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Benzodiazepines possess a wide spectrum of valuable pharmacological effects and are among the leading drugs, commonly prescribed ones for various pathologies. Herein we describe the continuous flow synthesis of six benzodiazepines from aminobenzophenones: diazepam, fludiazepam, nordazepam, nitrazepam, clonazepam, oxazepam. [ABSTRACT FROM AUTHOR]

In this study, red wines from V. vinifera L. cv. Vranec and Merlot (harvest 2021) have been produced by three different fermentation methods, applying classical, roto and punch down fermenters, in order to study their influence on the wine quality. The chemical parameters that confirm the basic wine quality have been determined, including alcohol, dry extract, specific density, reducing sugars, total and volatile acidity, pH, free and total SO2. The Vranec wines contained relatively higher content of alcohol compared to the Merlot wines, due to the higher content of sugars in the grapes. Wines produced with roto fermenter presented higher values of dry extract and total acidity, compared to the wine produced with classical and punch down fermenters, which confirms that roto fermentation is most suitable for production of complex and structured wines. The alcohol content in all wines ranged from 12.08 to 12.4%, total acidity was between 5.8 to 6.3 g/L and the dry extract from 39 to 45 g/L, while the content of volatile acidity was in range from 0.41 to 0.45 g/L. All wines were dry wines, with content of reducing sugar lower than 4 g/L and all of them were well protected from the oxidation. It was concluded that the type of fermentation affected the wine quality, confirming that applied wine technology is important for production of quality red wines. [ABSTRACT FROM AUTHOR]

• New organoselenium bicycle 7,8-dimethoxy-9-selenabicyclo[4.2.1]nonane 1 is prepared. • Bicycle 1 is oxidized much faster than its 2,6-dimethoxy bicyclo[3.3.1]nonane isomer 2. • GPx-like activity of 1 assessed from oxidation of dithiothreitol exceeds that of 2. The first representative of a new class of organoselenium bicyclic compounds, 7,8-dimethoxy-9-selenabicyclo[4.2.1]nonane, was prepared by the iodine-mediated reaction of elemental selenium and 1,3-cyclooctadiene. Comparative kinetics of the oxidation of 7,8-dimethoxy-9-selenabicyclo[4.2.1]nonane 1 and its isomer 2,6-dimethoxy-9-selenabicyclo[3.3.1]nonane 2 were studied by 1H NMR spectroscopy and found to be dozens of times faster for the former. The catalytic activity of 7,8-dimethoxy-9-selenabicyclo[4.2.1]nonane 9-oxide formed in situ from 1 and simulating the GPx-like activity in oxidation of thiols by H 2 O 2 in MeOH, is shown to be higher than that of the isomeric 2,6-dimethoxy-9-selenabicyclo[3.3.1]nonane 9-oxide. [Display omitted] [ABSTRACT FROM AUTHOR]

We describe the total flow synthesis of the widely prescribed anti-inflammatory COX-2 inhibitor Celecoxib from 2-bromo-3,3,3-trifluoropropene, as a convenient and available trifluoromethyl building block, to generate trifluoropropynyl lithium and to trap it immediately with an aldehyde. Oxidation of the obtained alcohol into ketone followed by condensation with 4-sulfamidophenylhydrazine afforded the targeted drug with full regioselectivity. It is noteworthy that the quality of these flow reactions (50% overall yield within 1 h cumulated residence time over 3 steps) directly furnished the target API and intermediates with excellent purity. [ABSTRACT FROM AUTHOR]

The present study examined the impact of refrigerated curd (1 °C, 2 months), so called "Cagliata" on Kashkaval cheese chemical characteristics. Changes of cheese components during ripening as well as proteolysis, biogenic amines formation, fatty acid profile, lipolysis and oxidation of milk fat were investigated. Kashkaval cheese samples were characterized by similar dry matters and protein contents but the results obtained for the components such as milk fat, minerals, salt and active acidity were significantly different (P<0.05). A more pronounced proteolysis was found in the cheese produced from refrigerated curd but no accumulation of biogenic amines in both analyzed samples was established. A greater lipolysis and oxidation of milk fat was observed in the cheese obtained from fresh milk. Cheese produced from refrigerated curd could be successfully used as a cheaper alternative of traditional Kashkaval or when a fresh curd is not available without compromising on its quality. [ABSTRACT FROM AUTHOR]

The aim of the present study was to establish the influence of different storage tem- peratures on lipolysis and milk fat oxidation of Bulgarian Kashkaval cheese. Cheese samples were stored at four different temperatures for 12 months and were taken for analysis every month. It was found that the intensity of lipolytic and oxidative processes in Kashkaval cheese was greatly influenced by the storage temperature. A significant increase (p < 0.05) of milk fat acid values (3.88 ± 0.03 mg KOH/g) was established when Kashkaval cheese was stored at 1 and 4°C. More pronounced oxidation process, with milk fat peroxide value equal to 1.18 ± 0.03 meq O2 /kg, was observed only in samples stored at 4°C, which correlated with the higher content of free fatty acids in these samples. No significant differences (p > 0.05) in the fatty acid quality composition were established. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxide composites containing Cu and Al of different phase composition were synthesized. • X-ray amorphous gibbsite subjected to centrifugal thermal activation was used as a precursor. • The CuAl 2 O 4 spinel-like phase which are high active and selective in NH 3 -SCO. Using the methods of X-ray, thermal, microscopic, adsorption and chemical analyzes, the possibility of obtaining aluminum-copper mixed oxide catalysts by preliminary hydrothermal treatment of a suspension of the product of centrifugal thermal activation of gibbsite with an aqueous solution of copper nitrate and subsequent heat treatment of the obtained precursor was studied. The heat treated in the range of 450–750 °C catalysts are mainly mixtures of CuO and CuAl 2 O 4 phases in different ratio. The different ratio of active phases allows them to be used as catalysts for low-temperature purification of NH 3 and high-temperature combustion of NH 3 as a fuel at various power plants. Testing of catalysts in the process of selective oxidation of ammonia (NH 3 -SCO) showed that prepared aluminum-copper catalysts are not inferior in their catalytic properties to known catalysts, including aluminum-platinum ones, and the proposed synthesis method is resource-saving compared to known methods, including those with many options for preparing these systems by "sol-gel" technology. [ABSTRACT FROM AUTHOR]

