Incorporation Of Titanium Research Articles

Microwave-induced fast incorporation of titanium into UiO-66 metal-organic frameworks for enhanced photocatalytic properties.

UiO-66 metal-organic frameworks (MOFs) can be endowed with greatly enhanced photocatalytic properties by introducing titanium into the frameworks. A microwave-assisted method was developed to substitute the zirconium with titanium in UiO-66, which was accomplished within a few hours compared to several days reported previously, with the crystallinity well maintained and photocatalytic activities tremendously improved.

Influence of titanium doping on the Raman spectra of nanocrystalline ZnAl2O4

The local structural changes within the normal spinel structure of a ZnAl2O4 host caused by the titanium incorporation as studied by the Raman spectroscopy and computationally using the density functional theory have been analyzed. The lattice dynamics calculation of the ZnAl2O4 phonons were performed within the density functional theory for the 3D periodic crystal structures. Band structure calculations by the grid-based PAW method predicted a direct band gap in the pure ZnAl2O4 sample to be 4.732 eV, while doping with Ti4+ produced a density of states in the middle of the gap. The lattice dynamics calculations using Gaussian-type wavefunctions as basis set and a local density approximation gave a good agreement between observed and predicted Raman bands. Doping with Ti4+ causes the infrared active T1u phonons as well as the inactive phonons (T1g, A2u, Eu and T2u symmetries) to appear in the Raman spectra and breaking of the symmetry selection rules.

Chiral Mesoporous Silicates Immobilizing Titanium Dioxide for Catalytic Asymmetric Epoxidation of Alkenes

Two kinds of titanium-containing silicates were prepared by doping of titanium salt and chiral additive in a sol-gel process, which were further modified by chiral sulfonyl chloride in order for catalytic asymmetric epoxidation of alkenes. These titanium-containing materials had good porosities, ordered pore size distributions, high titanium incorporation yields, ordered morphologies, as well as internal chiral configurations. Particularly, they contained a lot of titanium dioxide particles according to TEM. In catalysis, the titanium silicates showed good conversion of alkenes, satisfactory yields and e.e. values of epoxides. The chiral inducing synergy appeared between silicate matrix and attached ligand, which was significant for transformations of styrene and α-methylstyrene. Moreover, iodosylbenzene, tert-butyl hydroperoxide and hydrogen peroxide were all promising oxidants. In addition, the present titanium catalysts showed satisfactory recycling behaviors and chemical stabilities. This work would contribute to the design of efficient chiral catalysts.

Titanium particle incorporation in block copolymer templates

Abstract Template-directed formation of titanium structures on block copolymer templates has been recently reported [1]. Here, the incorporation of titanium in a thin film template is studied. We show that the surface free energy contrast in microphase-separated polystyrene-block-polyethylene oxide templates is not limited to the template film surface, but directs the assembly of titanium atoms in the template thin film. The details of the self-assembly of titanium particles on the block copolymer nanostructured surface and inside the 3D film structure are studied with selected amounts of titanium. Evaporated titanium preferentially wets the polystyrene block of the block copolymer film and diffuses inside the film, conserving the block copolymer nanostructure. Increasing deposition leads to the formation of a mesoporous titanium layer on the block copolymer film, which reproduces that of the underlying template, in this particular case with a thickness of 12 nm and a periodic pore-to-pore distance of 35 nm. The formation of a mesoporous titanium layer prevents from further titanium diffusion inside the block copolymer film. The combination of the X-ray scattering techniques presented here provides sufficient sensitivity to follow the titanium formation in the three dimensional network of the block copolymer films.

Phenol and methylene blue photodegradation over Ti/SBA-15 materials under uv light

Abstract Ordered SBA-15 mesoporous silica supports have been synthesized and used for incorporation of titanium with different Ti/Si weight ratio via incipient wetness impregnation. Titanium tetraisopropoxide (TTIP) was used as a source of Ti. Obtained catalysts were characterized to investigate the chemical framework and morphology by nitrogen sorption measurements, powder X-ray diffraction (XRD), X-ray fluorescence elemental analysis (XRF), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS). The photocatalytic degradation of phenol and methylene blue water solutions were selected as a probe reactions to the photoactivity test of prepared samples and to verify the potential application of these materials for water purification. Experimental results indicate that the photocatalytic activity of Ti/Si mixed materials depends on the adsorption ability of composites and the photocatalytic activity of the titanium oxide.

