Method and system for producing nitrobenzene
AssigneeBayer Intellectual Property GmbH
InventorsBernd Pennemann, Juergen Munnig, Wulf Dietrich, Andreas Karl Rausch
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Abstract
The present invention relates to a process and a plant for the production, in particular the continuous production, of nitrobenzene by means of adiabatic nitration of benzene with nitric acid in the presence of sulfuric acid, in which, following the nitration, a multi-stage concentration of the sulfuric acid is carried out by means of heating at a pressure that is reduced as compared with ambient pressure, and wherein the heating takes place using the heat generated in the adiabatic nitration of benzene.
Claims7
A process for the production of nitrobenzene by means of adiabatic nitration of benzene with nitric acid in the presence of sulfuric acid, in which
- a) the product mixture obtained in the nitration is separated into spent acid and crude nitrobenzene and
- b) at least the water contained in the spent acid is partially separated from the sulfuric acid contained therein and
- c) the sulfuric acid so concentrated is fed to the nitration again,
- which process is characterised in that
- i) the separation according to step b) is carried out by evaporation in two stages with an absolute pressure that falls from the first stage to the second stage from 100 mbar to 300 mbar to 50 mbar to 150 mbar;
- ii) a proportion of at least 90% of the heat for the evaporation comes from the reaction enthalpy of the adiabatic nitration reaction and
- iii) the product mixture obtained in the nitration has a temperature of at least 110° C.
The process according to any one of the preceding claims, characterised in that the feed of spent acid to the first stage according to i) contains from 60 to 75% by mass H2SO4.
Dependencies are inferred from the claim text.