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STABILITY constants, IONIC strength, PERMITTIVITY, OXIDATION kinetics, and HYDROCHLORIC acid

The kinetics of tetrahydrofuran oxidation by sodium N-chloro-p-toluene sulfonamide in the hydrochloric acid medium was studied in this work at 308 K. The reaction rate shows a first-order dependence on [CAT] and fractional-order dependence each on [THF] and [H+]. The derivative rate law, which suitable for experimental results, is Equation 24. The first-order rate constant has been evaluated from the relationship of the plot of Log [CAT] versus Time. The variation of the ionic strength by the addition of sodium perchlorate (NaClO4) and chloride ion on the medium showed no significant effect on the reaction. The reaction rate raised with decreasing dielectric constant (D), while the addition of p-toluene sulfonamide retards the rate of reaction. The oxidation reaction of tetrahydrofuran have been studied at a different temperature, The equilibrium constants for the formation of hypochlorous acid, protonated hydrochlorous acid and protonated hydrochlorous acid-THF complex and its decomposition constant have been estimated. Also, the rate constant for the slow (rate-determining step) and the activation parameter have been calculated. A suitable mechanism for the oxidation reaction of tetrahydrofuran was proposed based on the experimental finding. The mechanism includes the reaction of active species (H2OCl) of the oxidizing agent with the tetrahydrofuran in a fast step to give the complex(X). This complex will then transformed into complex (X̅) in slow step then to γ-butyrolactone in another fast step. [ABSTRACT FROM AUTHOR]

SUNFLOWER seed oil, OZONIZATION, CARBONYL compounds, FATTY acids, OXIDATION, and PEROXIDES

Vegetable oils are usually rich in unsaturated fatty acids which are susceptible to oxidation. The oxidation of vegetable oils has been one of the most widely studied fields within lipid chemistry, because it alters their properties and nutritive value, inducing the formation of harmful compounds and off-flavors. Moreover, oxidized vegetable oils display altered physical and chemical properties which are conferred by the newer oxygenated compounds they contain. This is the case of ozonized oils. Ozone is a powerful oxidizing agent that mainly acts on olefinic compounds which generate ozonides and other peroxidic species that can decompose into carbonilic fragments. The action of the oxidant and the later reactions depend on the chemical environment of the reaction as well as the carbonyl termination products resulting from peroxide cleavage. In recent years, sunflower oils with different fatty acid compositions have been developed by breeding and mutagenesis. They displayed higher contents of oleic, stearic or palmitic acids, which mainly alters their triacylglycerol composition. Therefore, four different sunflower oils, common, high oleic, high stearic-high oleic and high palmitic-high oleic, were oxidized with ozone and the progress of the reaction was monitored by measuring the level of oil peroxygenation and the changes in the oils' fatty acid compositions. The peroxidated species formed during ozonation were studied by FT-IR spectroscopy. The main conclusions of this work were that ozonation caused linear oxidation rates that were similar in all the oils assayed. The addition of water accelerated oxidation, which tended to occur in linoleic polyunsaturated fatty acid The FT-IR pointed to the presence of ozonide-derived peroxides as the major oxygenated species. [ABSTRACT FROM AUTHOR]

CORN oil, ANTIOXIDANTS, MICROWAVE cooking, EFFECT of heat on food, OXIDATION, and HEXANAL

Four different corn oil samples including stripped (SCO, Control), refined (RCO), stripped corn oil enriched with rosemary extract (SCO+ROS) and ascorbyl palmitate (SCO+AP) were exposed to microwave (MWH) and conventional heating (CVH). For both heating methods, peroxide value (PV) and conjugated dienes increased at up to 230 °C, at which temperature hexanal (HEX) and conjugated trienes started to increase instead. Kinetic analysis revealed that PV and HEX formation were first ordered and the reaction rate among the samples was as follows: Control > SCO+ROS > RCO > SCO+AP for PV and SCO+ROS > RCO > SCO+AP > Control for HEX. The unsaturated fatty acid contents of CVH and MWH treated samples showed 9.5 and 12.9% reduction in SCO, while they were 2.9 and 7.7% in RCO, 3.6 and 6.1% in SCO+ROS, and finally 4.0 and 4.8% in SCO+AP. It was concluded that MWH led to a more severe deterioration and that the antioxidant activity of ROS was superior to that of AP for both heating methods. [ABSTRACT FROM AUTHOR]

