Search results

1

Microwave saturation of EPR spectra of oxidised coal

100%

Pilawa B., Więckowski A., Pietrzak R., Wachowska H.

Open Chemistry

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2007

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vol. 5

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issue 1

330-340

EN

Microwave saturation of multi-component EPR spectra of oxidized lignite Mequinenza (Spain) with a carbon content of 65.1 wt % and with a high sulphur content of 10.3 wt % was studied. The coal was oxidized with nitric acid (NHO3), peroxyacetic acid (PAA), and in O2/Na2CO3 system. Three different groups of paramagnetic centres exist in the coal samples analyzed. The EPR spectrum of the demineralised coal was a superposition of broad Gauss (ΔB pp = 0.75 mT), broad Lorentz 1 (ΔB pp = 0.42 mT) and narrow Lorentz 3 lines (ΔB pp = 0.08 mT). The three EPR components with linewidths: 0.58–0.77 mT (Gauss line), 0.30–0.39 mT (Lorentz 1 line) and 0.05–0.06 mT (Lorentz 3 line) were recorded for the oxidized coal. The g-values were obtained for the samples studied in the ranges 2.0043–2.0046 (Gauss lines), 2.0035–2.0038 (Lorentz 1 lines) and 2.0032–2.0034 (Lorentz 3 lines). The broad Gauss and Lorentz 1 lines saturate at low microwave powers. The narrow Lorentz 3 lines of demineralised coal were not saturated at microwave power from the range considered. After the coal oxidation with HNO3, PAA and in O2/Na2CO3 system, the microwave saturation of the narrow Lorentz 3 lines was also observed, which indicated a degradation of the multi-ring aromatic structures upon oxidation. [...]

2

The role of benzoate secreted by Desulfotomaculum acetoxidans DSM 771 in sulfate uptake

100%

Pawłowska-Ćwięk L., Pado R.

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2005

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vol. 52

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issue 4

797-802

EN

This work was designed to find the cause of the delay in hydrogen sulfide dissimilation in Desulfotomaculum acetoxidans DSM 771, which is dependent on the sulfate uptake. This bacterium grown without addition of any aromatic compound was shown by spectrum analysis with the methylene method to contain hydroxy-benzoate derivatives. The presence of these compounds was confirmed by HPLC in fractions obtained from cell walls after 15 days of culture. The test with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt seemed to indicate the presence of peroxidase, which probably oxidized benzoate to its hydroxy derivatives. The test with 5-sulfo-salicylic acid proved the ability of the investigated strain to utilize arylsulfates and to reduce sulfate group to hydrogen sulfide. On the basis of the above data, we propose the following sequence of reactions: 1, benzoate secretion; 2, benzoate hydroxylation; 3, sulfonation of hydroxy-benzoate derivatives.

3

Kinetics and mechanism of meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate

100%

Kungumathilagam D., Karunakaran K.

Polish Journal of Chemical Technology

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2013

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vol. 15

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issue 2

107-111

EN

Developing catalyst is very significant for biologically important reactions which yield products, used as drugs. Mechanistic study on meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate in aqueous acetic acid medium have been carried out. The reaction follows a fractional order with respect to substrate and catalyst. The order with respect to oxidant was found to be one. Increase in the percentage of acetic acid and increase in the concentration of [H+] decreased the rate. The reaction fails to initiate polymerization, and a radical mechanism is ruled out. Activation and thermodynamic parameters have been computed. A suitable kinetic scheme based on these observations has been proposed. Significant catalytic activity is observed for the reaction system in the presence of TPP.

4

Properties of atmospheric pressure plasma oxidized layers on silicon wafers

100%

Skácelová D., Sládek P., Sťahel P., Pawera L., Haničinec M., Meichsner J., Černák M.

Open Chemistry

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2015

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vol. 13

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issue 1

EN

In this research a new process of plasma oxidation of crystalline silicon at room temperature is studied. The plasma oxidation was carried out using Diffuse Coplanar Surface Barrier Discharge (DCSBD) operating in ambient air and oxygen at atmospheric pressure. The influence of exposition time, plasma parameters and crystallographic orientation of silicon on oxidized layers and their dielectric properties were investigated. Thickness, structure and morphology of these layers were studied by ellipsometry, infrared absorption spectroscopy and scanning electron microscopy. During the treatment time, from 1 to 30 minutes, oxidized layers were obtained with thickness from 1 to 10 nm. Their roughness depends on the crystallographic orientation of silicon surface and exposure time. Electrical parameters of the prepared layers indicate the presence of an intermediate layer between silicon substrate and the oxidized layer.

