Combination ion exchange resin bed for the synthesis of bisphenol A

In an ion exchange bed for producing bisphenol A from phenol and acetone in a fixed bed reactor containing a gel-form or macroporous sulfonic acid ion exchange resin catalyst bed, the improvement comprising a resin catalyst bed having an upper layer and a lower layer wherein:

• the lower layer comprises a resin which has a higher degree of crosslinking than the upper layer and which comprises 50 to 95% of the bed volume as a whole and
• the upper layer of the bed, which comprises 5 to 50% of the bed volume as a whole, comprises either
• an unmodified resin having a low degree of crosslinking or
• a resin having a low degree of crosslinking in which 1 to 35 mol % of the sulfonic acid groups are covered with species containing alkyl-SH groups by ionic fixing.