General chemistry, physical chemistry, Chimie générale, chimie physique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie des réactions induites par rayonnements, particules et ultrasons, Physical chemistry of induced reactions (with radiations, particles and ultrasonics), Sonochimie, Ultrasonic chemistry, Cinétique, Kinetics, Cinética, Dégradation, Degradation, Degradación, Eau, Water, Agua, Mécanisme, Mechanism, Mecanismo, Oxydation, Oxidation, Oxidación, Ozone, Ozono, Sonochimie, Sonochemistry, Sonoquímica, Ultrason, Ultrasound, Ultrasonido, Mechanisms, Pathways, and Sulfamethoxazole

In this research, sulfamethoxazole (SMX) degradation was investigated using ultrasound (US), ozone (O3) and ultrasound/ozone oxidation process (UOOP). It was proved that ultrasound significantly enhanced SMX ozonation by assisting ozone in producing more hydroxyl radicals in UOOP. Ultrasound also made the rate constants improve by kinetics analysis. When ultrasound was added to the ozonation process, the reaction rate increased by 6-26% under different pH conditions. Moreover, main intermediates oxidized by US, O3 and UOOP system were identified. Although the main intermediates in ozonation and UOOP were similar, the introduction of ultrasound in UOOP had well improved the cleavage of S-N bond. In this condition SMX become much easier to be attacked, which led to enhanced SMX removal rate in UOOP compared to the other two examined processes. Finally, the SMX degradation pathways were proposed.

General chemistry, physical chemistry, Chimie générale, chimie physique, Environment, Environnement, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Physicochimie de surface, Surface physical chemistry, Echange d'ions, Ion-exchange, Zéolites: préparations et propriétés, Zeolites: preparations and properties, Métal transition, Transition metal, Metal transición, Ammoniac, Ammonia, Amoníaco, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Catalyseur, Catalyst, Catalizador, Cinétique, Kinetics, Cinética, Fer, Iron, Hierro, Oxydation, Oxidation, Oxidación, Oxyde d'azote, Nitrogen oxide, Nitrógeno óxido, Protection environnement, Environmental protection, Protección medio ambiente, Réaction catalytique, Catalytic reaction, Reacción catalítica, Réduction chimique, Chemical reduction, Reducción química, Zéolite, Zeolite, Zeolita, Ammonia oxidation, Iron zeolite, Nitrogen oxides, and Selective catalytic reduction

The steady-state kinetics of the selective catalytic reduction (SCR) of nitrogen oxides (NO and NO2) with ammonia over a commercial iron zeolite catalyst were studied in the temperature range of 250 to 450°C using an integral tubular reactor. Special attention was paid to the stoichiometric ratio of the conversion of ammonia and nitrogen oxides. For this purpose, both systematic SCR measurements at different feed gas compositions and independent studies of the catalytic oxidation of ammonia in the absence of NO and NO2 were carried out. Under all reaction conditions, a considerable deviation from the expected 1:1 stoichiometry was observed. The steady-state kinetics of the reacting system could be described by global Langmuir-Hinshelwood-type rate equations for standard SCR, fast SCR, NO/NO2 equilibrium and NH3 oxidation. For the correct calculation of the ammonia oxidation it was necessary to include two terms. A first one describing the reaction of NH3 with O2, which becomes important at temperatures above 400°C, and a second rate equation which is not only proportional to NH3 and O2 but also to the NO concentration and which is of particular relevance at low reaction temperatures. Additional measurements with different catalyst particle sizes including industrial extrudates could be successfully described with the aid of a reactor model which took film and pore diffusion phenomena into account.

General chemistry, physical chemistry, Chimie générale, chimie physique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie des réactions induites par rayonnements, particules et ultrasons, Physical chemistry of induced reactions (with radiations, particles and ultrasonics), Sonochimie, Ultrasonic chemistry, Electrochimie, Electrochemistry, Cinétique, Kinetics, Cinética, Electrochimie, Electrochemistry, Electroquímica, Electrolyse, Electrolysis, Electrólisis, Ibuprofène, Ibuprofen, Ibuprofeno, Oxydation, Oxidation, Oxidación, Sonochimie, Sonochemistry, Sonoquímica, Sonolyse, Sonolysis, Sonólisis, Ultrason, Ultrasound, Ultrasonido, Pseudo first-order kinetics, and Sonoelectrolysis

A hybrid advanced oxidation process combining sonochemistry (US) and electrochemistry (EC) for the batch scale degradation of ibuprofen was developed. The performance of this hybrid reactor system was evaluated by quantifying on the degradation of ibuprofen under the variation in electrolytes, frequency, applied voltage, ultrasonic power density and temperature in aqueous solutions with a platinum electrode. Among the methods examined (US, EC and US/EC), the hybrid method US/EC resulted 89.32%, 81.85% and 88.7% degradations while using NaOH, H2SO4 and deionized water (DI), respectively, with a constant electrical voltages of 30 V, an ultrasound frequency of 1000 kHz, and a power density of 100 W L-1 at 298 K in 1 h. The degradation was established to follow pseudo first order kinetics. In addition, energy consumption and energy efficiencies were also calculated. The probable mechanism for the anodic oxidation of ibuprofen at a platinum electrode was also postulated.

