Separation of trace amounts of titanium by the sorption of the titanium peroxocomplex on silica gel

Summary The possibility of the analytical use of the sorption of titanium peroxocomplex on silica gel for the determination of trace amounts of titanium was studied. The exchange capacity of silica gel in dependence on the time and the composition of the titanium peroxocomplex sorbed were described. A simple and very efficient separation procedure has been developed for the determination of traces of titanium in various waters and water-soluble salts.     

Synthesis of silica–titania composite oxide via “green” aqueous peroxo-route

The preparation procedure of silica–titania composite oxide using novel solution/sol single precursor containing titanium peroxocomplex and silicic acid has been described. Pechini-type sol–gel process has been used to prepare oxides from the aqueous precursor. Some structural, morphological and textural characteristics of the prepared material have been presented. Composite SiO₂/TiO₂ has high surface area (c.a. 300 m²/g), and it is composed of anatase nanoparticles with the mean diameter of 5 nm embedded in amorphous silica, then TiO₂ prepared via similar method is presented as a mixture of anatase and rutile phases. The proposed synthetic procedure meets the requirements of “green chemistry”.     

反应萃取法合成戊二醛中H3PMoxW12—xO40的催化作用

杂多酸Ｈ３ＰＭｏｘＷ１２－ｘＯ４０是通过其适宜的酸性,氧化性的双功能的配合催化,使Ｈ２Ｏ２氧化环戊烯为戊二醛,液－液相转移反应萃取氧化过程是杂多酸与相转移催化剂形成油溶性配合物,此配合物在相界面被Ｈ２Ｏ２氧化为过氧化杂多酸配合物,过氧化杂多酸配合物在有机相可能机理是Ｈ２Ｏ２氧化杂多酸为过氧化杂多酸。     

Analytical Problems with Preparation of Paraspinal Tissues from Patients with Spinal Fusion for Analysis of Titanium

Preparation of paraspinal tissue of patients with implants for elemental analysis is a challenge because it contains titanium in the ionic form, as well as metallic debris. Most literature reports focus on dissolving the tissue, but the impact of digestion conditions on metallic debris of Ti has not been investigated. In our work, various digestion conditions, including systems, compositions of oxidising mixture, and time, were tested aiming (i) to digest the tissue without digestion of metallic titanium to quantify soluble Ti and (ii) to digest metallic titanium debris to asses total Ti content in tissue. The experiments were performed in a closed mode using a microwave-assisted system and a carbon heating block. Our study revealed that total digestion of titanium was impossible in the tested conditions and the maximal level of digested titanium was below 70%. The mineralisation with the use of concentrated nitric acid was optimal to prepare paraspinal samples to analyse the soluble titanium form because metallic titanium passivated and did not migrate to the solution. The elaborated conditions were applied to determine titanium ion in the periimplant tissue of patients with three different titanium-based surgical systems, including traditional growing rod (TGR), guided growth systems (GGS), and vertical expandable prosthesis titanium rib (VEPTR).     

Oxidative dihydroxylation of alicyclic unsaturated hydrocarbons with vinyl- and norbornene fragments in pseudohomogenic system

Oxidation of alicyclic unsaturated hydrocarbons (4-vinylcyclohexene, 5-vinylnorbornene, 5-cyclohexenylnorbornene, and 5-vinylbicyclooctene) with 30% hydrogen peroxide solutions and percarbamide is studied. Reaction was carried out at 40–70°C in the presence of heterogenized peroxocomplex compounds of molybdenum and tungsten formed “in situ” in the reaction of metal oxohalides with H₃PO₄, nano-dimensional particles of carbon material, and hydrogen peroxide. Main oxidation products of alicyclic diene hydro-carbons are the corresponding unsaturated epoxides and diols. Depending on the reaction condition their ratio varies in a wide range.     

Dependence of the Reactivities of Titanium Enolates on How They Are Generated: Diastereoselective Coupling of Phenylacetic Acid Esters Using Titanium Tetrachloride

Oxidative coupling of phenylacetic acid esters was easily achieved by treating the esters with TiCl(4) and then adding Et(3)N to the resulting solution. The products consisted of dl- and meso-2,3-diphenylsuccinic acid esters with the Claisen condensation product, and the ratio of these products depended on the reaction conditions. Reaction conditions suitable for high dl selectivity were determined, and a dimer of titanium enolate was postulated as an intermediate responsible for the high dl selectivity. The selectivities were compared with those in known oxidative couplings in which titanium enolate intermediates are prepared through lithium enolates and silyl enol ethers. The results suggest that the reactivities of titanium enolates intermediates depend on how they are generated.     

Electrochemical co-deposition of Ti n+ phases with gold in ionic liquids

The electro-deposition of titanium from two different classes of ionic liquids has been studied. Gold ions in solution have been used as an additive in order to provide a stable nucleation site for titanium to deposit on via a co-deposition process. Despite evidence from previous literature, it was found that it was not possible to reduce titanium from the +4 state to titanium (0) due to problems of redox cycling and solubility of reduced titanium species in the various ILs trialled. It was however found that gold was a very effective nucleating agent for these reduced titanium species and that successful mixed Ti(n+)/gold electro-deposits were obtained. The content of titanium in these species could be varied according to the conditions and IL used.     

