Mixed oxide

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

Phase Stability and Permeation Behavior of a Dead-End Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta) Tube Membrane in High-Purity Oxygen Production

Abstract: Phase stability and oxygen permeation behavior of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) dead-end tube membranes were investigated in long-term oxygen production at 950 and 750 °C. At 950 °C, the BSCF tube membranes exhibit good long-term phase stability and a stable oxygen permeation flux. However, at the intermediate temperature of 750 °C, both the oxygen permeation flux and the oxygen purity decrease continuously. This behavior is related to the formation of two secondary phases that are a hexagonal perovskite, Ba0.5±xSr0.5±xCoO3−δ, and a trigonal mixed oxide, Ba1–xSrxCo2–yFeyO5, that evolved in the ceramic membrane made of cubic BSCF perovskite during the dynamic flow of oxygen through it. Tensile stress as a result of phase formation causes the development of cracks in the membrane, which spoil the purity of the permeated oxygen. The partial degradation of cubic BSCF perovskite in the intermediate temperature range (750 °C) was more pronounced under the strongly oxidizing conditions on the oxygen supply (fe...

Effect of calcination temperature on the structure and catalytic performance of copper–ceria mixed oxide catalysts in phenol hydroxylation

Abstract: We report on highly active CuO@CeO2 catalysts prepared by the surfactant-template method and calcined at different temperatures. Then the obtained catalysts were characterized by means of various analytical techniques. Our findings show that the BET surface area and pore volume of the CuO@CeO2 catalyst measured by N2 adsorption–desorption are decreasing with the elevation of calcination temperature. From the results of XRD and XPS, we determined the oxidation state of copper in the copper–ceria mixed oxide catalysts. The CuO@CeO2 catalysts displayed good catalytic activity for the phenol hydroxylation using H2O2 as an oxidant. Moreover, we found that the catalytic activity is improved for high calcining temperature and the optimum conditions were obtained when the catalyst CuO@CeO2 is calcined at 800 °C, which lead to higher phenol conversion of 54.62% with 92.87% of selectivity for catechol and hydroquinone. More importantly, the catalyst seems to be easily recovered by simple centrifugation. The results of catalyst recycling illustrated that the catalytic activity remained high even after five cycles with slight Cu leaching and slight loss of activity. Finally, a possible mechanism in phenol hydroxylation by H2O2 over CuO@CeO2 catalyst was also proposed.

Properties of Acid Sites on TiO2–SiO2 and TiO2–Al2O3 Mixed Oxides Measured by Infrared Spectroscopy

Abstract: Both Lewis and Bronsted acid sites were found on the surface of TiO2–SiO2 mixed oxide, thouth no Bronsted acid sites were detected on the surface of pure TiO2 and SiO2 While on the surface of TiO2–Al2O3 mixed oxide, no Bronsted acid sites were generated The rate of isomerization of 1-butene was found to be enhanced on the Bronsted acid sites formed on the TiO2–SiO2 mixed oxide

Formation, sintering and thermal expansion behaviour of Sr- and Mg-doped LaCrO3 as SOFC interconnector prepared by the ethylene glycol polymerized complex solution synthesis method

Abstract: Sr- and Mg-doped LaCrO3 nanosized powders were succesfully synthesized from a polymeric precursor solution containing the respective aqueous solution of metal nitrate, chromium (III) nitrate, nitric acid, and ethylene glycol. The presence of a chromate solid solution of the type La 0.8 Sr0.2 Cr1-xMgx O 4 (x⩽0.2) as a low-temperature intermediate to perovskite-type is experimentally established using TG/DTA and XRD. In Sr, Mg-substituted LaCrO3, single-phase perovskite La0.8Sr0.2Cr1-xMgx O3 was formed at about 770 °C by decomposition of the chromate phase solid solution, which crystallizes at about 520 °C from amorphous powders. La0.8Sr0.2Cr1-x Mgx O3 perovskite solid solution powders with surface areas as high as 11 m2/g and nanosized particles sintered at 1550 °C for 6 h in air were higher than 97% dense materials. Such an improvement in densification can be attributed to a two-stage shrinkage process, i.e., liquid phase formation and solid perovskite particle rearrangement in the liquid, respectively. No significant variations in both the final density and grain size with increasing Mg content were detected. Compositions La0.8 Sr0.2 Cr0.9 Mg0.1O3 and La0.8 Sr0.2 Cr0.85 Mg0.15 O3 here investigated were shown to have negligible thermal expansion mismatch with YSZ electrolytes. The mixed oxide route was also used for comparison.