Method for preparing acrylic acid

Abstract

Provided is a method for preparing an acrylic acid, in which a lactic acid aqueous solution is dehydrated to prepare a reaction product stream, from which by-products are removed using an extraction column, an extractant recovery column, a first separation column, a second separation column, and a refining column to prepare a high-purity acrylic acid. Figure 1

Description

Acrylic acid manufacturing method

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2021-0137931, filed October 15, 2021, and Korean Patent Application No. 10-2022-0091840, filed July 25, 2022, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a method for producing acrylic acid, and more specifically, to a method for producing acrylic acid through a dehydration reaction of lactic acid, while reducing the loss of acrylic acid and effectively removing byproducts.

[0005] Acrylic acid is a polymer raw material used in fibers, adhesives, paints, textile processing, leather, and construction materials, and its demand is growing. Furthermore, acrylic acid is also used as a raw material for absorbent resins, widely used industrially in absorbent products such as paper diapers and sanitary pads, as well as in agricultural and horticultural water retention agents and industrial water-repellents.

[0006] Conventional acrylic acid manufacturing methods typically involve air oxidation of propylene. However, this method involves converting propylene into acrolein through a gas-phase catalytic oxidation reaction, which is then subjected to a gas-phase catalytic oxidation reaction to produce acrylic acid. However, acetic acid is produced as a byproduct, which is difficult to separate from acrylic acid. Furthermore, the method for manufacturing acrylic acid using propylene uses propylene, which is obtained by refining crude oil, a fossil resource, as a raw material, and considering recent issues such as rising crude oil prices and global warming, there are problems in terms of raw material costs and environmental pollution.

[0007] In this regard, research has been conducted on methods for producing acrylic acid from carbon-neutral biomass raw materials. For example, there is a method for producing acrylic acid (AA) through a gas-phase dehydration reaction of lactic acid (LA). This method generally produces acrylic acid through an intramolecular dehydration reaction of lactic acid at a high temperature of 300°C or higher and in the presence of a catalyst. However, during the dehydration reaction of lactic acid, side reactions occur in addition to the dehydration reaction, resulting in the production of byproducts including hydroxy acetone (HA) in addition to acrylic acid as a reaction product. In this case, there was a problem that it was difficult to completely remove hydroxy acetone, a byproduct produced through the dehydration reaction of lactic acid.

[0008] The problem to be solved in the present invention is to provide a method for effectively removing byproducts and minimizing the loss of acrylic acid during the production of acrylic acid through a dehydration reaction of lactic acid, in order to solve the problems mentioned in the technology that forms the background of the invention.

[0009] According to one embodiment of the present invention for solving the above problem, the present invention provides a method for producing acrylic acid, comprising the steps of: supplying a reaction product stream produced by dehydrating an aqueous lactic acid solution to an extraction tower, separating an upper discharge stream containing acrylic acid using an extractant in the extraction tower, and supplying the upper discharge stream containing acrylic acid to an extractant recovery tower; separating a lower discharge stream containing acrylic acid from the extractant recovery tower and supplying the lower discharge stream containing acrylic acid to a first separation tower; separating a low-boiling-point by-product to the upper portion in the first separation tower, and separating a lower discharge stream containing acrylic acid and supplying the lower discharge stream containing acrylic acid to a second separation tower; separating a high-boiling-point by-product to the lower portion in the second separation tower, and supplying the upper discharge stream containing acrylic acid to a purification tower; and separating an upper discharge stream containing acrylic acid from the purification tower, and refluxing a lower discharge stream containing hydroxyacetone to the extraction tower.

[0010] According to the method for producing acrylic acid of the present invention, by completely removing hydroxyacetone, which has a boiling point similar to that of acrylic acid, from a reaction product containing acrylic acid, the problem of lowering the purity of the acrylic acid product due to the residue of the hydroxyacetone is solved, and the loss of acrylic acid can be minimized in the process of separating and removing the hydroxyacetone.

[0011] Figure 1 is a process flow diagram according to a method for manufacturing acrylic acid in one embodiment of the present invention.

