Method for purifying light acrylates
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-05-15
- Publication Date
- 2026-04-01
AI Technical Summary
The production of light (meth)acrylic esters, such as methyl or ethyl acrylate, faces challenges in purifying C1-C2 alkyl acrylates due to the presence of by-products like methyl methoxy propionate, which are difficult to eliminate due to their close boiling temperatures with acrylic acid and formation of azeotropes with water, leading to complex and energy-intensive distillation processes.
A process involving azeotropic distillation followed by liquid/liquid extraction, multiple distillation columns, and continuous evaporation with successive condensations to separate and recycle alkyl acrylate, eliminate alkyl alkoxy propionate, and recover polymerization inhibitors, ensuring high purity and minimizing material losses.
This process effectively eliminates alkyl alkoxy propionate, reduces material losses, and achieves high purity alkyl acrylate production by recycling polymerization inhibitors, simplifying the purification train and optimizing material balance.
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Abstract
Description
[0001] PROCESS FOR PURIFYING LIGHT ACRYLATES
[0002] TECHNICAL FIELD
[0003] The present invention relates to the production of light (meth)acrylic esters such as methyl or ethyl (meth)acrylate, by direct esterification of (meth)acrylic acid with the corresponding light alcohol.
[0004] The invention more particularly relates to a process for the recovery / purification of C1-C2 alkyl acrylate comprising evaporation and partial condensation steps making it possible to eliminate a fraction rich in alkyl alkoxy propionate by-product, which cannot be recovered by a cracking process and is very difficult to eliminate, whether when it is pure, because its boiling temperature is close to that of acrylic acid, or when it is in the form of an azeotrope with water, because its boiling temperature is close to that of the acrylic ester.
[0005] PRIOR ART AND TECHNICAL PROBLEM
[0006] It is known to produce (meth)acrylic esters by implementing an esterification reaction between an alcohol and a (meth)acrylic acid. This reaction is a balanced catalyzed reaction with generation of water. It is also accompanied by side reactions producing impurities.
[0007] It is necessary to remove the produced water to shift the equilibrium, remove impurities, as well as recycle unreacted reagents.
[0008] To this end, a series of distillations and / or extractions and decantations are generally carried out, which is both relatively complex to implement, particularly due to the presence of azeotropic mixtures, and costly in terms of energy.
[0009] The problems that arise during the manufacture of light (meth)acrylic esters, in particular C1-C2 alkyl acrylic esters, will now be explained, for convenience, on the basis of the example of methyl acrylate obtained by esterification of acrylic acid with methanol. However, the problems and the solution proposed by the invention can be applied to the use of ethanol in the esterification reaction. As side reactions during the manufacture of methyl acrylate, unreacted acrylic acid can form oligomers, such as 3-acryloxypropionic acid (n=2) or 3-acryloxy 3-propioxy propionic acid, (n=3), which are heavy by-products with a higher boiling point than acrylic acid.
[0010] As another side reaction, Michael addition can produce Michael adducts, particularly methyl methoxypropionate formed between methyl acrylate and methanol.
[0011] Methyl methoxy propionate (MPM) is a so-called heavy by-product that is formed in significant quantities in the process as the esterification reaction progresses along with acrylic acid oligomers. Its boiling point is close to that of acrylic acid (144°C, atmospheric P), but it can also form an azeotrope with water (97.3°C, atmospheric P) during azeotropic distillation.
[0012] MPM is the lightest of the heavy by-products compared to acrylic acid oligomers, it can interfere in the final purification of methyl acrylate (80°C, atmospheric P) and alter the quality of the finished product.
[0013] In order to limit the formation of MPM, it was proposed in document US 6,025,520 to carry out the esterification reaction under reduced pressure with an excess of acid. These conditions make it possible to improve the yield and selectivity of the esterification reaction and to significantly reduce the formation of heavy by-products such as MPM, which is problematic for the purification train of the desired ester.
[0014] The process described in WO 2015 / 063388 proposes to significantly reduce the formation of alkyl alkoxy propionate during the synthesis of methyl (meth)acrylate by carrying out the esterification reaction in a fixed bed reactor under atmospheric pressure and under conditions where the acid is in excess of the alcohol and where the hourly volumetric velocities are high.
