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1.
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. 相似文献
2.
Katherine M. E. Stewart 《高分子科学杂志,A辑:纯化学与应用化学》2016,53(10):610-618
Four different metal oxide nanoparticles, copper oxide (CuO), aluminum oxide (Al2O3), nickel oxide (NiO), and titanium dioxide (TiO2), were added to poly (2,5-dimethyl aniline) (P25DMA) during synthesis to create different polymer nanocomposites. These polymer nanocomposites were evaluated as potential sensing materials for six different gas analytes (acetaldehyde, acetone, benzene, ethanol, formaldehyde, and methanol). It was found that CuO did not incorporate into the P25DMA and only a small percentage of Al2O3 was incorporated. However, both NiO and TiO2 were incorporated into the P25DMA at the same concentration as during the synthesis step. Overall, the type of metal oxide significantly affected the morphology of the sensing material and the amount of each analyte sorbed. For example, P25DMA doped with 5 wt% Al2O3 had high selectivity towards ethanol, whereas P25DMA doped with 20 wt% TiO2 sorbed the most ethanol. However, P25DMA doped with 20 wt% TiO2 also sorbed a high amount of formaldehyde, making P25DMA doped with 20 wt% TiO2 less selective than P25DMA doped with 5 wt% Al2O3 towards ethanol with respect to formaldehyde. 相似文献
3.
A. Barrera F. TzompantziR. Gómez 《Journal of photochemistry and photobiology. A, Chemistry》2012,227(1):45-50
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. 相似文献
4.
The concept of fabricating hollow fibers with double-layer mixed-matrix materials using the same polymeric matrix has been demonstrated for gas separation. Polyethersulfone (PES)–beta zeolite/PES–Al2O3 dual-layer mixed-matrix hollow fiber membranes with enhanced separation performance have been fabricated. This study presents an innovative approach of utilizing low cost PES and Al2O3 to replace expensive polyimides as the supporting medium for dual-layer mixed-matrix hollow fibers and eliminating interlayer de-lamination problems. The incorporations of 20 wt% beta zeolite in the outer selective layer and 60 wt% Al2O3 in the inner layer coupled with spinning at high elongational draw ratios yield membranes with an O2/N2 selectivity of 6.89. The presence of Al2O3 particles enables the membrane to retain its porous substructure morphology in the course of annealing above the glass transition temperature of PES. Moreover, spinning at high elongational draw ratios results in the re-distribution of Al2O3 particles towards both edges of the inner layer. Not only do the permeance and selectivity of the fibers increase, but also greater mechanical properties and lower degree of shrinkages are obtained. Therefore, the combination of PES–beta zeolite and PES–Al2O3 nanoparticles with a reasonable draw ratio may be another promising approach to produce hollow fibers with double-layer mixed-matrix materials. 相似文献
5.
R. łopatka L. Wachowski H. Boniuk I. CieŚlowska J. Zawadzki W. Skupiński 《Journal of Thermal Analysis and Calorimetry》1996,46(6):1599-1611
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. 相似文献
6.
The influence of coating of 5.0 (w/w%) Cu/γ‐Al2O3 catalyst by different ratios of polystyrene on the physicochemical and textural properties was studied. The physicochemical and textural properties of polystyrene‐`Cu/γ‐Al2O3 catalysts were investigated by N2 adsorption, O2 chemisorption, FTIR, XRD, TEM, and SEM. In addition, the kinetics of H2O2 decomposition as a model redox reaction over polymer coated and uncoated catalysts was investigated. The highest activity was achieved by 0.06 wt% polystyrene‐5.0Cu/γ‐Al2O3 catalyst. The parent 5.0Cu/γ‐Al2O3 catalyst showed auto‐catalytic first order mechanism, which was subjected to a pronounced modification to a simple first order one upon coating by polystyrene. This modification in the mechanism was accompanied with an increase in the apparent activation energy of the reaction. The observed high activity of 0.06 wt% polystyrene‐5.0Cu/γ‐Al2O3 catalyst was attributed to the role of polymer in enhancement of the degree of dispersion of the surface copper. However, the modification in kinetics of the reaction was attributed to the difference in the nature of Cu active sites namely, the polymer protected the metallic copper species on the surface of γ‐Al2O3 support against possible oxidation to copper sub‐oxides and/or that polymer might change the hydrophilic properties of the reaction media. 相似文献
7.