[0012] Figures 2 and 3 are process flow diagrams according to the acrylic acid manufacturing method in comparative examples.

[0013] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0014] In the present invention, the term "stream" may refer to the flow of fluid within a process, and may also refer to the fluid itself flowing within a pipe. Specifically, the stream may refer to both the fluid itself flowing within the pipe connecting each device and the flow of the fluid. Furthermore, the fluid may include one or more components of gas, liquid, and solid.

[0015]

[0016] Hereinafter, to help understand the present invention, the present invention will be described in more detail with reference to FIG. 1.

[0017] According to the present invention, a method for producing acrylic acid is provided. More specifically, the method comprises the steps of: supplying a reaction product stream produced by dehydrating an aqueous lactic acid solution to an extraction tower (100), separating an upper discharge stream containing acrylic acid using an extractant in the extraction tower (100), and supplying the upper discharge stream containing acrylic acid to an extractant recovery tower (200); separating a lower discharge stream containing acrylic acid in the extractant recovery tower (200) and supplying the lower discharge stream containing acrylic acid to a first separation tower (300); separating a low-boiling-point by-product into an upper portion in the first separation tower (300), and separating a lower discharge stream containing acrylic acid and supplying the lower discharge stream containing acrylic acid to a second separation tower (310); separating a high-boiling-point by-product into a lower portion in the second separation tower (310), and supplying the upper discharge stream containing acrylic acid to a purification tower (400); And it may include a step of separating an upper discharge stream containing acrylic acid from the purification tower (400) and refluxing a lower discharge stream containing hydroxy acetone to the extraction tower (100).

[0018] Specifically, the conventional method for manufacturing acrylic acid is generally a method for oxidizing propylene in the air, but this method converts propylene into acrolein through a gas-phase catalytic oxidation reaction, and manufactures acrylic acid by subjecting this to a gas-phase catalytic oxidation reaction. However, acetic acid is produced as a by-product, and this has the problem of being difficult to separate from acrylic acid. In addition, the method for manufacturing acrylic acid using propylene uses propylene obtained by refining crude oil, a fossil resource, as a raw material, and considering recent issues such as the rise in crude oil prices and global warming, there are problems in terms of raw material costs and environmental pollution.

[0019] To address the problems of the conventional acrylic acid production methods, research has been conducted on methods for producing acrylic acid from carbon-neutral biomass raw materials. For example, there is a method for producing acrylic acid (AA) through a gas-phase dehydration reaction of lactic acid (LA). This method typically produces acrylic acid through an intramolecular dehydration reaction of lactic acid at high temperatures and in the presence of a catalyst. However, during the dehydration reaction of lactic acid, side reactions occur in addition to the dehydration reaction, resulting in the production of byproducts other than acrylic acid, particularly hydroxyacetone (HA), which has a boiling point similar to that of acrylic acid. In this case, it is difficult to completely remove hydroxyacetone through distillation.

[0020] In this regard, in order to solve the above-mentioned conventional problem, the present invention uses an extraction method to completely remove by-products produced by the dehydration reaction of lactic acid, especially hydroxyacetone (boiling point: 145°C), which is difficult to separate due to its similar boiling point to acrylic acid (boiling point: 141°C), while producing acrylic acid through an extraction reaction. At this time, the present invention seeks to provide a method for completely removing the hydroxyacetone and at the same time minimizing the loss of acrylic acid.

[0021] According to one embodiment of the present invention, a reaction product stream produced by dehydrating an aqueous lactic acid solution can be supplied to an extraction tower (100). At this time, the reaction product may be a condensate condensed through a cooling tower.

[0022] Specifically, a lactic acid aqueous solution can be supplied to a reactor and subjected to a dehydration reaction to produce a reaction product containing acrylic acid. At this time, the dehydration reaction can be performed as a gas phase reaction in the presence of a catalyst. For example, the lactic acid concentration of the lactic acid aqueous solution can be 10 wt% or more, 20 wt% or more, or 30 wt% or more, and 40 wt% or less, 50 wt% or less, 60 wt% or less, or 70 wt% or less.

