Advanced Materials Research Vols. 781-784

Abstract: Nanocrystalline TiO₂ powders were obtained at a low temperature between 50 and 80 °C by a hydrolysis of TiCl₄ in a mixed solution of distilled water and alcohol. The as-synthesized TiO₂ powders were characterized by X-ray diffraction analysis, transmission electron microscopy, and UVvisible absorption spectroscopy. Effects of the reaction temperature and the NH₄F concentration on the formation of the nanocrystalline TiO₂ powders were investigated. Results indicate that the reaction temperature greatly affects the particle size of the as-synthesized samples, and the NH₄F concentration has a great effect on the phase structure of the as-synthesized samples. In addition, the photocatalytic activities of the as-synthesized samples for rhodamine B were also measured, and it is found that the sample synthesized from the NH₄F concentration of 30 mM exhibits a higher photocatalytic activity than the P25 powder due to a high surface area and a pure anatase phase.

Abstract: Talc was used as support for synthesis of TiO₂-based photocatalyst with varying TiO₂ loading. A simple sol-gel method was used to impregnate titanium sol into the interlayers of talc with high speed stirring, followed by calcination at different temperature. The XRD analysis and SEM observation indicated that the anatase phases of TiO₂ were synthesized and individually distributed on the surface of the talc particles. FTIR were used to investigate the molecular group of TiO₂/talc. The wettability of talc was improved by TiO₂ particle coating. The efficiency of the TiO₂-talc composites to remove methylene blue from its aqueous solution was evaluated under UV irradiation. Different sintering temperature influenced the catalytic activity, TiO₂-talc composites enhanced dye degradation in contrast with physical adsorption of Talc or photo-catalytic of pure TiO₂.

Abstract: A series of ionic liquids were used as a co-solvent in the reaction of one-pot synthesis of phenols from aromatics and hydroxylamine. Then an eco-friendly catalytic system, i.e., [HSO₃-bmi [CF₃SO₃]-H₂O-HAc media with (NH₄)₆Mo₇O₂₄·4H₂O catalyst, was designed for the reaction. The results showed that aromatics were successfully hydroxylated to give the corresponding phenols. Recycling experiments suggested that the catalytic system was stable enough to be recycled.

Abstract: The adsorption of propylene oxide (PO) onto MgO, ZnO and Al₂O₃ was investigated by using in situ-IR measurements. Detailed mechanisms for PO adsorption onto these metal oxides are proposed. It was found that the PO epoxide ring exhibits two opening tendencies, depending on the acid-base properties of the metal oxide. PO adsorbed onto MgO is preferentially opened at the O-C (1) bond. The epoxide ring provides two ways to open, at the O-C (1) or the O-C(2) bond on Al₂O₃. PO adsorbed onto ZnO showed no chemical adsorption on its surface.

Abstract: An important liquid crystal intermediate of 4'-Bromoethynyl-4-pentyl-biphenyl was synthesized by bromo-reaction using N-bromosuccinimide as brominating agent, 4-Ethynyl-4'- pentyl-biphenyl as raw material, benzoyl peroxide (BPO) as catalyst and carbon tetrachloride (CCl₄) as reaction solvent. The effects of reaction variables were systematically optimized to achieve product with yield as high as possible. Under the optimal synthesis condition, where the temperature was 80oC, the mol ratio between 4-Ethynyl-4'- pentyl-biphenyl and NBS was 1:2, the weight rate of BPO to 4-Ethynyl-4'-pentyl-biphenyl was 2.5%, and the reaction time was 8 h, the product attained the best yield of 93.1%.

Abstract: Pyrene was adsorbed to a TiO2 surface from water-alcohol mixture solutions at 25°C and pyrene-TiO2 particles were recovered by filtration. We found that the surface of TiO2 thus recovered is relatively hydrophobic and pyrene is not decomposed but keep its fluorescence characteristics on the spectral measurement under ultraviolet excitation.

Abstract: A novel method for the catalytic oxidation of o-chlorotoluene (OCT) to o-chlorobenzaldehyde (CBD) was proposed using vanadium doped anatase mesoporous TiO₂ (V/MTiO₂), the catalytic reaction conditions were investigated. Under the optimum catalytic reaction conditions: 10 mL of acetic acid 100 °C of reaction temperature, 10 h of reaction time and 100 mg of catalyst, the conversion rate of OCT could reach to 95.3%, with a selectivity of 63.5%.

Abstract: New type of Co-based catalyst was prepared using (CO)₆Co₂CC(COOH)₂ as precursor supported on γ-Al₂O₃ support. The effects of pretreatment pressures on the catalysts properties and the F-T synthesis performance were investigated in details. Combined with TEM characterization technology, it was found that under different pretreatment pressures (0 MPa, 1.0 MPa, 2.0 MPa), the structure of carbonyl clusters underwent different changes. Moreover, the aggregation degree of cobalt species depends on the pretreated pressure applied. In addition, the catalytic performance of the cobalt carbonyl catalyst pretreated with different pressures was performed and both CO conversion and C₅⁺ selectivity exhibited the order of Co₂/2MPa/Al₂O₃ > Co₂/1MPa/Al₂O₃ > Co₂/0MPa/Al₂O₃.

Abstract: The synthesis of isoamyl acetate with ammonium 9-molybdate manganese heteropolyacid salt supported activated carbon as catalyst was studied. The optimum reaction conditions are obtained as follows: isoamyl alcohol to acetic acid molar ratio = 1.646, the weight of catalyst is 40% of total weigh, m (acidulate catalyst)=0.2g, m (water carrying reagent toluene) = 3ml, reaction time is about 63 minutes. Selectivity is 100% and conversion rate is 89.48%.

Abstract: To improve the structure order and catalytic activity of mesoporous materials, cubic (SBU-MCM-48) and hexagonal (SBU-MCM-41) mesoporous aluminosilicates containing secondary building units characteristic of zeolite Beta have been prepared, and characterized by means of XRD, N₂ adsorption, IR spectroscopy, catalytic cracking reaction compared with the corresponding MCM-41. We found that the introduction of secondary building units characteristic of zeolite Beta into the mesopore wall could be an effective route to improve the acidity of mesoporous materials. Moreover, cubic SBU-MCM-48 has been more active than hexagonal SBU-MCM-41 for cumene cracking reaction.