Production of supported asymmetric catalysts in a fluidised bed

Abstract

The production of supported catalysts by impregnation method of porous supports can be carried out in a fluidized bed. This technique allows to obtain, in only one apparatus, catalysts which by the traditional way must successively undergo the stages of impregnation, filtration, drying and calcination/activation. This paper deals with the results of experiments related to the manufacture of traditional catalysts and new generation catalysts containing various metals (nickel, manganese, copper, palladium) deposited on a porous support such as alumina or silica gel. Moreover, it was shown that the reproducible synthesis of metallic nanoparticles of size, composition and controlled surface quality could be carried out under mild conditions with organometallic precursors. The principle of this technique consists in the spraying of a solution containing a metallic precursor into a hot fluidised bed of porous fine particles as chosen support. The adequate choice of operating conditions makes possible a uniform deposit of the metal precursor inside the porous matrix. After the impregnation step, the decomposition of the metallic precursor and metal activation can be operated in the same reactor. For organometallic complexes the decomposition/activation is achieved at low temperature ( T < 80 °C) under a reactive atmosphere (H 2/N 2 mixture) giving then rise to the synthesis of metal nanoparticles with controlled size and composition. Feasibility studies and optimisation of the operating conditions have been carried out, solid characterization and catalytic tests have been conducted to validate the process. In the case of asymmetric catalysts, Pd nanoparticles associated to cinchonidine as an asymmetric ligand inside silica particles have been prepared by this process for the ethyl pyruvate hydrogenation.