5397-34-2

108-95-2

80-09-1

5397-34-2

Under stirring conditions, 100 g (1.0 mol) of sulfuric acid at a concentration of 98% was slowly added dropwise to a mixed system containing 144 g of homotrimethylbenzene, 189 g (2.0 mol) of phenol and 11.9 g (0.05 mol) of benzene-1,3-disulfonic acid. The reaction mixture was heated in an oil bath at 200°C. As the temperature approached 145°C, the reaction mixture began to boil. The distillate was condensed by means of a condenser and separated into two phases by means of a trap. The upper organic phase is continuously returned to the reaction system. The distillation process continues for 5 hours before the temperature of the reaction mixture reaches 165°C, at which point the volume of the lower aqueous phase separated by the trap stabilizes at 38 ml. Crystals precipitated out of the reaction system and formed a slurry. A small amount of the reaction slurry was taken and analyzed by high performance liquid chromatography (HPLC), which showed that the weight ratios of 4,4'-bisphenol S (4,4'-BS), 2,4'-dihydroxydiphenylsulfone (2,4'-BS), and trihydroxytriphenyl disulfone were 96.0%, 3.0%, and 1.0%, respectively. Subsequently, 237 g of crystal product was obtained according to the same post-treatment method as in Example 1. The composition (weight ratio) of this crystal product was 4,4'-BS / 2,4'-BS / trihydroxytriphenyl disulfone = 99.5 / 0.5 / 0. The yield of 4,4'-BS was 94% based on starting sulfuric acid. No sulfonic acids were detected in the crystalline product, which consisted mainly of benzene-1,3-disulfonic acid and phenolsulfonic acid.