JPH11124347A - Recovery of methanol - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing methyl (meth)acrylate in an economically advantageous way through such a process that a vapor comprising methyl (meth)acrylate, methanol and water is condensed, the resulting condensate is separated into an oily phase and an aqueous phase, and the methanol is recovered as an aqueous phase; wherein the methanol is transferred into the aqueous phase in high extraction rate. SOLUTION: When a vapor comprising methyl (meth)acrylate, methanol and water is to be condensed by a condenser, the vapor is subjected to gas/liquid contact with water; alternatively, when a vapor comprising methyl (meth) acrylate and methanol is to be condensed by a condenser, water is added to the vapor to effect a gas/liquid contact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for recovering methanol. More specifically, the present invention provides, for example, an esterification reaction of (meth) acrylic acid
(Meth) acrylate is produced by a transesterification reaction between methyl (meth) acrylate, methanol and water obtained in a process for producing methyl acrylate, or, for example, methyl (meth) acrylate and alcohol. The present invention relates to a method for efficiently recovering methanol from steam containing methyl (meth) acrylate and methanol obtained in a process.

[0002] In the present invention, methyl acrylate and methyl methacrylate are collectively referred to as methyl (meth) acrylate.

[0003]

2. Description of the Related Art Methyl (meth) acrylate is produced by an esterification reaction of (meth) acrylic acid and methanol, and (meth) acrylic ester is produced by a transesterification reaction of methyl (meth) acrylate and alcohol. Is produced industrially. In the case of the esterification reaction, the reaction solution contains unreacted methanol, unreacted (meth) acrylic acid and generated water, in addition to methyl (meth) acrylate as a target product. .

[0004] As a method for separating unreacted methanol and the like from the reaction solution obtained by the above esterification reaction to obtain the desired methyl (meth) acrylate, the reaction solution is distilled in the presence of an azeotropic solvent. A method is known in which methyl (meth) acrylate is removed from the bottom of the column, and methanol is recovered from the top of the column together with an azeotropic solvent or an azeotropic solvent and water (for example, see JP-A-8-268938).

As a method without using an azeotropic solvent, a reaction solution obtained by the esterification reaction is distilled, and (meth) acrylic acid or the like which has not been reacted during the esterification reaction is removed from the bottom of the distillation column. From the top, distill steam such as methyl (meth) acrylate, unreacted methanol, and produced water,
This steam is cooled in a condenser and separated into an oil phase and an aqueous phase,
A method for recovering methyl (meth) acrylate from the oil phase and recovering unreacted methanol from the aqueous phase (for example, Japanese Patent Application Laid-Open No.
No. 139,947) is known. In the method described in Japanese Patent Application Laid-Open No. 1-139547, a methanol-containing aqueous phase separated by an oil-water separator (7) is supplied to an alcohol recovery column (8), where methanol is recovered, circulated and recycled. On the other hand, as for methanol contained in the oil phase, the oil phase is supplied to the light-boiling substance separation column (9), and the methanol contained in the oil phase is recovered from the top of the column, and the alcohol recovery column (8) Is circulating.

[0006]

The above-mentioned method for recovering methanol without using an azeotropic solvent is currently widely used in industry. According to the method described in Japanese Patent Application Laid-Open No. 1-139547, substantially all unreacted methanol can be recovered and reused.

In the above method, in the oil / water separator (7), the methanol extraction rate in the aqueous phase is increased, that is, the amount of methanol mixed in the oil phase is reduced, and most of the methanol is removed from the alcohol recovery column ( The recovery in step 8) is advantageous in terms of energy cost because the reflux ratio in the light-boiling substance separation column (9) can be set small, and further reduces the load on the light-boiling substance separation column (9). There are great advantages such as miniaturization. Also, in the case of condensing the vapor from the top of the light-boiling matter separation tower (9), it is advantageous from the viewpoint of energy cost to increase the extraction rate of methanol into the aqueous phase because the reflux ratio can be set smaller. It is convenient.

