Method for preparing acrylic acid

Abstract

Provided is a method for preparing an acrylic acid including: supplying a lactic acid aqueous solution to a reactor and performing a dehydration reaction to prepare a reaction product including an acrylic acid; supplying a reactor discharge stream including the reaction product to a first cooling tower and supplying an upper discharge stream from the first cooling tower to a second cooling tower; supplying a first acrylic acid aqueous solution stream discharged from a lower portion of the second cooling tower to an extraction column; supplying an upper discharge stream from the extraction column and a second acrylic acid aqueous solution stream discharged from a lower portion of the first cooling tower to a distillation column; and separating the acrylic acid from a lower discharge stream from the distillation column.

Description

Acrylic acid manufacturing method

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2021-0137933, filed October 15, 2021, 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 reducing the loss of acrylic acid and saving energy used in producing acrylic acid through a dehydration reaction of lactic acid.

[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 typically produces acrylic acid through an intramolecular dehydration reaction of lactic acid at high temperatures (over 300°C) and in the presence of a catalyst. However, when lactic acid is used at high concentrations, oligomers such as dimers and trimers are generated, which reduces the concentration of lactic acid participating in the reaction. Furthermore, when the lactic acid concentration is lowered, the amount of water generated increases significantly, leading to the problem of increased energy consumption for water removal.

[0008] The problem to be solved in the present invention is to provide a method for reducing the energy required to separate and remove water during the production of acrylic acid through a dehydration reaction of lactic acid and minimizing the loss of acrylic acid in order to solve the problems mentioned in the technology that forms the background of the above 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 lactic acid aqueous solution to a reactor and performing a dehydration reaction to produce a reaction product containing acrylic acid; supplying a reactor discharge stream containing the reaction product to a first cooling tower, and supplying an upper discharge stream of the first cooling tower to a second cooling tower; supplying a first acrylic acid aqueous solution stream discharged from a lower portion of the second cooling tower to an extraction tower; supplying an upper discharge stream of the extraction tower and a second acrylic acid aqueous solution stream discharged from a lower portion of the first cooling tower to a distillation tower; and separating acrylic acid from a lower discharge stream of the distillation tower.

[0010] According to the method for producing acrylic acid of the present invention, a reaction product containing acrylic acid is separated into a first acrylic acid aqueous solution stream and a second acrylic acid aqueous solution stream having compositions advantageous for separation in a distillation tower and an extraction tower, respectively, using two cooling towers, and supplied to the extraction tower and the distillation tower, respectively, thereby reducing energy usage for water separation and reducing loss of acrylic acid.

[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 the comparative example, respectively.

[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 may include the steps of: supplying a lactic acid aqueous solution to a reactor and subjecting it to a dehydration reaction to produce a reaction product containing acrylic acid; supplying a reactor discharge stream containing the reaction product to a first cooling tower (100), and supplying an upper discharge stream of the first cooling tower (100) to a second cooling tower (110); supplying a first acrylic acid aqueous solution stream discharged from the lower portion of the second cooling tower (110) to an extraction tower (200); supplying an upper discharge stream of the extraction tower (200) and a second acrylic acid aqueous solution stream discharged from the lower portion of the first cooling tower (100) to a distillation tower (300); and separating acrylic acid from a lower discharge stream of the distillation tower (300).

[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 generally produces acrylic acid through an intramolecular dehydration reaction of lactic acid at high temperatures and in the presence of a catalyst. However, when a high-concentration aqueous lactic acid solution is used as a raw material, oligomers such as dimers and trimers are formed through an equilibrium reaction, which reduces the content of lactic acid monomers participating in the reaction. In addition, when a low-concentration aqueous lactic acid solution is used as a raw material, the water content in the reaction product of the lactic acid dehydration reaction is significantly higher than that in the conventional process for producing acrylic acid through propylene oxidation. This significantly increases the energy consumption required for water separation.

[0020] Accordingly, in order to solve the above-mentioned conventional problem, the present invention provides a method for producing acrylic acid through a dehydration reaction of lactic acid, while reducing the amount of energy required for water separation and minimizing the loss of acrylic acid.

