Method and system for producing nitrobenzene
AssigneeBayer Intellectual Property GmbH
InventorsBernd Pennemann, Juergen Munnig, Wulf Dietrich, Andreas Karl Rausch
Life of this patent
Estimating the term…
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.
Claims10
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) the heat used for the evaporation according to step i) comes substantially from the reaction enthalpy of the nitration and
- iii) the product mixture obtained in the nitration has a temperature of at least 110° C.
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.
Process according to any one of the preceding claims, characterised in that the steam separated in each stage according to i) is liquefied by condensation.
Process according to any one of the preceding claims, characterised in that the concentrated sulfuric acid according to step c), after passing through both stages of step i), has a content by mass of H2SO4 of not less than 65%.
Plant for the production of nitrobenzene, comprising a reactor (1), a phase separator (2), two evaporator and condensation devices connected to vacuum installations (7, 9), and optionally a storage container (5)
- characterised in that
- the plant has a first evaporator (3) with an associated first condenser (8) and a connected vacuum installation (9) and a second evaporator (4) with an associated second condenser (6) and a connected vacuum installation (7), and wherein the first evaporator (3) is connected directly to the second evaporator (4) for the transfer of components that have not been evaporated, and wherein further the heat exchange surface of the first condenser (8) is less than or equal to twice the heat exchange surface of the second condenser (6).
Dependencies are inferred from the claim text.