HK1051529B - Method for producing bisphenols - Google Patents

Description

Process for producing bisphenol

Technical Field

The present invention relates to bisphenols, and in particular to a process for the preparation of bisphenols.

Background

Bisphenols are raw materials for the manufacture of polycondensation materials such as epoxy molding compounds, polyether sulfones, polyether ketones or polycarbonates. Bisphenols are generally prepared by the reaction of phenol or substituted derivatives thereof with a suitable ketone in the presence of an acidic catalyst with the simultaneous separation of water. The most commercially important bisphenol is bisphenol A (BPA), which is produced from phenol and acetone. Bisphenols derived from cycloalkanes, such as the condensation product of phenol with 3, 3, 5-trimethylcyclohexanone, are also important starting materials for the manufacture of polycarbonates.

Homogeneously dissolved acids, such as hydrogen chloride, or heterogeneous acidic fixed bed catalysts, such as sulfonated crosslinked polystyrene resins, i.e., acidic ion exchange resins, can be used as catalysts for the preparation of bisphenols. Although in some respects it is better to use heterogeneous catalysts than homogeneous catalysts, it has been found in EP-A995737 that for certain ketones, adequate reaction rates and selectivities are not obtained with such catalysts. Thus, for many ketones, particularly cyclic ketones, it is preferred to use a strong acid catalyst such as hydrochloric acid. In order to further accelerate the ketone reaction and to increase the selectivity of the reaction, sulfur-containing organic compounds, such as alkyl mercaptans, thiocarboxylic acids or dialkyl sulfides, are used as cocatalysts, as described in U.S. Pat. No. 5210328. The use of specific alkyl mercaptans is disclosed in U.S. Pat. No. 5336812, whereas the use of alkyl mercaptans having from 1 to 12 carbon atoms is proposed in EP-A995737.

The reaction of phenol with ketones under the conditions described above generally results in a mixture containing the desired bisphenol, isomers, intermediates, secondary products of the desired product, unreacted starting materials, water, catalyst and cocatalyst employed, and optionally reaction products thereof with the reaction system components. In order to obtain bisphenol products of a quality suitable for the manufacture of advanced polymeric materials, it is necessary to separate these by-products and reaction components from the bisphenol reaction product as completely as possible. For this purpose, various conventional purification operations, such as crystallization, extraction or distillation, are usually carried out in combination. Various problems may arise in such a process. The bisphenols produced are generally thermally unstable, especially in the presence of catalytically active compounds such as acids or bases. This is particularly problematic when uniformly distributed acids are used as catalysts, which acids remain in the product mixture. Neutralization with a base as described in EP-A995737 or addition of a water-extractive acid as described in EP-A679151 is disadvantageous, since in these processes large amounts of organic-substance-containing waste water are produced, which waste water is treated with costly purification operations. It is also difficult to carry out the reaction continuously with separation of the catalyst in this way and it is not possible to ensure sufficient separation of the sulfur-containing cocatalyst used from the reaction mixture. Residual co-catalyst in the purified bisphenol can reduce the suitability of the bisphenol for use in the manufacture of advanced polycondensation materials.

Another problem in the preparation of bisphenols from phenol and ketones containing more than 5 carbon atoms is that the reaction mixture containing a significant amount of bisphenol product becomes a solid as the bisphenol crystallizes, thereby preventing effective continuous reaction control and catalyst separation. To avoid this problem, subsequent melting of the reaction mixture or carrying out the reaction at elevated temperatures can lead to undesirable side reactions and reduced selectivity. The incomplete reaction with a large excess of phenol or ketone to control the reaction in order to avoid high bisphenol product concentrations is disadvantageous, since the space-time yield is thus reduced. When the reaction product is worked up, the excess phenol and ketone must also be separated off. EP-A995737 proposes that phenol and ketone are prereacted and that, after at least 90 mol% of the ketone has reacted, further amounts of phenol and/or aromatic hydrocarbon are added to the reaction mixture. This method is inconvenient and does not solve the problem of separating the catalyst and even introduce other substances which must be separated later.

Disclosure of Invention

It is an object of the present invention to provide an acid-catalyzed process for the production of bisphenols in the presence of a sulfur-containing promoter. This process has a high space-time yield and high selectivity and provides a product which can be further purified without costly processing steps.

