Aqueous Peroxide Research Articles

Hydrogen peroxide kinetics in water radiolysis

The kinetics of the formation and reaction of hydrogen peroxide in the long time γ- radiolysis of water is examined using a combination of experiment with model calculations. Escape yields of hydrogen peroxide on the microsecond time scale are easily measured with added radical scavengers even with substantial amounts of initial added hydrogen peroxide. The γ-radiolysis of aqueous hydrogen peroxide solutions without added radical scavengers reach a steady state limiting concentration of hydrogen peroxide with increasing dose, and that limit is directly proportional to the initial concentration of added hydrogen peroxide. The dose necessary to reach that limiting hydrogen peroxide concentration is also proportional to the initial concentration, but dose rate has a very small effect. The addition of molecular hydrogen to aqueous solutions of hydrogen peroxide leads to a decrease in the high dose limiting hydrogen peroxide concentration that is linear with the initial hydrogen concentration, but the amount of decrease is not stoichiometric. Proton irradiations of solutions with added hydrogen peroxide and hydrogen are more difficult to predict because of the decreased yields of radicals; however, with a substantial increase in dose rate there is a sufficient decrease in radical yields that hydrogen addition has little effect on hydrogen peroxide decay.

Functional composition and electrochemical characteristics of oxidized nanosized carbon

The functional composition and electrochemical behavior of the samples of N121 oxidized nanosized technical carbon in aqueous electrolytes are studied. For oxidation a 30% aqueous hydrogen peroxide (H2O2) solution and 2% H2O2 with the addition of singlet oxygen or ozone were used. By means of X-ray photoelectron spectroscopy data and the analysis of the near edge X-ray absorption fine structure the features of the chemical structure of the samples are found. The oxygen concentration did not exceed 5 at.% in the samples. The analysis of cyclic voltammograms reveals that at low scan rates the specific capacitance of the material is determined by the functional composition of the surface. The sample oxidized by 30% H2O2 solution and containing the largest number of–OH and–COOH groups demonstrated the highest capacitance in 6M KOH and in 1М H2SO4 it was the sample with the highest concentration of C=O groups formed during the oxidation with singlet oxygen. The stability of carbon electrodes is studied in supercapacitor models.

On the stability of Al13 Keggin cation in aqueous hydrogen peroxide solutions

We report the first attempt to study the behavior of the [AlO4Al12(OH)25(H2O)11]6+ (Al13) Keggin cation (KC) in water–peroxide solutions. Addition of hydrogen peroxide into an aqueous solution containing the Al13 KC reduces pH due to the acidity of hydrogen peroxide. According to the 27Al NMR studies of water–peroxide solutions prepared just before the NMR experiment, with their pH adjusted to the initial value of 5.5 with aqueous NaOH, the Al13 KC concentration decreases immediately once hydrogen peroxide is added to the initial system. Addition of 18.2 wt % hydrogen peroxide to the initial 0.88 mM Al13 solution gives rise to a fourfold decline in Al13 polyoxo cation concentration to 0.22 mM. Then, the KC concentration in the test system remains unchanged for 1 week. Large hydrogen peroxide amounts (27.9 wt % or higher) added to the initial system almost completely degrade the KC. Sodium sulfate added to the initial water–peroxide solution of Al13 chloride where the hydrogen peroxide concentration is 5.5 wt % precipitates the earlier described Al13 sulfate [AlO4Al12(OH)25(H2O)11](SO4)3 · 16H2O, where the aluminum polyoxo cation does not contain coordinated hydrogen peroxide molecules, peroxo or hydroperoxo groups as shown by X-ray diffraction.

Simultaneous quantification of aqueous peroxide, nitrate, and nitrite during the plasma–liquid interactions by derivative absorption spectrophotometry

A derivative absorption spectroscopic method is used in situ to simultaneously trace and quantify the aqueous peroxide (H2O2), nitrate () and nitrite () generated during plasma–liquid interactions. The results indicate that the time evolutions of H2O2, and generated from the plasma–liquid interactions strongly depend on the solution’s pH value, which varies with the plasma treatment. The concentrations of aqueous H2O2, and increase independently from each other during the plasma treatment when the solution’s pH value is higher than 3.0. However, when the solution’s pH value is less than 3.0, most of the aqueous (~71.5%) will exist in the form of molecular nitrous acid since the pKa of nitrous acid is 3.4, the aqueous is mainly formed from the reaction between H2O2 and as well as the decomposition of molecular HNO2, which leads to a continuous increase of concentration and an appearance of the maximum concentrations of H2O2 and as the pH value of the solution reaches 3.0.

