Process for preparing a bisphenol

A process of preparing a bisphenol comprising the steps of:

• a) reacting a phenolic compound selected from the group consisting of phenol, cresols, xylenols, chlorophenols, thymol, carvacrol, cumenol, 2-methyl-6-ethylphenol, 2,4-dimethyl-3-ethylphenol, 4-ethylphenol, 2-ethyl-4-methylphenol, 2,3,6-trimethylphenol, 2-methyl-4-tertiary-butylphenol, 2,4-ditertiary-butyl-phenol, 4-methyl-2-tertiary-butylphenol, 2-teritary-butyl-4-methylphenol, 2,3,5,6-tetramethylphenol, 2,6-dimethylphenol, 2,6- ditertiary-butylphenol, 3,5-dimethylphenol, 3,5-diethylphenol, 2-methyl-3,5-diethylphenol, o-phenylphenol, p-phenylphenol, tetraphenolethane, the naphthols and phenanthrol with a carbonyl compound having the formula:
• ##STR3## wherein R.sub.1 is selected from the group consisting of aliphatic, cycloaliphatic and aromatic radicals, and R.sub.2 is selected from the group consisting of aliphatic, cycloaliphatic, aromatic radicals and hydrogen in a reaction mixture, containing said carbonyl compound, a stoichiometric excess of said phenolic compound and a strongly acidic ion exchange resin catalyst, to produce a product mixture containing a bisphenol;
• b) separating bisphenol from the product mixture to leave a motor liquor;
• and
• c) recycling at least a portion of the mother liquor to the reaction mixture,
• wherein at least one of the following steps is conducted:
• i) at least a portion of the phenolic compound is contacted with a strongly acidic cation exchange resin and a strongly basic anion exchange resin before the phenolic compound is used in reaction step a);
• ii) at least a portion of the product mixture is contacted with a strongly acidic cation exchange resin and a strongly basic anion exchange resin before mother liquor is recycled to the reaction mixture;
• or
• iii) at least a portion of the mother liquor is contacted with a strongly acidic cation exchange resin and a strongly basic anion exchange resin before mother liquor is recycled to the reaction mixture.