Bayer Materialscience Ag

Rob Eek

Michael Prein

Raymond Audenaert

Ulrich Blaschke

Christian Münnich

Gert Tytgat

Processes for producing bisphenols (e.g., bisphenol A (BPA)) having a purity greater than 99.7% are described, such processes including reacting a phenol and acetone in the presence of an acidic catalyst to form a product mixture comprising a bisphenol; removing at least a portion of the bisphenol from the product mixture in the form of a bisphenol/phenol adduct by crystallization, filtration and washing to provide bisphenol/phenol adduct crystals; and removing at least a portion of the phenol from the bisphenol/phenol adduct crystals to provide the bisphenol having a purity of more than 99.7%; wherein the crystallization comprises continuous suspension crystallization and is carried out in at least three crystallization devices arranged such that the product mixture is first cooled in a first stage of the crystallization to a temperature of 50 to 70&#xb0; C. in a first crystallization device and a second crystallization device connected in parallel, and subsequently cooled in a second stage of the crystallization to a temperature of 40 to 50&#xb0; C. in a third crystallization device connected downstream in series to the first and second crystallization devices, and wherein a total dwell time of the product mixture in the crystallization is more than 4 hours.

Crystallization processes for producing bisphenols

A continuous process for the separation of phenol is disclosed. The process includes (a) feeding a stream of material, produced while preparing bisphenol A by reacting phenol with acetone, into a distillation column containing at least 5 theoretical separation stages, b) distilling-off the phenol as a top product and discharging from the column a bottom product containing secondary components, c) continuously introducing a portion of the bottom product into a dwell-time container operating at process parameters sufficient to cause, in the presence of an acidic catalyst, at least partial isomerization of the secondary components to form an isomerized product and d) introducing the isomerized product to the distillation column. The introducing of the bottom product is at a rate that is more than 30% of the rate of feeding of the stream at temperatures greater than 190&#xb0; C. and hydrodynamic dwell time of at least 120 minutes.

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Hong Kong, China

Rob Eek