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 deactivated by thiophene and partially regenerated by oxidation-reduction cycles. The obtained data demonstrates that during the regeneration process sintering of the metal particles takes place. Besides this, the best fit of the completely sulphided catalysts requires the presence of a sulphur shell in the nickel coordination sphere. The average coordination number of sulphur as well as the Ni-S distance suggest the formation of an in depth sulphide layer during the poisoning process. This implies a reconstruction of the metal particles when interacting at 0.034 kPa and 473 K with thiophene.