Process for purifying light alkyl acrylates

Abstract

The invention relates to the production of light (meth) acrylates, such as methyl (meth) acrylates or ethyl (meth) acrylates, by direct esterification of (meth) acrylic acid with the corresponding light alcohols. In particular, the present invention relates to a process for recovering / purifying C1-C2 alkyl acrylates, comprising a hydrolysis step that makes it possible to convert a Michael adduct into an acid product having a boiling point that is very different from that of acrylic acid, thereby simplifying the purification sequence.

Description

Technical Field

[0001] The present invention relates to the production of light (meth)acrylic acid esters such as methyl (meth)acrylate or ethyl (meth)acrylate by direct esterification of (meth)acrylic acid with corresponding light alcohols.

[0002] More particularly, the present invention relates to a process for the recovery / purification of C1-C2 alkyl acrylates comprising an acid hydrolysis step which makes it possible to convert the Michael adducts into acidic products having a boiling point much higher than that of acrylic acid, thereby simplifying the purification sequence. Background Art

[0003] It is a known practice to produce (meth)acrylates by esterification between alcohols and (meth)acrylic acid. This reaction is a balanced catalytic reaction with the production of water. It is also accompanied by side reactions that produce impurities.

[0004] The produced water must be removed in order to shift the equilibrium, remove impurities and recycle unreacted reactants.

[0005] For this purpose, a series of distillations and / or extractions, separations by sedimentation are usually carried out, which are relatively complex to implement, in particular due to the presence of azeotropic mixtures, and energetically expensive.

[0006] For the sake of convenience, the problems arising during the production of light (meth)acrylates, in particular C1-C2 alkyl acrylates, will now be described based on the example of methyl acrylate obtained by esterifying acrylic acid with methanol. However, the problems and solutions proposed by the present invention can also be applied to the use of ethanol in the esterification reaction.

[0007] As a side reaction during the production of methyl acrylate, unreacted acrylic acid may form oligomers such as 3-acryloyloxypropionic acid (n=2) or 3-acryloyloxy-3-propoxypropionic acid (n=3), which are heavy byproducts having a boiling point higher than that of acrylic acid.

[0008] As a further side reaction, Michael addition can give rise to Michael adducts; in particular, Michael addition between the already formed methyl acrylate and methanol leads to the formation of methyl methoxypropionate.

[0009] Methyl methoxypropionate (MMP) is a "heavy" by-product because its boiling point (142°C at atmospheric pressure) is significantly higher than that of the produced methyl acrylate (80°C at atmospheric pressure) and it is formed in large quantities during the process as the esterification reaction proceeds, simultaneously with the formation of oligomers of acrylic acid.

[0010] Methyl methoxypropionate is problematic because it exhibits a vapor pressure close to that of acrylic acid. Its boiling point is close to that of acrylic acid (144°C at atmospheric pressure), and it can form an azeotrope with water. It concentrates primarily in the recycle loop for unreacted acrylic acid. This recycle loop then has to be purged, which can result in significant acrylic acid losses. Furthermore, compared to acrylic acid oligomers, MMP is the lightest of the heavy byproducts; it can interfere with the final purification of methyl acrylate and adversely affect the quality of the finished product.

[0011] In order to limit the formation of methyl methoxypropionate, document US Pat. No. 6,025,520 proposes carrying out the esterification reaction under reduced pressure with an excess of acid. These conditions make it possible to increase the yield and selectivity of the esterification reaction and significantly reduce the formation of heavy by-products such as methyl methoxypropionate, which are generated by the addition of methanol and which pose a problem for the purification of the desired ester sequence.

[0012] The process described in document WO 2015 / 063388 proposes to significantly reduce the formation of alkyl alkoxypropionates during the synthesis of methyl or ethyl (meth)acrylate in conventional fixed-bed reactor technology by carrying out the esterification reaction at atmospheric pressure with an excess of acid relative to the alcohol and high hourly space velocity.

[0013] The process described in US 2001 / 0047106 proposes converting the oxygenated esters formed during esterification by catalytic cracking at high temperatures (150 to 250°C) with the addition of acrylic acid and water. The products formed are then primarily esters, and the addition of water makes it possible to limit the formation of olefins and ethers at high temperatures. However, this type of reaction requires a large amount of energy to reach these temperatures.

