Composition of aluminium oxide and cerium oxide with a particular porosity profile

Abstract

The present invention relates to a composition based on Al and Ce in the form of oxides (composition C1); or based on Al, Ce and La in the form of oxides (composition C2), with the following proportions: —the proportion of CeOis between 3.0 wt % and 35.0 wt %; —the proportion of LaO(for composition Conly) is between 0.1 wt % and 6.0 wt %; —the remainder as AlO; exhibiting the following porosity profile: —a pore volume in the range of pores with a size of between 5 nm and 100 nm which is between 0.35 and 1.00 mL/g; and—a pore volume in the range of pores with a size of between 100 nm and 1000 nm which is less than or equal to 0.15 mL/g, these pore volumes being determined by means of the mercury porosimetry technique; and the following properties: —a mean size of the crystallites after calcination in air at 1100° C. for 5 hours (denoted D1100° C.-5 h) which is lower than 45.0 nm, preferably lower than 40.0 nm; —a mean size of the crystallites after calcination in air at 900° C. for 2 hours (denoted D900° C.-2 h) which is lower than 25.0 nm, preferably lower than 20.0 nm, even more preferably lower than 15.0 nm; and—an increase ΔD of the mean size of the crystallites lower than 30.0 nm, preferably lower than 25.0 nm, ΔD being calculated with the following formula: ΔD=D-D; the mean size of the crystallites being obtained by XRD from the diffraction peak [111] of the cubic phase corresponding to cerium oxide, generally present at 2Φ between 28.0 and 30.0.