Destructive distillation

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Destructive distillation

Destructive distillation is the process of pyrolysis

Pyrolysis

Pyrolysis is the chemical decomposition of a condensed substance by heating. The word is coined from the Greek language-derived morphemes pyro "fire" and lysys "decomposition"....
conducted in a distillation apparatus (retort

Retort

In a chemistry laboratory, a retort is a glassware device used for distillation or dry distillation of substances. It consists of a sphere vessel with a long downward-pointing neck....
) to allow the volatile products to be collected. The process led to the discovery of many chemical compounds before such compounds could be prepared synthetically. Destructive distillation is not a unit operation

Unit operation

In chemical engineering and related fields, a unit operation is a basic step in a process. For example in milk processing, homogenization, pasteurization, chilling, and packaging are each unit operations which are connected to create the overall process....
as true distillation

Distillation

Distillation is a method of separation process mixtures based on differences in their Volatility in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
, but a chemical reaction. It is a strongly reductive

Redox

Redox describes all chemical reactions in which atoms have their oxidation number changed.This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane , or it can be a complex process such as the oxidation of sugar in the human body through a ser...
reaction, cracking macromolecules into smaller, more volatile, components.

A historically significant example of destructive distillation is tar

Tar

Tar is modified resin produced from the wood and roots of pine by destructive distillation under pyrolysis. It is a viscosity black liquid. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America....
making.

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Encyclopedia

Destructive distillation is the process of pyrolysis

Pyrolysis

Retort

Unit operation

Distillation

Redox

Tar

Terpene

Terpenes are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium....
s, are heated in an airless container causing the material to decompose. The by-products are turpentine

Turpentine

Turpentine is a fluid obtained by the distillation of resin obtained from trees, mainly pine trees. It is composed of terpenes, mainly the monoterpenes alpha-Pinene and beta-Pinene....
and charcoal

Charcoal

Charcoal is the blackish residue consisting of impure carbon obtained by removing water and other volatile constituents from animal and vegetation substances....
. This process is still used in Scandinavia for tar-making. Coal tar pitch

Pitch (resin)

Pitch is the name for any of a number of highly viscosity liquids which appear solid. Pitch can be made from petroleum products or plants. Petroleum-derived pitch is also called bitumen....
volatile

Volatile organic compound

Volatile organic compounds are organic chemical compounds that have high enough vapor pressures under normal conditions to significantly vaporize and enter the atmosphere....
s (CTPV) are the result of destructive distillation of bituminous coal

Bituminous coal

Bituminous coal is a relatively soft coal containing a tarlike substance called bitumen. It is of higher quality than lignite but poorer quality than Anthracite....
. These CTPVs often contain polynuclear aromatic hydrocarbons (PNA's), which sublime readily and are carcinogenic. Other examples of substances that are commonly destructively distilled to extract chemicals and other materials include:

Wood
Wood

Wood is an organic material; in the strict sense wood is produced as secondary xylem in the stems of woody plants, notably trees but also shrubs, etc....
to give methanol
Methanol

Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula carbonhydrogen3oxygenhydrogen ....
, terpene
Terpene

Terpenes are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium....
s and guaiacol
Guaiacol

Guaiacol is a naturally occurring organic compound with the Chemical formula C6H4. This colourless aromatic oil is derived from guaiacum or wood creosote....
.
Coking refers to the transformation of coal or heavy oil into coke, typically at temperatures near 1,000 °C.
Coal
Coal

Coal is a readily combustion black or brownish-black sedimentary rock. The harder forms, such as anthracite, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure....
(lower grades) to give Coal gas
Coal gas

Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities....
and coal tar
Coal tar

Coal tar is a brown or black liquid of high viscosity, which smells of naphthalene and aromatic hydrocarbons. Coal tar is among the by-products when coal is...

Destructive distillation

See also