CHARACTERIZATION OF THE CATALYTIC ACTIVITY OF A THERMALLY ACTIVATED HYDROTALCITE-LIKE COMPOUND IN PROPYLENE OLIGOMERIZATION

A hydrotalcite-like compound, Ni4Al2(OH)12CO3· nH2O, was precipitated on silica in order to obtain a precursor frequently used as a catalyst in propylene oligomerization, after thermal treatment up to 773 K. The effect of the decomposition temperature of Ni4Al2(OH)12CO3·nH 2O was studied and the temperature programmed reduction, made in order to establish the optimum pretreatment conditions. As revealed by ESR the chosen treatment yelded Ni(I) sites, responsible for the reaction. The significance of these Ni(I) sites was confirmed both by the minor role played in the reaction by the strongest Bronsted acid sites and by the experiments with adsorbed carbon monoxide, which revealed that, once the reduced metal ion sites are blocked, the catalytic activity became very low . Temperature programmed desorption runs with adsorbed propylene were also carried out in order to characterize the interactions between propylene and the catalyst. © 1990.