钛硅分子筛ETS-10的合成和表征

以硅酸钠溶胶、硫酸钛为起始原料,在含KF碱性水热体系中制备出ETS-10钛硅酸盐分子筛;考察了原料的配比、晶化时间与温度对ETS-10合成的影响。应用XRD、SEM、EDX、FTIR和N2吸附技术表征了合成的ETS-10的结构和物性。结果表明,用组成为n(SiO2)∶n(TiO2)∶n(Na2O)∶n(KF)∶n(H2O)=7.5∶1.0∶5.0∶3.0∶198的凝胶,在463K(48h)和无模板剂的条件下,合成出结晶度良好的ETS-10。ETS-10晶体具有规则的四方切角锥形晶貌和微孔性质,比表面积和孔容分别为383.75cm2/g和0.16cm3/g;典型样品的化学组成接近已知的ETS-10组成表达式(Na,K)2TiSi5O13.4H2O。     

The strong basicity of the microporous titanosilicate ETS-10

Base-catalysed reactions in general are of great importance. In zeolite chemistry, alkali-metal-exchanged zeolites, such as zeolite X, display very strong basicity coupled with high catalytic activity. However, in order to achieve this strong basicity, considerable post-synthesis modification is necessary. In this report, it is shown that strong basicity is exhibited by the microporous titanosilicate ETS-10 in the as-prepared form which is superior to the presently known suite of zeolite catalysts. This opens up a new class of material for heterogeneous base catalysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

ETS-10 Modulation to Alumina Support and its Promotion for Hydrodesulfurization

A composite support with ETS-10 stabilized in alumina, was firstly developed for hydrodesulfurization (HDS). It can impede inactive nickel spinel formation and favor more polymeric tungsten species formation, which facilitates the promotion effect of nickel on tungsten and leads to increasing activity in HDS of 4,6-DMDBT.     

Hydrodesulfurization and hydrodearomatization activities of catalyst containing ETS-10 and AlPO4-5 on Daqing FCC diesel

A Ni–W loaded ETS-10/AlPO₄-5/Al₂O₃ composite support catalyst was optimized and used in hydrodesulfurization (HDS) and hydrodearomatization (HDA) of Daqing FCC diesel feedstock. The result indicated that ETS-10 and AlPO₄-5 showed positive synergism effect. The effects of operating conditions on its catalytic performance were investigated by using a 100 mL hydrotreating test unit. The catalyst showed a remarkable HDS conversion of 99.9% and a HDA conversion of 73.2%. A clean diesel product with ultra-low sulfur content (<1.0 μg/g) and very low polycyclic aromatic content (<2.0 wt.%) was obtained.     

On the effects of the sol-gel synthesis parameters on textural and structural characteristics of TiO2

The effects of alcohol/alkoxide, water/alkoxide molar ratios, acid addition, type of solvent, reaction temperature and calcination temperature on textural, structural and morphological characteristics of TiO₂ were studied. The results show that surface area, pore size distribution and crystalline phases were very sensitive to preparation conditions.     

Nonisothermal Crystallization and Melting Behaviors of PP/PA6/TiO2 Nanocomposites

Titanium dioxide nanoparticles were functionalized with toluene-2,4-diisocyanate and then polypropylene/polyamide 6 blends containing functionalized titanium dioxide were prepared using a twin-screw extruder. The nonisothermal crystallization and melting behaviors of the as-prepared nanocomposites were investigated using differential scanning calorimetry. The nonisothermal crystallization differential scanning calorimetry data were analyzed by the modified-Avrami (Jeziorny) and combination of Ozawa and Avrami (Mo) methods. It can be found that the Jeziorny method can be used to describe the main crystallization process, and the Mo method can better deal with nonisothermal crystallization kinetics of the polypropylene and polyamide 6 phase in polypropylene/polyamide 6-based nanocomposites. The nonisothermal crystallization analysis shows that the titanium dioxide nanoparticles have two effects on polypropylene/polyamide 6 blends, i.e., it can favor the improvement of crystallization ability and decrease the crystallization rate of the polypropylene and polyamide 6 phase in polypropylene/polyamide 6-based nanocomposites. For one thing, the functionalized titanium dioxide nanoparticles in the polypropylene/polyamide 6-based nanocomposites act as effective nucleation agents and result in higher crystallization temperature (T₀) than that of the polypropylene and polyamide 6 in pure polypropylene/polyamide 6 blends, which indicated titanium dioxide nanoparticles favor the improvement of crystallization ability of the polypropylene and polyamide 6 phase. For another, the existence of functionalized titanium dioxide nanoparticles hinders the free movement of polymer chains and results in lower crystallinity than that of the polypropylene and polyamide 6 in pure polypropylene/polyamide 6 blends, which indicated titanium dioxide nanoparticles decrease the crystallization rate of the polypropylene and polyamide 6 phase in polypropylene/polyamide 6-based nanocomposites. The nonisothermal crystallization melting behaviors show that there is single or double melting peak, which varies with different cooling rates for the polyamide 6 phase in polypropylene/polyamide 6-based nanocomposites. Multiple melting peak is mainly caused by the different crystalline structure of the polyamide 6 phase, the melting peak I is mainly caused by γ crystal of the polyamide 6 phase, while the melting peak II corresponds to the thermodynamic stability of α crystal. Besides, the recrystallization of the polyamide 6 phase in the heating process, and the effect of the incorporation of the titanium dioxide nanoparticles may have some contributions to the appeared multiple melting peak of the polyamide 6 phase in the polypropylene/polyamide 6-based nanocomposites.     

