Method for separating methanol and methyl (meth)acrylate

Abstract

The present invention relates to a method for producing a distillation product having a methanol concentration higher than that of the minimum boiling azeotropic mixture of methanol and methyl (meth)acrylate from a mixture having a methanol concentration lower than that of the minimum boiling azeotropic mixture of methanol and methyl (meth)acrylate in a distillation column, and further relates to a method for producing a distillation product having a methanol concentration higher than that of the minimum boiling azeotropic mixture of methanol and methyl (meth)acrylate from methyl (meth)acrylate. 22 The present invention provides a transesterification process for preparing alkyl, aryl, or alkenyl (meth)acrylates of the formula:

Description

[Technical Field]

[0001] Field of Invention The present invention relates to a method for breaking down an azeotrope mixture of methanol and methyl (meth)acrylate, and further relates to a method for breaking down C6-C6 from methyl (meth)acrylate. 22 The present invention provides a transesterification method for preparing alkyl, aryl, or alkenyl (meth)acrylates.

[0002] As used in the context of the present invention, the term "destroying the azeotrope of methanol and methyl (meth)acrylate" refers to a method of producing a distillation product having a methanol concentration higher than the methanol concentration in the lowest boiling point azeotrope of methanol and methyl (meth)acrylate from a mixture having a methanol concentration less than or equal to the methanol concentration in the lowest boiling point azeotrope of methanol and methyl (meth)acrylate in a distillation column.

[0003] Background of the Invention Alkyl, aryl, or alkenyl (meth)acrylates are generally produced by transesterification of methyl (meth)acrylate with their respective alcohols.

[0004] The transesterification of methyl (meth)acrylate with an alcohol produces methanol, which is usually recovered by distillation in the form of a mixture of methanol and methyl (meth)acrylate. While the resulting distillate can have a methanol concentration as high as that of the azeotropic composition, it is typically lower than this maximum value. This leads to an undesirable loss of methyl (meth)acrylate. The distillate thus obtained must undergo additional processing steps to isolate and reuse the methyl (meth)acrylate. For economic reasons, it would be particularly desirable to mitigate the effects of azeotropic mixture formation, resulting in a reduction in the loss of methyl (meth)acrylate in the distillation product.

[0005] From the above perspective, the object of the present invention is to provide a method for disrupting methanol / methyl (meth)acrylate azeotrope mixtures as a process independent of transesterification, or as part of an improved process for preparing alkyl, aryl, or alkenyl (meth)acrylates, respectively, by transesterification, thereby significantly reducing the amount of methyl (meth)acrylate in the distillate, and potentially reducing, or even avoiding, the additional separation steps currently required for distillates.

[0006] Summary of the Invention For alkyl, aryl, or alkenyl (meth)acrylates having linear or branched acyclic or cyclic alkyl, aryl, or alkenyl groups having 6 to 22 carbon atoms, this problem is solved by the method according to the present invention.

[0007] Unexpectedly, the inventors found that the azeotropic mixture was separated by a distillation column, with each C6-C 22 When processed with an alcohol feed stream, the methanol concentration in the distillate can exceed the azeotropic concentration of methanol (i.e., the azeotropic mixture is broken down), and methyl (meth)acrylate decreases in the distillation stream, instead of C6~C 22 We found that the distillate contained a large amount of alcohol. As a result, the methanol concentration in the distillate increased rapidly, reaching a methyl (meth)acrylate concentration significantly lower than the azeotropic concentration of methyl (meth)acrylate. This greatly improved the efficiency of the process in terms of methyl (meth)acrylate yield.