General chemistry, physical chemistry, Chimie générale, chimie physique, Environment, Environnement, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Physicochimie des réactions induites par rayonnements, particules et ultrasons, Physical chemistry of induced reactions (with radiations, particles and ultrasonics), Photochimie, Photochemistry, Composé de métal de transition, Transition element compounds, Cétone, Ketone, Cetona, Acétone, Acetone, Acetona, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Cinétique, Kinetics, Cinética, Haute fréquence, High frequency, Alta frecuencia, Oxydation, Oxidation, Oxidación, Oxyde de titane, Titanium oxide, Titanio óxido, Photocatalyse, Photocatalysis, Fotocatálisis, Protection environnement, Environmental protection, Protección medio ambiente, Simulation, Simulación, Vapeur, Vapor, Controlled periodic illumination, Reaction kinetics simulation, Titanium dioxide, and UV LED

We investigated the effect of controlled periodic illumination on quantum efficiency of acetone vapor photocatalytic oxidation. It was demonstrated that quantum efficiency increases with the increase of light pulses frequency and decrease of the duty cycle and at some point reaches its maximum value which is equal to the quantum efficiency obtained under the same average photon flux. Several kinetic models were applied to the experimental data. The general conclusion was made that there are only two kinetically distinguishable active species on TiO2 surface with the lifetimes in 10-3-101 s range.

General chemistry, physical chemistry, Chimie générale, chimie physique, Environment, Environnement, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Physicochimie des réactions induites par rayonnements, particules et ultrasons, Physical chemistry of induced reactions (with radiations, particles and ultrasonics), Photochimie, Photochemistry, Accepteur électron, Electron acceptor, Aceptor electrón, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Cinétique, Kinetics, Cinética, Dégradation photochimique, Photochemical degradation, Degradación fotoquímica, Mécanisme, Mechanism, Mecanismo, Oxydant, Oxidant, Oxidante, Oxydation, Oxidation, Oxidación, Oxyde de tungstène, Tungsten oxide, Wolframio óxido, Photocatalyse, Photocatalysis, Fotocatálisis, Protection environnement, Environmental protection, Protección medio ambiente, Séparation charge, Charge separation, Separación carga, WO3, Alternative electron acceptor, Inorganic oxidant, Photocatalytic oxidation, and Visible light activity

This study evaluates the capacity of various inorganic oxidants (IO4-, HSO5-, S2O82-, H2O2, and BrO3-) to act as alternative electron acceptors for WO3-mediated photocatalytic oxidation. Combination with IO4- drastically increased the rate of photocatalytic degradation of 4-chlorophenol by WO3, while the other oxyanions only negligibly improved the photocatalytic activity. The extent of the photocatalytic performance enhancement in the presence of inorganic oxidants correlated well with the efficiencies for: (1) hydroxylation of benzoic acid as an OH• probe, (2) dechlorination of dichloroaceate as a hole scavenger, and (3) water oxidation with O2 evolution. The results suggest that the promoted charge separation primarily causes kinetic enhancement in photocatalytic degradation using the WO3/IO4- system. In marked contrast to the substrate-dependent activity of the photochemically activated IO4- (generating selective IO3•), the efficiency of the WO3/IO4- system for photocatalytic degradation did not sensitively depend on the type of target organic compound, which implies the existence of a minor contribution of the photocatalytic reduction pathway associated with the production of IO3• as a secondary oxidant. On the other hand, the insignificant inhibitory effect of methanol as an OH• quencher may reveal the possible involvement of SO4•- in the improved photocatalytic activity of the WO3/HSO5- system. The alternative use of platinized WO3, where the interfacial electron transfer occurs in a concerted step, achieved a highly accelerated photocatalytic oxidation in the presence of HSO5- and polyoxometalates as electron scavengers. In particular, the surface loading of nanoscale platinum appeared to retard the reaction route for SO4•- generation associated with a one-electron transfer.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Energie, Energy, Energie. Utilisation thermique des combustibles, Energy. Thermal use of fuels, Etudes théoriques. Données et constantes. Mesures, Theoretical studies. Data and constants. Metering, Combustion. Flammes, Combustion. Flame, Combustion des combustibles liquides, Combustion of liquid fuels, Biocarburant, Biofuel, Biocarburante, Chaîne courte, Short chain, Cadena corta, Cinétique, Kinetics, Cinética, Combustion, Combustión, Ester, Flamme laminaire, Laminar flame, Llama laminar, Oxydation, Oxidation, Oxidación, Propagation flamme, Flame propagation, Propagación llama, Acide alcanoïque ester méthyle, Acide alcanoïque ester éthyle, Alkyl esters, Ethyl esters, Laminar flames, and Methyl esters

