REGENERATION OF NI AL2O3 POISONED BY THIOPHENE DURING THE SELECTIVE HYDROGENATION OF STYRENE/

The poisoning by thiophene and the regeneration of a Ni/Al2O3 catalyst during the selective hydrogenation of styrene at 353 K was studied. I t was determined by X-ray photoelectron spectroscopy and Fourier trans form infrared spectroscopy that the sulfur species adsorbed during the catalyst poisoning is thiophene, which is adsorbed coplanarly to the surface. The catalyst was regenerated by Hz treatments for different t imes and at several pressures. Part of the sulfur remained irreversibl y adsorbed after regeneration, and hence the activity and selectivity values corresponding to the nonpoisoned catalyst were never recovered. After the regeneration treatments at 473 K, a modification on the ads orbed sulfur electronic state was detected, which can be ascribed to t hiophene hydrogenolysis, thus producing superficial sulfide adsorbed s pecies.