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

摘要

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 N2 physisorption (BET/BJH methods), X-ray diffraction, temperature programmed reduction analysis, H2 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 °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.