Method for producing acrylic acid

Abstract

The present invention relates to a method for producing acrylic acid, and provides a method for producing high-purity acrylic acid by removing by-products from a reaction product stream produced by dehydrating an aqueous lactic acid solution using an extraction tower, an extractant recovery tower, a first separation tower, a second separation tower and a purification tower.

Description

[Technical field]

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2021-0137931 filed on October 15, 2021 and Korean Patent Application No. 10-2022-0091840 filed on July 25, 2022, and all contents disclosed in the documents of the relevant Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a method for producing acrylic acid, and more particularly to a method for reducing loss of acrylic acid and effectively removing by-products when producing acrylic acid by dehydration reaction of lactic acid. [Background technology]

[0003] Acrylic acid is used as a polymer raw material for fibers, adhesives, paints, fiber processing, leather, building materials, etc., and the demand for it is expanding. The acrylic acid is also used as a raw material for water-absorbent resins, and is widely used industrially in water-absorbent articles such as paper diapers and sanitary napkins, agricultural and horticultural water retention agents, and industrial water-stopping materials.

[0004] Conventional methods for producing acrylic acid generally involve air oxidation of propylene, which is a method in which propylene is converted into acrolein by gas-phase catalytic oxidation, and this is then subjected to gas-phase catalytic oxidation to produce acrylic acid, and this method produces acetic acid as a by-product, which is problematic in that it is difficult to separate from acrylic acid. In addition, the method for producing acrylic acid using propylene uses propylene obtained by refining crude oil, a fossil resource, as a raw material, and in consideration of the recent rise in crude oil prices and problems such as global warming, there are problems in terms of raw material costs and environmental pollution.

[0005] In response to this, research has been conducted into 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 high temperatures of 300°C or higher and in the presence of a catalyst. However, during the dehydration reaction of lactic acid, a side reaction occurs in addition to the dehydration reaction, which produces by-products including hydroxyacetone (HA) in addition to acrylic acid as a reaction product. In this case, there was a problem in that it was difficult to completely remove hydroxyacetone, a by-product produced by the dehydration reaction of lactic acid. Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a method for effectively removing by-products and minimizing loss of acrylic acid when producing acrylic acid by dehydration of lactic acid, in order to solve the problems mentioned in the Background of the Invention. [Means for solving the problem]

[0007] According to one embodiment of the present invention for solving the above problems, 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 to an extractant recovery tower; separating a lower discharge stream containing acrylic acid in the extractant recovery tower and supplying the lower discharge stream to a first separation tower; separating a low boiling by-product to an upper part in the first separation tower and a lower discharge stream containing acrylic acid to a second separation tower; separating a high boiling by-product to a lower part 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 in the purification tower and refluxing a lower discharge stream containing hydroxyacetone to the extraction tower. Effect of the Invention

[0008] According to the method for producing acrylic acid of the present invention, hydroxyacetone, which has a boiling point similar to that of acrylic acid, is completely removed from a reaction product containing acrylic acid, thereby solving the problem of low purity of the acrylic acid product due to residual hydroxyacetone, and minimizing loss of acrylic acid in the process of separating and removing hydroxyacetone. [Brief description of the drawings]

[0009] [Figure 1] 1 is a process flow chart of a method for producing acrylic acid according to one embodiment of the present invention. [Diagram 2] 1 is a process flow chart of a comparative example of a method for producing acrylic acid. [Diagram 3] 1 is a process flow chart of a method for producing acrylic acid in a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The terms and words used in the description and claims of the present invention should not be interpreted limitedly to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0011] In the present invention, the term "stream" may refer to the flow of fluid in a process, or may refer to the fluid itself flowing in a pipe. Specifically, the term "stream" refers to the fluid flowing in a pipe connecting each device. The term "fluid" can refer to both the fluid itself and the flow of a fluid. The fluid can include one or more of gas, liquid, and solid components.

[0012] In order to facilitate understanding of the present invention, the present invention will now be described in more detail with reference to FIG.

