JP2003171347A - Method for producing acrylic ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economically excellent and industrially advantageous method for producing an acrylic ester by eliminating troubles such as plugging with a polymer of an apparatus such as piping, reduction in the quality basic unit of a raw material, and reduction of product quality. <P>SOLUTION: This method for producing the acrylic ester involves reacting acrylic acid obtained by a vapor phase catalytic oxidation reaction of propylene with an alcohol. Acrylic acid containing ≤2,000 wt.ppm maleic anhydride, ≤1,000 wt.ppm β-acryloxypropionic acid and ≤500 wt.ppm total of furfural and benzaldehyde is used as the acrylic acid. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an acrylic acid ester by reacting acrylic acid with an alcohol. More specifically, among the high-boiling-point impurities by-produced in the acrylic acid production process, by producing an acrylic acid ester using acrylic acid obtained by purifying and removing only specific impurities to a specific concentration, an unfavorable polymerization reaction or The present invention relates to a method for industrially producing an acrylate ester, such as suppressing the formation reaction of impurities.

[0002]

2. Description of the Related Art Conventionally, a method of producing an acrylic acid ester by an esterification reaction between acrylic acid and an alcohol has been generally adopted. The acrylic acid to be used may be one which has been subjected to a gas phase oxidation reaction of propylene and subsequent purification treatments such as dehydration, removal of light boiling impurities and further removal of high boiling impurities, but those not subjected to high boiling impurities are used. It has been said that the acrylic acid is advantageous because the cost for purifying acrylic acid is low (Japanese Patent Laid-Open No. 9-157213,
JP-A-10-237012, JP-A-10-30605
2, JP-A 2001-213839). However, when acrylic acid containing high boiling impurities is used as a raw material,
Since an unfavorable polymerization reaction or side reaction occurs, there are problems such as clogging of equipment such as piping due to the polymer, deterioration of the main raw material unit of acrylic acid or alcohol, and deterioration of product quality.

[0003]

DISCLOSURE OF THE INVENTION The present invention avoids conventional problems such as clogging of equipment such as piping due to a polymer, deterioration of raw material consumption, and deterioration of product quality, and is industrially excellent in economic efficiency. The present invention provides a method for producing an acrylate ester, which is advantageous to

[0004]

Means for Solving the Problems The inventors of the present invention have conducted various studies in order to solve the above-mentioned problems, and as a result, as a raw material for producing an acrylate ester, an acrylic acid containing a specific impurity at a specific concentration or less When an acid is used, a polymerization reaction, which is an undesired side reaction, is suppressed, and piping, a device is blocked by the polymer, deterioration of the basic unit of raw material acrylic acid and raw material alcohol due to the undesired side reaction, and an undesired side reaction. It is possible to avoid the deterioration of the quality of the product acrylic acid ester due to the product, and the economy throughout propylene to acrylic acid ester is excellent,
The present invention has been accomplished by finding that it is extremely effective industrially.

That is, the present invention provides a method for producing acrylic acid by a gas phase catalytic oxidation reaction of propylene and producing an acrylic ester using the acrylic acid as a raw material. A gist of the present invention is to provide a method for producing an acrylate ester, which comprises using acrylic acid containing a high-boiling point impurity at a specific concentration or less.

More specifically, the present invention relates to acrylic acid in which the concentration of high-boiling impurities is set to a specific level or less, and the total amount of furfural and benzaldehyde is 500 wt ppm or less and / or maleic anhydride and 2000 wt ppm or less. And / or acrylic acid containing β-acryloxypropionic acid in an amount of 1000 ppm by weight or less is used.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. <Acrylic Acid Ester> Examples of the acrylic acid ester of the present invention include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tertiary butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate. , Methoxyethyl acrylate and the like can be exemplified. In the process of producing acrylic acid ester, methyl alcohol, ethyl alcohol, n-
Butyl alcohol, isobutyl alcohol, tertiary butyl alcohol, 2-ethylhexyl alcohol,
Esterification reaction step in which an alcohol such as isononyl alcohol or methoxyethyl alcohol is reacted with an inorganic acid such as sulfuric acid, an organic acid such as p-toluenesulfonic acid or methanesulfonic acid, or a solid acid such as a cationic ion exchange resin as a catalyst The purification step of washing, liquid-liquid separation, extraction, evaporation, distillation and the like as a unit operation for carrying out catalyst separation, concentration, purification and the like on the crude acrylic acid ester solution obtained by the reaction. Raw material molar ratio of acrylic acid and alcohols in the esterification reaction, catalyst species and amount used, reaction method,
Reaction conditions and the like are appropriately set depending on the raw material species of the alcohol used. In addition, β-acryloxypropionic acid and its esters, which are high-boiling impurities by-produced in the esterification reaction, β-hydroxypropionic acid and its esters, etc., by thermal decomposition or catalytic decomposition using a catalyst,
A decomposition step for recovering the raw material acrylic acid and alcohols may be provided.

