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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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TL;DR: In this article, an atomic layer deposition (ALD) was used to controllably modify Rh catalysts with MnO, by depositing manganese oxide as a support layer or an overlayer, in order to identify the function of the Mn promoter.
Abstract: Rhodium (Rh) catalysts are among the major candidates for syngas conversion to higher oxygenates (C2+oxy), with manganese (Mn) as a commonly used promoter for enhancing the activity and selectivity toward C2+oxy. In this study, we use atomic layer deposition (ALD) to controllably modify Rh catalysts with MnO, by depositing manganese oxide as a support layer or an overlayer, in order to identify the function of the Mn promoter. We also compare the ALD-modified catalysts with those prepared by coimpregnation. An ultrathin MnO support layer shows the most effective enhancement for C2+oxy production. Transmission electron microscopy, temperature-programmed reduction, and diffuse reflectance infrared Fourier transform spectroscopy characterization indicates that formation of Rh–MnO interface sites is responsible for the observed activity and selectivity improvements, while ruling out Rh nanoparticle size and alloy or mixed oxide formation as significant contributors. MnO overlayers on Rh appear to suffer from ...

63 citations

Journal ArticleDOI
TL;DR: In this paper, the performance of synthesized CaLaO mixed oxide catalysts was examined by characterizing it through instruments such as XRD, BET and CO2-TPD, revealed that the Ca/La atomic ratio strongly affects the phase structure, catalyst basic sites, and thus the catalytic reactivity.
Abstract: The catalytic transesterification of crude Jatropha curcus oil (JCO) with supercritical methanol (scMeOH), in the presence of calcium lanthanum mixed oxide (CaLaO) heterogeneous base catalyst was carried out using a batch reactor at near critical temperatures and pressures. The performance of synthesized CaLaO mixed oxide catalysts was examined by characterizing it through instruments such as XRD, BET and CO2-TPD, revealed that the Ca/La atomic ratio strongly affects the phase structure, catalyst basic sites, and thus the catalytic reactivity. The reaction parameters including Ca/La atomic molar ratio in the mixed metal oxide catalyst, molar ratio of methanol to oil, catalyst concentration, reaction pressure, temperature and time were varied one at a time and optimized based on the content of fatty acid methyl esters (FAMEs). The highest FAME yield for supercritical methanolysis reached 93% under the optimum reaction conditions: 240 °C, 8.2 MPa, a molar ratio of methanol to oil of 21:1, and reaction time of 10 min in the presence of 1 wt.% catalyst. The results demonstrated that the presence of CaLaO mixed oxide catalyst in the reaction system effectively reduced reaction temperature, time and pressure of supercritical conditions. It required a very low concentration to mitigate the harsh operation conditions (290 °C, 15 MPa, 60 min) of the scMeOH process. On the other hand, supercritical reaction compensated for low conversion rate of solid catalytic transesterification whereby, it takes one step further by improving the role of catalyst with supercritical conditions to achieve higher yield and shorter processing time. The reusability of CaLaO mixed oxide catalyst for repeated use was tested, the catalytic activity was >80% when the catalyst was employed for fourth time. The study concluded that slight leaching of Ca2+ (0.52–6.07 ppm) and La3+ (0.34–2.33 ppm) occurred during transesterification reaction, however it is below acceptable levels of metals as ASTM D6751 (United State) and in Europe, EN 14214 (Europe) standards. This proved that heterogeneous catalytic supercritical reaction process is more promising than non-catalytic processes and it can be turned to practical use in the near future.

63 citations

Journal ArticleDOI
TL;DR: Li, Co and Ni mixed oxides of composition LiNi x Co 2−−x O 4 (x = 0.25, 0.5,0.75 and 1) were prepared at 280°C by the Pechini sol-gel method as discussed by the authors.

63 citations

Journal ArticleDOI
TL;DR: In this article, Ni-based catalysts supported on CeO2-MgO mixed oxides (0.20% CeO 2 molar content) were prepared and employed in DRM.
Abstract: Dry reforming of methane (DRM) is becoming an appealing research topic because of the urgent need to minimize global warming and the demand for alternative energy resources. However, DRM commercialization and industrial scale application are limited by the deactivation of the applied catalysts. In this work, Ni-based catalysts supported on CeO2–MgO mixed oxides (0–20% CeO2 molar content) were prepared and employed in DRM. The support was synthesized via a coprecipitation method followed by impregnation of Ni metal. The catalysts prepared were characterized by X-ray diffraction, Brunauer–Emmett–Teller (BET) analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy (FESEM) techniques. The catalytic performance of the catalysts was evaluated in a fixed-bed continuous reactor with an equimolar (CH4/CO2) ratio at 1073 K. The addition of CeO2, as a promoter to the support, altered the interaction between Ni and MgO and modulated the properties ...

63 citations

Journal ArticleDOI
TL;DR: In this article, a three-step cycle using an alkali hydroxide (NaOH or KOH) in an activation reaction to improve oxidation and to facilitate water-splitting during the third step.

63 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202265
2021184
2020198
2019175
2018178