Rare earth modified silica-aluminas as supports for bifunctional catalysis

Abstract We have explored rare earth oxide-modified amorphous silica-aluminas as “permanent” intermediate strength acids used as supports for bifunctional catalysts. The addition of well dispersed weakly basic rare earth oxides “titrates” the stronger acid sites of amorphous silica-alumina and lowers the acid strength to the level shown by halided aluminas. Physical and chemical probes, as well as model olefin and paraffin isomerization reactions show that acid strength can be adjusted close to that of chlorided and fluorided aluminas. Metal activity is inhibited relative to halided alumina catalysts, which limits the direct metal-catalyzed dehydrocyclization reactions during paraffin reforming but does not interfere with hydroisomerization reactions.