Anhydrous ethanol is the raw material of many important chemical products and intermediates. At present, benzene azeotropic distillation is mostly used to produce anhydrous ethanol on a large scale. However, because the product of azeotropic distillation contains benzene, it can not be used in medicine and chemical reagents, and benzene poisoning is easy to occur in the production process. Therefore, the method of producing anhydrous ethanol is constantly improving and developing.

In recent years, there are many new methods to produce anhydrous ethanol. There are two main methods: using pentane as azeotropic agent, anhydrous ethanol is prepared by azeotropic distillation; Absolute ethanol was prepared by continuous distillation-pervaporation technology. The water content in industrial ethanol is generally around 5.0%. Because ethanol and water can form a constant boiling mixture (95.5% ethanol and 4.4% water) with a boiling point of 78℃, conventional distillation methods have been unable to remove water from it.

The key of "desiccant+distillation";

Generally, calcium oxide, anhydrous calcium chloride, anhydrous sodium sulfate and anhydrous magnesium sulfate can be used as desiccants for industrial ethanol. Among these desiccants, calcium oxide is the first choice, followed by calcium chloride.

The advantages of calcium oxide are low price, no side reaction during drying and good drying effect. The dried product calcium hydroxide Ca(OH)2 can be directly used in other products, but the disadvantage is that the dosage is large, and a large amount of calcium hydroxide Ca(OH)2 is unfavorable to the operation process because of its excessive viscosity. The advantage of anhydrous calcium chloride is that the dosage is small. 1 molecule anhydrous calcium chloride combines with 6 molecules of water to form calcium chloride hexahydrate. The disadvantage is that calcium chloride is easily complexed with a small amount of ethanol under certain conditions.