Rhodium nanoparticles stabilised by phosphorus based ligands. Synthesis, characterisation and application in selective hydrogenations

Identifier:  TDX:2776

Handle: https://hdl.handle.net/20.500.11797/TDX2776

Authors:  Llop Castelbou, Jessica

Abstract:
This thesis describes the synthesis and characterisation of rhodium nanoparticles stabilised by two families of phosphine and phosphite ligands. The effect of the nature, the amount and the steric and electronic properties of these stabilising agents were evaluated on the structure and the catalytic performances of the resulting NPs. Their structure was investigated using characterisation techniques such as TEM, HRTEM, XRD, XPS, TGA and their surface study was completed by a study of CO adsorption in correlation with IR spectroscopy. These soluble nanoparticles were active catalysts in the selective hydrogenation of arenes and aromatic ketones. In the hydrogenation of disubstituted arenes, styrene, toluene and benzene, high activities were obtained for phosphine stabilised catalysts while significant amounts of partially hydrogenated products were achieved using phosphite-covered nanoparticles. These catalysts were also active in the hydrogenation of aromatic ketones, and the results obtained with the NPs Rh1 and Rh4 stabilised by PPh3 and dppb, respectively, were compared to the analogous ruthenium systems. For some of the substrates, high selectivity for the hydrogenation of aromatic ring over keto group hydrogenation was achieved. The last part of this thesis describes a preliminary study on the anchoring of the rhodium nanoparticles onto a modified silica using two different approaches: first, an in situ synthesis of the NPs in presence of the support was tested and compared with the second method that included the anchoring of pre-synthesised NPs.