[0015] In document FR 3083233, the applicant company has shown that it is possible to eliminate MPM by side withdrawal during the azeotropic distillation of the reaction mixture carried out in a single distillation column equipped with a side withdrawal. This solution remains, however, difficult to implement because it requires very stable operating conditions, both at the level of the esterification reaction and at the level of the azeotropic distillation column.
[0016] There is still a need to eliminate methyl methoxy propionate, which is detrimental to the material balance of the process (loss of raw materials during purges) and to the purification train (complexity to achieve high purity).
[0017] One of the objectives of the present invention is therefore to provide an improved process for the recovery / purification of methyl acrylate, and more generally of methyl or ethyl acrylate, allowing efficient removal of methyl methoxy propionate, by continuously implementing evaporation of the bottom of the methyl acrylate purification column and at least two successive condensations of the gas phase. A methyl acrylate stream, a methyl methoxy propionate stream and an inhibitor-rich evaporator bottom stream are thus obtained.
[0018] SUMMARY OF THE INVENTION
[0019] The present invention relates to a process for the recovery / purification of C1-C2 alkyl acrylate from a reaction mixture resulting from the esterification of acrylic acid with an alcohol chosen from methanol and ethanol carried out in the presence of polymerization inhibitor(s), said process comprising at least the following steps: azeotropic distillation of said reaction mixture using a first distillation column, leading to the separation of: o at the top, a stream comprising the alkyl acrylate, the unreacted alcohol and water; o at the bottom, a fraction comprising the unreacted acrylic acid and heavy products, the treatment of the top stream of the first distillation column by liquid / liquid extraction generating an aqueous phase containing essentially alcohol, and an organic phase rich in alkyl acrylate;the treatment by distillation of said aqueous phase in a second distillation column to separate: o at the top, alcohol, which will be recycled in the esterification reaction, and o at the bottom, a stream depleted in alcohol; the treatment of the bottom stream of the first distillation column using a third distillation column and / or an evaporator, which separates: o at the top, a stream comprising residual acrylic acid and lighter products, and o at the bottom, a stream consisting of heavy products; the treatment of said organic phase rich in alkyl acrylate in a fourth distillation column, called a purification column, to separate: o at the top, the purified alkyl acrylate and o at the bottom, the heavy products and the polymerization inhibitors;
[0020] - the continuous treatment of the bottom flow of the purification column, by evaporation, and at least two successive condensations of the gaseous phase resulting from the evaporation, making it possible to obtain: o an alkyl acrylate flow to be recycled to the purification column, o an alkyl alkoxy propionate flow, and o a residue containing the polymerization inhibitors.
[0021] This process minimizes alkyl acrylate losses and recycles polymerization inhibitors contained at different points in the process while eliminating a concentrated fraction rich in alkyl alkoxy propionate by-product.
[0022] According to various embodiments, said method comprises the following characteristics, possibly combined. The contents indicated are expressed by weight, unless otherwise indicated. Within the ranges of values indicated, the limits are included.
[0023] Azeotropic distillation means the separation of an azeotrope (or azeotropic mixture) consisting of a ternary mixture of alkyl acrylate / alcohol / water.
[0024] In one embodiment, the alcohol is methanol, the alkyl acrylate is methyl acrylate, and the alkyl alkoxy propionate is methyl methoxy propionate (MPM).
[0025] In one embodiment, the alcohol is ethanol, the alkyl acrylate is ethyl acrylate, and the alkyl alkoxy propionate is ethyl ethoxy propionate (EPE).
[0026] According to one embodiment, the azeotropic distillation column may be provided with a side draw. According to one embodiment, the azeotropic distillation column does not have a side draw.
[0027] According to one embodiment, the azeotropic distillation is carried out by two distillation columns in series.
[0028] According to one embodiment, the final purification to obtain commercial grade alkyl acrylate (purity greater than 99.5% by weight) is carried out by implementing at least one purification column such as a tailing column and a topping column.
[0029] According to one embodiment, said at least one purification column is a dividing wall column (DWC).
[0030] According to one embodiment, said at least one purification column is a side-draw column.
[0031] According to one embodiment, the evaporation step is carried out using a thin-film evaporator.
[0032] According to one embodiment, the treatment of the bottom stream of the first distillation column is carried out using a thin-film evaporator.
[0033] According to one embodiment, when the alkyl acrylate is methyl acrylate, obtaining methyl acrylate having a purity greater than 99.5% by weight is carried out in a distillation column known as a tailing column or a partition column operating in a pressure range of 10,000 Pa to 50,000 Pa and temperatures ranging from 80°C to 110°C.