[0014] In patent FR 3083233, the applicant company demonstrated that methyl methoxypropionate could be partially removed via a side stream draw during the azeotropic distillation of a reaction mixture in a single distillation column equipped with a side stream draw. This invention made it possible to remove the MMP / water azeotrope without affecting the MMP present in the bottom portion of the azeotropic stream, which is composed primarily of acrylic acid.

[0015] However, the methyl methoxypropionate formed during the methyl acrylate synthesis still needs to be removed, which is detrimental to the mass balance of the process (loss of starting material during the bleed) and to the purification sequence (complexity of achieving high purity). Summary of the Invention

[0016] Surprisingly, the present inventors have found that it is possible to remove methyl methoxypropionate (or ethyl methoxypropionate) and obtain high-purity methyl acrylate (or ethyl acrylate) by effectively removing the Michael adduct formed in the process by acid hydrolysis, which converts the Michael adduct into a high-boiling acid that can then be removed at the bottom of the cracker. Thus, the alkyl ester stream is purified and can be recycled to the reaction.

[0017] It is therefore an object of the present invention to provide a process for the recovery / purification of methyl acrylate, and more generally methyl acrylate or ethyl acrylate, which allows the efficient removal of methyl methoxypropionate by continuously carrying out an acidolysis reaction in the presence of acrylic acid to form 3-methoxypropionic acid and methyl acrylate.

[0018] A subject of the present invention is a process for recovering / purifying C1-C2-alkyl acrylates from the reaction mixture obtained by the esterification of acrylic acid with an alcohol chosen from methanol and ethanol, characterized in that the process comprises an acidolysis treatment, whereby alkoxy esters of methyl acrylate or ethyl acrylate are continuously converted into alkoxypropionic acid.

[0019] According to one embodiment, the acidolysis reaction occurs at a temperature close to that of the esterification reaction.

[0020] According to one embodiment, the alcohol is methanol, the alkyl acrylate is methyl acrylate, the alkyl alkoxypropionate is methyl methoxypropionate (MMP), and the alkoxypropionic acid is methoxypropionic acid (MPA).

[0021] According to one embodiment, the alcohol is ethanol, the alkyl acrylate is ethyl acrylate, the alkyl alkoxypropionate is ethyl ethoxypropionate (EEP), and the alkoxypropionic acid is ethoxypropionic acid (EPA).

[0022] According to one embodiment, the reaction mixture is obtained from the esterification of acrylic acid with a stoichiometric excess of alcohol.

[0023] According to one embodiment, the reaction mixture is obtained by esterification of acrylic acid with an alcohol in the presence of a stoichiometric excess of acid.

[0024] The acid hydrolysis treatment involves the following reaction: In the presence of water and acrylic acid (AA), MMP is hydrolyzed to form methoxypropionic acid and methanol (MeOH). MMP reacts with acrylic acid to form methyl acrylate and methoxypropionic acid.

[0025] MMP hydrolysis reaction:

[0026] MMP+H2O-->MPA(methoxypropionic acid)+MeOH

[0027]

[0028] -MMP acidolysis reaction:

[0029] MMP+AA-->MPA(methoxypropionic acid)+AM

[0030]

[0031] One or both of these reactions occur depending on the reactants present.

[0032] These reactions are carried out in a temperature range close to that of the esterification reaction (75° C.-85° C.); they are catalyzed by strong acids, such as strong cationic resins.

[0033] This reaction converts methyl methoxypropionate into methoxypropionic acid (boiling point: 206° C. at atmospheric pressure), which can be easily separated from acrylic acid because its vapor pressure is very different from that of acrylic acid.

[0034] The product from the reactor is sent to an azeotropic column. Azeotropic distillation is understood to mean the separation of an azeotrope (or azeotropic mixture) consisting of a ternary alkyl acrylate / alcohol / water mixture. As described in document FR3083233, this azeotropic column for separating the reaction mixture can be equipped with a side stream outlet to allow removal of the MMP / water azeotrope. The bottom stream of the azeotropic column is fed in whole or in part to a heavies treatment column. This column separates a stream containing unreacted (meth) acrylic acid and trace alcohols and light products at the top, and a stream of heavy by-products at the bottom.

[0035] These heavy by-products rich in alkoxy ester adducts and oligomers can be subjected to thermal treatment in a cracking reactor, releasing a stream of economically upgraded products that are returned to the reaction and produce a residue.

[0036] The overhead stream from the azeotropic column is fed to a liquid / liquid extractive purification train and one or two distillation columns, enabling the recovery of purified esters.

