THE GROWTH-MECHANISM OF NICKEL IN THE PREPARATION OF NI AL2O3 CATALYSTS STUDIED BY LEIS, XPS AND CATALYTIC ACTIVITY/

A series of Ni/Al2O3 catalysts prepared from vapor phase by the atomic layer epitaxy (ALE) technique have been studied, A model is proposed for the growth mechanism of nickel in its oxidic form on alumina, from sequences of treatments with Ni(acac)2 and air. In the study activity measurements were combined with surface analysis by LEIS and XPS. Dur ing the first preparation sequence (< 5 wt%Ni) atomically dispersed ni ckel is obtained on the alumina support. The nickel atoms are catalyti cally inactive, but act as nuclei for the growth of the catalytically active Ni-species during the subsequent preparation sequences. The hig hest utilization of nickel atoms in the hydrogenation of toluene was o btained when the nickel nuclei were covered with one layer of active n ickel species.