PURPOSE: To obtain 4,4'-diphenyldisulfonic acid as dipotassium salt and at the same time separate the by-produced potassium sulfite, and to enable the repeated use of excess caustic potash, by carrying out the alkali fusion of 4,4'-diphenyldisulfonic acid adjusting the concentration of the caustic potash twice.
CONSTITUTION: 4,4'-Diphenyldisulfonic acid is subjected to the alkalifusion with caustic potash, and the reaction mixture is mixed with water to adjust the caustic potash concentration to 20W25%. The precipitated crystalline dipotassium salt of 4,4'-dihydroxydiphenyl (DHDP) is separated from the filtrate, and the filtrate is concentrated to a caustic potash concnetration of 40W60%. The precipitated potassium sulfite is separated from the aqueous solution of caustic potash. DHDP dipotassium salt is neutralized with an acid and treated with activated charcoal in a solvent to obtain high purity DHDP having an inorganic salt content of ≤100ppm. Since the separated caustic potash solution is 40W60% in concentration, it can be used repeatedly only by treating with activated charcoal.
| JPH10265422 | PRODUCTION OF HYDROXYNAPHTHALENE |
| JPH04145038 | PRODUCTION OF NAPHTHOL |
| JPS5756435 | PREPARATION OF BETA-NAPHTHOL |
HASHIMOTO TAKESHI
SATOU KATSUHIKO
NISHIHARA KOUJI
