Chantal Diverchy

Bismuth-palladium heterometallic carboxylate as a single-source precursor for the carbon-supported Pd-Bi/C catalysts.

The heterometallic complex [Bi(2)Pd(2)(O(2)CCF(3))(10)(HO(2)CCF(3))(2)] (1) was obtained by the solid state reaction of Bi(III) trifluoroacetate/trifluoroacetic acid adduct with unsolvated trinuclear Pd(II) trifluoroacetate. The crystal structure of 1 consists of discrete tetranuclear molecules, in which two paddlewheel [BiPd(O(2)CCF(3))(4)] units are connected by two chelating-bridging trifluoroacetate ligands through bismuth ends. There are no metal-metal bonds in the tetrameric structure of 1, since both Bi...Pd (3.0843(4) A) and Bi...Bi (4.5074(4) A) distances are too long to be considered as bonding interactions. A study of the solution behavior revealed that not only the coordinated trifluoroacetic acid in 1 can be effectively replaced by other donor solvent molecules but also the tetranuclear complex can be cleaved in solution into discrete dinuclear Bi-Pd species. Complex 1 was used as precursor for the preparation of a bimetallic Pd-Bi carbon-supported catalyst. The preparation procedure included the modification of the carbon support to increase the number of oxygenated functions at its surface followed by grafting complex 1 via ligand exchange for surface carboxylates and activating thermally. The resulting catalyst, consisting of small supported metallic particles, was found to be more active than the reference materials prepared from multisource homometallic Pd and Bi precursors.

Grafting of coordination compounds onto functionalized carbon supports as precursors for bimetallic Pd-Ru/C catalysts

Abstract An activated carbon was functionalized using nitric acid and the surface acidity was evaluated by Boehm’s titrations and XPS. Chosen Pd and Ru complexes were then grafted onto the unmodified and the modified carbon supports. After thermal activation, the obtained Pd-Ru/C catalysts were tested in a selective hydrogenation reaction. The amount of metal grafted in the final catalysts was measured by ICP and seemed to be correlated to the surface acidity. Results from catalytic testing in the hydrogenation of 2-methyl-2-nitropropane (MNP) showed that the activity is linked to other factors than only the amount of metal grafted.

Preparation of Pd-Bi catalysts by grafting of coordination compounds onto functionalized carbon supports

Abstract HNO 3 functionalized carbons are used as supports for the preparation of bimetallic PdBi/C catalysts. The aim is to take advantage of the oxygenated surface functions introduced on the carbon, which are expected to act as anchoring sites. Two neutral coordination complexes were selected to incorporate the two metals onto differently functionalized carbon supports. The grafted samples are then submitted to an activation treatment and characterized by SEM, XRD and XPS. It appears that the order of incorporation strongly influences the surface properties of the catalysts and thus modifies their activity in the oxidation of glucose.

Functionalization of carbon xerogels for the preparation of Pd/C catalysts by grafting of Pd complex

Abstract A mesoporous carbon xerogel was functionalized by treatments with nitric acid in order to introduce oxygenated functions at its surface. The carbon supports were characterized by Boehms titrations, XPS and nitrogen adsorption, and the results were compared with those obtained with a microporous activated carbon. It was shown that carbons with high oxygen content were obtained. The oxygenated functions were then used as anchors for the grafting of a palladium complex. High Pd surface concentrations are observed by XPS but it appears that the Pd particles are not homogeneous in size and repartition.