Editing Methanol (section)

==Production==

===From synthesis gas===
Carbon monoxide and hydrogen react over a catalyst to produce methanol. Today, the most widely used catalyst is a mixture of copper and [[zinc oxide]]s, [[catalyst support|supported]] on [[alumina]], as first used by [[Imperial Chemical Industries|ICI]] in 1966. At 5–10 MPa (50–100&nbsp;atm) and {{convert|250|C}}, the reaction

:{{chem2 | CO + 2 H2 -> CH3OH }}

is characterized by high selectivity (>99.8%). The production of [[syngas|synthesis gas]] from methane produces three [[Mole (unit)|mole]]s of hydrogen for every mole of carbon monoxide, whereas the synthesis consumes only two moles of hydrogen gas per mole of carbon monoxide. One way of dealing with the excess hydrogen is to inject [[carbon dioxide]] into the methanol synthesis reactor, where it, too, reacts to form methanol according to the equation

:{{chem2 | CO2 + 3 H2 -> CH3OH + H2O }}

In terms of mechanism, the process occurs via initial conversion of CO into {{chem2|CO2}}, which is then [[hydrogenation|hydrogenated]]:<ref>Deutschmann, Olaf; Knözinger, Helmut; Kochloefl, Karl and Turek, Thomas (2012) "Heterogeneous Catalysis and Solid Catalysts, 3. Industrial Applications" in ''Ullmann's Encyclopedia of Industrial Chemistry''. Wiley-VCH, Weinheim. {{doi|10.1002/14356007.o05_o03}}</ref>

:{{chem2 | CO2 + 3 H2 -> CH3OH + H2O }}

where the {{chem2|H2O}} byproduct is recycled via the [[water gas shift reaction|water-gas shift reaction]]

:{{chem2 | CO + H2O -> CO2 + H2 }}

This gives an overall reaction

:{{chem2 | CO + 2 H2 -> CH3OH }}

which is the same as listed above. In a process closely related to methanol production from synthesis gas, a feed of hydrogen and {{chem2|CO2}} can be used directly.<ref>{{Cite journal|last1=Bozzano|first1=Giulia|last2=Manenti|first2=Flavio|date=2016|title=Efficient methanol synthesis: Perspectives, technologies and optimization strategies|url=https://www.sciencedirect.com/science/article/pii/S0360128515300484|journal=Progress in Energy and Combustion Science|language=en|volume=56|page=76|doi=10.1016/j.pecs.2016.06.001|bibcode=2016PECS...56...71B |issn=0360-1285}}</ref> The main advantage of this process is that [[Carbon capture and storage|captured {{chem2|CO2}}]] and hydrogen sourced from [[Electrolysis of water|electrolysis]] could be used, removing the dependence on fossil fuels.

===Biosynthesis===
The catalytic conversion of methane to methanol is effected by enzymes including [[methane monooxygenase]]s. These enzymes are mixed-function oxygenases, i.e. oxygenation is coupled with production of water<ref>{{cite journal|title=Mechanistic Studies on the Hydroxylation of Methane by Methane Monooxygenase|author=Mu-Hyun Baik |author2=Martin Newcomb |author3=Richard A. Friesner |author4=Stephen J. Lippard |journal=Chem. Rev.|year=2003|volume=103|issue=6|pages=2385–2420|doi=10.1021/cr950244f|pmid=12797835}}</ref> and [[Nicotinamide adenine dinucleotide|{{chem2|NAD+}}]]:<ref name=":0" />

