Incorporation Of Vanadium Research Articles

The design, synthesis and catalytic performance of vanadium-incorporated mesoporous silica with 3D mesoporous structure for propene epoxidation.

V-containing mesoporous silica with 3D structure was prepared by a hydrothermal procedure using NH4VO3 as the vanadium precursor and with varied reaction mixture pH values (pH = 3 and pH = 5). The combined use of DR UV-vis and H2-TPR techniques confirmed the successful incorporation of vanadium into the structure of the mesoporous silica material. The number of acid sites, evidenced by ammonia TPD, strongly correlates with the vanadium content. Propene oxidation with N2O revealed the noticeable activity of the synthesised vanadium-containing mesoporous materials in epoxidation reactions. The activity of the synthesized vanadosilicates is compared with the performance of vanadium-supported catalysts (on mesoporous silica of 3D structures) prepared by wet-impregnation method. On the basis of TOF analysis indicating the activity of particular vanadium ions, it was evidenced that although the presence of isolated V species is crucial in propene epoxidation, the availability of the active species is of paramount importance for proper vanadium utilization.

Synthesis of ETS-10-like vanadosilicates using 2,6-dimethylpiperidinium cation derivatives as organic templates

Systematic vanadosilicate syntheses were performed using derivatives of 2,6-dimethylpiperidine as organic structure-directing agents (SDAs). Physicochemical analyses of the vanadosilicate materials obtained were carried out by X-ray diffraction (XRD), Raman spectroscopy, infrared (IR) spectroscopy, UV–visible (UV–Vis) spectroscopy, and solid-state NMR spectroscopy (29Si and 51V MAS NMR). The experimental results indicated that the presence of the organic templates had different effects on the final phases of the synthesized vanadosilicates. The XRD results showed that 1,1,2,6-tetramethylpiperidinium (SDA 1) favored synthesis of the known AM-6 vanadosilicates, isostructural to the ETS-10 titanosilicate, while the other organic templates 1,1-diethyl-2,6-dimethylpiperidinium (SDA 2), 6,10-dimethyl-5-azoniaspiro[4.5]decane (SDA 3), and 1,5-dimethyl-6-azoniaspiro[5.5]undecane (SDA 4) directed the formation of vanadosilicates with different phases, such as EVS-10. Strong Raman bands at 870 and 1035 cm−1 indicated vibrational modes associated with the highly symmetric vanadia octahedra. Chemical shifts at −96 ppm (29Si MAS NMR), −610, and −570 ppm (51V MAS NMR) provided further evidence of the incorporation of vanadium into the structures of the vanadosilicates prepared using these novel derivatives of 2,6-dimethylpiperidinium cations as SDAs.

Structural and Photocatalytic Behavior of Vanadium Incorporated ETS-4 Zeolite

In this research Ti-zorite phase (ETS-4) was examined as a photo catalyst for degradation of malachite green dye. Incorporation of Vanadium into framework of ETS-4 was performed in different Ti:V mole ratio within the same preparation conditions. XRD, UV. Visible diffuse reflectance, IR, SEM, and EDX analysis were used to characterize the prepared zeolites. In addition, Photo catalytic degradation of malachite green was chosen as a model reaction to examine the prepared zeolites. The results showed that the pure phase of ETS-4 was attained as only pure phase. Incorporation of Vanadium increases the crystallinity of ETS-4 phase reaches maximum crystallinity at 50% V after which crystallinity decreases again reaches null at 80–100% V samples. SEM and EDX analysis in addition to XRD lattice analysis proved the successful incorporation of V into the framework of zeolite matrix. More than one evidence were arisen that both vanadium and titanium active centers was responsible for photo catalytic degradation. A correlation between the structure and surface titanium active centers were put to elucidate the photo catalytic activity. Three dimensional synergism function was written, finding that, maximum synergism was attained at 5–20 min at 50–70% V.