H. Karimian 《Journal of Dispersion Science and Technology》2013,34(4):457-464
Dispersion behavior of colloidal Al2O3 aqueous suspensions was investigated in the presence of highly charged CeO2 nanoparticles and polymeric additives. It was found that among the investigated parameters, ceria nanoparticles concentration had the highest significant effect on the stability of Al2O3-CeO2 suspensions. However, the low influence of dispersant concentration may be due to significant role of ceria nanoparticles stabilizing alumina microspheres by “nanoparticle halo” formation. The stabilization of the bidispersed suspensions was also evidenced by scanning electron microscopy and elemental analysis of the sediment layers after three weeks. 相似文献
8.
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. 相似文献
9.
The objectives of this paper are to study the crystallization behavior and fracture characteristics of spherical alumina (Al2O3) nanoparticle‐filled polypropylene (PP) composites. Nanocomposites containing 1.5–5.0 wt % of the Al2O3 nanoparticles (pretreated with silane coupling agent) were prepared for this investigation. Wide angle X‐ray diffraction (WAXD) results show that a small amount of β‐crystal of PP forms after adding the Al2O3 nanoparticles. According to differential scanning calorimetric (DSC) and optical microscopy (OM) measurements, the Al2O3 nanoparticles make PP spherulite size reduced and crystallization temperature of PP enhanced, by acting as effective nucleating agents. However, there are no obvious differences in the crystallinity for the virgin PP and the Al2O3/PP nanocomposites. Tensile test shows that both the Young's modulus and the yield strength of the Al2O3/PP nanocomposites increase with the particle content increasing, suggesting that the interfacial interaction between the nanoparticles and PP matrix is relatively strong. Under quasi‐static loading rate, the fracture toughness (KIC) of the Al2O3/PP nanocomposites was found to be insensitive to nanoparticle content. Under impact loading rate, the Izod impact strength and the impact fracture toughness (Gc) indicate that the impact fracture toughness increases initially with the addition of 1.5 wt % of the Al2O3 nanofillers into the PP matrix. However, with the further addition of up to 3.0 and 5.0 wt % nanoparticles, both the Izod impact strength and impact Gc change very little. By observing the single‐edge‐double‐notch (SEDN) specimens with optical microscopy after four point bending (4PB) tests, it was found that numerous crazes and microcracks form around the subcritical crack tip, indicating that crazing and microcracking are the dominant fracture mechanisms. Scanning electron microscopy (SEM) observation confirms this result. In addition, when the strain rate of 4PB tests was increased, some wave‐like branches were formed along the fractured edge for the Al2O3/PP nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3652–3664, 2005 相似文献
10.
Crystal-chemistry of mullite-type aluminoborates Al18B4O33 and Al5BO9: A stoichiometry puzzle 总被引:1,自引:0,他引:1
Orthorhombic Al2O3-rich aluminoborate is an important ceramic material for which two slightly different compositions have been assumed: Al5BO9 (5Al2O3:B2O3) and Al18B4O33 (9Al2O3:2B2O3). The formula Al18B4O33 (=Al4.91B1.09O9) was derived from results of chemical analyses when crystal structure data were not yet available. Subsequent structural investigations indicated Al5BO9 composition. Nevertheless, Al18B4O33 was still accepted as the correct stoichiometry assuming that additional B replaces 9% Al.Powder samples of both compositions and ones with excess boron were prepared by solid state reactions between α-Al2O3 and B2O3/H3BO3 at temperatures above 1100 °C and single-crystals were grown from flux at 1100 and 1550 °C. Products were investigated by single-crystal and powder XRD, 11B and 27Al solid-state MAS-NMR, Raman and FTIR spectroscopy as well as Laser-ablation ICP-MS. No indication of the predicted 9% B→Al substitution was found. LA ICP-MS indicated 12.36(27) wt% B2O3 corresponding to Al4.97B1.03O9. Hence, the suggested Al18B4O33 stoichiometry can be excluded for all synthesized samples. A very low amount of Al vacancies at a five-fold coordinated site are likely, charge balanced by an additional nearby three-fold coordinated B site. All evidences indicate that the title compound should be reported as Al5−xB1+xO9 with x<0.038(6), which is close to Al5BO9. 相似文献
11.