The oxidation characteristics of several small methyl and ethyl esters with carbon number less than six were investigated in laminar flames. The kinetics of such fuels are subsets of those of larger alkyl esters that are constituents of practical biodiesel fuels. A total of seven fuels, namely methyl formate, methyl acetate, methyl propionate, methyl butanoate, ethyl formate, ethyl acetate, and ethyl propionate were considered. Experiments were conducted at atmospheric pressure, elevated reactant temperatures, and over a wide range of equivalence ratios. Laminar flame speeds were determined in the counterflow configuration in which flow velocities were measured using particle image velocimetry. Several detailed kinetic models were tested against the experimental data, and insight was provided into the high-temperature combustion kinetics of the aforementioned fuels. Based on comparisons between experimental and computed results it became apparent that the chemistry of alkyl-ester combustion chemistry is evolving and much needs to be done in order to derive improved rate constants for a wide range of elementary steps.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Physicochimie des réactions induites par rayonnements, particules et ultrasons, Physical chemistry of induced reactions (with radiations, particles and ultrasonics), Photochimie, Photochemistry, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Cinétique, Kinetics, Cinética, Modélisation, Modeling, Modelización, Oxydation, Oxidation, Oxidación, Oxygène, Oxygen, Oxígeno, Photocatalyse, Photocatalysis, Fotocatálisis, Photochimie, Photochemistry, Fotoquímica, Photosensibilisation, Photosensitization, Fotosensibilización, Protection environnement, Environmental protection, Protección medio ambiente, Résonance, Resonance, Resonancia, Spin, Electron spin resonance, Environmental photochemistry, and Kinetic modeling

Photooxidation of Fe(II) at acidic pH occurs in photocatalytic processes of Fe(III) species, but its reaction mechanism is not well understood. The kinetics of Fe(II) oxidation in irradiated aqueous solutions at pH 3.0 have been investigated in terms of kinetic modeling approach, rate constant estimation and the significance of various oxidation pathways. Fe(II) oxidation kinetics strongly rely on the availability of UV light, Fe(III) ions and oxygen. The presence of a portion of Fe(III) in Fe(II)-containing solutions favors the rapid oxidation of Fe(II). At high concentration of Fe(II), excitation of Fe(III) species may be quenched by Fe(II) in deaerated systems or may sensitize Fe(II) oxygenation under oxic conditions. By incorporation of this photosensitization pathway, the established model in this study is shown to be able to adequately describe the oxidation of Fe(II) at pH 3.0. Sensitivity analysis indicates that photolysis of Fe(III) species is critically important for overall Fe(II) oxidation kinetics. Fe(III)-catalyzed oxygenation of Fe(II), and oxidation of Fe(II) by HO2• and •OH also exerts a marked impact on the oxidation of Fe(II). Therefore, Fe(III)-catalyzed oxygen activation and their secondary reactive oxygen species (ROS) account for the oxidation kinetics of FE(II) at acidic pH.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Physicochimie de surface, Surface physical chemistry, Echange d'ions, Ion-exchange, Zéolites: préparations et propriétés, Zeolites: preparations and properties, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Catalyseur, Catalyst, Catalizador, Cinétique, Kinetics, Cinética, Epuration effluent gazeux, Flue gas purification, Depuración efluente gaseoso, Gaz échappement, Exhaust gas, Gas escape, Modélisation, Modeling, Modelización, Oxydation, Oxidation, Oxidación, Urée, Urea, Urées, Ureas, Zéolite, Zeolite, Zeolita, Cold start, Kinetic modeling, NO oxidation, Urea-SCR, and Zeolite catalyst

In this contribution a mathematical model suitable to simulate cold start effects over metal-promoted zeolite SCR catalysts is developed and included into an existing SCR converter model. We start from a recently published microkinetic scheme, which describes the NO2 related SCR reactions at temperatures above about 100 C on the basis of a complex reaction network, taking into account NO2 storage with formation of nitrates and their subsequent decomposition/reactivity. In order to describe material and thermal cold start effects observed from room temperature we extend such a kinetic scheme to include the low-T NO oxidation to NO2, NO2 physisorption and H2O adsorption. The rate parameters are fitted to our data from lab-scale runs analyzing each individual step. We show that the resulting model can reproduce the transient effects related to cold start both at the lab scale and in engine test bench experiments.