[0037] The acidolysis reactor processes all the heavy MMP-rich streams and allows recovery of economically upgradeable feedstock and conversion of methyl methoxypropionate to methoxypropionic acid.

[0038] According to one embodiment, the process according to the invention is carried out in an installation comprising an esterification reactor, an azeotropic distillation column, an acidolysis reactor, a second distillation column and / or a film evaporator, a cracking reactor, a liquid / liquid extraction column, a purification system optionally comprising a distribution column.

[0039] According to one embodiment, the acidolysis reactor is located at the feed of a treatment column for heavies from the bottom of the azeotropic column.

[0040] According to one embodiment, an acidolysis reaction located at the feed of the heavies treatment column treats the stream from the bottom of the azeotropic column, optionally the stream from the side draw, and optionally the effluent stream from the bottom of the purification column.

[0041] According to one embodiment, the method according to the invention comprises the following steps:

[0042] a) azeotropic distillation of the reaction mixture using a first distillation column makes it possible to separate, at the top, an azeotropic mixture comprising alkyl acrylate, unreacted alcohol and water, and at the bottom, a fraction comprising unreacted acrylic acid and heavy by-products, a fraction enriched in alkyl alkoxypropionate by-product being removed by side stream discharge;

[0043] b) an acidolysis step which makes it possible to convert the alkyl alkoxypropionate into alkoxypropionic acid, thereby producing a stream free of alkyl alkoxypropionate which is fed to a heavies separation column;

[0044] c) separating the bottom stream from the azeotropic column by column into a stream comprising essentially unreacted acrylic acid, which stream is recycled to the esterification reactor, and a stream comprising essentially heavy by-products, which stream is subjected to thermal cracking to release a recyclable stream of economically upgraded products;

[0045] d) a cracking step which allows economical upgrading of the feedstock contained in the by-products and removal of the residues;

[0046] e) subjecting the top stream from the first distillation column to a liquid / liquid extraction with an aqueous stream, making it possible to separate an organic phase essentially comprising alkyl acrylates and an aqueous phase, distilling the aqueous phase to recover, on the one hand, a fraction rich in alcohol that can be recycled to the reactor and, on the other hand, a fraction rich in water that can be used as the aqueous stream in the liquid / liquid extraction step;

[0047] f) purifying the organic phase so that the purified alkyl acrylate can be recovered;

[0048] g) After the acid hydrolysis step, optionally recycling the alkoxy ester-rich purge from the purification train.

[0049] The present invention makes it possible to overcome the disadvantages of the prior art associated with the formation of alkyl alkoxypropionate by-products in the processes for the synthesis of methyl acrylate or ethyl acrylate by direct esterification of acrylic acid with the corresponding alcohols.

[0050] The process according to the invention makes it possible to remove alkyl alkoxypropionate efficiently and to reduce the loss of economically upgradeable product in the purification train caused by discharges forced by the accumulation of alkyl alkoxypropionate.

[0051] The present invention thus provides a simplified process for producing high-purity methyl acrylate or ethyl acrylate and optimizes the mass balance of the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A plant for producing methyl acrylate comprising an acid hydrolysis step according to the invention is schematically represented. DETAILED DESCRIPTION

[0053] The present invention will now be described in more detail in the following description in a non-limiting manner by comparison with prior art methods.

[0054] For simplicity, the description is based on the example of methyl acrylate obtained by esterification of acrylic acid with methanol. The solution proposed by the present invention is applicable in the same manner to the use of ethanol in the esterification reaction and also to other configurations of the purification sequence (processes with azeotropic distillation without a side stream draw, an overhead column and a rectification column or distribution column for the final purification).

[0055] The prior art equipment for producing methyl acrylate is Figure 1 Shown in.

[0056] The reaction section comprises an esterification reactor R1. Reactor R1 is fed by acrylic acid feed line 1 and methanol feed line 2. The reactor preferably contains a heterogeneous catalyst of the acidic cation exchange resin type. In the case of homogeneous catalysis, the reactor is additionally fed via a catalyst feed line (not shown). The esterification reaction can be carried out in an excess of methanol or an excess of acrylic acid.

[0057] The esterification reaction can be carried out in an excess of alcohol - in which case the acid / alcohol molar ratio is between 0.6 and 1 - or in an excess of acrylic acid - in which case the acid / alcohol molar ratio is between 1.05 and 3, it being understood that the acid / alcohol molar ratio refers to the acid and alcohol content of all streams fed to the esterification reactor (pure product streams and recycled streams).

