JPH0532572A - Monovalent phenol compound, bisphenol compound and condensation treatment of steam-containing stripping gas - Google Patents

Abstract

PURPOSE:To perform efficient condensation treatment without stripping gas pressure raising. CONSTITUTION:A stripping gas containing a monovalent phenol compound, bisphenol compound and steam 3 is maintained under a reduced pressure of <=30Torr and under such temperature conditions as to maintain the steam in a gaseous state and part of the monovalent phenol compound in a liquid state, and put to counter current contact with the first cooling medium 5 comprising the monovalent phenol compound or its mixture with the bisphenol compound to effect condensation of the virtually whole quantity of the bisphenol compound in said stripping gas and part of the monovalent phenol compound, and obtaining a mixed gas 8 of uncondensed steam and the monovalent phenol compound. Said mixed gas 8 is then put to counter current contact with the second cooling medium 9 comprising an aqueous solution of the monovalent phenol compound under a reduced pressure of <=30Torr and under such temperature conditions as to condense the virtually total quantity of said mixed gas 8 to effect condensation of the virtually total quantity of said mixed gas 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for condensing a stripping gas containing a monohydric phenol compound, a bisphenol compound and steam.

[0002]

BACKGROUND OF THE INVENTION It is known to react excess monohydric phenol compounds with aldehydes or ketones in the presence of acid catalysts to produce bisphenol compounds. Further, in order to separate and recover a high-purity bisphenol compound from this reaction product, the reaction product is cooled to crystallize an adduct of the bisphenol compound and the monohydric phenol compound, and the monohydric phenol is obtained from the obtained adduct crystal. It is also known to remove compounds. As one method for separating and removing the monohydric phenol compound from the adduct of the bisphenol compound and the monohydric phenol compound, the adduct was heat-melted, and the melt was removed as-is or from most of the monohydric phenol compound. After that, a method of steam stripping is known (for example, JP-A-2-28126 and JP-A-63-1).
32850). This steam stripping method
The melt of the bisphenol compound containing the monohydric phenol compound is countercurrently contacted with steam in a gas-liquid contact device such as a packed tower, a wetting wall tower, or a centrifugal thin-film evaporator, to obtain a monohydric phenol compound in the melt. Is a method of evaporating and removing steam. In this case, a reduced pressure condition is adopted to accelerate the evaporation removal of the monohydric phenol compound by the steam stripping, and the lower the absolute pressure or the higher the reduced pressure (vacuum), the more efficient the monohydric phenol compound is. The bisphenol compound of higher purity can be obtained.

Further, in this steam stripping method, as exhaust gas, vapor of a monohydric phenol compound,
A stripping gas consisting of bisphenol compound vapors and steam is obtained, which gas is subjected to a cooling treatment in order to condense and recover each of these components. This cooling temperature is dominated by the condensation temperature of steam, with lower pressures requiring lower cooling temperatures. Under relatively high pressure conditions, there is no particular problem in the stripping gas condensation process, but if the pressure conditions are set to a low pressure of 30 Torr or less in order to improve the purity of the bisphenol compound, the stripping gas will be The condensation temperature of the steam becomes lower than the freezing point of the bisphenol compound or monohydric phenol compound, and during cooling, the condensation of the bisphenol compound or monohydric phenol compound occurs before the steam condenses, and The solids will be deposited and adhere to the. When the solid of the bisphenol compound or the monohydric phenol compound adheres to the cooler, the cooling effect of the cooler is significantly deteriorated and the cooler becomes clogged. On the other hand, in order to avoid such a problem, it is also possible to pressurize the stripping gas to a condition such that coagulation of the bisphenol compound or the monohydric phenol compound does not occur, and then perform cooling treatment, but in this case, Since a large compressor is required and a large amount of energy is consumed, it is not an industrially advantageous method.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to a low-pressure stripping gas obtained when a bisphenol compound containing a monohydric phenol as an impurity is purified by a steam stripping method, and a bisphenol compound or a monohydric phenol compound contained in the stripping gas. It is an object of the present invention to provide a method for efficiently performing condensation treatment without causing solidification of the above and without increasing the pressure of the stripping gas.