[0023] The above reactor may be a reactor capable of performing a conventional dehydration reaction of lactic acid, and the reactor may include a reaction tube filled with a catalyst, and a reaction gas containing volatile components of a raw material lactic acid aqueous solution may be passed through the reaction tube to dehydrate lactic acid through a gas phase contact reaction to produce acrylic acid. The reaction gas may further include, in addition to lactic acid, one or more dilution gases selected from the group consisting of steam, nitrogen, and air for concentration adjustment.

[0024] The operating conditions of the above reactor may be set under typical lactic acid dehydration reaction conditions. In this case, the operating temperature of the reactor may refer to the set temperature of a heat medium, etc., used to control the temperature of the reactor.

[0025] The catalyst used in the dehydration reaction of the lactic acid may include, for example, at least one selected from the group consisting of a sulfate-based catalyst, a phosphate-based catalyst, and a nitrate-based catalyst. As a specific example, the sulfate may include Na2SO4, K2SO4, CaSO4, and Al2(SO4)3, the phosphate may include Na3PO4, Na2HPO4, NaH2PO4, K3PO4, K2HPO4, KH2PO4, CaHPO4, Ca3(PO4)2, AlPO4, CaH2P2O7, and Ca2P2O7, and the nitrate may include NaNO3, KNO3, and Ca(NO3)2. In addition, the catalyst may be supported on a support. The support may include, for example, at least one selected from the group consisting of diatomaceous earth, alumina, silica, titanium dioxide, carbide, and zeolite.

[0026] The reaction product manufactured through the dehydration reaction of the above lactic acid may further include byproducts such as water (H2O) and hydroxyacetone in addition to the desired product, acrylic acid.

[0027] The above reaction product can be cooled by supplying it to a cooling tower. Specifically, the reaction product produced through the dehydration reaction of the lactic acid is in a gaseous state and can be condensed by passing through the cooling tower. The upper part of the cooling tower can separate the gaseous byproducts, and the liquid condensate can be discharged to the lower part. In this case, the condensate can be the reaction product stream supplied to the extraction tower (100) in the present invention.

[0028] According to one embodiment of the present invention, in the extraction tower (100), acrylic acid contained in the reaction product stream can be separated into an upper discharge stream using a separate extractant.

[0029] The extractant may include, for example, at least one selected from the group consisting of benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptene, 1-heptene, ethylbenzene, methylcyclohexane, n-butylacetate, isobutylacetate, isobutyl acrylate, n-propyl acetate, isopropyl acetate, methylisobutyl ketone, 2-methyl-1-heptene, 6-methyl-1-heptene, 4-methyl-1-heptene, 2-ethyl-1-hexene, ethylcyclopentane, 2-methyl-1-hexene, 2,3-dimethylpentane, 5-methyl-1-hexene, and isopropylbutyl ether. As a specific example, the extractant may be toluene.

[0030] Any known method can be used to supply the extractant to the above extraction tower (100) and extract it. For example, any method such as cross current, counter current, or co-current can be used without any special restrictions.

[0031] In the above extraction tower (100), the reaction product stream and the extractant can be brought into contact to separate the extractant and the raffinate. For example, the extractant may be acrylic acid dissolved in the extractant, and the extractant may be discharged as a top discharge stream of the extraction tower (100). In this case, the top discharge stream of the extraction tower (100) may be supplied to an extractant recovery tower (200).

[0032] In addition, the above-mentioned residual liquid is wastewater containing water and can be separated into the lower part of the extraction tower (100). At this time, hydroxyacetone among the by-products can be separated and discharged together with water from the lower part of the extraction tower (100), but there is a problem that not all of it is discharged, and some of it flows out as an extract and is transported to the later part together with acrylic acid. Specifically, the amount of extractant used can be adjusted to remove hydroxyacetone in the extraction tower (100), but even if the amount of extractant used is increased, it is difficult to remove all of the injected hydroxyacetone, and in this case, there may be a problem that the content of acrylic acid discharged together with water from the lower part of the extraction tower (100) increases, resulting in an increase in the loss of acrylic acid.