[0021] According to one embodiment of the present invention, lactic acid can be supplied to a reactor and dehydrated to produce a reaction product containing acrylic acid. At this time, the lactic acid can be supplied to the reactor in the form of an aqueous solution, and 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The reaction product manufactured through the dehydration reaction of the above lactic acid may further include by-products such as water (H2O), acetaldehyde (ACHO), carbon monoxide (CO), carbon dioxide (CO2), diluted gas, low-boiling point substances, and high-boiling point substances in addition to the desired product, acrylic acid.

[0026] The ratio of water content to acrylic acid content in the above reaction product may be 2.0 or more, 2.3 or more, or 2.5 or more, and 2.6 or less, 3.0 or less, 3.3 or less, or 3.5 or less. When a reaction product having a ratio of water content to acrylic acid content within the above range is prepared and acrylic acid is separated from the reaction product by the method according to the present invention, water can be effectively separated using less energy, and the amount of acrylic acid loss can be reduced, thereby increasing the recovery rate.

[0027] According to one embodiment of the present invention, the reactor discharge stream containing the reaction product can be supplied to the first cooling tower (100) for cooling. Specifically, since the reactor discharge stream containing the reaction product is discharged in a gaseous state, it can be supplied to the first cooling tower (100) for condensation. The condensate condensed in this process is discharged as a lower discharge stream of the first cooling tower (100), and the upper discharge stream of the first cooling tower (100) containing a gaseous component can be supplied to the second cooling tower (110).

[0028] A portion of the bottom discharge stream of the first cooling tower (100) may be refluxed to the first cooling tower (100) through a cooler, and the remaining stream may be supplied to the distillation tower (300) as a second acrylic acid aqueous solution stream.

[0029]

[0030] The upper discharge stream of the first cooling tower (100) may include water, acrylic acid, and gas components, and the second acrylic acid aqueous solution stream may include water and acrylic acid. The upper discharge stream of the first cooling tower (100) may have a higher water content and a lower acrylic acid content than the second acrylic acid aqueous solution stream.

[0031] The ratio of the water content to the acrylic acid content of the second acrylic acid aqueous solution stream may be, for example, 1.0 or more, 1.2 or more, or 1.4 or more, and 1.8 or less, 1.9 or less, 2.0 or less, or 2.1 or less. By controlling the composition of the second acrylic acid aqueous solution stream within the above range, it may be advantageous in terms of energy and prevention of acrylic acid loss during separation by supplying it to the distillation tower (300) without passing through the extraction tower (200).

[0032] According to one embodiment of the present invention, the upper discharge stream of the first cooling tower (100) is supplied to the second cooling tower (110), and gas components can be removed in the second cooling tower (110). Specifically, the upper discharge stream of the first cooling tower (100) supplied to the second cooling tower (110) is a gaseous component, and can be condensed in the second cooling tower (110). The condensate condensed in this process can be discharged to the lower portion of the second cooling tower (110) as the first acrylic acid aqueous solution stream and supplied to the extraction tower (200). Specifically, a portion of the first acrylic acid aqueous solution stream can be refluxed to the second cooling tower (110) through a cooler, and the remaining stream can be supplied to the extraction tower (200).

[0033] In addition, the second cooling tower (110) can separate and remove gas components upward, and the gas components can include acetaldehyde along with water, carbon monoxide, carbon dioxide, and dilution gas. When separating the gas components upward of the second cooling tower (110), a small amount of acrylic acid can be separated together. In the present invention, the reaction product including acrylic acid is separated using two cooling towers, thereby minimizing the amount of acrylic acid lost by being discharged together with the gas components.

