When methylnaphthalene is used to synthesize products, the nitrogen-containing, sulfur-containing and oxygen-containing compounds must be restricted to prevent catalyst poisoning and inhibit side reactions. Nitrogen-containing compounds are easily removed by pickling and alkali fusion, while sulfur-containing compounds are more difficult to remove. The sulfide in methyl naphthalene is dominated by methyl thiophene, its boiling point is close to methyl naphthalene, and can co-crystallize with methyl naphthalene, so the sulfide can not be completely removed by rectification and recrystallization. After heat treatment with anhydrous ALCL3, the ALCL3 is extracted with water or sulfuric acid solution, and then refined by crystallization method, which can effectively remove methylthiophene.
