Purification of 2,6‐Dimethylnaphthalene From Light Cycle Oil

Recovering 2,6‐dimethylnaphthalene (2,6‐DMN) from light cycle oil (LCO) requires removal of the complex hydrocarbon matrix followed by selective separation of the closely related DMN isomers. An integrated process comprising vacuum distillation, 3‐nitrobenzoic acid (3‐NBA) complexation, and solvent crystallization was developed. Vacuum distillation increased the 2,6‐DMN content from 2.56% to 8.64%. Complexation at a 3‐NBA‐to‐2,6‐DMN molar ratio of 4:1 and 20°C increased the content to 41.02%, with a stage yield of 68.20%. Subsequent crystallization in methanol–acetonitrile increased the GC‐FID area‐normalized content to 91.54% and 99.80% after the first and second crystallizations, respectively. Processing the combined mother liquors afforded an additional product containing 99.60% 2,6‐DMN by the same chromatographic method. The overall 2,6‐DMN recovery was 19.5%, comprising 14.44% from the main crystallization product and 5.11% from the mother‐liquor recovery route.