Ionic liquid assisted vanadium pentoxide synthesis through sol-gel method: Catalyst support for broad molecular weight distribution polyethylene synthesis

Ionic liquid (IL) mediated vanadium pentoxide (VP) was synthesized by sol-gel method with 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and 1-octyl-3 methyl-imidazolium tetrafluoroborate ([OMIM][BF4]). Synthesized nano- to micro-VP particles were examined by scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET) characterization, Fourier transform infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). The VP particles morphology, surface area as well as crystallinity are found to be influenced by the type of ionic liquid used during synthesis. Synthesized VP particles were used as support for synthesis of titanium catalyst for ethylene polymerization. Higher titanium incorporation was observed for IL assisted VP. Activity of titanium catalyst for ethylene polymerization was higher when [BMIM][BF4] based VP was used. Further, IL assisted VP supported catalyst based polyethylene has shown much broad molecular weight distribution.

Mechanochemical Synthesis of TiO₂ Nanocomposites as Photocatalysts for Benzyl Alcohol Photo-Oxidation.

TiO2 (anatase phase) has excellent photocatalytic performance and different methods have been reported to overcome its main limitation of high band gap energy. In this work, TiO2-magnetically-separable nanocomposites (MAGSNC) photocatalysts with different TiO2 loading were synthesized using a simple one-pot mechanochemical method. Photocatalysts were characterized by a number of techniques and their photocatalytic activity was tested in the selective oxidation of benzyl alcohol to benzaldehyde. Extension of light absorption into the visible region was achieved upon titania incorporation. Results indicated that the photocatalytic activity increased with TiO2 loading on the catalysts, with moderate conversion (20%) at high benzaldehyde selectivity (84%) achieved for 5% TiO2-MAGSNC. These findings pointed out a potential strategy for the valorization of lignocellulosic-based biomass under visible light irradiation using designer photocatalytic nanomaterials.

Cubic WO3 stabilized by inclusion of Ti: Applicable in photochromic glazing

We report on the development of WO3 layers with increased symmetry induced by the incorporation of titanium into a crystalline WO3 matrix. The atomic ratio between W and Ti was varied stepwise from 100:1 to 100:20 with pure WO3 layers, made using peroxo sol–gel synthesis, as a reference. Layers were then formed by dip-coating from the corresponding sols. IR spectroscopy and XRD analysis of layers and powders heat-treated at 450°C proved that the presence of titanium ions induces ordering and increases the symmetry of WO6 octahedra in the WO3 crystalline matrix leading to the transformation of the cell symmetry from monoclinic through tetragonal up to the cubic. Cyclic voltammetry confirmed that this increased symmetry leads to an up-shift in redox potential, which favors the coloration of the layers in photochromic devices. According to our knowledge, this is the first report of colorless cubic WO3 layers, which have potential applications in optoelectronic devices and sensors.

Titania-silica monolithic multichannel microreactors. Proof of concept and fabrication/structure/catalytic properties in the oxidation of 2,3,6-trimethylphenol

Titania-silica monoliths with 3D hierarchical porosity in μm and nm scales were fabricated using either direct or post-synthesis method, to find that they enable very fast continuous-flow oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-1,4-benzoquinone with hydrogen peroxide as the oxidant. Extensive characterization of the monoliths using N2 adsorption, mercury porosimetry, SEM, energy dispersive X-ray mapping, FT-IR and UV–Vis spectroscopy showed a strong impact of the fabrication method on the structural properties and also coordination/dispersion of the titanium ions incorporated into the silica. Systematic study of the monolithic microreactors and corresponding powders in the continuous-flow and batch systems, revealed a large complexity of performance/structure/catalytic properties relationships. A direct method resulted in titanium active centres highly dispersed in microporous skeleton, and therefore larger TOF, compared to the surface titanium entities in monoliths obtained from the post-synthesis approach. However, owing to the lower porosity and much smaller flow-through (macro)pores the pressure drops were almost two orders of magnitude larger. The highly porous monolithic microreactors fabricated by the post-synthesis incorporation of titanium appeared to be superior; the substrate conversions of 85% were obtained in about 12 min compared to those of ca. 75% obtained in batch systems after 1 h. This could be explained by very intensive mass transport in macro- and mesopore size scales.

Anionic polymer as a quasi-neutral medium for low-cost synthesis of titanosilicate molecular sieves in the presence of high-concentration alkali metal ions

Titanosilicate molecular sieve (TS-1) is an important commercial catalyst for green production of oxyfunctionalized chemicals such as alcohols, ketones, epoxides, and oximes. Active TS-1 can normally be achieved in the synthetic media strictly free of alkali metal cations (e.g., Na+ and K+). This condition severely raises the purity demands of starting reagents, which greatly increases the production cost. Herein, we developed a method to achieve highly active titanosilicates in the presence of high-concentration alkali metal cations using anionic polymer-based quasi-neutral media. This synthetic route could effectively inhibit the adverse influence of alkali metal cations on the incorporation of active titanium(IV) sites into the framework of titanosilicate, directly affording the maximal framework titanium content (2.0wt.%) with almost 100% yield. This development shows a great commercial potential and opens the possibility of preparing silica-based molecular sieves/zeolites in non-fluoride neutral media.

