Editing Pyrolysis (section)

==Terminology==
Pyrolysis is one of the various types of chemical degradation processes that occur at higher temperatures (above the boiling point of water or other solvents). It differs from other processes like [[combustion]] and [[hydrolysis]] in that it usually does not involve the addition of other reagents such as [[oxygen]] ({{chem|O|2}}, in combustion) or water (in hydrolysis).<ref>{{cite book |doi=10.1115/IMECE2009-11256 |chapter=Time Resolved Measurements of Pyrolysis Products from Thermoplastic Poly-Methyl-Methacrylate (PMMA) |title=Volume 3: Combustion Science and Engineering |date=2009 |last1=Kramer |first1=Cory A. |last2=Loloee |first2=Reza |last3=Wichman |first3=Indrek S. |last4=Ghosh |first4=Ruby N. |pages=99–105 |isbn=978-0-7918-4376-5 }}</ref> Pyrolysis produces solids ([[Char (chemistry)|char]]), [[condensation|condensable]] liquids, (light and heavy oils and [[tar]]), and non-condensable gasses.<ref>{{cite journal |last1=Ramin |first1=Leyla |last2=Assadi |first2=M. Hussein N. |last3=Sahajwalla |first3=Veena |title=High-density polyethylene degradation into low molecular weight gases at 1823K: An atomistic simulation |journal=Journal of Analytical and Applied Pyrolysis |date=November 2014 |volume=110 |pages=318–321 |doi=10.1016/j.jaap.2014.09.022 |arxiv=2204.08253 |bibcode=2014JAAP..110..318R }}</ref><ref name="jimjones">{{cite web |last1=Jones |first1=Jim |title=Mechanisms of pyrolysis |url=https://www.anzbiochar.org/2011%20Regional%20Meeting%20Presentations/JRJones%20-%20Mechanisms%20of%20Pyrolysis%20-%20Melb%2029%20Sept%202011.pdf |access-date=19 May 2019}}</ref><ref name="banagrass">{{cite journal |last1=George |first1=Anthe |last2=Turn |first2=Scott Q. |last3=Morgan |first3=Trevor James |title=Fast Pyrolysis Behavior of Banagrass as a Function of Temperature and Volatiles Residence Time in a Fluidized Bed Reactor |journal=PLOS ONE |date=26 August 2015 |volume=10 |issue=8 |pages=e0136511 |doi=10.1371/journal.pone.0136511 |pmid=26308860 |pmc=4550300 |bibcode=2015PLoSO..1036511M |doi-access=free }}</ref><ref name="Zhou-2014">{{cite journal |last1=Zhou |first1=Hui |last2=Wu |first2=Chunfei |last3=Meng |first3=Aihong |last4=Zhang |first4=Yanguo |last5=Williams |first5=Paul T. |title=Effect of interactions of biomass constituents on polycyclic aromatic hydrocarbons (PAH) formation during fast pyrolysis |journal=Journal of Analytical and Applied Pyrolysis |date=November 2014 |volume=110 |pages=264–269 |doi=10.1016/j.jaap.2014.09.007 |bibcode=2014JAAP..110..264Z |url=https://eprints.whiterose.ac.uk/89455/1/AS%20RE-SUBMITTED%20-%20JAAP%20-%20SEPTEMBER%202014%20.pdf }}</ref>

Pyrolysis is different from [[gasification]]. In the chemical process industry, pyrolysis refers to a partial thermal degradation of carbonaceous materials that takes place in an [[Inert gas|inert]] (oxygen free) atmosphere and produces both gases, liquids and solids. The pyrolysis can be extended to full gasification that produces mainly gaseous output,<ref>{{cite book |doi=10.1002/9780470666883.ch33 |chapter=Pyrolysis and Gasification |title=Solid Waste Technology & Management |date=2010 |last1=Astrup |first1=Thomas |last2=Bilitewski |first2=Bernd |pages=502–512 |isbn=978-0-470-66688-3 }}</ref> often with the addition of e.g. water steam to gasify residual carbonic solids, see [[Steam reforming]].

