Haber process

The Haber process, also called the Haber–Bosch process, is the main industrial method for making ammonia. It combines nitrogen from the air with hydrogen, using an iron catalyst, to form ammonia (NH3). Most of the ammonia is used to make nitrogen fertilizer, either directly or as ammonium nitrate and urea. NA2+3HA2↽−−⇀2NHA3ΔH298 K∘=−92.28 kJ per mole of NA2 The German chemists Fritz Haber and Carl Bosch developed the process in the first decade of the 20th century. It was more efficient than earlier methods, such as the Birkeland–Eyde process and Frank–Caro process. Haber showed it working in the laboratory in 1909, and Bosch scaled it up for the German company BASF. The first industrial plant opened in 1913 at Oppau. Haber won the Nobel Prize in Chemistry in 1918, and Bosch won it in 1931. During World War I, Germany used the process to make nitric acid for explosives, which it could no longer import because of the Allied blockade. In the Haber process, nitrogen and hydrogen gas react on the surface of a solid catalyst, usually iron, to form ammonia. Both gases first stick (adsorb) to the catalyst surface. The two nitrogen atoms in each nitrogen molecule are held together by a very strong triple bond, which must be broken before they can react. This is the slowest step, so it controls the speed of the whole process. Bonding to the catalyst surface releases enough energy to make this step possible. The nitrogen atoms then pick up hydrogen one atom at a time, forming NH, then NH2, then NH3, which leaves the surface as ammonia gas. The reaction needs high pressure and high temperature. Only about 15% of the gases turn into ammonia on each pass through the reactor, so the ammonia is cooled and removed as a liquid, and the unused gases are fed back in. Most of the hydrogen comes from natural gas. The Haber process can be combined with steam reforming to produce ammonia with just three chemical inputs: water, natural gas, and atmospheric nitrogen. In 2018 the process produced about 230 million tonnes of ammonia. However, the process uses 1–2% of the world's energy and causes about 3% of global carbon dioxide emissions.

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