[0013] According to the present invention, a method for producing acrylic acid is provided. More specifically, the method includes 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 it to an extractant recovery tower 200; separating a lower discharge stream containing acrylic acid in the extractant recovery tower 200 and supplying it to a first separation tower 300; separating low boiling by-products to the upper part in the first separation tower 300 and separating a lower discharge stream containing acrylic acid to a second separation tower 310; separating high boiling by-products to the lower part in the second separation tower 310 and supplying an upper discharge stream containing acrylic acid to a purification tower 400; and separating an upper discharge stream containing acrylic acid in the purification tower 400 and refluxing a lower discharge stream containing hydroxyacetone to the extraction tower 100.

[0014] Specifically, the conventional method for producing acrylic acid generally involves air oxidation of propylene, which is a method in which propylene is converted into acrolein by a gas-phase catalytic oxidation reaction, and this is then subjected to a gas-phase catalytic oxidation reaction to produce acrylic acid, and this method produces acetic acid as a by-product, which is problematic in that it is difficult to separate from acrylic acid. In addition, the method for producing acrylic acid using propylene uses propylene obtained by refining crude oil, a fossil resource, as a raw material, and in consideration of the recent rise in crude oil prices and problems such as global warming, there are problems in terms of raw material costs and environmental pollution.

[0015] In order to solve the problems of the conventional acrylic acid production method, research has been conducted on a method of producing acrylic acid from carbon-neutral biomass raw materials. For example, there is a method of producing acrylic acid (AA) by the gas-phase dehydration reaction of lactic acid (LA). This method generally produces acrylic acid by the intramolecular dehydration reaction of lactic acid at high temperature and in the presence of a catalyst. However, during the dehydration reaction of lactic acid, a side reaction occurs in addition to the dehydration reaction, which produces by-products other than acrylic acid as the reaction product, in particular hydroxyacetone (HA), which has a boiling point similar to that of acrylic acid. In this case, it is difficult to completely remove hydroxyacetone by distillation.

[0016] In the present invention, in order to solve the above-mentioned problems, acrylic acid is produced by dehydration of lactic acid, and an extraction method is used to completely remove the by-products generated thereby, particularly hydroxyacetone (boiling point: 145°C) which is difficult to separate because it has a similar boiling point to acrylic acid (boiling point: 141°C). Here, a method for completely removing hydroxyacetone and a method for minimizing the loss of acrylic acid are provided.

[0017] According to one embodiment of the present invention, a reaction product stream produced by dehydrating an aqueous lactic acid solution may be supplied to an extraction tower 100. Here, the reaction product may be a condensate condensed through a cooling tower.

[0018] Specifically, a reaction product containing acrylic acid can be produced by supplying an aqueous lactic acid solution to a reactor and carrying out a dehydration reaction. Here, the dehydration reaction can be carried out by a gas phase reaction in the presence of a catalyst. For example, the lactic acid concentration of the aqueous lactic acid 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.

[0019] The reactor may be a reactor capable of performing a normal dehydration reaction of lactic acid, and may include a reaction tube filled with a catalyst, and may produce acrylic acid by dehydrating lactic acid through a gas-phase contact reaction while passing a reaction gas containing a volatile component of the raw material lactic acid aqueous solution through the reaction tube. In addition to lactic acid, the reaction gas may further include one or more dilution gases selected from water vapor, nitrogen, and air for adjusting the concentration.

[0020] The reactor may be operated under normal lactic acid dehydration reaction conditions. Here, the reactor operating temperature may refer to the set temperature of a heat medium or the like used to control the temperature of the reactor.

[0021] The catalyst used in the dehydration reaction of lactic acid may include, for example, one or more selected from the group consisting of sulfate catalysts, phosphate catalysts, and nitrate catalysts. 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. The catalyst may also be supported on a support. The support may include, for example, one or more selected from the group consisting of diatomaceous earth, alumina, silica, titanium dioxide, carbide, and zeolite.

[0022] The reaction product produced by the dehydration reaction of lactic acid may contain by-products such as water (H2O) and hydroxyacetone in addition to the desired product, acrylic acid.

