In this paper, 2,5-furandicarboxylic acid (FDCA) was efficiently prepared by the direct oxidation of 5-hydroxymethylfurfural (5-HMF) using hydrogen peroxide (H2O2) in alkaline conditions without any catalysts. The effects of reaction parameters on the process were systematically investigated and the optimal parameters were obtained as follows: molar ratio of 5-HMF:KOH: H2O2 was 1:4:8, reaction temperature and reaction time were determined as 70°C and 15 minutes, respectively. Under these conditions, the yield of FDCA was 55.6% and the purity of FDCA could reach 99%. Moreover, we have speculated the detailed oxidation mechanism of 5-HMF assisted by hydrogen peroxide in alkaline condition to synthesize FDCA.
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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.
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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.
The properties of fast cutting steel SW7M, stainless steel 1H18N9T, and tool steel NC11 coated with a TiN protective layer were studied using 57Fe Conversion Electron Mössbauer Spectroscopy. The adhesion of the coatings is determined by the thickness of Fe-N and Fe-Ti interface. The model of the abrasion of the protected tools, based on fast diffusion of Fe ions to the surface though the TiN layer and further oxidation is proposed.
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W pracy scharakteryzowano procesy utleniania frakcji naftowych oraz możliwości ich inhibitowania. Za pomocą pomiarów absorpcji światła i mętności badano przebieg starzenia średniego destylatu z hydrokrakingu pozostałości próżniowej. Z kilku zbadanych dodatków, sól cynkowa kwasu dialkiloditiofosforowego okazała się stosunkowo najlepszym stabilizatorem badanej frakcji.
EN
In this work processes of petroleum fractions oxidation and capabilities of their inhibition were characterized. The ageing run of middle distillate from hydrocracking of vacuum residue has investigated with assistance of measurement of absorption light and turbidity. Out of several researched additives zinc salt of dialkyditiophosfate acid has turned out relatively most effective stabilizer of the researched fraction.
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Selenium(IV) oxide, poly(bis-1,2-phenylene) diselenide, bis[2-(N-benzisoselenazol- 3(2H)-onyl]diselenide and particularly 2-phenyl-1,2-benzisoselenazol-3(2H)-one (ebselen), were employed as the catalysts for hydrogen peroxide and t-butyl hydroperoxide oxidation of benzylamines. A reaction of primary amines proceeded via hydroxylamine and oxime, and the nitriles accompanied by imines, carboxylic acids and aldehydes were the final products. The secondary amines produced mainly the nitrones, while tetrahydroisoquinoline was dehydrogenated to isoquinoline.
Surface decarburization of high silicon spring steel in ambient air was studied. The experimental results confirmed the decarburized mechanism under AC1 temperature, in the temperature range of AC1-AC3 and AC3-G. Under AC1 temperature, pearlite spheroidization and surface decarburization are carried out simultaneously and pearlite spheroidization is reinforced. Considering the oxidation loss depth, the “true ferrite decarburized depth” at 850 °C (AC3-G) is still smaller than that at 760°C (AC1-AC3). That is because an “incubation period” must pass away before ferrite decarburization occurs in the temperature range of AC3-G, and the ferrite decarburized rate is limited to being equal to the partial decarburized rate.
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Zsyntezowano nową grupę heterogenicznych katalizatorów zawierających kobalt(II) i nikiel(II). Są to kompleksy tych metali z 8-hydroksychinoliną. Jako nośnika dla otrzymanych katalizatorów użyto polianiliny (PANI), poli(o-anizydyny) (POA) i poli(o-toluidyny) (POT). Aktywność katalityczną sprawdzano w reakcjach utleniania związków organicznych na wymienionych katalizatorach w obecności tlenu cząsteczkowego. Głównymi produktami reakcji były epoksydy i ketony, otrzymane z dobrą selektywnością i względnie dobrą wydajnością.
EN
Complexes of 8-hydroxyquinoline with Co or Ni acetate were prepd. and supported on conjugated polymers like polyaniline, poly-o-toluidine, or poly-o-anisidine. These heterogeneous systems were used to catalyze the oxidn of a-pinene, limonene, 1-decene with mol. O2 dissolved in acetonitrile at 60°C, with isobutyraldehyde as oxygen transfer agent. Epoxide products were obtained in 20-80% yields at high selectivities.
