Pyrolysis is a thermal decomposition of materials at elevated
temperatures in an inert atmosphere such as a vacuum gas. It
involves the change of chemical composition and is irreversible. The
word is coined from the Greek-derived elements pyro "fire" and lysis
Pyrolysis is most commonly applied to the treatment of organic
materials. It is one of the processes involved in charring wood,
starting at 200–300 °C (390–570 °F). In general,
pyrolysis of organic substances produces volatile products and leaves
a solid residue enriched in carbon, char. Extreme pyrolysis, which
leaves mostly carbon as the residue, is called carbonization.
The process is used heavily in the chemical industry, for example, to
produce ethylene, many forms of carbon, and other chemicals from
petroleum, coal, and even wood, to produce coke from coal.
Aspirational applications of pyrolysis would convert biomass into
syngas and biochar, waste plastics back into usable oil, or waste into
safely disposable substances.
1 Process terminology and mechanism
2 Occurrence and uses
2.2 Coke, carbon, charcoals, and chars
3 Fine chemical synthesis
5 See also
7 External links
Process terminology and mechanism
Certain uses of pyrolysis are called dry distillation, destructive
distillation, or cracking. The processes involve thermal
depolymerization, i.e. the breaking of chemical bonds in
macromolecules to give smaller fragments. The phenomenon involves
exceeding the ceiling temperature of polymers.
Pyrolysis differs from other processes like combustion and hydrolysis
in that it usually does not involve the addition of other reagents
such as oxygen (O2, in combustion) or water (in hydrolysis). In
practice, it is often not practical to achieve a completely O2- or
water-free conditions, especially as pyrolysis is often conducted on
complex mixtures. The term has also been applied to the decomposition
of organic material in the presence of superheated water or steam
(hydrous pyrolysis), for example, in the steam cracking of oil.
Pyrolysis has been assumed to take place during catagenesis, the
conversion of buried organic matter to fossil fuels. In vacuum
pyrolysis, organic material is heated in a vacuum to decrease its
boiling point and avoid adverse chemical reactions. Called flash
vacuum pyrolysis, this approach is used in organic synthesis.
Pyrolysis can be analyzed by pyrolysis gas chromatography mass
spectrometry (Py-GC-MS). In that technique, the volatile products from
pyrolysis are separated by gas chromatography, and identified by MS.
The technique is applied to many aspects of pyrolysis
Pyrolysis is also used in carbon-14 dating.
Occurrence and uses
Pyrolysis is used to produce ethylene, the chemical compound produced
on the largest scale industrially (>110 million tons/year in 2005).
In this process, hydrocarbons from petroleum are heated to around 600
°C in the presence of steam, i.e. steam cracking. The resulting
ethylene is used to make antifreeze (ethylene glycol), PVC (via vinyl
chloride), and many polymers, such as polyethylene and polystyrene.
Coke, carbon, charcoals, and chars
Carbon and carbon-rich materials have desirable properties but, are
nonvolatile, even at high temperatures. Consequently, pyrolysis is
used to produce many kinds of carbon; these can be used for fuel, as
reagents in steelmaking (coke), and as structural materials.
High temperature pyrolysis is used on a industrial scale to convert
coal into coke for metallurgy, especially steelmaking. Volatile
products are often useful, including benzene and pyridine. Coke can
also be produced from the solid residue left from petroleum refining.
Typical organic products obtained by pyrolysis of coal (X = CH, N).
The coke-making or "coking" process consists of heating the material
in "coking ovens" to very high temperatures (up to 900 °C or
1,700 °F) so that those molecules are broken down into lighter
volatile substances, which leave the vessel, and a porous but hard
residue that is mostly carbon and inorganic ash. The amount of
volatiles varies with the source material, but is typically 25–30%
of it by weight.
The original vascular structure of the wood and the pores created by
escaping gases combine to produce a light and porous material. By
starting with a dense wood-like material, such as nutshells or peach
stones, one obtains a form of charcoal with particularly fine pores
(and hence a much larger pore surface area), called activated carbon,
which is used as an adsorbent for a wide range of chemical substances.
Biochar is the residue of incomplete organic pyrolysis, e.g., from
cooking fires. They are a key component of the terra preta soils
associated with ancient indigenous communities of the Amazon basin.
Terra preta is much sought by local farmers for its superior fertility
compared to the natural red soil of the region. Efforts are underway
to recreate these soils through biochar, the solid residue of
pyrolysis of various materials, mostly organic waste.
Carbon fibers are filaments of carbon that can be used to make very
strong yarns and textiles.
