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.

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 gasses 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.

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

Hazards

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

See Also

• Ostwald process