Method for continuous production of nitrobenzene
The invention relates to a method for producing nitrobenzene, in which crude nitrobenzene is first produced by nitrating benzene and said crude nitrobenzene is then washed in succession in at least one acid wash, in at least one alkaline wash and in at least one neutral wash, at least one additional wash with an aqueous solution of a potassium salt being interposed between the last alkaline wash and the first neutral wash.
1. A method for producing nitrobenzene by comprising:
a) nitrating benzene with nitric acid or a mixture of nitric acid and sulfuric acid and subsequently phase separating into an aqueous phase and an organic phase containing nitrobenzene,
b) washing the organic nitrobenzene containing phase obtained in step a) in at least one wash and subsequently phase separating into an aqueous phase and an organic phase containing nitrobenzene,
c) washing the organic nitrobenzene-containing phase obtained in step b) in at least one alkaline wash with an aqueous solution of a base selected from the group consisting of
sodium hydroxide, sodium carbonate and sodium hydrogen carbonate,
and subsequently phase separating into an aqueous phase and an organic phase containing nitrobenzene,
d) washing the organic nitrobenzene-containing phase obtained in step c) in at least one wash with an aqueous solution of a potassium salt and subsequently phase separating into an aqueous phase and an organic phase containing nitrobenzene,
e) washing the organic nitrobenzene-containing phase obtained in step d) in at least one neutral wash with water subsequently phase separating into an aqueous phase and an organic phase containing nitrobenzene,
f) processing the organic nitrobenzene-containing phase obtained in step e) to obtain purified nitrobenzene.
2. The method according to claim 1 , wherein in step c) and aqueous solution of sodium hydroxide is used.
3. The method according to claim 1 , wherein in step d) a molar ratio of potassium to sodium ions of 1:1 to 20:1 is maintained.
4. The method according to claim 1 , wherein step e) electrophoresis is used in the last neutral wash.
5. The method according to claim 1 , wherein the potassium salt used in step d) is selected from the group consisting of potassium hydroxide, potassium sulfate, potassium carbonate and potassium nitrate.
6. The method according to claim 5 , wherein the potassium salt used in step d) is potassium hydroxide.
7. The method according to claim 5 , wherein the potassium salt used in step d) is potassium sulfate.
8. A method comprising producing nitrobenzene by the method according to claim 1 , and subsequently hydrogenating said nitrobenzene in the presence of a catalyst to produce aniline.
9. The method according to claim 8 , wherein a multi-component catalyst containing at least palladium, vanadium, and lead as active components on a support, on a-aluminum oxide is used as catalyst.
10. The method according to claim 9 , wherein the same catalyst is used only for as long as a conversion of nitrobenzene of greater than or equal to 99.7% is achieved in a production cycle for at least some of the time.
11. The method according to claim 10 , wherein the catalyst that is no longer used is processed in a manner such that the active components are at least partly recovered and used in the production of new catalyst.