Abstract: In a semicontinuous method for manufacturing bisphenols, reduced fouling in the pre-reactor is achieved by using two or more prereactors are used to continuously condense the dihydric phenol and the ketone or aldehyde to produce a partial reaction product in which the reaction of the dihydric phenol and the ketone or aldehyde is 10 to 70% complete. This partial reaction product is continuously removed from the pre-reactors, combined and introduced to a batchwise completion reactor. A stream of water or aqueous hydrochloric acid is added in alternating intervals to the pre-reactors, such that one is being cleaned by shifting the solubility of the bisphenol product at the same time that the other(s) continue to product a normal product stream which includes seed crystals for enhancing the performance of the batchwise completion reactor.

Abstract: An alternative and improved method for cleaning cooling and/or crystallization surfaces of a crystallizer fouled with a crystallized bisphenol as a result of processing a slurry derived from the production of bisphenol is provided. The method includes the steps of: (a) draining from 20 to 80%, and preferably about 50% of the slurry from the crystallizer; (b) replacing the drained slurry with a solvent comprising phenol, thereby forming a diluted slurry; (c) increasing the temperature in the crystallizer to a temperature at which the crystallized bisphenol is dissolved in the diluted slurry, and then rapidly cooling the diluted slurry to a temperature of 45 to 55° C.; and (d) adding a seed slurry containing solid bisphenol at a concentration of 5 to 30%. The seed slurry has a temperature of 45 to 55° C. and is added until conditions are established at which bisphenol crystals added to the crystallizer do not redissolve.