The effect of sulfidation on the Ni distribution in Ni/USY zeolites

NI/USY zeolite catalysts have been prepared by either an ion-exchange or an impregnation procedure. The modification of support and the effect of sulfidation on the Ni distribution were examined by various techniques (water adsorption, FT i.r. spectroscopy of chemisorbed NO, XPS, Xe-129 n.m.r. and Xe adsorption). in all catalysts the sulfidation of Ni is incomplete and the method of Ni introduction influenced the Ni distribution in Ni/USY zeolites. In unsulfided samples ion-exchange technique led to Ni located essentially in hexagonal prisms, whereas in the other samples prepared by impregnation procedure the Ni concentrates were located at or near the outer zeolite surface. Some nickel redistribution has been observed during catalyst sulfidation. (C) Elsevier Science Inc. 1997.