Separation and Recovery of Dimethylnaphthalene Isomers from Light Cycle Oil by Distillation‐Extraction Combination

Abstract

Light cycle oil (LCO) contains a lot of valuable aromatic components, including 2,6‐dimethylnaphthalene (2,6‐DMNA) that is focused as the elementary raw material for engineering plastic (PEN plastic) and polymer liquid crystal. We investigated the separation and recovery of dimethylnaphthalene (DMNA) isomers by distillation‐extraction combination as the pretreatment operation to separate and purify 2,6‐DMNA from LCO. The concentration of DMNA isomers from LCO was tested by batch distillation operation. Distillate with DMNA isomers of high concentration, such as 30.63 wt%, was recovered by mixing distillates distilled at 255 to 278°C. Furthermore, equilibrium extraction to investigate separation between DMNA isomers and paraffin components in the distillate was carried out using the mixture oil added a small quantity of n‐decane (DEC) to the distillate recovered through batch distillation operation as raw material and the aqueous N,N‐dimethylforamide as a solvent. Selectivity of DMNA isomers in reference to DEC increased by increasing the solvent moisture and the mass ratio of solvent to raw material, whereas, selectivity of DMNA isomers in reference to DEC decreased by increasing the operation temperature. The process of separation and recovery for DMNA isomers from LCO was studied by using the experimental results obtained from each operation (distillation, extraction) of this work.