It was established that the oxidation reactions of sulfur dioxide occur in aqueous solutions of sodium fluoride and in suspensions of calcium fluoride at room temperature and atmospheric pressure. It was found that the solutions of NaF and CaF2 can be repeatedly used after their regeneration with atmospheric oxygen. [ABSTRACT FROM AUTHOR]

Electronic structure of molybdenum oxides obtained by the oxidation of molybdenum at an oxygen pressure of 1 Torr (thin film) and air (thick film) was studied. It was shown that a thick oxide film is formed from MoO3 oxide, and a thin film from a mixture of MoO3 and MoO2 oxides, which is reflected in the form of valence band spectra. Oxygen on the surface belongs both in molybdenum oxide and in the hydroxyl group, which is associated with dissociative adsorption of water during the oxidation of molybdenum in air for a thick film. [ABSTRACT FROM AUTHOR]

Abstract Four different preparation routes were used to synthesize Sr 2 TiO 4 with the structure of layered perovskite: sol-precipitation (SP), co-precipitation (CO), citrate precursor (CT) and mechanochemical (MA) methods with further calcinations at 1100 °C. The XDR, XPS, BET, SEM techniques showed that the different preparation routes caused the formation of layered perovskite phase with different admixture phases, particle sizes and the surface enrichment with layered perovskite (for SP and MA samples) or strontium oxide (for CO and CT samples). The trend of increasing of CH 4 conversion and C 2 -yield in oxidative coupling of methane at 800-900 °C was found to be the following: SP≈MA > CO > CT samples. The C 2 -yield of the most active catalysts was measured to be about 12%. Graphical abstract Unlabelled Image Highlights • Sr2TiO4 with the structure of layered perovskite was prepared by different routes. • The presence of strontium compounds on the catalysts surface provides low CH4 conversion. • Mechanochemical activation is the most attractive method to synthesize Sr2TiO4. • The C2-yield of the most active catalysts was measured to be 12% at 850oC. [ABSTRACT FROM AUTHOR]

We show that the first stages of interaction between NO and reduced ceria comprise the formation of azides, N3−, with simultaneous oxidation of Ce3+ to Ce4+. This finding imposes revision on some current views of catalytic NO conversion and may contribute to design of new deNOx materials and processes. [ABSTRACT FROM AUTHOR]

A new approach has been proposed to the determination of antioxidants using an oxidized form of metal in a complex compound as a model oxidizer. A method of the quantitative determination of antioxidants in aqueous solutions with RSD 2-4% has been developed. [ABSTRACT FROM AUTHOR]

The Pd/AlO catalysts were prepared by the impregnation of aluminum hydroxide, which was synthesized by precipitation in the presence of polyvinyl alcohol, with a solution of palladium nitrate and were heat-treated at different temperatures. The resulting samples were characterized by X-ray diffraction, electron microscopy, diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy and were tested in CO oxidation in two modes: in a temperature-programmed reaction and under isothermal conditions at 20°C in the absence and in the presence of water vapor. The activity of the catalysts in the former mode was almost independent of support preparation conditions, but it was different in the latter mode. The catalyst whose support was obtained in the presence of polyvinyl alcohol and treated at 300°C in an atmosphere of nitrogen exhibited the highest activity in CO oxidation at 20°C. In the absence of water vapor from the reaction mixture, the initial conversion of CO reached 40% and then decreased. In the presence of water vapor, a continuous increase in the conversion of CO to 88% was observed, and the activity was stabilized at this level. The smallest size of palladium metal nanoparticles, the nearly monolayer carbon surface coverage, and the presence of OH groups, which are formed upon the dissociation of water present in the reaction mixture, facilitate an increase in activity. [ABSTRACT FROM AUTHOR]

The study encompassed experimental mass spectrometric and theoretical quantum chemical studies on adsorption of uranium species in different oxidation states of the metal ion, and oxides of U x O y n+ type, where x = 1 or 3, y = 2 or 8, and n = 0, 1 or 2 onto nanosize-particles of saltrock oxides MO (M = MgII, CaII, NiII, CoII, SrII or BaII), M2O y (M = AuIII or AgI, y = 3 or 1) silicates 3Al2O3.2SiO2, natural kaolinite (Al2O2·2SiO2·2H2O), illite (K0.78Ca0.02Na0.02(Mg0.34Al1.69FeIII 0.02)[Si3.35Al0.65]O10(OH)2·nH2O), CaSiO3, 3MgO·4SiO2,H2O, and M1M2(SiO4)X2 (M1 = M2 = Al or M1 = K, M2 = Al, X = F or Cl), respectively. The UV-MALDI-Orbitrap mass spectrometry was utilized in solid-state and semi-liquid colloidal state, involving the laser ablation at λ ex = 337.2 nm. The theoretical modeling and experimental design was based on chemical-, physico-chemical, physical and biological processes involving uranium species under environmental conditions. Therefore, the results reported are crucial for quality control and monitoring programs for assessment of radionuclide migration. They impact significantly the methodology for evaluation of human health risk from radioactive contamination. The study has importance for understanding the coordination and red-ox chemistry of uranium compounds as well. Due to the double nature of uranium between rare element and superconductivity like materials as well as variety of oxidation states ∈ (+1)–(+6), the there remain challenging areas for theoretical and experimental research, which are of significant importance for management of nuclear fuel cycles and waste storage. [ABSTRACT FROM AUTHOR]

