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Abstract
There are a lot of valuable aromatic components in light cycle oil (LCO). Among them, 2,6-dimethylnaphthalene is focused as the elementary raw material for engineering plastic (PEN plastic) and polymer liquid crystal, etc. We investigated the separation and recovery of valuable aromatic components (bicyclic aromatic components: carbon number 10–12) in LCO by solvent extraction method. Sulfolane, dimethylsulfoxide (DMSO), diethyleneglycol, and dimethylformamide were used as extraction solvents to measure distribution equilibrium. It was found that DMSO was a promising extraction solvent based on the distribution coefficient of bicyclic aromatic component and selectivity for n-Nonane. The effect of operation factors on extraction performance for bicyclic aromatic components in LCO using DMSO as extraction solvent was also studied. With increasing moisture content of solvent, the distribution coefficient of bicyclic aromatic components decreased and selectivity increased. Increasing operation temperature resulted in decreasing the distribution coefficient and selectivity. The lower the carbon number, the higher the distribution coefficient and selectivity of bicyclic aromatic components. Because boiling temperature of DMSO overlapped with that of component, it was difficult to recover extract component of extract phase. Benzene, toluene, m-xylene, n-hexane (HX), and n-octane were used as secondary solvents, and the distribution equilibrium between extract phase (re-extraction feed) and secondary solvent was measured. It was found that HX was a promising solvent for recovering bicyclic aromatic components. To examine the effect of operation factors on recovering bicyclic aromatic components, HX was used as a re-extraction solvent. The distribution coefficient of bicyclic aromatic components decreased smoothly while increasing the mass ratio of solvent to re-extraction feed and operation temperature. The higher the carbon number, the higher the distribution coefficient of bicyclic aromatic components. To examine the process of separation and recovery for dimethylnaphthalene mixture with 10 structural isomers in the LCO, the experiment result obtained from equilibrium extraction and equilibrium re-extraction were used.