A process for the preparation of bisphenols is disclosed. The process entails reacting a reaction mixture comprising at least one first reactant and at least one second reactant in a reactor in the presence of a hydrogen chloride catalyst and a volatile sulfur compound promoter comprising SH bonds. The first reactant is selected from a first group consisting of phenols and substituted phenols, and the second reactant is selected from a second group consisting of ketones and glycols. The reaction product is a mixture comprising a bisphenol, a first reactant, and a second reactant. The catalyst, cocatalyst and reaction water are separated by distillation. The reaction is characterized by high reaction rate and selectivity.

Detailed Description

The above object can be achieved by a process for producing bisphenols by reacting a phenol or a substituted phenol with a ketone or a diol in the presence of hydrogen chloride and a volatile sulfur compound having an SH bond. The bisphenol formed is separated from unreacted starting materials and catalyst by distillation.

In contrast to known processes for the production of bisphenols, the present invention does not have a neutralization step. Further, in the process for producing bisphenols, it is not known to isolate the product by distillation. The reaction rate can be reduced or the reaction can be stopped completely by adding water. Any volatile components such as catalyst, promoter, water and unreacted starting materials of suitably high volatility can be separated from the reaction mixture by distillation.

The reaction rate is much higher than in the known processes. The process of the invention provides high selectivities and high space-time yields. The catalyst and cocatalyst can be substantially separated from the reaction product without decomposition or rearrangement reactions occurring to a significant extent. By separating and recycling the unreacted ketone, the reaction can be conducted with high selectivity for partial ketone conversion without the reaction mixture being converted to a solid which must be diluted or with loss of ketone.

The starting materials for the process of the present invention are phenol and a number of phenol derivatives which have no electron-withdrawing substituents and are unsubstituted in the 2-and/or 4-position. Suitable phenol derivatives are, for example, 2-alkylphenols such as o-cresol, 2-ethylphenol, 2-isopropylphenol or 2-tert-butylphenol, 2, 6-dialkylphenols such as 2, 6-dimethylphenol, 2, 6-diethylphenyl, 2-methyl-6-isopropylphenol, 2-methyl-6-tert-butylphenol, 2, 6-diisopropylphenol, 2, 6-di-tert-butylphenol and 2, 4-dialkylphenols such as 2, 4-dimethylphenol. Particularly preferably used are phenol and o-cresol. These compounds are both reaction raw materials and reaction solvents.

Other starting materials which are reacted with the abovementioned starting materials in the process of the present invention are ketones or diols. These ketone or diol components may be cyclic or acyclic aliphatic ketone compounds or aromatic-aliphatic ketone compounds. Suitable examples include acetone, butanone, 2-pentanone, 3-pentanone, cyclopentanone, 3-alkylcyclopentanone (the alkyl group contains 1 to 12 carbon atoms), 3-dialkylcyclopentanone (the alkyl group contains 1 to 12 carbon atoms, which may be the same or different), 3, 5-trialkylcyclohexanone (the alkyl group contains 1 to 12 carbon atoms, which may be the same or different), cyclohexanone, 3-alkylcyclohexanone (the alkyl group contains 1 to 12 carbon atoms), 4-alkylcyclohexanone (the alkyl group contains 1 to 12 carbon atoms), 3-dialkylcyclohexanone (the alkyl group contains 1 to 12 carbon atoms, which may be the same or different), 3, 5-trialkylcyclohexanone (the alkyl group contains 1 to 12 carbon atoms, which may be the same or different), Acetophenone. Particularly preferred is cyclohexanone substituted with an alkyl group having 1 to 5 carbon atoms. The ketone or diol component may be used in a concentration of 1 to 25% by weight, preferably 1 to 20% by weight, based on the weight of the reaction mixture.

Suitable catalysts are highly volatile acids, such as concentrated hydrochloric acid and hydrogen chloride gas. Concentrated hydrochloric acid, hydrogen chloride, hydrobromic acid and trifluoroacetic acid are preferred. Volatile sulfur compounds containing SH bonds are used as cocatalysts. Such compounds include hydrogen sulfide, methyl mercaptan, ethyl mercaptan and propyl mercaptan. Hydrogen sulfide is preferred. The process of the present invention is preferably carried out under conditions in which hydrogen chloride gas and hydrogen sulfide are used as catalyst and promoter. The concentration of the catalyst may be from 0.3 to 5% by weight, preferably from 0.5 to 2% by weight, based on the weight of the reaction mixture. The concentration of the cocatalyst can be from 50ppm to 1% by weight, preferably from 100ppm to 0.5% by weight, based on the weight of the reaction mixture.

