Destructive distillation
Encyclopedia
Destructive distillation is the chemical process
involving the decomposition
of feedstock
by heating to a high temperature; the term generally applies to processing of organic
material in the absence of air or in the presence of limited amounts of oxygen or other reagents, catalysts
, or solvents, such as steam
or phenols
. The process breaks up or 'cracks'
large molecules, generally into a mixture of hundreds of different compounds. The molecules distilled off generally are smaller and more volatile than the feedstock molecules, but some reactions polymerise small molecules into larger molecules, including heat-stable tar
ry substances and char
s. Some feedstocks react to produce only a few products, though that is not common with organic materials, which generally produce very many.
Historically the process of destructive distillation led to the discovery of many chemical compounds before contemporary organic chemists had developed the processes to synthesise those molecules. Also, investigation of the products of destructive distillation enabled chemists to deduce the chemical nature of many natural materials.
can be conducted in a distillation apparatus (retort
) to form the volatile products, which are then collected. The mass of resulting product will represent only a part of the mass of the feedstock, because much of the material remains as char and non-volatile tars. This is in contrast to simple burning
in the presence of oxygen, where the (generally useless) molecules of combustion products include the oxygen; typically the combustion
products of say, a hydrocarbon
fuel amount to roughly four times the mass of the fuel consumed.
Destructive distillation and related processes are in effect the modern industrial versions of traditional charcoal burning crafts. As such they are of industrial significance in many countries, being particularly prominent in Scandinavia. The modern processes are sophisticated and require careful engineering to produce the most valuable possible products from the available feedstocks, as profitably as may be.
Wood
can be used to produce guaiacol
, tar
, terpene
s, turpentine
and Methanol
together with a solid residue of charcoal
.
Coal
is used to produce Coal gas
and coal tar
and Coke
. The destructive distillation of bituminous coal
produces 'coal tar pitch
' a Volatile organic compound
(CTPV) which contain a wide variety of polycyclic aromatic hydrocarbon
s (PAH's); or polynuclear aromatic hydrocarbons, or (PNA's) including naphthalene
and anthracene
which sublime readily, which is convenient when it is necessary to refine them and also pyrene
. Many PNA's, in particular Benzopyrene
s, in particular Benzo(a)pyrene are carcinogenic should only be handled and used care.
Isoprene
was first isolated by destructive distillation of natural rubber which is the biochemical starting point for the biosynthesis
of terpene
s and for many industrial syntheses as well.
It also is an increasingly promising method for recycling monomers derived from waste polymer
s.
Chemical process
In a "scientific" sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by somebody. Such a chemical process commonly involves a chemical reaction of some sort...
involving the decomposition
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
of feedstock
Raw material
A raw material or feedstock is the basic material from which a product is manufactured or made, frequently used with an extended meaning. For example, the term is used to denote material that came from nature and is in an unprocessed or minimally processed state. Latex, iron ore, logs, and crude...
by heating to a high temperature; the term generally applies to processing of organic
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
material in the absence of air or in the presence of limited amounts of oxygen or other reagents, catalysts
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
, or solvents, such as steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
or phenols
Phenols
In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group...
. The process breaks up or 'cracks'
Cracking (chemistry)
In petroleum geology and chemistry, cracking is the process whereby complex organic molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products...
large molecules, generally into a mixture of hundreds of different compounds. The molecules distilled off generally are smaller and more volatile than the feedstock molecules, but some reactions polymerise small molecules into larger molecules, including heat-stable tar
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...
ry substances and char
Char
Char is the solid material that remains after light gases and tar coal tar have been driven out or released from a carbonaceous material during the initial stage of combustion, which is known as carbonization, charring, devolatilization or pyrolysis.Further stages of efficient combustion are...
s. Some feedstocks react to produce only a few products, though that is not common with organic materials, which generally produce very many.
Historically the process of destructive distillation led to the discovery of many chemical compounds before contemporary organic chemists had developed the processes to synthesise those molecules. Also, investigation of the products of destructive distillation enabled chemists to deduce the chemical nature of many natural materials.
Process
The process of pyrolysisPyrolysis
Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...
can be 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 spherical vessel with a long downward-pointing neck. The liquid to be distilled is placed in the vessel and heated...
