Method for upgrading heavy by-products from acrylic acid production

Abstract

The present invention relates to a method for regenerating acrylic acid (AA) by thermal decomposition 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 and decomposition, which are carried out batchwise in the same reactor, and 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 and decomposition, which are carried out batchwise in the same reactor and improve 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 adds to the double bond of an unsaturated carbonyl-containing monomer by a 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 eventually, they cannot even be taken out from the decomposition reactor.

[0005] The main factor limiting the regeneration efficiency of compounds derived from the Michael reaction 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 apparatus 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 remain sufficiently fluid even after cooling and is processed for destruction purposes after being transported.

[0007] When the production of light esters (methyl acrylate (MA) or ethyl acrylate (EA)) is near the AA production plant, 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 apparatus.

[0008] Therefore, in European Patent No. 717031, when decomposition is carried out using a mixture of heavy products generated from an AA production apparatus and an acrylic ester (EA) production apparatus, it is shown that the recovery efficiency of these upgradable inert products can be improved compared to the case of decomposing the heavy streams generated from these apparatuses 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 column, 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 column, it is necessary to introduce fresh polymerization inhibitor at the top of the column in order to prevent the formation of polymers at the upper part of the column.

[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 pyrolyzed 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 during the cracking of the residue, a higher alcohol is added, and 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.

[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 when not in an 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 heavy by-products (AAHP) from an acrylic acid production apparatus. The aforementioned method comprises the following steps: i A step of introducing the heavy by-products into a reactor; ii A step of heating the heavy product at a temperature of 80°C to 200°C; iii At the same time as ii or at the final temperature, water is gradually added over a period of 1 to 10 h, preferably 1 to 5 h, until a water / AA heavy product ratio of 0.1 to 1.3 (including the limit values) is reached, resulting in a step of obtaining a mixture of hydrolysis products; iv In the same reactor, batch pyrolysis is performed on the mixture containing the hydrolyzed heavy product and water to produce a gaseous upper stream containing acrylic acid and water and a concentrated bottom stream (residue) of the heavy product; v A step of recovering a light fraction rich in AA and water that can be recycled at various stages of the method; vi A step of recovering the residue for the purpose of removal treatment; and includes.

[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 reactor is under atmospheric pressure or a slight atmospheric pressure (a pressure reaching up to 2 MPa). According to one embodiment, the temperature at which water is added varies between 80°C and 200°C, preferably between 100°C and 150°C.

[0023] According to one embodiment, the decomposition temperature is 140°C to 260°C, preferably 160°C to 210°C.

[0024] According to one embodiment, the residence time of the reaction mixture in the decomposition reactor is 0.5 h to 10 h, preferably 1 h to 4 h.

[0025] According to one embodiment, the pyrolysis reaction is carried out at atmospheric pressure or under slight pressure (up to 0.2 MPa).

[0026] According to one embodiment, the aforementioned gaseous upper stream containing acrylic acid and water is injected into a condenser.

[0027] 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, for example, measured using a cone / plate type Brookfield "CAP 1000+" viscometer.

[0028] According to one embodiment, the pyrolysis reaction is carried out without a catalyst.

Advantages of the Invention

[0029] 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 formed residue without relying on another manufacturing apparatus. This is achieved by combining the step of continuously adding water to hydrolytically pretreat heavy by-products from an acrylic acid production apparatus and subsequently batchwise pyrolyzing the hydrolyzed product, and the two steps are carried out in the same reactor.

[0030] The main advantages of the method according to the present invention are: · It is a simple method and in practice, it does not require additional equipment compared to only the decomposition step, so it is inexpensive in terms of investment; · A method capable of reducing emissions by reducing the amount of decomposition residue; · The decomposition temperature is lower compared to decomposition without a hydrolysis step, thus enabling energy savings; · 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 can also avoid special treatments such as adding a solvent to fluidize the residue to ensure the discharge of the residue; ·By further promoting the decomposition reaction, compared with a solution without hydrolysis, the reaching of the viscosity limit of the residue is delayed, and the recovery efficiency of the inert product from the heavy Michael derivative product existing in the flow of the heavy product from the AA plant is improved; That is.

Brief Description of the Drawings

[0031]

Figure 1

Embodiments for Carrying out the Invention

[0032] The present invention will be described in more detail and in a non-limiting manner in the following description.

[0033] The term "heavy by-products derived from an acrylic acid production apparatus" means: ·A derivative obtained by adding acrylic acid to the double bond of another acrylic acid molecule: 3-acryloyloxypropionic acid, also called "acrylic acid dimer" or "AA dimer"; ·Derivatives obtained by adding acrylic acid to the double bond of AA dimer molecules to form "AA trimer", and other oligomers formed by continuously adding acrylic acid to the double bonds 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 bonds of AA or the above oligomers are included.

[0034] The present invention is a combination of a batch-type hydrolysis operation pre-implemented on heavy by-products from an AA production apparatus based on a batch-type pyrolysis process, and the two processes are carried out in the same reactor. This may be a conventional stirred reactor or a heat exchanger.

[0035] 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.

[0036] Hydrolysis in batch mode is carried out under a pressure in the range of 0.1 to 2 MPa.

[0037] 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.

[0038] 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.

[0039] 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 acrylic acid recovered / 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.