A Simple and Green Protocol for the Synthesis of 3,4-dihydropyrimidin-2(1H)-ones Using 11-Molybdo-1-vanado phosphoric Acid as a Catalyst Under Ultrasound Irradiation

A one-pot three-component reaction of ethyl acetoacetate, aldehydes and urea has efficiently been carried out in the presence of 11-molybdo-1-vanadophosphoric acid in ethanol at room temperature under ultrasound irradiation to form the corresponding 3,4-dihydropyrimidin 2(1H)-ones in high yields. The 11-molybdo-1-vanadophosphoric acid (H 4 PMo 11 V 1 O 40 ) was prepared and characterized by FT-IR spectroscopy, TG-DTA analysis and XRD analysis techniques. The presence of Keggin structure and incorporation of vanadium into the Keggin structure of synthesized H 4 PMo 11 V 1 O 40 catalyst was confirmed by FT-IR and powder XRD analysis techniques. TG-DTA analysis results indicated that H 4 PMo 11 V 1 O 40 catalyst was thermally stable up to the temperature 434 °C. The present catalytic system is recyclable and can be reused without greater loss of reactivity. DOI: http://dx.doi.org/10.17807/orbital.v11i5.1423

Incorporation of Vanadium and Molybdenum into Yttrium-Arsenotungstates Supported by Amino Acid Ligands

The preference for incorporation of molybdenum over tungsten into specific sites of a family of yttrium-arsenotungstates with amino acid ligands prompted exploration of the incorporation of other metals, affording three new vanadium-containing (V/W and V/Mo/W) analogues: K2(GlyH)10[As4(V2W2)W44Y4O160(Gly)8(H2O)12]·11Gly (1), (MBAH)9(L-NleH)3[As4(V2W2)W44Y4O160(L-Nle)8(H2O)12] (2), and (MBAH)9(L-NleH)3[As4(V2W2)Mo2W42Y4O160(L-Nle)8(H2O)12] (3) (Gly=glycine and L-Nle=l-norleucine, MBAH=4-methylbenzylammonium). These hybrid polyoxometalates all possess a tetrametallic oxo-bridged {VIV2WVI2} central core surrounded by an amino acid-ligated cyclic metal-oxo framework. X-Ray photoelectron, UV-visible reflectance, and electron paramagnetic resonance spectroscopy, together with metal analysis, confirm the incorporation of vanadium into the polyoxometalates, while single crystal X-ray diffraction analysis supports the location of the vanadium atoms in the central core.

Optical Properties, Electronic Structures, and Photocatalytic Performances of Bandgap-Tailored SrBi2Nb2−xVxO9 Compounds

Layered perovskite compounds of SrBi2Nb2−xVxO9 (x = 0.0, 0.02, 0.04, 0.06, and 0.08) were synthesized via a solid-state reaction method. Their optical properties, electronic band structures, and photocatalytic activities under visible light irradiation were investigated for the first time. The incorporation of vanadium into the SrBi2Nb2O9 lattice reduced the bandgap energies, allowing the compounds to effectively absorb visible light. Electronic band structure calculations revealed that the V 3d orbitals caused bandgap narrowing by forming an additional band below the conduction band, while the O 2p and Bi 6p orbitals dominantly contributed to the formation of the valence band. The photocatalytic activity tested under visible light irradiation (>420 nm) revealed that it increased linearly with the V content in the SrBi2Nb2−xVxO9 compounds until saturation at x = 0.06, which was attributed to improved visible light absorption originating from the reduced bandgap energies.

Facile Microemulsion Synthesis of Vanadium-Doped ZnO Nanoparticles to Analyze the Compositional, Optical, and Electronic Properties.

In this work, microemulsion method has been followed to synthesize vanadium-doped Zn1−xVxO (with x = 0.0, 0.02, 0.04, 0.06, 0.08, and 0.10) nanoparticles. The prepared samples are characterized by several techniques to investigate the structural, morphology, electronic, functional bonding, and optical properties. X-ray diffractometer (XRD) analysis confirms the wurtzite phase of the undoped and V-doped ZnO nanoparticles. Variation in the lattice parameters ensures the incorporation of vanadium in the lattice of ZnO. Scanning electron microscopy (SEM) shows that by increasing contents of V ions, the average particle size increases gradually. X-ray Absorption Near Edge Spectroscopy (XANES) at the V L3,2 edge, oxygen K-edge, and Zn L3,2 edge reveals the presence and effect of vanadium contents in the Zn host lattice. Furthermore, the existence of chemical bonding and functional groups are also asserted by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). UV–Visible analysis shows that by increasing V+ contents, a reduction up to 2.92 eV in the energy band gap is observed, which is probably due to an increase in the free electron concentration and change in the lattice parameters.

