Open AccessEffects of Cu over Pd based catalysts supported on silica or niobia
Author(s) -
M.N.S.C. Roma,
D.S. Cunha,
G.M. Cruz,
Antonio José Gomez Cobo
Publication year - 2000
Publication title -
brazilian journal of chemical engineering/brazilian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.313
H-Index - 52
eISSN - 1678-4383
pISSN - 0104-6632
DOI - 10.1590/s0104-66322000000400058
Subject(s) - catalysis , bimetallic strip , chemisorption , dehydrogenation , palladium , extended x ray absorption fine structure , chemistry , inorganic chemistry , copper , alloy , metal , hydrogen , titration , dispersion (optics) , materials science , organic chemistry , absorption spectroscopy , physics , quantum mechanics , optics
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