Amount Of Titanium Isopropoxide Research Articles

Controlling Phase Composition, Properties and Activity of TiO₂ Nano-Photocatalyst Synthesized by Hydrothermal Technique in the Degradation of Cinnamic Acid Solution.

In this work, titanium oxide catalysts were synthesized by the hydrothermal method from titanium isopropoxide (TTIP) as a precursor under acidic (Ti-A1 and Ti-A2), neutral (Ti-W) and alkaline (Ti-B) media. Characteristics of the catalysts were identified by various methods including X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller adsorption, UV-Vis diffuse reflectance spectroscopy, transmission electron microscopy, and Raman spectroscopy. The phase composition and PZC value of the obtained catalysts depended on the hydrothermal medium and the amount of TTIP: pure anatase and brookite phase formed at neutral and alkaline medium, respectively; whereas acidic medium favored the formation of anatase/rutile mixed phase and anatase phase decreased with the increasing amount of TTIP. The band gap energy of the synthesized catalysts was approximately 3.08-3.23 eV. Photocatalytic activity of synthesized catalysts was surveyed in the degradation of cinnamic acid (CA) solution at various pH in the region from 3.8 to 9.0 under UV irradiation. Photocatalytic oxidation was favorable in an acidic environment. At acidic pH values (3.8 and 5.0), the CA conversion was in the order of Ti-A2 ≥ Ti-A1 > Ti-P25 > Ti-W ≫ Ti-B, whereas it followed Ti-P25 > Ti-A1 > Ti-A2 ≈ Ti-W > Ti-B at pH 7.0 as well as pH 9.0.

Development of SiO2@TiO2 core-shell nanospheres for catalytic applications

Silica-titania core-shell nanospheres, CSNp, were prepared via a simple and environmentally friendly two step route. First, silica cores were prepared through the hydrolysis-condensation reaction of silicic acid in the presence of hyperbranched poly(ethylene)imine (HBPEI) followed by repeating washing, centrifugation and, finally, calcination steps. To create the core-shell structure, various amounts of titanium isopropoxide were added to the cores and after that a HBPEI-water solution was added to hydrolyze the titanium precursor. Washing with ethanol and heat treatment followed. The optimization of processing parameters led to well-developed core-shell structures bearing a homogeneous nanocrystalline anatase coating over each silica core. The photocatalytic activity for NO was examined in a continuous flux photocatalytic reactor under real environmental conditions. The results revealed a very potent photocatalyst as the degradation percentage reached 84.27% for the core-shell material compared to the 82% of pure titania with the photodecomposition rates measured at 0.62 and 0.55 μg·m−2·s−1, respectively. In addition, catalytic activities of the CSNp and pure titania were investigated by monitoring the reduction of 4-nitrophenol to 4-aminophenol by an excess of NaBH4. Both materials exhibited excellent catalytic activity (100%), making the core-shell material a promising alternative catalyst to pure titania for various applications.

Preparation and characterization of TiO2/HZSM-11 zeolite for photodegradation of dichlorvos in aqueous solution

The TiO2/HZSM-11 materials were synthesized using titanium isopropoxide as a TiO2 precursor and HZSM-11 a medium pore size zeolite with high thermal and chemical resistance as support. The amount of titanium isopropoxide was varied in order to obtain TiO2 concentrations of 3, 10, 20, 30 and 50wt% in the final material. They were characterized by a series of complementary techniques: X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectroscopy (DRS), transmittance Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The surface area of the TiO2/HZSM-11 samples decreased with the increment of TiO2 loading. As result of the increment of the calcination temperature from 450 to 800°C an increase in the size of the anatase crystals was observed. However, the X-ray diffraction patterns of the solids only presented the characteristic peaks of the anatase phase. The catalytic activity of the materials in the photodegradation of Dichlorvos (DDVP) depended on the TiO2 amount the thermal treatment temperature. The sample containing 30% TiO2 calcined at 450°C showed the best catalytic performance and it can be reused without noticeable activity loss during at least four cycles. The catalytic performance was similar to that of the P25 Degussa used as a reference but its separation, recovery and reuse was easier.

Study of the surface acidity of TiO 2/SiO 2 catalysts by means of FTIR measurements of CO and NH 3 adsorption

Samples were prepared by grafting different amounts of titanium isopropoxide (Ti(O Pr i ) 4) onto silica surface in N 2 atmosphere, followed by steam hydrolysis and calcination. Either dioxane or toluene was used as a solvent. The surface properties of TiO 2/SiO 2 catalysts were studied by means of FTIR spectroscopy of adsorbed probe molecules, CO, and ammonia. Adsorption of CO at nominal 77 K exhibited different surface sites: (i) two families of Ti 4+ cations, namely associated and isolated sites, with bands in the 2183–2194 and 2173–2177 cm −1 ranges respectively, shifting with coverage; (ii) surface Si OH groups; and (iii) at titanium loadings >8 wt% TiO 2, corresponding to the alkoxide monolayer coverage of silica, TiOH species exhibiting an acidity higher than expected (observed shift Δ ν = 200 cm −1 ), probably due to interaction with the support. With increasing the titanium loading, the band at 2176 cm −1 disappears, indicating that associated Ti 4+ sites form at the expense of isolated ones. Adsorption of ammonia at room temperature confirms the data obtained with CO. The use of apolar solvents seems to cause anchoring of the Ti alkoxide on the dehydrated portions of the silica surface, with consequences for the final state of the catalyst. In agreement with this observation, activity was lower for catalysts prepared in toluene than in those prepared using dioxane. Prepared catalysts were rather effective in the transesterification of refined oils with methanol.

Studies on the Titanium‐Catalyzed Cyclopropanation of Nitriles.

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Chemical fabrication SrBi 4Ti 4O 15 thin films

The ferroelectric compound SrBi 4Ti 4O 15 that belongs to the so-called Aurivillius family could be promising for the fabrication of ferroelectric thin film memories. Pure SrBi 4Ti 4O 15 powders were obtained after heating adequate sols (bismuth and strontium 2-ethylhexanoates in 2-ethylhexanoic acid and appropriate amount of titanium isopropoxide) at 350°C for 12 h and subsequently putting the samples directly in an electric oven at 700–900°C for 3 h. When spin-coated on silicon wafers and submitted to a similar process, the same sols always led to a mixture of SBT and the pyrochlore phase Bi 2Ti 2O 7. In order to avoid the presence of this impurity, extra bismuth content (0–40 mol%) was added during the preparation of the sols. The pyrochlore formation was completely eliminated when using 20% bismuth excess and the following process: (spin-coating 250°C/5 min–750°C/1 min)/10 times + final annealing at 800°C/1 h

PREPARATION OF CRACK-FREE T1TAN1A-SILICA GELS

ABSTRACT In light of recent models for drying and densifying gels from alkoxide solutions, results to date on titania-silica gels have been reevaluated. In this case, the goal was to prepare crack-free flat disks of densified gel, This goal had been achieved in pure silica some years ago. It was repeated for comparison with the titania-silica composition. Silica gels were prepared from tetraethylorthosilicate (TEOS)-water-isopropanol mixtures and titania-silica gels were prepared with the appropriate amount of titanium isopropoxide. Solvent was removed from reacted solutions prior to casting by attaching a vacuum pump to the flask. Gels were formed in disk-shaped molds, 7 cm in diameter, and then were dried closed, open, and supported on nylon mesh. Samples were characterized for shrinkage, distortion and microstruc-ture. Dried samples were heat treated. There is qualitative agreement for both silica and titania-silica gels with current drying and densification models.