A process for preparing a catalyst comprising the following steps: 1)a) preparing a colloidal solution A with a defined pH containing particles in the form of an oxide, hydroxide or (hydroxide) of a cation M z+ selected from the group constituted by cations from columns 2, 3, 4, 13 and 14 according to the IUPAC periodic classification in the CRC Handbook of Chemistry and Physics, 2000-2001 by dissolving, at a temperature in the range 5°C to 100°C, a salt of a precursor of the cation M z+ which is soluble in aqueous solution, the concentration of the cation being in the range 0.01 to 1 mole/litre, in a volume V of a solution of sodium hydroxide with a concentration of 0.01 to 1 mole/litre or in a volume V of water or in a volume V of water to which a volume V' of a solution of sodium hydroxide with a concentration of 0.01 to 1 mole/litre has been added; 1)b) using a commercial aqueous colloidal solution (solution A) with a defined pH containing particles in the form of an oxide, hydroxide or (hydroxide) of a cation M z+ selected from the group constituted by cations from columns 2, 3, 4, 13 and 14 according to the IUPAC periodic classification in the CRC Handbook of Chemistry and Physics, 2000-2001; 2) adding in an aqueous solution B containing a precursor salt of a metal of columns 8 to 10 according to the IUPAC periodic classification in the CRC Handbook of Chemistry and Physics, 2000-2001 with a concentration of 0.001 to 1 mole/litre, the precursor salt of the metal being soluble under the pH conditions used in step 1, 3) impregnating the solution obtained after step 2 onto a support with a BET specific surface area in the range 5 to 300 m 2 /g; 4) drying at a temperature of 120°C or less then calcining at a temperature in the range 100°C to 600°C. 1)a) preparing a colloidal solution A with a defined pH containing particles in the form of an oxide, hydroxide or (hydroxide) of a cation M z+ selected from the group constituted by cations from columns 2, 3, 4, 13 and 14 according to the IUPAC periodic classification in the CRC Handbook of Chemistry and Physics, 2000-2001 by dissolving, at a temperature in the range 5°C to 100°C, a salt of a precursor of the cation M z+ which is soluble in aqueous solution, the concentration of the cation being in the range 0.01 to 1 mole/litre, in a volume V of a solution of sodium hydroxide with a concentration of 0.01 to 1 mole/litre or in a volume V of water or in a volume V of water to which a volume V' of a solution of sodium hydroxide with a concentration of 0.01 to 1 mole/litre has been added; 1)b) using a commercial aqueous colloidal solution (solution A) with a defined pH containing particles in the form of an oxide, hydroxide or (hydroxide) of a cation M z+ selected from the group constituted by cations from columns 2, 3, 4, 13 and 14 according to the IUPAC periodic classification in the CRC Handbook of Chemistry and Physics, 2000-2001; 2) adding in an aqueous solution B containing a precursor salt of a metal of columns 8 to 10 according to the IUPAC periodic classification in the CRC Handbook of Chemistry and Physics, 2000-2001 with a concentration of 0.001 to 1 mole/litre, the precursor salt of the metal being soluble under the pH conditions used in step 1, 3) impregnating the solution obtained after step 2 onto a support with a BET specific surface area in the range 5 to 300 m 2 /g; 4) drying at a temperature of 120°C or less then calcining at a temperature in the range 100°C to 600°C.