5

Application of artificial neural nerworks in oxidation kinetic analysis of nanocomposites

100%

Straszko J., Biedunkiewicz A., Strzelczak A.

Polish Journal of Chemical Technology

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2008

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vol. 10

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issue 3

21-28

EN

This study concerns the application of artificial neural networks in oxidation kinetic analysis of ceramic nanocomposites. The oxidation of the Ti-Si-C ceramic nanocomposite in dry air was studied. The size of the nanoparticles was determined by scanning electron microscopy (SEM). The gaseous oxidation products were analysed by mass spectroscopy (MS) while the solid oxidation products by X-ray diffraction (XRD). The kinetic analysis of the oxidation was based on the Coats-Redfern equation. The kinetic models were identified for the consecutive stages and then the A and E parameters of the Arrhenius equations were evaluated. Artificial neural networks were used at each step of the kinetic calculations.

6

Catalytic synthesis of 2-methyl-1,4- naphthoquinone in 1%Au/HPS presence

100%

Shimanskaya E. I., Sulman E. M., Doluda V. Y.

Catalysis for Sustainable Energy

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2014

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vol. 2

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issue 1

EN

In this paper, theoxidation process of 2 -methylnaphthalene to vitamin K3, using a gold catalyst systems will be discussed. This catalysis process is based on the hypercrosslinked polystyrene, synthesized by the impregnation with solutions of precursors − HAuCl4·2H2O and Ph3PAuCl. The use of gold catalyst system, which has been synthesized using Ph3PAuCl, allows to obtain the main product − 2-methyl-1,4-naphthoquinone − with 72% yield.

7

The influence of the phosphorothioate diester bond on the DNA oxidation process

88%

Karwowski B. T.

Open Chemistry

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2015

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vol. 13

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issue 1

EN

This study describes the influence of the phosphorothioate internucleotide bond on the deoxyribonucleic acid (DNA) oxidation process. The interaction of an ultraviolet radiation (UVA) with a targeted double-stranded (ds) oligonucleotide, in which one strand contains an antraquinone (AQ) moiety on the 5’-end, may lead to a hole migration process through the double helix. In the end, the migration of theformed radical cation terminates in a suitable place. Usually, this is a guanine-rich sequence. In another experiment, phosphorothioate internucleotide bonds were detected in the bacterial genome as a natural modification. In this study, a polyacrylamide gel electrophoresis (PAGE) autoradiogram analysis of irradiated ds-DNA showed that the oxidation reaction was not inhibited by an isolated guanine. Instead, irrespective of the absence or presence of a phosphorothioate bond, the termination of the ds-DNA oxidation process was predominantly observed on the thymine moieties. Based on the obtained results, it can be concluded that in the discussed case, a hole migration by a hopping mechanism is in competition with an oxidation reaction with a superoxide radical anion. Alternatively, the radical cation migration process is sequence-dependent due to its different ionization potentials. Therefore, the presence of a phosphorothioate internucleotide bond did not change the stability of ds-DNA under UVA irradiation conditions.

8

RuO4-mediated oxidation ofN-benzylated tertiary amines. Are amineN-oxides and iminium cations reaction intermediates?

88%

Petride H., Drãghici C., Florea C., Petride A.

Open Chemistry

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2004

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vol. 2

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issue 2

302-322

EN

N-Benzylmorpholine,-piperidine, and-pyrrolidine (1A-C, resp.) are oxidised by RuO4 (generatedin situ) at both endocyclic and exocyclic (benzylic)N-α-methylene positions to afford lactams (and dioxo-derivatives) and benzaldehyde (and benzoyl derivatives), respectively. TheN-oxides of1A-C, formed by a minor side reaction, are not involved as intermediates. Control experiments showed the transient formation of endo- and exocyclic iminium cations trapped with NaCN as the corresponding nitriles. The proposed course of the RuO4-mediated oxidation of1A-C involves the consecutive steps1⇒iminium cations+cyclic enamine⇒oxidation products. The endocyclic/exocyclic regioselectivity of the oxidation reaction lies between 0.8 (for1A) and 2.1 (for1B). The amine cation radical and theN-α-C· carbon-centered radical seem not to be involved.