Highlights: [•] We simulate the methane–oxygen–steam reforming in a filtration combustion reactor. [•] A detailed kinetic mechanism of methane oxidation with soot formation is suggested. [•] Combustion-wave temperature for rich methane–oxygen mixtures is lower than 1500K. [•] The steam-soot reaction reduces soot formation and increases hydrogen production. [ABSTRACT FROM AUTHOR]

N-(2-Vinyloxyethyl)phosphinothioamides and -phosphinoselenoamides prepared by oxidative cross-coupling of 2-vinyloxyethylamine with secondary phosphine chalcogenides undergo thermal (75–100 °C) cyclization into the corresponding 3-(diorganylchalcogenophosphoryl)-2-methyl-1,3-oxazolidines in 80–90% yields. [ABSTRACT FROM AUTHOR]

Abstract: An overview of several techniques considered for fuel and co-deposits removal is given. The methods were tested both on plasma-facing components from the TEXTOR tokamak and on laboratory-prepared layers: (a) chemical approach based on oxidative or nitrogen-assisted plasma; (b) photonic methods with laser-induced fuel desorption or ablation of co-deposits; (c) thermal desorption in vacuum or under oxidative conditions at a broad range of temperatures. The emphasis is on outstanding issues associated with every technique aiming at the reduction of fuel content: the efficiency of fuel and co-deposit removal, the surface state of PFC following the treatment and dust generation. [Copyright &y& Elsevier]

The kinetics of Fe oxidation and buildup of luminol oxidation products during Fenton's reaction at pH 2 have been calculated. The characteristics of the process in neutral (pH 6) and alkaline (pH 12) media have been evaluated. The calculation results have been compared with experimental data on the yield of chemiluminescence induced by Fenton's reagent and luminol. It has been shown that trivalent iron ions suppress the luminol emission. The presence of iron or another transition metal in the sample can significantly reduce the chemiluminescence quantum yield after luminol introduction if. [ABSTRACT FROM AUTHOR]

It is analytically shown that the chain ignition region is extended in the reaction of hydrogen oxidation due to the nonlinear interaction H + HO = 2 OH. As a result, the reaction propagates isothermally under the isothermal conditions outside the ignition region, which is calculated by the scheme taking into account only linear reactions with respect to radicals, if the reaction is initiated by additives of hydrogen atoms. The ignition limits were calculated with allowance for the above interaction, and the mathematical modeling of propagation of the hydrogen oxidation reaction under the isothermal conditions was performed. [ABSTRACT FROM AUTHOR]

Abstract: Sr–hexaferrites prepared by co-precipitation method and calcined at 700–1000°С have been characterized by thermogravimetric and differential thermal analysis (TG–DTA), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), and Ar adsorption techniques. It has been shown that hexaferrite phase formed after calcination at 700°С is amorphous and its crystallization occurs at 800°С. Specific surface area (S BET) of the samples calcined at 700°С is 30–60m2/g. Reduction in hydrogen proceeds in several steps, Fe(III) in the hexaferrite structure being practically reduced to Fe0. Amount of hydrogen necessary for the reduction of the samples decrease in the order: SrMn2Fe10O19 >SrFe12O19 >SrMn6Fe6O19 >SrMn2Al10O19. Surface composition of the ferrites differs from bulk. According to XPS data, the surface is enriched with strontium. Sr segregation is most probably explained by the formation of surface carbonates and hydroxocarbonates. The main components on the surface are in oxidized states: Mn3+ and Fe3+. Maximum activity in the methane oxidation is achieved for the SrMn x Fe12− x O19 (0⩽ x ⩽2) catalysts. These samples are characterized by highest amount of the hexaferrite phase, which promotes change of oxidation state Mn(Fe)3+ ↔Mn(Fe)2+. [Copyright &y& Elsevier]

Abstract: Platinum and palladium catalysts supported on γ-Al2O3 were studied by XRD, UV–vis DRS, HRTEM, TPR-H2, XPS together with measurements of their catalytic properties. The properties of the catalysts denoted as Pt(Pd)/Al2O3(X)-Y (X—the calcination temperature of support,°C; Y—the calcination temperature of catalyst,°C) were studied as a function of the temperatures used for calcination of the support and/or the catalyst in oxygen or in a reaction mixture of CO+O2. It was found that the deposition of Pt or Pd on γ-Al2O3 did not alter the structure of the support. Two types of the Pt and Pd particles were typically present on the γ-Al2O3 surface: individual particles with dimensions of 1.5–3nm and agglomerates about 100nm in size. In the catalysts calcined at relatively low temperatures (Pt/Al2O3(550)-450), platinum was present in the form of metal clusters. However, in the Pd/Al2O3(550)-450 catalyst, the palladium particles were almost completely decorated with a thin layer of an aluminate phase. These structures are not reduced in hydrogen in the temperature range of −15 to 450°C, and are stable to treatment in a reaction mixture of CO+O2. Pd deposition on the γ-Al2O3-800 support was found to result in stabilization of the active component in two main forms, Pdo and PdO, with varying degrees of interaction due to the decoration effect. Calcination at the low temperature of 550°C led to the formation of a so-called “core–shell structure”, where a palladium metal core is covered with a thin shell of an aluminate phase. Depending on the calcination temperature of the catalyst in the range of 450–1000°C, the morphological form of the active component was converted from the “core-shell” state to a state consisting of two phases, Pdo and PdO, with a gradual decrease of the Pdo/PdO ratio, weakening the interaction with the support and the growth of palladium particles. Under the action of the reaction mixture, the Pd/Al2O3(800)-(450,600,800,1000) catalysts underwent changes in the Pdo/PdO ratio, which regulates the light-off temperature. After catalyst calcination at the highest temperature used in this study, 1200°C, the palladium particles became much larger due to the loss of the palladium interaction with the support. Only the metal phase of palladium was observed in these catalysts, and their catalytic activity decreases substantially. [Copyright &y& Elsevier]

