| abstract |
The present invention relates to a process for the preparation of 1-aminonaphthalene-3,6,8-trisulfonic acid (Koch's acid, T-acid) as a salt by hydrogenation of an aqueous solution of salts of 8-nitronaphthalene-3,6,8-trisulfonic acid in Presence of one or more sulfides and metals cobalt, nickel, iron, rhenium, platinum, molybdenum, ruthenium and / or palladium at a pH of 7.5-12, at temperatures from 30 to 150 ° C and at 5 to 150 bar hydrogen pressure. The process has the advantage that the catalyst can be separated off well, the resulting mixtures can be worked up well, the hydrogenation proceeds with good yields and selectivities and there is virtually no elimination of sulfonic acid groups. |