Haber process

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.

Process

Atmospheric pressure

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.

Tungsten

Apparently Tungsten can also be used as a catalyst at about 600°C and atmospheric pressure.

High Pressure

platinum

• Yield: 4-5%

promoted iron

• 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.

Hazards

• At the extremely high temperatures and pressures involved, rupture and explosion of the reaction vessel is a serious concern.

See Also

• Ostwald process