PROCESS FOR THE PREPARATION OF 1-NAPHTHYLAMINE-4,6-DISULFONIC ACID AND 1-NAPHTHYLAMINE-2,4,6-TRISULFONIC ACID

摘要

Improved process for the preparation of 1-naphthylamine-4,6-disulphonic acid wherein the sulphonation of the 1-naphthylamine-6-sulphonic acid is carried out by adding the oleum at a temperature of 10 DEG to 70 DEG C., either to initially introduce sulphuric acid simultaneously with the 1-naphthylamine-6-sulphonic acid or to 1-naphthylamine-6-sulphonic acid, which is dissolved or suspended in sulphuric acid, and by using such a molar ratio of sulphur trioxide to 1-naphthylamine-6-sulphonic acid that 1.2 to 3 mols of sulphur trioxide are present per mol of 1-naphthylamine-6-sulphonic acid. The sulphonation mixture formed in the preparation can be sulphonated in a second sulphonation stage to 1-naphthylamine-2,4,6-trisulphonic acid.