JPH03284641A - Production of bisphenol a - Google Patents

Abstract

PURPOSE:To obtain a highly pure bisphenol A crystal in a high yield by reacting phenol with acetone in the presence of an acid catalyst, crystallizing, separating the reaction product, subjecting the remained mother solution to a purification process accompanied with the cleavage reactions of by-products to remove the impurities, and subsequently recycling the remained products. CONSTITUTION:Phenol is reacted with acetone in the presence of an acid catalyst and water and the catalyst are removed from the reaction solution containing crude bisphenol A. The solution is concentrated, cooled and subjected to a crystallization process and then to a solid-liquid separation process. Furthermore phenol contained in the solid phase portion is removed to obtain highly pure bisphenol A. The remained mother solution is concentrated, cooled and subsequently subjected to a solid-liquid separation process. The solid phase portion is mixed with the crude bisphenol A and recycled. The liquid phase portion is subjected to a cleavage reaction in the presence of an alkali catalyst to remove most of the reaction by-products. The reaction solution is subjected to a recombination reaction and subsequently recycled into the reaction system. The method does not cause the recyclization and accumulation of the impurities, minimizes the contamination of the processes and provides the slightly colored bisphenol A having a high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for producing 2°2-bis(4-hydroxyphenyl)propane, also known as bisphenol A.

Bisphenol A is a resin raw material widely used for epoxy resins, polycarbonate resins, and the like.

In order to obtain high-quality resin, highly purified bisphenol octane is required, and in particular, as a raw material for polycarbonate resin, which has seen an increase in demand for optical applications in recent years, bisphenol octatide, which is colorless and has a higher purity than before, is needed. is required.

[Conventional technology]

Bisphenol A is produced by reacting phenol and acetone using an acid catalyst. The reaction product contains, in addition to bisphenol A, unreacted phenol, unreacted acetone, catalyst, reaction product water, and reaction by-products.

Among the reaction by-products, the main one is 2-(2-hydroxyphenyl')-2-(4-hydroxyphenyl)propane (hereinafter sometimes referred to as 2,4'-isomer), and other Dyanin Compound (D 1anin's Com
(pound),) lisphenol, polyphenol, and coloring substances. These substances are undesirable because they degrade the quality of resins and the like produced using bisphenol A as a raw material.

One method for recovering high-purity bisphenol A from a reaction product is to remove the catalyst, reaction product water, and some unreacted phenol from the reaction product by distillation, etc., and then cool the remaining liquid mixture. There is a method in which bisphenol A is crystallized as an adduct with phenol, the crystals are separated from a mother liquor containing reaction by-products, and then phenol is removed to recover bisphenol A.

In the mother liquor from which the crystals have been separated, in addition to unreacted raw materials and reaction by-products, a large amount of bisphenol 8 still remains, so this mother liquor can be recycled to the reaction system. However, if dianine compounds, polyphenols, coloring substances, etc. are circulated as they are, they will further react with raw material phenol and acetone, increase their molecular weight, and accumulate in the system.
The crystals thus deteriorate the purity and color of the product.

Japanese Patent Publication No. 52-46946 discloses a method of further concentrating the mother liquor to extract crystals (second crystals) and supplying the crystals to the main crystallization step. However, the mother liquor from which this second crystal is removed contains a large amount of bisphenol A, 2,4'-isomers and trisphenol that can be converted to bisphenol A, but at the same time, it is It also contains high amounts of polyphenols and coloring substances that cannot be recycled and must be discarded.

On the other hand, Japanese Patent Publication No. 55-34779 discloses that a part of the mother liquor remaining after recovering the crystals (first crystal) is cleaved with an alkali catalyst, decomposed into phenol and barisopropenylphenol, and purified by distillation. A method is disclosed in which, after removing the compound, a recombination reaction is performed with an acid catalyst to form bisphenol A, which is then recycled to the main reaction step. However, the cleavage reaction inevitably produces low-boiling compounds other than phenol and barisopropenylphenol.

Furthermore, U.S. Pat. No. 4,400,555 discloses a method in which the 2.4"-isomer in the mother liquor is isomerized to bisphenol A using an acid catalyst and then recycled, but polyphenols and colored substances are recycled as they are. This is not preferred as a method for obtaining high-purity products.

JP-A-1230538 discloses that as a bisphenol A production process including mother liquor treatment, sub-processes consisting of cleavage reaction, recombination reaction, concentration, crystallization, and solid-liquid separation are made independent, and the crystals are circulated to the main process. A method is disclosed. According to this method, after crystallization and solid-liquid separation of the reaction liquid obtained by the recombination reaction, a part of the liquid phase portion is recycled to the cleavage reaction again, which is not efficient. In addition, the cleavage reaction is usually carried out under a high reduced pressure of 5 to 30 mmHg at 150 to 25 mmHg.
Since the process is carried out at a high temperature of 0° C., further circulation of bisphenol A is uneconomical and undesirable because it increases the amount of low-boiling compounds produced.