[0005]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems.

That is, according to the present invention, a monohydric phenol compound, a bisphenol compound, and a steam obtained when steam-stripping a mixed melt of a monohydric phenol compound and a bisphenol compound under a low pressure condition of 30 Torr or less are obtained. In the method of condensing the contained stripping gas, the stripping gas is kept under a low pressure condition of 30 Torr or less and under a temperature condition of keeping steam in a gas state and part of a monohydric phenol compound in a liquid state. Countercurrently contacting with a first cooling medium composed of a monohydric phenol compound containing a polyhydric phenol compound or a bisphenol compound to condense substantially all of the bisphenol compound contained in the stripping gas and a part of the monohydric phenol compound. Mixing uncondensed steam with monohydric phenol compounds A first cooling step to obtain a gas, first
A second aqueous solution of a monohydric phenol compound, wherein the mixed gas obtained in the cooling step is under a low pressure condition of 30 Torr or less and a temperature condition for condensing substantially the entire amount of the mixed gas;
A method for condensing a stripping gas comprising a second cooling step of condensing substantially all of the mixed gas in countercurrent contact with a cooling medium is provided.

The bisphenol compound in the present invention is
As described above, it is obtained by reacting a monohydric phenol compound with an aldehyde or a ketone in the presence of an acid catalyst,
The reaction is known. As the bisphenol compound, bisphenol A [2,2-bis (4-hydroxyphenyl) obtained by reacting phenol and acetone is used.
Propane] is a typical example, but other bisphenol compounds can be similarly produced and applied as the bisphenol compound in the present invention.

The steam stripping step is a step in which steam is countercurrently contacted with a bisphenol compound containing a monohydric phenol compound to evaporate and remove the monohydric phenol compound together with the steam, which is a conventionally known step. The bisphenol compound containing the monohydric phenol compound to be steam stripped may be a melt of an adduct of the bisphenol compound and the monohydric phenol compound as described above, or the melt may be subjected to a distillation treatment. Then, most of the monohydric phenol compound may be removed, and further, most of the monohydric phenol compound may be removed by another method such as an extraction method. The steam stripping step in the present invention is applied to any bisphenol compound containing a monohydric phenol compound. The content of monohydric phenol in the bisphenol compound supplied to the steam stripping step in the present invention is usually 29 to 42% by weight, preferably 35% by weight or less.

In the present invention, a bisphenol compound containing a monohydric phenol compound is supplied in a molten state to a steam stripping step, where it is brought into countercurrent contact with steam. Examples of the stripping device include a packed tower, a wet wall tower, a centrifugal thin film evaporator, and the like, and the structure thereof is not particularly limited as long as it is a device capable of countercurrently contacting a liquid and a gas.

The temperature of the bisphenol compound containing the monohydric phenol compound (hereinafter also referred to as the raw material bisphenol compound) supplied to the steam stripping step is at least 15 ° C. higher than its melting point, and when the bisphenol compound is bisphenol A, 170-20
The temperature is 0 ° C, preferably 175 to 190 ° C. The temperature of steam is at least 15 than that of the raw bisphenol compound.
When the bisphenol compound is bisphenol A, the temperature is 170 ° C to 200 ° C, preferably 175 ° C.
It is 190 ° C. The weight ratio of the raw material bisphenol compound and steam is 15 or more, preferably 20 or more. The stripping process is carried out under reduced pressure and the pressure is 3
It is 0 torr or less, preferably 5 to 20 torr.

From the steam stripping step, a high-purity bisphenol compound from which the monohydric phenol compound has been removed by evaporation is obtained as a purified product, and a stripping gas consisting of the monohydric phenol compound, the bisphenol compound and steam is discharged. Obtained as. The weight ratio of each component in the stripping gas is 0.4 to 0.8 part by weight, preferably 0.5 to 0.8 part by weight, and 0.05 to 0 part by weight of bisphenol compound per 1 part by weight of steam. 0.25 parts by weight, preferably 0.05-0.
15 parts by weight, and the weight ratio of the monohydric phenol compound to the bisphenol compound is 2 to 10, preferably 3 or more.