General chemistry, physical chemistry, Chimie générale, chimie physique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Composé binaire, Binary compound, Compuesto binario, Métal transition, Transition metal, Metal transición, Alumine, Alumina, Alúmina, Biomasse, Biomass, Biomasa, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Catalyseur, Catalyst, Catalizador, Cinétique, Kinetics, Cinética, Or, Gold, Oro, Oxydation, Oxidation, Oxidación, Oxyde d'aluminium, Aluminium oxide, Aluminio óxido, Al2O3, Hydroxymatairesinol, and Lignans

Lignan hydroxymatairesinol (HMR) extracted from Norway spruce knots was oxidized to the lignan oxo-matairesinol (oxoMAT) in a semi-batch glass reactor under the atmospheric pressure in the presence of oxygen (5-49 vol.% in nitrogen) over 2 wt.% Au/Al2O3 catalyst, using propan-2-ol-water mixture as a solvent. The following kinetic parameters were determined: adsorption constants, rate constants, reaction order for reagents, and energy of activation. Through the parameter estimation the experimental data were fitted to the advanced kinetic model demonstrating a good correlation between the model and experiments.

General chemistry, physical chemistry, Chimie générale, chimie physique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Physicochimie de surface, Surface physical chemistry, Matériaux adsorbants, Adsorbents, Métal transition, Transition metal, Metal transición, Biomasse, Biomass, Biomasa, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Catalyseur sur support, Supported catalyst, Catalizador sobre soporte, Catalyseur, Catalyst, Catalizador, Charbon actif, Activated carbon, Carbón activado, Cinétique, Kinetics, Cinética, Mécanisme, Mechanism, Mecanismo, Or, Gold, Oro, Oxydation, Oxidation, Oxidación, Platine, Platinum, Platino, Réaction catalytique, Catalytic reaction, Reacción catalítica, Gold catalysis, and Platinum catalysis

The reaction mechanism of 5-hydroxymethylfurfural (HMF) oxidation in neutral aqueous solution with O2 to 5-hydroxymethyl-2-furancarboxylic acid (HFCA) and 2,5-furandicarboxylic acid (FDCA) was evaluated over a 3 wt% Pt/activated carbon catalyst in a semibatch reactor and confirmed that the mechanism was the same as that determined at high pH. In addition, the reaction kinetics of intermediate HFCA oxidation to FDCA over supported Pt at high pH were investigated. The combination of reaction kinetics and isotopic labeling studies using 18O-labeled H2O and O2 was used to suggest a reaction mechanism in which H2O inserts oxygen into the product and O2 scavenges electrons from the metal catalyst. Carbon nanofibers (CNF) containing excess acid or base groups were also used as supports for Pt and Au nanoparticles and evaluated as catalysts in HMF oxidation. Although the CNF-supported samples catalyzed HMF oxidation at rates similar to other carbon-supported Pt and Au catalysts, the CNF support with basic groups improved the ability of supported Au to form FDCA from HMF under mild conditions.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Energie, Energy, Energie. Utilisation thermique des combustibles, Energy. Thermal use of fuels, Etudes théoriques. Données et constantes. Mesures, Theoretical studies. Data and constants. Metering, Combustion. Flammes, Combustion. Flame, Divers, Miscellaneous, Biocarburant, Biofuel, Biocarburante, Cinétique, Kinetics, Cinética, Ester, Jet gaz, Gas jet, Chorro gas, Liaison double, Double bond, Enlace doble, Modèle cinétique, Kinetic model, Modelo cinético, Modélisation, Modeling, Modelización, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Oxydation, Oxidation, Oxidación, Réacteur agité, Stirred tank reactor, Reactor agitado, Stéréoisomère trans, Trans stereoisomer, Estereoisómero trans, Hex-3-énoïque acide ester méthyle, Jet-stirred reactor, Mechanism, Methyl-3-hexenoate, and Unsaturated methyl ester

