Thermal Decomposition Of Peroxides Research Articles

Preparation of ZnO1-x by peroxide thermal decomposition and its room temperature gas sensing properties

Preparation of ZnO1-x by peroxide thermal decomposition and its room temperature gas sensing properties

Adsorption and Decomposition of Peroxides on the Surfaces of Dispersed Oxides Fe2O3, Cr2O3 and V2O5

The adsorption of peroxides on dispersed oxides Fe2O3, Cr2O3 and V2O5 was studied. It is shown that the adsorption of peroxides is described by the Langmuir equation. The adsorption of benzoyl peroxide grows within Fe2O3<Cr2O3<V2O5. Adsorption-desorption equilibrium constants (K) for Cr2O3 and V2O5 are the same, but for Fe2O3 this value is 6 times higher. The decomposition of peroxides is observed in the solution and on the surface of adsorbents. The effective activation energy (E) of the thermal decomposition of peroxides in the studied systems is in the range of 80–140 kJ/mol. The activation energy of degradation of peroxides on the surface (Es) of the dispersed oxides studied is lower. The degradation reaction of peroxides on the surface of Fe2O3 and V2O5 has an oxidation-reducing nature, during which free radicals are produced. On the surface of Cr2O3, there is a heterolytic decay of peroxides. The parameters of the reaction of peroxides decomposition are found. The decomposition of peroxides in the presence of Fe2O3, Cr2O3 and V2O5 in styrene is accompanied by the formation of polystyrene both in the solution and on the surface of the adsorbent.

Numerical study of hydrogen peroxide thermal decomposition in a shock tube

Hydrogen peroxide (H2O2) has its significance during the combustion of heavy hydrocarbons in the internal combustion (IC) engines. Owing to its importance the measurements of H2O2 dissociation rate have been reported mostly using the shock tube apparatus. These types of experimental measurements are although quite reliable but require high cost. On the other hand, numerical simulations provide low cost and reliable solutions especially using computation fluid dynamics (CFD) software. In the current study an experimental shock tube flow is modeled using open access platform OpenFOAM to investigate the thermal decomposition of H2O2. Using two different convective schemes, limitedLinear and upwind, the propagation of shock wave and resultant dissociation reaction are simulated. The results of the simulations are compared with the experimental data. It is observed that the rate constant measured using the simulation data deviates from the experimental results in the low temperature range and approaches the experimental values as the temperature is raised.

Thermal decompositions of dialkyl peroxides studied by DSC

Studies on the thermal decompositions of diamyl peroxide (DAPO), dicumyl peroxide (DCPO), and tert-butyl cumyl peroxide (TBCP) were conducted by DSC. Heat of decomposition, exothermic onset point, and chemical kinetics were determined and compared to those data of di-tert-butyl peroxide (DTBP), a model compound for studying thermokinetics of organic peroxide and standardization of a calorimeter. Similarities and differences of decomposition mechanisms between these organic peroxides were proposed and verified. Kinetics on decomposition of uni-molecular reaction via these similar alkoxyl radials accompanying β C–C bond scission were discussed and compared to the results from ab initio calculations. The ranking of thermal stability on dialkyl peroxides is determined to be in the following sequence: DCPO < TBCP < DAPO < DTBP. This rate-determining step in thermal decomposition of dialkyl peroxides possessed an average eigenvalue of log A at about 13.1 ± 1.2. Activation energy on the thermal decomposition of these peroxides was calculated to be 139.5 ± 14.4 kJ mol−1.

Determination of formal kinetic constants of thermal decomposition of aqueous hydrogen peroxide solution in a mixture of magnetic powder, based on experimental thermogram, obtained in adiabatic conditions