Zhiqiang Jiang Ya Li Yirui Shen Jian Yang Zongyong Zhang Yujing You Zhongda Lv Lihui Yao 《Molecules (Basel, Switzerland)》2021,26(9)
Hydrogel adhesives are attractive for applications in intelligent soft materials and tissue engineering, but conventional hydrogels usually have poor adhesion. In this study, we designed a strategy to synthesize a novel adhesive with a thin hydrogel adhesive layer integrated on a tough substrate hydrogel. The adhesive layer with positive charges of ammonium groups on the polymer backbones strongly bonds to a wide range of nonporous materials’ surfaces. The substrate layer with a dual hydrogen bond system consists of (i) weak hydrogen bonds between N,N-dimethyl acrylamide (DMAA) and acrylic acid (AAc) units and (ii) strong multiple hydrogen bonds between 2-ureido-4[1H]-pyrimidinone (UPy) units. The dual hydrogen-bond network endowed the hydrogel adhesives with unique mechanical properties, e.g., toughness, highly stretchability, and insensitivity to notches. The hydrogel adhesion to four types of materials like glass, 316L stainless steel, aluminum, Al2O3 ceramic, and two biological tissues including pig skin and pig kidney was investigated. The hydrogel bonds strongly to dry solid surfaces and wet tissue, which is promising for biomedical applications. 相似文献
12.
Hyoung Lim Koh Sang Ho Lee Kyung Lim Kim 《Reaction Kinetics and Catalysis Letters》2000,71(2):239-244
The effect of MoO3 addition to alumina supported vanadia catalysts on the catalytic activity for the selective catlaytic reduction of NO is investigated. Upon the addition of MoO3, catalytic activity is enhanced and the particle size of V2O5 which is shown by the results of XRD and Raman spectroscopy is decreased. The MoO3-V2O5/Al2O3 catalyst also exhibits more resistance to SO2 deactivation than V2O5/Al2O3 does. 相似文献
13.
Hai Hu Wenjun Xiao Jian Yuan Jianwei Shi Dannong He Wenfeng Shangguan 《Journal of Sol-Gel Science and Technology》2008,45(1):1-8
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. 相似文献
14.
Ravishankar Sathyamurthy Wael M. El-Maghlany Mohammed El Hadi Attia A. E. Kabeel Mohamed Abdelgaied Moataz M. Abdel-Aziz A. S. Abdullah S. Vasanthaseelan 《Molecules (Basel, Switzerland)》2022,27(24)
The traditional method of obtaining fresh water for drinking is by burning fossil fuels, emitting greenhouse gases into the atmosphere. However, renewable energy is gaining more traction since it is available free of cost for producing fresh water. In this study, Al2O3 nanoparticles were distributed in a phase change material (paraffin wax) that had been fixed at a hemispherical distiller water basin. Three scenarios with three hemispherical distillers were examined. A conventional hemispherical distiller (CHD), a conventional hemispherical distiller with paraffin wax as a phase change material (CHD-PCM), and a conventional hemispherical distiller with PCM partially filled with Al2O3 nanoparticles (CHD-N-PCM) were tested under the same climatic conditions. The experimental results showed that CHD gave a daily yield of 4.85 L/m2/day, while CHD-PCM increased the yield to up to 6.2 L/m2/day with a 27.84% daily yield enhancement. The addition of Al2O3 nanoparticles to paraffin wax CHD-N-PCM improved hemispherical distillate yield up to 8.3 L/m2/day with a 71.13% increase over CHD yield. 相似文献
15.
