Method for purifying (METH)acrylic acid, including optimized effluent treatment

Abstract

The present invention relates to the production of (meth)acrylic acid in a method for recovering (meth)acrylic acid based on the implementation of two separation steps. More particularly, the invention relates to combustion treatment in an oxidation reactor of the effluents from the first separation step, followed by partial condensation, partial recycling of the gases leaving the oxidizer upstream thereof, and purging of these carbon dioxide-rich gases, which can easily be recovered.

Description

[0001] PROCESS FOR THE PURIFICATION OF (METH)ACRYLIC ACID INCLUDING OPTIMIZED EVENT MANAGEMENT

[0002] TECHNICAL FIELD

[0003] The present invention relates to the production of (meth)acrylic acid in a (meth)acrylic acid recovery process based on the implementation of two separation stages. More particularly, it relates to the treatment by combustion in an oxidation reactor of the vents from the first separation stage, followed by partial condensation, partial recycling of the gases exiting this oxidizer upstream of it, and purging of these gases rich in carbon dioxide, which can then be easily utilized.

[0004] TECHNICAL BACKGROUND AND TECHNICAL PROBLEM

[0005] The large-scale industrial process for synthesizing acrylic acid involves a catalytic oxidation reaction of propylene in the presence of oxygen or an oxygen-containing mixture. Oxidation in the presence of atmospheric oxygen is the most common method.

[0006] 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.

[0007] The gaseous mixture from the second step consists, apart from acrylic acid, of untransformed compounds from the reactants involved or impurities generated during at least one of the two reaction steps, namely:

[0008] - of light compounds that are not condensable under the temperature and pressure conditions usually employed, namely essentially: propylene, propane, nitrogen, unconverted oxygen, carbon monoxide and carbon dioxide;

[0009] - of light condensable compounds, essentially: water, unconverted acrolein, light aldehydes such as formaldehyde, glyoxal and acetaldehyde, formic acid, acetic acid or propionic acid;

[0010] - of compounds having a boiling point slightly higher than that of acrylic acid: furfuraldehyde, benzaldehyde, maleic acid and anhydride, benzoic acid, 2-butenoic acid, phenol, protoanemonin; - finally, of heavy compounds derived from the addition of compounds with nucleophilic properties to the double bond of unsaturated carbonyl monomers, by Michael reaction.

[0011] Some of the unprocessed compounds from the synthesis process, such as propylene or unconverted oxygen, are reused in the process to reduce emissions and increase yield. The extraction, purification, and end-of-cycle disposal processes for these byproducts also generate carbon dioxide, which is a direct byproduct of the oxidation reactions of propylene and then acrolein to acrylic acid. All of this contributes to the increase in greenhouse gas concentrations. It therefore seems desirable to manufacture acrylic and methacrylic acids while helping to reduce these environmental impacts. Thus, document FR 2958185 implements a selective CO oxidation treatment to CO2 in order to recycle as much of the reaction gas as possible and reduce emissions.This selective CO oxidation treatment can be accompanied by a membrane permeation process to recover unconverted propylene before final incineration of residual organic compounds.

[0012] Documents EP 2066613 and EP 2334633, based on a so-called "solvent-free" technology, describe a process for recovering (meth)acrylic acid obtained by the air oxidation of propylene. This process employs two distillation columns to purify the cooled gaseous reaction mixture: a dehydration column and a finishing column (or purification column) fed by a portion of the bottom stream from the dehydration column. According to this process, the cooled gaseous reaction stream undergoes dehydration in the first column. The 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. The uncondensed gaseous effluent is at least partially returned to the reaction, and the remainder, which constitutes the vent, is removed by catalytic and / or thermal combustion.The acrylic acid obtained is generally of greater than 98.5% mass purity and contains less than 0.5% mass water and less than 0.4% mass acetic acid.

