Uptake of Uranium on ETS-10 Microporous Titanosilicate

Two samples of the microporous titanosilicate ETS-10 synthesised by different preparation procedures were compared for their ability to take up uranium from aqueous solutions using a batch-type technique. The ETS-10 samples were synthesised using either TiO₂ or TiCl₃ as a titanium source. The uptake of uranium on the materials was compared by determining the distribution coefficient and percentage sorption as a function of contact time, uranium concentration, and sorbent concentration. It was found that the difference in the synthesis procedures of the materials had a significant influence on the uptake of uranium.     

ETS-10 synthesized from gels with dodecyltrimethylammonium bromide

The aim of this paper is to define the characteristics of crystalline phase ETS-10 obtained from gel with dodecyltrimethylammonium bromide, as an organic template. ETS-10 zeolites has been synthesised under hydrothermal conditions from gels of composition 5Na₂O–3KF–TiO₂–6.4HCl– xC₁₂TMAB –7.45SiO₂–197.5H₂O (where x=0.0, 0.25, 0.55, 1.0 and 1.5) with dodecyltrimethylammonium bromide. The crystalline phases synthesised with organic salt have an exothermal peak at ca. 360°C, due to the degradation of organic entrapped in the porous structure. Physical-chemical properties of C₁₂TMAB -ETS-10 are studied by XRD, SEM and thermal analyses.     

Ion transport in the microporous titanosilicate ETS-10

Impedance spectroscopy was used to investigate ion transport in the microporous crystalline framework titanosilicate ETS-10 in the frequency range from 1 Hz to 10 MHz. These data were compared to measured data from the microporous aluminosilicate zeolite X. Na-ETS-10 was found to have a lower activation energy for ion conduction than that of NaX, 58.5 kJ/mol compared to 66.8 kJ/mol. However, the dc conductivity and ion hopping rate for Na-ETS-10 were also lower than NaX. This was found to be due to the smaller entropy contribution in Na-ETS-10 because of its high cation site occupancy. This was verified by ion exchanging Na(+) with Cu(2+) in both microporous frameworks. This exchange decreases the cation site occupancy and reduces correlation effects. The exchanged Cu-ETS-10 was found to have both lower activation energy and higher ionic conductivity than CuX. Zeolite X has the highest ion conductivity among the zeolites, and thus the data shown here indicate that ETS-10 has more facile transport of higher valence cations which may be important for ion-exchange, environmental remediation of radionucleotides, and nanofabrication.     

The sorption of some radiocations on microporous titanosilicate ETS-10

The microporous titanosilicate ETS-10 synthesized from gel with following molar composition: 1.0 Na₂O: 1.49 SiO₂ : 0.2 TiO₂ : 0.6 KF : 1.28 HCl : 39.5 H₂O was subjected to sorption of radioactive cations ¹¹⁵Cd²⁺, ²⁰⁴Hg²⁺, ⁶⁰Co²⁺ and ¹³⁷Cs⁺ (M) from aqueous solution, in the absence of ionic competition. The uptake of these cations on the ETS-10 was compared by means of the distribution coefficient (K_d) versus contact time and sorption capacity (R) at equilibrium. The FT-IR spectra of M-ETS-10 sorption products exhibit a modification of the absorption band, principally at 381 cm^-1.     

Thermochemistry of n-alkylamines interaction with ETS-10 titaniunsilicate

According to the data from calorimetric adsorption of methylamine, under the best experimental conditions, 10 mg ETS-10 was saturated with 20 μl portions of an aqueous solution of methylamine at 0.05 mol dm⁻³ concentration corresponding to 0.490 mmol of methylamine per gram of solid. From calorimetric titration data, the thermodynamic values of ΔH, ΔG and ΔS were calculated, showing favourable n-alkylamine-ETS-10 interactions, from which the most favourable occurs for n-butylamine. The adsorption of these bases did not affect the structure of the titaniunsilicate as the XRD profile of ETS-10 is not altered. The FTIR spectra showed that with the increase in the amine mass the bands corresponding to the symmetric and asymmetric deformations at 1390 and 1467 cm⁻¹ increase in intensity along with the NH₂ deformation at 1530 cm⁻¹ as expected. The thermogravimetry shows two mass losses for ETS-10 that correspond to physisorbed water and water in smaller channels and cavities. After methylamine adsorption, the same behaviour was observed, however for butyl- and pentylamine three other mass losses were observed corresponding to decomposition and/or release of n-alkylamines.     

