Decomposition Of Peroxide Research Articles

A Physical Basis for Kinetic Compensation.

Kinetic compensation is a strong, positive correlation between the Arrhenius activation energy E and the frequency factor A for a reaction between the same reactants under similar experimental conditions or similar reactants under the same conditions, even though these parameters are supposed to be independent. The kinetic compensation effect (KCE) is demonstrated by a linear relationship between ln[A] and E/R in the eponymous Constable plot and has been the subject of more than 50 000 publications over the past 100 years, with no consensus opinion about the cause of this effect. In this paper, it is suggested that the linear relationship between ln[A] and E is the result of a real or spurious path dependence of the reaction history between the initial state of the pure reactant(s) and the final state of the pure product(s) having standard enthalpy and entropy differences, ΔH° and ΔS°, respectively. The single-step rate law approximation of a reversible reaction leads to T0 = H°/ΔS° as the dynamic thermal (thermodynamic) equilibrium temperature and 1/T0 = (ln[A̅/k0])/(E̅/R) as the slope of a Constable/KCE plot or the crossover temperature of Arrhenius lines in an isokinetic relationship (IKR), where A̅ and E̅ are mean values for the ensemble of compensating {Ei, Ai} pairs and k0 is a constant that accounts for the path dependence of the reaction history and reconciles the KCE with the IKR. This proposed physical basis for the KCE and IKR is supported by qualitative agreement between ΔH° and ΔS° calculated from the statistics of compensating {Ei, Ai} pairs in the literature, and the difference in the standard enthalpies and entropies of formation of the products and reactants for thermal decomposition of organic peroxides, calcium carbonate, and poly(methyl methacrylate).

Sulfur adlayer on gold surface for attaining H2O2 reduction in alkaline medium: Catalysis, kinetics, and sensing activities

The sensitive detection of hydrogen peroxide (HP) on Au surface is quite challenging owing to the potential dependent decomposition of HP. The current study investigated the development of chemisorbed sulfur adlayer onto the surface of the polycrystalline gold electrode to attain electroreduction of hydrogen peroxide in an alkaline medium using cyclic voltammetry (CV), chronoamperometry, and square wave voltammetry (SWV) measurement techniques. The sulfur adsorbed layer significantly reduces the decomposition of hydrogen peroxide onto the Au (pc) electrode surface allowing the hydrogen peroxide reduction process to proceed. The kinetic diagnosis suggests that the reduction is mass transfer controlled process where electron transfer is the rate determining step in the concerned reduction reaction. The presented electrochemical sensor exhibited high sensitivity and a quick amperometric response to HP in the concentration range of 10–2000 μM, with a detection limit of 6.0 μM.

The Experimental Investigation of a 98% Hydrogen Peroxide Monopropellant Thruster Comprising the Metal-Foam-Supported Manganese Oxide Catalyst

The article presents alternative metal-supported catalysts for decomposition of the highest-class hydrogen peroxide: 98%+ (Type 98 HP, according to MIL-PRF-16005F). The aim of this study was the experimental investigation of an alternative solution for decomposition of 98%+ hydrogen peroxide, strictly for chemical propulsion. High-porosity open cell metal foams have been identified as structures with great potential. Low density, good mechanical and thermal properties, availability of various materials and alloys as well as new technologies of manufacturing, make metal foam a potential solution for many different propellants, not only hydrogen peroxide. Open cell NiCrAl foam has been processed to prepare several catalysts, with different content and dispersion of the active phase. Cleaning and drying were performed to prepare carriers for further processing: wet impregnation, slow drying, and calcination. Simple drop tests with 98% hydrogen peroxide have been conducted to estimate activity level of catalysts, in a simplified scale: low, medium, high. Then, real-environment tests have been performed in a catalyst bed. Temperature, pressure along the bed and propellant mass flow rate were measured while testing. The analysis of the test results provided a general conclusion that metal foam supported manganese oxide catalyst is a promising solution for hydrogen peroxide propulsion.

