Method for producing (METH) acrylate

Abstract

Provided is a technique for improving the selectivity of a (meth) acrylic acid ester. The present invention relates to a method for producing a (meth) acrylic acid ester, comprising: reacting (meth) acrylic acid with a secondary alcohol in a reactor in the presence of an acid-type esterification catalyst and a polymerization inhibitor; and supplying an olefin-containing material obtained in the production of the (meth) acrylic acid ester to the reactor such that the ratio of the olefin concentration to the secondary alcohol concentration in the reactor is 0.001 or more.

Description

Technical Field

[0001] The present invention relates to a method for producing a (meth)acrylate. In particular, the present invention relates to a method for producing a (meth)acrylate by direct esterification of (meth)acrylic acid with a secondary alcohol. Background Art

[0002] It is a well-known technique to produce a (meth)acrylate by an esterification reaction between an alcohol and (meth)acrylic acid. As described below, this reaction is an equilibrium reaction accompanied by the generation of water.

[0003] [Chemical Formula 1]

[0004]

[0005] In order to shift the equilibrium reaction in the direction of the formation of the (meth)acrylate, it is necessary to remove the water generated in the reaction. On the other hand, this reaction is usually accompanied by side reactions that generate impurities. From the viewpoint of obtaining a high-purity (meth)acrylate that meets the technical requirements for use as a monomer for manufacturing polymers that can be used in many application fields, it is necessary to remove these impurities. Also, for economic reasons, it is preferable to recycle as much as possible the useful products present in the crude reaction mixture, particularly the unreacted reaction materials and the catalyst, in the process.

[0006] To achieve these purposes, a series of separation / purification processes including a combination of distillation, extraction, and / or decantation are usually carried out, but this process is particularly difficult to carry out due to the presence of azeotropic mixtures and is costly in terms of energy.

[0007] For example, in U.S. Patent No. 6,072,076, a method for producing an alkyl (meth)acrylate by esterification of (meth)acrylic acid with an alkanol having a chain length in the range of 1 or more and 8 or less carbon atoms in the presence of an acid esterification catalyst is disclosed.

[0008] Furthermore, in Japanese Patent Application Laid-Open No. 2014-534972 (corresponding to U.S. Patent Application Publication No. 2015 / 0299093), a method for continuously producing 2-octyl acrylate with very high purity in high yield is disclosed, which is a method for continuously producing 2-octyl acrylate by direct esterification, and this method includes: using a single reactor, and recycling of useful compounds, such as recycling of unreacted reaction materials on the one hand and an acid catalyst (particularly a sulfur-containing acid-type esterification catalyst, especially a sulfonic acid-type acid catalyst) on the other hand. Summary of the Invention

[0009] However, the method disclosed in the specification of U.S. Patent No. 6,072,076 cannot be applied to the production of (meth)acrylate by the esterification reaction of (meth)acrylic acid with a secondary alcohol. As reasons therefor, it can be cited that secondary alcohols are more likely to undergo dehydration reactions that result in the formation of olefins and water in the presence of an acid catalyst. The formation of this water accumulates due to at least a part of the aqueous phase formed by the esterification reaction being re-introduced into the system, and there is a risk that the target (meth)acrylate is more easily decomposed into the secondary alcohol and (meth)acrylic acid by hydrolysis. Also, according to the specification of U.S. Patent No. 6,072,076, the purification of the crude reaction mixture containing the desired (meth)acrylate and the residual alcohol is carried out by distillation in a distillation apparatus with a long residence time in the presence of an acid catalyst. In the case of synthesizing (meth)acrylate using a secondary alcohol, there are technical problems that olefins and water are generated by this distillation, and in addition, the (meth)acrylate decomposes (i.e., the selectivity of the (meth)acrylate is low).

[0010] In addition, in the technology disclosed in Japanese Patent Application Laid-Open No. 2014-534972 (corresponding to the specification of U.S. Patent Application Publication No. 2015 / 0299093), there is a technical problem that the intramolecular dehydration reaction of the secondary alcohol in the esterification reaction cannot be suppressed (i.e., the selectivity of the (meth)acrylate is low).

[0011] As described above, in the technologies disclosed in the specification of U.S. Patent No. 6,072,076 and Japanese Patent Application Laid-Open No. 2014-534972 (corresponding to the specification of U.S. Patent Application Publication No. 2015 / 0299093), the selectivity of the (meth)acrylate cannot be said to be sufficient.

[0012] Therefore, the present invention has been completed in view of the above circumstances, and an object thereof is to provide a technology for improving the selectivity of (meth)acrylate.

[0013] The inventors of the present invention conducted in-depth research to solve the above technical problems. As a result, it was found that by appropriately controlling the ratio of the olefin concentration to the secondary alcohol concentration in the reactor, the above technical problems can be solved, and thus the present invention was completed.

[0014] That is, the above object is achieved by the following method for producing (meth)acrylate, the method for producing (meth)acrylate including: reacting (meth)acrylic acid with a secondary alcohol in a reactor in the presence of an acid-type esterification catalyst and a polymerization inhibitor; and supplying an olefin-containing substance obtained in the production of the (meth)acrylate to the reactor such that the ratio of the olefin concentration to the secondary alcohol concentration in the reactor is 0.001 or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1It is a schematic diagram for explaining an embodiment of a (meth)acrylate manufacturing process.

[0016] Figure 2 It is a schematic diagram for explaining another embodiment of a (meth)acrylate manufacturing process.

[0017] Figure 3 It is a schematic diagram for explaining another embodiment of a (meth)acrylate manufacturing process.

[0018] Figure 4 It is a schematic diagram for explaining yet another embodiment of a (meth)acrylate manufacturing process. Detailed Embodiments

[0019] The present invention provides a method for manufacturing a (meth)acrylate, which includes: reacting (meth)acrylic acid with a secondary alcohol in a reactor in the presence of an acid-type esterification catalyst and a polymerization inhibitor; and supplying an olefin-containing substance obtained in the manufacture of the (meth)acrylate to the reactor such that the ratio of the olefin concentration in the reactor to the secondary alcohol concentration is 0.001 or more. According to the present invention, a technique for increasing the selectivity of the (meth)acrylate is provided.

[0020] Hereinafter, embodiments of the present invention will be described. It should be noted that the present invention is not limited to the following embodiments, and various changes can be made within the scope of the claims. In addition, the embodiments described in this specification can be combined arbitrarily to form other embodiments.

[0021] In this specification, the "ratio of the olefin concentration in the reactor to the secondary alcohol concentration" is also simply referred to as the "olefin / secondary alcohol concentration ratio" or the "olefin / secondary alcohol concentration ratio of the present invention". In this specification, the acid-type esterification catalyst is also simply referred to as the "esterification catalyst" or the "esterification catalyst of the present invention". In this specification, the term "(meth)acryloyl" includes both acryloyl and methacryloyl. Therefore, for example, the term "(meth)acrylic acid" includes both acrylic acid and methacrylic acid.

[0022] Unless otherwise specified, the measurement of physical properties and the like is carried out under the condition of room temperature (25 ± 5°C).

[0023] In addition, unless otherwise specified, the terms used in this specification should be understood to be used in the meanings commonly used in the art. Therefore, unless otherwise defined, all technical terms and chemical technical terms used in this specification have the same meanings as the ordinary understanding of those skilled in the art to which the present invention pertains. In case of contradictions, this specification (including definitions) shall prevail. Throughout this specification, unless otherwise specified, expressions in the singular form should be understood to also include the concepts in their plural forms. Therefore, unless otherwise specified, articles in the singular form (for example, in the case of English, "a", "an", "the", etc.) should be understood to also include the concepts in their plural forms.

[0024] The present invention is characterized in that an olefin is supplied (recycled) into a reactor in such a manner that the olefin is present in the reactor in a specific proportion or more relative to a secondary alcohol. By this configuration, the selectivity of (meth)acrylate can be improved. The detailed mechanism for exerting the above effect is not yet clear, but it is considered as follows. The present inventors found that in the process of manufacturing (meth)acrylate, an intramolecular dehydration reaction of the secondary alcohol occurs to generate an olefin, but this reaction is an equilibrium reaction. For example, when the secondary alcohol is 2-octanol, the following intramolecular dehydration equilibrium reaction occurs.

[0025] [Chemical formula 2]

[0026]

[0027] The present inventors speculated that by recycling the olefin generated in the process of manufacturing (meth)acrylate through in-system circulation into the reactor, the intramolecular dehydration of the secondary alcohol can be inhibited, and the equilibrium reaction can be shifted to the side of the secondary alcohol. Further in-depth studies were carried out on the above speculation. As a result, surprisingly, in a batch reaction, by charging (supplying, recycling, hereinafter also collectively referred to as "charging") an olefin into the reactor in such a manner that the ratio of the olefin concentration to the secondary alcohol concentration (olefin / secondary alcohol concentration ratio) in the reactor at the time of charging becomes 0.001 or more and starting the batch reaction, the equilibrium reaction shifts in the direction of inhibiting the intramolecular dehydration of the secondary alcohol, that is, the reaction shifts to the side of the secondary alcohol, and the generation of the olefin can be inhibited. Therefore, the reaction between the secondary alcohol and (meth)acrylic acid can proceed more selectively, and the selectivity of the (meth)acrylate as the final product can be improved. In addition, the yield of the (meth)acrylate as the final product can also be improved.

[0028] It should be noted that the above mechanism is a speculation and does not limit the technical scope of the present invention.

[0029] The ratio of the olefin concentration to the secondary alcohol concentration (olefin / secondary alcohol concentration ratio) in the reactor of the present invention (during feeding) is 0.001 or more. Here, if the olefin / secondary alcohol concentration ratio is less than 0.001, the equilibrium reaction cannot be shifted in the direction of converting the olefin in the reactor into a secondary alcohol (dehydration of the secondary alcohol) will occur, and the selectivity of the (meth)acrylate will decrease. From the viewpoint of further improving the selectivity of the (meth)acrylate, etc., the ratio of the olefin concentration to the secondary alcohol concentration (olefin / secondary alcohol concentration ratio) in the reactor (during feeding) is preferably 0.002 or more, more preferably 0.004 or more, further preferably more than 0.004, still more preferably 0.008 or more, further preferably more than 0.008, further preferably 0.080 or more, particularly preferably more than 0.080, and most preferably 0.150 or more. It should be noted that the intramolecular dehydration of the secondary alcohol is an equilibrium reaction. Even if an amount of olefin exceeding the amount required to reach the equilibrium reaction is introduced, the reaction only completely shifts to the secondary alcohol side (the olefin becomes a secondary alcohol). Therefore, from the viewpoint of the effect of improving the selectivity of the (meth)acrylate, there is no particular limitation on the upper limit of the ratio of the olefin concentration to the secondary alcohol concentration (olefin / secondary alcohol concentration ratio) in the reactor (during feeding). The ratio of the olefin concentration to the secondary alcohol concentration (olefin / secondary alcohol concentration ratio) in the reactor (during feeding) is, for example, 1.0 or less, preferably 0.5 or less, more preferably less than 0.300, and further preferably less than 0.250. If it is below the above upper limit, the amount of liquid recovered in the reaction can be suppressed, the charging amount of the new raw material for each batch can be sufficiently ensured, and the productivity of the (meth)acrylate can be improved.

