Process for the hydroprocessing of a hydrocarbonaceous feedstock with an atomic H/C ratio of at least 0.25, in the presence of hydrogen and at least one catalyst in at least one reactor, said process comprising a reaction step performed in a reaction section comprising a hydroconversion reactor and a hydrotreatment reactor, each reactor being fed with at least one pressurized slurry issued from a preparation reactor, this slurry consisting of a hydrocarbonaceous feedstock containing activated catalyst, hydrogen and eventually other additives, and a separation step performed in a separation section, characterised in that it comprises: - a step of preparation of at least one catalyst in at least two preparation reactors upstream from the reaction section, wherein each catalyst being prepared by activation of a catalytic precursor in a stirred batch, said activation consisting in conversion of the metal contained in the precursor to active sulphur species, wherein - (i) at least one preparation reactor feeds one or more reactor of the reaction section, or - (ii) each preparation reactor is dedicated for catalysts fed to at least a hydroconversion reactor or at least a hydrotreatment reactor of the reaction section; - the catalyst precursor dedicated to hydroconversion being bis (cyclopentadienyl) molybdenum dichloride, - a step of separation of the solids contained in the liquid effluents issued from the reaction section, said step being performed in a liquid/solid separation apparatus of the separation section, - a step of treatment of the residues issued from the separation section, comprising a partial oxidation step performed in a partial oxidation section wherein said residues are partially oxidized to produce carbon monoxide, hydrogen and a metal containing residue. - a step of preparation of at least one catalyst in at least two preparation reactors upstream from the reaction section, wherein each catalyst being prepared by activation of a catalytic precursor in a stirred batch, said activation consisting in conversion of the metal contained in the precursor to active sulphur species, wherein - (i) at least one preparation reactor feeds one or more reactor of the reaction section, or - (ii) each preparation reactor is dedicated for catalysts fed to at least a hydroconversion reactor or at least a hydrotreatment reactor of the reaction section; - the catalyst precursor dedicated to hydroconversion being bis (cyclopentadienyl) molybdenum dichloride, - (i) at least one preparation reactor feeds one or more reactor of the reaction section, or - (ii) each preparation reactor is dedicated for catalysts fed to at least a hydroconversion reactor or at least a hydrotreatment reactor of the reaction section; - the catalyst precursor dedicated to hydroconversion being bis (cyclopentadienyl) molybdenum dichloride, - a step of separation of the solids contained in the liquid effluents issued from the reaction section, said step being performed in a liquid/solid separation apparatus of the separation section, - a step of treatment of the residues issued from the separation section, comprising a partial oxidation step performed in a partial oxidation section wherein said residues are partially oxidized to produce carbon monoxide, hydrogen and a metal containing residue.