Abstract
Aromatics extraction was investigated using aqueous solution of sulfolane as the solvent phase and model gasoline, consisting of a benzene, toluene, xylene and hexane mixture, and reformate gasoline as the feed phase. Firstly, the liquid-liquid equilibrium was measured to examine the distribution coefficient and the separation selectivity of aromatics relative to hexane. The distribution coefficients and selectivities of benzene were the highest, followed by those of toluene and xylene. Increased water content of the solvent phase reduced the distribution coefficients and increased the selectivities. The measured equilibria were compared with the results estimated by the UNIFAC method. Countercurrent extraction was conducted, using a packed column with glass Rashig rings as the contactor. The solvent and feed phases were contacted as the continuous and dispersed phases, respectively, and the flow rates of both phases and the water content in the solvent phase were selected as experimental parameters to examine the yield, separation selectivity and volumetric overall mass transfer coefficient. The selectivities for benzene were the highest, followed by toluene and xylene. In the case of extraction from the reformate gasoline with 9 wt% water content in the solvent phase, the selectivity for benzene was approximately equal to 20, showing higher selectivities for aromatic components. The volumetric overall mass transfer coefficients were mainly affected by the flow rate of the continuous phase and the mass transfer resistance in the continuous phase was the controlling factor in the overall mass transfer resistance.
