The invention concerns a preparation process for 2,6-dimethylnaphthalene in which 1-(p-tolyl)-2-methylbutane and/or 1-(p-tolyl)-2-methylbutene are dehydrocyclisized using a reduced vanadium catalyst. 2,6-dimethylnaphthalene can be used as starting material when manufacturing polyethylenenaphthalate. The conversion of this method is good and the selectivity of 2,6-dimethylnaphthalene can be improved by reducing the catalyst.