[0013] This purification process can also be implemented in alternative processes using renewable, so-called bio-based, natural materials. For example, as in documents WO 2006 / 087083 and WO 2015 / 124856, glycerol is used as a raw material. The transformation of glycerol takes place in two steps: first, acrolein is obtained by dehydrating the glycerol, followed by a conventional oxidation of acrolein to acrylic acid. In WO 2015 / 124856, the vent at the top of the dehydration column is subjected to a combustion treatment, and the energy produced is used to vaporize the glycerol prior to the dehydration reaction. In these "solvent-free" processes, the treatment of the vents, which were sent for combustion treatment, was addressed little or not at all.The compounds obtained after this combustion are essentially, by volume percentage, nitrogen (70%-80%), oxygen (1%-5%), carbon dioxide (2%-6%) and water (10%-15%); these gases, also called fumes, are in principle sent into the atmosphere.

[0014] The oxidation of organic matter into carbon dioxide and water is a process known since ancient times and very often used to treat organic waste and produce heating steam. Thermal oxidation, often incorrectly called incineration (INRS ED4261), consists of raising the gaseous effluents to a temperature high enough for the reaction with oxygen or air to occur. Several methods exist to achieve this oxidation or combustion: increasing the temperature, the amount of oxygen, or the organic compound content in the stream to be treated, or decreasing the activation energy.

[0015] The present invention aims to recover a portion of the fumes produced during combustion in the vent of an acrylic or methacrylic acid synthesis process, which contain a high CO2 content, and to recycle them upstream of the acrylic or methacrylic acid synthesis reactor(s) as an inert gas. The remaining fumes are recovered and utilized, for example, by reaction with hydrogen to produce methane, methanol, or ethanol.

[0016] It also appeared to the inventors that this invention could also be applied to acrylic acid produced from sources other than propylene, to methacrylic acid, as well as to (meth)acrylic acids derived from renewable raw materials, which implement a process of treating vents by combustion.

[0017] SUMMARY OF THE INVENTION

[0018] The present invention relates to a process for recovering (meth)acrylic acid from a gaseous mixture comprising (meth)acrylic acid, said process comprising at least the following steps: a) obtaining said gaseous mixture comprising (meth)acrylic acid by reaction, in one or more catalytic synthesis reactors, of a precursor of (meth)acrylic acid in the presence of an inert gas and molecular oxygen; b) said gaseous reaction mixture is subjected to dehydration in a first dehydration column, leading to a headflow and a tailflow;c) the bottom stream of the dehydration column is sent at least in part to a distillation column called the finishing column, allowing the separation of a bottom stream containing heavy compounds, a top stream containing light compounds, at least part of which is returned to the dehydration column and a lateral withdrawal stream of (meth)acrylic acid; d) the top stream of the dehydration column is partly condensed and returned to the dehydration column, the uncondensed part being sent, on the one hand, for recycling to the inlet of the (meth)acrylic acid synthesis reactor(s), and on the other hand, to a thermal or catalytic oxidizer; e) the gases obtained, or fumed, at the outlet of said oxidizer are partly recycled upstream of the catalytic reactor(s) for the synthesis of (meth)acrylic acid, or purged to a process for the recovery of these gases.

[0019] The present invention overcomes the drawbacks of the prior art. More specifically, it provides a process for obtaining high-purity acrylic or methacrylic acid, incorporating a method for utilizing the vent from the dehydration column. This process thus provides a purge of residual gas rich in carbon dioxide, which can be chemically recovered or stored or recovered as carbon dioxide. Indeed, the process according to the invention makes it possible to obtain a residual gas with a carbon dioxide content by volume greater than 50%, advantageously greater than 80%. Compared to the solvent-free process described in documents EP 2066613 and EP 2334633, the residual gas is concentrated by a factor of 5 to 50, thereby avoiding the need for additional, very costly processes, such as amine adsorption, to achieve carbon dioxide recovery or capture.

[0020] Other features and advantages of the invention will become clearer upon reading the detailed description that follows, with reference to the attached figures which represent:

[0021] - Figure 1: Overall diagram of the process according to the invention for the synthesis of acrylic acid.