[0008] Therefore, the present invention provides a method for breaking an azeotropic mixture of methanol and methyl (meth) acrylate in a distillation column, that is, a method for producing a distillation product having a methanol concentration higher than the methanol concentration in the minimum-boiling azeotropic mixture of methanol and methyl (meth) acrylate from a mixture of methanol and methyl (meth) acrylate having a methanol concentration below the methanol concentration in the minimum-boiling azeotropic mixture of methanol and methyl (meth) acrylate, comprising the step of contacting a mixture of methanol and methyl (meth) acrylate having a methanol concentration below the methanol concentration in the minimum-boiling azeotropic mixture of methanol and methyl (meth) acrylate with an alcohol of formula (I) HO-R 1 (I) [wherein, R 1 is a linear or branched acyclic or cyclic alkyl, aryl, or alkenyl group having 6 to 22 carbon atoms] The present invention further provides a process for preparing a (meth) acrylate of formula (II)

[0009] CH2=C(R 2 )-CO-OR 1 (II) (II) [wherein, R 2 is hydrogen or methyl, and R 1 is a linear or branched acyclic or cyclic alkyl, aryl, or alkenyl group having 6 to 22 carbon atoms] The method comprises reacting a methyl (meth) acrylate of formula (III) CH2=C(R 2 )-CO-OMe (III) [wherein, R 2 is as defined above] with an alcohol of formula (I) HO-R 1 (I) [wherein, R 1 is as defined above] by reacting with an alcohol, The methanol produced by the transesterification reaction is separated from the methyl (meth) acrylate of formula (III) at a methanol concentration below the azeotropic composition of methanol and the methyl (meth) acrylate of formula (III) using a distillation column; the resulting mixture is further concentrated to a methanol concentration higher than the methanol concentration in the azeotropic composition of methanol and the methyl (meth) acrylate of formula (III) by adding further alcohol of formula (I) via an alcohol feed stream arranged in the distillation column.

[0010] The process according to the invention can be carried out batchwise or continuously.

[0011] Detailed description of the invention The distillation column used in the process of the invention is preferably an extractive distillation column. The extractive distillation column may further comprise a rectification section and / or a stripping section in addition to the extraction section.

[0012] In one embodiment of the invention, the extractive distillation column is divided into three sections: (1) a rectification section between the top of the column and the alcohol feed position, (2) an extraction section between the alcohol feed position and the azeotrope feed position, and (3) a stripping section located below the azeotrope feed position.

[0013] In a different embodiment of the invention, the extractive distillation column has two sections: (1) a rectification section between the top of the column and the alcohol feed position, and (2) an extraction section between the alcohol feed position and the azeotrope feed position.

[0014] In the process according to the invention, the alcohol feed stream is arranged at the top of the distillation column, for example, at the top of the distillation column or in the top region of the distillation column.

[0015] Preferably, the alcohol supply stream is located in the top region of the distillation column. As used in the context of the present invention, the term “top region of the distillation column” refers to a location within the extractive distillation column where the number of separation trays in the extraction section is equal to or greater than the number of separation trays in the rectification section.

[0016] However, supplying alcohol to the top of the column can result in the loss of alcohol used as an extractant. Therefore, to maximize the separation capacity of the extraction section while avoiding excessive alcohol loss, sufficient rectification is performed, and the alcohol is favorably supplied near the top of the distillation column (i.e., the top region, see above). In other words, the preferred position for the alcohol supply stream is where sufficient column height is provided for extraction.

[0017] Preferably, above the alcohol supply stream, there are theoretical separation trays of at least 0.01 and up to 10 to avoid undesirable concentration in the direction returning to the azeotropic composition.

[0018] The alcohol of formula (I) can be added, for example, via an alcohol feed stream at a temperature of 0°C to 70°C.

[0019] The addition of the alcohol of formula (I) via a distillation column can be carried out in batch or continuous order.

[0020] To prevent undesirable polymerization of (meth)acrylate, polymerization inhibitors can be used in the methods according to the present invention. Advantageously, these methods are carried out in the presence of an inhibitor composition comprising or consisting of at least one phenolic polymerization inhibitor.

[0021] These compounds, such as hydroquinone, hydroquinone ether, such as hydroquinone monomethyl ether or di-tert-butylcatechol, phenothiazine, N,N'-(diphenyl)-p-phenylenediamine, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, p-phenylenediamine, methylene blue, or sterically hindered phenols, are widely known in the art. These compounds can be used individually or in mixtures and are widely available commercially. The mechanism of action of stabilizers is usually to act as free radical scavengers against free radicals generated during polymerization. Based on the total weight of the reaction mixture, the proportion of the inhibitor, individually or in mixtures, can usually be 0.001-0.5% (weight / weight).

