Process for the preparation of isolated 3,4-diaminobenzenesulphonic acid
AssigneeBayer Chemicals AG
InventorsGünter Rauchschwalbe, Herbert Emde, Wolfram Kissener
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Abstract
Described herein is a process for the preparation of 3,4-diaminobenzenesulphonic acid, characterized in that 1,2-diaminobenzene is reacted with anhydrous sulphuric acid which optionally comprises SO3 in up to stoichiometric amount, at a temperature in the range from 100 to 160° C. with stirring for a reaction time of from 1 to 20 hours; water or ice is added to the reaction mixture, optionally with cooling, up to a sulphuric acid concentration in the range from 30 to 75% by weight, based on the total mixture; the 3,4-diaminobenzenesulphonic acid precipitated out of the reaction mixture is filtered off, optionally washed with dilute sulphuric acid and worked up.
Claims5
Process for the preparation of 3,4-diaminobenzenesulphonic acid, comprising reacting
- a) 1,2-diaminobenzene with anhydrous sulphuric acid which optionally comprises SO3 in up to stoichiometric amount, at a temperature in the range from 100 to 160° C. with stirring for a reaction time of from 1 to 20 hours,
- b) adding water or ice to the reaction mixture, optionally with cooling, up to a sulphuric acid concentration in the range from 30 to 75% by weight, based on the total mixture,
- c) filtering off the 3,4-diaminobenzenesulphonic acid precipitated out of the reaction mixture, optionally washing it with dilute sulphuric acid, and work-up.
Dependencies are inferred from the claim text.