Solid state synthesis and structural characterization of zinc titanates

Zinc titanate composite materials were synthesized via solid state sintering process using high-purity metal oxide powders (purity ∼99.99%). The titanium incorporation into ZnO matrix was investigated by X-ray diffraction which revealed the coexistence of spinel Zn2TiO4 and hexagonal ZnTiO3 with the ZnO wurtzite structures. No reflection peaks of rutile TiO2 phase were detected. The IR spectroscopy and Raman scattering spectroscopy were used to characterize the structural and chemical properties of the ZnO/TiO2 composites. The IR bands and vibrational modes of all crystalline phases were detected. The effect of TiO2 doping rates (x = 3, 5 and 7 wt%) on bands shifting, Raman intensity and structural quality was discussed.

Sputter deposited W1–x–yNixTiyO3 thin films: Electrochromic properties and durability

Previous research demonstrated that a small amount of nickel enhances the coloration efficiency of tungsten-nickel oxide electrochromic (EC) thin films with respect to that of pure tungsten oxide (WO3) films. Furthermore the incorporation of titanium gives an improvement in the durability of tungsten-titanium oxide EC thin films. In this work we investigated the EC performance of tungsten-nickel-titanium oxide (W1–x–yNixTiyO3) EC thin films with emphasis on durability. The films were deposited on indium tin oxide covered glass by reactive dc sputtering from tungsten, tungsten-titanium alloy and nickel targets. Cyclic voltammetry was performed using 1 M LiClO4 in propylene carbonate as electrolyte. The voltage window was chosen to induce fast degradation of the samples within 80 cycles. Elemental compositions were obtained by Rutherford Backscattering Spectroscopy.

Synthesis of bimetallic Zr(Ti)-naphthalendicarboxylate MOFs and their properties as Lewis acid catalysis

Bimetallic Zr(Ti)-NDC based metal–organic frameworks (MOFs) have been prepared by incorporation of titanium(iv) into zirconium(iv)-NDC-MOFs (UiO family).

The synthesis, characterization and catalytic activity of the hierarchical TS-1 with the intracrystalline voids and grooves

Hierarchical TS-1 with grooves and intracrystalline voids was prepared by TPAOH/NaOH treatment. With increasing NaOH concentration, the dissolution–recrystallization process was intensified, the relative crystallinity and microporous properties decreased, the secondary pore volume increased. Although the dissolved species could be recrystallized, Na+ prevented the titanium incorporation, which increased the extra-framework titanium content. In phenol hydroxylation, improved activity and H2O2 efficiency were achieved when NaOH was no more than 0.1mol/L, which may be a result of the positive influences of the secondary pores. At higher NaOH concentration (>0.1mol/L), the activity and H2O2 efficiency decreased due to the negative influences of the non-framework titanium.

Influence of the synthesis conditions on the structure and composition of the titanium–magnesium nanocatalyst and on its activity in isoprene polymerization

Synthesis of titanium–magnesium nanocatalyst in a high-pressure reactor under the conditions modeling the industrial conditions was studied. A laboratory scale plant including the units for the product synthesis, washing, and filtration was developed. The effect of elevated pressure (10–90 atm) on the process course, on the properties of the catalyst formed, and on the isoprene polymerization was studied for the first time. An increase in pressure leads to an increase in titanium incorporation into the catalyst from 1.52 to 2–2.3 wt % and simultaneously to an increase in the trivalent titanium content to 81 wt %. The titanium–magnesium nanocatalyst with such properties exhibits enhanced performance in isoprene polymerization without deteriorating the polymer microstructure. The development of the catalyst synthesis procedure on the laboratory scale plant will allow pilot-scale modeling of this process in the future.

