along with a discussion of the oxidation behavior of these materials and the impact of the lack of oxidation resistance to their deployment as accident tolerant nuclear fuels.

Total Oxidation of Model Volatile Organic Compounds over Some Commercial Catalysts

Czech Academy of Sciences Publication Activity Database

Matějová, Lenka; Topka, Pavel; Jirátová, Květa; Šolcová, Olga

2012-01-01

Roč. 443, NOV 7 (2012), s. 40-49 ISSN 0926-860X R&D Projects: GA MPO FR-TI1/059 Institutional support: RVO:67985858 Keywords : volatile organic compounds * oxidation * ethanol Subject RIV: DM - Solid Waste and Recycling Impact factor: 3.410, year: 2012

Melamine phosphomolybdate - a new ion selective compound for caesium

International Nuclear Information System (INIS)

Mehta, B.J.; Baxi, D.R.

1976-01-01

Preparation of melamine phosphomolybdate is described and its composition is determined. The compound is found to be granular having much higher selectivity for Cs + than that of ammonium phosphomolybdate. (orig.) [de

Screening SIRT1 Activators from Medicinal Plants as Bioactive Compounds against Oxidative Damage in Mitochondrial Function

Directory of Open Access Journals (Sweden)

Yi Wang

2016-01-01

Full Text Available Sirtuin type 1 (SIRT1 belongs to the family of NAD+ dependent histone deacetylases and plays a critical role in cellular metabolism and response to oxidative stress. Traditional Chinese medicines (TCMs, as an important part of natural products, have been reported to exert protective effect against oxidative stress in mitochondria. In this study, we screened SIRT1 activators from TCMs and investigated their activities against mitochondrial damage. 19 activators were found in total by in vitro SIRT1 activity assay. Among those active compounds, four compounds, ginsenoside Rb2, ginsenoside F1, ginsenoside Rc, and schisandrin A, were further studied to validate the SIRT1-activation effects by liquid chromatography-mass spectrometry and confirm their activities against oxidative damage in H9c2 cardiomyocytes exposed to tert-butyl hydroperoxide (t-BHP. The results showed that those compounds enhanced the deacetylated activity of SIRT1, increased ATP content, and inhibited intracellular ROS formation as well as regulating the activity of Mn-SOD. These SIRT1 activators also showed moderate protective effects on mitochondrial function in t-BHP cells by recovering oxygen consumption and increasing mitochondrial DNA content. Our results suggested that those compounds from TCMs attenuated oxidative stress-induced mitochondrial damage in cardiomyocytes through activation of SIRT1.

Study of bismuth oxide compounds as cathodic materials in lithium accumulators

International Nuclear Information System (INIS)

Apostolova, R.D.; Shembel', E.M.

1999-01-01

Two groups of bismuth oxide base compounds: rare earth bismuthides - SmBiO 3 and EuBiO 3 , as well as the Aurivillius phase - Bi 4 V 2 O 11 , were synthesized and electrochemically studied as novel cathodic materials for high-energy lithium current sources [ru

Chemical Reductive Transformations of Synthetic Organic Compounds

National Research Council Canada - National Science Library

Peyton, Gary

2001-01-01

Advanced Oxidation Processes (AOPs) can be used to selectively remove DNT (2,4-dinitrotoluene) from a complex waste stream by adding a precursor compound such as ethanol which forms a reducing radical upon reaction with hydroxyl radical...

The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

Energy Technology Data Exchange (ETDEWEB)

Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D

2004-05-10

X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca{sub 2}Ge{sub 0.8}Cr{sub 0.2}O{sub 4}, Ba{sub 2}Ge{sub 0.1}Cr{sub 0.9}O{sub 4}, Sr{sub 2}CrO{sub 4}, Ca{sub 2}(PO{sub 4}){sub x}(CrO{sub 4}){sub 1-x}Cl (x=0.25,0.5), Ca{sub 5}(CrO{sub 4}){sub 3}Cl, CrO{sub 3}, the octahedrally coordinated compounds Cr(II)-acetate, CrCl{sub 3}, CrF{sub 3}, Cr{sub 2}O{sub 3}, KCr(SO{sub 4}){sub 2} {center_dot} 12H{sub 2}O, CrO{sub 2} and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code.

Inhibitory effect of organotin compounds on rat neuronal nitric oxide synthase through interaction with calmodulin

International Nuclear Information System (INIS)

Ohashi, Koji; Kominami, Shiro; Yamazaki, Takeshi; Ohta, Shigeru; Kitamura, Shigeyuki

2004-01-01

Organotin compounds, triphenyltin (TPT), tributyltin, dibutyltin, and monobutyltin (MBT), showed potent inhibitory effects on both L-arginine oxidation to nitric oxide and L-citrulline, and cytochrome c reduction catalyzed by recombinant rat neuronal nitric oxide synthase (nNOS). The two inhibitory effects were almost parallel. MBT and TPT showed the highest inhibitory effects, followed by tributyltin and dibutyltin; TPT and MBT showed inhibition constant (IC 50 ) values of around 10 μM. Cytochrome c reduction activity was markedly decreased by removal of calmodulin (CaM) from the complete mixture, and the decrease was similar to the extent of inhibition by TPT and MBT. The inhibitory effect of MBT on the cytochrome c reducing activity was rapidly attenuated upon dilution of the inhibitor, and addition of a high concentration of CaM reactivated the cytochrome c reduction activity inhibited by MBT. However, other cofactors such as FAD, FMN or tetrahydrobiopterin had no such ability. The inhibitory effect of organotin compounds (100 μM) on L-arginine oxidation of nNOS almost vanished when the amount of CaM was sufficiently increased (150-300 μM). It was confirmed by CaM-agarose column chromatography that the dissociation of nNOS-CaM complex was induced by organotin compounds. These results indicate that organotin compounds disturb the interaction between CaM and nNOS, thereby inhibiting electron transfer from the reductase domain to cytochrome c and the oxygenase domain

Lipid and cholesterol oxidation, color changes, and volatile compounds production in irradiated raw pork batters with different fat content

International Nuclear Information System (INIS)

Jo, Cheo Run; Byun, Myung Woo

2000-01-01

An emulsion-type product was prepared to determine the effect of irradiation on lipid and cholesterol oxidation, color change, and volatile production in raw pork with different fat content. Lipid oxidation increased with an increase in fat content or irradiation dose. Irradiated batters had higher cholesterol oxides than did non-irradiated batters, and the major cholesterol oxides formed in irradiated pork batters were 7α- and 7β- hydroxycholesterol. Hunter color a- and b-values of raw pork batters were decreased by irradiation regardless of fat content. Irradiation significantly increased the amount of volatile compounds. Although lipid oxidation of high fat products (10 and 15% fat) was higher than that of low fat products (4%), high fat products did not always produce greater amount of volatile compounds in raw pork batters. In summary, irradiation increased lipid and cholesterol oxidation, and volatile compounds production, and had detrimental effects on the color of raw pork batter under aerobic conditions

Unprecedented Selective Oxidation of Styrene Derivatives using a Supported Iron Oxide Nanocatalyst in Aqueous Medium

Science.gov (United States)

Iron oxide nanoparticles supported on mesoporous silica-type materials have been successfully utilized in the aqueous selective oxidation of alkenes under mild conditions using hydrogen peroxide as a green oxidant. Catalysts could be easily recovered after completion of the reac...

Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosol

Science.gov (United States)

Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 d...

Hydrogen charging/discharging system with liquid organic compounds: a lacunar oxide catalyst to hydrogenate the unsaturated organic compound

International Nuclear Information System (INIS)

Jalowiecki-Duhamel, L.; Carpentier, J.; Payen, E.; Heurtaux, F.

2006-01-01

Lacunar mixed oxides based on cerium nickel and aluminium or zirconium CeM 0.5 Ni x O y s (M = Zr or Al), able to store high quantities of hydrogen, have been analysed in the hydrogenation of toluene into methyl-cyclohexane (MCH). When these solids present very good toluene hydrogenation activity and selectivity towards MCH in presence of H 2 , in absence of gaseous hydrogen, the reactive hydrogen species stored in the solid can hydrogenate toluene into MCH. The hydrogenation activity under helium + toluene flow decreases as a function of time and becomes nil. The integration of the curve obtained allows to determine the extractable hydrogen content of the solid used, and a value of 1.2 wt % is obtained at 80 C on a CeAl 0.5 Ni 3 O y compound pre-treated in H 2 at 300 C. To optimise the system, different parameters have been analysed, such as the catalyst formulation, the metal content, the pre-reducing conditions as well as the reaction conditions under helium + toluene. (authors)

Synthesis of trialkyloboron from boric oxide and organoaluminium compounds

International Nuclear Information System (INIS)

Synoradzki, L.; Boleslawski, M.; Pasynkiewicz, S.; Zawada, T.

1981-01-01

The reaction of organoaluminium compounds with boric oxide has been studied. The facility of forming trialkyloboron decreases corresponding to the sequence: RAlCl 2 >R 3 Al 2 Cl 3 >R 2 AlCl>R 3 Al. The best yields have been obtained at the temperature of the boiling point of the reaction mixture and at a vigorous mixing. The new method of simultaneous obtaining of trialkyloboron and alkylaluminium chloride having an industrial significance has been proposed. (author)

Selecting a Response in Task Switching: Testing a Model of Compound Cue Retrieval

Science.gov (United States)

Schneider, Darryl W.; Logan, Gordon D.

2009-01-01

How can a task-appropriate response be selected for an ambiguous target stimulus in task-switching situations? One answer is to use compound cue retrieval, whereby stimuli serve as joint retrieval cues to select a response from long-term memory. In the present study, the authors tested how well a model of compound cue retrieval could account for a…

Mixed valence transition metal 2D-oxides: Comparison between delafossite and crednerite compounds

Science.gov (United States)

Martin, Christine; Poienar, Maria

2017-08-01

Transition metal oxides offer large opportunities to study relationships between structures and properties. Indeed these compounds crystallize in numerous frameworks corresponding to different dimensionalities and, accordingly, show a huge variety of properties (as high Tc superconductivity, colossal magnetoresistivity, multiferroicity..). The control of the oxidation state of the transition metal, via the monitoring of the oxygen content, is of prime importance to understand and optimize the properties, due to the strong coupling that exists between the lattice and the charges and spins of the transition metals. In this large playground for chemists, we reinvestigated several 2D-compounds derived from delafossite structure. Considering this paper as a very short review, we report here the results obtained on CuMO2 compounds (with M = Cr, Mn or Mn+Cu) by using a combination of techniques, as X-ray, neutrons and/or electrons diffraction on poly-crystals for structural characterisations that are correlated with electrical and/or magnetic properties. The complementarity of studies is also addressed by the synthesis and characterization of single crystals in addition to poly-crystals. Moreover the comparison of the structures of similar Cr and Mn based oxides highlights the crucial role of the Jahn-Teller effect of trivalent manganese to lift the degeneracy, which is responsible of the magnetic frustration in CuCrO2.

Oxidation of (Cr,Ti)_2AlC Compounds at 700-1000 °C for One Year in Air

International Nuclear Information System (INIS)

Lee, Jae Chun; Won, Sung Bin; Lee, Dong Bok; Park, Sang Whan

2013-01-01

(Cr,Ti)_2AlC compounds were synthesized by hot pressing, and oxidized at 700, 850, and 1000 °C in air for up to one year. They consisted of Ti-incorporated Cr_2AlC phase, Ti-rich phase, and Cr-rich phase. The formed scales divided into a uniform oxide layer and oxide nodules. The uniform oxide layer consisted primarily of a thin Al_2O_3 scale. The oxide nodules that originated from the Ti-rich phase consisted of TiO_2, which grew by both the outward diffusion of Ti"4+ ions and inward diffusion of O"2‒ ions. Chromium did not appreciably enter the oxide scale. Instead, it existed in the Ti-incorporated Cr_7C_3 sublayer after oxidation. (Cr,Ti)_2AlC compounds had good oxidation resistance, because of formation of the Al_2O_3 barrier layer.

Protective effects of organoselenium compounds against methylmercury-induced oxidative stress in mouse brain mitochondrial-enriched fractions

Directory of Open Access Journals (Sweden)

D.F. Meinerz

2011-11-01

Full Text Available We evaluated the potential neuroprotective effect of 1-100 µM of four organoselenium compounds: diphenyl diselenide, 3’3-ditri-fluoromethyldiphenyl diselenide, p-methoxy-diphenyl diselenide, and p-chloro-diphenyl diselenide, against methylmercury-induced mitochondrial dysfunction and oxidative stress in mitochondrial-enriched fractions from adult Swiss mouse brain. Methylmercury (10-100 µM significantly decreased mitochondrial activity, assessed by MTT reduction assay, in a dose-dependent manner, which occurred in parallel with increased glutathione oxidation, hydroperoxide formation (xylenol orange assay and lipid peroxidation end-products (thiobarbituric acid reactive substances, TBARS. The co-incubation with diphenyl diselenide (100 µM completely prevented the disruption of mitochondrial activity as well as the increase in TBARS levels caused by methylmercury. The compound 3’3-ditrifluoromethyldiphenyl diselenide provided a partial but significant protection against methylmercury-induced mitochondrial dysfunction (45.4 ± 5.8% inhibition of the methylmercury effect. Diphenyl diselenide showed a higher thiol peroxidase activity compared to the other three compounds. Catalase blocked methylmercury-induced TBARS, pointing to hydrogen peroxide as a vector during methylmercury toxicity in this model. This result also suggests that thiol peroxidase activity of organoselenium compounds accounts for their protective actions against methylmercury-induced oxidative stress. Our results show that diphenyl diselenide and potentially other organoselenium compounds may represent important molecules in the search for an improved therapy against the deleterious effects of methylmercury as well as other mercury compounds.

Exploratory Characterization of Phenolic Compounds with Demonstrated Anti-Diabetic Activity in Guava Leaves at Different Oxidation States

Science.gov (United States)

Díaz-de-Cerio, Elixabet; Verardo, Vito; Gómez-Caravaca, Ana María; Fernández-Gutiérrez, Alberto; Segura-Carretero, Antonio

2016-01-01

Psidium guajava L. is widely used like food and in folk medicine all around the world. Many studies have demonstrated that guava leaves have anti-hyperglycemic and anti-hyperlipidemic activities, among others, and that these activities belong mainly to phenolic compounds, although it is known that phenolic composition in guava tree varies throughout seasonal changes. Andalusia is one of the regions in Europe where guava is grown, thus, the aim of this work was to study the phenolic compounds present in Andalusian guava leaves at different oxidation states (low, medium, and high). The phenolic compounds in guava leaves were determined by HPLC-DAD-ESI-QTOF-MS. The results obtained by chromatographic analysis reported that guava leaves with low degree of oxidation had a higher content of flavonols, gallic, and ellagic derivatives compared to the other two guava leaf samples. Contrary, high oxidation state guava leaves reported the highest content of cyanidin-glucoside that was 2.6 and 15 times higher than guava leaves with medium and low oxidation state, respectively. The QTOF platform permitted the determination of several phenolic compounds with anti-diabetic properties and provided new information about guava leaf phenolic composition that could be useful for nutraceutical production. PMID:27187352

Exploratory Characterization of Phenolic Compounds with Demonstrated Anti-Diabetic Activity in Guava Leaves at Different Oxidation States

Directory of Open Access Journals (Sweden)

Elixabet Díaz-de-Cerio

2016-05-01

Full Text Available Psidium guajava L. is widely used like food and in folk medicine all around the world. Many studies have demonstrated that guava leaves have anti-hyperglycemic and anti-hyperlipidemic activities, among others, and that these activities belong mainly to phenolic compounds, although it is known that phenolic composition in guava tree varies throughout seasonal changes. Andalusia is one of the regions in Europe where guava is grown, thus, the aim of this work was to study the phenolic compounds present in Andalusian guava leaves at different oxidation states (low, medium, and high. The phenolic compounds in guava leaves were determined by HPLC-DAD-ESI-QTOF-MS. The results obtained by chromatographic analysis reported that guava leaves with low degree of oxidation had a higher content of flavonols, gallic, and ellagic derivatives compared to the other two guava leaf samples. Contrary, high oxidation state guava leaves reported the highest content of cyanidin-glucoside that was 2.6 and 15 times higher than guava leaves with medium and low oxidation state, respectively. The QTOF platform permitted the determination of several phenolic compounds with anti-diabetic properties and provided new information about guava leaf phenolic composition that could be useful for nutraceutical production.

Exploratory Characterization of Phenolic Compounds with Demonstrated Anti-Diabetic Activity in Guava Leaves at Different Oxidation States.

Science.gov (United States)

Díaz-de-Cerio, Elixabet; Verardo, Vito; Gómez-Caravaca, Ana María; Fernández-Gutiérrez, Alberto; Segura-Carretero, Antonio

2016-05-11

Psidium guajava L. is widely used like food and in folk medicine all around the world. Many studies have demonstrated that guava leaves have anti-hyperglycemic and anti-hyperlipidemic activities, among others, and that these activities belong mainly to phenolic compounds, although it is known that phenolic composition in guava tree varies throughout seasonal changes. Andalusia is one of the regions in Europe where guava is grown, thus, the aim of this work was to study the phenolic compounds present in Andalusian guava leaves at different oxidation states (low, medium, and high). The phenolic compounds in guava leaves were determined by HPLC-DAD-ESI-QTOF-MS. The results obtained by chromatographic analysis reported that guava leaves with low degree of oxidation had a higher content of flavonols, gallic, and ellagic derivatives compared to the other two guava leaf samples. Contrary, high oxidation state guava leaves reported the highest content of cyanidin-glucoside that was 2.6 and 15 times higher than guava leaves with medium and low oxidation state, respectively. The QTOF platform permitted the determination of several phenolic compounds with anti-diabetic properties and provided new information about guava leaf phenolic composition that could be useful for nutraceutical production.

Photo-oxidation of 6-thioguanine by UVA: the formation of addition products with low molecular weight thiol compounds.

Science.gov (United States)

Ren, Xiaolin; Xu, Yao-Zhong; Karran, Peter

2010-01-01

The thiopurine, 6-thioguanine (6-TG) is present in the DNA of patients treated with the immunosuppressant and anticancer drugs azathioprine or mercaptopurine. The skin of these patients is selectively sensitive to UVA radiation-which comprises >90% of the UV light in incident sunlight-and they suffer high rates of skin cancer. UVA irradiation of DNA 6-TG produces DNA lesions that may contribute to the development of cancer. Antioxidants can protect 6-TG against UVA but 6-TG oxidation products may undergo further reactions. We characterize some of these reactions and show that addition products are formed between UVA-irradiated 6-TG and N-acetylcysteine and other low molecular weight thiol compounds including β-mercaptoethanol, cysteine and the cysteine-containing tripeptide glutathione (GSH). GSH is also adducted to 6-TG-containing oligodeoxynucleotides in an oxygen- and UVA-dependent nucleophilic displacement reaction that involves an intermediate oxidized 6-TG, guanine sulfonate (G(SO3) ). These photochemical reactions of 6-TG, particularly the formation of a covalent oligodeoxynucleotide-GSH complex, suggest that crosslinking of proteins or low molecular weight thiol compounds to DNA may be a previously unrecognized hazard in sunlight-exposed cells of thiopurine-treated patients. © 2010 The Authors. Journal Compilation. The American Society of Photobiology.

Selective oxidation of n-butane to maleic anhydride under oxygen-deficient conditions over V-P-O mixed oxides

NARCIS (Netherlands)

Bosch, H.; Bruggink, A.A.; Ross, J.R.H.

1987-01-01

The selective oxidation of n-butane to maleic anhydride over V-P-O mixed oxides was studied under oxygen deficient conditions. The mixed oxides were prepared with P/V atomic ratios ranging from 0.7 to 1.0. Catalysts with P/V <1.0 did not show any selectivity to maleic anhydride formation, regardless

Efficient and Highly Aldehyde Selective Wacker Oxidation

KAUST Repository

Teo, Peili; Wickens, Zachary K.; Dong, Guangbin; Grubbs, Robert H.

2012-01-01

A method for efficient and aldehyde-selective Wacker oxidation of aryl-substituted olefins using PdCl 2(MeCN) 2, 1,4-benzoquinone, and t-BuOH in air is described. Up to a 96% yield of aldehyde can be obtained, and up to 99% selectivity can be achieved with styrene-related substrates. © 2012 American Chemical Society.

Efficient and Highly Aldehyde Selective Wacker Oxidation

KAUST Repository

Teo, Peili

2012-07-06

A method for efficient and aldehyde-selective Wacker oxidation of aryl-substituted olefins using PdCl 2(MeCN) 2, 1,4-benzoquinone, and t-BuOH in air is described. Up to a 96% yield of aldehyde can be obtained, and up to 99% selectivity can be achieved with styrene-related substrates. © 2012 American Chemical Society.

Composite catalyst for carbon monoxide and hydrocarbon oxidation

Science.gov (United States)

Liu, Wei; Flytzani-Stephanopoulos, Maria

1996-01-01

A method and composition for the complete oxidation of carbon monoxide and/or hydrocarbon compounds. The method involves reacting the carbon monoxide and/or hydrocarbons with an oxidizing agent in the presence of a metal oxide composite catalyst. The catalyst is prepared by combining fluorite-type oxygen ion conductors with active transition metals. The fluorite oxide, selected from the group consisting of cerium oxide, zirconium oxide, thorium oxide, hafnium oxide, and uranium oxide, and may be doped by alkaline earth and rare earth oxides. The transition metals, selected from the group consisting of molybdnum, copper, cobalt, maganese, nickel, and silver, are used as additives. The atomic ratio of transition metal to fluorite oxide is less than one.

A method for nitric oxide radical scavenging properties of sulfur containing compounds.

NARCIS (Netherlands)

Vriesman, M.F.; Haenen, G.R.M.M.; Westerveld, G.J.; Paquay, J.B.G.; Voss, H.P.; Bast, A.

1997-01-01

A new method for the quantification of the nitric oxide (NO) scavenging activity of compounds in aqueous solutions is described using an amperometric NO sensor. After correction for the spontaneous degradation of NO, second-order rate kinetics of the scavenging reaction are observed.

Inhibitory mechanism of chroman compound on LPS-induced nitric oxide production and nuclear factor-κB activation

International Nuclear Information System (INIS)

Kim, Byung Hak; Reddy, Alavala Matta; Lee, Kum-Ho; Chung, Eun Yong; Cho, Sung Min; Lee, Heesoon; Min, Kyung Rak; Kim, Youngsoo

2004-01-01

6-Hydroxy-7-methoxychroman-2-carboxylic acid phenylamide (KL-1156) is a novel chemically synthetic compound. In the present study, the chroman KL-1156 compound was found to inhibit lipopolysaccharide (LPS)-induced nitric oxide production in macrophages RAW 264.7. KL-1156 compound attenuated LPS-induced synthesis of both mRNA and protein of inducible nitric oxide synthase (iNOS), in parallel, and inhibited LPS-induced iNOS promoter activity, indicating that the chroman compound down-regulated iNOS expression at transcription level. As a mechanism of the anti-inflammatory action shown by KL-1156 compound, suppression of nuclear factor (NF)-κB has been documented. KL-1156 compound exhibited a dose-dependent inhibitory effect on LPS-induced NF-κB transcriptional activity in macrophages RAW 264.7. Furthermore, the compound inhibited LPS-induced nuclear translocation of NF-κB p65 and DNA binding activity of NF-κB complex, in parallel, but did not affect IκBα degradation. Taken together, this study demonstrated that chroman KL-1156 compound interfered with nuclear translocation step of NF-κB p65, which was attributable to its anti-inflammatory action

Process for selected gas oxide removal by radiofrequency catalysts

Science.gov (United States)

Cha, Chang Y.

1993-01-01

This process to remove gas oxides from flue gas utilizes adsorption on a char bed subsequently followed by radiofrequency catalysis enhancing such removal through selected reactions. Common gas oxides include SO.sub.2 and NO.sub.x.

[Protective effect and mechanism of compound Ginkgo biloba granules on oxidative stress injury of HUVEC].

Science.gov (United States)

Li, Qi; Chen, Xi; Kan, Xiao-Xi; Li, Yu-Jie; Yang, Qing; Wang, Ya-Jie; Chen, Ying; Weng, Xiao-Gang; Cai, Wei-Yan; Huang, He-Fei; Zhu, Xiao-Xin

2016-02-01

To reveal the protective and anti-apoptosis effect of compound Ginkgo biloba granules on oxidative stress injury of human umbilical vein endothelial cells (HUVEC). Negative control group, H2O2 model group and 4 drug pretreatment groups (80, 160, 320, 640 mg• L⁻¹) were established. The cell proliferation, morphological changes in each group after oxidative stress injury was detected by MTT assay and through microscope observation respectively. The content of LDH, MDA, SOD and NO and SOD activity in supernatant were detected to judge the protection effect of the drugs on endothelial cells. The protective effect on HUVEC apoptosis was analyzed by Caspase-3 activity test and Annexin V-FITC/PI staining. Western blot was used to observe the expression of apoptosis-related proteins Bcl-2 and Bax. Results showed that 1 200 μmol• L⁻¹ H2O2 can induce oxidative stress injury in endothelial cells and reduce the cell survival rate; cell proliferation inhibition degree is positively correlated with the effect time of H2O2. Besides, 80, 160, 320 640 mg•L⁻¹ compound Ginkgo biloba granules can protect HUVEC from oxidative stress injury, recover the normal proliferation level of cells, improve their state, prohibit cell apoptosis, and can up-regulate and down-regulate the expression level of Bcl-2 and Bax respectively. In conclusion, compound G. biloba granules can protect HUVEC from the oxidative stress injury induced by H2O2, its mechanism may be correlated with inhibition of the mitochondrial apoptotic pathway in HUVEC. Copyright© by the Chinese Pharmaceutical Association.

Effect of antioxidant properties of lecithin emulsifier on oxidative stability of encapsulated bioactive compounds.

Science.gov (United States)

Pan, Yuanjie; Tikekar, Rohan V; Nitin, N

2013-06-25

Oxidation of encapsulated bioactive compounds in emulsions is one of the key challenges that limit shelf life of emulsion containing products. Oxidation in these emulsions is triggered by permeation of free radicals generated at the emulsion interface. The objective of this study was to evaluate the role of antioxidant properties of common emulsifiers (lecithin and Tween 20) in reducing permeation of free radicals across the emulsion interface. Radical permeation rates were correlated with oxidative stability of a model bioactive compound (curcumin) encapsulated in these emulsions. Rate of permeation of peroxyl radicals from the aqueous phase to the oil phase of emulsion was inversely proportional to the antioxidant properties of emulsifiers. The rate of radical permeation was significantly higher (plecithin compared to native lecithin that showed higher antioxidant activity. Free radical permeation rate correlated with stability of curcumin in emulsions and was significantly higher (plecithin stabilized emulsions as compared to Tween 20 emulsions. Overall, this study demonstrates that antioxidant activity of emulsifiers significantly influences permeation of free radicals across the emulsion interface and the rate of oxidation of bioactive encapsulant. Copyright © 2013 Elsevier B.V. All rights reserved.

Bitropic D3 Dopamine Receptor Selective Compounds as Potential Antipsychotics.

Science.gov (United States)

Luedtke, Robert R; Rangel-Barajas, Claudia; Malik, Mahinder; Reichert, David E; Mach, R H

2015-01-01

Neuropsychiatric disorders represent a substantial social and health care issue. The National Institutes of Health estimates that greater than 2 million adults suffer from neuropsychiatric disorders in the USA. These individuals experience symptoms that can include auditory hallucinations, delusions, unrealistic beliefs and cognitive dysfunction. Although antipsychotic medications are available, suboptimal therapeutic responses are observed for approximately one-third of patients. Therefore, there is still a need to explore new pharmacotherapeutic strategies for the treatment of neuropsychiatric disorders. Many of the medications that are used clinically to treat neuropsychiatric disorders have a pharmacological profile that includes being an antagonist at D2-like (D2, D3 and D4) dopamine receptor subtypes. However, dopamine receptor subtypes are involved in a variety of neuronal circuits that include movement coordination, cognition, emotion, affect, memory and the regulation of prolactin. Consequently, antagonism at D2-like receptors can also contribute to some of the adverse side effects associated with the long-term use of antipsychotics including the a) adverse extrapyramidal symptoms associated with the use of typical antipsychotics and b) metabolic side effects (weight gain, hyperglycemia, increased risk of diabetes mellitus, dyslipidemia and gynecomastia) associated with atypical antipsychotic use. Preclinical studies suggest that D3 versus D2 dopamine receptor selective compounds might represent an alternative strategy for the treatment of the symptoms of schizophrenia. In this review we discuss a) how bitropic Nphenylpiperazine D3 dopamine receptor selective compounds have been developed by modification of the primary (orthosteric) and secondary (allosteric or modulatory) pharmacophores to optimize D3 receptor affinity and D2/D3 binding selectivity ratios and b) the functional selectivity of these compounds. Examples of how these compounds might be

Titanium Oxide/Platinum Catalysis: Charge Transfer from a Titanium Oxide Support Controls Activity and Selectivity in Methanol Oxidation on Platinum

KAUST Repository

Hervier, Antoine

2011-11-24

Platinum films of 1 nm thickness were deposited by electron beam evaporation onto 100 nm thick titanium oxide films (TiOx) with variable oxygen vacancy concentrations and fluorine (F) doping. Methanol oxidation on the platinum films produced formaldehyde, methyl formate, and carbon dioxide. F-doped samples demonstrated significantly higher activity for methanol oxidation when the TiOx was stoichiometric (TiO 2), but lower activity when it was nonstoichiometric (TiO 1.7 and TiO1.9). These results correlate with the chemical behavior of the same types of catalysts in CO oxidation. Fluorine doping of stoichiometric TiO2 also increased selectivity toward partial oxidation of methanol to formaldehyde and methyl formate, but had an opposite effect in the case of nonstoichiometric TiOx. Introduction of oxygen vacancies and fluorine doping both increased the conductivity of the TiO x film. For oxygen vacancies, this occurred by the formation of a conduction channel in the band gap, whereas in the case of fluorine doping, F acted as an n-type donor, forming a conduction channel at the bottom of the conduction band, about 0.5-1.0 eV higher in energy. The higher energy electrons in F-doped stoichiometric TiOx led to higher turnover rates and increased selectivity toward partial oxidation of methanol. This correlation between electronic structure and turnover rate and selectivity indicates that the ability of the support to transfer charges to surface species controls in part the activity and selectivity of the reaction. © 2011 American Chemical Society.

Protective effects of sweet orange (Citrus sinensis) peel and their bioactive compounds on oxidative stress.

Science.gov (United States)

Chen, Zong-Tsi; Chu, Heuy-Ling; Chyau, Charng-Cherng; Chu, Chin-Chen; Duh, Pin-Der

2012-12-15

Protective effects of sweet orange (Citrus sinensis) peel and their bioactive compounds on oxidative stress were investigated. According to HPLC-DAD and HPLC-MS/MS analysis, hesperidin (HD), hesperetin (HT), nobiletin (NT), and tangeretin (TT) were present in water extracts of sweet orange peel (WESP). The cytotoxic effect in 0.2mM t-BHP-induced HepG2 cells was inhibited by WESP and their bioactive compounds. The protective effect of WESP and their bioactive compounds in 0.2mM t-BHP-induced HepG2 cells may be associated with positive regulation of GSH levels and antioxidant enzymes, decrease in ROS formation and TBARS generation, increase in the mitochondria membrane potential and Bcl-2/Bax ratio, as well as decrease in caspase-3 activation. Overall, WESP displayed a significant cytoprotective effect against oxidative stress, which may be most likely because of the phenolics-related bioactive compounds in WESP, leading to maintenance of the normal redox status of cells. Copyright © 2012 Elsevier Ltd. All rights reserved.

Selective Oxidative Carbonylation of Aniline to Diphenylurea with Ionic Liquids

DEFF Research Database (Denmark)

Zahrtmann, Nanette; Claver, Carmen; Godard, Cyril

2018-01-01

A catalytic system for the selective oxidative carbonylation of aniline to diphenylurea based on Pd complexes in combination with imidazolium ionic liquids is presented. Both oxidants, Pd complexes and ionic liquids affect the activity of the reaction while the choice of oxidant determines...

Fracton pairing mechanism for unconventional superconductors: Self-assembling organic polymers and copper-oxide compounds

DEFF Research Database (Denmark)

Milovanov, A.V.; Juul Rasmussen, J.

2002-01-01

Self-assembling organic polymers and copper-oxide compounds are two classes of unconventional superconductors, whose challenging behavior does not comply with the traditional picture of Bardeen-Cooper-Schrieffer (BCS) superconductivity in regular crystals. In this paper, we propose a theoretical...... or holes) exchange fracton excitations, quantum oscillations of fractal lattices that mimic the complex microscopic organization of the unconventional superconductors. For the copper oxides, the superconducting transition temperature T-c as predicted by the fracton mechanism is of the order of similar to......150 K. We suggest that the marginal ingredient of the high-temperature superconducting phase is provided by fracton coupled holes that condensate in the conducting copper-oxygen planes owing to the intrinsic field-effect-transistor configuration of the cuprate compounds. For the gate...

Wet oxidation of glycerol into fine organic acids: catalyst selection and kinetic evaluation

Directory of Open Access Journals (Sweden)

J. E. N. Brainer

2014-12-01

Full Text Available The liquid phase oxidation of glycerol was performed producing fine organic acids. Catalysts based on Pt, Pd and Bi supported on activated carbon were employed to perform the conversion of glycerol into organic acids at 313 K, 323 K and 333 K, under atmospheric pressure (1.0 bar, in a mechanically agitated slurry reactor (MASR. The experimental results indicated glycerol conversions of 98% with production of glyceric, tartronic and glycolic acids, and dihydroxyacetone. A yield of glyceric acid of 69.8%, and a selectivity of this compound of 70.6% were reached after 4 h of operation. Surface mechanisms were proposed and rate equations were formulated to represent the kinetic behavior of the process. Selective formation of glyceric acid was observed, and the kinetic parameter values indicated the lowest activation energy (38.5 kJ/mol for its production reaction step, and the highest value of the adsorption equilibrium constant of the reactant glycerol (10-4 dm³/mol.

Synthesis of Complex-Alloyed Nickel Aluminides from Oxide Compounds by Aluminothermic Method

Directory of Open Access Journals (Sweden)

Victor Gostishchev

2018-06-01

Full Text Available This paper deals with the investigation of complex-alloyed nickel aluminides obtained from oxide compounds by aluminothermic reduction. The aim of the work was to study and develop the physicochemical basis for obtaining complex-alloyed nickel aluminides and their application for enhancing the properties of coatings made by electrospark deposition (ESD on steel castings, as well as their use as grain refiners for tin bronze. The peculiarities of microstructure formation of master alloys based on the Al–TM (transition metal system were studied using optical, electronic scanning microscopy and X-ray spectral microanalysis. There were regularities found in the formation of structural components of aluminum alloys (Ni–Al, Ni-Al-Cr, Ni-Al-Mo, Ni-Al-W, Ni-Al-Ti, Ni-Cr-Mo-W, Ni-Al-Cr-Mo-W-Ti, Ni-Al-Cr-V, Ni-Al-Cr-V-Mo and changes in their microhardness, depending on the composition of the charge, which consisted of oxide compounds, and on the amount of reducing agent (aluminum powder. It is shown that all the alloys obtained are formed on the basis of the β phase (solid solution of alloying elements in nickel aluminide and quasi-eutectic, consisting of the β′ phase and intermetallics of the alloying elements. The most effective alloys, in terms of increasing microhardness, were Al-Ni-Cr-Mo-W (7007 MPa and Al-Ni-Cr-V-Mo (7914 MPa. The perspective is shown for applying the synthesized intermetallic master alloys as anode materials for producing coatings by electrospark deposition on steel of C1030 grade. The obtained coatings increase the heat resistance of steel samples by 7.5 times, while the coating from NiAl-Cr-Mo-W alloy remains practically nonoxidized under the selected test conditions. The use of NiAl intermetallics as a modifying additive (0.15 wt. % in tin bronze allows increasing the microhardness of the α-solid solution by 1.9 times and the microhardness of the eutectic (α + β phase by 2.7 times.

Hypervalent iodine/TEMPO-mediated oxidation in flow systems: a fast and efficient protocol for alcohol oxidation

Directory of Open Access Journals (Sweden)

Nida Ambreen

2013-07-01

Full Text Available Hypervalent iodine(III/TEMPO-mediated oxidation of various aliphatic, aromatic and allylic alcohols to their corresponding carbonyl compounds was successfully achieved by using microreactor technology. This method can be used as an alternative for the oxidation of various alcohols achieving excellent yields and selectivities in significantly shortened reaction times.

Synthesis, Characterization and Catalytic Performance in the Selective Oxidation of Alcohols by Metallophthalocyanines Supported on Zinc Oxide Nanoparticles

Directory of Open Access Journals (Sweden)

Amin Ebadi

2017-01-01

Full Text Available Unsubstituted phthalocyanines of Co, Fe and Mn supported on zinc oxide nanoparticles were prepared and were well characterized with X-ray diffraction and scanning electron microscopy. The oxidation of alcohols with tert-butylhydroperoxide, in the presence of metallophthalocyanines supported on zinc oxide nanoparticles was investigated. These MPc/ZnO nanocomposites were effective catalysts for the oxidation of alcohols such as cyclohexanol (83.4% conversion; 100% selectivity, benzyl alcohol (70.5% conversion; 100% selectivity and hexanol (62.3% conversion; 100% selectivity. The influences of reaction time, various metals and type of substrates and oxidants on the oxidation of alcohols were also studied, and optimized conditions were investigated. Under these reaction conditions, the activity of the catalysts decreases in the following order:  CoPc/nano-ZnO > FePc/nano-ZnO > MnPc/nano-ZnO. It shows that TBHP is more efficient oxidant due to weaker O-O bond with respect to H2O2 and the following order has been observed for the percentage of conversions of alcohols: 2º > benzylic > 1º.

Effect of different cooking methods on lipid oxidation and formation of volatile compounds in foal meat.

Science.gov (United States)

Domínguez, Rubén; Gómez, María; Fonseca, Sonia; Lorenzo, José M

2014-06-01

The influence of four different cooking methods (roasting, grilling, microwaving and frying) on cooking loss, lipid oxidation and volatile profile of foal meat was studied. Cooking loss were significantly (Pcooking methods increased TBARs content, since high temperature during cooking causes increased oxidation in foal steaks, this increase was significantly (Pcooking methods led to increased total volatile compounds (between 366.7 and 633.1AU×10(6)/g dry matter) compared to raw steaks (216.4AU×10(6)/g dry matter). The roasted steaks showed the highest volatile content, indicating that increased cooking temperature increases the formation of volatile compounds. Aldehydes were the most abundant compounds in cooked samples, with amounts of 217.2, 364.5, 283.5 and 409.1AU×10(6)/g dry matter in grilled, microwaved, fried and roasted samples, respectively, whereas esters were the most abundant compounds in raw samples, with mean amounts of 98.8AU×10(6)/g dry matter. Copyright © 2014 Elsevier Ltd. All rights reserved.

Intra-molecular selectivity of muonium towards chlorinated aromatic compounds

International Nuclear Information System (INIS)

Venkateswaran, K.; Stadlbauer, J.M.; Laing, M.E.; Klugkist, J.; Chong, D.P.; Porter, G.B.; Walker, D.C.

1994-01-01

Muon resonance studies show that muonium atoms (Mu) in ethanol add selectively to certain C-sites of aromatic compounds containing -Cl and -OH substituents. The sites chosen seem to be those carrying the lowest electron density. This helps to characterize Mu as a nucleophile in addition reactions and, in this respect, Mu differs from ordinary H-atoms. The study shows no apparent inter-molecular selectivity between a pair of aromatic solutes in an equimolar mixture, but strong intra-molecular selectivity in an ether composed of those two aromatic rings. This difference between intra- and inter-molecular selectivity is interpreted as kinetic in origin - arising from the 'caging effect' of the solvent and peculiar to reactions close to the diffusion-controlled limit. (orig.)

Characteristics and possibilities of software tool for metal-oxide surge arresters selection

Directory of Open Access Journals (Sweden)

Đorđević Dragan

2012-01-01

Full Text Available This paper presents a procedure for the selection of metal-oxide surge arresters based on the instructions given in the Siemens and ABB catalogues, respecting their differences and the characteristics and possibilities of the software tool. The software tool was developed during the preparation of a Master's thesis titled, 'Automation of Metal-Oxide Surge Arresters Selection'. An example is presented of the selection of metal-oxide surge arresters using the developed software tool.

Readily-accessible oxidation of d0 organozirconium compounds: The electronic structure of (η5-C5H5)3ZrX compounds

International Nuclear Information System (INIS)

Strittmatter, R.J.; Bursten, B.E.; Rhodes, L.F.; Morris, D.E.; Rogers, R.D.

1990-01-01

In an effort to obtain a comparison between organotransition metal and organoactinide complexes, a series of Cp 3 ZrX compounds have been synthesized. A single crystal X-ray crystallographic study of Cp 3 ZrCl reveals that all three Cp ligands are bound in an η 5 fashion. Electrochemical investigations of this series show a first oxidation of these d 0 compounds approximately one volt less positive than the d 0 Cp 2 ZrX 2 compounds and approximately one-half volt less positive than the d 0 f 0 Cp 3 ThCl compound. These results will be presented along with a discussion of the electronic structure of this series, as determined by Xα-SW and Fenske-Hall calculations

Efficient and selective α-bromination of carbonyl compounds with N-bromosuccinimide under microwave

KAUST Repository

Guan, Xiao-Yu

2014-02-07

A highly efficient method for the synthesis of α-halocarbonyl compounds has been achieved via selective monobromination of aromatic and aliphatic carbonyl compounds with N-bromosuccinimide catalyzed by p-toluenesulfonic acid under microwave irradiation within 30 min.

Efficient and selective α-bromination of carbonyl compounds with N-bromosuccinimide under microwave

KAUST Repository

Guan, Xiao-Yu; Al-Misba'a, Zahra; Huang, Kuo-Wei

2014-01-01

A highly efficient method for the synthesis of α-halocarbonyl compounds has been achieved via selective monobromination of aromatic and aliphatic carbonyl compounds with N-bromosuccinimide catalyzed by p-toluenesulfonic acid under microwave irradiation within 30 min.

Solid-state ionics: Studies of lithium-conducting sulfide glasses and a superconducting oxide compound

International Nuclear Information System (INIS)

Ahn, Byung Tae.

