EXAFS CHARACTERIZATION OF SMALL METALLIC CLUSTERS SUPPORTED ON ZEOLITE NAY

Small mono-(Rh and Pt) and bimetallic (Rh-Pt) clusters were synthesise d using zeolite NaY as support. The combined analysis of the monometal lic and bimetallic clusters allowed a better determination of the size and shape of the bimetallic clusters. Very high metal dispersions wer e obtained, with first metal-metal coordination numbers around 7. The size and shape of the clusters were independent of the metal loading. The second and third shell coordination numbers of the monometallic cl usters are in accordance with a spherical shape of the metal clusters, just fitting within the supercages of the Y zeolite structure.