In situ FTIR study on the active oxygen species for the conversion of methane to methanol

1995 ◽  
Vol 35 (3-4) ◽  
pp. 259-263 ◽  
Author(s):  
Ye Wang ◽  
Kiyoshi Otsuka ◽  
Kohki Ebitani
Keyword(s):  
Active Oxygen Species ◽  
Active Oxygen ◽  
Oxygen Species ◽  
In Situ Ftir ◽  
Ftir Study ◽  
Conversion Of Methane

Active oxygen species in the liver of rats submitted to chronic hypobaric hypoxia

1993 ◽  
Vol 264 (6) ◽  
pp. C1395-C1400 ◽  
Author(s):  
L. E. Costa ◽  
S. Llesuy ◽  
A. Boveris
Keyword(s):  
Steady State ◽  
Singlet Oxygen ◽  
Active Oxygen Species ◽  
Liver Mitochondria ◽  
Active Oxygen ◽  
Female Rats ◽  
H2o2 Production ◽  
Oxygen Species ◽  
State Concentration

The spontaneous in situ liver chemiluminescence of female rats submitted to 4,400 m (simulated altitude) for 2 mo and of their corresponding controls at sea level was determined as an approach to the measurement of the intracellular steady-state concentrations of singlet oxygen and oxygen free radicals. Spontaneous liver chemiluminescence was decreased by approximately 40% in hypoxic rats, whereas CCl4-induced chemiluminescence was unchanged. Liver mitochondria isolated from hypoxic rats showed a 53% decreased rate of H2O2 production and an increased content of cytochrome b (36%), with normal content of cytochromes c1, c, and a-a3. Superoxide dismutase showed a 26% decrease in activity, whereas catalase and glutathione peroxidase activities were not significantly decreased by this extent of hypoxia. Cytochrome P-450 and glutathione contents were unchanged. There were no significant differences in the hydroperoxide-initiated chemiluminescence (an estimation of tissue chain-breaker antioxidants) of homogenates, mitochondria, and microsomes. Results suggest that in chronic hypoxia there is a lower rate of generation of active oxygen species in liver, leading to a decreased steady-state concentration of singlet oxygen.

In Situ Observation of Active Oxygen Species in Fe-Containing Ni-Based Oxygen Evolution Catalysts: The Effect of pH on Electrochemical Activity

2015 ◽  
Vol 137 (48) ◽  
pp. 15112-15121 ◽  
Author(s):  
Bartek J. Trześniewski ◽  
Oscar Diaz-Morales ◽  
David A. Vermaas ◽  
Alessandro Longo ◽  
Wim Bras ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Electrochemical Activity ◽  
In Situ Observation ◽  
Oxygen Species ◽  
Effect Of Ph

Investigation of hydrogen abstraction from methyl glucoside by active oxygen species under oxygen delignification conditions. Part 1: Study on the anomeric position

Holzforschung ◽  
2009 ◽  
Vol 63 (1) ◽  
Author(s):  
Fumiko Konishi ◽  
Tomoya Yokoyama ◽  
Yuji Matsumoto
Keyword(s):  
Active Oxygen Species ◽  
Hydrogen Abstraction ◽  
Active Oxygen ◽  
Anomeric Effect ◽  
Oxygen Species ◽  
Oxygen Delignification ◽  
Paper Mills ◽  
Kinetic Isotope ◽  
Hydrogen Peroxide Treatment

Abstract We investigated whether active oxygen species (AOS) abstract the anomeric hydrogen from a carbohydrate model compound, methyl β-d-glucopyranoside (MGPβ) under conditions simulating oxygen delignification in pulp and paper mills (0.5 mol l-1 NaOH, 0.36 mmol l-1 Fe3+, 1.1 MPa O2, 95°C). The simulation involved in situ AOS generation by reaction of 2,4,6-trimethylphenol with O2, so that various types of AOS were operative in the system. MGPβ was degraded slightly more than methyl α-d-glucopyranoside (MGPα) when they were jointly reacted with AOS. Thus, we suggest that the configurational difference in their anomeric positions has some effects on their reactions with AOS. When MGPβ and methyl β-d-(1-2 H)glucopyranoside (MGPβ-1D) were jointly reacted with AOS, MGPβ was degraded slightly more than MGPβ-1D. This difference results from the kinetic isotope effect, indicating that the anomeric hydrogen of MGPβ is undoubtedly abstracted by AOS, although the contribution of this abstraction to the overall degradation of MGPβ has not been clarified yet. MGPβ and MGPβ-1D were also jointly subjected to alkaline hydrogen peroxide treatment (0.5 mol l-1 NaOH, 0.36 mmol l-1 Fe3+, 95°C) in which the oxyl anion radical (O-·), the conjugate base of hydroxyl radical (HO·), is likely only one of the AOS to degrade these compounds. Since no difference in degradation was observed, some AOS other than O-· must participate in anomeric hydrogen abstraction from MGPβ in these oxygen-alkali treatments. When MGPα and methyl α-d-(1-2 H)glucopyranoside were jointly reacted with AOS, almost no difference in degradation was observed. This result suggests that abstraction of the anomeric hydrogen from MGPα by AOS is no more than a very minor reaction. It was confirmed that the anomeric hydrogen of MGPβ is activated towards AOS reaction owing to the anomeric effect, which is in fact a stereoelectronic effect.

