Gold, palladium and gold-palladium supported on silica catalysts prepared by sol-gel method: synthesis, characterization and catalytic behavior in the ethanol steam reforming

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Noble-metal-based catalysts supported on silica (Au/SiO2, Pd/SiO2 and Au-Pd/SiO2) were prepared by the sol-gel method and were evaluated in the steam reforming of ethanol for hydrogen production. The catalysts were characterized by N-2 physisorption (BET/BJH methods), X-ray diffraction, temperature programmed reduction analysis, H-2 chemisorption, atomic absorption spectrophotometry and Raman spectroscopy. The structural characterization of the Au- and Pd-containing catalysts after calcination showed that the solids are predominantly formed by Au-0, Pd-0 and PdO species and was observed that the metallic Pd dispersion diminished in the presence of Au-0. The results revealed that the catalytic behavior could be influenced by the experimental conditions and the nature of the catalyst employed. The Pd/SiO2 catalyst showed the best performance among the catalysts tested at the highest reaction temperature (600 A degrees C) due to the more effective action of the metallic active phase, which covers a greater area in this sample. At this same reaction temperature, the Au-Pd/SiO2 catalyst showed a significant deactivation, probably due to the lower Pd dispersion presented by this catalyst.672273281Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FINEPFundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Allylic oxdation of alkenes with molecular oxygen catalyzed by porous coordination polymers Fe-MIL-101 and Cr-MIL-101

BIOVERT+ISK:ASOThe catalytic performances of Cr-MIL-101 and Fe-MIL-101 porous coordination polymers have been investigated in the allylic oxidation of alkenes, including natural terpenes, with molecular oxygen (1 atm) under mild solvent-free conditions. Both catalysts remain stable under optimal conditions (40A degrees C for Fe-MIL-101 and 60A degrees C for Cr-MIL-101) and can be recycled, at least, four times without loss of the catalytic properties. Fe-MIL-101 favours the formation of unsaturated alcohols, while Cr-MIL-101 mediates the formation of unsaturated ketones. The oxidation process involves the formation of alkene hydroperoxide via conventional radical chain process and its further transformations over the MIL-101 catalysts. The mechanism of the hydroperoxide transformation strongly depends on the metal nature