1989-01-01

The first part of this work studies lithium-conducting sulfide glasses for battery applications, while the second part studies the thermodynamic properties of a superconducting oxide compound by using an oxide electrolyte. Lithium conducting glasses based on the SiS 2 -Li 2 S system are possible solid electrolytes for high-energy-density lithium batteries. The foremost requirement for solid electrolytes is that they should have high ionic conductivities. Unfortunately, most crystalline lithium conductors have low ionic conductivities at room temperature. However, glass ionic conductors show higher ionic conductivities than do crystalline forms of the same material. In addition to higher ionic conductivities, glasses appear to have several advantages over crystalline materials. These advantages include isotropic conductivity, absence of grain boundary effects, ease of glass forming, and the potential for a wide range of stability to oxidizing and reducing conditions. Using pyrolitic graphite-coated quartz ampoules, new ternary compounds and glasses in the SiS 2 -Li 2 S system were prepared. Several techniques were used to characterize the materials: powder x-ray diffraction, differential thermal analysis, differential scanning calorimetry, and AC impedance spectroscopy. The measured lithium conductivity of the sulfide glasses was one of the highest among the known solid lithium conductors. Measuring the equilibrium open circuit voltages assisted in determining the electrochemical stabilities of the ternary compounds and glasses with respect to pure Li. A solid-state ionic technique called oxygen coulometric titration was used to measure the thermodynamic stability, the oxygen stoichiometry, and the effects of the oxygen stoichiometry, and the effects of the oxygen stoichiometry and the cooling rate on superconductivity of the YBa 2 Cu 3 O 7-x compound were investigated

Study of the behaviour of P-oxides produced in the combustion of phosphorus-bearing organic compounds and their absorption on suitable substances by means of compounds labelled with 32P. I

International Nuclear Information System (INIS)

Binkowski, J.; Gizinski, S.; Kaminski, R.; Reimschuessel, W.

1976-01-01

During the pyrolytic reaction of phosphorus-bearing compounds in an atmosphere of oxygen, there are produced P-oxides, which interfere in the determination of carbon and hydrogen. The behaviour of these P-oxides was studied intensively in the empty combustion tube in dependence on temperature, velocity of the carrier gas, the nature of the combustion and the positioning of the tube. The P-oxides were determined by the employment of 32 P-labelled aniline phosphate and by activation measurement of the 32 P directly through the tube walls as well as in the finely divided material. In conventional combustions the P-oxides separate abundantly on the walls of the tube provided that the gas velocity is low, especially in those zones of the tube where there is marked temperature lowering, or where very high temperature prevail. Deposited P-oxides are swept out of the tube only in the course of a very long time. Consequently a tube in which the P-bearing compounds have been burned will interfere because of the eluted P-oxides and hence will interfere also if P-free compounds are burned in this same tube

Nitrile in the Hole: Discovery of a Small Auxiliary Pocket in Neuronal Nitric Oxide Synthase Leading to the Development of Potent and Selective 2-Aminoquinoline Inhibitors.

Science.gov (United States)

Cinelli, Maris A; Li, Huiying; Chreifi, Georges; Poulos, Thomas L; Silverman, Richard B

2017-05-11

Neuronal nitric oxide synthase (nNOS) inhibition is a promising strategy to treat neurodegenerative disorders, but the development of nNOS inhibitors is often hindered by poor pharmacokinetics. We previously developed a class of membrane-permeable 2-aminoquinoline inhibitors and later rearranged the scaffold to decrease off-target binding. However, the resulting compounds had decreased permeability, low human nNOS activity, and low selectivity versus human eNOS. In this study, 5-substituted phenyl ether-linked aminoquinolines and derivatives were synthesized and assayed against purified NOS isoforms. 5-Cyano compounds are especially potent and selective rat and human nNOS inhibitors. Activity and selectivity are mediated by the binding of the cyano group to a new auxiliary pocket in nNOS. Potency was enhanced by methylation of the quinoline and by introduction of simple chiral moieties, resulting in a combination of hydrophobic and auxiliary pocket effects that yielded high (∼500-fold) n/e selectivity. Importantly, the Caco-2 assay also revealed improved membrane permeability over previous compounds.

Nanocarbons as catalyst for selective oxidation of acrolein to acrylic acid

Energy Technology Data Exchange (ETDEWEB)

Frank, B.; Blume, R.; Rinaldi, A.; Trunschke, A.; Schloegl, R. [Fritz Haber Institute of the Max Planck Society, Berlin (Germany). Dept. of Inorganic Chemistry

2011-07-01

Selective oxidations are key steps of industrial oil and gas processing for the synthesis of high-value chemicals. Mixed metal oxides based on redox active V or Mo are frequently used for oxidative C-H bond activation. However, multiple processes require precious metals or suffer from low product selectivity demanding an ongoing search for cost-effective alternatives. Recently, the nanostructured carbon was reported to catalyze the metal-free selective alkane activation by oxidative dehydrogenation (ODH). Electron-rich surface carbonyls coordinate this reaction and mimic the active oxygen species in metal oxide catalysts. Here we show that the graphitic carbon, beyond ODH, has the potential to selectively mediate the insertion of an oxygen atom into an organic molecule, i.e., acrolein. Multi-step atom rearrangements considerably exceed the mechanistic complexity of hydrogen abstraction and were so far believed to be the exclusive domain of metal (oxide) catalysis. In the carbon catalyzed process, the nucleophilic oxygen atoms terminating the graphite (0001) surface abstract the formyl hydrogen and the activated aldehyde gets oxidized by epoxide-type mobile oxygen, thus the sp{sup 2} carbon acts as a bifunctional catalyst. Substantial similarities between the metal oxide- and carbon-catalyzed reactions could be identified. Our results shed light on a rarely known facet of applications of nanostructured carbon materials being decorated with diverse oxygen functionalities to coordinate complex catalytic processes. We could successfully transfer the results obtained from the graphite model to carbon nanotubes (CNTs) providing a higher surface area, defect density, and intrinsic activity, to substantially increase the reactivity per catalyst volume. Indeed, low dimensional nanostructured carbon is a highly flexible and robust material which can be modified in a multiple manner to optimize its properties with respect to the intended application. The exploration of

Garlic Organosulfur Compounds Reduce Inflammation and Oxidative Stress during Dengue Virus Infection

Science.gov (United States)

Hall, Alex; Troupin, Andrea; Londono-Renteria, Berlin; Colpitts, Tonya M.

2017-01-01

Dengue virus (DENV) is a mosquito-borne flavivirus that causes significant global human disease and mortality. One approach to develop treatments for DENV infection and the prevention of severe disease is through investigation of natural medicines. Inflammation plays both beneficial and harmful roles during DENV infection. Studies have proposed that the oxidative stress response may be one mechanism responsible for triggering inflammation during DENV infection. Thus, blocking the oxidative stress response could reduce inflammation and the development of severe disease. Garlic has been shown to both reduce inflammation and affect the oxidative stress response. Here, we show that the garlic active compounds diallyl disulfide (DADS), diallyl sulfide (DAS) and alliin reduced inflammation during DENV infection and show that this reduction is due to the effects on the oxidative stress response. These results suggest that garlic could be used as an alternative treatment for DENV infection and for the prevention of severe disease development. PMID:28644404

Garlic Organosulfur Compounds Reduce Inflammation and Oxidative Stress during Dengue Virus Infection.

Science.gov (United States)

Hall, Alex; Troupin, Andrea; Londono-Renteria, Berlin; Colpitts, Tonya M

2017-06-23

Dengue virus (DENV) is a mosquito-borne flavivirus that causes significant global human disease and mortality. One approach to develop treatments for DENV infection and the prevention of severe disease is through investigation of natural medicines. Inflammation plays both beneficial and harmful roles during DENV infection. Studies have proposed that the oxidative stress response may be one mechanism responsible for triggering inflammation during DENV infection. Thus, blocking the oxidative stress response could reduce inflammation and the development of severe disease. Garlic has been shown to both reduce inflammation and affect the oxidative stress response. Here, we show that the garlic active compounds diallyl disulfide (DADS), diallyl sulfide (DAS) and alliin reduced inflammation during DENV infection and show that this reduction is due to the effects on the oxidative stress response. These results suggest that garlic could be used as an alternative treatment for DENV infection and for the prevention of severe disease development.

Comparative study of the addition compounds between lanthanides methane sulfonates (III) and aromatic amino-oxides as ligands

International Nuclear Information System (INIS)

Rosario Matos, J. do.

1989-01-01

The main goal of this thesis is to further develop the studies on the preparation and characterization of addition compounds obtained from the reaction of lanthanide methane sulfonates and aromatic amino oxides as ligands, pyridine-N-oxides as the picoline-N-oxides (2-pic NO, 3-pic NO and 4-picNO) in order to make a comparative study. (author)

VOC removal and deodorization of effluent gases from an industrial plant by photo-oxidation, chemical oxidation, and ozonization.

Science.gov (United States)

Domeño, Celia; Rodríguez-Lafuente, Angel; Martos, J M; Bilbao, Rafael; Nerín, Cristina

2010-04-01

The efficiency of photo-oxidation, chemical oxidation by sodium hypochlorite, and ozonization for the industrial-scale removal of volatile organic compounds (VOCs) and odors from gaseous emissions was studied by applying these treatments (in an experimental system) to substances passing through an emission stack of a factory producing maize derivatives. Absorption and ozonization were the most efficient treatment, removing 75% and 98% of VOCs, respectively, while photo-oxidation only removed about 59%. The emitted chemical compounds and odors were identified and quantified by gas chromatography-mass spectrometry (in full-scan mode). In addition to presenting the results, their implications for selecting optimal processes for treating volatile emissions are discussed.

CO2-selective PEO–PBT (PolyActive™)/graphene oxide composite membranes

KAUST Repository

Karunakaran, Madhavan; Shevate, Rahul; Kumar, Mahendra; Peinemann, Klaus-Viktor

2015-01-01

CO2-selective graphene oxide (GO) nano-composite membranes were prepared for the first time by embedding GO into a commercially available poly(ethylene oxide)–poly(butylene terephthalate) (PEO–PBT) copolymer (PolyActive™). The as-prepared GO membrane shows high CO2 permeability (143 Barrer) and CO2/N2 selectivity (α = 73).

CO2-selective PEO–PBT (PolyActive™)/graphene oxide composite membranes

KAUST Repository

Karunakaran, Madhavan

2015-07-31

CO2-selective graphene oxide (GO) nano-composite membranes were prepared for the first time by embedding GO into a commercially available poly(ethylene oxide)–poly(butylene terephthalate) (PEO–PBT) copolymer (PolyActive™). The as-prepared GO membrane shows high CO2 permeability (143 Barrer) and CO2/N2 selectivity (α = 73).

Synthesis of Heteroaromatic Compounds by Oxidative Aromatization Using an Activated Carbon/Molecular Oxygen System

Directory of Open Access Journals (Sweden)

Masahiko Hayashi

2009-08-01

Full Text Available A variety of heteroaromatic compounds, such as substituted pyridines, pyrazoles, indoles, 2-substituted imidazoles, 2-substituted imidazoles, 2-arylbenzazoles and pyrimidin-2(1H-ones are synthesized by oxidative aromatization using the activated carbon and molecular oxygen system. Mechanistic study focused on the role of activated carbon in the synthesis of 2-arylbenzazoles is also discussed. In the final section, we will disclose the efficient synthesis of substituted 9,10-anthracenes via oxidative aromatization.

Thermodynamic properties of compounds of Na2O with the oxides of chromium, nickel, and iron

International Nuclear Information System (INIS)

Shaiu, B.J.

1976-10-01

Results of emf measurements on Na 2 O solid electrolytes in binary compounds with Cr 2 O 3 , FeO, and NiO are presented along with thermodynamic properties of these compounds. It was found that reliable thermodynamic data for compounds of NaCrO 2 , Na 2 FeO 2 , NaFeO 2 , Na 2 NiO 2 , and NaNiO 2 at 500 to 800 0 can be obtained by using emf measurements with solid electrolyte cells. The pretreatment of heating the cells in a vacuum of 10 -2 torr at 500 0 C or above for about 12 hours causes the emf dependence on temperature to be very small. The measurements were carried out over the temperature range in which no phase transformations occurred, the ΔC/sub p/ for the compounds involved was reasonably considered as approximately zero. Linear emf-temperature plots were therefore expected for these cells and the equation of ΔG 0 /sub f/ was indeed valid for constant values of ΔH 0 /sub f/ and ΔS 0 /sub f/. The formation of compound NaCrO 2 is thermodynamically favorable in a sodium loop made of austenic stainless steels. The critical oxygen concentration for the formation of NaCrO 2 shows that it is stable in liquid sodium in temperature range from 400 to 1100 0 C and Cr 2 O 3 does not exist with the double oxide in liquid sodium. The existence temperature for (Na 2 O) 2 .FeO in equilibrium with oxygen saturated liquid sodium is 693 0 K or above, for Na 2 FeO 2 it is 1141 0 K or above and for NaFeO 2 it is greater than or equal to 1173 0 K. The double oxides of nickel with sodium oxide are much less stable than the iron double oxides and do therefore not exist in liquid sodium. The nickel in austenitic stainless steel shows the least attack by oxygen saturated liquid sodium

Research advances in the catalysts for the selective oxidation of ethane to aldehydes

Institute of Scientific and Technical Information of China (English)

ZHANG Zhe; ZHAO Zhen; XU Chunming

2005-01-01

Selective oxidation of ethane to aldehydes is one of the most difficult processes in the catalysis researches of low alkanes. The development of selective oxidation of ethane to aldehydes (formaldehyde, acetaldehyde and acrolein) is discussed. The latest progress of the catalysts, including bulk or supported metal oxide catalysts, highly dispersed and isolated active sites catalysts, and the photo-catalytic ethane oxidation catalysts, partial oxidation of ethane in the gas phase, and the proposed reaction pathways from ethane to aldehydes are involved.

ADVANCED OXIDATION PROCESSES (AOX) TEXTILE WASTEWATER

OpenAIRE

Salas C., G.

2014-01-01

Advanced Oxidation Processes (AOX) are based on the in situ generation of hydroxyradicals (·OH), which have a high oxidation potential. In the case of Fenton processes !he generation of hydroxy radicals takes place by the combination of an oxidation agent (H202) with a catalyst (Fe(II)). These radicals are not selective and they react very fast with the organic matter,being able to oxidize a high variety of organic compounds. This property allows the degradation of pollutants into more biodeg...

Sinularin Selectively Kills Breast Cancer Cells Showing G2/M Arrest, Apoptosis, and Oxidative DNA Damage

Directory of Open Access Journals (Sweden)

Hurng-Wern Huang

2018-04-01

Full Text Available The natural compound sinularin, isolated from marine soft corals, is antiproliferative against several cancers, but its possible selective killing effect has rarely been investigated. This study investigates the selective killing potential and mechanisms of sinularin-treated breast cancer cells. In 3-(4,5-dimethylthiazol-2-yl-5-(3-carboxymethoxyphenyl-2-(4-sulfophenyl-2H- tetrazolium, inner salt (MTS assay, sinularin dose-responsively decreased the cell viability of two breast cancer (SKBR3 and MDA-MB-231 cells, but showed less effect on breast normal (M10 cells after a 24 h treatment. According to 7-aminoactinomycin D (7AAD flow cytometry, sinularin dose-responsively induced the G2/M cycle arrest of SKBR3 cells. Sinularin dose-responsively induced apoptosis on SKBR3 cells in terms of a flow cytometry-based annexin V/7AAD assay and pancaspase activity, as well as Western blotting for cleaved forms of poly(ADP-ribose polymerase (PARP, caspases 3, 8, and 9. These caspases and PARP activations were suppressed by N-acetylcysteine (NAC pretreatment. Moreover, sinularin dose-responsively induced oxidative stress and DNA damage according to flow cytometry analyses of reactive oxygen species (ROS, mitochondrial membrane potential (MitoMP, mitochondrial superoxide, and 8-oxo-2′-deoxyguanosine (8-oxodG. In conclusion, sinularin induces selective killing, G2/M arrest, apoptosis, and oxidative DNA damage of breast cancer cells.

Tantalum oxide-based compounds as new non-noble cathodes for polymer electrolyte fuel cell

International Nuclear Information System (INIS)

Ishihara, Akimitsu; Tamura, Motoko; Matsuzawa, Koichi; Mitsushima, Shigenori; Ota, Ken-ichiro

2010-01-01

Tantalum oxide-based compounds were examined as new non-noble cathodes for polymer electrolyte fuel cell. Tantalum carbonitride powder was partially oxidized under a trace amount of oxygen gas at 900 o C for 4 or 8 h. Onset potential for oxygen reduction reaction (ORR) of the specimen heat-treated for 8 h was 0.94 V vs. reversible hydrogen electrode in 0.1 mol dm -3 sulfuric acid at 30 o C. The partial oxidation of tantalum carboniride was effective to enhance the catalytic activity for the ORR. The partially oxidized specimen with highest catalytic activity had ca. 5.25 eV of ionization potential, indicating that there was most suitable strength of the interaction of oxygen and tantalum on the catalyst surface.

Electrocatalytic Materials and Techniques for the Anodic Oxidation of Various Organic Compounds

Energy Technology Data Exchange (ETDEWEB)

Treimer, Stephen Everett [Iowa State Univ., Ames, IA (United States)

2001-01-01

The focus of this thesis was first to characterize and improve the applicability of Fe(III) and Bi(V) doped PbO₂ film electrodes for use in anodic O-transfer reactions of toxic and waste organic compounds, e.g. phenol, aniline, benzene, and naphthalene. Further, they investigated the use of alternative solution/electrode interfacial excitation techniques to enhance the performance of these electrodes for remediation and electrosynthetic applications. Finally, they have attempted to identify a less toxic metal oxide film that may hold promise for future studies in the electrocatalysis and photoelectrocatalysis of O-transfer reactions using metal oxide film electrodes.

Synthesis and characterization of porous metal oxides and desulfurization studies of sulfur containing compounds

Science.gov (United States)

Garces Trujillo, Hector Fabian

This thesis contains two parts: 1) synthesis and characterization of porous metal oxides that include zinc oxide and a porous mixed-valent manganese oxide with an amorphous structure (AMO) 2) the desulfurization studies for the removal of sulfur compounds. Zinc oxide with different nano-scale morphologies may result in various porosities with different adsorption capabilities. A tunable shape microwave synthesis of ZnO nano-spheres in a co-solvent mixture is presented. The ZnO nano-sphere material is investigated as a desulfurizing sorbent in a fixed bed reactor in the temperature range 200 to 400 °C and compared with ZnO nanorods and platelet-like morphologies. Fresh and sulfided materials were characterized by X-ray diffraction (XRD), BET specific surface area, pore volume, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (SEM/EDX), Raman spectroscopy, and thermogravimetric analysis (TGA). The tunable shape microwave synthesis of ZnO presents a high sulfur sorption capacity at temperatures as low as 200 °C which accounts for a three and four fold enhancement over the other preparations presented in this work, and reached 76 % of the theoretical sulfur capacity (TSC) at 300 °C. Another ZnO material with a bimodal micro- and mesopore size distribution investigated as a desulfurizing sorbent presents a sorption capacity that reaches 87% of the theoretical value for desulfurization at 400 °C at breakthrough time. A deactivation model that considers the activity of the solid reactant was used to fit the experimental data. Good agreement between the experimental breakthrough curves and the model predictions are obtained. Manganese oxides are a type of metal oxide materials commonly used in catalytic applications. Little is known about the adsorption capabilities for the removal of sulfur compounds. One of these manganese oxides; amorphous manganese oxide (AMO) is highly promising material for low temperature sorption processes. Amorphous

Vanadium-substituted heteropolyacids immobilized on amine- functionalized mesoporous MCM-41: A recyclable catalyst for selective oxidation of alcohols with H2O2

International Nuclear Information System (INIS)

Dong, Xinbo; Wang, Danjun; Li, Kebin; Zhen, Yanzhong; Hu, Huaiming; Xue, Ganglin

2014-01-01

Graphical abstract: Vanadium-substituted phosphotungstic acids are immobilized on amine- functionalized mesoporous MCM-41 and the hybrid catalyst is proved to be a highly efficient solid catalyst for the oxidation of aromatic alcohols to the corresponding carbonyl compounds with H 2 O 2 , featured by the high conversion and selectivity, easy recovery, and quite steady reuse. - Highlights: • Vanadium-substituted phosphotungstic acid immobilized on amine-functionalized mesoporous MCM-41 are prepared. • HPAs were fixed on the inner surface of mesoporous MCM-41 by chemical bonding to aminosilane groups. • The hybrid catalyst showed much higher catalytic activity than the pure HPAs. • The hybrid catalyst is a highly efficient recyclable solid catalyst for the selective oxidation of aromatic alcohols. - Abstract: New hybrid materials of vanadium-substituted phosphotungstic acids (VHPW) immobilized on amine-functionalized mesoporous MCM-41 (VHPW/MCM-41/NH 2 ) are prepared and characterized by FT-IR, XRD, N 2 adsorption, elemental analysis, SEM and TEM for their structural integrity and physicochemical properties. It is found that the structure of the heteropolyacids is retained upon immobilization over mesoporous materials. The catalytic activities of these hybrid materials are tested in the selective oxidation of alcohols to the carbonyl products with 30% aqueous H 2 O 2 as oxidant in toluene. The catalytic activities of different number of vanadium-substituted phosphotungstic acid are investigated, and among the catalysts, H 5 [PV 2 W 10 O 40 ] immobilized on amine-functionalized MCM-41 exhibits the highest activity with 97% conversion and 99% selectivity in the oxidation of benzyl alcohol to benzaldehyde. The hybrid catalyst is proved to be a highly efficient recyclable solid catalyst for the selective oxidation of aromatic alcohols to the corresponding aldehydes with H 2 O 2

Synergy effects in mixed Bi2O3, MoO3 and V2O5 catalysts for selective oxidation of propylene

DEFF Research Database (Denmark)

Nguyen, Tien The; Le, Thang Minh; Truong, Duc Duc

2012-01-01

% Bi2Mo3O12 and 78.57 mol% BiVO4), corresponding to the compound Bi1-x/3V1-xMoxO4 with x = 0.45 (Bi0.85V0.55Mo0.45O4), exhibited the highest activity for the selective oxidation of propylene to acrolein. The mixed sample prepared chemically by a sol–gel method possessed higher activity than...

Friction behaviour of anodic oxide film on aluminum impregnated with molybdenum sulfide compounds

Energy Technology Data Exchange (ETDEWEB)

Maejima, M.; Saruwatari, K. [Fujikura Ltd., Tokyo (Japan); Takaya, M. [Faculty of Engineering, Chiba Institute of Technology 17-1, Tsudanuma 2-Chome, 275-0016, Narasino-shi Chiba (Japan)

2000-10-23

In order to improve the lubricity and wear resistance of aluminum anodic oxide films, it is necessary to ensure the film layers are dense to prevent cracking, and to harden the films as well as reduce the shear stress of the film surfaces. From this view point, lubricious, hard anodic oxide films have been studied in the past, but fully satisfactory results have yet to be realized. In this paper, we report on our study of the re-anodizing of anodic oxide film in an aqueous solution of (NH)MoS. Molybdenum sulfide and compounds filled the 20-nm diameter pores of the film, creating internal stress which compressed the film, suppressing the occurrence of cracks and reducing the friction coefficient. (orig.)

Investigation of selective oxidation in bake hardenable steel

International Nuclear Information System (INIS)

Madeira, Laureanny; Lins, Vanessa Cunha Freitas; Faria, Guilherme Augusto de; Guimaraes, Juliana Porto; Alvarenga, Evandro de Azevedo; Vilela, Jose Mario Carneiro

2010-01-01

The present work aims to characterize a steel bake hardenable (BH), annealed in three different dew points (-60°C, -30°C and 0°C), as the occurrence of selective oxidation, using the techniques of X-ray photo electronic spectroscopy (XPS), glow discharge optical emission spectroscopy (GDOES) and atomic force microscopy (AFM). The analysis by XPS showed that the alloying elements oxidized at different intensities for each dew point. Analysis by GDOES revealed that the surface and subsurface concentrations of these elements also varied with the dew point. The AFM images revealed that the size and shape of the oxides were different for each dew point. At the dew points of -30°C and -60°C the formation of oxides was local, while at 0°C the growth of oxides occurred uniform y on the surface of steels. (author)

Understanding the role of manganese dioxide in the oxidation of phenolic compounds by aqueous permanganate.

Science.gov (United States)

Jiang, Jin; Gao, Yuan; Pang, Su-Yan; Lu, Xue-Ting; Zhou, Yang; Ma, Jun; Wang, Qiang

2015-01-06

Recent studies have shown that manganese dioxide (MnO2) can significantly accelerate the oxidation kinetics of phenolic compounds such as triclosan and chlorophenols by potassium permanganate (Mn(VII)) in slightly acidic solutions. However, the role of MnO2 (i.e., as an oxidant vs catalyst) is still unclear. In this work, it was demonstrated that Mn(VII) oxidized triclosan (i.e., trichloro-2-phenoxyphenol) and its analogue 2-phenoxyphenol, mainly generating ether bond cleavage products (i.e., 2,4-dichlorophenol and phenol, respectively), while MnO2 reacted with them producing appreciable dimers as well as hydroxylated and quinone-like products. Using these two phenoxyphenols as mechanistic probes, it was interestingly found that MnO2 formed in situ or prepared ex situ greatly accelerated the kinetics but negligibly affected the pathways of their oxidation by Mn(VII) at acidic pH 5. The yields (R) of indicative products 2,4-dichlorophenol and phenol from their respective probes (i.e., molar ratios of product formed to probe lost) under various experimental conditions were quantified. Comparable R values were obtained during the treatment by Mn(VII) in the absence vs presence of MnO2. Meanwhile, it was confirmed that MnO2 could accelerate the kinetics of Mn(VII) oxidation of refractory nitrophenols (i.e., 2-nitrophenol and 4-nitrophenol), which otherwise showed negligible reactivity toward Mn(VII) and MnO2 individually, and the effect of MnO2 was strongly dependent upon its concentration as well as solution pH. These results clearly rule out the role of MnO2 as a mild co-oxidant and suggest a potential catalytic effect on Mn(VII) oxidation of phenolic compounds regardless of their susceptibility to oxidation by MnO2.

Selective nitrergic neurodegeneration in diabetes mellitus–a nitric oxide-dependent phenomenon

Science.gov (United States)

Cellek, Selim; Rodrigo, José; Lobos, Edgar; Fernández, Patricia; Serrano, Julia; Moncada, Salvador

1999-01-01

In vitro and in vivo studies have demonstrated a dysfunctional nitrergic system in diabetes mellitus, thus explaining the origin of diabetic impotence. However, the mechanism of this nitrergic defect is not understood.In the penises of streptozotocin (STZ)-induced diabetic rats, here, we show by immunohistochemistry that nitrergic nerves undergo selective degeneration since the noradrenergic nerves which have an anti-erectile function in the penis remained intact.Nitrergic relaxation responses in vitro and erectile responses to cavernous nerve stimulation in vivo were attenuated in these animals, whereas noradrenergic responses were enhanced.Activity and protein amount of neuronal nitric oxide synthase (nNOS) were also reduced in the penile tissue of diabetic rats.We, thus, hypothesized that NO in the nitrergic nerves may be involved in the nitrergic nerve damage, since only the nerves which contain neuronal NO synthase underwent degeneration.We administered an inhibitor of NO synthase, NG-nitro-L-arginine methyl ester (L-NAME), in the drinking water of rats for up to 12 weeks following the establishment of diabetes with STZ.Here we demonstrate that this compound protected the nitrergic nerves from morphological and functional impairment. Our results show that selective nitrergic degeneration in diabetes is NO-dependent and suggest that inhibition of NO synthase is neuroprotective in this condition. PMID:10588937

Pressure effect on magnetic and magnetotransport properties of intermetallic and colossal magnetoresistance oxide compounds

Czech Academy of Sciences Publication Activity Database

Arnold, Zdeněk; Ibarra, M. R.; Algarabel, P. A.; Marquina, C.; De Teresa, J. M.; Morellon, L.; Blasco, J.; Magen, C.; Prokhnenko, Olexandr; Kamarád, Jiří; Ritter, C.

2005-01-01

Roč. 17, - (2005), S3035-S3055 ISSN 0953-8984 Institutional research plan: CEZ:AV0Z10100521 Keywords : pressure effect * intermetallic compounds * magnetic properties * magnetic phase transitions * magnetotransport properties * oxides Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.145, year: 2005

Compound specific radiocarbon content of lignin oxidation products from the Altamaha river and Coastal Georgia

Energy Technology Data Exchange (ETDEWEB)

Culp, Randy, E-mail: rculp@uga.edu [Center for Applied Isotope Studies, University of Georgia, Athens, Georgia (United States)

2013-01-15

Compound-specific isotope analysis (CSIA) is a powerful tool in organic geochemistry by providing detailed information about an individual organic compound's history with regard to its source and process of formation. Most CSIA involves measurement of the stable isotope ratio of carbon ({sup 13}C/{sup 12}C) and hydrogen (D/H) following separation by gas or liquid chromatography. New applications are being developed using compound-specific radiocarbon ({sup 14}C) content for delineating age of materials, rates of decomposition and residence time in various environments. This paper details the isotopic work on specific lignin monomers derived from terrestrial plants transported and deposited within the Altamaha River, estuary and off-shore Georgia in the Atlantic Ocean. By using gas chromatographic separation and identification of selected lignin oxidation products (LOP), the harvesting of these compounds using preparative fraction collection, and measurement of their {sup 14}C content using accelerator mass spectrometry, details of the age and presence of specific biomarkers unique to a given terrestrial source are revealed. Radiocarbon ages determined from water-column particulate organic carbon and sediment LOPs indicate a range of ages from modern to well over 5,000 years for the former and latter respectively. Transport mechanisms and particle size associations on mineral grains may play a significant role in {sup 14}C distribution in estuary and near-shore coastal environments. This data indicates higher than modern {sup 14}C activities in large particle-size sediment fractions in contrast to older LOP {sup 14}C ages found associated with the same coarse grain sediments. Individual LOP ages substantiate older terrestrial materials persist in the off-shore environment even though in the presence of modern marine {sup 14}C sources.

Synthesis of a molecularly defined single-active site heterogeneous catalyst for selective oxidation of N-heterocycles.

Science.gov (United States)

Zhang, Yujing; Pang, Shaofeng; Wei, Zhihong; Jiao, Haijun; Dai, Xingchao; Wang, Hongli; Shi, Feng

2018-04-13

Generally, a homogeneous catalyst exhibits good activity and defined active sites but it is difficult to recycle. Meanwhile, a heterogeneous catalyst can easily be reused but its active site is difficult to reveal. It is interesting to bridge the gap between homogeneous and heterogeneous catalysis via controllable construction of a heterogeneous catalyst containing defined active sites. Here, we report that a molecularly defined, single-active site heterogeneous catalyst has been designed and prepared via the oxidative polymerization of maleimide derivatives. These polymaleimide derivatives can be active catalysts for the selective oxidation of heterocyclic compounds to quinoline and indole via the recycling of -C=O and -C-OH groups, which was confirmed by tracing the reaction with GC-MS using maleimide as the catalyst and by FT-IR analysis with polymaleimide as the catalyst. These results might promote the development of heterogeneous catalysts with molecularly defined single active sites exhibiting a comparable activity to homogeneous catalysts.

Determination of chlorine in nuclear-grade uranium compounds

International Nuclear Information System (INIS)

Yang Chunqing; Liu Fuyun; Huang Dianfan

1988-01-01

The determination of chlorine in nuclear-grade uranium compounds is discribed. Chlorine is separated from uranium oxide pyrohydrolytically with stream of wet oxygen in a furnace at 800 ∼ 900 deg C. Chlorine is volatilized as hydrochloric acid, absorbed in a dilute alkaline solution and measured with chlorine-selective electrode. This method covers the concentration range of 10 ∼ 500 pm chlorine in uranium oxide. Precision of at least ± 10% and recovery of 85 ∼ 108% have been reported

Role of vitamin C transporters and biliverdin reductase in the dual pro-oxidant and anti-oxidant effect of biliary compounds on the placental-fetal unit in cholestasis during pregnancy

International Nuclear Information System (INIS)

Perez, Maria J.; Castano, Beatriz; Jimenez, Silvia; Serrano, Maria A.; Gonzalez-Buitrago, Jose M.; Marin, Jose J.G.

2008-01-01

Maternal cholestasis causes oxidative damage to the placental-fetal unit that may challenge the outcome of pregnancy. This has been associated with the accumulation of biliary compounds able to induce oxidative stress. However, other cholephilic compounds such as ursodeoxycholic acid (UDCA) and bilirubin have direct anti-oxidant properties. In the present study we investigated whether these compounds exert a protective effect on cholestasis-induced oxidative stress in placenta as compared to maternal and fetal livers, and whether this is due in part to the activation of anti-oxidant mechanisms involving vitamin C uptake and biliverdin/bilirubin recycling. In human placenta (JAr) and liver (HepG2) cells, deoxycholic acid (DCA) similar rates of free radical generation. In JAr (not HepG2), the mitochondrial membrane potential and cell viability were impaired by low DCA concentrations; this was partly prevented by bilirubin and UDCA. In HepG2, taurocholic acid (TCA) and UDCA up-regulated biliverdin-IXα reductase (BVRα) and the vitamin C transporter SVCT2 (not SVCT1), whereas bilirubin up-regulated both SVCT1 and SVCT2. In JAr, TCA and UDCA up-regulated BVRα, SVCT1 and SVCT2, whereas bilirubin up-regulated only SVCT2. A differential response to these compounds of nuclear receptor expression (SXR, CAR, FXR and SHP) was found in both cell types. When cholestasis was induced in pregnant rats, BVRα, SVCT1 and SVCT2 expression in maternal and fetal livers was stimulated, and this was further enhanced by UDCA treatment. In placenta, only BVRα was up-regulated. In conclusion, bilirubin accumulation and UDCA administration may directly and indirectly protect the placental-fetal unit from maternal cholestasis-induced oxidative stress

Controlling site selectivity in Pd-catalyzed oxidative cross-coupling reactions.

Science.gov (United States)

Lyons, Thomas W; Hull, Kami L; Sanford, Melanie S

2011-03-30

This paper presents a detailed investigation of the factors controlling site selectivity in the Pd-mediated oxidative coupling of 1,3-disubstituted and 1,2,3-trisubstituted arenes (aryl-H) with cyclometalating substrates (L~C-H). The influence of both the concentration and the steric/electronic properties of the quinone promoter are studied in detail. In addition, the effect of steric/electronic modulation of the carboxylate ligand is discussed. Finally, we demonstrate that substitution of the carboxylate for a carbonate X-type ligand leads to a complete reversal in site selectivity for many arene substrates. The origins of these trends in site selectivity are discussed in the context of the mechanism of Pd-catalyzed oxidative cross-coupling.

Quantitative analysis by GC-MS/MS of 18 aroma compounds related to oxidative off-flavor in wines.

Science.gov (United States)

Mayr, Christine M; Capone, Dimitra L; Pardon, Kevin H; Black, Cory A; Pomeroy, Damian; Francis, I Leigh

2015-04-08

A quantitation method for 18 aroma compounds reported to contribute to "oxidative" flavor in wines was developed. The method allows quantitation of the (E)-2-alkenals ((E)-2-hexenal, (E)-2-heptenal, (E)-2-octenal, and (E)-2-nonenal), various Strecker aldehydes (methional, 2-phenylacetaldehyde, 3-methylbutanal, and 2-methylpropanal), aldehydes (furfural, 5-methylfurfural, hexanal, and benzaldehyde), furans (sotolon, furaneol, and homofuraneol), as well as alcohols (methionol, eugenol, and maltol) in the same analysis. The aldehydes were determined after derivatization directly in the wine with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride; the formed oximes along with the underivatized aroma compounds were isolated by solid-phase extraction and analyzed by means of GC-MS/MS. The method was used to investigate the effect of different closures (synthetic closures, natural corks, and screw cap) on the formation of oxidation-related compounds in 14 year old white wine. Results showed a significant increase in the concentration of some of the monitored compounds in the wine, particularly methional, 2-phenylacetaldehyde, and 3-methylbutanal.

Physiology and genetics of sulfur-oxidizing bacteria.

Science.gov (United States)

Friedrich, C G

1998-01-01

Reduced inorganic sulfur compounds are oxidized by members of the domains Archaea and Bacteria. These compounds are used as electron donors for anaerobic phototrophic and aerobic chemotrophic growth, and are mostly oxidized to sulfate. Different enzymes mediate the conversion of various reduced sulfur compounds. Their physiological function in sulfur oxidation is considered (i) mostly from the biochemical characterization of the enzymatic reaction, (ii) rarely from the regulation of their formation, and (iii) only in a few cases from the mutational gene inactivation and characterization of the resulting mutant phenotype. In this review the sulfur-metabolizing reactions of selected phototrophic and of chemotrophic prokaryotes are discussed. These comprise an archaeon, a cyanobacterium, green sulfur bacteria, and selected phototrophic and chemotrophic proteobacteria. The genetic systems are summarized which are presently available for these organisms, and which can be used to study the molecular basis of their dissimilatory sulfur metabolism. Two groups of thiobacteria can be distinguished: those able to grow with tetrathionate and other reduced sulfur compounds, and those unable to do so. This distinction can be made irrespective of their phototrophic or chemotrophic metabolism, neutrophilic or acidophilic nature, and may indicate a mechanism different from that of thiosulfate oxidation. However, the core enzyme for tetrathionate oxidation has not been identified so far. Several phototrophic bacteria utilize hydrogen sulfide, which is considered to be oxidized by flavocytochrome c owing to its in vitro activity. However, the function of flavocytochrome c in vivo may be different, because it is missing in other hydrogen sulfide-oxidizing bacteria, but is present in most thiosulfate-oxidizing bacteria. A possible function of flavocytochrome c is discussed based on biophysical studies, and the identification of a flavocytochrome in the operon encoding enzymes involved

Treatment of reduced sulphur compounds and SO2 by Gas Phase Advanced Oxidation

DEFF Research Database (Denmark)

Meusinger, Carl; Bluhme, Anders Brostrøm; Ingemar, Jonas L.

2017-01-01

Reduced sulphur compounds (RSCs) emitted from pig farms are a major problem for agriculture, due to their health and environmental impacts and foul odour. This study investigates the removal of RSCs, including H2S, and their oxidation product SO2 using Gas Phase Advanced Oxidation (GPAO). GPAO...... is a novel air cleaning technique which utilises accelerated atmospheric chemistry to oxidise pollutants before removing their oxidation products as particles. Removal efficiencies of 24.5% and 3.9% were found for 461 ppb of H2S and 714 ppb of SO2 in a laboratory system (volumetric flow Q = 75 m3/h......). A numerical model of the reactor system was developed to explore the basic features of the system; its output was in fair agreement with the experiment. The model verified the role of OH radicals in initiating the oxidation chemistry. All sulphur removed from the gas phase was detected as particulate matter...

Mechanism of catalytic action of oxide systems in reactions of aldehyde oxidation to carboxylic acids

International Nuclear Information System (INIS)

Andrushkevich, T.V.

1997-01-01

Mechanism of selective action of oxide catalysts (on the base of V 2 O 4 , MoO 3 ) of aldehyde oxidation to acids is considered, reaction acrolein oxidation to acrylic acid is taken as an example. Multistage mechanism of the process is established; it involves consequent transformation of coordination-bonded aldehyde into carbonyl-bonded aldehyde and symmetric carboxylate. Principles of active surface construction are formulated, they take into account the activity of stabilization center of concrete intermediate compound and bond energy of oxygen with surface. (author)

Highly selective oxidation of styrene to benzaldehyde over a tailor-made cobalt oxide encapsulated zeolite catalyst.

Science.gov (United States)

Liu, Jiangyong; Wang, Zihao; Jian, Panming; Jian, Ruiqi

2018-05-01

A tailor-made catalyst with cobalt oxide particles encapsulated into ZSM-5 zeolites (Co 3 O 4 @HZSM-5) was prepared via a hydrothermal method with the conventional impregnated Co 3 O 4 /SiO 2 catalyst as the precursor and Si source. Various characterization results show that the Co 3 O 4 @HZSM-5 catalyst has well-organized structure with Co 3 O 4 particles compatibly encapsulated in the zeolite crystals. The Co 3 O 4 @HZSM-5 catalyst was employed as an efficient catalyst for the selective oxidation of styrene to benzaldehyde with hydrogen peroxide as a green and economic oxidant. The effect of various reaction conditions including reaction time, reaction temperature, different kinds of solvents, styrene/H 2 O 2 molar ratio and catalyst dosage on the catalytic performance were systematically investigated. Under the optimized reaction condition, the yield of benzaldehyde can achieve 78.9% with 96.8% styrene conversion and 81.5% benzaldehyde selectivity. Such an excellent catalytic performance can be attributed to the synergistic effect between the confined reaction environment and the proper acidic property. In addition, the reaction mechanism with Co 3 O 4 @HZSM-5 as the catalyst for the selective oxidation of styrene to benzaldehyde was reasonably proposed. Copyright © 2018 Elsevier Inc. All rights reserved.

Determination of Volatile Organic Compounds in Selected Strains of Cyanobacteria

Directory of Open Access Journals (Sweden)

Ivan Milovanović

2015-01-01

Full Text Available Microalgal biomass can be used in creating various functional food and feed products, but certain species of microalgae and cyanobacteria are known to produce various compounds causing off-flavour. In this work, we investigated selected cyanobacterial strains of Spirulina, Anabaena, and Nostoc genera originating from Serbia, with the aim of determining the chemical profile of volatile organic compounds produced by these organisms. Additionally, the influence of nitrogen level during growth on the production of volatile compounds was investigated for Nostoc and Anabaena strains. In addition, multivariate techniques, namely, principal component analysis (PCA and hierarchical cluster analysis (HCA, were used for making distinction among different microalgal strains. The results show that the main volatile compounds in these species are medium chain length alkanes, but other odorous compounds such as 2-methylisoborneol (0.51–4.48%, 2-pentylfuran (0.72–8.98%, β-cyclocitral (0.00–1.17%, and β-ionone (1.15–2.72% were also detected in the samples. Addition of nitrogen to growth medium was shown to negatively affect the production of 2-methylisoborneol, while geosmin was not detected in any of the analyzed samples, which indicates that the manipulation of growth conditions may be useful in reducing levels of some unwanted odor-causing components.

Method of making metal oxide ceramic powders by using a combustible amino acid compound

Science.gov (United States)

Pederson, Larry R.; Chick, Lawrence A.; Exarhos, Gregory J.