Nonradical oxidative degradation of amino-G acid by hydrogen peroxide induced by copper cerium plate catalyst: Electron transfer mechanisms

Advanced oxidation processes based on nonradical oxidation pathways have become promising pollutant removal methods because of their selectivity and adaptability. In this study, three ceria with different morphologies were synthesized: plate (p-CeO2), rod (r-CeO2), and cubic (c-CeO2). p-CeO2 was observed to have the highest activity for hydrogen peroxide (H2O2) decomposition. Cu doping further improved the catalytic activity of p-CeO2 for H2O2 decomposition compared to other metals, such as Mn, Co, Cu, and Zn. The plate copper-ceria material (p-Cu/CeO2-3) activated the H2O2 and completely degraded amino-G acids (10 mg L–1) within 90 min under optimal conditions (0.3 g L–1p-Cu/CeO2-3, 5 mM H2O2). Through a comprehensive study of the scavenging and pretreatment experiment, electron paramagnetic resonance (EPR), and in situ Raman spectroscopy, it was proven that the catalytic oxidation of amino-G acid on p-Cu/CeO2-3 was mainly mediated by an electron transfer mechanism·H2O2 can be absorbed on the surface of p-Cu/CeO2-3 to form the Ce-hydrogen peroxide surface complex (Ce(III)− •OOH), which can act as an electron acceptor when the amino G acid is in close proximity to the complex. In addition, p-Cu/CeO2-3 showed excellent catalytic performance over a wide pH range (3−9). This study provides a new system for the degradation of amino-G acid through electron transfer pathways.

Chromium and cobalt bimetallic MOF material as an effective and stable catalyst for the decomposition of cyclohexyl hydrogen peroxide

The decomposition of cyclohexyl hydrogen peroxide (CHHP) is a crucial step in the preparation process of cyclohexanone by non-catalytic oxidation of cyclohexane in industry. In this study, the chromium-cobalt bimetallic MOF material MIL-101(Cr, Co) was first successfully prepared by hydrothermal synthesis. Its structure was characterized by various means, and it was applied to CHHP decomposition to estimate the stability of the material. The results showed that Cr3+ and Co2+ were successfully coordinated with carboxyl groups of terephthalic acid by Cr–O and Co–O bond, respectively, MIL-101(Cr, Co) has excellent performance as a catalyst in the CHHP decomposition reaction, and the introduction of Co2+ as a metal node makes MIL-101(Cr, Co) have a high specific surface area, as well as improves the conversion rate of CHHP to 91.6%, which was clearly higher than MIL-101(Cr) (70.3%). The most important thing is that the framework structure of the MIL-101(Cr, Co) is stable during the six recycling runs, and the loss amount of chromium and cobalt in the reaction solution during reuse is less than 1 ppm.

Simulation of Low-Temperature Oxidation and Combustion of N-Dodecane Droplets under Microgravity Conditions

Fires are considered among the most dangerous accidents on manned spacecraft. That is why several programs of combustion experiments were implemented at the International Space Station (ISS) since 2008. In the experiments with n-heptane and n-dodecane droplet combustion, a new phenomenon was discovered, namely, the phenomenon of the radiative extinction of a burning droplet with subsequent multiple flashes of flame. In this paper, n-dodecane droplet ignition, combustion, radiative extinction, and subsequent low-temperature oxidation with multiple flashes of cool, blue, and hot flames under microgravity conditions are studied computationally. The mathematical model takes into account multiple elementary chemical reactions in the vicinity of a droplet in combination with heat and mass transfer in liquid and gas, heat release, convection, soot formation, and heat removal by radiation. The model is based on the non-stationary one-dimensional differential equations of the conservation of mass and energy in liquid and gas phases with variable thermophysical properties within the multicomponent diffusion concept in the gas phase. Calculations confirm the important role of the soot shell formed around the droplet and low-temperature reactions in the phenomenon of droplet radiative extinction with multiple flame flashes in the space experiment at the ISS. Calculations reveal the decisive role of the blue flame, arising due to the decomposition of hydrogen peroxide, in the multiple flame flashes. Calculations with forced ignition of the droplet reveal the effect of the ignition procedure on droplet evolution in terms of the timing and the number of cool, blue, and hot flame flashes, as well as in terms of the combustion rate constant of the droplet. Calculations with droplet self-ignition reveal the possible existence of new modes of low-temperature oxidation of droplets with the main reaction zone located very close to the droplet surface and with only partial conversion of fuel vapor in it.

