POISONING AND REGENERATION OF AN NI SIO2 CATALYST/

The poisoning effect of thiophene during the hydrogenation of styrene on an Ni/SiO2 catalyst, and the regenerating role of both pure hydroge n and 2-butyne in the presence of hydrogen on the poisoned catalyst, w ere studied. The treatments induced the elimination of sulfur and prom oted an important recovery of the catalytic activity and selectivity. XPS analyses show that the sulfur species adsorbed during the catalyst poisoning is thiophene. Part of the sulfur remained irreversibly adso rbed after the regeneration treatments carried out at 473 K; a modific ation on the adsorbed sulfur electronic state was detected, which can be ascribed to thiophene hydrogenolysis induced by the regenerating te mperature.