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Effects of Cu over Pd based catalysts supported on silica or niobia

Roma,M.N.S.C.; Cunha,D.S.; Cruz,G.M.; Cobo,A.J.G.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2000 EN
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Palladium and palladium-copper catalysts supported on silica and niobia were characterized by H2 chemisorption and H2-O2 titration. Systems over silica were also analyzed by transmission electron microscopy and EXAFS. The metallic dispersion decreased from 20% to 7% when the content of Pd was increased from 0.5wt.-% to 3wt.-% in monometallic catalysts. The addition of 3 wt.-% Cu to obtain Pd-Cu catalysts caused a remarkable capacity loss of hydrogen chemisorption. TPR analysis suggested an interaction between the two metals and EXAFS characterization of the catalyst supported on silica confirmed the formation of Pd-Cu alloy. Pd/Nb2O5 catalysts showed turnover numbers higher than those obtained with the Pd/SiO2 systems in the cyclohexane dehydrogenation. However, the bimetallic catalysts showed very low turnover numbers.