Rectification ternary mixtures

Serafimov, L. A. Timofeev, V. S., Balashov, M. I. (1973b). Rectification of Multicomponent Mixtures. 4. Non-Local Characteristics of Continuous Rectification, Trajectories for Ternary Mixtures at Finite Reflux Ratios. Acta Chimica Academiae Scientiarum Hungarical, 75,255-70. 

Lewis and Smoley (Ref. 22) studied the plate efficiency in the rectification of mixtures of (1) benzene-toluene, (2) benzene-toluene-xylene, and (3) naphtha and mixtures of pinene and aniline in naphtha. An experimental column 8 in. in diameter with 10 plates spaced 16 in. apart was used. The bubble cap was rectangular, being 2 in. high and 2 in. wide, and extended across the column. There were 24 slots % by Ke on each side of the cap, giving a ratio of slot area to superficial area of about 0.16. The investigators found average plate efficiencies of 60 per cent for the benzene-toluene mixture, 76 per cent for the ternary mixture, and 80 to 95 per cent for the naphtha mixtures. 

Petlyuk, F. B. (1986). Rectification Diagrams for Ternary Azeotropic Mixtures. Theor. Round. Chem. Eng., 20,175-85. 

Sometimes the new azeotrope which is formed contains all three constituents. The dehydration of ethanol-water mixture with benzene as added substance is an example. Dilute ethanol-water solutions can be continuously rectified to give at best mixtures containing 89.4 mole percent ethanol at atmospheric pressure, since this is the composition of the minimum-boiling azeotrope in the binary system. By introducing benzene into the top of a column fed with an ethanol-water mixture, the ternary azeotrope containing benzene (53.9 mol %), water (23.3 mol %), ethanol (22.8 mol %), boiling at 64.9°C, is readily separated from the ethanol (bp — 78.4 C), which leaves as a residue product. In this case also the azeotropic overhead product separates into two liquid layers, one rich in benzene which is returned to the top of the column as reflux, the other rich in water which is withdrawn. Since the latter contains appreciable quantities of both benzene and ethanol, it must be rectified separately. The ternary azeotrope contains nearly equal molar proportions of ethanol and water, and consequently dilute ethanol-water solutions must be given a preliminary rectification to produce substantially the alcohol-rich binary azeotrope which is used as a feed. 

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