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Daza C.E.,Estado Solido y Catalisis Ambiental | Cabrera C.R.,University of Puerto Rico at San Juan | Moreno S.,Estado Solido y Catalisis Ambiental | Molina R.,Estado Solido y Catalisis Ambiental
Applied Catalysis A: General | Year: 2010

Ce-doped Ni, Mg and Al hydrotalcites were synthesized through the reconstruction method in the presence of the [Ce(EDTA)]- complex. The hydrotalcites and the mixed oxides derived after their thermal decomposition at 500 °C (16 h) were characterized by XRD, TGA-DTA, ICPS, IR, Raman, SEM-EDX, TEM, TPR-H2, TPD-CO2, XPS and N2 sorptometry. The reconstruction of the mixed oxide is not total in [Ce(EDTA)]- solutions with Ce between 1 and 10%wt. The hydrotalcite is reconstructed as hydroxyl-type phase; the reconstruction takes place in the external edges of the oxide granules. The complex is deposited, with high distribution, on the external surface of the reconstructed layered structure as species of Ce4+ and after the calcination generates surface CeO2-doped periclase oxides. Solids were used in the production of syngas through CO2 reforming of methane (CH4:CO2:Ar 5/5/40) using a total fixed flow of 50 mL min-1 and WHSV = 30 L g-1 h-1 between 500 and 800 °C with prior reduction. The increase in the Ce load had a promoter effect in catalytic conversions. H2/CO ratios between 0.8 and 1.2 were obtained. Ce had a positive effect in the elimination of coke, since a nominal optimal value of 3%wt. was obtained. © 2010 Elsevier B.V. All rights reserved.


Daza C.E.,Estado Solido y Catalisis Ambiental | Gallego J.,University of Antioquia | Mondragon F.,University of Antioquia | Moreno S.,Estado Solido y Catalisis Ambiental | Molina R.,Estado Solido y Catalisis Ambiental
Fuel | Year: 2010

Ce-promoted Ni/Mg-Al catalysts were synthesized by means of a methodology that involves the doping of Ni-Mg-Al mixed oxides derived from hydrotalcites with [Ce(EDTA)]- and subsequent thermal decomposition. The effect of the nominal load of Ce in the catalytic performance of the materials was studied. The solids were characterized by means of XRD, BET area, TPR-H2, TPD-CO2, chemical analysis by ICPs, TGA, SEM and TEM and were evaluated in CO2 reforming of methane at 700 °C. The results indicate the partial reconstruction of the periclase phase during the doping with [Ce(EDTA)]- and the formation of a mixture of crystalline periclase and fluorite phases after the calcination. Catalysts with particle sizes of Ni0 between 5 and 9 nm were obtained. Ce presents a promote effect in the degree of reduction of Ni and the amount and strength of the basic sites. It was evident a beneficial effect of cerium in the catalytic activity and selectivity of the doped materials. The increase of the nominal Ce load between 1 and 10% causes no considerable effect in the catalytic activity and selectivity or in the size of crystallite in these materials but in the inhibition of the coke formation. The catalysts show excellent catalytic performance under drastic conditions of reaction and long operation times. The Ce-doped Ni/Mg-Al catalyst is stable up to 100 h of reaction using a feed mixture of CH4/CO2/He 10/10/80 at 24 L g-1 h-1, up to 20 h of reaction using CO2/CH4 20/20 at 48 L g-1 h-1 and up to 15 h of reaction using CO2/CH4 40/40 at 96 L g-1 h-1. The filamentous coke formation is demonstrated on the surface of the catalyst when gas of dilution in the reactants is not used. The developed method of synthesis becomes an interesting methodology for obtaining catalysts for CO2 reforming of methane. © 2009.

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