Haber process

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The Haber Process (aka Haber-Bosch process) is the reaction of nitrogen and hydrogen to produce ammonia.

The nitrogen and hydrogen are reacted over an iron catalyst under conditions of 200 atmospheres, 450'C:

 N2(g) + 3H2(g)  <-->  2NH3(g)  ΔH-     ...(1)

The process was developed by Fritz Haber and Carl Bosch in 1909 and patented in 1910. First used on an industrial scale by the Germans during WWI, the ammonia was used to produce explosives to sustain their war effort.

The nitrogen is obtained from the air, and the hydrogen is obtained from water natural gas in the reaction:

 CH4(g) + H2O(g) -> CO(g) + 3H2(g)     ...(2)

Equilibrium and the Haber Process

The reaction of nitrogen and hydrogen (1) is reversible and lowering the temperature favours the forward reaction. However, the lower the temperature the slower the reaction. The temperature is a compromise between the two.

The forward reaction favours high pressures because there are less products on the right side. So the only compromise in pressure is the economical situation trying to increase the pressure as much as possible.

The iron catalyst has no effect on the position of equilibrium - it speeds up the forward and the backward reaction.

The ammonia is formed as a gas but cools in the condensor and is removed as a liquid. Unreacted nitrogen and hydrogen is fed back in to the reaction.