The term Haber-Bosch Process describes the industrial production of ammonia.

The chemical process for converting nitrogen and hydrogen to ammonia with the use of a catalyst was developed in 1908 by Fritz Haber, patented in 1910 by Haber and Robert Le Rossignol and won Haber a Nobel Prize in 1918

The reaction itself is simple:

N2 + 3 H2 <--> 2 NH3

Kp = 6 x 10 5

The ammonia producing reaction is reversible and exothermic, favoring the production of ammonia at room temperature (by Le Chatelier's principle) but the rate of reaction is too slow to reach equilibrium, due to the inert nature of N2. An optimum temperature of 450-550 ÂșC is used to increase the reaction rate, along with an iron catalyst which contains promoters. These promoters include a combination of silicon, magnesium, potassium or aluminum oxides. The 1910 US patent specifies the use of an osmium catalyst. The increase in temperature gives a thermodynamic effect favoring the reverse reaction (ie the production of nitrogen and hydrogen rather than ammonia), so the process is performed at high pressures (200- 270 atm) to combat this effect.

The industrial application of this process was designed by Carl Bosch; a chemical engineer who was awarded a Nobel Prize in 1931 for his design of ammonia production plants. In the Haber-Bosch process, the nitrogen is obtained from the air, while hydrogen is obtained by reacting natural gas with steam in the presence of a nickel catalyst.

Sources: Shriver, Atkins & Langford Inorganic Chemistry 1994, , 1999, Oxford Paperback Encyclopedia, 1998

A good overview of the history and importance of this process can be found at http://www.ri.sch.edu.sg/Departments/GEP/SHOWCASE/IRS/Mini-chemistry/ammonia/home.htm

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