[0033] In this regard, in the present invention, by controlling the operating conditions of the purification tower (400) at the rear end to effectively separate hydroxy acetone and reflux it to the extraction tower (100), all of the hydroxy acetone can be separated and removed as a lower discharge stream of the extraction tower (100), and at this time, the loss of acrylic acid can be minimized.

[0034] For example, the content ratio of hydroxy acetone separated into the lower portion of the extraction tower (100) relative to the content of hydroxy acetone included in the reaction product stream may be 0.95 to 1, 0.97 to 1, or 0.99 to 1, and specifically, the entire amount of hydroxy acetone included in the reaction product stream supplied to the extraction tower (100) may be removed in the extraction tower (100). Through this, high-purity acrylic acid can be separated in the purification tower (400).

[0035] The top discharge stream of the extraction tower (100) may include acrylic acid, and furthermore, may include an extractant and hydroxy acetone. The content of hydroxy acetone in the top discharge stream of the extraction tower (100) may be 0.2% to 15%, 3% to 13% by weight, or 5% to 10% by weight of the content of hydroxy acetone contained in the reaction product stream. Specifically, by controlling the content of hydroxy acetone in the top discharge stream of the extraction tower (100) as described above, the content of acrylic acid lost together with water to the bottom of the extraction tower (100) can be minimized, and the energy usage for separation in the purification tower (400) can be reduced.

[0036] According to one embodiment of the present invention, the upper discharge stream of the extraction tower (100) is supplied to the extractant recovery tower (200), and a lower discharge stream containing acrylic acid may be separated from the extractant recovery tower (200) and supplied to the first separation tower (300). In addition, the extractant may be separated into an upper discharge stream in the extractant recovery tower (200), and a portion of the upper discharge stream of the extractant recovery tower (200) may be refluxed to the extraction tower (100) to reuse the extractant. At this time, the lower discharge stream of the extractant recovery tower (200) may include, in addition to acrylic acid, low-boiling-point by-products, high-boiling-point by-products, and hydroxyacetone as by-products.

[0037] The operating conditions of the extractant recovery tower (200) vary depending on the content of the components supplied to the extractant recovery tower (200) and the type of extractant. The operating temperature of the extractant recovery tower (200) may be, for example, 40°C to 150°C, 45°C to 130°C, or 50°C to 110°C. In addition, the operating pressure of the extractant recovery tower (200) may be 35 torr to 300 torr, 70 torr to 250 torr, or 100 torr to 200 torr. When the extractant recovery tower (200) is operated as described above, the side reactions occurring at high temperatures can be suppressed, thereby increasing the recovery rate of acrylic acid.

[0038] According to one embodiment of the present invention, the first separation tower (300) may be for separating low-boiling-point by-products among the by-products included in the reaction product. Specifically, the bottom discharge stream of the extractant recovery tower (200) may be supplied to the first separation tower (300), the low-boiling-point by-products may be separated upward in the first separation tower (300), and the bottom discharge stream containing acrylic acid may be separated and supplied to the second separation tower (310).

[0039] According to one embodiment of the present invention, the second separation tower (310) may be for separating high-boiling-point by-products among the by-products included in the reaction product. Specifically, the lower discharge stream of the first separation tower (300) may be supplied to the second separation tower (310), the high-boiling-point by-products may be separated into the lower stream in the second separation tower (310), and the upper discharge stream containing acrylic acid may be separated and supplied to the second separation tower (310).

[0040] According to one embodiment of the present invention, the first separation tower (300) and the second separation tower (310) may be devices for separating components by using the difference in boiling points through distillation. At this time, low-boiling-point by-products and high-boiling-point by-products included in the lower discharge stream of the extractant recovery tower (200) are removed while passing through the first separation tower (300) and the second separation tower (310), but hydroxyacetone, which has a similar boiling point to acrylic acid, is not separated and is discharged together when acrylic acid is separated as an upper discharge stream from the second separation tower (310). Therefore, when acrylic acid is commercialized as a product using the upper discharge stream of the second separation tower (310), there is a problem that the purity of the product is lowered.

