Syngas

Syngas is produced by steam reforming or partial oxidation of natural gas or liquid hydrocarbons, or coal gasification.{{cite journal |last1=Beychok |first1=Milton R. |title=Coal gasification and the Phenosolvan process |journal=Am. Chem. Soc., Div. Fuel Chem., Prepr.; (United States) |date=1974 |volume=19 |issue=5 |osti=7362109 |s2cid=93526789 |url=http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/19_5_ATLANTIC%20CITY_09-74_0085.pdf |archive-url=https://web.archive.org/web/20160303221005/http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/19_5_ATLANTIC%20CITY_09-74_0085.pdf |archive-date=3 March 2016 }}

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

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

:{{chem2|C + CO2 -> 2CO }}

Steam reforming of methane is an endothermic reaction requiring 206 kJ/mol of energy:

:{{chem2|CH4 + H2O -> CO + 3 H2}}

In principle, but rarely in practice, biomass and related hydrocarbon feedstocks could be used to generate biogas and biochar in waste-to-energy gasification facilities.{{Cite web|title=Sewage treatment plant smells success in synthetic gas trial - ARENAWIRE|url=https://arena.gov.au/blog/logan-gasification-sewage-treatment-plant/|access-date=2021-01-25|website=Australian Renewable Energy Agency|date=11 September 2019 |language=en-AU|archive-date=2021-03-07|archive-url=https://web.archive.org/web/20210307141645/https://arena.gov.au/blog/logan-gasification-sewage-treatment-plant/|url-status=live}} The gas generated (mostly methane and carbon dioxide) is sometimes described as syngas but its composition differs from syngas. Generation of conventional syngas (mostly H₂ and CO) from waste biomass has been explored.{{cite journal | last=Zhang | first=Lu | display-authors=etal | title=Clean synthesis gas production from municipal solid waste via catalytic gasification and reforming technology | journal=Catalysis Today | volume=318 | year=2018 | issn=0920-5861 | doi=10.1016/j.cattod.2018.02.050 | pages=39–45| s2cid=102872424 }}{{Cite journal |last=Sasidhar |first=Nallapaneni |date=November 2023 |title=Carbon Neutral Fuels and Chemicals from Standalone Biomass Refineries |url=https://www.ijee.latticescipub.com/wp-content/uploads/papers/v3i2/B1845113223.pdf |access-date=29 December 2023 |journal=Indian Journal of Environment Engineering |issn=2582-9289 |volume=3 |issue=2|pages=1–8 |doi=10.54105/ijee.B1845.113223 |s2cid=265385618}}

The chemical composition of syngas varies based on the raw materials and the processes. Syngas produced by coal gasification generally is a mixture of 30 to 60% carbon monoxide, 25 to 30% hydrogen, 5 to 15% carbon dioxide, and 0 to 5% methane. It also contains lesser amount of other gases.{{cite web|title=Syngas composition|url=http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition|publisher=National Energy Technology Laboratory, U.S. Department of Energy|access-date=7 May 2015|archive-date=27 March 2020|archive-url=https://web.archive.org/web/20200327190358/http://www.netl.doe.gov/research/coal/energy-systems/gasification/gasifipedia/syngas-composition|url-status=live}} Syngas has less than half the energy density of natural gas.{{cite book |last1=Beychok |first1=M R |title=Process and environmental technology for producing SNG and liquid fuels |date=1975 |publisher=Environmental Protection Agency |oclc=4435004117 |osti=5364207 }}{{page needed|date=November 2021}}

The first reaction, between incandescent coke and steam, is strongly endothermic, producing carbon monoxide (CO) and hydrogen {{chem|H|2}} (water gas in older terminology). When the coke bed has cooled to a temperature at which the endothermic reaction can no longer proceed, the steam is then replaced by a blast of air.

The second and third reactions then take place, producing an exothermic reaction—forming initially carbon dioxide and raising the temperature of the coke bed—followed by the second endothermic reaction, in which the latter is converted to carbon monoxide. The overall reaction is exothermic, forming "producer gas" (older terminology). Steam can then be re-injected, then air etc., to give an endless series of cycles until the coke is finally consumed. Producer gas has a much lower energy value, relative to water gas, due primarily to dilution with atmospheric nitrogen. Pure oxygen can be substituted for air to avoid the dilution effect, producing gas of much higher calorific value.

In order to produce more hydrogen from this mixture, more steam is added and the water gas shift reaction is carried out:

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

The hydrogen can be separated from the {{CO2}} by pressure swing adsorption (PSA), amine scrubbing, and membrane reactors. A variety of alternative technologies have been investigated, but none are of commercial value.{{cite book |doi=10.1002/14356007.a12_169.pub3|chapter=Gas Production, 1. Introduction |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2011 |last1=Hiller |first1=Heinz |last2=Reimert |first2=Rainer |last3=Stönner |first3=Hans-Martin |isbn=978-3527306732 }} Some variations focus on new stoichiometries such as carbon dioxide plus methane{{Cite web|url=http://www.diebrennstoffzelle.de/wasserstoff/herstellung/kvaerner.shtml|title=dieBrennstoffzelle.de - Kvaerner-Verfahren|website=www.diebrennstoffzelle.de|access-date=2019-12-17|archive-date=2019-12-07|archive-url=https://web.archive.org/web/20191207063249/http://www.diebrennstoffzelle.de/wasserstoff/herstellung/kvaerner.shtml|url-status=live}}{{cite patent |country=EU |number=3160899B1 |status=patent |title=Method and apparatus for producing h2-rich synthesis gas |gdate=12 December 2018 |inventor1-last=Kühl |inventor1-first=Olaf }} or partial hydrogenation of carbon dioxide. Other research focuses on novel energy sources to drive the processes including electrolysis, solar energy, microwaves, and electric arcs.{{cite web|title=Sunshine to Petrol|url=http://energy.sandia.gov/wp/wp-content/gallery/uploads/S2P_SAND2009-5796P.pdf|publisher=Sandia National Laboratories|access-date=April 11, 2013|archive-date=February 19, 2013|archive-url=https://web.archive.org/web/20130219194404/http://energy.sandia.gov/wp/wp-content/gallery/uploads/S2P_SAND2009-5796P.pdf|url-status=dead}}{{cite web|title=Integrated Solar Thermochemical Reaction System|url=http://www1.eere.energy.gov/solar/sunshot/csp_sunshotrnd_pnnl.html|publisher=U.S. Department of Energy|access-date=April 11, 2013|archive-date=August 19, 2013|archive-url=https://web.archive.org/web/20130819063840/http://www1.eere.energy.gov/solar/sunshot/csp_sunshotrnd_pnnl.html|url-status=live}}{{cite news|title=New Solar Process Gets More Out of Natural Gas|url=https://www.nytimes.com/2013/04/11/business/energy-environment/new-solar-process-gets-more-out-of-natural-gas.html|access-date=April 11, 2013|newspaper=The New York Times|date=April 10, 2013|author=Matthew L. Wald|archive-date=November 30, 2020|archive-url=https://web.archive.org/web/20201130012407/https://www.nytimes.com/2013/04/11/business/energy-environment/new-solar-process-gets-more-out-of-natural-gas.html|url-status=live}}{{cite web|title=A solar booster shot for natural gas power plants|url=http://www.pnnl.gov/news/release.aspx?id=981|publisher=Pacific Northwest National Laboratory|access-date=April 12, 2013|author=Frances White|archive-date=April 14, 2013|archive-url=https://web.archive.org/web/20130414234802/http://www.pnnl.gov/news/release.aspx?id=981|url-status=live}}{{cite journal |last1=Foit |first1=Severin R. |last2=Vinke |first2=Izaak C. |last3=de Haart |first3=Lambertus G. J. |last4=Eichel |first4=Rüdiger-A. |title=Power-to-Syngas: An Enabling Technology for the Transition of the Energy System? |journal=Angewandte Chemie International Edition |date=8 May 2017 |volume=56 |issue=20 |pages=5402–5411 |doi=10.1002/anie.201607552 |pmid=27714905 }}{{cite patent |country=US |number=5159900A |status=patent |title=Method and means of generating gas from water for use as a fuel |gdate=3 November 1992 |inventor1-last=Dammann |inventor1-first=Wilbur A. }}

Electricity generated from renewable sources is also used to process carbon dioxide and water into syngas through high-temperature electrolysis. This is an attempt to maintain carbon neutrality in the generation process. Audi, in partnership with company named Sunfire, opened a pilot plant in November 2014 to generate e-diesel using this process.{{cite news|title=Audi in new e-fuels project: synthetic diesel from water, air-captured CO2 and green electricity; "Blue Crude"|url=http://www.greencarcongress.com/2014/11/20141114-audibluecrude.html|access-date=29 April 2015|work=Green Car Congress.|date=14 November 2014|archive-date=27 March 2020|archive-url=https://web.archive.org/web/20200327190343/https://www.greencarcongress.com/2014/11/20141114-audibluecrude.html|url-status=live}}

Syngas that is not methanized typically has a lower heating value of 120 BTU/scf.{{cite conference |last1=Oluyede |first1=Emmanuel O. |last2=Phillips |first2=Jeffrey N. |title=Volume 3: Turbo Expo 2007 |chapter=Fundamental Impact of Firing Syngas in Gas Turbines |conference=Proceedings of the ASME Turbo Expo 2007: Power for Land, Sea, and Air. Volume 3: Turbo Expo 2007 |location=Montreal, Canada |date=May 2007 |pages=175–182 |publisher=ASME |doi=10.1115/GT2007-27385 |isbn=978-0-7918-4792-3 |citeseerx=10.1.1.205.6065 }} Untreated syngas can be run in hybrid turbines that allow for greater efficiency because of their lower operating temperatures, and extended part lifetime.

Syngas is used as a source of hydrogen as well as a fuel (see fuel cell). It is also used to directly reduce iron ore to sponge iron.{{cite book |last1=Chatterjee |first1=Amit |title=Sponge iron production by direct reduction of iron oxide |date=2012 |publisher=PHI Learning |isbn=978-81-203-4659-8 |oclc=1075942093 }}{{page needed|date=November 2021}} Chemical uses include the production of methanol which is a precursor to acetic acid and many acetates; liquid fuels and lubricants via the Fischer–Tropsch process and previously the Mobil methanol to gasoline process; ammonia via the Haber process, which converts atmospheric nitrogen (N₂) into ammonia which is used as a fertilizer; and oxo alcohols via an intermediate aldehyde.{{Cn|date=November 2024}}

{{Portal|Energy|Renewable energy}}

{{Div col}}

• Boudouard reaction
• Claus process
• Coal gas
• Industrial gas
• Integrated gasification combined cycle
• Partial oxidation
• Reformer sponge iron cycle
• Syngas fermentation
• Underground coal gasification

{{Div col end}}

{{Reflist}}

• [https://arena.gov.au/blog/logan-gasification-sewage-treatment-plant/ "Sewage treatment plant smells success in synthetic gas trial" ARENA, accessed December 6 2020]
• [http://www.fischer-tropsch.org/ Fischer Tropsch archive]
• https://www.technologyreview.com/s/508051/a-cheap-trick-enables-energy-efficient-carbon-capture/

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