首先制备了未掺杂和5%(摩尔分数)Al3+掺杂SnO2的多孔性基片, 然后将基片与85%的H3PO4在600℃下反应, 分别得到了致密的未掺杂和5%Al3+掺杂的SnP2O7-SnO2复合陶瓷样品. 采用X射线衍射(XRD), 扫描电子显微镜(SEM)和X射线能量色散谱(EDS)测试方法对样品进行了表征, 采用电化学阻抗谱法(EIS)测试了样品在中温(100-250℃)下, 湿润空气和湿润氢气气氛中的电导率. 结果表明, 在湿润空气和湿润氢气中, 5%Al3+掺杂的SnP2O7-SnO2复合陶瓷样品的电导率均高于未掺杂的SnP2O7-SnO2复合陶瓷样品的电导率, 且该复合陶瓷样品在湿润空气和湿润氢气中250℃下, 电导率分别达到最大值: 4.30×10-2和6.25×10-2 S·cm-1, 高于至今报道的SnP2O7-SnO2基复合陶瓷及SnP2O7基陶瓷在类似条件下的电导率. 以5%Al3+掺杂的SnP2O7-SnO2复合陶瓷样品(厚度: 1.45 mm)为电解质, 多孔性铂为电极组装成的氢气/空气燃料电池具有良好的中温电池性能, 175、200、250℃的最大输出功率密度分别为52.0、61.9、82.3 mW·cm-2. 良好的中温电池性能与该复合陶瓷电解质较高的电导率和致密度及该燃料电池较低的界面极化电阻有关. 相似文献
16.
Polystyrene coated silica(SiO2@PS) core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO2 nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO2@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO2 and silane modified SiO2 nanoparticles.Suspensions of the untreated and the silane modified SiO2 exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO2 at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution. 相似文献
17.
An innovative procedure for functionalization of polyolefins was developed. It was found that synthesized polyolefins end‐capped with trimethoxysilane (silylated polyolefins) are new polyolefin‐based adhesives. To prepare the mentioned materials,1‐octene as a higher α‐olefin was cooligomerized with two linear, nonconjugated dienes (ie, 1,5‐hexadiene and 1,7‐octadiene) by using metallocene catalyst system, Cp2HfCl2/MAO, at room temperature. Then, amine‐terminated trimethoxysilane (3‐aminopropyltrimethoxysilane) was reacted with unsaturated bonds of synthesized cooligomers in the presence of palladium(II) acetate. Embedding of the dienes on 1‐octene oligomeric chains was explored by Fourier transform infrared (FTIR), 1H, and 13C‐NMR spectroscopy. On the basis of the results, 1,5‐hexadiene showed both 1‐butene branch and five‐member ring. On the other hand, 1,7‐octadiene was incorporated by 1,2‐addition, forming both 1‐hexene branch and seven‐member ring in the cooligomer backbone. Mole percentage of C?C and cyclic moieties reached to a value of 28.54, 18.59% mol in 1‐octene/1,5‐hexadiene, and 38.04, 6.71% mol in 1‐octene/1,7‐octadiene cooligomers, respectively. Reaction of synthesized cooligomers with 3‐aminopropyltrimethoxysilane was confirmed by FTIR spectroscopy, which yielded targeted adhesives. To study the adhesion properties, resulting adhesives were applied to different substrates. Obtained results demonstrated that tensile shear strength of synthesized adhesives to polar substrates was 2.21% to 2.84% more than nonpolar substrates. Among studied systems, the best performance was achieved by1‐octene/1,7‐octadiene–based adhesive and Al substrate with tensile shear strength of 1.45 N/mm2. 相似文献
18.
19.
Toshiaki Kabe Atsushi Ishihara Weihua Qian Azumi Funato Takenobu Kawano 《Reaction Kinetics and Catalysis Letters》1999,68(1):69-75
In hydrodesulfurization of radioactive35S-labeled dibenzothiophene catalyzed by CrO3/Al2O3, it was found that sulfur on sulfided CrO3/Al2O3 was more labile than those on MoO3/Al2O3 and WO3/Al2O3, while the amount of sulfur was less than that on MoO3/Al2O3.
Dedicated to Professor Pál Tétényi on the occasion of his 70th birthday 相似文献
20.
The effect of H2S on the activity and selectivity of catalysts (Ru/Al2O3, Pd/Al2O3 and Ru and Pd promoted molydena-alumina) was different (on differnt catalysts and different conversions of cyclohexene). Ru-containing catalysts showed higher sulfur sensitivities than the Pd-containing ones. The sequence of catalysts by their H2S uptake related to mass of catalyst was PdMo/Al2O3RuMo/Al2O3Mo/Al2O3>Pd/Al2O3Ru/Al2O3. 相似文献