The oxidation of trans-methyl-3-hexenoate (CAS Number 2396-78-3) under 3 different equivalence ratios of 0.6, 1.0 and 2.0 was investigated in a jet-stirred reactor over the temperature range of 560-1220 K at 10 atm and τ = 0.7 s. Mole fractions of 22 species were quantified as the function of temperature under each condition. Compared to the saturated ester methyl hexanoate, the absence of cool flame and negative temperature coefficient regions in the present work reflects the influence of C=C double bond to fuel oxidation. A mechanism based on previous work of methyl hexanoate was developed and validated against the experimental data with satisfactory agreement. Through analysis of the experimental and modeling results, the role of C=C double bond in the oxidation process and the resulting reaction pathways that feature the oxidation of methyl-3-hexenoate are discussed.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Acide carboxylique, Carboxylic acid, Acido carboxílico, Aldéhyde, Aldehyde, Aldehído, Acide acétique, Acetic acid, Acético ácido, Activation, Activación, Acétaldéhyde, Acetaldehyde, Acetaldehído, Acétonitrile, Acetonitrile, Acetonitrilo, Cinétique, Kinetics, Cinética, Complexe de fer, Iron complex, Hierro complejo, Fer III, Iron III, Hierro III, Nitrile, Nitrilo, Oxydation, Oxidation, Oxidación, Oxygène, Oxygen, Oxígeno, Protection environnement, Environmental protection, Protección medio ambiente, Température ambiante, Room temperature, Temperatura ambiente, Technologie bas carbone, Acetaldehyde oxidation, Dioxygen activation, Iron-oxygen complex, and Michaelis-Menten kinetics

We show that highly efficient acetaldehyde-to-acetic acid oxidation is achieved in a diluted FeCl3-acetonitrile solution (5-100 μM), which proceeds rather rapidly and follows the enzymatic-like Michaelis-Menten kinetics. Interestingly, by adjusting the concentration of FeCl3. we are able to accelerate or shut down the oxidation process conveniently. Based on the catalytic results, spectroscopic evidences and successive DFT calculations, a reactant-initiated, putative mononuclear non-heme iron-oxygen complex, [FeCl(MeCN)4(O)]2+, is proposed as the active oxidizing species to conduct the room temperature reaction with relatively high TOF values (~1.2s-1). Finally, the putative iron-oxygen complexes are employed to the selective oxidation of benzyl alcohol under ambient conditions.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Energie, Energy, Energie. Utilisation thermique des combustibles, Energy. Thermal use of fuels, Etudes théoriques. Données et constantes. Mesures, Theoretical studies. Data and constants. Metering, Combustion. Flammes, Combustion. Flame, Biocarburant, Biofuel, Biocarburante, Butyle éther, Dibutylether, Butilo éter, Cinétique, Kinetics, Cinética, Combustion, Combustión, Délai inflammation, Ignition delay, Retardo encendido, Ecoulement laminaire, Laminar flow, Flujo laminar, Ether, Eter, Flamme laminaire, Laminar flame, Llama laminar, Lignocellulose, Lignocellulosics, Lignocelulosa, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Oxydation, Oxidation, Oxidación, Propagation flamme, Flame propagation, Propagación llama, Réacteur, Reactor, Temps retard, Delay time, Tiempo retardo, Di-n-butyl ether, Ethers, and Laminar flames

The combustion characteristics of promising alternative fuels have been studied extensively in the recent years. Nevertheless, the pyrolysis and oxidation kinetics for many oxygenated fuels are not well characterized compared to those of hydrocarbons. In the present investigation, the first chemical kinetic study of a long-chain linear symmetric ether, di-n-butyl ether (DBE), is presented and a detailed reaction model is developed. DBE has been identified recently as a candidate biofuel produced from lignocellulosic biomass. The model includes both high temperature and low temperature reaction pathways with reaction rates generated using appropriate rate rules. In addition, experimental studies on fundamental combustion characteristics, such as ignition delay times and laminar flame speeds have been performed. A laminar flow reactor was used to determine the ignition delay times of lean and stoichiometric DBE/air mixtures. The laminar flame speeds of DBE/air mixtures were measured in the stagnation flame configuration for a wide rage of equivalence ratios at atmospheric pressure and an unburned reactant temperature of 373 K. All experimental data were modeled using the present kinetic model. The agreement between measured and computed results is satisfactory, and the model was used to elucidate the oxidation pathways of DBE. The dissociation of keto-hydroperoxides, leading to radical chain branching was found to dominate the ignition of DBE in the low temperature regime. The results of the present numerical and experimental study of the oxidation of di-n-butyl ether provide a good basis for further investigation of long chain linear and branched ethers.

