Editing Distillation (section)

{{short description|Method of separating mixtures}}
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{{Use dmy dates|date=July 2019}}

[[File:Simple distillation apparatus.svg|thumb|upright|300px|'''Laboratory model of a still.'''<br /><br />'''1:''' The heat source to boil the mixture<br />'''2:''' round-bottom flask containing the mixture to be boiled<br />'''3:''' the head of the still<br />'''4:''' mixture boiling-point thermometer<br />'''5:''' the condenser of the still<br />'''6:''' the cooling-water inlet of the condenser<br />'''7:''' the cooling-water outlet of the condenser<br />'''8:''' the distillate-receiving flask<br />'''9:''' vacuum pump and gas inlet<br />'''10:''' the receiver of the still<br />'''11:''' the heat control for heating the mixture<br />'''12:''' stirring mechanism speed control<br />'''13:''' stirring mechanism and heating plate<br />'''14:''' heating bath (oil/sand) for the flask<br />'''15:''' the stirring mechanism (not shown, e.g. [[boiling chip]]s or mechanical stirring machine)<br />'''16:''' the distillate-cooling water bath.<ref name="Harwood_Moody" />{{rp|pages=141–143}}]]

'''Distillation''', also '''classical distillation''', is the process of [[separation process|separating]] the component substances of a liquid [[mixture]] of two or more chemically discrete substances; the separation process is realized by way of the selective [[boiling]] of the mixture<!--please do not change this to evaporation: it is not the same thing--> and the [[condensation]] of the vapors in a [[still]].

Distillation can operate over a wide range of pressures from 0.14 [[Bar (unit)|bar]] (e.g., [[ethylbenzene]]/[[styrene]]) to nearly 21 bar (e.g.,[[propylene]]/[[propane]]) and is capable of separating feeds with high volumetric flowrates and various components that cover a range of relative volatilities from only 1.17 ([[O-Xylene|o-xylene]]/[[m-xylene]]) to 81.2 (water/[[ethylene glycol]]).<ref>J. D. Seader, E. J. Henley and D. K. Roper, Separation Process Principles, Wiley, 3rd edn, 2011.</ref> Distillation provides a convenient and time-tested solution to separate a diversity of chemicals in a continuous manner with high purity. However, distillation has an enormous environmental footprint, resulting in the consumption of approximately 25% of all industrial energy use.<ref>D. S. Sholl and R. P. Lively, Nature, 2016, 532, 435–437.</ref> The key issue is that distillation operates based on phase changes, and this separation mechanism requires vast energy inputs.

[[Dry distillation]] ([[thermolysis]] and [[pyrolysis]]) is the heating of solid materials to produce gases that condense either into [[fluid]] products or into solid products. The term ''dry distillation'' includes the separation processes of [[destructive distillation]] and of [[Cracking (chemistry)|chemical cracking]], breaking down large [[hydrocarbon]] molecules into smaller hydrocarbon molecules. Moreover, a partial distillation results in partial separations of the mixture's components, which process yields nearly-pure components; partial distillation also realizes partial separations of the mixture to increase the concentrations of selected components. In either method, the separation process of distillation exploits the differences in the [[relative volatility]] of the component substances of the heated mixture.

In the industrial applications of classical distillation, the term ''distillation'' is used as a [[unit operation|unit of operation]] that identifies and denotes a process of physical separation, not a [[chemical reaction]]; thus an industrial installation that produces [[liquor|distilled beverages]], is a distillery of [[Alcohol (drug)|alcohol]]. These are some applications of the chemical separation process that is distillation:
* Distilling [[Fermentation in food processing|fermented]] products to yield alcoholic beverages with a high content by volume of [[Ethanol|ethyl alcohol]].
* [[Desalination]] to produce potable water and for medico-industrial applications.
* [[Crude oil stabilisation]], a partial distillation to reduce the vapor pressure of crude oil, which thus is safe to store and to transport, and thereby reduces the volume of atmospheric emissions of volatile [[hydrocarbon]]s.
* [[Fractional distillation]] used in the midstream operations of an [[oil refinery]] for producing [[fuel]]s and chemical [[raw material]]s for livestock feed.<ref>Schaschke, C., 2014. A Dictionary of Chemical Engineering. Oxford University Press.</ref><ref>2019. Distillation: The Historical Symbol of Chemical Engineering. The University of Toledo. URL https://www.utoledo.edu/engineering/chemical-engineering/distillation.html {{Webarchive|url=https://web.archive.org/web/20210414230219/https://www.utoledo.edu/engineering/chemical-engineering/distillation.html |date=14 April 2021 }}</ref><ref>2017. Products made from petroleum. Ranken Energy Corporation. URL https://www.ranken-energy.com/index.php/products-made-from-petroleum/ {{Webarchive|url=https://web.archive.org/web/20210416193229/https://www.ranken-energy.com/index.php/products-made-from-petroleum/ |date=16 April 2021 }}</ref>
* Cryogenic [[Air separation]] into the component gases — [[oxygen]], [[nitrogen]], and [[argon]] — for use as [[industrial gas]]es.
* [[Chemical synthesis]] to separate impurities and unreacted materials.