<Acrylic Acid> Acrylic acid, which is the object of the present invention, is acrylic acid produced by a gas phase oxidation reaction of propylene. In order to obtain acrylic acid that can be used as a raw material for an acrylic ester from a catalytic gas-phase oxidation reaction product of propylene, an acrylic acid-containing gas is brought into contact with water to collect acrylic acid as an aqueous acrylic acid solution. There are several methods for separating water from this acrylic acid aqueous solution, but typical methods are shown below. As an example, there is a method in which acrylic acid is extracted from water using an extraction solvent, and then acrylic acid and the extraction solvent are separated by distillation. Furthermore, as an example, there is a method of separating water and an azeotropic agent from acrylic acid by azeotropic distillation using an azeotropic agent with water. At this time, water and acetic acid can be separated at the same time by adding an azeotropic agent that azeotropes with acetic acid, which is an impurity having a boiling point lower than that of acrylic acid. When only water is separated and acetic acid is not separated at the same time, the low-boiling point component can be substantially removed by subjecting it to a distillation step for separating low-boiling point impurities containing acetic acid as a main component. Since high-purity acrylic acid is required as a raw material for the highly water-absorbent resin, a distillation step for obtaining high-purity acrylic acid is required to further remove high-boiling impurities. on the other hand,
High-purity acrylic acid is not always necessary as the acrylate ester raw material, and it is better to use acrylic acid that does not separate high-boiling-point impurities, since this distillation step is unnecessary, which reduces construction costs and is useful for steam and other purposes. It has been regarded as economically advantageous because it allows for savings.

<Details of Problems to be Solved> When acrylic acid containing high-boiling point impurities is used as a raw material, unfavorable polymerization reactions and side reactions occur, so that the polymerization products block the equipment such as piping, acrylic acid and alcohol. However, there were problems such as deterioration of the main raw material intensity and deterioration of product quality. The solid polymer generated in the unfavorable polymerization reaction accumulates in the filter, pump strainer, nozzle, etc., and often needs to be switched and washed, and finally there was a problem that operation was stopped due to blockage. . In addition, the soluble polymer produced in the polymerization reaction has a problem that it causes an adverse effect such as formation of an emulsion in the catalyst separation and washing steps and a loss of raw material acrylic acid.

The unfavorable side reactions are acetalization reaction, esterification / transesterification reaction, oxidation reaction, etc., resulting in wasteful consumption of acrylic acid or alcohol or impurities contaminating the acrylic ester of the product. It means a side reaction such as formation of a substance that promotes a polymerization reaction, or generation of an impurity that causes an inconvenience in operation. The present inventors have found that a particular impurity is a major factor in the above problems, and have reached the present invention.

<Specific Impurities> Specific high boiling impurities contained in the acrylic acid of the present invention are benzaldehyde, furfural, maleic anhydride and β-acryloxypropionic acid. These concentrations normally contained in acrylic acid before removing high boiling impurities are 300 to 1000 ppm by weight of benzaldehyde and furfural.
200-500 ppm by weight, maleic anhydride 0.3-
1.0% by weight, β-acryloxypropionic acid 1.0-
It is 3.0% by weight.

Benzaldehyde and furfural carry out an acetalization reaction with alcohols in the esterification reaction step, not only wastefully consumes the raw material alcohol, but also the produced acetal and unreacted aldehyde are mixed in the product ester, resulting in a product. It was found that it adversely affects the polymerization behavior of
Furthermore, benzaldehyde and furfural, and those acetals produced in the esterification reaction are susceptible to oxidation by oxygen added to prevent polymerization in the purification system,
It has been found that it produces peroxides and accelerates undesired polymerization reactions.