EXAFS and XANES investigation of the ETS-10 microporous titanosilicate

In this work, we report state-of-the-art analysis of both Ti K-edge high-resolution XANES and EXAFS data collected on the ETS-10 molecular sieve at the GILDA BM8 beamline of the ESRF facility. The interatomic distances and the angles obtained in our EXAFS study are in fair agreement with the single-crystal XRD data of Wang and Jacobson (Chem. Commun. 1999, 973) and with the recent ab initio periodic study of Damin et al. (J. Phys. Chem. B 2004, 108, 1328) Differently from previous EXAFS work (J. Phys. Chem. 1996, 100, 449), our study supports a model of ETS-10 where the Ti atoms are bonded with two equivalent axial oxygen atoms. This model is also able to reproduce the edge and the post-edge region of the XANES spectrum. Conversely, the weak but well-defined pre-edge peak at 4971.3 eV can be explained only by assuming that a fraction of Ti atoms are in a local geometry similar to that of the pentacoordinated Ti sites in the ETS-4 structure. These Ti atoms in ETS-10 should be the terminal of the -Ti-O-Ti-O-Ti- chains, of which the actual number is strongly increased by the high crystal defectivity (Ti vacancies).     

Influence of zirconium on the crystallization of ETS-10 molecular sieve

Summary The ETS-10 is a newly formed titano-silicate the structure of which was resolved thanks to the XRD, EDS, HREM and mass NMR. The ETS-10 is a potentially good catalyst. The aim of this research is to study the physicochemical properties of ET(Zr)S-10 obtained from a gel containing different amounts of Zr. The analyses used are XRD, thermal analysis (TG-DSC), SEM, and ²⁹Si NMR.     

Sorption of thallous ion from acidic aqueous solutions onto ETS-10 titanosilicate

The sorption of the thallous ion from aqueous acidic solution (pH = 1.5) onto as-synthesized and modified ETS-10 titanosilicates was studied by using an isotope dilution method and a batch-mode technique. The present results show that the thallium(I) sorption was effective onto all three considered materials and is enhanced by the porosity and acidity modification of the ETS-10 titanosilicate. The best uptake performance was achieved by the meso-ETS-10. This behavior is explained based on the newly created additional mesoporous system and enriching the external surface with silanol groups. Also, the presence of phosphorus enhanced the inherent porosity allowing thus better internal diffusion properties of crystalline material. However, the chemically modified surface seems to have a negative contribution to the kinetic uptake of thallous ion as shown by the positive value of the activation energy E _a, in comparison with the processes more favorable energetically for ETS-10 and meso-ETS-10 materials.     

Photoreactivity of 3-thujopsanone

The photoreactivity in the liquid phase of the polysubstituted cyclohexanones 3-thujopsanones results from a primary process of Norrish I type, but is modified by the opening of the cyclopropyl ring. Quantum yields are higher than for less substituted cycloalkanones. In aprotic solvents, only hydrocarbons are formed either with the loss of a C₂H₂O group leading to the main photoproduct 4 or with decarbonylation of the ketone leading to a new cyclopropyl chain. In alcohol solvent, two isomeric compounds with an oxygenated heterocycle are obtained from the addition of solvent to a carbene intermediate.     

稀土负载钛-硅沸石 ETS-10 的制备及其光催化性质(英文)

以水玻璃和四氯化钛为原料, 在不使用有机模板剂、氟离子和晶种的条件下, 用水热法合成了钛-硅沸石 ETS-10, 将 La、Ce、Pr 和 Nd 四种稀土元素负载到合成的 ETS-10 上. 通过 X 射线粉末衍射、N2 吸附-脱附、29Si 魔角旋转核磁共振、紫外漫反射光谱、X 射线荧光光谱等表征手段对负载前后的 ETS-10 进行了表征. 以有机染料甲基橙为底物, 考察了负载各种稀土及氢氟酸腐蚀对 ETS-10 的光催化活性的影响. 结果表明, 四种稀土元素的引入均可有效提高 ETS-10 的光催化活性. 反应活性提高的程度与稀土元素负载量有关. 对 ETS-10 同时进行氢氟酸腐蚀和稀土元素的负载, 可以将 ETS-10 的光催化活性提高近一倍, 与锐钛矿相 TiO2 相当, 但前者更易分离.     