At the start of the process of the invention, the feedstock and concentrated hydrochloric acid may be placed in a reactor. The catalyst and cocatalyst are then added, preferably while stirring the reaction mixture. The cocatalyst can also be prepared in situ. For this purpose, ammonium hydrosulfide may be added to the acidic reaction mixture.

The reaction can be carried out at atmospheric pressure or overpressure. The reaction is preferably carried out at an overpressure of from 0.1 to 0.5MPa (1 to 5 bar). The temperature of the reaction mixture may be 10-80 deg.C, preferably 25-60 deg.C, and most preferably 30-40 deg.C.

Water is formed during the reaction. The reaction products reduce the reaction rate. In order to maintain the reaction rate, catalyst and cocatalyst must be added. The catalyst and cocatalyst can be added to the reaction mixture in liquid, solid or gaseous form, individually or in admixture. They are preferably blown into the reaction mixture in gaseous form. The reaction mixture is preferably saturated with the catalyst and the cocatalyst. The process of the invention can be carried out in a continuous or discontinuous manner, preferably in a continuous manner.

The reaction solution can be discharged from the lower part of the reactor and fed directly or via a receiver to a distillation apparatus. During the distillation, the catalyst, water and unreacted raw materials are separated from the reaction solution.

Thus, the water can be completely evaporated at a not too high temperature. The distillation may be carried out under vacuum, the degree of vacuum being adjusted to such an extent that the bulk temperature does not decompose the product, typically at a temperature of 130 ℃ or less. At around 130 ℃, the bisphenols are dissolved and the distillation of the starting compounds such as phenol and cresol only proceeds to the extent that a homogeneous solution is maintained. This process can substantially completely remove the water, catalyst and promoter and provide a clean concentrated product solution. This product solution can be crystallized cleanly and economically on cooling. The pressure in the distillation column is from 50 to 120 mbar, preferably from 90 to 110 mbar.

Depending on the boiling point of the product, the product taken off from the bottom of the distillation column contains phenol and possibly also ketones in addition to the bisphenol product. The phenol and ketone content is 0-15% by weight based on the weight of the solution. The product at 100-130 ℃ was fed to a conventional crystallizer. The crystallization is preferably carried out in a rotary crystallizer. Depending on the product obtained, recrystallization can be carried out one to three times, preferably one to two times. When TMC phenol is used, a second recrystallization is generally sufficient to obtain a very pure product. With BPA, one recrystallization is generally sufficient to obtain a very pure product. The recrystallization is preferably carried out with phenol. Thus, the difficulty of separating mixtures of phenol and other solvents is avoided.

The phenol can then be purified from the crystallized product. This purification can be carried out, for example, by thermal desorption of phenol at high temperatures while passing nitrogen. Since temperatures above 190 ℃ are required in the process of the invention, decomposition products are formed. Thus, according to a particularly preferred embodiment of the present invention, the crystalline product is washed with water, during which phenol is liberated from the bisphenol/phenol adduct. The water temperature used to wash the phenol can be 20-100 c, preferably 70-80 c. The thermal decomposition of the bisphenol can be avoided by removing phenol from the bisphenol/phenol mixed crystals with water.

The process of the invention can be carried out in a stirred tank reactor, a loop reactor or a cascade reactor. The distillation may be continuous or discontinuous. The reaction solution may be fed to the distillation apparatus between two separation steps of complete removal of phenol under reflux. The lower part of the distillation apparatus is preferably equipped to enable water, catalyst, cocatalyst and optionally starting materials to be removed together with the phenol vapour.

The diphenols obtained by the process according to the invention are preferably represented by the following general formula (I):

in the formula

A is a single bond, C₁-C₂Alkylene radical, C₂-C₅Alkylene (alkyls), C₅-C₆Cycloalkylene, -O-, -SO-, -CO-, -S-, -SO₂C which may be condensed with an aromatic ring optionally containing hetero atoms₆-C₁₂Aryl or a group represented by the general formula (II) or (III):

b is respectively C₁-C₁₂Alkyl (preferably methyl), halogen (preferably chlorine and/or bromine),

x is each 0, 1 or 2,

p is a number of 1 or 0,

each X¹R of (A) to⁵And R⁶Each represents hydrogen or C₁-C₆Alkyl, preferably hydrogen, methyl or ethyl,

X¹is carbon

m is an integer from 4 to 7, preferably 4 or 5, with the proviso that at least one X¹At atom, R⁵And R⁶And is an alkyl group.