[0034] The operating temperature of the second cooling tower (110) may be 40°C or higher, 50°C or higher, or 60°C or higher and 130°C or lower, 150°C or lower, or 200°C or lower, and the operating pressure may be 1 kg / cm 2 Above, 1.5 kg / cm 2 or more than 2 kg / cm 2 Above and 5 kg / cm 2 Below 10 kg / cm 2 Less than or equal to 20 kg / cm 2 It may be as follows. By controlling the operating conditions of the second cooling tower (110) with the operating temperature and operating pressure within the above range, the composition of the gas component separated into the upper portion of the second cooling tower (110) can be controlled, thereby minimizing the loss of acrylic acid while simultaneously removing the diluted gas and acetaldehyde to the outside of the system, and the composition of the first acrylic acid aqueous solution stream discharged from the lower portion of the second cooling tower (110) can be controlled.

[0035] The ratio of the water content to the acrylic acid content of the first acrylic acid aqueous solution stream may be, for example, 3.0 or more, 3.1 or more, 3.2 or more, or 3.3 or more, and 3.8 or less, 4.0 or less, or 4.5 or less. By controlling the composition of the second acrylic acid aqueous solution stream within the above range, the composition of the first acrylic acid aqueous solution stream can be controlled to a composition that is advantageous in terms of energy and in terms of preventing acrylic acid loss during separation by supplying it to the distillation tower (300) after passing through the extraction tower (200).

[0036] According to one embodiment of the present invention, the first acrylic acid aqueous solution stream is supplied to an extraction tower (200), and acrylic acid and water can be separated using an extractant in the extraction tower (200). Specifically, an extractant may be supplied to the extraction tower (200), and the extractant may include at least one selected from the group consisting of, for example, 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.

[0037] In the above extraction tower (200), the first acrylic acid aqueous solution 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 an upper discharge stream of the extraction tower (200). In addition, the raffinate is wastewater containing water, and may be separated as a lower discharge stream of the extraction tower (200). At this time, the lower discharge stream of the extraction tower (200) may contain a small amount of acrylic acid in addition to water. In the present invention, the reaction product containing acrylic acid is separated into a first acrylic acid aqueous solution stream and a second acrylic acid aqueous solution stream having compositions advantageous for separation in each of the distillation tower (300) and the extraction tower (200) using two cooling towers, and the streams are supplied to the extraction tower (200) and the distillation tower (300), respectively, thereby minimizing the loss of acrylic acid discharged in the wastewater.

[0038] According to one embodiment of the present invention, the upper discharge stream of the extraction tower (200) and the second acrylic acid aqueous solution stream discharged from the lower portion of the first cooling tower (100) can be supplied to a distillation tower (300) to separate components through distillation.

[0039] The upper discharge stream of the extraction tower (200) and the second acrylic acid aqueous solution stream can form a mixed stream and be supplied to the distillation tower (300). By supplying the mixed stream having a flow rate ratio within the above range to the distillation tower (300), the amount of energy required for separation in the distillation tower (300) can be reduced, and water and acrylic acid can be separated using the extractant included in the upper discharge stream of the extraction tower (200) without using an additional azeotropic agent.

[0040] The distillation tower (300) can separate the extractant contained in the mixed stream into the upper portion and recycle it to the extraction tower (200) for reuse. In addition, the distillation tower (300) can separate the acrylic acid contained in the mixed stream into a bottom discharge stream and separate the water into a side discharge stream.

[0041] The operating temperature of the distillation tower (300) may be 10°C or higher, 20°C or higher, or 40°C or higher and 100°C or lower, 120°C or lower, or 150°C or lower, and the operating pressure may be 10 torr or higher, 50 torr or higher, or 100 torr or higher and 200 torr or lower, 300 torr or lower, or 500 torr or lower. By controlling the operating conditions of the distillation tower (300) with the operating temperature and operating pressure within the above ranges, the extractant can be effectively separated from the upper portion of the distillation tower (300), water from the side, and acrylic acid from the lower portion.

[0042] The bottom discharge stream of the distillation tower (300) may contain acrylic acid and a small amount of byproducts. Therefore, if necessary, the bottom discharge stream of the distillation tower (300) may be supplied to a purification unit to remove byproducts, thereby obtaining high-purity acrylic acid.

[0043] 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.

[0044] 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.

