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

Abstract

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

Influence of niobium on carbon nanofibres based Cu/ZrO 2 catalysts for liquid phase hydrogenation of CO 2 to methanol

“…However in concomitant to these two traditional peak, a new broad reduction peak (peak ␥) starting at 350 • C with a tail at 490 • C was observed in Nb promoted catalysts. Roma et al investigated TPR profile of Cu/Nb 2 O 5 catalysts and observed a broad peak for CuO reduction around 450 • C [27]. Based on this observation, peak ␥ in this work could be due to higher interaction of Cu or Cu-Nb 2 O 5 composites.…”

Heterogeneous Catalyzed Chemoselective Reductive Amination of Halogenated Aromatic Aldehydes

“…Roma et al. have indeed showed that the reduction of Cu(II) species is facilitated in the presence of Pd [16] . The results of the reductive amination reactions with different bimetallic Pd−Cu/C catalysts are given in Table 2 and Table S2.…”

“…Roma et al have indeed showed that the reduction of Cu(II) species is facilitated in the presence of Pd. [16] The results of the reductive amination reactions with different bimetallic PdÀ Cu/C catalysts are given in Table 2 and Table S2. While a monometallic Pd on carbon catalyst resulted in a large amount of dehalogenation reaction (Entry 1, Table 2), switching to a catalyst composed of a 1 : 1 Pd : Cu molar ratio suppressed the dehalogenation reactions significantly (Entry 2, Table 2).…”