JP2003226669A - Method for producing (meth)acrylic acid ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering a (meth)acrylic acid ester by the thermal decomposition of e.g. the Michael addition reaction product formed as a by-product in a (meth)acrylic acid ester production process while stably keeping a high recovery rate. <P>SOLUTION: The process for the production of a (meth)acrylic acid ester comprises a reaction step to form the (meth)acrylic acid ester, a purification step to separate the (meth)acrylic acid ester from a reaction mixture obtained by the (meth)acrylic acid ester production reaction and containing the (meth) acrylic acid ester and a step to recover the (meth)acrylic acid ester by the thermal decomposition of the by-product separated by the purification step. The thermal decomposition reaction is carried out essentially in a liquid phase and at least a part of the thermal decomposition reaction product is returned to the purification step. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a (meth) acrylic acid ester, and in particular, a step of decomposing a by-product of a reaction for producing a (meth) acrylic acid ester and recovering the (meth) acrylic acid ester and the like. And a method for producing a (meth) acrylic acid ester having

In this specification, (meth) acrylic acid is a generic term for acrylic acid and methacrylic acid, and either one or both may be used.

[0003]

2. Description of the Related Art As is well known, there is a propylene gas phase oxidation method as an acrylic acid production reaction for producing an acrylic acid ester. In the method of oxidizing acrylic acid to oxidize propylene, the conditions for oxidizing acrolein and acrylic acid in the next step are different. There is a process of directly oxidizing acrylic acid.

FIG. 2 is a process diagram of producing acrylic acid by two-step oxidation to produce acrylic acid and then esterification reaction. First reaction in which propylene, steam and air are filled with a molybdenum-based catalyst or the like. It is oxidized in two stages through the reactor and the second reactor to become an acrylic acid-containing gas.
The acrylic acid-containing gas is brought into contact with water in a condensing tower to form an aqueous solution of acrylic acid, an appropriate extraction solvent is added to the aqueous solution for extraction in the extraction tower, and the extraction solvent is separated in the solvent separation tower. Then, acetic acid is separated in an acetic acid separation column to obtain crude acrylic acid, and a by-product is separated from this crude acrylic acid in a rectification column to obtain a purified acrylic acid product. After this acrylic acid (purified product) undergoes an esterification reaction in an esterification reaction tower, it is converted into a crude acrylic acid ester through an extraction tower and a light separation tower, and this crude acrylic acid ester is a by-product (high The boiling point product) is separated to obtain a purified product of acrylic acid ester.

Depending on the type of acrylic ester, the process of FIG. 3 may be adopted. In this case, the by-product is obtained as a bottom product of the acrylic acid separation column.

In the acrylic ester production process of FIG. 3, acrylic acid, alcohol, recovered acrylic acid,
Each recovered alcohol is fed to the esterification reactor. The esterification reactor is filled with a catalyst such as a strongly acidic ion exchange resin. The esterification reaction mixture composed of the produced ester, unreacted acrylic acid, unreacted alcohol, produced water and the like taken out from this reactor is supplied to the acrylic acid separation column.

The bottom liquid containing unreacted acrylic acid is withdrawn from the bottom of this acrylic acid separation column and circulated to the esterification reactor. A part of the bottom liquid is supplied to the high boiling decomposition reactor and decomposed. Decomposition products, including valuables generated by decomposition, are recycled to the process. The location within the cycled process depends on the process conditions. High boiling impurities such as polymers are removed from the high boiling decomposition reactor to the outside of the system.

Acrylic acid ester, unreacted alcohol and produced water are distilled from the top of this acrylic acid separation column. A part of the distillate is circulated as a reflux liquid to the acrylic acid separation column, and the rest is supplied to the extraction column.

Water for alcohol extraction is supplied to this extraction tower. Water containing alcohol flowing out from the bottom of the tower is supplied to the alcohol recovery tower. The distilled alcohol is recycled to the esterification reactor.

The crude acrylic acid ester flowing out from the top of the extraction column is supplied to the light boiling separation column, and the light boiling substance is extracted from the top of the column and circulated into the process. The location within the cycled process depends on the process conditions. The crude acrylic acid ester from which the light-boiling substances have been removed is supplied to the acrylic acid ester product purification tower, and a high-purity acrylic acid ester is obtained from the tower top. Since the bottom liquid contains a large amount of acrylic acid, it is circulated into the process. The location in the cycled process depends on the process conditions.