[0041] In this regard, in the present invention, the upper discharge stream of the second separation tower (310) is supplied to the purification tower (400), and an upper discharge stream containing high-purity acrylic acid and a lower discharge stream containing hydroxy acetone and acrylic acid are separated from the purification tower (400), and the lower discharge stream of the purification tower (400) is refluxed to the extraction tower (100), thereby removing all of the hydroxy acetone in the extraction tower (100) and separating acrylic acid with high purity from the upper discharge stream of the purification tower (400).

[0042] Specifically, hydroxyacetone, a by-product, may be separated and discharged together with water from the bottom of the extraction tower (100). However, if not all of the hydroxyacetone is discharged, the hydroxyacetone that is not discharged flows out as an extract and is transported to the subsequent stage together with acrylic acid. In this case, since hydroxyacetone must be separated in the purification tower (400), a problem may arise in that the yield of high-purity acrylic acid decreases.

[0043] Meanwhile, the amount of extractant used can be adjusted to remove hydroxy acetone in the above extraction tower (100), but in this case, even if the amount of extractant used is increased, it is difficult to remove all of the injected hydroxy acetone, and in particular, there may be a problem that the content of acrylic acid discharged together with water to the bottom of the above extraction tower (100) increases, resulting in increased loss of acrylic acid.

[0044] Therefore, when the bottom discharge stream of the purification tower (400) containing hydroxy acetone is refluxed to the extraction tower (100) and hydroxy acetone is separated as a raffinate by extraction in the extraction tower (100), not only can all of the hydroxy acetone introduced into the acrylic acid purification system be removed, but there is also an advantage in that high-purity acrylic acid can be obtained in a high yield from the upper portion of the purification tower (400).

[0045] According to one embodiment of the present invention, the operating temperature of the purification tower (400) may be, for example, 60°C to 200°C, 80°C to 150°C, or 90°C to 110°C. In addition, the operating pressure of the purification tower (400) may be 35 torr to 500 torr, 70 torr to 350 torr, or 100 torr to 200 torr. When the purification tower (400) is operated as described above, high-purity acrylic acid can be separated as an upper discharge stream without the problem of acrylic acid loss due to side reactions, and hydroxyacetone can be separated together while discharging a portion of the acrylic acid as a lower discharge stream.

[0046] The upper discharge stream of the second separation tower (310) may be supplied in stages of 50% to 90%, 55% to 85%, or 60% to 80% of the total number of stages of the purification tower (400). By adjusting the supply stage of the purification tower (400) within the above range, the separation efficiency in the purification tower (400) may be increased, and thereby the composition of the bottom discharge stream of the purification tower (400) that is refluxed to the extraction tower (100) may be controlled. At this time, the total number of stages of the purification tower (400) may be 15 to 70 stages, 18 to 55 stages, or 20 to 35 stages.

[0047] The bottom discharge stream of the purification tower (400) can be supplied to the extraction tower (100) by forming a mixed stream with the reaction product stream. As the reaction product stream is supplied to the extraction tower (100) by forming a mixed stream with the bottom discharge stream of the purification tower (400) that is refluxed in the purification tower (400), the loss of acrylic acid can be minimized while the entire amount of hydroxy acetone can be removed from the bottom of the extraction tower (100).

[0048] According to one embodiment of the present invention, in the acrylic acid manufacturing method, if necessary, additional devices such as a distillation tower, a condenser, a reboiler, a valve, a pump, a separator, and a mixer may be additionally installed.

[0049] Above, the method for producing acrylic acid according to the present invention has been described and illustrated in the drawings, but the description and illustration of the drawings describe and illustrate only the core components for understanding the present invention, and in addition to the processes and devices described and illustrated in the drawings, processes and devices not described and illustrated separately can be appropriately applied and utilized to carry out the method for producing acrylic acid according to the present invention.

