Pd nanoparticles prepared by grafting of Pd complexes on phenol-functionalized carbon supports for liquid phase catalytic applications

• An activated carbon was functionalized to introduce phenol groups on its surface.
• Palladium was grafted by ligand exchange at the functionalized carbon surface.
• Pd/C catalysts were tested in the hydrogenation of 2-methyl-2-nitropropane (MNP).
• The activity was enhanced by using carbon with phenol rather than carboxylates groups.
• The activity was explained by grafting robustness and possible role of phenols in the reaction.

An activated carbon was functionalized by oxidation with HNO3 or H2O2 to increase the number of acidic groups on its surface. A sample of HNO3-oxidized carbon was treated thermally to remove unstable functions. Detailed characterization by a combination of techniques revealed that this stabilization procedure allowed selecting weaker acid sites of phenolic type. H2O2 functionalization gave also mainly surface phenols but in lower amounts. Palladium grafting was carried out in water at room temperature by ligand exchange between a carboxylate complex and the surface oxygenated groups. Activation was carried out thermally and the samples grafted on the most oxidized supports proved more difficult to reduce. The catalytic activity of the obtained Pd/C catalysts was evaluated in the reduction of 2-methyl-2-nitropropane (MNP) into t-butylamine (TBA). The most active materials were those prepared on H2O2-modified carbon and on the stabilized support. In the latter case, the superior activity was explained by the robustness of the grafting anchors which could not decompose during thermal activation together with the active role of weak acidic groups in the catalytic reaction itself.

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