Aluminium and Zirconium-Based Mixed Oxide

A mixed oxide of aluminium, of zirconium, of lanthanum and optionally of at least one rare-earth metal other than cerium and other than lanthanum (denoted REM), the proportions by weight of these elements being as follows:

• between 20.0 wt % and 45.0 wt % of aluminium, between 25.0 wt % and 40.0 wt %, or between 25.0 wt % and 35.0 wt %;
• between 1.0 wt % and 15.0 wt % of lanthanum, between 1.0 wt % and 10.0 wt %, between 1.0 wt % and 7.0 wt %, or between 2.0 wt % and 7.0 wt %;
• between 0 and 10.0 wt %, between 1.0 wt % and 10.0 wt %, between 10.0 wt % and 7.0 wt %, or between 2.0 and 7.0% for the rare-earth metal other than cerium and other than lanthanum, on condition that if the mixed oxide comprises more than one rare-earth metal other than cerium and other than lanthanum, this proportion applies to each of these rare-earth metals optionally wherein the total proportion of the rare-earth metal other than cerium and other than lanthanum is less than 25.0 wt %, or less than 20%;
• between 50.0 wt % and 70.0 wt, or between 55.0 wt % and 65.0 wt % of zirconium;
• these proportions being expressed as oxide equivalent with respect to the total weight of the mixed oxide,
• wherein after calcination in air at 1100° C. for 5 hours, the specific surface area (BET) of the mixed oxide is at least 25.0 m2/g;
• and in that after calcination in air at 950° C. for 3 hours, the porosity of the mixed oxide determined by N2 porosimetry is such that:
• in the domain of the pores with a size lower than 100 nm, the porogram of the mixed oxide exhibits a peak which is located at a diameter Dp, 950° C./3 h between 15 and 30 nm;
• the ratio V<40 nm, 950° C./3 h/Vtotal, 950° C./3 h is greater than or equal to 0.80, greater than or equal to 0.85, or greater than or equal to 0.90;
• Vtotal, 950° C./3 h is greater than or equal to 0.35 ml/g, greater than or equal to 0.40 ml/g, or greater than or equal to 0.45 ml/g;
• V<40 nm, 950° C./3 h, Vtotal, 950° C./3 h denoting respectively the pore volume for the pores with a size lower than 40 nm and the total pore volume of the mixed oxide after calcination in air at 950° C. for 3 hours;
• the mixed oxide being further characterized by one or more of the three characteristics (i), (ii), (iii) below:
• (i) Δ is lower than 82.0%, Δ being calculated by the following formula:
• Δ
• =
• (
• S
• 950
• ⁢
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• .
• /
• 3
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• -
• S
• 1200
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• 950
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• ⁢
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• 3
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• ×
• 100
• ;
• (ii) Δ* is lower than 55.0%, Δ* being calculated by the following formula:
• Δ
• *
• =
• (
• S
• 950
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• .
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• 3
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• -
• S
• 1100
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• 100
• ;
• (iii) S1200° C./5 h is strictly higher than 15.0 m2/g;
• wherein S950° C./3 h, S1100° C./5 h and S1200° C./5 h denotes respectively the BET specific surface areas for the mixed oxide after calcination in air at respectively 950° C. for 3 hours, 1100° C. for 5 hours and 1200° C. for 5 hours.