[0034] According to one embodiment, the process according to the invention comprises the following steps: a) azeotropic distillation of the reaction mixture using a first distillation column making it possible to separate at the top an azeotropic mixture comprising the alkyl acrylate, the unreacted alcohol and water, and at the bottom a fraction comprising the unreacted acrylic acid and heavy by-products, b) separation of the bottom stream of the first distillation column into a stream essentially comprising the unreacted acrylic acid, this stream being all or part recycled into the esterification reactor, c) liquid / liquid extraction of the top stream of the first distillation column by an aqueous stream making it possible to separate an organic phase essentially comprising the alkyl acrylate, and an aqueous phase, d) purification of said organic phase using a separation assembly comprising at least one alkyl acrylate purification column,such as a tailing column and a topping column, a side draw column or a separating wall column (DWC), allowing the recovery of the purified alkyl acrylate at the top and at the bottom a stream containing heavy by-products such as alkyl alkoxy propionate, e) treatment of the bottom stream of this purification column, on a thin-film evaporator in order to recycle the alkyl acrylate to the purification column, to eliminate a final residue comprising the polymerization inhibitors and to send to the purge for incineration a stream very concentrated in alkyl alkoxy propionate.,
[0035] According to one embodiment, when the alkyl acrylate is methyl acrylate, the bottom stream of the purification column for obtaining methyl acrylate is subjected to successive evaporation and condensation of the gas phase of the evaporator. This evaporation operation generates three streams:
[0036] - a stream of methyl acrylate to be recycled to the purification column,
[0037] - a flow of MPM, and
[0038] - a residue stream containing polymerization inhibitors which can be advantageously recycled in the process.
[0039] Reaction temperature and evaporator pressure T are related so that methyl acrylate and MPM are evaporated off.
[0040] According to one embodiment, the evaporation is carried out in a temperature range from 80°C to 110°C and more especially between 90°C and 100°C.
[0041] According to one embodiment, the maintained pressure of the evaporator is between 10000 Pa and 80000 Pa.
[0042] According to one embodiment, the overhead flow of this evaporator is cooled in two successive stages: Partial condensation in a temperature range from 70 to 110°C, preferably between 80°C-90°C, at the same pressure as that of the evaporator, to obtain on the one hand a liquid flow of Michael adducts to be purged and on the other hand a vapor flow;
[0043] Condensation of this vapor flow in a temperature range from 20°C to 50°C, more specifically 30°C-40°C, before recovery of this liquid flow by a pump and feeding of the purification column.
[0044] The mass composition of the feed product to the evaporator at the bottom of the purification column in the case of the manufacture of methyl acrylate in the presence of hydroquinone as a polymerization inhibitor is as follows:
[0045] - Methyl acrylate (60-100%),
[0046] - Butyl methoxy propionate (MPM) 5-40%,
[0047] - Hydroquinone: 0.1 to 2%.
[0048] According to one embodiment, the alkyl alkoxy propionate-rich fraction contains alkyl alkoxy propionate at a mass content ranging from about 20% to about 80%.
[0049] According to one embodiment, the reaction mixture is obtained from the esterification of acrylic acid with a stoichiometric excess of alcohol.
[0050] According to one embodiment, the reaction mixture is obtained from the esterification of acrylic acid with an alcohol under conditions of stoichiometric excess of acid.
[0051] According to one embodiment, the azeotropic distillation is carried out under slight vacuum under a pressure ranging from 200 to 600 mm Hg.
[0052] According to one embodiment, the temperature at the bottom of the azeotropic distillation column is less than 110°C, preferably less than 100°C.
[0053] The reaction is carried out in the presence of one or more polymerization inhibitors which are introduced into the reactor, at a rate of 500 to 5000 ppm relative to the crude reaction mixture. As polymerization inhibitors which may be used, mention may be made, for example, of phenothiazine, hydroquinone, hydroquinone monomethyl ether, diterbutyl para-cresol (BHT), paraphenylenediamine, TEMPO (2,2,6,6-tetramethyl-l-piperidinyloxy), di-tert-butylcatechol, or TEMPO derivatives, such as OH-TEMPO, alone or their mixtures in any proportions. An additional addition of polymerization inhibitor is generally carried out at the level of the subsequent purification treatment.