===Types===
Specific types of pyrolysis include: 
* [[Carbonization]], the complete pyrolysis of organic matter, which usually leaves a solid residue that consists mostly of elemental [[carbon]].
* [[#Methane pyrolysis for hydrogen|Methane pyrolysis]], the direct conversion of methane to [[hydrogen]] fuel and separable solid [[carbon]], sometimes using molten metal catalysts.
* [[Hydrous pyrolysis]], in the presence of [[superheated water]] or steam, producing hydrogen and substantial atmospheric carbon dioxide.
* [[Dry distillation]], as in the original production of [[sulfuric acid]] from [[sulfate]]s.
* [[Destructive distillation]], as in the manufacture of [[charcoal]], [[coke (fuel)|coke]] and [[activated carbon]].
** [[Charcoal burning]], the production of charcoal.
** [[Tar]] production by destructive distillation of wood in [[tar kiln]]s.
* [[Caramelization]] of sugars.
* High-temperature [[cooking]] processes such as [[roasting]], [[frying]], toasting, and [[grilling]].
* [[Cracking (chemistry)|Cracking]] of heavier [[hydrocarbon]]s into lighter ones, as in [[oil refining]].
* [[Thermal depolymerization]], which breaks down plastics and other polymers into [[monomer]]s and [[oligomer]]s.
* [[Ceramization]]<ref name=pdcs>{{cite journal |last1=Wang |first1=Xifan |last2=Schmidt |first2=Franziska |last3=Hanaor |first3=Dorian |last4=Kamm |first4=Paul H. |last5=Li |first5=Shuang |last6=Gurlo |first6=Aleksander |title=Additive manufacturing of ceramics from preceramic polymers: A versatile stereolithographic approach assisted by thiol-ene click chemistry |journal=Additive Manufacturing |date=May 2019 |volume=27 |pages=80–90 |doi=10.1016/j.addma.2019.02.012 |arxiv=1905.02060 }}</ref> involving the formation of [[polymer derived ceramics]] from [[preceramic polymers]] under an [[inert atmosphere]].
* [[Catagenesis (geology)|Catagenesis]], the natural conversion of [[kerogen|buried organic matter]] to [[fossil fuels]].
* [[Flash vacuum pyrolysis]], used in [[organic synthesis]].


Other pyrolysis types come from a different classification that focuses on the pyrolysis operating conditions and heating system used, which have an impact on the yield of the pyrolysis products. 
{| class="wikitable"
! Pyrolysis
! Operating conditions
! Pyrolysis product yield (wt%)
|-
|'''Slow low temperature pyrolysis'''<ref name="auto">{{cite book |doi=10.1016/B978-0-12-804568-8.00008-1 |chapter=Pyrolysis of Biomass for Aviation Fuel |title=Biofuels for Aviation |date=2016 |last1=Jenkins |first1=R.W. |last2=Sutton |first2=A.D. |last3=Robichaud |first3=D.J. |pages=191–215 |isbn=978-0-12-804568-8 }}</ref>
|Temperature: 250-450 °C

Vapor residence time: 10-100 min

Heating rate: 0.1-1 °C/s

Feedstock size: 5-50 mm
|Bio-oil ~30

Biochar~35

Gases~35
|-
|'''Intermediate pyrolysis'''<ref name="auto2">{{cite journal |last1=Tripathi |first1=Manoj |last2=Sahu |first2=J.N. |last3=Ganesan |first3=P. |title=Effect of process parameters on production of biochar from biomass waste through pyrolysis: A review |journal=Renewable and Sustainable Energy Reviews |date=March 2016 |volume=55 |pages=467–481 |doi=10.1016/j.rser.2015.10.122 |bibcode=2016RSERv..55..467T }}</ref>
|Temperature: 600-800 °C

Vapor residence time: 0.5-20 s

Heating rate: 1.0-10 °C/s

Feedstock size: 1-5 mm
|Bio-oil~50

Biochar~25

Gases~35
|-
|'''Fast low temperature pyrolysis'''<ref name="auto"/>
|Temperature: 250-450°C

Vapor residence time: 0.5-5 s

Heating rate: 10-200 °C/s

Feedstock size: <3 mm
|Bio-oil ~50

Biochar~20

Gases~30
|-
|'''Flash pyrolysis'''<ref name="auto"/>
|Temperature: 800-1000 °C

Vapor residence time: <5 s

Heating rate: >1000 °C/s

Feedstock size: <0.2 mm
|Bio-oil ~75

Biochar~12

Gases~13
|-
|'''Hydro pyrolysis'''<ref name="auto2"/>
|Temperature: 350-600 °C

Vapor residence time: >15 s

Heating rate: 10-300 °C/s
|Not assigned
|-
|'''High temperature pyrolysis'''
|Temperature: 800-1150 °C
Vapor residence time: 10-100 min

Heating rate: 0.1-1 °C/s
|Bio-oil ~43
Biochar~22

Gases~45
|}