Oxidation of benzyl alcohol by K<Subscript>2</Subscript>FeO<Subscript>4</Subscript> to benzaldehyde over zeolites

A novel and green procedure for benzaldehyde synthesis by potassium ferrate oxidation of benzyl alcohol employing zeolite catalysts was studied. The prepared oxidant was characterized by SEM and XRD. The catalytic activity of various solid catalysts was studied using benzyl alcohol as a model compound. USY was found to be a very efficient catalyst for this particular oxidation process. Benzaldehyde yields up to 96.0% could be obtained at the following optimal conditions: 0.2 mL of benzyl alcohol, 4 mmol of K₂FeO₄, 0.5 g of USY zeolite; 20 mL of cyclohexene, 0.3 mL of acetic acid (36 wt %), 30°C temperature, 4 h reaction time.     

Comparative study of the synthesis of CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> in silica through the polymerized complex route of the sol–gel method

In this work the synthesis of CoFe₂O₄-SiO₂ and NiFe₂O₄-SiO₂ nanocomposites was studied via the sol–gel method, using the polymerized complex route. The polymerized precursors obtained by the reaction of citric acid, ethylene glycol, tetraethylorthosilicate, ferric nitrate, and cobalt nitrate or nickel chloride were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. NMR and IR spectra of the precursors, without and with metallic ions, show the formation of polymeric chains with ester and ether groups and complexes of metal-polymeric precursor. The nanocomposites were obtained by the thermal decomposition of the organic fraction and characterized by X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). XRD patterns show the formation of CoFe₂O₄ and NiFe₂O₄ in an amorphous silica matrix above 400 °C in both cases. When the calcination temperature was 800 °C the particle size of the crystalline phases, calculated using the Scherrer equation, reached ∼35 nm for the two oxides. VSM plots show the ferrimagnetic behavior that is expected for this type of magnetic material; the magnetization at 12.5 KOe of the CoFe₂O₄-SiO₂ and NiFe₂O₄-SiO₂ compounds was 29.5 and 17.4 emu/g, respectively, for samples treated at 800 °C.     

Tin trifluoroacetylacetonate [Sn(C<Subscript>5</Subscript>H<Subscript>4</Subscript>O<Subscript>2</Subscript>F<Subscript>3</Subscript>)<Subscript>2</Subscript>] as a precursor of tin dioxide in APCVD process

A new method of synthesis of volatile complex, tin trifluoroacetylacetonate [Sn(C₅H₄O₂F₃)₂], was proposed. The prepared compound was identified by IR spectroscopy, CH analysis, X-ray powder diffraction, and DTA/TGA, the composition was confirmed by MALDI-TOF mass spectrometry, crystal structure was established. Thin films of tin dioxide on silicon were obtained by atmospheric pressure chemical vapor deposition using [Sn(C₅H₄O₂F₃)₂] as a precursor. The morphology and composition of the films were studied by scanning electron microscopy, EDX elemental analysis, and X-ray powder diffraction. Surface resistance and light transmission in visible and near IR region were studied.     

Preparation of Solid Superacid Catalysts and Oil Oxidative Desulfurization Using K<Subscript>2</Subscript>FeO<Subscript>4</Subscript>

A \(\rm{SO_4^{2-}}\)/MCM-41 superacid catalyst was prepared by impregnation and characterized by various methods. A novel procedure for oxidative desulfurization of simulated light fuel oil using K₂FeO₄ over \(\rm{SO_4^{2-}}\)/MCM-41 was developed. Fourier transform infrared spectroscopy (FTIR) and low-angle X-ray diffractometry (XRD) show that the material synthesized by the precipitation-sol-hydrothermal method is mobil composition of matter no. 41 (MCM-41). Thermogravimetry/differential thermal analysis (TG-DTA) shows that when the calcination temperature is higher than 300°.     

Electrochemical Characterisations of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–13%TiO<Subscript>2</Subscript> Coated by Atmospheric Plasma Spray

Atmospheric plasma sprayed alumina–titania (Al₂O₃–13%TiO₂), coated on stainless steel (XC18), were characterized. The coating structure and morphology were studied by scanning electron microscopy. Their presented micro cracks, laminar splats. The coatings were studied by X-ray diffraction. The main phase transformation is that of α-Al₂O₃ into metastable γ-Al₂O₃. The α-Al₂O₃ phase is due to the occurrence of partially melted particles Electrochemical behaviours of coatings were mainly investigated by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.01 M [K₃Fe(CN)₆/K₄Fe(CN)₆] as a function of process parameters. Also, schematic equivalent circuit was proposed. The results were expected to facilitate the understanding and improvement of the coating behaviours.     