Different Dimensional Copper-Based Metal–Organic Frameworks with Enzyme-Mimetic Activity for Antibacterial Therapy

Fighting against bacterial infection and accelerating wound healing remain important and challenging in infected wound care. Metal-organic frameworks (MOFs) have received much attention for their optimized and enhanced catalytic performance in different dimensions of these challenges. The size and morphology of nanomaterials are important in their physiochemical properties and thereby their biological functions. Enzyme-mimicking catalysts, based on MOFs of different dimensions, display varying degrees of peroxidase (POD)-like activity toward hydrogen peroxide (H2O2) decomposition into toxic hydroxyl radicals (•OH) for bacterial inhibition and accelerating wound healing. In this study, we investigated the two most studied representatives of copper-based MOFs (Cu-MOFs), three-dimensional (3D) HKUST-1 and two-dimensional (2D) Cu-TCPP, for antibacterial therapy. HKUST-1, with a uniform and octahedral 3D structure, showed higher POD-like activity, resulting in H2O2 decomposition for •OH generation rather than Cu-TCPP. Because of the efficient generation of toxic •OH, both Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus could be eliminated under a lower concentration of H2O2. Animal experiments indicated that the as-prepared HKUST-1 effectively accelerated wound healing with good biocompatibility. These results reveal the multivariate dimensions of Cu-MOFs with high POD-like activity, providing good potential for further stimulation of specific bacterial binding therapies in the future.

The Disturbance of the Antioxidant System Results in Internal Blue Discoloration of Postharvest Cherry Radish (Raphanus sativus L. var. radculus pers) Roots.

Internal blue discoloration in cherry radish (Raphanus sativus L. var. radculus pers) roots can appear after harvest. The antioxidant system and content of reactive oxygen species (ROS) will affect the blue discoloration. Currently, the reason for the blue discoloration is not yet clear. In order to reveal the mechanism of the blue discoloration of cherry radish, we selected the blue discolored cherry radish as the research object and the white cherry radish as the control. The difference in the antioxidant system between them were compared, including related enzymes and non-enzymatic antioxidants in this system. Meanwhile, the changes in the contents of 4-hydroxyglucobrassicin as a precursor substance and ROS were compared. The results showed that the activities of typical antioxidant enzymes decreased and the cycle of Glutathione peroxidase (GPX) and Ascorbic acid-Glutathione (ASA-GSH) was disturbed, leading to the reduction of antioxidant effect and the failure of timely and effective decomposition of superoxide anions (O2•-) and hydrogen peroxide (H2O2). In addition, the elevated level of O2•- and H2O2 led to the disorder of the antioxidant system, while the 4-hydroxybrassinoside was oxidized under the catalysis of peroxidase (POD) and eventually led to the internal blue discoloration in cherry radish. These results can provide a theoretical basis for solving the blue discoloration problem.