Synthesis and photocatalytic properties of H2La2Ti3O10/TiO2 intercalated nanomaterial

H₂La₂Ti₃O₁₀/ TiO₂ intercalated nanomaterial was fabricated by successive intercalation reactions of H₂La₂Ti₃O₁₀ with n-C₆H₁₃NH₂/C₂H₅OH mixed solution and acid TiO₂ sol, followed by irradiating with a high-pressure mercury lamp. The intercalated materials possess a gallery height of 0.46 nm and a specific surface area of 31.58 m²·g⁻¹, which indicate the formation of a porous material. H₂La₂Ti₃O₁₀/TiO₂ shows photocatalytic activity for the decomposition of organic dye under irradiation with visible light and the activity of TiO₂ intercalated material was superior to the unsupported one.     

Effect of rapid thermal annealing on the structural and electrical properties of TiO2 thin films prepared by plasma enhanced CVD

Titanium oxide thin films were deposited on p-type Si(100), SiO₂/Si, and Pt/Si substrates by plasma enhanced chemical vapor deposition using high purity Ti(O-i-C₃H₇)₄ and oxygen. As-deposited amorphous TiO₂ thin films were treated by rapid thermal annealing (RTA) in oxygen ambient, and the effects of RTA conditions on the structural and electrical properties of TiO₂ films were studied in terms of crystallinity, microstructure, current leakage, and dielectric constant. The dominant crystalline structures after 600 and 800 ‡C annealing were an anatase phase for the TiO₂ film on SiO₂/Si and a rutile phase for the film on a Pt/Si substrate. The dielectric constant of the as-grown and annealed TiO₂ thin films increased depending on the substrate in the order of Si, SiO₂/Si, and Pt/ Si. The SiO₂ thin layer was effective in preventing the formation of titanium silicide at the interface and current leakage of the film. TEM photographs showed an additional growth of SiO_x from oxygen supplied from both SiO₂ and TiO₂ films when the films were annealed at 1000 ‡C in an oxygen ambient. Intensity analysis of Raman peaks also indicated that optimizing the oxygen concentration and the annealing time is critical for growing a TiO₂ film having high dielectric and low current leakage characteristics.     

Photocatalytic reduction of N2O on metal-supported TiO2 powder at room temperature in the presence of H2O and CH3OH vapor

Ag- and Cu-supported TiO₂ photocatalysts showed high activity for the reduction of N₂O to N₂ at room temperature in the presence of CH₃OH and H₂O vapor. The suppression by H₂O on the activity was not observed in the present photocatalyst system. The remarkable behavior of the Ag and Cu co-catalysts for TiO₂ photocatalysts agreed well with that of electro- and thermal catalyses. This revised version was published online in July 2006 with corrections to the Cover Date.     

Efficient synthesis of titania nanotubes and enhanced photoresponse of Pt decorated TiO2 for water splitting

We investigated the effect of HMT (hexamethylenetetraamine) on the anodic growth of TiO₂ nanotube arrays. The tube length increases to 4.3 μm with HMT concentration increasing to 0.04 mol·L⁻¹. Adsorption of HMT on the TiO₂ surface is shown to markedly decrease the chemical dissolution rate of tube mouth, resulting in longer nanotube length. Furthermore, Pt nanoparticles were successfully deposited on the surface of TiO₂ nanotubes by ac electrodeposition method. The TiO₂/Pt composites were characterized by field emission scanning electron microscope (FESEM), X-ray photoelectron spectra (XPS), and photoelectrochemistry. An enhancement in photocurrent density has been achieved upon modification of TiO₂ nanotubes with Pt nanoparticles.     

