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Distillation

physical science Maturity 7-9 Next article →

Distillation is a fundamental chemical process used to separate components within a liquid mixture. This method works by selectively boiling a mixture and then condensing the resulting vapors. It is a physical separation technique rather than a chemical reaction. This means the substances are pulled apart based on their properties, not changed into new molecules. Distillation is vital for creating high-purity chemicals and essential resources. However, it is also an energy-intensive process. It currently accounts for approximately 25% of all industrial energy consumption worldwide.

Simple distillation apparatus
Simple distillation apparatus

The mechanism of distillation relies on differences in relative volatility. Relative volatility describes how easily a substance turns into a gas compared to others in a mixture. The process begins by applying heat to a liquid mixture in a still. As the temperature rises, the components with lower boiling points turn into vapor first. This vapor then travels into a condenser, which is a cooling device. When the hot vapor hits the cool surfaces of the condenser, it undergoes condensation. This phase change turns the gas back into a liquid. This collected liquid is called the distillate.

BatchDistill
BatchDistill

There are several specific types of distillation used depending on the goal. Partial distillation results in the partial separation of a mixture. This method is used to increase the concentration of specific components or to yield nearly pure substances. Dry distillation, also known as thermolysis or pyrolysis, involves heating solid materials. This process produces gases that later condense into either fluid or solid products. Another form is fractional distillation. This is often used in oil refineries to separate crude oil into various fuels and chemical raw materials.

Continuous Binary Fractional Distillation
Continuous Binary Fractional Distillation

The history of distillation stretches back to ancient civilizations. Early evidence appears on Akkadian tablets from Mesopotamia, describing perfumery operations. In ancient India, archaeologists found baked clay retorts and receivers at sites like Taxila. These "Gandhara stills" were made of terracotta to imitate bamboo. In the 1st century CE, alchemists in Alexandria, Egypt, were also practicing distillation. During the Islamic Golden Age, chemists like Abū Bakr al-Rāzī experimented with many substances. They performed fractional distillation on animal and vegetable matter. By the 12th century, Latin works began describing how to produce ethanol by distilling wine with salt.

Zosimos distillation equipment
Zosimos distillation equipment

Modern distillation technology has evolved significantly from these early methods. In 1500, Hieronymus Brunschwig published the first book dedicated solely to the subject. As chemistry advanced, scientists moved from using glass retorts to copper alembics. These were often used in pot stills to make alcohol. In the early 19th century, engineers developed modern techniques like pre-heating and reflux. Anthony Perrier developed one of the first continuous stills in 1822. Aeneas Coffey improved this design in 1830. His patent for the Coffey still became a model for modern petrochemical units.

My retort
My retort

Today, distillation is used in many essential industrial applications. It is used in desalination to produce potable water for drinking and medical use. In the oil industry, crude oil stabilization is a form of partial distillation. This process reduces vapor pressure to make oil safer to store and transport. It also helps reduce atmospheric emissions of volatile hydrocarbons. Cryogenic air separation uses distillation to extract oxygen, nitrogen, and argon from the air. These gases are then used for various industrial purposes.

Colonne distillazione
Colonne distillazione

Distillation can operate under many different conditions. It can function at pressures ranging from 0.14 bar to nearly 21 bar. It is capable of separating mixtures with a wide range of relative volatilities. For example, it can separate water from ethylene glycol, which has a volatility of 81.2. It can also separate o-xylene from m-xylene, which has a much lower volatility of 1.17. Despite the rise of massive industrial towers, some traditional methods remain. Pot stills made of wood, clay, or stainless steel are still used to produce fine spirits like cognac, whisky, and tequila.

UkrainianVodkaStill
UkrainianVodkaStill
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🖼️ Images & Media (14)
File:Simple distillation apparatus.svg
Simple distillation apparatus.svg
File:Zosimos distillation equipment.jpg
Zosimos distillation equipment.jpg
File:Hieronymus Brunschwig Liber de arte Distillandi CHF AQ13x3.jpg
Hieronymus Brunschwig Liber de arte...
File:My retort.jpg
My retort.jpg
File:Distillation by Retort.png
Distillation by Retort.png
File:UkrainianVodkaStill.jpg
UkrainianVodkaStill.jpg
File:Dorf Lore - Schnaps-Destillation.jpg
Dorf Lore - Schnaps-Destillation.jpg
File:BatchDistill.svg
BatchDistill.svg
File:Vacuum distillation of DMSO at 70C.jpg
Vacuum distillation of DMSO at 70C.jpg
File:perkin triangle distillation apparatus.svg
perkin triangle distillation apparatus.svg
File:short path distillation apparatus.svg
short path distillation apparatus.svg
File:Colonne distillazione.jpg
Colonne distillazione.jpg

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