Electrochemical Synthesis of Functional Coatings and Nanomaterials in Molten Salts and Their Application

Nanomaterials are widely used in modern technologies due to their unique properties. Developing methods for their production is one of the most important scientific problems. In this review, the advantages of electrochemical methods for synthesis in molten salts of nanostructured coatings and nanomaterials for different applications were discussed. It was determined that the nanostructured Mo2C coatings on a molybdenum substrate obtained by galvanostatic electrolysis have a superior catalytic activity for the water-gas shift reaction. The corrosion-resistant and wear-resistant coatings of refractory metal carbides on steels were synthesized by the method of currentless transfer. This method also was used for the production of composite carbon fiber/refractory metal carbide materials, which are efficient electrocatalysts for the decomposition of hydrogen peroxide. The possibility to synthesize GdB6 nanorods and Si and TaO nanoneedles by potentiostatic electrolysis was shown.

Activatable G-quadruplex based catalases for signal transduction in biosensing.

Discovery of oxidative catalysis with G-quadruplex•hemin constructs prompted a range of exciting developments in the field of biosensor design. Thus, G-quadruplex based DNAzymes with peroxidase activity found a niche as signal transduction modules in a wide range of analytical applications. The ability of nucleic acid scaffolds to recognise a variety of practically meaningful markers and to translate the recognition events into conformational changes powers numerous sensor design possibilities. In this work, we establish a catalase activity of G-quadruplex•hemin scaffolds. Catalase activated hydrogen peroxide decomposition generates molecular oxygen that forms bubbles. Observation of bubbles is a truly equipment free signal readout platform that is highly desirable in limited resources or do-it-yourself environments. We take a preliminary insight into a G-quadruplex structure-folding topology-catalase activity correlation and establish efficient operating conditions. Further, we demonstrate the platform's potential as a signal transduction modality for reporting on biomolecular recognition using an oligonucleotide as a proof-of-concept target. Ultimately, activatable catalases based on G-quadruplex•hemin scaffolds promise to become valuable contributors towards accessible molecular diagnostics applications.

Potential degradation of norfloxacin using UV-C/Fe2+/peroxides-based oxidative pathways

• Different peroxides-based oxidative pathways were compared towards NOR degradation. • The peroxide HSO 5 − performed best in the degradation of NOR under UV-C and Fe 2+ . • The peroxides yield ● OH and SO 4 ●− under activation by UV-C and Fe 2+ activation. • The ● OH and SO 4 ●− scavengers inhibited degradation of NOR. • Degradation products and ecotoxicities of NOR as well as its DPS were estimated. The removal of norfloxacin (NOR), a widely used pharmaceutical and emerging water pollutant, was studied using UV-C and Fe 2+ catalyzed peroxides-based oxidative processes (e.g., UV-C/Fe 2+ /H 2 O 2 , UV-C/Fe 2+ /S 2 O 8 2− and UV-C/Fe 2+ /HSO 5 − ) and compared with UV-C and UV-C/Fe 2+ . The UV-C and UV-C/Fe 2+ degraded NOR to 38 and 55%. However, use of peroxides, i.e., H 2 O 2 , S 2 O 8 2− , HSO 5 − with UV-C and UV-C/Fe 2+ promoted NOR %degradation to 75, 83, and 90% using [peroxides] 0 = 50 mg/L, [Fe 2+ ] 0 = 1 mg/L, and [NOR] 0 = 10 mg/L, respectively. The significant impact of peroxides on NOR degradation was due to their decomposition into ● OH and SO 4 ●− which showed high activity towards NOR degradation. The ● OH and SO 4 ●− formation from peroxides decomposition and their contribution in NOR degradation was verified by different scavenger studies. Among the UV-C/Fe 2+ /peroxides processes, UV-C/Fe 2+ /HSO 5 − showed better performance. The changing concentrations of peroxides, Fe 2+ , and NOR affected degradation of NOR. The use of different pH and inorganic anions also influenced NOR degradation. The degradation pathways of NOR were established and analyzed acute as well as chronic toxicities of NOR and its DPs.

Rational Design of Platinum-Bismuth Sulfide Schottky Heterostructure for Sonocatalysis-Mediated Hydrogen Therapy.

