EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE STUDY OF SULFUR POISONED NI SIO2 CATALYSTS/

Extended X-ray absorption fine structure analysis was performed of the oscillations at the Ni K edge of Ni/SiO2 catalysts completely deactiv ated by thiophene and partially regenerated by oxidation-reduction cyc les. The obtained data demonstrates that during the regeneration proce ss sintering of the metal particles takes place. Besides this, the bes t fit of the completely sulphided catalysts requires the presence of a sulphur shell in the nickel coordination sphere. The average coordina tion number of sulphur as well as the Ni-S distance suggest the format ion of an in depth sulphide layer during the poisoning process. This i mplies a reconstruction of the metal particles when interacting at 0.0 34 kPa and 473 K with thiophene.