Carbon fiber items are often produced by
spinning and weaving the desired item from fibers of a suitable
polymer, and then pyrolyzing the material at a high temperature (from
1,500–3,000 °C or 2,730–5,430 °F). The first carbon
fibers were made from rayon, but polyacrylonitrile has become the most
common starting material. For their first workable electric lamps,
Joseph Wilson Swan
Joseph Wilson Swan and
Thomas Edison used carbon filaments made by
pyrolysis of cotton yarns and bamboo splinters, respectively.
Pyrolysis is the reaction used to coat a preformed substrate with a
layer of pyrolytic carbon. This is typically done in a fluidized bed
reactor heated to 1,000–2,000 °C or 1,830–3,630 °F.
Pyrolytic carbon coatings are used in many applications, including
artificial heart valves.
See also: Biofuel
Pyrolysis is the basis of several methods for producing fuel from
biomass, i.e. lignocellulosic biomass. Crops studied as biomass
feedstock for pyrolysis include native North American prairie grasses
such as switchgrass and bred versions of other grasses such as
Miscantheus giganteus. Other sources of organic matter as feedstock
for pyrolysis include greenwaste, sawdust, waste wood, nut shells,
straw, cotton trash, rice hulls. Animal waste including poultry
litter, dairy manure, and potentially other manures are also under
evaluation. Some industrial byproducts are also suitable feedstock
including paper sludge and distillers grain.
Synthetic diesel fuel by pyrolysis of organic materials is not yet
economically competitive. Higher efficiency is sometimes achieved
by flash pyrolysis, in which finely divided feedstock is quickly
heated to between 350 and 500 °C (660 and 930 °F) for less
than 2 seconds.
The low quality of oils produced through pyrolysis can be improved by
physical and chemical processes, which might drive up production
costs, but may make sense economically as circumstances change.
There is also the possibility of integrating with other processes such
as mechanical biological treatment and anaerobic digestion. Fast
pyrolysis is also investigated for biomass conversions. Fuel
bio-oil can also be produced by hydrous pyrolysis.
The process of metalorganic vapour phase epitaxy (MOCVD) entails
pyrolysis of volatile organometallic compounds to give semiconductors,
hard coatings, and other applicable materials. The reactions entail
thermal degradation of precursors, with deposition of the inorganic
component and release of the hydrocarbons as gaseous waste. Since it
is an atom-by-atom deposition, these atoms organize themselves into
crystals to form the bulk semiconductor. Silicon chips are produced by
the pyrolysis of silane:
SiH4 → Si + 2 H2
Gallium arsenide, another semiconductor, forms upon co-pyrolysis of
trimethylgallium and arsine.
Illustration of the MOCVD process, which entails pyrolysis of volatile
Pyrolysis can also be used to treat plastic waste. The main advantage
is the reduction in volume of the waste. In principle, pyrolysis will
regenerate the monomers (precursors) to the polymers that are treated,
but in practice the process is neither clean nor economically
competitive source of monomers.
In tire recycling, tire pyrolysis is well developed technology.
Other products from car tire pyrolysis include steel wires, carbon
black and bitumen. The area faces legislative, economic, and
marketing obstacles. Oil derived from tire rubber pyrolysis
contains high sulfur content, which gives it high potential as a
pollutant and should be desulfurized.
Pyrolysis is also used for thermal cleaning, an industrial application
to remove organic substances such as polymers, plastics and coatings
from parts, products or production components like extruder screws,
spinnerets and static mixers. During the thermal cleaning process,
at temperatures between 600 °F to 1000 °F (310 C° to 540
C°), organic material is converted by pyrolysis and oxidation
into volatile organic compounds, hydrocarbons and carbonized gas.
Inorganic elements remain.
Several types of thermal cleaning systems use pyrolysis:
Molten Salt Baths belong to the oldest thermal cleaning systems;
cleaning with a molten salt bath is very fast but implies the risk of
dangerous splatters, or other potential hazards connected with the use
of salt baths, like explosions or highly toxic hydrogen cyanide
Fluidized Bed Systems use sand or aluminium oxide as heating
medium; these systems also clean very fast but the medium does not
melt or boil, nor emit any vapors or odors; the cleaning process
takes one to two hours.
Vacuum Ovens use pyrolysis in a vacuum avoiding uncontrolled
combustion inside the cleaning chamber; the cleaning process takes
8 to 30 hours.
Burn-Off Ovens, also known as Heat-Cleaning Ovens, are gas-fired and
used in the painting, coatings, electric motors and plastics
industries for removing organics from heavy and large metal parts.
Fine chemical synthesis
Pyrolysis is used in the production of chemical compounds, mainly, but
not only, in the research laboratory.
The area of boron-hydride clusters started with the study of the
pyrolysis of diborane (B2H6) at ca. 200 °C. Products include the
clusters pentaborane and decaborane. These pyrolyses involve not only
cracking (to give H2), but also recondensation.
