Aluminum oxidation
4
Technology Description
Hydrogen can be produced by water/steam aluminum oxidation. The reaction can be carried out in different ways depending on pressure and temperature operating conditions:
2Al+6H2O --> ‚Üí2Al(OH)3+3H2 -886 kJ/mol (1)
2Al+4H2O --> ‚Üí2AlO(OH)+3H2 -862 kJ/mol (2)
2Al+3H2O --> ‚ÜíAl2O3+3H2 -817 kJ/mol (3).
Reactions (1) and (2) are typical of oxidation with water and are carried under pressure (up to 40 bar and over for recent supercritical water applications) and low temperatures, i.e., up to 300°C (requiring catalysts). They have notable drawbacks tied to the need of using alkaline compound (to promote the reaction inibited by the oxide layer formation). Other methods include mechanical activation and metal alloying. Good results in terms of H2 yield and reaction time are obtained in batch operating conditions, but not suitable for continuous operation required by H2 use in fuel cells and turbine.
Relevance for Net Zero
Other alternative technologies for hydrogen production from fossil sources with CCS and electrolysis are currently more developed and cost-competitive. However, this technology has the potential to deliver low-emission hydrogen and new processes which could significantly lower cost and improve efficiency are at the lab scale.
Key Countries
Europe, United States
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