Incidentally, in recent years, the recovery of acrylic acid from the above-mentioned aqueous solution of acrylic acid is carried out by distilling water and an azeotropic solvent instead of the solvent extraction method using an extraction solvent, and the azeotropic separation column An azeotropic separation method in which an azeotropic mixture of water and an azeotropic solvent is distilled from the column top and acrylic acid is recovered from the column bottom is also used.

In the case of the synthesis of methacrylic acid ester, isobutylene or t-butyl alcohol is used instead of propylene, and a purified methacrylic acid ester product is obtained through a similar oxidation process and subsequent esterification process.

As a method for producing a (meth) acrylic acid ester (acrylic acid ester, methacrylic acid ester), a transesterification reaction of a lower alcohol (meth) acrylic acid ester and a higher alcohol with an acid or the like as a catalyst is carried out. Then, a method for producing a (meth) acrylic acid ester of a higher alcohol is also performed. The crude (meth) acrylic acid ester obtained by this transesterification reaction is made into a purified (meth) acrylic acid ester through steps such as catalyst separation, concentration, and rectification.

The fractions obtained by distilling the above crude acrylic acid ester and crude methacrylic acid ester contain useful by-products such as Michael adducts. ) Acrylic acid, its ester, alcohol, etc. are collected.

As a method for decomposing the Michael adduct of acrylic acid ester, a method of decomposing by heating in the presence of a Lewis acid or a Lewis base has been adopted (JP-A-49).
-55614, Japanese Patent Laid-Open No. 09-110791). Also, while performing the decomposition reaction of Michael adduct,
A method of distilling off a desired decomposition reaction product by distillation is also known (Japanese Patent Laid-Open No. 9-110791 and Japanese Patent Laid-Open No. 9-110791).
No. 1245511 and Japanese Unexamined Patent Publication No. 8-225486).

[0016]

[Patent Document 1] Japanese Patent Laid-Open No. 49-55614

[Patent Document 2] Japanese Patent Laid-Open No. 09-110791

[Patent Document 3] Japanese Patent Laid-Open No. 9-110791

[Patent Document 4] Japanese Unexamined Patent Publication No. 9-124551

[Patent Document 5] JP-A-8-225486

[0017]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention A Michael addition reaction product by-produced in the production process of (meth) acrylic acid ester is decomposed by using a Lewis acid or a Lewis base as a catalyst to obtain (meth) acrylic acid, (meth ) In the method of recovering acrylic acid ester and alcohol, if the decomposition reaction conditions are adopted so as to obtain a high recovery rate of these (meth) acrylic acid, (meth) acrylic acid ester and alcohol, the decomposition products will not be The mass is concentrated and the viscosity increases,
Flowability may be reduced and piping may be blocked.

The present invention solves the above-mentioned conventional problems,
A high recovery rate can be stably obtained in the method of thermally decomposing a by-product such as a Michael addition reaction product by-produced in the production process of (meth) acrylic acid ester to recover (meth) acrylic acid ester. The purpose is to provide a method.

[0019]

The method for producing a (meth) acrylic acid ester according to the present invention comprises a (meth) acrylic acid ester forming reaction step and a (meth) acrylic ester from the (meth) acrylic acid ester forming reaction step. It has a purification step of separating the (meth) acrylic acid ester from the reaction mixture containing the acid ester, and a step of thermally decomposing the by-product separated from the purification step to recover the (meth) acrylic acid ester (meth). In the method for producing an acrylate ester, the thermal decomposition reaction is carried out substantially in a liquid phase, and at least a part of the thermal decomposition reaction product is returned to the purification step.

As described above, by thermally decomposing the by-product such as Michael adduct in the liquid phase and recycling at least a part of the thermal decomposition reaction product, the (meth) acrylic acid ester is produced at a high rate. It can be recovered and the process is prevented from being blocked.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

The (meth) acrylic acid ester of the present invention is not particularly limited, but includes (meth) acrylic acid methyl, ethyl (meth) acrylate, and (meth) acrylic acid n.
Examples include-butyl, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, and the like.