[0030] The olefin concentration in the reactor can be, for example, 100 mass ppm or more (0.01 mass% or more), or 0.10 mass% or more, or 0.24 mass% or more, or more than 0.24 mass%, or 0.48 mass% or more, or more than 0.48 mass%, or 0.65 mass% or more. Alternatively, from the viewpoint of further improving the selectivity of the (meth)acrylate, it is preferred that the olefin concentration in the reactor is high. The olefin concentration in the reactor is, for example, 2.0 mass% or more, preferably 2.4 mass% or more, more preferably more than 2.4 mass%, further preferably 4.4 mass% or more, still more preferably more than 4.4 mass%, still more preferably 4.5 mass% or more, still more preferably more than 4.5 mass%, still more preferably 7.5 mass% or more, still more preferably more than 7.5 mass%, particularly preferably 8.5 mass% or more, and most preferably more than 8.5 mass%. It should be noted that, as described above, the intramolecular dehydration of the secondary alcohol The reaction is an equilibrium reaction. Even if an amount of olefin exceeding the amount required to reach the equilibrium reaction is introduced, the reaction simply shifts completely to the secondary alcohol side (the olefin becomes a secondary alcohol). Therefore, from the viewpoint of the effect of increasing the selectivity of (meth)acrylate, there is no particular limitation on the upper limit of the olefin concentration in the reactor (at the time of feeding). The olefin concentration in the reactor is, for example, 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 15% by mass or less. If it is below the above upper limit, the amount of liquid recovered during the reaction can be suppressed, the charging amount of fresh raw materials per batch can be sufficiently ensured, and the productivity of (meth)acrylate can be increased. It should be noted that the "olefin concentration in the reactor" refers to the olefin concentration when the olefin-containing substance is charged (supplied, recycled) into the reactor.

[0031] From the viewpoint of suppressing the selectivity of olefin, it is preferable that the secondary alcohol concentration in the reactor is low. The secondary alcohol concentration in the reactor is, for example, 30% by mass or more, preferably 35% by mass or more, more preferably 40% by mass or more, further preferably 45% by mass or more, still further preferably 50% by mass or more, and particularly preferably 55% by mass or more. In addition, from the viewpoint of further suppressing the selectivity of olefin, the upper limit of the secondary alcohol concentration in the reactor is, for example, 80% by mass or less, preferably 75% by mass or less, more preferably 70% by mass or less, further preferably 65% by mass or less, further preferably 55% by mass or less, particularly preferably 50% by mass or less, and most preferably less than 50% by mass. The "secondary alcohol concentration in the reactor" refers to the secondary alcohol concentration when the olefin-containing substance is charged (supplied, recycled) into the reactor.

[0032] In this specification, the secondary alcohol concentration and olefin concentration in the reactor, and the ratio of the olefin concentration to the secondary alcohol concentration (olefin / secondary alcohol concentration ratio) are measured by the following method.

[0033] [Calculation method of olefin / secondary alcohol concentration ratio]

[0034] The secondary alcohol concentration and olefin concentration in the reactor are measured by the following method, and the obtained olefin concentration is divided by the secondary alcohol concentration and the fourth digit after the decimal point is rounded off, and the value thus obtained is used. For example, when the olefin / secondary alcohol concentration ratio is calculated to be "0.0019...", the digit "9" in the fourth digit after the decimal point is rounded off, and the olefin / secondary alcohol concentration ratio is "0.002".

[0035] (Measurement method of secondary alcohol concentration and olefin concentration in the reactor)

[0036] The secondary alcohol concentration and olefin concentration are quantitatively analyzed according to the quantitative methods and conditions of 2-octanol, 2-octene, and 1-methylheptyl acrylate in the reaction solution described in the following examples.

[0037] Hereinafter, with reference to Figure 1 One embodiment of the method for producing a (meth)acrylate of the present invention will be described. In one embodiment of the present invention,

[0038] (a) An acid-type esterification catalyst, (meth)acrylic acid, a secondary alcohol, and a polymerization inhibitor (and other components (such as an organic solvent, etc.) if used) are supplied to the reactor 1. While reacting the (meth)acrylic acid with the secondary alcohol in the presence of the esterification catalyst and the polymerization inhibitor, the water generated in the esterification reaction is distilled off from the top of the first distillation column 2 in the form of an azeotropic composition with the secondary alcohol and / or the organic solvent if used. The obtained distillate is condensed and allowed to stand, whereby it is separated into an oil phase and a water phase. On the other hand, in the reactor 1, a reaction mixture A containing a (meth)acrylate and an olefin is obtained (step (a));

[0039] (b) The reaction mixture A is withdrawn from the bottom of the reactor 1 and supplied to the neutralization and washing tank 3. After neutralizing and washing the reaction mixture A in the neutralization and washing tank 3, it is heated to obtain a gas or its condensate. On the other hand, the remaining part (oil phase) in the neutralization and washing tank 3 is obtained as a reaction mixture B (step (b));

[0040] (c) The reaction mixture B is supplied to the second distillation column 4 for distillation, and separated into a bottom liquid of the second distillation column containing a (meth)acrylate and a recovered alcohol containing an olefin (step (c));

[0041] (d) The bottom liquid of the second distillation column 4 is withdrawn from the bottom of the second distillation column 4 and supplied to the third distillation column 5 for distillation, and separated into a purified (meth)acrylate as the final product and a bottom liquid of the third distillation column 5. The purified (meth)acrylate is withdrawn from the top of the third distillation column 5 (step (d));

[0042] (e) The bottom liquid of the third distillation column 5 is withdrawn from the bottom of the third distillation column 5 and supplied to the treatment device 6, and separated into a recovered (meth)acrylate and waste oil (step (e)).

[0043] It should be noted that, except for charging (supplying, recycling) an olefin into the reactor in such a manner that the ratio of the olefin concentration to the secondary alcohol concentration in the reactor (at the time of feeding) falls within a specific range, it can be used in the same manner as or with appropriate modifications to the conventionally known methods, and is not limited to the following embodiments.

[0044] [Step (a)]

[0045] In this step, (meth)acrylic acid, secondary alcohol, an acid-type esterification catalyst, a polymerization inhibitor, and, if necessary, an organic solvent (reaction materials) are supplied to the reactor 1 via the pipe 11a. Compounds other than these may also be further supplied to the reactor 1. It should be noted that in Figure 1 , (meth)acrylic acid, secondary alcohol, an acid-type esterification catalyst, a polymerization inhibitor, and, if necessary, an organic solvent are supplied via the same pipe 11a, or they may be supplied via different pipes. Specifically, (meth)acrylic acid may be directly introduced into the reactor via the pipe 11a, and the acid-type esterification catalyst and the polymerization inhibitor may be directly introduced into the reactor via another pipe (not shown). It is also possible that a part of the secondary alcohol is directly introduced into the reactor via a pipe, and the other part is introduced into the top of the first distillation column 2 via another pipe 11c to ensure reliable reflux of the column. Or, as will be described in detail below, the recovered alcohol (a fluid rich in secondary alcohol) obtained from the second distillation column 4 (the purification stage at the subsequent stage) may be supplied to the reactor 1 via the pipe 11b. Or, as will be described in detail below, the recovered (meth)acrylate obtained from the treatment device 6 may be supplied to the reactor 1 via the pipes 64 and 11b.

[0046] Here, as the acid-type esterification catalyst, an acid-type esterification catalyst containing sulfur and an acidic cation exchange resin can be used. Among them, as the acid-type esterification catalyst containing sulfur, for example, sulfur-containing acid compounds such as sulfuric acid and organic sulfonic acids are used, such as sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, dodecylsulfonic acid, xylenesulfonic acid, etc. As the acidic cation exchange resin, it is not limited by resin physical properties such as the structure and crosslinking degree of the resin. For example, any resin among porous or gel-type strong acidic cation exchange resins and weak acidic cation exchange resins can be used, and porous or gel-type strong acidic cation exchange resins are preferably used. Examples of the porous strong acidic cation exchange resin include: MSC-1 (manufactured by Dow), PK-208, PK-212, PK-216, PK-220, PK-228 (above, manufactured by Mitsubishi Chemical), AMBERLYST (registered trademark)-16, IR-116, IR-118, IR-122, C-26, C-26TR, C-264, C-265 (above, manufactured by Rohm and Haas), SPC-108, SPC-112 (above, manufactured by Bayer), KC-470 (manufactured by Sumitomo Chemical), etc. In addition, examples of the gel-type strong acidic cation exchange resin include: HCR-S, HCR-W2, HGR-W2 (above, manufactured by Dow), SK-1B, SK-106, SK-110 (above, manufactured by Mitsubishi Chemical), DUOLITE (registered trademark)C20H, C255LFH (above, manufactured by Rohm and Haas), K1221, K1431 (above, manufactured by Bayer), etc. These esterification catalysts can be used alone or in combination of two or more. Among them, from the aspects of operability and cost, an acid-type esterification catalyst containing sulfur is preferred, and sulfuric acid, p-toluenesulfonic acid, and methanesulfonic acid are more preferred. The acid-type esterification catalyst containing sulfur preferably contains a sulfur-containing acid compound, more preferably contains at least one compound selected from the group consisting of sulfuric acid and organic sulfonic acids, further preferably contains at least one compound selected from the group consisting of sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, dodecylsulfonic acid, and xylenesulfonic acid, particularly preferably contains at least one compound selected from the group consisting of sulfuric acid, p-toluenesulfonic acid, and methanesulfonic acid, and most preferably is at least one compound selected from the group consisting of sulfuric acid, p-toluenesulfonic acid, and methanesulfonic acid. In addition, the addition amount of the esterification catalyst is, for example, 0.5 parts by mass or more and 10 parts by mass or less, preferably 1 part by mass or more and 5 parts by mass or less, based on 100 parts by mass of (meth)acrylic acid. It should be noted that in the case of using two or more esterification catalysts in combination, the addition amount of the esterification catalyst refers to the total amount of these esterification catalysts.

[0047] The acid-type esterification catalyst (esterification catalyst, especially an acid-type esterification catalyst containing sulfur) can be supplied to the reactor as it is or in the form of a solution (such as an aqueous solution). In the latter case, the concentration of the esterification catalyst in the solution can be, for example, 50 to 90% by mass, preferably about 60 to 80% by mass, but is not limited to the above. It should be noted that when two or more esterification catalysts are used in combination, the concentration of the esterification catalyst refers to the total concentration of these esterification catalysts in the solution.

