Distillation of Ethanol

Perhaps no chemical process has had a more storied and rich past as the distillation of ethanol. Ethanol has long been valued as a tonic and elixir for recreational purposes as well as an antiseptic for medicinal uses. Today, ethanol is part of a growing clean energy approach to replace fossil fuels.

Ethanol is a clear liquid and is readily mixed with water. It is primarily produced by the fermentation of plant materials such as corn, rye, potatoes, and sugar cane. Most spirits contain about 40% alcohol by volume, and by using simple distillation, concentrations of up to 96.5% alcohol can be reached by double and triple distillation. It is possible to get concentrations higher than that by adding chemicals such as benzene or by the use of molecular sieves. These processes are beyond the scope of most distillers and are used to produce industrial or lab grade ethanol not intended for human consumption.

Distillation is a simple process in which an alcohol/water mixture is heated and the resulting hot vapors are drawn off and cooled. Once cooled, the ethanol rich vapors condense and yield a liquid in which the ethanol is greatly concentrated. Starting concentrations in the original solution (called the “mash”) usually range in the neighborhood of 6 to 12 percent when simple fermentation is used.

The most simple distillation apparatus consists of a container to heat the alcohol/water mixture (the “pot”), a horizontal tapering tube (the “arm”) attached to the top of the pot and a tube (the “coil”) bent into a helix shape to cool the hot vapors. Often, the coil is surrounded by a water jacket to ensure condensation. Depending on the starting concentration, the mixture will begin to boil somewhere between 90 and 96 degrees Celsius and yield a product consisting of between 35 and 60 percent alcohol on the first pass.

As alcohol is evaporated from the mash, the temperature of the mash will begin to increase as it becomes closer to pure water and the corresponding product will begin to decrease in alcohol concentration. Usually the very first liquid that is condense is discarded, as it may contain impurities such as methanol or other chemicals. Usually, the last condensate coming from the coil is recycled and distilled again to further increase the alcohol yield.


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