[0050]

[0051] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present invention, and the scope of the present invention is not limited to these examples alone.

[0052]

[0053] Example

[0054] Example 1

[0055] According to the process flow diagram shown in Fig. 1, the acrylic acid manufacturing process was simulated using Aspen Plus simulator from Aspen.

[0056] Specifically, a 50 wt% lactic acid aqueous solution and nitrogen (N2) as a dilution gas were supplied to the reactor to produce a reaction product including acrylic acid (AA) through a dehydration reaction, and the reactor discharge stream including the reaction product was supplied to a cooling tower, and gaseous byproducts were separated upward from the cooling tower, and the liquid reaction product as a condensate was supplied to an extraction tower (100).

[0057] In the above extraction tower (100), toluene was used as an extractant to separate acrylic acid as an upper discharge stream and supplied to the extractant recovery tower (200), and water was separated as a lower stream. At this time, the operating temperature of the extraction tower (100) was controlled at 40°C and the operating pressure was controlled at 750 torr.

[0058] The extractant was separated as an upper discharge stream from the extractant recovery tower (200), and a portion of the upper discharge stream of the extractant recovery tower (200) was refluxed to the extraction tower (100). In addition, the lower discharge stream of the extractant recovery tower (200) containing the acrylic acid was supplied to the first separation tower (300). At this time, the operating temperature of the extractant recovery tower (200) was controlled to 54.1°C at the upper portion and 96.9°C at the lower portion, and the operating pressure was controlled to 110 torr.

[0059] In the first separation tower (300), low-boiling-point by-products were separated from the upper portion, and the lower discharge stream containing acrylic acid was supplied to the second separation tower (310). In addition, in the second separation tower (310), high-boiling-point by-products were separated from the lower portion, and the upper discharge stream containing acrylic acid was supplied to stage 15 of the purification tower (400).

[0060] High-purity acrylic acid was separated from the upper part of the purification tower (400), and the lower discharge stream containing byproducts hydroxyacetone and acrylic acid was refluxed to the extraction tower (100). At this time, the operating temperature of the purification tower (400) was controlled to 62.5°C at the upper part and 65.6°C at the lower part, the operating pressure was controlled to 110 torr, and the total number of stages of the purification tower (400) was 20.

[0061] At this time, the temperature and pressure of each stream and the flow rate (kg / hr) of each component within each stream are shown in Table 1 below.

[0062]

[0063]

[0064] Example 2

[0065] In the above Example 1, the same method as in Example 1 was performed except that the concentration of the lactic acid aqueous solution was changed to 20 wt%.

[0066] At this time, the temperature and pressure of each stream and the flow rate (kg / hr) of each component within each stream are shown in Table 2 below.

[0067]

[0068]

[0069]

[0070] Comparative example

[0071] Comparative Example 1

[0072] According to the process flow diagram shown in Fig. 2, the acrylic acid manufacturing process was simulated using Aspen Plus simulator from Aspen.

[0073] Specifically, a 50 wt% lactic acid aqueous solution and nitrogen (N2) as a dilution gas were supplied to the reactor to produce a reaction product including acrylic acid (AA) through a dehydration reaction, and the reactor discharge stream including the reaction product was supplied to a cooling tower, and gaseous byproducts were separated upward from the cooling tower, and the liquid reaction product as a condensate was supplied to an extraction tower (100).

[0074] In the above extraction tower (100), toluene was used as an extractant to separate acrylic acid as an upper discharge stream and supplied to the extractant recovery tower (200), and water was separated as a lower stream. At this time, the operating temperature of the extraction tower (100) was controlled at 40°C and the operating pressure was controlled at 750 torr.

[0075] The extractant was separated as an upper discharge stream from the extractant recovery tower (200), and a portion of the upper discharge stream of the extractant recovery tower (200) was refluxed to the extraction tower (100). The lower discharge stream of the extractant recovery tower (200) containing the acrylic acid was supplied to the first separation tower (300). At this time, the operating temperature of the extractant recovery tower (200) was controlled to 54.1°C at the upper part and 96.9°C at the lower part, and the operating pressure was controlled to 110 torr.

