Heterogeneous Decomposition Of Hydrogen Peroxide Research Articles

Iron-Based Nanoparticles for Toxic Organic Degradation: Silica Platform and Green Synthesis.

Iron and iron oxide nanoparticles (NPs) are finding wide applications for the remediation of various toxic chloro-organic compounds (such as trichloroethylene, TCE), via reductive and oxidative processes. In this study, Fe NPs (30-50 nm) are synthesized by reduction from ferric ions immobilized (by ion exchange) on a platform (two types of sulfonated silica particles), in order to prevent the NP agglomeration. Next, the Fe NPs are oxidized and their effectiveness for the oxidative dechlorination of TCE via the heterogeneous decomposition of hydrogen peroxide to OH• on the surface of the iron oxide NPs was demonstrated. For the reductive approach, the use of ascorbic acid as a "green" reducing agent in conjunction with a secondary metal (Pd) inhibits NP oxidation and agglomeration through surface adsorbed species. The Fe/Pd NPs have been successfully applied for the dechlorination of TCE (k(SA), surface-area normalized reaction rate, = 8.1 ×10(-4) L/m(2)h).

Reaction Kinetics of the Heterogenous Decomposition of Hydrogen Peroxide in Microemulsions

Abstract Kinetic study for the heterogeneous decomposition of hydrogen peroxide over different non-soluble metal oxides (CuO, Fe2O3 and PbO2) was taken as a model reaction, mainly in normal micellar, inverse micellar microemulsion of sodium dodecyl sulfate (SDS). Other micellar phases of different surfactants [sodium dioctylsulfosuccinate (AOT), cetyle trimethyl ammonium bromide (CTAB) and triton X100] have been studied. Different organic solvents have been investigated. A promotional effect was generally observed. The reaction rate determining step was estimated. Reaction rate constants and thermodynamic parameters (ΔG*, ΔH* and ΔS*) were calculated. It was found that the highest promotional influence was observed in the case of (SDS/Fe3O4) in micellar and inverse micellar micro-emulsion media.

Correlation of Oxidation States in LaFexNi1-xO3+δ Oxides with Catalytic Activity for H2O2 Decomposition

Mixed oxides of the type LaFexNi1−xO3 with a perovskite structure were prepared by thermal decomposition of citrate mixtures at temperatures ranging from 773 to 1373 K. Temperature-programmed reduction profiles showed a low temperature step (450–500 K) due to the reduction of Ni3+ to Ni2+ and a high temperature step (650–1170 K) associated with the reduction of Ni2+ to Ni0 and Fe3+ to Fe0. From the microgravimetric reduction profiles it was established that the samples exhibit oxidative nonstoichiometry LaFexNi1−xO3+δ with δ=0.00–0.08. All the catalysts were tested in the heterogeneous decomposition of hydrogen peroxide (H2O2→H2O+1/2 O2) in alkaline medium. It was found that the active sites for the reaction are the highly oxidized transition metals (NiIII and FeIV). The concentration of these sites, as determined by iodometric titration, varied with catalyst composition and also with the calcination temperature of the precursors. The compensation effect was observed in all the catalysts investigated for hydrogen peroxide decomposition. The appearance of this effect was interpreted in terms of the catalytic reaction occurring on a heterogeneous catalytic surface, that is, a surface with active sites bearing different activation energies.

Changes in the Surface Chemistry and Adsorptive Properties of Active Carbon Previously Oxidised and Heat-Treated at Various Temperatures. I. Physicochemical Properties of the Modified Carbon Surface

Several active carbon samples with different quantities of surface oxides were obtained by annealing previously oxidised material under vacuum at various temperatures (ranging from 180°C to 900°C). Concentrated HNO3 was used as the oxidiser. The oxygen content, the pH of the aqueous slurry and the concentration of surface functional groups were determined for all the carbons. Spectral studies (FT-IR, XPS) were performed for selected samples. The heterogeneous decomposition of hydrogen peroxide was also studied. The catalytic activity for H2O2 decomposition correlated well with the acid consumption on the carbon materials. A linear relationship was derived between the oxygen reduction potentials and the logarithm of the peroxide decomposition rate constants.

