Novel mesoporous aluminosilicate supported palladium-rhodium catalysts for diesel upgrading : I. Preparation and characterisation

Bimetallic PdRh (with Pd/Rh mole ratio = 2/1) catalysts supported on a mesoporous aluminosilicate have been prepared and three methods of metal incorporation in the support have been compared: direct incorporation into the synthesis gel, impregnation and ion-exchange. Physico-chemical characterisations (nitrogen adsorption–desorption, hydrogen chemisorption, transmission electron microscopy, X-ray photoelectron and extended X-ray absorption fine structure spectroscopies), as well as simulated coking and regeneration tests are described. The dispersion, metal particle size and the formation of bimetallic particles within the material depend on the method of metal incorporation. Direct incorporation and ion-exchange methods lead to co-existence of PdRh intermetallic aggregates and segregated Pd; on the other hand, the impregnation method leads to the formation of very small and well dispersed PdRh alloy particles, with Pd preferentially located on the alloy particle surface.

The preparation and characterisation of novel bimetallic PdRh catalysts supported on a mesoporous aluminosilicate are described. The association of a range of different techniques including adsorption from the gas-phase and element-specific spectroscopies (such as XPS and EXAFS) provide converging results indicating the existence of intermetallic particles with palladium preferentially located on the particle surfaces. Figure optionsDownload as PowerPoint slide