[0054] The effectiveness of the inhibitors is also linked to the injection of air or depleted air into the different columns used.
[0055] According to one embodiment, the separation assembly comprises at least one alkyl acrylate purification column such as a tailing column and a topping column.
[0056] According to one embodiment, the separation assembly comprises at least one alkyl acrylate purification column such as a divider wall column (DWC).
[0057] According to one embodiment, the separation assembly comprises at least one alkyl acrylate purification column such as a side draw column.
[0058] According to one embodiment, purification step d) is carried out by distillation, using a purification column comprising at least one distillation column, preferably two distillation columns in series.
[0059] The invention makes it possible to limit the losses of recoverable materials such as acrylic acid, alcohol or alkyl acrylate in a process for producing light alkyl acrylate by direct esterification.
[0060] According to one embodiment, the final purification to obtain methyl acrylate can be carried out using a topping column and a tailing column.
[0061] The invention makes it possible to efficiently remove alkyl alkoxy propionate, and to reduce the losses of recoverable products caused by the purges imposed by the accumulation of alkyl alkoxy propionate in the purification train and to recycle the polymerization inhibitors advantageously in the process.
[0062] Thus the invention provides a simplified process for producing high purity methyl or ethyl acrylate, and optimizes the material balance of the process.
[0063] BRIEF DESCRIPTION OF THE FIGURES
[0064] Figure 1 schematically represents an installation for producing methyl acrylate by implementing the recovery / purification process according to the invention. DETAILED DESCRIPTION OF THE INVENTION
[0065] The invention is now described in more detail and in a non-limiting manner in the following description. For simplification, the description is based on the example of methyl acrylate obtained by esterification of acrylic acid with methanol. The solution proposed by the invention applies in the same way to the use of ethanol in the esterification reaction, as well as to other configurations of the purification train (process with an azeotropic distillation equipped with a side draw-off, partition column for the final purification)
[0066] A methyl acrylate production facility is shown in Figure 1.
[0067] The reaction section comprises an esterification reactor R. The reactor R is fed by an acrylic acid supply line 1, a methanol supply line 2. The reactor preferably contains a heterogeneous catalyst of the acid cation exchange resin type. In the case of homogeneous catalysis, the reactor is further fed by a catalyst supply line (not shown). The esterification reaction can be carried out in excess methanol or in excess acrylic acid.
[0068] At the outlet of the reactor R, the reaction mixture 3 is sent to an azeotropic distillation unit shown in Figure 1 by two distillation columns in series C1 and C3, the first column C1 being connected to the second column C3 by the gas phase 9, and the second column C3 separating at the bottom a flow 10 of water consisting of a part of the water formed by the esterification reaction and water injected in the form of steam into the column C3.
[0069] According to one embodiment, the azeotropic distillation unit comprises a single distillation column Cl operating under vacuum under the same conditions.
[0070] According to one embodiment, the azeotropic distillation unit comprises a distillation column equipped with a side draw-off.
[0071] The distillation column C1 separates, at the bottom, a stream 6 comprising essentially the unreacted acrylic acid, traces of light products (boiling temperature lower than that of acrylic acid), and the heavy products having a boiling temperature higher than acrylic acid (oligomers of acrylic acid and Michael adducts). The stream 6 is sent to a distillation column C2 which separates a stream 7 comprising the residual acrylic acid and the lighter products, and a stream 8 consisting essentially of the heavy products. The stream 7 is advantageously recycled into the reactor R.
[0072] The overhead stream 11 from the azeotropic distillation unit is sent to a liquid / liquid L / L extraction section (decanter or contactor) which generates, on the one hand, an aqueous phase 17 containing essentially methanol and on the other hand, an organic phase 12.
[0073] In the installation described in Figure 1, the aqueous phase 17 is subjected to distillation on a distillation column C5 to separate the methanol which is recycled into the reactor (stream 5), and an aqueous stream 18 depleted in methanol which can be partially recycled into the liquid / liquid extraction phase.
[0074] The organic phase 12 may be subjected to one or more additional serial distillation steps. For example, a topping column C6 extracts the residual light compounds 13 at the top, and a tailing column C7 which separates at the bottom a stream 16 essentially comprising the residual heavy compounds with methyl acrylate and a stream 15 of purified methyl acrylate at the top.
