ACRYLIC (METH) PURIFICATION PROCESS

Abstract

The present invention relates to the production of (meth)acrylic acid in a (meth)acrylic acid recovery process based on the use of two distillation columns in the absence of external solvents. External solvents include those used in absorption processes, azeotropic solvents, and solvents used for liquid-liquid extraction. More particularly, the invention relates to the use of a plate heat exchanger as a reboiler for the dehydration column. The invention also relates to an installation adapted for implementing this process.

Description

Title of the invention: PROCESS FOR PURIFYING (METH)ACRYLIC ACID Technical field

[0001] The present invention relates to the production of (meth)acrylic acid in a (meth)acrylic acid recovery process based on the use of two distillation columns in the absence of an external solvent. External solvents include those used in absorption processes, azeotropic solvents, and solvents used for liquid-liquid extraction. More particularly, the invention relates to the use of a plate heat exchanger as a reboiler for the dehydration column. The invention also relates to an installation adapted for implementing this process. TECHNICAL BACKGROUND AND TECHNICAL PROBLEM

[0002] The acrylic acid synthesis process, exploited on a large industrial scale, implements a catalytic oxidation reaction of propylene in the presence of oxygen.

[0003] This reaction is generally carried out in the gas phase and most often in two steps: the first step carries out the substantially quantitative oxidation of propylene into a mixture rich in acrolein, then, in the second step, carries out the selective oxidation of acrolein into acrylic acid.

[0004] The gaseous mixture from the second step consists, apart from acrylic acid, of untransformed compounds from the reactants involved or of impurities generated during at least one of the 2 reaction steps, namely:

[0005] - of light, non-condensable compounds under the temperature and conditions of pressures usually implemented, essentially: propylene, propane, nitrogen, unconverted oxygen, carbon monoxide and carbon dioxide formed in small quantities by ultimate oxidation;

[0006] - of light condensable compounds, namely essentially: water, non-acrolin converted, light aldehydes such as formaldehyde, glyoxal and acetaldehyde, formic acid, acetic acid or propionic acid;

[0007] - of compounds having a boiling point higher than that of acid acrylic: furfuraldehyde, benzaldehyde, maleic acid and anhydride, benzoic acid, 2-butenoic acid, phenol, protoanemonin;

[0008] - finally, heavy compounds, derived from the addition of compounds with properties nucleophilic on the double bond of unsaturated carbonyl monomers, by Michael reaction.

[0009] These compounds are heavy products that reduce the recovery yield by consuming the acrylic acid (AA) monomer. In the case of an AA production unit, these are essentially:

[0010] - of derivatives of the addition of acrylic acid to the double bond of another molecule acrylic acid: 3-acryloxypropionic acid also called "acrylic acid dimer" or "AA dimer";

[0011] - of derivatives of acrylic acid addition to the double bond on a molecule of AA dimer, to form the "AA trimer" and other oligomers formed by successive additions of acrylic acid to the double bonds of the preceding AA oligomers,

[0012] - of carboxylic acid addition derivatives formed as by-products of the acid acrylic or water on the double bond of the AA or the oligomers mentioned above.

[0013] This covalent reaction for the formation of Michael derivatives is strongly favored by temperature, residence time, and the presence of water, which further increases the kinetics of dimer formation. These dimer formation kinetics were, for example, described in the publication by C. Pfeifer, C. Scholz, K. Vogel, A. Drochner, and H. Vogel in Chemical Engineering and Technology (2017), 40(4), pp. 755–759.

[0014] Consequently, the implementation of equipment (column bottom, boiler, etc.) in terms of size or efficiency in transmitting heat will constitute an important design parameter to meet the quality requirements of acrylic acid and limit product losses, which are often compensated only by an additional high-temperature cracking treatment of Michael derivatives to regenerate the acrylic acid monomer.

[0015] The recovery of valuable monomers from heavy Michael-derived compounds is difficult in the case of heavy compounds from an AA production unit. Indeed, during the thermal cracking process which regenerates acrylic acid, which is distilled and valorized, a residue remains whose viscosity increases sharply when high cracking yields are sought, until it can no longer be extracted from the cracking reactor.

