Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1992-04-07
1993-09-28
Lone, Werren B.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568722, 568728, C07C 3720
Patent
active
052488390
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for controlling reaction conditions and liquid transfer conditions in the preparation of bisphenol A by reacting phenol with acetone. More particularly, the invention relates to a preparation process of high-purity bisphenol A by controlling the reaction conditions in the reaction of phenol with acetone through the on-line estimation of a computer of the composition of the reaction mixture, the saturated solubility of bisphenol A and the slurry concentration of the adduct of bisphenol A with phenol (hereinafter refferred to as bisphenol A-phenol adduct) in the reactor, and further controlling the liquid transfer conditions of the resulting reaction mixture to the next step.
2. Description of the Related Art
There has been an increased demand for bisphenol as a material for engineering plastics in addition to polycarbonate resin and epoxy resin. Colorless and high purity bisphenol A is required for these uses.
In a process for preparing high purity bisphenol A, for example, phenol is reacted with acetone in the presence of an acid catalyst, and the reaction product is treated to remove the catalyst, water and a small amount of phenol. The residual liquid mixture is cooled to crystallize bisphenol A in the form of a phenol adduct, precipitated crystals are separated from the mother liquor, and phenol is removed from the bisphenol A adduct to recover bisphenol A.
Japanese Laid-Open Patent Hei 01-180843 has disclosed a process for reacting phenol and acetone in a continuous type reactor, completely reacting the reaction mixture which contains unreacted acetone in the presence of an hydrochloric acid catalyst in a batch type reactor so as to decrease unreacted acetone to substantially zero, and thereafter treating the reaction product in a purification step.
The process carries out the reaction to form minimum amounts of by-products and impurities, and makes a post-treatment step as simple as possible to prepare high-purity bisphenol A. However, no disclosure is found on the realtime analyzing and controlling method required for carrying out the process.
In cases of conducting the reaction through two steps composed of continuous and batch type reactors, an important and difficult technique is how to maintain the command on the reaction system which is continuously affected by the changing operational environment and disturbances.
As a practical problem, for example, when the reaction has progressed exceeding the set point in the first step in the continuous type reactor, bisphenol A-phenol adduct crystallizes in said reactor and it becomes difficult to transfer the reaction mixture to the second step in the batch type reactor. Further, when the heat of reaction is removed by an external heat exchanger, crystals of said adduct severely decrease the heat transfer efficiency of the heat exchanger and therefore increase the reaction temperature. As a result, by-products and impurities are formed in large amounts, which increased, lead to separation cost for these substances in the post treatment step, and result in a decrease of the purity of the product bisphenol A. In the worst case, operation of the whole production steps must be stopped.
On the other hand, when the set point in the first step reaction is low in order to avoid the above problems, the reaction time in the batch type reactor of the second step increases, requires scale up of said reactor and leads to a severe reduction of production efficiency. In order to solve these problems, it is important to prescribe suitable set points and to carry out rapid and adequate control on the rate of reaction so as to always coincide practical operating conditions with the set points.
In order to conduct adequate control, it is required to know the reaction rate in every second within a short time. The rate of reaction is affected by various factors such as the raw materials phenol and acetone, catalyst hydrochloric acid, formed bisphenol A and water, by-products and
REFERENCES:
patent: 2730553 (1956-01-01), Williamson
patent: 4935553 (1990-06-01), Iimuro et al.
patent: 4946877 (1990-08-01), Iimuro et al.
patent: 4954661 (1990-09-01), Iimuro et al.
Houri Toshio
Iimuro Shigeru
Kawamura Tsuguo
Ohmura Kenichi
Yamada Akira
Lone Werren B.
Mitsui Toatsu Chemicals Inc.
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