[0058] The esterification reaction can be carried out under a pressure ranging from atmospheric pressure (100,000 Pa) to 3 times the atmospheric pressure (300,000 Pa), or under reduced pressure.

[0059] The esterification reaction is carried out in the presence of an acid catalyst, for example, an acidic cation exchange resin in the case of heterogeneous catalysis; alternatively, in the case of homogeneous catalysis, sulfuric acid or an organic sulfonic acid, such as methanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid or dodecylsulfonic acid, or a mixture thereof, can be used as a catalyst. The esterification reaction is preferably carried out under atmospheric pressure in the case of heterogeneous catalysis.

[0060] The reaction is generally 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.

[0061] At the outlet of the reactor R1, the reaction mixture 3 is sent to the azeotropic distillation unit C8. The configuration of the distillation column C8 makes it possible to separate, at the top, a stream 11 consisting of an azeotropic mixture containing the formed methyl acrylate, unreacted methanol and water produced by the reaction, as well as light and heavy impurities; at the bottom, a stream 6 consisting essentially of unreacted acrylic acid, traces of light and heavy products; and a stream 19 withdrawn as a side stream.

[0062] Stream 19 comprises the majority of the MMP formed as a by-product during the esterification. Stream 19 is a stream rich in MMP, but may contain methyl acrylate, methanol, acrylic acid and water.

[0063] The stream 19 may advantageously be sent to the acidolysis reactor R2 , which will make it possible to convert the MMP into MPA, which is then fed to the column C2 for the treatment of heavy by-products.

[0064] Alternatively, stream 19 can be subjected to a purification (not shown) in order to recover, on the one hand, purified methyl methoxypropionate and, on the other hand, economically upgradeable compounds such as methyl acrylate, methanol and acrylic acid.

[0065] Distillation column C8 separates off, at the bottom, stream 6 which comprises essentially unreacted acrylic acid, traces of light products (boiling point below that of acrylic acid) and heavy products (oligomers of acrylic acid and Michael adducts) boiling point above that of acrylic acid.

[0066] Stream 6 is sent in whole or in part to the acidolysis reactor R2 and then to a distillation column and / or film evaporator C2 which separates stream 7 comprising residual acrylic acid and lighter products and stream 8 consisting essentially of heavy products. Stream 7 is advantageously recycled to the reactor R1.

[0067] Stream 8 can be subjected to thermal cracking, which allows the recycling of valuable products (starting compounds or finished products) that can potentially be recovered from the heavy product fraction. Thermal cracking is generally carried out at a temperature ranging from 120° C. to 220° C., for example, optionally in the presence of an acid catalyst such as sulfuric acid or sulfonic acid. The final residue from the cracker is sent for incineration, while the economically upgraded products are recycled to the reaction via stream 23.

[0068] The azeotropic distillation unit separates off, at the top, a stream 11 consisting of an azeotropic mixture comprising the methyl acrylate formed, unreacted methanol and water resulting from the reaction, as well as light and heavy impurities.

[0069] The top stream 11 from the azeotropic distillation unit is sent to a settling section (settling tank or contactor), which produces, on the one hand, an essentially methanol-containing aqueous phase 17A and, on the other hand, an organic phase 12 .

[0070] The liquid / liquid extraction section usually consists of a packed column or a stirred liquid / liquid extraction column, a mixer-settling tank group, and one or more settling tanks connected in series. It produces an alcohol-depleted organic phase 14 and an aqueous phase 17B.

[0071] exist Figure 1 In the apparatus described in , the aqueous phase 17 undergoes distillation in a distillation column C5 to separate off methanol, which is optionally recycled to the reactor (stream 5) after a dehydration step, and the methanol-depleted aqueous stream 18 can be recycled for the liquid / liquid extraction phase.

[0072] The organic phase 14 is subjected to a purification sequence to recover methyl acrylate having the purity necessary for its subsequent use. Typically, a purity greater than 99.5%, or even greater than 99.8%, is desired.

[0073] To this end, the organic phase 14 can be subjected to one or more supplementary distillation steps in series.

[0074] According to one embodiment of the invention, the organic phase 14 is purified using a purification system comprising at least one distribution column equipped with an internal partial distribution plate (generating a separation zone in the column) and a settling tank. Figure 1 In the reactor, represented by C9, there are separated, at the top, a stream 13 comprising mostly light compounds; at the bottom, a stream 16 comprising a large amount of heavy compounds; and a stream 15 of purified methyl acrylate, which is withdrawn as a side stream.