[0016] Furthermore, despite the use of inhibitors commonly employed for the distillation of this monomer, polymer deposits are observed, particularly on the hot wall of the boiler. The formation of these solid deposits quickly leads to problems such as pipe blockages or changes in heat exchange, requiring the installation to be shut down for cleaning.

[0017] Document EP1484309 describes a process for manufacturing acrylic acid comprising an acrylic acid absorption column by adding water external to the process, vacuum distillation followed by crystallization. It does not describe specific conditions for limiting the formation of heavy by-products, but indicates (0051) that an additional tank can be added to treat the by-products formed by temperature.

[0018] Document EP 3480183 recommends the implementation of a multitubular condenser with an injection of inhibitors to limit polymerization phenomena but does not recommend a solution for the limitation or treatment of heavy by-products.

[0019] Document EP 2 066 613 describes a process for recovering acrylic acid. This process uses two distillation columns to purify the cooled gaseous reaction mixture:

[0020] a) a dehydration column,

[0021] b) a finishing column (or purification column) fed by a portion of the footflow from the dehydration column.

[0022] According to this process, the cooled gaseous reaction stream is dehydrated in a first column. The distilled gas stream at the top of the column is sent to a condenser where the lighter compounds are partially condensed and returned to the dehydration column as liquid reflux. The uncondensed gaseous effluent is returned, at least partially, to the reaction, and the remainder is discarded. The bottom stream of the dehydration column is sent to a second column, called the finishing column. During the purification / finishing step, a stream rich in heavy compounds is discarded at the bottom, and a distillate comprising water and light by-products is recovered at the top. This distillate is condensed and then recycled to the bottom of the first dehydration column, thus forming a recirculation loop. This bottom stream of the dehydration column may contain insoluble solid particles that must be filtered.A stream of purified acrylic acid is recovered in liquid or vapor form by lateral withdrawal from the finishing column. The acrylic acid obtained is generally of a purity greater than 98.5% by mass.

[0023] Despite the advantages of the process described in document EP 2 066 613, some drawbacks related to its implementation remain. In particular, the residence time and the optimal type of equipment to be used to limit the formation of dimers are not addressed, nor are the risks of polymerization or clogging due to the presence of solids.

[0024] The solids present at the bottom of the dehydration column are of diverse origin: dust from the abrasion of catalysts, derivatives of heavy compounds such as phthalics, high molecular weight acrylic acid oligomers, or polymers insoluble in acrylic acid.

[0025] In fact, in addition to reducing the formation of dimers, particular attention must be paid to preventing fouling phenomena, whether particulate, chemical or corrosive, as well as to preventing the risks of fouling through the choice of reboiler to be implemented, in particular at the bottom of the dehydration column where the presence of water will increase the rate of dimer formation.

[0026] The choice of a heat exchanger for a given application depends on many parameters: temperature and pressure range of the fluids, physical properties and aggressiveness of these fluids, maintenance and size.

[0027] There are different types of heat exchangers. Tubular heat exchangers, using tubes as the main component of the heat exchange wall, are the most widespread, for both economic and historical reasons. Among so-called multitubular heat exchangers, we can distinguish between separate tube heat exchangers, closely spaced tube heat exchangers, and shell and tube heat exchangers. Plate heat exchangers can be plate and gasket heat exchangers with straight or chevron grooves, welded or brazed plate heat exchangers, plate, spiral, or shell and plate heat exchangers.

[0028] The inventors have now discovered that the use of a suitably chosen plate heat exchanger greatly limits the formation of acrylic acid or methacrylic acid dimers, while reducing the undesirable formation of polymers and fouling by solids, while being easily cleanable.