1992-01-01

This invention is directed to the formation of homogeneous, aqueous precursor mixtures of at least one substantially soluble metal salt and a substantially soluble, combustible co-reactant compound, typically an amino acid. This produces, upon evaporation, a substantially homogeneous intermediate material having a total solids level which would support combustion. The homogeneous intermediate material essentially comprises highly dispersed or solvated metal constituents and the co-reactant compound. The intermediate material is quite flammable. A metal oxide powder results on ignition of the intermediate product which combusts same to produce the product powder.

A study on the alkali leaching of complex compound for molybdenum trioxide and ferric oxide

International Nuclear Information System (INIS)

Kim, C.G.; Whang, Y.K.

1981-01-01

This study is to determine the alkali-leaching meachanism by which complex compound by the reaction made between molybdenite (MoS 2 ) and ferric oxide (Fe 2 O 3 ) in the roasted are when molybdenum trioxide (MoO 3 ) is formed by the roasting reaction of molybdenite concentrate. The results obtained from this experiment are summarized as follows: The heating reaction analysis shows that the complex compound of iron molybdates (Fe 2 O 3 .3-4 MoO 3 ) is formed by the reaction of molybdenum trioxide and ferric oxide at temperatures of above 500 0 C. It is shown that at various reaction temperature below 400 0 C molybdenum trioxide is almost completely leached by caustic soda irrespective of the mole ratio of two chemical samples used for the experiment, whereas at temperature above 400 0 C the leaching rate of molybdenum trioxide decreases except that it varies from 70.77% at a temperature of 900 0 C at which the mole ratio is 1 to 1 to 84.08% at a temperature of 1000 0 C. The x-ray diffraction analysis has shown that the complex compound reacted at a temperature of 1000 0 C produces a complex compound with the crystal structure of iron molybdates, and the alkali-leached residues even with 19.0% of molybdenum trioxide, however, contain only α-Fe 2 O 3 , without showing iron molybdates. The crystalline compound of iron molybdates obtained as a result of heating reaction was leached by using caustic soda, while MoO 3 and Fe 2 O 3 in the leaching residue was found to contain other compounds unable to be leached by caustic soda. (author)

Reaction of bromine and chlorine with phenolic compounds and natural organic matter extracts--Electrophilic aromatic substitution and oxidation.

Science.gov (United States)

Criquet, Justine; Rodriguez, Eva M; Allard, Sebastien; Wellauer, Sven; Salhi, Elisabeth; Joll, Cynthia A; von Gunten, Urs

2015-11-15

Phenolic compounds are known structural moieties of natural organic matter (NOM), and their reactivity is a key parameter for understanding the reactivity of NOM and the disinfection by-product formation during oxidative water treatment. In this study, species-specific and/or apparent second order rate constants and mechanisms for the reactions of bromine and chlorine have been determined for various phenolic compounds (phenol, resorcinol, catechol, hydroquinone, phloroglucinol, bisphenol A, p-hydroxybenzoic acid, gallic acid, hesperetin and tannic acid) and flavone. The reactivity of bromine with phenolic compounds is very high, with apparent second order rate constants at pH 7 in the range of 10(4) to 10(7) M(-1) s(-1). The highest value was recorded for the reaction between HOBr and the fully deprotonated resorcinol (k = 2.1 × 10(9) M(-1) s(-1)). The reactivity of phenolic compounds is enhanced by the activating character of the phenolic substituents, e.g. further hydroxyl groups. With the data set from this study, the ratio between the species-specific rate constants for the reactions of chlorine versus bromine with phenolic compounds was confirmed to be about 3000. Phenolic compounds react with bromine or chlorine either by oxidation (electron transfer, ET) or electrophilic aromatic substitution (EAS) processes. The dominant process mainly depends on the relative position of the hydroxyl substituents and the possibility of quinone formation. While phenol, p-hydroxybenzoic acid and bisphenol A undergo EAS, hydroquinone, catechol, gallic acid and tannic acid, with hydroxyl substituents in ortho or para positions, react with bromine by ET leading to quantitative formation of the corresponding quinones. Some compounds (e.g. phloroglucinol) show both partial oxidation and partial electrophilic aromatic substitution and the ratio observed for the pathways depends on the pH. For the reaction of six NOM extracts with bromine, electrophilic aromatic substitution

The Study and Development of Metal Oxide Reactive Adsorbents for the Destruction of Toxic Organic Compounds

National Research Council Canada - National Science Library

Mitchell, Mark B

2008-01-01

... and other toxic organic compounds. The research program that was developed built upon earlier results achieved in the room temperature oxidative decomposition of a chemical warfare agent simulant, dimethyl methylphosphonate (DMMP...

THE DIMINISHING OF THE CONTENT OF TEXTILE DIRECT DYES AND AUXILIARY COMPOUNDS DURING THEIR CATALYTIC OXIDATION

Directory of Open Access Journals (Sweden)

Maria Gonta

2014-06-01

Full Text Available Advanced oxidation methods of organic compounds lead to their partial mineralization and increase of the adsorption process efficiency on the surface of oxidized activated carbon. We have studied the oxidation process using model solutions containing mixture of dye direct brown (DB, ethylene glycol (EGL and sodium lauryl sulfate (SLS under the action of Fenton reagent, in the presence and absence of UV irradiation or under the action of electric current (in the electrochemical cell. The same studies were performed by replacing the iron (II ion with titanium dioxide.

Studies of Deactivation of Methanol to Formaldehyde Selective Oxidation Catalyst

DEFF Research Database (Denmark)

Raun, Kristian Viegaard; Schumann, Max; Høj, Martin

This work presents a study of the deactivation behavior of Fe-Mo oxide catalyst during selective oxidation of methanol to formaldehyde in a period of 5 days. The structural changes in the catalyst have been investigated in situ for the initial 10 h by Raman spectroscopy, and the structure after 5...

A gravimetric method for the determination of oxygen in uranium oxides and ternary uranium oxides by addition of alkaline earth compounds

International Nuclear Information System (INIS)

Fujino, Takeo; Tagawa, Hiroaki; Adachi, Takeo; Hashitani, Hiroshi

1978-01-01

A simple gravimetric determination of oxygen in uranium oxides and ternary uranium oxides is described. In alkaline earth uranates which are formed by heating in air at 800-1100 0 C, uranium is in the hexavalent state over certain continuous ranges of alkaline earth-to-uranium ratios. Thus, if an alkaline earth uranate or a compound containing an alkaline earth element, e.g. MgO, is mixed with the oxide sample and heated in air under suitable conditions, oxygen can be determined from the weight change before and after the reaction. The standard deviation of the O:U ratio for a UOsub(2+x) test sample is +-0.0008-0.001, if a correction is applied for atmospheric moisture absorbed during mixing. (Auth.)

Vanadium-substituted heteropolyacids immobilized on amine- functionalized mesoporous MCM-41: A recyclable catalyst for selective oxidation of alcohols with H{sub 2}O{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Dong, Xinbo [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); Wang, Danjun [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); College of Chemistry Chemical Engineering, Yanan University, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan' an 716000 (China); Li, Kebin [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); Zhen, Yanzhong [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); College of Chemistry Chemical Engineering, Yanan University, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan' an 716000 (China); Hu, Huaiming [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China); Xue, Ganglin, E-mail: xglin707@163.com [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Department of Chemistry (Ministry of Education), Northwest University, Xi' an 710069 (China)

2014-09-15

Graphical abstract: Vanadium-substituted phosphotungstic acids are immobilized on amine- functionalized mesoporous MCM-41 and the hybrid catalyst is proved to be a highly efficient solid catalyst for the oxidation of aromatic alcohols to the corresponding carbonyl compounds with H{sub 2}O{sub 2}, featured by the high conversion and selectivity, easy recovery, and quite steady reuse. - Highlights: • Vanadium-substituted phosphotungstic acid immobilized on amine-functionalized mesoporous MCM-41 are prepared. • HPAs were fixed on the inner surface of mesoporous MCM-41 by chemical bonding to aminosilane groups. • The hybrid catalyst showed much higher catalytic activity than the pure HPAs. • The hybrid catalyst is a highly efficient recyclable solid catalyst for the selective oxidation of aromatic alcohols. - Abstract: New hybrid materials of vanadium-substituted phosphotungstic acids (VHPW) immobilized on amine-functionalized mesoporous MCM-41 (VHPW/MCM-41/NH{sub 2}) are prepared and characterized by FT-IR, XRD, N{sub 2} adsorption, elemental analysis, SEM and TEM for their structural integrity and physicochemical properties. It is found that the structure of the heteropolyacids is retained upon immobilization over mesoporous materials. The catalytic activities of these hybrid materials are tested in the selective oxidation of alcohols to the carbonyl products with 30% aqueous H{sub 2}O{sub 2} as oxidant in toluene. The catalytic activities of different number of vanadium-substituted phosphotungstic acid are investigated, and among the catalysts, H{sub 5}[PV{sub 2}W{sub 10}O{sub 40}] immobilized on amine-functionalized MCM-41 exhibits the highest activity with 97% conversion and 99% selectivity in the oxidation of benzyl alcohol to benzaldehyde. The hybrid catalyst is proved to be a highly efficient recyclable solid catalyst for the selective oxidation of aromatic alcohols to the corresponding aldehydes with H{sub 2}O{sub 2}.

Observations of oxidation products above a forest imply biogenic emissions of very reactive compounds

Directory of Open Access Journals (Sweden)

R. Holzinger

2005-01-01

Full Text Available Vertical gradients of mixing ratios of volatile organic compounds have been measured in a Ponderosa pine forest in Central California (38.90° N, 120.63° W, 1315m. These measurements reveal large quantities of previously unreported oxidation products of short lived biogenic precursors. The emission of biogenic precursors must be in the range of 13-66µmol m-2h-1 to produce the observed oxidation products. That is 6-30 times the emissions of total monoterpenes observed above the forest canopy on a molar basis. These reactive precursors constitute a large fraction of biogenic emissions at this site, and are not included in current emission inventories. When oxidized by ozone they should efficiently produce secondary aerosol and hydroxyl radicals.

Selective oxidation of refractory sulfur compounds for the production of low sulfur transportation fuel

Energy Technology Data Exchange (ETDEWEB)

Jeong, Kwang-Eun; Kim, Tae-Wan; Kim, Joo-Wan; Chae, Ho-Jeong; Kim, Chul-Ung; Jeong, Soon-Yong [Korea Research Institute of Chemical Technology, Daejeon (Korea, Republic of); Park, Young-Kwon [University of Seoul, Seoul (Korea, Republic of)

2013-03-15

The current technologies for achieving low sulfur in diesel fuel are based on hydrotreating, which requires high temperature, high pressure and excessive supply of hydrogen. Oxidative desulfurization (ODS) is considered one of the promising new methods for super deep desulfurization, which could be carried out under very mild conditions (atmospheric pressure, <100 .deg.. C) without consumption of hydrogen. In this paper, development status of ODS process by major licensors are described as well as general concepts of ODS reaction. In addition, the ODS process has been categorized into single phasic and biphasic system according to the oxidants involved. Recent trends in both systems are reviewed in detail and future work is also proposed.

Selective oxidation of refractory sulfur compounds for the production of low sulfur transportation fuel

International Nuclear Information System (INIS)

Jeong, Kwang-Eun; Kim, Tae-Wan; Kim, Joo-Wan; Chae, Ho-Jeong; Kim, Chul-Ung; Jeong, Soon-Yong; Park, Young-Kwon

2013-01-01

The current technologies for achieving low sulfur in diesel fuel are based on hydrotreating, which requires high temperature, high pressure and excessive supply of hydrogen. Oxidative desulfurization (ODS) is considered one of the promising new methods for super deep desulfurization, which could be carried out under very mild conditions (atmospheric pressure, <100 .deg.. C) without consumption of hydrogen. In this paper, development status of ODS process by major licensors are described as well as general concepts of ODS reaction. In addition, the ODS process has been categorized into single phasic and biphasic system according to the oxidants involved. Recent trends in both systems are reviewed in detail and future work is also proposed

Gold-catalyzed oxidation of substituted phenols by hydrogen peroxide

KAUST Repository

Cheneviere, Yohan

2010-10-20

Gold nanoparticles deposited on inorganic supports are efficient catalysts for the oxidation of various substituted phenols (2,6-di-tert-butyl phenol and 2,3,6-trimethyl phenol) with aqueous hydrogen peroxide. By contrast to more conventional catalysts such as Ti-containing mesoporous silicas, which convert phenols to the corresponding benzoquinones, gold nanoparticles are very selective to biaryl compounds (3,3′,5,5′-tetra-tert-butyl diphenoquinone and 2,2′,3,3′,5,5′-hexamethyl-4,4′- biphenol, respectively). Products yields and selectivities depend on the solvent used, the best results being obtained in methanol with yields >98%. Au offers the possibility to completely change the selectivity in the oxidation of substituted phenols and opens interesting perspectives in the clean synthesis of biaryl compounds for pharmaceutical applications. © 2010 Elsevier B.V. All rights reserved.

Effect of high-temperature treatment on Fe/ZSM-5 prepared by chemical vapor deposition of FeCl3. II. Nitrous oxide decomposition, selective oxidation of benzene to phenol, and selective reduction of nitric oxide by isobutane

NARCIS (Netherlands)

Zhu, Q.; Teeffelen, van R.M.; Santen, van R.A.; Hensen, E.J.M.

2004-01-01

The catalytic performance (nitrous oxide decomposition, hydroxylation of benzene to phenol with nitrous oxide, and selective reduction of nitric oxide by i-butane) was evaluated for a set of HZSM-5 and sublimed Fe/ZSM-5 catalysts, which have been extensively characterized in an earlier contribution

Solvent-Free Selective Oxidation of Toluene with O2 Catalyzed by Metal Cation Modified LDHs and Mixed Oxides

Directory of Open Access Journals (Sweden)

Xiaoli Wang

2016-01-01

Full Text Available A series of metal cation modified layered-double hydroxides (LDHs and mixed oxides were prepared and used to be the selective oxidation of toluene with O2. The results revealed that the modified LDHs exhibited much higher catalytic performance than their parent LDH and the modified mixed oxides. Moreover, the metal cations were also found to play important roles in the catalytic performance and stabilities of modified catalysts. Under the optimal reaction conditions, the highest toluene conversion reached 8.7% with 97.5% of the selectivity to benzyldehyde; moreover, the catalytic performance remained after nine catalytic runs. In addition, the reaction probably involved a free-radical mechanism.

A screening method for cardiovascular active compounds in marine algae.

Science.gov (United States)

Agatonovic-Kustrin, S; Kustrin, E; Angove, M J; Morton, D W

2018-05-18

The interaction of bioactive compounds from ethanolic extracts of selected marine algae samples, separated on chromatographic plates, with nitric/nitrous acid was investigated. The nature of bioactive compounds in the marine algae extracts was characterised using UV absorption spectra before and after reaction with diluted nitric acid, and from the characteristic colour reaction after derivatization with anisaldehyde. It was found that diterpenes from Dictyota dichotoma, an edible brown algae, and sterols from green algae Caulerpa brachypus, bind nitric oxide and may act as a nitric oxide carrier. Although the carotenoid fucoxanthin, found in all brown marine algae also binds nitric oxide, the bonds between nitrogen and the fucoxanthin molecule are much stronger. Further studies are required to evaluate the effects of diterpenes from Dictyota dichotoma and sterols from green algae Caulerpa brachypus to see if they have beneficial cardiovascular effects. The method reported here should prove useful in screening large numbers of algae species for compounds with cardiovascular activity. Copyright © 2018 Elsevier B.V. All rights reserved.

Influence of Laccase and Tyrosinase on the Antioxidant Capacity of Selected Phenolic Compounds on Human Cell Lines

Directory of Open Access Journals (Sweden)

Matthias Riebel

2015-09-01

Full Text Available Polyphenolic compounds affect the color, odor and taste of numerous food products of plant origin. In addition to the visual and gustatory properties, they serve as radical scavengers and have antioxidant effects. Polyphenols, especially resveratrol in red wine, have gained increasing scientific and public interest due to their presumptive beneficial impact on human health. Enzymatic oxidation of phenolic compounds takes place under the influence of polyphenol oxidases (PPO, including tyrosinase and laccase. Several studies have demonstrated the radical scavenger effect of plants, food products and individual polyphenols in vitro, but, apart from resveratrol, such impact has not been proved in physiological test systems. Furthermore, only a few data exist on the antioxidant capacities of the enzymatic oxidation products of phenolic compounds generated by PPO. We report here first results about the antioxidant effects of phenolic substances, before and after oxidation by fungal model tyrosinase and laccase. In general, the common chemical 2,2-diphenyl-1-picrylhydrazyl assay and the biological tests using two different types of cell cultures (monocytes and endothelial cells delivered similar results. The phenols tested showed significant differences with respect to their antioxidant activity in all test systems. Their antioxidant capacities after enzymatic conversion decreased or increased depending on the individual PPO used.

Molten salt oxidation as a technique for decommissioning: selection of low melting point salt mixtures

International Nuclear Information System (INIS)

Lainetti, Paulo E.O.; Garcia, Vitor F.; Benvegnu, Guilherme

2013-01-01

During the 70 and 80 years, IPEN built several facilities in pilot scale, destined to the technological domain of the Nuclear Fuel Cycle. In the nineties, radical changes in the Brazilian nuclear policy determined the interruption of the activities and the shut-down of pilot plants. Nowadays, IPEN has been facing the problem of the dismantling and decommissioning of its Nuclear Fuel Cycle old facilities. The facility CELESTE-I of the IPEN is a laboratory where reprocessing studies were accomplished during the decade of 80 and in the beginning of the 90s. The last operations occurred in 92-93. The research activities generated radioactive wastes in the form of organic and aqueous solutions of different compositions and concentrations. For the treatment of these liquid wastes it was proposed a study of waste thermal decomposition based on the molten salt oxidation process.Decomposition tests of different organic wastes have been performed in laboratory equipment developed at IPEN, in the range of temperatures of 900 to 1020 deg C, demonstrating the complete oxidation of the compounds. The reduction of the process temperatures would be of crucial importance. Besides this, the selection of lower melting point salt mixtures would have an important impact in the reduction of equipment costs. Several experiments were performed to determine the most suitable salt mixtures, optimizing costs and melting temperatures as low as possible. This paper describes the main characteristics of the molten salt oxidation process, besides the selection of salt mixtures of binary and ternary compositions, respectively Na 2 CO 3 - NaOH and Na 2 CO 3 - K 2 CO 3 -Li 2 CO 3 . (author)

Flavour Compounds in Fungi

DEFF Research Database (Denmark)

Ravasio, Davide Antonio

. This selection of strains was used in fermentations with the aim of identifying new interesting flavour producers. Fermentation profiles, volatile analyses, off-flavour identification and resistance to osmotic/oxidative stress have been addressed to highlight new candidates to use for industrial applications....... This resulted in the identification of Wickerhamomyces anomalus and Pichia kluyveri as high producers of esters fruity compounds, which contribute to enhance the complexity of wine and beer product. In addition the strain Debaromyces subglobosus showed high yields of aldehydes and fruity ketones, which...

Anti-oxidant activity and attenuation of bladder hyperactivity by the flavonoid compound kaempferol.

Science.gov (United States)

Huang, Yaw-Bin; Lin, Ming-Wei; Chao, Yun; Huang, Chi-Te; Tsai, Yi-Hung; Wu, Pao-Chu

2014-01-01

To evaluate the anti-oxidant activity of the flavonoid compound, kaempferol, and to examine its role in the suppression of oxidative stress and attenuation of bladder hyperactivity in a rat model of bladder injury. The anti-oxidative activity of kaempferol was examined in lipopolysaccharide-treated RAW264.7 macrophages by using flow cytometry. For in vivo studies, rats were pretreated with kaempferol or vehicle for 24 h. The rat urothelium was injured by the administration of protamine sulfate for 1.5 h and irritated by the subsequent infusion of potassium chloride for 4 h. Oxidative stress in the bladder tissue was assessed using chemiluminescence assay, and the bladder pressure was determination by cystomertrogram. Kaempferol significantly suppressed lipopolysaccharide-induced reactive oxygen species production in RAW264.7 rat macrophages. Exposure of the rat bladder to sequential infusion of protamine sulfate and potassium chloride induced bladder hyperactivity. Pretreatment with kaempferol, prevented the formation of reactive oxygen species and prolonged the intercontraction interval. Kaempferol suppresses oxidative stress and attenuates bladder hyperactivity caused by potassium chloride after protamine sulfate-induced bladder injury. © 2013 The Japanese Urological Association.

Distribution of enantiomers of volatile organic compounds in selected fruit distillates.

Science.gov (United States)

Vyviurska, Olga; Zvrškovcová, Helena; Špánik, Ivan

2017-01-01

The enantiomer ratios of chiral volatile organic compounds in fruit distillates were determined by multidimensional gas chromatography using solid-phase microextraction (SPME) as a sample treatment procedure. Linalool and its oxides, limonene, α-terpineol, and nerolidol, were present at the highest concentration levels, while significantly lower amounts of β-citronellol and lactones were found in the studied samples. However, almost all terpenoids mainly occur as a racemic or near-racemic mixture; enantiomer distribution of some chiral organic compounds in fruit distillates correlated to a botanical origin. In particular, a significant enantiomeric excess of (R)-linalool and (S)-α-terpineol was found only for pear brandy, and likewise the dominance (R)-limonene and the second eluted enantiomer of nerolidol for Sorbus domestica and strawberry, respectively. The distribution of γ-lactones stereoisomers was more nonspecific, with a general excess of the R-enantiomer. © 2016 Wiley Periodicals, Inc.

Permanganate oxidation of sulfur compounds to prevent poisoning of Pd catalysts in water treatment processes.

Science.gov (United States)

Angeles-Wedler, Dalia; Mackenzie, Katrin; Kopinke, Frank-Dieter

2008-08-01

The practical application of Pd-catalyzed water treatment processes is impeded by catalyst poisoning by reduced sulfur compounds (RSCs). In this study, the potential of permanganate as a selective oxidant for the removal of microbially generated RSCs in water and as a regeneration agent for S-poisoned catalysts was evaluated. Hydrodechlorination using Pd/Al2O3 was carried out as a probe reaction in permanganate-pretreated water. The activity of the Pd catalysts in the successfully pretreated reaction medium was similar to that in deionized water. The catalyst showed no deactivation behavior in the presence of permanganate at a concentration level or = 0.08 mM, a significant but temporary inhibition of the catalytic dechlorination was observed. Unprotected Pd/Al2O3, which had been completely poisoned by sulfide, was reactivated by a combined treatment with permanganate and hydrazine. However, the anthropogenic water pollutants thiophene and carbon disulfide were resistant against permanganate. Together with the preoxidation of catalyst poisons, hydrophobic protection of the catalysts was studied. Pd/zeolite and various hydrophobically coated catalysts showed a higher stability against ionic poisons and permanganate than the uncoated catalyst. By means of a combination of oxidative water pretreatment and hydrophobic catalyst protection, we provide a new tool to harness the potential of Pd-catalyzed hydrodehalogenation for the treatment of real waters.

Compound specific radiocarbon content of lignin oxidation products from the Altamaha river and Coastal Georgia

International Nuclear Information System (INIS)

Culp, Randy

2013-01-01

Compound-specific isotope analysis (CSIA) is a powerful tool in organic geochemistry by providing detailed information about an individual organic compound’s history with regard to its source and process of formation. Most CSIA involves measurement of the stable isotope ratio of carbon ( 13 C/ 12 C) and hydrogen (D/H) following separation by gas or liquid chromatography. New applications are being developed using compound-specific radiocarbon ( 14 C) content for delineating age of materials, rates of decomposition and residence time in various environments. This paper details the isotopic work on specific lignin monomers derived from terrestrial plants transported and deposited within the Altamaha River, estuary and off-shore Georgia in the Atlantic Ocean. By using gas chromatographic separation and identification of selected lignin oxidation products (LOP), the harvesting of these compounds using preparative fraction collection, and measurement of their 14 C content using accelerator mass spectrometry, details of the age and presence of specific biomarkers unique to a given terrestrial source are revealed. Radiocarbon ages determined from water-column particulate organic carbon and sediment LOPs indicate a range of ages from modern to well over 5,000 years for the former and latter respectively. Transport mechanisms and particle size associations on mineral grains may play a significant role in 14 C distribution in estuary and near-shore coastal environments. This data indicates higher than modern 14 C activities in large particle-size sediment fractions in contrast to older LOP 14 C ages found associated with the same coarse grain sediments. Individual LOP ages substantiate older terrestrial materials persist in the off-shore environment even though in the presence of modern marine 14 C sources.

Effects of selected bioactive food compounds on human white adipocyte function

DEFF Research Database (Denmark)

Björk, Christel; Wilhelm, Uta; Mandrup, Susanne

2016-01-01

BACKGROUND: Previous studies suggest that intake of specific bioactive compounds may have beneficial clinical effects on adipose tissue partly due to their anti-inflammatory and insulin-sensitizing properties. With the overall aim to contribute to better understanding of the mechanisms of selecte...... uptake albeit only with the combination of DHA and AC. Taken together, our results may link the reported health benefits of the selected bioactives on metabolic disorders such as insulin resistance, hypertension and dyslipidemia to effects on white adipocytes....

Development of selective catalytic oxidation (SCO) for NH{sub 3} and HCN removal from gasification gas; Selektiivisen katalyyttisen hapetusprosessin (SCO) kehittaeminen kaasutuskaasun NH{sub 3}:n ja HCN:n poistoon

Energy Technology Data Exchange (ETDEWEB)

Leppaelahti, J.; Koljonen, T.; Heiskanen, K. [VTT Energy, Espoo (Finland)

1997-10-01

In gasification, reactive nitrogen compounds (mainly NH{sub 3} and HCN) are formed from fuel nitrogen. If the gas containing NH{sub 3} is burned, a high NO{sub x} emission may be formed. The content of nitrogen compounds of the hot gasification gas could be reduced in Selective Catalytic Oxidation (SCO) process. In this process small amounts of reactive oxidisers are injected into the gas in order to convert NH{sub 3} to N{sub 2}. The utilization of SCO process together with low NO{sub x} burners in advanced gasification power stations might offer an alternative for flue gas treatment technologies like SCR (Selective Catalytic Reduction). In the earlier research, conditions were found, where oxidizers reacted selectively with ammonia in the gasification gas. Highest ammonia reduction took place in the aluminium oxide bed in the presence of NO and O{sub 2}. The aim of this study is to examine the reaction mechanism in order to be able to further evaluate the development possibilities of this kind process. The effect of composition and the amount of added oxidizer, the content of combustible gas components, space velocity, pressure and temperature will be studied. The experiments are carried out with the laboratory scale high pressure flow reactor of VTT Energy. Kinetic modelling of the experimental results is carried out in co-operation with the combustion chemistry group of Aabo Akademi. The aim of the modelling work is to bring insight to the gas-phase reactions that are important for the SCO-process. (orig.)

Crystallization inhibitors for amorphous oxides

International Nuclear Information System (INIS)

Reznitskij, L.A.; Filippova, S.E.

1993-01-01

Data for the last 10 years, in which experimental results of studying the temperature stabilization of x-ray amorphous oxides (including R 3 Fe 5 O 12 R-rare earths, ZrO 2 , In 2 O 3 , Sc 2 O 3 ) and their solid solution are presented, are generalized. Processes of amorphous oxide crystallization with the production of simple oxides, solid solutions and chemical compounds with different polyhedral structure, are investigated. Energy and crystallochemical criteria for selecting the doping inhibitor-components stabilizing the amorphous state are ascertained, temperatures and enthalpies of amorpous oxide crystallization are determined, examination of certain provisions of iso,orphous miscibility theory is conducted

Reactivity of lignin and problems of its oxidative destruction with peroxy reagents

International Nuclear Information System (INIS)

Demin, Valerii A; Shereshovets, Valerii V; Monakov, Yurii B

1999-01-01

Published data on reactivity and oxidation of lignin and model compounds with hydrogen peroxide, ozone and chlorine dioxide as well as on oxidative destruction of the sulfate pulp lignin with various reagents during bleaching are systematised and generalised. Concepts of lignin activation towards its selective oxidation and kinetic features of sulfate pulp oxidative delignification are considered. The bibliography includes 157 references.

Photocatalytic oxidation of organic compounds in a hybrid system composed of a molecular catalyst and visible light-absorbing semiconductor.

Science.gov (United States)

Zhou, Xu; Li, Fei; Li, Xiaona; Li, Hua; Wang, Yong; Sun, Licheng

2015-01-14

Photocatalytic oxidation of organic compounds proceeded efficiently in a hybrid system with ruthenium aqua complexes as catalysts, BiVO4 as a light absorber, [Co(NH3)5Cl](2+) as a sacrificial electron acceptor and water as an oxygen source. The photogenerated holes in the semiconductor are used to oxidize molecular catalysts into the high-valent Ru(IV)=O intermediates for 2e(-) oxidation.

Aerosol generation by oxidation and combustion of plutonium and its compounds: literature survey

International Nuclear Information System (INIS)

Ballereau, P.

1987-09-01

Generation of aerosols by oxidation or combustion is one of the greatest risks due to plutonium. A review is made of the most interesting documents available on this topic. Following a brief study of plutonium oxydation conditions, characteristics of aerosols generated by accidents of fires involving metallic Pu and some of its compounds are assessed. Nuclear weapons are not included in this review [fr

Selectivity and Activity of Iron Molybdate Catalysts in Oxidation of Methanol

OpenAIRE

Khalid Khazzal Hummadi; Karim H. Hassan; Phillip C.H. Mitchell

2009-01-01

The selectivity and activity of iron molybdate catalysts prepared by different methods are compared with those of a commercial catalyst in the oxidation of methanol to formaldehyde in a continuous tubular bed reactor at 200-350 oC (473-623 oK), 10 atm (1013 kPa), with a methanol-oxygen mixture fixed at 5.5% by volume methanol: air ratio. The iron(III) molybdate catalyst prepared by co-precipitation and filtration had a selectivity towards formaldehyde in methanol oxidation comparable with a c...

Intramolecular charge separation in spirobifluorene-based donor–acceptor compounds adsorbed on Au and indium tin oxide electrodes

International Nuclear Information System (INIS)

Heredia, Daniel; Otero, Luis; Gervaldo, Miguel; Fungo, Fernando; Dittrich, Thomas; Lin, Chih-Yen; Chi, Liang-Chen; Fang, Fu-Chuan; Wong, Ken-Tsung

2013-01-01

Surface photovoltage (SPV) measurements were performed with a Kelvin-probe in spirobifluorene-based donor (diphenylamine)–acceptor (dicyano or cyanoacrylic acid moieties) compounds adsorbed from highly diluted solutions onto Au and indium tin oxide electrode surfaces. Strong intramolecular charge separation (negative SPV signals up to more than 0.1 V) due to directed molecule adsorption was observed only for spirobifluorene donor–acceptor compounds with carboxylic acid moiety. SPV signals and onset energies of electronic transitions depended on ambience conditions. - Highlights: ► Fluorene donor–acceptor derivatives were adsorbed at Au and indium tin oxide. ► Surface photovoltage measurements were performed with a Kelvin-probe. ► Strong intra-molecular charge separation was observed. ► SPV signals depended on ambience conditions

Garlic Sulfur Compounds Suppress Cancerogenesis and Oxidative Stress: a Review

Directory of Open Access Journals (Sweden)

Dvořáková M.

2015-06-01

Full Text Available Garlic has long been considered a food with many health benefits. Several studies have confirmed that sulfur compounds are responsible for the positive effects of garlic on organisms. Garlic acts as an antioxidant by increasing antioxidant enzyme activity, reducing reactive oxygen species generation, and protecting proteins and lipids from oxidation. Garlic suppresses carcinogenesis through several mechanisms: (1 it reduces oxidative stress, and therefore, prevents damage to DNA; (2 it induces apoptosis or cell cycle arrest in cancer cells; and (3 it modifies gene expression through histon acetylation. The positive effects of garlic could be mediated by several mechanisms. It influences signalling pathways of gasotransmitters such as hydrogen sulfide. Garlic enhances hydrogen sulfide production both through its direct release and through an increase in activity of enzymes which produce hydrogen sulfide. Hydrogen sulfide acts as a signalling molecule in various tissues and participates in the regulation of many physiological processes. We can presume that garlic, which is able to release hydrogen sulfide, exhibits effects similar to those of this gasotransmitter.

Electrochemical oxidation of selective estrogen receptor modulator raloxifene

International Nuclear Information System (INIS)

Li, Xi-Qian; He, Jian-Bo; Liu, Lu; Cui, Ting

2013-01-01

Highlights: ► Application and analysis of in situ thin-layer spectroelectrochemistry. ► Cyclic voltabsorptometry used for a drug study. ► Highly pH-dependent oxidative metabolism of raloxifene. ► A complex parallel-consecutive mechanism proposed for oxidation of raloxifene. -- Abstract: Raloxifene is a selective estrogen receptor modulator that may produce toxic oxidative species in metabolism. The oxidation mechanism of raloxifene with different pH values was studied by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), in situ UV–vis spectral analysis and cyclic voltabsorptometry based on a long optical-path thin-layer electrochemical cell. Time-derivative cyclic voltabsorptograms were obtained for comparative discussion with the corresponding cyclic voltammograms. Raloxifene was initially oxidized to reactive phenoxyl radicals, followed by a series of transformation steps leading to different final products in different pH media. A parallel-consecutive reaction mechanism was proposed for the pH-dependent formation of 7-hydroxyraloxifene, raloxifene 6,7-o-quinone and two raloxifene dimers, each pathway following a complex electrochemical-chemical mechanism. Both raloxifene diquinone methide and its N-oxides were not detected by in situ UV–vis spectroscopy and XPS analysis. This work provides an electrochemical viewpoint and comparable information for better understanding of the oxidative metabolism and chemical toxicology of raloxifene under physiological conditions in vivo or in vitro

Formation of nitrogen-containing compounds during slow pyrolysis and oxidation of petroleum coke

Energy Technology Data Exchange (ETDEWEB)

Furimsky, E.; Ohtsuka, Y. [IMAF Group, Ottawa, ON (Canada)

1997-09-01

The petroleum coke from a fluid coking process was pyrolyzed in helium and oxidized in 1% and 4% O{sub 2} and in air, with the aim to determine N-containing compounds such as HCN, NH{sub 3}, NO, and N{sub 2}O. The experiments were performed with and without limestone. NO was the major product during all oxidation runs. N{sub 2}O was formed only in air. In this case, N{sub 2}O formation was delayed when compared with that of NO. The addition of limestone decreased formation of HCN and increased that of NH{sub 3}, whereas NO formation was least affected. 36 refs., 8 figs., 6 tabs.

Properties of tritium and its compounds

International Nuclear Information System (INIS)

Belovodskij, L.F.; Gaevoj, V.K.; Grishmanovskij, V.I.

1985-01-01

Ways of tritium preparation and different aspects of its application are considered. Physicochemical properties of this isotope and some compounds of it - tritium oxides, lithium, titanium, zirconium, uranium tritides, tritium organic compounds - are discussed. In particular, diffusion of tritium and its oxide through different materials, tritium oxidation processes, decomposition of tritium-containing compounds under the action of self-radiation are considered. Main radiobiological tritium properties are described

Reactivity Of Radiolytically-Produced Nitrogen Oxide Radicals Toward Aromatic Compounds

International Nuclear Information System (INIS)

Elias, Gracy

2010-01-01

radiolysis of the modifier (Cs-7SB), which solvates both metal complexes, is responsible for this change. These reactions presumably occur due to reactions with radiolytically-produced nitrogen-centered radicals like (sm b ullet)NO, (sm b ullet)NO 2 and (sm b ullet)NO 3 . Anisole (C 6 H 5 -OCH 3 ) was used in this study as a surrogate for Cs-7SB, since both are aryl ethers. Toluene was used as a surrogate for Cs-7SB because of the alkyl group on the benzene ring in both molecules. Anisole, highly reactive in acids, is a small molecule compared to Cs-7SB and the nitration products are easier to identify compared to those for the larger Cs-7SB molecule. Toluene is less reactive than anisole. Therefore, the highly reactive anisole and the less reactive toluene were considered in this study as model compounds to compare the reaction mechanisms and the nitrated products in acidic media under irradiation. Experiments were designed to elucidate the mechanism of the nitration of aromatic rings in γ-irradiated aqueous nitric acid. Since a suite of radical and ionic reactive species are produced in this condensed-phase system, solutions of nitric acid, neutral nitrate and neutral nitrite were irradiated in separate experiments to isolate selected reactive species. Product nitration species were assessed by high performance liquid chromatography (HPLC) with a reversed phase C-18 column and photodiode array detector. The nitrated anisole product distributions were the same with and without radiation in acidic solution, although more products were formed with radiation. In the irradiated acidic condensed phase, radiation-enhanced nitrous acid-catalyzed nitrosonium ion electrophilic aromatic substitution followed by oxidation reactions dominated over radical addition reactions. In contrast, the distribution of nitrated derivatives for toluene showed nitronium ion electrophilic substitution in the unirradiated acidic medium as a result of thermal nitration only at elevated temperatures

Color-selective photodetection from intermediate colloidal quantum dots buried in amorphous-oxide semiconductors.

Science.gov (United States)

Cho, Kyung-Sang; Heo, Keun; Baik, Chan-Wook; Choi, Jun Young; Jeong, Heejeong; Hwang, Sungwoo; Lee, Sang Yeol

2017-10-10

We report color-selective photodetection from intermediate, monolayered, quantum dots buried in between amorphous-oxide semiconductors. The proposed active channel in phototransistors is a hybrid configuration of oxide-quantum dot-oxide layers, where the gate-tunable electrical property of silicon-doped, indium-zinc-oxide layers is incorporated with the color-selective properties of quantum dots. A remarkably high detectivity (8.1 × 10 13 Jones) is obtained, along with three major findings: fast charge separation in monolayered quantum dots; efficient charge transport through high-mobility oxide layers (20 cm 2  V -1  s -1 ); and gate-tunable drain-current modulation. Particularly, the fast charge separation rate of 3.3 ns -1 measured with time-resolved photoluminescence is attributed to the intermediate quantum dots buried in oxide layers. These results facilitate the realization of efficient color-selective detection exhibiting a photoconductive gain of 10 7 , obtained using a room-temperature deposition of oxide layers and a solution process of quantum dots. This work offers promising opportunities in emerging applications for color detection with sensitivity, transparency, and flexibility.The development of highly sensitive photodetectors is important for image sensing and optical communication applications. Cho et al., report ultra-sensitive photodetectors based on monolayered quantum dots buried in between amorphous-oxide semiconductors and demonstrate color-detecting logic gates.

Beta-galactosidase catalyzed selective galactosylation of aromatic compounds.

Science.gov (United States)

Bridiau, Nicolas; Taboubi, Selma; Marzouki, Nejib; Legoy, Marie Dominique; Maugard, Thierry

2006-01-01

A new approach to galacto-oligosaccharides and galacto-conjugates synthesis performed by the beta-galactosidase from Kluyveromyces lactis is reported. The enzymatic galactosylation of eight kinds of adsorbed aromatic primary alcohols, in particular the two drugs guaifenesin and chlorphenesin, gave the corresponding beta-D-galacto-pyranosides in yields ranging between approximately 10% and 96%. For the first time, we have showed that the adsorption of acceptor substrates onto solid supports such as silica gel influences the yield and the selectivity of galacto-conjugates synthesis. In particular, we observed that adsorption of acceptor favored the synthesis of digalactosylated compounds.

Size-Selective Oxidation of Aldehydes with Zeolite Encapsulated Gold Nanoparticles

DEFF Research Database (Denmark)

Højholt, Karen Thrane; Laursen, Anders Bo; Kegnæs, Søren

2011-01-01

Here, we report a synthesis and catalytic study of hybrid materials comprised of 1–3 nm sinter-stable Au nanoparticles in MFI-type zeolites. An optional post-treatment in aqua regia effectively remove Au from the external surfaces. The size-selective aerobic aldehyde oxidation verifies that the a......Here, we report a synthesis and catalytic study of hybrid materials comprised of 1–3 nm sinter-stable Au nanoparticles in MFI-type zeolites. An optional post-treatment in aqua regia effectively remove Au from the external surfaces. The size-selective aerobic aldehyde oxidation verifies...... that the active Au is accessible only through the zeolite micropores....

Selective Extraction of Perrhenate and Pertechnetate by New Macrocyclic Compounds

International Nuclear Information System (INIS)

Paviet-Hartmann, Patricia; Horkley, Jared; Wolfrom, Earle; Pak, Joshua

2008-01-01

The long half-life of technetium-99 and its ability to form an anionic species makes it a major concern when considering long-term disposal of high-level radioactive waste. Furthermore, as its most stable species in the environment, the pertechnetate ion, TcO 4 - is highly mobile and is considered as a long-term hazard in nuclear waste disposal. There is a need for the development of new extractant systems, such as systems based on crown ethers that may serve to selectively extract and separate this long lived radionuclide from different streams for potential industrial application. In this paper, we are reporting the design and synthesis of new macrocyclic compounds to selectively extract technetium and rhenium from complex mixtures. Preliminary tests performed for the selective extraction of pertechnetate and perrhenate are presented. (authors)

submitter Elemental composition and clustering behaviour of α-pinene oxidation products for different oxidation conditions

CERN Document Server

Praplan, A P; Bianchi, F; Rissanen, M P; Ehn, M; Jokinen, T; Junninen, H; Adamov, A; Amorim, A; Dommen, J; Duplissy, J; Hakala, J; Hansel, A; Heinritzi, M; Kangasluoma, J; Kirkby, J; Krapf, M; Kürten, A; Lehtipalo, K; Riccobono, F; Rondo, L; Sarnela, N; Simon, M; Tomé, A; Tröstl, J; Winkler, P M; Williamson, C; Ye, P; Curtius, J; Baltensperger, U; Donahue, N M; Kulmala, M; Worsnop, D R

2015-01-01

This study presents the difference between oxidised organic compounds formed by α-pinene oxidation under various conditions in the CLOUD environmental chamber: (1) pure ozonolysis (in the presence of hydrogen as hydroxyl radical (OH) scavenger) and (2) OH oxidation (initiated by nitrous acid (HONO) photolysis by ultraviolet light) in the absence of ozone. We discuss results from three Atmospheric Pressure interface Time-of-Flight (APi-TOF) mass spectrometers measuring simultaneously the composition of naturally charged as well as neutral species (via chemical ionisation with nitrate). Natural chemical ionisation takes place in the CLOUD chamber and organic oxidised compounds form clusters with nitrate, bisulfate, bisulfate/sulfuric acid clusters, ammonium, and dimethylaminium, or get protonated. The results from this study show that this process is selective for various oxidised organic compounds with low molar mass and ions, so that in order to obtain a comprehensive picture of the elemental composition o...

