Catalytic oxidation of 4-tert-butyltoluene over Ti-MCM-41

The surface-grafted titanium MCM-41 materials were prepared by anchoring titanocene onto the inner walls of MCM-41. The materials were characterized by powder X-ray diffraction (XRD), N2 adsorption-desorption isotherm and diffuse reflectance UV-visible (UV-vis) spectroscopies. The catalytic properties of Ti-MCM-41 were tested in oxidation of 4-tert-butyltoluene with tert-butylhydroperoxide (TBHP) in liquid phase. MCM-41 with loading 4.8 mol% Ti gave the maximal conversions of 23.6% of 4-tert-butyltoluene with a complete selectivity to 4-tert-butylbenzaldehyde.     

Solvent effect on the kinetics of oxidation of [Co(en)2amS]2+ by IO4−

The dependence of the rate constants for the oxidation of [Co(en)2amS]2+ (amS=–SCH2CH2NH2 2– by IO4– on solvent composition has been established for aqueous mixtures of MeOH, i-PrOH, t-BuOH, urea (U), ethylene carbonate (EC), acetonitrile (AN), dimethyl formamide (DMF) and acetone (Me2CO). Addition of aprotic cosolvents leads to marked decrease in the reaction rate in comparison to monohydroxylic alcohols. Alcohols inhibit the reaction rate in order MeOH < i-PrOH < t-BuOH. The change in solvation on going from the initial to the transition state are discussed in terms of the Gibbs transfer function, Gt0.     

Catalytic behavior of nanoparticle α-PtO2 for ethanol oxidation

Fusion method is used to prepare α-PtO₂ and has a special needle-like microcrystalline morphology, with a diameter of ca. 6 nm and a length of ca. 50 nm. The two Pt–O bonds of α-PtO₂ are different in strength and α-PtO₂ decomposes thermally to Pt⁰ in two steps. α-PtO₂ is a p-type oxide semiconductor with a band-gap of 1.84 eV. α-PtO₂ is easily reduced by ethanol, its reduction product, Pt⁰, can directionally catalyze the oxidation of ethanol to acetic acid in the presence of air, while acetaldehyde, acetal and ethyl acetate are intermediates.     

Practical and versatile oxidation of alcohol using novel Na2WO4–H2O2 system under neutral conditions

This paper presents a novel Na₂WO₄–H₂O₂ oxidation system. The oxidation of alcohol to ketone or aldehyde was carried out by using N,N-dimethylacetamide, hydrogen peroxide, and a catalytic amount of disodium tungstate dihydrate under neutral conditions. This method is very simple, practical for large-scale manufacturing, and applicable to a variety of substrates including an acid-sensitive substrate. Disodium tetraperoxotungstate dihydrate (Na₂[W(O₂)₄]·2H₂O) was isolated from a mixture of N,N-dimethylacetamide, hydrogen peroxide, and disodium tungstate dihydrate, and a proposal reaction mechanism is discussed in this paper.     

Photochemistry of (Me3P)4Mo(η-CO2)2: Deoxygenation of coordinated carbon dioxide and phosphine oxidation

Irradiation of the title compound 1 through quartz in toluene solution at − 20°C produces cis-Mo(CO)₂(PMe₃)₄ and OPMe₃ as the major products along with lesser amounts of mer- and _fac-Mo(CO)₃(PMe₃)₃ and Mo(CO)PMe₃) ₅. Irradiation of 1 through Pyrex produces in addition substantial amounts of an unstable species formulated as trans-Mo (CO)₂(PMe₃)₄.     

Synthesis of anisotropic Cu2−xS-based nanostructures by thermal oxidation

Journal of Thermal Analysis and Calorimetry - Flower-like copper sulfides nanostructures were synthesized via the solvothermal route. The structural, optical and electrochemical properties of the...     

Microwave-assisted Kornblum oxidation of organic halides

Microwave-assisted Kornblum oxidation is proved to be an effective way to obtain aldehyde and ketones from their corresponding chlorides. Under microwave irradiation, not only the reaction time was greatly decreased, due to avoiding the by-product, the yield was increased. It is noteworthy that the scope of the method was broadly expanded.     

Electrochemical oxidation of organosilicon compounds: V. Electrochemical oxidation of α-silyethers. remarkable effect of silicon on oxidation potentials and reaction pathways

Substitution of a silyl group for hydrogen at the α-position of ethers caused a significant decrease in their oxidation potentials. This effect is attributed to an interaction of the carbonsilicon σ-bond with the lone pair of the oxygen atom. The preparative anodic oxidation of α-silylethers proceeded smoothly in methanol and the carbonsilicon bond was selectively cleaved to give the corresponding acetals.     