[0040] According to an embodiment of the method shown in FIG. 1, a stream from an acrylic acid production plant (AAHP) is introduced into reactor R. The contents of the reactor are heated to the required temperature. Water is gradually added over a determined period, either simultaneously with the heating or at the final temperature, in order to reach the desired water / AA heavy product ratio. Once the addition is complete, the reactor is heated to the temperature required to decompose the Michael addition derivative, and light compounds are obtained which are extracted in the form of a gas mixture (2) at the top of the reactor.

[0041] This vapor stream, which is rich in acrylic acid and contains some heavy compounds containing inhibitors at low concentration, is advantageously recycled as stream (3) to the acrylic acid production process, either directly in the form of vapor or after total condensation in condenser E1.

[0042] 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.

[0043] The stream (4) of residue recovered at the bottom of the reactor is cooled and removed in the form of a liquid of suitable viscosity, so that it can be pumped without problems, for example to a storage tank or an incinerator.

Examples

[0044] The following examples are described without limiting the present invention.

[0045] The depletion rate is defined as the ratio of the mass of the distillate / 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 distillate amount.

[0046] [Example 1: Batch hydrolysis and decomposition in the same reactor (according to the present invention)]

[0047] 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, and a condenser. The AA heavy product was introduced into the reactor and heated to the desired temperature. At this temperature, an amount of water corresponding to the selected water / AAHP ratio was added over a defined period. When the addition of water was completed, the mixture was heated at the decomposition temperature until it reached the target volume reduction rate. The liquid (distillate) was collected in a receiving flask and analyzed. The residue was discharged from the valve at the bottom of the reactor.

[0048] Test time: 7h Hydrolysis: T = 146 °C, residence time: 6h, atmospheric pressure, water / AA heavy product ratio = 0.5 Decomposition: T = 178 °C, atmospheric pressure, residence time: 1h, water / AA heavy product ratio = 0.5 URR = 35.30% Decomposition rate = 52% Corrected depletion rate = 31.4% Viscosity = 0.085 Pa.s

[0049] [Example 2 (comparison): Decomposition without prior hydrolysis] In this case, a known mass of the AA heavy product was directly introduced into a glass reactor with a total volume of 500 cm 3 and heated by recirculating oil through the double walls. The reactor is equipped with a stirrer, a temperature probe immersed in the liquid phase, an upper vertical pipe for extracting steam, and a condenser. The liquid (distillate) was collected in a receiving flask and analyzed.

[0050] Heated at 146 °C for 6 hours without adding water, and then the temperature was increased: Tmax = 183 °C, atmospheric pressure, residence time 1 h, water / AA heavy product ratio = 0.5. URR = 3.0% Viscosity = 0.068 Pa·s Depletion rate = 3.5% Decomposition rate = 4.5%

[0051] This example can show that it hardly decomposes at 183 °C.

[0052] [Example 3 (comparison): Decomposition without prior hydrolysis] The same procedure as in Example 2. Heated at 146 °C for 6 hours without adding water, and then the temperature was increased: Tmax = 199 °C, atmospheric pressure, residence time 1 h, water / AA heavy product ratio = 0.5. URR = 29.2% Viscosity = 0.41 Pa·s Depletion rate = 32.7% Decomposition rate = 44%

[0053] The comparative example can show that the decomposition after the hydrolysis step can be carried out at a temperature lower than the temperature required for the decomposition of the stream that has not undergone the hydrolysis step. Specifically, in Example 2, the maximum temperature was 183 °C, and the decomposition rate was equal to 4.5% compared to 52% in Example 1 where the maximum temperature was 178 °C. When the decomposition temperature was raised to 199 °C, a decomposition rate of 44% could be obtained. However, the viscosity of the residue was 5 times higher.

Claims

1. A method for regenerating heavy by-products (AAHP) from an acrylic acid production apparatus, i. A step of introducing the heavy by-product into the reactor; ii. A step of heating the heavy product at a temperature of 80°C to 200°C; Simultaneously with or at the final temperature, water is gradually added over a period of 1 to 10 hours until a water / AA heavy product ratio of 0.1 to 1.3 is reached, resulting in a mixture of hydrolysis products; iv. A step in which the mixture containing the hydrolyzed heavy product and water are subjected to batch thermal decomposition in the same reactor to produce a gaseous upper stream containing acrylic acid and water, and a bottom stream (residue) in which the heavy product is concentrated. v A process for recovering a light fraction rich in AA and water, which can be recycled to various stages of the above method. vi. A step of recovering the residue for the purpose of removal treatment. Methods that include...

2. The method according to claim 1, wherein step i) is performed under atmospheric pressure or a small pressure range of up to 2 MPa.

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

4. The method according to claim 1 or 2, wherein the decomposition temperature is 140°C to 260°C.

5. The method according to claim 1 or 2, wherein the residence time of the reaction mixture in the decomposition reactor is 0.5h to 10h.

6. The method according to claim 1 or 2, wherein the bottom flow (residue) from the reactor obtained as a result of the thermal decomposition operation has a dynamic viscosity of less than 1 Pa·s when measured at 100°C.

7. The method according to claim 1 or 2, further comprising the step of injecting the gaseous upper flow 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 capacitor.

9. The method according to claim 1 or 2, wherein the thermal decomposition reaction is carried out without a catalyst.

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