Isotopically modified compounds

International Nuclear Information System (INIS)

Kuruc, J.

2009-01-01

In this chapter the nomenclature of isotopically modified compounds in Slovak language is described. This chapter consists of following parts: (1) Isotopically substituted compounds; (2) Specifically isotopically labelled compounds; (3) Selectively isotopically labelled compounds; (4) Non-selectively isotopically labelled compounds; (5) Isotopically deficient compounds.

Effect of selective removal of organic matter and iron oxides on the ...

African Journals Online (AJOL)

The effect of selective removal of organic matter and amorphous and crystalline iron oxides on N2-BET specific surface areas of some soil clays was evaluated. Clay fractions from 10 kaolinitic tropical soils were successively treated to remove organic matter by oxidation with Na hypochlorite, amorphous Fe oxide with acid ...

Nanostructure and Volatile Organic Compounds Sensing Properties of α-Fe2O3/Reduced Graphene Oxide Nanocomposite Derived by Spray Method

Science.gov (United States)

Zolghadr, S.; Kimiagar, S.; Khojier, K.

2017-12-01

This paper investigates the α-Fe2O3/reduced graphene oxide (rGO) nanocomposite as a volatile organic compounds (VOCs) sensor. The α-Fe2O3/reduced graphene oxide nanocomposites of about 370 nm thickness were synthesized by a spray method with different rGO contents (3%, 4%, and 5%) on SiO2/Si substrates. The samples were structurally and morphologically characterized by x-ray diffraction, and field emission scanning electron microscopy. These analyses showed that an increase in rGO content decreases the crystallinity of the samples. In order to study the VOCs sensing properties, the sensitivity and selectivity of the samples were tested with different VOCs vapors including ethanol, methanol, toluene, benzene, and formic acid in the temperature range of 200-400°C. The results show that the α-Fe2O3/rGO nanocomposites are more selective to ethanol than the other vapors, while an increase in rGO content decreases the sensitivity of the samples. The α-Fe2O3/rGO (3%)-based ethanol sensor also shows a good stability with respect to relative humidity in the range of 20-50% with a 1-ppm detection limit at the operating temperature of 280°C.

Cuprous oxide nanoparticles selectively induce apoptosis of tumor cells

Science.gov (United States)

Wang, Ye; Zi, Xiao-Yuan; Su, Juan; Zhang, Hong-Xia; Zhang, Xin-Rong; Zhu, Hai-Ying; Li, Jian-Xiu; Yin, Meng; Yang, Feng; Hu, Yi-Ping

2012-01-01

In the rapid development of nanoscience and nanotechnology, many researchers have discovered that metal oxide nanoparticles have very useful pharmacological effects. Cuprous oxide nanoparticles (CONPs) can selectively induce apoptosis and suppress the proliferation of tumor cells, showing great potential as a clinical cancer therapy. Treatment with CONPs caused a G1/G0 cell cycle arrest in tumor cells. Furthermore, CONPs enclosed in vesicles entered, or were taken up by mitochondria, which damaged their membranes, thereby inducing apoptosis. CONPs can also produce reactive oxygen species (ROS) and initiate lipid peroxidation of the liposomal membrane, thereby regulating many signaling pathways and influencing the vital movements of cells. Our results demonstrate that CONPs have selective cytotoxicity towards tumor cells, and indicate that CONPs might be a potential nanomedicine for cancer therapy. PMID:22679374

Evaluating Acidithiobacillus ferrooxidans bacterial oxidation of sulphur compounds using FTIR and X-ray diffraction assays

Directory of Open Access Journals (Sweden)

Alexandra Muñoz

2003-01-01

Full Text Available A native bacterial strain capable of oxidising ferrous iron and sulphur compounds was isolated from effluent and material from the La Maruja gold mine in the municipality of Marmato (Caldas; this was biochemically identified as being Acidithiobacillus ferrooxidans. This strain's ability to oxidise metallic sulphide concentrates having two differ-ent pulp proportions and two particle sizes was evaluated. Sulphide bio-oxidation was observed after 15 days showing this strain's catalytic action on the mineral break-down process. Key words: bio-oxidation; bio-leaching; A. ferrooxidans; sulphides

Phenolic Compounds Protect Cultured Hippocampal Neurons against Ethanol-Withdrawal Induced Oxidative Stress

Directory of Open Access Journals (Sweden)

Marianna E. Jung

2009-04-01

Full Text Available Ethanol withdrawal is linked to elevated oxidative damage to neurons. Here we report our findings on the contribution of phenolic antioxidants (17β-estradiol, p-octyl-phenol and 2,6-di-tert-butyl-4-methylphenol to counterbalance sudden ethanol withdrawal-initiated oxidative events in hippocampus-derived cultured HT-22 cells. We showed that ethanol withdrawal for 4 h after 24-h ethanol treatment provoked greater levels of oxidative damage than the preceding ethanol exposure. Phenolic antioxidant treatment either during ethanol exposure or ethanol withdrawal only, however, dose-dependently reversed cellular oxidative damage, as demonstrated by the significantly enhanced cell viability, reduced malondialdehyde production and protein carbonylation, compared to untreated cells. Interestingly, the antioxidant treatment schedule had no significant impact on the observed neuroprotection. In addition, the efficacy of the three phenolic compounds was practically equipotent in protecting HT-22 cells in spite of predictions based on an in silico study and a cell free assay of lipid peroxidation. This finding implies that free-radical scavenging may not be the sole factor responsible for the observed neuroprotection and warrants further studies to establish, whether the HT-22 line is indeed a suitable model for in vitro screening of antioxidants against EW-related neuronal damage.

Activation of Persulfates by Graphitized Nanodiamonds for Removal of Organic Compounds.

Science.gov (United States)

Lee, Hongshin; Kim, Hyoung-Il; Weon, Seunghyun; Choi, Wonyong; Hwang, Yu Sik; Seo, Jiwon; Lee, Changha; Kim, Jae-Hong

2016-09-20

This study introduces graphited nanodiamond (G-ND) as an environmentally friendly, easy-to-regenerate, and cost-effective alternative catalyst to activate persulfate (i.e., peroxymonosulfate (PMS) and peroxydisulfate (PDS)) and oxidize organic compounds in water. The G-ND was found to be superior for persulfate activation to other benchmark carbon materials such as graphite, graphene, fullerene, and carbon nanotubes. The G-ND/persulfate showed selective reactivity toward phenolic compounds and some pharmaceuticals, and the degradation kinetics were not inhibited by the presence of oxidant scavengers and natural organic matter. These results indicate that radical intermediates such as sulfate radical anion and hydroxyl radical are not majorly responsible for this persulfate-driven oxidation of organic compounds. The findings from linear sweep voltammetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, and electron paramagnetic resonance spectroscopy analyses suggest that the both persulfate and phenol effectively bind to G-ND surface and are likely to form charge transfer complex, in which G-ND plays a critical role in mediating facile electron transfer from phenol to persulfate.

Thiophene Conversion and Ethanol Oxidation on SiO2-Supported 12-PMoV-Mixed Heteropoly Compounds

Czech Academy of Sciences Publication Activity Database

Spojakina, A. A.; Kostova, N. G.; Sow, Bineta; Stamenova, M. W.; Jirátová, Květa

2001-01-01

Roč. 65, 2-4 (2001), s. 315-321 ISSN 0920-5861 Institutional research plan: CEZ:AV0Z4072921 Keywords : thiophene conversion * ethanol oxidation * mixed heteropoly compounds Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.333, year: 2001

1,3-Dipolar cycloaddition reactions of nitrile oxides in the synthesis of natural compounds and their analogues

International Nuclear Information System (INIS)

Kotyatkina, Anna I; Zhabinsky, Vladimir N; Khripach, Vladimir A

2001-01-01

The published data on the use of 1,3-dipolar cycloaddition reactions of nitrile oxides in the synthesis of natural compounds and their analogues are systematised and reviewed. The bibliography includes 145 references.

Quantitative and qualitative sensing techniques for biogenic volatile organic compounds and their oxidation products.

Science.gov (United States)

Kim, Saewung; Guenther, Alex; Apel, Eric

2013-07-01

The physiological production mechanisms of some of the organics in plants, commonly known as biogenic volatile organic compounds (BVOCs), have been known for more than a century. Some BVOCs are emitted to the atmosphere and play a significant role in tropospheric photochemistry especially in ozone and secondary organic aerosol (SOA) productions as a result of interplays between BVOCs and atmospheric radicals such as hydroxyl radical (OH), ozone (O3) and NOX (NO + NO2). These findings have been drawn from comprehensive analysis of numerous field and laboratory studies that have characterized the ambient distribution of BVOCs and their oxidation products, and reaction kinetics between BVOCs and atmospheric oxidants. These investigations are limited by the capacity for identifying and quantifying these compounds. This review highlights the major analytical techniques that have been used to observe BVOCs and their oxidation products such as gas chromatography, mass spectrometry with hard and soft ionization methods, and optical techniques from laser induced fluorescence (LIF) to remote sensing. In addition, we discuss how new analytical techniques can advance our understanding of BVOC photochemical processes. The principles, advantages, and drawbacks of the analytical techniques are discussed along with specific examples of how the techniques were applied in field and laboratory measurements. Since a number of thorough review papers for each specific analytical technique are available, readers are referred to these publications rather than providing thorough descriptions of each technique. Therefore, the aim of this review is for readers to grasp the advantages and disadvantages of various sensing techniques for BVOCs and their oxidation products and to provide guidance for choosing the optimal technique for a specific research task.

4β-Hydroxywithanolide E selectively induces oxidative DNA damage for selective killing of oral cancer cells.

Science.gov (United States)

Tang, Jen-Yang; Huang, Hurng-Wern; Wang, Hui-Ru; Chan, Ya-Ching; Haung, Jo-Wen; Shu, Chih-Wen; Wu, Yang-Chang; Chang, Hsueh-Wei

2018-03-01

Reactive oxygen species (ROS) induction had been previously reported in 4β-hydroxywithanolide (4βHWE)-induced selective killing of oral cancer cells, but the mechanism involving ROS and the DNA damage effect remain unclear. This study explores the role of ROS and oxidative DNA damage of 4βHWE in the selective killing of oral cancer cells. Changes in cell viability, morphology, ROS, DNA double strand break (DSB) signaling (γH2AX foci in immunofluorescence and DSB signaling in western blotting), and oxidative DNA damage (8-oxo-2'deoxyguanosine [8-oxodG]) were detected in 4βHWE-treated oral cancer (Ca9-22) and/or normal (HGF-1) cells. 4βHWE decreased cell viability, changed cell morphology and induced ROS generation in oral cancer cells rather than oral normal cells, which were recovered by a free radical scavenger N-acetylcysteine (NAC). For immunofluorescence, 4βHWE also accumulated more of the DSB marker, γH2AX foci, in oral cancer cells than in oral normal cells. For western blotting, DSB signaling proteins such as γH2AX and MRN complex (MRE11, RAD50, and NBS1) were overexpressed in 4βHWE-treated oral cancer cells in different concentrations and treatment time. In the formamidopyrimidine-DNA glycolyase (Fpg)-based comet assay and 8-oxodG-based flow cytometry, the 8-oxodG expressions were higher in 4βHWE-treated oral cancer cells than in oral normal cells. All the 4βHWE-induced DSB and oxidative DNA damage to oral cancer cells were recovered by NAC pretreatment. Taken together, the 4βHWE selectively induced DSB and oxidative DNA damage for the ROS-mediated selective killing of oral cancer cells. © 2017 Wiley Periodicals, Inc.

Selective C(sp3 )-H Aerobic Oxidation Enabled by Decatungstate Photocatalysis in Flow.

Science.gov (United States)

Laudadio, Gabriele; Govaerts, Sebastian; Wang, Ying; Ravelli, Davide; Koolman, Hannes F; Fagnoni, Maurizio; Djuric, Stevan W; Noël, Timothy

2018-04-03

A mild and selective C(sp 3 )-H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both activated and unactivated C-H bonds (30 examples). The ability to selectively oxidize natural scaffolds, such as (-)-ambroxide, pregnenolone acetate, (+)-sclareolide, and artemisinin, exemplifies the utility of this new method. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Ionic liquid [OMIm][OAc] directly inducing oxidation cleavage of the β-O-4 bond of lignin model compounds.

Science.gov (United States)

Yang, Yingying; Fan, Honglei; Meng, Qinglei; Zhang, Zhaofu; Yang, Guanying; Han, Buxing

2017-08-03

We explored the oxidation reactions of lignin model compounds directly induced by ionic liquids under metal-free conditions. In this work, it was found that ionic liquid 1-octyl-3-methylimidazolium acetate as a solvent could promote the aerobic oxidation of lignin model compound 2-phenoxyacetophenone (1) and the yields of phenol and benzoic acid from 1 could be as high as 96% and 86%, respectively. A possible reaction pathway was proposed based on a series of control experiments. An acetate anion from the ionic liquid attacked the hydrogen from the β-carbon thereby inducing the cleavage of the C-O bond of the aromatic ether. Furthermore, it was found that 2-(2-methoxyphenoxy)-1-phenylethanone (4) with a methoxyl group could also be transformed into aromatic products in this simple reaction system and the yields of phenol and benzoic acid from 4 could be as high as 98% and 85%, respectively. This work provides a simple way for efficient transformation of lignin model compounds.

Gas-phase fragmentation of coordination compounds: loss of CO(2) from inorganic carbonato complexes to give metal oxide ions

Science.gov (United States)

Dalgaard; McKenzie

1999-10-01

Using electrospray ionization mass spectrometry, novel transition metal oxide coordination complex ions are proposed as the products of the collision-induced dissociation (CID) of some carbonato complex ions through the loss of a mass equivalent to CO(2). CID spectra of [(tpa)CoCO(3)](+) (tpa = tris(2-pyridylmethyl)methylamine), [(bispicMe(2)en)Fe(&mgr;-O)(&mgr;-CO(3))Fe(bispicMe(2)en)]2+ (bispicMe(2)en = N,N'-dimethyl-N,N'-bis(2-pyridylmethy)eth- ane-1, 2-diamine) and [(bpbp)Cu(2)CO(3)](+) (bpbp(-) = bis[(bis-(2-pyridylmethyl)amino)methyl]-4-tertbutylpheno-lato(1-)), show peaks assigned to the mono- and dinuclear oxide cations, [(tpa)CoO](+), [(bispicMe(2)en)(2)Fe(2)(O)(2)]2+ and [(bpbp)Cu(2)O](+), as the dominant species. These results can be likened to the reverse of typical synthetic reactions in which metal hydroxide compounds react with CO(2) to give metal carbonato compounds. Because of the lack of available protons in the gas phase, novel oxide species rather than the more common hydroxide ions are generated. These oxide ions are relevant to the highly oxidizing species proposed in oxygenation reactions catalysed by metal oxides and metalloenzymes. Copyright 1999 John Wiley & Sons, Ltd.

Simple Copper Catalysts for the Aerobic Oxidation of Amines: Selectivity Control by the Counterion.

Science.gov (United States)

Xu, Boran; Hartigan, Elizabeth M; Feula, Giancarlo; Huang, Zheng; Lumb, Jean-Philip; Arndtsen, Bruce A

2016-12-19

We describe the use of simple copper-salt catalysts in the selective aerobic oxidation of amines to nitriles or imines. These catalysts are marked by their exceptional efficiency, operate at ambient temperature and pressure, and allow the oxidation of amines without expensive ligands or additives. This study highlights the significant role counterions can play in controlling selectivity in catalytic aerobic oxidations. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mixing-assisted oxidative desulfurization of model sulfur compounds using polyoxometalate/H2O2 catalytic system

OpenAIRE

Angelo Earvin Sy Choi; Susan Roces; Nathaniel Dugos; Meng-Wei Wan

2016-01-01

Desulfurization of fossil fuel derived oil is needed in order to comply with environmental regulations. Dibenzothiophene and benzothiophene are among the predominant sulfur compound present in raw diesel oil. In this study, mixing-assisted oxidative desulfurization of dibenzothiophene and benzothiophene were carried out using polyoxometalate/H2O2 systems and a phase transfer agent. The effects of reaction time (2–30 min) and temperature (30–70 °C) were examined in the oxidation of model sulfu...

Selective Extraction of Perrhenate and Pertechnetate by New Macrocyclic Compounds

Energy Technology Data Exchange (ETDEWEB)

Paviet-Hartmann, Patricia; Horkley, Jared; Wolfrom, Earle [Idaho State University/Idaho National Laboratory, 1776 Science Center Drive, Idaho Falls, ID 83402 (United States); Pak, Joshua [Idaho State University, 921 S. 8th Avenue, Pocatello, ID 83209 (United States)

2008-07-01

The long half-life of technetium-99 and its ability to form an anionic species makes it a major concern when considering long-term disposal of high-level radioactive waste. Furthermore, as its most stable species in the environment, the pertechnetate ion, TcO{sub 4}{sup -} is highly mobile and is considered as a long-term hazard in nuclear waste disposal. There is a need for the development of new extractant systems, such as systems based on crown ethers that may serve to selectively extract and separate this long lived radionuclide from different streams for potential industrial application. In this paper, we are reporting the design and synthesis of new macrocyclic compounds to selectively extract technetium and rhenium from complex mixtures. Preliminary tests performed for the selective extraction of pertechnetate and perrhenate are presented. (authors)

Superoxide radical-mediated photocatalytic oxidation of phenolic compounds over Ag"+/TiO_2: Influence of electron donating and withdrawing substituents

International Nuclear Information System (INIS)

Xiao, Jiadong; Xie, Yongbing; Han, Qingzhen; Cao, Hongbin; Wang, Yujiao; Nawaz, Faheem; Duan, Feng

2016-01-01

Highlights: • A weak EWG benefited photocatalytic oxidation of phenols the most. • Phenolic compounds were dominantly oxidized by ·O_2"−, rather than ·OH, "1O_2 or h"+. • ·O_2"− preferred to nucleophilically attack EDG substituted phenols. • ·O_2"− more likely electrophilically attacked EWG substituted phenols. • ·O_2"− simultaneously nucleophilically and electrophilically assaulted p-chlorophenol. - Abstract: A comparative study was constructed to correlate the electronic property of the substituents with the degradation rates of phenolic compounds and their oxidation pathways under UV with Ag"+/TiO_2 suspensions. It was verified that a weak electron withdrawing substituent benefited photocatalytic oxidation the most, while an adverse impact appeared when a substituent was present with stronger electron donating or withdrawing ability. The addition of p-benzoquinone dramatically blocked the degradation, confirming superoxide radicals (·O_2"−) as the dominant photooxidant, rather than hydroxyl radicals, singlet oxygen or positive holes, which was also independent of the substituent. Hammett relationship was established based on pseudo-first-order reaction kinetics, and it revealed two disparate reaction patterns between ·O_2"− and phenolic compounds, which was further verified by the quantum chemical computation on the frontier molecular orbitals and Mulliken charge distributions of ·O_2"− and phenolic compounds. It was found that electron donating group (EDG) substituted phenols were more likely nucleophilically attacked by ·O_2"−, while ·O_2"− preferred to electrophilically assault electron withdrawing group (EWG) substituted phenols. Exceptionally, electrophilic and nucleophilic attack by ·O_2"− could simultaneously occur in p-chlorophenol degradation, consequently leading to its highest rate constant. Possible reactive positions on the phenolic compounds were also detailedly uncovered.

Selective oxidations on vanadiumoxide containing amorphous mixed oxides (AMM-V) with tert.-butylhydroperoxide

Energy Technology Data Exchange (ETDEWEB)

Deng, Y.; Hunnius, M.; Storck, S.; Maier, W.F. [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

1998-12-31

The catalytic oxygen transfer properties of vanadium containing zeolites and vanadium based sol-gel catalysts with hydrogen peroxides are well known. The severe problem of vanadium leaching caused by the presence of the by-product water has been addressed. To avoid any interference with homogeneously catalyzed reactions, our study focusses on selective oxidations in a moisture-free medium with tert.-butylhydroperoxide. We have investigated the catalytic properties of amorphous microporous materials based on SiO{sub 2}, TiO{sub 2}, ZrO{sub 2} and Al{sub 2}O{sub 3} as matrix material and studied the effects of surface polarity on the oxidation of 1-octene and cyclohexane. (orig.)

Partial oxidation of n- and i-pentane over promoted vanadium-phosphorus oxide catalysts

Energy Technology Data Exchange (ETDEWEB)

Zazhigalov, V.A.; Mikhajluk, B.D.; Komashko, G.A. [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Fizicheskoj Khimii

1998-12-31

It is known, that the cost of raw materials for catalytic oxidation processes is about 60% of the product price. Cheap initial compounds to produce variety of products and to replace olefins and aromatic hydrocarbons are paraffins. That is why catalytic systems which could be possibly rather efficient in selective oxidation of paraffin hydrocarbons are under very close investigation now. One of such processes in n-pentane oxidation. The obtained results on n-pentane oxidation over VPO catalysts were quite encouraging in respect of possible reach high selectivity and yield of phthalic anhydride. However, in our work it was shown that the main product of n-pentane oxidation in the presence of VPO catalytic system as well as VPMeO was maleic anhydride. Some later our results were confirmed in, where to grow the selectivity towards phthalic anhydride the Co-additive was introduced. On the basis of the proposal made before on the mechanism of paraffins conversion over the vanadyl pyrophosphate surface with their activation at the first and fourth carbon atoms, we assumed possible methylmaleic (citraconic) anhydride forming at n- and i-pentane oxidation. This assumption has been recently supported by both our and other researchers` experimental results. In it was also hypothized possible mechanistic features for phthalic anhydride forming from n-pentane. The present work deals with the results of n- and i-pentane oxidation over VPO catalysts promoted with Bi, Cs, Te, Zr. (orig.)

Simple ortho- and para-hydroquinones as compounds neuroprotective against oxidative stress in a manner associated with specific transcriptional activation

International Nuclear Information System (INIS)

Satoh, Takumi; Saitoh, Sachie; Hosaka, Manami; Kosaka, Kunio

2009-01-01

Electrophilic compounds protect neurons through the activation of the Keap1/Nrf2 pathway and the induction of phase-2 enzymes [T. Satoh, S.A. Lipton, Redox regulation of neuronal survival by electrophilic compounds, Trends Neurosci. 30 (2007) 38-45; T. Satoh, S. Okamoto, J. Cui, Y. Watanabe, K. Furuta, M. Suzuki, K. Tohyama, S.A. Lipton, Activation of the Keap1/Nrf2 pathway for neuroprotection by electrophilic phase II inducers. Proc. Natl. Acad. Sci. USA 103 (2006) 768-773]. Hydroquinone-type electrophilic compounds such as tert-butyl hydroquinone (TBHQ) and carnosic acid (CA) have attracted special attention, because the oxidative conversion of 'hydroquinone' to 'quinone' is essential for the transcriptional activation of the above-mentioned enzymes [T. Satoh, K. Kosaka, K. Itoh, A. Kobayashi, M. Yamamoto, Y. Shimojo, C. Kitajima, J. Cui, J. Kamins, S. Okamoto, T. Shirasawa, S.A. Lipton, Carnosic acid, a catechol-type electrophilic compound, protect neurons both in vitro and in vivo through activation of the Keap1/Nrf2 pathway via S-alkylation of specific cysteine, J. Neurochem. 104 (2008) 1161-1131; A.D. Kraft, D.A. Johnson, J.A. Johnson, Nuclear factor E2-related factor 2-dependent antioxidant response element activation by tert-butylhydroquinone and sulforaphane occurring preferentially in astrocytes conditions neurons against oxidative insult, J. Neurosci. 24 (2004) 1101-1112]. In the present study, we examined the relationship between electrophilicity and the protective effects afforded by electrophilic compounds. Electrophilicity was assessed in terms of the ability of a compound to bind to a cysteine on bovine serum albumin, by which we found that neuroprotective hydroquinones [TBHQ (para-) and CA (ortho-)] had distinctive patterns of cysteine binding compared with other electrophilic compounds. Further, we found that isomers of simple ortho- and para-hydroquinones such as 2-methylhydroquinone (para-) and 4-methyl-catechol (ortho-) [not in abstract] had

Preparation, properties, and ESCA characterization of vanadium surface compounds on silicagel. 1

International Nuclear Information System (INIS)

Horvath, B.; Strutz, J.; Geyer-Lippmann, J.; Horvath, E.G.

1981-01-01

Binding energies (BE) or 18 pure vanadium compounds (V 2psup(3/2) niveau) were measured in selected oxygen and chlorine environments, linearity of BE vs. oxidation states scrutinized and appropriate model compounds chosen as comparative standards. The general trend is an increase of BE with formal oxidation state; in particular, it could be counterbalanced by electron donating/withdrawing ligands on the V atom. A graphical (computerized) background substraction method was utilized to remove an interfering O 1s satellite peak and to enhance accuracy of BE values in surface compounds. BEs of (triple bond Si-O) 3 V=O, (triple bond Si-O) 3 V, and (triple bond Si-O) 3 V-(O 2 ) were determined. By comparison to standards positive BE shifts of about 2.1 eV were derived indicating the strong electron withdrawing ('electron sink') effect of the support on V in surface compounds. This is the first reported ESCA data on a surface peroxo complex. (author)

Oxidation kinetics of polycyclic aromatic hydrocarbons by permanganate.

Science.gov (United States)

Forsey, Steven P; Thomson, Neil R; Barker, James F

2010-04-01

The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but little kinetic information is available. This study investigated the oxidation kinetics of a selected group of coal tar creosote compounds and alkylbenzenes in water using permanganate, and the correlation between compound reactivity and physical/chemical properties. The oxidation of naphthalene, phenanthrene, chrysene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole isopropylbenzene, ethylbenzene and methylbenzene closely followed pseudo first-order reaction kinetics. The oxidation of pyrene was initially very rapid and did not follow pseudo first-order kinetics at early times. Fluoranthene was only partially oxidized and the oxidation of anthracene was too fast to be captured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene were non-reactive under the study conditions. The oxidation rate was shown to increase with increasing number of polycyclic rings because less energy is required to overcome the aromatic character of a polycyclic ring than is required for benzene. Thus the rate of oxidation increased in the series naphthalenepermanganate. 2010 Elsevier Ltd. All rights reserved.

Micro- and Nanostructured Metal Oxide Chemical Sensors for Volatile Organic Compounds

Science.gov (United States)

Alim, M. A.; Penn, B. G.; Currie, J. R., Jr.; Batra, A. K.; Aggarwal, M. D.

2008-01-01

Aeronautic and space applications warrant the development of chemical sensors which operate in a variety of environments. This technical memorandum incorporates various kinds of chemical sensors and ways to improve their performance. The results of exploratory investigation of the binary composite polycrystalline thick-films such as SnO2-WO3, SnO2-In2O3, SnO2-ZnO for the detection of volatile organic compound (isopropanol) are reported. A short review of the present status of the new types of nanostructured sensors such as nanobelts, nanorods, nanotube, etc. based on metal oxides is presented.

Datasets used in the manuscript titled "Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms and organic aerosol"

Data.gov (United States)

U.S. Environmental Protection Agency — This dataset documents that all of the data used in the manuscript "Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic...

Additional compound semiconductor nanowires for photonics

Science.gov (United States)

Ishikawa, F.

2016-02-01

GaAs related compound semiconductor heterostructures are one of the most developed materials for photonics. Those have realized various photonic devices with high efficiency, e. g., lasers, electro-optical modulators, and solar cells. To extend the functions of the materials system, diluted nitride and bismide has been paid attention over the past decade. They can largely decrease the band gap of the alloys, providing the greater tunability of band gap and strain status, eventually suppressing the non-radiative Auger recombinations. On the other hand, selective oxidation for AlGaAs is a vital technique for vertical surface emitting lasers. That enables precisely controlled oxides in the system, enabling the optical and electrical confinement, heat transfer, and mechanical robustness. We introduce the above functions into GaAs nanowires. GaAs/GaAsN core-shell nanowires showed clear redshift of the emitting wavelength toward infrared regime. Further, the introduction of N elongated the carrier lifetime at room temperature indicating the passivation of non-radiative surface recombinations. GaAs/GaAsBi nanowire shows the redshift with metamorphic surface morphology. Selective and whole oxidations of GaAs/AlGaAs core-shell nanowires produce semiconductor/oxide composite GaAs/AlGaOx and oxide GaOx/AlGaOx core-shell nanowires, respectively. Possibly sourced from nano-particle species, the oxide shell shows white luminescence. Those property should extend the functions of the nanowires for their application to photonics.

Structure-activity relationship of 9-methylstreptimidone, a compound that induces apoptosis selectively in adult T-cell leukemia cells.

Science.gov (United States)

Takeiri, Masatoshi; Ota, Eisuke; Nishiyama, Shigeru; Kiyota, Hiromasa; Umezawa, Kazuo

2012-01-01

We previously reported that 9-methylstreptimidone, a piperidine compound isolated from a culture filtrate of Streptomyces, induces apoptosis selectively in adult T-cell leukemia cells. It was screened for a compound that inhibits LPS-induced NF-kappaB and NO production in mouse macrophages. However, 9-methystreptimidone is poorly obtained from the producing microorganism and difficult to synthesize. Therefore, in the present research, we studied the structure-activity relationship to look for new selective inhibitors. We found that the structure of the unsaturated hydrophobic portion of 9-methylstreptimidone was essential for the inhibition of LPS-induced NO production. Among the 9-methylstreptimidone-related compounds tested, (+/-)-4,alpha-diepi-streptovitacin A inhibited NO production in macrophage-like cells as potently as 9-methylstreptimidone and without cellular toxicity. Moreover, this compound selectively induced apoptosis in adult T-cell leukemia MT-1 cells.

A combined Fisher and Laplacian score for feature selection in QSAR based drug design using compounds with known and unknown activities.

Science.gov (United States)

Valizade Hasanloei, Mohammad Amin; Sheikhpour, Razieh; Sarram, Mehdi Agha; Sheikhpour, Elnaz; Sharifi, Hamdollah

2018-02-01

Quantitative structure-activity relationship (QSAR) is an effective computational technique for drug design that relates the chemical structures of compounds to their biological activities. Feature selection is an important step in QSAR based drug design to select the most relevant descriptors. One of the most popular feature selection methods for classification problems is Fisher score which aim is to minimize the within-class distance and maximize the between-class distance. In this study, the properties of Fisher criterion were extended for QSAR models to define the new distance metrics based on the continuous activity values of compounds with known activities. Then, a semi-supervised feature selection method was proposed based on the combination of Fisher and Laplacian criteria which exploits both compounds with known and unknown activities to select the relevant descriptors. To demonstrate the efficiency of the proposed semi-supervised feature selection method in selecting the relevant descriptors, we applied the method and other feature selection methods on three QSAR data sets such as serine/threonine-protein kinase PLK3 inhibitors, ROCK inhibitors and phenol compounds. The results demonstrated that the QSAR models built on the selected descriptors by the proposed semi-supervised method have better performance than other models. This indicates the efficiency of the proposed method in selecting the relevant descriptors using the compounds with known and unknown activities. The results of this study showed that the compounds with known and unknown activities can be helpful to improve the performance of the combined Fisher and Laplacian based feature selection methods.

Novel nitric oxide generating compound glycidyl nitrate enhances the therapeutic efficacy of chemotherapy and radiotherapy.

Science.gov (United States)

Ning, Shoucheng; Bednarski, Mark; Oronsky, Bryan; Scicinski, Jan; Knox, Susan J

2014-05-09

Selective release of nitric oxide (NO) in tumors could improve the tumor blood flow and drug delivery for chemotherapeutic agents and radiotherapy, thereby increasing the therapeutic index. Glycidyl nitrate (GLYN) is a NO generating small molecule, and has ability to release NO on bioactivation in SCC VII tumor cells. GLYN-induced intracellular NO generation was significantly attenuated by NO scavenger carboxy-PTIO (cPTIO) and NAC. GLYN significantly increases tumor blood flow, but has no effect on the blood flow of normal tissues in tumor-bearing mice. When used with cisplatin, GLYN significantly increased the tumor growth inhibition effect of cisplatin. GLYN also had a modest radiosensitizing effect in vitro and in vivo. GLYN was well tolerated and there were no acute toxicities found at its effective therapeutic doses in preclinical studies. These results suggest that GLYN is a promising new drug for use with chemotherapy and radiotherapy, and provide a compelling rationale for future studies of GLYN and related compounds. Copyright © 2014 Elsevier Inc. All rights reserved.

In situ spectroscopic investigation of the cobalt-catalyzed oxidation of lignin model compounds in ionic liquids

NARCIS (Netherlands)

Zakzeski, J.|info:eu-repo/dai/nl/326160256; Bruijnincx, P.C.A.|info:eu-repo/dai/nl/33799529X; Weckhuysen, B.M.|info:eu-repo/dai/nl/285484397

2011-01-01

The cobalt-catalyzed oxidation of lignin and lignin model compounds using molecular oxygen in ionic liquids proceeds readily under mild conditions, but mechanistic insight and evidence for the species involved in the catalytic cycle is lacking. In this study, a spectroscopic investigation of the

Revealing the fate of the phenylcoumaran linkage during lignin oxidation reactions.

Science.gov (United States)

Lahive, Ciaran W; Lancefield, Christopher S; Codina, Anna; Kamer, Paul C J; Westwood, Nicholas J

2018-03-14

The fate of most lignin linkages, other than the β-O-4, under selective oxidation conditions is largely unknown. In this work we use advanced β-5 lignin model compounds to identify the fate of phenylcoumaran units in a softwood lignin during oxidation with DDQ. By using model compounds combined with detailed characterisation of the oxidised lignin polymer using HSQC and HMBC NMR we show that phenylcoumarones are a major product, and therefore constitute a novel non-native β-5 linkage in oxidised lignins. Additionally, the reactivity of these units in lignin led us to further investigate their connectivity in lignin, showing that they are found as both phenolic and etherified units. The findings and approach developed here will help improve the efficiency of selective oxidative lignin depolymerisation processes, particularly those aimed at the upgrading of softwood lignin in which phenylcoumarans are a major linkage.

Study of the oxidation process of disperse Fe-C containing waste in order to obtain graphite intercalation compounds

Directory of Open Access Journals (Sweden)

Володимир Олександрович Маслов

2016-11-01

Full Text Available Graphite processing into intercalation compounds followed by thermoshock heating is known in literature. The result is an ultra-light dispersed graphite (thermographenit used in lots of industries. Graphite intercalation compounds are formed as a result of the introduction of atomic and molecular layers of different chemical particles between the layers of graphite plates. The object of this work is to obtain a new material by intercalation of graphite followed by thermoshock heating, which could be used for products protecting biological and technical facilities from electromagnetic and thermal radiation. In the present work the parameters of oxidation and of graphite thermoshock expansion in order to obtain graphite intercalation compounds and thermographenit were investigated. The experiments were performed under laboratory non-isothermal conditions. Graphite GAK-2 obtained from metallurgical wastes was used. First the fraction of +0,16 mm with the ash content of 0,3% was extracted by scattering. The oxidation of graphite was carried out by potassium bichromate dissolved in concentrated sulphuric acid. The original sample of graphite was mixed with finely grounded potassium bichromate. Then this mass was poured over with 98% concentrated sulphuric acid when being actively stirred and kept. Then the capacitance for oxidation was filled with distilled water. Decantation was carried out until pH=7 in the waste water was got. Separation of the oxidized graphite from the main mass of water was carried out by means of a suction filter until pH=7 was got. Experiments were performed at different ratios of potassium bichromate, sulphuric acid and graphite. The optimum ratio of the components (sulphuric acid : (dichromate of potash : (graphite = 2,8 : 0,15 : 1 was found. The oxidation time was 4–5 minutes. The oxidized graphite turned into thermographenit with bulk density of 2,7–9,5 kg/m3.upon subsequent heating up to 1000oC within the regime of

Selective oxidation of dual phase steel after annealing at different dew points

Science.gov (United States)

Lins, Vanessa de Freitas Cunha; Madeira, Laureanny; Vilela, Jose Mario Carneiro; Andrade, Margareth Spangler; Buono, Vicente Tadeu Lopes; Guimarães, Juliana Porto; Alvarenga, Evandro de Azevedo

2011-04-01

Hot galvanized steels have been extensively used in the automotive industry. Selective oxidation on the steel surface affects the wettability of zinc on steel and the grain orientation of inhibition layer (Fe-Al-Zn alloy) and reduces the iron diffusion to the zinc layer. The aim of this work is to identify and quantify selective oxidation on the surface of a dual phase steel, and an experimental steel with a lower content of manganese, annealed at different dew points. The techniques employed were atomic force microscopy, X-ray photoelectron spectroscopy, and glow discharge optical emission spectroscopy. External selective oxidation was observed for phosphorus on steel surface annealed at 0 °C dp, and for manganese, silicon, and aluminum at a lower dew point. The concentration of manganese was higher on the dual phase steel surface than on the surface of the experimental steel. The concentration of molybdenum on the surface of both steels increased as the depth increased.

Selective Oxidation of Styrene to Benzaldehyde by Co-Ag Codoped ZnO Catalyst and H2O2 as Oxidant

Directory of Open Access Journals (Sweden)

Abderrazak Aberkouks

2018-01-01

Full Text Available Various ratio of Co-Ag supported on ZnO have been evaluated in the selective catalytic oxidation of styrene to benzaldehyde, using H2O2 as an oxidant. The catalysts were prepared by a sol-gel process and were characterized using XRD, FT-IR, TG-DTG, BET, and SEM/EDX. The performance of the prepared catalyst was investigated under different parameters such as solvent, temperature, substrate/oxidant molar ratios, reaction time, and doping percent. The Zn1−x−yAgxCoyO catalysts exhibit a good activity and a high selectivity towards benzaldehyde (95% with the formation of only 5% of acetophenone.

Photocatalytic oxidation of organic compounds via waveguide-supported titanium dioxide films

Science.gov (United States)

Miller, Lawrence W.

A photochemical reactor based on titanium dioxide (TiO2)-coated silica optical fibers was constructed to explore the use of waveguide-supported TiO2 films for photocatalytic oxidation of organic compounds. The reactor was used for the photocatalytic oxidation of 4-chlorophenol in water. It was confirmed that TiO2 films could be securely attached to silica optical fibers. The 4-chlorophenol (100 mumol/L in water) was successfully oxidized on the TiO2 surface when UV light (310 nm--380 nm) was propagated through the fibers to the films. Rates of 4-chlorophenol oxidation and UV light flux to the fibers were measured. The quantum efficiency of 4-chlorophenol oxidation [defined as the change in 4-chlorophenol concentration divided by the UV light absorbed by the catalyst] was determined as a function of TiO2 catalyst film thickness and internal incident angle of propagating UV light. A maximum quantum efficiency of 2.8% was measured when TiO2 film thickness was ca. 80 nm and the maximum internal incident angle of propagating light was 84°. Quantum efficiency increased with increasing internal angle of incidence of propagating light and decreased with TiO2 film thickness. UV-Visible internal reflection spectroscopy was used to determine whether UV light propagated through TiO2-coated silica waveguides in an ATR mode. Propagation of UV light in an ATR mode was confirmed by the similarities between internal reflection spectra of phenolphthalein obtained with uncoated and TiO2-coated silica crystals. Planar silica waveguides coated with TiO2 were employed in a photocatalytic reactor for the oxidation of formic acid (833 mumol/L in water). It was shown that the quantum yield of formic acid oxidation [defined as the moles of formic acid oxidized divided by the moles of UV photons absorbed by the catalyst] on the waveguide-supported TiO2 surface is enhanced when UV light propagates through the waveguides in an ATR mode. A maximum quantum yield of 3.9% was found for formic

Selective oxidation of benzene and cyclohexane using amorphous microporous mixed oxides; Selektive Oxidation von Benzol und Cyclohexan mit amorphen mikroporoesen Mischoxiden

Energy Technology Data Exchange (ETDEWEB)

Stoeckmann, M.

2000-07-01

Phenol was to be produced by direct oxidation of benzene with environment-friendly oxidants like hydrogen peroxide, oxygen, or ozone. Catalysts were amorphous microporous mixed oxides whose properties can be selected directly in the sol-gel synthesis process. Apart from benzene, also cyclohexane was oxidized with ozone using AMM catalysts in order to get more information on the potential of ozone as oxidant in heterogeneously catalyzed reactions. [German] Ziel dieser Arbeit war die Herstellung von Phenol durch die Direktoxidation von Benzol mit umweltfreundlichen Oxidationsmitteln wie Wasserstoffperoxid, Sauerstoff oder Ozon. Als Katalysatoren dienten amorphe mikroporoese Mischoxide, da deren Eigenschaften direkt in der Synthese durch den Sol-Gel-Prozess gezielt eingestellt werden koennen. Neben Benzol wurde auch Cyclohexan mit Ozon unter der Verwendung von AMM-Katalysatoren oxidiert, um das Potential von Ozon als Oxiationsmittel in heterogen katalysierten Reaktionen naeher zu untersuchen. (orig.)

Mixing-assisted oxidative desulfurization of model sulfur compounds using polyoxometalate/H2O2 catalytic system

Directory of Open Access Journals (Sweden)

Angelo Earvin Sy Choi

2016-07-01

Full Text Available Desulfurization of fossil fuel derived oil is needed in order to comply with environmental regulations. Dibenzothiophene and benzothiophene are among the predominant sulfur compound present in raw diesel oil. In this study, mixing-assisted oxidative desulfurization of dibenzothiophene and benzothiophene were carried out using polyoxometalate/H2O2 systems and a phase transfer agent. The effects of reaction time (2–30 min and temperature (30–70 °C were examined in the oxidation of model sulfur compounds mixed in toluene. A pseudo first-order reaction kinetic model and the Arrhenius equation were utilized in order to evaluate the kinetic rate constant and activation energy of each catalyst tested in the desulfurization process. Results showed the order of catalytic activity and activation energy of the different polyoxometalate catalysts to be H3PW12O40 > H3PM12O40 > H4SiW12O40 for both dibenzothiophene and benzothiophene.

Aldehyde-Selective Wacker-Type Oxidation of Unbiased Alkenes Enabled by a Nitrite Co-Catalyst

KAUST Repository

Wickens, Zachary K.; Morandi, Bill; Grubbs, Robert H.

2013-01-01

Breaking the rules: Reversal of the high Markovnikov selectivity of Wacker-type oxidations was accomplished using a nitrite co-catalyst. Unbiased aliphatic alkenes can be oxidized with high yield and aldehyde selectivity, and several functional groups are tolerated. 18O-labeling experiments indicate that the aldehydic O atom is derived from the nitrite salt.