The antioxidation activity of 5-substituted 6-methyluracils was quantitatively estimated in the model system of initiated radical-chain oxidation of 1,4-dioxane. The rate constants of the reactions of 1,4-dioxane peroxide radicals with 6-methyluracil (1), 6-methyl-5-piperidinouracil (2), 6-methyl-5-morpholinomethyluracil (3), 6-methyl-5-morpholinouracil (4), 6-methyl-5-methylaminouracil (5), 5-ethylamino-6-methyluracil (6), and 5-hydroxy-6-methyluracil (7) were measured. Among compounds 1-7, derivative 7 is most efficient with an inhibition rate constant of (5.2±0.1) · 10 L mol s (60 °C). [ABSTRACT FROM AUTHOR]

Abstract: Fe–FER zeolites were characterized by FTIR spectroscopy of adsorbed CO and NO. Two aged samples (Fe–FER-1 and Fe–FER-4 with Fe content of 1.1 and 3.7wt%, respectively) and one freshly prepared 57Fe rich sample (57Fe–FER, designed for Mössbauer studies and containing 1.5wt% Fe) were studied. Both CO and NO are adsorbed onto Fe2+ cations and have different sensitivities to their location and/or coordination state. CO adsorption on Fe–FER-1 reveals two kinds of Fe2+ sites with the respective complexes observed at 2195 and 2189cm−1. The principal carbonyls (2195cm−1) are easily converted into dicarbonyls (2188cm−1) at low temperature and high CO equilibrium pressure. NO is less sensitive than CO to the environment of Fe2+ ions and NO adsorption gives rise to a single band at 1878cm−1. However, careful analysis reveals that this band consists of two closely located components. With the Fe–FER-4 sample a third family of iron sites was detected by CO at 2196cm−1. These carbonyl species are stepwise converted to di- (∼2188cm−1) and tricarbonyls (∼2180cm−1). With these sites NO forms another nitrosyls clearly detected at 1895cm−1. The latter are converted with time into polynitrosyls. These new sites are very sensitive to the preliminary treatment and easily change their oxidation state, forming Fe2+/Fe3+ redox couples. The sample preliminary treated with oxygen at 673K is characterized by Fe3+–OH groups (3674cm−1) and reactive oxygen that produces carbonates when reacting with CO, and NO+ when interacting with NO. Adsorption of NO on a freshly prepared 57Fe–FER sample confirms the presence of the three distinct Fe2+ sites which is consistent with Mössbauer data. Finally, summarizing all the data, location of the different sites inside the FER structure is proposed. The results obtained are discussed in relation with the catalytic performance of Fe–FER. [Copyright &y& Elsevier]

Abstract: Physicochemical and catalytic properties of compositions Fe(Ce)–Mn–O/support (gamma-, theta-, alpha-Al2O3, SiO2 as the support) and Pt/CeO2/theta-Al2O3 for oxidation of soot were characterized. It was established that the phase composition of the initial catalysts depended mainly on the nature of the active component and preparation conditions. Non-isothermal treatment of the soot–catalyst compositions at the temperature up to 1000°C resulted in a change in the phase composition depending mainly on the final treatment temperature. The catalyst surface area was determined by the support nature. It was established that catalyst activities for oxidation of soot are determined by both catalyst nature and composition of gas mixture. The process of the soot oxidation is thought to involve oxygen from the catalyst surface. The higher proportion of weakly bound surface oxygen, the higher was the catalyst activity. An increase in the oxygen concentration from 5% O2/N2 to 15% O2/N2 is shown to lead to a decrease of the temperature of the soot oxidation. The influence of the oxygen concentration on the process of soot oxidation becomes weaker in the presence of water vapor. Results showed that the presence of NO in the gas mixture favors a decrease in the oxidation temperature of the soot, the higher being the nitrogen oxide concentration, the more pronounced effect. Introduction of SO2 in amount of 50ppm in the gas mixture has no noticeable effect on the process of the soot oxidation. Among the catalysts under study, Fe–Mn–K–O/gamma-Al2O3 is most effective to oxidation of the soot at otherwise identical conditions. [Copyright &y& Elsevier]

Abstract: Cobalt oxide modified SBA-15, KIT-5 and KIT-6 mesoporous silicas with different pore size/pore entrances have been synthesized by a conventional wet impregnation method using cobalt nitrate as the precursor. The modified materials were characterized by N2-physisorption, XRD, TEM-EDX, XPS, FT-IR, UV–vis and TPR-TG with hydrogen. Their catalytic activities in total oxidation of ethyl acetate were evaluated. A good correlation was observed between the catalytic activity, and the presence of spinel-type Co3O4 in the materials. Supports with larger mesopores facilitated the formation of such easily reducible spinel particles. However, the interconnectivity of the mesopores and the uniformity of the channel dimensions also had an influence on the catalytic activity, implying that mass-transfer effects, especially in the case of supports with cage-like mesopores. [Copyright &y& Elsevier]

Abstract: A novel approach to nitro-substituted cyclopropanes and spiropentanes via oxidation of the corresponding amines with dimethyldioxirane is reported. The method is used successfully for the preparation of a series of nitrocyclopropanes as well as for the first synthesis of 1,4-dinitrospiro[2.2]pentane. [Copyright &y& Elsevier]

For the noble metal flotation reagents, the authors propose a new test method of selective adsorption on surface of minerals covered with noble metal grains, by using a scanning electron microscope equipped with an X-ray energy-dispersive microanalyzer. Sorption of DTPINa was recorded by SEM and thin layer chromatography on surface of platinum metal grains in the form of a compound identical to the synthesized compound Pt[(iso-C4H9)2PS2]2. It has been found that interaction of DTPI and platinum ions can run in unheated aqueous solutions at a rate sufficient for flotation. In pH 4–9 range, the rate of platinum DTPI formation is maximal. [ABSTRACT FROM AUTHOR]