9

Catalytic air oxidation of manganese in synthetic waters

88%

Kaya N., Karadurmus E., Alicilar A.

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EN

An attempt was made to study the oxidation of manganese by air in synthetic waters. A series of batch experments were performed at differnet values of concentration, temperature and pH. Unoxidized manganese in the solution was determined by formaldoxime spectrometric method. Results of these studies indicated that the air oxidation of manganese soluble in water can be effectively performed in basic media and that oxidation yield increasedwith an increase in pH and concentration. The yield was very high in the presence of manganese dioxide, sepiolite or clinoptilolite in solution and, the oxidation was almost completed especially at high values of pH and concentration. The reaction was found to be first order with respect to Mn2+ with a very low activation energy. A yield of 62% was obtained for the air oxidation of wastewater taken from the treatment plant of Corum Municipality.

10

Aqueous p-nitrotoluene oxidation induced with direct glow discharge plasma

88%

Gao J., Liu Y., Yang W., Pu L., Yu J., Lu Q.

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EN

A plasma induced degradation process has been studied to treat 4-nitrotoluene (4-NT) present as an aqueous pollutant. The plasma was locally generated from a glow discharge around a tip of a platinum anode in an electrolytic solution. The influence of initial pH and Fe2+ on the degradation was examined. Major intermediates resulting from the degradation process were identified. Amongst the aromatic intermediates, p-hydroxybenzoic acid was the predominant degradation product. The formation of oxalic acid, malic acid was also observed. The final products of degradation were NH4+, NO3− and CO2. Based on the analysis of intermediates and the kinetic considerations, the degradation was shown to follow a pseudo-first order reaction hence, a possible reaction pathway was proposed.

11

Preparation of iron oxide nanocatalysts and application in the liquid phase oxidation of benzene

88%

Lokhat D., Oliver M., Carsky M.

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EN

A series of iron oxide nanocatalysts were prepared using an ultrasonically assisted co-precipitation technique. Molybdenum promoted Fe3O4 and Fe2O3 were prepared from the original materials by wet impregnation using a solution of ammonium molybdate. The catalysts were tested in the liquid phase oxidation of benzene at atmospheric pressure and at 60°C using molecular oxygen. Phenol yields between 7% and 14.5% were obtained. The major products were pyrogallol and catechol.

12

1,3-bis(2,4,6-trinitrophenylaminooxy)propane and its 4-cyano-2,6-dinitrophenyl congener: Synthesis and properties

88%

Covaci I., Ionita P., Caproiu M., Socoteanu R., Constantinescu T., Balaban A.

|

EN

Starting from N-hydroxyphthalimide (5) and 1,3-dibromopropane (6) we obtained 1,3-bis(phthalimidooxy)propane (7) which led to 1,3-bis(aminooxy)propane dihydrochloride (8). From its reaction with picryl chloride or 4-cyano-2,6-dinitrochlorobenzene, the two title compounds (4b, 4a) were obtained. 1H-NMR and 13C-NMR spectra are presented. For comparison with the analogous N-methoxy-2,6-dinitro-4-R-anilines 1a, 1b (R=CN or R=NO2), wer report the hydrophobic characteristics (by RPTLC), electronic spectra for the neutral compounds and their anions, pKa values, and the behavior towards oxidizers (DPPH, PbO2, Pb(CH3COO)4, KMnO4 and Ag2O); DPPH converts compounds 1a, 1b and 4a, 4b into betainic structures 2a, 2b respectively.

13

Characterization of vanadia catalysts on structured micro-fibrous glass supports for selective oxidation of hydrogen sulfide

88%

Larina T. V., Cherepanova S. V., Rudina N. A., Kolesov B. A., Zagoruiko A. N.

