RELATIONSHIP BETWEEN SULFUR RESISTANCE AND ELECTRONIC STATE OF THE METAL ON SUPPORTED PALLADIUM CATALYSTS

The effect of the metal precursor and reduction temperature on the sulphur resistance of supported palladium catalysts during styrene and ethylbenzene hydrogenations were studied. The presence of surface-charged palladium species (Pdn+) was observed on catalysts prepared from acidic solutions of PdCl2 and reduced at low temperatures. The Pdn+ species increased the catalysts' resistance to thiols during ethylbenzene hydrogenation. Catalysts containing only superficial Pd0 were the most thio-tolerant during styrene hydrogenation. The sulphur resistance is mainly governed by electronic factors, but geometric effects, such as dilution of the Pd0 surface by unreduced species, are also important factors. © 1990.