Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-10-30
2004-04-27
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06727394
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an improved process for producing bisphenol A {2, 2-bis(4-hydroxyphenyl)propane}. More particularly, it pertains to a process for efficiently producing bisphenol A having favorable hue as the objective product from phenol and acetone through a continuous multi-stage fixed-bed reaction system in the presence of a cation exchange resin as a catalyst, while maintaining the feed rate of acetone at a relatively low level.
BACKGROUND ART
It is well-known that bisphenol A is an important compound as a starting raw material for epoxy resin or an engineering plastic such as polycarbonate resin and polyarylene resin, and accordingly it tends to increasingly expand its demand year by year.
Bisphenol A is produced by the condensation reaction of excess phenol with acetone in the presence of an acidic catalyst and as the case may be, a sulfur compound as a cocatalyst.
There has heretofore been employed an inorganic mineral acid such as sulfuric acid and hydrogen chloride as an acid catalyst to be used in the reaction. In recent years, however, attention has been paid to cationic exchange resins, which have been brought into industrial applications (refer to UK Patent GB 842209, 849565 and 883391).
On the other hand, it is known that useful sulfur compounds to be used as a cocatalyst include alkyl mercaptans with or without a substituent group such as methyl mercaptan, ethyl mercaptan and thioglycol acid (refer to U.S. Pat. Nos. 2,359,242 and 2,775,620). The mercaptans have a function of increasing the rate of reaction and at the same time, enhancing the selectivity. For instance, in the production of bisphenol A, there are formed as a reaction by-product, 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)-propane (o, p′-isomers) as a principal component and in addition thereto, trisphenol and polyphenol. In particular, bisphenol A, when being employed as a starting raw material for polycarbonate resin or polyarylene, is required to be minimized in contents of the above-mentioned by-products, highly pure and free from coloration. As such, the mercaptans are employed to increase the rate of reaction, suppress the formation of the by-products, and enhance the selectivity.
In the case of industrially producing bisphenol A by subjecting phenol and acetone to condensation reaction, there is generally adopted a continuous multi-stage fixed-bed reaction system composed of at least two reactors that are connected in series and each filled in with the aforesaid cation exchange resin as a catalyst.
In such a reaction system, the deterioration of catalyst becomes more serious towards a precedent stage reactor from a succedent stage reactor. As such in the case of replacing the most seriously deteriorated catalyst with a fresh catalyst, when the fresh catalyst is brought in the place of catalyst to be replaced therewith, namely the most precedent stage reactor in the reaction system, there is brought about unfavorable circumstances in that the catalyst as a whole is not effectively utilized, thus lowering the yield of bisphenol A throughout the reactors, whereby deterioration of the catalyst is unfavorably accelerated thereby. In such circumstances, an attempt is made to locate a reactor which is filled inside with a fresh or regenerated cation exchange resin on the most downstream side in the reaction system in replacing the most seriously deteriorated catalyst with the fresh or regenerated catalyst {(refer to Japanese Patent Application Laid-Open No.25042/1994 (Heisei 6)).
Nevertheless, the above-mentioned technique is intended to effectively exhaust the catalyst and thus, further contrivance is necessary in order to maintain the quality of bisphenol A as the objective product. That is to say, when the catalyst becomes deteriorated, the feed rate of acetone is increased to maintain the production (to maintain the conversion of phenol), but in this case there is caused such a problem as an increase in the formation of impurities that are unfavorable for the hue of bisphenol A as the objective product.
On the other hand, there is known a method in which acetone is separately supplied to each of the reactors located in series {(refer to Japanese Patent Application Laid-Open No.19952/1979 (Showa 54)).
DISCLOSURE OF THE INVENTION
Under such circumstances, it is a general object of the present invention to provide a process for efficiently producing bisphenol A having favorable hue as the product from phenol and acetone through a continuous multi-stage fixed-bed reaction system in the presence of a cation exchange resin as a catalyst, while maintaining the feed rate of acetone at a relatively low level.
Other objects of the present invention will become obvious from the text of the specification hereinafter disclosed.
In such circumstances, intensive extensive research and investigation were accumulated by the present inventors in order to achieve the above-mentioned objects. As a result, it has been found that the objects of the present invention can be achieved by separately supplying acetone to each of the reactors in a continuous multi-stage fixed-bed reaction system, arranging a reactor which is filled inside with a fresh or regenerated cation exchange resin on the final stage in the reaction system in replacing the most seriously deteriorated cation exchange resin in catalytic activity with the fresh or regenerated cation exchange resin, and operating the reactor on the final stage so that the ratio of feed rate to the consumption rate for acetone falls within a prescribed range. The present invention has been accomplished on the basis of the foregoing findings and information.
Specifically, the present invention provides a process for producing bisphenol A by continuously supplying phenol to a first-stage reactor in a continuous multi-stage fixed-bed reaction system composed of at least two reactors that are connected in series and each filled in with a cation exchange resin as a catalyst and at the same time, continuously supplying acetone separately to each of the reactors, characterized by arranging a reactor which is filled inside with a fresh or regenerated cation exchange resin on the final stage of the reaction system in replacing the most seriously deteriorated cation exchange resin in catalytic activity with the fresh or regenerated cation exchange resin, and operating the final stage reactor so that the ratio R of the feed rate of acetone to the consumption rate thereof falls within the range of more than one to less than 3.
BEST MODE FOR PRACTICING THE INVENTION
The process according to the present invention is that for producing bisphenol A by subjecting phenol and acetone to condensation reaction through a continuous multi-stage fixed-bed reaction system using a cation exchange resin as a catalyst. The aforesaid cation exchange resin is not specifically limited, but can be selected for use from the cation exchange resins that have hitherto been customarily used as a catalyst for producing bisphenol A. Thus from the viewpoint of catalytic activity and the like, sulfonic acid type cation exchange resin is suitable in particular.
The foregoing sulfonic acid type cation exchange resin is not specifically limited provided that it is a strongly acidic cation exchange resin bearing a sulfonic acid group, but is exemplified by sulfonated styrene/divinyl benzene copolymer, sulfonated and crosslinked styrene polymer, phenol formaldehyde/sulfonic acid resin and benzene formaldehyde/sulfonic acid resin and the like. Any of the exchange resins may be used alone or in combination with at least one other.
In the condensation reaction, mercaptans are usable as a cocatalyst as necessary. The mercaptans, which are the compounds bearing at least one SH group in a free form in a molecule, can be selected for use from alkyl mercaptans and alkyl mercaptans which have at least one substituent such as carboxyl group, amino group and hydroxyl group and which are exemplified by mercaptocarboxylic acid, aminoalkanethiol and mercaptoalcohol. Specific
Idemitsu Petrochemical Co. Ltd.
Shippen Michael L.
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