Reactivity of solid BaCe0.9Y0.1O3 towards liquid V2O5

In this work the reactivity in solid BaCe0.9Y0.1O3-δ - liquid V2O5 system was investigated in order to evaluate the possibility of composite formation in this system. Impregnation of melted vanadium(V) oxide into solid Y-doped BaCeO3 was performed in various temperature and time conditions. Due to the relatively high reactivity of components in this system an analysis of the synthesized materials was divided into discussion of the properties of the reactive layer and the inner part. As was shown, decomposition of Y-doped BaCeO3 in contact with melted vanadium(V) oxide occurs already at temperature 700 °C and results in formation of CeVO4 as one of the main phases. Moreover, the presence of Ba8V7O22 as the intermediate phase was observed. The extension of reaction time and increase of temperature resulted in significant changes in the microstructure and chemical composition of the reactive layer. The incorporation of vanadium into yttrium doped BaCeO3 structure for inner parts of the synthesized materials was postulated based on the modification of the materials electrical properties and chemical stability towards CO2 and H2O. Also, the presence of additional phase in the intergranular voids of doped-BaCeO3 was suggested.

Temperature-Induced Formation of Lubricous Oxides in Vanadium Containing Iron-Based Arc Sprayed Coatings

In the field of surface engineering, the use of self-lubricous coatings with the incorporation of vanadium represent a promising approach to reduce friction, thus contributing to the wear behavior. For vanadium containing hard coatings produced by means of thin film technology, the reduction in friction at elevated temperatures was repeatedly attributed to temperature-induced and tribo-oxidatively formed oxides which act as solid lubricant. Only very few studies focused on the tribological characteristics of vanadium containing arc sprayed coatings. In this study, the tribological characteristics of a vanadium containing iron-based arc sprayed deposit were investigated in dry sliding experiments under ambient conditions and different temperatures. Types of wear at the worn surfaces and counterparts were examined by means of electron microscopy and energy dispersive X-ray (EDX) spectroscopy. The speciation of vanadium in the superficial layer was determined using X-ray absorption near edge structure (XANES) spectroscopy. It was found that the vanadium-containing coating exhibited a distinctly reduction of the coefficient of friction above 450 °C which further decreased with increasing temperature. XANES spectroscopy indicated an increased oxidation state for the V component on the coating surface, suggesting the prevalence of specific vanadium oxides which promote a self-lubricating ability of the coating.

Vanadosilicate with MWW zeolite structure synthesized from VCl3 by cooperative assembly of organic templates

Abstract Aluminum-free MWW structure containing vanadium was easily prepared from a mixture of suitable templates (N,N,N-trimethyl-1-adamantamonium hydroxide (TMAdaOH) and hexamethyleneimine (HMI)). Besides, the use of VCl3 as vanadium source, in which this metal is in low oxidation state (V3+) and the preparation of the synthesis gel under inert atmosphere are crucial to get an efficient incorporation of vanadium into the zeolitic framework. UV–Vis spectrum of the as-synthesized material whose oxidation was prevented by working under inert atmosphere reveals the presence of isolated V3+ sites isomorphically coordinated. Besides, the 29Si MAS NMR spectra and the V K-edge X-ray Absorption Spectroscopy (XAS) analysis show that the vanadium was incorporated into the zeolite framework with formation of V O Si linkages. 13C MAS NMR evidences that both templates are present in the as-synthesized material, showing that the mixture of TMAdaOH and HMI is crucial for obtaining pure crystalline vanadosilicate phase. XAS measurements of the V-containing zeolite during calcination under air showed that initially the sample contains V4+ sites in a square pyramidal geometry, which were completely oxidized to isolated V5+ in Td coordination after calcination.

Crystal Chemistry of Vanadium-Bearing Ellestadite Waste Forms.

