Abstract: There is disclosed a method for isomerizing dimethylnaphthalene (DMN) in liquid phase under atmospheric pressure by using a catalyst comprising hydrogen-form mordenite which has a molar ratio of silica to alumina (SiO.sub.2 /Al.sub.2 O.sub.3 ratio) of at least 100 and is molded by incorporating alumina as the molding aid therein. According to the above method, the objective 2,6-DMN minimized in the contents of impurities can stably be produced in high selectivity and high yield under mild reaction conditions for a long period of time, while side reactions and deterioration of the catalyst are suppressed to a minimum.

Abstract: Dimethylnaphthalenes are isomerized into 2,6-dimethylnaphthalene by utilizing hydrogen fluoride as a catalyst and straight chain saturated aliphatic hydrocarbons having carbon atoms in the range from 5 to 12 as the solvent. Isomerization to other undesirable isomers such as 2,7-dimethylnaphthalene and side reactions such as disproportionation are suppressed and a very high degree of the isomerization to 2,6-DMN can be attained.