Catalysis for Sustainable Energy

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2014

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vol. 2

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issue 1

EN

This work is focused on the characterization of a novel vanadium pentoxide catalysts on a glass-fiber support. The catalyst support consists of a non-porous glass-fiber fabric covered with an additional external surface layer of porous secondary support of SiO2. The vanadia active component is synthesized from vanadyl oxalate precursor by means of an impulse surface thermo-synthesis method. Such catalysts demonstrate high activity and appropriate selectivity in the reaction of H2S oxidation by oxygen into sulfur in the practically important temperature range below 200°C. According to the characterization data, the freshly prepared vanadia catalyst partially consists of mostly the amorphous and badly ordered vanadia with some part of the wellcrystallized V2O5 phase. Under the reaction conditions the main part of vanadia in the catalyst remains in the amorphous V2O5 form, while the less part becomes reduces into of VO2 and other vanadium oxides (such as VO, V2O3 V3O7 and V4O9). Most probably, the crystallized V2O5 in course of reaction is responsible for the deep oxidation of hydrogen sulphide into SO2, while the lower vanadium oxides promote the selective H2S oxidation into elemental sulfur.

14

Oxidation of glycerol-3-phosphate in porcine and bovine adrenal cortex mitochondria.

75%

Popinigis J., Antosiewicz J., Kaczor J. J., Rauchová H., Lenaz G.

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vol. 51

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issue 4

1075-1080

EN

The capabilities of porcine adrenal cortex mitochondria to oxidize glycerol-3-phosphate (GP) were studied. In comparison with bovine adrenal cortex mitochondria, porcine mitochondria oxidized GP about three times more actively (18.9 vs 6.1 nmol O2/min per mg protein in the presence of ADP) and the activity of mitochondrial glycerol-3-phosphate dehydrogenase was about four times higher (33.4 vs 8.2 nmol/min per mg protein). In porcine adrenal cortex mitochondria we found similar values for succinate and GP oxidation both in the absence and presence of ADP or deoxycorticosterone (DOC). Rotenone sensitivity of DOC stimulation of GP oxidation indicated that porcine adrenal cortex mitochondria are able to oxidize GP and thus to generate NADPH from GP, presumably via reverse electron transport followed by energy-dependent NADH-NADP transhydrogenation.

15

Investigation of oxidation process of 3-aminotoluene with ozone in presence of manganese bromide catalyst

75%

Galstyan A., Galstyan G., Timoshyna L.

Teka Commission of Motorization and Power Industry in Agriculture

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2016

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vol. 16

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issue 2

16

Combined Effect of Zr and Si on Isothermal Oxidation of Ti

75%

Ha S.-H., Kim B.-H., Yoon Y.-O., Lim H.-K., Kim S. K.

Archives of Metallurgy and Materials

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2018

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vol. 63

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issue 3

17

Oxygenic bismuth minerals in the NE part of the Karkonosze pluton (West Sudetes, SW Poland)

75%

Kozłowski A., Matyszczak W.

Acta Geologica Polonica

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2018

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vol. 68

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issue 4

18

Assessing the Influence of the Presence of Heavy Metals Adsorbed on Activated Carbon on the Efficiency of Degradation of Phenol Using Selected Oxidizing Agents

63%

Dąbek L., Ozimina E., Picheta-Oleś A.

Ecological Chemistry and Engineering S

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2012

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vol. 19

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issue 2

249-257

EN

Removing organic substances from wastewater is a complex problem. Different methods are used for this purpose. Recently, much attention has been given to the application of sorption and advanced oxidation processes (AOPs), which contribute also to the regeneration of activated carbon. The analysis presented in this paper focused on determining the influence of Cu(II) and Fe(II) ions adsorbed on activated carbon on the efficiency of oxidation of phenol by means of H2O2, Fenton's reagent Fe2+/H2O2 and 1:1 HNO3 solution exposed to 2450 MHz microwaves, and, accordingly, the influence of Cu(II) and Fe(II) ions on the sorptive capacity of regenerated activated carbons. The results show that the chemical regeneration of activated carbon using AOPs resulted in partial oxidation of the adsorbed organic substance. The presence of Cu(II) or Fe(II) ions increased the regeneration efficiency. Using nitric acid to oxidize adsorbed phenol brought about a dramatic decline in the sorptive capacity of activated carbon with respect to this substance and an increase in the sorptive capacity of carbon with respect to metal ions. A serious drawback of this method, however, is that the oxidation of adsorbed phenol caused a significant loss of mass of activated carbon regardless of the oxidizing agent used.

