Method for upgrading heavy by-products from acrylic acid production

Abstract

The present invention relates to a method for regenerating acrylic acid (AA) by pyrolysis from heavy by-products (residues called AAHP) from an acrylic acid production apparatus and reusing it in an acrylic acid production plant. This method consists of two steps: hydrolysis performed in a batch manner and decomposition performed continuously, and it improves the current performance of the decomposition plant.

Description

Technical Field

[0001] The present invention relates to a method for regenerating acrylic acid (AA) by pyrolysis from heavy by-products (residues called AAHP) from an acrylic acid production apparatus and reusing it in an acrylic acid production plant. This method consists of two steps, hydrolysis carried out batchwise and decomposition carried out continuously, and improves the current performance of the decomposition plant.

Background Art

[0002] Due to the influence of temperature in the distillation process, the production of acrylic acid involves the formation of heavy compounds, which are derivatives in which a compound having nucleophilicity at the double bond of an unsaturated carbonyl-containing monomer is added by Michael reaction. Compounds having a boiling point higher than that of the produced acrylic monomer are called "heavy" compounds.

[0003] In the case of an AA production apparatus, these are basically: Derivatives in which acrylic acid is added to the double bond of another acrylic acid molecule: 3-acryloyloxypropionic acid, also called "acrylic acid dimer" or "AA dimer"; Derivatives in which acrylic acid is added to the double bond of an AA dimer molecule to form an "AA trimer", and other oligomers formed by continuously adding acrylic acid to the double bond of the aforementioned AA oligomers; and Derivatives of carboxylic acids formed as by-products of acrylic acid, or adducts of water to the double bond of AA or the above oligomers are.

[0004] In the case of heavy products from an AA production apparatus, it is difficult to recover upgradable monomers from heavy Michael derivative compounds. Specifically, in the pyrolysis step of regenerating acrylic acid, acrylic acid is distilled and upgraded, and residues remain. When high decomposition efficiency is required, the viscosity of the residues increases significantly, and finally, they cannot even be taken out of the decomposition reactor.

[0005] The main factor limiting the regeneration efficiency of compounds derived from Michael reactions contained in the flow of heavy compounds from the AA plant is the increase in the viscosity of the heavy residue obtained at the bottom of the pyrolysis unit when the acrylic monomer-rich fraction is evaporated.

[0006] Evaporation of the light compounds during decomposition concentrates the heavy products in the residue stream and increases the viscosity of this stream. However, the residue must continue to be sufficiently fluid after cooling and is transported and then treated for the purpose of destruction.

[0007] If the production of light esters (methyl acrylate (MA) or ethyl acrylate (EA)) is near the AA production unit, the situation can be improved and the decomposition residue can be made more fluid by co-decomposing the respective heavy products. The proposed solution enables the recovery of the maximum amount of AA for each decomposition operation while managing the viscosity of the residue formed without relying on another manufacturing unit.

[0008] Therefore, in European Patent No. 717031, it has been shown that when decomposition is carried out using a mixture of heavy products generated from an AA production unit and an acrylic ester (EA) production unit, it is possible to improve the recovery efficiency of these upgradable inert products compared to the case of decomposing the heavy streams generated from these units individually. The effect of adding the heavy product derived from the ester unit (EAHP) to the heavy product derived from the AA unit (AAHP) is to lower the viscosity of the final residue. The decomposition reaction is carried out using a mixture with a ratio of AA heavy product / ester heavy product of 9 / 1 to 1 / 9, at a temperature of 180°C to 220°C under atmospheric pressure, with a residence time of 0.5 to 3 hours. In this process, evaporation of the decomposed and generated light compounds is carried out in the reactor, the generated gas stream is sent to the distillation column, and finally the bottom stream from the distillation column is recycled to the reactor.

[0009] On the one hand, since the light fraction obtained by decomposition mainly consists of AA and ester acrylic monomers which are particularly sensitive to polymerization, in order to prevent the formation of polymers in the tower, the distillation stage must necessarily be carried out under reduced pressure and the temperature must be lowered. Furthermore, the rectifying plates of the distillation column bring about an efficient separation of the polymerization inhibitor mixed in the mixed gas. However, since the polymerization inhibitor flows back to the bottom of the tower, it is necessary to introduce fresh polymerization inhibitor to the top of the tower in order to prevent the formation of polymers at the upper part of the tower.

[0010] Therefore, the reaction stage carried out at high pressure and the distillation stage carried out under reduced pressure must be separated. Thus, the equipment for implementing this method must include a reactor and an upper condenser operated at the same pressure, and a distillation column operated under reduced pressure, to which the condensed product is supplied, and which includes a boiler at the bottom, a condenser, a reflux device, and a supply device for the inhibitor at the top. This arrangement is complex and expensive.

