Topic
Mixed oxide
About: Mixed oxide is a research topic. Over the lifetime, 5224 publications have been published within this topic receiving 115567 citations.
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24 Oct 1972TL;DR: An improved vanadium-phosphorus mixed oxide was prepared by a unique method employing an organic medium as discussed by the authors, and the substantial intrinsic surface area and the microcrystalline structure of the new oxide result in advantageous activity and selectivity effects in the catalyzed vapor phase oxidation of n-butane to maleic anhydride.
Abstract: An improved vanadium-phosphorus mixed oxide is prepared by a unique method employing an organic medium. The substantial intrinsic surface area and the microcrystalline structure of the new oxide result in advantageous activity and selectivity effects in the catalyzed vapor phase oxidation of n-butane to maleic anhydride. These oxides are also useful for the production of acid anhydrides from suitable hydrocarbon feeds.
75 citations
TL;DR: In this article, various magnesium-lanthanum mixed oxide catalysts having different mg/La molar ratio were compared and their catalytic activities for the transesterification of dimethyl carbonate (DMC) with glycerol for the synthesis of GLC were compared.
75 citations
TL;DR: In this paper, the rate of oxygen adsorption−desorption on Pt sites, support surface, oxygen transfer (spillover) from Pt to the support as well as the amount of oxygen accumulated in the oxide bulk, and oxygen diffusion coefficient were estimated.
Abstract: The kinetics of 18O/16O isotopic exchange over CeO2−ZrO2−La2O3 and Pt/CeO2−ZrO2 catalysts have been investigated under the conditions of dynamic adsorption−desorption equilibrium at atmospheric pressure and a temperature range of 650−850 °C. The rates of oxygen adsorption−desorption on Pt sites, support surface, oxygen transfer (spillover) from Pt to the support as well as the amount of oxygen accumulated in the oxide bulk, and oxygen diffusion coefficient were estimated. The nanocrystalline structure of lanthana-doped ceria-zirconia prepared via the Pechini route with a developed network of domain boundaries and specific defects guarantees a high oxygen mobility in the oxide bulk (D = (1.5 ÷ 2.0)·10-18 m2 s-1 at 650 °C) and allows accumulation of over-stoichiometric/excess oxygen. For Pt/CeO2−ZrO2, oxygen transfer from Pt to support (characteristic time < 10-2 s) was shown to be responsible for the fast exchange between the gas-phase oxygen and oxygen adsorbed on the mixed oxide surface. The rate of dire...
75 citations
TL;DR: In this paper, a detailed knowledge of long-term deactivation of Ni catalysts in CO2 methanation was provided, where Ni particle growth and a decrease in the BET surface area lead to deactivation.
Abstract: This work provides detailed knowledge of long-term deactivation of Ni catalysts in CO2 methanation. NiAlOx mixed oxides with varying Ni loading as well as a 17 wt-% Ni/γ-Al2O3 catalyst were synthesized via co-precipitation and incipient wetness impregnation, respectively. The catalysts were aged at 523, 573 and 623 K under equilibrium conditions up to 165 h. Periodic activity measurements under differential conditions reveal severe deactivation. The stability of co-precipitated systems increases with decreasing Ni content on the expense of catalyst activity. Ni/γ-Al2O3 exhibits a lower stability as a comparable mixed oxide. A power law model is applied for the kinetic description of deactivation. Catalyst samples are characterized by means of temperature programmed desorption of H2 (H2-TPD) and CO2 (CO2-TPD), pulsed H2 chemisorption, XRD, FT-IR spectroscopy, XPS and N2 physisorption. Main deactivation mechanisms in the co-precipitated samples are found to be Ni particle sintering, a loss of BET surface area as well as a reduction of CO2 adsorption capacity and medium basic sites, along with structural changes of the mixed oxide phase. Ni particle growth and a decrease in BET surface area lead to deactivation of the impregnated sample. Structure-activity correlations imply a complex interplay of governing deactivation phenomena as well as structure sensitivity.
75 citations
TL;DR: In this article, carbon dioxide reforming of methane was studied over nanostructure Co-MgO mixed oxide catalysts with different cobalt contents using XRD, BET, TEM, TPR, SEM and TPO techniques.
75 citations