Editing Destructive distillation

{{Short description|Chemical process}}
'''Destructive distillation''' is a [[chemical process]] in which [[Thermal decomposition|decomposition]] of [[Raw material|unprocessed material]] is achieved by heating it to a high temperature; the term generally applies to processing of [[Organic chemistry|organic]] material in the absence of air or in the presence of limited amounts of oxygen  or other [[reagents]], [[Catalysis|catalysts]], or [[solvents]], such as [[steam]] or [[phenols]]. It is an application of [[pyrolysis]]. The process breaks up or "[[Cracking (chemistry)|cracks]]" large molecules. [[Coke (fuel)|Coke]], [[coal gas]], [[gas carbon|gaseous carbon]], [[coal tar]], [[ammonium hydroxide|ammonia liquor]], and [[coal oil]] are examples of commercial products historically produced by the destructive distillation of [[coal]].

[[Image:Distillation_by_Retort.png|thumb|300px|Many early experiments used [[retort]]s for destructive distillation.]]

Destructive distillation of any particular inorganic feedstock produces only a small range of products as a rule, but destructive distillation of many organic materials commonly produces very many compounds, often hundreds, although not all products of any particular process are of commercial importance. The distillate are generally lower molecular weight. Some fractions however [[polymerise]] or [[Condensation reaction|condense]] small molecules into larger molecules, including heat-stable [[tar]]ry substances and [[Char (chemistry)|char]]s. Cracking feedstocks into liquid and volatile compounds, and polymerising, or the forming of chars and solids, may both occur in the same process, and any class of the products might be of commercial interest.

Currently the major industrial application of destructive distillation is to [[coal]].<ref>{{cite book |last=Lunge |first=George |title=Coal-tar and ammonia |publisher=Gurney and Jackson |year=1887 |url=https://archive.org/details/coaltarandammon00lunggoog }}</ref><ref>{{cite book |last=Speight |first=James G. |title=The Refinery of the Future |publisher=William Andrew |year=2010 |isbn=978-0-8155-2041-2 }}</ref>

Historically the process of destructive distillation and other forms of pyrolysis led to the discovery of many chemical compounds or elucidation of their structures before contemporary organic chemists had developed the processes to synthesise or specifically investigate the parent molecules. It was especially in the early days that investigation of the products of destructive distillation, like those of other destructive processes, played parts in enabling chemists to deduce the chemical nature of many natural materials.<ref>{{cite book |last1=Schorlemmer |first1=Carl |last2=Smithells |first2=Arthur |title=The rise and development of organic chemistry |publisher=Macmillan |year=1894 |url=https://archive.org/details/risedevelopmento00schorich }}</ref> Well known examples include the deduction of the structures of [[pyranose]]s and [[furanose]]s.<ref>I.L. Finar Organic Chemistry vol 1 ( 4th.ed.) Longmans 1963 plus I.L. Finar Organic Chemistry vol 2 ( 3rd.ed.) Longmans Green & Co. 1964 May be downloaded from: https://archive.org/details/OrganicChemistryVol1 plus https://archive.org/details/OrganicChemistryVol2</ref>

==History==
[[File:Pliny the Elder, Loggia del Consiglio, Piazza dei Signori, Verona (37520060770) (cropped).jpg|alt=Head of a statue of Pliny the Elder|thumb|169x169px|Pliny the Elder]]
In his encyclopedic work ''[[Natural History (Pliny)|Natural History]]'' ({{langx|la|Naturalis Historia}}) the Roman naturalist and author [[Pliny the Elder]] (23/24 –79 CE) describes how, in the destructive distillation of pine wood, two liquid fractions are produced: a lighter (aromatic oils) and a heavier ([[pitch_(resin)|pitch]]). The lighter fraction is released in the form of gases, which are condensed and collected.<ref>{{Cite book |last=Pliny the Elder |url=https://www.gutenberg.org/ebooks/author/50041 |title=The Natural History of Pliny: Translated, with Copious Notes and Illustrations |publisher=Henry G. Bohn |year=1855 |volume=III |translator-last=Bostock |translator-first=John |chapter=XVI.21(11) |orig-date=Pliny published the first 10 books in 77 CE. The rest was published posthumously by Pliny the Younger |translator-last2=Riley |translator-first2=Henry Thomas |chapter-url=https://www.gutenberg.org/cache/epub/59131/pg59131-images.html#BOOK_XVI_CHAP_21}}</ref>
{{Blockquote|text=In Europe, tar is extracted from the torch-tree [''[[Pinus mugo]]''] by the agency of fire; it is employed for coating ships and for many other useful purposes. The wood of the tree is chopped into small billets, and then put into a furnace ... The first steam that exudes flows in the form of [a liquid] into a reservoir made for its reception: in Syria this substance is known as “cedrium” {{bracket|[[cedar oil]]}}; and it possesses such remarkable strength, that in Egypt the bodies of the dead, after being steeped in it, are [[Mummy|preserved from all corruption]]. The liquid that follows is of a thicker consistency, and constitutes pitch.}}

==Process==
The process of [[pyrolysis]] can be conducted in a distillation apparatus ([[retort]]) to form the volatile products for collection. The mass of the product will represent only a part of the mass of the feedstock, because much of the material remains as char, ash, and non-volatile tars. In contrast, [[combustion]] consumes most of the organic matter, and the net weight of the products amount to roughly the same mass as the fuel and oxidant consumed.

Destructive distillation and related processes are in effect the modern industrial descendants of traditional [[charcoal]] burning crafts. As such they are of industrial significance in many regions, such as Scandinavia. The modern processes are sophisticated and require careful engineering to produce the most valuable possible products from the available feedstocks.<ref>Bates, John S.; Distillation of hardwoods in Canada; Pub: Ottawa, F. A. Acland, 1922. May be downloaded from: [https://archive.org/details/distillationofha00baterich]</ref><ref>Klar, Max; Rule, Alexander; The technology of wood distillation, with special reference to the methods of obtaining the intermediate and finished products from the primary distillate; Pub: London Chapman & Hall 1925. May be downloaded from: [https://archive.org/details/technologyofwood00klaruoft]</ref>

==Applications==
* Destructive distillation of [[wood]] produces [[methanol]] and [[acetic acid]], together with a solid residue of [[charcoal]].<ref>{{cite book |doi=10.1002/14356007.a04_099 |chapter=Biomass Chemicals |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Tokay |first1=Barbara A. |isbn=978-3-527-30385-4 }}</ref>
* Destructive distillation of a tonne of [[coal]] can produce 700&nbsp;kg of [[Coke (fuel)|coke]], 100 liters of [[Ammonium hydroxide|liquor ammonia]], 50 liters of [[coal tar]] and 400 m<sup>3</sup> of [[coal gas]].
* Destructive distillation is an increasingly promising method for recycling monomers derived from waste [[polymer]]s.
* Destructive distillation of [[natural rubber]] resulted in the discovery of [[isoprene]] which led to the creation of synthetic rubbers such as [[neoprene]].

==See also==
* [[Dry distillation]]
* [[Pyrolysis]]
* [[Thermal decomposition|Thermolysis]]
* [[Cracking (chemistry)]]

==References==
<references/>

==External links==
* [http://www.wisegeek.com/what-is-destructive-distillation.htm What is destructive distillation ?]

{{Distillation}}

[[Category:Distillation]]
[[Category:Pyrolysis]]