A radical route from methane to methanol

Catalysis The conversion of methane into chemicals usually proceeds through high-temperature routes that first form more reactive carbon monoxide and hydrogen. Agarwal et al. report a low-temperature (50°C) route in aqueous hydrogen peroxide (H2O2) for oxidizing methane to methanol in high yield (92%). They used colloidal gold-palladium nanoparticles as a catalyst. The primary oxidant was O2; isotopic labeling showed that H2O2 activated methane to methyl radicals, which subsequently incorporated O2. Science , this issue p. [223][1] [1]: /lookup/doi/10.1126/science.aan6515

Interfacial contributions of H2O2 decomposition-induced reaction current on mesoporous Pt/TiO2 systems

We report on conversion of energy released due to chemical reactions into current for the decomposition of aqueous hydrogen peroxide solution on single phases Pt and TiO2, in addition to Pt and TiO2 simultaneously. We observe that H2O2 decomposition-induced current on TiO2 drastically overshadows the current generated by H2O2 decomposition on Pt. Photo-effects avoided, H2O2 decomposition was found to yield a conversion efficiency of 10−3 electrons generated per H2O2 molecule. Further understanding of chemical reaction-induced current shows promise as a metric with which the surface reaction may be monitored and could be greatly extended into the field of analytical chemistry.

Selective Oxidation of Methane with Hydrogen Peroxide Towards Formic Acid in a Micro Fixed‐Bed Reactor

AbstractSelective oxidation of methane by using aqueous hydrogen peroxide solution as oxidant was investigated. Colloidal nanosized Cu‐Fe‐silicalite‐1 was prepared and a micro reactor was used to intensify mass transport. It was found that the oxygenate productivity could be enhanced nearly three orders of magnitude while simultaneously ensuring high turn‐over‐frequencies of some 100 h−1. However, the main product in liquid phase was not methanol, but formic acid. At optimized reaction conditions, a selectivity to formic acid of 96.7 % at a methane conversion of 10.3 % could be achieved.

Aqueous Au-Pd colloids catalyze selective CH4 oxidation to CH3OH with O2 under mild conditions.

The selective oxidation of methane, the primary component of natural gas, remains an important challenge in catalysis. We used colloidal gold-palladium nanoparticles, rather than the same nanoparticles supported on titanium oxide, to oxidize methane to methanol with high selectivity (92%) in aqueous solution at mild temperatures. Then, using isotopically labeled oxygen (O2) as an oxidant in the presence of hydrogen peroxide (H2O2), we demonstrated that the resulting methanol incorporated a substantial fraction (70%) of gas-phase O2 More oxygenated products were formed than the amount of H2O2 consumed, suggesting that the controlled breakdown of H2O2 activates methane, which subsequently incorporates molecular oxygen through a radical process. If a source of methyl radicals can be established, then the selective oxidation of methane to methanol using molecular oxygen is possible.

Mechanistically Driven Development of an Iron Catalyst for Selective Syn-Dihydroxylation of Alkenes with Aqueous Hydrogen Peroxide.

Product release is the rate-determining step in the arene syn-dihydroxylation reaction taking place at Rieske oxygenase enzymes and is regarded as a difficult problem to be resolved in the design of iron catalysts for olefin syn-dihydroxylation with potential utility in organic synthesis. Toward this end, in this work a novel catalyst bearing a sterically encumbered tetradentate ligand based in the tpa (tpa = tris(2-methylpyridyl)amine) scaffold, [FeII(CF3SO3)2(5-tips3tpa)], 1 has been designed. The steric demand of the ligand was envisioned as a key element to support a high catalytic activity by isolating the metal center, preventing bimolecular decomposition paths and facilitating product release. In synergistic combination with a Lewis acid that helps sequestering the product, 1 provides good to excellent yields of diol products (up to 97% isolated yield), in short reaction times under mild experimental conditions using a slight excess (1.5 equiv) of aqueous hydrogen peroxide, from the oxidation of a broad range of olefins. Predictable site selective syn-dihydroxylation of diolefins is shown. The encumbered nature of the ligand also provides a unique tool that has been used in combination with isotopic analysis to define the nature of the active species and the mechanism of activation of H2O2. Furthermore, 1 is shown to be a competent synthetic tool for preparing O-labeled diols using water as oxygen source.

Mechanism of Catalytic Oxidation of Styrenes with Hydrogen Peroxide in the Presence of Cationic Palladium(II) Complexes.