However, in the case of the above method, the separation of the oil phase and the aqueous phase in the oil-water separator (7) may not be sufficient, and the mixing ratio of methanol into the oil phase may increase to some extent, and A decrease in the methanol extraction rate was unavoidable. The same applies to the case of vapor condensation from the light-boiling matter separation column (9).

Thus, an object of the present invention is to produce methyl (meth) acrylate by an esterification reaction of methyl (meth) acrylate, methanol and water, in particular, methanol and (meth) acrylic acid. In the process of (1), the reaction solution obtained by the esterification reaction is distilled in a distillation column, and (meth)
When condensing a vapor containing methyl acrylate, methanol and water to separate it into an oil phase and an aqueous phase, or further separating methyl (meth) acrylate, methanol and water obtained from the top of a light boiler separation tower When the contained steam is condensed and separated into an oil phase and an aqueous phase, the extraction rate of methanol into the aqueous phase is increased, and as a result, the above-mentioned target product, methyl (meth) acrylate, is produced economically and advantageously. It is to provide a way to do it.

Another object of the present invention is to provide a process for producing a (meth) acrylate by a transesterification reaction of a vapor containing methyl (meth) acrylate and methanol, particularly methyl (meth) acrylate and an alcohol. (Meth) obtained from the top of a methanol distillation column for removing methanol produced by the transesterification reaction
When the vapor containing methyl acrylate and methanol is condensed with water and separated into an oil phase and an aqueous phase, methanol is separated into an aqueous phase with a high extraction rate, and as a result, the (meth) acrylic An object of the present invention is to provide a method for producing an acid ester economically and advantageously.

[0011]

According to the study of the present inventors, a reaction solution obtained by an esterification reaction between (meth) acrylic acid and methanol is distilled in a distillation column, and obtained from the top of the column. When vapor containing methyl (meth) acrylate, methanol and water is introduced into the condenser and condensed, a necessary amount of water is introduced to make gas-liquid contact, and then the condensate is separated into an aqueous phase and an oil phase. It was found that the separation rate of methanol improved the extraction rate of methanol into the aqueous phase. The present invention has been completed based on such findings.

That is, the present invention provides a method for condensing a vapor containing methyl (meth) acrylate, methanol and water by a condenser, separating the vapor into an oil phase and an aqueous phase, and then recovering methanol from the aqueous phase. Wherein the vapor is brought into gas-liquid contact with a required amount of water when the vapor is condensed by a condenser.

A preferred embodiment of the method is as follows.

In the process of producing methyl (meth) acrylate by the esterification reaction of (meth) acrylic acid and methanol, (a) the reaction solution is introduced into a distillation column and distilled, and (b) obtained from the top of the column. The obtained vapor containing methyl (meth) acrylate, methanol and water is condensed by a condenser, (c) the condensate is separated into an oil phase and an aqueous phase, and (d)
The aqueous phase is introduced into an alcohol recovery column, and methanol is recovered from the top. (E) On the other hand, a part of the oil phase is introduced into a light boiler separation column and distilled, and (f) is obtained from the top. Vapor containing methyl (meth) acrylate, methanol and water is condensed by a condenser; (g) the condensate is separated into an oil phase and an aqueous phase;
(H) When the aqueous phase is circulated to the alcohol recovery column to recover methanol, the step (b) or the step (b) is performed.
And a step (f) in which a vapor containing methyl (meth) acrylate, methanol and water is brought into gas-liquid contact with a required amount of water.

In the present invention, when recovering methanol from a vapor containing methyl (meth) acrylate and methanol, the vapor is brought into gas-liquid contact with a required amount of water when the vapor is condensed by a condenser. A method for recovering methanol, comprising separating an oil phase and an aqueous phase and recovering methanol from the aqueous phase.

A preferred embodiment of this method is specified as follows.