[0022] - Figure 2: overall diagram of the acrylic acid synthesis process according to the state of the art EP2066613.

[0023] DETAILED DESCRIPTION OF THE INVENTION The present invention provides a process for obtaining acrylic acid or methacrylic acid of purity greater than 98.5% by mass, incorporating a process for valorizing the vent from the dehydration column.

[0024] The term "(meth)acrylic acid" refers to acrylic acid or methacrylic acid.

[0025] According to one embodiment, the process according to the invention relates to acrylic acid.

[0026] According to one embodiment, the process according to the invention relates to methacrylic acid.

[0027] According to various implementations, the said process includes the following characteristics, possibly combined.

[0028] The process according to the invention may further include other preliminary, intermediate or subsequent steps.

[0029] The present invention relates to a process for recovering (meth)acrylic acid from a gaseous mixture comprising (meth)acrylic acid obtained by dehydration reaction or by gas-phase oxidation of a precursor of (meth)acrylic acid in one or more catalytic synthesis reactors in the presence of an inert gas.

[0030] For the sake of clarity, the process according to the invention will be described with reference to the preparation of acrylic acid; however, a person skilled in the art will be able to easily transpose it to the preparation of methacrylic acid.

[0031] According to one embodiment of the invention, the precursor of acrylic acid is acrolein.

[0032] According to one embodiment of the invention, acrolein is obtained by oxidation of propylene.

[0033] According to one embodiment of the invention, acrolein is obtained by oxidative dehydrogenation of propane.

[0034] According to one embodiment of the invention, acrolein is obtained by dehydration of reuterin.

[0035] 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 from renewable sources. According to another embodiment of the invention, the gaseous reaction mixture comprising acrylic acid is obtained by gas-phase dehydration of 3-hydroxypropionic acid or 2-hydroxypropionic acid.

[0036] According to one embodiment of the invention, the precursor of acrylic acid is derived from glycerol or isopropanol.

[0037] To facilitate understanding of the invention, it will be described using propylene as a precursor of acrolein.

[0038] According to this embodiment, the gaseous reaction mixture comprises propylene-derived acrylic acid obtained by a two-step oxidation process. In the first step, propylene is converted to acrolein by oxidation in a first oxidation reactor. Then, the acrolein is oxidized to acrylic acid in a second oxidation reactor.

[0039] According to this embodiment, the molar content of propylene in the feed mixture of the first reactor is between 7% and 10%.

[0040] According to this embodiment, the molar content of oxygen relative to that of propylene at the inlet of the first reactor is between 1.7 and 2.

[0041] According to this embodiment, the molar content of carbon dioxide at the inlet of the first reactor is between 20% and 80%, preferably from 60% to 80%.

[0042] According to this embodiment, the volumetric content of water vapor at the inlet of the first reactor varies between 4% and 25%.

[0043] According to this embodiment, the temperature in the first reactor for the oxidation of propylene to acrolein varies between 300°C and 400°C and that of the second reactor for the oxidation of acrolein to acrylic acid varies between 250°C and 350°C.

[0044] According to the invention, the purification of the gas mixture exiting the acrolein-to-acrylic acid oxidation reactor (the second oxidation reactor) is achieved by using two separation columns to purify the cooled gaseous reaction mixture, namely: a dehydration column and a finishing column. In this process, the cooled gaseous reaction mixture is dehydrated in a first column. The 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. The uncondensed gaseous effluent is returned, at least in part, to the propylene-to-acrolein oxidation reactor (the first oxidation reactor), with the remainder sent to a thermal or catalytic oxidizer. The bottom stream of the dehydration column is partly sent to the finishing column and partly recycled back into the dehydration column.Acrylic acid, with a purity exceeding 98.5% by mass, is obtained by lateral withdrawal from the finishing column. The upper stream of the finishing column is recycled to the dehydration column, while the lower stream of this finishing column contains heavy products that can still be recovered.