Kinetic studies, isotope labeling, and in situ high-resolution mass spectrometry are used to elucidate the mechanism for the catalytic oxidation of styrenes using aqueous hydrogen peroxide (H2O2) and the cationic palladium(II) compound, [(PBO)Pd(NCMe)2][OTf]2 (PBO = 2-(pyridin-2-yl)benzoxazole). Previous studies have shown that this reaction yields acetophenones with high selectivity. We find that H2O2 binds to Pd(II) followed by styrene binding to generate a Pd-alkylperoxide that liberates acetophenone by at least two competitive processes, one of which involves a palladium enolate intermediate that has not been previously observed in olefin oxidation reactions. We suggest that acetophenone is formed from the palladium enolate intermediate by protonation from H2O2. We replaced hydrogen peroxide with t-butyl hydroperoxide and found that, although the palladium enolate intermediate was observed, it was not on the major product-generating pathway, indicating that the form of the oxidant plays a key role in the reaction mechanism.

Toward an inherently safer alternative for operating N-oxidation of alkylpyridines: Effect of N-oxide on lutidine – water phase separation

The N-oxidation of alkylpyridines is an industrially important reaction since it produces alkylpyridine N-oxides that are pharmaceutical intermediates. The aqueous hydrogen peroxide used to oxidize the alkylpyridine has a tendency to decompose during the reaction thereby introducing serious hazards for the process. The decomposition is accelerated during the N-oxidation of higher order alkylpyridines (lutidines, collidines) due to mass transfer limitations caused by the separation of the liquid into organic and aqueous phase. Also, the presence of phosphotungstic acid (catalyst) in the aqueous phase further intensifies the peroxide decomposition reducing the safety and efficiency of the process. The current work investigates the influence of the product N-oxide on the mixing between alkylpyridine and water, which is primarily responsible for the liquid phase heterogeneity during the N-oxidation. Ternary mixtures of 2,6-lutidine, 2,6-lutidine N-oxide and water were analyzed at 110°C to determine phase separation compositions. It was found that extent of heterogeneity between 2,6-lutidine and water is reduced dramatically by the presence of 2,6-lutidine-N-oxide as indicated by the phase diagram. The results could be used to implement the inherent safety concept – “hybridization” to the N-oxidation system wherein the concentration of product N-oxide can be controlled to maintain a less hazardous environment.

Mesoporous molecular sieves containing niobium(V) as catalysts for the epoxidation of fatty acid methyl esters and rapeseed oil

Niobium-containing mesoporous silica (Nb–SiO2) catalysts, which showed previously promising performances in the liquid-phase epoxidation of alkenes, were here applied to the epoxidation of unsaturated fatty acid methyl esters (FAMEs), selectively hydrogenated FAMEs and rapeseed oil triglyceride with aqueous hydrogen peroxide. Niobium-silica solids were prepared via grafting of niobocene dichloride onto the surface of different porous silica-based supports (non-ordered SiO2, ordered mesoporous MCM-41 and SBA-15 molecular sieves) via a dry impregnation procedure. Promising performance with very good selectivity towards desired monoepoxides were obtained, in particular over a Nb-grafted silica catalyst prepared from a commercial non-ordered silica support.

Catalytic Asymmetric Epoxidation of Electron‐Deficient Enynes Promoted by Chiral N,N′‐Dioxide‐Scandium(III) Complex

AbstractAn asymmetric epoxidation of electron‐deficient enynes with environmentally benign aqueous hydrogen peroxide as oxidant has been accomplished by developing a chiral N,N′‐dioxide‐Scandium(III) complex catalytic system. In the presence of 0.5–2 mol% catalyst, a variety of trisubstituted alkynyl oxiranes were obtained in high yields (up to 97%) with excellent ee values (up to 99%). Furthermore, control experiments provide a fundamental insight into the reaction mechanism.magnified image

Tuning Selectivity in Aliphatic C–H Bond Oxidation of N-Alkylamides and Phthalimides Catalyzed by Manganese Complexes

Site selective C–H oxidation of N-alkylamides and phthalimides with aqueous hydrogen peroxide catalyzed by manganese complexes is described. These catalysts are shown to exhibit substantially improved performance in product yields and substrate scope in comparison with their iron counterparts. The nature of the amide and imide group and of the N-alkyl moiety are shown to be effective tools in order to finely tune site selectivity between proximal (adjacent to the nitrogen) and remote C–H bonds on the basis of steric, electronic, and stereoelectronic effects. Moreover, formation of the α-hydroxyalkyl product in good yield and with excellent product chemoselectivity was observed in the reactions of the pivalamide and acetamide derivatives bearing an α-CH2 group, pointing again toward an important role played by stereoelectronic effects and supporting the hypothesis that these oxidations proceed via hydrogen atom transfer (HAT) to a high-valent manganese–oxo species. Good product yields and mass balances are...