In a process for producing a (meth) acrylate by transesterification of methyl (meth) acrylate and an alcohol, (a) a vapor containing methyl (meth) acrylate and methanol obtained from a methanol distillation column is removed. When condensing with a condenser, it is brought into gas-liquid contact with the required amount of water, (b) the condensate is separated into an oil phase and an aqueous phase, and (c) the aqueous phase is introduced into an alcohol recovery column, And recovering methanol from the methanol.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a method for recovering methanol from a vapor containing methyl (meth) acrylate, methanol and water obtained in an esterification reaction between (meth) acrylic acid and methanol will be described. FIG. 1 is a flow sheet diagram showing one embodiment of this methanol recovery method.

In FIG. 1, a reaction solution from an esterification reactor (not shown) is introduced into a distillation column 10 from a line 1 and distilled, and unreacted (meth) acrylic acid is removed from the column bottom during the esterification reaction. Acid and the like are extracted from line 2. On the other hand, vapor containing methyl (meth) acrylate, methanol and water is extracted from the top of the tower.

The vapor from the top of the distillation column 10 is introduced from a line 3 into a condenser 20 to be condensed. The present invention is characterized in that at the time of this condensation, a required amount of water is introduced from the line 4 and brought into gas-liquid contact with steam.

The gas-liquid contact between the steam and the water may be such that the steam contacts the water before or simultaneously with the condensation in the condenser. For example, it is preferable to introduce water in the form of spray from the jet port 15 provided at the position shown in FIGS.

The amount of water introduced is not particularly limited, but too much water is not preferred because the dissolution of methyl (meth) acrylate in the aqueous phase increases. On the other hand, if the amount is too small, the extraction of methanol becomes insufficient and the methanol extraction rate into the aqueous phase decreases.
It is preferable to introduce water in an amount of 10 to 10 times by weight, preferably 1 to 5 times by weight. The temperature of the water may be lower than the boiling point at the pressure of the portion to be introduced, but is usually 5 ° C. or higher, preferably 10 ° C. or lower than the vapor condensation temperature. The pressure for introducing water is not particularly limited. However, in order to increase the extraction rate of methanol into the aqueous phase, it is preferable that the water be brought into contact with steam in a spray state. It is preferable that the pressure is introduced at a pressure that can maintain the spray state.

As described above, the vapor containing methyl (meth) acrylate, methanol, and water from the top of the distillation column 10 is brought into gas-liquid contact with water during the condensation, so that the water phase is formed. The extraction rate of methanol can be increased. It is considered that the reason for this is that the methanol in the steam is easily transferred to the aqueous phase due to the close contact between the steam and the water.

The liquid condensed in the condenser 20 is supplied to the oil / water separator 30.
Where it is separated into an aqueous phase and an oil phase. The aqueous phase is introduced from line 5 into the alcohol recovery tower 40. Note that a part of the aqueous phase can be circulated to the line 4 and used as water introduced from the line 4 for condensation of steam from the distillation column 10. Thereby, the extraction rate of methanol into the aqueous phase can be further increased.

From the top of the alcohol recovery tower 40, methanol partially containing methyl (meth) acrylate is recovered and recycled from the line 7 to the esterification reactor. Water from the bottom of the column is withdrawn from the line 8, and this water can be reused as water introduced from the line 4. On the other hand, a part of the oil phase containing methanol and the like in addition to methyl (meth) acrylate is introduced into the light boiler separation column 50 through the line 6 and distilled.