[0022] These polymerization inhibitors can each be added before or at the start of the reaction or distillation. Furthermore, small amounts of the polymerization inhibitors used can be introduced during transesterification. The process in which some of the polymerization inhibitors are added via column reflux is of particular interest here. In particular, it is advantageous to use a mixture containing methyl (meth)acrylate, hydroquinone monomethyl ether, and 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl. This measure makes it possible to avoid undesirable polymerization, especially in the distillation column.

[0023] Furthermore, gaseous oxygen can also be used as an inhibitor. This can be used, for example, in the form of air, and the amount introduced is, advantageously, such that the content in the gas phase above the reaction mixture remains below the limiting oxygen concentration of the explosive region. An amount of air in the range of 0.05 to 0.5 liters per hour and per mole of primary alcohol is particularly preferred. It is equally possible to use inert gas / oxygen mixtures, such as nitrogen / oxygen or argon / oxygen mixtures.

[0024] In certain embodiments of the present invention, a combination of oxygen and hydroquinone monomethyl ether (HQME) can be used for inhibition.

[0025] Alternatively, the method according to the present invention may be optionally carried out in combination with a phenolic polymerization inhibitor, or in the presence of an inhibitor composition comprising a polymerization inhibitor selected from the group consisting of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, 2,2-diphenyl-1-picrylhydrazyl, phenothiazine, N,N'-diphenyl-p-phenylenediamine, nigrosine, para-benzoquinone, and capferon.

[0026] In the context of the present invention, the term "alkyl, aryl, or alkenyl (meth)acrylate" is understood to mean alkyl, aryl, or alkenyl esters of both methacrylic acid and acrylic acid.

[0027] In the alkyl, aryl, or alkenyl (meth)acrylate of formula (II) and the alcohol of formula (I), R 1 The group can be selected from linear or branched acyclic or cyclic alkyl, aryl, or alkenyl groups having 6 to 22 carbon atoms. The term "cyclic alkyl group" refers to monocyclic or polycyclic alkyl species, and therefore includes bicyclic groups such as isobornyl. Preferably, R 1 These are linear or branched acyclic or cyclic alkyl, aryl, or alkenyl groups having 7 to 20, preferably 8 to 18, carbon atoms.

[0028] R 1 The group is understood to mean, for example, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, 2-octyl, 2-ethylhexyl, nonyl, 2-methyloctyl, 2-tert-butylheptyl, 3-isopropylheptyl, decyl, undecyl, 5-methylundecyl, dodecyl, stearyl and / or behenyl groups, as well as / or cycloalkyl groups, such as cyclohexyl, tert-butylcyclohexyl, cycloheptyl, cyclooctyl, bornyl and / or isobornyl. Furthermore, R1 The base is optionally substituted (C6~C 14 )-aryl-(C1~C8)-alkyl group, preferably (C6~C 12 )-aryl-(C1~C4)-alkyl groups, such as benzyl, naphthylmethyl, naphthylethyl, 2-phenylethyl, 2-phenoxyethyl, 4-phenylbutyl, 3-phenylbutyl, 2-phenylbutyl, and / or 2-biphenylethyl groups.

[0029] Methyl (meth)acrylate of formula (III) can be introduced into the transesterification process according to the present invention as a pure substance, or as a mixture containing a methanol concentration below that of the azeotropic composition (from a previous reaction), for example, or as a combination of a mixture of methyl (meth)acrylate of formula (III) and methanol having a methanol concentration below that of the azeotropic composition of methanol and methyl (meth)acrylate of formula (III), and fresh / pure methyl (meth)acrylate of formula (III). Such a process setup is particularly suitable for transesterification processes carried out in a continuous form.

[0030] The method according to the present invention can be implemented, for example, in a single plant. Any alcohol that does not form an azeotropic mixture with the methyl (meth)acrylate of formula (III) (i.e., the alcohol of formula (I)) is added via a first column to break up the azeotropic mixture. Then, in a second column, the methyl (meth)acrylate of formula (III) is separated from the alcohol of formula (I), and the alcohol is subsequently reused in the first column.

