Abstract: The transalkylation of1,2,4,5-tetramethylbenzene (TeMB) with 2-methylnaphthalene (2-MN) to synthesize2,6-dimethylnaphthalene (2,6-DMN) by ionic liquid Et3NHCl-AlCl3 was investigated, and the effects of the acidic strength of the ionic liquid and the reaction conditions on the transalkylation were studied. The results showed that a high selectivity for2,6-DMN can be obtained by controlling the acid strength of the ionic liquid and optimizing the reaction conditions. Using cyclohexane as the solvent and Et3NHCl-AlCl3(x(AlCl3)=0.71) as the catalyst, 48.8% 2-MN conversion, 81.2% selectivity for DMN, 52.4% molar ratio of2,6-DMN/total dimethylnaphthalenes, and 20.8% yield of2,6-DMN were obtained under the reaction conditions of 20 ℃,6 h, and 2-MN∶TeMB molar ratio of 1∶1. In addition, the catalyst exhibited 100% molar ratio of2,6-DMN/total dimethylnaphthalenes with 3.7% 2-MN conversion during2 hreaction under the optimized reaction conditions. A high selectivity for2,6-DMN was also obtained when a feed of mixed methylnaphthalene or naphthalene was used. The reuse of the ionic liquid was investigated and the main reason for the catalyst deactivation was discussed.

Key words: ionic liquid, 5-tetramethylbenzene, 2-methylnaphthalene, transalkylation, 6-dimethylnaphthalene