TiO2-coated nanostructures for dye photo-degradation in water

The photocatalytic efficiency of a thin-film TiO₂-coated nanostructured template is studied by dye degradation in water. The nanostructured template was synthesized by metal-assisted wet etching of Si and used as substrate for the deposition of a thin film of TiO₂ (10 nm thick) by atomic layer deposition. A complete structural characterization was made by scanning and transmission electron microscopies. The significant photocatalytic performance was evaluated by the degradation of two dyes in water: methylene blue and methyl orange. The relevance of the reported results is discussed, opening the route toward the application of the synthesized nanostructured TiO₂ for water purification.     

Organic-skinned inorganic nanoparticles: surface-confined polymerization of 6-(3-thienyl)hexanoic acid bound to nanocrystalline TiO2

There are many practical difficulties in direct adsorption of polymers onto nanocrystalline inorganic oxide surface such as Al2O3 and TiO2 mainly due to the insolubility of polymers in solvents or polymer agglomeration during adsorption process. As an alternative approach to the direct polymer adsorption, we propose surface-bound polymerization of pre-adsorbed monomers. 6-(3-Thienyl)hexanoic acid (THA) was used as a monomer for poly[3-(5-carboxypentyl)thiophene-2,5-diyl] (PTHA). PTHA-coated nanocrystalline TiO2/FTO glass electrodes were prepared by immersing THA-adsorbed electrodes in FeCl3 oxidant solution. Characterization by ultraviolet/visible/infrared spectroscopy and thermal analysis showed that the monolayer of regiorandom-structured PTHA was successfully formed from intermolecular bonding between neighbored THA surface-bound to TiO2. The anchoring functional groups (-COOH) of the surface-crawling PTHA were completely utilized for strong bonding to the surface of TiO2.     

TiO2/ZnO Supported on Sepiolite: Preparation,Structural Characterization,and Photocatalytic Degradation of Flumequine Antibiotic in Aqueous Solution

In this study, TiO₂, ZnO, TiO₂/ZnO (Ti/Zn), and TiO₂/ZnO/Sep (Ti/Zn/Sep) catalysts have been synthesized using sol–gel and chemical precipitation method. Their photocatalytic performances have been compared using Flumequine (FLQ) antibiotic. X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), N₂-adsorption, and the determination of a zero point charge has been used to characterize the synthesized catalysts. The degradation studies showed that the catalytic efficiency of Ti/Zn/Sep is higher than that for other catalysts. The operational parameters such as pH, initial FLQ concentration, and catalyst dosage were evaluated. UV–vis and high-resolution mass spectroscopy (HRMS) analyses were used to determine the degradation efficiency and products. ZnO played a major role in the FLQ degradation process, and sepiolite contributed to adsorption of FLQ on the catalyst surface enormously. The catalysts exhibited 11%, 23%, 63%, and 85% degradation efficiency for ZnO, TiO₂, Ti/Zn, and Ti/Zn/Sep in the decomposition of FLQ, respectively.     

An in-situ Reduction/Oxidation XAS Study on the EL10V8 VO x /TiO2(Anatase) Powder Catalyst

The structural changes of the supported vanadium oxide in the V₂O₅/TiO₂(anatase) EUROCAT EL10V8 powder catalyst during reduction and oxidation at 420 and 490 °C were studied with in-situ X-ray absorption spectroscopy (XAS). The Vanadium K-edge XAS results are compared with pure bulk V₂O₅. For the reduction–oxidation cycle at 420 °C, similar structural changes as for bulk V₂O₅ were observed for the supported vanadium oxide: a reduction to the VO₂ structure and re-oxidation back to V₂O₅. After reduction at 490 °C however, a different structure was obtained: very regular “VO₆” octahedra with a V^2.8+ valence. This may point to a structural support effect.     

Bandgap Modulation of TiO2 and its Effect on the Activity in Photocatalytic Oxidation of 2-isopropyl-6-methyl-4-pyrimidinol

Nano-size TiO₂ particles were obtained using various mesoporous materials and the particle sizes were determined by the pore sizes of mesoporous materials. The bandgap increments due to quantum size effect were observed in both anatase TiO₂ and rutile TiO₂. The bandgap increment in anatase TiO₂ did not affect the efficiency of photocatalytic oxidation of 2-isopropyl-6-methyl-4-pyrimidinol. However, the bandgap increment in rutile TiO₂ enhanced the photocatalytic activity by virtue of the increase in redox potential of TiO₂.     

