Editing Steam reforming (section)

{{Short description|Method for producing hydrogen and carbon monoxide from hydrocarbon fuels}}
{{distinguish|catalytic reforming}}
[[File:SMR+WGS-1.png|thumb|Illustrating inputs and outputs of steam reforming of natural gas, a process to produce hydrogen and CO<sub>2</sub> greenhouse gas that may be captured with CCS|330x330px]]'''Steam reforming''' or '''steam methane reforming (SMR)''' is a method for producing [[syngas]] ([[hydrogen]] and [[carbon monoxide]]) by reaction of [[hydrocarbon]]s with water. Commonly, [[natural gas]] is the feedstock. The main purpose of this technology is often [[hydrogen production]], although syngas has multiple other uses such as production of [[Ammonia production|ammonia]] or [[methanol]]. The reaction is represented by this equilibrium:<ref>{{cite book|doi=10.1002/9780470561256|title=Hydrogen and Syngas Production and Purification Technologies|year=2009|isbn=9780470561256|editor1-last=Liu|editor1-first=Ke|editor2-last=Song|editor2-first=Chunshan|editor3-last=Subramani|editor3-first=Velu}}</ref>

:<chem>CH4 + H2O <=> CO + 3 H2</chem>

The reaction is strongly [[endothermic]] (Δ''H''<sub>SR</sub> = 206 kJ/mol).

Hydrogen produced by steam reforming is termed [[grey hydrogen|'grey' hydrogen]] when the waste carbon dioxide is released to the atmosphere and [[blue hydrogen|'blue' hydrogen]] when the carbon dioxide is (mostly) captured and stored geologically—see [[carbon capture and storage]]. Zero carbon [[green hydrogen|'green' hydrogen]] is produced by [[Thermochemical cycle|thermochemical water splitting]], using solar thermal, low- or zero-carbon electricity or waste heat,<ref>{{Cite journal|url=https://www.sciencedirect.com/science/article/abs/pii/S0196890419311884|doi = 10.1016/j.enconman.2019.112182|title = A review and comparative evaluation of thermochemical water splitting cycles for hydrogen production|year = 2020|last1 = Safari|first1 = Farid|last2 = Dincer|first2 = Ibrahim|journal = Energy Conversion and Management|volume = 205|page = 112182| bibcode=2020ECM...20512182S |s2cid = 214089650|url-access = subscription}}</ref> or [[electrolysis]], using low- or zero-carbon electricity. Zero carbon emissions 'turquoise' hydrogen is produced by one-step [[methane pyrolysis]] of natural gas.<ref>{{cite journal |last1=Lumbers |first1=Brock |title=Mathematical modelling and simulation of the thermo-catalytic decomposition of methane for economically improved hydrogen production |url=https://www.sciencedirect.com/science/article/abs/pii/S0360319921044438 |journal=International Journal of Hydrogen Energy |year=2022 |volume=47 |issue=7 |pages=4265–4283 |doi=10.1016/j.ijhydene.2021.11.057 |bibcode=2022IJHE...47.4265L |s2cid=244814932 |access-date=16 March 2022}}</ref>

Steam reforming of [[natural gas]] produces most of the world's hydrogen. Hydrogen is used in the [[Ammonia production|industrial synthesis of ammonia]] and other chemicals.<ref>{{cite tech report|url=http://www.me.ncu.edu.tw/energy/CleanEnergyTechnology/The%20Hydrogen%20Economy_Addition.pdf |date=2004 |first1=George W. |author-link1=George Crabtree|last1=Crabtree |first2=Mildred S. |last2=Dresselhaus |author-link2=Mildred Dresselhaus|first3=Michelle V. |last3=Buchanan |title=The Hydrogen Economy}}</ref>