:{{chem2 | CH4 + O2 + NADPH + H+ -> CH3OH + H2O + NAD+ }}

Both Fe- and Cu-dependent enzymes have been characterized.<ref name=":0">{{cite journal|author1=Lawton, T. J. |author2=Rosenzweig, A. C. |title=Biocatalysts for methane conversion: big progress on breaking a small substrate|journal=Curr. Opin. Chem. Biol.|year=2016|volume=35|pages=142–149|doi=10.1016/j.cbpa.2016.10.001|pmid=27768948|pmc=5161620}}</ref> Intense but largely fruitless efforts have been undertaken to emulate this reactivity.<ref name="Alayon">{{Cite journal|last1=Alayon|first1=E. M. C.|last2=Nachtegaal|first2=M.|last3=Ranocchiari|first3=M.|last4=Van Bokhoven|first4=J. A.|title=Catalytic Conversion of Methane to Methanol Using Cu-Zeolites|doi=10.2533/chimia.2012.668|journal=CHIMIA International Journal for Chemistry|volume=66|issue=9|pages=668–674|year=2012|pmid=23211724|url=https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A20913|doi-access=free|access-date=10 May 2021|archive-date=26 May 2021|archive-url=https://web.archive.org/web/20210526070248/https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A20913|url-status=live}}</ref><ref name="Catalytic and Mechanic Insights">{{Cite journal|doi=10.1002/chem.201202802|pmid=23150452|title=Catalytic and Mechanistic Insights of the Low-Temperature Selective Oxidation of Methane over Cu-Promoted Fe-ZSM-5|journal=Chemistry: A European Journal|volume=18|issue=49|pages=15735–45|year=2012|last1=Hammond|first1=C.|last2=Jenkins|first2=R. L.|last3=Dimitratos|first3=N.|last4=Lopez-Sanchez|first4=J. A.|last5=Ab Rahim|first5=M. H.|last6=Forde|first6=M.M.|last7=Thetford|first7=A.|last8=Murphy|first8=D.M.|last9=Hagen|first9=H.|last10=Stangland|first10=E.E.|last11=Moulijn|first11=J.M.|last12=Taylor|first12=S. H.|last13=Willock|first13=D. J.|last14=Hutchings|first14=G.J.}}</ref> Methanol is more easily oxidized than is the feedstock methane, so the reactions tend not to be selective. Some strategies exist to circumvent this problem. Examples include [[Shilov system]]s and Fe- and Cu-containing zeolites.<ref>{{Cite journal|last1=Snyder|first1=Benjamin E. R.|last2=Bols|first2=Max L.|last3=Schoonheydt|first3=Robert A.|last4=Sels|first4=Bert F.|last5=Solomon|first5=Edward I.|date=19 December 2017|title=Iron and Copper Active Sites in Zeolites and Their Correlation to Metalloenzymes|journal=Chemical Reviews|volume=118|issue=5|pages=2718–2768|doi=10.1021/acs.chemrev.7b00344|pmid=29256242|url=https://limo.libis.be/primo-explore/fulldisplay?docid=LIRIAS1644877&context=L&vid=Lirias&search_scope=Lirias&tab=default_tab&lang=en_US&fromSitemap=1|access-date=25 September 2021|archive-date=26 May 2021|archive-url=https://web.archive.org/web/20210526075141/https://limo.libis.be/primo-explore/fulldisplay?docid=LIRIAS1644877&context=L&vid=Lirias&search_scope=Lirias&tab=default_tab&lang=en_US&fromSitemap=1|url-status=live}}</ref> These systems do not necessarily mimic the mechanisms employed by [[metalloenzymes]], but draw some inspiration from them. Active sites can vary substantially from those known in the enzymes. For example, a dinuclear active site is proposed in the [[Methane monooxygenase|sMMO]] enzyme, whereas a mononuclear iron ([[alpha-Oxygen|alpha-oxygen]]) is proposed in the Fe-zeolite.<ref>{{Cite journal|last1=Snyder|first1=Benjamin E. R.|last2=Vanelderen|first2=Pieter|last3=Bols|first3=Max L.|last4=Hallaert|first4=Simon D.|last5=Böttger|first5=Lars H.|last6=Ungur|first6=Liviu|last7=Pierloot|first7=Kristine|last8=Schoonheydt|first8=Robert A.|last9=Sels|first9=Bert F.|s2cid=4467834|title=The active site of low-temperature methane hydroxylation in iron-containing zeolites|journal=Nature|volume=536|issue=7616|pages=317–321|doi=10.1038/nature19059|pmid=27535535|bibcode=2016Natur.536..317S|year=2016}}</ref>

Global emissions of methanol by plants are estimated at between 180 and 250 million tons per year.<ref>{{Cite journal |last1=Stavrakou |first1=T. |last2=Guenther |first2=A. |last3=Razavi |first3=A. |last4=Clarisse |first4=L. |last5=Clerbaux |first5=C. |last6=Coheur |first6=P.-F. |last7=Hurtmans |first7=D. |last8=Karagulian |first8=F. |last9=De Mazière |first9=M. |last10=Vigouroux |first10=C. |last11=Amelynck |first11=C. |last12=Schoon |first12=N. |last13=Laffineur |first13=Q. |last14=Heinesch |first14=B. |last15=Aubinet |first15=M. |date=25 May 2011 |title=First space-based derivation of the global atmospheric methanol emission fluxes |url=https://acp.copernicus.org/articles/11/4873/2011/ |journal=Atmospheric Chemistry and Physics |language=en |volume=11 |issue=10 |pages=4873–4898 |doi=10.5194/acp-11-4873-2011 |bibcode=2011ACP....11.4873S |s2cid=54685577 |issn=1680-7324 |doi-access=free |access-date=26 September 2022 |archive-date=26 September 2022 |archive-url=https://web.archive.org/web/20220926161749/https://acp.copernicus.org/articles/11/4873/2011/ |url-status=live}}</ref> This is between two and three times larger than man-made industrial production of methanol.