[0029] It also appeared to the inventors that this invention could be applied to acrylic acid produced from sources other than propylene, to methacrylic acid, as well as to those acids derived from renewable raw materials, which are likely to pose the same purification problems. Summary of the invention

[0030] The present invention relates firstly to a process for recovering (meth)acrylic acid without using an external solvent, from a gaseous reaction mixture comprising (meth)acrylic acid obtained in the gas phase from a precursor of (meth)acrylic acid, comprising at least the following steps: i. the gaseous reaction mixture is subjected to dehydration in a first column called the dehydration column, leading to a head flow, at least part of which is condensed and returned to the dehydration column as reflux, and to a foot flow; ii. at least part of the bottom stream of the dehydration column is subjected to distillation at a pressure lower than atmospheric pressure in a second column called the finishing column, leading to a top stream, and a bottom stream containing heavy compounds; iii. a (meth)acrylic acid stream is recovered by lateral withdrawal from the finishing column, and / or at the bottom of the finishing column; iv. Part of the bottom flow from the dewatering column and the top flow from the finishing column are sent to a heat exchanger and then reinjected into the dewatering column, thus forming a recirculation loop,

[0031] said process being characterized in that said exchanger is a plate exchanger.

[0032] According to certain particular embodiments, the invention also presents a or, preferably, several of the advantageous features listed below:

[0033] - the finishing column is fluidly connected at the base of said column Dehydration; by "fluidic connection" or "fluidically connected," we mean that there is a connection via a system of pipes capable of transporting a flow of matter. This connection system may include valves and branches.

[0034] - the finishing column is a column with a separating wall.

[0035] - the plate heat exchanger has a primary surface. The heat exchange surface is then Composed of parallel, rectangular metal plates, fitted with gaskets, clamped together by tie rods between two flanges, one fixed and the other movable, allowing for easy maintenance. It can be flat, with joined plates, hybrid, with straight or chevron grooves, or with welded or brazed plates. Preferably, the heat exchanger is flat, meaning it consists of an assembly of stamped flat plates. The fluid circulation channels are formed by roller welding in pairs, and these pairs are then joined together by edge welding.

[0036] - the exchanger has a volume one to five times smaller than that of an exchanger tubular with equivalent heating surface area.

[0037] According to a second aspect, the invention relates to an installation adapted for implementing the (meth)acrylic acid recovery process according to the invention, comprising at least:

[0038] a) a dehydration column;

[0039] b) a finishing column fluidly connected at the bottom of said dehydration column;

[0040] c) at least one plate heat exchanger which receives part of the bottom flow from the dehydration column, then reinjects it into the dehydration column, so as to constitute a recirculation loop.

[0041] The present invention overcomes the drawbacks of the prior art. More particularly, it provides a process for obtaining a high-purity technical acrylic acid, greater than 98.5% by mass, preferably at least 99% and more preferably at least 99.5% acrylic acid, said process incorporating a plate heat exchanger as a reboiler for the dehydration column, limiting the formation of dimers while reducing the risks of polymerization and fouling by solids, and being easily cleanable.

[0042] The use of this exchanger allows for gains in efficiency, energy consumption, and process reliability.

[0043] Other features and advantages of the invention will become clearer from the following detailed description, with reference to the attached [Fig.1] which represents a diagram of a process for the production of acrylic acid illustrating the solvent-free recovery / purification process according to the preferred mode of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] The process according to the invention employs a suitably chosen plate heat exchanger which greatly limits the formation of dimers while reducing the undesirable formation of fouling polymers by solids, while being easily cleanable.

[0045] According to various embodiments, said process comprises the following characteristics, possibly combined.

[0046] The process according to the invention may further include other preliminary, intermediate or subsequent steps provided that they do not negatively affect the obtaining of purified (meth)acrylic acid.

[0047] According to one embodiment, the process according to the invention aims at a process for recovering acrylic acid.

[0048] According to one embodiment, the process according to the invention aims at a process for recovering methacrylic acid.

[0049] According to one embodiment, the gaseous reaction mixture containing (meth)acrylic acid is obtained from a bio-based precursor. These bio-based precursors are derived from renewable organic matter (biomass) of biological origin (microorganisms, plants or animals), as opposed to raw materials of fossil origin.

[0050] According to one embodiment of the invention, the precursor of acrylic acid is acrolein.

[0051] According to one embodiment of the invention, acrolein is obtained by oxidation of propylene or by oxidative dehydrogenation of propane.

[0052] According to one embodiment of the invention, the gaseous reaction mixture comprising acrylic acid obtained by gas-phase oxidation of an acrylic acid precursor comprises carbon of renewable origin.

