Ultradeep Hydrodesulfurization of Dibenzothiophene (DBT) Derivatives over Mo-Sulfide Catalysts Supported on TiO2-Coated Alumina Composite

The present paper reviews in detail the different studies now being conducted by our research team concerning the ultradeep hydrodesulfurization (HDS) of dibenzothiophene (DBT) derivatives over Mo/TiO₂ and Mo/TiO₂–Al₂O₃ catalysts. First, a detailed characterization of Mo/TiO₂ (P-25 Degussa, 50 m²/g) catalysts prepared by equilibrium adsorption technique shows that Mo- species are highly and uniformly dispersed on the surface of titania up to 6.6 wt% MoO₃ loading. Above this value, some aggregation of Mo occurs, leading to the formation of bulk MoO₃. Below 6.6 wt% MoO₃ loading, the Raman spectroscopy data of the calcined samples show that the supported Mo-species possess a highly distorted octahedral MoO₆ structure. TiO₂–Al₂O₃ composites were prepared by chemical vapor deposition (CVD) using TiCl₄ as a precursor. Using several characterization techniques, we demonstrated that the support composite presents a high dispersion of TiO₂ over -Al₂O₃ without forming precipitates up to ca. 11 wt% loading. Moreover, the textural properties of the composite support are comparable to those of alumina. Under the present sulfidation conditions (673 K, 5%H₂S/95%H₂), Mo-species supported on TiO₂ are better sulfided than on alumina, as demonstrated using XPS. This can be attributed to the relatively lower interaction between Mo-species and titania. The state of sulfide species supported on the composite support can be considered as a transition state between TiO₂ and Al₂O₃. However, at relatively higher TiO₂ loadings (ca. 11 wt%), Mo/TiO₂–Al₂O₃ catalysts exhibit sulfidability similar to that of Mo/TiO₂. The HDS tests conducted in both the laboratory and in industry show that sulfide catalysts supported on TiO₂–Al₂O₃ (ca. 11 wt% TiO₂) are more active than those supported on TiO₂ or Al₂O₃.     

Application of response surface methodology for optimization of the stability of asphaltene particles in crude oil by TiO2/SiO2 nanofluids under static and dynamic conditions

In this work, the onset of asphaltene flocculation for an Iranian crude oil by titration of samples with heptane in the presence and absence of the TiO₂/SiO₂ nanofluids was obtained by Near-IR spectroscopy. Nanoparticles and nanocomposites were characterized by BET, FESEM, EDX, XRD, and XRF analysis. Modeling and optimization of inhibition of asphaltene flocculation process by TiO₂/SiO₂ nanofluids were conducted by response surface methodology (RSM). Under optimum conditions (nanocomposite composition = 0.04 wt% (80%TiO₂:20%SiO₂), salinity = 4.01 wt%, and pH = 3.42), the onset point increased. For nanofluids stability analysis, the optimum nanofluid was compared with the two other nanofluids (SiO₂ and TiO₂) by visual observation method. The results indicated that high stability and surface area of the 80%TiO₂ nanocomposites increase asphaltene adsorption on the particles surface that subsequently increases the onset point. In addition, the optimum nanofluid performance on the carbonate rocks was evaluated by contact angle and core flooding experiments. The 80% TiO₂ nanofluid changed the wettability of carbonate rocks from strongly oil-wet to strongly water-wet condition and also decreased the residual oil saturation and enhanced the oil recovery with an increase in the recovery factor of about 15%.     

Titania supported copper catalysts for methanol synthesis from carbon dioxide

The effect of co-catalyst (ZnO or ZrO₂) has been tested for hydrogenation of CO₂ on CuO/TiO₂ and CuO/Al₂O₃. CuO−ZnO/TiO₂ catalyst showed the highest activity for methanol synthesis. Kinetic parameters were also determined.     

