Editing Haber process (section)

=== Synthesis parameters ===
{| class="wikitable floatright"
|+Change of the equilibrium constant K<sub>eq</sub> as a function of temperature<ref name="brown">{{Cite book |last1=Brown |first1=Theodore L. |title=Chemistry the Central Science |last2=LeMay |first2=H. Eugene |last3=Bursten |first3=Bruce Edward |date=2003 |publisher=Prentice Hall |isbn=978-0-13-038168-2 |editor-last=Brunauer |editor-first=Linda Sue |edition=9th |location=Upper Saddle River, New Jersey, Pakistan Punjab|language=en}}</ref>
|-
! temperature (°C)
! K<sub>eq</sub>
|-
|align="center" | 300
| 4.34 × 10<sup>−3</sup>
|-
|align="center" | 400
| 1.64 × 10<sup>−4</sup>
|-
|align="center" | 450
| 4.51 × 10<sup>−5</sup>
|-
|align="center" | 500
| 1.45 × 10<sup>−5</sup>
|-
|align="center" | 550
| 5.38 × 10<sup>−6</sup>
|-
|align="center" | 600
| 2.25 × 10<sup>−6</sup>
|}

The reaction is:

:<math chem>\ce{N2 + 3H2 <=> 2NH3} \qquad {\Delta H^\circ_{\mathrm{298~K}} = -92.28 \; \ce{kJ/mol}}) </math><ref name="Holleman">{{Holleman&Wiberg|edition=102|pages=662–665}}</ref>

The reaction is an exothermic equilibrium reaction in which the gas volume is reduced. The equilibrium constant K<sub>eq</sub> of the reaction (see table) and obtained from:

: <math chem>K_{eq} = \frac{p^2 \ce{(NH3)}}{p \ce{(N2)}\cdot p^3 \ce{(H2)}}</math>

Since the reaction is [[Exothermic reaction|exothermic]], the equilibrium of the reaction shifts at lower temperatures to the ammonia side. Furthermore, four volumetric units of the raw materials produce two volumetric units of ammonia. According to [[Le Chatelier's principle]], higher pressure favours ammonia. High pressure is necessary to ensure sufficient surface coverage of the catalyst with nitrogen.<ref name="cornils">{{Cite book |last1=Cornils |first1=Boy |title=Catalysis from A to Z: A Concise Encyclopedia |last2=Herrmann |first2=Wolfgang A. |last3=Muhler |first3=M. |last4=Wong |first4=C. |date=2007 |publisher=Verlag Wiley-VCH |isbn=978-3-527-31438-6 |page=31}}</ref> For this reason, a ratio of nitrogen to hydrogen of 1 to 3, a [[pressure]] of 250 to 350 bar, a temperature of 450 to 550&nbsp;°C and α iron are optimal.

The catalyst [[Ferrite (iron)|ferrite]] (α-Fe) is produced in the reactor by the reduction of magnetite with hydrogen. The catalyst has its highest efficiency at temperatures of about 400 to 500&nbsp;°C. Even though the catalyst greatly lowers the [[activation energy]] for the cleavage of the [[triple bond]] of the nitrogen molecule, high temperatures are still required for an appropriate reaction rate. At the industrially used reaction temperature of 450 to 550&nbsp;°C an optimum between the decomposition of ammonia into the starting materials and the effectiveness of the catalyst is achieved.<ref name="Oberstufe">{{Cite book |title=Fokus Chemie Oberstufe Einführungsphase |date=2010 |publisher=Cornelsen-Verlag |isbn=978-3-06-013953-8 |location=Berlin |page=79 |language=de}}</ref> The formed ammonia is continuously removed from the system. The volume fraction of ammonia in the gas mixture is about 20%.

The inert components, especially the noble gases such as [[argon]], should not exceed a certain content in order not to reduce the [[partial pressure]] of the reactants too much. To remove the inert gas components, part of the gas is removed and the argon is separated in a [[gas separation plant]]. The extraction of pure argon from the circulating gas is carried out using the [[Linde process]].<ref name="ullmann">P. Häussinger u. a.: ''Noble Gases.'' In: ''Ullmann's Encyclopedia of Industrial Chemistry.'' Wiley-VCH, Weinheim 2006. {{doi|10.1002/14356007.a17_485}}</ref>