[0048] Acrylic acid or methacrylic acid used as a starting material is produced by a known method. For example, it is industrially produced from propylene or isobutene. Independent of the use of renewable alcohols, the present invention encompasses the use of renewable (meth)acrylic acid during esterification. For example, acrylic acid can be obtained by a method including a stage of gas-phase oxidation of the obtained acrolein after a first stage of dehydration of glycerol used to obtain acrolein from glycerol; or it can also be obtained by dehydration of 2-hydroxypropionic acid (lactic acid) or 3-hydroxypropionic acid and their esters. As the (meth)acrylic acid used as a starting material, it preferably contains at least one compound selected from the group consisting of acrylic acid and methacrylic acid. In one embodiment of the present invention, the (meth)acrylic acid used as a starting material includes acrylic acid. In one embodiment of the present invention, the (meth)acrylic acid used as a starting material is acrylic acid. In one embodiment of the present invention, the (meth)acrylic acid used as a starting material includes methacrylic acid. In one embodiment of the present invention, the (meth)acrylic acid used as a starting material is methacrylic acid. In one embodiment of the present invention, the (meth)acrylic acid used as a starting material is a mixture of acrylic acid and methacrylic acid. The addition amount of (meth)acrylic acid is, for example, 10 parts by mass or more and 50 parts by mass or less, preferably 20 parts by mass or more and 35 parts by mass or less, based on 100 parts by mass of the total amount of the reaction materials ((meth)acrylic acid, secondary alcohol, acid-type esterification catalyst (especially an acid-type esterification catalyst containing sulfur), inhibitor, and, in the case of addition, the total amount of the organic solvent). It should be noted that when (meth)acrylic acid is added in portions, the addition amount of the (meth)acrylic acid refers to the total amount of the (meth)acrylic acid. In addition, when acrylic acid and methacrylic acid are used in combination, the addition amount of the (meth)acrylic acid refers to the total amount of acrylic acid and methacrylic acid.

[0049] As the secondary alcohol, there is no particular limitation, and examples thereof include: isopropyl alcohol, 2-pentanol, 3-pentanol, 2-heptanol, 3-heptanol, 2-octanol, 3-octanol, 4-octanol, 2-nonanol, 2-decanol, 2-undecanol, 2-dodecanol, 2-tridecanol, 2-tetradecanol, 2-pentadecanol, 2-hexadecanol, 2-heptadecanol, 2-octadecanol, 2-nonadecanol, 2-eicosanol, 2-docosanol, etc. These secondary alcohols can be used alone or in combination of two or more. The secondary alcohol preferably contains at least one compound selected from the group consisting of isopropyl alcohol, 2-pentanol, 3-pentanol, 2-heptanol, 3-heptanol, 2-octanol, 3-octanol, 4-octanol, 2-nonanol, 2-decanol, 2-undecanol, 2-dodecanol, 2-tridecanol, 2-tetradecanol, 2-pentadecanol, 2-hexadecanol, 2-heptadecanol, 2-octadecanol, 2-nonadecanol, 2-eicosanol, and 2-docosanol, more preferably contains at least one compound selected from the group consisting of 2-heptanol, 3-heptanol, 2-octanol, 3-octanol, 4-octanol, and 2-nonanol, and still more preferably contains 2-octanol. Among them, it is still more preferably at least one compound selected from the group consisting of 2-octanol, 3-octanol, and 4-octanol, and particularly preferably 2-octanol. 2-Octanol is a renewable alcohol. Specifically, it is obtained as a by-product of sebacic acid obtained by cracking castor oil and is useful as a bioacrylic 1-methylheptyl ester (bio(meth)acrylate). That is, in a preferred embodiment of the present invention, the secondary alcohol is 2-octanol ((meth)acrylic 1-methylheptyl ester can be produced). (Meth)acrylic 1-methylheptyl ester has the following structure.

[0050] [Chemical Formula 3]

[0051] 1-Methylheptyl acrylate

[0052]

[0053] 1-Methylheptyl methacrylate

[0054]

[0055] In addition, the (meth)acrylate is obtained by reacting a secondary alcohol with (meth)acrylic acid in equimolar amounts, but it is preferable to use more of the secondary alcohol. Specifically, the addition amount of the secondary alcohol is substantially equimolar or more with respect to (meth)acrylic acid. For example, it is 0.9 mol or more and 3.0 mol or less, preferably 1.0 mol or more and 2.0 mol or less, per 1 mol of (meth)acrylic acid. It should be noted that when two or more secondary alcohols are used in combination, the addition amount of the secondary alcohol refers to the total amount of these secondary alcohols. Similarly, when acrylic acid and methacrylic acid are used in combination, the addition amount of (meth)acrylic acid refers to the total amount of acrylic acid and methacrylic acid. As Figure 1 shown, a part of the secondary alcohol is directly introduced into the reactor 1 via the pipe 11a. In addition, a part of the secondary alcohol can also be introduced into the top of the first distillation column 2 via the pipe 11c. Thereby, reflux of the first distillation column 2 can be more reliably achieved.

[0056] The polymerization inhibitor is not particularly limited, and examples thereof include: phenothiazine, hydroquinone, p-methoxyphenol, methyl hydroquinone, benzoquinone, hydroquinone monomethyl ether, di(tert-butyl)-p-cresol (BHT), p-phenylenediamine, TEMPO (2,2,6,6-tetramethyl-1-piperidine oxide), p-tert-butylcatechol, di(tert-butyl)catechol, TEMPO derivatives such as OH-TEMPO, 2,6-tert-butyl-4-methylphenol, and copper(II) dibutyldithiocarbamate. These polymerization inhibitors can be used alone or in combination of two or more. The polymerization inhibitor preferably contains at least one compound selected from the group consisting of phenothiazine, hydroquinone, p-methoxyphenol, methyl hydroquinone, benzoquinone, hydroquinone monomethyl ether, di(tert-butyl)-p-cresol (BHT), p-phenylenediamine, TEMPO (2,2,6,6-tetramethyl-1-piperidine oxide), p-tert-butylcatechol, di(tert-butyl)catechol, TEMPO derivatives (such as OH-TEMPO, etc.), 2,6-tert-butyl-4-methylphenol, and copper(II) dibutyldithiocarbamate, and more preferably contains phenothiazine. Among them, phenothiazine is preferred. In addition, the addition amount of the polymerization inhibitor is, for example, 0.05 parts by mass or more and 5 parts by mass or less, preferably 0.1 parts by mass or more and 2 parts by mass or less, per 100 parts by mass of (meth)acrylic acid. It should be noted that when two or more polymerization inhibitors are used in combination, the addition amount of the polymerization inhibitor refers to the total amount of these polymerization inhibitors. The polymerization inhibitor can also be additionally added in a subsequent purification treatment step. In this case, the addition amount of the polymerization inhibitor refers to the total amount of the amount initially added to the reactor and the amount additionally added in the subsequent purification treatment step.

[0057] An esterification catalyst, (meth)acrylic acid, a secondary alcohol, and a polymerization inhibitor are supplied to a reactor. In this case, water generated by the esterification reaction and / or water additionally introduced into the reactor form an azeotropic composition with the secondary alcohol. The amount of the secondary alcohol (total supply amount of the secondary alcohol) used to form the azeotropic composition is preferably 150 parts by mass or more and 500 parts by mass or less, more preferably 200 parts by mass or more and 350 parts by mass or less, relative to 100 parts by mass of (meth)acrylic acid. Alternatively, the amount of the secondary alcohol (total supply amount of the secondary alcohol - supply amount of the secondary alcohol used for reacting with (meth)acrylic acid) used to form the azeotropic composition is preferably 20 parts by mass or more and 100 parts by mass or less, more preferably 30 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass of (meth)acrylic acid.

[0058] Alternatively, in addition to supplying an esterification catalyst, (meth)acrylic acid, a secondary alcohol, and a polymerization inhibitor to the reactor, an organic solvent can also be supplied to the reactor. In this case, water generated by the esterification reaction and / or water additionally introduced into the reactor form an azeotropic composition with the secondary alcohol and / or the organic solvent when in use. Examples of the organic solvent that can be used when additionally supplying an organic solvent to the reactor include: aliphatic hydrocarbons such as hexane, heptane, pentane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ethers such as diethyl ether, diisopropyl ether, methyl tert-butyl ether, and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, diisopropyl ketone, and methyl isobutyl ketone, etc. These organic solvents can be used alone or two or more of them can be used in combination. The organic solvent preferably contains at least one solvent selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons, ethers, and ketones, more preferably contains aromatic hydrocarbons, further preferably contains at least one solvent selected from the group consisting of toluene and xylene, and particularly preferably contains toluene. Among them, toluene is preferred. It should be noted that the organic solvent does not contain a secondary alcohol.

[0059] In addition, the addition amount of the organic solvent is preferably introduced in a ratio of 10 parts by mass or more and 60 parts by mass or less, more preferably more than 10 parts by mass and 45 parts by mass or less, further preferably 15 parts by mass or more and 40 parts by mass or less, and further preferably 20 parts by mass or more and 35 parts by mass or less, relative to 100 parts by mass of (meth)acrylic acid. It should be noted that when two or more organic solvents are used in combination, the addition amount of the organic solvent refers to the total amount of these organic solvents.

[0060] After supplying (meth)acrylic acid, secondary alcohol, an esterification catalyst, a polymerization inhibitor, and, if necessary, an organic solvent to a reactor, (meth)acrylic acid and the secondary alcohol are batch-reacted in the reactor in the presence of the esterification catalyst. Here, the batch reaction conditions are not particularly limited, and the same conditions as those known in the art can be applied. For example, the reaction temperature is preferably 40°C or higher and 120°C or lower, more preferably 50°C or higher and 110°C or lower. In particular, by setting the reaction temperature within the above range, the formation of impurities such as olefins can be effectively suppressed. In addition, the reaction rate can be ensured, and sufficient productivity can be achieved. Regarding the reaction time, as the reaction time after reaching the specified reaction temperature, it is preferably 4 hours or more and 24 hours or less, more preferably 5 hours or more and 15 hours or less. The pressure during the reaction is not particularly limited and can be appropriately selected from atmospheric pressure, reduced pressure, or increased pressure according to the reaction mode. It is preferably atmospheric pressure or reduced pressure, more preferably reduced pressure, and particularly preferably the pressure (reduced pressure) is adjusted to reach the above reaction temperature. After the reaction for a specified time, the reaction can be terminated by cooling the reactor.

[0061] The reactor 1 may also be equipped with an external heating unit (such as a heat exchanger), and in this case, it is heated to a specified temperature by this heating unit. In addition, the reactor 1 may also be equipped with a stirrer. In addition, as described below, the esterification reaction is an equilibrium reaction accompanied by the generation of water. Therefore, in order to shift the reaction to the ester formation side, it is necessary to remove the generated water out of the system.