[0031] In a batch process, the azeotropic mixture is fed into the reactor before the alcohol, and boiling can be maintained under complete reflux. The alcohol required for the reaction is then fed into the column. While this alcohol extracts the methyl (meth)acrylate of formula (III) from the boiling azeotropic mixture, the transesterification reaction also begins.

[0032] In a particularly preferred embodiment of the present invention, the (meth)acrylate of formula (II) is 2-ethylhexyl methacrylate, the methyl (meth)acrylate of formula (III) is methyl methacrylate, and the alcohol of formula (I) is 2-ethylhexanol.

[0033] The molar ratio of the alcohol of formula (I) to the methyl (meth)acrylate of formula (III) supplied to the transesterification reactor is preferably in the range of 10:1 to 1:10, more preferably 1:1 to 1:5, and most preferably 1:1.1 to 1:2.5. The latter ratio is particularly suitable for a continuous transesterification process.

[0034] In a preferred embodiment of the present invention, after the initial reaction period, an additional amount (or the remaining equivalent) of alcohol(I) is introduced into the reaction mixture via a distillation column to concentrate methanol to a concentration higher than the methanol concentration in the azeotropic mixture.

[0035] The addition of alcohol(I) via the distillation column can be started immediately after the start of transesterification, or after the reaction has reached a steady state. In a batch process, the supply of alcohol to the distillation column can be started at the beginning of the batch, or at some point after the batch.

[0036] To catalyze this transesterification, catalysts selected from the group consisting of alkyl titanates (e.g., tetraisopropyl titanate, tetrakis(ethylhexyl) titanate), zirconium acetylacetonate, dialkyltin compounds, lithium compounds (e.g., lithium oxide, lithium hydroxide, lithium chloride, lithium amide (LiNH2), lithium alcoholate (preferably LiOMe), calcium compounds (e.g., calcium oxide and calcium hydroxide), or acids (e.g., p-toluenesulfonic acid, sulfuric acid, methanesulfonic acid) can be used alone or in any combination of the catalysts mentioned above.

[0037] Particularly suitable catalysts include, for example, tetraisopropyl titanate, tetrakis(ethylhexyl) titanate, and zirconium acetylacetonate. Catalysts can be purchased in ready-to-use form, prepared in situ, or obtained by recycling from downstream processes.

[0038] Advantageously, it is possible to use 0.2 to 10 mmol, more preferably 0.5 to 8 mmol, of the catalyst per mole of alcohol of formula (I).

[0039] The reaction time depends particularly on selected parameters such as pressure and temperature. However, they are typically in the range of 1 to 24 hours, preferably 5 to 20 hours, and very preferably 6 to 18 hours. For continuous processes, the reactor residence time is typically in the range of 1 to 24 hours, preferably 2 to 20 hours, and very preferably 2.5 to 10 hours.

[0040] The reaction can preferably be carried out with stirring, and the stirring speed is particularly preferably in the range of 50 to 2000 rpm, and very particularly preferably in the range of 100 to 500 rpm.

[0041] A suitable plant for this transesterification may be, for example, a stirred-tank reactor equipped with a stirrer, a steam heater, a distillation column (azeotropic column), and a condenser. The size of the plant depends on the amount of alkyl (meth)acrylate to be produced, and the method according to the present invention can be carried out on a laboratory scale (reactor volume 0.5 to 20 liters) or, particularly advantageously, on an industrial scale. Thus, in certain embodiments, the stirred-tank reactor may be 0.25 m 3 ~50m 3 Preferably 1m 3 ~50m 3 , more comfortably 3m 3 ~25m 3 The tank volume may be within the range of [specified range]. The agitator of the reactor tank can be configured in the form of an anchor agitator, impeller, paddle agitator, or INTERMIG® agitator.

[0042] A distillation column (azeotropic column) can have one, two, or more separation stages. The number of separation stages refers to the number of trays in a tray column, or the theoretical number of stages in a structured-packed or irregularly-packed column.

[0043] Examples of multi-stage distillation columns with trays include those having a bubble cap tray, sieve tray, tunnel cap tray, valve tray, slot tray, slot sieve tray, bubble cap sieve tray, jet tray, centrifugal tray, and the like.