Formation of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–TiO<Subscript>2</Subscript> bilayer using atomic layer deposition and its application to dynamic random access memory

To enhance film conformality together with electrical property suitable for dynamic random access memory (DRAM) capacitor dielectric, the effects of oxidant and post heat treatment were investigated on aluminum and titanium oxide (Al₂O₃–TiO₂) bilayer (ATO) thin film formed by atomic layer deposition method. For the conformal deposition of Al₂O₃ thin film, the O₃ oxidant required a higher deposition temperature, more than 450 °C, while H₂O or combined oxygen sources (H₂O+O₃) needed a wide range of deposition temperatures ranging from 250 to 450 °C. Conformal deposition of the TiO₂ thin film was achieved at around 325 °C regardless of the oxidants. The charge storage capacitance, measured from the ATO bilayer (4 nm Al₂O₃ and 2 nm TiO₂) deposited at 450 °C for Al₂O₃ and 325 °C for TiO₂ with O₃ oxidant on the phosphine-doped poly silicon trench, showed about 15% higher value than that of 5 nm Al₂O₃ single layer thin film without any increase of leakage current. To maintain the improved electrical property of the ATO bilayer for DRAM application, such as enhanced charge capacitance without increase of leakage current, upper electrode materials and post heat treatments after electrode formation must be selected carefully. Dedicated to Professor Su-Il Pyun on the occasion of his 65th birthday.     

Au改性TiO2纳米复合物对人结肠癌细胞的光催化杀伤作用

提出了通过TiO₂表面修饰纳米Au的方法来提高纳米TiO₂光催化杀伤癌细胞的效率. 采用化学还原法合成了Au改性的TiO₂ (Au/TiO₂)纳米复合物, 并研究了不同掺杂量(1 wt%, 2 wt%, 4 wt%)的Au/TiO₂对人结肠癌LoVo细胞的光催化杀伤效应. 结果显示, Au的掺杂大大地提高了TiO₂纳米粒子光催化杀伤结肠癌LoVo细胞的效率, 而且Au掺杂量的高低影响Au/TiO₂光催化杀伤癌细胞的效率, 掺金量为2%的Au/TiO₂对结肠癌LoVo细胞具有最高的光催化杀伤效率. 在光强为1.8 mW/cm²的紫外灯(λ_max＝365 nm)下光照110 min, 50 μg/mL掺金量为2%的Au/TiO₂能够杀死所有的癌细胞, 而同样浓度的TiO₂只能杀死70%的癌细胞.     

High photocatalytic activity and stability for decomposition of gaseous acetaldehyde on TiO2/Al2O3 composite films coated on foam nickel substrates by sol-gel processes

A set of anatase titanium dioxide (TiO₂) films coated on foam nickel that modified by Al₂O₃ films as transition layer (indicated as TiO₂/Al₂O₃ films) were synthesized via sol-gel route. The bulk and surface properties of the TiO₂/Al₂O₃ films were characterized by thermal gravimetric and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), and BET. The photocatalytic activities of TiO₂/Al₂O₃ films were investigated based on the degradation of gaseous acetaldehyde under ultraviolet (UV) irradiation. The foam nickel is a promising substrate material in practical applications because of its excellent hydrodynamic properties for gas passing. The TiO₂/Al₂O₃ composite films showed much higher photocatalytic activity and stability for degradation of gaseous acetaldehyde than the onefold TiO₂ films. The significant enhancement in photocatalytic activity and stability can be ascribed to the coating of Al₂O₃ transition layer, which concentrates the target substances around TiO₂ particles and increases the specific surface area (SSA) of the substrate (the SSAs of bare foam nickel and Al₂O₃ modified foam nickel are 0.12 and 113.7 m²/g, respectively) to provide more sites for TiO₂ loading.     

The formation and physicochemical characterization of Al2O3-doped manganese ferrites

Mn/Fe mixed oxide solids doped with Al₂O₃ (0.32-1.27 wt.%) were prepared by impregnation of manganese nitrate with finely powdered ferric oxide, then treated with different amounts of aluminum nitrate. The obtained samples were calcined in air at 700-1000 °C for 6 h. The specific surface area (S_BET) and the catalytic activity of pure and doped precalcined at 700-1000 °C have been measured by using N₂ adsorption isotherms and CO oxidation by O₂. The structure and the phase changes were characterized by DTA and XRD techniques. The obtained results revealed that Mn₂O₃ interacted readily with Fe₂O₃ to produce well-crystallized manganese ferrite (MnFe₂O₄) at temperatures of 800 °C and above. The degree of propagation of this reaction increased by Al₂O₃-doping and also by increasing the heating temperature. The treatment with 1.27 wt.% Al₂O₃ followed by heating at 1000 °C resulted in complete conversion of Mn/Fe oxides into the corresponding ferrite phase. The catalytic activity and S_BET of pure and doped solids were found to decrease, by increasing both the calcination temperature and the amount of Al₂O₃ added, due to the enhanced formation of MnFe₂O₄ phase which is less reactive than the free oxides (Mn₂O₃ and Fe₂O₃). The activation energy of formation (ΔE) of MnFe₂O₄ was determined for pure and doped solids. The promotion effect of aluminum in formation of MnFe₂O₄ was attributed to an effective increase in the mobility of reacting cations.     

