Olin Raschig process

Raschig synthesis also Raschig process, is a large-scale process for the synthesis of hydrazine. The reactants are chlorine, sodium hydroxide and ammonia.

The process

The synthesis is divided into several steps. The first step is the preparation of the required sodium hypochlorite, which proceeds according to the following reaction equation:

Instead of sodium hypochlorite salts is also the use of other possible reasons of cost, however, recommend the use of low- sodium hydroxide.

The hypochlorite produced is now housed in the actual reaction with ammonia to react. In aqueous medium forms from the hypochlorite hypochlorous acid. Then arises the following equation, first the intermediate chloramine:

Here, the nitrogen is oxidized by the oxidation state of from -3 to -1. In the next step the chloramine formed is then converted to hydrazine. This happens through reaction of a molecule with one molecule of chloramine ammonia according to the following equation:

The net reaction thus results:

To grasp the obtained hydrazine from this reaction solution, however, is difficult because the resulting hydrazine in a fast reaction is oxidized to molecular nitrogen with ammonium chloride is formed:

The situation is exacerbated by the fact that the formation of hydrazine from chloramine proceeds very slowly, while it is in the oxidation of hydrazine to nitrogen in relation to a rapid reaction. This means that already formed hydrazine reacts further shortly after emergence. To avoid this chloramine will be first prepared at low temperatures and then placed in an ammonia solution, with a high excess of ammonia must be present. Due to the onset of the exothermic reaction, the temperature increases in the reaction mixture. Under these conditions, the synthesis of hydrazine proceeds rapidly and the chloramine used is completely consumed in a short time. In the absence of chloramine can not drain the oxidation of hydrazine to nitrogen. After distilling off the excess ammonia, hydrazine than 64 % hydrazine hydrate can be distilled.

Swell

  • AF Holleman, N. Wiberg: Textbook of Inorganic Chemistry, 101 Edition, page 660, de Gruyter, Berlin 1995, ISBN 3-11-012641-9.
  • F. Raschig: Lecture experiments in chemistry of inorganic nitrogen compounds, in: Chem. 1907, 40, 4580-4588; doi: 10.1002/cber.190704004106.
  • E. Abel: To Raschig synthesis of hydrazine, in: Monatsh. Chem 1956, 87, 164-175; doi: 10.1007/BF00903601.
  • Chemical- technical process
  • Name reaction
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