The underpotential deposition and oxidation of cadmium atom layers on n-Si/Te and n-Si/CdTe heterostructures were studied. This process on the indicated electrodes is markedly irreversible. This conclusion is based on the finding that the oxidation of cadmium adatoms on surface tellurium atoms (on elemental cadmium and in the telluride structure) is possible only upon illumination of the electrode. [ABSTRACT FROM AUTHOR]

Abstract: Vanadium modified mesoporous silicas type MCM-41, MCM-48, and SBA-15 are obtained by a solid state method. The samples are characterized and compared at the different steps of their preparation by X-ray diffraction, N2-physisorption, FTIR, UV–vis, XPS, and TG-TPR. Samples catalytic activity is tested in ethylacetate oxidation. Formation of various vanadium species, mainly isolated and small oligomeric ones, grafted to the support surface silanol groups, is observed. It is found that the state and the properties of the vanadium species depend on the porous characteristics of the silica host matrix. The nature of the catalytic active center in the ethylacetate oxidation is discussed. [Copyright &y& Elsevier]

Abstract: Au/Nb2O5 and Au/CeO2 catalysts were studied for the selective hydrogenation of crotonaldehyde, both in liquid (batch reactor, 4atm, 60°C, solvent: isopropanol) and in gas (flow microreactor, 120°C, atmospheric pressure) phases. Samples were characterized by TPR and XRD and tested for the CO oxidation reaction. Large differences in support reducibility between both catalysts were determined from the TPR results. The XRD and CO oxidation results demonstrated that the gold particles were lower than 5nm. The dependence of the selectivity towards crotyl alcohol and of the conversion on time on stream was measured. The niobia-supported catalyst was mainly unselective, the selectivity towards crotyl alcohol value being 20% for both liquid and gas phases. The Au/CeO2 catalyst is highly selective in gas phase (78% of selectivity towards crotyl alcohol). Under liquid phase conditions, a high selectivity level was not reached mainly due to secondary reactions. [Copyright &y& Elsevier]

The feedbacks between aerosols, cloud microphysics, and cloud chemistry are investigated in a mesoscale model. A simple bulk aqueous-phase sulfur chemistry scheme was fully coupled to the existing aerosol and microphysics schemes. The representation of aerosol and microphysics follows the explicit bulk double-moment approach. A case of summertime stratocumulus cloud system is simulated at high resolution (3-km grid spacing), and the evolution of an observed continental aerosol spectrum that changes during the course of the simulation as a result of cloud processing is examined. The results demonstrate that the bulk approach to the aerosol and droplet spectra correctly represents the feedbacks in the coupled system. The simulations capture the characteristic bimodal aerosol size spectrum resulting from cloud processing, with the first mode consisting of particles that did not participate as cloud condensation nuclei and the second mode, in the region of 0.08–0.12-μm radii, comprising the particles that were affected by processing. New information is revealed about the impact of the two main processing pathways and about the spatial distribution of the processed aerosol. One cycle of physical processing produced a relatively modest impact of 3%–5% on the processed particle mean radius of the order that was comparable to the impact of chemical processing, while continuous physical recycling produced a much larger impact as high as 30%–50%. A strong constraint on the chemical processing was found to be the initial chemistry input and the assumption of bulk chemical composition. Simple tests with a more slowly depleting primary oxidant (H2O2) and including the droplet chemical heterogeneity effect favor stronger sulfate production, by, respectively, the H2O2 and O3 oxidation reaction, and both show a larger impact on the processed particle mean radius of similar magnitude, 10%–20%. Spatially, the impact of processing is found initially in the downdraft regions below cloud and at later times at substantial distances downwind. It is shown that cloud processing can either enhance or suppress the number of activated drops in subsequent cycles. [ABSTRACT FROM AUTHOR]

It is proved by testing that the effect of nanosecond powerful electromagnetic pulses (PEMP) tends to give rise to both pyrrhotite disintegration and alterations of its particles’ surface chemistry. It is found that PEMP exerts an effect on the surface composition, floatability, sorption ability and solubilization intensity of pyrrhotite. The non-monotone variation of sulphur content, removed from pyrrhotite surface under hexane action, and ferrous and ferric sulfates detected in the aqueous phase of suspension, are found to induce a nonmonotone alteration of sorption and flotation properties of the mineral depending on the number of pulses. The mode has been established for the preliminary PEMP treatment for pyrrhotite and pentlandite, aimed at improving the flotation separation as compared to a conventional mode. [ABSTRACT FROM AUTHOR]

The effects of synthetic conditions, component ratios, and the nature of the transition metal on the physicochemical and catalytic properties of Ce-Zr-Y-La-M-O (M = Mn, Fe, Co) systems are studied. The Ce-Zr-Y-La-M-O samples precipitated at ∼23°C and calcined at 600°C are single-phase and are solid solutions with a fluorite structure, which persists upon calcination at 1150°C. The Ce-Zr-Y-La-Fe(Co)-O samples precipitated at 70°C and calcined at 1150°C consist of two solid solutions, one cubic, and the other tetragonal. The specific surface area ( S sp) of the samples precipitated at ∼23°C and calcined at 600°C increases in the order Ce-Zr-Y-La-O < Ce-Zr-Y-La-Mn-O < Ce-Zr-Y-La-Co-O ≈ Ce-Zr-Y-La-Fe-O. The specific surface area of the samples precipitated at 70°C is independent of M and is ∼110 m2/g. Calcination at 1150°C reduces S sp approximately by two orders of magnitude. The TPR of the unpromoted systems in H2 proceeds in two steps at 600–650 and 750–840°C. The introduction of M decreases the reduction temperatures and gives rise to a lower temperature peak between 150 and 300°C. The most effective promoter is cobalt. The fluorite-type catalysts containing no noble metal are active in NO reduction ( X NO ≈ 100%) at T react = 400–450°C. The cobalt-containing catalysts are the most active in the oxidation of CO ( X max = 28%) and hydrocarbons ( X max = 4.3%). [ABSTRACT FROM AUTHOR]