[0062] [Chemical formula 4]

[0063]

[0064] Therefore, the reactor 1 is equipped with a distillation column (first distillation column) 2. Thus, the generated water can be distilled out of the system, and the water can be removed from the reaction system. Here, the first distillation column 2 can be, for example, a packed distillation column or a plate distillation column with a theoretical plate number of 5 or more and 15 or less (for example, about 10). It should be noted that in Figure 1 , the reactor 1 and the first distillation column 2 are described as separate devices, but the reactor 1 and the first distillation column 2 can also be an integrated device.

[0065] As the distillation method in the first distillation column 2, known methods such as simple distillation (such as flash distillation), molecular distillation (thin-film distillation), etc. can be used, but it is not particularly limited thereto. At this time, simple distillation refers to batch distillation without a rectification section and can be implemented by a usual device. Molecular distillation (thin-film distillation) can use a Hickman-type distiller, a falling-film distiller, a rotating disk (rotor tra y) type distillers, wiped film molecular distillers, etc. The first distillation column 2 can be heated by a heating unit such as a thermosyphon or a forced circulation external heat exchanger. In this case, it is heated to a specified temperature by this heating unit. When the reactor 1 and the first distillation column 2 are equipped with external heating units, the heating units of the reactor 1 and the first distillation column 2 can be provided separately or can be the same (shared). The distillation conditions are not particularly limited. The distillation pressure is, for example, under reduced pressure between 30 Torr and 650 Torr (1 Torr = about 1.3 hPa) or under atmospheric pressure, but is not limited thereto. The distillation temperature (especially the bottom temperature of the column) is, for example, 40 °C or higher and 110 °C or lower, preferably 50 °C or higher and 100 °C or lower, etc., but is not limited thereto. The distillation time is, for example, 4 hours or longer and 24 hours or shorter, preferably 5 hours or longer and 15 hours or shorter, etc., but is not limited thereto. Under such conditions, the water generated can be efficiently distilled out of the system.

[0066] The water generated by the esterification reaction forms an azeotropic composition with the secondary alcohol and / or the organic solvent (if used) and distills out from the top of the first distillation column 2 in the form of a gas. This gas is condensed into a liquid by a condenser (not shown) and put into an intermediate tank (not shown) and allowed to stand, whereby it is separated into an oil phase and a water phase (oil-water separation). A part or all of the oil phase can be fed back (recycled) to the first distillation column 2 (not shown). Among them, the oil phase contains the (meth)acrylate, olefin, and a small amount of (meth)acrylic acid generated by the esterification reaction, as well as the secondary alcohol and the organic solvent (if used). Therefore, a part of this oil phase can be supplied (recycled) to the reactor 1 via the pipes 22a and 11b so that the olefin / secondary alcohol concentration ratio in the reactor 1 (at the time of feeding) becomes 0.001 or higher (or within the above-mentioned preferred range). It should be noted that the supply (recycling) of this oil phase is usually carried out batchwise. That is, in one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth)acrylate is (i) the azeotropic composition of the water generated in the reaction and / or the water introduced into the reactor and the secondary alcohol is supplied to the first distillation column for distillation, and the gas distilled out from the top of the first distillation column is condensed to obtain the oil phase. In one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth)acrylate is (ii) the reaction is further carried out in the presence of an organic solvent (excluding the secondary alcohol), and the azeotropic composition of the water generated in the reaction and / or the water introduced into the reactor and the secondary alcohol and / or the organic solvent is supplied to the first distillation column for distillation, and the gas distilled out from the top of the first distillation column is condensed to obtain the oil phase.

[0067] As described above, in the esterification reaction, a mixture mainly containing secondary alcohol and / or an azeotropic composition of an organic solvent and water used, and a small amount of (meth)acrylic acid is distilled, and after condensation, it is separated into two phases, an oil phase and a water phase. Therefore, the reactor 1 and the first distillation column (e.g., a packed distillation column) 2 may also be equipped with a condenser supplied with water (e.g., water at 25°C) and a decanter that receives the condensed azeotropic composition. The decanter may be a decanter equipped with a system that can automatically remove the generated reaction water by opening a solenoid valve, thereby controlling the lower water phase in a positioned manner. In addition, it may also be operated under reduced pressure by adjusting with a vacuum system.

[0068] In addition, a part of the water phase part may be discarded, or a part or all of it may be supplied to the neutralization and washing tank 3 via the pipe 22b. The water phase part is not introduced back into the first distillation column 2. Thereby, the balance of the esterification reaction can be continuously shifted to the (meth)acrylate production side (that is, the selectivity and yield can be improved). Alternatively, before biologically treating and discharging the water phase part, the secondary alcohol and (meth)acrylic acid contained at a low concentration may be recovered by performing a distillation treatment.

[0069] Through the above esterification reaction, a reaction mixture (reaction mixture A) containing (meth)acrylate and an olefin is generated in the reactor 1. This reaction mixture A usually contains, in addition to (meth)acrylate and an olefin, unreacted secondary alcohol, unreacted (meth)acrylic acid, an esterification catalyst, a polymerization inhibitor, and other high-boiling by-products, etc. Usually, (meth)acrylate is contained in the reaction mixture A in a proportion of about 50% by mass or more and 95% by mass or less.

[0070] [Process (b)]

[0071] In this process, the reaction mixture A obtained in the above process (a) is withdrawn from the bottom of the reactor 1 and supplied to the neutralization and washing tank 3 via the pipe 31. In addition, the water phase separated from the first distillation column 2 is supplied to the neutralization and washing tank 3 via the pipe 22b. The water phase is supplied, and if necessary, water is additionally supplied, and the reaction mixture A is neutralized and washed in the neutralization and washing tank 3. Thereby, the acid components and base components in the reaction mixture A are removed. Here, the neutralization and washing tank 3 may be equipped with a stirring device and may be a tank (stirring and retention tank) or a mixer that retains while stirring.

[0072] Neutralization is carried out using a base. Thereby, the acid components in reaction mixture A are neutralized. As the base, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium carbonate, etc. are used. These bases can be used alone or two or more of them can be used in combination. The base preferably contains at least one compound selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, and ammonium carbonate, and more preferably contains sodium hydroxide. Among them, sodium hydroxide is preferred. In addition, the base can also be used in the form of an aqueous solution. The addition amount of the base is only required to be an amount capable of neutralizing the acid components in reaction mixture A, and can be appropriately selected considering the supply amount of the esterification catalyst to the reactor, etc.

[0073] After neutralization, (stop stirring if stirring is being carried out,) the resulting mixture is allowed to stand, whereby the mixture is separated into an oil phase and an aqueous phase (oil-water separation). The aqueous phase part (containing the acid component and the base component (base) of the esterification catalyst) is removed out of the system via pipe 33, and only the oil phase remains in the neutralization and washing tank 3 (neutralization step).

[0074] Next, water is introduced into the neutralization and washing tank 3, and stirring is carried out if necessary to remove the base remaining in the oil phase (washing). After washing, (stop stirring if stirring is being carried out,) the resulting mixture is allowed to stand, whereby the mixture is separated into an oil phase and an aqueous phase (oil-water separation). Among them, the aqueous phase part (base component (base)) is removed out of the system via pipe 33, and only the oil phase remains in the neutralization and washing tank 3 (washing step).

[0075] The neutralization step and the washing step can be carried out in different steps in a batch operation, or neutralization and washing can also be carried out continuously in a continuous extraction tower. In addition, the neutralization step and the washing step can each be carried out once, or can also be repeated.

[0076] Through this step, most or all of the esterification catalyst contained in reaction mixture A is removed out of the system in the form of an aqueous phase.

[0077] On the other hand, the oil phase after water washing is heated. As a result, secondary alcohol, olefin, and (organic solvent in case of use) are recovered in the form of gas and condensed if necessary. The gas or condensate contains the olefin generated by the esterification reaction. Therefore, the gas or condensate can be supplied (recycled) to the reactor 1 via the pipes 32 and 11b so that the olefin / secondary alcohol concentration ratio in the reactor 1 (at the time of charging) becomes 0.001 or more (or within the above-mentioned preferred range). That is, in one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth)acrylate is (iii) the gas or its condensate obtained by supplying the reaction mixture A obtained in the reaction to a neutralization and water washing tank, and subjecting the reaction mixture A to neutralization and water washing. In one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth)acrylate is (iii') the gas or its condensate obtained by supplying the reaction mixture A obtained in the reaction to a neutralization and water washing tank, subjecting the reaction mixture A to neutralization and water washing, separating it into an aqueous phase and an oil phase, and then heating the oil phase. It should be noted that the supply (recycling) of the gas or condensate is usually carried out batchwise.

[0078] As a method for heating the oil phase after water washing, there is no particular limitation, and it can be heated with a heater or distilled. Preferably, the oil phase after water washing is distilled. As a distillation method when distilling the oil phase after water washing, known methods such as simple distillation (e.g., flash distillation) and molecular distillation (thin-film distillation) can be used, but it is not particularly limited thereto. For example, distillation columns such as packed columns and plate columns with a theoretical plate number of 5 or more and 15 or less can be used. The distillation column can be heated by a heater such as a thermosyphon or a forced-circulation external heat exchanger. At this time, the distillation conditions are not particularly limited. The distillation pressure is, for example, under reduced pressure between 20 Torr and 200 Torr (1 Torr = about 1.3 hPa) or at atmospheric pressure, but is not limited thereto. The distillation temperature (especially the bottom temperature of the column) is 50°C or more and 150°C or less, preferably 70°C or more and 120°C or less, etc., but is not limited thereto. The distillation time is 4 hours or more and 24 hours or less, preferably 5 hours or more and 15 hours or less, etc., but is not limited thereto. Under such conditions, gas (secondary alcohol, olefin, etc.) can be efficiently distilled out of the system.

[0079] After the above treatment, the oil phase (reaction mixture B) containing (meth)acrylate remains in the neutralization and water washing tank 3.

[0080] It should be noted that in the present embodiment, as Figure 1 shown, step (a) and step (b) are carried out in different apparatuses. In addition, step (a) and step (b) are carried out batchwise. Therefore, as Figure 2As shown, the processes (a) and (b) can also be carried out in one apparatus (another embodiment (I)). That is, in another embodiment (I), the reactor 1 also functions as the neutralization and water washing tank 3 ( Figure 2 “1(3)” in Figure 3 ). Specifically, in this another embodiment (I), after the reaction in process (a) ends, water phase or water separated from the first distillation column 2 is supplied via the pipe 22b to the reaction mixture A in the reactor 1(3) obtained in the process (a). In this another embodiment (I), the reactor 1 for processes (a) and (b) is integrated with the neutralization and water washing tank 3 (using the reactor 1(3)), and except for this, it is carried out in the same manner as the processes (a) and (b). In addition, in the case of this another embodiment (I), it may also include: a tank 25 that separately stores the water phase separated from the first distillation column 2 until it is supplied to the reactor 1(3). Or, as Figure 4 shown, the water phase separated from the first distillation column 2 may also be removed via the pipe 22c (waste water). In this case, water is additionally supplied to carry out process (b) (neutralization process, water washing process). It should be noted that in Figure 3 and Figure 4 , all of the water phase separated from the first distillation column 2 is removed via the pipe 22c, but a part may also be removed via the pipe 22c, and the remaining part may be supplied to the neutralization and water washing tank 3 or the reactor 1(3) (not shown). In addition, as Figure 2 and Figure 4 shown, it may also be that a part or all of the oil phase obtained by condensation and / or oil-water separation of the gas distilled from the top of the first distillation column 2 is supplied (recycled) to the reactor 1(3) via the pipes 22a(32), 11b so as to achieve a desired olefin / secondary alcohol concentration ratio.