Process of thermal decomposition of hydrogen peroxide aqueous solution with the addition of magnetic powder in the form of toner for printers and lanthanum manganite were considered. Obtained resulting from an experiment in the Dewar container conducted thermogram analyzed using mass balance equations and heat. Formal kinetic parameters determined, and conclude that the magnetic powder in the mixture does not have catalytic properties. The described technique is recommended as a rapid analysis of the kinetics of the various reactions to substances having predefined thermal and thermodynamic properties. Recently, it has been suggested to use fluids mixed with a fine powder to change the thermophysical features of coolants in order to increase the heat exchanger efficiency. Application of magnetic powders allows for additional control over unit operation using the magnetic field. An aqueous hydrogen peroxide solution is often suggested to be used as a coolant in a variety of heat exchangers (such as solar collectors). The aqueous hydrogen peroxide solution with additives of fine magnetic powder can significantly improve the efficiency of heat exchangers. To study the kinetics of thermal decomposition of hydrogen peroxide aqueous solution with added magnetic powder, series of experiments were done to determine the process thermogram in adiabatic conditions of Dewar vessels. Dynamic heat balance equation for the reaction of thermal decomposition of hydrogen peroxide aqueous solution, considering the presence of magnetic powder particles and the reaction of hydrogen peroxide thermal decomposition are recorded under the assumption of the process equilibrium within the entire time interval . During experiments the mixture temperature variations from the initial to final did not exceed 8.5K, which allows, according to the Hess's law, heat of reaction (qd,, J/mol) to be taken as constant. The thermodynamic system is a colloidal solution of hydrogen peroxide, oxygen in water (with current masses, respectively, mH2O2,mO2, mH2O) and fine magnetic powder, consisting of toner for printers and lanthanum manganite (LaySrMnO3−X( y< x)) of the total mass mmp. Specific heat components, respectively, cH2O2, cO2, cH2O & cmp are temperature functions for a general case. Heat from the

Adsorption and decomposition of diacylic peroxides on the surfaces of dispersed oxides

The adsorption of oligo(sebacoyl peroxide) on Aerosil and MgO and benzoyl peroxide on Fe2O3, Cr2O3, and V2O5 has been studied. It has been established that peroxide adsorption on the considered adsorbents is described by the Langmuir equation. Benzoyl-peroxide adsorption increases in the series Fe2O3 < Cr2O3 < V2O5. The process of thermal decomposition of peroxides in the presence of the listed adsorbents has been studied. The overall reaction of peroxide decomposition comprises two components, i.e., the decomposition processes occurring in a solution and on an adsorbent surface. Kinetic and activation parameters of the thermal-decomposition reactions in the solutions and on the surfaces have been determined.

Measurement of the Rate of Hydrogen Peroxide Thermal Decomposition in a Shock Tube Using Quantum Cascade Laser Absorption Near 7.7 μm

ABSTRACTHydrogen peroxide (H2O2) is formed during hydrocarbon combustion and controls the system reactivity under intermediate temperature conditions. Here, we measured the rate of hydrogen peroxide decomposition behind reflected shock waves using midinfrared absorption of H2O2 near 7.7 µm. We performed the experiments in diluted H2O2/Ar mixtures between 930 and 1235 K and at three different pressures (1, 2, and 10 atm). Under these conditions, the decay of hydrogen peroxide is sensitive only to the decomposition reaction rate, H2O2 + M → 2OH + M (k1). The second‐order rate coefficient at low pressures (1 and 2 atm) did not exhibit any pressure dependence, suggesting that the reaction was in the low‐pressure limit. The rate data measured at 10 atm exhibited falloff behavior. The measured decomposition rates can be expressed in Arrhenius forms as follows: urn:x-wiley:05388066:kin20827:equation:kin20827-math-0001 urn:x-wiley:05388066:kin20827:equation:kin20827-math-0002

Thermal Oscillations in the Decomposition of Organic Peroxides: Identification of a Hazard, Utilization, and Suppression

The purpose of this research is to identify and characterize oscillatory thermal instability in organic peroxides that are used in vast quantities in industry and misused by terrorists. The explosive thermal decompositions of lauroyl peroxide, methyl ethyl ketone peroxide, and triacetone triperoxide are investigated computationally, using a continuous stirred tank reactor model and literature values of the kinetic and thermal parameters. Mathematical stability analysis is used to identify and track the oscillatory instability, which may be violent. In the mild oscillatory regime it is shown that, in principle, the oscillatory thermal signal may be used in microcalorimetry to detect and identify explosives. Stabilization of peroxide thermal decomposition via Endex coupling is investigated. It is usually assumed that initiation of explosive thermal decomposition occurs via classical (Semenov) ignition at a turning point or saddle-node bifurcation, but this work shows that oscillatory ignition is also characteristic of thermoreactive liquids and that Semenov theory and purely steady state analyses are inadequate for identifying a thermal hazard in such systems.