[0045]

[0046] 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.

[0047]

[0048] Example

[0049] Example 1

[0050] According to the process flow diagram shown in Fig. 1, the acrylic acid manufacturing process was simulated using Aspen Plus simulator from Aspen.

[0051] Specifically, a reaction product including acrylic acid (AA) was produced through a dehydration reaction by supplying a lactic acid aqueous solution and nitrogen (N2) as a dilution gas to a reactor, and at this time, the content of water relative to acrylic acid in the reaction product was adjusted to be 2.5 times.

[0052] The reactor discharge stream containing the above reaction product was supplied to the first cooling tower (100), and a portion of the bottom discharge stream of the first cooling tower (100) was refluxed to the first cooling tower (100) through a cooler, and the remaining stream, i.e., the second acrylic acid aqueous solution stream, was supplied to the distillation tower (300). At this time, the operating temperature of the first cooling tower (100) was controlled to 114°C at the top and 117°C at the bottom, and the operating pressure was 2 kg / cm 2 Controlled by .

[0053] The reactor discharge stream was condensed in the first cooling tower (100), the upper discharge stream of the first cooling tower (100) was supplied to the second cooling tower (110), the gas component was discharged upward from the second cooling tower (110), a portion of the lower discharge stream of the second cooling tower (110) was refluxed to the second cooling tower (110) through a cooler, and the remaining stream, i.e., the first acrylic acid aqueous solution stream, was supplied to the extraction tower (200). At this time, the operating temperature of the second cooling tower (110) was controlled to 88°C at the upper portion and 113°C at the lower portion, and the operating pressure was 2 kg / cm 2 Controlled by .

[0054] In the above extraction tower (200), acrylic acid was dissolved using toluene as an extractant, and then separated into an upper discharge stream from the extraction tower (200), and water was separated into a lower discharge stream.

[0055] The upper discharge stream of the above extraction tower (200) and the second acrylic acid aqueous solution stream formed a mixed stream and were supplied to the distillation tower (300).

[0056] In the distillation tower (300), the extractant was separated from the top and refluxed to the extraction tower (200), and a side discharge stream containing water and a bottom discharge stream containing acrylic acid were separated.

[0057] At this time, the flow rate (kg / hr) of each component in each stream is shown in Table 1 below.

[0058] 123456789N2101.2101.2101.20.00.00.00.00.00.0CO / CO228.528.528.50.00.00.00.00. 00.0ACHO14.013.813.60.20.10.22.60.20.0H2O597.3309.738.5271.1287.6268.20.6290. 50.0AA240.580.86.474.4159.74.40.40.3229.4Byproduct18.57.90.97.010.61.93.82.013.7Toluene0.00.00.00.00.00.2781.90.20.0Total1000.0541.9189.1352.7458.0274.9789.3293.2243.1

[0059] The above total is the value obtained from the Aspen Plus simulator, rounded to the first decimal place.

[0060] Referring to Table 1 above, in the case of Example 1, the ratio of water content to acrylic acid content of the first acrylic acid aqueous solution stream was 3.6, the ratio of water content to acrylic acid content of the second acrylic acid aqueous solution stream was 1.8, and when separating the gas component to the upper part of the second cooling tower (110), the amount of acrylic acid loss was 6.4 kg / hr, and when removing water to the lower part of the extraction tower (200), the amount of acrylic acid loss was 4.4 kg / hr.

[0061] Additionally, the energy consumption used in the distillation tower (300) was confirmed to be 0.370 Gcal / hr.

[0062] In addition, the acrylic acid recovery rate in the above Example 1 was calculated through the ratio of the acrylic acid flow rate of the bottom discharge stream of the distillation tower (300) to the acrylic acid flow rate of the reactor discharge stream, and the acrylic acid recovery rate was found to be 95.4%.

[0063]

[0064] Example 2

[0065] According to the process flow diagram shown in Fig. 1, the acrylic acid manufacturing process was simulated using Aspen Plus simulator from Aspen.