[0044] Examples of multistage distillation columns with irregular packing include those with Raschig rings, Raschig super rings, Lessing rings, Pall rings, Berl saddles, Intalox saddles, etc.; examples of multistage rectification columns with structured packing include Mellapak type (Sulzer), MellapakPlus, Rombopak type (Kuehni), Montz-Pak type (Montz), etc. Preferably, above the alcohol feed stream, there are up to 10 theoretical separation trays, at least 0.01, to avoid undesirable concentration in the direction returning to the azeotropic composition.

[0045] For example, it is also possible to use distillation columns with different internal combinations, such as having structured packing in the first column section and tray or irregular packing in the second column section.

[0046] After the reaction is complete, the resulting alkyl (meth)acrylates often already meet the general requirements for each alkyl (meth)acrylate product, and therefore, further purification is usually unnecessary. However, the products can also be isolated by distillation after the reaction is complete.

[0047] To further improve quality, particularly to remove catalysts, the resulting mixture can be purified by known processes. Due to the polymerization tendency of monomers, it is prudent to employ a distillation process that minimizes thermal stress on the substance to be distilled. Highly suitable apparatuses are those in which monomers evaporate continuously from a thin layer, such as drip-film evaporators or evaporators with rotating wiper systems. Short-pass evaporators can also be used. For example, distillation can be performed using a continuous evaporator with a rotating wiper system and an accompanying column. This distillation can be performed at pressures in the range of 1 to 60 mbar and evaporator temperatures of 60°C to 130°C (surface temperature of a wipe-film evaporator).

[0048] The present invention will be described below with reference to non-limiting and exemplary embodiments.

[0049] Examples: Comparative Example 1: In a continuous transesterification system consisting of a reactor equipped with an azeotropic column and an additional column for work-up of continuously withdrawn crude reactor products, from which unreacted raw materials are separated and recycled, alcohol, MMA, and a catalyst (titanium(IV) alkoxide) are continuously supplied to the reactor. The reactants are introduced into the reactor. In this example, 2-ethylhexanol was used as the alcohol. The methanol produced by the reaction conversion is continuously withdrawn from the reactor via the azeotropic column in the form of a mixture containing methanol at a concentration below the azeotropic concentration of methanol. To evaluate the concentration during operation, the density of the distillate is measured and recorded in real time and used to calculate the methanol-to-MMA ratio (from the temperature-corrected density of the pure substances). As a result of thermodynamic limitations on the separation performance of the azeotropic mixture, the concentration at the top of the column is typically 78 wt% methanol. After reaching a steady state, samples of the recovered methanol distillate were withdrawn and analyzed. The results are reported in Table 1.

[0050] Example 1: In a continuous transesterification system comprising a reactor equipped with an azeotropic column and an additional column for work-up of continuously withdrawn reactor crude products, from which unreacted raw materials are separated and recycled, alcohol, MMA, and catalyst (titanium(IV) alkoxide) are continuously supplied to the reactor. The reactants are introduced into the reactor, and without preheating the alcohol, the alcohol supply point is moved to a position near the top of the azeotropic column. The alcohol temperature was 20°C. A structured packing element with a theoretical separation capacity of approximately 0.8 trays is positioned above the alcohol supply point. In this example, 2-ethylhexanol was used as the alcohol. The methanol produced by the reaction conversion is continuously withdrawn from the reactor via the azeotropic column in the form of a mixture containing methanol at a concentration lower than the azeotropic concentration of methanol. To evaluate the concentration during operation, the density of the distillate is measured and recorded in real time and used to calculate the ratio of methanol to MMA (from the temperature-corrected density of the pure substance). The reactor was started according to Comparative Example 1, and after reaching a steady state, the alcohol supply point was changed as described above. The methanol concentration in the distillate clearly reacted within 2 minutes of the change in the feed point, and the recovered methanol distillate is estimated to have a methanol concentration of over 78 wt%. After 30 minutes, the first sample of the distillate was taken at a calculated methanol concentration of 90 wt%; the analytical results were nearly identical. After 2 hours, the second sample, with a calculated purity of 93 wt%, contained an analytical content of 92.7 wt% methanol, and the third sample, after 4 hours, which achieved a steady state of 94.5 wt% methanol, contained an analytical content of 93.25 wt% methanol. As methanol concentration in the distillate increased, the total amount of distillate extracted decreased. As the concentration of MMA extracted in the azeotropic mixture decreased, the feed flow of MMA to the reactor decreased after reaching a steady state. The column top temperature remained unchanged. At the bottom vapor inlet of the column, the temperature decreased by 20°C, from 94°C to 74°C. The differential pressure in the column remained unchanged.