[0053] According to one embodiment of the invention, the precursor of acrylic acid is derived from glycerol, 3-hydroxypropionic acid or 2-hydroxypropionic acid (lactic acid).

[0054] According to a preferred embodiment of the invention, the gaseous reaction mixture comprises propylene-derived acrylic acid obtained by a two-step oxidation process.

[0055] According to one embodiment, the precursor of methacrylic acid is methacrolein obtained by oxidation of isobutylene and / or tert-butanol or from oxidative dehydrogenation of butane and / or isobutane.

[0056] According to one embodiment, purification is carried out with a process as described in EP 2066613.

[0057] According to the embodiment shown in [Fig. 1], relating to a process for purifying acrylic acid, an acrylic acid precursor stream 1 (for example, propylene) and stream 9 obtained after compression by compressor c of the recycle gas stream 8, and air stream 31 are mixed (Af R1 / R2), and then introduced into the reaction section composed of two reactors R1 / R2. The gaseous reaction mixture stream 2, comprising acrylic acid, obtained by gas-phase oxidation of an acrylic acid precursor, feeds, after cooling by El of the gases (stream 3), at a temperature between 150°C and 200°C, a dehydration column C100.

[0058] The dehydration column C100 leads to a head stream 5, at least part of which is condensed in a condenser E2 and returned to the dehydration column as reflux 6, the other part (stream 7) comprising the light non-condensable compounds being generally recycled stream 8, preferably in a stage located upstream of the compressor c. The other part of the head gas stream is sent for destruction to an oxidizer (stream 21).

[0059] The dehydration step generates a head stream 5 comprising mostly water and light compounds, with acrylic acid and heavy compounds in very small quantities, and a foot stream 10 depleted in light compounds comprising mostly acrylic acid with heavy by-products and water.

[0060] The dehydration column generally comprises 5 to 50 theoretical trays

[0061] Advantageously, the dehydration column operates at pressure atmospheric or slightly higher, up to an absolute pressure of 1.5 x 0.5 Pa.

[0062] Advantageously, the temperature in the upper part of the dehydration column is at least 40°C. The temperature of the bottom flow of the dehydration column preferably does not exceed 120°C.

[0063] The foot stream 10 of the dehydration column is sent at least in part (stream 11) to the top of a second distillation column C200, called the purification column or finishing column, in which a top stream 12 and a foot stream 13 are separated.

[0064] Part of the liquid flow 10 foot of the dehydration column is sent by a pump into a plate heat exchanger E6, which can be a heater, preferably a reboiler and reinjected into the dehydration column (flow 30), so as to constitute a recirculation loop.

[0065] According to one embodiment, the E6 heat exchanger is a primary surface plate heat exchanger with welded and brazed plates, the type of which is defined by a specific stamping process that gives them a given efficiency due to the turbulent flow, which keeps the fine solid particles in suspension. This allows the volume of the exchanger to be significantly reduced while providing a very large exchange surface area. This plate heat exchanger has few dead zones where the fluid stagnates.

[0066] According to one embodiment, the exchanger is chosen from exchangers such as the Alpha Rex from ALFA LAVAL, the Platulaire® from Barriquand, the Compabloc from ALFA LAVAL, the Heatex® from KAPP, or the Packinox from ALFA LAVAL.

[0067] The E6 heat exchanger is preferably made of 316L stainless steel or any other metal resistant to corrosion by organic acids. To combat fouling, this E6 heat exchanger can be instrumented with inlet and outlet process fluid temperature measurements, or wall temperature measurements to prevent fouling by chemical reactions such as polymerization (not shown). Advantageously, this heat exchanger will be equipped with pressure drop measurements both upstream and downstream.

[0068] According to one embodiment, a second exchanger E6bis (not shown) can be installed in parallel or a bypass can be provided.

[0069] According to one embodiment, the operating temperature of the plate heat exchanger E6 is between 20°C and 200°C, preferably 80°C to 140°C on the process side. A plate heat exchanger has two circulating fluids: one for the heat transfer fluid, such as steam in this case, and the other for the product of the recirculation loop. Generally, the process fluid is referred to as the "process side," and the heat transfer fluid as the "utilities side."