A study of the oxidation of titanium hydride powder by measurements of its electrical resistance

The oxidation of titanium hydride powder by air oxygen and the influence of oxidation conditions on the degree of oxidation of hydride particles, specific gas content in the powder, and kinetics of its thermal decomposition were studied. The resistometry method was used to determine the effective activation energy of oxidation of titanium hydride by air oxygen. The content of the surface nonconducting phase formed by titanium oxide and oxohydride films under various oxidation conditions was estimated.     

Effect of support and pre-treatment conditions on Pt-Sn catalysts: application to nitrate reduction in water

The effect of the support (activated carbon or titanium dioxide) on the catalytic activity and selectivity to nitrogen of Pt-Sn catalysts in nitrate reduction was studied. The effects of the preparation conditions and the Pt:Sn atomic ratio were also evaluated. It was observed that the support plays an important role in nitrate reduction and that different preparation conditions lead to different catalytic activities and selectivities. Generally, the catalysts supported on activated carbon were less active but more selective to nitrogen than those supported on titanium dioxide. The monometallic Pt catalyst is active for nitrate reduction only when supported on titanium dioxide, which is explained by the involvement of the support in the reaction mechanism. The catalysts were characterized by different techniques, and significant changes on metal chemical states were observed for the different preparation conditions used. Only metallic Pt and oxidized Sn were observed at low calcination and reduction temperatures, but some metallic Sn was also present when high temperatures were used, being also possible the formation of Pt-Sn alloys.     

An Investigation into the Optimum Thickness of Titanium Dioxide Thin Films Synthesized by Using Atmospheric Pressure Chemical Vapour Deposition for Use in Photocatalytic Water Oxidation

Twenty eight films of titanium dioxide of varying thickness were synthesised by using atmospheric pressure chemical vapour deposition (CVD) of titanium(IV) chloride and ethyl acetate onto glass and titanium substrates. Fixed reaction conditions at a substrate temperature of 660 °C were used for all depositions, with varying deposition times of 5–60 seconds used to control the thickness of the samples. A sacrificial electron acceptor system composed of alkaline sodium persulfate was used to determine the rate at which these films could photo‐oxidise water in the presence of 365 nm light. The results of this work showed that the optimum thickness for CVD films on titanium substrates for the purposes of water oxidation was ≈200 nm, and that a platinum coating on the reverse of such samples leads to a five‐fold increase in the observed rate of water oxidation.     

Application of experimental design for investigating the determination of titanium in glass ceramics by flame atomic absorption spectrometry

Interferences of the matrix elements of glass ceramics (Al, Mg, Na and Si) on the titanium signal obtained by atomic absorption spectrometry with a nitrous oxide/acetylene flame were studied by means of experimental design. Quadratic polynomials were chosen as the model; full factorial designs with two, three and four variables at three levels were applied. As expected, aluminium increased the titanium signal, while magnesium reduced it. All the investigated elements interfered nonadditively with the titanium signal; the standard addition method therefore does not provide accurate results. Graphic evaluation of the empirical response surfaces was used to establish optimum conditions for titanium; these surfaces were compared with the polynomial surfaces to check the models. The results obtained on interactions in the system are used with some thermodynamic data to estimate the nature of the compounds formed in the flame. The strong interferences on the titanium signal requires fairly close matrix matching between the standard and sample solutions. The proposed method allows the determination of 3–6% Ti in glass ceramics with a relative standard deviation of 1%.     

Synthesis of pharmacologically active hydrogels based on combined silicon and titanium polyolates

The target synthesis of new biologically active hydrogels based on combined silicon and titanium polyolates was carried out. The optimum conditions for hydrogel formation and their composition were determined. The type of hydrogels and mechanisms of gelation depend on the nature of polyols: gels based on combined silicon and titanium polyethylene glycolates are polymeric and formed via the polycondensation mechanism, whereas gels based on combined silicon and titanium glycerolates are colloidal and formed via the coagulation-condensation mechanism. The combined hydrogels based on silicon dimethyl glycerolates and titanium tetraglycerolate exhibit enhanced transcutaneous, wound healing, and regenerating activity.     

Determination of small amounts of titanium in pure molybdenum,tungsten, vanadium and their oxides after separation on silica gel

A new method for the separation of titanium from molybdenum, tungsten and vanadium is described, based on sorption of the titanium complex with hydrogen peroxide on silica gel under dynamic conditions. The eluted titanium is determined spectrophotometrically with diantipyrylmethane. The method can be applied to the determination of small amounts of titanium in tungsten, molybdenum and vanadium metals and in their oxides.     

