EFFECT OF THERMAL TREATMENTS ON SURFACE CHEMICAL-DISTRIBUTION AND CATALYST ACTIVITY IN NICKEL ON SILICA SYSTEMS

The reducibility of several nickel on silica systems prepared by incip ient wetness impregnation and precipitation-deposition has been studie d using TPR and TG. The analysis of the results has allowed us to dete rmine the minimum drying and reduction temperatures for both impregnat ion and precipitation catalysts. From an analysis of the obtained resu lts, together with X-ray diffraction and the study of the reduction de gree, dispersion and nickel particle size of catalysts activated at di fferent reduction temperatures, conclusions on the nickel surface chem ical distribution have been derived. An optimal reduction temperature for the catalysts has been determined from activity considerations in the hydrogenation of sunflower seed oil.