Vanadate ellestadites Ca10(SiO4) x(VO4)6-2 x(SO4) xCl2, serving as prototype crystalline matrices for the fixation of pentavalent toxic metals (V, Cr, As), were synthesized and characterized by powder X-ray and neutron diffraction (PXRD and PND), electron probe microanalysis (EPMA), Fourier transform infrared spectroscopy (FTIR), and solid-state nuclear magnetic resonance (SS-NMR). The ellestadites 0.19 < x < 3 adopt the P63/ m structure, while the vanadate endmember Ca10(VO4)6Cl2 is triclinic with space group P1̅. A miscibility gap exists for 0.77 < x < 2.44. The deficiency of Cl in the structure leads to short-range disorder in the tunnel. Toxicity characteristic leaching testing (TCLP) showed the incorporation of vanadium increases ellestadite solubility, and defined a waste loading limit that should not exceed 25 atom % V to ensure small release levels.

The highly selective oxidation of cyclohexane to cyclohexanone and cyclohexanol over VAlPO4 berlinite by oxygen under atmospheric pressure

BackgroundThe oxidation of cyclohexane under mild conditions occupies an important position in the chemical industry. A few soluble transition metals were widely used as homogeneous catalysts in the industrial oxidation of cyclohexane. Because heterogeneous catalysts are more manageable than homogeneous catalysts as regards separation and recycling, in our study, we hydrothermally synthesized and used pure berlinite (AlPO4) and vanadium-incorporated berlinite (VAlPO4) as heterogeneous catalysts in the selective oxidation of cyclohexane with molecular oxygen under atmospheric pressure. The catalysts were characterized by means of by XRD, FT-IR, XPS and SEM. Various influencing factors, such as the kind of solvents, reaction temperature, and reaction time were investigated systematically.ResultsThe XRD characterization identified a berlinite structure associated with both the AlPO4 and VAlPO4 catalysts. The FT-IR result confirmed the incorporation of vanadium into the berlinite framework for VAlPO4. The XPS measurement revealed that the oxygen ions in the VAlPO4 structure possessed a higher binding energy than those in V2O5, and as a result, the lattice oxygen was existed on the surface of the VAlPO4 catalyst. It was found that VAlPO4 catalyzed the selective oxidation of cyclohexane with molecular oxygen under atmospheric pressure, while no activity was detected on using AlPO4. Under optimum reaction conditions (i.e. a 100 mL cyclohexane, 0.1 MPa O2, 353 K, 4 h, 5 mg VAlPO4 and 20 mL acetic acid solvent), a selectivity of KA oil (both cyclohexanol and cyclohexanone) up to 97.2% (with almost 6.8% conversion of cyclohexane) was obtained. Based on these results, a possible mechanism for the selective oxidation of cyclohexane over VAlPO4 was also proposed.ConclusionsAs a heterogeneous catalyst VAlPO4 berlinite is both high active and strong stable for the selective oxidation of cyclohexane with molecular oxygen. We propose that KA oil is formed via a catalytic cycle, which involves activation of the cyclohexane by a key active intermediate species, formed from the nucleophilic addition of the lattice oxygen ion with the carbon in cyclohexane, as well as an oxygen vacancy formed at the VAlPO4 catalyst surface.

Anion–Cation Double Substitution in Transition Metal Dichalcogenide to Accelerate Water Dissociation Kinetic for Electrocatalysis

AbstractUntil now, many works have shown that the hydrogen evolution reaction (HER) performance can be improved by anion or cation substitution into the crystal lattice of pyrite‐structure materials. However, the synergistic effects of anion–cation double substitution for overall enhancement of the catalytic activity remains questionable. Here, the simultaneous incorporation of vanadium and phosphorus into the CoS2 moiety for preparing 3D mesoporous cubic pyrite‐metal Co1‐xVxSP is presented. It is demonstrated that the higher catalytic activity of CoS2 after V incorporation can be primarily attributed to abundance active sites, whereas P substitution is responsible for improving HER kinetics and intrinsic catalyst. Interestingly, due to the synergistic effect of P–V double substitution, the 3D Co1‐xVxSP shows superior electrocatalysis toward the HER with a very small overpotential of 55 mV at 10 mA cm−2, a small Tafel slope of 50 mV dec−1, and a high turnover frequency of 0.45 H2 s−1 at 10 mA cm−2, which is very close to commercial 20% Pt/C. Density functional theory calculation reveals that the superior catalytic activity of the 3D Co1‐xVxSP is contributed by the reduced kinetic energy barrier of rate‐determining HER step as well as the promotion of the desorption H2 gas process.