Wear properties of carbon composite reinforced by vapor-grown carbon fibers treated with nitric acid and aqueous hydrogen peroxide

Carbon nanofiber-reinforced carbon composites (C/C composites) were prepared from furan resins filled with vapor-grown carbon fibers (VGCFs) that had previously been treated with nitric acid or aqueous hydrogen peroxide. Their wear properties were compared to those of C/C composites reinforced by untreated fibers. The relative wear volumes of C/C composites reinforced by HNO3-treated fibers were slightly lower and those of C/C composites by H2O2aq.-treated fibers were significantly lower than those of C/C composites by untreated fibers. The higher wear resistance is inferred to be due to improved anchoring of the fibers in the C/C composites because of roughening of the fiber surface after treatment with H2O2aq. A lubricous sliding surface, which is suggested to be controlled by the adhesive wear mechanism, was formed on the C/C composite prepared from H2O2aq.-treated fibers after the wear tests. The mechanism is implied to be responsible for the higher wear resistance.

Catalytic epoxidation of β-pinene with aqueous hydrogen peroxide

Epoxidation of β-pinene with 35–38% aqueous hydrogen peroxide in a new catalytic system containing manganese sulfate, salicylic acid, sodium bicarbonate and polar solvent (DMF, acetonitrile, methanol) is described. The method of quantitavive determination of β-pinene and its epoxide is developed.

酸化マンガン（IV）を固定化した陶土の調製とそれを利用した実践研究―過酸化水素水中の上下運動の観察―

酸化マンガン（IV）を固定化した陶土の調製とそれを利用した実践研究―過酸化水素水中の上下運動の観察―

Cu-Schiff base complex grafted onto graphene oxide nanocomposite: Synthesis, crystal structure, electrochemical properties and catalytic activity in oxidation of olefins

Copper(II) Schiff base complex has been immobilized onto graphene oxide (GO) via covalent bonding. The nanocomposite was characterized using powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV–visible spectroscopies, transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA) and the energy-dispersive X-ray spectroscopy (EDX). The amount of catalyst loading on the solid support was determined by atomic absorption spectroscopy. The thermogravimetric analysis (TGA) demonstrated that the nanocatalyst was stable up to almost 220°C, exhibiting high thermostability. Highly active and selective catalyst was found with excellent turnover numbers (up to 47,000 for oxidation of styrene) for the epoxidation of olefins in ethanol using aqueous hydrogen peroxide as oxidant. It could be readily reused for successive ten times without discernible activity and selectivity deterioration, which displays potential for practical applications.

Mechanism and Kinetic Model for Autocatalysis in Liquid–Liquid System: Oxidation of Dibutyl Sulfide with Aqueous Hydrogen Peroxide

The oxidation of dibutyl sulfide with aqueous hydrogen peroxide as a liquid–liquid reaction was investigated. The autocatalysis, solubility of H2O2 in organic phase, and effects of temperature, stirring speed, initial organic DBSO concentration, and initial aqueous H2O2 concentration were studied. Solvent effect of dibutyl sulfoxide was proposed for liquid–liquid autocatalysis. The intrinsic reaction was considered as the determining step, and all the other steps were considered as equilibrium processes. Considering interfacial reaction and dynamic equilibrium of hydrogen peroxide between the two phases, the reaction was divided into exterior and interior stages. Exterior and interior mechanisms were proposed for the corresponding stages, and kinetic models were established. The parameters of kinetic model were estimated with the experimental data, and the activation energies of exterior and interior reaction were 30.62 and 73.50 kJ/mol. The validity of the kinetic models with estimated parameters was stu...

Baeyer–Villiger Oxidation of Cyclic Ketones by Using Tin–Silica Pillared Catalysts

AbstractThe Baeyer–Villiger oxidation is an important transformation of ketones into esters and particularly for cyclic ketones to lactones. We report here preparation and catalytic activity of layered Sn–silicate catalysts and mesoporous ordered silica catalysts in this reaction. Sn was introduced by using so‐called tin–silica pillaring or by impregnation with a mixture of tetraethylorthosilicate and tin(IV) alkoxide. The prepared catalysts were characterized by XRD, N2 physisorption, SEM, UV/Vis, and inductively coupled plasma optical emission spectroscopy (ICP‐OES) techniques and the catalysts were studied in the Baeyer–Villiger oxidation of cyclopentanone, norcamphor, and 2‐adamantanone with aqueous hydrogen peroxide. Norcamphor and 2‐adamantanone were oxidized easily with selectivity up to 99 %. Sn‐MS and IPC‐1‐SnPI materials exhibited the highest conversions (e.g., norcamphor: Sn‐MS 37 %, IPC‐1‐SnPI 36 % after 8 h vs. Sn‐MCM‐41 22 %). On the other hand, oxidation of cyclopentanone suffered from product hydrolysis to the corresponding 4‐hydroxybutanoic acid.