| abstract |
Azeotropic mixtures are separated into their components by submitting the mixture to dialysis using a membrane of plastic material, and separating the components from one or both of the liquids obtained by distillation, leaving a fraction which approximates to the original azeotropic mixture, which is re-cycled. The plastic membrane selected is hydrophyllic or hydrophobic in accordance with the nature of the liquid component to permeate through it. The following are specified (1) hydrophyllic, cellulose acetate, regenerated cellulose, polyacrylonitrile, hydrolysed P.V.A., nylon; hydrophobic, the higher esters or ethers of cellulose, polyethylene and polystyrene. The permeation step may be effected with the feed liquid under pressure and at elevated temperature, and the permeate removed with vapours (e.g. steam or butane) and at low pressure. In examples, the process is applied to azeotropic mixtures of benzene and methanol, alcohol and water, and CS2 and acetone. |