[0045] According to one embodiment, the purification of the gas mixture exiting the acrolein to acrylic acid oxidation reactor (the second oxidation reactor) is carried out by a purification process by absorption with an external solvent or with an azeotropic solvent.

[0046] According to one embodiment, the finishing column is stabilized by an injection at the bottom of the column of pure oxygen, by an oxygen / carbon dioxide mixture or by an oxygen / carbon dioxide / nitrogen mixture, or oxygen / nitrogen.

[0047] In one embodiment, the separation columns and ancillary equipment are stabilized by the injection of one or more inhibitors. Examples of usable polymerization inhibitors include phenothiazine (PTZ), hydroquinone (HQ), hydroquinone monomethyl ether (EMHQ), di-tert-butyl paracresol (BHT), paraphenylenediamine, TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy), di-tert-butylcatechol, or TEMPO derivatives such as OH-TEMPO, manganese acetate, alone or in mixtures thereof, at concentrations in the reaction medium ranging from 50 ppm to 5000 ppm, possibly in the presence of depleted air, but generally at concentrations between 150 ppm and 1000 ppm.

[0048] According to one embodiment, the gas obtained at the outlet of the oxidizer (or smoke) is partially recycled after compression at the inlet of the first reactor for obtaining acrolein (first oxidation reactor).

[0049] According to one embodiment, the gas obtained at the outlet of the oxidizer is composed essentially of CO2. The molar fraction of this gas comprises at least 50% CO2, at least 70%, preferably more than 80%.

[0050] According to one embodiment, the gas obtained at the outlet of the oxidizer is partly recycled to the inlet of the oxidizer, mixed with molecular oxygen.

[0051] According to one embodiment, the gas obtained at the outlet of the oxidizer is used to heat the head gas of the dehydration column via a counter-current exchanger before introduction into the oxidizer.

[0052] In one embodiment, the gas obtained at the outlet of the oxidizer is used to heat water via a counter-current heat exchanger, in order to generate steam with a pressure greater than 14l0 5 Absolute pressure. According to one embodiment, the oxygen used to carry out the oxidation of propylene to acrolein and then to acrylic acid, as well as that required for vent combustion in the thermal oxidizer, is obtained by electrolysis of water, or by fractional distillation of liquefied air, or by decomposition of oxygenated salts, solid oxides, or hydrogen peroxide, or by pressure-reversed adsorption (PSA) to concentrate oxygen from ambient air. This adsorption, also called pressure-reversed adsorption or PSA, is a process for separating gas mixtures in which the adsorption of a gas by a solid or liquid at a given pressure, followed by its desorption at a lower pressure, occurs alternately.

[0053] According to one embodiment, the gases concentrated in carbon dioxide at the outlet of the catalytic oxidizer (flue gases) are partially purged and recovered by carbon dioxide sequestration, more simply called carbon trapping by biological and geological processes, or as a reagent to manufacture methane, methanol, ethanol or derivatives of these products.

[0054] According to one embodiment, the volumetric composition of the fumes at the outlet of the oxidizer comprises at least 50%, preferably more than 80%, of carbon dioxide.

[0055] According to the process shown in Figure 1, a precursor of acrylic acid (stream 1) (e.g., propylene) and stream 9 obtained after compression by compressor c of the recycled gas stream 8, oxygen stream 31, and the outlet stream 35 from the exchanger E9 are mixed (AlimR1 / R2) and then introduced into the reaction section composed of two oxidation reactors R1 / R2 used to oxidize propylene to acrolein and then acrolein to acrylic acid. The gaseous reaction mixture stream 2, comprising acrylic acid in the gaseous phase, feeds an exchanger E1 which cools it to a temperature between 150°C and 200°C and then feeds (stream 3) the dehydration column C1.

