Haber-Bosch process

Industrial process in which ammonia is manufactured by direct combination of its elements, nitrogen and hydrogen. The reaction is carried out at 752-932°F/400-500°C and at a pressure of 200 bar. The two gases, in the proportions of 1:3 by volume, are passed over a catalyst of finely divided iron.

Around 10% of the reactants combine, and the unused gases are recycled. The ammonia is separated by either dissolving in water or cooling to liquid form.

The equation

N₂ + 3H₂ ⇌ 2NH₃

predicts that the volume of the gas mix should be reduced by half if the reactants were completely converted to ammonia. Thus, following Le Chatelier's principle, high pressure can be used to shift the equilibrium to the right hand side.

Even though nitrogen (N2) represents the main component of the air that we breathe, there is no easy way of making this very inert molecule amenable to chemical reactions and tapping into this vast supply of an element that is essential for all living organisms.

The process that overcame this challenge was developed by Fritz Haber in 1905-10 on a laboratory scale. Carl Bosch was responsible for its implementation on an industrial scale between 1908 and 1913. Its global application for the production of fertilizers has had an unprecedented impact on food production in the 20th century. The total turnover of the industrial process is now comparable to the output of the corresponding natural process, nitrogen fixation. It has been estimated that today roughly half the nitrogen content of the world population is coming out of the Haber-Bosch process.