The synthesis of nanoparticles, zirconia and oxides
utilizing an ultrasonic nozzle in a process called ultrasonic spray
Pyrolysis has been used for turning wood into charcoal since ancient
times. Many important chemical substances, such as phosphorus and
sulfuric acid, were first obtained by this process. In their embalming
process, the ancient Egyptians used methanol, which they obtained from
the pyrolysis of wood. The dry distillation of wood remained the major
source of methanol into the early 20th Century.
^ "Archived copy". Archived from the original on 2018-01-10. Retrieved
^ Burning of wood Archived 2010-02-09 at the Wayback Machine.,
InnoFireWood's website. Accessed on 2010-02-06.
^ Cory A. Kramer, Reza Loloee, Indrek S. Wichman and Ruby N. Ghosh,
2009, Time Resolved Measurements of
Pyrolysis Products From
Thermoplastic Poly-Methyl-Methacrylate (PMMA) Archived 2014-11-06 at
the Wayback Machine. ASME 2009 International Mechanical Engineering
Congress and Exposition
^ Goodacre, R.; Kell, D. B. (1996). "
Pyrolysis mass spectrometry and
its applications in biotechnology". Curr. Opin. Biotechnol. 7:
20–28. doi:10.1016/S0958-1669(96)80090-5. CS1 maint: Uses
authors parameter (link)
^ Peacock, P. M.; McEwen, C. N. (2006). "Mass Spectrometry of
Synthetic Polymers. Anal. Chem". 78: 3957–3964.
doi:10.1021/ac0606249. CS1 maint: Uses authors parameter (link)
^ Zimmermann, Heinz; Walz, Roland (2008). "Ethylene". Ullmann's
Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH.
^ Ludwig Briesemeister, Andreas Geißler, Stefan Halama, Stephan
Herrmann, Ulrich Kleinhans, Markus Steibel, Markus Ulbrich, Alan W.
Scaroni, M. Rashid Khan, Semih Eser, Ljubisa R. Radovic (2002). "Coal
Pyrolysis". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim:
Wiley-VCH. doi:10.1002/14356007.a07_245.pub2. CS1 maint: Uses
authors parameter (link)
^ Lehmann, Johannes. "Biochar: the new frontier". Archived from the
original on 2008-06-18. Retrieved 2008-07-10.
^ Ratner, Buddy D. (2004). Pyrolytic carbon. In Biomaterials science:
an introduction to materials in medicine Archived 2014-06-26 at the
Wayback Machine.. Academic Press. pp. 171-180.
^ Evans, G. "Liquid Transport Biofuels – Technology Status Report"
Archived September 19, 2008, at the Wayback Machine., "National
Non-Food Crops Centre", 14-04-08. Retrieved on 2009-05-05.
Biomass Feedstock for Slow Pyrolysis". BEST Pyrolysis, Inc.
website. BEST Energies, Inc. Archived from the original on 2012-01-02.
Pyrolysis and Other
Thermal Processing". US DOE. Archived from the
original on 2007-08-14.
^ Ramirez, Jerome; Brown, Richard; Rainey, Thomas (1 July 2015). "A
Review of Hydrothermal Liquefaction Bio-Crude Properties and Prospects
for Upgrading to Transportation Fuels". Energies. 8: 6765–6794.
^ Marshall, A. T. & Morris, J. M. (2006) A Watery Solution and
Sustainable Energy Parks Archived 2007-09-28 at the Wayback Machine.,
CIWM Journal, pp. 22–23
^ Westerhof, Roel Johannes Maria (2011). Refining fast pyrolysis of
biomass. Thermo-Chemical Conversion of
Biomass (Thesis). University of
Twente. Archived from the original on 2013-06-17. Retrieved
^ Kaminsky, Walter (2000). "Plastics, Recycling". Ullmann's
Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH.
^ N.J. Themelis et al. "Energy and Economic Value of Nonrecyclable
Plastics and Municipal Solid Wastes that are Currently Landfilled in
the Fifty States" Columbia University Earth Engineering Center
Archived 2014-05-08 at the Wayback Machine.
Plastic to Oil Machine AJ – Canada's Environmental Voice
Archived 2015-09-09 at the Wayback Machine.. Alternativesjournal.ca
(2016-12-07). Retrieved on 2016-12-16.
Thai) Jidgarnka, S. "
Pyrolysis of Expired Car Tires: Mechanics of
Producing High Quality Fuels" Archived 2015-02-20 at the Wayback
Machine.. Chulalongkorn University Department of Petrochemistry
^ Roy, C.; Chaala, A.; Darmstadt, H. (1999). "The vacuum pyrolysis of
used tires". Journal of Analytical and Applied Pyrolysis. 51: 201.