The Effect of TiO₂ Doped Photocatalytic Nano-Additives on the Hydration and Microstructure of Portland and High Alumina Cements.

Mortars with two different binders (Portland cement (PC) and high alumina cement (HAC)) were modified upon the bulk incorporation of nano-structured photocatalytic additives (bare TiO2, and TiO2 doped with either iron (Fe-TiO2) or vanadium (V-TiO2)). Plastic and hardened state properties of these mortars were assessed in order to study the influence of these nano-additives. Water demand was increased, slightly by bare TiO2 and Fe-TiO2, and strongly by V-TiO2, in agreement with the reduction of the particle size and the tendency to agglomerate. Isothermal calorimetry showed that hydration of the cementitious matrices was accelerated due to additional nucleation sites offered by the nano-additives. TiO2 and doped TiO2 did not show pozzolanic reactivity in the binding systems. Changes in the pore size distribution, mainly the filler effect of the nano-additives, accounted for the increase in compressive strengths measured for HAC mortars. A complex microstructure was seen in calcium aluminate cement mortars, strongly dependent on the curing conditions. Fe-TiO2 was found to be homogeneously distributed whereas the tendency of V-TiO2 to agglomerate was evidenced by elemental distribution maps. Water absorption capacity was not affected by the nano-additive incorporation in HAC mortars, which is a favourable feature for the application of these mortars.

Investigation on the oxidation behavior of AlCrVxN thin films by means of synchrotron radiation and influence on the high temperature friction

Abstract Friction minimization is an important topic which is pursued in research and industry. In addition to the use of lubricants, friction-reducing oxide phases can be utilized which occur during. These oxides are called Magneli phases and especially vanadium oxides exhibit good friction reducing properties. Thereby, the lubrication effect can be traced back to oxygen deficiencies. AlCrN thin films are being used as coatings for tools which have to withstand high temperatures. A further improvement of AlCrN thin films concerning their friction properties is possible by incorporation of vanadium. This study analyzes the temperature dependent oxidation behavior of magnetron sputtered AlCrVN thin films with different vanadium contents up to 13.5 at.-% by means of X-ray diffraction and X-ray absorption near-edge spectroscopy. Up to 400 °C the coatings show no oxidation. A higher temperature of 700 °C leads to an oxidation and formation of Magneli phases of the coatings with vanadium contents above 10.7 at.-%. Friction coefficients, measured by ball-on-disk test are correlated with the oxide formation in order to figure out the effect of vanadium oxides. At 700 °C a decrease of the friction coefficient with increasing vanadium content can be observed, due to the formation of VO 2 , V 2 O 3 and the Magneli phase V 4 O 7 .

Surfactant templated synthesis of porous VOx-ZrO2 catalysts for ethanol conversion to acetaldehyde

Synthesis of VOx-ZrO2 catalysts with hierarchical porosity is reported here for first time. Surface areas of prepared materials reached values up to 211m2/g with the intrinsic porosity on the border between micro- and mesopores. Physico-chemical properties and catalytic activity in ethanol oxidative dehydrogenation to acetaldehyde of these materials are compared with VOx/ZrO2 catalyst obtained by vanadia deposition on the surface of the already synthesized zirconia support with the hierarchical micro-meso-macroporosity with macrochannels of 200–500nm in size. The VOx/ZrO2 sample prepared by deposition of vanadium on hierarchical zirconia exhibits high catalytic activity (TOF=106.9h−1 at 200°C), and especially high selectivity towards acetaldehyde. Acetaldehyde selectivity under reaction conditions varied between 99 and 92%. Directly synthesized VOx-ZrO2 catalysts showed higher selectivity to acetaldehyde compared to VOx/ZrO2 catalyst obtained by vanadia deposition on the surface of the already synthesized zirconia, but significantly lower activity probably due to incorporation of vanadium during the synthesis inside the channel walls where vanadium is not accessible to the gas molecules.