[0011] Furthermore, the co-decomposition of the AA heavy product mixed with the EA heavy product leads to operational constraints. Specifically, when the esterification device is shut down, the decomposition operation must also be shut down. This leads to economic losses.

[0012] In other situations, the AA heavy product is thermally decomposed batchwise without adding the ester heavy product, generating a very viscous residue, which limits the performance of this decomposition and causes problems in the storage and transfer of the residue.

[0013] In order to overcome the problems related to viscosity, it is also known to add a solvent to the decomposition residue of the AA heavy product.

[0014] European Patent No. 3255030 teaches that a higher alcohol is added during the cracking of the residue, and the maleic anhydride present in the residue is converted into a maleic ester which is less sensitive to polymerization.

[0015] U.S. Patent No. 6414183 teaches diluting the discharged residue with a solvent such as acetic acid, water, methanol, etc.

[0016] International Publication No. 2021 / 224044 describes a method for decomposing a Michael adduct of acrylic acid by dilution with a solvent 1 having a boiling point of at least 170 °C at 1013 hPa and a solubility in water of at least 20 g per 100 g of water at 25 °C, wherein the aforementioned solvent is selected from alcohols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and 2-ethoxyethanol, carboxamides such as N,N-dimethylacetamide, N-methylacetamide, and N,N-dimethylformamide, sulfoxides such as dimethyl sulfoxide, and sulfones such as sulfolane.

[0017] However, this solution has several drawbacks, such as the generation of waste to be burned in the case of non-internal flow and the installation of additional equipment for mixing. Furthermore, most of these solvents produce nitrogen-containing or sulfur-containing derivatives during combustion.

Prior Art Documents

Patent Documents

[0018]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0019] As a result, it is necessary to improve the regeneration efficiency of heavy compounds derived only from the AA unit by thermal decomposition.

Means for Solving the Problem

[0020] The present invention relates to a method for regenerating a mixture of heavy by-products (AAHP) from an acrylic acid production apparatus, and the aforementioned method comprises the following steps: i. Introducing the heavy by-products and water into a hydrolysis apparatus in a range where the water:AAHP ratio is 0.1 to 1.3, and subjecting the heavy by-products and the water to batch hydrolysis for 1 to 10 hours, preferably 1 to 5 hours, to obtain a mixture of hydrolysis products as a result. ii. Injecting the mixture of hydrolysis products into a reactor and subjecting it to continuous pyrolysis to produce a gaseous upper stream containing acrylic acid and water and a concentrated bottom stream (residue) of heavy products. iii. Recovering a light fraction rich in AA and water that can be recycled at various stages of the method. iv. Recovering the residue for the purpose of removal treatment. including.

[0021] According to various embodiments, the aforementioned steps have the following characteristics if they are an appropriate combination.

[0022] According to one embodiment, the pressure in the hydrolysis apparatus varies between 0.1 to 2 MPa, preferably between 0.5 to 1.5 MPa.

[0023] According to one embodiment, the temperature in the hydrolysis apparatus varies between 80°C and 200°C, preferably between 150°C and 200°C.

[0024] According to one embodiment, the decomposition temperature is 140°C to 260°C, preferably 160°C to 210°C.

[0025] According to one embodiment, the residence time of the reaction mixture in the decomposition reactor is 0.5 hours to 10 hours, preferably 1 hour to 2 hours.

[0026] According to one embodiment, the pyrolysis reaction is carried out at atmospheric pressure or under a slight pressure (up to 0.2 MPa).

[0027] According to one embodiment, the aforementioned gaseous upper stream containing acrylic acid and water is injected into a condenser.

[0028] According to one embodiment, the bottom stream (residue) from the reactor, which results from the pyrolysis operation, has a dynamic viscosity of less than 1 Pa·s at a temperature of 100 °C, measured using, for example, a cone / plate type Brookfield "CAP 1000+" viscometer.

[0029] According to one embodiment, the pyrolysis reaction is carried out without a catalyst.

Advantages of the Invention

[0030] The present invention makes it possible to overcome the drawbacks of the prior art. The present invention makes it possible to recover the maximum amount of AA for each decomposition operation while managing the viscosity of the residue formed without relying on another manufacturing apparatus. This is achieved by combining the step of hydrolyzing heavy by-products from an acrylic acid production apparatus and the step of thermally decomposing the hydrolyzed product.

[0031] The main advantages of the method according to the present invention are: · It is a simple method and, in practice, only one additional piece of equipment (a hydrolysis apparatus) is required compared to just the decomposition step, so it is inexpensive in terms of investment; · A method capable of reducing emissions by reducing the amount of decomposition residue; · Residue with a lower viscosity compared to decomposition without a hydrolysis step; · The decomposition step does not depend on other apparatuses (especially an esterification apparatus); · Hydrolysis also makes it possible to avoid special treatments for ensuring the discharge of residues, such as the addition of a solvent for fluidizing the residue; · By further promoting the decomposition reaction, the arrival at the viscosity limit of the residue is delayed compared to a solution without hydrolysis, and the recovery efficiency of inert products from heavy Michael derivative products present in the heavy product stream from the AA plant is improved; That is.

