INFLUENCE OF THE PREPARATION METHOD AND THE NATURE AND CONTENT OF R2O3 (R = Y, LA, OR CE) ON THE PHYSICAL AND CHEMICAL-PROPERTIES OF R2O3-AL2O3 COMPOUNDS

Physical and chemical properties of R2O3-Al2O3 compounds (R = Y, La, C e), prepared either by coprecipitation or by mixing the components, ar e studied. The interaction between the components weakens in the seque nce: Y2O3-Al2O3 > La2O3-Al2O3 > Ce2O3-Al2O3 (no interaction in the las t system). All other conditions being the same, the interaction in the precipitated samples exceeds that in the mixed sample. Coprecipitated R2O3-Al2O3 samples demonstrate high dispersion and thermal stability; the specific surface area for the mixed samples is somewhat smaller t han that for the coprecipitated samples. The pore structure of the sam ples is determined by the R2O3 nature: yttria-alumina and lanthana-alu mina samples demonstrate a polydispersed distribution of pore sizes, a nd narrow micropores are typical of the ceria-alumina system.