A visible light photocatalyst: effects of vanadium substitution on ETS-10

Hybrid density functional theory/molecular mechanics (DFT/MM) methods have been used to investigate the effects of vanadium substitution in ETS-10. Models have been developed to contain varying concentrations of V(IV) and V(V) within the O-M-O (M = Ti, V) chain. Most of the V-substituted models have a localized mid-gap state. The occupation of this localized state depends upon the dopant oxidation state, leading to the addition of multiple low energy transitions. A linear correlation has been identified between band gap energies estimated using ground state orbital energies and those calculated using the more accurate and computationally demanding time-dependent DFT (TDDFT) method for a variety of transition metal substituted models of ETS-10. Consistent with experimental data for V substitution, our models predict a decrease in the optical band gap with increasing [V], due to a lowering of the delocalized d-orbital states at the bottom of the conduction band with increasing V d-orbital character. This effect is more pronounced in the case of V(V) substitution than V(IV). Excitation energies for the V-doped models, calculated with TDDFT methods correlate well with experimental data, allowing for the assignment of specific optical transitions to experimental UV-Vis spectra. The electronic structure of V-substituted ETS-10 at high V concentration demonstrates band gap energies within the visible range of the spectrum. Additionally, at high [V] the band gap energy and presence of low energy electron traps can be controlled by the relative concentration of V(IV) and V(V) along the O-M-O chain, establishing V-substituted ETS-10 as a promising visible light photocatalyst.     

Studies on the synthesis of ETS-10 II. Use of organic templates

ETS-10 has been synthesized using titanosilicate gels and organic templating agents such as choline chloride [OHCH₂CH₂(CH₃)₃N⁺Cl⁻] and the bromide salt of hexaethyl diquat-5 [Br⁻(C₂H₅)₃N⁺(CH₂)₅N⁺(C₂H₅)₃Br⁻]. The influences of temperature and concentration of the ingredients on the kinetics of synthesis are reported. Physicochemical characterizations of the samples have been carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and differential thermogravimetric analysis (DTA)/thermogravimetric analysis (TGA), and adsorption of water, n-hexane and mesitylene. The catalytic activities of H-ETS-10 in the dehydration of n-butanol and in the isomerization of m-xylene and 1,3,5-trimethylbenzene are reported.     

Solid state morphology and band gap studies of ETS-10 supported CdS nanoparticles

Engelhard titanosilicate (ETS-10) supported cadmium sulphide (CdS) nanoparticles were synthesized and characterized by various solid state techniques including: XRD, DR UV-Vis, TEM and FESEM. The effect of different synthesis routes of CdS nanoparticles on its physicochemical character was studied. It was observed that CdS nanoparticles prepared by both in situ sulphur reduction (CdS-IS) and reverse micelle (CdS-RM) methods showed similar roperties. However, CdS-IS nanoparticles are more feasible and economically practical. The reflectance measurements of the as-synthesized CdS nanoparticles are apparently blue-shifted compared to bulk CdS. This phenomenon of blue-shifted absorption edge has been ascribed to an increase in bandgap energy with a decrease in particle sizes. The bandgap of the as-synthesized CdS samples was calculated from the linear correlation of [F(R) hν]² and hν. The bandgap of CdS in ETS-10 was noticeably slightly reduced when compared with the as-synthesized CdS (8 nm) due to the formation of cluster arrays on the pores of ETS-10.     

On the crystallization mechanism of ETS-10 titanosilicate synthesized in gels containing TAABr

Thermal analysis of the products resulted during crystallization of ETS-10 by using starting co gels with molar composition 5.0 Na₂O-3.0 KF-TiO₂-6.4 HCl-TAABr-7.45 SiO₂-197.5 H₂O, where tetralkylammonium (TAA) are tetramethyl (TMA), tetraethyl (TEA), tetrapropyl (TPA) and tetrabutylammonium (TBA), was performed. The effect of TAA⁺ cations (ionic radius in hydrated forms, shapes and hydrophilic/hydrophobic character) on the crystallization of ETS-10 is evident from the induction time, t_i (TMA⁺ ? TEA⁺ < TPA⁺ < TBA⁺), the rate of crystallization, R (TMA⁺ < TEA⁺ < TPA⁺ < TBA⁺), morphology and size of crystallites. Organic cations play a “pore filling” role rather than as a “structure-directing” agent. The relatively flexible molecules of the symmetric tetraalkylammonium cations mixed with alkali cations (Na⁺, K⁺) participate directly at prenucleation and nucleation steps by their interaction with the silicate and titanate in aqueous colloidal dispersion.     