) to form the volatile products, which are then collected. The mass of resulting product will represent only a part of the mass of the feedstock, because much of the material remains as char and non-volatile tars. This is in contrast to simple burning
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
in the presence of oxygen, where the (generally useless) molecules of combustion products include the oxygen; typically the combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
products of say, a hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
fuel amount to roughly four times the mass of the fuel consumed.
Destructive distillation and related processes are in effect the modern industrial versions of traditional charcoal burning crafts. As such they are of industrial significance in many countries, being particularly prominent in Scandinavia. The modern processes are sophisticated and require careful engineering to produce the most valuable possible products from the available feedstocks, as profitably as may be.
Products
Destructive distillation is an important chemical process producing thousands of distinct chemical compounds.Wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
can be used to produce guaiacol
Guaiacol
Guaiacol is a naturally occurring organic compound with the formula C6H4. Although it is biosynthesized by a variety of organisms, this colorless aromatic oil is usually derived from guaiacum or wood creosote. Samples darken upon exposure to air and light. Guaiacol is present in wood smoke,...
, tar
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...
, terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
s, 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 Methanol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
together with a solid residue of charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...
.
Coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
is used to produce Coal gas
Coal gas
Coal gas is a flammable gaseous fuel made by the destructive distillation of coal containing a variety of calorific gases including hydrogen, carbon monoxide, methane and volatile hydrocarbons together with small quantities of non-calorific gases such as carbon dioxide and nitrogen...
and coal tar
Coal tar
Coal tar is a brown or black liquid of extremely high viscosity, which smells of naphthalene and aromatic hydrocarbons. Coal tar is among the by-products when coal iscarbonized to make coke or gasified to make coal gas...
and Coke
Coke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
. The destructive distillation of bituminous coal
Bituminous coal
Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen. It is of higher quality than lignite coal but of poorer quality than Anthracite...
produces 'coal tar pitch
Pitch (resin)
Pitch is the name for any of a number of viscoelastic, solid polymers. Pitch can be made from petroleum products or plants. Petroleum-derived pitch is also called bitumen. Pitch produced from plants is also known as resin. Products made from plant resin are also known as rosin.Pitch was...
' a Volatile organic compound
Volatile organic compound
Volatile organic compounds are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and...
(CTPV) which contain a wide variety of polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbon
Polycyclic aromatic hydrocarbons , also known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons, are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest example of a PAH...
s (PAH's); or polynuclear aromatic hydrocarbons, or (PNA's) including naphthalene
Naphthalene
Naphthalene is an organic compound with formula . It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings...
and anthracene
Anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon consisting of three fused benzene rings. It is a component of coal-tar. Anthracene is used in the production of the red dye alizarin and other dyes...
which sublime readily, which is convenient when it is necessary to refine them and also pyrene
Pyrene
Pyrene is a polycyclic aromatic hydrocarbon consisting of four fused benzene rings, resulting in a flat aromatic system. The chemical formula is . This colourless solid is the smallest peri-fused PAH...
. Many PNA's, in particular Benzopyrene
Benzopyrene
Benzo[a]pyrene, C20H12, is a five-ring polycyclic aromatic hydrocarbon whose metabolites are mutagenic and highly carcinogenic. Benzo[a]pyrene is listed as a Group 1 carcinogen by the IARC. It belongs to a class of polycyclic aromatic compounds known as benzopyrenes, which consist of a benzene...
s, in particular Benzo(a)pyrene are carcinogenic should only be handled and used care.
Isoprene
Isoprene
Isoprene , or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=CCH=CH2. Under standard conditions it is a colorless liquid...
was first isolated by destructive distillation of natural rubber which is the biochemical starting point for the biosynthesis
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
of terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
s and for many industrial syntheses as well.
It also is an increasingly promising method for recycling monomers derived from waste polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s.
See also
- Dry distillationDry distillationDry distillation is the heating of solid materials to produce gaseous products . The method may or may not involve pyrolysis/thermolysis. The products are condensed and collected. This method usually requires higher temperatures than classical distillation. The method has been used to obtain...
- PyrolysisPyrolysisPyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...
- Thermolysis
- Cracking (chemistry)Cracking (chemistry)In petroleum geology and chemistry, cracking is the process whereby complex organic molecules such as kerogens or heavy hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products...