Measurement of neutron emission from a Ti−D2 system

Neutron emission from the d-d nuclear fusion reaction, D/d,n/³He, in and on titanium metals /titanium sponge and the mixture of titanium powder/ trapped deuterium at about 1 atm has been ascertained by using a high resolution liquid scintillation detector. The neutron emissions from 11 samples which were provided under wide varieties of conditions were measured by temperature change in the range of liquid nitrogen temperature to 350 °C. As a result, it was proved that the neutron emission observed can be divided into two types, such as cooling and heating, by the evolved conditions. Moreover, by estimating the neutron emission efficiencies of samples, it was suggested that the neutron emission reactions are closely related to the deuterium trapped in the surface of titanium metal.     

The electronic and spin properties of excited Se-O<Subscript>2</Subscript> intermediates

Nonempirical calculations performed by various methods were used to estimate the structure and stability of Se-O₂ intermediates containing active oxygen forms and reveal possible channels of their formation. The electronic and spin properties of ground and excited states of the SeOO (C _s ) superoxocomplex, Se(O₂) (C _2v) peroxocomplex, and SeO₂ (C _2v) selenium dioxide were analyzed. Calculations revealed rules that governed changes in the spectral and spin properties of oxygen in the formation of such systems.     

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.     

Investigation of thermal power of reaction of titanium slag with sulphuric acid

Enriched titanium raw materials with high titanium content called titanium slags are received by the electrothermal reduction of ilmenite. Titanium slags are most frequently used in the titanium dioxide industry. The reaction of titanium slags with sulphuric acid is strongly exothermic and creates danger of thermal explosion. Kinetics of this reaction depends on the parameters such as temperature of initiation, sulphuric acid concentration and dimension of particles of titanium slag. The reaction of titanium slag with sulphuric acid was investigated at non-isothermal conditions in a special construction calorimeter. The observed thermal power changes in the calorimeter (“calorimeter run”), are the basis for estimation of reaction kinetics. A proposed model describing the thermal power changes and taking into account the moment of initiation of reaction is presented. The calorimetric investigations showed, that reaction rate of titanium slags with sulphuric acid depends on initial temperature of reaction, size of particles of titanium raw material and sulphuric acid concentration.     

Electrochemical formation of cerium-containing oxide coatings on titanium

Possibility and conditions of obtaining cerium-containing oxide coatings on titanium alloys by microarc oxidation in electrolytes with tartrate and citrate cerium complexes were determined. The effect of organic cerium complexes on the kinetic parameters of the microarc oxidation of titanium alloys was studied. Porous oxides coatings containing up to 20% cerium were obtained.     

水热一步法合成Ti-SBA-15分子筛及其催化性能研究

采用钛酸丁酯和乙酰丙酮作用后的产物作为钛的前驱体，水热法一步合成出了 Ti-SBA-15分子筛。通过X射线衍射、N2气吸附脱附、紫外—可见漫反射等表征手段 ，证明在Si/Ti＝50，25，20时，钛原子成功地取代了SBA-15中的硅原子而没有改 变SBA-15高度有序的介孔二维六角结构，其中钛全部以四配位状态存在，而且高度 分散。当Si/Ti＝12．5时，钛的分散度降低，部分钛聚集生成二氧化钛。与用两步 法合成的Ti-SBA-15比较，一步法合成的Ti-SBA-15中钛分散度好，添加量高，对催 化氧化环己烯有较高的催化活性。对一步法和两步法合成Ti-SBA-15的机理以及相 应产物在结构以及催化活性上的差异进行了探讨。     

Sol–gel reactions of titanium alkoxides and water: influence of pH and alkoxy group on cluster formation and properties of the resulting products

In this work the effect of pH and the titanium precursor on the cluster and particle formation during titanium alkoxide based sol–gel processes was investigated using electrospray ionization mass spectrometry (ESI-MS) and dynamic light scattering (DLS). The influence of pH and the titanium precursor on the particle size, morphology, crystallinity and chemical composition of the resulting particles were investigated using differentiel scanning calometry (DSC), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), BET-adsorption isotherms and high resolution transmission electron microscopy (HR-TEM). ESI-MS investigation of the titanium clusters present during the nucleation and growth period showed that the number of titanium atoms in the clusters varied dependent on the alkoxide used. Moreover, it was found that the titanium clusters formed using titanium tetraethoxide (TTE) were smaller than the clusters formed by titanium tetraisopropoxide (TTIP) and titanium tetrabutoxide (TTB) under similar conditions. pH was not found to influence the nature of the titanium clusters present in the sol–gel solution. HR-TEM investigation of the TiO₂ particles prepared at pH 7 and 10 showed that the primary particle size of the particles was around 3 nm. However, it was found that these primary particles aggregated to form larger secondary particles in the size order of 300–500 nm range. At pH 3 the particles grew significantly during the drying process due to destabilization of the colloidal solution leading to the formation of a gel. The highest specific surface area was found for particles synthesized under neutral or alkaline conditions based on TTIP. XRD analysis of the TiO₂ particles showed that the particles synthesized at 25 °C were amorphous. First after heating the samples to above 300 °C the formation of anatase were observed.