The Michael adduct is a by-product produced in the reaction step and the purification step when producing (meth) acrylic acid ester, and is present in these production steps (meth).
It is a compound in which (meth) acrylic acid, alcohol, water, or acetic acid is added by Michael to the α-position or β-position of the (meth) acryloyl group of the compound having an acryloyl group. The compound having a (meth) acryloyl group present in the production process includes a starting material (meth) acrylic acid, a (meth) acrylic acid ester, and a β-acrylic acid obtained by Michael-adding (meth) acrylic acid to the (meth) acrylic acid. Roxypropionic acid or β-methacryloxyisobutyric acid (hereinafter referred to as dimer), (meth) acrylic acid Michael-added to this dimer (meth) acrylic acid trimer (hereinafter referred to as trimer), and further to this trimer (meth) Carboxylic acid having a (meth) acryloyl group such as (meth) acrylic acid tetramer (hereinafter, tetramer) to which acrylic acid is added by Michael, and these carboxylic acids having a (meth) acryloyl group are esterified with alcohol. There is a corresponding (meth) acrylic acid ester. Specific examples of the Michael adduct of the present invention include β-acryloxypropionic acid and β-methacryloxyisobutyric acid and esters thereof, β-alkoxypropionic acid or β-alkoxyisobutyric acid and esters thereof, β-hydroxypropionic acid or Isobutyric acid and its ester, as well as dimer, trimer, tetramer, etc., and their esters, and their β-acryloxy form, β-
There is a hydroxy form.

In the present invention, the (meth) acrylic acid for producing the (meth) acrylic acid ester is preferably one obtained by a catalytic gas phase oxidation reaction of propane, propylene, acrolein, isobutylene, t-butyl alcohol or the like. That is, the gaseous oxidation reaction product is rapidly cooled and quenched with water, and then water and acrylic acid are separated by an azeotropic distillation method using an azeotropic solvent or an extraction method using a solvent, and further, a reduction such as acetic acid is performed. After separating the boiling point compound, it is separated from the heavy components such as Michael adduct to produce high-purity (meth) acrylic acid. Note that water and acetic acid may be simultaneously separated by using an azeotropic agent.

In the present invention, the method for producing the (meth) acrylic acid ester may be a method in which (meth) acrylic acid is esterified with an alcohol, and the acrylic ester of a lower alcohol and a higher alcohol are transesterified. Alternatively, a method of producing an acrylic acid ester of a higher alcohol may be used. Further, the manufacturing process may be either batch type or continuous type. An acid catalyst is generally used as a catalyst for esterification or transesterification of these.

The (meth) acrylic acid ester production process is preferably carried out by a reaction step and washing, extraction, evaporation, etc. for carrying out catalyst separation, concentration / purification, etc. of the crude acrylic acid ester solution obtained in this reaction step. It consists of a purification process such as distillation. The raw material molar ratio of (meth) acrylic acid or (meth) acrylic acid ester to alcohol in the reaction step, the catalyst species and amount used in the reaction, the reaction system, the reaction conditions and the like are appropriately selected depending on the alcohol raw material species used.

The Michael adduct mainly produced as a by-product in the esterification reaction step is concentrated as a heavy component at the bottom of a distillation column (in the case of FIG. 1, an acrylic ester rectification column in the case of FIG. 1) for recovering the active ingredient. To be done. The above-mentioned Michael adduct is concentrated in this bottom liquid, but in addition to this, a considerable amount of acrylic acid and / or acrylic acid ester is contained, and further, the polymerization inhibitor used in the process, the process Heavy substances such as oligomers and polymers generated in step 1, high-boiling point impurities in raw materials or reaction products thereof are contained. Further, it may include the catalyst used in the esterification or transesterification step.

This bottom liquid is decomposed by heating in the presence of Lewis acid or Lewis base, and the obtained active ingredient is recovered in the reaction step or the purification step. The distillation column for separating heavy components includes a distillation column for separating acrylic acid and heavy components, a distillation column for separating acrylic acid esters and heavy components, acrylic acid and alcohol, and acrylic acid esters and heavy components. It may be a distillation column or the like.

The distillation column is preferably equipped with a reboiler. As this reboiler, the viscosity of the bottom liquid is high, and since it has polymerizability,
Thin film evaporators are preferred. There is no particular limitation on the type of thin film evaporator. As the reboiler, a reboiler such as a thermosiphon type or a forced circulation type may be provided, and a thin film evaporator may be supplementarily used for any of these.

In the present invention, as the reaction process for carrying out the decomposition reaction of the Michael adduct, any system such as a continuous system, a batch system, a semi-batch system or an intermittent extraction system can be adopted, but a continuous system is preferred. The form of the reactor is not particularly limited, and any form such as a flow tube reactor, a complete mixing tank type stirring tank reactor, a circulating complete mixing tank reactor, or a simple hollow reactor can be adopted.

