Nano γ-Al2O3 Research Articles

The Effect of Porosity and Morphology of Nano γ-Al2O3 and Commercial γ-Al2O3 Catalysts on the Conversions of Methanol to DME

The conversion of methanol to dimethyl ether was carried out over the commercial γ-Al2O3 and synthesized nano γ-Al2O3 to evaluate their catalytic performances. The synthesized catalyst was characterized by SEM, XRD, and BET. The catalyst has a high surface area and low bulk density, which results in better stability and lower pressure drop because of their pore spongy structures at the same temperature and WHSV (weight hourly space velocity). The results showed that maximum conversion of reaction was observed at a temperature range of 310 to 350°C and WHSV of 15 h−1 with methanol conversion of 80% for commercial catalyst (spherical particles) and 83% for synthesized catalyst (spongy particles).

Effect of ZrO2 on the catalytic performance of nano γ-Al2O3 in dehydration of methanol to dimethyl ether at relatively low temperature

A series of ZrO2/γ-Al2O3 catalysts were prepared by incipient wetness impregnation of zirconyl nitrate hydrate aqueous solutions on nano-γ-Al2O3 with ZrO2 loadings (1–30 % w/w) and calcined at 450 and 550 °C for 3 h in a static air atmosphere. Physicochemical properties of the catalysts were determined using TG, DTA, XRD, FT-IR, Raman spectroscopy, TEM, and N2 sorption measurements. The surface acidity of the catalysts was investigated by dehydration of isopropanol and adsorption of pyridine, 2,6-dimethyl pyridine and TPD–pyridine. This series of catalysts was used for vapor-phase dehydration of methanol to dimethyl ether in a fixed bed reactor. It was found that all catalysts in this study were active and selective for DME synthesis. According to the experimental results, 1 % ZA catalyst exhibited the highest activity with selectivity of 100 % toward DME.

Two component reaction for the synthesis of Quinolines in the presence of γ-Al 2 O 3 and Cu/ZnO nanoparticles

Two-component reaction of 2-aminobenzophenones with acetylenic esters in the presence of γ-Al2O3 and Cu/ZnO as suitable heterogeneous catalysts has been studied. Nano γ-Al2O3 and Cu/ZnO showed high activities when used as surface catalysts for the synthesis of quinoline derivatives. After completion of the reaction, the catalyst was recovered and reused several times under the same reaction conditions.

Microstructural observation, consolidation and mechanical behaviour of AA 6061 nanocomposites reinforced by γ-Al2O3 nanoparticles

AA 6061 nanocomposites of nanocrystallite powders reinforced with nano-alumina particles were synthesized and investigated in this study. A uniform distribution of nano γ-Al2O3 in the AA 6061 nanocrystallite matrix was successfully obtained after 30h of mechanical alloying (MA). The compressibility and sinterability of the prepared nanocomposite powders at varying sintering temperatures and varying compaction pressures was also studied. The consolidation behaviour of the AA 6061/γ-Al2O3 nanocomposites was evaluated using the Balshin, Heckel, Panelli and Ambrosio Filho, and Ge linear compaction equations. The compression strength of the green samples and the Vickers hardness of the nanocomposites were also evaluated. A maximum green compression strength of 176MPa and a maximum hardness of 740MPa were obtained for the addition of 2wt.% Al2O3 nanoparticles to the AA 6061 matrix after 30h of MA.

Regioselective Multi-component Synthesis of 7-Aryl-benzo[h][1,2,4]-triazolo[5,1-b]quinazoline-5,6-diones Catalyzed by n-Propylsulfonated γ-Al2O2