X-ray fluorescence determination of the FeO/Fe<Subscript>2</Subscript>O<Stack><Subscript>3</Subscript><Superscript>tot</Superscript></Stack> ratio in rocks

Chances for estimating the FeO/Fe₂O₃^tot ratio in rocks by the K and L series of X-ray fluorescence spectra are studied. The errors in the determination of FeO/Fe₂O₃^tot by the intensity ratio of the Kβ_2,5/Kβ_1,3 and Lβ/Lα_1,2 lines are compared. The relative standard deviation of determining FeO using a set of 49 standard samples of eruptive rocks varies in the range 5–16%, depending on the ratio FeO/Fe₂O₃^tot and the concentration of FeO. The better precision is attainable for a ratio above 0.45 at a FeO concentration in the range 5–15%. For samples of andesites and basalts, the relative standard deviation is better than 4%, for rocks of the granite family it is 23% at FeO concentrations below 3%. For samples of metamorphic and sedimentary rocks, the error of FeO determination is higher than that for the eruptive ones. For samples with the ratio FeO/Fe/Fe₂O₃^tot < 0.25, the deviation may exceed 30 rel %. In contrast to chemical analysis, the X-ray fluorescence method appears advantageous in time and cost of sample preparation and can be used for routine analysis in geochemical research.     

H<Subscript>3</Subscript>PMo<Subscript>12</Subscript>O<Subscript>40</Subscript> immobilized chitosan/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> as a novel efficient,green and recyclable nanocatalyst in the synthesis of pyrano-pyrazole derivatives

A novel nanomagnetic composite heteropolyacid immobilized chitosan/Fe₃O₄ was prepared via a facile one-pot synthetic approach. This magnetically recoverable nanocatalyst, H₃PMo₁₂O₄₀/chitosan/Fe₃O₄ (PMo/chit/Fe₃O₄), was fully characterized by XRD, FTIR, SEM and EDX analysis methods. A rapid, efficient and the chemoselective synthesis of different pyrano-pyrazole derivatives was achieved in excellent yields via a one-pot four-component reaction in the presence of catalytic amount of PMo/Chit/Fe₃O₄.     

Determination of the enthalpy of fusion of K<Subscript>3</Subscript>TaO<Subscript>2</Subscript>F<Subscript>4</Subscript> and KTaF<Subscript>6</Subscript>

Areas of fusion and crystallization peaks of K₃TaO₂F₄ and KTaF₆ were measured using the DSC mode of a high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities, considering the temperature dependence of the calorimeter sensitivity, values of the fusion enthalpy of K₃TaO₂F₄ at the fusion temperature of 1181 K of (43 ± 4) kJ mol⁻¹ and of KTaF₆ at the fusion temperature of 760 K of (8 ± 1) kJ mol⁻¹ were determined.     

Whitlockite solid solutions in the Ca<Subscript>3</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript>-K<Subscript>3</Subscript>VO<Subscript>4</Subscript>-NdVO<Subscript>4</Subscript> system

Phase equilibria in the Ca₃(VO₄)₂-K₃VO₄-NdVO₄ system have been studied. An extensive calcium orthovanadate-based solid solution was found to form with the boundary compositions as follows: Ca₃(VO₄)₂-Ca₉Nd(VO₄)₇-Ca_9.33K_2.33(VO₄)₇-Ca_7.88K_2.63Nd_0.87(VO₄)₇. The unit cell parameters of the whit-lockite vanadates synthesized increase as the potassium and neodymium contents increase. Phase transitions from the low-temperature β phase to the β′ centrosymmetrical structure in Ca_{9.33 − 5z} K_{2.33 + z} Nd_3z (VO₄)₇ vanadates have been studied dilatometrically. The increase in the β ai β′ transition temperature caused by potassium is interpreted as arising from the filling in of vacant cation positions M(4) and M(6).     

Synthesis and characterization of macroporous Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>/C composites as cathode materials for Li-ion batteries

The macroporous Li₃V₂(PO₄)₃/C composite was synthesized by oxalic acid-assisted carbon thermal reaction, and the common Li₃V₂(PO₄)₃/C composite was also prepared for comparison. These samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical performance tests. Based on XRD and SEM results, the sample has monoclinic structure and macroporous morphology when oxalic acid is introduced. Electrochemical tests show that the macroporous Li₃V₂(PO₄)₃/C sample has a high initial discharge capacity (130 mAh g⁻¹ at 0.1 C) and a reversible discharge capacity of 124.9 mAh g⁻¹ over 20 cycles. Moreover, the discharge capacity of the sample is still 91.5 mAh g⁻¹, even at a high rate of 2 C, which is better than that of the sample with common morphology. The improvement in electrochemical performance should be attributed to its improved lithium ion diffusion coefficient for the macroporous morphology, which was verfied by cyclic voltammetry and electrochemical impedance spectroscopy.     