scholarly journals Evidence for an active oxygen species on Au/TiO2(110) model catalysts during investigation with in situ X-ray photoelectron spectroscopy

2012 ◽  
Vol 181 (1) ◽  
pp. 20-25 ◽  
Author(s):  
K. Dumbuya ◽  
G. Cabailh ◽  
R. Lazzari ◽  
J. Jupille ◽  
L. Ringel ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Model Catalysts ◽  
Oxygen Species ◽  
X Ray

Characterization and functional properties of new everbearing strawberry (Fragaria x ananasa Duch.) cultivar, ‘Summertiara’ berries

2014 ◽  
Vol 4 (1) ◽  
pp. 1 ◽  
Author(s):  
Takeshi Nagai ◽  
Misuzu Tamai ◽  
Masato Sato ◽  
Yasuhiro Tanoue ◽  
Norihisa Kai ◽  
...  
Keyword(s):  
Vitamin C ◽  
Sensory Evaluation ◽  
Functional Properties ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Antihypertensive Activity ◽  
Oxygen Species ◽  
Total Anthocyanins ◽  
Strawberry Cultivar ◽  
The Stability

Background: In recent years, a new everbearing strawberry cultivar, ‘Summertiara’ was cultivated to supply the strawberries in pre-harvest season from July to October in Japan. For highly research and development of processing of this cultivar, ‘Summertiara’ berries, the objective of this study was to characterize these berries, with relation to chemical parameters, total phenols, total flavonoids, total vitamin C, and total anthocyanins, and was to investigate the solubility and the stability of anthocyanins from the berries. Moreover, the functional properties such as antioxidative activity, active oxygen species scavenging activity, and antihypertensive activity were also evaluated.Methods: Chemical analysis, colour measurement, and sensory evaluation of new everbearing strawberry cultivar, ‘Summertiara’ berries were performed. Next, the solubility of anthocyanins from the berries and stability of these against pH, temperature, and an incandescent lighting were investigated. Moreover, functional properties of the extracts prepared from berries were elucidated using 5 different methods.Results: The contents of water, proteins, lipids, carbohydrates, and ash were the same as those of other cultivar berries. The sugar-acid ratio in the berries was low; these were acidulous. By sensory evaluation, the main factors were vivid red colour, aroma, and acidity. The berries were rich in phenols, flavonoids, vitamin C, and anthocyanins. The anthocyanins of the berries became unstable by heat treatment and light exposures such as visible rays. On the other hand, the extracts prepared from the berries showed the functionalities such as antioxidant activity, active oxygen species scavenging activities, and antihypertensive activity.  Conclusions: The strawberry cultivar, ‘Summertiara’ berries were the most suitable for processing ingredient of strawberry-derived products with superior health promoting functionalities.Keywords: Summertiara, everbearing strawberry cultivar, characterization, sensory evaluation, color and storage, functional property

scholarly journals Ambient base-free glycerol oxidation over bimetallic PdFe/SiO2 by in situ generated active oxygen species

2021 ◽  
Author(s):  
Ricci Underhill ◽  
Mark Douthwaite ◽  
Richard J. Lewis ◽  
Peter J. Miedziak ◽  
Robert D. Armstrong ◽  
...  
Keyword(s):  
Heterogeneous Catalysts ◽  
Bimetallic Catalyst ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Active Oxygen Species ◽  
Catalytic Performance ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Paramagnetic Resonance ◽  
Temperature Oxidation

AbstractLow temperature oxidation of alcohols over heterogeneous catalysts is exceptionally challenging, particularly under neutral conditions. Herein, we report on an efficient, base-free method to oxidise glycerol over a 0.5%Pd-0.5%Fe/SiO2 catalyst at ambient temperature in the presence of gaseous H2 and O2. The exceptional catalytic performance was attributed to the in situ formation of highly reactive surface-bound oxygenated species, which promote the dehydrogenation on the alcohol. The PdFe bimetallic catalyst was determined to be significantly more active than corresponding monometallic analogues, highlighting the important role both metals have in this oxidative transformation. Fe leaching was confirmed to occur over the course of the reaction but sequestering experiments, involving the addition of bare carbon to the reactions, confirmed that the reaction was predominantly heterogeneous in nature. Investigations with electron paramagnetic resonance spectroscopy suggested that the reactivity in the early stages was mediated by surface-bound reactive oxygen species; no homogeneous radical species were observed in solution. This theory was further evidenced by a direct H2O2 synthesis study, which confirmed that the presence of Fe in the bimetallic catalyst neither improved the synthesis of H2O2 nor promoted its decomposition over the PdFe/SiO2 catalyst.

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