[0075] According to one embodiment, columns C6 and C7 can be replaced by a partition column (DWC).
[0076] The heavy concentrated stream 16 is treated on a thin-film evaporator. The bottom of the evaporator 19, rich in polymerization inhibitors, can be mixed and recycled with stream 4. The gas phase from this EP evaporator is partially condensed to obtain a first liquid stream 20 rich in Michael adducts and, after a second condensation, a methyl acrylate stream 21 which can advantageously be recycled into the feed stream 14 of C7.
[0077] Referring to Figure 1, the C7 column has an equivalent of 10 and 30 theoretical plates, preferably 10 to 15 theoretical stages, and operates in a pressure range of 10000 Pa to 50000 Pa and temperatures from 80°C to 110°C at the bottom of the column. The internals used for the column can be valve trays or perforated weir trays, cross-flow trays such as Dual Flow, Ripple Trays, Turbo Grid Shell, or ordered packing. The bottom flow is concentrated on a thin film evaporator EP very well suited to viscous, fouling products and dirty liquids. The evaporation is carried out in a temperature range from 90°C to 110°C, and more specifically between 90°C and 100°C, in a pressure range between 10000 Pa and 80000 Pa.
[0078] When the purification system used includes a partition column according to WO2017 / 125637, the thin-layer evaporator will treat the same flow 16 at the bottom of the DWC column by generating a flow of polymerization inhibitors at the bottom to be recycled to the inlet of the reactor R, two liquid condensation products: the purged and eliminated MPM and the methyl acrylate recycled to the feed of the partition column.
[0079] The process for the recovery / purification of methyl acrylate according to the invention applies to a reaction mixture 3 resulting from the esterification of acrylic acid 1 with methanol 2 in reactor R.
[0080] The following examples illustrate the present invention and are not intended to limit the scope of the invention as defined by the appended claims.
[0081] EXPERIMENTAL PART
[0082] In the examples, percentages are given by weight unless otherwise stated and the following abbreviations have been used:
[0083] AM: Methyl acrylate
[0084] MPM: methyl methoxy propionate
[0085] HQ: polymerization inhibitor
[0086] AA: acrylic acid
[0087] MeOH: methanol
[0088] Example 1 according to the invention
[0089] Simulations using a thermodynamic model were carried out for a reaction mixture obtained by reacting methanol with excess AA on an acidic cationic resin.
[0090] The inlet flow rate of the reaction mixture into the purification train is adjusted to ensure a production of methyl acrylate AM of approximately 160 t / d.
[0091] The flow rate of methyl methoxy propionate MPM to be purged is of the order of 65 kg / h corresponding to the quantity of MPM formed in the reaction at a rate of 160 t / d. Two configurations were compared; they differ in the implementation of the treatment of the bottom of column C7:
[0092] A direct purge of the C7 column foot to eliminate MPM and prevent its accumulation, and
[0093] A foot treatment prior to purging the MPM to limit the loss of AM and polymerization inhibitor (HQ) according to the invention using a thin-film evaporator and partial condensation of the steam. Table 1 below compares the distribution of the different MPM purge flow rates, expressed in kg / h, in the two configurations: according to the prior art (Reference) and according to the invention.
[0094] [Table 1]
[0095] Table 2 shows the material balance of the MPM purge point in each of the two processes, respectively stream 16 at the bottom of column C7 in the reference process and stream 20 at the bottom of the first condenser of the EP section in the process according to the invention.
[0096] [Table 2}
[0097] In the reference process, the simulation indicates significant losses of AM which is concentrated at 79% in the bottom of the C7 tailing column. On the contrary, the process according to the invention makes it possible to limit the content of recoverable product in the purge. Comparative example 2: Process for eliminating MPM at the side draw-off according to FR 3083233
[0098] The pilot used implements a distillation column filled with structured packing elements equivalent to 25 theoretical stages.
[0099] It is fed in the lower part with 10 kg / h of synthetic mixture (AA, MeOH, water, MPM).
[0100] Reflux is provided by an external flow of 5.7 kg / h of AM and lateral withdrawal is carried out (30 g / h) in the upper part. Polymerization inhibitors are injected at the top in the reflux and in the condenser as well as in the feed.
[0101] For this study and to show the sensitivity of the performance of this process to operating conditions, the foot withdrawal flow rate was modified, while the flow rates and compositions of the external feed and reflux were kept constant.
