Pd-Cu bimetallic

Thermal decomposition of metal acetates in the presence of PVP was proposed by Bradley et al. (30), where the preparative procedure of Esumi et al. (31) was modified. Thus, heating of palladium and copper acetates in a solvent with a high boiling point (ethoxyethanol) provides PVP-stabilized Pd/Cu bimetallic nanoparticles. In this method, not only thermal decomposition but also reduction by ethoxyethanol could be involved. However, the Bradley method can provide Cu/Pd bimetallic nanoparticles that contain less than 50 mol% of Cu, while our method mentioned earlier can provide fine particles with 80 mol% of Cu. In Esumi s original procedure, methyl iso-butyl ketone (MIBK) was used as a solvent without a stabilizer. In his method, Cu" was not completely reduced to Cu°, but Cu20 was involved in the bimetallic nanoparticles. Probably, thanks to Cu1 species in the surface of the particles, no stabilizer is necessary for the stable dispersion. 

The activation treatment of the precursors has been carried out by decomposition under flowing Ar up to 670 K (0.5 K/mn). Indeed, previous works on Pd and PdCu supported on silica have shown that such an Ar treatment leads to metallic Pd and Pd-Cu bimetallic phases, well dispersed on the support (8). To remove the carbonaceous residues, all the samples have been calcined under O2 at 720 K and reduced under H2 at 870 K. Their compositions have been controlled by chemical analysis... 

Quantitative rate data on the catalytic reduction of nitrates in drinkable water are relatively scarce. One of the first works concerning kinetics is that of Tacke and Vorlop who employed a Pd-Cu bimetallic catalyst containing 5wt.% of Pt and 1.25 wt.% of Cu in a slurry reactor. Measurements of the initial rates resulted in a power-law rate expression. They reported a power of 0.7 with respect to the nitrate concentration, and an independency on the hydrogen partial pressure providing this pressure exceeded 1 bar. Pintar efa/. reported a complete kinetic model of the Langmuir-Hinshelwood type written in the form... 

Pintar A., Batista J., Arcon 1. and Kodre A. 1998. Characterization of gamma-Al203 supported Pd-Cu bimetallic catalysts by EXAFS, AES and kinetic measurements. Stud. Sufr. Sci. Catal., 118, 127-136. 

F re 3.17 The application of core-loss EELS spectroscopy to a catalyst system consisting of y-AljOj supported Pd-Cu bimetallic particles. The results depict the EELS response collected at several points near and within a core shell particle exhibiting surface enrichment of Pd (top), as exhibited by the consistent Pd signal (b) from aU three points and the lack of Cu signal (c) near the perimeter. Also shown are similar results collected from a more homogeneous particle (bottom), where the Pd (b) and Cu (c) signals are more consistent from all of the analytical regions. 

Alcaide, B., Almendros, P. and Rodriguez-Acebes, R. (2005) Pd—Cu bimetallic catalyzed domino cyclizalion of a-aUenols followed by a coupling reaction new sequence leading to functionalized spirolactams. Chem. Eur. J., 11, 5708-12. 

Pereira MM, Noronha FB, Schmal M. SMSI effect in the butadiene hydrogenation on Pd-Cu bimetallic catalysts. Catal Today. 1993 16 407. 

Kamijo S, Yamamoto Y. A new Pd -Cu bimetallic catalyst for the synthesis of indoles from isocyanates and allyl carbonates. Angew. Chem. Int. Ed. 2002 41(17) 3230-3233. 

Fig. 5.3 Pd/Cu bimetallic catalytically active species 10 formed under anaerobic conditions with DMF.

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