Conventional sonodynamic therapy is unavoidably limited by the tumor microenvironment, although many sonosensitizers have been developed to improve them to a certain extent. Given this, a concept of sonocatalytic hydrogen evolution is proposed, which is defined as an oxygen-independent therapeutics. To demonstrate the feasibility of the concept, the narrow-bandgap semiconductor bismuth sulfide (Bi2 S3 ) is selected as the sonocatalyst and platinum (Pt) nanoparticles are grown in situ to optimize their catalytic performance. In this nanocatalytic system, the Pt nanoparticles help to capture sonoexcited electrons, whereas intratumoral overexpressed glutathione (GSH), as a natural hole sacrificial agent, can consume sonoexcited holes, which greatly improves the charge-separation efficiency and promotes controllable and sustainable H2 generation. Even under hypoxic conditions, the Pt-Bi2 S3 nanoparticles can also produce sufficient H2 under ultrasound irradiation. Mechanistically, mitochondrial dysfunction caused by H2 and intratumoral redox homeostasis destruction by GSH depletion synergistically damage DNA to induce tumor cells apoptosis. At the same time, the Pt nanoparticles and holes can also trigger the decomposition of hydrogen peroxide into O2 to relieve tumor hypoxia,thusbeing synergistic with GSH depletion to reverse tumor immunosuppressive microenvironment. The proposed sonocatalysis-mediated therapy will provide a new direction to realize facile and efficient cancer therapy.

Enzyme assisted magnetic hybrids as self-activated cascade reagent with synergistic activity for antimicrobial application

The abuse of antibiotics seriously threatens the public health, which leads to the urgent need to develop novel antimicrobial strategies. Reactive oxygen species (ROS) have been considered as an alternative approach for bacterial inactivation. At present, magnetic materials, especially iron oxide (Fe3O4) nanoparticles have gained widely application in biomedical field. Owing to the intrinsic peroxidase-like activity, Fe3O4 can catalyze the decomposition of hydrogen peroxide (H2O2) to generate hydroxyl radical (⋅OH) under acidic conditions. Recently, Fe3O4-based peroxidase mimics have been developed for wound infection therapy. However, the direct introduction of H2O2 with relative high concentration may induce undesired effect to normal tissues, and the infection site with near neutral pH still limits the antibacterial efficiency. Herein, carboxyl modified Fe3O4 immobilized silver nanoparticles (Ag NPs) and glucose oxidase (GOx) were synthesized as a self-activated cascade regent. GOx endowed the hybrids with catalytic activity, which could convert glucose into gluconic acid, which activated the peroxidase-like activity of Fe3O4 by decreasing the pH value. Moreover, the self-supplied H2O2 was subsequently catalyzed by Fe3O4 to generate ⋅OH. By combining the excellent antimicrobial performance of Ag NPs, the enzyme assisted magnetic hybrids exhibited robust antibacterial activity, which exhibited a great potential in bacteria-infected wound therapy.

Ion transfer voltammetric and LC/MS investigations of the oxidative degradation process of fentanyl and some of its structural analogs

Ion transfer voltammetry at a polarized ionic liquid membrane and LC/MS technique were used to investigate the oxidative time-resolved degradation of the frequently (mis)used opioid fentanyl and some of its structural analogs.The degradation is based on the reaction of opioids with hydroxyl radicals produced by the catalytic decomposition of hydrogen peroxide. Using the voltammetric technique, it was confirmed that the presence of Fe2+ions and hydrogen peroxide is essential in the degradation process of fentanyl(s). An increasing concentration of ferrous ions accelerates the described reactions, while the reaction rate is much less affected by the concentration of fentanyl.In an excess of ferrous ions, the course of the reaction can be approximated by a pseudo-first-order reaction with a half-time of 3.85 min. The generation of HO• radicals was proved to be the rate-determining step. Oxidative degradation processes of all investigated fentanyl-related drugs exhibit similar kinetics. A wide variety of fentanyl degradation products were detected and characterized using LC/MS analysis. Mono-, di- and trihydroxylated derivatives in several isomeric forms were observed most abundantly in a relatively short reaction time (5–30 min). The formation of norfentanyl has also been demonstrated.

