Process for the preparation of 2-perfluoropropoxy-perfluoropropionyl fluoride by dimerization of hexafluoropropene epoxide in aprotic polar medium, in the presence of N,N,N',N'-tetrasubstituted diaminodifluoromethane as catalyst, characterized in that the dimerization reaction is carried out in the presence of a co-catalyst constituted by a nitrogenous organic base having structure of aniline, or of pyridine, or of a derivative thereof, wherein the nitrogen atom is not linked to hydrogen atoms and, in the case of the pyridine-type structure, it is sterically hindered by substituent groups on ortho-position relatively to it.