From the top of the light boiler separation column 50, (meth)
A vapor containing methyl acrylate, methanol and water is obtained, which vapor is withdrawn from line 9 and
After condensing at 0, the oil-water separator 70 separates the oil phase and the aqueous phase, and the aqueous phase containing methanol is circulated to the methanol recovery tower 40 via the line 11, while the oil phase is sent to the light-boiling separation tower 50. Circulate. At the time of condensation in the condenser 60, a vapor containing methyl (meth) acrylate, methanol and water is brought into gas-liquid contact with water introduced from the line 10,
By separating the oil phase and the aqueous phase with the oil-water separator 70,
The extraction rate of methanol into the aqueous phase can be increased. As a result, the methanol concentration in the reflux liquid decreases, and the reflux ratio of the light-boiling substance separation column can be set small, which is advantageous from the viewpoint of energy cost. Further, a part of the aqueous phase can be circulated to the line 10 and used for vapor condensation by gas-liquid contact with water.

The amount of water introduced, the temperature and the pressure are the same as in the case where water is introduced from the line 4 in the condenser 20 and condensed. The same applies to the method of introducing water. Regarding the water to be introduced, line 8
Water extracted from the line 10 may be supplied from the line 10,
Further, a part of the water phase separated by the oil-water separator 70 can be circulated to the line 10.

In the present invention, at least the distillation column 10
When the vapor containing methyl (meth) acrylate, methanol and water from the top of the column is condensed, gas-liquid contact between the vapor and water is performed, and at the same time, from the top of the light boiler separation column 50 When the vapor containing methyl (meth) acrylate, methanol and water is condensed, gas-liquid contact between the vapor and water may be performed. Thereby, the extraction rate of methanol into the water phase in the oil-water separator 20, or the oil-water separator 20 and the oil-water separator 60 can be increased, and as a result, the target methyl (meth) acrylate is economically advantageous. Can be manufactured.

Methyl (meth) acrylate is withdrawn from the bottom of the light-boiling matter separation column 50 and introduced into the high-boiling matter separation column 80 through the line 12. In the high-boiling matter separation column 80, methyl (meth) acrylate is purified and
To obtain a product methyl (meth) acrylate, and a high-boiling substance is withdrawn from the line 14 from the bottom of the column.

Next, a method for recovering methanol from a vapor containing methyl (meth) acrylate and methanol obtained in a transesterification reaction between methyl (meth) acrylate and alcohol will be described. FIG. 2 is a flow sheet diagram showing one embodiment of this methanol recovery method.

In FIG. 2, the transesterification reactor 100
Then, the methanol-containing vapor extracted to advance the transesterification reaction is introduced into the distillation column 10, and a vapor containing methyl (meth) acrylate and methanol is taken out from the top of the distillation column 10. This vapor is introduced into the condenser 20 from the line 3 to be condensed. The present invention is characterized in that, during this condensation, a required amount of water is introduced from the line 4 and brought into gas-liquid contact with the vapor. .

The amount of water introduced, the temperature, the pressure, and the like at this time are the same as those in the above-described process for producing methyl (meth) acrylate in the case where water is introduced from the line 4 in the condenser 20 and condensed. is there. The same applies to the method of introducing water. As for water to be introduced, water extracted from the line 7 may be supplied from the line 4, and for water to be introduced, water extracted from the line 8 may be supplied from the line 10.

As a result, the extraction rate of methanol into the aqueous phase can be increased, and as a result, (meth) acrylic acid esters can be produced economically and advantageously.

The oil phase obtained in the oil / water separator 30 is
Cycle to zero. The aqueous phase is introduced into the alcohol recovery column 40 via the line 5 and distilled, and methanol is recovered from the top via the line 6. On the other hand, water is extracted from the bottom of the tower as wastewater through line 7, and this water can be reused as water introduced from line 4. In addition, a part of the aqueous phase can be circulated to the line 4 and used as water used for gas-liquid contact with steam from the distillation column 10.

[0035]

According to the present invention, in a process for producing methyl (meth) acrylate by an esterification reaction between (meth) acrylic acid and methanol, the reaction solution is distilled in a distillation column and obtained from the top of the column. , Methyl (meth) acrylate, methanol and water are condensed by a condenser, and then separated into an oil phase and an aqueous phase. When methanol is recovered from the aqueous phase, the vapor By bringing gas and liquid into contact with water, the extraction rate of methanol into the aqueous phase can be increased, and as a result, the desired methyl (meth) acrylate can be produced economically and advantageously.

