The water-gas shift reaction (WGS/Dussan Reaction) is a chemical reaction in which carbon monoxide reacts with water vapor to form carbon dioxide and hydrogen:
- CO + H2O → CO2 + H2
The water-gas shift reaction is an important industrial reaction. It is often used in conjunction with steam reforming of methane or other hydrocarbons,[1] which is important for the production of high purity hydrogen for use in ammonia synthesis. The water-gas shift reaction was discovered by Italian physicist Felice Fontana in 1780. The reaction is slightly exothermic, yielding 42 kJ (10 kcal) per mole.[1]
The carbon monoxide can also be generated by bogs or other waste regenerative means by physical/chemical processes such as bog and landfill fires.
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Applications
This reaction has been used as a CO removal method from the reformate for fuel cell applications.
The reverse water gas shift reaction has recently found a possible application in In-Situ Resource Utilization on Mars to provide oxygen for fuel for the Mars Direct mission concept.
Reaction Conditions
The water gas shift reaction is sensitive to temperature, with the tendency to shift towards reactants as temperature increases due to Le Chatelier's principle. In fuel-rich hydrocarbon combustion processes, the water gas reaction at equilibrium state is often employed as a means to provide estimates for molar concentrations of burnt gas constituents.
The process is often used in two stages, stage one a high temperature shift (HTS) at 350 °C (662 °F) and stage two a low temperature shift (LTS) at 190–210 °C (374–410 °F).[2] Standard industrial catalysts for this process are iron oxide promoted with chromium oxide for the HTS step and copper on a mixed support composed of zinc oxide and aluminum oxide for the LTS shift step.[3]
Catalysts
Attempts to lower the reaction temperature of this reaction have been done primarily with a catalyst such as Fe3O4 (magnetite), or other transition metals and transition metal oxides. Another catalyst is the Raney copper catalyst.[4]
See also
- Water gas
- In-Situ Resource Utilization
- Lane hydrogen producer
- PROX
- Gasification, gasifier, pyrolysis, pyrolyser
References
- ^ a b "HFCIT Hydrogen Production: Natural Gas Reforming". United States Department of Energy. 2006-11-08. http://www1.eere.energy.gov/hydrogenandfuelcells/production/natural_gas.html. Retrieved 2008-01-07.
- ^ Stages
- ^ Schumacher, N.; et, al. (2005), "Trends in low-temperature water–gas shift reactivity on transition metals", Journal of Catalysis 229: 265-275
- ^ http://researchspace.csir.co.za/dspace/handle/10204/776
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