Under constant pressure, when the alcohol-water mixture reaches 95.57% (w/w), the volume fraction reaches 97.2% (v/v), a coboiling mixture is formed at that concentration, Which means using a ordinary distillation method can not reach alcohol purity over 97.2% (v/v).
To produce high-purity anhydrous alcohol, adopt variable pressure adsorption (PSA) molecular sieve, with 99.5% concentration to 99.98% (v/v) after dehydration and condensation. Compared with the traditional ternary azeotropic distillation method, with good dehydration effect, high product quality, advanced technology and low energy consumption.
Ethanol dehydration molecular sieve adsorption method is a technique for absorb water of feed ethanol. Using a molecular sieve of YM, the water molecule is 3A, and the 2.8A, ethanol molecule is 4.4A. Because ethanol molecules are larger than water molecules, water molecules can be adsorbed in the hole, ethanol molecules can not adsorb are excluded. When the water-containing ethanol adsorbed neatly through the molecular sieve, the molecular sieve adsorbs the water parts, while the ethanol vapor passes the adsorption bed and becomes a pure ethanol product.