Kinetics of heterogeneous decomposition of hydrogen peroxide with some transition metal complexes supported on silica-alumina in aqueous medium

Silica-alumina in the form of diethylamine (deam)-, dimethylamine (dmam)-, ethylamine (eam)-, ammonia (amm)- and aniline (an) -copper(II) complexes as well as deam-cobalt (II) complex have been used as potentially active catalysts for H 2O 2 decomposition in an aqueous medium. The reaction was first order with respect to the H 2O 2 concentration and the rate constants (per g of dry silica-alumina) were determined. A coloured compound, a peroxo-metal complex, which formed at the beginning of the reaction in each case, was found to contain the catalytically active species. The activation energy and the change in the entropy of activation increased with the basicity of the ligands in the following order: an < amm < eam < dmam < deam, which is also the probability sequence for the formation of the activated complex. A reaction mechanism was proposed.

Study of the heterogeneous decomposition of hydrogen peroxide: its application to the development of catalysts for carbon-based oxygen cathodes

The heterogeneous decomposition of hydrogen peroxide was studied in alkaline electrolytes on LaFe x Ni 1- x O 3 perovskite-type oxides. The reaction is first order in HO 2 − concentration. Maximum catalytic activity was found for x = 0.25. This increase in activity was attributed to the appearance of mixed oxidation states of iron and nickel. The optimum temperature of synthesis was between 600°C and 700°C, this being a compromise between a sufficiently high temperature to synthesize the perovskite structure and a sufficiently low temperature to produce a high surface area catalyst with a low number of oxygen vacancies. The catalytic activity for O 2 reduction on carbon-based electrodes correlates very well with the catalytic activity for HO 2 − decomposition. A linear relationship was derived between the electrode potential at constant current and the logarithm of the peroxide decomposition rate constant. This relationship is followed quite well at relatively low current densities.

ChemInform Abstract: Catalytic Activity of Pure Copper Oxide and Samples Containing Different Concentrations of Aluminum Oxide in Heterogeneous Decomposition of Hydrogen Peroxide

Abstractis determined and correlated with the non‐stoichiometry of the different samples and electrical conductivity measurements.

Heterogeneous Decomposition of Hydrogen Peroxide with Transition Metal-Ammine Complexes

Heterogeneous Decomposition of Hydrogen Peroxide with Transition Metal-Ammine Complexes

Catalytic decomposition of hydrogen peroxide on fine particle ferrites and cobaltites

The kinetics of heterogeneous decomposition of hydrogen peroxide on fine particle ferrites, $MFe_20_4$, and cobaltites, $MCo_2O_4$, where M = Mn, Fe, Co, Ni, Zn and Mg, have been investigated. The decomposition of $H_2O_2$, was found to be first order at low concentration (0.3%) and zero order at high concentration (30%) of $H_20_2$. The catalytic activity of cobaltites on the decomposition of $H_20_2$ is found to be better than ferrites. The observed catalytic behaviour of ferrites and cobaltites has been attributed to their fine particle nature, large surface area and electronic structure.

Heterogeneous Decomposition of Hydrogen Peroxide with Transition Metal-Ammine Complexes

Article Heterogeneous Decomposition of Hydrogen Peroxide with Transition Metal-Ammine Complexes was published on January 1, 1987 in the journal Zeitschrift für Physikalische Chemie (volume 268O, issue 1).

Kinetics of heterogeneous decomposition of hydrogen peroxide

The kinetics of the decomposition of hydrogen peroxide was studied in aqueous medium in the temperature range 25–40°C in the presence of Wofatit KPS-resin in the form of Cu(II)-ammine complex ions. The rate constant was deduced at various degrees of resin cross-linkage and different concentrations of hydrogen peroxide. The order of the decomposition reaction varied from first order to half order, i.e., the order of the reaction decreased with increasing the concentration of H2O2. The decomposition process was found to be a catalytic reaction which was controlled by the chemical reaction of H2O2 molecules with the active species inside the resin particles. The mechanism of the reaction can be summarized by the equation\( - {\text{d}}\left[ {{\text{H}}_{\text{2}} {\text{O}}_{\text{2}} } \right]/{\text{d}}t = k_1 {\text{ }}\sqrt {K_1 } K_2 \left[ {{\text{H}}_{\text{2}} {\text{O}}_{\text{2}} } \right]\left[ {{\text{Cu}}\left( {{\text{NH}}_{\text{3}} } \right)_4 } \right]^{2{\text{ }} + } /\left[ {{\text{H}}^{\text{ + }} } \right]\) in which the subsequent reactions of the probable active complex are discussed.

