Process for producing bisphenol a

Details Process for producing bisphenol a Process for producing bisphenol a

2001-08-21

2002-08-06

Shippen, Michael L. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S727000

Reexamination Certificate

active

06429343

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for producing bisphenol A at a high yield per unit quantity of catalyst wherein an acid-type ion exchange resin as the catalyst which is partially modified with a sulfur-containing amine compound, exhibits a prolonged life. The thus produced bisphenol A is useful as raw materials of polycarbonate resins, epoxy resins, polyarylate resins and the like.
BACKGROUND ARTS
As well known in the arts, bisphenol A [2,2-bis(4-hydroxyphenyl) propane] is an important compound useful as raw materials of engineering plastics such as polycarbonate resins and polyarylate resins, or epoxy resins. Recently, the demand for the above compound tends to be more and more increased.
It is also known that bisphenol A is produced by reacting phenol with acetone in the presence of an acid-type ion exchange resin (acidic cation exchange resin) partially modified with a sulfur-containing amine compound as a catalyst together with alkylmercaptan as a co-catalyst (refer to Japanese Patent Laid-open No. 8-325185). However, the addition of alkylmercaptan solely fails to sufficiently prolong the life of the catalyst, and sufficiently increase a yield of bisphenol A per unit quantity of the catalyst. Also, there is known such a method in which the catalyst, when deteriorated in its catalytic activity, is regenerated by washing it with phenol or acidic solvents. However, the latter method suffers from problems such as low yield of the aimed product and complicated treatment of the waste solvents used for washing. Therefore, it has been required to develop a novel process for producing bisphenol A which is capable of not only prolonging the life of an acid-type ion exchange resin partially modified with a sulfur-containing amine compound as catalyst, but also increasing the yield of bisphenol A per unit quantity of the catalyst.
DISCLOSURE OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is to provide a process for producing bisphenol A which is capable of prolonging the life of an acid-type ion exchange resin partially modified with a sulfur-containing amine compound as catalyst, and increasing the yield of bisphenol A per unit quantity of the catalyst.
As a result of extensive studies, the inventors have found that the above object of the present invention is achieved by using a multi-stage reaction apparatus comprising at least two individual reactors connected in series to each other, and by increasing the molar ratio of total alkylmercaptan to total acetone and the molar ratio of total acetone to phenol as the conversion rate of phenol is decreased. The present invention has been accomplished based on this finding.
Thus, the present invention provides the following aspects:
(1) A process for producing bisphenol A by reacting acetone with phenol in the presence of an acid-type ion exchange resin partially modified with a sulfur-containing amine compound as catalyst together with alkylmercaptan as co-catalyst, said process comprising:
conducting said reaction using a multi-stage reaction apparatus comprising at least two individual reactors connected in series to each other, in such a manner that the molar ratio of total alkylmercaptan to total acetone and the molar ratio of total acetone to phenol are increased as the conversion rate of the phenol is decreased;
(2) the process according to the above aspect (1) wherein whole amount of the phenol is fed into a first-stage reactor of said multi-stage reaction apparatus, and the acetone is fed in separate parts into the respective reactors of said multi-stage reaction apparatus;
(3) the process according to the above aspect (1) or (2) wherein the molar ratio of total acetone to phenol at an initial stage of the reaction is in the range of 1/9 to 1/11;
(4) the process according to any one of the above aspects (1) to (3) wherein the molar ratio of total alkyl mercaptan to total acetone and the molar ratio of total acetone to phenol are increased when the phenol conversion rate measured at an outlet of the last stage reactor of said multi-stage reaction apparatus is decreased to 90 to 99% of the initial phenol conversion rate;
(5) the process according to any one of the above aspects (1) to (4) wherein the molar ratio of total alkylmercaptan to total acetone is increased so as not to exceed 1/20;
(6) the process according to any one of the above aspects (1) to (5) wherein the molar ratio of total acetone to phenol is increased so as not to exceed 1/3;
(7) the process according to any one of the above aspects (1) to (6) wherein said sulfur-containing amine compound is selected from the group consisting of mercaptoalkyl amines and thiazolidines;
(8) the process according to any one of the above aspects (1) to (7) wherein said acid-type ion exchange resin is a sulfonic acid-type cation exchange resin;
(9) the process according to any one of the above aspects (1) to (8) wherein said alkylmercaptan is ethylmercaptan; and
(10) the process according to any one of the above aspects (1) to (9) wherein the reaction is conducted at a temperature of 60 to 100° C.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described in detail below.
First, the respective steps of the process for the production of bisphenol A are described.
Step (1): Reaction Step
Bisphenol A is produced by reacting acetone with an excess amount of phenol in the presence of an acid-type ion exchange resin as catalyst and alkyl mercaptan as co-catalyst. As the suitable acid-type ion exchange resins as catalyst, there may be generally used sulfonic acid-type cation exchange resins. Examples of such acid-type ion exchange resin include sulfonated styrene-divinyl benzene copolymers, sulfonated cross-linked styrene polymers, phenol formaldehyde-sulfonic acid resins, benzene formaldehyde-sulfonic acid resins or the like. These acid-type ion exchange resins may be used alone or in the form of a mixture of any two or more thereof.
As the sulfur-containing amine compounds used to partially modify the acid-type ion exchange resin, there may be used mercaptoalkyl amines such as 2-mercaptoethyl amine and 3-mercaptobutyl amine; thiazolidines such as 2,2-dimethyl thiazolidine, 2-methyl-2-ethyl thiazolidine, cycloalkyl thiazolidines, 2-methyl-2-phenyl thiazolidine and 3-methyl thiazolidine; aminothiophenols such as 1,4-aminothiophenol; mercaptoalkyl pyridines such as 3-mercaptomethyl pyridine, 3-mercaptoethyl pyridine and 4-mercaptoethyl pyridine; and the like. Among these sulfur-containing amine compounds, mercaptoalkyl amines and thiazolidines are preferred. The amount of the sulfur-containing amine compound used for modifying the acid-type ion exchange resin is preferably 2 to 50 mol %, more preferably 5 to 30 mol % based on a sulfonic group contained in the acid-type ion exchange resin.
The acid-type ion exchange resin may be modified by reacting the resin with the sulfur-containing amine compound in water or an organic solvent. As the organic solvents, there may be used phenol, acetone, methanol or the like. The modification reaction is preferably conducted in water. The reaction may also be conducted at ordinary temperature or under heated condition. It is not required to conduct the reaction for a too long period of time, and the modification of the acid-type ion exchange resin is sufficiently completed by conducting the above reaction for several tens minutes. The reaction mixture is preferably stirred for uniform reaction thereof
The suitable alkylmercaptans used as co-catalyst are such mercaptans having a C
1
-C
10
alkyl group. Examples of the alkylmercaptans include methylmercaptan, ethylmercaptan, propylmercaptan, octylmercaptan, cyclohexylmercaptan or the like. Among these alkylmercaptans, ethylmercaptan is especially preferred. Meanwhile, these alkylmercaptans may be used alone or in the form of a mixture of any two or more thereof.
The resultant reaction mixture contains, in addition to bisphenol A, unreacted phenol, unreacted acetone, by-pr

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