Importance of the study of the influence of coal oxidability on vitrinite reflectance (VR) as a criterion of the quality of coals and indicator of paleogeothermal regime is shown. Overview of relevant concepts demonstrates that this issue remains debatable. Carboniferous coals of the Dobrudja foredeep, which belong to the class of helitolites in terms of their microcomponent composition, were studied. They were subjected to oxidation during storage outdoors. Consequently, the VR value of high volatile bituminous (long-flame and gas ranks, according to the Russian classification) coals decreased, but this parameter remained virtually unaltered for medium volatile bituminous (fat) coals. Bulgarian researchers obtained similar results for Carboniferous coals of the Dobrudja basin represented by helitolites and mixtohumolites. In our opinion, the VR decrease in the course of coal oxidation is caused by decrease in the condensation and density of aromatic structures and increase in the share of nonaromatic carbon atoms. [ABSTRACT FROM AUTHOR]

The article examines the interaction between platinum aerosol particles formed on the oxidation of ammonia on a platinum catalyst and calcium oxide supported on a high-temperature silicon-containing material, a glass fabric, at temperature of 900°C. The nascent nanofibers represented quartz containing dissolved calcium, Si(Ca)O2, the calcium concentration being higher on the top of the fibers. The initial glass fabric is composed of interlaced threads according to scanning electron microscopy. High resolution images of electron microscopy show that CaO occurs on the glass fiber surface as porous particles. The energy dispersive x-ray spectrum shows that the nanofibers contain Si:O = 1:2. The crystal structure of nanofibers has a multitude of planar defects.

A detailed study of the processes of anaerobic methane oxidation and sulfate reduction in the bacterial mats occurring on coral-like carbonate structures in the region of methane seeps in the Black Sea, as well as of the phenotypic diversity of sulfate-reducing bacteria developing in this zone, has been performed. The use of the radioisotopic method shows the microbial mat structure to be heterogeneous. The peak activity of the two processes was revealed when a mixture of the upper (dark) and underlying (intensely pink) layers was introduced into an incubation flask, which confirms the suggestion that methanotrophic archaea and sulfate-reducing bacteria closely interact in the process of anaerobic methane oxidation. Direct correlation between the rate of anaerobic methane oxidation and the methane and electron acceptor concentrations in the medium has been experimentally demonstrated. Several enrichment and two pure cultures of sulfate-reducing bacteria have been obtained from the near-bottom water and bacterial mats. Both strains were found to completely oxidize the substrates to CO2 and H2S. The bacteria grow at temperatures ranging from −1 to 18 (24)°C, with an optimum in the 10–18°C range, and require the presence of 1.5–2.5% NaCl and 0.07–0.2% MgCl 2⋅6H2O. Regarding the aggregate of their phenotypic characteristics (cell morphology, spectrum of growth substrates, the capacity for complete oxidation), the microorganisms isolated have no analogues among the psychrophilic sulfate-reducing bacteria already described. The results obtained demonstrate the wide distribution of psychrophilic sulfate-reducing bacteria in the near-bottom water and bacterial mats covering the coral-like carbonate structures occurring in the region of methane seeps in the Black Sea, as well as the considerable catabolic potential of this physiological group of psychrophilic anaerobes in deep-sea habitats [ABSTRACT FROM AUTHOR]

Abstract: This paper is devoted to the development of a low-dimensional kinetic model of CO oxidation on a metallic catalyst surface and theoretical study of arising nonlinear phenomena and relaxation oscillations of the reaction rate. Experimental results of studies on the adsorbed oxygen are presented and its significance in the CO oxidation mechanism on Ir catalyst is shown. We consider the conventional Langmuir–Hinshelwood mechanism of catalytic CO oxidation and take into account the possibility of a metallic surface modification during reaction due to the oxygen penetration into subsurface layers. We suggest that when the adsorbed oxygen concentration exceeds some critical value, a surface modification occurs and the reaction capability of adsorbed oxygen changes, so that the activation energy of the interaction between the adsorbed species sharply increases. Construction of bifurcation curves on the parametric plane (P CO, ) permits us to separate areas of CO and O2 partial pressures, for which self-oscillations and/or multiplicity of steady states appear. This paper deals with parametric analysis of a new two-variable kinetic model of CO oxidation on Ir catalyst surface, but the approach developed is rather general and can be applied to studies of different catalytic reactions. [Copyright &y& Elsevier]

The kinetics of the initial step of methane oxidation in a wide range of the external parameters is studied using a simplified model including complete branched cycles of peroxide formation and decomposition. An analytical formula for the ignition criterion is obtained by analysis of the structure of the reaction scheme (graph). Qualitative assessment and calculation of the critical parameters of this criterion in the framework of a linear model provide a new notion of the configuration of the methane chain ignition region. This notion implies that the kinetics and product composition vary in going from one portion of the ignition region boundary to another and provides an explanation for this behavior. The evolution of the system in the region itself is discussed in terms of nonlinear contributions to the dependence of the criterion on the parameters. [ABSTRACT FROM AUTHOR]

BET, XRD, XPS, and TPR by hydrogen were used for investigation of supported Mn–Bi oxide catalysts for ammonia oxidation into nitrous oxide. The catalysts were synthesized by impregnation of γ-, α-Al2O3 and SiO2 with solutions of manganese and bismuth nitrates. The character of phase transformations, surface concentration, and state of the active component were shown to depend on the nature of the support. The sequence stabilization of active constituents of the Mn–Bi–O/α-Al2O3 catalyst and types of the stabilized species were determined. The activity of the Mn–Bi–O supported catalysts calcined at 400 °C was established to equal 95–97% and to be practically independent of the support nature, while the activity decreased with elevation of the calcination temperature. The Mn–Bi–O/α-Al2O3 catalysts exhibited the highest selectivity to N2O (84.4%) under identical conditions. The correlation between the Mn3+/Mnδ+ (2<δ<3) ratio in the catalyst and the selectivity to N2O was revealed. [Copyright &y& Elsevier]

