SUPERBASE CHARACTER OF ALUMINA LOADED WITH POTASSIUM BY IMPREGNATION FROM AMMONIACAL SOLUTION

Al2O3 has been loaded with potassium by impregnation from an ammoniacal solution and heated under vacuum at 573 K. The resulting catalyst [K(NH3)/Al2O3] showed extremely high catalytic activity for the isomerization of alkenes. These catalysts had much greater activity than that of Al2O3 loaded with alkali metals by vapour deposition. The isomerization, over K(NH3)/Al2O3, of pent-1-ene to pent-2-ene gave a 98% yield in 6 min at 201 K. The temperature-programmed desorption and IR spectra of Al2O3 after impregnation indicated that the metal amide-like species formed on the alumina is a catalytically active species. Al2O3 loaded with KNH2 was found to be more active than K(NH3)/Al2O3 for the isomerization of 2,3-dimethylbut-1-ene,The basic strength of these catalysts was estimated to be at least H--=37.