Structural analysis of co‐evaporated In2S3 and In2S3:V for solar cell absorber applications

In this study we use co‐evaporation to grow In2S3 thin films on glass substrates and X‐ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDX) to analyse the structural properties of annealed In2S3 and V‐doped In2S3 for intermediate band solar cell application. We find co‐evaporated In2S3 to be polycrystalline on float glass and with improved crystallinity after annealing in S‐atmosphere. We confirm that excessive incorporation of vanadium into the host structure is possible without formation of secondary crystalline phases. The analysis indicates a reduced crystalline quality after V doping.

Incorporation of vanadium into the framework of hydroxyapatites: importance of the vanadium content and pH conditions during the precipitation step.

Even though vanadium-modified hydroxyapatite (V-HAp) samples are very promising systems for oxidative dehydrogenation of propane, the incorporation of vanadium into the hydroxyapatite framework was reported to be limited and to lead to over-stoichiometric compounds. Here, the synthesis of a Ca10(PO4)6-x(VO4)x(OH)2 stoichiometric solid solution using a co-precipitation method is monitored in the whole composition range (0 ≤ x ≤ 6) by controlling the pH of the precipitation medium, with continuous (the first series of samples) or periodic (the second series of samples) addition of NH4OH during the precipitation step or during the maturation step, respectively. It is demonstrated that the changes in pH conditions result in materials of a substantial difference in terms of the final composition. From XRD patterns and Rietveld refinements, a solid solution V-HAp phase was found to be exclusively obtained for the first series of samples for x varying from 0 to 6. This also occurred in the second series of samples but only for x lower than 4. For 4 ≤ x ≤ 5.22, the materials were composed of a mixture of V-HAp and Ca2V2O7, whereas for a x value of 6 only Ca2V2O7 was formed. The predominance of polymeric V species in solution at a high vanadium concentration deduced from the diagram of speciation of vanadium accounts for the preferential formation of Ca2V2O7 under these particular conditions. However, provided that a higher pH value was maintained, isolated VO3(OH)2- species are predominant, which accounts for the incorporation of isolated vanadates into the hydroxyapatite framework and for the well-controlled stoichiometry with Ca/(P + V) ratios found to be close to 1.67. Such a very good accommodation of vanadium in the hydroxyapatite framework is illustrated by the characterization of the local surrounding of phosphorus and vanadium species using 31P and 51V NMR, Raman and UV-vis spectroscopies.

Doping-induced stability in vanadium-doped ZnO quantum well wires (QWW): Combination of DFT calculations within experimental measurements

ZnO quantum well wires (QWW) have grown on glass substrates by an inexpensive, simplified and enhanced spray pyrolysis technique then doped by Vanadium. The effects of V-doping on the structural, morphological and optical properties of the QWW were investigated experimentally and theoretically. The accuracy of control can be achieved on functional performance by adjusting vanadium doping extent. The incorporation of Vanadium in ZnO-QWW induced the formation of band tailing in states. The interactions with phonons and the presence of a tail absorption profile are following the empirical Urbach law. The electronic structure using density functional theory have shown the changes induced by vanadium doping in ZnO-QWW, where the phonon band structure and density of states were reported. The DFT results showed a good agreement with the lattice compatibility theory as well as with the experimental results.

Synthesis and physico-chemical studies of vanadium doped zinc oxide nanoparticles and its photocatalysis

In this work we report the synthesis of vanadium doped zinc oxide nanoparticles by a sol–gel processing technique, and the vanadium concentrations in zinc oxide varied from 1 to 5 at.%. In our approach, the water for hydrolysis was slowly released by esterification reaction followed by a supercritical drying in ethyl alcohol. All synthesized samples were annealed in air at 500 °C for 2 h. The obtained catalysts were characterized by fluorescence X, X-ray diffraction, transition electron microscopy and UV measurements. The structural properties showed that the obtained nanoparticles are single phase wurtzite structure and no secondary phases were detected which indicated that V ions substituted for Zn ions. The energy gap decreased gradually by increasing the doping concentration of V. The photocatalytic activities of powders were evaluated by the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Compared with undoped ZnO and TiO2 P25 Degussa, it was found that the incorporation of vanadium in ZnO enhances the photocatalytic degradation, and ZnO:V3% is most active photocatalyst for MB degradation than the other V-doped samples.