Kinetics of Peroxide Vulcanization of Natural Rubber

This study was undertaken to optimize the vulcanization conditions and explore the effect of residual peroxide in the peroxide vulcanization of natural rubber. The study was followed through the kinetics of the vulcanization reaction at various temperatures viz. 150,155,160 and 165°C. Dicumyl peroxide (DCP) was used as the crosslinking agent. The Monsanto Rheometer was used to investigate the different crosslinking stages and vulcanization kinetics. The thermal decomposition of peroxide followed a first order free radical decomposition reaction. Half-lives at various temperatures were determined. The percentage of residual peroxide was calculated from the cure kinetic data. The effect of residual peroxide on mechanical properties was studied at various peroxide levels and also by extending the cure time (from t90 to t95 and then to t100). Mechanical properties such as tensile strength, elongation at break, modulus and compression set (70 and 100°C) were measured. Excess peroxide was found to cause a high compression set at elevated temperature and the cure time was selected to achieve minimum residual peroxide in the product. Results indicate that peroxide concentration is the dominant factor controlling the crosslink density and hence the properties of the vulcanizates.

Polypropylene degradation: Theoretical and experimental investigations

The controlled-rheology peroxide degradation of polypropylene is a major issue for the industry. Combining DFT calculations – about H-abstraction onto model 2,4,6-trimethylheptane by model radicals such as t-butoxyl, methyloxyl, and methylperoxyl – with degradation studies of short chain polypropylene, we showed that the degradation depended a lot on the amount of oxygen, on the temperature, on the concentrations of both polypropylene and peroxide, and on the radicals generated from the thermal decomposition of peroxide. Besides the expected enthalpic control on the H-abstraction reaction, the bulkiness of both the oxyl radical and the reactive centre modified dramatically the regioselectivity, i.e., preferred H-abstraction from the terminal primary carbon atom by the tert-butoxyl radical vs the H-abstraction from the terminal tertiary carbon atom by methoxyl and methylperoxyl radicals. Graphical abstract [Display omitted]

A chemiluminescence and fluorescence spectroscopy study: An investigation of photocrosslinking processes in polymer systems

Chemiluminescence emission is shown to be a valuable method for the analysis and monitoring of the photochemical transformation process in BZMA- co-S copolymers. BZMA- co-S copolymer films are synthesized and irradiated at λ > 400 nm, in order to induce the phototransformation of benzyl (BZ) to benzoyl peroxide (BP) pendant groups, resulting in thermal decomposition and crosslinking. The chemiluminescence emission increases with irradiation time, and is shown to be related to the benzoyl peroxide moieties generated during irradiation. The increase in chemiluminescence intensity is interrupted at longer periods of irradiation, when the concentration of these species tends to a nearly constant value. In this case, others factors are considered to influence the chemiluminescence emission, for example the increasing crosslinking on irradiated samples, which would restrict the mobility of radicals to recombine due to crosslinking of the network. A good correlation between fluorescence, FTIR and CL measurements during photochemical formation and thermal decomposition of peroxides is found. In this work, an intramolecular excimer forming fluorescent probe, DiPyM, is also used to analyse the crosslinking process. The results obtained contribute significantly to the development of chemiluminescence as a highly sensitive methodology for assessing the photocrosslinking of a polymeric material in the early stages of the process and is due to its sensitivity in comparison to that of fluorescence analysis.

Life detection experiments of the Viking Mission on Mars can be best interpreted with a Fenton oxidation reaction composed of H2O2 and Fe2+ and iron-catalysed decomposition of H2O2

AbstractThe findings of the life detection experiments carried out during the Viking mission to Mars were reinterpreted with a chemical hypothesis. The labelled release (LR), pyrolytic release (PR) and gas exchange (GEx) experiments were interpreted with Fenton chemistry. Oxygen and carbon dioxide evolution from Martian soil upon wetting and nutrient addition could be attributed to competition reactions between the Fenton-type oxidation of organic nutrients with the aqueous (hydrogen peroxide+Fe(II)) combination and the iron-catalysed decomposition of hydrogen peroxide. A substantial evolution of radioactive gas upon addition of labelled organic nutrient solution to soil, whereas the ceasing of this gas with a heat treated sample in the LR experiments, was attributed to Fenton oxidation and hydrogen peroxide thermal decomposition, respectively. The peculiar kinetics of LR and PR experiments – that cannot be fully explained by other chemical or biochemical scenarios – were easily explained with this new hypothesis, i.e. limitation of the Fenton reaction may arise from the depletion of reactants, the build-up of ferric hydroxide on soil and excessive scavenging by the organic nutrients of the generated hydroxyl radicals. Reabsorption or adsorption of evolved or introduced CO2 may involve the formation of carbonate compounds (e.g., magnesium carbonate and bicarbonate) on the surface of alkalinized soil as a result of the Fenton reaction.A critical evaluation of the recent biological hypothesis assuming the utilization of a hydrogen peroxide–water intracellular fluid by putative organisms (Houtkooper &amp; Schulze-Makuch 2007) is also made.