In a process for producing a (meth) acrylate by transesterification of methyl (meth) acrylate with an alcohol, a vapor containing methyl (meth) acrylate and methanol obtained from a methanol distillation column is removed. After being condensed by a condenser, it is separated into an oil phase and an aqueous phase, and when recovering methanol from the aqueous phase, the vapor is condensed by the condenser and brought into gas-liquid contact with water to form an aqueous phase. Can be increased, and as a result, the desired (meth) acrylic acid ester can be produced economically and advantageously.

[0037]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. In addition,% means weight%.

Example 1 According to the flow sheet shown in FIG. 1, a 20-stage Oldershaw distillation column having an inner diameter of 32 mm was used as the distillation column 10.
A Dimroth is used as the condenser 20, and a stationary oil / water separator is used as the oil / water separator 30, while a part of the separated oil phase is refluxed to the top of the distillation column 10 so as to have a reflux ratio of 0.5. Distillation vapor was condensed.

The esterification reaction product (composition: 29.0% of methacrylic acid, 59.0% of methyl methacrylate, 5.0% of methanol, 6.5% of water, 0.5% of others) was fed from line 1 to a distillation column. The mixture was fed to the bottom of column 10 at 180 g / h and distilled under normal pressure. From the bottom of the column, a liquid containing 52.2% of methacrylic acid, 44.4% of methyl methacrylate, 1.0% of methanol, 1.5% of water, and 0.9% of other liquid was supplied to the column 2 through line 2.
g / h. On the other hand, when the vapor containing methyl methacrylate, methanol and water from the top is supplied to the condenser 20 by the line 3 and condensed,
0 ° C. water is introduced in a mist at 10 g / h and brought into gas-liquid contact,
The vapor was condensed in the condenser 20. Next, the condensed liquid was introduced into the oil / water separator 30, where it was separated into an oil phase and an aqueous phase.

From line 6, methyl methacrylate
The oil phase containing 4%, methanol 3.8% and water 1.8% is 65 g / h, and from line 5, water containing 2.0% methyl methacrylate, 22.0% methanol and 76.0% water A phase was obtained at 25 g / hr. Here, the extraction ratio of methanol into the aqueous phase: (methanol in aqueous phase) /
(Methanol in aqueous phase + methanol in oil phase)
8%.

Example 2 According to the flow sheet shown in FIG.
0, a 30-stage Oldershaw distillation column having an inner diameter of 32 mm, a Dimroth as a condenser 60, and a stationary oil / water separator as an oil / water separator 70, and the separated oil phase was a column of a light boiler separation column 50. The distillate vapor was condensed while refluxing to the top.

The oil phase obtained in Example 1 and containing 94.4% of methyl methacrylate, 3.8% of methanol and 1.8% of water from the line 6 was subjected to the light boiler separation column 5 at 150 g / h.
The mixture was fed to the top of column 0 and distilled under atmospheric pressure. From the bottom of the column, crude methyl methacrylate was withdrawn at 168 g / h via line 12.

On the other hand, steam containing methyl methacrylate, methanol and water from the top of the column
When water is condensed and supplied to the condenser 10, water at 30 ° C. is introduced in a mist state from the line 10 at a rate of 32 g / h and brought into gas-liquid contact.
Within 0, the distillate vapor was condensed. Next, the condensate was introduced into an oil-water separator 70, where it was separated into an oil phase and an aqueous phase. From line 11, an aqueous phase containing 4.4% methyl methacrylate, 15.5% methanol and 80.1% water was 44 g /
h. Here, the extraction ratio of methanol into the aqueous phase: (methanol in the aqueous phase) / (methanol supplied to the light-boiling matter separation column 50) was almost 100%.

