PARTICLE-SIZE STUDIES OF SUPPORTED METAL-CATALYSTS - A COMPARATIVE-STUDY BY X-RAY-DIFFRACTION, EXAFS AND ELECTRON-MICROSCOPY

Supported ruthenium and iridium metal catalysts are studied by X-ray diffraction (XRD), EXAFS analysis and transmission electron microscopy (TEM). Estimates of the mean particle size from these techniques range from 20 to 25 angstrom from XRD, 13 to 16 angstrom from EXAFS and 25 to 32 angstrom from TEM. The strengths and weaknesses of these instrumental methods are discussed, as is the intrinsic comparability of these techniques. From a combination of these methods, the average particle size is estimated to be of the order of 20-30 angstrom.