Maleic anhydride undergoes an esterification reaction with alcohols in an esterification reaction step to produce half-esters and diesters, wasteful consumption of raw material alcohol, and a process having a decomposition step of high boiling point components. It was found that, in addition to maleic anhydride, maleic acid and its ester, they circulate and accumulate in the system as fumaric acid and ester which are their isomers. The isomerization reaction from maleic acids to fumaric acids is a reaction that occurs because the high-boiling point component decomposition step is performed at a relatively high temperature of 150 to 250 ° C., and has a behavior characteristic of a process having a high-boiling point component decomposition step. is there. Accumulation of maleic anhydride and fumaric acid, as well as their esters, causes problems such as reduction of processing capacity in the process of decomposing high-boiling components, sometimes leading to precipitation problems of maleic acid and fumaric acid, and contamination of product esters. I found to wake up.

Β-acryloxypropionic acid not only wastes alcohols by performing esterification reaction and transesterification reaction with alcohols in the esterification reaction step, but also β-acryloxypropionic acid itself is acrylic acid. It has been found to accelerate the polymerization of The upper limit of the amount of high-boiling impurities contained in the acrylic acid of the present invention is such that the total amount of benzaldehyde and furfural is 500 weight pp.
m, maleic anhydride at 2000 ppm by weight, and β-
Acryloxypropionic acid is 1000 ppm by weight, preferably 500 ppm by weight. In addition, each component enhances the precision of distillation (increased reflux ratio, increased number of theoretical plates)
However, the practical condition may be determined by the balance between the cost required and the effect of the reduction. Regarding the lower limit, the total amount of benzaldehyde and furfural is 50 ppm, and maleic anhydride is 50 p.
pm, and β-acryloxypropionic acid is 10 pp
m is considered as a guide.

<Method for Producing Specific Acrylic Acid of the Present Invention> The total concentration of benzaldehyde and furfural which are the specific high boiling point impurities of the present invention is 500 ppm by weight or less, and the concentration of maleic anhydride is 2000 ppm by weight or less. And the concentration of β-acryloxypropionic acid is 100
As a method for producing acrylic acid containing a specific concentration of 0 ppm by weight, preferably 500 ppm by weight or less, several methods can be exemplified. Conventionally, the production method of acrylic acid that does not remove high boiling impurities for ester production, which has been frequently used, is as described above, but using this as a raw material, a unit operation such as crystallization, distillation, or evaporation is performed, or an amine is used. Although the specific acrylic acid of the present invention can be produced by combining an aldehyde removal reaction using compounds and hydrazines, one-stage flash distillation or a very simple distillation method with a low theoretical plate number and a low reflux ratio is adopted. Is preferable from the viewpoint of economy.

<Overall Economic Efficiency of Propylene from Acrylate Ester> Acrylic acid esters prepared by using the acrylic acid specified in the present invention and an acrylic resin containing a large amount of high-boiling point impurities, which is a conventional technique. When comparing the production cost of acrylic acid ester from propylene, which is the starting material when acrylic acid ester is produced using acid, including the equipment cost for reducing specific high boiling point impurities in acrylic acid to specific concentration The increase in manufacturing cost is not significant, and the tangible and intangible effects such as the improvement of the raw material consumption rate in the acrylic acid ester manufacturing process, the increase of product production, the improvement of product quality, and the reduction of the frequency of operation stop are far better. The method of the present invention is very advantageous in terms of size and cost.

[0017]

EXAMPLES In order to specifically describe the present invention,
This will be described in detail with reference to Examples and Comparative Examples. Example 1 (Preparation of acrylic acid) A one-stage continuous flash distillation was performed using acrylic acid at the bottom of an azeotropic distillation column from which an azeotropic agent, water and acetic acid in an acrylic acid production plant were removed as a distillate. To obtain acrylic acid of the present invention. Table 1 shows the results of gas chromatography analysis of the compositions of the raw materials and the distillate. The flash distillation column was operated at a pressure of 10 kPa and a temperature of 80 ° C., and was operated so that the flash ratio with respect to the feed liquid was 40%.

[0018]

[Table 1]               Table 1 Acrylic acid production raw materials and products of the present invention Composition of acrylic acid                                           Feed material Distillate       Acrylic acid purity (wt%) 96.00 99.70       High boiling impurities         Benzaldehyde 421 ppm by weight 279 ppm by weight         Furfural 242 wtppm 203 wtppm         Maleic anhydride 0.69% by weight 0.157% by weight         β-acryloxypropionic acid 2.26 wt% 290 wtppm       Total other impurities 0.96 wt% 760 wt ppm

