Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-02-23
2002-10-01
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S806000
Reexamination Certificate
active
06459004
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cleavage method of bisphenols. More specifically, the invention relates to a cleavage method of bisphenols capable of producing cleavage products made of isopropenylphenol and phenol as main constituents at high purity by cleaving a mixture containing bisphenols and impurities such as chroman derivatives and flavan derivatives formed as by-products in the production process of bisphenols.
The cleavage product obtained by the method of the invention contains isopropenylphenol and phenol together with small amounts of impurities. Usually, the product is circulated to a production step of bisphenols as it is and then reproduced to bisphenols. The invention is preferably applied to the cleavage of a mixture containing bisphenol A and impurities formed as by-products in the production process of bisphenol A, such as chroman derivatives and flavan derivatives.
2. Description of the Related Art
It is known that, when bisphenol A or a bisphenol A-containing compound is heated in the presence of a catalyst, a cleavage reaction proceeds to form phenol, 4-isopropenylphenol, and 4-isopropenylphenol polymers, etc.
Usually, the cleavage reaction is carried out in the presence of a basic catalyst or an acidic catalyst at a high temperature of from 150 to 260° C. under a reduced pressure condition (for example, Japanese Patent Laid-Open Nos. 27108/1980 and 148441/1987).
4-Isopropenylphenol has a very high reactivity, and particularly, in the case where it is in a liquid state, the polymerization occurs quickly to cause lowering of the cleavage yield. Accordingly, in the conventional technology, the cleavage product made of 4-isopropenylphenol and phenol as major components is distilled out in a vapor state from a reaction vessel, and operations such as distillation for purification are not carried out. For this reason, various kinds of impurities contained in cleavage raw materials and/or formed as by-products during the cleavage reaction are incorporated in the cleavage distillate to cause lowering of the purity of the cleavage product.
Usually, a cleavage reaction product is circulated to a production step of bisphenol A as it is and then reproduced to bisphenol A. For this reason, when the cleavage reaction product contains a large amount of impurities, it causes lowering of the purity of bisphenol A produced. Also, it causes lowering of the production efficiency of bisphenol A. Isopropenylphenol is a very unstable substance, and generally, it has been said that in the distillation for purification, the yield of isopropenylphenol is lowered, and the distillation column is clogged by a dimer of isopropenylphenol, etc. formed as by-products. For this reason, in the conventional technology, the distillation for purification is not carried out, and the cleavage reaction product is used for the above-described utilization as it is.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, the invention has been made, and an object of the invention is to provide a cleavage method of bisphenols capable of yielding a product containing high-purity isopropenylphenol and phenol.
As the result of various investigations, the present inventors have found that by supplying a cleavage reaction product in a vapor state to a distillation column and carrying out a cleavage reaction of bisphenols while distilling at a specific reflux ratio without disposing a heating source such as a reboiler in a distillation step, the above-described object can be attained, leading to accomplishment of the invention.
Specifically, the invention is to provide a cleavage method of bisphenols for producing a product containing isopropenylphenol and phenol by cleaving a mixture containing bisphenols together with chroman derivatives and flavan derivatives formed as by-products in the production process of bisphenols, which comprises
(1) a cleavage step of supplying the mixture containing bisphenols together with chroman derivatives and flavan derivatives formed as by-products in the production process of bisphenols to a cleaving vessel and carrying out a cleavage reaction in the presence of a basic or acidic catalyst at a temperature of from 150 to 260° C. under a reduced pressure condition of not higher than 300 mmHg,
(2) a distillation step of supplying the cleavage step product in a vapor state in the cleavage step to a distillation column and distilling at a temperature of from 130 to 200° C. and under a reduced pressure condition of not higher than 300 mmHg, and
(3) a reflux step of condensing the distillate formed in the distillation step, refluxing a part thereof to the distillation step at a reflux ratio of from 0.01 to 3, and discharging out the rests from the system.
The feature of the invention resides in that in the above-described constructions, particularly, the cleavage reaction product is supplied in a vapor state to a distillation column, and the cleavage reaction of bisphenols is carried out while distilling at a specific reflux ratio without disposing a heating source such as a reboiler to the distillation step. In addition, as preferred embodiments of the invention, there are included the above-described cleavage method of returning the bottom liquid of the distillation step to the cleavage step; the above-described cleavage method by side cutting at least 1% by weight of the reflux liquid of the distillation column and discharging out the reflux liquid from the system; the above-described cleavage method of introducing the distillate (reflux residue) of the reflux step to the bisphenol production step and recovering, etc. A method to which the invention is preferably applied is the cleavage method of the mixture containing bisphenol A together with impurities formed as by-products in the production process of bisphenols A, such as chroman derivatives and flavan derivatives.
According to the invention, because the cleavage reaction product is supplied in a vapor state to the distillation column, the occurrence of polymerization of highly reactive isopropenylphenol is prevented, whereby the formation of oligomers such as dimers and trimers can be restrained. Accordingly, it is possible to yield high-purity phenol and isopropenylphenol, and further, even when the distillate (reflux residue) of the reflux step is circulated to, for example, the production step of bisphenol A, etc., the quality of the bisphenol A as the product is not lowered, resulting in rather improving the purity and reducing the production cost.
DETAILED DESCRIPTION OF THE INVENTION
The invention is described below in detail.
The invention relates to a cleavage method of bisphenols by supplying a mixture containing bisphenols and impurities formed as by-products in the production process of bisphenols, such as chroman derivatives and flavan derivatives, to a cleaving vessel to cleave the mixture, supplying the cleavage product in a vapor state to the distillation column, and distilling the product while refluxing at a specific reflux ratio to produce a product containing isopropenylphenol and phenol.
As the cleavage reaction raw materials in the invention, a mixture containing bisphenols such as bisphenol A and bisphenol F and impurities formed as by-products in the production process of the bisphenols, such as chroman derivatives and flavan derivatives. Examples include an effluent from the distillation column of bisphenol A obtained in the production step of bisphenol A and a crystallization mother liquor of bisphenol A from which phenol has been removed. Hereinafter, these are generally called “bisphenols”.
The cleavage reaction method of the invention is a method of obtaining a cleavage reaction product made of 4-isopropenylphenol and phenol as major components by cleaving bisphenols, and generally, the cleavage reaction is carried out in the presence of a basic catalyst or an acidic catalyst at a temperature of from 150 to 260° C. under a reduced pressure of not higher than 300 mmHg. Also, in order to improve the yield, bubbling of a
Mizuma Kiyoshi
Ono Yuzo
Shibasaki Mikio
Terada Kouichirou
Burns Doane Swecker & Mathis L.L.P.
Mitsui Chemicals Inc.
Shippen Michael L.
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