Hydrogen peroxide decomposition in serpentine mini channel with silver catalyst

Micro thrusters were used to produce thrust in the order of a few Newtons to position satellites and other designed space objects. For such applications, monopropellant thrusters using hydrogen peroxide are preferred for their high maneuverability, accurate positioning, and attitude control. Hydrogen peroxide is a green monopropellant that forms the products (water and vapor) after it gets decomposed in contact with a catalyst. Complete catalytic decomposition of hydrogen peroxide is still a challenging task. In the present work, 30% of hydrogen peroxide concentration with silver catalyst (modified geometry) were used to increase reaction rate. The effect of silver placed at different locations in serpentine and straight mini channels (same dimensions) is analyzed. The analysis is done for a varied number of silver catalysts placed at different locations in serpentine and straight mini channels having a diameter of 0.25 cm. The serpentine mini channel shows better decomposition of hydrogen peroxide especially at shorter length of 10 cm than the straight mini channel with the same length of catalyst because of its better mixing capability due to non-uniformity in the flow field, especially at the bend sections. The results will be useful in determining the appropriate geometry and placement of the catalyst for efficient monopropellant decomposition.

Bacteria-targeted delivery of black phosphorus quantum dots facilitates photothermal therapy against hypoxic tumors and complementary low-dose radiotherapy.

Many approaches have been employed to relieve hypoxia in solid tumors to enhance sensitivity to radiotherapy (RT), including O2 delivery or hydrogen peroxide (H2O2) decomposition strategies. To date, however, these modalities have been restricted by poor O2 loading, rapid O2 leakage, and limited endogenous H2O2 levels. To overcome these limitations, we therefore sought to develop an effective approach for the oxygen-independent treatment of hypoxic tumors. In this study, we designed a novel black phosphorus quantum dot (BPQD)/Escherichia coli (E. coli) hybrid system (BE) capable of facilitating the photothermal therapy (PTT) of hypoxic tumors. A simple electrostatic adsorption approach was used to conjugate BPQDs to E. coli. BE is capable of reliably targeting hypoxic tumors and mediating PTT. BPQDs in BE can directly facilitate X-ray-mediated radiosensitization of tumors, thereby achieving significant RT efficacy in response to lower doses of radiation, effectively and specifically damaging hypoxic tumor tissues to suppress the growth of tumors. Our results highlight this BE system as a novel approach to tumor radiosensitization with great potential for clinical application.

Iron-chelated semiconducting oligomer nanoparticles for NIR-II fluorescence imaging-guided enhanced chemodynamic/photothermal combination therapy.

Chemodynamic therapy (CDT) has attracted increasing attention owing to its high tumor specificity and low number of side effects. However, the low absolute concentration of reactive oxygen species (ROS) within tumor cells restricts the CDT efficacy. Herein, we use dihydroartemisinin (DHA) to enhance the CDT efficacy and combine photothermal therapy (PTT) to further improve the anticancer effect. To achieve such a goal, an iron-containing semiconducting oligomer nanoparticle (DHA@FePSOD) is prepared by loading DHA into a Fe3+-chelated NIR-II fluorescent semiconducting oligomer (FePSOD). The Fe3+ ion within DHA@FePSOD can be reduced to the Fe2+ ion by glutathione (GSH) and subsequently catalyze the decomposition of hydrogen peroxide (H2O2) into the highly toxic hydroxyl radical (˙OH) for CDT. The loaded DHA may be further reduced by Fe2+ and generate a DHA radical to enhance the CDT efficacy. In addition, DHA@FePSOD shows a good photothermal effect and intense NIR-II fluorescence signal under 808 nm laser irradiation. Both in vitro and in vivo studies prove the better anticancer effect of DHA@FePSOD than FePSOD, which is attributed to the loaded DHA. Furthermore, DHA@FePSOD can effectively accumulate into a tumor and delineate the tumor via NIR-II fluorescence imaging. This study thus provides an efficient approach for developing a NIR-II fluorescence imaging-guided enhanced chemodynamic/photothermal combination therapeutic nanoplatform.