Synthesis and characterization of magnetically nanoparticles of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@APTMS@ZrCp<Subscript>2</Subscript> as a novel and reusable catalyst for convenient reduction of nitro compounds with glycerol

The present paper describes the synthesis of magnetically nanoparticles of zirconocene-modified magnetite, Fe₃O₄@APTMS@ZrCp₂, as a new generation in heterogeneous and reusable type nanocatalysts. The prepared zirconocene nanocomposite was characterized using FT-IR, SEM, XRD, EDX, AGFM, ICP–OES, TGA and BET analyses. The core–shell nanocatalyst exhibited an excellent catalytic activity towards glycerol reduction of various nitro compounds to the corresponding amines. All reactions were carried out in H₂O at room temperature (40–90 min) to afford amines in high to excellent yields. Reusability of the core–shell zirconocene was examined 5 times without significant loss of its catalytic activity.     

Preparation and characterization of superconducting YBa<Subscript>2</Subscript>(Cu<Subscript>1−x</Subscript>Cr<Subscript>x</Subscript>)<Subscript>4</Subscript>O<Subscript>8</Subscript> oxides by thermal analysis

In this study the formation of chromium substituted YBa₂Cu₄O₈ (Y-124) superconductors has been investigated by TG/DTA measurements. The YBa₂(Cu_1−xCr_x)₄O₈ ceramics with nominal compositions of x=0.01, 0.03, 0.05, 0.10 and 0.20 have been prepared by an aqueous sol-gel method using aqueous mixtures of the corresponding metal acetates and nitrates. Homogeneous precursor gels were obtained by complexing metal ions with tartaric acid. To assist the interpretation of the results obtained the synthesis products were additionally characterized by X-ray powder diffraction (XRD) and resistivity measurements. It was determined that doping the YBa₂Cu₄O₈ phase with chromium has a strong effect on the phase purity and superconducting properties of the synthesis products.     

Synthesis of ammonia from natural gas at atmospheric pressure with doped ceria–Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>–K<Subscript>3</Subscript>PO<Subscript>4</Subscript> composite electrolyte and its proton conductivity at intermediate temperature

A new type of oxide–salt composite electrolyte, yttrium doped ceria YDC–Ca₃(PO₄)₂–K₃PO₄, was developed and demonstrated for its promising use for ammonia synthesis. Using this composite electrolyte, ammonia was synthesized from nitrogen and natural gas at atmospheric pressure in the solid-state proton conducting cell reactor, and the optimal condition for ammonia production was determined . The evolved rate of ammonia is up to 6.95×10⁻⁹ mol s⁻¹ cm⁻².     

Low-temperature catalytic preparation of multi-wall MoS<Subscript>2</Subscript> nanotubes

In the catalytic reduction atmosphere of H₂+CH₄+C₄H₄S, the ball-milled precursor (NH₄)₂MoS₄ is heated to 300°C for decomposition. The as-synthesized product is characterized by XRD, SEM, HRTEM, EDX, and BET. The results show that multi-wall MoS₂ nanotubes are obtained. The length of the nanotubes is around 3–5 μm. The diameters of the nanotubes are homogeneous, with an inner diameter of ∼15 nm, an outer diameter of ∼30 nm, and an interlayer (002) d-spacing of 0.63 nm. This catalytic thermal reaction occurring at low temperatures is important for the large-scale preparation of similar transition-metal disulfide nanotubes.     

Obtaining of Ni<Subscript>0.65</Subscript>Zn<Subscript>0.35</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposites by thermal decomposition of complex compounds embedded in silica matrix

This article presents the results of our investigation on the obtaining of Ni_0.65Zn_0.35Fe₂O₄ ferrite nanoparticles embedded in a SiO₂ matrix using a modified sol–gel synthesis method, starting from tetraethylorthosilicate (TEOS), metal (Fe^III,Ni^II,Zn^II) nitrates and ethylene glycol (EG). This method consists in the formation of carboxylate type complexes, inside the silica matrix, used as forerunners for the ferrite/silica nanocomposites. We prepared gels with different compositions, in order to obtain, through a suitable thermal treatment, the nanocomposites (Ni_0.65Zn_0.35Fe₂O₄)_x–(SiO₂)_100–x (where x=10, 20, 30, 40, 50, 60 mass%). The synthesized gels were studied by differential thermal analysis (DTA), thermogravimetry (TG) and FTIR spectroscopy. The formation of Ni–Zn ferrite in the silica matrix and the behavior in an external magnetic field were studied by X-ray diffraction (XRD) and quasi-static magnetic measurements (50 Hz).     