[0056] The dehydration column leads to a headstream 5, at least part of which (stream 6) is condensed in a condenser E2 and then returned to the dehydration column Cl, the other part (stream 7) comprising the light non-condensable compounds being generally sent partially or totally to an oxidizer (stream 21) or recycled (stream 8), preferably in a stage upstream of the compressor c.

[0057] The oxidizer is preferentially catalytic. The catalyst consists of an active species and an inorganic support, for example, alumina. There are two main types of catalysts: those based on precious metals (platinum, palladium, rhodium) or metal oxides, such as chromium, iron, molybdenum, or tungsten. Catalysts can be in various forms, such as beads, pellets, granules, or, preferably, in monolithic honeycomb structures. In one embodiment, the oxidizer is composed of a bed of 1 to 20 layers of honeycomb catalyst.

[0058] The dehydration column vent stream 21 and the oxygen (stream 27) are heated in the heat exchanger E10 to a temperature of approximately 300°C by counter-current circulation of the flue gas recirculation stream 25. The stream 23 exiting E10 is sent to the oxidizer. An excess of oxygen / organic material to be burned in stream 23 is fixed so that the oxygen content at the oxidizer outlet (stream 24) is between 1% and 5% by volume.

[0059] The temperature at the outlet of the oxidizer of flow 24 reaches 650°C to 850°C due to the heat of the oxidation reaction.

[0060] The 28 stream exiting the oxidizer feeds a water-cooled heat exchanger E1, preferably a cross-flow tubular heat exchanger. The water to be converted into steam flows horizontally (not shown) through the tubes, while the flue gases (stream 28) pass outside the tubes from top to bottom. Finally, after passing through mixer M, the 26 and 32 streams, consisting of the flue gases after passing through E10 and E1, are divided into two streams: stream 34, which is partially cooled in heat exchanger E9 and then recycled upstream of compressor C at a temperature between 30°C and 80°C, and stream 33, which is sent to a system for the recovery of this stream.

[0061] Finally, the CO2-rich stream 9, with a carbon dioxide molar content of at least 50%, preferably more than 70%, is recycled from the oxidizer. It feeds reactors R1 / R2. Oxidation in these reactors is then carried out using CO2 as the inert gas rather than nitrogen, as specified in EP 2066813.

[0062] The condensed portion (not shown) after condensation in the E9 exchanger is sent to a water treatment plant or can be used as a supplement to hydrothermal gasification.

[0063] The foot stream 10 from the dehydration column is sent at least in part (stream 11) to the top of a second distillation column C2, 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 from the foot of the dehydration column is sent into a heat exchanger E6 and reinjected into the dehydration column, so as to constitute a bottom recirculation loop.

[0065] The C2 finishing column is generally a classic distillation column and is associated at the bottom with at least one E7 reboiler and at the top with an E5 condenser.

[0066] The top gas stream 12 from the finishing column is sent to the condenser E5, and the outgoing liquid stream 12T is returned to the dehydration column, mixed with the bottom loop stream of the dehydration column. The uncondensed stream 19 exiting E5, consisting mainly of inert gas and water vapor, is sent to a vacuum system (not shown).

[0067] The lateral withdrawal flow 16 located in the first third of the bottom of the finishing column comprises technical acrylic acid of purity greater than 98.5% by weight.

[0068] This flow 13 partly recirculates in the reboiler E7 (flow 15) or is sent (flow 14) to an evaporator (not shown).

[0069] According to the process shown in Figure 2, a precursor of acrylic acid (stream 1, e.g., propylene) and stream 9, obtained after compression of the recycled gases (stream 8) and air (stream 31), are introduced after mixing (feed R1 / R2) into the reaction section composed of two reactors R1 / R2 used to oxidize propylene to acrolein and then acrolein to acrylic acid. The gaseous reaction mixture (stream 2), containing acrylic acid in the gaseous phase, feeds a heat exchanger E1 which cools it to a temperature between 150°C and 200°C, and then feeds (stream 3) the dehydration column CL.

