The separation of aromatic compounds from paraffins is essential in producing many polyesters that are used in a variety of products. When aromatics and paraffins have the same number of carbon atoms, they often have similar vapor pressures, which makes them difficult to separate by distillation. Extraction is a viable alternative, as illustrated by the following simple system.
Sulfolane (an industrial solvent) and octane may be considered completely immiscible. At 25°C, the ratio of the mass fraction of xylene in the octane-rich phase to the mass fraction of xylene in the sulfolane rich phase is 0.25. One hundred kg of pure sulfolane are added to 100 kg of a mixture containing 75 wt% octane and 25%xylene, and the resulting system is allowed to equilibrate. How much xylene transfers to the sulfolane phase?