General chemistry, physical chemistry, Chimie générale, chimie physique, Environment, Environnement, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Alcool, Alcohol, Composé benzénique, Benzenic compound, Compuesto bencénico, Acide, Acids, Acido, Air humide, Wet air, Aire húmedo, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Catalyseur, Catalyst, Catalizador, Cinétique, Kinetics, Cinética, Eau usée, Waste water, Agua residual, Mécanisme, Mechanism, Mecanismo, Oxydation, Oxidation, Oxidación, Phénol, Phenol, Fenol, Phénols, Phenols, Fenoles, Polluant, Pollutant, Contaminante, Protection environnement, Environmental protection, Protección medio ambiente, Réaction catalytique, Catalytic reaction, Reacción catalítica, Réfractaire, Refractory, Refractario, C1-C2 acids, Catalytic wet air oxidation (CWAO), Industrial wastewater, and Mechanism-Kinetics

The reactivity pattern of a model MnCeOx catalyst (Mnat:Ceat, 1) in the wet air oxidation (CWAO) of toxic (phenol) and refractory (acetic, oxalic and formic acids) organic pollutants has been probed, using a stirred batch reactor with continuous oxygen feeding (PO2, 0,9 MPa). In the range of 110―150°C the MnCeOx catalyst (wcat/wsub, 5) shows high abatement and mineralization efficiency toward all the substrates. Parallel trends of substrate and total organic carbon (TOC) conversion prove that adsorption is the primary reaction step, while slower mineralization rates signal that surface oxidation is rate determiningstep (r.d.s.). Activity data in the pH range of 3―10 and straight relationships between conversion and dissociation constant (Ka) signal that acids adsorption is driven by electrostatic interactions with acid sites (EAds ≈ 80 kJ/mol), while a low energetic barrier (EAds ≈ 16 kJ/mol) discloses the physical nature of phenol adsorption. A kinetic analysis of conversion-selectivity data, based on a dual-site Langmuir―Hinshelwood (L―H) mechanism, sheds light into the CWAO pattern of MnCeOx catalyst toward different classes of organic pollutants.

General chemistry, physical chemistry, Chimie générale, chimie physique, Environment, Environnement, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Electrochimie, Electrochemistry, Cinétique et mécanisme des réactions, Kinetics and mechanism of reactions, Composé binaire, Binary compound, Compuesto binario, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Cinétique, Kinetics, Cinética, Electrocatalyse, Electrocatalysis, Electrocatálisis, Electrochimie, Electrochemistry, Electroquímica, Electrode, Electrodes, Electrodo, Oxydation, Oxidation, Oxidación, Oxyde d'étain, Tin oxide, Estaño óxido, Phosphate, Phosphates, Fosfato, Protection environnement, Environmental protection, Protección medio ambiente, O Sn, SnO2, Advanced oxidation process, Dichlorvos (2,2-dichlorovinyl dimethyl phosphate), Langmuir-Hinshelwood kinetics, and Metal oxide electrode

The effects of electrode potential and the initial concentration of 2,2-dichlorovinyl dimethyl phosphate (dichlorvos, DDVP) on its oxidation/mineralization reaction kinetics, using an electrochemical oxidation system based on SnO2—Sb2O5 anodes, have been studied. Electrochemical degradation followed the Langmuir―Hinshelwood mechanism, with adsorption equilibrium constant K = 0.082 L mg―1 of dichlorvos on the electrode material surface, and reaction rate constant K = 0.021 mg L―1 s―1 of the organic compound-electrocatalyst adduct. Chemical oxygen demand and CO2 measurements in neutral media suggest that the rate limiting step for mineralization is the same as for the electrochemical oxidation. The results show that the electrochemical mineralization of dichlorvos was readily possible at potentials more positive than 2.5 V vs. SCE, with lower reaction half-lives than obtained with other advanced oxidation process. The fastest overall degradation rate constants were obtained at limiting low concentrations of dichlorvos in aqueous solution, kobs = kK = 0.0017 s―1.

