Mixed oxide

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

Three-way catalyst

Abstract: A double-layer three-way catalyst for purification of the exhaust gases from internal combustion engines which has excellent activity and thermal stability is described. The catalyst contains active aluminum oxide and a first cerium/zirconium mixed oxide which are both catalytically activated with palladium in the first layer applied to a catalyst support. In the second layer which is in direct contact with the exhaust gas, the catalyst likewise contains an active aluminum oxide and a second cerium/zirconium mixed oxide which are both catalytically activated with rhodium. The second cerium/zirconium mixed oxide has a higher zirconium oxide content than the first mixed oxide.

Titania-zirconia mixed oxide aerogels as supports for hydrotreating catalysts

Abstract: Supercritical fluid (SFC) extraction was used to make aerogels of TiO 2 , ZrO 2 and two TiO 2 /ZrO 2 mixed oxides, having surface areas from two to five times greater than their conventionally prepared equivalents; additionally the mixed oxides have higher surface acidities than the two single component oxides Heat treatments, either during catalyst preparation or reactor testing, always resulted in small to significant decreases in surface areas in the aerogel-containing samples These samples were used as supports for Mo-Ni catalysts for the hydroprocessing of gas oil in a pilot-plant scale reactor The high ZrO 2 containing materials were found to be unstable under reaction conditions and were nearly inactive; in contrast, the high TiO 2 containing catalysts, while somewhat unstable, are more active on a surface area basis than Al 2 O 3 or conventional TiO 2 equivalent supported Mo-Ni catalysts This improvement is attributed to properties inherent in the SCF prepared supports; these results also indicate that support acidity contributes to hydrotreating activity

Catalytic hydrogen transfer from 2-propanol to cyclohexanone over basic Mg–Al oxides

Abstract: Magnesium–aluminium mixed oxides in mole ratios from 2 to 4 were obtained by thermal decomposition of layered double hydroxides (LDHs) as precursors. The effect of the Mg/Al ratio on the structure and surface properties of the resulting oxides was studied by using various instrumental techniques including X-ray diffraction (XRD), thermogravimetric analyses (TGA), MAS NMR, X-ray photoelectron spectroscopy (XPS) and gas adsorption–desorption, and so was their influence on the catalytic activity of the solids in the hydrogen transfer from 2-propanol to cyclohexanone. The results were compared with those for a pure MgO oxide and the Mg–Al mixed oxide obtained from the LDH with an Mg/Al ratio of 2 was found to provide the best catalytic activity. The influence on catalytic activity of other experimental variables including the pH of the medium used to synthesize the precursor LDHs, the temperature employed to prepare the Mg–Al oxides and the amount of catalyst used was also examined. Catalyst recycling tests were also conducted. Based on the results, a mechanism is proposed for the overall catalytic hydrogen transfer.

Transparent, conducting ATO thin films by epoxide-initiated sol-gel chemistry: a highly versatile route to mixed-metal oxide films.

Abstract: A robust synthesis approach to transparent conducting oxide (TCO) materials using epoxide assisted sol-gel chemistry is reported. The new route utilizes simple tin and antimony chloride precursors in aqueous solution, thus eliminating the need for organometallic precursors. Propylene oxide acts as a proton scavenger and drives metal hydroxide formation and subsequent polycondensation reactions. Thin films of antimony-doped tin oxide (ATO) were prepared by dip-coating of mixed metal oxide sols. After annealing at 600 °C in air, structural, electrical and optical properties of undoped and Sb-doped tin oxide films were characterized. Single layer films with 5 mol % Sb doping exhibited an optical transparency which was virtually identical to that of the plain glass substrate and an electrical resistivity of 2.8 × 10(-2) Ω cm. SEM and AFM analysis confirmed the presence of surface defects and cracks which increased with increasing Sb dopant concentration. Multiple depositions of identical ATO films showed a roughly 1 order of magnitude decrease in the film resistivity after the third layer, with typical values below 5 × 10(-3) Ω cm. This suggests that a second and third deposition fill up residual cracks and defects in the first layer and thus brings out the full performance of the ATO material. The epoxide-assisted sol chemistry is a promising technique for the preparation of mixed oxide thin film materials. Its superiority over conventional alkoxide and metal salt-based methods is explained in the context of a general description of the reaction mechanism.