[0081] Through the process (b), the oil phase (reaction mixture B) is obtained in the neutralization and water washing tank 3 ( Figure 1 , Figure 3 ) or the reactor 1(3) ( Figure 2 , Figure 4 ).

[0082] [Process (c)]

[0083] In this process, the oil phase (reaction mixture B) obtained in the process (b) is supplied via the pipe 41 to the second distillation column 4 for distillation. As a result, it is separated into the bottom liquid of the second distillation column containing (meth)acrylate and the recovered alcohol (fluid rich in secondary alcohol) (light boiling impurities) containing olefins and secondary alcohols. As described above, processes (a) and (b) are usually carried out batchwise, but are carried out continuously after this process (continuous operation).

[0084] In the second distillation column 4, the oil phase (reaction mixture B) obtained in the neutralization and water washing tank 3 or the reactor 1(3) is distilled. The gas distilled from the top of the column or its condensate contains olefins, secondary alcohols, (meth)acrylic acid, and a small amount of (meth)acrylate (low-boiling impurities) generated by the esterification reaction. Therefore, the gas or condensate can be supplied (recycled) to the reactor 1 via pipes 42 and 11b so that the olefin / secondary alcohol concentration ratio in the reactor 1 during charging becomes 0.001 or more (or within the preferred range). That is, in one embodiment of the present invention, the olefin-containing material obtained in the production of (meth)acrylate is (iv) the reaction mixture A obtained in the reaction is supplied to the neutralization and water washing tank, after neutralizing and washing the reaction mixture A, the obtained reaction mixture B is supplied to the second distillation column for distillation, and the gas or its condensate distilled from the top of the second distillation column. In one embodiment of the present invention, the olefin-containing material obtained in the production of (meth)acrylate is (iv') the reaction mixture A obtained in the reaction is supplied to the neutralization and water washing tank, after neutralizing and washing the reaction mixture A and separating it into an aqueous phase and an oil phase (reaction mixture B), the oil phase (reaction mixture B) is supplied to the second distillation column for distillation, and the gas or its condensate distilled from the top of the second distillation column. It should be noted that the supply (recycling) of this gas or condensate (recovered alcohol) is usually carried out batchwise.

[0085] In one embodiment of the present invention, the olefin-containing material obtained in the production of (meth)acrylate is at least one selected from the following (i) to (iv):

[0086] (i) The azeotropic composition of water generated in the reaction and / or water introduced into the reactor and the secondary alcohol is supplied to the first distillation column for distillation, and the oil phase obtained by condensing the gas distilled from the top of the first distillation column;

[0087] (ii) The reaction is further carried out in the presence of an organic solvent (excluding secondary alcohol), the azeotropic composition of water generated in the reaction and / or water introduced into the reactor and the secondary alcohol and / or the organic solvent is supplied to the first distillation column for distillation, and the oil phase obtained by condensing the gas distilled from the top of the first distillation column;

[0088] (iii) The reaction mixture A obtained in the reaction is supplied to the neutralization and water washing tank, and the gas or its condensate obtained after neutralizing and washing the reaction mixture A; and

[0089] (iv) The reaction mixture A obtained in the said reaction is fed to a neutralization and water washing tank. After neutralizing and washing the reaction mixture A, the resulting reaction mixture B is fed to a second distillation column for distillation, and the gas distilled from the top of the second distillation column or its condensate.

[0090] Herein, as the distillation method in the second distillation column 4, known methods such as simple distillation (e.g., flash distillation), molecular distillation (thin film distillation), etc. can be used, but it is not particularly limited thereto. As the second distillation column 4, a packed column and a plate column with a theoretical plate number of 5 or more and 20 or less (e.g., theoretical plate number = about 15) can be used. In addition, the second distillation column 4 can be heated by a heater such as a thermosyphon or a forced circulation type external heat exchanger. At this time, the distillation conditions are not particularly limited. The distillation pressure is, for example, under reduced pressure between 5 Torr and 50 Torr (1 Torr = about 1.3 hPa) or at atmospheric pressure, but is not limited thereto. The distillation temperature (especially the bottom temperature) is, for example, 80 °C or higher and 150 °C or lower, preferably 100 °C or higher and 130 °C or lower, etc., but is not limited thereto. Under such conditions, components with a lower boiling point (light boiling impurities containing secondary alcohol as the main component) can be efficiently distilled out of the system. If necessary, a polymerization inhibitor can also be introduced from the top of the second distillation column 4. At this time, the polymerization inhibitor can also be used in the form of a solution dissolved in secondary alcohol.

[0091] A fluid (bottom liquid) containing a large amount of (meth)acrylate (reaction mixture C) remains at the bottom of the second distillation column 4.

[0092] The operation after the second distillation column 4 is continuous. However, in this case, the recycling (return) of the gas or its condensate (recovered alcohol) is a batch operation because the return destination is a batch operation. On the other hand, the bottom liquid of the second distillation column 4 containing (meth)acrylate is sent to the third distillation column 5 via a pipe 51.

[0093] [Process (d)]

[0094] In this process, the bottom liquid (reaction mixture C) of the second distillation column 4 obtained in the said process (c) is withdrawn from the bottom of the second distillation column 4 and fed to the third distillation column 5 via a pipe 51 for distillation. Thereby, the purified (meth)acrylate as the final product is distilled out from the top of the distillation column 5 via a pipe 52, and the bottom liquid (bottom liquid D) remains at the bottom of the third distillation column 5. The purified (meth)acrylate is usually shipped as a product. On the other hand, the bottom liquid (bottom liquid D) of the third distillation column 5 contains high boiling point impurities (e.g., Michael adducts formed by the addition of secondary alcohol to (meth)acrylate, esters of (meth)acrylic acid dimers) and a polymerization inhibitor, and is transported to the next process (processing device 6) via a pipe 61.

[0095] Here, as the distillation method in the third distillation column 5, known methods such as simple distillation (e.g., flash distillation) and molecular distillation (thin-film distillation) can be used, but it is not particularly limited thereto. For example, a packed column and a plate column with a theoretical plate number of 5 or more and 20 or less (e.g., theoretical plate number = about 5 plates or more and 10 plates or less) can be used. In addition, the third distillation column 5 can be heated by a heater such as a thermosyphon or a forced circulation type external heat exchanger. At this time, the distillation conditions are not particularly limited. The distillation pressure is, for example, under reduced pressure between 5 Torr and 50 Torr (1 Torr = about 1.3 hPa) or at atmospheric pressure, but is not limited thereto. The distillation temperature (especially the bottom temperature of the column) is, for example, 80°C or higher and 150°C or lower, preferably 100°C or higher and 130°C or lower, etc., but is not limited thereto. Under such conditions, the purified (meth)acrylate can be efficiently distilled out of the system. If necessary, a polymerization inhibitor can also be introduced from the top of the third distillation column 5. At this time, the polymerization inhibitor can also be used in the form of a solution dissolved in (meth)acrylate.

[0096] It should be noted that in the present embodiment, as Figure 1 shown, steps (c) and (d) are carried out in different apparatuses, but it is also possible, as Figure 3 shown, to carry out steps (c) and (d) in one apparatus (another embodiment (II)). That is, in another embodiment (II), the second distillation column 4 and the third distillation column 5 are used as the same apparatus ( Figure 3In the case of the other embodiment (II), steps (c) and (d) are carried out in one distillation column, and are carried out under the same conditions as those described in steps (c) and (d). Here, when steps (c) and (d) are carried out in a batch operation, the oil phase (reaction mixture B) obtained in step (b) is supplied to the second distillation column 4(5) via pipe 41 for distillation (first distillation), and then the bottom liquid (reaction mixture C) remaining at the bottom of the second distillation column 4(5) is distilled (second distillation). The gas or condensate (light-boiling impurities) distilled from the top of the second distillation column 4(5) in step (c) (first distillation) is supplied (recycled) to the reactor 1 via pipes 42 and 11b. At this time, it can be supplied (recycled) in such a way as to achieve a desired olefin / secondary alcohol concentration ratio. Then, by step (d) (second distillation), the distillate line is switched, and the final product, i.e., purified (meth)acrylate, is distilled from the top of the second distillation column 4(5) via pipe 52a. Finally, the bottom liquid (bottom liquid D) remains at the bottom of the second distillation column 4(5). In addition, when steps (c) and (d) are carried out in a continuous operation, similarly, the gas or condensate (light-boiling impurities) distilled from the top of the second distillation column 4(5) in step (c) is supplied (recycled) to the reactor 1 via pipes 42 and 11b, and the purified (meth)acrylate as the final product is distilled out (side stream cut) from the side line of the second distillation column 4(5) via pipe 52b. At this time, it can be supplied (recycled) in such a way as to achieve a desired olefin / secondary alcohol concentration ratio. Finally, the bottom liquid (bottom liquid D) remains at the bottom of the second distillation column 4(5).

[0097] In addition, the embodiments described in this specification can be combined in any combination to form other embodiments. For example, as Figure 4 shown, it is also possible to combine Figure 2 the other embodiment (I) and Figure 3 the other embodiment (II) (yet another embodiment (III)).

[0098] [Step (e)]

[0099] In this step, the bottom liquid (bottom liquid D) of the third distillation column 5 obtained in step (d) is withdrawn from the bottom of the third distillation column 5 and supplied to the treatment device 6 via pipe 61. Thereby, it is separated into the active ingredient (recovered (meth)acrylate) contained in the bottom liquid (bottom liquid D) and waste oil.

[0100] The processing device 6 can be a distillation column. Here, as the distillation method in the processing device 6, well-known methods such as simple distillation (e.g., flash distillation), molecular distillation (thin-film distillation), etc. can be used, but it is not particularly limited thereto. Preferably, the processing device 6 is a molecular distillation column (thin-film distillation column). Alternatively, the processing device 6 can be heated by a heater such as a thermosyphon or a forced-circulation external heat exchanger. At this time, the distillation conditions are not particularly limited. The distillation pressure is, for example, under reduced pressure between 5 Torr and 50 Torr (1 Torr = about 1.3 hPa) or at atmospheric pressure, but it is not limited thereto. The distillation temperature (especially the bottom temperature of the column) is, for example, 80°C or higher and 150°C or lower, preferably 100°C or higher and 130°C or lower, etc., but it is not limited thereto. Under such conditions, the active ingredient (hereinafter sometimes also referred to as recovered (meth)acrylate) contained in the bottom liquid D can be efficiently separated from the waste oil.

