The water-gas shift reaction (WGS) is a chemical reaction that plays a central role in the production of hydrogen from hydrocarbons or coal. It is typically used as a subsequent reaction in processes such as steam reforming.
Meaning of the reaction
- Increased hydrogen yield:
It converts carbon monoxide, a byproduct of steam reforming, into hydrogen, which increases the efficiency of the overall process. - Reduction of carbon monoxide levels:
Reaction conditions
The water-gas shift reaction takes place in two stages to ensure optimal hydrogen production:
- High-temperature shift (HTS):
- Temperature: 300–450 °C
- Catalyst: Iron oxide (Fe₃O₄) with chromium oxide (Cr₂O₃) as promoter
- Goal: Rapid conversion of CO to CO₂ and H₂
- Low Temperature Shift (LTS):
- Temperature: 200–250 °C
- Catalyst: Copper oxide (CuO) with zinc oxide (ZnO) and aluminum oxide (Al₂O₃)
- Goal: To maximize hydrogen content through further CO conversion
Applications
The water-gas shift reaction is primarily used in processes for hydrogen production, e.g.:
- Steam reforming: After the primary reaction, to produce hydrogen.
- Coal gasification: The conversion of coal into synthesis gas (CO and H₂).
- Fuel cells: To clean the fuel, as CO can poison the fuel cell catalysts.
