Spheroidal alumina particles with improved mechanical strength having a macroporous median diameter in the range 0.05 to 30 μm

A process for the production of spheroidal alumina particles having a BET specific surface area of 150 to 300 m2/g, a mean particle diameter 1.2 to 3 mm and a particle diameter dispersion, expressed as the standard deviation, not exceeding 0.1, a total pore volume, measured by mercury porosimetry, of 0.50 to 0.85 mL/g, a degree of macroporosity within a particle of less than 30%, and a dispersion of the diameters of macropores, expressed as the ratio D90/D50, not exceeding 8, comprising:

• a) preparing a suspension comprising water, an acid and at least one boehmite powder,
• b′) adding at least one liquid pore-forming agent, at least one surfactant and optionally water, or an emulsion comprising at least one liquid pore-forming agent, at least one surfactant and water, to the suspension obtained in a),
• b″) dispersing the suspension obtained in b′) with a disperser functioning at a shear rate in the range 1000 to 200000 s−1,
• c) mixing the suspension dispersed in b″) until the viscosity of said mixture is in the range 200 to 700 mPa·s,
• d) shaping the spheroidal particles by drop coagulation using the mixture obtained in step c),
• e) drying the particles obtained in d),
• f) calcining the particles obtained in e).

A process for the preparation of spherical alumina particles having a BET specific surface area of 150 to 300 m2/g, a mean particle diameter 1.2 to 3 mm and a particle diameter dispersion, expressed as the standard deviation, not exceeding 0.1, a total pore volume, measured by mercury porosimetry, of 0.50 to 0.85 mL/g, a degree of macroporosity within a particle of less than 30%, and a dispersion of the diameters of macropores, expressed as D90/D50, not exceeding 8 comprising:

• a) preparing a suspension comprising water, an acid and at least one boehmite powder,
• b) adding a solid pore-forming agent having a particle size in the range 0.05 to 30 μm to the suspension obtained in a),
• c) mixing the suspension obtained in b) until the viscosity of said mixture is in the range 200 to 700 mPa·s,
• d) shaping the spheroidal particles by drop coagulation using the mixture obtained in c),
• e) drying the particles obtained in d),
• f) calcining the particles obtained in (e),
• in which the suspension of a) further comprises a charge of alumina or alumina precursor constituted by particles with a volumetric median diameter of 50 μm or less.