Liquid–liquid equilibrium in the systems furfural + light lubricating oils using UNIFAC

In the lubricating oil manufacturing process, the aromatic content of vacuum distillates is reduced by solvent extraction, frequently with furfural. The complex composition of such mixtures makes the description of the liquid–liquid equilibrium involved difficult. In previous studies, the possibility to describe such equilibrium by using a reduced number of pseudo-components and the NRTL model has been stated. In this work, a different approach model was checked by using four model-molecules and a group contribution method. The molecular structure of model-molecules was determined regarding their different chemical nature and their physical properties. Dortmund modified UNIFAC model was used and the interaction parameters were calculated by correlating equilibrium data using AspenPlus©. The developed model was applied to describe the extraction operation of a light lubricating oil with furfural. Two sets of extraction experiments were considered. One of them was used to fit the needed parameters and the second one to check the predictive capability of the model. In both cases good agreement was obtained between experimental and calculated values for yields, furfural content composition and sulfur content of the involved mixtures. Most calculated values are as accurate as those obtained with the previously model, but a better description of the sulfur content was obtained.