Modeling, simulation, and optimization for producing ultra-low sulfur and high-octane number gasoline by separation and conversion of fluid catalytic cracking naphtha

Abstract

Contradiction between the desulfurization and loss of octane number (ON) for fluid catalytic cracking (FCC) naphtha is the long-term problem of clean gasoline production. Moreover, ON loss is substantially aggravated during deep hydrodesulfurization because of the global limited supply of sulfur for gasoline. This paper introduced a novel process for ultra-clean gasoline production that solves the above problem by using a unique separation approach. The components were separated by the coupling of distillation and solvent extraction, which the separation efficiency depends on the relationship between solvent and feedstock components. However, the compositions of FCC naphtha are complicated and always changing due to different processing technologies. Therefore, changes in the material composition must be considered during production. In this study, ternary liquid–liquid equilibrium (LLE) was explored to investigate the interaction of olefin, sulfide, and sulfolane solvent. A universal quasi-chemical functional group activity coefficient (UNIFAC) group contribution model was selected to predict the product composition when the FCC naphtha was treated by this process. The lack and necessity of group interaction parameters for the prediction were obtained through the regressive calculation of LLE results. A simulation method was established by Aspen Plus, and the reliability was well illustrated. Finally, the high olefin content of FCC naphtha critical components was analyzed by this simulation method. The sulfur and olefin levels of the product were 9.0 mg/kg and 18.6 wt%, respectively. The operation conditions simulated using the proposed technique met the requirements for the latest commercial gasoline worldwide.