Aldehyde-Selective Wacker-Type Oxidation of Unbiased Alkenes Enabled by a Nitrite Co-Catalyst

KAUST Repository

Wickens, Zachary K.

2013-09-13

Breaking the rules: Reversal of the high Markovnikov selectivity of Wacker-type oxidations was accomplished using a nitrite co-catalyst. Unbiased aliphatic alkenes can be oxidized with high yield and aldehyde selectivity, and several functional groups are tolerated. 18O-labeling experiments indicate that the aldehydic O atom is derived from the nitrite salt.

New cytotoxic and anti-inflammatory compounds isolated from Morus alba L.

Science.gov (United States)

Qin, Jing; Fan, Min; He, Juan; Wu, Xing-De; Peng, Li-Yan; Su, Jia; Cheng, Xiao; Li, Yan; Kong, Ling-Mei; Li, Rong-Tao; Zhao, Qin-Shi

2015-01-01

Six Diels-Alder adducts (1-6) and nine prenylated flavanones (7-15) were isolated from the root bark of Morus alba L. Among them, soroceal B (1) and sanggenol Q (7) were new compounds. Their structures were elucidated on the basis of extensive spectroscopic methods, including 1D and 2D NMR techniques. Compounds 1-3, 9, 10, 12, 13 and 15 exhibited cytotoxic activity against five human tumour lines and compound 2 inhibited significantly selective cytotoxic activities towards HL-60 and AGS cells with IC50 of 3.4 and 3.6 μM. Compounds 3, 5, 9 and 12 exhibited moderate inhibitory activity against nitric oxide production in LPS-activated RAW264.7.

Block of the Mevalonate Pathway Triggers Oxidative and Inflammatory Molecular Mechanisms Modulated by Exogenous Isoprenoid Compounds

Directory of Open Access Journals (Sweden)

Paola Maura Tricarico

2014-04-01

Full Text Available Deregulation of the mevalonate pathway is known to be involved in a number of diseases that exhibit a systemic inflammatory phenotype and often neurological involvements, as seen in patients suffering from a rare disease called mevalonate kinase deficiency (MKD. One of the molecular mechanisms underlying this pathology could depend on the shortage of isoprenoid compounds and the subsequent mitochondrial damage, leading to oxidative stress and pro-inflammatory cytokines’ release. Moreover, it has been demonstrated that cellular death results from the balance between apoptosis and pyroptosis, both driven by mitochondrial damage and the molecular platform inflammasome. In order to rescue the deregulated pathway and decrease inflammatory markers, exogenous isoprenoid compounds were administered to a biochemical model of MKD obtained treating a murine monocytic cell line with a compound able to block the mevalonate pathway, plus an inflammatory stimulus. Our results show that isoprenoids acted in different ways, mainly increasing the expression of the evaluated markers [apoptosis, mitochondrial dysfunction, nucleotide-binding oligomerization-domain protein-like receptors 3 (NALP3, cytokines and nitric oxide (NO]. Our findings confirm the hypothesis that inflammation is triggered, at least partially, by the shortage of isoprenoids. Moreover, although further studies are necessary, the achieved results suggest a possible role for exogenous isoprenoids in the treatment of MKD.

Efficient and Selective Reduction of Aromatic Nitro Compounds to Aromatic Amines by NbCl{sub 5}/Indium System

Energy Technology Data Exchange (ETDEWEB)

Yoo, Byung Woo; Kim, Duckil; Kim, Hyung Min; Kang, Sung Ho [Korea Univ., Seoul (Korea, Republic of)

2012-09-15

Aromatic amines find applicability in diverse fields including dyes, pharmaceuticals, agrochemicals, and photographic materials. To date, there are a variety of methods, which can be used to convert aromatic nitro compounds to their corresponding amines. Some of them include Cp{sub 2}TiCl{sub 2}/In, Al/NH{sub 4}Cl, (NH{sub 4}){sub 2}SO{sub 4}/NaBH{sub 4}, NiCl{sub 2}6H{sub 2}O/In, HI, Sm/I{sub 2}, In/NH{sub 4}Cl, B{sub 4}H{sub 10}/Pd/C, Co{sub 2}(CO){sub 8}/H{sub 2}O and In/HCl. However, most methods still lack the desired chemo-selectivity when other reducible functional groups are present in the nitroarene and often require long reaction times, or harsh reaction conditions. Consequently, efficient and selective methods for the reduction of aromatic nitro compounds continue to be developed. It has been reported that NbCl{sub 5}/Zn system is used as a reagent for reducing sulfoxides, epoxides, and amine N-oxides.12 Because of the close resemblance of indium to zinc in several respects, including first ionization potential, we considered that NbCl{sub 5}/In system can be an efficient reducing agent for the conversion of aromatic nitro compounds to the corresponding amines. Recently, indium metal has attracted much attention for its unique properties such as low toxicity and high stability in water and air compared with other metals. In continuation of our interest in exploring the utility of metal-metal salt system in organic synthesis, we would like to report an efficient and chemo-selective method for the reduction of various aromatic nitro compounds to the corresponding amines by treatment with NbCl{sub 5}/In system (eq. 1). The new reduction system was generated by the addition of indium powder to a stirred solution of niobium(V) chloride in THF under sonication. The generation of low-valent niobium species was examined at room temperature with an excess of indium metal. The observations suggest that this procedure can be applied for the chemo-selective

The structure of active centers and the kinetic isotopic effect in the ionic polymerization of heterocyclic compounds

International Nuclear Information System (INIS)

Ponomarienko, W.A.; Berman, E.L.

1979-01-01

The method of kinetic isotopic effect has been applied to the elucidation of the structure of the active growth centres in the polymerization of some selected heterocyclic compounds. The cationic polymerization of ehtylene oxide, tetrahydrofuran and 1.3-dioxolane as well as the anionic and coordination polymerization of ethylene oxide have been discussed. (author)

Lithium-Vanadium bronzes as model catalysts for the selective reduction of nitric oxide

NARCIS (Netherlands)

Bosch, H.; Bongers, Annemie; Enoch, Gert; Snel, Ruud; Ross, Julian R.H.

1989-01-01

The effect of alkali metals on the selective reduction of nitric oxide with ammonia has been studied on bulk iron oxide and bulk vanadium oxide. The influence of additions of LiOH, NaOH and KOH on the activity was screened by pulse experiments carried out in the absence of gaseous oxygen; FTIR

Peracetic Acid Depolymerization of Biorefinery Lignin for Production of Selective Monomeric Phenolic Compounds

Energy Technology Data Exchange (ETDEWEB)

Ma, Ruoshui [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA; Guo, Mond [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA; Lin, Kuan-ting [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA; Hebert, Vincent R. [Food and Environmental Laboratory, Washington State, University-TriCities, 2710 Crimson Way Richland WA 99354 USA; Zhang, Jinwen [Wood Materials and Engineering Laboratory, Washington State University, Pullman WA 99164 USA; Wolcott, Michael P. [Wood Materials and Engineering Laboratory, Washington State University, Pullman WA 99164 USA; Quintero, Melissa [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA; Ramasamy, Karthikeyan K. [Chemical and Biological Process Development Group, Pacific Northwest National Laboratory, Richland WA 99354 USA; Chen, Xiaowen [National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd Golden CO 80127 USA; Zhang, Xiao [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA

2016-07-04

Lignin is the largest source of renewable material with an aromatic skeleton. However, due to the recalcitrant and heterogeneous nature of the lignin polymer, it has been a challenge to effectively depolymerize lignin and produce high-value chemicals with high selectivity. In this study, a highly efficient lignin-to-monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment was reported. PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC-H) and monomeric phenolic acid compounds (MPC-A) including 4-hydroxy-2-methoxyphenol, p-hydroxybenzoic acid, vanillic acid, syringic acid, and 3,4-dihydroxybenzoic acid. The maximized MPC yields obtained were 18 and 22 % based on the initial weight of the lignin in SESPL and DACSL, respectively. However, we found that the addition of niobium pentoxide catalyst to PAA treatment of lignin can significantly improve the MPC yields up to 47 %. The key reaction steps and main mechanisms involved in this new lignin-to-MPC valorization pathway were investigated and elucidated.

Peracetic Acid Depolymerization of Biorefinery Lignin for Production of Selective Monomeric Phenolic Compounds

Energy Technology Data Exchange (ETDEWEB)

Ma, Ruoshui [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA; Guo, Mond [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA; Lin, Kuan-ting [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA; Hebert, Vincent R. [Food and Environmental Laboratory, Washington State, University-TriCities, 2710 Crimson Way Richland WA 99354 USA; Zhang, Jinwen [Wood Materials and Engineering Laboratory, Washington State University, Pullman WA 99164 USA; Wolcott, Michael P. [Wood Materials and Engineering Laboratory, Washington State University, Pullman WA 99164 USA; Quintero, Melissa [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA; Ramasamy, Karthikeyan K. [Chemical and Biological Process Development Group, Pacific Northwest National Laboratory, Richland WA 99354 USA; Chen, Xiaowen [National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd Golden CO 80127 USA; Zhang, Xiao [Voiland School of Chemical Engineering and Bioengineering, Bioproducts, Science & Engineering Laboratory, Washington State University, 2710 Crimson Way Richland WA 99354 USA

2016-07-04

Lignin is the largest source of renewable material with an aromatic skeleton. However, due to the recalcitrant and heterogeneous nature of the lignin polymer as well as its complex side chain structures, it has been a challenge to effectively depolymerize lignin and produce high value chemicals with high selectivity. In this study, a highly efficient lignin-to-monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment was reported. PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC-H) and monomeric phenolic acid compounds (MPC-A) inclduing 4-hydroxy-2-methoxyphenol, p-hydroxybenzoic acid, vanillic acid, syringic acid, and 3,4-dihydroxybenzoic acid. The maximized MPCs yields obtained were 18% and 22% based on the initial weight of the lignin in SESPL and DACSL respectively. However, we found that the addition of niobium pentoxide catalyst to PAA treatment of lignin can significantly improve the MPC yields up to 47%. The key reaction steps and main mechanisms involved in this new lignin-to-MPC valorization pathway were investigated and elucidated.

Passive sampling of selected endocrine disrupting compounds using polar organic chemical integrative samplers

International Nuclear Information System (INIS)

Arditsoglou, Anastasia; Voutsa, Dimitra

2008-01-01

Two types of polar organic chemical integrative samplers (pharmaceutical POCIS and pesticide POCIS) were examined for their sampling efficiency of selected endocrine disrupting compounds (EDCs). Laboratory-based calibration of POCISs was conducted by exposing them at high and low concentrations of 14 EDCs (4-alkyl-phenols, their ethoxylate oligomers, bisphenol A, selected estrogens and synthetic steroids) for different time periods. The kinetic studies showed an integrative uptake up to 28 days. The sampling rates for the individual compounds were obtained. The use of POCISs could result in an integrative approach to the quality status of the aquatic systems especially in the case of high variation of water concentrations of EDCs. The sampling efficiency of POCISs under various field conditions was assessed after their deployment in different aquatic environments. - Calibration and field performance of polar organic integrative samplers for monitoring EDCs in aquatic environments

Bibliography of work on the photocatalytic removal of hazardous compounds from water and air

Energy Technology Data Exchange (ETDEWEB)

Blake, D.M.

1994-05-01

This is a bibliography of information in the open literature on work that has been done to date on the photocatalytic oxidation of compounds, principally organic compounds. The goal of the listing is removing hazardous oompounds from water or air. It contains lists of substances and literature citations. The bibliography includes information obtained through the middle of 1993 and some selected references for the balance of that year.

Effect of photo-selective nettings on post-harvest quality and bioactive compounds in selected tomato cultivars.

Science.gov (United States)

Selahle, Maphoko Kamogelo; Sivakumar, Dharini; Soundy, Puffy

2014-08-01

Photo-selective coloured netting is referred to as a 'new agro-technological' concept adopted to manipulate light quality changes that can induce favourable responses in plants. Tomato (Solanum lycopersicum L.) cultivars AlvaV, Irit and SCX 248 grown under the black net (commercial net, 25% shading) showed higher weight loss, loss of firmness, ascorbic acid content and decline in the ratio of soluble solids content/titrable acidity during post-harvest storage (low-temperature storage at 10°C and 90% relative humidity for 21 days followed by market shelf conditions at 25°C for 2 days). During post-harvest storage, lycopene, β-carotene, total phenolic content and antioxidant scavenging activity were higher in cvs AlfaV and Irit grown under the black or pearl nets. However, the β-carotene, total phenolic content and antioxidant scavenging activity were higher in SCX 248 grown under the red net during post-harvest storage. Cultivar AlfaV grown under the red and pearl nets had a higher number of odour active aroma compounds during post-harvest storage. Panellists preferred cv. AlfaV grown under the pearl nets after storage based on taste, overall appearance and firm textured fruits. Pearl photo-selective nets retained the overall fruit quality and bioactive components in cvs AlfaV and Irit during post-harvest storage. Red photo-selective nets, however, showed greater influence on retention of overall fruit quality and bioactive compounds in cv. SCX 248 during post-harvest storage. © 2013 Society of Chemical Industry.

Enthalpies of formation of selected Co{sub 2}YZ Heusler compounds

Energy Technology Data Exchange (ETDEWEB)

Yin, Ming, E-mail: myin1@hawk.iit.edu; Chen, Song; Nash, Philip

2013-11-15

Highlights: •Enthalpies of formation of selected Co{sub 2}YZ were measured by drop calorimeters. •Enthalpy decreases as the Z element approaches the top right corner of the periodic table. •For the Y element, enthalpy increases on increasing the number of d electrons. •Result of L2{sub 1} structured compounds agrees with first principles data. •Lattice parameters and related phase relationships were consistent with literature data. -- Abstract: Standard enthalpies of formation at 298 K of selected ternary Co{sub 2}-based Heusler compounds Co{sub 2}YZ (Y = Fe, Hf, Mn, Ti, V, Zr; Z = Al, Ga, In, Si, Ge, Sn) were measured by high temperature direct synthesis calorimetry. The measured enthalpies of formation (in kJ/mole of atoms) of the L2{sub 1} compounds are: Co{sub 2}FeGa (−25.8 ± 2.6); Co{sub 2}FeSi (−38.4 ± 2.2); Co{sub 2}FeGe (−11.6 ± 2.1); Co{sub 2}MnGa (−30.1 ± 2.3); Co{sub 2}MnSi (−42.4 ± 1.2); Co{sub 2}MnGe (−31.6 ± 3.0); Co{sub 2}MnSn (−15.6 ± 2.8); Co{sub 2}TiAl (−55.0 ± 3.7); Co{sub 2}TiGa (−54.2 ± 2.6); Co{sub 2}TiSi (−61.4 ± 1.7); Co{sub 2}TiGe (−59.3 ± 3.8); Co{sub 2}TiSn (−38.4 ± 2.0); Co{sub 2}VGa (−28.4 ± 1.1) and for the B2 compounds: Co{sub 2}FeAl (−22.5 ± 2.5), Co{sub 2}MnAl (−27.6 ± 2.7). Values are compared with those from first principles calculation when available and the extended semi-empirical model of Miedema. Trends in enthalpy of formation with element atomic number are discussed. Lattice parameters of the compounds with L2{sub 1} structure are determined by X-ray diffraction analysis.

Chemical oxidation methods in the closure of paper mill water circulations; Hapetustekniikoiden kaeyttoe metsaeteollisuuden vesikiertojen sulkemisessa - EKT 04

Energy Technology Data Exchange (ETDEWEB)

Laari, A.; Kallas, J. [Lappeenranta Univ. of Technology (Finland); Korhonen, S. [Kuopio Univ. (Finland); Tuhkanen, T. [Mikkelin Ammattikorkeakoulu, Mikkeli (Finland)

1998-12-31

When water circulations are closed some harmful compounds tend to accumulate in the circulation waters. These compounds include lipophilic extractives, like resin and fatty acids, triglycerides and sterols, but also other compounds, like lignins, lignans and sugars. Microbial growth will increase due to elevated organic concentrations. The purpose of this project is to find out the possibilities of the use of ozonation and wet oxidation in the treatment of paper mill water circulations. In chemical oxidation organic matter is destroyed in oxidation reactions. Especially lipophilic extractives are selectively oxidated by ozone. Chemical oxidation reactions are carried out in gas-liquid reactors, where ozone or oxygen are transferred from gas to liquid phase where the oxidation reactions happen. One target of the project is to estimate kinetic parameters for different groups of compounds on the basis of experimental data. Kinetic parameters are then used in modelling of reactors and in estimation of process costs. (orig.)

Chemical oxidation methods in the closure of paper mill water circulations; Hapetustekniikoiden kaeyttoe metsaeteollisuuden vesikiertojen sulkemisessa - EKT 04

Energy Technology Data Exchange (ETDEWEB)

Laari, A; Kallas, J [Lappeenranta Univ. of Technology (Finland); Korhonen, S [Kuopio Univ. (Finland); Tuhkanen, T [Mikkelin Ammattikorkeakoulu, Mikkeli (Finland)

1999-12-31

When water circulations are closed some harmful compounds tend to accumulate in the circulation waters. These compounds include lipophilic extractives, like resin and fatty acids, triglycerides and sterols, but also other compounds, like lignins, lignans and sugars. Microbial growth will increase due to elevated organic concentrations. The purpose of this project is to find out the possibilities of the use of ozonation and wet oxidation in the treatment of paper mill water circulations. In chemical oxidation organic matter is destroyed in oxidation reactions. Especially lipophilic extractives are selectively oxidated by ozone. Chemical oxidation reactions are carried out in gas-liquid reactors, where ozone or oxygen are transferred from gas to liquid phase where the oxidation reactions happen. One target of the project is to estimate kinetic parameters for different groups of compounds on the basis of experimental data. Kinetic parameters are then used in modelling of reactors and in estimation of process costs. (orig.)

Comparison of Oxidation Characteristics of Selected Nuclear Graphite Grades

International Nuclear Information System (INIS)

Chi, Se Hwan; Kim, Gen Chan

2010-02-01

The oxidation behavior of some selected nuclear graphite grades (i.e., IG-110, IG-430, NBG-18, NBG-25) were compared in view of their filler coke type and the physical property of the grades. Oxidation rates were determined at six temperatures between 600 ∼ 960 .deg. C in air by using a three-zone vertical tube furnace at a 10 L/min air flow rate. The specimens were a cylinder with a 25.4 mm diameter and a 25.4 mm length. Results showed that, even though the four examined nuclear graphite grades showed a highly temperature-sensitive oxidation behavior through out the test temperature range of 600 ∼ 950 .deg. C, the differences between the grades were not significant. The oxidation rates determined for a 5∼10 % weight loss at the six temperatures were nearly the same except for 702 and 808 .deg. C, where the pitch coke graphites showed an apparent decrease in their oxidation rate, more so than the petroleum coke graphites. These effects of the coke type reduced or nearly disappeared with an increasing temperature. The average activation energy determined for 608 ∼ 808 .deg. C was 161.5 ± 7.3 kJ/mol, showing that the dominant oxidation reaction occurred by a chemical control

Microwave-Accelerated Iodination of Some Aromatic Amines, Using Urea-Hydrogen Peroxide Addition Compound (UHP as the Oxidant

Directory of Open Access Journals (Sweden)

Lech Skulski

2002-12-01

Full Text Available A fast and simple method for the oxidative iodination of some aromatic amines, under microwave irradiation, is reported, using diiodine and the the strongly Hbonded urea-hydrogen peroxide addition compound (H2NCONH2···H2O2, UHP as the oxidant. The reactions were carried out in boiling CHCl3 under a reflux condenser to afford, within 10 minutes, the purified monoiodinated products in 40-80% yields.

Design of Highly Selective Gas Sensors via Physicochemical Modification of Oxide Nanowires: Overview

Directory of Open Access Journals (Sweden)

Hyung-Sik Woo

2016-09-01

Full Text Available Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO2, ZnO, and In2O3 are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C2H5OH and NO2, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors.

Enantiomeric distribution of major chiral volatile organic compounds in juniper-flavored distillates.

Science.gov (United States)

Pažitná, Alexandra; Spánik, Ivan

2014-02-01

The enantiomeric ratios of chiral volatile organic compounds in juniper-flavored spirits produced by various processing technologies in different EU countries were determined by multidimensional GC using solid-phase microextraction and liquid-liquid extraction as a sample pretreatment procedure. In total, more than 260 compounds were detected in studied spirits from which linalool, α-terpineol, 4-terpineol, linalool oxides, α-pinene, and verbenone were selected for enantiomeric separation. The significant differences in enantiomeric ratio of linalool and cis-linalool oxide allowed us to distinguish between samples produced in Slovakia and the United Kingdom from those produced in Germany, Czech Republic, and Belgium. The pure enantiomer of trans-linalool oxide was found only in samples from Germany. It was shown that the enantiomeric ratio is independent of the sample treatment procedure, and only small differences up to 1% were observed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantitative production of compound I from a cytochrome P450 enzyme at low temperatures. Kinetics, activation parameters, and kinetic isotope effects for oxidation of benzyl alcohol.

Science.gov (United States)

Wang, Qin; Sheng, Xin; Horner, John H; Newcomb, Martin

2009-08-05

Cytochrome P450 enzymes are commonly thought to oxidize substrates via an iron(IV)-oxo porphyrin radical cation transient termed Compound I, but kinetic studies of P450 Compounds I are essentially nonexistent. We report production of Compound I from cytochrome P450 119 (CYP119) in high conversion from the corresponding Compound II species at low temperatures in buffer mixtures containing 50% glycerol by photolysis with 365 nm light from a pulsed lamp. Compound I was studied as a reagent in oxidations of benzyl alcohol and its benzylic mono- and dideuterio isotopomers. Pseudo-first-order rate constants obtained at -50 degrees C with concentrations of substrates between 1.0 and 6.0 mM displayed saturation kinetics that gave binding constants for the substrate in the Compound I species (K(bind)) and first-order rate constants for the oxidation reactions (k(ox)). Representative results are K(bind) = 214 M(-1) and k(ox) = 0.48 s(-1) for oxidation of benzyl alcohol. For the dideuterated substrate C(6)H(5)CD(2)OH, kinetics were studied between -50 and -25 degrees C, and a van't Hoff plot for complexation and an Arrhenius plot for the oxidation reaction were constructed. The H/D kinetic isotope effects (KIEs) at -50 degrees C were resolved into a large primary KIE (P = 11.9) and a small, inverse secondary KIE (S = 0.96). Comparison of values extrapolated to 22 degrees C of both the rate constant for oxidation of C(6)H(5)CD(2)OH and the KIE for the nondeuterated and dideuterated substrates to values obtained previously in laser flash photolysis experiments suggested that tunneling could be a significant component of the total rate constant at -50 degrees C.

Addition compounds between lanthanide (III) and yttrium (III) and methanesulfonates (MS) and 3-picoline-N-oxide (3-pic NO)

International Nuclear Information System (INIS)

Zinner, L.B.

1984-01-01

The preparation and characterization of addition compounds between lanthanide methanesulfonates and 3-picoline-N-oxide of general formula Ln (MS) 3 .2(3-pic No), Ln being La, Yb and Y, were carried out. The techniques employed for characterization were: elemental analysis, X-ray diffraction, infrared absorption spectroscopy, electrolytic conductance in methanol, melting ranges and emission spectrum of the Eu (III) compound. (Author) [pt

Hard X-ray PhotoElectron Spectroscopy of transition metal oxides: Bulk compounds and device-ready metal-oxide interfaces

International Nuclear Information System (INIS)

Borgatti, F.; Torelli, P.; Panaccione, G.

2016-01-01

Highlights: • Hard X-ray PhotoElectron Spectroscopy (HAXPES) applied to buried interfaces of systems involving Transition Metal Oxides. • Enhanced contribution of the s states at high kinetic energies both for valence and core level spectra. • Sensitivity to chemical changes promoted by electric field across metal-oxide interfaces in resistive switching devices. - Abstract: Photoelectron spectroscopy is one of the most powerful tool to unravel the electronic structure of strongly correlated materials also thanks to the extremely large dynamic range in energy, coupled to high energy resolution that this form of spectroscopy covers. The kinetic energy range typically used for photoelectron experiments corresponds often to a strong surface sensitivity, and this turns out to be a disadvantage for the study of transition metal oxides, systems where structural and electronic reconstruction, different oxidation state, and electronic correlation may significantly vary at the surface. We report here selected Hard X-ray PhotoElectron Spectroscopy (HAXPES) results from transition metal oxides, and from buried interfaces, where we highlight some of the important features that such bulk sensitive technique brings in the analysis of electronic properties of the solids.

Hard X-ray PhotoElectron Spectroscopy of transition metal oxides: Bulk compounds and device-ready metal-oxide interfaces

Energy Technology Data Exchange (ETDEWEB)

Borgatti, F., E-mail: francesco.borgatti@cnr.it [Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), Consiglio Nazionale delle Ricerche (CNR), via P. Gobetti 101, Bologna I-40129 (Italy); Torelli, P.; Panaccione, G. [Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, Trieste I-34149 (Italy)

2016-04-15

Highlights: • Hard X-ray PhotoElectron Spectroscopy (HAXPES) applied to buried interfaces of systems involving Transition Metal Oxides. • Enhanced contribution of the s states at high kinetic energies both for valence and core level spectra. • Sensitivity to chemical changes promoted by electric field across metal-oxide interfaces in resistive switching devices. - Abstract: Photoelectron spectroscopy is one of the most powerful tool to unravel the electronic structure of strongly correlated materials also thanks to the extremely large dynamic range in energy, coupled to high energy resolution that this form of spectroscopy covers. The kinetic energy range typically used for photoelectron experiments corresponds often to a strong surface sensitivity, and this turns out to be a disadvantage for the study of transition metal oxides, systems where structural and electronic reconstruction, different oxidation state, and electronic correlation may significantly vary at the surface. We report here selected Hard X-ray PhotoElectron Spectroscopy (HAXPES) results from transition metal oxides, and from buried interfaces, where we highlight some of the important features that such bulk sensitive technique brings in the analysis of electronic properties of the solids.

Nitroxyl-mediated oxidation of lignin and polycarboxylated products

Energy Technology Data Exchange (ETDEWEB)

Stahl, Shannon S.; Rafiee, Mohammad

2018-02-27

Methods of selectively modifying lignin, polycarboxylated products thereof, and methods of deriving aromatic compounds therefrom. The methods comprise electrochemically oxidizing lignin using stable nitroxyl radicals to selectively oxidize primary hydroxyls on .beta.-O-4 phenylpropanoid units to corresponding carboxylic acids while leaving the secondary hydroxyls unchanged. The oxidation results in polycarboxylated lignin in the form of a polymeric .beta.-hydroxy acid. The polymeric .beta.-hydroxy acid has a high loading of carboxylic acid and can be isolated in acid form, deprotonated, and/or converted to a salt. The .beta.-hydroxy acid, anion, or salt can also be subjected to acidolysis to generate various aromatic monomers or oligomers. The initial oxidation of lignin to the polycarboxylated form renders the lignin more susceptible to acidolysis and thereby enhances the yield of aromatic monomers and oligomers obtained through acidolysis.

Evaluation of the kinetic oxidation of aqueous volatile organic compounds by permanganate.

Science.gov (United States)

Mahmoodlu, Mojtaba G; Hassanizadeh, S Majid; Hartog, Niels

2014-07-01

The use of permanganate solutions for in-situ chemical oxidation (ISCO) is a well-established groundwater remediation technology, particularly for targeting chlorinated ethenes. The kinetics of oxidation reactions is an important ISCO remediation design aspect that affects the efficiency and oxidant persistence. The overall rate of the ISCO reaction between oxidant and contaminant is typically described using a second-order kinetic model while the second-order rate constant is determined experimentally by means of a pseudo first order approach. However, earlier studies of chlorinated hydrocarbons have yielded a wide range of values for the second-order rate constants. Also, there is limited insight in the kinetics of permanganate reactions with fuel-derived groundwater contaminants such as toluene and ethanol. In this study, batch experiments were carried out to investigate and compare the oxidation kinetics of aqueous trichloroethylene (TCE), ethanol, and toluene in an aqueous potassium permanganate solution. The overall second-order rate constants were determined directly by fitting a second-order model to the data, instead of typically using the pseudo-first-order approach. The second-order reaction rate constants (M(-1) s(-1)) for TCE, toluene, and ethanol were 8.0×10(-1), 2.5×10(-4), and 6.5×10(-4), respectively. Results showed that the inappropriate use of the pseudo-first-order approach in several previous studies produced biased estimates of the second-order rate constants. In our study, this error was expressed as a function of the extent (P/N) in which the reactant concentrations deviated from the stoichiometric ratio of each oxidation reaction. The error associated with the inappropriate use of the pseudo-first-order approach is negatively correlated with the P/N ratio and reached up to 25% of the estimated second-order rate constant in some previous studies of TCE oxidation. Based on our results, a similar relation is valid for the other volatile

Adsorption of aromatic compounds from the biodegradation of azo dyes on activated carbon

Science.gov (United States)

Faria, P. C. C.; Órfão, J. J. M.; Figueiredo, J. L.; Pereira, M. F. R.

2008-03-01

The adsorption of three selected aromatic compounds (aniline, sulfanilic acid and benzenesulfonic acid) on activated carbons with different surface chemical properties was investigated at different solution pH. A fairly basic commercial activated carbon was modified by means of chemical treatment with HNO 3, yielding an acid activated carbon. The textural properties of this sample were not significantly changed after the oxidation treatment. Equilibrium isotherms of the selected compounds on the mentioned samples were obtained and the results were discussed in relation to their surface chemistry. The influence of electrostatic and dispersive interactions involved in the uptake of the compounds studied was evaluated. The Freundlich model was used to fit the experimental data. Higher uptakes are attained when the compounds are present in their molecular form. In general, adsorption was disfavoured by the introduction of oxygen-containing groups on the surface of the activated carbon.

Catalytic properties of a titanium-antimony oxide system in oxidative ammonolysis of propylene

Energy Technology Data Exchange (ETDEWEB)

Zenkovets, G.A.; Tarasova, D.V.; Andrushkevich, T.V.; Aleshina, G.I.; Nikoro, T.A.; Ravilov, R.G.

1979-03-01

The catalytic properties of titanium-antimony oxide system in oxidative ammonolysis of propylene at 450/sup 0/C depended both on the catalyst and the reactant compositions. Stable and high (75-80Vertical Bar3<) selectivities for acrylonitrile and high activities were observed over catalysts containing 5-60 mole Vertical Bar3< Sb/sub 2/O/sub 4/ with 2Vertical Bar3< propylene and 3Vertical Bar3< ammonia in air at Vertical Bar3; 70Vertical Bar3< conversions. The selectivities of the catalysts for acetonitrile and acrolein did not exceed 5 and 1Vertical Bar3<, respectively. At high ammonia and propylene contents in the reaction mixture and over individual TiO/sub 2/ or Sb/sub 2/O/sub 4/ catalysts, the reaction selectivity shifted toward deep oxidation products. These findings were attributed to the reducing effect of propylene and ammonia at high concentrations on the active components of the catalyst, a solid solution of Sb in TiO/sub 2/ containing 5-7 mole Vertical Bar3< of Sb/sub 2/O/sub 4/ and a chemical compound with TiSb/sub 2/O/sub 6/ composition.

BCL-2 inhibition targets oxidative phosphorylation and selectively eradicates quiescent human leukemia stem cells

Science.gov (United States)

Lagadinou, Eleni D.; Sach, Alexander; Callahan, Kevin; Rossi, Randall M.; Neering, Sarah J.; Minhajuddin, Mohammad; Ashton, John M.; Pei, Shanshan; Grose, Valerie; O’Dwyer, Kristen M.; Liesveld, Jane L.; Brookes, Paul S.; Becker, Michael W.; Jordan, Craig T.

2013-01-01

Summary Most forms of chemotherapy employ mechanisms involving induction of oxidative stress, a strategy that can be effective due to the elevated oxidative state commonly observed in cancer cells. However, recent studies have shown that relative redox levels in primary tumors can be heterogeneous, suggesting that regimens dependent on differential oxidative state may not be uniformly effective. To investigate this issue in hematological malignancies, we evaluated mechanisms controlling oxidative state in primary specimens derived from acute myelogenous leukemia (AML) patients. Our studies demonstrate three striking findings. First, the majority of functionally-defined leukemia stem cells (LSCs) are characterized by relatively low levels of reactive oxygen species (termed “ROS-low”). Second, ROS-low LSCs aberrantly over-express BCL-2. Third, BCL-2 inhibition reduced oxidative phosphorylation and selectively eradicated quiescent LSCs. Based on these findings, we propose a model wherein the unique physiology of ROS-low LSCs provides an opportunity for selective targeting via disruption of BCL-2-dependent oxidative phosphorylation. PMID:23333149

Innovative reactor technology for selective oxidation of toxic organic pollutants in wastewater by ozone

NARCIS (Netherlands)

Boncz, M.A.; Bruning, H.; Rulkens, W.H.

2003-01-01

Ozonation can be a suitable technique for the pre-treatment of wastewater containing low concentrations of toxic or non-biodegradable compounds that cannot be treated with satisfactory results when only the traditional, less expensive biological techniques are applied. In this case, the oxidation

Cuprous oxide nanoparticles selectively induce apoptosis of tumor cells

Directory of Open Access Journals (Sweden)

Wang Y

2012-05-01

Full Text Available Ye Wang,1,2,* Xiao-Yuan Zi,1,* Juan Su,1 Hong-Xia Zhang,1 Xin-Rong Zhang,3 Hai-Ying Zhu,1 Jian-Xiu Li,1 Meng Yin,3 Feng Yang,3 Yi-Ping Hu,11Department of Cell Biology, 2School of Clinical Medicine, 3Department of Pharmaceuticals, Second Military Medical University, Shanghai, People's Republic of China*Authors contributed equally.Abstract: In the rapid development of nanoscience and nanotechnology, many researchers have discovered that metal oxide nanoparticles have very useful pharmacological effects. Cuprous oxide nanoparticles (CONPs can selectively induce apoptosis and suppress the proliferation of tumor cells, showing great potential as a clinical cancer therapy. Treatment with CONPs caused a G1/G0 cell cycle arrest in tumor cells. Furthermore, CONPs enclosed in vesicles entered, or were taken up by mitochondria, which damaged their membranes, thereby inducing apoptosis. CONPs can also produce reactive oxygen species (ROS and initiate lipid peroxidation of the liposomal membrane, thereby regulating many signaling pathways and influencing the vital movements of cells. Our results demonstrate that CONPs have selective cytotoxicity towards tumor cells, and indicate that CONPs might be a potential nanomedicine for cancer therapy.Keywords: nanomedicine, selective cytotoxicity, apoptosis, cell cycle arrest, mitochondrion-targeted nanomaterials

Peracetic Acid Depolymerization of Biorefinery Lignin for Production of Selective Monomeric Phenolic Compounds.

Science.gov (United States)

Ma, Ruoshui; Guo, Mond; Lin, Kuan-Ting; Hebert, Vincent R; Zhang, Jinwen; Wolcott, Michael P; Quintero, Melissa; Ramasamy, Karthikeyan K; Chen, Xiaowen; Zhang, Xiao

2016-07-25

Lignin is the largest source of renewable material with an aromatic skeleton. However, due to the recalcitrant and heterogeneous nature of the lignin polymer, it has been a challenge to effectively depolymerize lignin and produce high-value chemicals with high selectivity. In this study, a highly efficient lignin-to-monomeric phenolic compounds (MPC) conversion method based on peracetic acid (PAA) treatment was reported. PAA treatment of two biorefinery lignin samples, diluted acid pretreated corn stover lignin (DACSL) and steam exploded spruce lignin (SESPL), led to complete solubilization and production of selective hydroxylated monomeric phenolic compounds (MPC-H) and monomeric phenolic acid compounds (MPC-A) including 4-hydroxy-2-methoxyphenol, p-hydroxybenzoic acid, vanillic acid, syringic acid, and 3,4-dihydroxybenzoic acid. The maximized MPC yields obtained were 18 and 22 % based on the initial weight of the lignin in SESPL and DACSL, respectively. However, we found that the addition of niobium pentoxide catalyst to PAA treatment of lignin can significantly improve the MPC yields up to 47 %. The key reaction steps and main mechanisms involved in this new lignin-to-MPC valorization pathway were investigated and elucidated. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deep oxidative desulfurization of dibenzothiophene in simulated oil and real diesel using heteropolyanion-substituted hydrotalcite-like compounds as catalysts.

Science.gov (United States)

Yu, Fengli; Wang, Rui

2013-11-05

Three heteropolyanion substituted hydrotalcite-like compounds (HPA-HTLcs) including Mg₉Al₃(OH)₂₄[PW₁₂O₄₀](MgAl-PW₁₂), Mg₉Al₃(OH)₂₄[PMo₁₂O₄₀] (MgAl-PMo₁₂) and Mg₁₂Al₄(OH)₃₂[SiW₁₂O₄₀] (MgAl-SiW₁₂), were synthesized, characterized and used as catalysts for the oxidative desulfurization of simulated oil (dibenzothiophene, DBT, in n-octane). MgAl-PMo₁₂ was identified as an effective catalyst for the oxidative removal of DBT under very mild conditions of atmospheric pressure and 60 °C in a biphasic system using hydrogen peroxide as oxidant and acetonitrile as extractant. The conversion of DBT was nearly 100%. As a result, because of the influence of the electron density and the space steric hindrance, the oxidation reactivity of the different sulfur compounds in simulated oil followed the order DBT > 4,6-dimethyldibenzothiophene (4,6-DMDBT) > benzothiophene (BT) > thiophene (TH). When the reaction is finished, the catalysts can be recovered from the acetonitrile phase by filtration. The recovered MgAl-PMo₁₂ retains nearly the same catalytic activity as the fresh material. Moreover, MgAl-PMo₁₂ was found to exhibit an ideal catalytic activity in the oxidative desulfurization of real diesel resulting in a total remaining sulfur content of 9.12 ppm(w).

Deep Oxidative Desulfurization of Dibenzothiophene in Simulated Oil and Real Diesel Using Heteropolyanion-Substituted Hydrotalcite-Like Compounds as Catalysts

Directory of Open Access Journals (Sweden)

Rui Wang

2013-11-01

Full Text Available Three heteropolyanion substituted hydrotalcite-like compounds (HPA-HTLcs including Mg9Al3(OH24[PW12O40](MgAl-PW12, Mg9Al3(OH24[PMo12O40] (MgAl-PMo12 and Mg12Al4(OH32[SiW12O40] (MgAl-SiW12, were synthesized, characterized and used as catalysts for the oxidative desulfurization of simulated oil (dibenzothiophene, DBT, in n-octane. MgAl-PMo12 was identified as an effective catalyst for the oxidative removal of DBT under very mild conditions of atmospheric pressure and 60 °C in a biphasic system using hydrogen peroxide as oxidant and acetonitrile as extractant. The conversion of DBT was nearly 100%. As a result, because of the influence of the electron density and the space steric hindrance, the oxidation reactivity of the different sulfur compounds in simulated oil followed the order DBT > 4,6-dimethyldibenzothiophene (4,6-DMDBT > benzothiophene (BT > thiophene (TH. When the reaction is finished, the catalysts can be recovered from the acetonitrile phase by filtration. The recovered MgAl-PMo12 retains nearly the same catalytic activity as the fresh material. Moreover, MgAl-PMo12 was found to exhibit an ideal catalytic activity in the oxidative desulfurization of real diesel resulting in a total remaining sulfur content of 9.12 ppm(w.

Recent trends in the development of nanophytobioactive compounds and delivery systems for their possible role in reducing oxidative stress in Parkinson’s disease models

Science.gov (United States)

Ganesan, Palanivel; Ko, Hyun-Myung; Kim, In-Su; Choi, Dong-Kug

2015-01-01

Oxidative stress plays a very critical role in neurodegenerative diseases, such as Parkinson’s disease (PD), which is the second most common neurodegenerative disease among elderly people worldwide. Increasing evidence has suggested that phytobioactive compounds show enhanced benefits in cell and animal models of PD. Curcumin, resveratrol, ginsenosides, quercetin, and catechin are phyto-derived bioactive compounds with important roles in the prevention and treatment of PD. However, in vivo studies suggest that their concentrations are very low to cross blood–brain barrier thereby it limits bioavailability, stability, and dissolution at target sites in the brain. To overcome these problems, nanophytomedicine with the controlled size of 1–100 nm is used to maximize efficiency in the treatment of PD. Nanosizing of phytobioactive compounds enhances the permeability into the brain with maximized efficiency and stability. Several nanodelivery techniques, including solid lipid nanoparticles, nanostructured lipid carriers, nanoliposomes, and nanoniosomes can be used for controlled delivery of nanobioactive compounds to brain. Nanocompounds, such as ginsenosides (19.9 nm) synthesized using a nanoemulsion technique, showed enhanced bioavailability in the rat brain. Here, we discuss the most recent trends and applications in PD, including 1) the role of phytobioactive compounds in reducing oxidative stress and their bioavailability; 2) the role of nanotechnology in reducing oxidative stress during PD; 3) nanodelivery systems; and 4) various nanophytobioactive compounds and their role in PD. PMID:26604750

Platinum-Catalyzed, Terminal-Selective C(sp(3))-H Oxidation of Aliphatic Amines.

Science.gov (United States)

Lee, Melissa; Sanford, Melanie S

2015-10-14

This Communication describes the terminal-selective, Pt-catalyzed C(sp(3))-H oxidation of aliphatic amines without the requirement for directing groups. CuCl2 is employed as a stoichiometric oxidant, and the reactions proceed in high yield at Pt loadings as low as 1 mol%. These transformations are conducted in the presence of sulfuric acid, which reacts with the amine substrates in situ to form ammonium salts. We propose that protonation of the amine serves at least three important roles: (i) it renders the substrates soluble in the aqueous reaction medium; (ii) it limits binding of the amine nitrogen to Pt or Cu; and (iii) it electronically deactivates the C-H bonds proximal to the nitrogen center. We demonstrate that this strategy is effective for the terminal-selective C(sp(3))-H oxidation of a variety of primary, secondary, and tertiary amines.