[0023] The reaction product can be cooled by supplying it to a cooling tower. Specifically, the reaction product produced by the dehydration reaction of lactic acid can be condensed in the gas phase through the cooling tower. Gas by-products can be separated at the top of the cooling tower, and liquid condensate can be discharged at the bottom, where the condensate can be the reaction product stream supplied to the extraction tower 100 in the present invention.

[0024] According to one embodiment of the present invention, extraction column 100 may use a separate extractant to separate the acrylic acid contained within the reaction product stream as an overhead draw stream.

[0025] The extractant may include, for example, one or more selected from the group consisting of benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptene, 1-heptene, ethylbenzene, methylcyclohexane, n-butyl acetate, isobutyl acetate, isobutyl acrylate, n-propyl acetate, isopropyl acetate, methyl isobutyl 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 isopropyl butyl ether. As a specific example, the extractant may be toluene.

[0026] The method of supplying the extractant to the extraction tower 100 for extraction can be any well-known method, such as cross current, counter current, co-current, etc., without any particular limitation.

[0027] In the extraction tower 100, the reaction product stream may be contacted with an extractant to separate an extract and a raffinate. For example, the extract may be acrylic acid dissolved in the extractant, and the extract may be discharged as an upper discharge stream from the extraction tower 100. Here, the upper discharge stream from the extraction tower 100 may be supplied to an extractant recovery tower 200.

[0028] In addition, the raffinate may be separated as wastewater containing water at the bottom of the extraction tower 100. Here, hydroxyacetone, which is a by-product, may be separated and discharged together with water at the bottom of the extraction tower 100, but not all of it may be discharged, and some of it may flow into the extraction liquid and be transferred to the subsequent stage together with acrylic acid. Specifically, the amount of extractant used may be adjusted to remove hydroxyacetone in the extraction tower 100, but it is difficult to remove all of the hydroxyacetone introduced even if the amount of extractant used is increased. In this case, the amount of acrylic acid discharged together with water at the bottom of the extraction tower 100 increases, which may cause a problem of increased loss of acrylic acid.

[0029] In contrast, in the present invention, the operating conditions of the downstream purification column 400 are controlled to effectively separate hydroxyacetone and reflux it to the extraction column 100, so that the entire amount of hydroxyacetone can be separated and removed as a bottom discharge stream of the extraction column 100, thereby minimizing the loss of acrylic acid.

[0030] For example, the ratio of the content of hydroxyacetone separated at the bottom of the extraction tower 100 to the content of hydroxyacetone contained in the reaction product stream may be 0.95 to 1, 0.97 to 1, or 0.99 to 1. Specifically, the total amount of hydroxyacetone contained in the reaction product stream supplied to the extraction tower 100 may be removed in the extraction tower 100. As a result, high-purity acrylic acid can be separated in the purification tower 400.

[0031] The top discharge stream of the extraction tower 100 may contain acrylic acid, and may further contain an extractant and hydroxyacetone. The content of hydroxyacetone 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 hydroxyacetone in the reaction product stream. Specifically, by controlling the content of hydroxyacetone 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 amount of energy used for separation in the purification tower 400 can be reduced.

[0032] According to one embodiment of the present invention, the top discharge stream of the extraction tower 100 is supplied to the extractant recovery tower 200, and the bottom discharge stream containing acrylic acid is separated in the extractant recovery tower 200 and supplied to the first separation tower 300. In addition, in the extractant recovery tower 200, the extractant can be separated as the top discharge stream, and a part of the top discharge stream of the extractant recovery tower 200 can be refluxed to the extraction tower 100 to reuse the extractant. Here, the bottom discharge stream of the extractant recovery tower 200 can contain low boiling point by-products, high boiling point by-products and hydroxyacetone as by-products in addition to acrylic acid.

[0033] The operating conditions of the extractant recovery column 200 vary depending on the content of the components supplied to the extractant recovery column 200 and the type of the extractant. The operating temperature of the extractant recovery column 200 may be, for example, 40°C to 150°C, 45°C to 130°C, or 50°C to 110°C. The operating pressure of the extractant recovery column 200 may be 35 torr to 300 torr, 70 torr to 250 torr, or 100 torr to 200 torr. When the extractant recovery column 200 is operated as described above, it is possible to suppress side reactions occurring at high temperatures and increase the recovery rate of acrylic acid.

