Search results for "OXIDATION"
showing 10 items of 1913 documents
Combined CO/CH4 oxidation tests over Pd/Co3O4 monolitic catalyst: effects of high reaction temperature and SO2 exposure on the deactivation process
2007
Abstract CO and CH 4 combined oxidation tests were performed over a Pd (70 g/ft 3 )/Co 3 O 4 monolithic catalyst in conditions of GHSV = 100,000 h −1 and feed composition close to that of emission from bi-fuel vehicles. The effect of SO 2 (5 ppm) on CO and CH 4 oxidation activity under lean condition ( λ = 2) was investigated. The presence of sulphur strongly deactivated the catalyst towards methane oxidation, while the poisoning effect was less drastic in the oxidation of CO. Saturation of the Pd/Co 3 O 4 catalytic sites via chemisorbed SO 3 and/or sulphates occurred upon exposure to SO 2 . A treatment of regeneration to remove sulphate species was attempted by performing a heating/coolin…
Co3O4/CeO2 composite oxides for methane emissions abatement: Relationship between Co3O4–CeO2 interaction and catalytic activity
2006
Abstract Co 3 O 4 /CeO 2 composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co 3 O 4 ) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co 3 O 4 and CeO 2 were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out. An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co 3 O 4 in correspondence of Co 3 O 4 –CeO 2 containing 30% by weight of Co 3 O 4 . The combined effect of cobalt oxide…
Biological activities of the LXRα and β agonist, 4β-hydroxycholesterol, and of its isomer, 4α-hydroxycholesterol, on oligodendrocytes: effects on cel…
2013
The biochemical and biological properties of 4β-hydroxycholesterol and of its isomer, 4α-hydroxycholesterol, are not well known. So, we determined the ability of 4α- and 4β-hydroxycholesterol to react with LXRα and LXRβ, and we characterized the activities of these oxysterols on oligodendrocytes which are myelin synthesizing cells. The effects of 4α- and 4β-hydroxycholesterol were studied on 158N murine oligodendrocytes to assess their activities on cell growth and viability, oxidative and inflammatory status. To this end different parameters were used: cell counting with trypan blue; identification of dead cells and cell cycle analysis with propidium iodide; evaluation of mitochondrial dep…
Prevention of 7-ketocholesterol-induced side effects by natural compounds
2018
Cholesterol oxidation products, also named oxysterols, can be formed either by cholesterol auto-oxidation, enzymatically or both. Among these oxysterols, 7-ketocholesterol (7KC) is mainly formed during radical attacks that take place on the carbon 7 of cholesterol. As increased levels of 7KC have been found in the tissues, plasma and/or cerebrospinal fluid of patients with major diseases, especially age-related diseases (cardiovascular diseases, eye diseases, neurodegenerative diseases), some cancers, and chronic inflammatory diseases, it is suspected that 7KC, could contribute to their development. Since 7KC, provided by the diet or endogenously formed, is not or little efficiently metabol…
Side effects of oxysterols: cytotoxicity, oxidation, inflammation, and phospholipidosis.
2008
Oxysterols are 27-carbon atom molecules resulting from autoxidation or enzymatic oxidation of cholesterol. They are present in numerous foodstuffs and have been demonstrated to be present at increased levels in the plasma of patients with cardiovascular diseases and in atherosclerotic lesions. Thus, their role in lipid disorders is widely suspected, and they might also be involved in important degenerative diseases such as Alzheimer's disease, osteoporosis, and age-related macular degeneration. Since atherosclerosis is associated with the presence of apoptotic cells and with oxidative and inflammatory processes, the ability of some oxysterols, especially 7-ketocholesterol and 7β-hydrox…
One-Pot Synthesis of Pyrrole-2-carboxylates and -carboxamides via an Electrocyclization/Oxidation Sequence
2014
An electrocyclic ring closure is the key step of an efficient one-pot method for the synthesis of pyrrole-2-carboxylates and -carboxamides from chalcones and glycine esters or amides. The 3,4-dihydro-2H-pyrrole intermediates generated in situ are oxidized to the corresponding pyrroles by stoichiometric oxidants or by catalytic copper(II) and air in moderate to high yields. A wide range of functional groups are tolerated, and further combination with an in situ bromination gives access to polyfunctional pyrrole scaffolds.
SrTiO 3 -based perovskites: Preparation, characterization and photocatalytic activity in gas–solid regime under simulated solar irradiation
2015
Strontium titanate-based perovskites have been prepared in the presence of Y and Co with the aim to substitute Sr and Ti, respectively, in the ST crystalline structure. The obtained samples have been characterized by XRD, Raman spectroscopy, FE-SEM, XPS and tested as photocatalysts in two gas-solid regime reactions: (i) 2-propanol complete mineralization and (ii) propene partial oxidation, using a system simulating solar irradiation. All the tested samples resulted active as photocatalysts but with significant differences. The lattice substitution of Sr by Y displays a beneficial effect on the 2-propanol photodegradation. Conversely, the partial presence of cobalt on the ST surface, as Co-o…
Selective oxidation of C3–C4 olefins over Mo-containing catalysts with tetragonal tungsten bronze structure
2009
Abstract Mo–V–Nb–P–O-based catalysts with a tetragonal tungsten bronze-type (TTB) structure have been prepared hydrothemally from a H 3 PMo 12 O 40 Keggin-type heteropolyacid. These catalysts have been tested in the oxidation of C 3 –C 4 olefins (propene, isobutene and 1-butene). Although the catalytic performance depends on the nature of the olefin fed the TTB-type catalysts prepared in the presence of elements of the V and VI groups such as Te, Sb and Bi have shown a high selectivity to partial oxidation products, especially that with Te. However, in the absence of these elements the TTB-catalysts present a high catalytic activity to deep oxidation. The selectivity to partial oxidation pr…
Neutrophil Extracellular Traps as a Drug Target to Counteract Chronic and Acute Inflammation
2019
Neutrophil extracellular traps (NET), extruded decondensated chromatin entangled with neutrophil proteases, have been first identified in neutrophils stimulated with bacteria or phorbol myristate acetate (PMA) via activation of NADPH oxidase and the generation of reactive oxygen species. Although the first findings demonstrated the beneficial role of NET formation by trapping the bacteria and limiting their dissemination, numerous studies in the recent decade revealed the multifunctional aspects of NET formation which manifests itself not only in the context of anti-microbial effect but also as a pathological trigger. Uncontrolled and exaggerated NET formation or inability to digest and rem…
Small-angle X-ray scattering reveals differences between the quaternary structures of oxygenated and deoxygenated tarantula hemocyanin
1996
Small-angle X-ray scattering (SAXS) curves have been recorded for the oxygenated and deoxygenated states of the 4 x 6-meric hemocyanin from the tarantula Eurypelma californicum. A comparison of the curves shows that the quaternary structures of the two states are different by three criteria, which all indicate that the hemocyanin is less compact in the oxygenated compared to the deoxygenated form: (a) The radius of gyration is 8.65 +/- 0.05 nm for the deoxy- and 8.80 +/- 0.05 nm for the oxy-form. (b) The maximum particle dimension amounts to 25.0 +/- 0.5 nm for the deoxy- and to 27.0 +/- 0.5 nm for the oxy-form. (c) A dip in the intramolecular distance distribution function p(r) is more pro…