Unveiling Latent Photoreactivity of Imines

Unlike carbonyl compounds, it has long been common understanding that excited imines show virtually no photoreactivity, and hence their properties and potential utility in chemical science remain largely unexplored. Now, a strategy is presented for eliciting latent photoreactivity of imines based on the introduction of a donor–acceptor (D‐A) structure to extend the lifetime of their photoexcited states. A series of spectroscopic analyses and density functional theory calculations reveal unique photophysical properties of the D‐A‐type imines. Furthermore, the reactivity of the D‐A‐type imines is demonstrated by using them as a photoredox catalyst for atom‐transfer radical addition. These findings illuminate a previously neglected chemical space in the field of photochemistry, which will be exploited by taking advantage of the inherent structural modularity of imines.     

Electronic and geometric properties of ETS-10: QM/MM studies of cluster models

Hybrid DFT/MM methods have been used to investigate the electronic and geometric properties of the microporous titanosilicate ETS-10. A comparison of finite length and periodic models demonstrates that band gap energies for ETS-10 can be well represented with relatively small cluster models. Optimization of finite clusters leads to different local geometries for bulk and end sites, where the local bulk TiO6 geometry is in good agreement with recent experimental results. Geometry optimizations reveal that any asymmetry within the axial O-Ti-O chain is negligible. The band gap in the optimized model corresponds to a O(2p) --> Tibulk(3d) transition. The results suggest that the three Ti atom, single chain, symmetric, finite cluster is an effective model for the geometric and electronic properties of bulk and end TiO6 groups in ETS-10.     

On the influence of ion exchange on the local structure of the titanosilicate ETS-10

The effect of ion exchange with different monovalent cations (NH(4)(+), K(+), Na(+) and Cs(+)) on the local structure of the titanosilicate ETS-10 has been studied by (29)Si MAS NMR and Raman spectroscopy. Although X-ray diffraction shows no significant influence of ion exchange on the long range order, ammonium exchange is found to result in substantial damage to the local structure. Ion exchange experiments with alkali cations under significantly more acidic conditions clearly show that the structural damage brought about by ammonium exchange is not caused by the low pH of the exchange solution. The exchange with potassium and caesium ions also leads to significant changes in the (29)Si NMR and Raman spectra. However, these changes can largely be reversed by sodium back-exchange.     

Selective photocatalytic transformations on microporous titanosilicate ETS-10 driven by size and polarity of molecules

Photocatalytic activity of microporous titanosilicate ETS-10 has been studied in water. The photoactivated ETS-10 shows catalytic activity driven by size and polarity of substrates. ETS-10 efficiently catalyzes a conversion of substrates with a size larger than the pore diameter of ETS-10. In contrast, the reactivity of small substrates depends strongly on substrate polarity; less polar substrates show higher reactivity on ETS-10. Electron spin resonance analysis reveals that large substrates or less polar substrates scarcely diffuse inside the highly polarized micropores of ETS-10 and, hence, react efficiently with hydroxyl radicals (*OH) formed on titanol (Ti-OH) groups exposed on the external surface of ETS-10. In contrast, small polar substrates diffuse easily inside the micropores of ETS-10 and scarcely react with *OH, resulting in low reactivity. The photocatalytic activity of ETS-10 is successfully applicable to selective transformations of large reactants or less polar reactants to small polar products, enabling highly selective dehalogenation and hydroxylation of aromatics.     

Impact of photogenerated charge behaviors on luminescence of Eu3+-incorporated microporous titanosilicate ETS-10

A series of Eu³⁺-incorporated ETS-10 samples were successfully prepared based on the traditional ion exchange method. The relationship between photogenerated charge behaviors and luminescent properties has been investigated in detail. It has been demonstrated that as a result of the charge transfer from the titanate quantum wires to Eu³⁺ crystal field states, the host matrix ETS-10 functions as the sensitizer of Eu³⁺ to enhance the red luminescence, while Eu³⁺ cations contribute to the recombination of photogenerated charges. The behavior of photogenerated charges has significant impact on the luminescent properties of Eu³⁺-incorporated ETS-10 materials.