[0034] According to an embodiment of the present invention, the first separation tower 300 may be for separating low boiling point by-products from the by-products contained in the reaction product. Specifically, the bottom discharge stream of the extractant recovery tower 200 may be supplied to the first separation tower 300, and the low boiling point by-products may be separated into an upper portion in the first separation tower 300, and a bottom discharge stream containing acrylic acid may be separated and supplied to the second separation tower 310.

[0035] According to an embodiment of the present invention, the second separation tower 310 may be for separating high boiling point by-products from the by-products contained in the reaction product. Specifically, the bottom discharge stream of the first separation tower 300 may be supplied to the second separation tower 310, where the high boiling point by-products may be separated into the bottom portion and the top discharge stream containing acrylic acid may be separated and supplied to the purification tower 400.

[0036] According to an embodiment of the present invention, the first separation column 300 and the second separation column 310 may each be an apparatus for separating components by distillation using the boiling point difference between the components. Here, low boiling point by-products and high boiling point by-products contained in the bottom discharge stream of the extractant recovery column 200 are removed through the first separation column 300 and the second separation column 310, but hydroxyacetone, which has a boiling point similar to that of acrylic acid, is not separated and is discharged together with acrylic acid as the top discharge stream in the second separation column 310 when separating acrylic acid. Therefore, when acrylic acid is commercialized as the top discharge stream of the second separation column 310, there is a problem that the purity of the product is low.

[0037] In contrast, in the present invention, the upper discharge stream from the second separation column 310 is supplied to the purification column 400, and the purification column 400 separates an upper discharge stream containing high-purity acrylic acid and a lower discharge stream containing hydroxyacetone and acrylic acid. The lower discharge stream from the purification column 400 is refluxed to the extraction column 100, whereby the total amount of hydroxyacetone is removed in the extraction column 100, and high-purity acrylic acid can be separated as the upper discharge stream from the purification column 400.

[0038] Specifically, hydroxyacetone, which is a by-product, can be separated and discharged together with water at the bottom of the extraction tower 100, but if the entire amount of hydroxyacetone is not discharged, the remaining hydroxyacetone flows into the extraction liquid and is transferred to the subsequent stage together with acrylic acid. In this case, since hydroxyacetone must be separated in the purification tower 400, a problem of a decrease in the amount of high-purity acrylic acid obtained may occur.

[0039] Meanwhile, in order to remove hydroxyacetone in the extraction tower 100, the amount of the extractant used can be adjusted. In this case, however, even if the amount of the extractant used is increased, it is difficult to remove all of the hydroxyacetone introduced. In particular, the amount of acrylic acid discharged together with water to the bottom of the extraction tower 100 increases, which may cause a problem of increased loss of acrylic acid.

[0040] Therefore, when hydroxyacetone is separated as a raffinate by extraction in the extraction column 100 by refluxing the bottom discharge stream of the purification column 400 containing hydroxyacetone to the extraction column 100, there is an advantage that not only can the total amount of hydroxyacetone introduced into the acrylic acid purification system be removed, but also high purity acrylic acid can be obtained in a large yield from the upper part of the purification column 400.

[0041] According to one embodiment of the present invention, the operating temperature of purification column 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 purification column 400 may be 35 torr to 500 torr, 70 torr to 350 torr, or 100 torr to 200 torr. When purification column 400 is operated as described above, there is no problem of acrylic acid loss due to side reactions, and high purity acrylic acid can be separated as an upper discharge stream, and a part of the acrylic acid can be discharged as a lower discharge stream while separating hydroxyacetone.

[0042] The top discharge stream of the second separation column 310 may be supplied to 50% to 90%, 55% to 85%, or 60% to 80% of the total number of stages of the purification column 400. By adjusting the number of stages supplied to the purification column 400 within the above range, the separation efficiency in the purification column 400 can be increased, and thus the composition of the bottom discharge stream of the purification column 400 that is refluxed to the extraction column 100 can be controlled. Here, the total number of stages of the purification column 400 may be 15 to 70 stages, 18 to 55 stages, or 20 to 35 stages.

