INFLUENCE OF REDUCING AND SULFIDING TREATMENTS ON CO-AL2O3 AND MO-AL2O3 CATALYSTS - X-RAY PHOTOELECTRON-SPECTROSCOPY STUDY

X-ray photoelectron spectroscopy (XPS) has been used to investigate the phase transformations induced by various pretreatments of Co/Al2O3 and Mo/Al2O3. Upon sulfiding by H2-H2S, Co2+ is partly reduced to Co0 while the Mo6+ species is completely transformed into MoS2. The behavior of molybdenum is similar to that observed in Co-Mo/Al2O3 hydrodesulfurization catalysts. In contrast, cobalt gives Co0 in Co/Al2O3 systems whereas Co9S8 is observed for HDS catalysts. A nonreducible alumina bound Co is also observed in both the presence and absence of molybdenum. In the oxide form, molybdenum species are in strong interaction with the support but this interaction does not exist after sulfiding. © 1978 American Chemical Society.