Stoichiometric photocatalytic decomposition of pure water in Pt/TiO2 aqueous suspension system

The influence of the direction of ultraviolet irradiation upon the yields of the photocatalytic decomposition of pure water has been investigated in Pt/TiO₂ aqueous suspension system. The yields of the photocatalytic decomposition irradiated from the top of the reaction cell are about 10³ times higher than those irradiated from the bottom. The difference seems due to the reverse reaction of the formed H₂ and O₂ in the suspension.     

Electrochemical characterization of TiO2/WOx nanotubes for photocatalytic application

TiO₂/WO_x nanotubes have unique photo-energy retention properties that have gathered scientific interest. Herein, we report the synthesis, morphological characterization, and the electrochemical characterization of TiO₂/WO_x nanotubes compared with pure TiO₂ nanotubes, prepared by anodization technique. Significant structural differences were not observed in TiO₂/WO_x nanotubes as observed by using scanning electron microscopy and transmission electron microscopy. The charge transfer resistance of TiO₂/WO_x before and after photo irradiation determined by using electrochemical impedance spectroscopy proves the inherent energy retention property which was not observed in pure TiO₂ nanotubes.     

Photocatalytic oxidation of ethylene to CO2 and H2O on ultrafine powdered TiO2 photocatalysts: Effect of the presence of O2 and H2O and the addition of Pt

The complete photocatalytic oxidation of C₂H₄ with O₂ into CO₂ and H₂O has been achieved on ultrafine powdered TiO₂ photocatalysts and the addition of H₂O was found to enhance the reaction. The photocatalytic reaction has been studied by IR, ESR, and analysis of the reaction products. UV irradiation of the photocatalysts at 275 K led to the photocatalytic oxidation of C₂H₄ with O₂ into CO₂, CO, and H₂O. The large surface area of the photocatalyst is one of the most important factors in achieving a high efficiency in the photocatalytic oxidation of C₂H₄. The photoformed OH species as well as O ₂ ⁻ and O ₃ ⁻ anion radicals play a significant role as a key active species in the complete photocatalytic oxidation of C₂H₄ with O₂ into CO₂ and H₂O. Interestingly, small amount of Pt addition to the TiO₂ photocatalyst increased the amount of selective formation of CO₂ which was the oxidation product of C₂H₄ and O₂.     

Prediction of a highly sensitive molecule sensor for SOx detection based on TiO2/MoS2 nanocomposites: a DFT study

First principles calculations within density functional theory have been carried out to investigate the adsorptions of SO_x (x?=?1, 2) molecules on TiO₂/MoS₂ nanocomposites in order to fully discover the gas sensing capabilities of TiO₂/MoS₂ composite systems. The van der Waals interactions were included to obtain the most stable geometrical structures of TiO₂/MoS₂ nanocomposites with adsorbed SO_x molecules. SO_x molecules preferentially interact with the doped nitrogen and fivefold coordinated titanium sites of the TiO₂ anatase nanoparticles because of their higher activities in comparison with the other sites. The results presented include structural parameters such as bond lengths and bond angles and energetics of the systems such as adsorption energies. The variation of electronic structures are discussed in view of the density of states and molecular orbitals of the SO_x molecules adsorbed on the nanocomposites. The results show that the adsorption of the SO_x molecule on the N-doped TiO₂/MoS₂ nanocomposite is energetically more favorable than the adsorption on the undoped one, implying that the nitrogen doping helps to strengthen the interaction of SO_x molecules with TiO₂/MoS₂ nanocomposites. These calculated results thus provide a theoretical basis for the potential applications of TiO₂/MoS₂ nanocomposites in the removal and sensing of harmful SO_x molecules.     

Effect of γ-ray Irradiation on the Wettability of TiO2 Single Crystals

The contact angles of the water droplets on TiO₂ single crystal surfaces decreased and became superhydrophilic state by γ-ray irradiation. It was found that these behaviors were dependent on γ-ray irradiation atmosphere, i.e., in air and in N₂ atmosphere (r. h.; 30%) as well as crystal faces of TiO₂ single crystals, i.e., TiO₂ (100) and (110) surfaces. It was also found from the results of UV–Vis and ESR measurements that γ-ray irradiation under N₂ atmosphere led to the oxygen vacancies and associated Ti³⁺, regardless of the presence of gaseous water. Moreover, it was suggested that the organic molecules adsorbed on TiO₂ single crystal surfaces decomposed by γ-ray irradiation.