(10b) Synthesis of Metal Nanoparticles inside a Porous Support in Fluidized Bed: Application to Supported Catalysts

Nowadays, numerous researches are devoted to heterogeneous catalysts synthesis. The production of supported catalysts by impregnation of porous supports can be carried out in a fluidized bed. This technique allows obtaining, in only one apparatus, catalysts which, by the traditional way, must successively undergo the stages of impregnation, filtration, drying and calcination/activation. This paper describes three examples of composite materials containing metal nanoparticles elaborated by deposition of transition metals on a porous support such as silica gel or alumina, in a fluidized bed. As metal source, three different types of precursors have been used : - an inorganic precursor with iron nitrate Fe(NO3)2 and also a metal amide complex such as Fe[N(SiMe3)2]2 - an organometallic precursor containing palladium such as [PdCl(C3H5)]2 and Pd2(dba)3 - and a colloidal solution containing preformed rhodium nanoparticles Firstly, iron nanoparticles deposition has been operated by spraying metal salts and a stage of calcination/activation. Operating conditions have been fixed in order to deposit the metal inside the porous particles. The composite materials so-obtained were used in the carbon-nanotubes synthesis successfully. Secondly, the pulverisation of a solution containing a metallic precursor into a hot fluidised bed of porous particles was performed. The adequate choice of operating conditions makes possible uniform deposit of the metal precursor inside the porous matrix. After the impregnation step, the metallic precursor decomposition and metal activation have been operated in the same reactor. In the case of palladium, the catalytic activity of the composite materials has been investigated in hydrogenation reactions. It appeared that such catalysts permit a total conversion with a low metal loading. Finally, tests were made to spray a stabilized aqueous colloidal suspension of rhodium on silica gel. The obtained composite materials present good characteristics.