Despite its negative redox potential, nitroxyl (HNO) can trigger reactions of oxidation. Mechanistically, these reactions were suggested to occur with the intermediate formation of either hydroxyl radical (⋅OH) or peroxynitrite (ONOO[sup -]). In this work, we present further experimental evidence that HNO can generate ⋅OH. Sodium trioxodinitrate (Na[sub 2]N[sub 2]O[sub 3]), a commonly used donor of HNO, oxidized phenol and Me[sub 2]SO to benzene diols and ⋅CH[sub 3], respectively. The oxidation of Me[sub 2]SO was O[sub 2]independent, suggesting that this process reflected neither the intermediate formation of ONOO[sup -] nor a redox cycling of transition metal ions that could initiate Fenton-like reactions. In solutions of phenol, Na[sub 2]N[sub 2]O[sub 3] yielded benzene-1,2-diol and benzene-1,4-diol at a ratio of 2:1, which is consistent with the generation of free 7sdot;OH. Ethanol and Me[sub 2]SO, which are efficient scavengers of ⋅OH, impeded the hydroxylation of phenol. A mechanism for the hydrolysis of Na[sub 2]N[sub 2]O[sub 3] is proposed that includes dimerization of HNO to cis-hyponitrous acid (HO-N=N-OH) with a concomitant azo-type homolytic fission of the latter to N[sub 2] and ⋅OH. The HNO-dependent production of ⋅OH was with 1 order of magnitude higher at pH 6.0 than at pH 7.4. Hence, we hypothesized that HNO can exert selective toxicity to cells subjected to acidosis. In support of this thesis, Na[sub 2]N[sub 2]O[sub 3] was markedly more toxic to human fibroblasts and SK-N-SH neuroblastoma cells at pH 6.2 than at pH 7.4. Scavengers of ⋅OH impeded the cytotoxicity of Na[sub 2]N[sub 2]O[sub 3]. These results suggest that the formation of HNO may be viewed as a toxicological event in tissues subjected to acidosis. [ABSTRACT FROM AUTHOR]

A surprising effect is the direct action of Ca2+ on redox reactions of ortho-quinoid compounds. The effect of Ca2+ on oxidation of the sea urchin pigment 6-ethyl-2,3,5,7,8-pentahydroxy-1,4-naphthoquinone (echinochrome A) has been studied by electron paramagnetic resonance (EPR) spectroscopy, by UV/VIS absorbance spectroscopy, and by measurement of oxygen consumption. Echinochrome A per se reacted with dioxygen only in an alkaline solution; 2,3-semiquinone anion-radical of echinochrome A and superoxide anion-radical were the intermediates of the oxidation. Addition of calcium ions sharply increased the rate of echinochrome A autooxidation at alkaline pH and provoked oxidation at neutral pH. To explain this phenomenon we have focused on changes of the acid–base properties of echinochrome A in the presence of calcium and on stabilization of 2,3-semiquinone anion-radical of echinochrome A by Ca2+. Dissociation constants (pKa1, pKa2, and pKa3) of echinochrome A determined by potentiometric titration were 5.20, 6.78, and >10 in calcium-free solution and 5.00, 6.10, and 7.15 in the presence of Ca2+. We have found that Ca2+ forms an insoluble adduct with the 2,3-semiquinone anion-radical. Thus, the effect of redox-inert calcium on the free radical reactions could be explained (i) by additional deprotonation of echinochrome A and (ii) by formation of a Ca2+-naphtho-2,3-semiquinone complex (calcium semiquinonate). Additionally, we have shown that the dried red spines from Strongylocentrotus intermedius possess paramagnetic properties; the EPR signal of the natural spines was similar to that of calcium semiquinonate obtained in our artificial chemical system. [Copyright &y& Elsevier]

The comparative kinetic study of two glucose oxidizing enzymes, FAD-dependent glucose oxidase and PQQ-dependent glucose dehydrogenase, is presented in the artificial electron transfer mediator system based on ruthenium(III) compounds. It is demonstrated that FAD-dependent glucose oxidase and PQQ-dependent glucose dehydrogenase follow Michaelis kinetics in the D-glucose/ruthenium(III) system. PQQ-dependent glucose dehydrogenase is more active than FAD-dependent glucose oxidase in the process of D-glucose oxidation by ruthenium(III) compounds, this being due to the different catalytic mechanisms of these enzymes. [ABSTRACT FROM AUTHOR]

This study is focused on the design control of Cu–Zr–Ti oxide composites by the variation of the Zr/Ti ratio and the copper deposition procedure used. For the first time, these ternary composites were obtained by a combination of template-assisted hydrothermal techniques for the preparation of mesoporous ZrO2–TiO2 mixed oxides with diverse compositions, followed by the consecutive chemisorption and hydrolysis of copper ammonia complexes on them. The nitrogen physisorption, XRD, SEM, HRTEM, TPR, XPS, UV-Vis, and Raman spectroscopies were applied for the catalysts' characterization. Methanol decomposition and the total oxidation of ethyl acetate, both of which with potential for sustainable environmental protection, were used as catalytic tests. The complex relationship between the phase composition, structure, and morphology of titania–zirconia mixed oxides and the state and catalytic behavior of the copper oxide species supported on them was investigated. In comparison with the conventional impregnation technique, the novel preparation procedure revealed the generation of more uniform and homogeneously dispersed needle-like copper oxide crystallites in the mesoporous TiO2–ZrO2 host matrix, which typically ensure improved catalytic performance. The synergistic activity between the loaded copper species and TiO2–ZrO2 support was discussed. All ternary composites exhibited superior catalytic activity in total oxidation of ethyl acetate. The specific behavior of the catalysts in methanol decomposition was related to the irreversible phase transformations by the influence of the reaction medium. [ABSTRACT FROM AUTHOR]

The article presents a study on the direct voltammetric measurement of peak potential (Ep) for silver (Ag) electrochemical oxidation as a function of Ag nanoparticle (NP) size. The study synthesized and characterized different Ag NPs with the use of optical methods, atomic force microscopy (AFM), linear sweep voltammograms (LSVs), and scanning electron microscopy (SEM). Results show that the shif in Ep is caused by size-dependent change in redox potential (E0) .