Kinetics of the decomposition of hydrogen peroxide catalysed by copper and nickel ferrites

The kinetic activities of the heterogeneous decomposition of hydrogen peroxide by metal–iron spinel oxides, MxFe3–xO4(M = Cu or Ni), have been investigated with a view to defining the effects of composition and microstructure on their catalytic activity. The entire composition range, 0 < x < 3, was prepared and characterized. Although the series of nickel catalysts was found to possess a lower aggregate diameter than the copper series, the decomposition activity of the former was surprisingly much less than the latter. This poor performance of the nickel series is explained in terms not of a consideration of microstructural defects but rather of the restricted redox couple represented by Mn/Mn–1 in the electronic composition of the catalysts and, possibly, the absence of a more active ion (Mn) at high compositions on the octahedral lattice sites which may initiate the cyclic electron-transfer process on the catalyst surface, as proposed by Abel and Cota et al. The value of x corresponding to maximum activity was experimentally evaluated for each catalyst series by determining the highest specific rate constant having minimum values of the Arrhenius pre-exponential factor, rather than minimum values of the activation energy.

Quantitative measurements of hydroperoxy and alkylperoxy radicals in gas-phase oxidation reactions from overlapping electron paramagnetic resonance spectra

Two numerical methods are presented for the analysis of overlapping electron spin resonance spectra of peroxy radicals obtained by freezing. One is devoted to the determination of a simple lineshape parameter and the other uses a data collecting and processing system and a least-squares fitting treatment. Examples are provided for quantitative measurements of peroxy species obtained during gas-phase oxidation of hydrocarbons and heterogeneous decomposition of hydrogen peroxide.

Linear Free Energy Relationships in Heterogeneous Catalysis. XII. Interpretation of the Catalytic Activity of Decomposition of Hydrogen Peroxide over Nickel Oxide on the Basis of Oxidation Power Distribution

Abstract Kinetic studies have been carried out on the heterogeneous decomposition of hydrogen peroxide over several nickel oxide catalysts calcined at different temperatures. Kinetic parameters such as reaction order and apparent activation energy depend somewhat on the reaction conditions, but show practically no change with catalyst. The catalytic activity changes with calcination temperature, becoming minimum at 550 °C and maximum at 600 °C. The trend does not change with pretreatment of the catalyst, resembling the behavior of surface excess oxygen having a relatively higher oxidation power. Thus the distribution of oxidation power is closely related to catalytic activity for the decomposition of hydrogen peroxide. We therefore applied the regional analysis assuming that the surface excess oxygen represents active sites for catalysis, and a specific regional activity corresponds to each regional oxygen. It was found that the fifth region (the range of free energy change of adsorption of oxygen being from −11.1 to −12.6 kcal/mol) markedly contributes to the reaction rate, and the calculated rates agree with the observed ones. The nature of the active site was discussed as regards pretreatment of the catalyst.

Studies of the reactions of hydroxyl radicals. I

This paper describes how the homogeneous decomposition of hydrogen peroxide vapour has been successfully used as a source of hydroxyl radicals in a kinetic study of the relative rates of reaction of hydroxyl radicals with methane, carbon monoxide, formaldehyde and hydrogen peroxide. It has been found that the method is of general applicability provided subsequent reactions of radicals formed can be controlled. With hydroxyl radicals so produced from the decomposition of hydrogen peroxide, surprisingly consistent values were obtained for the relative rates of reaction of methane and carbon monoxide with hydroxyl radicals. Thus, within an accuracy of 10%, the ratios of rate constants for reaction of hydroxyl radicals with methane and carbon monoxide were found to be 3.6 at 650 °C, 2.1 at 525 °C and 0.85 at 400 °C. The rates of reaction of hydroxyl radicals with formaldehyde and hydrogen peroxide were less accurately determined because of expected additional reactions. Within an accuracy of about 50% it was estimated that hydroxyl radicals reacted ten times as fast with hydrogen peroxide as with carbon monoxide at 525 °C. At the same temperature hydroxyl radicals reacted 33 ± 6 times as fast with formaldehyde as with methane. Data were obtainable at temperatures as low as 400 °C even though heterogeneous decomposition of hydrogen peroxide was relatively more important at these temperatures. This was because heterogeneous decomposition of hydrogen peroxide did not cause oxida­tion of the other gases which were also present. A preliminary account (Hoare 1962) of this work has previously been published.