Published January 1998
SINOPEC Technology Company (STC) of China has developed a new technology for producing bisphenol A (BPA) from phenol and acetone. ABB Lummus Global of USA offers that technology for sale under license from STC. The new process employs a catalytic stripping reactor and a highly selective catalyst that make the process simpler and more economical than existing production technologies. The reactor consists of a column containing multiple catalyst beds supported on perforated trays. The catalyst is kept in suspension in the reaction mixture by an inert gas stream that also strips water formed in the reaction, resulting in increased equilibrium conversion. The net result is that material recycles and, hence, process equipment size is reduced making the process more economical. This Review presents a preliminary evaluation of the technology and a design for producing BPA of ultrahigh purity, as well as a polycarbonate grade. We have primarily derived the design bases from patents assigned to China Petrochemical Corporation, and from nonconfidential disclosures by ABB Lummus. We highlight areas in which our process differs from the STC-Lummus process.
Our version of the ultrahigh-purity process consists of five stages. In the first stage, acetone and phenol are reacted in a catalytic stripping column reactor with multiple beds of sulfonated polystyrene divinylbenzene copolymer resin. Nitrogen gas, flowing countercurrently from the bottom of the column, strips off water formed in the reaction along with some acetone and phenol. The effluent gas is cooled, and the acetone and phenol are recovered after condensation. In the second stage, the condensation products—unreacted phenol, BPA, and BPA isomers—are cooled to precipitate phenol-BPA adduct crystals, which are separated in a centrifuge. The crystals are melted and then dephenolized under vacuum in distillation columns. In the third stage, phenol is recovered from the mother liquor in a concentrator and recycled. The mother liquor, containing BPA and its isomers with some residual phenol, is cooled in a secondary crystallizer to precipitate additional BPA. In the fourth stage, the isomer-rich liquor is sent to the cracking and rearrangement reactor where most of the isomers are converted to BPA and tarry products; the tars are eliminated from the process. In the final stage, the BPA is further purified by recrystallizing it in toluene, with subsequent centrifugation and drying of the crystals to obtain a BPA of ultrahigh purity.
Our review is based on a 180 million lb/yr (82,000 t/yr) plant. We have evaluated the technology both for polycarbonate-grade BPA and ultrahigh-purity BPA. Our estimates indicate that the Sinopec-Lummus process has lower capital investment and production costs than other BPA production technologies. We present process economics for the two process types in the cost estimates section.
