Method and catalyst for making bisphenol

In a method of making bisphenol, based on the reaction between a ketone and a phenol in the presence of an effective amount of a sulfonated polystyrene cation-exchange resin in acid form modified by the neutralization of 5-25% of a cation-exchange capacity with a promoter in the form of a C.sub.2 -C.sub.4 alkyl mercapto amine whereby the promoter is incorporated onto the cation-exchange resin backbone by an acid-amine salt ionic bond which is susceptible to excessive loss from the cation-exchange resin due to leaching as the result of the degradation of the acid-amine salt ionic bond during the use of the ion-exchange resin in phenol-ketone condensation reaction, the improvement which comprises utilizing as the cation-exchange resin, a sulfonated polystyrene having 5-25% of its cation-exchange capacity occupied by an organo mercapto amine covalently bonded to the cation-exchange backbone by nitrogen sulfur linkages.