[0102] The results were grouped in Table 3.
[0103] Table 3
[0104] A fluctuation of less than a few percent results in MPM purge performance and makes this process difficult to operate. This sensitivity to the operating conditions of the side draw does not occur in the case of the process according to the invention, because the composition and flow rate of the stream 16 remain constant, which ensures continuous performance of the EP evaporator.
Claims
CLAIMS 1. Process for the recovery / purification of C1-C2 alkyl acrylate from a reaction mixture resulting from the esterification of acrylic acid with an alcohol chosen from methanol and ethanol carried out in the presence of polymerization inhibitor(s), said process comprising at least the following steps: azeotropic distillation of said reaction mixture using a first distillation column, leading to the separation of: o at the top, a stream comprising the alkyl acrylate, the unreacted alcohol and water; o at the bottom, a fraction comprising the unreacted acrylic acid and heavy products, the treatment of the top stream of the first distillation column by liquid / liquid extraction generating an aqueous phase containing essentially alcohol, and an organic phase rich in alkyl acrylate;the treatment by distillation of said aqueous phase in a second distillation column to separate: o at the top, alcohol, which will be recycled in the esterification reaction, and o at the bottom, a stream depleted in alcohol; the treatment of the bottom stream of the first distillation column using a third distillation column and / or an evaporator, which separates: o at the top, a stream comprising residual acrylic acid and lighter products, and o at the bottom, a stream consisting of heavy products; the treatment of said organic phase rich in alkyl acrylate in a fourth distillation column, called a purification column, to separate: o at the top, the purified alkyl acrylate and o at the bottom, the heavy products and the polymerization inhibitors; - the continuous treatment of the bottom flow of the purification column, by evaporation, and at least two successive condensations of the gaseous phase resulting from the evaporation, making it possible to obtain: o a flow of alkyl acrylate to be recycled to the purification column, o an alkyl alkoxy propionate stream, and o a residue containing the polymerization inhibitors.
2. Process according to claim 1, in which the azeotropic distillation column is provided with a side withdrawal of the fraction rich in alkyl alkoxy propionate.
3. A method according to claim 1, wherein the azeotropic distillation is carried out by two distillation columns in series.
4. Process according to one of claims 1 and 2, in which the evaporation of the bottom of the alkyl acrylate purification column is carried out in a temperature range from 80°C to 110°C, more especially between 90°C and 100°C. 5 Method according to any one of the preceding claims, in which the maintained pressure of the evaporator is between 10000 Pa and 80000 Pa. 6 A process according to any one of the preceding claims, wherein the azeotropic distillation is carried out under slight vacuum under a pressure ranging from 200 to 600 mm Hg.
7. The method of claim 1, wherein said at least one alkyl acrylate purification column comprises a tailing column and a topping column.
8. The method of claim 1 wherein said at least one alkyl acrylate purification column comprises a partition wall column.
9. The method of claim 6, wherein said at least one alkyl acrylate purification column comprises a side draw column.
10. Method according to claim 1, in which the head flow of the evaporator is cooled in two successive stages: - Partial condensation in a temperature range from 70 to 110°C, preferably between 80°C-90°C, at the same pressure as that of the evaporator, to obtain on the one hand a liquid flow of Michael adducts to be purged and on the other hand a flow of vapor; - Condensation of this vapor flow in a temperature range from 20°C to 50°C, more specifically 30°C-40°C, before recovery of this liquid flow by a pump and feeding of the purification column.
11. Method according to claim 1, in which step d) of purification is carried out by distillation, using a purification column comprising at least one distillation column, preferably two distillation columns in series.
12. A method according to any one of claims 1 to 11, wherein the alcohol is methanol, the alkyl acrylate is methyl acrylate, and the alkyl alkoxy propionate is methyl methoxy propionate.
13. Process according to claim 12, in which the production of methyl acrylate having a purity greater than 99.5% by weight is carried out in a distillation column known as a tailing column or a partition column operating in a pressure range of 10000 Pa to 50000 Pa and temperatures ranging from 80°C to 110°C.
14. A method according to any one of claims 1 to 11, wherein the alcohol is ethanol, the alkyl acrylate is ethyl acrylate, and the alkyl alkoxy propionate is ethyl ethoxy propionate.
15. A method according to any preceding claim, wherein the evaporation step is carried out by means of a thin film evaporator.