PL

Usuwanie zanieczyszczeń organicznych ze ścieków jest złożonym problemem wymagającym stosowania różnych metod. Coraz częściej rozważa się możliwość wykorzystania do tego celu procesu sorpcji i metod pogłębionego utleniania (AOPs), co jednocześnie skutkuje regeneracją węgla aktywnego. W prezentowanej pracy prowadzono badania wpływu zaadsorbowanych na węglu aktywnym jonów Cu(II) i Fe(II) na skuteczność utleniania fenolu z wykorzystaniem H2O2, reakcji Fentona Fe2+/H2O2 oraz roztworu 1:1 HNO3 w obecności mikrofal 2450 MHz, a tym samym wpływu na zdolność sorpcyjną zregenerowanych węgli aktywnych. Wykazano, że chemiczna regeneracja węgla aktywnego z wykorzystaniem metod AOP skutkuje częściowym utlenieniem zaadsorbowanej substancji organicznej. Obecność jonów Cu(II) lub Fe(II) zwiększa skuteczność regeneracji. Wykorzystanie kwasu azotowego do utleniania zaadsorbowanego fenolu skutkuje drastycznym obniżeniem zdolności sorpcyjnych węgla aktywnego względem tej substancji i wzrostem zdolności sorpcyjnych względem jonów metali. Niestety negatywnym skutkiem procesu utleniania zaadsorbowanego fenolu, niezależnie od zastosowanego czynnika utleniającego, jest znaczący ubytek masy węgla aktywnego.

19

Kinetics of oxidation of manganese by potassium permanganate and chloride in the Velekinca water treatment plant, Kosovo

63%

Beluli V. M., Beluli V. M.

Journal of Water and Land Development

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2020

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issue 47

20

New transformation of cycloalkanone acetals by peracids α,ω-dicarboxylic acids synthesis

63%

Terent'ev A., Chodykin S.

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EN

A new process of oxidation of cycloalkanone acetals under the action of in situ generated performic acid has been found. The main products of the reaction are α, ω-dicarboxylic acids obtained with the yield up to 77% depending on the size of acetals ring. The process has been explored and optimized on the example of the dodecanedioic acid synthesis (a valuable industrial product).

Refine search results

Microwave saturation of EPR spectra of oxidised coal

The role of benzoate secreted by Desulfotomaculum acetoxidans DSM 771 in sulfate uptake

Kinetics and mechanism of meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate

Properties of atmospheric pressure plasma oxidized layers on silicon wafers

Application of artificial neural nerworks in oxidation kinetic analysis of nanocomposites

Catalytic synthesis of 2-methyl-1,4- naphthoquinone in 1%Au/HPS presence

The influence of the phosphorothioate diester bond on the DNA oxidation process

RuO4-mediated oxidation ofN-benzylated tertiary amines. Are amineN-oxides and iminium cations reaction intermediates?

Catalytic air oxidation of manganese in synthetic waters

Aqueous p-nitrotoluene oxidation induced with direct glow discharge plasma

Preparation of iron oxide nanocatalysts and application in the liquid phase oxidation of benzene

1,3-bis(2,4,6-trinitrophenylaminooxy)propane and its 4-cyano-2,6-dinitrophenyl congener: Synthesis and properties

Characterization of vanadia catalysts on structured micro-fibrous glass supports for selective oxidation of hydrogen sulfide

Oxidation of glycerol-3-phosphate in porcine and bovine adrenal cortex mitochondria.

Investigation of oxidation process of 3-aminotoluene with ozone in presence of manganese bromide catalyst

Combined Effect of Zr and Si on Isothermal Oxidation of Ti

Oxygenic bismuth minerals in the NE part of the Karkonosze pluton (West Sudetes, SW Poland)

Assessing the Influence of the Presence of Heavy Metals Adsorbed on Activated Carbon on the Efficiency of Degradation of Phenol Using Selected Oxidizing Agents

Kinetics of oxidation of manganese by potassium permanganate and chloride in the Velekinca water treatment plant, Kosovo

New transformation of cycloalkanone acetals by peracids α,ω-dicarboxylic acids synthesis