[0043] The bottom discharge stream of the purification tower 400 may form a mixed stream with the reaction product stream and be supplied to the extraction tower 100. The reaction product stream forms a mixed stream with the bottom discharge stream of the purification tower 400, which is refluxed to the purification tower 400, and is supplied to the extraction tower 100, thereby minimizing the loss of acrylic acid and removing all of the hydroxyacetone at the bottom of the extraction tower 100.

[0044] According to one embodiment of the present invention, in the method for producing acrylic acid, if necessary, further devices such as a distillation column, a condenser, a reboiler, a valve, a pump, a separator and a mixer can be installed.

[0045] The method for producing acrylic acid according to the present invention has been described and illustrated in the drawings. However, the description and the drawings only describe and illustrate the essential components for understanding the present invention. In addition to the steps and apparatuses described and illustrated in the drawings, other steps and apparatuses not described or illustrated can be appropriately applied and used to carry out the method for producing acrylic acid according to the present invention.

[0046] The present invention will be described in more detail with reference to the following examples. However, the following examples are merely for the purpose of illustrating the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical idea of ​​the present invention, and the scope of the present invention is not limited to these examples.

[0047] Working Example Example 1 According to the process flow chart shown in FIG. 1, the acrylic acid production process was simulated using an Aspen Plus simulator manufactured by Aspen Corporation.

[0048] Specifically, a 50 wt% aqueous lactic acid solution and nitrogen (N2) as a dilution gas were supplied to a reactor, and a reaction product containing acrylic acid (AA) was produced by a dehydration reaction. The reactor discharge stream containing the reaction product was supplied to a cooling tower, where gas by-products were separated at the top, and the liquid phase reaction product, which was a condensate, was supplied to an extraction tower 100.

[0049] In the extraction tower 100, toluene was used as an extractant to separate acrylic acid as a top discharge stream and feed it to the extraction agent recovery tower 200, and water was separated at the bottom. Here, the operation temperature of the extraction tower 100 was controlled at 40° C., and the operation pressure was controlled at 750 torr.

[0050] The extractant was separated as an upper discharge stream in the extractant recovery column 200, and a part of the upper discharge stream of the extractant recovery column 200 was refluxed to the extraction column 100. In addition, the lower discharge stream of the extractant recovery column 200 containing the acrylic acid was supplied to the first separation column 300. Here, the operating temperature of the extractant recovery column 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.

[0051] In the first separation tower 300, low boiling by-products were separated at the top, and the bottom discharge stream containing acrylic acid was supplied to the second separation tower 310. In addition, in the second separation tower 310, high boiling by-products were separated at the bottom, and the top discharge stream containing acrylic acid was supplied to the 15th stage of the purification tower 400.

[0052] In the purification tower 400, high purity acrylic acid was separated at the top, and the bottom discharge stream containing by-products hydroxyacetone and acrylic acid was refluxed to the extraction tower 100. Here, the operating temperature of the purification tower 400 was controlled to 62.5°C at the top and 65.6°C at the bottom, the operating pressure was controlled to 110 torr, and the total number of stages of the purification tower 400 was 20.

[0053] The temperature and pressure of each stream and the flow rate (kg / hr) of each component in each stream are shown in Table 1 below.

[0054] [Table 1]

[0055] Example 2 The same procedure as in Example 1 was repeated, except that the concentration of the aqueous lactic acid solution was 20% by weight.

[0056] The temperature and pressure of each stream and the flow rate (kg / hr) of each component in each stream are shown in Table 2 below.

[0057] [Table 2]

[0058] Comparative Example Comparative Example 1 The acrylic acid production process was simulated using an Aspen Plus simulator manufactured by Aspen Corporation, according to the process flow chart shown in FIG.