The thermal decomposition reaction of the Michael adduct is carried out not in the reactive distillation system but under the condition that the liquid phase is substantially maintained. A Lewis acid or Lewis base catalyst can be used, although a catalyst for thermal decomposition is not necessary.

The decomposition reaction temperature is 120 to 280 ° C., especially 14
0-240 degreeC is preferable. The liquid retention time based on the extracted liquid is preferably 0.5 to 50 hours, particularly 1 to 10 hours. When the decomposition reaction is carried out as a continuous reaction, the reaction time can be regarded as the reaction time which is the liquid retention time converted by the withdrawal liquid. For example, when the liquid volume in the reactor is 500 L and the liquid withdrawal amount is 100 L / H, the residence time is 5 hours.

In the present invention, at least a part of the thermal decomposition reaction product, preferably 50% or more, is recycled to the refining step. The remaining part is extracted as decomposition residue and becomes waste or fuel. The recycling destination of the thermal decomposition reaction product is not particularly limited, but it is preferably fed to the bottom of the heavy component separation column or a thin film evaporator which is a reboiler of the heavy component separation column. A higher recycling ratio is preferable because it reduces the amount of residues discharged. Specifically, it is preferable to recycle 80% or more of the thermal decomposition reaction product. The higher the recycling ratio, the higher the recovery rate, the higher the viscosity of the residue, and the worse the fluidity. Therefore, the upper limit is appropriately selected within the range where continuous operation is possible.

[0034]

EXAMPLES In order to specifically describe the present invention,
This will be described in detail with reference to Examples and Comparative Examples.

Example 1 As shown in FIG. 1, a decomposition reaction was carried out using the bottom liquid of a heavy fraction separation column equipped with a thin film evaporator as a reboiler in the acrylic acid methyl ester production process as a raw material. The composition of the bottom liquid was 19% by weight of acrylic acid, 1% by weight of β-hydroxypropionic acid, 7% by weight of β-hydroxypropionate, 8% by weight of β-acryloxypropionate and 6% of β-acryloxypropionate. % By weight, 40% by weight of β-methoxypropionic acid, 11% by weight of methyl β-methoxypropionate, 8% by weight of other heavy substances, 865 kg
/ H to the decomposition reactor. The decomposition reactor has an inner diameter of 10
It was a stirring tank made of Hastelloy C having a height of 00 mm and a height of 2000 mm. A heating medium was supplied to the outer jacket to control the reaction temperature at 200 ° C., and the liquid retention time was controlled by the liquid level in the decomposition reactor. The reaction pressure is 500 kP, which is the pressure to maintain the liquid phase.
kept at a. The recycling amount to the reboiler of the heavy component separation column is set to 80 so that the retention time based on the withdrawal liquid is 10 hours.
0 kg / h and the amount of withdrawal as a residue were 65 kg / h. As for the operation, there was no blockage of the pipe, etc., and stable continuous operation could be performed for 3 months. The composition of the residue was analyzed by gas chromatography, and the results were: water 0.6% by weight, methanol 10% by weight, methyl acrylate 11% by weight, acrylic acid 44% by weight, β-hydroxypropionic acid 0.4% by weight, β -Methyl hydroxypropionate 4% by weight, β-acryloxypropionate 2% by weight, β-acryloxypropionate methyl 1% by weight, β-methoxypropionate 14% by weight, β-methoxypropionate methyl 4% by weight, and others The amount of heavy substances was 9% by weight.

