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'Vacuum distillation' is a method of distillation whereby the pressure above the liquid mixture to be distilled is reduced to less than its vapor pressure (usually less than atmospheric) causing evaporation of the least volatile liquid(s) (those with the highest boiling points). This distillation method works on the principle that boiling occurs when the vapor pressure of a liquid exceeds the ambient pressure. Vacuum distillation is used with or without heating the solution.

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Applications

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References

Applications

The process is used when liquids to be distilled have high atmospheric boiling points or chemically change at temperatures near their atmospheric boiling points. Temperature sensitive materials (such as beta carotene) also require vacuum distillation to remove solvents from the mixture without damaging the product. Another reason vacuum distillation is used is that compared to steam distillation there is a lower level of residue build up. This is important in commercial applications where temperature transfer is produced using heat exchangers.
Vacuum distillation is sometimes referred to as low temperature distillation. Typical industrial applications utilize the heat pump cycle to maximize efficiency. This type of distillation is in use in the oil industry where common ASTM standards are D1160, D2892, D5236. These standards describe typical applications of vacuum distillation at pressures ~1-100 mbar. Pilot plants up to 200 L can be built in accordance with these standards.

Gallery

Image:Short path distillation apparatus.png| Short path vacuum distillation apparatus
Image:Perkin triangle distillation apparatus.png| Perkin triangle - for air-sensitive vacuum distillation

References

★ Vacuum Distillation: New Method for Analyzing Organic Chemicals in a Wide Array of Samples at United States Environmental Protection Agency

★ What is vacuum distillation? at NEWTON Ask-A-Scientist

★ Distillation at CU Boulder Organic Chemistry Teaching Labs