Naphthoquinones constitute a major class of naturally occurring compounds, and interests in their chemistry continues unabated because of their wide range of biological and therapeutic properties such as antioxidant, antifungal, anti-inflammatory, antiallergic, antiviral, and anticancer activity. Triazoloquinazolines are ‘privileged medicinal scaffolds’ which are used for the development of pharmaceutical agents of various applications. Compounds with these motif show a wide range of pharmacological activities such as anticonvulsant, anti-inflammatory, antimicrobial, and antiviral. Considering the above reports, development of new and simple synthetic methods for efficient preparation of new ortho-naphthoquinones involving the “triazoloquinazoline” synthons are therefore an interesting challenge. In continuation of our efforts to develop novel reaction methodologies using nano n-propylsulfonated γ-Al2O3, 11 we now report herein a highly regioselective procedure for the preparation of 7-aryl-benzo[h][1,2,4]-triazolo[5,1-b]quinazoline-5,6-diones using nano n-propylsulfonated γ-Al2O3 as an efficient and versatile catalyst under solvent-free conditions (Scheme 1). First, to achieve suitable conditions for the synthesis of 7-arylbenzo[h][1,2,4]-triazolo[5,1-b]quinazoline-5,6-diones, we tested the three-component reaction of benzaldehyde, 2hydroxy-1,4-naphthoquinone, and 3-amino-1,2,4-triazole as a simple model system at 100 °C under solvent free conditions using various catalysts (Table 1). As shown in Table 1, the best result was obtained with 100 mg/mmol of nano npropylsulfonated γ-Al2O3 as the catalyst at 100 °C under solvent free conditions (Table 1, entry 3). Using less catalyst resulted in lower yields, whereas higher amounts of catalyst did not affect the reaction times and yields. When this reaction was carried out without nano n-propylsulfonated γAl2O3 or with other catalysts such as FeCl3, AlCl3, and nano γ-Al2O3, the yield of the expected product was much lower (< 30%). In the presence of p-TsOH, Fe(HSO4)3, or other nano n-propyl-sulfonated metal oxide such as nano npropyl-sulfonated SiO2, nano n-propylsulfonated ZnO the product was obtained still in lower yield (52-70%). After the successful preparation of 4a, we decided to introduce more diversity in the benzo[h][1,2,4]-triazolo[5,1b]quinazoline-5,6-dione scaffolds. With the optimized reaction conditions in hand we examined a variety of aldehydes and 2-hydroxy-1,4-naphthoquinone with 3-amino-1,2,4triazole and found that nano n-propylsulfonated γ-Al2O3 is an excellent catalyst system for the synthesis of a large spectrum of benzo[h][1,2,4]-triazolo[5,1-b] quinazoline-5,6diones (Table 2). Clearly, these reactions proceeded very cleanly under mild reaction conditions and no para-quinone isomeric systems were observed. It is worthwhile to mention that aromatic aldehydes with electron-donating and electronwithdrawing groups as well as heterocyclic aldehydes afforded the correspond products in excellent yields. The structure of the ortho-quinone structures 4 is in full agreement with H NMR, C NMR, MS and elemental analysis as illustrated below for a representative example (compound 4c). The Scheme 1. Synthesis of 7-aryl-benzo[h][1,2,4]-triazolo[5,1-b]quinazoline-5,6-diones using nano n-propylsulfonated γ-Al2O3. Table 1. Catalyst optimization for the synthesis 7-phenyl-benzo[h] [1,2,4]-triazolo[5,1-b]quinazoline-5,6-dionea

Sulfonic Acid Functionalized Nano Γ-Al2O3: a New, Efficient, and Reusable Catalyst for Synthesis of Thioamides

Sulfonic acid functionalized nano γ-Al2O3 is easily prepared by the reaction of nano γ-Al2O3 with 1,3-propane sulfone. This reagent can be used as an eficient catalyst for the synthesis of thioamides. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be recovered for several times.

Sulfonic Acid Functionalized Nano γ-Al2O3Catalyzed Synthesis of Thioethers

A series of thioethers were synthesized efficiently in high yields by reaction of thiols with alcohols in the presence of sulfonic acid functionalized nano γ-Al2O3 at room temperature under solvent-free conditions. All products were character- ized by 1 H NMR, 13 C NMR spectra and elemental analysis.

Sulfonic acid functionalized nano γ-Al2O3 catalyzed per-O-acetylated of carbohydrates

A simple and clean synthesis of per-O-acetylation carbohydrate derivatives has been accomplished by treatment of sugars with a stoichiometric quantity of acetic anhydride under solvent-free conditions in the presence of sulfonic acid functionalized nano γ-Al2O3 as an efficient and environmentally benign catalyst.

Reaction kinetics determination and neural networks modeling of methanol dehydration over nano γ-Al2O3 catalyst

In this research nano γ-Al2O3 catalyst was synthesized through precipitation process then characterized and utilized for methanol dehydration reaction in a slurry batch reactor in route to the indirect synthesis of the dimethyl ether (DME). In this venue, effects of the key parameters on methanol conversion and catalyst stability were investigated. Moreover, the internal and external mass transfer resistances were eliminated; hence the intrinsic kinetics controlled the reaction. Therefore, the optimum conditions for temperature, methanol concentration, catalyst mass and stirrer speed were determined to be 300°C, 1.18mol/l, 1.5g and 1100rpm, respectively. Next, different reaction rate equations from literature were applied to the measured experimental data where their generality compared to a new reaction rate equation examined. Ultimately, artificial neural networks applied to determine a model for the reaction rate estimation. It has been shown that the proposed reaction rate equation might be used rather satisfactorily to provide a base model for the neural networks; consequently a very good proximity to the reaction dynamics resulted.

