A process for the preparation of an amorphous mesoporous and macroporous alumina, said process comprising at least the following steps: a) a step for dissolving an acidic precursor of aluminium selected from aluminium sulphate, aluminium chloride and aluminium nitrate in water, at a temperature in the range 20°C to 90°C, at a pH in the range 0.5 to 5, for a period in the range 2 to 60 minutes; b) a step for adjusting the pH by adding, to the suspension obtained in step a), at least one basic precursor selected from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide, at a temperature in the range 20°C to 90°C, and at a pH in the range 7 to 10, for a period in the range 5 to 30 minutes; c) a step for co-precipitation of the suspension obtained at the end of step b) by adding to the suspension at least one basic precursor selected from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide and at least one acidic precursor selected from aluminium sulphate, aluminium chloride, aluminium nitrate, sulphuric acid, hydrochloric acid and nitric acid, at least one of the basic or acidic precursors comprising aluminium, the relative flow rate of the acidic and basic precursors being selected so as to obtain a pH in the range 7 to 10 in the reaction medium and the flow rate of the acidic and basic precursor or precursors containing aluminium being adjusted so as to obtain a final concentration of alumina in the suspension in the range 10 to 38 g/L; d) a step for filtration of the suspension obtained at the end of the co-precipitation step c) in order to obtain an alumina gel; e) a step for drying said alumina gel obtained in step d) in order to obtain a powder; f) a step for shaping the powder obtained at the end of step e) in order to obtain a green material; g) a step for heat treatment of the green material obtained at the end of step f) at a temperature in the range 500°C to 1000°C, in the presence or otherwise of a stream of air containing up to 60% by volume of water. a) a step for dissolving an acidic precursor of aluminium selected from aluminium sulphate, aluminium chloride and aluminium nitrate in water, at a temperature in the range 20°C to 90°C, at a pH in the range 0.5 to 5, for a period in the range 2 to 60 minutes; b) a step for adjusting the pH by adding, to the suspension obtained in step a), at least one basic precursor selected from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide, at a temperature in the range 20°C to 90°C, and at a pH in the range 7 to 10, for a period in the range 5 to 30 minutes; c) a step for co-precipitation of the suspension obtained at the end of step b) by adding to the suspension at least one basic precursor selected from sodium aluminate, potassium aluminate, ammonia, sodium hydroxide and potassium hydroxide and at least one acidic precursor selected from aluminium sulphate, aluminium chloride, aluminium nitrate, sulphuric acid, hydrochloric acid and nitric acid, at least one of the basic or acidic precursors comprising aluminium, the relative flow rate of the acidic and basic precursors being selected so as to obtain a pH in the range 7 to 10 in the reaction medium and the flow rate of the acidic and basic precursor or precursors containing aluminium being adjusted so as to obtain a final concentration of alumina in the suspension in the range 10 to 38 g/L; d) a step for filtration of the suspension obtained at the end of the co-precipitation step c) in order to obtain an alumina gel; e) a step for drying said alumina gel obtained in step d) in order to obtain a powder; f) a step for shaping the powder obtained at the end of step e) in order to obtain a green material; g) a step for heat treatment of the green material obtained at the end of step f) at a temperature in the range 500°C to 1000°C, in the presence or otherwise of a stream of air containing up to 60% by volume of water.