SURFACE-AREA CONTROL DURING THE SYNTHESIS AND REDUCTION OF HIGH AREA CERIA CATALYST SUPPORTS

Precipitation of ceria from (NH4)(2)[Ce(NO3)(6)] with a 'ammonium carb onate' solution produces powders, with surface areas determined by the initial [Ce] concentrations. Samples, free of carbonate impurities an d with reproducible surface areas of up to 200 m(2) g(-1), have been o btained after controlled dehydration and calcination to 600 degrees C. Temperature-programmed reduction (in 3% H-2/N-2) of samples with a ra nge of surface areas, has confirmed that the net hydrogen uptake by ce ria between 120 and 700 degrees C comprises two components. The first is a constant amount which represents sorption of interstitial hydroge n into the ceria lattice. The second is proportional to the surface ar ea of the sample and originates from partial reduction of surface Ce-I V and hydroxylation of the surface oxide.