Mixed oxide

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

Influence of calcination temperature on the structure and catalytic performance of CuOx-CoOy-CeO2 ternary mixed oxide for CO oxidation

Abstract: Influence of calcination temperature (400−800 °C) on the structure and catalytic activity of CuO x -CoO y -CeO 2 ternary mixed oxide (atomic Cu:Co:Ce ratio of 1:5:5) prepared by co-precipitation method is investigated by N 2 physisorption, XRD, TPR, TEM, TG-DTA, XPS, and CO oxidation reaction. The as-synthesized CuO x -CoO y -CeO 2 undergoes successive structural changes with the calcination temperature, involving the hydroxide dehydration below 400 °C, enhanced interaction between Co 3 O 4 and CeO 2 at ca. 600 °C, and Co 3 O 4 decomposition to CoO at 700 °C. The catalyst calcined at 600 °C shows a relative enrichment of Cu + on the surface of CuO x -CoO y -CeO 2 and an enhanced interaction between Co 3 O 4 and CeO 2 along with the appearance of oxygen vacancies in CeO 2 , which seems to be responsible for its highest catalytic activity for CO oxidation among all the tested catalysts. The complete conversion of CO is obtained at 70 °C and about 50% of CO conversion is reached at 55 °C.

Stabilization of Catalytically Active Cu+ Surface Sites on Titanium–Copper Mixed‐Oxide Films

Abstract: The oxidation of CO is the archetypal heterogeneous catalytic reaction and plays a central role in the advancement of fundamental studies, the control of automobile emissions, and industrial oxidation reactions. Copper-based catalysts were the first catalysts that were reported to enable the oxidation of CO at room temperature, but a lack of stability at the elevated reaction temperatures that are used in automobile catalytic converters, in particular the loss of the most reactive Cu+ cations, leads to their deactivation. Using a combined experimental and theoretical approach, it is shown how the incorporation of titanium cations in a Cu2O film leads to the formation of a stable mixed-metal oxide with a Cu+ terminated surface that is highly active for CO oxidation.

Analysis of structural transformations during the synthesis of a MoVTeNb mixed oxide catalyst

Abstract: This work presents a detailed investigation of the preparation routine for the multi-metal oxide Mo 1 V 0.30 Te 0.23 Nb 0.125 O x used as catalyst for the selective oxidation of propane to acrylic acid. In situ Raman spectroscopy on the initial aqueous polyoxometalate solution prepared from ammonium heptamolybdate, ammonium metavanadate and hexaoxotelluric acid reveals the coexistence of Anderson-type anions [TeM 6 O 24 ] n − , M = Mo, V; n ≥ 6 and protonated decavanadate species [H x V 10 O 28 ] (6− x )− . Raman analysis showed that the monomeric motif of the Anderson-type tellurate is preserved after addition of the Nb precursor and the subsequent spray-drying process. Calcination of the X-ray amorphous spray-dried material in air at 548 K seems to be the essential step, leading to a re-arrangement of the tellurate building blocks, generating nanocrystalline precursors of the phases finally established during treatment in helium at 873 K.

Kinetic Study of Oxidative Dehydrogenation of Ethane over MoVTeNb Mixed-Oxide Catalyst

Abstract: A MoVTeNb multimetallic mixed oxide was studied for the oxidative dehydrogenation of ethane, a promising alternative for catalytic ethylene production. Lab-scale steady-state experimental reaction data were obtained according to a 3k experimental design to investigate the simultaneous effect of temperature (400–480 °C) and space–time [23–70 gcat h (mol of ethane)−1]. A fixed-bed reactor at atmospheric pressure was employed, feeding a mixture of ethane, oxygen, and nitrogen. Ethane conversion varied from 17 to 85%, whereas selectivity for ethylene and COx varied from 94 to 76% and from 4.0 to 24%, respectively. These types of analyses are useful for determining the optimum reaction conditions to enhance the catalytic performance of the mixed oxides presented herein.