[0101] The recovered (meth)acrylate separated in the processing device 6 contains the olefin generated by the esterification reaction. Therefore, the recovered (meth)acrylate can be supplied (recycled) to the reactor 1 via the pipes 64 and 11b so that the olefin / secondary alcohol concentration ratio in the reactor 1 (during feeding) becomes 0.001 or more (or within the above preferred range). That is, in one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth)acrylate is the active ingredient (recovered (meth)acrylate) obtained by supplying the reaction mixture A obtained in the above reaction to at least one distillation column for distillation and then supplying the bottom liquid of the distillation column to the processing device. In one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth)acrylate is the active ingredient obtained by subjecting the reaction mixture A obtained in the above reaction to the steps (b), (c), and (d) and then supplying the bottom liquid of the third distillation column to the processing device.

[0102] Alternatively, the recovered (meth)acrylate can also be supplied (recycled) to the neutralization and water washing tank 3 via the pipe 62 ( Figure 1 , 3 in the case of Figure 2 , 4The case). The recovered (meth) acrylate supplied (recycled) to the neutralization and water washing tank 3 is subjected to the same neutralization process, water washing process as in the step (b) and the distillation process if necessary. It should be noted that the gas or condensate after the above process contains the olefin generated by the esterification reaction. Therefore, this gas or condensate can be supplied (recycled) to the reactor 1 and adjusted so that the olefin / secondary alcohol concentration ratio in the reactor 1 (during feeding) is 0.001 or more (or within the above preferred range). That is, in one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth) acrylate is obtained by supplying the reaction mixture A obtained in the above reaction to a distillation column for distillation, supplying the bottom liquid of the distillation column to a treatment device to recover the active ingredient (gas or its condensate), supplying the active ingredient to a neutralization and water washing tank, and neutralizing and washing the oil phase in the neutralization and water washing tank to obtain the gas or its condensate. In one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth) acrylate is obtained by subjecting the reaction mixture A obtained in the above reaction to the step (b), step (c) and step (d), supplying the bottom liquid of the third distillation column to a treatment device to recover the active ingredient (gas or its condensate), supplying the oil phase in the neutralization and water washing tank to the neutralization and water washing tank, neutralizing and washing the oil phase, separating it into an aqueous phase and an oil phase, and then distilling the oil phase to obtain the gas or its condensate.

[0103] The operation after the second distillation column 4 is continuous, but the recycling (return) of the recovered (meth) acrylate is a batch operation because the return destination is for batch operation.

[0104] In one embodiment of the present invention, the olefin-containing substance obtained in the production of (meth) acrylate is at least one selected from the following (i) to (vi):

[0105] (i) The azeotropic composition of water generated in the reaction and / or water introduced into the reactor and the secondary alcohol is supplied to a first distillation column for distillation, and the oil phase obtained by condensing the gas distilled from the top of the first distillation column;

[0106] (ii) The reaction is further carried out in the presence of an organic solvent (except secondary alcohol), the azeotropic composition of water generated in the reaction and / or water introduced into the reactor and the secondary alcohol and / or the organic solvent is supplied to a first distillation column for distillation, and the oil phase obtained by condensing the gas distilled from the top of the first distillation column;

[0107] (iii) The reaction mixture A obtained in the reaction is supplied to a neutralization and water washing tank, and the gas or its condensate obtained after neutralizing and washing the reaction mixture A;

[0108] (iv) The reaction mixture A obtained in the said reaction is fed to a neutralization and water washing tank. After neutralizing and washing the reaction mixture A, the obtained reaction mixture B is fed to a second distillation column for distillation, and the gas distilled from the top of the second distillation column or its condensate;

[0109] (v) The reaction mixture A obtained in the said reaction is fed to a distillation column for distillation. The bottom liquid of the distillation column is fed to a treatment device to recover the active ingredient (gas or its condensate), and the active ingredient is fed to a neutralization and water washing tank. The gas or its condensate obtained after neutralizing and washing the oil phase in the neutralization and water washing tank; and

[0110] (vi) The reaction mixture A obtained in the said reaction is fed to at least one distillation column for distillation. The bottom liquid of the distillation column is fed to a treatment device, and the obtained active ingredient (recovered (meth)acrylate) is obtained.

[0111] The waste oil separated in the treatment device 6 is discarded via the pipe 63.

[0112] According to the said method, (meth)acrylate can be manufactured with a high selectivity. In addition, (meth)acrylate can be manufactured with a high purity and / or a high yield. According to the said method, (meth)acrylate can be manufactured at a low cost.

[0113] The embodiments of the present invention have been described in detail, but obviously this is only illustrative and exemplary, not restrictive. The scope of the present invention should be interpreted by the appended claims.

[0114] The present invention includes the following schemes and modes.

[0115] 1. A method for manufacturing (meth)acrylate, the manufacturing method comprising: reacting (meth)acrylic acid with a secondary alcohol in a reactor in the presence of an acid-type esterification catalyst and a polymerization inhibitor; and

[0116] feeding the olefin-containing substance obtained in the manufacture of the (meth)acrylate to the reactor in such a manner that the ratio of the olefin concentration to the secondary alcohol concentration in the reactor is 0.001 or more;

[0117] 2. The manufacturing method according to 1. above, wherein the olefin concentration in the reactor is 100 mass ppm or more;

[0118] 3. The manufacturing method according to 1. or 2. above, wherein the olefin-containing substance obtained in the manufacture of the (meth)acrylate is at least one selected from the following (i) to (iv):

[0119] (i) The azeotropic composition of water generated in the reaction and / or water introduced into the reactor with the secondary alcohol is supplied to a first distillation column for distillation, and the oil phase obtained by condensing the gas distilled from the top of the first distillation column;

[0120] (ii) The reaction is further carried out in the presence of an organic solvent (excluding secondary alcohol), and the azeotropic composition of water generated in the reaction and / or water introduced into the reactor with the secondary alcohol and / or the organic solvent is supplied to a first distillation column for distillation, and the oil phase obtained by condensing the gas distilled from the top of the first distillation column;

[0121] (iii) The reaction mixture A obtained in the reaction is supplied to a neutralization and washing tank, and the gas or its condensate obtained after neutralizing and washing the reaction mixture A; and

[0122] (iv) The reaction mixture A obtained in the reaction is supplied to a neutralization and washing tank, and after neutralizing and washing the reaction mixture A, the obtained reaction mixture B is supplied to a second distillation column for distillation, and the gas or its condensate distilled from the top of the second distillation column;

[0123] 4. The production method according to any one of 1. to 3. above, wherein the olefin-containing substance obtained in the production of the (meth)acrylate is obtained by supplying the reaction mixture A obtained in the reaction to a distillation column for distillation, supplying the bottom liquid of the distillation column to a treatment device and recovering the active ingredient (gas or its condensate), supplying the active ingredient to a neutralization and washing tank, and neutralizing and washing the oil phase in the neutralization and washing tank to obtain the gas or its condensate;

[0124] 5. The production method according to any one of 1. to 4. above, wherein the olefin-containing substance obtained in the production of the (meth)acrylate is the active ingredient (recovering (meth)acrylate) obtained by supplying the reaction mixture A obtained in the reaction to at least one distillation column for distillation and supplying the bottom liquid of the distillation column to a treatment device;

[0125] 6. The production method according to any one of 1. to 5. above, wherein the secondary alcohol is 2-octanol.

[0126] Examples

[0127] The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. It should be noted that in the following examples, unless otherwise specified, the operations are carried out at room temperature (25 ± 5 °C). In addition, unless otherwise specified, "%" and "parts" respectively refer to "mass %" and "mass parts".

[0128] Comparative Example 1

[0129] Into a 500 mL glass round-bottom flask equipped with a stirrer, 60.0 g of acrylic acid, 130.1 g of 2-octanol (1.2 moles relative to 1 mole of acrylic acid), 21.2 g of toluene, 1.2 g of sulfuric acid (2% by mass relative to acrylic acid, 0.6% by mass relative to the total volume of the charged liquid), and 0.3 g of phenothiazine were charged, and then it was immersed in an oil bath and heating was started. It should be noted that in this example, 2-octene as an olefin was not added. Therefore, the ratio of 2-octene concentration to 2-octanol was 0, and the 2-octene concentration in the reactor was 0% by mass.

[0130] The pressure in the system was slowly reduced from 800 hPa to 180 hPa to keep the liquid temperature in the round-bottom flask at 110 °C.

[0131] Starting from the time point when the liquid temperature in the round-bottom flask reached 110 °C, after 8 hours, the round-bottom flask was taken out of the oil bath and cooled to end the esterification reaction.

[0132] The reaction liquid after the reaction was analyzed according to the following method, and 2-octene as an impurity was confirmed. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on alcohol (2-octanol) were calculated for the reaction liquid after the reaction according to the following method, and the results were 1.5 mol% and 92.2 mol%, respectively. In addition, the conversion rates of acrylic acid and alcohol (2-octanol) were calculated for the reaction liquid after the reaction according to the following method, and the results were 98.6 mol% and 84.5 mol%, respectively.

[0133] (Method for measuring the concentrations of 2-octanol, 2-octene, acrylic acid, and 1-methylheptyl (meth)acrylate)

[0134] The concentrations of 2-octanol, 2-octene, acrylic acid, and 1-methylheptyl (meth)acrylate were measured by quantitatively analyzing 2-octanol, 2-octene, acrylic acid, and 1-methylheptyl (meth)acrylate in the reaction liquid using gas chromatography (GC). It should be noted that the conditions for this quantitative analysis are as follows.

[0135] Gas chromatography: GC-2014 manufactured by Shimadzu Corporation.

[0136] Column: DB-1 manufactured by Agilent Technologies, Inc. (column length 30 m × inner diameter 0.25 mm × film thickness 0.25 μm).

[0137] Column temperature: 70 °C.

[0138] Carrier gas: He.

[0139] (Method for measuring the concentration of methacrylic acid)

[0140] The concentration of methacrylic acid is measured by quantitatively analyzing methacrylic acid in the reaction solution using gas chromatography (GC). It should be noted that the conditions for this quantitative analysis are as described below.

[0141] Gas chromatography: GC-2014 manufactured by Shimadzu Corporation.

[0142] Column: DB-1701 manufactured by Agilent Technologies, Inc. (column length 30 m × inner diameter 0.53 mm × film thickness 1.0 μm).

[0143] Column temperature: 70 °C.

[0144] Carrier gas: He.

[0145] (Method for measuring the selectivity of 2-octene and 1-methylheptyl (meth)acrylate)

[0146] Based on the results of the above quantitative analysis, the selectivities of 2-octene and 1-methylheptyl (meth)acrylate are calculated using the following formulas.