Scale Formation of Alloy 602 CA During Isothermal Oxidation at 800–1100 °C in Different Types of Water Vapor Containing Atmospheres

The oxidation behavior of the nickel base Alloy 602 CA in atmospheres, relevant to gas separation units in fossil fired power plants, was investigated in the temperature range 800 to 1100 °C. Isothermal oxidation kinetics were determined in Ar–7 %H2O, Ar–4 %H2–7 %H2O, Ar–20 %O2–7 %H2O and, for comparative purposes, in Ar–20 %O2. The alloy formed an external alumina scale during oxidation at 800 °C, regardless of the atmosphere. Increasing the temperature results in gradual replacement of the alumina scale by an external chromia layer and internal alumina precipitates. The chromia growth rate is affected by the gas composition, due to titanium incorporation in the scale and outwardly protruding metallic nodules. The external alumina scale formation was strongly affected by surface cold work during specimen grinding. This effect, which promoted external alumina scale formation, was retained during exposure at 800 °C but was rapidly lost at higher temperatures resulting in external chromia scale formation and internal oxidation of aluminum.

First-principles investigation of titanium doping into β-SiAlON crystal in TiN–SiAlON composites for EDM applications

Following the experimental work on the incorporation of titanium into β-SiAlON crystal in TiN–SiAlON composites for electrical discharge machining (EDM) applications, Ti doping mechanisms in β-Si6−z AlzOzN8−z have been systematically investigated by means of density functional theory based formation energy calculations. A series of calculations, performed considering the random distributions of Ti–O/N, Al–O/N, and Si–O/N bonds in β-Si6−z TizOzN8−z crystal, showed that the structures with enriched Ti–O and Si–N bonds have lower formation energy than those of Ti–N and Si–O bonds. In addition, it was determined that there is a notable difference between the average bond lengths of Ti-X and Al-X (X=O, N). Electronic structure calculations demonstrated that there is no correlation between either the z values or the number of Ti–O bonds and the one-electron band gap. However, in the case of β-Si6−z AlzOzN8−z, there was a decreasing trend regarding the energy on one-electron band gap with respect to increasing z values.

Titanium(IV) in the organic-structure-directing-agent-free synthesis of hydrophobic and large-pore molecular sieves as redox catalysts.

Titanium(IV) incorporated into the framework of molecular sieves can be used as a highly active and sustainable catalyst for the oxidation of industrially important organic molecules. Unfortunately, the current process for the incorporation of titanium(IV) requires a large amount of expensive organic molecules used as organic-structure-directing agents (OSDAs), and this significantly increases the production costs and causes environmental problems owing to the removal of OSDAs by pyrolysis. Herein, an OSDA-free process was developed to incorporate titanium(IV) into BEA-type molecular sieves for the first time. More importantly, the hydrophobic environment and the robust, 3 D, and large pore structure of the titanium(IV)-incorporated molecular sieves fabricated from the OSDA-free process created a catalyst that was extremely active and selective for the epoxidation of bulky cyclooctene in comparison to Ti-incorporated BEA-type molecular sieves synthesized with OSDAs and commercial titanosilicate TS-1.

Titanium Containing Aluminophosphate Molecular Sieve for Oxidation of Styrene

Microporous aluminophosphate (AlPO-5) and titanium aluminophosphate (TAPO-5) molecular sieves, which are zeolite-like materials have been synthesized by direct hydrothermal method using two different templates; triethylamine (TEA) as organic base and tetraethylammonium hydroxide (TEAOH) as alkali base. XRD patterns confirmed that the TAPO-5 catalysts are identical with AFI structure but the crystallinity of the catalysts had decreased after the incorporation of titanium into the framework. Besides that, characterization of TAPO-5 catalysts using DRUV-Vis confirmed the coordination of titanium species and this evidenced also supported by the result 27Al MAS NMR. Catalytic performance of the TAPO-5 catalysts was tested in the oxidation of styrene to produce benzaldehyde and phenylacetaldehyde in the presence of hydrogen peroxide as oxidant. TAPO-5 catalysts showed higher activity in styrene oxidation compared to AlPO-5. Keywords: zeolite; aluminophosphate; titanium; organic template; styrene

Titanium doped cupric oxide for photovoltaic application

The potential of titanium (Ti) incorporation into cupric oxide (CuO) is demonstrated. The optical, electrical, microstructural, material quality, chemical composition, surface morphology, and photovoltaic properties of Ti doped CuO, CuO(Ti) have been systematically investigated. It is shown that Ti doped CuO reduces sheet resistance and improved the charge transport properties. Furthermore, by tuning the Ti concentration, the conductivity of CuO(Ti) can be improved, while retaining the optical properties and crystallinity of the samples. Heterojunction solar cells of p-type Ti doped CuO on n-type silicon (Si) substrate, p-CuO(Ti)/n-Si, prepared by using conventional sputter deposition at room temperature followed by rapid thermal annealing at 300°C to investigate the impact of Ti doped CuO on the performance of photovoltaic properties. The short circuit current and efficiency of p-CuO(Ti)/n-Si heterojunction have been significantly improved compared to the cells without Ti doped CuO.