The following ester was produced using the distillate in the above table as the raw material (raw material A) of the present invention and the feed raw material in the above table as the raw material (raw material B) in Comparative Example. Example 2 (Production of Methyl Acrylate) Acrylic acid as a raw material A was used as a raw material, and acrylic acid recovered through an acid separation column and a heavy fraction separation column and fresh methyl alcohol and recovered methyl alcohol from an alcohol recovery column were combined. , H type strong acid ion exchange resin DIA-
Aeon PK-208 (manufactured by Mitsubishi Chemical Corporation) 1400
The esterification reactor filled with 1 was continuously fed at 1300 kg / hr for reaction. The reaction conditions were methyl alcohol: acrylic acid = 1.0: 1.0 (molar ratio) and a temperature of 80 ° C. The reaction product has a tower top pressure of 27 kPa and a tower bottom temperature of 93.
C., the column top temperature was 41.degree. C., and the reflux ratio (R / D) was 1.0. The crude acrylic acid methyl ester obtained from the top of the tower is sent to the product tower via the alcohol extraction tower and the low boiling point component separation tower, and is fed at 860 kg / hr.
Acrylic acid methyl ester of The acrylic acid-rich fraction at the bottom of the column collects acrylic acid from the top of the column in the heavy separation column, and the heavy fraction at the bottom of the column has a temperature of 20 at the high boiling point decomposition reactor.
A thermal decomposition reaction was performed at 0 ° C to recover the active ingredient. As a result of continuous operation for 3 months, the product productivity is 20.6 ton / da.
y was kept stable. Further, it was not necessary to switch the strainer of the extraction pump at the bottom of the acid separation column and to wash it. Furthermore, the conversion rate in the heavy substance decomposition process (conversion rate of β-acryloxypropionic acid methyl ester) was 62% during this period.
Maintained.

Comparative Example 1 Using acrylic acid as a raw material B as a raw material, operation was continued for 3 months under the same conditions as in Example 2. Productivity at the beginning of product operation
It was 20.4 ton / day, but after 3 months it was 19.9 ton / day.
It decreased to day. In addition, the pump strainer at the bottom of the acid separation column had to be switched twice, disassembled and washed because the differential pressure increased due to the clogging of solids. In addition, the conversion rate in the heavy substance decomposition step decreased from 60% at the initial stage to 53% after 3 months. Comparative Example 2 (Production of 2-ethylhexyl acrylate) Using raw material B, p-toluenesulfonic acid was used as a catalyst. And 2
The product acrylic acid 2-ethylhexyl ester was prepared by esterification with -ethylhexyl alcohol. As a result of carrying out the polymerization test (*) of the product, the induction period of the polymerization was 18 minutes on average. Example 3 Acrylic acid 2-ethylhexyl ester was similarly produced using the raw material A. As a result of conducting the polymerizability test of the product,
The average induction period of polymerization was 15 minutes. (*) Polymerization determination test method product Acrylic acid 2-ethylhexyl ester (polymerization inhibitor: contains 15 ppm of p-methoxyphenol) 10 ml
Was placed in a container having an internal volume of 30 ml equipped with a thermocouple and a gas blowing tube, and was immersed in an oil bath while blowing air at a rate of 30 ml / min to raise the internal temperature of the container to 150 ° C. The internal temperature of the vessel once reaches an equilibrium at 150 ° C, and then starts increasing due to the heat of polymerization when polymerization is disclosed. Therefore, the time from when the internal temperature starts increasing to 155 ° C is defined as the induction period. .

[0021]

As described above, by using acrylic acid as a raw material in which specific impurities of the present invention are controlled to have a specific concentration, clogging of equipment such as piping due to a polymer, deterioration of raw material consumption, product It is possible to provide an industrially advantageous method for producing an acrylate ester, which is capable of avoiding conventional problems such as deterioration of quality and is excellent in economic efficiency.

   ─────────────────────────────────────────────────── ─── 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 AC46 AC48 BA72 BS10                       KA06                 4H039 CA66 CL25

Claims (3)

[Claims] 1. A method for producing an acrylic acid ester by reacting acrylic acid with an alcohol, wherein the acrylic acid is β-acryloxypropionic acid in an amount of 1000 ppm by weight or less, and furfural and benzaldehyde in a total amount of 500 ppm by weight or less, and A method for producing an acrylate ester, which comprises using acrylic acid containing 2,000 ppm by weight or less of maleic anhydride. 2. The method for producing an acrylate ester according to claim 1, wherein the content of β-acryloxypropionic acid is 500 ppm by weight or less. 3. The method for producing an acrylic ester according to claim 1, wherein the acrylic acid is acrylic acid obtained by a gas phase catalytic oxidation reaction of propylene.