In the present invention, the stripping gas obtained from the steam stripping step as described above is supplied to the first cooling step in the reduced pressure state thereof and contains the monohydric phenol compound or the bisphenol compound. The first cooling medium composed of a monohydric phenol compound is brought into countercurrent contact and cooled. This first cooling step is carried out so that substantially all of the bisphenol compound in the stripping gas is dissolved in the cooling medium. The steam in the stripping gas is not substantially condensed in this first cooling step and is sent to the next second cooling step. Part of the monohydric phenol compound in the stripping gas is condensed in this first cooling step, and the remaining uncondensed one is sent to the next second cooling step together with steam. A part of the mixed liquid of the bisphenol compound and the monohydric phenol compound separated and recovered from the stripping gas in the first cooling step can be used as a cooling medium. The temperature of the first cooling medium is
The temperature is about 1 to 50 ° C. higher than the freezing point of the monohydric phenol compound. The recovery rate of the monohydric phenol compound in the first cooling step is 70% by weight or more, preferably 85% by weight or more, based on the total amount of the monohydric phenol compound supplied to the first cooling step.

The cooling medium used in the first cooling step may be an amount sufficient to cool the stripping gas to a desired temperature, and usually, in a weight ratio to the stripping gas,
It is 5 to 10, preferably 5 to 6. The weight ratio of the bisphenol compound contained in the stripping gas obtained in the first cooling step to the monohydric phenol compound contained in the cooling medium in which the monohydric phenol compound is dissolved is 0.05 to 0.20, Preferably 0.
It is 08 to 0.14. In the first cooling step of the present invention, since the excess monohydric phenol compound is present with respect to the bisphenol compound, the adduct between the bisphenol compound and the monohydric phenol compound is present even at a cooling temperature below the freezing point of the bisphenol compound. It does not crystallize out.

The pressure of the first cooling step is 30 Torr or less,
It is preferably from 5 to 20 torr and corresponds to the pressure in the steam stripping step. The temperature in the first cooling step is a temperature at which steam holds a gas and a part of the monohydric phenol compound holds a liquid under the pressure condition. The preferred cooling temperature (the temperature at which the bisphenol compound is condensed) is a temperature about 1 to 50 ° C. higher than the freezing point of the monohydric phenol compound. When the bisphenol compound is bisphenol A, the cooling temperature is 42 to 90 ° C, preferably 45 to 55 ° C.

The mixed gas of steam and the monohydric phenol compound sent to the second cooling step is cooled by being countercurrently contacted with a second cooling medium composed of an aqueous solution of the monohydric phenol compound. This second cooling step is carried out so that substantially all of the steam and monohydric phenol compound sent to this step are condensed and liquefied, and an aqueous solution of the monohydric phenol compound is recovered from this step. A part of the aqueous solution of the monohydric phenol compound obtained in the second cooling step can be used as the second cooling medium. The concentration of the monohydric phenol compound in the aqueous solution depends on the composition of the stripping gas and the first
Although it depends on the conditions of the cooling step, it is usually 55 to 75% by weight. The temperature of the second cooling medium is about 1 to 10 ° C. lower than the condensation temperature of steam.

The second cooling medium used in the second cooling step may be an amount sufficient to condense the total amount of the mixed gas, and normally the steam sent from the first cooling step and the monohydric phenol compound are mixed. 100 to 30 by weight ratio to gas
It is 0, preferably 190 to 250. The pressure in this second cooling step is less than or equal to 30 Torr, preferably 5 to 20 Torr and corresponds to the pressure in the first cooling step. The cooling temperature (steam condensing temperature) in the second cooling step may be a temperature at which the total amount of the mixed gas of steam and the monohydric phenol compound is condensed and liquefied under the pressure conditions.

