Preparation methods: azeotropic rectification 2113 method, extractive rectification method, molecular sieve dewatering 5261 water method, membrane separation method 4102, the above four have already been mass-produced in 1653; quicklime method, potassium acetate and sodium acetate mixed liquid dehydration method, Vacuum distillation method, starch adsorption method, ion exchange resin dehydration method, sodium, magnesium drying method, etc.

　　 Industrial preparation method

　　 1. Azeotropic distillation method

The method is: putting ethanol-water-benzene (or cyclohexane, pentane, etc., referred to as entrainer) together into an azeotropic distillation column, in which water-ethanol-benzene forms a ternary azeotrope (Constant boiling point 64.9℃) Steamed, all the water is taken away, and the distilled ethanol is almost pure.

　　 2. Membrane separation method

　　 The components have different diffusion rates when passing through the membrane. Fast diffusion first passes through the membrane, and slow diffusion does not pass through the membrane, so that the purpose of separating components can be achieved. There are two modes, one is to pass the liquid into steam after passing through the membrane, and the other is to vaporize the liquid and let the steam pass through the membrane for separation.

　　 3. Molecular sieve dehydration method

The water molecule diameter is 2.6Å (1Å=10^-10m), the ethanol molecule diameter is 4.7Å, and the molecular sieve with a pore size of 3Å is selected. The mixed liquid is heated to become steam, and it passes through the molecular sieve. The water molecules will be strongly adsorbed and condensed. High-purity ethanol is available.

　　 4. Extractive distillation method

Add ethanol solution of salt (potassium acetate, calcium chloride, copper chloride, sodium chloride, etc.) or alkali (sodium hydroxide, potassium hydroxide, etc.) to the ethanol-water mixing system, rectify together, and distill ethanol The output concentration is greater than 99.5%.