[0147] [Formula 1]

[0148] Selectivity of 2-octene (based on OH) (mol%)

[0149] = [(moles of 2-octene after the reaction end) - (moles of 2-octene at the reaction feed)] × 100 / [(moles of 2-octanol at the reaction feed) - (moles of 2-octanol at the reaction end)]

[0150] [Formula 2]

[0151] Selectivity of 1-methylheptyl (meth)acrylate (based on OH) (mol%)

[0152] = [(moles of 1-methylheptyl (meth)acrylate after the reaction end) - (moles of 1-methylheptyl (meth)acrylate at the reaction feed)] × 100 / [(moles of 2-octanol at the reaction feed) - (moles of 2-octanol at the reaction end)]

[0153] (Method for measuring the conversion rates of (meth)acrylic acid and 2-octanol)

[0154] The conversion rates of (meth)acrylic acid and 2-octanol are calculated based on the results of the same quantitative analysis as described above, using the following formulas.

[0155] [Formula 3]

[0156] Conversion rate of (meth)acrylic acid (mol%)

[0157] = {1 - [(moles of (meth)acrylic acid after reaction completion) / (moles of (meth)acrylic acid at reaction feeding)]} × 100

[0158] [Formula 4]

[0159] Conversion rate of 2 - octanol (mol%)

[0160] = {1 - [(moles of 2 - octanol after reaction completion) / (moles of 2 - octanol at reaction feeding)]} × 100

[0161] Example 1

[0162] In Comparative Example 1, 10.0 g of 2 - octene was added, the addition amount of toluene was changed to 22.4 g, the addition amount of sulfuric acid was changed to 1.3 g, and the pressure in the system was slowly reduced from 800 hPa to 200 hPa to keep the liquid temperature in the round - bottom flask at 110 °C. Otherwise, the same operations as in Comparative Example 1 were carried out. It should be noted that in this example, the 2 - octanol concentration and 2 - octene concentration in the reactor were 58.1 mass% and 4.5 mass% respectively. Therefore, the ratio of 2 - octene concentration to 2 - octanol concentration was 0.077.

[0163] The reaction liquid after reaction completion was analyzed in the same way as in Comparative Example 1. As a result, the formation of 2 - octene as an impurity was confirmed. Therefore, the selectivities of 2 - octene and 1 - methylheptyl acrylate based on alcohol (2 - octanol) were calculated for the reaction liquid after reaction completion in the same way as in Comparative Example 1, and the results were 1.1 mol% and 92.9 mol% respectively. In addition, the conversion rates of acrylic acid and alcohol (2 - octanol) were calculated for the reaction liquid after reaction completion in the same way as in Comparative Example 1, and the results were 98.2 mol% and 84.1 mol% respectively.

[0164] Example 2

[0165] In Comparative Example 1, 20.0 g of 2 - octene was added, the addition amount of toluene was changed to 23.5 g, the addition amount of sulfuric acid was changed to 1.4 g, and the pressure in the system was slowly reduced from 800 hPa to 220 hPa to keep the liquid temperature in the round - bottom flask at 110 °C. Otherwise, the same operations as in Comparative Example 1 were carried out. It should be noted that in this example, the 2 - octanol concentration and 2 - octene concentration in the reactor were 55.3 mass% and 8.5 mass% respectively. Therefore, the ratio of 2 - octene concentration to 2 - octanol concentration was 0.154.

[0166] The reaction solution after the reaction was analyzed in the same manner as in Comparative Example 1, and 2-octene as an impurity was confirmed as a result. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 0.7 mol% and 93.3 mol%, respectively. In addition, the conversion rates of acrylic acid and the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 98.4 mol% and 83.7 mol%, respectively.

[0167] Example 3

[0168] In Comparative Example 1, 30.0 g of 2-octene was added, the amount of toluene added was changed to 24.6 g, the amount of sulfuric acid added was changed to 1.4 g, and the pressure in the system was slowly reduced from 800 hPa to 240 hPa to keep the liquid temperature in the round-bottom flask at 110 °C. Otherwise, the same operations as in Comparative Example 1 were carried out. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor were 52.8 mass% and 12.2 mass%, respectively. Therefore, the ratio of the 2-octene concentration to the 2-octanol concentration was 0.231.

[0169] The reaction solution after the reaction was analyzed in the same manner as in Comparative Example 1, and 2-octene as an impurity was confirmed as a result. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 0.3 mol% and 93.7 mol%, respectively. In addition, the conversion rates of acrylic acid and the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 98.5 mol% and 83.2 mol%, respectively.

[0170] Example 4

[0171] In Comparative Example 1, 12.5 g of 2-octene was added, toluene as an azeotropic solvent was not added (the amount of toluene added = 0 g), the amount of 2-octanol added was changed to 162.9 g (1.5 moles relative to 1 mole of acrylic acid), the amount of sulfuric acid added was changed to 1.4 g, and the pressure in the system was slowly reduced from 300 hPa to 40 hPa to keep the liquid temperature in the round-bottom flask at 110 °C. Starting from the time point when the liquid temperature in the round-bottom flask reached 110 °C, after 6 hours, the round-bottom flask was taken out of the oil bath and cooled to end the esterification reaction. Otherwise, the same operations as in Comparative Example 1 were carried out. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor were 68.7 mass% and 5.3 mass%, respectively. Therefore, the ratio of the 2-octene concentration to the 2-octanol concentration was 0.077.

[0172] The reaction solution after the reaction was analyzed in the same manner as in Comparative Example 1, and as a result, 2-octene as an impurity was confirmed. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were -1.3 mol% and 92.9 mol%, respectively. In addition, the conversion rates of acrylic acid and the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 93.6 mol% and 57.4 mol%, respectively.

[0173] Comparative Example 2

[0174] 60.0 g of acrylic acid, 116.4 g of 2-octanol (1.1 mol relative to 1 mol of acrylic acid), 20.2 g of toluene, 4.0 g of a 70 mass% aqueous solution of p-toluenesulfonic acid (PTS) (4.7 mass% relative to acrylic acid, 1.4 mass% relative to the total volume of the charged liquid (excluding the aqueous solution part)), and 0.3 g of phenothiazine were charged into a 500 mL glass round-bottom flask equipped with a stirrer, and then immersed in an oil bath and heating was started. It should be noted that in this example, 2-octene as an olefin was not added, and therefore, the ratio of 2-octene concentration to 2-octanol was 0, and the 2-octene concentration in the reactor was 0 mass%.

[0175] The pressure in the system was slowly reduced from 800 hPa to 190 hPa to keep the liquid temperature in the round-bottom flask at 110 °C.

[0176] Starting from the time point when the liquid temperature in the round-bottom flask reached 110 °C, after 9 hours, the round-bottom flask was taken out of the oil bath and cooled to end the esterification reaction.

[0177] The reaction solution after the reaction was analyzed in the same manner as in Comparative Example 1, and as a result, 2-octene as an impurity was confirmed. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 0.5 mol% and 92.6 mol%, respectively. In addition, the conversion rates of acrylic acid and the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 97.5 mol% and 90.4 mol%, respectively.

[0178] Example 5

[0179] In Comparative Example 2, 5.0 g of 2-octene was added, the addition amount of 2-octanol was changed to 119.4 g, the addition amount of toluene was changed to 21.0 g, the addition amount of 70 mass% PTS aqueous solution was changed to 4.2 g, and the pressure in the system was slowly reduced from 800 hPa to 200 hPa to keep the liquid temperature in the round-bottom flask at 110 °C. Otherwise, the same operations as in Comparative Example 2 were carried out. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor were 56.9 mass% and 2.4 mass% respectively. Therefore, the ratio of the 2-octene concentration to the 2-octanol concentration was 0.042.

[0180] The reaction liquid after the reaction was analyzed in the same manner as in Comparative Example 1, and 2-octene as an impurity was confirmed as a result. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same method as in Comparative Example 1, and the results were 0.0 mol% and 93.5 mol% respectively. In addition, the conversions of acrylic acid and alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same method as in Comparative Example 1, and the results were 98.8 mol% and 89.4 mol% respectively.

[0181] Example 6

[0182] In Comparative Example 2, 10.0 g of 2-octene was added, the addition amount of 2-octanol was changed to 119.4 g, the addition amount of toluene was changed to 21.4 g, the addition amount of 70 mass% PTS aqueous solution was changed to 4.3 g, and the pressure in the system was slowly reduced from 800 hPa to 210 hPa to keep the liquid temperature in the round-bottom flask at 110 °C. Otherwise, the same operations as in Comparative Example 2 were carried out. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor were 55.4 mass% and 4.6 mass% respectively. Therefore, the ratio of the 2-octene concentration to the 2-octanol concentration was 0.084.

[0183] The reaction liquid after the reaction was analyzed in the same manner as in Comparative Example 1, and 2-octene as an impurity was confirmed as a result. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same method as in Comparative Example 1, and the results were -0.5 mol% and 93.9 mol% respectively. In addition, the conversions of acrylic acid and alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same method as in Comparative Example 1, and the results were 98.7 mol% and 88.9 mol% respectively.

[0184] Comparative Example 3

[0185] Into a 500 mL glass round-bottom flask equipped with a stirrer, 60.0 g of acrylic acid, 119.3 g of 2-octanol (1.1 moles relative to 1 mole of acrylic acid), 20.0 g of toluene, 2.0 g of a 70% by mass methanesulfonic acid (MSA) aqueous solution (2.3% by mass relative to acrylic acid, 0.7% by mass relative to the total charged liquid (excluding the aqueous solution part)), and 0.3 g of phenothiazine were charged, and then it was immersed in an oil bath and heating was started. It should be noted that in this example, 2-octene as an olefin was not added, so the ratio of the 2-octene concentration to 2-octanol was 0, and the 2-octene concentration in the reactor was 0% by mass.

[0186] The pressure inside the system was slowly reduced from 800 hPa to 190 hPa to keep the liquid temperature inside the round-bottom flask at 110 °C.

[0187] Starting from the time point when the liquid temperature inside the round-bottom flask reached 110 °C, after 9 hours, the round-bottom flask was taken out of the oil bath and cooled to end the esterification reaction.

[0188] The reaction liquid after the reaction was analyzed in the same manner as in Comparative Example 1, and as a result, 2-octene as an impurity was confirmed. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same manner as in Comparative Example 1, and the results were 0.3 mol% and 93.1 mol%, respectively. In addition, the conversion rates of acrylic acid and alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same manner as in Comparative Example 1, and the results were 97.6 mol% and 91.4 mol%, respectively.

[0189] Example 7

[0190] In Comparative Example 3, 5.0 g of 2-octene was added, the addition amount of 2-octanol was changed to 119.3 g, the addition amount of toluene was changed to 20.7 g, the addition amount of a 70% by mass MSA aqueous solution was changed to 2.1 g, and the pressure inside the system was slowly reduced from 800 hPa to 200 hPa to keep the liquid temperature inside the round-bottom flask at 110 °C. Otherwise, the same operations as in Comparative Example 3 were carried out. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor were 57.5% by mass and 2.4% by mass, respectively, so the ratio of the 2-octene concentration to the 2-octanol concentration was 0.042.

