The product of either ethylene hydration or brewing is an ethanol-water mixture. For most industrial and fuel uses, the ethanol must be purified. Fractional distillation can concentrate ethanol to 95.6% by weight (89.5 mole%). The mixture of 95.6% ethanol and 4.4% water (percentage by weight) is an azeotrope with a boiling point of 78.2 °C, and cannot be further purified by distillation. Because of the difficulty of further purification, 95% ethanol/5% water is a fairly common solvent. There are several methods used to further purify ethanol beyond 95.6%:

Contents

• 1 Drying using lime or a salt
• 2 Addition of an entrainer
• 3 Molecular sieves
• 4 Membranes
• 5 Pressure Reduction
• 6 References

Drying using lime or a salt

After distillation ethanol can be further purified by "drying" it using lime (calcium oxide) or using a hygroscopic material such as rocksalt. When lime is mixed with the water in ethanol, calcium hydroxide forms. The calcium hydroxide can then be separated from the ethanol. Similarly, a hygroscopic material will dissolve some of the water content of the ethanol as it passes through, leaving a purer alcohol.

www.ethanolindustry.info
... info/business/energy/renewable/biomass/ethanol/ http ... info/corn_ethanol_industry/ http://www ... info/ethanol_purification/ http://www.ethanolindustry.info/ethanol ...
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Butanol Answers (Dehydration of Butanol, Carbocation ...
... of sodium sulphite and butanol in the purification process? ... - Thu Jan 22 21:57:16 2009 - Other - Science - 1 ... "Ethanol Industry Information" [
www.ethanolindustry.info/butanol/answers.htm

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