Controlled synthesis of graphene oxide/alumina nanocomposites using a new dry sol–gel method of synthesis

The present paper gives new insight into the problem of controlling the morphology of reduced graphene oxide/alumina (RGO/Al₂O₃) nanocomposites. The dry and simplified sol–gel methods of RGO/Al₂O₃ nanocomposite synthesis were compared and the influence of six key synthesis parameters on the morphology of the resulting nanocomposite powders was investigated to optimize the morphology of RGO/Al₂O₃ nanocomposites in terms of reducing the undesired agglomeration of RGO/Al₂O₃ nanocomposite flakes to a significant minority and obtaining the uniform coverage of RGO surface with Al₂O₃ nanoparticles. Our investigations indicate that, despite the high excess of Al₂O₃ used (95 wt%), the lowest RGO/Al₂O₃ flake agglomeration and the formation of a uniform layer composed of Al₂O₃ nanoparticles with the average size of 58 nm occurred only when 5 wt% of graphene oxide was used as a substrate for the deposition of Al₂O₃ nanoparticles together with triethyl aluminium as an Al₂O₃ precursor and dry hexane as the reaction environment. The resulting organic precursor was thermally decomposed at 280 °C for 3 h in air atmosphere (R4 reaction pathway). This was confirmed by the high BET-specific surface area (242.4 m²/g) and the high open porosity (0.7 cm³/g) of the obtained RGO(5 wt%)/Al₂O₃ nanocomposite. This is also the first study with a detailed discussion of the reactions expected to occur during the synthesis of an RGO/Al₂O₃ nanocomposite.     

Nano oxides incorporated sulfonated poly(ether ether ketone) membranes with improved selectivity and stability for vanadium redox flow battery

Three kinds of sulfonated poly(ether ether ketone) (SPEEK)/nano oxide (Al₂O₃, SiO₂, and TiO₂) composite membranes are fabricated for vanadium redox flow battery (VRFB) application. The composite membranes with 5 wt% of Al₂O₃, SiO₂, and TiO₂ (S/A-5 %, S/S-5 %, and S/T-5 %) exhibit excellent cell performance in VRFB. Incorporation of nano oxides (Al₂O₃, SiO₂, and TiO₂) in SPEEK membrane improves in aspect of thermal, mechanical, and chemical stabilities due to the hydrogen bonds’ interaction between SPEEK matrix and nano oxides. The energy efficiencies (EEs) of composite membranes are higher than that of Nafion 117 membrane, owing to the good balance between proton conductivity and vanadium ion permeability. The discharge–capacity retentions of composite membranes also overwhelm that of Nafion 117 membrane after 200 cycles, indicating their good stability in VRFB system. These low-cost SPEEK/nano oxide composite membranes exhibit great potential for the application in VRFB.     

Thermal behaviour of NH4ReO4 supported on inorganic gels

Results of TG and DTA studies as well as an analysis of the liberated gas products have led us to recognize differences in the mechanisms of transformations taking place in the systems NH₄ReO₄/Al₂O₃-SiO₂ (25 wt% SiO₂ and NH₄ReO₄/Al₂O₃ containing 1.1, 3.3 and 3.3, 9.9, 17.8 wt% NH₄ReO₄. Thermal decomposition of NH₄ReO₄ on the supports used begins with release of ammonia, which is strongly bound with the surface in the system of 3.3 wt% NH₄ReO₄/Al₂O₃, and undergoes oxidation to nitrogen oxides in the air atmosphere. In the other systems studied, the process of ammonia release starts already at 473 K and ammonia does not get oxidized. Moreover, it has been established that ammonia perrhenate supported on the surface of Al₂O₃-SiO₂ in the amount of 1.1 or 3.3 wt% undergoes partial thermal decomposition to ReO₂ which is further oxidized in the air atmosphere. As follows from the thermal studies as well as the measurements of activity in a reaction of 1-hexene metathesis, the active centres of the reaction of olefin metathesis are formed on the surface of the studied systems after their calcination at 473 K.     