Comparative Example 1 A decomposition reaction was carried out using the bottom liquid of a heavy fraction separation column equipped with a thin film evaporator as a reboiler in the acrylic acid methyl ester production process as a raw material. The composition of the bottom liquid is acrylic acid 20
%, Β-hydroxypropionic acid 1% by weight, β-hydroxypropionic acid 8% by weight, β-acryloxypropionic acid 8% by weight, β-acryloxypropionate methyl 7% by weight, β-methoxypropionic acid 41% by weight %, 12% by weight of methyl β-methoxypropionate, and 3% by weight of other heavy substances and the like were supplied to the decomposition reactor at 150 kg / h. The decomposition reactor has an inner diameter of 1000 mm and a height of 20.
It is a stirring tank made of Hastelloy C of 00 mm, the heat medium is supplied to the outer jacket to control the reaction temperature to 200 ° C.,
The reaction pressure was kept at 130 kPa. A column having an inner diameter of 400 mm, a height of 4000 mm, and a filler of 2000 mm packed in the upper part of the stirred tank reactor was further connected to a condenser to carry out the decomposition reaction by reactive distillation. The liquid retention time is controlled by the liquid level in the decomposition reactor, and the retention time based on the extracted liquid is 1
It was set to 0 hours. As a result, after one month of continuous operation, the operation was stopped due to a blocking problem downstream of the extraction pipe. During this period, the amount of residue extracted is 76 kg on average.
/ H, the result of gas chromatography analysis of the composition of the residue was 0.2% by weight of water, 0.2% by weight of methanol,
Methyl acrylate 0.3% by weight, acrylic acid 39% by weight, β-hydroxypropionic acid weight 0.3%, β-hydroxypropionate methyl 7% by weight, β-acryloxypropionic acid weight 4%, β-acryloxy Methyl propionate 4% by weight, β-methoxypropionic acid weight 31
%, 8% by weight of methyl β-methoxypropionate, and 6% by weight of other heavy substances.

As is clear from the results of Examples and Comparative Examples, the use of the method of the present invention not only makes it possible to increase the recovery rate of the active ingredient, but also makes it possible to reduce the amount of light in the residue. By increasing the amount, the fluidity of the residue increases, clogging troubles can be avoided, and stable continuous operation can be achieved.

[0038]

As described above, according to the present invention,
The Michael addition reaction product by-produced in the (meth) acrylic ester production process can be thermally decomposed to recover the (meth) acrylic ester at a high rate. Further, the (meth) acrylic acid ester can be stably produced without causing a blocking trouble in the process.

[Brief description of drawings]

FIG. 1 is a process drawing of the acrylic ester of the present invention.

FIG. 2 is a process diagram of a conventional method.

FIG. 3 is a process diagram of another conventional method.

Continued front page    (72) Inventor Yasuyuki Ogawa             1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Corporation             Inside the company (72) Inventor Yoshiro Suzuki             1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Corporation             Inside the company F-term (reference) 4H006 AA02 AC26 AC41 AC43 AC46                       AC48 AD11 AD30 BA28 BA32                       BA36 BC53 BD34 BD40 BD53

Claims (11)

[Claims] 1. A (meth) acrylic acid ester forming reaction step and a (meth) acrylic acid ester-containing reaction mixture obtained from the (meth) acrylic acid ester forming reaction step.
A purification step of separating the acrylate ester and a pyrolysis of the by-product separated from the purification step (meth)
And a step of recovering an acrylate ester (meth)
In the method for producing an acrylic ester, the thermal decomposition reaction is carried out substantially in a liquid phase, and at least a part of the thermal decomposition reaction product is returned to the purification step, the method for producing a (meth) acrylic ester. . 2. The method for producing a (meth) acrylic acid ester according to claim 1, wherein 50% or more of the thermal decomposition reaction product is returned to the purification step. 3. The method for producing (meth) acrylic acid ester according to claim 1, wherein the by-product is a bottom liquid of a distillation column for separating heavy components in the purification step. 4. The method for producing a (meth) acrylic acid ester according to claim 3, wherein the distillation column is equipped with a thin film evaporator as a reboiler. 5. The method according to claim 1, wherein the (meth) acrylic acid ester forming reaction is an esterification reaction of (meth) acrylic acid and an alcohol, and / or
Alternatively, the method for producing a (meth) acrylic acid ester is characterized by a transesterification reaction of a (meth) acrylic acid ester and an alcohol. 6. The method for producing a (meth) acrylic acid ester according to claim 5, wherein the alcohol is methanol, ethanol or butanol. 7. The method for producing a (meth) acrylic acid ester according to claim 1, wherein the by-product contains a Michael adduct. 8. The method according to claim 7, wherein the Michael adduct is a compound obtained by adding water, alcohol, (meth) acrylic acid or acetic acid to the α-position or β-position of a (meth) acryloyl group ( Method for producing (meth) acrylic acid ester. 9. The method for producing a (meth) acrylic acid ester according to claim 1, wherein the thermal decomposition reaction temperature is 120 to 280 ° C. 10. The method for producing a (meth) acrylic ester according to claim 1, wherein the thermal decomposition reaction time is 0.5 to 50 hours. 11. The method for producing a (meth) acrylic acid ester according to claim 1, wherein 80% or more of the thermal decomposition reaction product is returned to the purification step.