Preparation of Rhodium Catalysts Supported on Carbon Nanotubes by a Surface Mediated Organometallic Reaction

• Published in: European journal of inorganic chemistry Vol. 2003; no. 4; pp. 610 - 617
• Main Authors: Giordano, Roberto, Serp, Philippe, Kalck, Philippe, Kihn, Yolande, Schreiber, Joachim, Marhic, Christiane, Duvail, Jean-Luc
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.02.2003; WILEY‐VCH Verlag; Wiley
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Heterogeneous catalysis; Nanotubes; Physical Sciences; Rhodium; Science & Technology; Supported catalysts; Surface chemistry; OXIDATION; surface chemistry; HYDROGENATION; heterogeneous catalysis; SELECTIVE CATALYST; LIQUID-PHASE REACTIONS; supported catalysts; nanotubes; NANOPARTICLES; FIBERS; PALLADIUM CATALYST; rhodium; HYDROFORMYLATION; TIPS
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200390083

The dimeric complex [Rh2Cl2(CO)4] was grafted to multi‐walled carbon nanotubes (MWNTs) previously oxidised with nitric acid and then treated with sodium carbonate to produce carboxylate groups on their outer surface. The grafting mechanism involves bridge‐splitting and substitution of ‐COO for Cl, as evidenced by the presence of NaCl in the samples. A further reduction/decomposition step under dihydrogen at 573 K afforded highly dispersed rhodium nanoparticles (≈︁1.5−2.5 nm). This novel rhodium‐supported carbon material (Rh/MWNT‐COONa) was tested as a catalyst for the hydrogenation of trans‐cinnamaldehyde and the hydroformylation of hex‐1‐ene in the liquid phase: in both cases it was found to be very selective, toward C=C double‐bond hydrogenation and the production of linear and branched aldehydes, respectively. A comparison was made between its catalytic activity and that of rhodium supported on pristine MWNTs and on nitric acid‐oxidised MWNTs. We observed that these latter catalysts have larger particle sizes and lower activities, thus confirming the efficiency of our grafting procedure. Moreover, the better results obtained when using MWNT‐COONa as support with respect to carboxylate‐containing activated carbon also point to the important role played by the mesoporous nature of the carbon nanotube support, which can ameliorate transfer processes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)