Importance

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Abstract

The invention relates to a composition which is a composition C1 which is based on Al and Ce in the form of oxides; or a composition C2 which is based on Al, Ce and La in the form of oxides with the following proportions of CeO₂ is between 5.0 wt % and 35.0 wt %; La₂O₃ (for composition C2 only) is between 0.1 wt % and 6.0 wt %; the remainder being Al₂O₃; and exhibiting a specific porosity profile and exhibiting the following properties of a mean size of the crystallites after calcination in air at 1100° C. for 5 hours (denoted D_{1100° C.-5h}) which is lower than 45.0 nm; a mean size of the crystallites after calcination in air at 900° C. for 2 hours (denoted D_{900° C.-2h}) which is lower than 25.0 nm; and an increase ΔD of the mean size of the crystallites lower than 30.0 nm, ΔD being calculated with the following formula: ΔD=D_{1100° C.-5h}−D_{900° C.-2h}; the mean size of the crystallites being obtained by XRD from the diffraction peak of the cubic phase corresponding to cerium oxide, generally present at 2θ between 28.0° and 30.0°.

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First Claim