To a 500mL stainless steel autoclave equipped with a stirrer, gas introduction valve, thermocouple, manometer and siphon tube was added 75.2 g (0.80 mol) of molten phenol and cooled in an ice bath. When the internal temperature dropped below 10°C, an appropriate amount (12.05 mol) of HF was added, followed by 106.3 g (0.64 mol) of hexafluoroacetone (HFA) (the molar ratio of HFA to phenol was 0.8 and the molar ratio of HF to phenol was 15). The autoclave was sealed, stirred and heated up to 100 °C, and the reaction was maintained at this temperature for 2 hours. Upon completion of the reaction, analysis showed 96.2% of the target product 2,2-bis(4-hydroxyphenyl)hexafluoropropane (bisphenol AF) in the reaction solution (organic phase), with the remaining components being 0.1% phenol, 0.1% intermediate 2-(4-hydroxyphenyl)hexafluoropropan-2-ol, 2.9% intermediate isomer 2-(2-hydroxyphenyl)hexafluoropropan-2-ol, 0.4% bisphenol AF isomer, 0.2% HFA adduct of bisphenol AF and 0.1% other impurities. After the reaction, the autoclave was cooled to below 30 °C in an ice bath, and 388.4 g of the reaction solution was transferred to a HFA/HF recovery tower condenser pre-cooled to -15 °C using nitrogen pressure through a pipe connecting the outlet of the autoclave siphon and the bottom liquid transfer valve (capacity: 500 mL) to prevent the escape of HFA and HF. After the transfer was complete, the autoclave was removed and the bottom of the recovery tower was heated with a 40°C oil bath. After about 20 minutes, full reflux of the HFA/HF mixture was started, at which time the temperature at the bottom was 25.2°C and the temperature at the top of the tower was 16.9°C. After 30 minutes of full reflux, extraction was started at a reflux ratio (reflux:distillation = 10 s:5 s), keeping the temperature at the top of the tower below 20 °C. During extraction, the oil bath temperature was increased to 50°C at a rate of 5°C/30 min. When the bottom temperature reached 42°C, HFA/HF recovery was stopped, the extraction was completed, the oil bath was removed, and the bottom was cooled to below 20°C in an ice bath. After cooling, the bottom residue was transferred by nitrogen pressure to a polyethylene vessel containing 900 g of water to precipitate the solids. The precipitate was filtered and washed twice with about 450 g of water to give bisphenol AF with a purity of 99.1%.After drying, the yield of bisphenol AF was 95.0%. The recovered distillate weighed 179.0 g and was analyzed to show the presence of 147.8 g of HF and 32.3 g of HFA, with 66.7% recovery of HF and 84.8% recovery of HFA based on the initial addition. The COD value of the wash water was determined to be 9413 mg/L according to JIS K 0102.