[0076] In the first separation tower (300), low-boiling-point by-products were separated from the upper portion, and the lower discharge stream containing acrylic acid was supplied to the second separation tower (310). In addition, in the second separation tower (310), high-boiling-point by-products were separated from the lower portion, and acrylic acid was separated from the upper discharge stream.

[0077] At this time, the temperature and pressure of each stream and the flow rate (kg / hr) of each component within each stream are shown in Table 3 below.

[0078]

[0079]

[0080] Comparative Example 2

[0081] In the above comparative example 1, the same method as the above comparative example 1 was performed except that the flow rate of the extractant supplied to the extraction tower (100) was controlled.

[0082] At this time, the temperature and pressure of each stream and the flow rate (kg / hr) of each component within each stream are shown in Table 4 below.

[0083]

[0084]

[0085] Referring to Tables 1 to 4 above, in the case of Examples 1 and 2 in which by-products are separated and acrylic acid is recovered using the acrylic acid production method according to the present invention, it was confirmed that the purity of the acrylic acid was 99% or higher and the amount of acrylic acid lost in the extraction tower (100) was very small. In addition, it was confirmed that the entire amount of hydroxyacetone included in the reaction product was discharged together with water from the extraction tower (100).

[0086] In comparison, Comparative Example 1 is a case in which a purification tower (400) is not provided compared to Example 1, and it was confirmed that the amount of hydroxy acetone remaining in the upper discharge stream of the second separation tower (310) was large, so that the purity of acrylic acid was low, and the amount of acrylic acid lost in the extraction tower (100) increased.

[0087] In addition, Comparative Example 2 is a case where the amount of extractant supplied to the extraction tower (100) of Comparative Example 1 was reduced in order to remove all of the hydroxy acetone from the extraction tower (100). In this case, it was confirmed that the amount of acrylic acid lost and discharged together with water from the extraction tower (100) increased.

[0088]

[0089] Comparative Example 3

[0090] According to the process flow diagram shown in Fig. 3, the acrylic acid manufacturing process was simulated using Aspen Plus simulator from Aspen.

[0091] In the above Example 1, the same method as in the above Example 1 was performed except that the bottom discharge stream of the purification tower (400) was discharged without being refluxed to the extraction tower (100).

[0092] At this time, the temperature and pressure of each stream and the flow rate (kg / hr) of each component within each stream are shown in Table 5 below.

[0093]

[0094]

[0095] Comparative Example 4

[0096] In the above comparative example 3, the same method as the above comparative example 3 was performed except that the flow rate of the extractant supplied to the extraction tower (100) was controlled.

[0097] At this time, the temperature and pressure of each stream and the flow rate (kg / hr) of each component within each stream are shown in Table 6 below.

[0098]

[0099]

[0100] Referring to Tables 1 to 2 and Tables 5 to 6 above, in the case of Examples 1 and 2 in which by-products are separated and acrylic acid is recovered by the acrylic acid production method according to the present invention, it was confirmed that the purity of the acrylic acid was 99% or more, and the amount of acrylic acid lost in the extraction tower (100) was very small. In addition, it was confirmed that the entire amount of hydroxyacetone included in the reaction product was discharged together with water from the extraction tower (100).

[0101] In comparison, Comparative Examples 3 and 4 are cases where the bottom discharge stream of the purification tower (400) is not refluxed to the extraction tower (100) compared to Example 1, and it was confirmed that the hydroxy acetone, which is a by-product included in the stream introduced into the extraction tower (100), was not completely discharged to the bottom discharge stream of the extraction tower (100). In order to prevent accumulation of hydroxy acetone that was not discharged to the bottom discharge stream of the extraction tower (100) in the system, it was confirmed that some acrylic acid was lost from the bottom of the purification tower (400).