[Problem to be solved by the invention]

The purpose of the present invention is to provide a method for producing high-quality bisphenol A by recovering bisphenol 8 from a mother liquor from which crystals have been removed in a high yield, and removing colored substances and other impurities while minimizing their circulation. It is to provide.

[Means to solve the problem]

The manufacturing method of the present invention solves the above problems. That is, the method for producing bisphenol A consists of the following steps.

(a) A step of reacting phenol and acetone in the presence of an acid catalyst.

(b), a step of removing water and the catalyst from the reaction solution obtained in step (a);

(c), a step of adjusting the concentration of bisphenol A in the crude liquid obtained in step (b);

(Inc.), a step of cooling the concentration adjustment liquid obtained in step (c), crystallizing it, and separating it into solid and liquid.

(e) A step of removing phenol from the solid phase portion obtained in step (d) to obtain bisphenol A.

(f), a step of concentrating the liquid phase portion obtained in step (d);

A step of cooling the concentrated liquid obtained in (gl, step), crystallizing it, and separating it into solid and liquid.

Co., Ltd., a step in which the solid phase portion obtained in step Cg is combined with the crude liquid obtained in the process wholesale and fed to step (c).

(i) Step (Step of subjecting the liquid phase obtained from the odor to a cleavage reaction in the presence of an alkali catalyst.

(j) A step of subjecting the reaction solution obtained in step (i) to a recombination reaction in the presence of an acid catalyst.

(g) A step of supplying the reaction solution obtained in step (j) together with the reaction solution obtained in step (a) to step (c).

According to the method of the present invention, the portion of the reaction by-products that cannot be recovered as bisphenol 8 is circulated through each step to a minimum and is extracted from the system, thereby preventing contamination due to accumulation of reaction by-products. can.

The present invention will be described in detail below with reference to FIG. 1 of the accompanying drawings.

Step (a) Phenol 1 and acetone 2 are introduced into main reaction step 3 in excess of phenol. The molar ratio of phenol and acetone is
Usually the ratio is 4:1 to 15:1. The main reaction is carried out in the presence of an acid catalyst, but an inorganic acid such as hydrogen chloride may be used as the acid catalyst, or a solid acid catalyst such as a cation exchange resin may be used in a fixed bed or fluidized bed. The reaction may be carried out with The reaction temperature is about 40 to 90°C. The reaction time varies depending on the reaction type and especially the reaction temperature, but is about 0.5 to 10 hours. The reaction pressure is from atmospheric pressure to 5 kg/cffl.

Step (b) The reaction product obtained in step (a) is used in step (j
), in crude step 4,
By methods such as vacuum distillation, unreacted acetone 2 and reaction product water 5
, catalyst etc. are removed. When using a fixed bed reactor, there is no need for decatalyst. For vacuum distillation, the reaction temperature is 50 to 150°C,
The reaction is carried out at a pressure of 100 to 300 mmHg, and in this case, unreacted phenol is azeotropically distilled and a part of it is removed from the system.

Step (c) The crude liquid obtained by removing the above-mentioned substances from the reaction product is combined with the solid phase portion obtained in step (g) described below, and phenol is distilled off or added in the first concentration adjustment step 6. and adjust the concentration of bisphenol A. Concentration in bisphenol is 20-50% by weight, preferably 30-45%
Weight%. If the concentration in bisphenol is less than 20%, the yield will be low, and if it is more than 50%, the apparent viscosity of the concentrate will become high, causing a problem that it will be impossible to transport.

Step (ω) The concentration adjustment liquid obtained in step (c) is cooled to 35 to 60°C in the first crystallization step 7, and bisphenol A
The adduct of phenol and phenol crystallizes into a slurry.

Cooling is achieved by heat removal by external heat exchangers or by evaporation of water added to the crystallizer.

In the first separation step 8, the slurry-like concentration adjustment liquid is
Solid-liquid separation is performed by filtration, centrifugation, etc.

Step (e) The solid phase portion (crystals) obtained in the first separation step 8 of Step (Inc.) is washed, if necessary, simultaneously with or after the separation.

In the dephenolization step 9, the solid phase portion (crystals) is
Phenol 1 is removed by a method such as vacuum distillation to obtain bisphenol AIO product.

Step (f) The liquid phase portion (mother liquor) obtained in the first separation step 8 of step (g) is concentrated by removing a portion of phenol 1 in the second concentration adjustment step 11. The concentration of bisphenol A is
It is 20-50% by weight, preferably 30-45% by weight.

The concentrated liquid obtained in the second concentration adjustment step 11 of the step (odor step (0) is
In the second crystallization step 12, bisphenol A is cooled and
The adduct of phenol and phenol is crystallized, and the second separation step 1
3, solid-liquid separation is performed.

