Catalytic conversion of alcohols. Relation of hafnium-zirconium mixed oxide catalytic selectivity to surface composition measured by Raman spectroscopic methods

Abstract

The Raman spectra obtained for a series of mixed Hf-Zr oxide catalysts, prepared by coprecipitation, indicate that the surface composition is similar to the bulk composition. Hf, impregnated on calcined zirconia, remains on the surface following calcination at 600/sup 0/C but migrates into the bulk if calcination is effected at 1000/sup 0/C. The catalytic selectivity abruptly changes from that of pure hafnia to that of pure zirconia at a composition corresponding to Hf:Zr = ca. 1:9 rather than that undergoing a gradual change that follows the surface composition. Surface Hf may produce a significant background in the Raman spectra that increases for higher Hf compositions; the extent of the background depends upon both calcination temperature and Hf composition.