HIGH-RESOLUTION ELECTRON-MICROSCOPY CHARACTERIZATION OF SULFIDED PALLADIUM PARTICLES ON AMORPHOUS SIO2

The microstructure of palladium particles deposited on a porous silica support was examined by high resolution microscopy following various sulfidation treatments. For catalysts sulfided by the reaction itself (hydrodesulfurization of thiophene), the micrographs show large partic les where an amorphous sulfide layer surrounds the Pd core; in the cas e of small particles, the presence of PdS2 was identified. For catalys ts sulfided under 20% H2S/H-2 at 623 K, the particles show lattice pla nes compatible with PdS2 and PdS. By increasing the sulfidation temper ature to 723 K, faceted PdS particles are mostly formed. Some structur al defects related to the sulfidation treatment are also shown.