Step (sha) The solid phase portion (second boundary) obtained in the second separation step 13 of step (g) is supplied to step (c) together with the crude liquid obtained in step (sha). Since the raw material in step (g) contains the reaction by-products produced in the main reaction in a concentrated form, the second boundary is the solid phase portion obtained in the first separation step 8 of step (d) (
contains more impurities than crystals).

However, since the concentration of impurities in the second crystal is lower than the concentration in the reaction solution obtained in main reaction step 3 of step (a),
When Nibankai is supplied to the first crystallization step 7, the concentration of reaction by-products is reduced, and crystals with higher purity are obtained than when it is not supplied.

Step (i) The liquid phase portion obtained in the second separation step 13 of step (g) is
It contains bisphenol A in the same proportion as the liquid phase obtained in the first separation step 8 of step (d), but contains reaction by-products, namely 2,4'-isomer, dianine compound, trisphenol, polyphenol and Colored substances are more concentrated.

The liquid phase portion is sent to the cleavage reaction step 14 after being concentrated if necessary. The cleavage reaction is carried out in the presence of an alkaline catalyst. As an alkali catalyst, sodium hydroxide,
Examples include alkali metal hydroxides such as potassium hydroxide. The reaction is usually carried out at a reaction temperature of 150 to 250°C and a reaction pressure of 5 to 30 mmHg. By the cleavage reaction,
The 2,4°-isomer etc. are decomposed into isopropenylphenol and phenol. The reaction solution is purified by a method such as distillation, and colored substances and high-boiling compounds 15 that are not decomposed by the cleavage reaction are discharged from the system.

Step (j) From the barisopropenylphenol and phenol obtained in the cleavage reaction step 14 of step (i), bisphenol 8 is regenerated in the recombination reaction step 16. The recombination reaction proceeds rapidly in the presence of a solid acid catalyst such as a cation exchange resin or an inorganic acid such as hydrogen chloride.

Step (g) The reaction solution obtained in the recombination reaction step 16 of step (j) is
It is supplied to the crude step 4 of step (b) together with the reaction solution obtained in step (a).

Since the recombination reaction liquid has a color closer to colorless than the reaction liquid obtained in the main reaction step 3, the quality of the product bisphenol A is improved by supplying the recombination reaction liquid.

Low-boiling compounds produced in the cleavage reaction are easily removed in crude step 4.

By the above method, high quality bisphenol 8 can be obtained.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the examples, % represents weight %, and impurities were determined by liquid chromatography.

<Example 1> 940 g of phenol and 73 g of acetone were mixed, and a reaction was carried out at 55° C. for 9 hours while blowing hydrogen chloride gas into the mixture. The reaction product was then heated under reduced pressure to remove hydrochloric acid, water and some unreacted phenol. The obtained concentrate was 32.8% bisphenol A, 2.4"
- It contained 0.9% of isomers and 1.3% of other impurities, and the hue of its 50% ethanol solution was 60 APH8.

This concentrated solution was cooled from 90° C. to 45° C. to crystallize crystals, which were separated using a centrifuge, and the obtained crystals were washed with an equal amount of phenol to obtain 287 g of crystals.

Next, the crystals were melted and sent to a distillation column operated at 15 mmHg and 170° C., and most of the phenol was distilled off and recovered. Bisphenol A is extracted from the bottom of the tower, and residual phenol is completely removed by steam dripping.
200 g of bisphenol A product was obtained. The obtained bisphenol A contains 0.06% of the 2,4'-isomer and 0.22% of other impurities, and the hue of its 50% ethanol solution is 10APHA, which is sufficient for use as a raw material for optical polycarbonate. It had the highest possible purity.

The mother liquor separated by a centrifuge and the phenol used for washing the crystals were combined, and some of the phenol was distilled off under reduced pressure, resulting in bisphenol A of 28% and 2°4'-isomer of 2.6%.
%, and 300 g of a concentrated liquid containing 3.7% of other impurities was obtained.

This concentrated solution was cooled, and the second boundary was crystallized and separated using a centrifuge to obtain 85 g of crystals. This second world is 2.
1.1% 4'-isomer, 0.9% other impurities
The hue of its 50% ethanol solution is 35A.
It was PHA.

In the liquid phase part (mother liquor) from which the second boundary was separated, there were 25 g of bisphenol A and 7 g of the 2.4'-isomer.

Contained 10g of other impurities.

Add 0.1 g of sodium hydroxide to this mother liquor,
Distilled at 0°C and 10mmHg to produce a yellow distillate 2 consisting mainly of phenol and barisopropenylphenol.
00g was obtained.

This distillate was added to the cation exchange resin Amberlyst 15 (
Add 10g of Rohm & Hass, and heat at 60℃
After reacting for 2 hours, the mixture was filtered to remove the catalyst. The hue of the 50% ethanol solution of this recombination reaction solution is 20A.
It was PHA.