Brief Description of the Drawings

[0032]

Figure 1

Mode for Carrying Out the Invention

[0033] The present invention will be described in more detail and in a non - limiting manner in the following description.

[0034] The term "heavy by - products derived from acrylic acid production equipment" means: · A derivative in which acrylic acid is added to the double bond of another acrylic acid molecule: 3 - acryloyloxypropionic acid, also called "acrylic acid dimer" or "AA dimer"; · A derivative in which acrylic acid is added to the double bond of an AA dimer molecule to form an "AA trimer", and other oligomers formed by continuously adding acrylic acid to the double bond of the aforementioned AA oligomers; · Derivatives of carboxylic acids (e.g., acetic acid) formed as by - products of acrylic acid, or adducts of water to the double bond of AA or the above - mentioned oligomers and includes.

[0035] The term "hydrolysis device" refers to a reactor capable of carrying out a hydrolysis reaction on a mixture of water and AA heavy products. This reactor can be heated and maintain pressure. The latter may be a conventional stirred - type reactor or a heat exchanger.

[0036] The present invention combines a batch - type hydrolysis operation pre - carried out on heavy by - products from an AA production device based on a continuous thermal decomposition process.

[0037] The acrylic monomers involved in the Michael addition derivatives can be regenerated by hydrolyzing the oligomers before the heat treatment step. This hydrolysis reaction forms hydroxypropionic acid (HPA), which can be thermally decomposed to obtain acrylic acid. Hydrolysis makes it possible to reduce the oligomer chain and lower the viscosity of the residue.

[0038] Hydrolysis in batch mode is carried out under a pressure in the range of 0.1 - 2 MPa.

[0039] The regeneration efficiency (expressed as the decomposition efficiency) is: a / The parameters of hydrolysis: temperature and pressure, hydrolysis residence time, and water / AA heavy product ratio, and b / The parameters of decomposition: temperature and residence time of heat treatment is essentially dependent on.

[0040] An increase in these last two parameters (b / ) tends to improve the regeneration efficiency, but this is done at the expense of an increase in the viscosity of the decomposition residue.

[0041] The decomposition performance is characterized by two performances: URR, that is, the useful recovery rate: This is the amount of acrylic acid recovered after decomposition relative to the amount of AA heavy product supplied to the decomposition device: URR = mass of recovered acrylic acid / supply of acrylic acid heavy product in the decomposition device The decomposition rate, that is, the decomposition efficiency: This is the amount of acrylic acid recovered after decomposition relative to the total of upgradable compounds (acrylic acid (AA), acrylic acid dimer (AA2) and hydroxypropionic acid (HPA)) in the decomposition machine raw material is characterized by.

[0042] According to an embodiment of the method shown in FIG. 1, a stream containing the aforementioned heavy by-product (AAHP) from the acrylic acid production plant and water are introduced into reactor R1 together or separately. The AAHP stream is rich in heavy Michael addition derivative compounds generated in the acrylic acid synthesis and purification processes, and also contains other heavy compounds accumulated during the synthesis and purification processes, especially polymerization inhibitors.

[0043] A mixture (1) containing a heavy acrylic acid compound and water is heated to a temperature required for the hydrolysis of the Michael addition derivative to obtain a light compound. Stream (2) is recovered after the hydrolysis step is completed. This stream is then continuously introduced into a second reactor R2, heated to a temperature required for the decomposition of the Michael addition derivative, and lighter compounds are obtained which are extracted in the form of a gas mixture (3) at the top of the reactor.

[0044] This vapor stream, which is rich in acrylic acid and contains some heavy compounds containing inhibitors at low concentrations, is advantageously recycled as stream (4) directly in vapor form or after total condensation in condenser E1 to the acrylic acid production process.

[0045] According to one embodiment, at least one polymerization inhibitor is introduced into condenser E1. These inhibitors are polymerization inhibitors known to those skilled in the art: phenolic derivatives such as hydroquinone and its derivatives, for example hydroquinone methyl ether, 2,6-di(tert-butyl)-4-methylphenol (BHT) and 2,4-dimethyl-6-(tert-butyl)phenol (Topanol A), phenothiazine and its derivatives, manganese salts such as manganese acetate, salts of thiocarbamic acid or dithiocarbamic acid such as metal thiocarbamates and metal dithiocarbamates, for example copper di(n-butyl)dithiocarbamate, N-oxyl compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4-OH-TEMPO), compounds having a nitroso group, for example N-nitrosophenylhydroxylamine and its ammonium salts, amine compounds such as para-phenylenediamine derivatives, or mixtures thereof.