[0075] Stream 13 consists of the condensed light stream in the form of an aqueous phase and an organic phase. The organic phase is partially used as reflux for the distribution column and discharged; the aqueous phase is processed towards the biological station.

[0076] Stream 16 is discharged but can also be recycled to the acidolysis reactor R2.

[0077] Thus, the acid hydrolysis reactor R2 receives a combination of the MMP-rich streams: stream 19, stream 16 and stream 6; the feed contains at least 50% acrylic acid. To promote the reaction, an aqueous stream (stream 18) not shown can also be added.

[0078] The effectiveness of the inhibitor is also related to the injection of air or depleted air into the various towers used.

[0079] Examples of possible polymerization inhibitors include phenothiazine (PTZ), hydroquinone (HQ), hydroquinone monomethyl ether (HQME), di-tert-butyl-p-cresol (BHT), p-phenylenediamine, TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), di-tert-butylcatechol or TEMPO derivatives such as OH-TEMPO, alone or as mixtures thereof in any ratio, which may be present in the reaction medium in an amount between 50 ppm and 5000 ppm, optionally in the presence of depleted air, but generally in an amount between 150 ppm and 1000 ppm.

[0080] The addition of the polymerization inhibitor can be carried out at various locations, either accompanying the introduction of the reactants or at the top of the distillation column.

[0081] The present invention makes it possible to limit the loss of economically upgradeable materials such as acrylic acid, alcohols or alkyl acrylates in a process for producing light alkyl acrylates by direct esterification.

[0082] The acidolysis reactor, which is fed by multiple streams, contains large amounts of MMP and acrylic acid; depending on the added streams, this means variable amounts of light esters, water and oligomers.

[0083] The acidolysis catalyst is an acid catalyst selected from the following list: sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, and a strong acidic cationic resin.

[0084] According to one embodiment, the catalyst is a homogeneous catalyst. The homogeneous catalyst used may be an acid, such as sulfuric acid, methanesulfonic acid or p-toluenesulfonic acid.

[0085] According to one embodiment, the catalyst is a heterogeneous catalyst. In heterogeneous catalysis, the catalyst is a strongly acidic cationic resin, gel or macroporous, such as Amberlyst 131 or Amberlyst 15, used in the form of a fixed bed reactor or a stirred reactor (in suspension).

[0086] The residence time in the acidolysis reactor may vary between 0.2 and 6 hours, preferably between 0.5 and 5 hours. The temperature in the acidolysis reactor is close to the temperature of the esterification reaction, between 50°C and 100°C, preferably between 70°C and 90°C, while keeping the reactants in their liquid form.

[0087] According to one embodiment, the molar ratio between AA and MMP is from 1 to 11, preferably from 4 to 9. An aqueous stream may be added to the mixture to promote the hydrolysis reaction.

[0088] The following examples illustrate the invention and are not intended to limit the scope of the invention which is defined by the appended claims.

[0089] Experimental part

[0090] In the examples, unless otherwise indicated, percentages are expressed by weight and the following abbreviations are used:

[0091] AA: Acrylic acid

[0092] MA: Methyl acrylate

[0093] MMP: Methyl methoxypropionate

[0094] MeOH: methanol

[0095] Example 1 Acid hydrolysis of MMP with or without water: Acid hydrolysis of AA+MMP with excess AA (with and without water) Condition

[0096] MMP acidolysis reactions were performed batchwise in the absence or presence of water. In a round-bottom flask, tAA (technical-grade acrylic acid with a purity >99%) and MMP were introduced in an excess of AA (tAA / MMP molar ratio = 5), along with 20% by mass of dry resin. The mixture was held at 80°C for 5 hours and subjected to complete reflux. Table 1 summarizes the reaction conditions.

[0097] Degree of conversion = (no.mol - no.mol initial) / no.mol MeOH initial.

[0098]

[0099] Table 1

[0100] Under these conditions, in the absence of water, MMP was readily converted to methoxypropionic acid by acidolysis; a significant amount of MA was also formed (69% to 85% conversion). The presence of water promoted the disappearance of MMP, undoubtedly through a hydrolysis reaction.