<Example 2> 870 g of the main reaction product was obtained in the same manner as in Example 1.

200 g of the recombination reaction solution obtained in Example 1 was added to this and distilled under reduced pressure to remove produced water, catalyst, and the like.

85 g of Nibankai obtained in Example 1 was added thereto and dissolved. This solution contains 33°9% bisphenol A, 2.4°
- Contained 0.8% isomer and 1.3% other impurities.

This mixed solution was cooled from 90° C. to 45° C. to crystallize crystals, which were then separated using a centrifuge, and the obtained crystals were washed with an equal amount of phenol to obtain 385 g of crystals.

The crystals were dephenolated in the same manner as in Example 1 to obtain 265 g of bisphenol A product.

The obtained bisphenol A contained 0.4'-isomer.
0.5% and other impurities 0.20%, part 5
The hue of the 0% ethanol solution was 10APHA.

The mother liquor separated by a centrifuge and the phenol used for washing the crystals were combined, and some of the phenol was distilled off under reduced pressure, resulting in 29.0% bisphenol A and 2.4°-isomer 2.
．． 400g of concentrated liquid containing 1% and 3.6% of other impurities
I got it.

This concentrated solution was cooled, and the second boundary was crystallized and separated using a centrifuge to obtain 115 g of crystals. This second world is 2,
It contained 1.1% of the 4'-isomer and 0.8% of other impurities.

The liquid phase portion (mother liquor) from which the second boundary was separated was operated in the same manner as in Example 1 to obtain 260 g of a recombination reaction liquid.

<Example 3> 870 g of the main reaction product was obtained in the same manner as in Example 1.

260 g of the recombination reaction solution obtained in Example 2 was added to this and distilled under reduced pressure to remove produced water, catalyst, etc.

115 g of Nibankai obtained in Example 2 was added thereto and dissolved. This solution contains 33°5% bisphenol A, 2.4
It contained 0.7% of the °-isomer and 1.3% of other impurities.

This mixed solution was cooled from 90° C. to 45° C. to crystallize crystals, which were then separated using a centrifuge, and the obtained crystals were washed with an equal amount of phenol to obtain 410 g of crystals.

The crystals were dephenolated in the same manner as in Example 1 to obtain 280 g of a bisphenol product.

The mother liquor separated by the centrifuge and the phenol used for washing the crystals were combined and operated in the same manner as in Example 1 to obtain a Nibankai and recombination reaction solution.

The above operation was repeated three times using this Nibankai and recombination reaction solution.

The resulting bisphenol A contained 0.04% of the 2,4°-isomer and 0.13% of other impurities, and the hue of its 50% ethanol solution was 5APHA. Further, the freezing point was 156.8°C, and extremely high purity bisphenol A was obtained.

〔Effect of the invention〕

According to the production method of the present invention, most of the reaction by-products are removed by distillation and purification accompanying the cleavage reaction after passing through the crystallization step once, so there is no circulation or accumulation of impurities.
Contamination in each step is minimized, and high quality bisphenol A with little coloring is obtained.

In addition, a portion of trisphenol and polyphenols are also decomposed into phenol and barisopropenylphenol, which are converted to bisphenol A and recovered, so the yield is substantially increased.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the method for producing bisphenol A of the present invention. In the figure, l: Phenol 2: Acetone Main reaction step Crude step Reaction product water Second concentration adjustment step First crystallization step First separation step Phenol removal step Bisphenol A Second concentration adjustment step Second crystallization step Second separation step Cleavage reaction process High point compound, colored substance recombination reaction process

Claims (1)

[Claims] 1) A method for producing bisphenol A comprising the following steps. (a) A step of reacting phenol and acetone in the presence of an acid catalyst. (b), a step of removing water and the catalyst from the reaction solution obtained in step (a); (c), a step of adjusting the concentration of bisphenol A in the crude liquid obtained in step (b); (d) A step of cooling the concentration adjustment liquid obtained in step (c), crystallizing it, and separating it into solid and liquid. (e) A step of removing phenol from the solid phase portion obtained in step (d) to obtain bisphenol A. (f), a step of concentrating the liquid phase portion obtained in step (d); (g) A step of cooling the concentrated liquid obtained in step (f), crystallizing it, and performing solid-liquid separation. (h), a step of supplying the solid phase portion obtained in step (g) together with the crude liquid obtained in step (b) to step (c); (i) A step of subjecting the liquid phase portion obtained in step (g) to a cleavage reaction in the presence of an alkali catalyst. (j) A step of subjecting the reaction solution obtained in step (i) to a recombination reaction in the presence of an acid catalyst. (k), a step of supplying the reaction solution obtained in step (j) together with the reaction solution obtained in step (a) to step (b);