Catalisadores de paladio-cobre suportados sobre silica e niobia

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Palladium catalysts, copper and palladium-copper supported on silica and niobia were prepared with metallic contents of 0,5% or 3% of Pd and 3% of Cu (% mass). The incipient impregnation or coimpregnation method by using palladium chloride and copper sulfate was employed. After its drying, different thermal treatments at 3000C were carried out: calcination under synthetic air flow, reduction under hydrogen flow and its associations. These catalysts were characterized by inductively coupled plasma-atomic emission spectrometry, hydrogen chemisorption, H2-02 titration, transmission electron microscopy, energy dispersive spectrometry by scanning electron microscopy, temperature programmed reduction and extended X-ray absorption fine structure. The catalytic systems had its activities evaluated in the cyclohexane dehydrogenation and benzene oxidation reactions. The chemisorption results indicated that the metallic dispersion decreased from 20% to 7% when the content of Pd was increased from 0.5% to 3%. Such results were confirmed by transmission electron microscopy in specific case of Pd/Si O IND. 2 TPR analysis of calcined and reduced catalysts suggested a possible interaction among the two supported metaIs. EXAFS characterization of silica supported systems confirmed the formation of Pd-Cu alloys in the bimetallic systems with high Pd or Cu contents. With regard to Pd/Nb20s catalysts, the tumover number obtained in the cyclohexane dehydrogenation at 300°C was 40% higher than those obtained with the Pd/Si O IND. 2 systems. ...Note: The complete abstract is available with the full electronic digital thesis or dissertations.

ASSUNTO(S)

silica paladio catalisadores de metal compostos de niobio cobre desidrogenação

ACESSO AO ARTIGO

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