The cooler used in the first cooling step and the second cooling step may be any gas-liquid contact type device, and any one may be used. As such a cooler, for example, a packed tower or a spray tower can be used. When using a packed column, it is preferable to use a Raschig ring, a pole ring, a porous metal plate or the like as the packing so as to suppress the pressure loss. In addition, the first cooling step and the second
The coolers used in the cooling step may be installed separately, but may be a one-column type device including two coolers.

Next, one embodiment of the stripping gas condensation treatment method of the present invention will be described with reference to the drawings. In FIG. 1, 1 is a first cooler and 2 is a second cooler. Line 3 shows the stripping gas line that continues to the steam stripping device. Line 4 is a vacuum line connected to an exhaust pump (not shown) and a cooler, and the entire system including the steam stripping device (not shown) and the cooler is kept under reduced pressure. The stripping gas from the steam stripping device is supplied to the lower part of the first cooler 1 through the line 3, and here, the first cooling medium (which is introduced from the upper part of the first cooler through the line 5 ( Countercurrent contact with a monohydric phenol compound or a monohydric phenol compound containing a bisphenol compound). The cooling medium in which the bisphenol compound and the monohydric phenol compound condensed in the first cooler are dissolved is discharged from the bottom of the first cooler through the line 6 including the discharge pump 7. The cooling medium extracted through this line 6 can be recycled to the line 5 as a cooling medium after cooling a part thereof to a required temperature, if necessary.

The mixed gas of steam and monohydric phenol compound extracted from the top of the first cooler 1 through the line 8 is introduced into the lower part of the second cooler 2, where the line 9 is used.
Through countercurrent contact with a second cooling medium (an aqueous solution of a monohydric phenol compound) introduced from above the second cooler. In this second cooler, the mixed gas of steam and the monohydric phenol compound is condensed and liquefied, and this condensate is secondarily cooled with the cooling medium.
A line 10 including a pump 11 that is drawn from the bottom of the cooler
Through a line 13, a part thereof is cooled through a cooler 14 for a cooling medium, and then a line 9 is recycled to a second cooler. The rest of the cooling medium containing the condensed steam and the monohydric phenol compound extracted through the line 11 is extracted outside the system through the line 12.

FIG. 2 shows a flow sheet in the case of using the one-column type cooling device including the first cooler and the second cooler in the stripping gas condensation treatment method of the present invention. In FIG. 2, 30 is a first cooler 1 and a second cooler 2 inside thereof.
It is a one-column type cooling device equipped with. This cooling device has a structure in which a partition plate 25 having an opening in the center is arranged between the first cooler 1 and the second cooler 2, and a cylindrical body 23 is provided upright in the opening. In this device, the annular hollow chamber formed between the outer peripheral surface of the cylindrical body 23 and the inner wall of the cooling device 30 is for storing the liquid. Reference numeral 22 is a guide plate for guiding the liquid flowing down the second cooler 2 to the annular hollow chamber. The cylindrical space 24 shows a gas passage. In the reference numerals in FIG. 2, the same reference numerals as those shown in FIG. 1 have the same meaning. In addition, in FIG.
The flow control system shown in is not shown.

[0021]

According to the present invention, the steam obtained from the steam stripping step of a bisphenol compound containing a monohydric phenol compound, the stripping gas containing the monohydric phenol compound and the bisphenol compound, is heated to 30 Torr without pressurization. It can be cooled and condensed in the following reduced pressure state. Moreover, in the case of the present invention, 3
Despite adopting a low pressure condition of 0 torr or less and a low steam condensation temperature condition corresponding thereto, no crystals of the bisphenol compound or the monohydric phenol compound are precipitated. Therefore, in the stripping gas condensation treatment method of the present invention, the efficiency of the cooler and the clogging trouble of the cooler due to solid deposition do not occur at all.