Cp2TiCl‐catalyzed living radical polymerization of styrene initiated from peroxides

AbstractThe effects of the reaction conditions and nature of the initiator were investigated in the Cp2Ti(III)Cl‐catalyzed living radical polymerization of styrene initiated by benzoyl peroxide (BPO), tert‐butyl peroxide (TBPO), tert‐butyl peroxybenzoate (TBPOB), dicumyl peroxide (CPO), and tert‐butylperoxy 2‐ethylhexyl carbonate (TBPOEHC). The reversible termination of the growing chains with Cp2Ti(III)Cl affords a linear dependence of molecular weight on conversion over a wide range of temperatures (60–120 °C) with an optimum in polydispersity (Mw/Mn &lt; 1.2) for St/BPO/Cp2TiCl2/Zn = 100/1/3/6 at 60–90 °C. The similarity of the kinetic parameters from polymerizations initiated by peroxides with vastly different half‐life times (t = 1 h, t = 543 h) and the minimum peroxide/Ti = 1/2 ratio required for a living process indicate that initiation occurs primarily by the redox reaction of the peroxide with Cp2Ti(III)Cl rather than peroxide thermal decomposition. This is consistent with one Ti equivalent consumed in the redox initiation and the second one utilized in the reversible termination of the growing chains. Qualitatively, based on the livingness of the process, these initiators ranked as BPO &gt; TBPOB ∼ TBPO &gt; CPO &gt; TBPOEHC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1106–1116, 2006

Estimation of Enthalpies of Alkoxy Radical Formation and Bond Strengths in Alcohols and Ether

Kinetic data on the thermal decomposition of peroxides were analyzed, and energies of the O–O bond dissociation were calculated. Enthalpies of formation of various alkoxy radicals and peroxides were determined. The dissociation energies for the O–H bonds in alcohols and C–O bonds in ethers were estimated. Comparative analysis of literature and obtained data was performed.

Ozonolysis of 3-Caren-5-one

Cleavage by ozonolysis of a cyclic unsaturated ketone, 3-caren-5-one, was investigated under different conditions. The main reaction product is ketocaronic acid. A scheme of ketocaronic acid formation was suggested basing on kinetics of ozone reaction with 3-caren-5-one and thermal decomposition of peroxides.

Photo-induced graft polymerization surface modifications for the preparation of hydrophilic and low-proten-adsorbing ultrafiltration membranes

Heterogeneous surface modifications of PAN UF membranes with either simultaneous or sequential UV irradiation-initiated graft polymerizations of monomers from water solutions were studied. Previous coating with a photo-initiator (benzophenone, BP) and saturation of the monomer solutions with BP mainly promoted simultaneous graft polymerization onto the membrane surface. Photo-induced formation and thermal decomposition of peroxides were assayed with the DPPH assay and then used for sequential grafting. For both approaches, and with acrylic acid, 2-hydroxyethyl methacrylate and various poly(ethylene glycol) methacrylates (PEG-MA's and MePEG-MA's) the impact of photo-initiation as well as monomer type and concentration was described. The polymerization conditions could be used as means to adjust the total degree of graft polymerization (DG) and the graft polymer chain length. Modified membranes were characterized with FTIR-ATR spectroscopy and contact angle measurements; the main conclusion was that even at high DG (1–2 mg/cm 2) the modified layer on the outer surface was thin (< 1 μm) and the modification extended into the active layer pores of the membranes. Membrane permeabilities diminished systematically with increasing graft polymer mass. For UF membranes with sufficient degree of modification (DG > 400 μg/cm 2) reduced contact angles, very little protein adsorption and almost no fouling due to BSA adsorption were observed. Results of UF experiments with γ-globulins. BSA and cytochrome C, applied as single and mixed protein solutions, suggested that with PAN-g-MePEG200MA, in contrast to the unmodified PAN UF membranes, protein/protein UF separations may become feasible because protein/polymer surface interactions are diminished.

