Extraction of Aromatics in the Light Cycle Oil —Extraction Equilibrium and Extraction Rate of Naphthalene Group—

Abstract

Light cycle oil (LCO) contains valuable aromatic hydrocarbons, some of which become intermediates for engineering plastics. To select the best solvent for extraction of these aromatics (naphthalene group), several conventional solvents, which have been employed commercially as extraction solvents for the light aromatics, were tested, through measurement of distribution of several selected hydrocarbons between the solvent and oil phases. The solvents used were sulfolane, dimethyl sulfoxide (DMSO), diethylene glycol and dimethyl formamide. Among many components in the LCO A (LCO+nonane), several hydrocarbons with carbon number of 9-12 were selected for analysis. From the coefficients of distribution and selectivities of naphthalene group, in reference to nonane, DMSO seemed to be the best solvent for separation between naphthalene group and paraffin in the LCO. Furthermore, effects of operation parameters for extraction of naphthalene group in the LCO A were studied by batch equilibrium extraction with DMSO and water mixture as solvent. Distribution coefficients of naphthalene group were found to increase with decreasing temperature, whereas, selectivities of naphthalene group in reference to nonane increase with decreasing temperature. The effect of addition of water in solvent increases the selectivity, with a simultaneous decrease in coefficient of distribution. The coefficients of distribution and selectivities of naphthalene group, in reference to nonane or a mixture of 10 isomers of dimethylnaphthalenes, decreased with increasing carbon number. Selectivity of individual isomer, however, was roughly equal to unity. With DMSO and water mixture as solvent, mass transfer rates for naphthalene group were measured in a baffled batch vessel, agitated with six-flatblade turbines. Continuous phase mass transfer coefficients are measured. © 1995, The Japan Petroleum Institute. All rights reserved.