Recovery of Dimethylnaphthalene Isomers from Light Cycle Oil by O/W/O Emulsion Liquid Membrane Process.

Abstract

This paper simulates a process for recovering dimethylnaphthalene isomers (DMN) from light cycle oil (LCO), a by-product in cracked gasoline manufacture. The process involves a multistage emulsion liquid membrane permeator for separating aromatics from paraffins in LCO and four distillation towers of which two towers are used to recover solvent from raffinate and permeate and the others are used to separate DMN from other aromatics in permeate. Stirred vessels are employed as contactors. Prior to the simulation, a series of continuous experiments on emulsion liquid membrane permeation were conducted to collect permeation coefficient data. The permeation coefficient data obtained was thereafter used to develop an empirical correlation needed for the simulation. During the simulation, the effects of permeator variables on the energy demands of the distillation towers and on the yield of DMN were investigated at a fixed DMN concentration in the product. The permeator variables studied included solvent-to-feed ratio, stirring rate, number of stages, permeator reflux ratio, and stage volume, as well as the kinds of solvents. DMN yield increased with stirring rate, number of stages, and stage volume, decreasing with permeator reflux ratio, and not affected significantly with solvent-to-feed ratio. The lighter the solvent, the lower were the energy demand and DMN yield. In the conditions of the study, about 80% of DMN in LCO could be recovered. Most of the energy consumed was used to recover the solvent. A quick analysis showed that the energy demands might be met by utilizing the raffinate obtained.