[0102] In addition, Comparative Example 4 is a case where the amount of extractant supplied to the extraction tower (100) in order to remove all of the hydroxy acetone from the extraction tower (100) of Comparative Example 3 was doubled. In this case, even if the amount of toluene, which is the extractant, was increased, it was confirmed that the entire amount of hydroxy acetone was not discharged from the extraction tower (100), and that the amount of acrylic acid that was discharged together with water and lost increased. In particular, it was found that the mass flow rate of acrylic acid lost from the bottom of the extraction tower (100) in Comparative Example 4 increased by about 35% compared to the mass flow rate of acrylic acid lost from the bottom of the extraction tower (100) in Example 1.

[0103] Furthermore, in the case of Comparative Examples 3 and 4, where the lower discharge stream of the purification tower (400) was not refluxed to the extraction tower (100), it was possible to recover high-purity acrylic acid from the upper portion of the purification tower (400), but it was confirmed that the yield of high-purity acrylic acid was lower than that of Examples 1 and 2.

Claims

1. A step of supplying a reaction product stream produced by dehydrating an aqueous lactic acid solution to an extraction tower, and separating an upper discharge stream containing acrylic acid using an extractant in the extraction tower and supplying the stream to an extractant recovery tower; A step of separating a bottom discharge stream containing acrylic acid from the above extractant recovery tower and supplying it to a first separation tower; A step of separating low-boiling-point by-products from the first separation tower to the upper part and separating a bottom discharge stream containing acrylic acid and supplying it to the second separation tower; A step of separating high boiling point by-products from the second separation tower and supplying the upper discharge stream containing acrylic acid to the purification tower; and A method for producing acrylic acid, comprising the step of separating an upper discharge stream containing acrylic acid from the above purification tower and refluxing a lower discharge stream containing hydroxy acetone to an extraction tower.

2. In paragraph 1, A method for producing acrylic acid, wherein the above reaction product stream comprises acrylic acid, water, low boiling point by-products, high boiling point by-products and hydroxy acetone.

3. In paragraph 1, A method for producing acrylic acid by separating water and hydroxy acetone from the bottom of the above extraction tower.

4. In paragraph 3, A method for producing acrylic acid, wherein the content ratio of hydroxy acetone separated into the lower portion of the extraction tower relative to the content of hydroxy acetone included in the reaction product stream is 0.95 to 1.

5. In paragraph 1, A method for producing acrylic acid, wherein a portion of the upper discharge stream containing the extractant from the extractant recovery tower is refluxed to the extraction tower.

6. In paragraph 1, A method for producing acrylic acid, wherein the extractant is at least one selected from the group consisting of benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptene, 1-heptene, ethylbenzene, methylcyclohexane, n-butylacetate, isobutylacetate, isobutyl acrylate, n-propyl acetate, isopropyl acetate, methylisobutyl ketone, 2-methyl-1-heptene, 6-methyl-1-heptene, 4-methyl-1-heptene, 2-ethyl-1-hexene, ethylcyclopentane, 2-methyl-1-hexene, 2,3-dimethylpentane, 5-methyl-1-hexene, and isopropylbutyl ether.

7. In paragraph 1, A method for producing acrylic acid, wherein the above reaction product stream is a condensate that is condensed through a cooling tower.

8. In paragraph 1, A method for producing acrylic acid, wherein the content of hydroxy acetone in the upper discharge stream of the above extraction tower is 0.2% to 15% of the content of hydroxy acetone contained in the above reaction product stream.

9. In paragraph 1, A method for producing acrylic acid, wherein the bottom discharge stream of the above extractant recovery tower is supplied to 50% to 90% of the total number of stages of the above purification tower.

10. In paragraph 1, A method for producing acrylic acid, wherein the operating temperature of the above extractant recovery tower is 40°C to 150°C, and the operating pressure is 35 torr to 300 torr.

11. In paragraph 1, A method for producing acrylic acid, wherein the operating temperature of the above purification tower is 60°C to 200°C, and the operating pressure is 35 torr to 500 torr.