[0070] The dehydration column leads to a headstream 5, at least part of which is condensed in a condenser E2 and returned to the dehydration column as reflux 6 to absorb the acrylic acid, the other part (stream 7) comprising the light non-condensable compounds being generally sent partially or totally to an oxidizer (stream 21) or recycled (stream 8), preferably in a stage upstream of the compressor c.

[0071] The oxidizer can be thermal or catalytic. The oxidizer is fed by streams 21 and the air required for combustion (stream 27). The oxidizer outlet stream 24 is composed, by volume percentage, primarily of nitrogen (70%-80%), oxygen (1%-5%), carbon dioxide (2%-6%), and water (10%-15%). This stream 24 is, in principle, released into the atmosphere.

[0072] The foot stream 10 from the dehydration column is sent at least in part (stream 11) to the top of a second distillation column C2, called the purification column or finishing column, in which a top stream 12 and a foot stream 13 are separated.

[0073] Part of the liquid flow 10 from the foot of the dehydration column is sent into a heat exchanger E6 and reinjected into the dehydration column, so as to constitute a bottom recirculation loop.

[0074] The C2 finishing column is generally a classic distillation column to which is associated at the bottom at least one E7 reboiler and at the top an E5 condenser.

[0075] The top gas stream 12 from the finishing column is sent to the condenser E5, and the outgoing liquid stream 12T is returned to the dehydration column, mixed with the bottom loop stream of the dehydration column. The uncondensed stream 19 exiting E5, consisting mainly of inert gas and water vapor, is sent to a vacuum system (not shown).

[0076] The lateral withdrawal flow 16 comprises technical acrylic acid of purity greater than 98.5% by weight.

[0077] This stream 13 can be partly recycled in the bottom of the finishing column (stream 15), or sent (stream 14) to an evaporator (not shown).

[0078] The following examples illustrate the present invention without however limiting its scope.

[0079] EXPERIMENTAL SECTION

[0080] In the examples, percentages are given by weight unless otherwise indicated, and the following abbreviations have been used. Only the main components have been listed.

[0081] PTZ: Phenothiazine

[0082] AA: Acrylic acid

[0083] H2O: Water

[0084] DiAA: Acrylic acid dimer

[0085] ACRO: acrolein

[0086] PTZ: phenothiazine

[0087] ACOH: Acetic Acid

[0088] C3H6: propylene

[0089] N2: Nitrogen

[0090] CO2: carbon dioxide

[0091] Example 1: Process for manufacturing acrylic acid according to the invention

[0092] Example 1 results from a simulation under Aspen Plus V12.1 and presents the material balances of different flows numbered as in Figure 1 (Table 1).

[0093] Table 1

[0094] Table 1 shows the composition, by mass percentage, of the Alim R1 / R2 mixture feeding the first reactor for the oxidation of propylene to acrolein with molecular oxygen in the presence of carbon dioxide as an inert gas. It also shows the composition of stream 16, which corresponds to the production of high-purity acrylic acid, and stream 33, which corresponds to the purge output of the oxidizer, composed of approximately 97% CO2 and therefore easily recoverable, for example, by methanation.

[0095] - Example 2: Process for manufacturing Acrylic Acid according to the prior art (EP2066613).

[0096] Example 2 results from a simulation under Aspen Plus V12.1 and presents the material balances of different flows numbered as in figure 2.

[0097] Table 2

[0098] Table 2 shows the composition, by mass percentage, of the Alim R1 / R2 mixture feeding the first reactor for the oxidation of propylene to acrolein with molecular oxygen in the presence of nitrogen as an inert gas. It also shows the composition of stream 16, which corresponds to the production of high-purity acrylic acid, and stream 24, which corresponds to the purge from the oxidizer, composed of approximately 7.5% CO2. This low CO2 concentration will necessitate, contrary to the invention, an additional concentration step in the event of CO2 capture or chemical recovery.

