The present invention relates to a hydrogenolysis process wherein a hydrocarbon-based feedstock comprising aromatic compounds having at least 8 carbon atoms is treated by means of a hydrogen feed and in the presence of a catalyst, in order to convert C2+ alkyl chains of said aromatic compounds into methyl groups and to produce a hydrogenolysis effluent enriched in methyl-substituted aromatic compounds, wherein the catalyst comprises a support, comprising at least one refractory oxide, and an active phase comprising nickel and molybdenum, wherein: the nickel content being between 0.1 and 25% by weight relative to the total weight of the catalyst; the molybdenum content being between 0.1 and 20% by weight relative to the total weight of the catalyst; and the catalyst comprising a molar ratio of molybdenum to nickel of between 0.2 and 0.9. The present invention also relates to said catalyst and to the process for preparing said catalyst.