[0066] Specifically, a lactic acid aqueous solution was supplied to the reactor to produce a reaction product containing acrylic acid (AA) through a dehydration reaction, and at this time, the content of water relative to acrylic acid in the reaction product was adjusted to be three times that of water.

[0067] The reactor discharge stream containing the above reaction product was supplied to the first cooling tower (100), and a portion of the bottom discharge stream of the first cooling tower (100) was refluxed to the first cooling tower (100) through a cooler, and the remaining stream, i.e., the second acrylic acid aqueous solution stream, was supplied to the distillation tower (300). At this time, the operating temperature of the first cooling tower (100) was controlled to 126°C at the top and 127°C at the bottom, and the operating pressure was 3 kg / cm 2 Controlled by .

[0068] The reactor discharge stream was condensed in the first cooling tower (100), the upper discharge stream of the first cooling tower (100) was supplied to the second cooling tower (110), the gas component was discharged upward from the second cooling tower (110), a portion of the lower discharge stream of the second cooling tower (110) was refluxed to the second cooling tower (110) through a cooler, and the remaining stream, i.e., the first acrylic acid aqueous solution stream, was supplied to the extraction tower (200). At this time, the operating temperature of the second cooling tower (110) was controlled to 109°C at the upper portion and 122°C at the lower portion, and the operating pressure was 3 kg / cm 2 Controlled by .

[0069] In the above extraction tower (200), acrylic acid was dissolved using toluene as an extractant, and then separated into an upper discharge stream from the extraction tower (200), and water was separated into a lower discharge stream.

[0070] The upper discharge stream of the above extraction tower (200) and the second acrylic acid aqueous solution stream formed a mixed stream and were supplied to the distillation tower (300).

[0071] In the distillation tower (300), the extractant was separated from the top and refluxed to the extraction tower (200), and a side discharge stream containing water and a bottom discharge stream containing acrylic acid were separated.

[0072] At this time, the flow rate (kg / hr) of each component in each stream is shown in Table 2 below.

[0073] 123456789N20.00.00.00.00.00.00.00.00.0CO / CO227.727.727.70.00.00.00.00.00.0AC HO13.613.513.30.20.10.22.80.10.0H2O702.0404.730.3374.3297.3370.80.9300.90.0A A234.098.14.993.2135.95.20.60.4223.5Byproduct22.711.20.810.411.54.79.63.713.5Toluene0.00.00.00.00.00.31092.30.20.0Total1000.0555.277.0478.1444.8381.21106.2305.3237.0

[0074] Referring to Table 2 above, in the case of Example 2, the ratio of water content to acrylic acid content of the first acrylic acid aqueous solution stream was 4.0, the ratio of water content to acrylic acid content of the second acrylic acid aqueous solution stream was 2.2, and when separating the gas component to the upper part of the second cooling tower (110), the amount of acrylic acid loss was 4.9 kg / hr, and when removing water to the lower part of the extraction tower (200), the amount of acrylic acid loss was 5.2 kg / hr.

[0075] Additionally, the energy consumption used in the distillation tower (300) was confirmed to be 0.458 Gcal / hr.

[0076] Additionally, the acrylic acid recovery rate in Example 2 was found to be 95.5%.

[0077]

[0078] Comparative example

[0079] Comparative Example 1

[0080] According to the process flow diagram shown in Fig. 2, the acrylic acid manufacturing process was simulated using Aspen Plus simulator from Aspen.

[0081] Specifically, a reaction product including acrylic acid (AA) was produced through a dehydration reaction by supplying a lactic acid aqueous solution and nitrogen (N2) as a dilution gas to a reactor, and at this time, the content of water relative to acrylic acid in the reaction product was adjusted to be 2.5 times.

[0082] The reactor discharge stream containing the above reaction product was supplied to a cooling tower (120), and some of the bottom discharge stream of the cooling tower (120) was refluxed to the cooling tower (120) through a cooler, and the remaining stream was supplied to an azeotropic distillation tower (400), and the gas component was discharged to the top of the cooling tower (120). At this time, the operating temperature of the cooling tower (120) was controlled to 89°C at the top and 117°C at the bottom, and the operating pressure was 2 kg / cm 2 was controlled by .

