Selective Synthesis of 2,6-Dimethylnaphthalene by Transalkylation in the Presence of Acid Ionic Liqu

A highly selective synthesis of 2,6-dimethylnaphthanlene(2,6-DMN)by transalkylation between 2-methylnaphthanlene(2-MN)and 1,2,4,5-tetramethylbenzene(TeMB)was performed with 1-alkyl-3-methylimidazolium aluminum chloride([Cnmim]Cl-AlCl3)ionic liquids(ILs)as catalysts.The influences of the alkyl group as the organic cation,the acidic strength of[C4mim]Cl-AlCl3 ILs as well as the reaction conditions on the catalytic performance were investigated.[C4mim]Cl-AlCl3 ILs[x(AlCl3)=71％]exhibited high activity and selectivity toward 2,6-DMN.The selectivity to 2,6-DMN and the 2,6-DMN/2,7-DMN ratio reached up to 68.2％ and 3.7∶1,respectively.The UV-Vis spectrum of TeMB treated by different ILs shows that the protonated degree of TeMB dependeds on the acidity strength of ILs,which has a significant impact on the reaction results.The high protonated degree of TeMB is advantageous to enhancing the conversion of transalkylation and the large stereo-hindrance effect of TeMB is favorable to improving the selecivity to 2,6-DMN.