^ Martínez, Juan Daniel; Puy, Neus; Murillo, Ramón; García, Tomás;
Navarro, María Victoria; Mastral, Ana Maria (2013). "Waste tyre
pyrolysis – A review, Renewable and Sustainable". Energy Reviews.
23: 179–213. doi:10.1016/j.rser.2013.02.038.
^ Choi, G.-G.; Jung, S.-H.; Oh, S.-J.; Kim, J.-S. (2014). "Total
utilization of waste tire rubber through pyrolysis to obtain oils and
CO2 activation of pyrolysis char".
Fuel Processing Technology. 123:
^ Ringer, M.; Putsche, V.; Scahill, J. (2006) Large-Scale Pyrolysis
Oil Production: A Technology Assessment and Economic Analysis Archived
2016-12-30 at the Wayback Machine.; NREL/TP-510-37779; National
Renewable Energy Laboratory (NREL), Golden, CO.
^ Heffungs, Udo (June 2010). "Effective Spinneret Cleaning". Fiber
Journal. Archived from the original on 30 June 2016. Retrieved 19
^ a b c d Mainord, Kenneth (September 1994). "Cleaning with Heat: Old
Technology with a Bright New Future" (PDF). Pollution Prevention
Regional Information Center. The Magazine of Critical Cleaning
Technology. Archived (PDF) from the original on 8 December 2015.
Retrieved 4 December 2015.
^ a b c "A Look at
Thermal Cleaning Technology".
ThermalProcessing.org. Process Examiner. 14 March 2014. Archived from
the original on 8 December 2015. Retrieved 4 December 2015.
^ Davis, Gary; Brown, Keith (April 1996). "Cleaning Metal Parts and
Tooling" (PDF). Pollution Prevention Regional Information Center.
Process Heating. Archived (PDF) from the original on 4 March 2016.
Retrieved 4 December 2015.
^ Schwing, Ewald; Uhrner, Horst (7 October 1999). "Method for removing
polymer deposits which have formed on metal or ceramic machine parts,
equipment and tools". Espacenet. European Patent Office. Retrieved 19
^ Staffin, Herbert Kenneth; Koelzer, Robert A. (28 November 1974).
"Cleaning objects in hot fluidised bed – with neutralisation of
resultant acidic gas esp. by alkaline metals cpds". Espacenet.
European Patent Office. Retrieved 19 April 2016.
^ Dwan, Thomas S. (2 September 1980). "Process for vacuum pyrolysis
removal of polymers from various objects". Espacenet. European Patent
Office. Retrieved 26 December 2015.
Vacuum pyrolysis systems". thermal-cleaning.com. Archived from the
original on 15 February 2016. Retrieved 11 February 2016.
^ "Paint Stripping: Reducing Waste and Hazardous Material". Minnesota
Technical Assistance Program. University of Minnesota. July 2008.
Archived from the original on 8 December 2015. Retrieved 4 December
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the
Elements (2nd ed.). Butterworth-Heinemann.
ISBN 0-08-037941-9. gives Greenwood, Norman N.; Earnshaw,
Alan (1997). Chemistry of the Elements (2nd ed.).
Butterworth-Heinemann. ISBN 0-08-037941-9.
^ Pingali, Kalyana C.; Rockstraw, David A.; Deng, Shuguang (2005).
"Silver Nanoparticles from Ultrasonic Spray
Pyrolysis of Aqueous
Silver Nitrate" (PDF). Aerosol Science and Technology. 39 (10):
1010–1014. doi:10.1080/02786820500380255. Archived (PDF) from the
original on 2014-04-08.
^ Song, Y. L.; Tsai, S. C.; Chen, C. Y.; Tseng, T. K.; Tsai, C. S.;
Chen, J. W.; Yao, Y. D. (2004). "Ultrasonic Spray
Synthesis of Spherical Zirconia Particles" (PDF). Journal of the
American Ceramic Society. 87 (10): 1864–1871.
doi:10.1111/j.1151-2916.2004.tb06332.x. Archived (PDF) from the
original on 2014-04-08.
^ Hamedani, Hoda Amani (2008) Investigation of Deposition Parameters
in Ultrasonic Spray
Pyrolysis for Fabrication of Solid Oxide
Cathode Archived 2016-03-05 at the Wayback Machine., Georgia Institute
^ E. Fiedler, G. Grossmann, D. B. Kersebohm, G. Weiss, Claus Witte
(2005). "Methanol". Ullmann's Encyclopedia of Industrial Chemistry.
Weinheim: Wiley-VCH. doi:10.1002/14356007.
ISBN 978-3527306732. CS1 maint: Uses authors parameter
The dictionary definition of pyrolysis at Wiktionary
In Situ Catalytic Fast
Pyrolysis Technology Pathway National Renewable
Control of fire by early humans
Native American use of fire
Death by burning
Flame Research Foundation