[0083] In the above azeotropic distillation tower (400), toluene was used as an azeotropic agent, the azeotropic agent was separated from the upper discharge stream and refluxed to the azeotropic distillation tower (400), water was separated from the remaining stream, and a bottom discharge stream containing acrylic acid was separated.

[0084] At this time, the flow rate (kg / hr) of each component in each stream is shown in Table 3 below.

[0085] 12345N2101.2101.20.00.00.0CO / CO228.528.50.00.00.0ACHO14.013.70.20.30.0H2O597.238.9558.3558.30.0AA240.58.2232.32.0230.3Byproduct18.50.917.63.913.7Toluene0.00.00.00.40.0Total999.9191.4808.4564.9244.0

[0086] Referring to Table 3 above, in the case of Comparative Example 1, the ratio of water content to acrylic acid content of the stream supplied to the azeotropic distillation tower (400) was confirmed to be 2.4, and when separating the gas component to the upper part of the cooling tower (120), the loss of acrylic acid was 8.2 kg / hr, and when removing water to the upper part of the azeotropic distillation tower (400), the loss of acrylic acid was confirmed to be 2.0 kg / hr.

[0087] Additionally, the energy consumption used in the azeotropic distillation tower (400) was confirmed to be 0.697 Gcal / hr.

[0088] In addition, the acrylic acid recovery rate in the above comparative example 1 was calculated through the ratio of the acrylic acid flow rate of the bottom discharge stream of the azeotropic distillation tower (400) to the acrylic acid flow rate of the reactor discharge stream, and the acrylic acid recovery rate was found to be 95.8%.

[0089] In this case, it was confirmed that the energy consumption used in the azeotropic distillation tower (400) increased compared to Examples 1 and 2 by supplying the entire lower discharge stream of the cooling tower (120) to the azeotropic distillation tower (400) to azeotropically distill water and acrylic acid.

[0090]

[0091] Comparative Example 2

[0092] According to the process flow diagram shown in Fig. 3, the acrylic acid manufacturing process was simulated using Aspen Plus simulator from Aspen.

[0093] Specifically, a reaction product including acrylic acid (AA) was produced through a dehydration reaction by supplying a lactic acid aqueous solution and nitrogen (N2) as a dilution gas to a reactor, and at this time, the content of water relative to acrylic acid in the reaction product was adjusted to be 2.5 times.

[0094] The reactor discharge stream containing the above reaction product was supplied to a cooling tower (120), and some of the lower discharge streams of the cooling tower (120) were refluxed to the cooling tower (120) through a cooler, and the remaining streams were branched into a first stream and a second stream, and the first stream was supplied to an extraction tower (200), and the second stream was supplied to a distillation tower (300). In addition, the gas component was discharged to the upper part of the cooling tower (120). At this time, the operating temperature of the cooling tower (120) was controlled to 89°C at the upper part and 117°C at the lower part, and the operating pressure was 2 kg / cm 2 was controlled by .

[0095] In the above extraction tower (200), acrylic acid was dissolved using toluene as an extractant, and then separated into an upper discharge stream from the extraction tower (200), and water was separated into a lower discharge stream.

[0096] The upper discharge stream of the above extraction tower (200) was supplied to the distillation tower (300) together with the second stream, and the extractant was separated from the upper portion of the distillation tower (300) and refluxed to the extraction tower (200), and a side discharge stream containing water and a bottom discharge stream containing acrylic acid were separated.

[0097] At this time, the flow rate (kg / hr) of each component in each stream is shown in Table 4 below.

