Effect of carbon oxygen functionalization on the activity of Pd/C catalysts in hydrogenation reactions

The effects of oxygen functionalities on GNP (Graphene Nanoplatelets) has been investigated, functionalizing GNP in liquid phase using different oxidants (HNO₃, H₂O₂, KMnO₄), with the aim to tune the amount and the type of oxygen functionalities. Pd NPs have been deposited on the different functionalized carbon supports to be tested in benzaldehyde hydrogenation/hydrogenolysis to benzyl alcohol and toluene as model reaction.

Abstract

This paper presents a study on the effects of oxygen functionalities on a mesoporous and graphitized carbon support (GNP, Graphene Nanoplatelets), on the catalytic activity of Pd/GNP catalysts in hydrogenation reactions. A functionalization method in liquid phase has been employed, using different oxidants (HNO₃, H₂O₂, KMnO₄), with the aim to tune the amount and the type of introduced oxygen functionalities. Preformed Pd nanoparticles have been used as Pd-precursor to limit differences in metal particle size and dispersion on differently functionalized carbon. The catalytic behaviour in benzaldehyde hydrogenation/hydrogenolysis to benzyl alcohol and toluene revealed that the introduction of oxygen functionalities has a generally detrimental effect. NMR relaxometry studies highlighted the weaker interaction between the carbonyl group and the functionalized Pd/GNP surface than the non–functionalized Pd/GNP demonstrating that the origin of the different catalytic activity lies on the first step of the reaction. O-functionalities also impacted on the Pd⁰/Pd²⁺ ratio at the surface which is an established parameter correlated to the reaction rate.

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