[0059] Specifically, a 50 wt% aqueous lactic acid solution and nitrogen (N2) as a diluent gas were supplied to a reactor, and a reaction product containing acrylic acid (AA) was produced by a dehydration reaction. The reactor discharge stream containing the reaction product was supplied to a cooling tower, where gas by-products were separated at the top, and the liquid phase reaction product, which was a condensate, was supplied to an extraction tower 100.

[0060] In the extraction tower 100, toluene was used as an extractant, and acrylic acid was separated as a top discharge stream and fed to the extraction agent recovery tower 200, and water was separated at the bottom. Here, the operation temperature of the extraction tower 100 was controlled at 40° C., and the operation pressure was controlled at 750 torr.

[0061] The extractant was separated as an upper discharge stream in the extractant recovery column 200, and a part of the upper discharge stream of the extractant recovery column 200 was refluxed to the extraction column 100. The lower discharge stream of the extractant recovery column 200 containing the acrylic acid was supplied to the first separation column 300. Here, the operating temperature of the extractant recovery column 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.

[0062] In the first separation tower 300, low boiling point by-products were separated at the top, and the bottom 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 at the bottom, and acrylic acid was separated as the top discharge stream.

[0063] The temperature and pressure of each stream and the flow rate (kg / hr) of each component in each stream are shown in Table 3 below.

[0064] [Table 3]

[0065] Comparative Example 2 The same procedure as in Comparative Example 1 was carried out, except that the flow rate of the extractant supplied to the extraction tower 100 was controlled.

[0066] The temperature and pressure of each stream and the flow rate (kg / hr) of each component in each stream are shown in Table 4 below.

[0067] [Table 4]

[0068] Referring to Tables 1 to 4, in the case of Example 1 and Example 2 in which by-products are separated and acrylic acid is recovered in the method for producing acrylic acid according to the present invention, it was confirmed that the purity of the acrylic acid is 99% or more and the amount of acrylic acid lost in the extraction tower 100 is very small. In addition, it was confirmed that the entire amount of hydroxyacetone contained in the reaction product is discharged together with water from the extraction tower 100.

[0069] In comparison, Comparative Example 1 does not include the purification tower 400 compared to Example 1. It was confirmed that the amount of hydroxyacetone remaining in the top discharge stream of the second separation tower 310 was large, the purity of acrylic acid was low, and the amount of acrylic acid lost in the extraction tower 100 was increased.

[0070] In addition, in Comparative Example 2, the amount of extractant supplied to the extraction tower 100 in Comparative Example 1 was reduced in order to remove the entire amount of hydroxyacetone in the extraction tower 100. In this case, it was confirmed that the amount of acrylic acid discharged together with water from the extraction tower 100 and lost increased.

[0071] Comparative Example 3 The acrylic acid production process was simulated using an Aspen Plus simulator manufactured by Aspen Corporation, according to the process flow chart shown in FIG.

[0072] The same procedure as in Example 1 was carried out, except that the bottom discharge stream from the purification column 400 was discharged to the extraction column 100 instead of being refluxed thereto.

[0073] The temperature and pressure of each stream and the flow rate (kg / hr) of each component in each stream are shown in Table 5 below.

[0074] [Table 5]

[0075] Comparative Example 4 The same method as in Comparative Example 3 was performed, except that the flow rate of the extractant supplied to the extraction tower 100 was controlled.

[0076] The temperature and pressure of each stream and the flow rate (kg / hr) of each component in each stream are shown in Table 6 below.

[0077] [Table 6]

[0078] Referring to Tables 1-2 and Tables 5-6, in the case of Example 1 and Example 2 in which by-products are separated and acrylic acid is recovered in the method for producing acrylic acid according to the present invention, it was confirmed that the purity of the acrylic acid is 99% or more and the amount of acrylic acid lost in the extraction tower 100 is very small. In addition, it was confirmed that the entire amount of hydroxyacetone contained in the reaction product is discharged together with water from the extraction tower 100.

