Patent ID: 7371902

Claim:
A method for purifying p,p-bisphenol A, said method comprising: distilling a feedstream comprising p,p-bisphenol A in a distillation column at a pressure less than or equal to 20 millibars; producing a light fraction, an intermediate fraction, and a heavy fraction from the distillation column; feeding the heavy fraction to a second reactor and isomerizing impurities in the heavy fraction to produce additional p,p-bisphenol A; feeding a portion of the light fraction to a first reactor and purging a remaining portion of the light fraction in a third reactor, wherein feeding the portion to the first reactor converts impurities in the light fraction to produce additional p,p-bisphenol A, and wherein feeding the remaining portion to the third reactor removes impurities from the remaining portion; and recovering the intermediate fraction as a side draw of the distillation column, wherein the p,p-bisphenol A in the intermediate fraction contains less impurities than the p,p-bisphenol A in the feedstream.