Claims

DEMANDS 1. A process for recovering (meth)acrylic acid from a gaseous mixture comprising (meth)acrylic acid, said process comprising at least the following steps: a. obtaining said gaseous mixture comprising (meth)acrylic acid by reacting, in one or more catalytic synthesis reactors, a precursor of (meth)acrylic acid in the presence of an inert gas and molecular oxygen; b. said gaseous reaction mixture is subjected to dehydration in a first dehydration column, leading to a head stream and a tail stream; c. the tail stream of the dehydration column is sent at least in part to a second distillation column, called the finishing column, allowing the separation of a tail stream containing heavy compounds, a head stream containing light compounds, at least part of which is returned to the dehydration column, and a lateral withdrawal stream of (meth)acrylic acid; d.The head stream of the dehydration column is partly condensed and returned to the dehydration column, the uncondensed portion being sent on the one hand, for recycling to the inlet of the (meth)acrylic acid synthesis reactor(s), and on the other hand, to a thermal or catalytic oxidizer; e. the gases obtained, or fumed, at the outlet of said oxidizer are partly recycled upstream of the (meth)acrylic acid synthesis catalytic reactor(s), or purged to a process for the recovery of these gases.

2. A process according to claim 1, wherein the precursor of acrylic acid is acrolein, obtained by oxidation of propylene or by oxy dehydrogenation of propane.

3. A process according to claim 1, wherein acrylic acid is obtained by dehydration of reuterin.

4. A process according to claim 1, wherein the gaseous reaction mixture comprising acrylic acid is obtained by gas-phase dehydration of 3-hydroxypropionic acid or 2-hydroxypropionic acid.

5. A process according to claim 1, wherein the precursor of acrylic acid is derived from glycerol or isopropanol.

6. A process according to claim 1, wherein the gaseous reaction mixture comprises acrylic acid obtained by oxidation of propylene to acrolein in a first oxidation reactor, and then oxidation of acrolein to acrylic acid in a second oxidation reactor.

7. A method according to any one of claims 1 to 6, wherein the molar content of propylene in the feed mixture of the first reactor is between 7% and 10%.

8. A process according to any one of claims 1 to 7, wherein the molar content of oxygen relative to that of propylene at the inlet of the first reactor is between 1.7 and 2.

9. A method according to any one of claims 1 to 8, wherein the molar content of carbon dioxide at the inlet of the first reactor is between 20% and 80%, preferably from 60% to 80%.

10. A method according to any one of claims 1 to 9, wherein the water vapor volume content at the inlet of the first reactor varies between 4% and 25%.

11. A method according to any one of claims 1 to 10 wherein the volumetric composition of the fumes exiting the oxidizer comprises at least 50%, preferably at least 80%, of carbon dioxide.

12. A process according to any one of claims 1 to 11, wherein the carbon dioxide-concentrated gases exiting the catalytic oxidizer are partially purged and recovered by carbon dioxide sequestration, or as a reagent for manufacturing methane, methanol, ethanol or derivatives of these products.

13. A process according to any one of claims 1 to 11, wherein the gas obtained at the outlet of the oxidizer is partly recycled to the inlet of the oxidizer, mixed with molecular oxygen.

14. A method according to any one of claims 1 to 13 in which the finishing column is stabilized by an injection at the bottom of the column of pure oxygen, by an oxygen / carbon dioxide mixture or by an oxygen / carbon dioxide / nitrogen mixture, or oxygen / nitrogen.

15. A process according to any one of claims 1 to 14, wherein the gas obtained at the outlet of the oxidizer is partially recycled after compression at the inlet of the first reactor for obtaining acrolein.

16. A method according to any one of claims 1 to 15, wherein the gas obtained at the outlet of the oxidizer is used to reheat the overhead gas of the dehydration column via a counter-current exchanger before introduction into the oxidizer.

17. A method according to any one of claims 1 to 16, wherein the gas obtained at the outlet of the oxidizer is used to heat water via a counter-current heat exchanger, in order to generate steam having a pressure greater than 14l0 5 Absolutely not.

Images