[0098] 123456789N2101.2101.20.00.00.00.00.00.00.0CO / CO228.528.50.00.00.00.00.00.00. 0ACHO14.013.70.20.10.10.11.70.10.0H2O597.338.9558.4287.6270.8266.20.6292.20.0 AA240.58.2232.4119.7112.711.40.30.3220.6Byproduct18.50.917.69.18.51.93.71.913.7Toluene0.00.00.00.00.00.2781.90.20.0Total1000.0191.4808.6416.5392.1279.8788.2294.7234.3

[0099] Referring to Table 4 above, in the case of Comparative Example 2, the ratio of water content to acrylic acid content of the stream supplied to the extraction tower (200) and the stream supplied to the azeotropic distillation tower (400) was confirmed to be the same at 2.4, and when separating the gas component to the upper part of the cooling tower (120), the amount of acrylic acid loss was 8.2 kg / hr, and when removing water to the lower part of the extraction tower (200), the amount of acrylic acid loss was confirmed to be 11.4 kg / hr.

[0100] Additionally, the energy consumption used in the distillation tower (300) was confirmed to be 0.380 Gcal / hr.

[0101] In addition, the acrylic acid recovery rate in the above comparative example 2 was calculated through the ratio of the acrylic acid flow rate of the bottom discharge stream of the distillation tower (300) to the acrylic acid flow rate of the reactor discharge stream, and the acrylic acid recovery rate was found to be 91.7%.

[0102] In this case, the cooling tower (120) of the first unit was used, and the gas component was removed from the upper portion of the cooling tower (120), so that the amount of acrylic acid loss increased compared to Examples 1 and 2 when the gas component was removed from the cooling tower (120), and the lower discharge stream of the cooling tower (120) was branched and separately supplied to the extraction tower (200) and the distillation tower (300), so that the ratio of the water content to the acrylic acid content of the stream supplied to the extraction tower (200) and the distillation tower (300) could not be controlled, so that the amount of acrylic acid loss increased compared to Examples 1 and 2 when water was removed from the extraction tower (200).

Claims

1. A step of supplying a lactic acid aqueous solution to a reactor and performing a dehydration reaction to produce a reaction product containing acrylic acid; A step of supplying a reactor discharge stream containing the above reaction product to a first cooling tower, and supplying an upper discharge stream of the first cooling tower to a second cooling tower; A step of supplying a first acrylic acid aqueous solution stream discharged from the lower portion of the second cooling tower to an extraction tower; A step of supplying the upper discharge stream of the above extraction tower and the second acrylic acid aqueous solution stream discharged from the lower portion of the first cooling tower to a distillation tower; and A method for producing acrylic acid, comprising the step of separating acrylic acid from a bottom discharge stream of the distillation tower.

2. In paragraph 1, A method for producing acrylic acid, wherein the ratio of water content to acrylic acid content of the first acrylic acid aqueous solution stream is 3.0 to 4.

5.

3. In paragraph 1, A method for producing acrylic acid, wherein the ratio of water content to acrylic acid content of the second acrylic acid aqueous solution stream is 1.0 to 2.

1.

4. In paragraph 1, A method for producing acrylic acid, wherein the upper discharge stream of the above extraction tower and the second acrylic acid aqueous solution stream form a mixed stream and are supplied to a distillation tower.

5. In paragraph 1, A method for producing acrylic acid by separating gas components into the upper portion of the second cooling tower.

6. In paragraph 5, The above gas component is a method for producing acrylic acid containing acetaldehyde.

7. In paragraph 1, A method for producing acrylic acid, wherein an extractant is supplied to the above extraction tower, the extractant is discharged as an upper discharge stream of the extraction tower, supplied to the distillation tower, and separated from the upper portion of the distillation tower and circulated to the extraction tower.

8. In paragraph 1, A method for producing acrylic acid by separating water from the bottom discharge stream of the above extraction tower.

9. In paragraph 1, A method for producing acrylic acid by separating water from a side discharge stream of the distillation tower.

10. In paragraph 1, A method for producing acrylic acid, wherein the ratio of water content to acrylic acid content in the above reaction product is 2.0 to 3.

5.

11. In paragraph 1, The operating temperature of each of the first cooling tower and the second cooling tower is 40°C to 200°C, and the operating pressure is 1 kg / cm 2 Up to 20 kg / cm 2 Method for manufacturing acrylic acid.