Preferred diphenols are hydroquinone, resorcinol, dihydroxydiphenyl (dihydroxydiphenyl), bis (hydroxyphenyl) C₁-C₅Alkane, bis (hydroxyphenyl) C₅-C₆Cycloalkanes, bis (hydroxyphenyl) ethers, bis (hydroxyphenyl) sulfoxides, bis (hydroxyphenyl) ketones, bis (hydroxyphenyl) sulfones and α, α -bis (hydroxyphenyl) -diisopropylbenzenes, as well as their ring-brominated or chlorinated derivatives.

Particularly preferred diphenols are 4, 4 ' -dihydroxydiphenyl, bisphenol A, 2, 4-bis (4-hydroxyphenyl) -2-methylbutane, 1-bis (4-hydroxyphenyl) cyclohexane, 1-bis (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane, 4 ' -dihydroxydiphenyl sulfide, 4 ' -dihydroxydiphenyl sulfone as well as their di-and tetrabrominated or chlorinated derivatives, such as 2, 2-bis (3-chloro-4-hydroxyphenyl) propane, 2-bis (3, 5-dichloro-4-hydroxyphenyl) propane or 2, 2-bis (3, 5-dibromo-4-hydroxyphenyl) propane.

The present invention is illustrated by the following examples, but is not limited to these examples.

Examples

Example 1

500 g of the reaction solution was placed in a stirred tank reactor having a volume of 1 literIn (1). The reaction solution contained 95.5% by weight of phenol and 4.5% by weight of acetone. At the start of the reaction, 5% by weight aqueous HCl was added. The gas phase is maintained at a pressure of 2 bar with HCl gas. H was added to the gas stream at a rate of 3.3 l/H₂And (4) S gas. After about 30 minutes, the reaction solution was continuously pumped into the reactor at a rate of 0.8 liter/hour. The ratio phenol/acetone in the reaction solution corresponds to the ratio mentioned above. While the reaction solution was pumped from the reactor to the distillation column at a rate of 0.8 liter/hr. The volume in the reactor was controlled to the extent of a residence time of 30 minutes. The temperature of the reaction mixture was 40 ℃.

The reaction solution was heated to about 113 ℃ by a heat exchanger. The vacuum in the distillation column was adjusted to 100 mbar. The reflux ratio was adjusted to a value at which only a small amount of phenol was distilled off from the top of the column. The bottom of the column is heated to about 125 ℃. Condensed water, hydrogen chloride, hydrogen sulfide, residual unreacted ketone and the like, and subjected to post-treatment.

The bottom of the distillation column still contains only reaction products and phenol. The bisphenol/phenol adduct crystallizes from the hot product solution (45 ℃). The product was filtered off and washed with warm phenol. The mother liquor may be recycled. The washed adduct is then washed with hot water at a temperature of about 85 ℃ to separate phenol and bisphenol. After filtration, the product was dried in vacuo.

The selectivity in the reaction solution was 95.5% pp BPA and the purity of the dried product was 99.71%.

Example 2 (comparative)

The reaction was carried out under the same reaction conditions as in example 1, except that H2S was not added. The reaction time was doubled. But the acetone conversion decreased 1/3 and the selectivity decreased to 86.6% pp BPA. This comparative example demonstrates the importance of the promoter in the process of the invention.

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose. Various modifications may occur to those skilled in the art without departing from the spirit and scope of the invention. The scope of the invention is defined by the claims.

Claims (6)

1. A process for the preparation of bisphenols which comprises reacting in a reactor a reaction mixture comprising at least one first reactant selected from a first group consisting of phenols and substituted phenols and at least one second reactant selected from a second group consisting of ketones and diols in the presence of a hydrogen chloride catalyst and a volatile sulfur compound promoter containing SH bonds, said catalyst, promoter and reaction water being separated from said mixture by distillation, said volatile sulfur compound containing SH bonds being hydrogen sulfide, said reaction being carried out at an overpressure of from 0.1 to 0.5MPa, said process for the preparation of bisphenols being a one-step process.

2. The process of claim 1 wherein the catalyst and/or cocatalyst is in a liquid or gaseous state.

3. The method of claim 2, wherein the gaseous promoter is prepared in situ.

4. The method of claim 1, wherein the concentration of said catalyst and/or promoter in said reaction mixture is maintained constant at saturation concentration.

5. The method of claim 1, wherein the reaction mixture is maintained at a temperature of 10 ℃ to 80 ℃.

6. The process of claim 1, which is carried out continuously.