General and Efficient a-Oxygenation of Carbonyl Compounds by TEMPO Induced by Single-Electron-Transfer Oxidation of Their Enolates

Czech Academy of Sciences Publication Activity Database

Dinca, E.; Hartmann, P.; Smrček, Jakub; Dix, I.; Jones, P. G.; Jahn, Ullrich

-, č. 24 (2012), s. 4461-4482 ISSN 1434-193X Institutional support: RVO:61388963 Keywords : carbonyl compounds * oxidation * radicals * electron transfer * enolates Subject RIV: CC - Organic Chemistry Impact factor: 3.344, year: 2012

Standard enthalpies of formation of selected Rh2YZ Heusler compounds

International Nuclear Information System (INIS)

Yin, Ming; Nash, Philip

2015-01-01

The standard enthalpies of formation (Δ f H°) of selected ternary Rh-based Rh 2 YZ (Y = Cu, Fe, Mn, Ni, Ru, Ti, V; Z = Al, Ga, In, Si, Ge, Sn) compounds were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation (in kJ/mol of atoms) are, for the Heusler compound Rh 2 MnSn (−40.1 ± 3.6), for the B2-structured compounds: Rh 2 FeAl (−48.5 ± 2.9); Rh 2 MnAl (−72.4 ± 2.7); Rh 2 MnGa (−55.3 ± 2.0); Rh 2 MnIn (−35.3 ± 1.9), for the tetragonal compounds: Rh 2 FeSn (−28.9 ± 1.3); Rh 2 TiAl (−97.6 ± 2.2); Rh 2 TiGa (−79.0 ± 1.8); Rh 2 TiSn (−74.7 ± 3.1). Values are compared with those from first principles calculations in published papers and the Open Quantum Materials Database (OQMD). Lattice parameters of these compounds are determined using X-ray diffraction analysis (XRD). Microstructures were characterized using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). - Highlights: • Standard enthalpies of formation of Rh 2 YZ were measured using a drop calorimeter. • Measured enthalpies agree with first principles data in general. • Lattice parameters and related phase relationships were consistent with literature data. • Rh 2 TiSn of tI8 structure were reported for the first time.

Radiation-induced destruction of organic compounds in aqueous solutions by dual oxidation/reduction mechanism

Energy Technology Data Exchange (ETDEWEB)

Chaychiana, M.; Silverman, J.; Al-Sheikhly, M. [Department of Materials Science and Engineering, University of Maryland (United States); Poster, D.; Neta, P.; Huie, R. [Chemical Science and Technology Laboratory, National Institute of Standard and Technology (United States)

2011-07-01

This research presents the feasibility and mechanisms of using high energy electrons for the dechlorination of polychlorinated biphenyls (PCBs) in marine sediment, and hazardous organic compounds in waste water. The remediation of the organic contaminants by ionizing radiation is achieved by means of both reduction and oxidation processes. PCBs in marine sediment can be effectively dechlorinated by reduction, while toxic organic compounds in water are removed mainly by oxidation. Radiolytic degradation of aqueous suspensions of PCBs in marine sediments in the presence of isopropanol was also studied. Addition of isopropanol was necessary to enhance the radiolytic yield and the dechlorination of PCBs. Also presented are results from an examination of the oxidative and reductive effects of electron-beam irradiation on the concentrations of six organic solvents in water. The organic solvents in water were prepared to mimic a pharmaceutical waste stream. Radiation-induced destruction of benzene was also investigated using pulse radiolysis technique. Pulse radiolysis with spectrophotometric and conductometric detection was utilized to study the formation and reactions of radicals from benzene and dienes in aqueous solutions. The benzene OH adduct, {sup ●}C{sub 6}H{sub 6}OH, reacts with O{sub 2} (k = 3x10{sup 8} L mol{sup -1} s{sup -1}) in a reversible reaction. The peroxyl radical, HOC{sub 6}H{sub 6}O{sub 2}{sup ●}, undergoes O{sub 2}●- elimination, bimolecular decay, and reaction with benzene to initiate a chain reaction, depending on the dose rate, benzene concentration, and pH. The occurrence of the chain reaction is demonstrated in low-dose-rate gamma radiolysis experiments where the consumption of O{sub 2} was monitored. (author)

A PROCESS FOR THE CATALYTIC OXIDATION OF HYDROCARBONS

DEFF Research Database (Denmark)

1999-01-01

A process for producing an alcohol from a gaseous hydrocarbon, e.g. a lower alkane such as methane, via oxidative reaction of the hydrocarbon in a concentrated sulfuric acid medium in the presence of a catalyst employs an added catalyst comprising a substance selected from iodine, iodine compounds...

Study of the emission oxidative reactions of ruthenium (II) complex by cationic compounds in anionic micelles

International Nuclear Information System (INIS)

Bonilha, J.B.S.

1985-01-01

The oxidative quenching of the emission of the tetraanionic complex tris (4,4' dicarboxylate - 2,2' - bipyridine ruthenium (II) in aqueous solution, by both organic and inorganic compounds in presence of anionic detergents, above and below the critical micelle concentration is studied. The organic cations, the inorganic ion and detergents used are shown. (M.J.C.) [pt

Supramolecular Recognition Allows Remote, Site-Selective C-H Oxidation of Methylenic Sites in Linear Amines.

Science.gov (United States)

Olivo, Giorgio; Farinelli, Giulio; Barbieri, Alessia; Lanzalunga, Osvaldo; Di Stefano, Stefano; Costas, Miquel

2017-12-18

Site-selective C-H functionalization of aliphatic alkyl chains is a longstanding challenge in oxidation catalysis, given the comparable relative reactivity of the different methylenes. A supramolecular, bioinspired approach is described to address this challenge. A Mn complex able to catalyze C(sp 3 )-H hydroxylation with H 2 O 2 is equipped with 18-benzocrown-6 ether receptors that bind ammonium substrates via hydrogen bonding. Reversible pre-association of protonated primary aliphatic amines with the crown ether selectively exposes remote positions (C8 and C9) to the oxidizing unit, resulting in a site-selective oxidation. Remarkably, such control of selectivity retains its efficiency for a whole series of linear amines, overriding the intrinsic reactivity of C-H bonds, no matter the chain length. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rapid evaluation of the electrooxidation of fuel compounds with a multiple-electrode setup for direct polymer electrolyte fuel cells

Energy Technology Data Exchange (ETDEWEB)

Fujiwara, Naoko; Siroma, Zyun; Ioroi, Tsutomu; Yasuda, Kazuaki [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan)

2007-02-10

Electrochemical oxidation of fuel compounds in acidic media was examined on eight electrodes (Pt, Ru, PtRu, Rh, Ir, Pd, Au, and glassy carbon) simultaneously by multiple cyclic voltammetry (CV) with an electrochemical cell equipped with an eight-electrode configuration. Direct-type polymer electrolyte fuel cells (PEFCs), in which aqueous solutions of the fuel compounds are directly supplied to the anode, were also evaluated. The performances of direct PEFCs with various anode catalysts could be roughly estimated from the results obtained with multiple CV. This multiple evaluation may be useful for identifying novel fuels or electrocatalysts. Methanol, ethanol, ethylene glycol, 2-propanol, and D-glucose were oxidized selectively on Pt or PtRu, as reported previously. However, several compounds that are often used as reducing agents show electrochemical oxidation with unique characteristics. Large current was obtained for the oxidation of formic acid, hypophosphorous acid, and phosphorous acid on a Pd electrode. L-Ascorbic acid and sulfurous acid were oxidized on all of the electrodes used in the present study. (author)

Selective Production of Aromatic Aldehydes from Heavy Fraction of Bio-oil via Catalytic Oxidation

Energy Technology Data Exchange (ETDEWEB)

Li, Yan; Chang, Jie; Ouyang, Yong; Zheng, Xianwei [South China Univ. of Technology, Guangzhou (China)

2014-06-15

High value-added aromatic aldehydes (e. g. vanillin and syringaldehyde) were produced from heavy fraction of bio-oil (HFBO) via catalytic oxidation. The concept is based on the use of metalloporphyin as catalyst and hydrogen peroxide (H{sub 2}O{sub 2}) as oxidant under alkaline condition. The biomimetic catalyst cobalt(II)-sulfonated tetraphenylporphyrin (Co(TPPS{sub 4})) was prepared and characterized. It exhibited relative high activity in the catalytic oxidation of HFBO. 4.57 wt % vanillin and 1.58 wt % syringaldehyde were obtained from catalytic oxidation of HFBO, compared to 2.6 wt % vanillin and 0.86 wt % syringaldehyde without Co(TPPS{sub 4}). Moreover, a possible mechanism of HFBO oxidation using Co(TPPS{sub 4})/H{sub 2}O{sub 2} was proposed by the research of model compounds. The results showed that this is a promising and environmentally friendly method for production of aromatic aldehydes from HFBO under Co(TPPS{sub 4})/H{sub 2}O{sub 2} system.

Selective Production of Aromatic Aldehydes from Heavy Fraction of Bio-oil via Catalytic Oxidation

International Nuclear Information System (INIS)

Li, Yan; Chang, Jie; Ouyang, Yong; Zheng, Xianwei

2014-01-01

High value-added aromatic aldehydes (e. g. vanillin and syringaldehyde) were produced from heavy fraction of bio-oil (HFBO) via catalytic oxidation. The concept is based on the use of metalloporphyin as catalyst and hydrogen peroxide (H 2 O 2 ) as oxidant under alkaline condition. The biomimetic catalyst cobalt(II)-sulfonated tetraphenylporphyrin (Co(TPPS 4 )) was prepared and characterized. It exhibited relative high activity in the catalytic oxidation of HFBO. 4.57 wt % vanillin and 1.58 wt % syringaldehyde were obtained from catalytic oxidation of HFBO, compared to 2.6 wt % vanillin and 0.86 wt % syringaldehyde without Co(TPPS 4 ). Moreover, a possible mechanism of HFBO oxidation using Co(TPPS 4 )/H 2 O 2 was proposed by the research of model compounds. The results showed that this is a promising and environmentally friendly method for production of aromatic aldehydes from HFBO under Co(TPPS 4 )/H 2 O 2 system

Study of selective oxidation of methane catalyzed by solid superacid in unique reaction field; Tokushu hannoba no kotai chokyosan wo mochiiru methane no sentaku sanka hanno ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Misonoo, M; Tatsumi, T; Mizuno, T; Inumaru, T [The University of Tokyo, Tokyo (Japan)

1997-02-01

Selective oxidation of lower alkanes by use of heteropolymeric compounds is studied. Alkanes are activated on Cs2.5H0.5PW12O40 serving as catalyst, and their activity and selectivity improve when the catalyst is developed into a dual function catalyst in which Cs and Pt are combined. A success is reported of the synthesis of a heteropolymeric acid in which two molecules of the coordination element wolfram are replaced with a transition metal of the first period, on which acid the oxidation of cyclohexane is enhanced. Cs2.5Ni0.08H1.34PVMo11O40 as a metal/heteropolymeric acid dual function catalyst enables the direct oxidation (9% recovered at 340{degree}C) of isobutane into a methacrylic acid, which is attributed to the harmonious coordination of the oxidizing work of the catalyst and acidity. It is possible to oxidize propane into the acrylic acid, but not ethane into the acetic acid. In the case of Pd/Cs2.5H1.5PVMo11O40, the formic acid, methanol, etc., are produced upon addition of hydrogen to the system. This reaction in the hydrogen/oxygen system is supposed to take place via activated oxygen seeds as in the case of oxidation by hydrogen peroxide. 10 refs.

Activating AMP-activated protein kinase by an α1 selective activator compound 13 attenuates dexamethasone-induced osteoblast cell death

International Nuclear Information System (INIS)

Guo, Shiguang; Mao, Li; Ji, Feng; Wang, Shouguo; Xie, Yue; Fei, Haodong; Wang, Xiao-dong

2016-01-01

Excessive glucocorticoid (GC) usage may lead to non-traumatic femoral head osteonecrosis. Dexamethasone (Dex) exerts cytotoxic effect to cultured osteoblasts. Here, we investigated the potential activity of Compound 13 (C13), a novel α1 selective AMP-activated protein kinase (AMPK) activator, against the process. Our data revealed that C13 pretreatment significantly attenuated Dex-induced apoptosis and necrosis in both osteoblastic-like MC3T3-E1 cells and primary murine osteoblasts. AMPK activation mediated C13′ cytoprotective effect in osteoblasts. The AMPK inhibitor Compound C, shRNA-mediated knockdown of AMPKα1, or dominant negative mutation of AMPKα1 (T172A) almost abolished C13-induced AMPK activation and its pro-survival effect in osteoblasts. On the other hand, forced AMPK activation by adding AMPK activator A-769662 or exogenous expression a constitutively-active (ca) AMPKα1 (T172D) mimicked C13's actions and inhibited Dex-induced osteoblast cell death. Meanwhile, A-769662 or ca-AMPKα1 almost nullified C13's activity in osteoblast. Further studies showed that C13 activated AMPK-dependent nicotinamide adenine dinucleotide phosphate (NADPH) pathway to inhibit Dex-induced reactive oxygen species (ROS) production in MC3T3-E1 cells and primary murine osteoblasts. Such effects by C13 were almost reversed by Compound C or AMPKα1 depletion/mutation. Together, these results suggest that C13 alleviates Dex-induced osteoblast cell death via activating AMPK signaling pathway. - Highlights: • Compound 13 (C13) attenuates dexamethasone (Dex)-induced osteoblast cell death. • C13-induced cytoprotective effect against Dex in osteoblasts requires AMPK activation. • Forced AMPK activation protects osteoblasts from Dex, nullifying C13's activities. • C13 increases NADPH activity and inhibits Dex-induced oxidative stress in osteoblasts.

Activating AMP-activated protein kinase by an α1 selective activator compound 13 attenuates dexamethasone-induced osteoblast cell death

Energy Technology Data Exchange (ETDEWEB)

Guo, Shiguang [Department of Intensive Care Unit, Huai' an First People' s Hospital, Nanjing Medical University, Huai' an (China); Mao, Li [Department of Endocrinology, Huai' an First People' s Hospital, Nanjing Medical University, Huai' an (China); Ji, Feng, E-mail: huaiaifengjidr@163.com [Department of Orthopedics, Huai' an First People' s Hospital, Nanjing Medical University, Huai' an (China); Wang, Shouguo; Xie, Yue; Fei, Haodong [Department of Orthopedics, Huai' an First People' s Hospital, Nanjing Medical University, Huai' an (China); Wang, Xiao-dong, E-mail: xiaodongwangsz@163.com [The Center of Diagnosis and Treatment for Children' s Bone Diseases, The Children' s Hospital Affiliated to Soochow University, Suzhou (China)

2016-03-18

Excessive glucocorticoid (GC) usage may lead to non-traumatic femoral head osteonecrosis. Dexamethasone (Dex) exerts cytotoxic effect to cultured osteoblasts. Here, we investigated the potential activity of Compound 13 (C13), a novel α1 selective AMP-activated protein kinase (AMPK) activator, against the process. Our data revealed that C13 pretreatment significantly attenuated Dex-induced apoptosis and necrosis in both osteoblastic-like MC3T3-E1 cells and primary murine osteoblasts. AMPK activation mediated C13′ cytoprotective effect in osteoblasts. The AMPK inhibitor Compound C, shRNA-mediated knockdown of AMPKα1, or dominant negative mutation of AMPKα1 (T172A) almost abolished C13-induced AMPK activation and its pro-survival effect in osteoblasts. On the other hand, forced AMPK activation by adding AMPK activator A-769662 or exogenous expression a constitutively-active (ca) AMPKα1 (T172D) mimicked C13's actions and inhibited Dex-induced osteoblast cell death. Meanwhile, A-769662 or ca-AMPKα1 almost nullified C13's activity in osteoblast. Further studies showed that C13 activated AMPK-dependent nicotinamide adenine dinucleotide phosphate (NADPH) pathway to inhibit Dex-induced reactive oxygen species (ROS) production in MC3T3-E1 cells and primary murine osteoblasts. Such effects by C13 were almost reversed by Compound C or AMPKα1 depletion/mutation. Together, these results suggest that C13 alleviates Dex-induced osteoblast cell death via activating AMPK signaling pathway. - Highlights: • Compound 13 (C13) attenuates dexamethasone (Dex)-induced osteoblast cell death. • C13-induced cytoprotective effect against Dex in osteoblasts requires AMPK activation. • Forced AMPK activation protects osteoblasts from Dex, nullifying C13's activities. • C13 increases NADPH activity and inhibits Dex-induced oxidative stress in osteoblasts.

Selective neuronal vulnerability to oxidative stress in the brain

Directory of Open Access Journals (Sweden)

Xinkun Wang

2010-03-01

Full Text Available Oxidative stress (OS, caused by the imbalance between the generation and detoxification of reactive oxygen and nitrogen species (ROS/RNS, plays an important role in brain aging, neurodegenerative diseases, and other related adverse conditions, such as ischemia. While ROS/RNS serve as signaling molecules at physiological levels, an excessive amount of these molecules leads to oxidative modification and, therefore, dysfunction of proteins, nucleic acids, and lipids. The response of neurons to this pervasive stress, however, is not uniform in the brain. While many brain neurons can cope with a rise in OS, there are select populations of neurons in the brain that are vulnerable. Because of their selective vulnerability, these neurons are usually the first to exhibit functional decline and cell death during normal aging, or in age-associated neurodegenerative diseases, such as Alzheimer’s disease. Understanding the molecular and cellular mechanisms of selective neuronal vulnerability (SNV to OS is important in the development of future intervention approaches to protect such vulnerable neurons from the stresses of the aging process and the pathological states that lead to neurodegeneration. In this review, the currently known molecular and cellular factors that contribute to SNV to OS are summarized. Included among the major underlying factors are high intrinsic OS, high demand for ROS/RNS-based signaling, low ATP production, mitochondrial dysfunction, and high inflammatory response in vulnerable neurons. The contribution to the selective vulnerability of neurons to OS by other intrinsic or extrinsic factors, such as deficient DNA damage repair, low calcium-buffering capacity, and glutamate excitotoxicity, are also discussed.

Sensitivity, selectivity and stability of tin oxide nanostructures on large area arrays of microhotplates

Science.gov (United States)

Panchapakesan, Balaji; Cavicchi, Richard; Semancik, Steve; DeVoe, Don L.

2006-01-01

In this paper, the sensitivity, stability and selectivity of nanoparticle engineered tin oxide (SnO2) are reported, for microhotplate chemical sensing applications. 16 Å of metals such as nickel, cobalt, iron, copper and silver were selectively evaporated onto each column of the microhotplate array. Following evaporation, the microhotplates were heated to 500 °C and SnO2 was deposited on top of the microhotplates using a self-aligned chemical vapour deposition process. Scanning electron microscopy characterization revealed control of SnO2 nanostructures in the range of 20-121 nm. Gas sensing in seven different hydrocarbons revealed that metal nanoparticles that helped in producing faster nucleation of SnO2 resulted in smaller grain size and higher sensitivity. Sensitivity as a function of concentration and grain size is addressed for tin oxide nanostructures. Smaller grain sizes resulted in higher sensitivity of tin oxide nanostructures. Temperature programmed sensing of the devices yielded shape differences in the response between air and methanol, illustrating selectivity. Spiderweb plots were used to monitor the materials programmed selectivity. The shape differences between different gases in spiderweb plots illustrate materials selectivity as a powerful mapping approach for monitoring selectivity in various gases. Continuous monitoring in 80 ppm methanol yielded stable sensor response for more than 200 h. This comprehensive study illustrates the use of a nanoparticle engineering approach for sensitive, selective and stable gas sensing applications.

SEURAT-1 liver gold reference compounds: a mechanism-based review.

Science.gov (United States)

Jennings, Paul; Schwarz, Michael; Landesmann, Brigitte; Maggioni, Silvia; Goumenou, Marina; Bower, David; Leonard, Martin O; Wiseman, Jeffrey S

2014-12-01

There is an urgent need for the development of alternative methods to replace animal testing for the prediction of repeat dose chemical toxicity. To address this need, the European Commission and Cosmetics Europe have jointly funded a research program for 'Safety Evaluation Ultimately Replacing Animal Testing.' The goal of this program was the development of in vitro cellular systems and associated computational capabilities for the prediction of hepatic, cardiac, renal, neuronal, muscle, and skin toxicities. An essential component of this effort is the choice of appropriate reference compounds that can be used in the development and validation of assays. In this review, we focus on the selection of reference compounds for liver pathologies in the broad categories of cytotoxicity and lipid disorders. Mitochondrial impairment, oxidative stress, and apoptosis are considered under the category of cytotoxicity, while steatosis, cholestasis, and phospholipidosis are considered under the category of lipid dysregulation. We focused on four compound classes capable of initiating such events, i.e., chemically reactive compounds, compounds with specific cellular targets, compounds that modulate lipid regulatory networks, and compounds that disrupt the plasma membrane. We describe the molecular mechanisms of these compounds and the cellular response networks which they elicit. This information will be helpful to both improve our understanding of mode of action and help in the selection of appropriate mechanistic biomarkers, allowing us to progress the development of animal-free models with improved predictivity to the human situation.

Uranium-oxide-based catalysts for the destruction of volatile chloro-organic compounds

International Nuclear Information System (INIS)

Hutchings, G.; Heneghan, C.S.; Taylor, S.H.

1996-01-01

The industrial release of hydrocarbons and chlorine-containing organic molecules into the environment continues to attract considerable public concern, which in turn has led to governmental attempts to control such emissions. The challenge is to reduce pollution without stifling economic growth. Chlorine-containing pollutants are known to be particularly stable, and at present the main industrial process for their destruction involves thermal oxidation at 1,000 o C, an expensive process that can lead to the formation of highly toxic by-products such as dioxins and dibenzofurans. Catalytic combustion at lower temperatures could potentially destroy pollutants more efficiently (in terms of energy requirements) and without forming toxic by-products. Current industrial catalysts are based on precious metals that are deactivated rapidly by organochlorine compounds. Here we report that catalysts based on uranium oxide efficiently destroy a range of hydrocarbon and chlorine-containing pollutants, and that these catalysts are resistant to deactivation. We show that benzene, toluene, chlorobutane and chlorobenzene can be destroyed at moderate temperatures ( o C) and industrially relevant flow rates. (Author)

Selection of Suitable Microorganism for Biocatalytic Oxidation Reaction of Racemic Propranolol

Directory of Open Access Journals (Sweden)

Rahime SONGÜR

2017-12-01

Full Text Available Propranolol is one of the β-blockers which are pharmaceutically important, especially used for treatment of cardiovasculer disease. In this study, the production of enantiomerically pure propranolol was aimed via biocatalytic deracemization including tandem oxidation-reduction reactions of racemic propranolol. Within this content, firstly suitable microorganism for the oxidation of racemic propranolol was investigated. Alcohol dehydrogenase (ADH enzyme for oxidation of propranolol and NADH oxidase enzyme for cofactor regeneration were necessary for the oxidation reactions. For this reason, ADH and NADH oxidase enzymes activities of different microorganisms were measured to select the microorganism for using as enzyme source. These microorganisms are Lactobacillus kefir NRRL B-1839, Rhodotorula glutunis DSM 70398, Rhizopus oryzae CBS 111718, Rhizopus arhizus. The highest ADH and NADH oxidase activities were obtained for L. kefir.

Experimental investigation on regulated and unregulated emissions of a diesel/methanol compound combustion engine with and without diesel oxidation catalyst.

Science.gov (United States)

Zhang, Z H; Cheung, C S; Chan, T L; Yao, C D

2010-01-15

The use of methanol in combination with diesel fuel is an effective measure to reduce particulate matter (PM) and nitrogen oxides (NOx) emissions from in-use diesel vehicles. In this study, a diesel/methanol compound combustion (DMCC) scheme was proposed and a 4-cylinder naturally-aspirated direct-injection diesel engine modified to operate on the proposed combustion scheme. The effect of DMCC and diesel oxidation catalyst (DOC) on the regulated emissions of total hydrocarbons (THC), carbon monoxide (CO), NOx and PM was investigated based on the Japanese 13 Mode test cycle. Certain unregulated emissions, including methane, ethyne, ethene, 1,3-butadiene, BTX (benzene, toluene, xylene), unburned methanol and formaldehyde were also evaluated based on the same test cycle. In addition, the soluble organic fraction (SOF) in the particulate and the particulate number concentration and size distribution were investigated at certain selected modes of operation. The results show that the DMCC scheme can effectively reduce NOx, particulate mass and number concentrations, ethyne, ethene and 1,3-butadiene emissions but significantly increase the emissions of THC, CO, NO(2), BTX, unburned methanol, formaldehyde, and the proportion of SOF in the particles. After the DOC, the emission of THC, CO, NO(2), as well as the unregulated gaseous emissions, can be significantly reduced when the exhaust gas temperature is sufficiently high while the particulate mass concentration is further reduced due to oxidation of the SOF. Copyright 2009 Elsevier B.V. All rights reserved.

Formation of titanium oxide coatings on NiTi shape memory alloys by selective oxidation

International Nuclear Information System (INIS)

Pohl, M.; Glogowski, T.; Kuehn, S.; Hessing, C.; Unterumsberger, F.

2008-01-01

Materials used for medical devices that are in contact with human tissue must have good corrosion resistance and biocompatibility. NiTi shape memory alloys (SMAs) are often used in medical applications due to their special functional and mechanical properties (shape memory effect, pseudo elasticity). Because of the high Ni content in nearly stoichiometric NiTi SMAs, the possibility of Ni being released needs to be considered as Ni may cause problems in the human body. SMAs exhibit a high intrinsic corrosion resistance because of the thermodynamic stability of Ni (thermodynamic reason) and the low degree of disorder in a thin protective TiO 2 -layer (kinetic reason). While therefore there is no need to be concerned too much about a normal corrosive attack in the human body, it has to be kept in mind that in medical applications, these materials represent one part of a tribological system where wear processes need to be considered. The formation of a uniform TiO 2 -layer can be beneficial in this respect. The selective oxidation of Ti to TiO 2 on the surface is a promising method to decrease the Ni release significantly. This can be achieved by controlling the partial pressure of oxygen during a controlled oxidation process. The atmosphere must be adjusted so that TiO 2 is stable while NiO cannot yet form. The result of a selective oxidation is a TiO 2 -layer that has an excellent degree of purity and represents a safe barrier against Ni emission

Efficient Conversion of Oximes to the Corresponding Carbonyl Compounds with Tetrabutylammonium Chromate under Aprotic Conditions

International Nuclear Information System (INIS)

Pourali, Ali Reza; Goli, Arezou

2006-01-01

The solubility in several solvents, mildness, simple work-up and absence of side reactions provide advantages of using TBAC in deoximation reactions. This is an efficient and selective method for homogeneous deoximation of structurally different compounds under the moderately acidic and aprotic conditions in high yields. Regeneration of ketones and aldehydes from their oximes has assumed added importance since the discovery of the Barton reaction in which oximes are produced at non-activated hydrocarbon sites. Also, their synthesis from non-carbonyl compounds, such as by nitrosation of an active methylene group, nitrosation of an α-halo carbonyl compound and condensation of a nitro-alkene with an aldehyde provides a valid alternative pathway to carbonyl compounds. Therefore, there has been a continued interest in the effective regeneration of carbonyl compounds from the corresponding oximes especially under mild conditions. Oxidative and reductive methods have been found to show advantages over the classical hydrolytic methods. Although many oxidizing agents have been used, only a limited number of methods are efficient because of the low solubility of these metallic reagents in most organic solvents

Oxidation of the odorous compound 2,4,6-trichloroanisole by UV activated persulfate: Kinetics, products, and pathways.

Science.gov (United States)

Luo, Congwei; Jiang, Jin; Ma, Jun; Pang, Suyan; Liu, Yongze; Song, Yang; Guan, Chaoting; Li, Juan; Jin, Yixin; Wu, Daoji

2016-06-01

The transformation efficiency and products of an odorous compound 2,4,6-trichloroanisole (TCA) at the wavelength of 254 nm in the presence of persulfate were investigated for the first time. The effects of water matrix (i.e., natural organic matter (NOM), pH, carbonate/bicarbonate (HCO3(-)/CO3(2-)), and chloride ions (Cl(-))) were evaluated. The second order rate constant of TCA reacting with sulfate radical (SO4(-)) was determined to be (3.72 ± 0.10) × 10(9) M(-1) s(-1). Increasing dosage of persulfate increased the observed pseudo-first-order rate constant for TCA degradation (kobs), and the contribution of SO4(-) to TCA degradation was much higher than that of HO at each experimental condition. Degradation rate of TCA decreased with pH increasing from 4.0 to 9.0, which could be explained by the lower radical scavenging effect of dihydrogen phosphate than hydrogen phosphate in acidic condition (pH kinetic results could be described by a steady-state kinetic model. Furthermore, liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry at powerful precursor ion scan approach was used to selectively detect oxidation products of TCA. It was found that 2,4,6-trichorophenol (TCP) was the major oxidation product (i.e., the initial yield of TCP was above 90%). The second order rate constant between TCP and SO4(-) was estimated to be (4.16 ± 0.20) × 10(9) M(-1) s(-1). In addition, three products (i.e., 2,6-dichloro-1,4-benzoquinone and two aromatic ring-opening products) were detected in the reaction of TCP with SO4(-), which also appeared in the oxidation of TCA in the UV/persulfate process. A tentative pathway was proposed, where the initial one-electron oxidation of TCA by SO4(-) and further reactions (e.g., ipso-hydroxylation and aromatic ring-cleavage) of the formed cation intermediate TCA were involved. Copyright © 2016. Published by Elsevier Ltd.

Effect of drying method on properties of vanadium-molybdenum oxide catalysts

International Nuclear Information System (INIS)

Gorshkova, T.P.; Savchenko, L.A.; Tarasova, D.V.; Tret'yakov, Yu.D.; Olen'kova, I.P.; Nikoro, T.A.; Maksimov, N.G.

1981-01-01

Effect of drying method of molybdenum and vanadium salt solutions on physicochemical and catalytical properties of vanadium-molybdenum catalysts is studied. It is shown that the drying method of solutions determines the completeness of vanadium binding into oxide vanadium-molybdenum compounds and thus effects the activity and selectivity of catalysts in acrolein oxidation into acrylic acid. Besides the drying method determines the porous structure of catalysts [ru

Improvements in or relating to compounds

International Nuclear Information System (INIS)

Woodhead, J.L.

1983-01-01

The invention provides a process for the preparation of a dispersible product containing a cerium compound which comprises heating a cerium (IV) oxide hydrate in the presence of a salt to cause deaggregation of aggregated crystallites in the cerium (IV) oxide hydrate and produce a dispersible product containing a cerium compound. (author)

Highly efficient cobalt-doped carbon nitride polymers for solvent-free selective oxidation of cyclohexane

Directory of Open Access Journals (Sweden)

Yu Fu

2017-04-01

Full Text Available Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer (g-C3N4, was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C3N4 matrix and the characteristic structure of polymeric g-C3N4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet–visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C3N4 matrix as the form of Co(IIN bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C3N4 catalyst due to the synergistic effect of Co species and g-C3N4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C3N4 catalysts, among which the catalyst with 9.0 wt% Co content exhibited the highest yield (9.0% of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C3N4 catalysts was elaborated. Keywords: Selective oxidation of cyclohexane, Oxygen oxidant, Carbon nitride, Co-doping

Toward Annealing-Stable Molybdenum-Oxide-Based Hole-Selective Contacts For Silicon Photovoltaics

KAUST Repository

Essig, Stephanie

2018-02-21

Molybdenum oxide (MoOX) combines a high work function with broadband optical transparency. Sandwiched between a hydrogenated intrinsic amorphous silicon passivation layer and a transparent conductive oxide, this material allows a highly efficient hole-selective front contact stack for crystalline silicon solar cells. However, hole extraction from the Si wafer and transport through this stack degrades upon annealing at 190 °C, which is needed to cure the screen-printed Ag metallization applied to typical Si solar cells. Here, we show that effusion of hydrogen from the adjacent layers is a likely cause for this degradation, highlighting the need for hydrogen-lean passivation layers when using such metal-oxide-based carrier-selective contacts. Pre-MoOX-deposition annealing of the passivating a-Si:H layer is shown to be a straightforward approach to manufacturing MoOX-based devices with high fill factors using screen-printed metallization cured at 190 °C.

Ruthenium(III) diphenyldithiocarbamate as mediator for the electrocatalytic oxidation of sulfhydryl compounds at graphite electrode

International Nuclear Information System (INIS)

Nalini, B.; Sriman Narayanan, S.

1998-01-01

Ruthenium(III) diphenyldithiocarbamate was used as mediator to modify graphite electrode by abrasive method. The modified electrode was characterized electrochemically by cyclic voltammetry. The electrode was scanned between 0.0 V to +0.8 V. An anodic peak at + 0.39 V and a cathodic peak at +0.24 V have been observed for a scan rate of 100 mV/s. The electrode has been characterized at various scan rate and pHs in 0.1 M KNO 3 solution. Sulfhydryl compounds, cysteine and glutathione, were electro catalytically oxidised at the modified electrode. pH variation was studied to optimize the conditions for their estimation. Linear response for cysteine is in the range of 0.00-15.20 ppm, with a correlation coefficient (r), of 0.9993. The linear range for glutathione is 0.00-30.40 ppm, with a value of 0.999 for r. The electrocatalytic oxidation of both cysteine and glutathione gave reproducible current values with a standard deviation of 0.1686 for 10 repetitive determinations. The stability and reproducibility of the electrode for the determination of cysteine and glutathione were also discussed. The electrocatalytic oxidation of the sulfhydryl compounds were also studied in hydrodynamic environment. (author)

Solvent/oxidant-switchable synthesis of multisubstituted quinazolines and benzimidazoles via metal-free selective oxidative annulation of arylamidines.

Science.gov (United States)

Lin, Jian-Ping; Zhang, Feng-Hua; Long, Ya-Qiu

2014-06-06

A fast and simple divergent synthesis of multisubstituted quinazolines and benzimidazoles was developed from readily available amidines, via iodine(III)-promoted oxidative C(sp(3))-C(sp(2)) and C(sp(2))-N bond formation in nonpolar and polar solvents, respectively. Further selective synthesis of quinazolines in polar solvent was realized by TEMPO-catalyzed sp(3)C-H/sp(2)C-H direct coupling of the amidine with K2S2O8 as the oxidant. No metal, base, or other additives were needed.

Selective adsorption of volatile organic compounds in micropore aluminum methylphosphonate-alpha: a combined molecular simulation-experimental approach.

Science.gov (United States)

Herdes, Carmelo; Valente, Anabela; Lin, Zhi; Rocha, João; Coutinho, João A P; Medina, Francisco; Vega, Lourdes F

2007-06-19

Results concerning the adsorption capacity of aluminum methylphosphonate polymorph alpha (AlMePO-alpha) for pure ethyl chloride and vinyl chloride by measured individual adsorption isotherms of these pure compounds are presented and discussed here. The experimental data supports the idea of using these materials as selective adsorbents for separating these compounds in mixtures. To explore this possibility further, we have performed grand canonical Monte Carlo simulations using a recently proposed molecular simulation framework for gas adsorption on AlMePO, and the results are presented here. The molecular model of the material was used in a purely transferable manner from a previous work (Herdes, C.; Lin, Z.; Valente, A.; Coutinho, J. A. P.; Vega, L. F. Langmuir 2006, 22, 3097). Regarding the molecular model of the fluids, an existing model for ethyl chloride was improved to capture the experimental dipole value better; an equivalent force field for the vinyl chloride molecule was also developed for simulation purposes. Simulations of the pure compounds were found to be in excellent agreement with the measured experimental data at the three studied temperatures. Simulations were also carried out in a purely predictive manner as a tool to find the optimal conditions for the selective adsorption of these compounds prior experimental measurements are carried out. The influence of the temperature and the bulk composition on the adsorption selectivity was also investigated. Results support the use of AlMePO-alpha as an appropriate adsorbent for the purification process of vinyl chloride, upholding the selective adsorption of ethyl chloride.

Treatment of statin compounds by advanced oxidation processes: Kinetic considerations and destruction mechanisms

Science.gov (United States)

Razavi, Behnaz; Song, Weihua; Santoke, Hanoz; Cooper, William J.

2011-03-01

This study examined the use of advanced oxidation/reduction processes (AO/RPs) for the destruction of cholesterol lowering statin pharmaceuticals. AO/RPs which utilize the oxidizing hydroxyl radical ( rad OH) and reducing aqueous electron (e -aq), to degrade chemical contaminants are alternatives to traditional water treatment methods, and are alternatives as water reuse becomes more generally implemented. Four major statin pharmaceuticals, fluvastatin, lovastatin, pravastatin and simvastatin, were studied, and the absolute bimolecular reaction rate constants with rad OH determined, (6.96±0.16)×10 9, (2.92±0.06)×10 9, (4.16±0.13)×10 9, and (3.13±0.15)×10 9 M -1 s -1, and for e -aq (2.31±0.06)×10 9, (0.45±0.01)×10 9, (1.26±0.01)×10 9, and (0.69±0.02)×10 9 M -1 s -1, respectively. To provide additional information on the radicals formed upon oxidation, transient spectra were measured and the overall reaction efficiency determined. Radical-based destruction mechanisms for destruction of the statins are proposed based on the LC-MS determination of the stable reaction by-products formed using 137Cs γ-irradiation of statin solutions. Knowing the reaction rates, reaction efficiencies and destruction mechanisms of these compounds is essential for the consideration of the use of advanced oxidation/reduction processes for the destruction of statins in aqueous systems.

Treatment of statin compounds by advanced oxidation processes: Kinetic considerations and destruction mechanisms

International Nuclear Information System (INIS)

Razavi, Behnaz; Song Weihua; Santoke, Hanoz; Cooper, William J.

2011-01-01

This study examined the use of advanced oxidation/reduction processes (AO/RPs) for the destruction of cholesterol lowering statin pharmaceuticals. AO/RPs which utilize the oxidizing hydroxyl radical ( · OH) and reducing aqueous electron (e - aq ), to degrade chemical contaminants are alternatives to traditional water treatment methods, and are alternatives as water reuse becomes more generally implemented. Four major statin pharmaceuticals, fluvastatin, lovastatin, pravastatin and simvastatin, were studied, and the absolute bimolecular reaction rate constants with · OH determined, (6.96±0.16)x10 9 , (2.92±0.06)x10 9 , (4.16±0.13)x10 9 , and (3.13±0.15)x10 9 M -1 s -1 , and for e - aq (2.31±0.06)x10 9 , (0.45±0.01)x10 9 , (1.26±0.01)x10 9 , and (0.69±0.02)x10 9 M -1 s -1 , respectively. To provide additional information on the radicals formed upon oxidation, transient spectra were measured and the overall reaction efficiency determined. Radical-based destruction mechanisms for destruction of the statins are proposed based on the LC-MS determination of the stable reaction by-products formed using 137 Cs γ-irradiation of statin solutions. Knowing the reaction rates, reaction efficiencies and destruction mechanisms of these compounds is essential for the consideration of the use of advanced oxidation/reduction processes for the destruction of statins in aqueous systems.

Selection and Application of Sulfide Oxidizing Microorganisms Able to Withstand Thiols in Gas Biodesulfurization Systems.

Science.gov (United States)

Roman, Pawel; Klok, Johannes B M; Sousa, João A B; Broman, Elias; Dopson, Mark; Van Zessen, Erik; Bijmans, Martijn F M; Sorokin, Dimitry Y; Janssen, Albert J H

2016-12-06

After the first commercial applications of a new biological process for the removal of hydrogen sulfide (H 2 S) from low pressure biogas, the need arose to broaden the operating window to also enable the removal of organosulfur compounds from high pressure sour gases. In this study we have selected microorganisms from a full-scale biodesulfurization system that are capable of withstanding the presence of thiols. This full-scale unit has been in stable operation for more than 10 years. We investigated the microbial community by using high-throughput sequencing of 16S rRNA gene amplicons which showed that methanethiol gave a competitive advantage to bacteria belonging to the genera Thioalkalibacter (Halothiobacillaceae family) and Alkalilimnicola (Ectothiorhosdospiraceae family). The sulfide-oxidizing potential of the acclimatized population was investigated under elevated thiol loading rates (4.5-9.1 mM d -1 ), consisting of a mix of methanethiol, ethanethiol, and propanethiol. With this biomass, it was possible to achieve a stable bioreactor operation at which 80% of the supplied H 2 S (61 mM d -1 ) was biologically oxidized to elemental sulfur. The remainder was chemically produced thiosulfate. Moreover, we found that a conventionally applied method for controlling the oxygen supply to the bioreactor, that is, by maintaining a redox potential set-point value, appeared to be ineffective in the presence of thiols.

Potassium N-Iodo p-Toluenesulfonamide (TsNIK, Iodamine-T): A New Reagent for the Oxidation of Hydrazones to Diazo Compounds

Science.gov (United States)

Nicolle, Simon M; Moody, Christopher J

2014-01-01

A new reagent for the oxidation of hydrazones to diazo compounds is described. N-Iodo p-toluenesulfonamide (TsNIK, iodamine-T) allows the preparation of α-diazoesters, α-diazoamides, α-diazoketones and α-diazophosphonates in good yield and in high purity after a simple extractive work-up. α-Diazoesters were also obtained in high yield from the corresponding ketones through a one-pot process of hydrazone formation/oxidation. PMID:24615944

Effects of soy sauce and packaging method on volatile compounds and lipid oxidation of cooked irradiated beef patties

Science.gov (United States)

Kim, Hyun-Wook; Lee, Soo-Yeon; Hwang, Ko-Eun; Song, Dong-Heon; Kim, Yong-Jae; Ham, Yun-Kyung; Lee, Choong-Hee; Choi, Yun-Sang; Lee, Ju-Woon; Kim, Cheon-Jei

2014-10-01

The objective of this study is to determine the effect of soy sauce on volatile compounds and lipid oxidation of cooked irradiated beef patties. Sulfur-containing volatile components, which are produced by irradiation, were not found in all treatments. Volatile components derived from soy sauce, such as 3-hydroxy-2-butanone, acetic acid, 3-methyl-1-butanol and 2-methyl-1-butanol, were detected in beef patties containing soy sauce regardless of irradiation and packaging method. Volatile aldehydes, including hexanal, significantly decreased the irradiated beef patty prepared with soy sauce compared to those of irradiated beef patty made with NaCl at 1 day and 5 days after irradiation. In addition, combined use of vacuum packaging and soy sauce treatments could inhibit the formation of volatile compounds and 2-thiobarbituric acid reactive substances during chilled storage. Therefore, the use of soy sauce in cooked and irradiated beef could reduce the production of volatile components associated with the irradiation-induced off-flavor and lipid oxidation.