Microstructural features and properties of high-hardness and heat-resistant dispersion strengthened copper by reaction milling

The oxide dispersion strengthened copper alloys are attractive due to their excellent combination of thermal and electrical conductivities, high-temperature strength and microstructure stability. To date, the state-of-art to fabrication of them was the internal oxidation (IO) process. In this paper, alumina dispersion strengthened copper (ADSC) powders of nominal composition of Cu-2.5 vol%Al2O3 were produced by reaction milling (RM) process which was an in-situ gas-solid reaction process. The bulk ADSC alloys for electrical and mechanical properties investigation were obtained by sintering and thereafter hot extrusion. After the hot consolidation processes, the fully densified powder compacts can be obtained. The single γ-Al2O3 phase and profile broaden effects are evident in accordance with the results of X-ray diffraction (XRD); the HRB hardness of the ADSC can be as high as 95; the outcomes should be attributed to the pinning effect of nano γ-Al2O3 on dislocations and grain boundaries in the copper matrix. The electrical conductivity of the ADSC alloy is 55%IACS (International Annealing Copper Standard). The room temperature hardness of the hot consolidated material was approximately maintained after annealing for 1 h at 900 °C in hydrogen atmosphere. In terms of the above merits, the RM process to fabricating ADSC alloys is a promising method to improve heat resistance, hardness, electrical conductivity and wear resistance properties etc.

Effect of Al2O3 phases on the enhancement of thermal conductivity and viscosity of nanofluids in engine oil

Thermal conductivity of α-Al2O3 was measured using hot wire method. α-Al2O3 (20 nm in size) was synthesized by microwave method for which, the results were compared with commercially available γ-Al2O3. Thermal conductivity of nanofluids was investigated considering, it is dependency on Al2O3 phase. It was observed that by adding 3 wt% of nano γ-Al2O3 and α-Al2O3 to the engine oil, thermal conductivity increases by 37 and 31%, respectively. The corresponding viscosity increase for the same amount of nano γ-Al2O3 and α-Al2O3 were 36 and 38%, respectively. It was concluded that the differences in thermal conductivity originate from higher specific surface area of γ-Al2O3 compared to the α-Al2O3 which is the result of porosity difference, obtained during the synthesis process.

Effect of nano γ-Al2O3 addition on ion dynamics in polymer electrolytes

Polymer electrolytes, which hold the key of successful operation of all solid state ionic devices, have been investigated. An amorphous polymer was used to facsimile fast ion transport in the gel polymer electrolytes (GPE) and room temperature conductivity >10−3 S/cm can be attained. Further, these electrolytes were transformed into composites by dispersing inorganic particles of γ-Al2O3 (11 nm in size) in varying wt.%. An enhancement in the conductivity for an optimum concentration using LiClO4 as a salt can be obtained and is described in terms of free charge carrier concentration, while the other family of Lithium salts viz. LiTf, LiIm, LiBETI decreases the conductivity marginally. FTIR spectroscopy supports the observed decrease in terms of more association between fillers and salts. It has been realized that the mechanical integrity of these composites increases manifold, without affecting the conductivity, significantly.

Microstructural development and mechanical properties of self-reinforced alumina with CAS addition

Abstract In-situ development of platelike alumina grains were obtained by adding CAS glass powder (CaO–Al2O3–SiO2) into fine alpha alumina powder sintered in the range from 1550 to 1600°C. The sintering behavior, microstructural development and mechanical properties of self-reinforced alumina ceramics with different amount of additives were investigated. The theoretical densities of the samples sintered at 1550°C reached >97% which appeared to be the optimal sintering temperature and the addition of CAS slightly decreased the densities of samples sintered from 1300 to 1600°C, compared with the samples without CAS additive. The platelike grains were not formed in alumina ceramics without adding CAS, even sintered at 1600°C. When the 0.1∼0.5 wt.% CAS glass powder was added to the starting composition, the platelike grains were formed completely at 1550°C. The formation of platelike grains increased the fracture toughness but decreased the bending strength, the combined action of crack deflection and crack bridging accounted for the observed increase of fracture toughness. The mechanical properties decreased with increasing the sintering temperatures from 1550 to 1660°C. Adding nano γ-Al2O3 can enhance the mechanical properties of the samples sintered at 1550 and 1600°C.