The monitoring of physicо-chemical changes in the oleic type of sunflower oil when frying potatoes in restaurant conditions by using a professional MModular fryer at 180 °C and comparison with the use of the linoleic typeof sunflower oil was researched. In the oleic type of sunflower oil, there was a slight increase of the AV (acid value) observed till the second frying, after which there was detention within the limits of 0.15 to 0.20 % till the tenth frying. The peroxide value (PV, mеqО2/kg) increased significantly in both types of oil - oleic and linoleic, reaching the maximum at the fourth frying, and the value was close to the limiting value for vegetable oils from the linoleic type of sunflower oil - 10 mеqО2/kg. The induction period in the oleic type of sunflower oil was long - 22 hours, but it gradually decreased and after the tenth frying, it was 5 hours. In the linoleic type of sunflower oil, the induction period in the beginningwas 8.55 hours, and after the fourth frying, it decreased to 4 hours. The color numbers according to Lovibondon 10 oil samples from repeated frying of products were determined and this indicator increased with the number of fryings over time. Chlorophyll content was not been established. Theoleic type of sunflower oil produced in Bulgaria, when frying fresh potatoes, was more stable to the oxidation than the traditionally used sunflower oil - linoleic type. Itshowedstability during storage and long frying time of the used products in real working conditions. This made it more suitable for the preparation of food products, culinary items, main courses, starters and garnishes that require longer thermal treatment. This type of product can be recommended for use when frying in the restaurant business and in the area of nutrition. The methods in our research can be used to control the degree of oxidation of frying oils with vegetable origin in their repeated use, by taking samples on the first, fourth and tenth day of frying at different loads of fryers and to test for acidity, peroxide number and color number. [ABSTRACT FROM AUTHOR]

• 100% FDCA yield is achieved at low temperature and base concentration over Au/Al 2 O 3 catalyst. • Full HMF conversion in less than 10 min. • Catalyst stable under recycling conditions with slight deactivation after 5 runs. • CeO 2 (20 wt.%) introduction promotes HMF/intermediates oxidation. The catalytic activity of a simple Au/Al 2 O 3 catalytic system prepared by the direct anionic exchange (DAE) method was evaluated in the selective 5-hydroxymethylfurfural (HMF) oxidation under mild conditions, using molecular oxygen as the oxidant. The influence of the HMF/NaOH ratio and reaction time on product yield and distribution were studied and discussed in detail. Extremely high activity and selectivity were observed in mild conditions, with 99% of 2,5-furandicarboxylic acid (FDCA) production at full HMF conversion after 4 h with the use of only 4 equivalents of NaOH at 70 °C. Catalyst viability and stability were verified by repeating the cycle up to five times. Changes in the nature of the support were also contemplated by introducing some ceria fraction, i.e. 20 wt%. [ABSTRACT FROM AUTHOR]

The oxidizabilities of the principal lignocellulose feedstock constituents (cellulose, lignin, xylan) and feedstock exposed to gamma-radiation are investigated. The oxidizability of wheat straw by hydrogen peroxide increases if the absorbed gamma-radiation dose is increased to 200-300 kGy and the feedstock particle size is reduced to 0.8-1.2 mm. Hemicelluloses are practically completely degraded by catalytic peroxide treatment (mass loss of ~95%) whereas lignin is destroyed much less (mass loss of ~27%) under the same conditions. Pretreatment of the feedstock increases the cellulose content in the lignocellulose feedstock and can be used to produce biofuels (EtOH or 2,5-dimethylfuran). [ABSTRACT FROM AUTHOR]

A new method for the synthesis of benzofuro[3,2-d]pyrimidines was developed based on the oxidation of 2-(5-bromo-3,4-dihydropyrimidin-4-yl)phenols followed by the intramolecular nucleophilic aromatic substitution reaction. [ABSTRACT FROM AUTHOR]

The purpose of investigation was to appreciate the changes in quality of walnut oil obtained by cold pressing of kernels. The kinetics of chemical reactions of oil oxidation was studied. The accumulation of the primary and secondary compounds of oxidation process depending on the storage life was analyzed. The oil quality is subjected to permanent changes predominantly in the direction of nutritional quality losses. It has been established that the chemical and biochemical reactions of the oxidation of polyunsaturated fatty acids in the triglyceride structure are irreversible and consecutive. At the same time, it has been determined that during oil storage the reaction of primary compounds (hydroperoxides) formation by oxidation is of zero order, but the reaction rate is variable. At the initial stage of storage (20-21 days) the increasing of reaction rate constant (K, days-1) of hydroperoxides formation from K3=0.042days-1 at t=3°C to K60=1.82days-1 at t=60°C has been detected. The activation energy of the reactions was equal to 52.1kj/mol. However, the acidity index of oil increased in limited diapason from 0.12mgKOH/g to 0.19mgKOH/g. [ABSTRACT FROM AUTHOR]

The effect of the nature of calix[n]arenes [n = 4, 6, 8] added to a plastic lubricant on the oxidation resistance of the lubricant at high temperatures is studied. Such characteristics as the number of phenolic fragments in the calixarene structure, the presence of tert-butyl groups on the upper rim of the calix[n]arene, and presence of an O-alkyl substituent in the lower rim are examined. It is shown that calix[8]arenes are capable of inhibiting high-temperature oxidation of plastic lubricants, regardless of the presence of a tert-butyl substituent on the upper rim and an alkyl substituent on the lower rim. [ABSTRACT FROM AUTHOR]