UV spectra and OH-oxidation kinetics of gaseous phase morpholinic compounds

KAUST Repository

Rachidi, Mariam El

2014-05-01

This paper presents an experimental study of the UV spectra as well as the kinetics of gaseous phase OH-oxidation of morpholine, N-formylmorpholine (NFM) and N-acetlymorpholine (NAM). The spectra recorded using a UV spectrometer in the spectral range 200-280nm show that the analytes mainly absorb at wavelengths less than 280nm. This indicates that their photolysis potential in the troposphere is insignificant. Meanwhile, the OH-reactivity of these analytes was studied using a triple-jacket 2m long reactor equipped with a multi-reflection system and coupled to an FTIR spectrometer. The experiments were carried out at 295 and 313K for the amine and amides, respectively. The study was conducted in the relative mode using isoprene and benzaldehyde as reference compounds. The rate constants obtained are 14.0±1.9, 4.0±1.1 and 3.8±1.0 (in units of 10-11cm3molecule-1s-1) for morpholine, NFM and NAM respectively. These results are discussed in terms of reactivity and compared to those obtained for other oxy-nitrogenated species. In addition, the determined rate constants are used to estimate effective atmospheric lifetimes of the investigated morpholinic compounds with respect to reaction with OH radicals. © 2014 Elsevier Ltd.

UV spectra and OH-oxidation kinetics of gaseous phase morpholinic compounds

KAUST Repository

Rachidi, Mariam El; El Masri, A.; Roth, E.; Chakir, A.

2014-01-01

This paper presents an experimental study of the UV spectra as well as the kinetics of gaseous phase OH-oxidation of morpholine, N-formylmorpholine (NFM) and N-acetlymorpholine (NAM). The spectra recorded using a UV spectrometer in the spectral range 200-280nm show that the analytes mainly absorb at wavelengths less than 280nm. This indicates that their photolysis potential in the troposphere is insignificant. Meanwhile, the OH-reactivity of these analytes was studied using a triple-jacket 2m long reactor equipped with a multi-reflection system and coupled to an FTIR spectrometer. The experiments were carried out at 295 and 313K for the amine and amides, respectively. The study was conducted in the relative mode using isoprene and benzaldehyde as reference compounds. The rate constants obtained are 14.0±1.9, 4.0±1.1 and 3.8±1.0 (in units of 10-11cm3molecule-1s-1) for morpholine, NFM and NAM respectively. These results are discussed in terms of reactivity and compared to those obtained for other oxy-nitrogenated species. In addition, the determined rate constants are used to estimate effective atmospheric lifetimes of the investigated morpholinic compounds with respect to reaction with OH radicals. © 2014 Elsevier Ltd.

Interactions between iron, phenolic compounds, emulsifiers, and pH in omega-3-enriched oil-in-water emulsions

DEFF Research Database (Denmark)

Sørensen, Ann-Dorit Moltke; Haahr, Anne-Mette; Becker, E.M.

2008-01-01

The behavior of antioxidants in emulsions is influenced by several factors such as pH and emulsifier type. This study aimed to evaluate the interaction between selected food emulsifiers, phenolic compounds, iron, and pH and their effect on the oxidative stability of n-3 polyunsaturated lipids...... products. When iron was present, the pH was crucial for the formation of lipid oxidation products. At pH 3 some phenolic compounds, especially caffeic acid, reduced Fe3+ to Fe2+, and Fe2+ increased lipid oxidation at this pH compared to pH 6. Among the evaluated phenols, caffeic acid had the most...... significant effects, as caffeic acid was found to be prooxidative irrespective of pH, emulsifier type, and presence of iron, although the degrees of lipid oxidation were different at the different experimental conditions. The other evaluated phenols were prooxidative at pH 3 in Citrem-stabilized emulsions...

Pathway and Surface Mechanism Studies of 1,3-butadiene Selective Oxidation Over Vanadium-Molybdenum-Oxygen Catalysts

Energy Technology Data Exchange (ETDEWEB)

Schroeder, William David [Iowa State Univ., Ames, IA (United States)

2001-01-01

The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9-14 m²/g, and compositions were within the solid solution regime, i.e. below 15.0 mol % MoO₃/(MoO₃ + V₂O₅). Laser Raman Spectroscopy and XRD data indicated that solid solutions were formed, and pre- and post-reaction XPS data indicated that catalyst surfaces contained some V⁺⁴ and were further reduced in 1,3-butadiene oxidation. A reaction pathway for 1,3-butadiene partial oxidation to maleic anhydride was shown to involve intermediates such as 3,4-epoxy-1-butene, crotonaldehyde, furan, and 2-butene-1,4-dial. The addition of water to the reaction stream substantially increased catalyst activity and improved selectivity to crotonaldehyde and furan at specific reaction temperatures. At higher water addition concentrations, furan selectivity increased from 12% to over 25%. The catalytic effects of water addition were related to competitive adsorption with various V₂O₅-based surface sites, including the vanadyl V=O, corner sharing V-O-V and edge sharing V-O oxygen. Higher levels of water addition were proposed to impose acidic character by dissociative adsorption. In addition, a novel combinatorial synthesis technique for VMoO was used to investigate the phase transitions of V₂O₅, solid solutions of Mo in V₂O₅, V₉Mo₆O₄₀, and other reduced VMoO compounds, characterized by laser Raman spectroscopy. The natural composition gradient imposed by the sputter deposition apparatus was used to create VMoO arrays containing 225 samples ranging from 7.0-42 mol% MoO₃/(V₂O₅ + MoO₃), determined by EDS analysis.

Protective effects of novel organic selenium compounds against oxidative stress in the nematode Caenorhabditis elegans

Directory of Open Access Journals (Sweden)

Sílvio Terra Stefanello

2015-01-01

Full Text Available Organic selenium compounds possess numerous biological properties, including antioxidant activity. Yet, the high toxicity of some of them, such as diphenyl diselenide (DPDS, is a limiting factor in their current usage. Accordingly, we tested four novel organic selenium compounds in the non-parasite nematode Caenorhabditis elegans and compared their efficacy to DPDS. The novel organic selenium compounds are β-selenoamines 1-phenyl-3-(p-tolylselanylpropan-2-amine (C1 and 1-(2-methoxyphenylselanyl-3-phenylpropan-2-amine (C2 and analogs of DPDS 1,2-bis(2-methoxyphenyldiselenide (C3 and 1,2-bisp-tolyldiselenide (C4. Synchronized worms at the L4 larval stage were exposed for one hour in M9 buffer to these compounds. Oxidative stress conditions were induced by juglone (200 μM and heat shock (35 °C. Moreover, we evaluated C. elegans behavior, GST-4::GFP (glutathione S-transferase expression and the activity of acetylcholinesterase (AChE. All tested compounds efficiently restored viability in juglone stressed worms. However, DPDS, C2, C3 and C4 significantly decreased the defecation cycle time. Juglone-induced GST-4::GFP expression was not attenuated in worms pretreated with the novel compounds, except with C2. Finally, AChE activity was reduced by DPDS, C2, C3 and C4. To our knowledge, this is study firstly showed the effects of C1, C2, C3 and C4 selenium-derived compounds in C. elegans. Low toxic effects were noted, except for reduction in the defecation cycle, which is likely associated with AChE inhibition. The juglone-induced stress (reduced viability was fully reversed by compounds to control animal levels. C2 was also efficient in reducing the juglone-induced GST-4::GFP expression, suggesting the latter may mediate the stress induced by this compound. Future studies could be profitably directed at addressing additional molecular mechanisms that mediate the protective effects of these novel organic selenium compounds.

Effects of soy sauce and packaging method on volatile compounds and lipid oxidation of cooked irradiated beef patties

International Nuclear Information System (INIS)

Kim, Hyun-Wook; Lee, Soo-Yeon; Hwang, Ko-Eun; Song, Dong-Heon; Kim, Yong-Jae; Ham, Yun-Kyung; Lee, Choong-Hee; Choi, Yun-Sang; Lee, Ju-Woon; Kim, Cheon-Jei

2014-01-01

The objective of this study is to determine the effect of soy sauce on volatile compounds and lipid oxidation of cooked irradiated beef patties. Sulfur-containing volatile components, which are produced by irradiation, were not found in all treatments. Volatile components derived from soy sauce, such as 3-hydroxy-2-butanone, acetic acid, 3-methyl-1-butanol and 2-methyl-1-butanol, were detected in beef patties containing soy sauce regardless of irradiation and packaging method. Volatile aldehydes, including hexanal, significantly decreased the irradiated beef patty prepared with soy sauce compared to those of irradiated beef patty made with NaCl at 1 day and 5 days after irradiation. In addition, combined use of vacuum packaging and soy sauce treatments could inhibit the formation of volatile compounds and 2-thiobarbituric acid reactive substances during chilled storage. Therefore, the use of soy sauce in cooked and irradiated beef could reduce the production of volatile components associated with the irradiation-induced off-flavor and lipid oxidation. - Highlights: • Soy sauce (SS) could inhibit volatiles cooked irradiated beef patties. • Vacuum packaging and SS treatment is effective to prevent lipid oxidation. • Hexanal content was highly correlated with TBA value of the irradiated beef patties

Superoxide radical-mediated photocatalytic oxidation of phenolic compounds over Ag{sup +}/TiO{sub 2}: Influence of electron donating and withdrawing substituents

Energy Technology Data Exchange (ETDEWEB)

Xiao, Jiadong [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xie, Yongbing, E-mail: ybxie@ipe.ac.cn [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Han, Qingzhen [State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Cao, Hongbin [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Wang, Yujiao [Department of Chemical and Biomedical Engineering, University of Science and Technology Beijing (China); Nawaz, Faheem; Duan, Feng [National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing Engineering Research Center of Process Pollution Control, Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

2016-03-05

Highlights: • A weak EWG benefited photocatalytic oxidation of phenols the most. • Phenolic compounds were dominantly oxidized by ·O{sub 2}{sup −}, rather than ·OH, {sup 1}O{sub 2} or h{sup +}. • ·O{sub 2}{sup −} preferred to nucleophilically attack EDG substituted phenols. • ·O{sub 2}{sup −} more likely electrophilically attacked EWG substituted phenols. • ·O{sub 2}{sup −} simultaneously nucleophilically and electrophilically assaulted p-chlorophenol. - Abstract: A comparative study was constructed to correlate the electronic property of the substituents with the degradation rates of phenolic compounds and their oxidation pathways under UV with Ag{sup +}/TiO{sub 2} suspensions. It was verified that a weak electron withdrawing substituent benefited photocatalytic oxidation the most, while an adverse impact appeared when a substituent was present with stronger electron donating or withdrawing ability. The addition of p-benzoquinone dramatically blocked the degradation, confirming superoxide radicals (·O{sub 2}{sup −}) as the dominant photooxidant, rather than hydroxyl radicals, singlet oxygen or positive holes, which was also independent of the substituent. Hammett relationship was established based on pseudo-first-order reaction kinetics, and it revealed two disparate reaction patterns between ·O{sub 2}{sup −} and phenolic compounds, which was further verified by the quantum chemical computation on the frontier molecular orbitals and Mulliken charge distributions of ·O{sub 2}{sup −} and phenolic compounds. It was found that electron donating group (EDG) substituted phenols were more likely nucleophilically attacked by ·O{sub 2}{sup −}, while ·O{sub 2}{sup −} preferred to electrophilically assault electron withdrawing group (EWG) substituted phenols. Exceptionally, electrophilic and nucleophilic attack by ·O{sub 2}{sup −} could simultaneously occur in p-chlorophenol degradation, consequently leading to its highest rate

Identification of Oxide Compound in Dolomite Mineral from Aceh Tamiang Region

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Nirmala Sari

2013-08-01

Full Text Available Indonesia has abundant mineral especially carbonate-based mineral, ike dolomite. Particularly in Aceh province's, the largest dolomite deposits is available in Aceh Tamiang district around 1.9 billion tons. Unfortunately, current use of dolomite in the industry and other applications is still limited. In this work we report the advanced preparation of dolomite using calcinations method. Whereas, with this method, the dolomite mineral can be processed into calcium and magnesium oxide which has a very wide field of application and higher values. To obtain optimal results, we also identify the effect of temperature on the formation of oxide compounds. Preliminary study using XRF founded that dolomite in village Selamat is known as the highest concentration of CaO (61.20% followed by MgO (25.28%. It is also showed that the main phase obtained by XRD is dolomite (CaMg(CO32. Furthermore, after the calcinations process at 700 °C, it was founded that the formation of dolomite were CaCO3 and MgO, whereas at temperatures of 900 °C mostly the CaCO3 has decomposed into CaO. SEM observations showed that dolomite has the composition of particles distributed homogeneously along the particle agglomerate when it calcinations.

The content changes of selected phenolic compounds during processing of medicinal plants

OpenAIRE

GROŠAFTOVÁ, Blanka

2007-01-01

This work was aimed to the problem of change of the content of selected phenolic substances during treatment and storage of medical plants. Flavonoids represent small, but very important group of phenolic compounds. The biggest attention was paid to quercetin and rutine.Content of phenolic substances was determined by method of micellar electrokinetic capillary chromatography (MECC) in case of 6 medicinal plants usually used in traditional and modern medicine.

Selective catalytic oxidation of hydrocarbons as a challenge to the chemical engineer

Energy Technology Data Exchange (ETDEWEB)

Emig, G [Erlangen-Nuernberg Univ., Erlangen (Germany, F.R.). Inst. fuer Technische Chemie 1

1977-11-01

In the conversion of the most important chemical raw materials, natural oil and natural gas, to intermediate or end products, selective catalytic oxidation plays an increasing role. This method makes it possible in many cases to use more economical, single-step processes instead of the older multi-step processes. Using the typical example of propylene oxidation or ammonoxidation, the problems encountered by chemical engineers in the development of a heterogeneous-catalytic method of oxidation are demonstrated. The importance of systematic catalyst development is stressed. General aspects of the development of novel processes or the improvement of existing catalytic processes are discussed.

Effect of phenolic compounds on the growth of selected probiotic and pathogenic bacteria.

Science.gov (United States)

Pacheco-Ordaz, R; Wall-Medrano, A; Goñi, M G; Ramos-Clamont-Montfort, G; Ayala-Zavala, J F; González-Aguilar, G A

2018-01-01

Fruit extracts from different tissues (pulp, seed and peel) have shown antimicrobial and prebiotic activities related to their phenolic profile, although structure-specific evaluations have not been reported yet. The effect of five phenolic compounds (catechin and gallic, vanillic, ferulic and protocatechuic acids) identified in different fruits, particularly in mango, was evaluated on the growth of two probiotic (Lactobacillus rhamnosusGG ATCC 53103 and Lactobacillus acidophilusNRRLB 4495) and two pathogenic (Escherichia coli 0157:H7 ATCC 43890 and Salmonella enterica serovar Typhimurium ATCC 14028) bacteria. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of phenolic acids ranged from 15-20 mmol l -1 and 20-30 mmol l -1 against E. coli and S. Typhimurium, respectively. For catechin, the MIC and MBC were 35 mmol l -1 and >35 mmol l -1 against E. coli and S. Typhimurium, respectively. The presence of catechin and gallic, protocatechuic and vanillic acids in MRS broth without dextrose allowed the growth of lactobacilli. Catechin combined with protocatechuic or vanillic acid mildly allowed the growth of both probiotics. In conclusion, phenolic compounds can selectively inhibit the growth of pathogenic bacteria without affecting the viability of probiotics. This study provides relevant information about the effects of phenolic compounds commonly present in fruit and vegetables on the growth of probiotic and pathogenic bacteria. The compounds selectively allowed the growth of probiotic lactobacilli (Lactobacillus rhamnosus GG and Lactobacillus acidophilus) and inhibited pathogenic bacteria (Escherichia coli and Salmonella Typhimurium) at the same concentration (20 mmol l -1 ). These findings can contribute to the formulation of nutraceutical products, such as synbiotics, that can restore or maintain an optimal composition of human microbiota, potentially improving the overall health of the consumer. © 2017 The

QSAR analysis for nano-sized layered manganese-calcium oxide in water oxidation: An application of chemometric methods in artificial photosynthesis.

Science.gov (United States)

Shahbazy, Mohammad; Kompany-Zareh, Mohsen; Najafpour, Mohammad Mahdi

2015-11-01

Water oxidation is among the most important reactions in artificial photosynthesis, and nano-sized layered manganese-calcium oxides are efficient catalysts toward this reaction. Herein, a quantitative structure-activity relationship (QSAR) model was constructed to predict the catalytic activities of twenty manganese-calcium oxides toward water oxidation using multiple linear regression (MLR) and genetic algorithm (GA) for multivariate calibration and feature selection, respectively. Although there are eight controlled parameters during synthesizing of the desired catalysts including ripening time, temperature, manganese content, calcium content, potassium content, the ratio of calcium:manganese, the average manganese oxidation state and the surface of catalyst, by using GA only three of them (potassium content, the ratio of calcium:manganese and the average manganese oxidation state) were selected as the most effective parameters on catalytic activities of these compounds. The model's accuracy criteria such as R(2)test and Q(2)test in order to predict catalytic rate for external test set experiments; were equal to 0.941 and 0.906, respectively. Therefore, model reveals acceptable capability to anticipate the catalytic activity. Copyright © 2015 Elsevier B.V. All rights reserved.

Quantification of Selected Vapour-Phase Compounds using Thermal Desorption-Gas Chromatography

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McLaughlin DWJ

2014-12-01

Full Text Available A robust method for the analysis of selected vapour phase (VP compounds in mainstream smoke (MSS is described. Cigarettes are smoked on a rotary smoking machine and the VP that passes through the Cambridge filter pad collected in a TedlarA¯ bag. On completion of smoking, the bag contents are sampled onto an adsorption tube containing a mixed carbon bed. The tube is subsequently analysed on an automated thermal desorption (TD system coupled to a gas chromatography-flame ionization detector (GC-FID using a PoraPLOT-Q column. Quantification of 14 volatile compounds including the major carbonyls is achieved. Details of the method validation data are included in this paper. This method has been used to analyse the VP of cigarette MSS over a wide range of ‘tar’ deliveries and configurations with excellent repeatability. Results for the University of Kentucky reference cigarette 1R4F are in good agreement with reported values.

Selective removal of methyl mercaptan in coffee aroma using oxidized microporous carbon

Energy Technology Data Exchange (ETDEWEB)

Sakano, T. [Ajinomoto General Foods Inc., Tokyo (Japan). Central Research Laboratoties; Tamon, H.; Okazaki, M. [Kyoto University, Kyoto (Japan). Dept. of Chemical Engineering

1999-10-01

Coffee aroma recovered from the extraction process of roasted coffee beans is used to improve the quality of soluble coffee products. Coffee aroma often has an irritating sulfurous odor. In the present work, it is experimentally elucidated that methyl mercaptan could be selectively removed from the coffee aroma-containing gas by the oxidized microporous carbon. Breakthrough curves of coffee aroma-containing gas on zeolite 5A, microporous carbon (MSC 5A), and MSC 5A oxidized with 13.2N HNO{sub 3} aqueous solution revealed that the adsorption capacity of methyl mercaptan on the oxidized carbon was 4.2 times of that on the zeolite. The loss of desired coffee aroma was decreased using the oxidized carbon in the removal of methyl mercaptan. (author)

Characterisation of selected volatile organic compounds in ...

African Journals Online (AJOL)

GCMS), was used to identify volatile compounds at three different temperatures. Fifty volatile compounds, inclusive of 14 acids, 14 alcohols, and 22 esters were identified and quantified in the two brands of indigenous banana beer samples. Only 12 ...

Decarboxylative alkylation for site-selective bioconjugation of native proteins via oxidation potentials

Science.gov (United States)

Bloom, Steven; Liu, Chun; Kölmel, Dominik K.; Qiao, Jennifer X.; Zhang, Yong; Poss, Michael A.; Ewing, William R.; MacMillan, David W. C.

2018-02-01

The advent of antibody-drug conjugates as pharmaceuticals has fuelled a need for reliable methods of site-selective protein modification that furnish homogeneous adducts. Although bioorthogonal methods that use engineered amino acids often provide an elegant solution to the question of selective functionalization, achieving homogeneity using native amino acids remains a challenge. Here, we explore visible-light-mediated single-electron transfer as a mechanism towards enabling site- and chemoselective bioconjugation. Specifically, we demonstrate the use of photoredox catalysis as a platform to selectivity wherein the discrepancy in oxidation potentials between internal versus C-terminal carboxylates can be exploited towards obtaining C-terminal functionalization exclusively. This oxidation potential-gated technology is amenable to endogenous peptides and has been successfully demonstrated on the protein insulin. As a fundamentally new approach to bioconjugation this methodology provides a blueprint toward the development of photoredox catalysis as a generic platform to target other redox-active side chains for native conjugation.

Decarboxylative alkylation for site-selective bioconjugation of native proteins via oxidation potentials.

Science.gov (United States)

Bloom, Steven; Liu, Chun; Kölmel, Dominik K; Qiao, Jennifer X; Zhang, Yong; Poss, Michael A; Ewing, William R; MacMillan, David W C

2018-02-01

The advent of antibody-drug conjugates as pharmaceuticals has fuelled a need for reliable methods of site-selective protein modification that furnish homogeneous adducts. Although bioorthogonal methods that use engineered amino acids often provide an elegant solution to the question of selective functionalization, achieving homogeneity using native amino acids remains a challenge. Here, we explore visible-light-mediated single-electron transfer as a mechanism towards enabling site- and chemoselective bioconjugation. Specifically, we demonstrate the use of photoredox catalysis as a platform to selectivity wherein the discrepancy in oxidation potentials between internal versus C-terminal carboxylates can be exploited towards obtaining C-terminal functionalization exclusively. This oxidation potential-gated technology is amenable to endogenous peptides and has been successfully demonstrated on the protein insulin. As a fundamentally new approach to bioconjugation this methodology provides a blueprint toward the development of photoredox catalysis as a generic platform to target other redox-active side chains for native conjugation.

Surface Selective Oxide Reduction During the Intercritical Annealing of Medium Mn Steel

Science.gov (United States)

Jo, Kyoung Rae; Cho, Lawrence; Oh, Jong Han; Kim, Myoung Soo; Kang, Ki Cheol; De Cooman, Bruno C.

2017-08-01

Third generation advanced high-strength steels achieve an excellent strength-ductility balance using a cost-effective alloy composition. During the continuous annealing of medium Mn steel, the formation of an external selective oxide layer of MnO has a negative impact on the coating quality after galvanizing. A procedure to reduce the selective oxide was therefore developed. It involves annealing in the temperature range of 1073 K to 1323 K (800 °C to 1050 °C) in a HNx gas atmosphere. Annealing at higher temperatures and the use of larger H2 volume fractions are shown to make the gas atmosphere reducing with respect to MnO. The reduction of the surface MnO layer was observed by SEM, GDOES, and cross-sectional TEM analysis.

Biotransformation of natural gas and oil compounds associated with marine oil discharges.

Science.gov (United States)

Brakstad, Odd Gunnar; Almås, Inger K; Krause, Daniel Franklin

2017-09-01

Field data from the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico (GoM) suggested that oxidation of gas compounds stimulated biodegradation of oil compounds in the deep sea plume. We performed experiments with local seawater from a Norwegian fjord to examine if the presence of dissolved gas compounds (methane, ethane and propane) affected biodegradation of volatile oil compounds, and if oil compounds likewise affected gas compound oxidation. The results from the experiment showed comparable oil compound biotransformation rates in seawater at 5 °C between seawater with and without soluble gases. Gas oxidation was not affected by the presence of volatile oil compounds. Contrary to DWH deep sea plume data, propane oxidation was not faster than methane oxidation. These data may reflect variations between biodegradation of oil and gas in seawater environments with different history of oil and gas exposure. Copyright © 2017 Elsevier Ltd. All rights reserved.

Studies of Deactivation of Methanol to Formaldehyde Selective Oxidation Catalyst

DEFF Research Database (Denmark)

Raun, Kristian Viegaard; Schumann, Max; Høj, Martin

Formaldehyde (CH2O) may be synthesized industrially by selective oxidation of methanol over an iron-molybdate (Fe-Mo) oxide catalyst according to: CH3OH + ½O2 →CH2O + H2O. The reaction is normally carried out in a multitubular reactor with excess of air at 250-400 °C (yield = 90-95 %), known...... the activity of the catalyst [2]. Pure MoO3 in itself has low activity. Literature from the last decades agrees that the major reason for the deactivation is loss of molybdenum from the catalyst. Molybdenum forms volatile species with methanol, which can leave behind Mo poor zones. The catalyst is usually...

Effects of dew point on selective oxidation of TRIP steels containing Si, Mn, and B

Science.gov (United States)

Lee, Suk-Kyu; Kim, Jong-Sang; Choi, Jin-Won; Kang, Namhyun; Cho, Kyung-Mox

2011-04-01

The selective oxidation of Si, Mn, and B on TRIP steel surfaces is a widely known phenomenon that occurs during heat treatment. However, the relationship between oxide formation and the annealing factors is not completely understood. This study examines the effect of the annealing conditions (dew point and annealing temperature) on oxide formation. A low dew point of -40 °C leads to the formation of Si-based oxides on the surface. A high dew point of -20 °C changes the oxide type to Mn-based oxides because the formation of Si oxides on the surface is suppressed by internal oxidation. Mn-based oxides exhibit superior wettability due to aluminothermic reduction during galvanizing.

Spectroscopic studies of neutral and chemically oxidized species of β-carotene, lycopene and norbixin in CH2Cl2: Fluorescence from intermediate compounds

International Nuclear Information System (INIS)

Alwis, D.D.D.H; Chandrika, U.G.; Jayaweera, P.M.

2015-01-01

Radical cations, dications and oxidized intermediate species of three carotenoids, namely, β-carotene, lycopene and norbixin, were generated in CH 2 Cl 2 solutions via chemical oxidation using anhydrous FeCl 3 . UV–vis, fluorescence and fluorescence-excitation spectroscopic studies were performed to understand and compare the nature of intermediate species generated during the chemical oxidation process and subsequent degradation. The intense emission observed at 550 nm can be assigned to the S 2 →S 0 (1 1 B u →1 1 A g ) transition of the carotenoid molecules. The 350 nm excitation during the oxidation process for β-carotene, lycopene and norbixin exhibit intense fluorescence peaks at 492 nm, 493 nm and 500 nm, respectively. These peaks are assigned to intermediate peroxy/epoxy compounds of the three molecules that are formed with molecular oxygen prior to the formation of oxidized short-chain stable compounds. - Highlights: • Fluorescence and UV–vis studies on β-carotene, lycopene and norbixin. • Oxidation, induced by FeCl 3 in CH 2 Cl 2 shows blue shifted fluorescence peaks. • Fluorescence peaks were assigned to intermediate peroxy/epoxy forms of carotenoids. • The D0→D3 transition of radical cations are observed in the near IR region

Platinum-Catalyzed Terminal-Selective C(sp3)–H Oxidation of Aliphatic Amines

Science.gov (United States)

Lee, Melissa; Sanford, Melanie S.

2016-01-01

This paper describes the terminal-selective Pt-catalyzed C(sp3)–H oxidation of aliphatic amines without the requirement for directing groups. CuCl2 is employed as a stoichiometric oxidant, and the reactions proceed in high yield at Pt loadings as low as 1 mol %. These transformations are conducted in the presence of sulfuric acid, which reacts with the amine substrates in situ to form ammonium salts. We propose that protonation of the amine serves at least three important roles: (i) it renders the substrates soluble in the aqueous reaction medium; (ii) it limits binding of the amine nitrogen to Pt or Cu; and (ii) it electronically deactivates the C–H bonds proximal to the nitrogen center. We demonstrate that this strategy is effective for the terminal-selective C(sp3)–H oxidation of a variety of primary, secondary and tertiary amines. PMID:26439251

Design and development of self-passivating biodegradable magnesium alloys using selective element oxidation

Science.gov (United States)

Brar, Harpreet Singh

Metallic biomaterials such as stainless steels, titanium alloys, and cobalt-chromium alloys have been used as structural implant materials for many years. However, due to their limitations in temporary implant applications, there has been increased interest in the development of a biodegradable structural implant device. Magnesium (Mg) alloys have shown great potential as a material for biodegradable structural implant applications. However, low strength and high degradation rate of Mg under physiological conditions are major limitations, causing the implant to lose its structural integrity before the healing process is complete. The main aim of this work was to investigate the possibility of designing Mg-based alloys with ability to form selective protective oxides, thereby aiding in the reduction of the initial degradation rate. A thermodynamics-driven design was utilized to select three elements, namely Gadolinium (Gd), Scandium (Sc) and Yttrium (Y), due to the low enthalpy of formation associated with their oxide species. First, binary alloys were cast under inert atmosphere, solution treated and investigated for degradation rate in Hanks' solution. The Mg-Gd binary alloy showed the fastest degradation rate whereas the Mg-Sc binary alloy showed the slowest degradation rate. The degradation of Mg-Gd and Mg-Y was 18 and 5 times faster than Mg-Sc alloy, respectively. The microstructural analysis of the alloys was performed using X-ray Diffraction (XRD), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). It was observed that the grain size of Mg-Sc alloys is significantly smaller than Mg-Gd and Mg-Y alloys and can be a contributing factor to the reduction in degradation rate. The hardness behavior of the alloys was also investigated using Vickers microhardness Testing. To understand the oxidation behavior and kinetics, samples were oxidized in pure oxygen environment and investigated using microstructural and thermogravimetric analysis (TGA). Auger

Chromatographic air analyser microsystem for the selective and sensitive detection of atmospheric pollutants

International Nuclear Information System (INIS)

Sanchez, Jean-Baptiste; Lahlou, Houda; Mohsen, Yehya; Berger, Franck; Vilanova, Xavier; Correig, Xavier

2011-01-01

The development of industry and automotive trafic produces Volatile Organic Compounds (VOCs) whose toxicity can affect seriously human health and environment. The level of those contaminants in air must be as low as possible. In this context, there is a need for in situ systems that could monitor selectively the concentration of these compounds. The aim of this study is to demonstrate the efficiency of a system build with a pre-concentrator, a chromatographic micro-column and a tin oxide-based gas sensor for the selective and sensitive detection of atmospheric pollutants. In particular, this study is focused on the selective detection of benzene and 1,3 butadiene.

Complementation of biotransformations with chemical C-H oxidation: copper-catalyzed oxidation of tertiary amines in complex pharmaceuticals.

Science.gov (United States)

Genovino, Julien; Lütz, Stephan; Sames, Dalibor; Touré, B Barry

2013-08-21

The isolation, quantitation, and characterization of drug metabolites in biological fluids remain challenging. Rapid access to oxidized drugs could facilitate metabolite identification and enable early pharmacology and toxicity studies. Herein, we compared biotransformations to classical and new chemical C-H oxidation methods using oxcarbazepine, naproxen, and an early compound hit (phthalazine 1). These studies illustrated the low preparative efficacy of biotransformations and the inability of chemical methods to oxidize complex pharmaceuticals. We also disclose an aerobic catalytic protocole (CuI/air) to oxidize tertiary amines and benzylic CH's in drugs. The reaction tolerates a broad range of functionalities and displays a high level of chemoselectivity, which is not generally explained by the strength of the C-H bonds but by the individual structural chemotype. This study represents a first step toward establishing a chemical toolkit (chemotransformations) that can selectively oxidize C-H bonds in complex pharmaceuticals and rapidly deliver drug metabolites.

Recent trends in the development of nanophytobioactive compounds and delivery systems for their possible role in reducing oxidative stress in Parkinson’s disease models

Directory of Open Access Journals (Sweden)

Ganesan P

2015-10-01

Full Text Available Palanivel Ganesan,1,2 Hyun-Myung Ko,2 In-Su Kim,2 Dong-Kug Choi1,2 1Nanotechnology Research Center, Department of Applied Life Science, 2Department of Biotechnology, College of Biomedical and Health Science, Konkuk University, Chungju, Republic of Korea Abstract: Oxidative stress plays a very critical role in neurodegenerative diseases, such as Parkinson’s disease (PD, which is the second most common neurodegenerative disease among elderly people worldwide. Increasing evidence has suggested that phytobioactive compounds show enhanced benefits in cell and animal models of PD. Curcumin, resveratrol, ginsenosides, quercetin, and catechin are phyto-derived bioactive compounds with important roles in the prevention and treatment of PD. However, in vivo studies suggest that their concentrations are very low to cross blood–brain barrier thereby it limits bioavailability, stability, and dissolution at target sites in the brain. To overcome these problems, nanophytomedicine with the controlled size of 1–100 nm is used to maximize efficiency in the treatment of PD. Nanosizing of phytobioactive compounds enhances the permeability into the brain with maximized efficiency and stability. Several nanodelivery techniques, including solid lipid nanoparticles, nanostructured lipid carriers, nanoliposomes, and nanoniosomes can be used for controlled delivery of nanobioactive compounds to brain. Nanocompounds, such as ginsenosides (19.9 nm synthesized using a nanoemulsion technique, showed enhanced bioavailability in the rat brain. Here, we discuss the most recent trends and applications in PD, including 1 the role of phytobioactive compounds in reducing oxidative stress and their bioavailability; 2 the role of nanotechnology in reducing oxidative stress during PD; 3 nanodelivery systems; and 4 various nanophytobioactive compounds and their role in PD. Keywords: Parkinson’s disease, phytobioactive compounds, nanotechnology delivery systems, nanocurcumin

Electro-oxidation of reverse osmosis concentrates generated in tertiary water treatment.

Science.gov (United States)

Pérez, G; Fernández-Alba, A R; Urtiaga, A M; Ortiz, I

2010-05-01

This work investigates the application of the electro-oxidation technology provided with boron doped diamond (BDD), an electrode material which has shown outstanding properties in oxidation of organic and inorganic compounds, for the treatment of reverse osmosis (RO) concentrates generated in tertiary wastewater treatment plants (WWTP). Chemical oxygen demand (COD), ammonium and several anions were measured during the electro-oxidation process, and the influence of the applied current density (20-200A/m(2)) was analysed on process kinetics. Analytical assessment showed that several emerging pollutants (pharmaceuticals, personal care products, stimulants, etc.) were presented both in the effluent of the secondary WWTP as well as in the RO concentrate. For this reason, a group of 10 emerging pollutants, those found with higher concentrations, was selected in order to test whether electro-oxidation can be also applied for their mitigation. In the removal of emerging pollutants the electrical current density in the range 20-100A/m(2) did not show influence likely due to the mass transfer resistance developed in the process when the oxidized solutes are present in such low concentrations. Their removal rates were fitted to first order expressions, and the apparent kinetic constants for the anodic oxidation of each compound were calculated. Finally, the formation of trihalomethanes (THMs) has been checked; concluding that after selecting the appropriate operational conditions the attained concentration is lower than the standards for drinking water established in European and EPA regulations. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Treatment of statin compounds by advanced oxidation processes: Kinetic considerations and destruction mechanisms

Energy Technology Data Exchange (ETDEWEB)

Razavi, Behnaz, E-mail: brazavi@uci.ed [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175 (United States); Song Weihua, E-mail: wsong@uci.ed [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175 (United States); Santoke, Hanoz, E-mail: hsantoke@uci.ed [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175 (United States); Cooper, William J., E-mail: wcooper@uci.ed [Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, Irvine, CA 92697-2175 (United States)

2011-03-15

This study examined the use of advanced oxidation/reduction processes (AO/RPs) for the destruction of cholesterol lowering statin pharmaceuticals. AO/RPs which utilize the oxidizing hydroxyl radical ({sup {center_dot}O}H) and reducing aqueous electron (e{sup -}{sub aq}), to degrade chemical contaminants are alternatives to traditional water treatment methods, and are alternatives as water reuse becomes more generally implemented. Four major statin pharmaceuticals, fluvastatin, lovastatin, pravastatin and simvastatin, were studied, and the absolute bimolecular reaction rate constants with {sup {center_dot}O}H determined, (6.96{+-}0.16)x10{sup 9}, (2.92{+-}0.06)x10{sup 9}, (4.16{+-}0.13)x10{sup 9}, and (3.13{+-}0.15)x10{sup 9} M{sup -1} s{sup -1}, and for e{sup -}{sub aq} (2.31{+-}0.06)x10{sup 9}, (0.45{+-}0.01)x10{sup 9}, (1.26{+-}0.01)x10{sup 9}, and (0.69{+-}0.02)x10{sup 9} M{sup -1} s{sup -1}, respectively. To provide additional information on the radicals formed upon oxidation, transient spectra were measured and the overall reaction efficiency determined. Radical-based destruction mechanisms for destruction of the statins are proposed based on the LC-MS determination of the stable reaction by-products formed using {sup 137}Cs {gamma}-irradiation of statin solutions. Knowing the reaction rates, reaction efficiencies and destruction mechanisms of these compounds is essential for the consideration of the use of advanced oxidation/reduction processes for the destruction of statins in aqueous systems.

Catalytic Decomposition of Nitrous Oxide over Catalysts Prepared from Co/Mg-Mn/Al Hydrotalcite-like Compounds

Czech Academy of Sciences Publication Activity Database

Obalová, L.; Jirátová, Květa; Kovanda, F.; Pacultová, K.; Lacný, Z.; Mikulová, Zuzana

2005-01-01

Roč. 60, 3-4 (2005), s. 289-297 ISSN 0926-3373 R&D Projects: GA ČR(CZ) GA106/05/0366; GA ČR(CZ) GA104/04/2116; GA ČR(CZ) GA106/02/0523 Institutional research plan: CEZ:AV0Z40720504 Keywords : decomposition of nitrous oxide * hydrotalcite-like compounds Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.809, year: 2005

Zeolite and zeotype-catalysed transformations of biofuranic compounds

DEFF Research Database (Denmark)

Li, Hu; Yang, Song; Riisager, Anders

2016-01-01

,5-furandicarboxylic acid can be obtained from hexoses and pentoses via selective dehydration and subsequent etherification, hydrogenation, oxidation reactions, which show great potential for industrial applications to replace petroleum-based chemicals and fuels. Zeolite and zeotype micro- and mesoporous materials...... with tuneable acidity, good thermal stability and shape-selectivity have recently emerged as promising solid catalysts, exhibiting superior catalytic performance to other heterogeneous catalysts. This review focuses on the synthesis of biomass-derived furanic compounds catalysed by zeolitic materials, firstly...... introducing zeolite-catalysed hydrolysis of di-, oligo- and polysaccharides and isomerization reactions of monomeric sugars. Subsequently, the catalytic dehydration reactions of hexoses and pentoses to obtain HMF and furfural are reported. Particularly, a variety of reaction pathways towards upgrading...

Selective C(sp3)−H aerobic oxidation enabled by decatungstate photocatalysis in flow

NARCIS (Netherlands)

Laudadio, G.; Govaerts, S.; Wang, Y.; Ravelli, D.; Koolman, H.; Fagnoni, M.; Djuric, S.; Noel, T.

2018-01-01

A mild and selective C(sp3)−H aerobic oxidation enabled by decatungstate photocatalysis has been developed. The reaction can be significantly improved in a microflow reactor enabling the safe use of oxygen and enhanced irradiation of the reaction mixture. Our method allows for the oxidation of both

Photocatalytic selective oxidation of phenol in suspensions of titanium dioxide with exposed {0 0 1} facets

International Nuclear Information System (INIS)

Ye, Hengpeng; Lu, Shaoming

2013-01-01

Anatase TiO 2 nanocrystals with exposed {0 0 1} facets were tailored by hydrothermal treatment of Ti(OC 4 H 9 ) 4 –HF–H 2 O mixed solution. The photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms and X-ray photoelectron spectroscopy (XPS). The effect of structure of the photocatalyst on the photocatalytic selective oxidation of phenol under UV irradiation was studied. The experiment results showed that (1) the percentage of the exposed {0 0 1} facets of the nanocrystal increases with increasing the nominal atomic ratio of fluorine to titanium (R F ), (2) catechol and hydroquinone are main intermediates detected during photocatalytic oxidation of phenol, and (3) both photocatalytic oxidation of phenol and selectivity (yield) of catechol are positively correlated with the percentage of exposed {0 0 1} facets of the high-energy TiO 2 nanocrystals. The enhanced conversion of phenol and selectivity (yield) of catechol were ascribed to the synergistic effects of the exposed high-energy {0 0 1} facets and surface fluorination. This study may provide new insight into the selective oxidation of organics.

Comparison of UV irradiation and p-fluorphenylaline as selective agents for production of aromatic compounds in plant cell culture

International Nuclear Information System (INIS)

Quesnel, A.A.; Ellis, B.E.

1989-01-01

Resistance to UV irradiation, and to the toxicity of p-fluorophenylalanine, can both be mediateted in plants by enhanced synthesis of aromatic compounds. These selective agents were applied to cell cultures of Nicotiana tabacum, Anchusa officinalis and Catharanthus roseur, and the production of aromatic metabolites in the resulting resistant lines of each species was compared. While Nicotiana and Anchusa cultures responded to each selective agent ith an enhanced accumulation of aromatic compounds, the Catharanthus cultures acquired resistance through other, unknown, mechanisms. Some degree of cross-resistance was observed between cultures selected individually for resistance to each agent (author). 26 refs.; 2 figs.; 1 tab

Mild and selective vanadium-catalyzed oxidation of benzylic, allylic, and propargylic alcohols using air

Science.gov (United States)

Hanson, Susan Kloek; Silks, Louis A; Wu, Ruilian

2013-08-27

The invention concerns processes for oxidizing an alcohol to produce a carbonyl compound. The processes comprise contacting the alcohol with (i) a gaseous mixture comprising oxygen; and (ii) an amine compound in the presence of a catalyst, having the formula: ##STR00001## where each of R.sup.1-R.sup.12 are independently H, alkyl, aryl, CF.sub.3, halogen, OR.sup.13, SO.sub.3R.sup.14, C(O)R.sup.15, CONR.sup.16R.sup.17 or CO.sub.2R.sup.18; each of R.sup.13-R.sup.18 is independently alkyl or aryl; and Z is alkl or aryl.

Selective electrocatalytic oxidation of sorbitol to fructose and sorbose.

Science.gov (United States)

Kwon, Youngkook; de Jong, Ed; van der Waal, Jan Kees; Koper, Marc T M

2015-03-01

A new electrocatalytic method for the selective electrochemical oxidation of sorbitol to fructose and sorbose is demonstrated by using a platinum electrode promoted by p-block metal atoms. By the studying a range of C4, C5 and C6 polyols, it is found that the promoter interferes with the stereochemistry of the polyol and thereby modifies its reactivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Thermodynamic Properties of the f-Elements and their Compounds. Part 2. The Lanthanide and Actinide Oxides

Energy Technology Data Exchange (ETDEWEB)

Konings, Rudy J. M., E-mail: rudy.konings@ec.europa.eu; Beneš, Ondrej; Kovács, Attila; Manara, Dario; Sedmidubský, David [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, 76125 Karlsruhe (Germany); Gorokhov, Lev; Iorish, Vladimir S.; Yungman, Vladimir; Shenyavskaya, E.; Osina, E. [Joint Institute for High Temperatures, Russian Academy of Sciences, 13-2 Izhorskaya Street, Moscow 125412 (Russian Federation)

2014-03-15

A comprehensive review of the thermodynamic properties of the oxide compounds of the lanthanide and actinide elements is presented. The available literature data for the solid, liquid, and gaseous state have been analysed and recommended values are presented. In case experimental data are missing, estimates have been made based on the trends in the two series, which are extensively discussed.

