Mixed oxide

About: Mixed oxide is a research topic. Over the lifetime, 5224 publications have been published within this topic receiving 115567 citations.

Hydrothermal Synthesis, Characterization and Photocatalytic Activity of Nanosized TiO2 Based Catalysts for Rhodamine B Degradation

Abstract: Nanosize crystalline TiO2 and SiO2/TiO2 mixed oxide particles as a photocatalyst for rhodamine B dye (RB) degradation in aqueous media were synthesized by a hydrothermal process at 200 °C. They were characterized using XRD, SEM, FT-IR, UV/VIS and BET analysis. The effects of silica content on the crystallinity and photocatalytic activity of TiO2 were investigated. Photocatalytic activity of the nano-TiO2 was compared with that of SiO2/TiO2 mixed oxides at the same conditions for degradation of RB, and mixed oxide catalysts showed more effective catalytic activity than the TiO2. The results revealed that photodegradation of RB proceeds by pseudo-first-order reaction kinetics where the rate constant, k, for degradation of 30 mg/L RB using the catalyst with 0.05 SiO2/TiO2 mole ratio is 0.133 min-1.

Effect of the addition of Sn to zirconia on the acidicproperties of the sulfated mixed oxide

Abstract: Zirconium hydroxide, tin hydroxide and the mixed hydroxide of tin and zirconium (1:9) have been prepared, sulfated with a 0.1 Maqueous H 2 SO 4 solution and calcinated at 873 K. The chemical composition of these solids has been characterized by chemical analysis, differential thermal analysis (DTA), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray (EDX–) scanning transmission electron microscopy (STEM), and their structural and textural properties have been studied by BET surface area and XRD techniques. The nature of the acid sites (Bronsted or Lewis) was characterized by in situ IR study of pyridine adsorption and desorption and their amount was found to depend on the sulfate content. Catalytic properties have been studied for the isomerization reaction of n-butane to isobutane, in the 423 to 523 K range and for propan-2-ol conversion, in the 373 to 473 K range. Addition of Sn to ZrO 2 (SnO 2 :ZrO 2 =1:9) led to a solid solution and enhanced slightly (ca. 30%) the weak acid features of ZrO 2 and removed the basic properties of pure SnO 2 which was shown to convert propan-2-ol to acetone. Upon sulfation of ZrO 2 , SnO 2 –ZrO 2 [1:9] and SnO 2 , the acidity of the oxides was sharply enhanced. SO 4 2- /SnO 2 , which was inactive for the isomerization reaction, was only 60% less active than SO 4 2- /ZrO 2 for propan-2-ol dehydration. This shows that sulfation of SnO 2 generates acid sites of moderate strength. The presence of only 10% of SnO 2 in ZrO 2 decreased the reaction rates per SO 4 2- by a factor of six for the initial n-butane isomerization reaction and by a factor of seven for the propan-2-ol dehydration to propene and diisopropyl ether. It is suggested that the presence of Sn decreases the electron acceptor properties of Zr and thus its acidity strength. Since the rate per sulfated species of both reactions decreased in the same proportion, one may consider that on SO 4 2- /ZrO 2 and SO 4 2- /SnO 2 –ZrO 2 samples there is no site of moderate strength able to dehydrate propan-2-ol without isomerising n-butane.

Silicon-aluminum mixed oxide

Abstract: A silicon-aluminium mixed oxide produced by flame hydrolysis and having a composition of from 1 to 99.999 wt.% Al2O3, the remainder being SiO2. The mixed oxide exhibits an amorphous structure in the X-ray diffraction pattern and consists of intergrown primary particles. In these primary particles crystallites are present; these crystallites having sizes of between one and 200 nanometres and the specific surface area of the powder being between 5 and 300 m2/g. The silicon-aluminium mixed oxide is produced by a process wherein silicon halide and aluminium halide are vaporised in a particular ratio to one another, and are homogeneously mixed with air, oxygen and hydrogen in a mixing unit by means of a carrier gas. This mixture undergoes combustion in a burner of known construction and, after the separation of the solids from the vapour phase, any traces of halide possibly adhering to the product are separated off in a further processing step by means of moist air at elevated temperature.