Energy, Énergie, Geology, Géologie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Energie, Energy, Combustibles, Fuels, Energie. Utilisation thermique des combustibles, Energy. Thermal use of fuels, Pollution atmosphérique due à l'industrie des combustibles et à leur utilisation, Air pollution caused by fuel industries, Mesures. Contrôle, Metering. Control, Acétaldéhyde, Acetaldehyde, Acetaldehído, Additif, Additive, Aditivo, Argon, Argón, Butane, Butano, Cinétique, Kinetics, Cinética, Combustible remplacement, Alternative fuel, Combustible reemplazamiento, Combustion, Combustión, Composé aromatique polycyclique, Polycyclic aromatic compound, Compuesto aromático policíclico, Ecoulement laminaire, Laminar flow, Flujo laminar, Ether, Eter, Formaldéhyde, Formaldehyde, Formaldehído, Modélisation, Modeling, Modelización, Monoxyde de carbone, Carbon monoxide, Carbono monóxido, Mélange carburant, Fuel mixture, Mezcla carburante, Méthane, Methane, Metano, Méthyle éther, Methyl ether, Oxydation, Oxidation, Oxidación, Pollution air, Air pollution, Contaminación aire, Dimethyl ether, Equivalence ratio, Oxygenated additives, and n-Butane

Dimethyl ether (DME) is the simplest ether and it is used as an alternative fuel or fuel additive to reduce toxic emissions from combustion processes. The effects of DME on n-butane oxidation were investigated for two different concentrations of DME in the fuel mixture (i.e., 20% and 50%) and two different fuel-rich equivalence ratios (i.e., 2.6 and 3.0) using detailed chemical kinetic modeling. Reactor model was selected as atmospheric-pressure, adiabatic, tubular reactor, operated under laminar flow conditions. The concentration profiles of major, minor, and trace species were obtained for n-butane/DME/oxygen/argon at six different reactor inlet temperatures, and the results were compared with those attained for pure n-butane oxidation case (n-butane/oxygen/argon). Dimethyl ether addition decreased formations of various toxic species such as carbon monoxide, aromatic species, and polycyclic aromatic hydrocarbons, while it increased the formations of formaldehyde and acetaldehyde. Increasing equivalence ratio increased the formations of carbon monoxide, methane, aromatic species, and polycyclic aromatic hydrocarbons, while its effects on formaldehyde and acetaldehyde were not pronounced under the conditions studied.

Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Matériaux adsorbants, Adsorbents, Sciences appliquees, Applied sciences, Industrie des polymeres, peintures, bois, Polymer industry, paints, wood, Technologie des polymères, Technology of polymers, Formes d'application et semiproduits, Forms of application and semi-finished materials, Fibres et fils, Fibers and threads, Adsorption liquide solide, Liquid solid adsorption, Adsorción líquido sólido, Cellulose, Celulosa, Chélateur, Chelating agent, Quelante, Cinétique, Kinetics, Cinética, Condensation chimique, Condensation reaction, Condensación química, Diamine, Diamina, Dérivé de la cellulose, Cellulose derivatives, Celulosa derivado, Etude expérimentale, Experimental study, Estudio experimental, Fibre artificielle, Artificial fiber, Fibra artificial, Fibre coton, Cotton fiber, Fibra algodón, Formaldéhyde, Formaldehyde, Formaldehído, Ion métallique, Metal ion, Ión metálico, Isotherme adsorption, Adsorption isotherm, Isotermo adsorción, Mercure II, Mercury II, Mercurio II, Milieu aqueux, Aqueous medium, Medio acuoso, Modification chimique, Chemical modification, Modificación química, Morphologie, Morphology, Morfología, Oxydation, Oxidation, Oxidación, Polymère réticulé, Crosslinked polymer, Polímero reticulado, Polymère soufre, Sulfur containing polymer, Polímero azufre, Potassium Thiocyanate, Potassium Thiocyanates, Potasio Tiocianato, Préparation, Preparation, Preparación, Réticulation, Crosslinking, Reticulación, Sélectivité ionique, Ionic selectivity, Selectividad iónica, Empreinte ionique, Cotton fibers, Ion-imprinting, and Thiourea

In the present study, Hg2+ ion-imprinted chelating fibers based on thiourea modified natural cellulosic cotton fibers (Hg-C-TU) were synthesized and characterized using some instrumental techniques such as elemental analysis, scanning electron microscopy (SEM), FTIR, wide angle X-ray and XPS spectroscopy. The modified Hg-C-TU fibers were employed for selective removal of Hg2+ from aqueous solution. Effect of some essential parameters such as pH, temperature, adsorption times and adsorbate concentration were examined to evaluate the optimum adsorption condition. The adsorption kinetics followed the second-order kinetic model indicating that the chemical adsorption is the rate limiting step. Also, the adsorption isotherm experiments showed the best fit with Langmuir model with maximum adsorption capacities 110.3 and 61.8 mg/g for both Hg-C-TU and NI-C-TU, respectively.