Rationalization and in vitro modeling of the chemical mechanisms of the enzymatic oxidation of phenolic compounds in planta: from flavonols and stilbenoids to lignins.

Science.gov (United States)

Cottyn, Betty; Kollmann, Albert; Waffo-Teguo, Pierre; Ducrot, Paul-Henri

2011-06-20

Enzymatic oxidation of phenolic compounds is a widespread phenomenon in plants. It is responsible for the formation of many oligomers and polymers, which are generally described as the result of a combinatorial coupling of the different radicals formed through oxidation of the phenol group and delocalization of the radical. We focused our interest on several phenolic compounds that are present in plants and known to form, under enzymatic oxidation, oligomers with different type of linkages between monomers. To explain this diversity of inter-monomer linkages and their variation according to the experimental procedure used for the enzymatic oxidation, we report an alternative mechanistic pathway involving dismutation of the radicals, leading to the formation of carbocations which, thereafter, react with nucleophilic species present in the medium. This alternative pathway allows the understanding of peculiar linkages between monomeric units in the oligomer and offers new insights for understanding the formation of phenolic biopolymers in plants. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Base-Free Selective Oxidation of Glycerol over LDH Hosted Transition Metal Complexes Using 3% H2O2 as Oxidant

Directory of Open Access Journals (Sweden)

Xiaoli Wang

2016-07-01

Full Text Available A series of transition metal sulphonato-Schiff base complexes were intercalated into Mg–Al layered-double hydroxides (LDHs. The obtained catalysts were characterized by FTIR, XRD, N2 sorption, SEM and elemental analysis, and then were used in the selective oxidation of glycerol (GLY using 3% H2O2 as an oxidant. It was found that their catalytic performances were closely related to the loading of active complexes, the Schiff base ligands and the metal centers of the catalysts, as well as the reaction conditions. The optimal conversion of GLY was 85.0%, while the selectivity of 1,3-dihydroxyacetone (DHA was 56.5%. Moreover, the catalysts could be reused at least 10 times.

Stripping of organic compounds from wastewater as an auxiliary fuel of regenerative thermal oxidizer

International Nuclear Information System (INIS)

Chang, Meng-Wen; Chern, Jia-Ming

2009-01-01

Organic solvents with different volatilities are widely used in various processes and generate air and water pollution problems. In the cleaning processes of electronics industries, most volatile organic compounds (VOCs) are vented to air pollution control devices while most non-volatile organic solvents dissolve in the cleaning water and become the major sources of COD in wastewater. Discharging a high-COD wastewater stream to wastewater treatment facility often disturbs the treatment performance. A pretreatment of the high-COD wastewater is therefore highly desirable. This study used a packed-bed stripping tower in combination with a regenerative thermal oxidizer to remove the COD in the wastewater from a printed circuit board manufacturing process and to utilize the stripped organic compounds as the auxiliary fuel of the RTO. The experimental results showed that up to 45% of the COD could be removed and 66% of the RTO fuel could be saved by the combined treatment system.

Effects of iron-oxide nanoparticles on compound biofilms of streptococcus gordonii and fusobacterium nucleatum

Science.gov (United States)

Nguyen, Jane Q.; Withers, Nathan J.; Alas, Gema; Senthil, Arjun; Minetos, Christina; Jaiswal, Nikita; Ivanov, Sergei A.; Huber, Dale L.; Smolyakov, Gennady A.; Osiński, Marek

2018-02-01

The human mouth is a host of a large gamut of bacteria species, with over 700 of different bacteria strains identified. Most of these bacterial species are harmless, some are beneficial (such as probiotics assisting in food digestion), but some are responsible for various diseases, primarily tooth decay and gum diseases such as gingivitis and periodontitis. Dental plaque has a complicated structure that varies from patient to patient, but a common factor in most cases is the single species of bacterium acting as a secondary colonizer, namely Fusobacterium nucleatum, while the actual disease is caused by a variety of tertiary colonizers. We hypothesize that destruction of a compound biofilm containing Fusobacterium nucleatum will prevent tertiary colonizers (oral pathogens) from establishing a biofilm, and thus will protect the patient from developing gingivitis and periodontitis. In this paper, we report on the effects of exposure of compound biofilms of a primary colonizer Streptococcus gordonii combined with Fusobacterium nucleatum to iron oxide nanoparticles as possible bactericidal agent.

Protective Actions of 17β-Estradiol and Progesterone on Oxidative Neuronal Injury Induced by Organometallic Compounds

Directory of Open Access Journals (Sweden)

Yasuhiro Ishihara

2015-01-01

Full Text Available Steroid hormones synthesized in and secreted from peripheral endocrine glands pass through the blood-brain barrier and play a role in the central nervous system. In addition, the brain possesses an inherent endocrine system and synthesizes steroid hormones known as neurosteroids. Increasing evidence shows that neuroactive steroids protect the central nervous system from various harmful stimuli. Reports show that the neuroprotective actions of steroid hormones attenuate oxidative stress. In this review, we summarize the antioxidative effects of neuroactive steroids, especially 17β-estradiol and progesterone, on neuronal injury in the central nervous system under various pathological conditions, and then describe our recent findings concerning the neuroprotective actions of 17β-estradiol and progesterone on oxidative neuronal injury induced by organometallic compounds, tributyltin, and methylmercury.

Formation of biomineral iron oxides compounds in a Fe hyperaccumulator plant: Imperata cylindrica (L.) P. Beauv.

Science.gov (United States)

Fuente, V; Rufo, L; Juárez, B H; Menéndez, N; García-Hernández, M; Salas-Colera, E; Espinosa, A

2016-01-01

We report a detailed work of composition and location of naturally formed iron biominerals in plant cells tissues grown in iron rich environments as Imperata cylindrica. This perennial grass grows on the Tinto River banks (Iberian Pyritic Belt) in an extreme acidic ecosystem (pH∼2.3) with high concentration of dissolved iron, sulphate and heavy metals. Iron biominerals were found at the cellular level in tissues of root, stem and leaf both in collected and laboratory-cultivated plants. Iron accumulated in this plant as a mix of iron compounds (mainly as jarosite, ferrihydrite, hematite and spinel phases) was characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy (MS), magnetometry (SQUID), electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX; TEM-EDX; HRSTEM). A low fraction of phosphorous was detected in this iron hyperaccumulator plant. Root and rhizomes tissues present a high proportion of ferromagnetic iron oxide compounds. Iron oxides-rich zones are localized in electron dense intra and inter-cellular aggregates that appear as dark deposits covering the inner membrane and organelles of the cell. This study aims to contribute to a better understanding of the mechanisms of accumulation, transport, distribution of iron in Imperata cylindrica. Copyright © 2015 Elsevier Inc. All rights reserved.

Selective Oxidation of Alcohols Using Photoactive VO@g‑C3N4

Data.gov (United States)

U.S. Environmental Protection Agency — A photoactive VO@g-C3N4 catalyst has been developed for the selective oxidation of alcohols to the corresponding aldehydes and ketones. The visible light mediated...

AMP N1-Oxide, a Unique Compound of Royal Jelly, Induces Neurite Outgrowth from PC12 Vells via Signaling by Protein Kinase A Independent of that by Mitogen-Activated Protein Kinase

Directory of Open Access Journals (Sweden)

Noriko Hattori

2010-01-01

Full Text Available Earlier we identified adenosine monophosphate (AMP N1-oxide as a unique compound of royal jelly (RJ that induces neurite outgrowth (neuritegenesis from cultured rat pheochromocytoma PC12 cells via the adenosine A2A receptor. Now, we found that AMP N1-oxide stimulated the phosphorylation of not only mitogen-activated protein kinase (MAPK but also that of cAMP/calcium-response element-binding protein (CREB in a dose-dependent manner. Inhibition of MAPK activation by a MEK inhibitor, PD98059, did not influence the AMP N1-oxide-induced neuritegenesis, whereas that of protein kinase A (PKA by a selective inhibitor, KT5720, significantly reduced neurite outgrowth. AMP N1-oxide also had the activity of suppressing the growth of PC12 cells, which correlated well with the neurite outgrowth-promoting activity. KT5720 restored the growth of AMP N1-oxide-treated PC12 cells. It is well known that nerve growth factor suppresses proliferation of PC12 cells before causing stimulation of neuronal differentiation. Thus, AMP N1-oxide elicited neuronal differentiation of PC12 cells, as evidenced by generation of neurites, and inhibited cell growth through adenosine A2A receptor-mediated PKA signaling, which may be responsible for characteristic actions of RJ.

Standard enthalpies of formation of selected Rh{sub 2}YZ Heusler compounds

Energy Technology Data Exchange (ETDEWEB)

Yin, Ming, E-mail: myin1@hawk.iit.edu; Nash, Philip

2015-11-25

The standard enthalpies of formation (Δ{sub f}H°) of selected ternary Rh-based Rh{sub 2}YZ (Y = Cu, Fe, Mn, Ni, Ru, Ti, V; Z = Al, Ga, In, Si, Ge, Sn) compounds were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation (in kJ/mol of atoms) are, for the Heusler compound Rh{sub 2}MnSn (−40.1 ± 3.6), for the B2-structured compounds: Rh{sub 2}FeAl (−48.5 ± 2.9); Rh{sub 2}MnAl (−72.4 ± 2.7); Rh{sub 2}MnGa (−55.3 ± 2.0); Rh{sub 2}MnIn (−35.3 ± 1.9), for the tetragonal compounds: Rh{sub 2}FeSn (−28.9 ± 1.3); Rh{sub 2}TiAl (−97.6 ± 2.2); Rh{sub 2}TiGa (−79.0 ± 1.8); Rh{sub 2}TiSn (−74.7 ± 3.1). Values are compared with those from first principles calculations in published papers and the Open Quantum Materials Database (OQMD). Lattice parameters of these compounds are determined using X-ray diffraction analysis (XRD). Microstructures were characterized using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). - Highlights: • Standard enthalpies of formation of Rh{sub 2}YZ were measured using a drop calorimeter. • Measured enthalpies agree with first principles data in general. • Lattice parameters and related phase relationships were consistent with literature data. • Rh{sub 2}TiSn of tI8 structure were reported for the first time.

Selective Se-for-S substitution in Cs-bearing uranyl compounds

Energy Technology Data Exchange (ETDEWEB)

Gurzhiy, Vladislav V., E-mail: vladgeo17@mail.ru [Department of Crystallography, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia Federation (Russian Federation); Tyumentseva, Olga S.; Krivovichev, Sergey V. [Department of Crystallography, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia Federation (Russian Federation); Tananaev, Ivan G. [Far Eastern Federal University, Suhanova st. 8, Vladivostok 690950 (Russian Federation)

2017-04-15

Phase formation in the mixed sulfate-selenate aqueous system of uranyl nitrate and cesium nitrate has been investigated. Two types of crystalline compounds have been obtained and characterized using a number of experimental (single crystal XRD, FTIR, SEM) and theoretical (information-based complexity calculations, topological analysis) techniques. No miscibility gaps have been observed for Cs{sub 2}[(UO{sub 2}){sub 2}(TO{sub 4}){sub 3}] (T= S, Se), which crystallizes in tetragonal system, P-42{sub 1}m, a =9.616(1)–9.856(2), c =8.105(1)–8.159(1) Å, V =749.6(2)–792.5(3) Å{sup 3}. Nine phases with variable amount of S and Se have been structurally characterized. The structures of the Cs{sub 2}[(UO{sub 2}){sub 2}(TO{sub 4}){sub 3}] (T= S, Se) compounds are based upon the [(UO{sub 2}){sub 2}(TO{sub 4}){sub 3}]{sup 2-} layers of corner-sharing uranyl pentagonal bipyramids and TO{sub 4} tetrahedra. The layers contain two types of tetrahedral sites: T1 (3-connected, i.e. having three O atoms shared by adjacent uranyl polyhedra) and T2 (4-connected). The Se-for-S substitution in tetrahedral sites is highly selective with smaller S{sup 6+} cation showing a strong preference for the more tightly bonded T2 site. Crystallization in the pure Se system starts with the formation of Cs{sub 2}[(UO{sub 2})(SeO{sub 4}){sub 2}(H{sub 2}O)](H{sub 2}O) crystals, its subsequent dissolution and formation of Cs{sub 2}[(UO{sub 2}){sub 2}(SeO{sub 4}){sub 3}]. The information-based structural complexity calculations for these two phases support the rule that more topologically complex structures form at the latest stages of crystallization. - Graphical abstract: Nine phases representing the Cs{sub 2}[(UO{sub 2}){sub 2}(TO{sub 4}){sub 3}] (T= S, Se) solid solution series with variable amount of S and Se have been prepared by isothermal evaporation from aqueous solutions and characterized using a number of experimental and theoretical techniques. No immiscibility is observed between the

Development of Vanadium Phosphaate Catalysts for Methanol Production by Selective Oxidation of Methane.

Energy Technology Data Exchange (ETDEWEB)

McCormick, R.L.

1997-10-01

This DOE sponsored study of methane partial oxidation was initiated at Amax Research and Development in Golden, CO in October of 1993. Shortly thereafter the management of Amax closed this R&D facility and the PI moved to the Colorado School of Mines. The project was begun again after contract transfer via a novation agreement. Experimental work began with testing of vandyl pyrophosphate (VPO), a well known alkane selective oxidation catalyst. It was found that VPO was not a selective catalyst for methane conversion yielding primarily CO. However, promotion of VPO with Fe, Cr, and other first row transition metals led to measurable yields for formaldehyde, as noted in the summary table. Catalyst characterization studies indicated that the role of promoters was to stabilize some of the vanadium in the V{sup 5+} oxidation state rather than the V{sup 4+} state formally expected for (VO){sub 2}P{sub 2}O{sub 7}.

New evidence on the formation of oxidizing species in corona discharge in contact with liquid and their reactions with organic compounds.

Science.gov (United States)

Magureanu, M; Dobrin, D; Bradu, C; Gherendi, F; Mandache, N B; Parvulescu, V I

2016-12-01

The objective of these investigations is to understand in more detail how organic compounds in water are degraded during plasma treatment. The formation of oxidizing species (ozone (O 3 ), hydrogen peroxide (H 2 O 2 ) and hydroxyl radicals (OH)) in a pulsed corona discharge in contact with liquid is investigated. The degradation of a target organic compound (methylparaben) in aqueous solution was increased when combining plasma treatment with ozonation, using the O 3 generated in the discharge. Enhanced mass transfer of O 3 obtained in this plasma+O 3 configuration leads to a six fold increase of MeP oxidation rate. The evolution of oxidants concentration during treatment of MeP solutions provides information on their consumption in reactions with MeP and its oxidation products. The correlation of MeP degradation results (MeP removal and mineralization) with O 3 consumption and the identified reaction products confirms that although O 3 plays an important role in the degradation, for the mineralization OH radicals have an essential contribution. The concentration of OH radicals is diminished in the solutions containing MeP as compared to plasma-treated water, indicating OH consumption in reactions with the target compound and its degradation products. The concentration of H 2 O 2 in the liquid can be either increased or reduced in the presence of MeP, depending on its initial concentration. On the one hand, decomposition of H 2 O 2 by OH or O 3 is suppressed in the presence of MeP, but on the other hand less OH radicals are available for its formation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Aerobic and Electrochemical Oxidations with N-Oxyl Reagents

Science.gov (United States)

Miles, Kelsey C.

Selective oxidation of organic compounds represents a significant challenge for chemical transformations. Oxidation methods that utilize nitroxyl catalysts have become increasingly attractive and include Cu/nitroxyl and nitroxyl/NO x co-catalyst systems. Electrochemical activation of nitroxyls is also well known and offers an appealing alternative to the use of chemical co-oxidants. However, academic and industrial organic synthetic communities have not widely adopted electrochemical methods. Nitroxyl catalysts facilitate effective and selective oxidation of alcohols and aldehydes to ketones and carboxylic acids. Selective benzylic, allylic, and alpha-heteroatom C-H abstraction can also be achieved with nitroxyls and provides access to oxygenated products when used in combination with molecular oxygen as a radical trap. This thesis reports various chemical and electrochemical oxidation methods that were developed using nitroxyl mediators. Chapter 1 provides a short review on practical aerobic alcohol oxidation with Cu/nitroxyl and nitroxyl/NO x systems and emphasizes the utility of bicyclic nitroxyls as co-catalysts. In Chapter 2, the combination of these bicyclic nitroxyls with NOx is explored for development of a mild oxidation of alpha-chiral aryl aldehydes and showcases a sequential asymmetric hydroformylation/oxidation method. Chapter 3 reports the synthesis and characterization of two novel Cu/bicyclic nitroxyl complexes and the electronic structure analysis of these complexes. Chapter 4 highlights the electrochemical activation of various nitroxyls and reports an in-depth study on electrochemical alcohol oxidation and compares the reactivity of nitroxyls under electrochemical or chemical activation. N-oxyls can also participate in selective C-H abstraction, and Chapter 5 reports the chemical and electrochemical activation of N-oxyls for radical-mediated C-H oxygenation of (hetero)arylmethanes. For these electrochemical transformations, the development of

The Atmospheric Oxidation of Volatile Organic Compounds Through Hydrogen Shift Reactions

DEFF Research Database (Denmark)

Knap, Hasse Christian

a radical is denoted as a H-shift reaction. Quantum chemical calculations were carried out to investigate the potential energy surface of the H-shift reactions and the subsequent decomposition pathways. The transition state theory including the Eckart quantum tunneling correction have been used to calculate...... the reaction rate constants of the H-shift reactions. The autoxidation of volatile organic compounds is an important oxidation mechanism that produces secondary organic aerosols (SOA) and recycles hydroxyl (OH) radicals. The autoxidation cycle produces a second generation peroxy radical (OOQOOH) through...... a series of H-shift reactions and O2 attachments. I have investigated the H-shift reactions in two OOQOOH radicals (hydroperoxy peroxy radicals and hydroperoxy acyl peroxy radicals). The H-shift reaction rate constants have been compared with the bimolecular reaction rate constants of the peroxy radicals...

Effect of Support in Heterogeneous Ruthenium Catalysts Used for the Selective Aerobic Oxidation of HMF in Water

DEFF Research Database (Denmark)

Gorbanev, Yury; Kegnæs, Søren; Riisager, Anders

2011-01-01

Heterogeneous ruthenium-based catalysts were applied in the selective, aerobic oxidation of 5-hydroxymethylfurfural, a versatile biomass-derived chemical, to form 2,5-furandicarboxylic acid. The oxidation reactions were performed in water with dioxygen as the oxidant at different pressures without...

Photocatalytic and chemical oxidation of organic compounds in supercritical carbon dioxide. 1998 annual progress report

International Nuclear Information System (INIS)

Blake, D.M.

1998-01-01

'This report summarizes the results of work done during the first 1.3 years of a three year project. During the first nine months effort focussed on the design, construction and testing of a closed recirculating system that can be used to study photochemistry in supercritical carbon dioxide at pressures up to 5,000 psi and temperatures up to about 50 C. This was followed by a period of work in which the photocatalytic oxidation of benzene and acetone in supercritical, liquid, and gaseous carbon dioxide containing dissolved oxygen was demonstrated. The photocatalyst was titanium dioxide supported on glass spheres. This was the first time it was possible to observe photocatalytic oxidation in a supercritical fluid and to compare reaction in the three fluid phases of a solvent. This also demonstrated that it is possible to purify supercritical and liquid carbon dioxide using photochemical oxidation with no chemical additions other than oxygen. The oxidation of benzene produced no intermediates detectable using on line spectroscopic analysis or by gas chromatographic analysis of samples taken from the flow system. The catalyst surface did darken as the reaction proceeded indicating that oxidation products were accumulating on the surface. This is analogous to the behavior of aromatic compounds in air phase photocatalytic oxidation. The reaction of acetone under similar conditions resulted in the formation of low levels of by-products. Two were identified as products of the reaction of acetone with itself (4-methyl-3-penten-2-one and 4-hydroxy-4-methyl-2-pentanone) using gas chromatography with a mass spectrometer detector. Two other by-products also appear to be from the self-reaction of acetone. By-products of this type had not been observed in prior studies of the gas-phase photocatalytic oxidation of acetone. The by-products that have been observed can also be oxidized under the treatment conditions. The above results establish that photocatalytic oxidation of

Developing Selective Oxidation Catalysts of Light Alkanes:. from Fundamental Understanding to Rational Design

Science.gov (United States)

Fu, Gang; Yi, Xiaodong; Huang, Chuanjing; Xu, Xin; Weng, Weizheng; Xia, Wensheng; Wan, Hui-Lin

Selective oxidation of light alkanes remains to be a great challenge for the wider use of alkanes as feedstocks. To achieve high activity and at the same time high selectivity, some key issues have to be addressed: (1) the stability of the desired products with respect to the reactants; (2) the roles of the active components in the catalysts, the structure and the functionality of the active centers; (3) the reducibility of the metal cations, the Lewis acid sites and their synergic effects with the basic sites of the lattice oxygen anions; (4) spatial isolation of the active centers; and (5) the mechanisms for the formation and transformation of the intermediates and their kinetic controls. In this contribution, we took selective oxidation of propane to acrolein as our target reaction, and reviewed mainly our own work, trying to provide some thinking and answers to these five questions.

The adsorption and reaction of halogenated volatile organic compounds (VOC's) on metal oxides. 1998 annual progress report

International Nuclear Information System (INIS)

Goodman, D.W.; Haw, J.F.; Lunsford, J.

1998-01-01

'The goal of the research is to elucidate the properties of the materials responsible for the activation of halocarbons and the nature of the intermediates formed in the dissociative adsorption of this class of compounds. This information is essential for interpreting and predicting stoichiometric and catalytic pathways for the safe destruction of halocarbon pollutants. The specific objectives are: (1) to study the adsorption and reactivity of chloromethanes and chloroethanes on metal oxides; (2) to identify the reaction intermediates using spectroscopic methods; and (3) to develop kinetic models for the reaction of these halocarbons with oxide surfaces. This report summarizes work after 20 months of a 36-month project. Emphasis has been placed understanding the surfaces phases, as well as the bulk phases that are present during the reactions of chlorinated hydrocarbons with strongly basic metal oxides. Most of the research has been carried out with carbon tetrachloride.'

Oxidation kinetics of polycyclic aromatic hydrocarbons by permanganate

Energy Technology Data Exchange (ETDEWEB)

Forsey, S.P.; Thomson, N.R.; Barker, J.F. [University of Waterloo, Waterloo, ON (Canada). Dept. of Civil & Environmental Engineering

2010-04-15

The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but little kinetic information is available. This study investigated the oxidation kinetics of a selected group of coal tar creosote compounds and alkylbenzenes in water using permanganate, and the correlation between compound reactivity and physical/chemical properties. The oxidation of naphthalene, phenanthrene, chrysene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole isopropylbenzene, ethylbenzene and methylbenzene closely followed pseudo first-order reaction kinetics. The oxidation of pyrene was initially very rapid and did not follow pseudo first-order kinetics at early times. Fluoranthene was only partially oxidized and the oxidation of anthracene was too fast to be captured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene were non-reactive under the study conditions. The oxidation rate was shown to increase with increasing number of polycyclic rings because less energy is required to overcome the aromatic character of a polycyclic ring than is required for benzene. Thus the rate of oxidation increased in the series naphthalene < phenanthrene < pyrene. The rate of side chain reactivity is controlled by the C-H bond strength. For the alkyl substituted benzenes an excellent correlation was observed between the reaction rate coefficients and bond dissociation energies, but for the substituted PAHs the relationship was poor. A trend was found between the reaction rate coefficients and the calculated heats of complexation indicating that significant ring oxidation occurred in addition to side chain oxidation. Clar's aromatic sextet theory was used to predict the relative stability of arenes towards ring oxidation by permanganate.

Studies of vanadium-phosphorus-oxygen selective oxidation catalysts by sup 31 P and sup 51 V NMR spin-echo and volume susceptibility measurements

Energy Technology Data Exchange (ETDEWEB)

Li, Juan.

1991-10-01

The purpose of this work is to characterize the vanadium-phosphorous oxide (V-P-O) catalysts for the selective oxidation of n-butane and 1-butene to maleic anhydride. The utility of solid state nuclear magnetic resonance as an analytical tool in this investigation lies in its sensitivity to the electronic environment surrounding the phosphorous and vanadium nuclei, and proximity of paramagnetic species. Spin-echo mapping NMR of {sup 31}p and {sup 51}v and volume magnetic susceptibility measurements were used as local microscopic probes of the presence of V{sup 5+}, V{sup 4+}, V{sup 3+} species in the model compounds: {beta}-VOPO{sub 4}, {beta}-VOPO{sub 4} treated with n-butane/1-butene, (VO){sub 2}P{sub 2}O{sub 7} treated with n-butane/1-butene; and industrial catalysts with P/V (phosphorus to vanadium) ratio of 0.9, 1.0 and 1.1, before and after treatment with n-butane and 1-butene. The NMR spectra provide a picture of how the oxidation states of vanadium are distributed in these catalysts. 73 refs., 32 figs., 8 tabs.

[The evaluation of selected oxidative stress parameters in patients with hyperthyroidism].

Science.gov (United States)

Andryskowski, Grzegorz; Owczarek, Tomasz

2007-07-01

Hyperthyroidism induces the acceleration of the basic metabolism and increases cellular oxygen utilization, consequently intensifies reactive oxygen species production and disturbs the oxidant-antioxidant balance. The objective of this study was to evaluate the selected oxidative stress parameters in patients with hyperthyroidism by analysis of the reactive oxygen species neutralizing enzymes activity--superoxide dismutase (SOD), glutathione peroxidase (GSHPx) and catalase (CAT), the estimation of free radical processes intensity--concentration of malondialdehyde (MDA), sulfhydryl groups (SH) in proteins and by quantification of the serum total antioxidant status (TAS). . Twenty-seven patients treated for hyperthyroidism and 12 healthy individuals were enrolled in the study. Enzyme activity (SOD, GSHPx, CAT), MDA and concentration of SH groups were analysed in erythrocytes, while TAS was measured in serum. Patients with hyperthyroidism compared with healthy subjects were characterized by a higher GSHPx activity in erythrocytes, lower serum TAS, the lower content of SH groups in proteins and the lower MDA concentration in erythrocytes. Our results suggest that hyperthyroidism increases oxidative stress and disturbs oxidant-antioxidant balance in the body. Thyreostatic treatment, if not leads to whole metabolic compensation, may only reduce oxidant-antioxidant disorders, however is not able to eliminate them entirely.

Planar Indium Tin Oxide Heater for Improved Thermal Distribution for Metal Oxide Micromachined Gas Sensors

Directory of Open Access Journals (Sweden)

M. Cihan Çakır

2016-09-01

Full Text Available Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although they lack selectivity. To introduce selectivity, the operating temperature of a single sensor is swept, and the measurements are fed to a discriminating algorithm. The efficiency of those data processing methods strongly depends on temperature uniformity across the active area of the sensor. To achieve this, hot plate structures with complex resistor geometries have been designed and additional heat-spreading structures have been introduced. In this work we designed and fabricated a metal oxide gas sensor integrated with a simple square planar indium tin oxide (ITO heating element, by using conventional micromachining and thin-film deposition techniques. Power consumption–dependent surface temperature measurements were performed. A 420 °C working temperature was achieved at 120 mW power consumption. Temperature distribution uniformity was measured and a 17 °C difference between the hottest and the coldest points of the sensor at an operating temperature of 290 °C was achieved. Transient heat-up and cool-down cycle durations are measured as 40 ms and 20 ms, respectively.

Planar Indium Tin Oxide Heater for Improved Thermal Distribution for Metal Oxide Micromachined Gas Sensors.

Science.gov (United States)

Çakır, M Cihan; Çalışkan, Deniz; Bütün, Bayram; Özbay, Ekmel

2016-09-29

Metal oxide gas sensors with integrated micro-hotplate structures are widely used in the industry and they are still being investigated and developed. Metal oxide gas sensors have the advantage of being sensitive to a wide range of organic and inorganic volatile compounds, although they lack selectivity. To introduce selectivity, the operating temperature of a single sensor is swept, and the measurements are fed to a discriminating algorithm. The efficiency of those data processing methods strongly depends on temperature uniformity across the active area of the sensor. To achieve this, hot plate structures with complex resistor geometries have been designed and additional heat-spreading structures have been introduced. In this work we designed and fabricated a metal oxide gas sensor integrated with a simple square planar indium tin oxide (ITO) heating element, by using conventional micromachining and thin-film deposition techniques. Power consumption-dependent surface temperature measurements were performed. A 420 °C working temperature was achieved at 120 mW power consumption. Temperature distribution uniformity was measured and a 17 °C difference between the hottest and the coldest points of the sensor at an operating temperature of 290 °C was achieved. Transient heat-up and cool-down cycle durations are measured as 40 ms and 20 ms, respectively.

Selective catalytic oxidation of hydrocarbons as a challenge to the chemical engineer

Energy Technology Data Exchange (ETDEWEB)

Emig, G [Erlangen-Nuernberg Univ., Erlangen (Germany, F.R.). Lehrstuhl fuer Technische Chemie 1

1978-08-01

Selective catalytic oxidation is beginning to play a more and more significant role in the process of converting the most important chemical raw materials, crude oil and natural gas, into intermediate and end products. In many cases, this technique makes it possible to replace old processes consisting of many steps by more economical single-step reactions. The typical example of oxidation or ammoxidation of propylene demonstrates the problems which must be solved by the chemical engineer during the development of a heterogeneous catalytic oxidation process. The particular importance of a systematic development of a catalyst is emphasized. General aspects relating to the design of new catalytic processes, or the improvement of existing ones are also discussed.

Graphene-supported zinc oxide solid-phase microextraction coating with enhanced selectivity and sensitivity for the determination of sulfur volatiles in Allium species.

Science.gov (United States)

Zhang, Suling; Du, Zhuo; Li, Gongke

2012-10-19

A graphene-supported zinc oxide (ZnO) solid-phase microextraction (SPME) fiber was prepared via a sol-gel approach. Graphite oxide (GO), with rich oxygen-containing groups, was selected as the starting material to anchor ZnO on its nucleation center. After being deoxidized by hydrazine, the Zn(OH)2/GO coating was dehydrated at high temperature to give the ZnO/graphene coating. Sol-gel technology could efficiently incorporate ZnO/graphene composites into the sol-gel network and provided strong chemical bonding between sol-gel polymeric SPME coating and silica fiber surface, which enhanced the durability of the fiber and allowed more than 200 replicate extractions. Results indicated that pure ZnO coated fiber did not show adsorption selectivity toward sulfur compounds, which might because the ZnO nanoparticles were enwrapped in the sol-gel network, and the strong coordination action between Zn ion and S ion was therefore blocked. The incorporation of graphene into ZnO based sol-gel network greatly enlarged the BET surface area from 1.2 m2/g to 169.4 m2/g and further increased the adsorption sites. Combining the superior properties of extraordinary surface area of graphene and the strong coordination action of ZnO to sulfur compounds, the ZnO/graphene SPME fiber showed much higher adsorption affinity to 1-octanethiol (enrichment factor, EF, 1087) than other aliphatic compounds without sulfur-containing groups (EFsPDMS) and polydimethylsiloxane/divinylbenzene (PDMS/DVB) SPME fibers. Several most abundant sulfur volatiles in Chinese chive and garlic sprout were analyzed using the ZnO/graphene SPME fiber in combination with gas chromatography-mass spectrometry (GC-MS). Their limits of detection were 0.1-0.7 μg/L. The relative standard deviation (RSD) using one fiber ranged from 3.6% to 9.1%. The fiber-to-fiber reproducibility for three parallel prepared fibers was 4.8-10.8%. The contents were in the range of 1.0-46.4 μg/g with recoveries of 80.1-91.6% for four main

Sulfur-centered reactive intermediates derived from the oxidation of sulfur compounds of biological interest

Energy Technology Data Exchange (ETDEWEB)

Abedinzadeh, Z. [Lab. de Chimie Physique, UMR, Univ. Rene Descartes, Paris (France)

2001-02-01

Sulphur compounds play a central role in the structure and activity of many vital systems. In the living cell, sulfur constitutes an essential part of the defense against oxidative damage and is transformed into a variety of sulfur free radical species. Many studies of the chemistry of sulfur-centered radicals using pulse radiolysis and photolysis techniques to detect and measure the kinetics of these radicals have been published and reviewed. This paper discusses the present state of research on the formation and reactivity of certain sulfur-centered radicals [RS{sup .}, RSS{sup .}, RS{sup .+}, (RSSR){sup .+}] and their implications for biological systems. (author)

Sulfur-centered reactive intermediates derived from the oxidation of sulfur compounds of biological interest

International Nuclear Information System (INIS)

Abedinzadeh, Z.

2001-01-01

Sulphur compounds play a central role in the structure and activity of many vital systems. In the living cell, sulfur constitutes an essential part of the defense against oxidative damage and is transformed into a variety of sulfur free radical species. Many studies of the chemistry of sulfur-centered radicals using pulse radiolysis and photolysis techniques to detect and measure the kinetics of these radicals have been published and reviewed. This paper discusses the present state of research on the formation and reactivity of certain sulfur-centered radicals [RS . , RSS . , RS .+ , (RSSR) .+ ] and their implications for biological systems. (author)

Sequential electrochemical oxidation and site-selective growth of nanoparticles onto AFM probes.

Science.gov (United States)

Wang, Haitao; Tian, Tian; Zhang, Yong; Pan, Zhiqiang; Wang, Yong; Xiao, Zhongdang

2008-08-19

In this work, we reported an approach for the site-selective growth of nanoparticle onto the tip apex of an atomic force microscopy (AFM) probe. The silicon AFM probe was first coated with a self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) through a chemical vapor deposition (CVD) method. Subsequently, COOH groups were selectively generated at the tip apex of silicon AFM probes by applying an appropriate bias voltage between the tip and a flat gold electrode. The transformation of methyl to carboxylic groups at the tip apex of the AFM probe was investigated through measuring the capillary force before and after electrochemical oxidation. To prepare the nanoparticle terminated AFM probe, the oxidized AFM probe was then immersed in an aqueous solution containing positive metal ions, for example, Ag+, to bind positive metal ions to the oxidized area (COOH terminated area), followed by chemical reduction with aqueous NaBH 4 and further development (if desired) to give a metal nanoparticle-modified AFM probe. The formation of a metal nanoparticle at the tip apex of the AFM probe was confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA).

Origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid

Institute of Scientific and Technical Information of China (English)

Wang Liang-Yong; Liu Bo; Song Zhi-Tang; Liu Wei-Li; Feng Song-Lin; David Huang; S.V Babu

2011-01-01

We report on the investigation of the origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid. The oxide to nitride removal selectivity of the ceria slurry with picolinic acid is as high as 76.6 in the chemical mechanical polishing. By using zeta potential analyzer, particle size analyzer, horizon profilometer, thermogravimetric analysis and Fourier transform infrared spectroscopy, the pre-and the post-polished wafer surfaces as well as the pre-and the post-used ceria-based slurries are compared. Possible mechanism of high oxide to nitride selectivity with using ceria-based slurry with picolinic acid is discussed.

Quasi physisorptive two dimensional tungsten oxide nanosheets with extraordinary sensitivity and selectivity to NO2.

Science.gov (United States)

Khan, Hareem; Zavabeti, Ali; Wang, Yichao; Harrison, Christopher J; Carey, Benjamin J; Mohiuddin, Md; Chrimes, Adam F; De Castro, Isabela Alves; Zhang, Bao Yue; Sabri, Ylias M; Bhargava, Suresh K; Ou, Jian Zhen; Daeneke, Torben; Russo, Salvy P; Li, Yongxiang; Kalantar-Zadeh, Kourosh

2017-12-14

Attributing to their distinct thickness and surface dependent physicochemical properties, two dimensional (2D) nanostructures have become an area of increasing interest for interfacial interactions. Effectively, properties such as high surface-to-volume ratio, modulated surface activities and increased control of oxygen vacancies make these types of materials particularly suitable for gas-sensing applications. This work reports a facile wet-chemical synthesis of 2D tungsten oxide nanosheets by sonication of tungsten particles in an acidic environment and thermal annealing thereafter. The resultant product of large nanosheets with intrinsic substoichiometric properties is shown to be highly sensitive and selective to nitrogen dioxide (NO 2 ) gas, which is a major pollutant. The strong synergy between polar NO 2 molecules and tungsten oxide surface and also abundance of active surface sites on the nanosheets for molecule interactions contribute to the exceptionally sensitive and selective response. An extraordinary response factor of ∼30 is demonstrated to ultralow 40 parts per billion (ppb) NO 2 at a relatively low operating temperature of 150 °C, within the physisorption temperature band for tungsten oxide. Selectivity to NO 2 is demonstrated and the theory behind it is discussed. The structural, morphological and compositional characteristics of the synthesised and annealed materials are extensively characterised and electronic band structures are proposed. The demonstrated 2D tungsten oxide based sensing device holds the greatest promise for producing future commercial low-cost, sensitive and selective NO 2 gas sensors.

Oxidation of mercury across selective catalytic reduction catalysts in coal-fired power plants

Energy Technology Data Exchange (ETDEWEB)

Constance L. Senior [Reaction Engineering International, Salt Lake City, UT (United States)

2006-01-15

A kinetic model for predicting the amount of mercury (Hg) oxidation across selective catalytic reduction (SCR) systems in coal-fired power plants was developed and tested. The model incorporated the effects of diffusion within the porous SCR catalyst and the competition between ammonia and Hg for active sites on the catalyst. Laboratory data on Hg oxidation in simulated flue gas and slipstream data on Hg oxidation in flue gas from power plants were modeled. The model provided good fits to the data for eight different catalysts, both plate and monolith, across a temperature range of 280-420{sup o}C, with space velocities varying from 1900 to 5000 hr{sup -1}. Space velocity, temperature, hydrochloric acid content of the flue gas, ratio of ammonia to nitric oxide, and catalyst design all affected Hg oxidation across the SCR catalyst. The model can be used to predict the impact of coal properties, catalyst design, and operating conditions on Hg oxidation across SCRs. 20 refs., 9 figs., 2 tabs.

Kinetic and equilibrium studies of acrylonitrile binding to cytochrome c peroxidase and oxidation of acrylonitrile by cytochrome c peroxidase compound I

Energy Technology Data Exchange (ETDEWEB)

Chinchilla, Diana, E-mail: Diana_Chinchilla@yahoo.com; Kilheeney, Heather, E-mail: raindropszoo@yahoo.com; Vitello, Lidia B., E-mail: lvitello@niu.edu; Erman, James E., E-mail: jerman@niu.edu

2014-01-03

Highlights: •Cytochrome c peroxidase (CcP) binds acrylonitrile in a pH-independent fashion. •The spectrum of the CcP/acrylonitrile complex is that of a 6c–ls ferric heme. •The acrylonitrile/CcP complex has a K{sub D} value of 1.1 ± 0.2 M. •CcP compound I oxidizes acrylonitrile with a maximum turnover rate of 0.61 min{sup −1}. -- Abstract: Ferric heme proteins bind weakly basic ligands and the binding affinity is often pH dependent due to protonation of the ligand as well as the protein. In an effort to find a small, neutral ligand without significant acid/base properties to probe ligand binding reactions in ferric heme proteins we were led to consider the organonitriles. Although organonitriles are known to bind to transition metals, we have been unable to find any prior studies of nitrile binding to heme proteins. In this communication we report on the equilibrium and kinetic properties of acrylonitrile binding to cytochrome c peroxidase (CcP) as well as the oxidation of acrylonitrile by CcP compound I. Acrylonitrile binding to CcP is independent of pH between pH 4 and 8. The association and dissociation rate constants are 0.32 ± 0.16 M{sup −1} s{sup −1} and 0.34 ± 0.15 s{sup −1}, respectively, and the independently measured equilibrium dissociation constant for the complex is 1.1 ± 0.2 M. We have demonstrated for the first time that acrylonitrile can bind to a ferric heme protein. The binding mechanism appears to be a simple, one-step association of the ligand with the heme iron. We have also demonstrated that CcP can catalyze the oxidation of acrylonitrile, most likely to 2-cyanoethylene oxide in a “peroxygenase”-type reaction, with rates that are similar to rat liver microsomal cytochrome P450-catalyzed oxidation of acrylonitrile in the monooxygenase reaction. CcP compound I oxidizes acrylonitrile with a maximum turnover number of 0.61 min{sup −1} at pH 6.0.

Development of new methods in modern selective organic synthesis: preparation of functionalized molecules with atomic precision

International Nuclear Information System (INIS)

Ananikov, V P; Khemchyan, L L; Ivanova, Yu V; Dilman, A D; Levin, V V; Bukhtiyarov, V I; Sorokin, A M; Prosvirin, I P; Romanenko, A V; Simonov, P A; Vatsadze, S Z; Medved'ko, A V; Nuriev, V N; Nenajdenko, V G; Shmatova, O I; Muzalevskiy, V M; Koptyug, I V; Kovtunov, K V; Zhivonitko, V V; Likholobov, V A

2014-01-01

The challenges of the modern society and the growing demand of high-technology sectors of industrial production bring about a new phase in the development of organic synthesis. A cutting edge of modern synthetic methods is introduction of functional groups and more complex structural units into organic molecules with unprecedented control over the course of chemical transformation. Analysis of the state-of-the-art achievements in selective organic synthesis indicates the appearance of a new trend — the synthesis of organic molecules, biologically active compounds, pharmaceutical substances and smart materials with absolute selectivity. Most advanced approaches to organic synthesis anticipated in the near future can be defined as 'atomic precision' in chemical reactions. The present review considers selective methods of organic synthesis suitable for transformation of complex functionalized molecules under mild conditions. Selected key trends in the modern organic synthesis are considered including the preparation of organofluorine compounds, catalytic cross-coupling and oxidative cross-coupling reactions, atom-economic addition reactions, methathesis processes, oxidation and reduction reactions, synthesis of heterocyclic compounds, design of new homogeneous and heterogeneous catalytic systems, application of photocatalysis, scaling up synthetic procedures to industrial level and development of new approaches to investigation of mechanisms of catalytic reactions. The bibliography includes 840 references

Catalytic performance of advanced titanosilicate selective oxidation catalysts – a review

Czech Academy of Sciences Publication Activity Database