Synthesis,Structure and Isomerism of the [Fe<Subscript>3</Subscript>Pt(μ<Subscript>4</Subscript>-Q)(CO)<Subscript>9</Subscript>(dppm)] Clusters (Q = Se,Te; dppm = Ph<Subscript>2</Subscript>PCH<Subscript>2</Subscript>PPh<Subscript>2</Subscript>)

The reaction of K₂[Fe₃(μ₃-Q)(CO)₉] (Q = Se (K₂[1a]), Te (K₂[1b])) with [(dppm)PtCl₂] leads to the addition of a [(dppm)Pt]²⁺ unit to a Fe₂Q face of the initial cluster. By this way new heteronuclear clusters [Fe₃Pt(μ₃-Q)(CO)₉(dppm)] were obtained possessing a butterfly-shaped cluster core bridged by a μ₄-Q unit. It has been found that the resulting Fe-Pt clusters exist as equilibrium mixtures of two isomeric forms in solution differing by the dppm coordination mode: as a chelate ligand coordinated to Pt or as a bridging ligand coordinated to Pt and Fe atoms. The mixtures of isomers can be separated by chromatography and the pure isomers can be isolated as stable crystalline phases. Solutions of both isomers attain equilibrium at normal conditions in about 1 month as found by NMR. Dedicated to Professor Dieter Fenske in the occasion of his 65th birthday.     

Synthesis and structure of the framework coordination polymer based on the cluster anion [Nb<Subscript>4</Subscript>OTe<Subscript>4</Subscript>(CN)<Subscript>12</Subscript>]<Superscript>6−</Superscript> and Mn<Superscript>II</Superscript> aqua complexes

Dark-brown plate crystals of the [Mn₇(H₂O)₂₆{Nb₄OTe₄(CN)₁₂} ₂](OH)₂·11H₂O compound (1) were prepared by the reaction of an aqueous ammonia solution of the K₆[Nb₄OTe₄(CN)₁₂]{K₂CO₃{KOH{8H₂O complex with a glycerol solution of manganese(II) nitrate. The structure of complex 1 was established by X-ray diffraction. Compound 1 has a polymer structure containing four types of manganese atoms. The nitrogen atoms of eight cyano groups of the tetranuclear niobium cluster are coordinated to the manganese atoms to form a {2,3,8}-connected three-dimensional network. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 224–228, February, 2007.     

Constant current anodic stripping chronopotentiometric determination of uranium in uranium mineral ores via accumulation of K<Subscript>2</Subscript>UO<Subscript>2</Subscript>[Fe(CN)<Subscript>6</Subscript>] on the palladium plated aluminum electrode

In the present work the uranyl hexacyanoferrate (K₂UO₂[Fe(CN)₆]) is deposited on the palladized aluminum (Pd-Al) electrode from a \textUO₂^{2 +} + \textFe( \textCN )₆ ^{- 3} {\text{UO}}_{2}^{2 + } + {\text{Fe}}\left( {\text{CN}} \right)_{6}^{ - 3} solution. Then the anodic stripping chronopotentiometry (ASCP) was used to strip the K₂UO₂[Fe(CN)₆] from the Pd-Al surface. The operational conditions including: pH, K₃Fe(CN)₆ concentration, deposition potential, deposition time and stripping current were optimized. The ASCP calibration graph was linear in concentration range 10–460 μM. of \textUO₂^{2 +} {\text{UO}}_{2}^{2 + } and the detection limit was 8.5 μM. The interference of some concomitant ions during the deposition process of K₂UO₂[Fe(CN)₆] was studied. The proposed method was successfully applied for analysis of some uranium mineral ores.     

Synthesis,structure, and third-order nonlinear optical properties of W/S cluster [Fe(DMF)<Subscript>6</Subscript>][W<Subscript>2</Subscript>(μ<Subscript>2</Subscript>-S)<Subscript>2</Subscript>S<Subscript>4</Subscript>]

The homometal cluster [Fe(DMF)₆][W₂(μ₂-S)₂S₄] (I) was successfully synthesized by low-temperature solid-state reactions. X-ray single-crystal diffraction studies suggest that compound I is a dinuclear anion cluster. The compound was characterized by elemental analyses, IR spectra, and UV-Vis spectra. The third-order nonlinear optical (NLO) properties of the cluster were also investigated and exhibited nice nonlinear saturation absorption (α₂ < 0) that is rarer than reverse saturation absorption (α₂ > 0) and self-defocusing property (n ₂ < 0) and self-defocusing performance with modulus of the hyperpolarizabilities (9.547 × 10⁻³¹ esu) for I. The article was submitted by the authors in English.     

Determination of the enthalpy of fusion of K<Subscript>3</Subscript>NbO<Subscript>2</Subscript>F<Subscript>4</Subscript>

Areas of fusion and crystallization peaks of K₃NbO₂F₄ were measured using the DCS mode of a high-temperature calorimeter (SETARAM 1800 K). On the basis of these quantities, considering the temperature dependence of the calorimeter sensitivity, the value of the fusion enthalpy of K₃NbO₂F₄ of (98 ± 6) kJ mol⁻¹ was determined at the fusion temperature of 1257 K.