The Haber Process is a vital industrial process which produces "fixed" nitrogen from atmospheric nitrogen, allowing the production of fertilizers and other nitrogen-based compounds. Hydrogen and nitrogen are run over a heated catalyst at pressure and bond to produce ammonia.
plain iron oxide
Simple iron oxide can be used as a catalyst.
- The catalyst is purified Fe3O4 (magnetite) with the oxygen removed by exposure to hydrogen at high temperatures. This provides the appropriate porosity.
- The reaction takes place at 440-450°C and atmospheric pressure
- Yield is 0.25% ammonia
- Scaling: 100-200cc of gas per minute over 1kg of catalyst
See "The Direct Synthesis of Ammonia" for a description of producing the catalyst.
Apparently Tungsten can also be used as a catalyst at about 600°C and atmospheric pressure.
- Yield: 4-5%
- The catalyst is doped purified iron Fe + CaO + K2O + SiO2 + Al3O4
- The reaction takes place at 300–550 °C and 50–250 atmospheres.
- Yield is over 90%
The gases are refrigerated, the ammonia removed as a liquid, and the process is repeated. Iron oxide can be used in place of iron, because it will be rapidly reduced by the hydrogen gas to water and pure iron.
- At the extremely high temperatures and pressures involved, rupture and explosion of the reaction vessel is a serious concern.
- Lars, Alfred T. (1925)
J. Chem. Educ.
- Fromm, F. (1942) ; pp230.