Surface modification of ultrafiltration membranes by low temperature plasma II. Graft polymerization onto polyacrylonitrile and polysulfone

Low temperature plasma-induced surface modifications of polyacrylonitrile (PAN) and polysulfone (PSf) ultrafiltration (UF) membranes were studied. Treatment with water plasma and with He plasma drastically and almost permanently increased the surface hydrophilicity of PSf UF membranes. However, in contrast to the behavior of PAN UF membranes [23], the PSf surface pore structure was also changed as indicated by altered water permeabilities and reduced protein retentions. The lower permeability PSf membranes (nominal M w cut-off 10 kD) showed slower but more extended conversion due to plasma excitation and stronger indications of pore etching effects in comparison with 30 kD cut-off membranes. Polymer peroxides on PAN and PSf membranes created by plasma excitation were monitored by the 2,2-diphenyl 1-picryl hydrazyl (DPPH) assay. Graft polymerization of hydrophilic monomers such as 2-hydroxy-ethyl methacrylate (HEMA) and acrylic or methacrylic acid onto PAN and PSf UF membrane surfaces was initiated via thermal decomposition of peroxides. The degree of modification could be adjusted by polymerization conditions. Graft polymer modified surfaces were characterized with the help of Fourier transform infrared attenuated total reflection (FTIR-ATR) and electron spectroscopy for chemical analysis (ESCA) spectra. The hydrophilic character of the modified surfaces was increased as compared to that of the parent membranes. With about 1–1.4 mmol/cm 2 grafted HEMA, the contact angles (captive bubble technique; Θ octane/water) for PAN and PSf were reduced from 48 to 34° and from 92 to 43°, respectively. A clear dependency of PAN UF membrane water permeability on the amount of grafted monomer was observed. The monomer type influenced the water permeation flux per mole of grafted acrylate via specific swelling of the graft polymer layer in water. Hydrophilic PAN membranes, modified either by plasma treatment [23] or HEMA graft polymerization, showed significantly reduced fouling due to static protein adsorption, and improved protein UF performance. In particular, for water plasma treated PAN membranes with high initial retention, higher fluxes (up to 150%) with the same or even improved retentions were obtained. Hydrophilized PSf-g-HEMA membranes can provide improved performance in protein ultrafiltration over unmodified PSf UF membranes because pore etching effects are compensated for by the grafted layer yielding both improved filtrate flux (>30%) and protein retention of bovine serum albumin. Hence, plasma induced graft polymer modification of UF membranes can be used to adjust membrane performance by simultaneously controlling the surface hydrophilicity and permeability.

New ordered perovskites containing bismuth (V) [BaLaMBiO 6 (M = Mg, Ca, Sr)

New Bi (V) containing perovskites oxides of the type, BaLaMBiO 6 (M = Mg, Ca, Sr) have been synthesized under high oxygen pressure conditions using the thermal decomposition of peroxides in a tetrahedral anvil apparatus. These compounds have been characterized by X-ray powder diffraction and iodometric titration. All the BaLaMBiO 6 (M = Mg, Ca, Sr) compounds show 1:1 type ordering of cations at the octahedral sites of the perovskite structure. In the case of magnesium and calcium containing perovskites, comparison of the observed and the calculated X-ray powder diffraction intensities show that the A sites are occupied by barium and lanthanum in a disordered manner, and the octahedral sites are occupied by an ordered arrangement of bismuth and magnesium or bismuth and calcium. This in contrast to strontium containing phase, where the A sites are found to be occupied by barium and strontium in a disordered arrangement and the octahedral sites are occupied by lanthanum and bismuth. The oxygen content, hence the oxidation state of Bi, in the samples depends on the synthetic conditions employed. The electrical properties of the synthesized materials are discussed briefly.

Ignition of monomethyl amine

The ignition of monomethyl amine was studied in reflected shock waves over the temperature range from 1000 to 1300 K. In contrast to the behavior observed with hydrocarbons, monomethyl amine acts to accelerate rather than inhibit its own ignition. This behavior could be accounted for, based on extensive computer simulations of the ignition chemistry, as arising from the participation of hydrogen peroxide thermal decomposition as a chainbranching step in a manner that is not effective for the ignition of hydrocarbon fuels under similar conditions. The linear chain responsible for H 2O 2 formation in the induction zone is composed of the two reactions CH 3NH 2 + HO 2 → CH 2NH 2 + H 2O 2 and CH 2NH 2 + O 2 → CH 2NH + HO 2.

Addition of radicals to quinones—III. ESR study of some radical reactions of 2,6-dialkyl-1,4-benzoquinones

Reactions between 2,6-dialkyl-1,4-benzoquinones and various free radicals have been studied by ESR spectroscopy. The stable intermediates were identified on the basis of their spectra. It has been established that cyanoisopropyl, polystyryl and poly-(α-methylstyryl) radicals attack at the oxygen atom of the quinone, whereas the radicals formed in the thermal decomposition of peroxides (benzoyl and acetyl) attack the CC double bond in the quinone ring. A mechanism is proposed for the latter process.