Nanoparticles deposit location control on porous particles in fluidized bed

The nanoparticles synthesis and deposition can be carried out using an innovating technique named dry impregnation in a fluidized bed. Its principle consists in the spraying of a solution containing a metallic precursor or preformed nanoparticles into a hot fluidized bed of porous particles. The solvent vapour saturation rate value, s, defined as the ratio between the solvent content in the bed atmosphere and the maximum solvent content, appears as a key parameter allowing predicting the deposit location. Three operation conditions can be distinguished: • "Unstable conditions" for high s (between 1 and 0.8). The operation is unstable: a low increase of the liquid flow rate, or a reduction of the gas inlet temperature, can lead to wet quenching. • "Operating conditions" or "slow drying conditions" for intermediate values of s (between 0.8 and 0.2). • "Fast drying conditions" characterized by high bed temperatures and low solvent saturation rates (s < 0.2). This paper presents experimental results obtained during the dry impregnation of coarse and fine porous particles using different types of precursors: inorganic precursors (metallic salts), metal organic complexes and a colloidal suspension containing preformed metallic nanoparticles (rhodium). The operating conditions were chosen in order to study the three operation conditions previously described. Interesting results were obtained concerning the deposit distribution within the support grains at the local scale, Indeed, it appeared that a fast drying leads to a deposit located only at the external particle surface (like coating), whereas a uniform deposit on the whole particle volume is obtained with slow drying conditions