Haber-Bosch-process

the Haber-Bosch-process, designated after its developers Fritz Haber and Carl Bosch, serves the synthetic production of ammonia from the elements nitrogen and hydrogen. In order to make the reaction technically usable, a gas mixture becomes from hydrogen and nitrogen at a catalyst out Iron, an ferric oxide mixed catalyst so mentioned from iron (II/CIII) - oxide Fe ₃ O ₄, K ₂ O, CaO, aluminium ₂ O ₃ and SiO ₂ at approximately 450 bar pressure and 500°C brought to the reaction.

Chemical reaction:

<math> N_2 \ + \ 3 \ H_2 \ \ rightarrow \ 2 \ NH_3< /math>

Table of contents 1 synthesis conditions 2 technical production of ammonia 3 history and meaning 4 literature 5 Web on the left of 6 see also

to synthesis conditions

the optimal and/or. most economic reaction parameter certainly up:

• Pressure: 150-450 bar (atmosphere)
• temperature: 500°C
• quantitative proportion nitrogen: Hydrogen = 1: 3
• Use iron (II/CIII) - oxide Fe ₂ O ₃, K ₂ O, CaO, aluminium ₂ O ₃ and SiO ₂ - catalyst for reaction acceleration

By the assigned high pressure and the concentration change (remove ammonia and deliver subsequently Edukte) a shift of the chemical equilibrium becomes toward of theAmmonia reaches. This is necessary, in order to be able to operate a sufficient yield for received and the procedure economically meaningfully. Although a lower temperature for a higher ammonia yield would be favorable, one can be run off the reaction at higher temperatures, there only so one for the industrysuitable reaction rate results in.

The energy entry into the reaction (reached by the high temperature) is needed, in order to overcome the activation energy (despite catalyst still highly) of the reaction because of the triple bond of the nitrogen molecule. The ammonia synthesis is exothermic (Δ _R H ⁰ = -92.5 kJ/mol); the high temperaturethus and reduces therefore the yield (principle of Le Chatelier) works against the synthesis of ammonia. The principle of Le Chatelier is however used, by supplementing ammonia constantly from the reaction process isolated, far away and by Frischgas.

That percentage by volume <math> NH_3< /math> in the gas mixtureapproximately 17.6% amount to.

The hydrogen necessary for the reaction is today usually opened by the partial oxidation of natural gas, which nitrogen taken like already in the original procedure directly out of air, whereby the disturbing oxygen first by oxidation with hydrogen to water reshuffledand then one separated, today however with the cracking of liquid air one separates.

Modern ammonia plants produce already more than 3000 tons per day in a production line.

Due to high the conditions of temperature and pressure at the synthesis of ammonia are void approx. 3% of the world energy consumption upthe Haber-Bosch-process.

technical production of ammonia

ammonia develops in a Gleichgewichtsreaktion from the elements hydrogen and nitrogen.

As the first the synthesis gases are needed:

• <math> N_2< /math> from air
• <math> H_2< /math> from methane gas (<math> CH_4< /math>)

around the hydrogen from carbon to to separate we leave methane gas with water to carbon mono oxide and hydrogen react. (Primärreformer)

< math> CH_4 (g) + H_2O (l) \ quad \ rightarrow \ quad CO (g) + 3H_2 (g)< /math> <math> {\ delta H=+206 kJ/mol}< /math>

One can let methane gas further react with oxygen to carbon mono oxide and hydrogen. (Sekundärreformer)

< math> 2CH_4 (g) + O_2 (g) \ quad \ rightarrow \ quad 2CO (g) + 4H_2 (g)< /math> <math> {\ delta H=-71 kJ/mol}< /math>

As last step one must oxidize to carbon mono oxide to carbon dioxide, since carbon mono oxide works with the ammonia synthesis as catalyst poison. (Conversion)

< math> CO (g) + H_2O \ quad \ rightarrow \ quad CO_2 (g) + H_2 (g)< /math> <math> {\ delta H=-41 kJ/mol}< /math>

Carbon dioxide can be removed by washing with tri ethanol amine from the mixture.

historyand meaning

the substantial scientific achievements for the realization of this procedure were:

1. the investigation of the which is the basis chemical reaction (Haber, Nernst)
2. the systematic search for suitable catalysts (Alwin Mittasch)
3. the technical realization generally speaking yardstick, whereby partially perfectly new solutions are developedhad (Carl Bosch, Fritz Haber)

the Haber-Bosch-process by the BASF in the year 1910 to the patent one announced, an incorrect patent from Haber, submitted before, to the same topic at the same time one withdrew.

For the entire development several Nobelpreise were assigned, z. B. 1918 thatNobelpreis for chemistry at Fritz Haber as well as 1931 for Carl Bosch (together with Friedrich Bergius), for the first time for a technical conversion method.

Developed ammonia can be re-used for example in the Ostwald procedure for nitric acid or for fertilizer (reaction with _CO 2 for urea). Salpetera great importance for the armaments industry has, why also very fast strong interest in the structure of an industrial production existed, which was established and operated among other things in Leuna and bitter field by the BASF and after fusion in the German large concern of the industrial union colors.

By nowin large quantities need resulted available nitrogen fertilizer to extensive agricultural research, in order to determine according to the principle of the minimum ton the optimal fertilizer quantities depending upon soil and plant type. World-wide agricultural production could be increased by increasing fertilizer employment clearly, which a further outstanding,if does not even represent the most important aspect of the invention of the Haber-Bosch-process. Without nitrogen fertilizers became at least 2 billion humans of the population of world verhungern, since nearly half of the used up food was based on industrial mineral fertilizer.

A further, at that time desired side effect was the synthesis from war-technically valuable nitrate of ammonia toProduction of explosive. There the German Reich of natural sources of nitrogen (v. A. Guano, deposited bird excrement from the region south Pacific) by sea-blockade was blocked, was opened now a possibility of manufacturing ammunition and explosives further most efficiently.

literature

• Robert Schlögl: Catalytic one Ammonia synthesis - a “infinite history”? Applied chemistry 115 (18), S. 2050 - to 2055 (2003), ISSN of 0044-8249

Web on the left of

• http://www.seilnacht.tuttlingen.com/Lexikon/HaberBo.htm
• Haber-Bosch-processes
• ammonia procedures of the Uhde GmbH
• having he bosch

see also

portal: Chemistry,