Исследование двойного электрического слоя на композиционных материалах «карбид тугоплавкого металла — углеродное волокно» в пероксиде водорода и сульфате натрия

The electric double layer was studied by impedance spectroscopy on the surface of various composite materials: molybdenum, tantalum and niobium carbides in 1 M sodium sulfate solution and concentrated hydrogen peroxide solution. The data on the activation energy of the electrocatalytic decomposition of hydrogen peroxide on the surface of composite materials were compared with the capacity of the electrical double layer in hydrogen peroxide solution.

STUDY OF THE PROCESS OF CARBONIZATION OF POWDERED CELLULOSE GRANULES IMPREGNATED WITH AgNO3 AND Pd(NO3)2

A comparative study of the process of carbonization of powdered cellulose granules and powdered cellulose granules impregnated with silver and palladium nitrate salts was carried out. The process was carried out in the temperature range 200–600 °С. The influence of the presence of metals on the course of carbonization of powdered cellulose and the features of the reduction of silver and palladium during carbonization were studied by IR spectroscopy and X-ray phase analysis. It has been established that the presence of silver in powdered cellulose does not affect the yield of carbonized material. The presence of palladium in powdered cellulose leads to the fact that the yield of carbonizate in the temperature range of 300–600 °C is reduced relative to the yield of carbonizate simply from powdered cellulose. It has been established by IR spectroscopy that impregnation with salts and subsequent drying at 90 °C of powdered cellulose granules leads to the appearance of carboxyl groups in it, which are not observed in unimpregnated powdered cellulose. With an increase in the heat treatment temperature to 200 °C, the amount of these groups in the silver-containing material increases sharply, while in the palladium-containing material it remains unchanged. A significant increase in the number of C=O groups in the palladium-containing material begins at 300 °C. The increased relative content of C=O groups in the metal-containing material is also preserved in the temperature range of 300–500 °C. The presence of metals in powdered cellulose at pyrolysis temperatures of 300–500 °C leads to a decrease in the content of C=C groups in the carbon matrix relative to methylene (methine) groups. At 600 °C, the carbon matrix of all coals is completely carbonized. X-ray diffraction analysis recorded the appearance of metallic silver and palladium in metal-containing coals at a temperature of 300 °C As the carbonization temperature increases, the content of crystalline Ag(0) and Pd(0) in coals increases. No other forms of silver and palladium are found in the temperature range of 300–600 °С. Testing of metal-containing coals in a model reaction of hydrogen peroxide decomposition showed: in silver-containing carbonizates, the availability of silver particles for H2O2 increases due to an increase in the pyrolysis temperature; in Pd/C, an additional factor that increases the availability of metal particles is the interaction of palladium with carbonizate during pyrolysis.

The role of acetonitrile in the direct synthesis of hydrogen peroxide over palladium supported by ion-exchange resins

Acetonitrile is used as an effective, non-corrosive selectivity enhancer for the direct synthesis of hydrogen peroxide (HP). Palladium catalysts supported by activated carbon or poly-divinylbenzene are poisoned by acetonitrile, which makes them very little productive. Conversely the catalysts supported by strongly acidic ion-exchange resin are much more selective and productive in the presence of acetonitrile, and for relatively long time. TEM shows that the size of their metal nanoparticles can be decreased by a reconstruction process, possibly sustained by leached palladium(II) species. HP decomposition experiments show that acetonitrile inhibits the OO bonds splitting.