三维有序大孔复合材料Bi2O3/TiO2制备与多模式下光催化降解结晶紫

以TiO2为基体,在聚苯乙烯(PS)胶球和EO20PO70EO20(P123)两种模板剂作用下通过溶胶-凝胶及煅烧后处理方法制备了三维有序大孔纳米复合材料Bi2O3/TiO2.经傅里叶变换红外(FT-IR)光谱、X-射线衍射(XRD)、等离子体原子发射光谱(ICP-AES)、紫外-可见漫反射吸收光谱(UV-Vis DRS)、X-射线光电子能谱(XPS)、扫描电子显微镜(SEM)和N2吸附-脱附等物理测试手段对其组成、结构、形貌及表面物理化学性能进行了表征.结果表明,该复合材料晶型结构良好,孔结构排列整齐有序,孔壁呈介孔结构,属于三维有序大孔材料(3DOM).与TiO2相比,3DOM-Bi2O3/TiO2对光的吸收至少红移60 nm,且红移至可见区.在紫外光、可见光以及微波辅助等多模式光催化降解结晶紫的实验中,复合材料3DOM-Bi2O3/TiO2表现出良好的光催化活性,其活性明显高于P25、Bi2O3和Bi2O3/TiO2.同时,该复合材料针对不同类型的染料均表现出较好的紫外光降解效果,且3次循环实验后,依旧保持较高活性.     

The effect of B2O3 addition on the crystallization of amorphous TiO2-ZrO2 mixed oxide

The effect of B₂O₃ addition on the crystallization of amorphous TiO₂-ZrO₂ mixed oxide was investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA). TiO₂-ZrO₂ mixed oxide was prepared by co-precipitation method with aqueous ammonia as the precipitation reagent. Boric acid was used as a source of boria, and boria contents varied from 2 to 20 wt%. The results indicate that the addition of small amount of boria (<8 wt%) hinders the crystallization of amorphous TiO₂-ZrO₂ into a crystalline ZrTiO₄ compound, while a larger amount of boria (?8 wt%) promotes the crystallization process. FT-IR spectroscopy and ¹¹B MAS NMR results show that tetrahedral borate species predominate at low boria loading, and trigonal borate species increase with increasing boria loading. Thus it is concluded that highly dispersed tetrahedral BO₄ units delay, while a build-up of trigonal BO₃ promote, the crystallization of amorphous TiO₂-ZrO₂ to form ZrTiO₄ crystals.     

Preparation and Characterization of Bismuth Doped TiO2 Thin Films

A series of Bismuth-doped titanium oxide (Bi-doped TiO₂) thin films on glass substrates have been prepared by sol-gel dip coating process. The prepared catalysts were characterized by XRD and XPS. The photocatlytic activity of the thin film catalysts was evaluated through the photodegradation of aqueous methyl orange under UV illumination. The experiments demonstrated that the Bi-doped TiO₂ prepared was anatase phase. The doped bismuth was in the 3⁺ oxidation state. The presence of Bi significantly enhanced the photocatalytic activity of TiO₂ films. At calcination temperature of 500°C, with doping concentration of 2 wt %, Bi-doped TiO₂ thin film showed the highest photocatalyic activity.     

TiO2微粒功能化多孔Al2O3膜的光电化学研究

用恒电位法制备了多孔Al₂O₃薄膜, 通过在Al₂O₃薄膜孔内水蒸汽水解钛酸异丙酯生成了锐钛矿型TiO₂微粒, 制备出了Al₂O₃与TiO₂微粒的复合薄膜. 用XRD, SEM, 光电化学方法进行了研究. 实验表明: 该复合薄膜具有光电转换特性, 在光催化、光电化学太阳能转换中具有应用价值.     