[0051] [Table 1]

[0052] Example 2: 1.8 kg of a mixture of 75 wt% MeOH and 25 wt% MMA was initially placed in a V=3L glass flask equipped with a stirrer, an electrically heated mantle, a mirror-finish irregularly packed column (bottom height=0.3m, diameter=45mm, top height=0.7m, diameter=30mm), a condenser, and a reflux partition. Air was then blown into the reactor contents at a rate of 2 NL / hour. The mixture was stabilized with 1000 wt ppm HQME and 50 wt ppm Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl). Thermocouples were placed at both the flask and the top of the column to monitor the temperature. The mixture in the flask was heated to a boil and refluxed at the top of the column: the ratio of distillates to be extracted using the reflux partition was set to 1:1. After a stable column top temperature was reached, the recovered distillates were sampled and analyzed by GC.

[0053] After another 15 minutes, 8 g / min of 2-ethylhexanol is added to the top of the column under reflux using an HPLC pump and Coriolis mass flow meter. The resulting distillate is sampled again and analyzed at 10 minutes and 45 minutes. The 1:1 reflux:distillate ratio remains unchanged.

[0054] Example 3: The procedure is the same as in Example 2, but 7 g / min of i-decyl alcohol is added as the alcohol.

[0055] Example 4: The procedure is the same as in Example 2, but 6 g / min of C13.0 alcohol (Lorol Spezial) is added as the alcohol.

[0056] Example 5: The procedure is the same as in Example 2, but cyclohexanol at a rate of 7 g / min is added as the alcohol.

[0057] Comparative Example 2: The procedure is the same as in Example 2, but 7.3 g / min of n-BuOH is added as the alcohol.

[0058] The results of the distillate analysis from the experiment are summarized in Table 2.

[0059] [Table 2]

[0060] It is clear that without adding alcohol at the top of the column, a composition close to that of an azeotrope of MMA and MeOH can be obtained (approximately 85.5 wt% MeOH and 14.5 wt% MMA at 10¹³ mbar) (see reference for no alcohol addition).

[0061] In contrast, alcohols with sufficiently low polarity that have a standard boiling point higher than that of MMA (100°C) (e.g., C) n H 2n+1 -OH, n≧6;C n H 2n-1 -OH, n≧6, or C n H 2n-7 -OH (n≧6) selectively extracts MMA from a mixture of methanol and MMA to the bottom of the column, resulting in further concentration of methanol as the methanol concentration exceeds the azeotropic concentration of methanol.

[0062] In contrast, the more polar short-chain alcohol (Comparative Example 2) does not produce a distillation product with a methanol concentration higher than the methanol concentration in the lowest boiling point azeotrope mixture of methanol and methyl methacrylate.

Claims

1. A method for producing a distillation product having a methanol concentration higher than the methanol concentration in the minimum boiling point azeotrope of methanol and methyl (meth)acrylate from a mixture of methanol and methyl (meth)acrylate having a methanol concentration less than or equal to the methanol concentration in the minimum boiling point azeotrope of methanol and methyl (meth)acrylate in a distillation column, wherein A mixture of methanol and methyl (meth)acrylate having a methanol concentration less than or equal to the methanol concentration in the lowest boiling point azeotrope of methanol and methyl (meth)acrylate is added via an alcohol feed stream located in the distillation column (I). HO-R １ (I) [In the formula, R １ [It is a linear or branched acyclic or cyclic alkyl group having 6 to 22 carbon atoms.] A method characterized by including a step of contacting with alcohol.