Degradation of 4-chlorophenol in aqueous solution by γ-radiation and ozone oxidation

The application of radiation technology in the en-vironmental protection was listed as one of the mostimportant research fields by the International AtomicEnergy Agency (IAEA) for the peaceful use of nuclearenergy. It has great research value and potential appli-cation. Because of their broad-spectrum antimicrobialproperties, Cholophenols (CPs) have been used aspreservative agents for wood, paints, vegetable fibersand leather and as disinfectants. In addition, they havebeen widely employed…     

Spectroscopic characterization of mechanisms of oxidation of Phe by SO_4~- radical: A pulse radiolysis study

By using time-resolved kinetic spectrophotometry and pulse radiolysis technique, the oxidation of Phe by SO4- radical has been investigated both in aqueous and water/acetonitrilemixed solutions. The results reveal that attack of the oxidizing SO4- radical on Phe leads directlyto the formation of Phe cation radical 3 with a strong absorption peak at 310 nm, then it proceeds in three competitive reactions via either hydroxylation, deprotonation or decarboxylation, which were found to be strongly dependent upon the ionization state of the substitutes -COOH and -NH2 and the nature of the solvents. Decarboxylation takes place only when the carboxyl group is deprotonated. At high pH deprotonation of Phe cation radical 3 is much easier to occur than that in neutral or acid solutions. Moreover, with addition of acetonitrile, deprotonation is more predominant than hydroxylation, whereas in aqueous solutions hydroxylation is much easier to occur.     

Study on catalytic oxidation of planar binuclear copper phthalocyanine on 2-mercaptoethanol

Mononuclear copper phthalocyanine (CuPc) and binuclear copper phthalocyanine (Cu2Pc2) were synthesized by the phenylanhydride-urea route, and their catalytic oxidation activity on 2-mercaptoethanol was studied. Based on the experimental results, a catalytic mechanism of Cu2Pc2 on 2-mercaptoethanol has been proposed. Furthermore, the effects of pH, Cu2Pc2 concentration, and temperature on the catalytic oxidation activity were evaluated. The results showed that CuPc has no catalytic activity, while Cu2Pc2 has high catalytic oxidation activity towards 2-mercaptoethanol with the optimal activity at pH 11. The reaction can further be enhanced by increasing Cu2Pc2 concentration and temperature, due to its endothermic characteristics.     

Sol–gel preparation and photocatalytic performance of TiO2/SrAl2O4: Eu2+, Dy3+ toward the oxidation of gaseous benzene

It has been found that the photocatalytic activity of TiO₂ toward the decomposition of gaseous benzene can be greatly enhanced by loading TiO₂ on the surface of SrAl₂O₄: Eu²⁺, Dy³⁺ using sol–gel technology. The prepared photocatalyst was characterized by BET, XRD, and XPS analyses. XRD results reveal that the peaks of titania in either rutile or anatase form are not detected by XRD in the 2θ region from 20° to 50°. The binding energy values of Ti 2p of pure TiO₂ are 458.90 and 464.60 eV, while for TiO₂/SrAl₂O₄: Eu²⁺, Dy³⁺, the binding energy values of Ti 2p are 458.50 and 464.20 eV. The results indicate that the optimum loading of TiO₂ is 1 wt% and TiO₂/SrAl₂O₄: Eu²⁺, Dy³⁺ (1 wt%) demonstrates 1.4 times the photocatalytic activity of that of pure TiO₂, but the underlying mechanism of SrAl₂O₄: Eu²⁺, Dy³⁺ in the photocatalytic reaction remains to be unraveled.     

Kinetics of uncatalysed and Mn2+ -catalysed oxidation of hydrazine by [MnIV 3 (μ-O)4(bipy)4(H2O)2]4+ ion in aqueous acid

In aqueous acid, hydrazine reduces [Mn^IV ₃(-O)₄(bipy)₄(H₂O)₂]⁴⁺, (1), quantitatively to [Mn^III,IV ₂(-O)₂(bipy)₄]³⁺, (2), and Mn²⁺ if [N₂H⁺ ₅] 2 × (stoichiometric amount). At higher [N₂H⁺ ₅], reduction proceeds up to Mn²⁺. The reduction of (1) to (2) is strongly catalysed by Mn²⁺ and the absorbance (A _t ) versus time (t) graphs have sigmoidal shapes. The graphs become steeper with increasing amounts of added Mn²⁺ and N₂H⁺ ₅, but remain unchanged when [H⁺] is changed. The A _t – t graphs, under various experimental conditions, can all be simulated with a single set of second order rate constants, estimated for the individual steps in a proposed reaction scheme, in which the catalytic action of Mn²⁺ involves a one-electron and a two-electron reduced form of (1), but not (1) itself. The absence of any proton-dependence of the reaction rate refutes an electroprotic mechanism and an inner-sphere mechanism appears to be most likely for the reduction of (1) by N₂H⁺ ₅     