The low temperature oxidation processes which has taken place in lignites and their lithotypes (xylain, humovitrain, semifusain, fusain and liptain) from the East Maritza basin have been studied. The changes occurring in the coals/lithotypes composition and structure during their oxidation have been followed by examining reflectance, microhardness, proximate, ultimate, functional, and increment analyses. The main kinetic parameters such as duration of the induction period, maximum and stationary rates and the apparent activation energies were evaluated. The complex investigation provides a detailed information for the behaviour of low rank coals and their lithotypes towards the action of atmospheric oxygen. Thus some suggestions concerning the mechanisms of their oxidation reactions can be made. The individual way of the genesis of each one of the lithotypes and the resulting physicochemical structure predetermine the basic mechanism of these reactions. However, it has been found that in spite of the similar genesis the lithotypes differ in the mechanism of their oxidation. For xylain the oxidation takes place mainly via aryl radicals yielding tertiary peroxide and carbonyl groups. The oxidation of humovitrain is characterised by the dominant participation of aroxyl radicals resulting in accumulation of primary hydroperoxide and phenol groups. The oxidation of semifusain leads mainly to the formation of molecular products. The oxidation of fusain is found to be essentially different from that of other lithotypes. It is characterised by the formation of carbonyl groups attached to biphenyl aromatic structures. The peculiar petrographic composition and structure of liptain account for the occurrence of oxidation processes accompanied by destruction reactions at relatively lower temperatures. It has been established that the intensity of the oxidation processes varies from one lithotype to an other. Xylain and humovitrain oxidise most intensively. The intensity drops off from the first towards the second member of the corresponding genetic series, i.e. from xylain to humovitrain and from semifusain to fusain.
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Badano wpływ czasu utleniania na strukturę i skład chemiczny warstw ze stopu kobaltu wytworzonych metodą napawania laserowego. Do napawania użyto proszku o wysokiej zawartości chromu i średniej zawartości wolframu. Utlenianie przeprowadzono w temperaturze 1100°C w czasach od 15 minut do 50 godzin. Porównano uzyskane wyniki ze skutkami utleniania w temperaturze 750°C w czasie 200 godzin. Stwierdzono postępującą degenerację materiału napoiny, chociaż nie jest to proces niszczenia katastrofalnego.
EN
The influence of the oxidation time on the microstructure and chemical composition of the cobalt base laser clad layers was investigated. The powder used for cladding process contained high amount of chromium and medium amount of tungsten. The oxidations were carried on at 1100°C for times from 15 minutes to 50 hours. The effects were compared to results of oxidation at 750°C for 200 hours. The progressive degeneration was confirmed however it was not catastrophic process.
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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.
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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.
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.
Akinetic study of the oxidation of hexacyanoferrate(II) by peroxynitrite has been carried out, using a stopped-flow technique. The variation of the experimental rate constant over a wide concentration range of Fe(CN)6 4 has been investigated under different experimental conditions in terms of pH, ionic strength and temperature. Acorrelation between kexp and the substrate concentration has been obtained and this shows first-order behavior in substrate at high concentrations of Fe(CN)6 4 .Areaction mechanism is proposed, in which the hexacyanoferrate(II) reacts in competitive pathways with the peroxynitrous acid (direct oxidation) and with HOź and źNO2 radicals formed in the homolysis of the peroxide bond ofHOONO(indirect oxidation). Moreover, two individual constants, kc (the formation constant of the germinated radical pair [HOź źNO2]) and k7 (direct oxidation constant), have been evaluated together with the thermodynamic parameters of these elementary steps.
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In this paper we give a presentation of the recently developed approaches concerned of the rate of oxidation the Arema steel at high-temperature in first stage of this process. The comparison analysis was performed on the basis of the experimental results of oxidation of cylindrical specimens made of above steel. The experiment was carried out in chamber furnace on series of specimens with dimension '" = 20 . 1=30 mm. The specimens were oxidised at 1000°C for 10 - 2280 minutes in air and then quenched in silica sand, afterwards were measured both with and without of scale.
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Cobalt base clad layer underwent oxidation at 650° C and 750° C and corrosion in exhaust gases. The oxidation processes were run in two different ways; isothermal oxidation for 100 hours and cyc1ic oxidation for 200 hours. Corrosion in exhaust gases were run in a cyclic way for two month and about 200 hours at 6500 C. This clads were produced both laser and PTA cladding techniques. Thermal stability and oxidation behavior of the c1ads at different temperatures and environment were investigated. It appeared that exhaust gases were less harmful for this alloys than oxidizing atmosphere. The influence of the oxidation conditions (isothermal or cyclic oxidation) was established. Generally, the clad layers demonstrated good corrosion property in both atmospheres. The morphology changes of the clads were insignificant and the tiny oxide layer on the surface were noticed. The clads hardness changes were observed.
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Przedstawiono wyniki badań nad oczyszczaniem ścieku wodnego z procesu kondensacji aldolowej 2-metylopropanalu. W reakcji rozkładu zawartych w ścieku soli sodowych kwasów organicznych kwasem siarkowym(VI) mieszanina po reakcji uległa rozdziałowi na dwie fazy. Wydzieloną fazę organiczna można spalić w zakładowej kotłowni. Zanieczyszczenia organiczne zawarte w fazie wodnej utleniano nadtlenkiem wodoru do dwutlenku węgla i wody.
EN
The results of investigations on the purification of aqueous sewage from the condensations 2-methylpropanal are presented. The decomposition of the organic acid salt contained in the sewage with sulfuric acid makes the mixture divide into two phases. The organic phase would be burned for instance boiler room. While contained the aqueous phase with organic contained can be treated with hydrogen peroxide to give carbon divide and water.
The preparation of silica gel supported _-picolinium chlorochromate and its application as an efficient reagent for selective oxidation of oximes and alcohols into carbonyl compounds is reported. The trimethylsilyloxy and ester groups survived under the reaction conditions.
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