Further, in the present invention, the steam, the monohydric phenol compound and the bisphenol compound which constitute the stripping gas are all condensed, and the gases are not substantially flown into the vacuum exhaust system. Therefore, since the vacuum exhaust pump only keeps the device system under a predetermined depressurization condition, it requires only a small exhaust capacity and is very advantageous in terms of equipment cost and energy cost. In the present invention, as described above, the cooling condensation treatment of the stripping gas can be carried out at an extremely low pressure of 30 Torr or less, so that the steam stripping step in the preceding stage can be carried out at a low pressure. Therefore, from this steam stripping step, a high-purity bisphenol compound having an extremely low monohydric phenol compound content, for example, a very low-purity bisphenol compound having a monohydric phenol compound content of 50 ppm or less, particularly 20 ppm or less, can be obtained. You can

[0023]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example A stripping gas was continuously condensed according to the flow sheet shown in FIG. The operating conditions of the first cooler 1 and the second cooler 2 in this case are shown below. (Operation condition of the first cooler) (1) Stripping gas pressure introduced into the first cooler 1 from the line 3: 10 torr temperature: 180 ° C. Composition: bisphenol A 25 wt%, phenol 25 w
t%, steam 50 wt% (2) First cooling medium (phenol) introduced from line 5 Temperature: 50 ° C. Cooling medium / stripping gas weight ratio: 6 (3) Bisphenol A from stripping gas in cooler 1 Recovery rate: 100%

(Operating conditions of the second cooler) (1) Pressure of uncondensed gas introduced into the second cooler 2 through the line 8: 10 torr temperature: 51 ° C. Composition: 65 wt% phenol, 35 wt% steam (2) Second cooling medium (phenol aqueous solution) introduced into the second cooler 2 from the line 9 Temperature: 9 ° C. Cooling medium / uncondensed gas weight ratio: 190 (3) Phenol and steam from uncondensed gas in the cooler 1 Recovery rate Phenol recovery rate: 100% Steam recovery rate: 100%

[Brief description of drawings]

FIG. 1 shows a flow sheet for one embodiment of the present invention.

FIG. 2 shows a flow sheet for another embodiment of the present invention.

[Explanation of symbols]

1 first cooler 2 Second cooler 3 stripping gas line 4 vacuum line 30 One tower cooling device including a first cooler and a second cooler

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Sakashita             2-12 Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa             No. 1 in Chiyoda Kakoh Construction Co., Ltd. (72) Inventor Makoto Yasui             2-12 Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa             No. 1 in Chiyoda Kakoh Construction Co., Ltd. (72) Inventor Kaoru Shimokawara             2-12 Tsurumi Chuo, Tsurumi-ku, Yokohama-shi, Kanagawa             No. 1 in Chiyoda Kakoh Construction Co., Ltd.

Claims (4)

[Claims] 1. A stripping gas containing a monohydric phenol compound, a bisphenol compound and steam obtained when steam-stripping a mixed melt of a monohydric phenol compound and a bisphenol compound under a low pressure condition of 30 Torr or less. In the method of condensing,
The stripping gas is a monohydric phenol containing a monohydric phenol compound or a bisphenol compound under a low pressure condition of 30 Torr or less and a temperature condition in which steam is held in a gas and a part of the monohydric phenol compound is held in a liquid. In countercurrent contact with a first cooling medium composed of a compound, substantially all the amount of the bisphenol compound and a part of the monohydric phenol compound contained in the stripping gas are condensed, and the uncondensed steam and the monohydric phenol compound are condensed. A monohydric phenol compound under a first cooling step for obtaining a mixed gas, a low pressure condition of 30 Torr or less for the mixed gas obtained in the first cooling step, and a temperature condition for condensing substantially all of the mixed gas; Of the second cooling step in which the mixed gas is condensed in countercurrent contact with a second cooling medium composed of an aqueous solution of Condensation processing method of Ppingugasu. 2. The method according to claim 1, wherein a part of the condensate of the mixed gas obtained in the second cooling step is used as the second cooling medium. 3. The method according to claim 1, wherein the bisphenol compound is bisphenol A and the monohydric phenol compound is phenol. 4. The cooling temperature in the first cooling step is 42-.
The method of claim 3, which is 90 ° C.