Anodic composite deposition of RuO2·xH2O–TiO2 for electrochemical supercapacitors

This communication demonstrates the first work on anodic composite deposition of oxide nanocomposites. Rutile TiO₂ nanoflowers with an average petal size of ca. 10 nm in diameter and 100 nm in length were synthesized from a TiCl₃ solution purged with air at 25 °C for 12 days prior to the composite deposition. Hydrous ruthenium oxide (RuO₂·xH₂O) and TiO₂ nanoflowers were composite-deposited onto Ti substrates for supercapacitors. In comparing with RuO₂·xH₂O deposits, RuO₂·xH₂O–TiO₂ nanocomposites with a highly porous nature exhibit the weakly mass-dependent specific capacitance and high-power capacitive characteristics.     

Photodegradation of 2,4-D over PdO/Al2O3-Nd2O3 photocatalysts prepared by the sol-gel method

The photocatalytic activity of 1.0 wt% PdO supported on Al₂O₃-Nd₂O₃ binary oxides prepared by the sol-gel method was studied in the photodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The photocatalysts were characterized by N₂ physisorption, XRD and UV-vis spectroscopy. PdO supported on γ-Al₂O₃ photo-degrades the 2,4-D, however the addition of Nd₂O₃ to γ-Al₂O₃ notably improves the photocatalytic activity. As the concentration of Nd₂O₃ in the binary oxide increases from 2 to 10 wt%, the photodegradation of 2,4-D is highly enhanced. The catalytic test for PdO supported on pure Nd₂O₃ showed scarce photocatalytic activity. Total organic carbon (TOC) analysis showed that the 2,4-D has been completely destroyed on the PdO/Al₂O₃-Nd₂O₃ photocatalysts after 6 h under irradiation.     

应用原位漫反射红外-质谱技术研究CuO/Al2O3催化剂表面酸性及其反应性能

应用原位漫反射红外-质谱联用、程序升温和暂态响应技术研究了CuO/Al₂O₃催化剂表面酸性及其反应性能. 实验结果表明, CuO/Al₂O₃催化剂表面呈Lewis酸性, 硫化不仅可增强CuO/Al₂O₃催化剂的Lewis酸性, 而且可产生新的Brønsted酸性位; 吸附于Lewis酸性位的NH₃具有选择性催化还原(SCR)活性. 而在硫化样Cu8(400S)中Lewis和Brønsted酸性位同时存在的情况下, 吸附于Lewis和Brønsted酸性位的氨均具有SCR活性, 且后者较前者弱; CuO/Al₂O₃催化剂上的SCR反应遵循Eley-Rideal机理, 即SCR反应发生于吸附态NH₃与气相NO之间.     

Transparent poly(bisphenol A carbonate)-based nanocomposites with high refractive index nanoparticles

Transparent organic-inorganic nanocomposites were successfully synthesized from sulfonic acid-modified poly(bisphenol A carbonate) (SPC) and TiO₂ or ZrO₂ nanoparticles. The dispersibility of nanoparticles was significantly improved by both the surface treatment of nanoparticles with phosphoric acid 2-ethylhexyl esters (PAEH) and the introduction of a sulfonic acid moiety into the PC chain. It was found that in some cases, crystallization of the matrix caused a reduction in transparency. Efficient dispersion of nanoparticles and the absence of crystallization resulted in highly transparent nanocomposites with up to 42 wt% TiO₂ and 50 wt% ZrO₂ nanoparticles. The refractive indices of the nanocomposites based on SPC increased with the increasing amount of nanoparticles. Theoretical equation based on Maxwell-Garnett effective medium theory provided reasonably close estimation of the refractive indices to the experimentally observed values. The prepared nanocomposites had lower thermal stability than the host matrix polymers.     

Sol–gel synthesis and characterization of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–TiO<Subscript>2</Subscript> nanocrystalline powder

Al₂O₃–TiO₂ nanocrystalline powders were synthesized by sol–gel process. Aluminum sec-butoxide and titanium isopropoxide chemicals were used as precursors and ethyl acetoacetate was used as chelating agent. Thermal and crystallization behaviors of the precursor powders were investigated by thermal gravimetric-differential thermal analysis, Fourier-transform infrared spectrum and X-ray diffraction. The average crystalline size of heat treated Al₂O₃–TiO₂ powders at 1,100 °C is ~100 nm.