[0070] According to one embodiment, the pressure in the plate heat exchanger is between 100 kPa and 6000 kPa, preferably 100 to 1000 kPa, on the process side.

[0071] According to one embodiment, the thickness of the plates in the plate heat exchanger is between 1.5 mm and 2.5 mm, including terminals.

[0072] According to one embodiment, the spacing between two plates in the plate heat exchanger is between 3 and 30 mm, preferably between 10 and 15 mm.

[0073] According to one embodiment, the plates in the plate heat exchanger are welded together.

[0074] According to one embodiment, the volume of the plate heat exchanger compared to that of a tubular heat exchanger of the same exchange surface is one to five times smaller.

[0075] According to one embodiment, the residence time in this plate heat exchanger compared to that of a tubular heat exchanger of the same exchange surface is one to five times smaller.

[0076] According to one embodiment, the plate heat exchanger contains between 1 and 500 plates.

[0077] According to one embodiment, the dimension of a plate varies from 0.5m to 8m length and 0.1m to 2m in width, preferably 4m to 6m in length and 0.5m to 1.2m in width.

[0078] The C200 finishing column is generally a conventional distillation column comprising 5 to 30 theoretical trays, preferably 8 to 20 theoretical trays. This distillation column is connected at the bottom to at least one E7 reboiler and at the top to an E220 condenser.

[0079] Advantageously, the finishing column operates under an absolute pressure ranging from 5 kPa to about 60 kPa, the temperature of the head flow being advantageously between 40°C and about 90°C, and the temperature of the foot flow being between 60°C and 120°C.

[0080] The top gas flow 12 from the finishing column is sent into the condenser E220, and the outgoing liquid flow 12T is returned to the dehydration column, mixed with the flow from the recirculation loop of the dehydration column.

[0081] The lateral withdrawal stream 16 located in the first third of the bottom of the finishing column preferably above the theoretical tray 3 from the bottom of the column comprises technical acrylic acid of purity greater than 98.5% by mass, preferably at least 99% and more preferably at least 99.5% acrylic acid.

[0082] The stream 13 separated at the bottom of the finishing column includes the bulk of the heavy by-products as well as polymerization inhibitors.

[0083] This stream 13 can be partly recycled in the bottom of the finishing column (stream 15) through the exchanger E7, or sent (stream 14) to an evaporator (not shown).

[0084] According to one embodiment, the heat exchanger E7 is a commercial exchanger chosen from among exchangers such as the Alpha Rex from ALFA LAVAL, the Platulaire® from Barriquand, the Compabloc from ALFA LAVAL, the Heatex® from KAPP, or the Packinox from ALFA LAVAL.

[0085] To combat fouling, this E7 heat exchanger can be instrumented by measuring the inlet and outlet temperatures of the process fluid or by measuring the wall temperature to prevent fouling caused by chemical reactions such as polymerization. Advantageously, this heat exchanger is equipped with pressure drop measurements both upstream and downstream.

[0086] According to one embodiment, a second exchanger E7bis (not shown) can be installed in parallel or by providing a bypass.

[0087] According to one embodiment, the operating temperature of the plate heat exchanger E7 is between 20°C and 200°C, preferably 80°C to 140°C. According to one embodiment, the pressure in the plate heat exchanger E7 is between 100 kPa and 6000 kPa, preferably 100 to 1000 kPa. According to one embodiment, the plate thickness is between 1.5 mm and 2.5 mm, including the terminals. According to one embodiment, the spacing between two plates is between 3 and 30 mm, preferably between 10 and 15 mm.

[0088] According to one embodiment, the heat exchanger E7 can also be a multitubular exchanger formed of a bundle of tubes and a shell.

[0089] According to one embodiment, polymerization inhibitors are added. The addition of the polymerization inhibitors can be done at different locations at the top of the dehydration or finishing columns, at the condensers of the dehydration column heads, at the top of the finishing column, or on the one present at the lateral withdrawal of the finishing column.