[0191] The reaction solution after the reaction was analyzed in the same manner as in Comparative Example 1, and 2-octene as an impurity was confirmed as a result. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were -0.2 mol% and 94.1 mol%, respectively. In addition, the conversions of acrylic acid and the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 98.4 mol% and 89.7 mol%, respectively.

[0192] Example 8

[0193] In Comparative Example 3, 10.0 g of 2-octene was added, the addition amount of 2-octanol was changed to 119.5 g, the addition amount of toluene was changed to 21.3 g, the addition amount of 70 mass% MSA aqueous solution was changed to 2.2 g, and the pressure in the system was slowly reduced from 800 hPa to 210 hPa so that the liquid temperature in the round-bottom flask was maintained at 110 °C. Otherwise, the same operations as in Comparative Example 3 were carried out. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor were 56.0 mass% and 4.7 mass%, respectively. Therefore, the ratio of the 2-octene concentration to the 2-octanol concentration was 0.084.

[0194] The reaction solution after the reaction was analyzed in the same manner as in Comparative Example 1, and 2-octene as an impurity was confirmed as a result. Therefore, the selectivities of 2-octene and 1-methylheptyl acrylate based on the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were -0.4 mol% and 94.3 mol%, respectively. In addition, the conversions of acrylic acid and the alcohol (2-octanol) were calculated for the reaction solution after the reaction in the same manner as in Comparative Example 1, and the results were 99.1 mol% and 90.3 mol%, respectively.

[0195] Comparative Example 4

[0196] 60.0 g of methacrylic acid, 99.8 g of 2-octanol (1.1 mol relative to 1 mol of methacrylic acid), 18.2 g of toluene, 3.7 g of 70 mass% methanesulfonic acid (MSA) aqueous solution (4.3 mass% relative to acrylic acid, 1.4 mass% relative to the total amount of the charged liquid), and 0.3 g of phenothiazine were charged into a 500 mL glass round-bottom flask equipped with a stirrer, and then immersed in an oil bath and heating was started. It should be noted that in this example, 2-octene as an olefin was not added. Therefore, the ratio of the 2-octene concentration to the 2-octanol was 0, and the 2-octene concentration in the reactor was 0 mass%.

[0197] Slowly reduce the pressure in the system from 850 hPa to 320 hPa to keep the liquid temperature in the round-bottom flask at 120 °C.

[0198] Starting from the time point when the liquid temperature in the round-bottom flask reaches 120 °C, after 9 hours, take out the round-bottom flask from the oil bath and cool it to end the esterification reaction.

[0199] Analyze the reaction solution after the reaction in the same way as in Comparative Example 1. As a result, 2-octene as an impurity was confirmed. Therefore, calculate the selectivity of 2-octene and 1-methylheptyl methacrylate based on alcohol (2-octanol) for the reaction solution after the reaction in the same way as in Comparative Example 1. The results are 3.1 mol% and 90.6 mol% respectively. In addition, calculate the conversion rates of methacrylic acid and alcohol (2-octanol) for the reaction solution after the reaction in the same way as in Comparative Example 1. The results are 97.8 mol% and 95.7 mol% respectively.

[0200] Example 9

[0201] In Comparative Example 4, add 8.4 g of 2-octene, change the addition amount of 2-octanol to 100.0 g, change the addition amount of toluene to 19.3 g, change the addition amount of 70 mass% MSA aqueous solution to 3.9 g, and slowly reduce the pressure in the system from 850 hPa to 330 hPa to keep the liquid temperature in the round-bottom flask at 120 °C. Except for this, perform the same operations as in Comparative Example 4. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor are 52.1 mass% and 4.4 mass% respectively. Therefore, the ratio of 2-octene concentration to 2-octanol concentration is 0.084.

[0202] Analyze the reaction solution after the reaction in the same way as in Comparative Example 1. As a result, 2-octene as an impurity was confirmed. Therefore, calculate the selectivity of 2-octene and 1-methylheptyl methacrylate based on alcohol (2-octanol) for the reaction solution after the reaction in the same way as in Comparative Example 1. The results are 1.9 mol% and 93.4 mol% respectively. In addition, calculate the conversion rates of methacrylic acid and alcohol (2-octanol) for the reaction solution after the reaction in the same way as in Comparative Example 1. The results are 98.6 mol% and 94.0 mol% respectively.

[0203] Example 10

[0204] In Comparative Example 4, 15.0 g of 2-octene was added, the addition amount of 2-octanol was changed to 100.0 g, the addition amount of toluene was changed to 19.8 g, the addition amount of 70 mass% MSA aqueous solution was changed to 4.0 g, and the pressure in the system was slowly reduced from 850 hPa to 340 hPa to keep the liquid temperature in the round-bottom flask at 120 °C. Otherwise, the same operations as in Comparative Example 4 were carried out. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor were 50.2 mass% and 7.5 mass% respectively. Therefore, the ratio of the 2-octene concentration to the 2-octanol concentration was 0.150.

[0205] The reaction liquid after the reaction was analyzed in the same manner as in Comparative Example 1, and 2-octene as an impurity was confirmed as a result. Therefore, the selectivities of 2-octene and 1-methylheptyl methacrylate based on alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same method as in Comparative Example 1, and the results were 0.9 mol% and 94.4 mol% respectively. In addition, the conversions of methacrylic acid and alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same method as in Comparative Example 1, and the results were 98.7 mol% and 93.0 mol% respectively.

[0206] Example 11

[0207] In Comparative Example 4, 20.0 g of 2-octene was added, the addition amount of 2-octanol was changed to 100.0 g, the addition amount of toluene was changed to 20.3 g, the addition amount of 70 mass% MSA aqueous solution was changed to 4.2 g, and the pressure in the system was slowly reduced from 850 hPa to 350 hPa to keep the liquid temperature in the round-bottom flask at 120 °C. Otherwise, the same operations as in Comparative Example 4 were carried out. It should be noted that in this example, the 2-octanol concentration and 2-octene concentration in the reactor were 48.8 mass% and 9.8 mass% respectively. Therefore, the ratio of the 2-octene concentration to the 2-octanol concentration was 0.200.

[0208] The reaction liquid after the reaction was analyzed in the same manner as in Comparative Example 1, and 2-octene as an impurity was confirmed as a result. Therefore, the selectivities of 2-octene and 1-methylheptyl methacrylate based on alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same method as in Comparative Example 1, and the results were 0.1 mol% and 95.1 mol% respectively. In addition, the conversions of methacrylic acid and alcohol (2-octanol) were calculated for the reaction liquid after the reaction in the same method as in Comparative Example 1, and the results were 98.6 mol% and 92.2 mol% respectively.

[0209] From the comparison between Examples 1 to 3 and Comparative Example 1, the comparison between Examples 5 to 6 and Comparative Example 2, the comparison between Examples 7 to 8 and Comparative Example 3, and the comparison between Examples 9 to 11 and Comparative Example 4, it can be seen that by adding 2-octene (olefin) to the reactor in such a way that the olefin / secondary alcohol concentration ratio becomes a specified ratio, the selectivity of 1-methylheptyl acrylate can be significantly improved. It should be noted that the effect of increasing the selectivity from 92.2 mol% (Comparative Example 1) to 92.9 mol% (Example 1) is particularly a significant difference in effect in the case of mass-producing (meth)acrylates, and is very beneficial industrially. In addition, in this example, at the experimental level, 2-octene (olefin) is added to the reactor in such a way that the olefin / secondary alcohol concentration ratio becomes a specified ratio, but it is speculated that the same effect can also be obtained when applied to the (meth)acrylate manufacturing process as shown in Figures 1 to 4 the same effect can also be obtained.

[0210] It should be noted that Example 4 is an example using 2-octanol, which is the raw material secondary alcohol, as an azeotropic solvent, but shows the same selectivity as Example 1 in which no olefin (2-octene) is added, toluene is used as the azeotropic solvent, and otherwise substantially the same operations are carried out.

[0211] This application is based on Japanese Patent Application No. 2022-185001 filed on November 18, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0212] Symbol Explanation

[0213] 1: Reactor;

[0214] 2: First distillation column;

[0215] 3: Neutralization and water washing tank;

[0216] 4: Second distillation column;

[0217] 5: Third distillation column;

[0218] 6: Processing device.

Claims

1. A method for manufacturing a (meth)acrylate, the manufacturing method comprising: In the presence of an acid-type esterification catalyst and a polymerization inhibitor, (meth)acrylic acid is reacted with a secondary alcohol in a reactor; and An olefin-containing material obtained in the production of the (meth)acrylate is fed to the reactor such that the ratio of the olefin concentration to the secondary alcohol concentration in the reactor is 0.001 or more.

2. The manufacturing method according to claim 1, wherein, The olefin concentration in the reactor is 100 mass ppm or more.

3. The manufacturing method according to claim 1, wherein, The olefin-containing material obtained in the production of the (meth)acrylate is at least one selected from the following (i) to (iv): (i) An oil phase obtained by feeding an azeotropic composition of water generated in the reaction and / or water introduced into the reactor and the secondary alcohol to a first distillation column for distillation and condensing the gas distilled from the top of the first distillation column; (ii) The reaction is further carried out in the presence of an organic solvent. An azeotropic composition of water generated in the reaction and / or water introduced into the reactor and the secondary alcohol and / or the organic solvent is fed to a first distillation column for distillation, and an oil phase obtained by condensing the gas distilled from the top of the first distillation column, wherein the organic solvent is an organic solvent other than the secondary alcohol; (iii) A reaction mixture A obtained in the reaction is fed to a neutralization and water washing tank, and a gas or its condensate obtained after neutralizing and washing the reaction mixture A; and (iv) A reaction mixture A obtained in the reaction is fed to a neutralization and water washing tank, and after neutralizing and washing the reaction mixture A, the obtained reaction mixture B is fed to a second distillation column for distillation, and a gas or its condensate distilled from the top of the second distillation column.

4. The manufacturing method according to claim 1, wherein, The olefin-containing material obtained in the production of the (meth)acrylate is obtained by feeding a reaction mixture A obtained in the reaction to a distillation column for distillation, feeding the bottom liquid of the distillation column to a treatment device and recovering the effective component, i.e., a gas or its condensate, feeding the effective component to a neutralization and water washing tank, and neutralizing and washing the oil phase in the neutralization and water washing tank to obtain a gas or its condensate.

5. The manufacturing method according to claim 1, wherein, The olefin-containing material obtained in the production of the (meth)acrylate is obtained by feeding a reaction mixture A obtained in the reaction to at least one distillation column for distillation, feeding the bottom liquid of the distillation column to a treatment device, and recovering the effective component, i.e., (meth)acrylate.

6. The manufacturing method according to claim 1, wherein, The secondary alcohol is 2-octanol.

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