Effects of adding La and Ce to hydrotalcite-type Ni/Mg/Al catalyst precursors on ethanol steam reforming reactions

Catalyst precursors composed of Ni/Mg/Al oxides with added La and Ce were tested in ethanol steam reforming (ESR) reactions. La and Ce were added by anion-exchange. The oxides were characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) analysis. The catalyst precursors consist of a mixture of oxides, with the nickel in the form of NiO strongly interacting with the support Mg/Al. The XPS analysis showed a lanthanum-support interaction, but no interaction of Ce species with the support. The reaction data obtained with the active catalysts showed that the addition of Ce and La resulted in better H(2) production at 550 degrees C. The CeNi catalyst provided the higher ethanol conversion, with lower acetaldehyde production, possibly clue to a favoring of water adsorption on the weakly interacting clusters of CeO(2) on the surface. (C) 2010 Elsevier B.V. All rights reserved.

Silver Nanoparticles Obtained in PAH/PAA-Based Multilayers by Photochemical Reaction

Carboxylic acid groups in PAH/PAA-based multilayers bind silver cations by ion exchange with the acid protons. The aggregation and spatial distribution of the nanoparticles proved to be dependent oil the process used to reduce the silver acetate aqueous solution. The reducing method with ambient light formed larger nanoparticles with diameters ranging from 4-50 nm in comparison with the reduction method using UV light, which gave particles with diameters of 2-4 nm The high toughness of samples reduced by ambient light is a result of two population distributions of particle sizes caused by different mechanisms when compared with the UV light process. According to these phenomena, a judicious choice of the spectral source call be used as a way to control the type and size of silver nanoparticles formed on PEMs. Depending on the energy of the light source, the Ag nanoparticles present cubic and/or hexagonal crystallographic structures, as confirmed by XRD. Beyond the kinetically controlled process of UV photoinduced cluster formation, the annealing produced by UV light allowed a second mechanism to modify the growth rates, spatial distribution, and phases.