Co/Mg/Al hydrotalcite-type precursor, promoted with La and Ce, studied by XPS and applied to methane steam reforming reactions

Catalysts` precursor of Co/Mg/Al promoted with Ce and La were tested in the steam reforming of methane (SRM). The addition of promoters was made by anion-exchange. The oxides characterization was made by X-ray Photoelectron Spectroscopy (XPS) analysis that confirmed Co(2+) species in free form on surface and interacted with Mg and Al in the form of solid solution. In the SRM with high fed molar ratio of H(2)O:CH(4) = 4:1, the catalysts showed a great affinity with water and immediately deactivated by oxidation of the active sites. In the stoichiometric ratio of H(2)O:CH(4) = 2: 1 the catalysts were active and presented low carbon deposition during the time reaction tested. Also a test with low fed molar ratio H(2)O:CH(4) = 0.5:1 was carried out to evaluate the stability of the catalysts by CH(4) decomposition and all the catalysts were stable during 6 h of reaction. Promoted catalysts presented lower carbon deposition. (C) 2009 Elsevier B. V. All rights reserved.

CO preferential oxidation (CO-PROx) on La(1-x)Ce(x)NiO(3) perovskites

La(1-x)Ce(x)NiO(3) perovskites have been prepared, characterized by XRD. TPR and surface area and tested as catalysts for CO-PROx, with a feed of 2.5% CO, 5% O(2), 33% H(2) and N(2) to 100%. The samples exhibited an XRD pattern typical of the perovskite, with traces of NiO in the LaNiO(3) and La(0.95)Ce(0.05)NiO(3) samples, with some La(2)NiO(4) in the La(0.90)Ce(0.10)NiO(3) sample. All samples were active, but the perovskites with cerium showed good catalytic activity, demonstrating the promoter effect of cerium. The highest conversion of CO and H(2) was obtained with La(0.95)Ce(0.05)NiO(3), probably due to a synergy between Ni and Ce that enhanced O(2) mobility. (c) 2010 Elsevier B.V. All rights reserved.

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.

Effects of the partial replacement of La by M (M=Ce, Ca and Sr) in La(2-x)M(x)CuO(4) perovskites on catalysis of the water-gas shift reaction

The performance of La(2-x)M(x)CuO(4) perovskites (where M = Ce, Ca or Sr) as catalysts for the water-gas shift reaction was investigated at 290 degrees C and 360 degrees C. The catalysts were characterized by EDS, XRD, N(2) adsorption-desorption, XPS and XANES. The XRD results showed that all the perovskites exhibited a single phase (the presence of perovskite structure), suggesting the incorporation of metals in the perovskite structure. The XPS and XANES results showed the presence of Cu(2+) on the surface. The perovskites that exhibited the best catalytic performance were La(2-x)Ce(x)CuO(4) perovslcites, with CO conversions of 85%-90%. Moreover, these perovskites have higher surface areas and larger amounts of Cu on the surface. And Ce has a higher filled energy level than the other metals, increasing the energy of the valence band of Ce and providing more electrons for the reaction. Besides, the La(1.80)Ca(0.20)CuO(4) perovskite showed a good catalytic performance.

Characterization of protein hydrolysates of cosmetic use by CE-MS

Protein hydrolysates have been used as active principles in cosmetic products conferring different properties to the final formulations, which are mostly controlled by the peptide size and its amino acid sequence. In this work, capillary electrophoresis coupled to mass spectrometry analyses were carried out in order to investigate such characteristics of protein hydrolysates. Samples of different origins (milk, soy and rice) were obtained from a local company, and were analyzed without a previous preparation step. The background electrolyte (BGE) and sheath liquid compositions were optimized for each sample. The best BGE composition (860 mmol/L formic acid - pH 1.8 - in 70: 30 v/v water/methanol hydro-organic solvent) was chosen based on the overall peak resolution whereas the best sheath liquid was selected based on increased sensitivity and presented different compositions to each sample (10.9-217 mmol/L formic acid in 75: 25-25: 75 v/v water/methanol hydro-organic solvent). Most of the putative peptides in the hydrolysate samples under investigation presented molecular masses of 1000 Da or less. De novo sequencing was carried out for some of the analytes, revealing the hydrophobicity/polarity of the peptides. Hence, the technique has proved to be an advantageous tool for the quality control of industrial protein hydrolysates.