Synchronization of local oscillators in oxidation reactions of C1–C4 hydrocarbons over metal catalysts

The synchronization of reaction rate oscillations in the oxidation of C₁–C₄ hydrocarbons over polycrystalline nickel, cobalt, and palladium foils has been investigated. The synchronization of foil temperature oscillations during the reaction takes place via the diffusion of the reactants in the gas phase. For the nickel catalysts, the synchronization of the oscillators occurs in the same phase, while for the palladium catalysts, both in-phase and antiphase oscillations are observed. This distinction between the dynamic behaviors of the systems of two coupled oscillators is due to the fact that the mechanism of reaction rate oscillations varies from one metal to another.     

Swern oxidation of a hindered β-hydroxyester

The highly hindered β-hydroxyester 3 fails to oxidize under the usual Swern reaction conditions, whereas closely related compounds react successfully. Swern oxidation of 3 occurs if the work-up conditions are modified or if diazabicycloundecane (DBU) rather than triethylamine (TEA) is used as the base in the reation. A mechanistic rationale is proposed in which the kinetic acidity of a dimethylsulfoxonium salt derived from 3 is postulated to be suppressed by intramolecular complexation.     

Kinetics of oxidation of β-picoline to nicotinic acid over vanadia-titania catalyst. 4. Kinetic model

A kinetic model for the β-picoline oxidation over vanadia-titania catalyst is presented. The model covers the reaction mechanism, temperature dependences and a system of kinetic equations. The activation energies and constants in these equations are calculated.     

Surface oxidation and water desorption of CdS

The surface oxidation and HP desorption of powder CdS were studied by means of X-ray photoetectron spectroscopy (XPS), quadrupole mass spectrometry (QMS) and in-situ FTIR. The results show that with the changes of surface composition and the elongation of store time of CdS there are four types of H2O thermally desorbed at different temperatures. It has also been found that through high-temperature air treatment for a short time the oxidized surface layer of CdS can prevent O2 and H2O in air from further attacking the inner CdS molecules.     

The effect of hydrogen reduction of α-MnO2 on formaldehyde oxidation: The roles of oxygen vacancies

A series of α-MnO₂ catalysts with various Mn valence states were treated by hydrogen reduction for different periods of time. Their catalytic capacity for formaldehyde (HCHO) oxidation was evaluated. The results indicated that hydrogen reduction dramatically improves the catalytic performance of α-MnO₂ in HCHO oxidation. The α-MnO₂ sample reduced by hydrogen for 2 h possessed superior activity and could completely oxidize 150 ppm HCHO to CO₂ and H₂O at 70 °C. Multiple characterization results illustrated that hydrogen reduction contributed to the production of more oxygen vacancies. The oxygen vacancies on the catalyst surface enhanced the adsorption, activation and mobility of O₂ molecules, and thereby enhanced HCHO catalytic oxidation. This study provides novel insight into the design of outstanding MnO_x catalysts for HCHO oxidation at low temperature.     

Catalytic reduction of NOx and oxidation of dichloroethane over α-MnO2 catalysts: Properties-Reactivity relationship

The reduction ability of NO to N₂ and the oxidation performance of 1,2-dichloroethane (DCE) over α-MnO₂ catalysts were investigated. The results show that α-MnO₂-3 exhibited the highest catalytic activity in 63.5 % conversion of NO_x reduction by C₃H₈ at 250 °C, and 80 % conversion of DCE combustion by O₂ at 338 °C. It is revealed the active phase of α-MnO₂-3 is tetragonal α-MnO₂ with the selectively exposed plane of (2 1 1). It was proposed the high DCE decomposition of α-MnO₂-3 was ascribed to the redox properties. The overall characterization results revealed that α-MnO₂-3 catalyst preserves more active sites of low valence Mn and higher surface adsorbed oxygen (O_ads) /lattice oxygen (O_latt) at the outermost layers, and lower reduction temperature in H₂-TPR profiles than that of other catalysts. Meanwhile, NH₃-TPD profile of α-MnO₂-3 also shows a large number of acid sites promote NO_x reduction.