Claims

1. A method for purifying a C1-C2 alkyl acrylate from a reaction mixture obtained by esterification of acrylic acid with an alcohol selected from methanol and ethanol, characterized in that: Since the reaction mixture is rich in acrylic acid obtained by esterification, the process comprises an acidolysis treatment, whereby alkoxy esters of methyl acrylate or ethyl acrylate can be continuously converted into alkoxypropionic acid in the presence of a homogeneous or heterogeneous catalyst at a temperature of 50-100°C, preferably 70-90°C.

2. The process according to claim 1, which is carried out in a facility comprising an esterification reactor, an azeotropic distillation column, an acidolysis reactor, a second distillation column and / or a film evaporator, a cracking reactor, a liquid / liquid extraction column, and a purification system optionally comprising a distribution column.

3. The method according to claim 1 or 2, wherein since the alcohol is methanol and the alkyl acrylate is methyl acrylate, the alkyl alkoxypropionate is methyl methoxypropionate and the alkoxypropionic acid is methoxypropionic acid.

4. The method according to claim 1 or 2, wherein since the alcohol is ethanol and the alkyl acrylate is ethyl acrylate, the alkyl alkoxypropionate is ethyl ethoxypropionate and the alkoxypropionic acid is ethoxypropionic acid.

5. The process according to any one of the preceding claims, wherein the acidolysis catalyst is an acid catalyst selected from the following list: sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid and strongly acidic cationic resins.

6. The process according to any one of the preceding claims, wherein the temperature in the acid hydrolysis reactor is from 50 to 100°C, preferably from 70 to 90°C.

7. The process according to any one of the preceding claims, wherein the pressure in the acidolysis reactor is from 100 000 Pa to 300 000 Pa.

8. The process according to any one of the preceding claims, wherein the residence time in the acid hydrolysis reactor is from 0.2 to 6 hours.

9. The process according to any one of the preceding claims, wherein the molar ratio between acrylic acid (AA) and methyl methoxypropionate (MMP) at the inlet of the acidolysis reactor is from 1 to 11, preferably from 4 to 9.

10. The process according to any one of the preceding claims, wherein the reaction mixture is obtained from the esterification of acrylic acid with a stoichiometric excess of alcohol, the acid / alcohol molar ratio being from 0.6 to 1.

11. The process according to claim 1, wherein the reaction mixture is obtained by esterification of acrylic acid with an alcohol in the presence of a stoichiometric excess of acid, the acid / alcohol molar ratio being from 1.05 to 3.

12. The method according to claim 5, wherein when the catalyst is a strongly acidic cationic resin, the catalytic esterification reactor is a fixed bed reactor or a stirred reactor.

13. The process according to any one of the preceding claims, wherein the polymerization inhibitor is introduced into the esterification reactor at a rate of 500 to 5000 ppm relative to the crude reaction mixture.

14. The process according to any one of the preceding claims, wherein the azeotropic column can be equipped with a side stream draw.

15. A process according to any one of the preceding claims, wherein the cracking is thermal cracking in the absence of a catalyst.

16. The method according to claim 2, comprising the steps of: a) azeotropic distillation of the reaction mixture using a first distillation column makes it possible to separate, at the top, an azeotropic mixture comprising alkyl acrylate, unreacted alcohol and water, and at the bottom, a fraction comprising unreacted acrylic acid and heavy by-products, a fraction enriched in alkyl alkoxypropionate by-product being removed via a side stream draw; b) an acidolysis step which makes it possible to convert the alkyl alkoxypropionate into alkoxypropionic acid, thereby producing a stream free of alkyl alkoxypropionate which is fed to a heavies separation column; c) column separating the bottoms stream from the azeotropic column into a stream comprising essentially unreacted acrylic acid, which stream is recycled to the esterification reactor, and a stream comprising essentially heavy by-products, which is subjected to thermal cracking to release a recyclable stream of economically upgraded products; d) a cracking step which allows the economical upgrading of the feedstock contained in the by-products and the discharge of the residue; e) subjecting the top stream from the first distillation column to a liquid / liquid extraction with an aqueous stream, making it possible to separate an organic phase essentially comprising alkyl acrylates and an aqueous phase, distilling the aqueous phase to recover, on the one hand, a fraction rich in alcohol that can be recycled to the reactor and, on the other hand, a fraction rich in water that can be used as the aqueous stream in the liquid / liquid extraction step; f) purifying the organic phase so that the purified alkyl acrylate can be recovered; g) optionally recycling the alkoxy ester-rich effluent from the purification train after the acid hydrolysis step.

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