[0090] Examples of usable polymerization inhibitors include phenothiazine (PTZ), copper salts such as copper dibutyldithiocarbamate (CB), hydroquinone (HQ), hydroquinone monomethyl ether (EMHQ), di-tert-butyl paracresol (BHT), paraphenylenediamine, TEMPO (2,2,6,6-tetramethyl-l-piperidinyloxy), di-tert-butylcatechol, or derivatives of TEMPO, such as OH-TEMPO, manganese salts such as manganese acetate alone or mixtures thereof in any proportion, at concentrations in the reaction medium ranging from 10 ppm to 5000 ppm, possibly in the presence of depleted air, but generally at concentrations between 150 ppm and 1000 ppm.

[0091] To make the inhibitors more effective, oxygen, an oxygen / carbon dioxide mixture, an oxygen / carbon dioxide / nitrogen mixture, depleted air (7% O2 in nitrogen), or air can be injected at the bottom of the finishing column. Preferably, the amount of oxygen injected corresponds to a concentration of 0.1% to 0.5% relative to the amount of organic vapor in the column.

[0092] The following examples illustrate the present invention without however limiting its scope. EXPERIMENTAL SECTION

[0093] Abbreviations;

[0094] AA: acrylic acid

[0095] ACOH: acetic acid

[0096] DIAA: acrylic acid dimers Example 1#: Pilot Tests

[0097] Table 1 below presents the operating parameters at the bottom of the dehydration column obtained experimentally in accordance with [Fig.1].

[0098] [Tables 1] Flow 1 2 3 4 3 (Kg / h) 266 266 266 266 3 T°(°C) 180 179 175 175 C100 Column bottom level (%) 75 75 75 75 10 T° (°C) 88 88 87 85 30 (kg / h) 1444 1443 1366 1347 30 T° (°C) 105 105 105 105 10% H20 6.1 5.6 6 6.5 10% AA 89 89.8 89.3 88.8 10% ACOH 2.84 2.82 2.73 2.7

[0099] These conditions lead to obtaining the quantity of dimers in the stream 10 shown in Table 2.

[0100] [Tables2] Trials 1 2 3 4 % dimers 0.63 0.67 0.62 0.6 Kinetics of dimer formation

[0101] To represent the acrylic acid dimers, we used a kinetic model which allows us to represent the formation of the dimers as follows:

[0102] Dimer formation (ppm) = (A + B * T + C * [H2O] + D * T * [H2O]) * [AA] * time

[0103] where: - A, B, C, D are constants - T: temperature in °C - [H2O]): mass concentration of water - [AA]: mass concentration of acrylic acid - Time: length of stay in hours.

[0104] Applying this formula to tests 1-5 of the Pilot yields the values shown in Table 3:

[0105] [Tables3] Trials 1 2 3 4 % pilot dimers 0.63 0.67 0.62 0.6 % calculated dimers 0.65 0.64 0.6 0.62

[0106] As a first approximation, this formula allows us to predict the quantity of dimers obtained at the bottom of the dehydration column.

[0107] Estimation of the quantity of dimers generated at the level of the exchanger E6.

[0108] Consider the recirculation loop at the base of C100. It can be represented as a volume comprising: - The first part: from the bottom of column Cl00, the piping connecting this bottom of column to E6; - The second part: the volume of E6 which in the case of piloting is a tubular heat exchanger - The third part: the return line between E6 and Cl00.

[0109] Knowing the volumes at the pilot plant of these different parts, the compositions in water and acrylic acid, as well as the temperatures in the latter and finally the flow rate of the recirculation loop, we obtain the following table 4 for test 4 of example 1:

[0110] [Tables4] Overall Calculation T Bottom Section / Suction Inlet Section Exchanger Section Exchanger Section VOL! IfVlE TOTAL nr 1.0 0.9 0.0 0.1 Temperature 'C 85.0 85.0 85.0 85.0 Foot Draw-off Flow Rate ..............rpjTh............ ................................. ..................................1.3................................. < 3 1.3 Residence Time (hours) 0.7 0.7 0.00 0.04 AA Concentration Ass. 0.89 0.89 0.89 0.89 K2O Concentration Ass. 6.50 6.50 6.50 6.50 [DiAA] PPM 2173 1707 155 169.77

[0111] This provides an estimate of the quantity of dimers obtained in each part: - Part 1: 5127 ppm - Heat exchanger section: 451 ppm - Heat exchanger outlet: 618 ppm

[0112] Total: 6196 ppm.