2. The method according to claim 1, characterized in that the distillation column used is an extractive distillation column having at least an extraction section and a rectification section, and the alcohol supply flow is arranged in the extractive distillation column such that the number of separation trays in the extraction section is equal to or greater than the number of separation trays in the rectification section.

3. The method according to claim 1 or 2, characterized in that a theoretical separation tray with a minimum of 0.01 and a maximum of 10 is present above the alcohol supply flow.

4. The method according to claim 1 or 2, characterized in that the alcohol of formula (I) is added via the alcohol supply stream at a temperature of 0°C to 70°C.

5. The method according to claim 1 or 2, characterized in that it is performed in a batch or continuous manner.

6. Formula (II) CH ２ =C(R ２ )-CO-OR １ (II) [In the formula, R ２ is hydrogen or methyl, R １ [It is a linear or branched acyclic or cyclic alkyl group having 6 to 22 carbon atoms.] A method for preparing (meth)acrylate, Formula (III) CH ２ =C(R ２ )---OMe (---) [In the formula, R ２ This is defined above. The methyl (meth)acrylate of formula (I) HO-R １ (I) [In the formula, R １ This is defined above. This is done by reacting it with alcohol. The methanol produced by the transesterification reaction is separated from the methyl (meth)acrylate of formula (III) using a distillation column at a methanol concentration less than or equal to that of the azeotrope composition of methanol and the methyl (meth)acrylate of formula (III). The resulting mixture is further concentrated to a methanol concentration higher than that in the azeotropic composition of methanol and methyl (meth)acrylate of formula (III) by adding the alcohol of formula (I) via an alcohol feed stream arranged in the distillation column. method.

7. The distillation column used is an extractive distillation column having at least an extraction section and a rectification section, and the alcohol supply flow is arranged in the extractive distillation column such that the number of separation trays in the extraction section is equal to or greater than the number of separation trays in the rectification section, and / or The method according to claim 6, characterized in that a theoretical separation tray with a minimum of 0.01 and a maximum of 10 is present above the alcohol supply flow.

8. The method according to claim 6 or 7, characterized in that it is performed in a batch or continuous manner.

9. The method according to claim 6 or 7, characterized in that the addition of the alcohol of formula (I) via the distillation column is started after the reaction has reached a steady state.

10. As a mixture of the methyl (meth)acrylate of formula (III) and methanol, the methyl (meth)acrylate of formula (III) is introduced into the transesterification reaction. The mixture has a methanol concentration less than or equal to that of the azeotropic composition of methanol and methyl (meth)acrylate of formula (III), The mixture is obtained from a prior transesterification reaction involving methanol formation. or A mixture of the methyl (meth)acrylate of formula (III) and methanol, and the methyl (meth)acrylate of formula (III) are introduced into the transesterification reaction, The mixture has a methanol concentration less than or equal to that of the azeotropic composition of methanol and methyl (meth)acrylate of formula (III). The method according to claim 6 or 7, characterized in that it is a method according to claim 6 or 7.

11. In the (meth)acrylate of formula (II) and the alcohol of formula (I), R １ The method according to claim 6 or 7, characterized in that it has 7 to 20 carbon atoms and is a linear or branched acyclic or cyclic alkyl group.

12. The method according to claim 6 or 7, characterized in that the (meth)acrylate of formula (II) is 2-ethylhexyl methacrylate, the methyl (meth)acrylate of formula (III) is methyl methacrylate, and the alcohol of formula (I) is 2-ethylhexanol.

13. The method according to claim 6 or 7, characterized in that the alcohol of formula (I) is added at a temperature of 0°C to 70°C.

14. The method according to claim 6 or 7, characterized in that the transesterification is carried out in the presence of a catalyst, the catalyst being selected from the group consisting of alkyl titanate, zirconium acetylacetonate, dialkyltin compounds, lithium compounds, calcium compounds, or combinations thereof; and the catalyst being present in an amount of 0.2 to 10 mmol per mole of the alcohol of formula (I).

15. The transesterification process is carried out in the presence of an inhibitor composition containing or comprising at least one phenolic polymerization inhibitor. The method according to claim 6 or 7, characterized in that the phenolic polymerization inhibitor is hydroquinone, hydroquinone monomethyl ether, or a combination thereof.

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