Example 3 According to the flow sheet shown in FIG. 2, a 20-stage Oldershaw distillation column having an inner diameter of 32 mm was used as the distillation column 10.
Dimroth is used as the condenser 20, a stationary oil / water separator is used as the oil / water separator 30, and the transesterification reactor 100 is used.
A 3 L (liter) round bottom flask equipped with a stirrer was used. This transesterification reactor 100 was charged with 1290 g of methyl acrylate, 761 g of 2-methoxyethanol, 15 g of dibutyltin oxide and 3 g of phenothiazine, and reacted at normal pressure.

A vapor containing methyl acrylate and produced methanol is distilled from the top of the distillation column 10 and supplied to the condenser 20 from the line 3 to condense 100 g of water at 30 ° C. from the line 4. / H, the mixture was introduced into the mist, and distillate vapor was condensed in the condenser 20 by gas-liquid contact. Next, the condensed liquid was introduced into the oil / water separator 30, where it was separated into an oil phase and an aqueous phase.

The oil phase is refluxed to the top of the distillation column 10, and the bottom liquid of the distillation column 10 is passed through the line 2 to the transesterification reactor 10.
The reaction was continued while returning to 0, and was completed in 10 hours. 2
The reaction rate of methoxyethanol was 85.0%, and an aqueous phase 138 containing 10.0% of methyl acrylate, 18.0% of methanol and 72.0% of water was obtained from the oil / water separator 30.
0 g separated. Here, the methanol extraction ratio into the aqueous phase: (methanol in the aqueous phase) / (methanol produced) was 91.3%.

[Brief description of the drawings]

FIG. 1 is a flow sheet diagram showing one embodiment of an esterification reaction between (meth) acrylic acid and methanol.

FIG. 2 is a flow sheet diagram showing one embodiment in a transesterification reaction between (meth) acrylic acid and an alcohol.

FIG. 3 is an explanatory view showing one embodiment of gas-liquid contact.

FIG. 4 is an explanatory view showing another embodiment of gas-liquid contact.

[Explanation of symbols]

 1-14 line 15 Water inlet 10 Distiller 40 Alcohol recovery tower 50 Light boiler separation tower 20, 60 Condenser 30, 70 Oil water separator 80 High boiler separation tower 100 Transesterification reactor

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C07C 69/54 C07C 69/54 Z (72) Inventor Fumio Shibusawa 992 Koishihama, Nishioki, Aboshi-ku, Himeji-shi, Hyogo 1 Nippon Shokubai Co., Ltd.

Claims (5)

[Claims] 1. A method for condensing a vapor containing methyl (meth) acrylate, methanol and water with a condenser, separating the oil phase and the aqueous phase, and then recovering the methanol from the aqueous phase. A method for recovering methanol, comprising bringing a necessary amount of water into gas-liquid contact when condensing water with a condenser. 2. A process for producing methyl (meth) acrylate by an esterification reaction between (meth) acrylic acid and methanol in a process comprising the steps of: The process according to claim 1, wherein the product is obtained by distillation from a distillation column. 3. A process for producing a methyl (meth) acrylate in a process in which a vapor containing methyl (meth) acrylate, methanol and water is subjected to an esterification reaction between (meth) acrylic acid and methanol to produce a light boiler separation column. The method according to claim 1, which is obtained from the top of the above. 4. A method for recovering methanol from a vapor containing methyl (meth) acrylate and methanol, wherein when the vapor is condensed by a condenser, the vapor is brought into gas-liquid contact with a required amount of water, and then the condensate is oiled. A method for recovering methanol, comprising separating a phase into an aqueous phase and recovering methanol from the aqueous phase. 5. A process for producing a (meth) acrylate by transesterification of methyl (meth) acrylate and alcohol with a vapor containing methyl (meth) acrylate and methanol, wherein the methanol top is the top of a methanol distillation column. The method according to claim 4, which is obtained from: