Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-08-20
2004-05-18
Shippen, Michael L. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06737551
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of producing bisphenol A [2,2-bis (4-hydroxyphenyl) propane]. More specifically, the present invention relates to a method of producing bisphenol A in which, in the production of bisphenol A from phenol and acetone with the use of a cation exchange resin as a catalyst and optionally a free mercaptan as a promoter, the degree of conversion of phenol is maintained by changing the reaction conditions with the deterioration of the catalyst, so that bisphenol A is effectively produced.
BACKGROUND OF THE INVENTION
Bisphenol A has been known as an important compound for raw material for engineering plastics, such as polycarbonate resins, polyacrylate resins, etc, or for epoxy resins, and the demand for it tends to be still more growing recently.
Bisphenol A is produced by the condensation of an excess of phenol and acetone in the presence of an acid catalyst and optionally a promoter, such as a sulfur compound, etc.
As the acid catalyst for that reaction, inorganic mineral acids, such as sulfuric acid, hydrochloric acid, etc. were conventionally used. However, cation exchange resins have recently attracted attention (GB Patent Nos. 842209, 849565 and 883391), and have come to be industrially used.
On the other hand, it has been known that as for sulfur compounds used as the promoter, alkyl mercaptans with or without substituting groups, such as methyl mercaptan, ethyl mercaptan, thioglycolic acid, etc., are useful (U.S. Pat. Nos. 2,359,242 and 2,775,620). The mercaptans function to increase the reaction rate and improve the selectivity. For example, as reaction by-products in the production of bisphenol A, 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl) propane (a combination of o- and p′-types) is mainly formed, and tris-phenol, polyphenol, etc. are also formed. Especially, in cases where bisphenol A is used as raw material for polycarbonate resins, polyacrylate resins, etc., required is colorless high purity bisphenol A containing a reduced amount of those by-products. To this end, mercaptans are used as a promoter in order not only to increase the reaction rate but also to suppress the formation of the by-products and increase the selectivity.
With respect to the reaction conditions (the temperature, the molar ration of acetone/phenol) at which phenol and acetone are condensed to produce bisphenol A, various considerations have been made. For example, Japanese Unexamined Patent Publication No. 54(1979)-19951 discloses a method in which the molar ratio between phenol and a carbonyl compound is set to be in the range of 10:1 to 30:1 and the reaction temperature is controlled to be in the range of 40-100° C.; Japanese Unexamined Patent Publication No. 54(1979)-19952 discloses a method in which the molar ratio between phenol and a carbonyl compound is set to be in the range of 3:1 to 50:1 and the reaction temperature is controlled to be in the range of 30-120° C.; and Japanese Patent Publication No. 63(1988)-52021 discloses a method in which an excess of phenol is used in an amount of moles four to ten times more than the mole(s) of acetone and the reaction is carried out at a temperature in the range of 40-100° C.
However, it is the fact that it has not heretofore been practiced to effectively change the reaction conditions with the deterioration of the cation exchange resin.
It has been known that the effect of the reaction temperature on the improvement in the degree of conversion of phenol is small in the reaction system in which the cation exchange resin is used as a catalyst and the mercaptan is used as a promoter. In addition, if one tries to deal with the deterioration of the catalyst through the reaction temperature, an undesirable situation results: specifically, rapid increase in the reaction temperature is inevitable. In this case, it is considered that elimination of sulfonic groups introduced in general cation exchange resins is promoted, which may adversely affect the quality of bisphenol A as the product.
Further, the reason why the degree of conversion of phenol is unlikely to be improved even if the reaction temperature is increased is deemed to be that in that system the diffusion of the raw material or the product within the gel structure of the cation exchange resin is the rate-determining factor of the reaction rate.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an industrially useful method of producing bisphenol A in which, in the production of bisphenol A from phenol and acetone with the use of a cation exchange resin as a catalyst and optionally a mercaptan as a promoter, the degree of conversion of phenol is maintained by changing the reaction conditions with the deterioration of the catalyst, so that bisphenol A is effectively produced.
The inventors of the present invention have found, through extensive studies to achieve the above-mentioned object, that the degree of conversion of phenol can be effectively maintained and elimination of sulfonic groups from the cation exchange resin can be suppressed by increasing the molar ratio of acetone/phenol by not more than 1/20 at one time with the deterioration of the catalyst, whereby the above object can be achieved. The present invention has been made based on the above finding.
Specifically, the present invention provides a method of producing bisphenol A in which, in the production of bisphenol A by condensation of phenol and acetone with the use of a cation exchange resin as a catalyst, the degree of conversion of phenol is maintained by increasing the molar ratio of acetone/phenol by not more than 1/20 at one time with the deterioration of the catalyst.
BEST MODE FOR CARRYING OUT THE INVENTION
The method according to the present invention is a method of producing bisphenol A in which phenol and acetone are condensed with the use of a cation exchange resin as a catalyst and optionally a free mercaptan as a promoter. There is no specific limitation with respect to the kind of the cation exchange resin to be used, and any of those which are conventionally employed as catalysts for the production of bisphenol A can be used. However, sulfonic acid type cation exchange resins are preferred especially in terms of the catalytic activity.
There is no specific limitation with respect to the kind of the sulfonic acid type cation exchange resins to be used inasmuch as they are strong acidic cation exchange resins having sulfonic groups. Examples of the sulfonic acid type cation exchange resin include sulfonated styrene-divinyl benzene copolymer, sulfonated cross-linked styrene polymer, phenol formaldehyde-sulfonic acid resin, benzene formaldehyde-sulfonic acid resin, etc. These may be used singly or in combination.
The free mercaptan as the promoter as used herein means a compound having a free form of SH group in the molecule. As the free mercaptan, an alkyl mercaptan can be adopted, which may be either of a non-substituted alkyl mercaptan and a substituted alkyl mercaptan having at least one substituting group, such as a carboxylic group, an amino group, a hydroxyl group, etc. Examples of non-substituted mercaptans include methyl mercaptan, ethyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, etc. Examples of the substituted alkyl mercaptan include mercaptocarboxylic acids such as thioglycolic acid, &bgr;-mercaptopropionic acid, etc., aminoalkane thiols such as 2-amino ethane thiol, 2,2-dimethyl thiazolidine, etc., mercaptoalcohols such as mercaptoethanol, etc. Among these, the non-substituted alkyl mercaptans are especially preferred in terms of the cocatalytic action. In addition, these mercaptans may be used singly or in combination.
The amount of each of these mercaptans is generally selected to be in the range of 0.1-20 mole %, preferably in the range of 1-10 mole %, relative to acetone, which is one of the raw materials to be used.
Further, there is no specific limitation with respect to the ratio of the amount between phenol and acetone, but it is desirable that the amount of unreacted acetone is as small as pos
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Shippen Michael L.
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