[0046] The flow of residue (5) recovered at the bottom of the reactor is cooled and removed in the form of a liquid with an appropriate viscosity, so that it can be pumped without problems, for example, to a storage tank or an incinerator.

Example

[0047] The following examples illustrate the present invention without limiting it.

[0048] The depletion rate is defined as the ratio of the mass of the distillate to the mass of the heavy product. When water is added, this ratio becomes the "corrected depletion rate" by subtracting the mass of this water from the amount of distillate.

[0049] [Example 1: Batch hydrolysis and continuous decomposition (according to the present invention)] The assembly used for the hydrolysis operation consists of an AmAr experimental autoclave reactor made of HC276 that can maintain a maximum pressure of 80 bar @ 250 °C, and is equipped with an internal stirrer, a pressure gauge, a nitrogen inlet, a temperature immersion probe, and an adjustable external electric heating mantle. The usable capacity is 450 ml.

[0050] The mixture to be hydrolyzed is introduced into the reactor, and then the reactor is closed using a Joyce system for sealing. The reactor can be placed under a pressure of 6 bar before the temperature is raised by means of a nitrogen pipe connecting the reactor. Then, the mixture was heated to 150 °C for 1 hour. The pressure indicated on the pressure gauge was raised to 12 bar. When the hydrolysis was complete, the mixture was cooled to room temperature and then discharged from the bottom valve.

[0051] The assembly used for the decomposition operation consists of a 500 ml jacketed glass reactor equipped with a stirrer, a temperature probe immersed in the liquid phase, an upper vertical pipe for extracting steam, a horizontal branch connection that enables a certain amount to be obtained and enables the discharge of decomposition residues, and a condenser. The mixture previously hydrolyzed was continuously introduced into the reactor and heated to the desired temperature. The liquid (distillate) was collected in a receiving flask and analyzed. The residue discharged by overflow was collected in a receiving flask.

[0052] Test time: 61 h Hydrolysis: T = 150 °C, residence time: 1 h, P = 1.2 MPa, water / AA heavy product ratio = 0.5 Decomposition: T = 168 °C, atmospheric pressure, residence time: 4 h, water / AA heavy product ratio = 0.5 URR = 61% Corrected depletion rate = 66.5% Viscosity = 0.437 Pa·s

[0053] [Example 2: Continuous decomposition without hydrolysis (comparison)] Test time: 58 h Decomposition: T = 193 °C, residence time: 4 h, atmospheric pressure, water / AA heavy product ratio = 0.5 URR = 55.0% Corrected depletion rate = 62.15% Viscosity = 2.361 Pa·s

[0054] The comparison between Example 1 and the comparative example (Example 2) shows that decomposition can be carried out at a lower temperature when the flow to be decomposed is hydrolyzed first. Furthermore, the viscosity of the residue is lower.

Claims

1. A method for regenerating heavy by-products (AAHP) from an acrylic acid production apparatus, comprising: i. introducing the heavy by-products and water into a hydrolysis apparatus in a range where the water:AAHP ratio is from 0.1 to 1.3, and subjecting the heavy by-products and the water to batch hydrolysis for 1 to 10 hours, preferably 1 to 5 hours, to obtain a mixture of hydrolysis products; ii. injecting the mixture of hydrolysis products into a reactor and subjecting it to continuous pyrolysis to produce a gaseous upper stream containing acrylic acid and water and a concentrated bottom stream (residue) of heavy products; iii. recovering a light fraction rich in AA and water that can be recycled to various stages of the method; iv. recovering the residue for the purpose of removal treatment. A method comprising the above steps.

2. The method according to claim 1, wherein step i) is carried out at a pressure of 0.1 to 2 MPa, preferably 0.5 to 1.5 MPa.

3. The method according to claim 1 or 2, wherein the temperature of the hydrolysis is from 80°C to 200°C, preferably from 150°C to 200°C.

4. The method according to any one of claims 1 to 3, wherein the temperature of the pyrolysis is from 140°C to 260°C, preferably from 160°C to 210°C.

5. The method according to any one of claims 1 to 4, wherein the residence time of the reaction mixture in the reactor for the pyrolysis is from 0.5 h to 10 h, preferably from 1 h to 2 h.

6. The method according to any one of claims 1 to 4, wherein the bottom stream (residue) from the reactor obtained as a result of the pyrolysis operation has a dynamic viscosity of less than 1 Pa·s measured at 100°C.

7. The method according to any one of claims 1 to 6, further comprising injecting the gaseous upper stream containing acrylic acid and water into a condenser.

8. The method according to claim 7, wherein at least one polymerization inhibitor is introduced into the condenser.

9. The method according to any one of claims 1 to 7, wherein the pyrolysis reaction is carried out without a catalyst.

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