Deposition of metal nanoparticles on magnetic nanobeads and evaluation of their catalytic activity

Identifier:  TDX:2295

Handle: https://hdl.handle.net/20.500.11797/TDX2295

Authors:  Besostri, Francesca

Abstract:
The present dissertation presents a scientific work focused on the synthesis and catalytic evaluation of catalysts based on metallic nanoparticles (Pd, Pt, Au, Ni) deposited on magnetic nanobeads of Co and Fe2O3. Firstly, the evaluation of the activity for the Suzuki-Miyaura cross-coupling reaction of a catalyst composed by palladium nanoparticles deposited on the surface of the carbon-coated Co nanobeads was studied. High catalytic activity was observed for the coupling of phenylboronic acid with aryl iodides and bromides, employing low metal loading and short reaction times. A functionalisation consisting on a silica coating over the carbon shell and further incorporation of a palladium complex was also investigated in order to minimize leaching of metals observed with the previous catalyst. High catalytic activity was performed and the metal leaching (Pd and Co) was minimized. The deposition of small (~ 5 nm) catalytically active Pt, Au and Ni nanoparticles on the magnetic nanobeads was afterwards investigated. Active gold nanoparticles of less than 5 nm in size were obtained by reduction of HAuCl4 in presence of PVP and their potential for the catalytic hydrogenation of para-nitrophenol was evaluated. Contrarily, synthesising an active supported platinum catalyst proved to be more challenging. High metal loadings were achieved however formation of Pt clusters on the surface of the magnetic support precluded the activity of the samples. Similarly, formation of NiO and agglomeration of metallic Ni prevented the formation of active catalysts.