[0079] In comparison, in Comparative Examples 3 and 4, the bottom discharge stream of purification tower 400 was not refluxed to extraction tower 100 as compared to Example 1, and it was confirmed that the by-product hydroxyacetone contained in the stream introduced into extraction tower 100 was not entirely discharged as the bottom discharge stream of extraction tower 100. When hydroxyacetone not discharged as the bottom discharge stream of extraction tower 100 was discharged from the bottom of purification tower 400 to prevent accumulation in the system, it was confirmed that a loss of some acrylic acid occurred from the bottom of purification tower 400.

[0080] In addition, in Comparative Example 4, the amount of extractant supplied to extraction tower 100 was doubled in order to remove all of the hydroxyacetone in extraction tower 100 of Comparative Example 3. In this case, it was confirmed that even if the amount of toluene, which is the extractant, was increased, the entire amount of hydroxyacetone could not be discharged from extraction tower 100, and the amount of acrylic acid discharged together with water and lost increased. In particular, it can be seen that the mass flow rate of acrylic acid lost from the bottom of extraction tower 100 in Comparative Example 4 increases by about 35% compared to the mass flow rate of acrylic acid lost from the bottom of extraction tower 100 in Example 1.

[0081] Furthermore, in the case of Comparative Examples 3 and 4, in which the bottom 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 top of the purification tower 400, but it can be confirmed that the amount of high purity acrylic acid obtained was reduced compared to Examples 1 and 2.

Claims

1. Feeding a reaction product stream produced by dehydrating an aqueous lactic acid solution to an extraction tower, the reaction product stream comprising acrylic acid, water, low boiling by-products, high boiling by-products and hydroxyacetone; using an extractant in the extraction column to separate an overhead stream comprising acrylic acid and supplying the overhead stream to an extractant recovery column; Separating a bottoms effluent stream containing acrylic acid in the extractant recovery column and feeding the bottoms effluent stream to a first separation column; Separating the low-boiling by-products having a boiling point lower than that of acrylic acid in the first separation tower by distillation to the top, and separating the bottom discharge stream containing acrylic acid by distillation to supply it to a second separation tower; separating the high-boiling by-products having a boiling point higher than that of hydroxyacetone by distillation in the second separation column and feeding the top discharge stream containing acrylic acid to a purification column; separating an upper output stream containing acrylic acid from the purification column and a lower output stream containing hydroxyacetone being refluxed to the extraction column; A method for producing acrylic acid, comprising:

2. 2. The method for producing acrylic acid according to claim 1, wherein water and hydroxyacetone are separated in the lower part of the extraction column.

3. 3. The method for producing acrylic acid according to claim 2, wherein the ratio of the content of hydroxyacetone separated in the lower part of the extraction tower to the content of hydroxyacetone contained in the reaction product stream is 0.95 to 1.

4. 2. The method for producing acrylic acid according to claim 1, wherein a part of the top discharge stream containing the extractant in the extractant recovery tower is refluxed to the extraction tower.

5. The extractant is one or more selected from the group consisting of benzene, toluene, xylene, n-heptane, cycloheptane, cycloheptene, 1-heptene, ethylbenzene, methylcyclohexane, n-butyl acetate, isobutyl acetate, isobutyl acrylate, n-propyl acetate, isopropyl acetate, methyl isobutyl 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 isopropyl butyl ether. The method for producing acrylic acid according to claim 1.

6. 2. The method for producing acrylic acid according to claim 1, wherein the reaction product stream is a condensate condensed through a cooling tower.

7. 2. The method for producing acrylic acid according to claim 1, wherein the content of hydroxyacetone in the top discharge stream of the extraction tower is 0.2% to 15% of the content of hydroxyacetone in the reaction product stream.

8. The method for producing acrylic acid according to claim 1, wherein the bottom discharge stream of the extractant recovery tower is supplied to 50% to 90% of the total number of stages of the purification tower.

9. The method for producing acrylic acid according to claim 1, wherein the operating temperature of the extractant recovery tower is 40° C. to 150° C., and the operating pressure is 35 torr to 300 torr.

10. 2. The method for producing acrylic acid according to claim 1, wherein the operation temperature of the purification column is 60° C. to 200° C. and the operation pressure is 35 torr to 500 torr.

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