[0113] The tubular exchanger used in the pilot generates, due to its volume and the temperature within it, approximately 451 ppm of dimers.

[0114] If we reduce the volume of this tubular heat exchanger, hypothetically replacing it with a plate heat exchanger, this leads to a reduction in If the volume of E6 is reduced by a factor of 3, we would then obtain by calculation 137 ppm of dimers formed in the corresponding volume of the plate exchanger.

Claims

Demands

1. A process for recovering (meth)acrylic acid without using an external solvent, from a gaseous reaction mixture comprising (meth)acrylic acid obtained in the gas phase from a precursor of (meth)acrylic acid, said process comprising at least the following steps: i. the gaseous reaction mixture is subjected to dehydration in a first column, referred to as the dehydration column, leading to a head stream, at least a portion of which is condensed and returned to the dehydration column as reflux, and to a foot stream; ii. at least a portion of the foot stream from the dehydration column is subjected to distillation at a pressure below atmospheric pressure in a second column, referred to as the finishing column, leading to a head stream and a foot stream containing heavy compounds; iii.a flow of (meth)acrylic acid is recovered by lateral withdrawal from the finishing column, and / or at the bottom of the finishing column; iv. part of the bottom flow of the dehydration column and the top of the finishing column are sent into a heat exchanger, then reinjected into the dehydration column, so as to constitute a recirculation loop, said process being characterized in that said exchanger is a plate exchanger.

2. A method according to claim 1, wherein the plate heat exchanger is of the primary surface type, selected from plate heat exchangers, joined plate heat exchangers, hybrid heat exchangers, straight or chevron plate heat exchangers, welded plate heat exchangers or brazed plate heat exchangers.

3. A method according to any one of claims 1 or 2, wherein the operating temperature of the plate heat exchanger is between 20°C and 200°C, preferably 80°C to 140°C on the process side.

4. A method according to any one of claims 1 to 3, wherein the pressure in the plate heat exchanger is between 100 kPa and 6000 kPa, preferably 100 to 1000 kPa on the process side.

5. A method according to any one of claims 1 to 4, wherein the thickness of the plates in the plate heat exchanger is between 1.5 mm and 2.5 mm.

6. A method according to any one of claims 1 to 5, wherein the spacing between two plates in the plate heat exchanger is between 3 and 30 mm, preferably between 10 and 15 mm.

7. A method according to any one of claims 1 to 6, wherein the plates in the plate heat exchanger are welded together.

8. A process according to any one of the preceding claims for the recovery of acrylic acid, wherein the precursor of acrylic acid is acrolein, obtained by oxidation of propylene or by oxidative dehydrogenation of propane.

9. A process according to any one of claims 1 to 8 for the recovery of methacrylic acid, wherein the precursor of methacrylic acid is methacrolein obtained by oxidation of isobutylene and / or tert-butanol or from oxidative dehydrogenation of butane and / or isobutane.

10. A process according to any one of claims 1 to 8, wherein the precursor of (meth)acrylic acid comprises carbon from renewable sources.

11. A process according to claim 10, wherein the precursor of (meth)acrylic acid is derived from glycerol, 3-hydroxypropionic acid or 2-hydroxypropanoic acid.

12. A method according to any one of the preceding claims, wherein the finishing column is a column with a separating wall.

13. A method according to any one of the preceding claims, wherein the finishing column is stabilized by an injection at the bottom of the column of oxygen, an oxygen / carbon dioxide mixture, an oxygen / carbon dioxide / nitrogen mixture, oxygen-depleted air, or air.

14. Installation for carrying out the process of any one of claims 1 to 13, said installation adapted for carrying out the process of recovering (meth)acrylic acid without using an external solvent, according to the invention, comprising at least: a) a dehydration column; b) a finishing column connected fluidly at the bottom of said dehydration column; c) at least one plate heat exchanger which receives part of the bottom flow of the dehydration column, then reinjects it into the dehydration column, so as to constitute a bottom recirculation loop of the dehydration column.

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