BRONSTED AND LEWIS-ACID SITES ON BINARY OXIDES OF ALUMINA-YTTRIA

Different compositions of alumina-yttria were prepared by coprecipitat ion technique using aqueous NH3. The structure, surface characteristic s and thermal stability of the catalysts were determined by XRD, TGA, DTA, SEM and ESCA. Acid properties of alumina-yttria were investigated by means of infrared spectra of chemisorbed pyridine, MAS (27)AI NMR and Hammett indicators. Catalysts with higher alumina content preferen tially showed more octahedral coordination in the lattice. Bronsted ac id sites increased with alumina content of the catalyst, Lewis acidity of catalyst samples increased with amount of yttria in the samples.