Method for producing acrylic acid

Abstract

The present disclosure provides a novel method for producing acrylic acid which uses ethanol as a starting material and which makes it possible to suppress the production cost thereof. The above is achieved by a novel method for producing acrylic acid, the method including an acetone synthesis step (1), an acetone separation step (2), an acetone distillation step (3), a hydrogen separation step (4), an isopropanol synthesis step (5), an isopropanol separation step (6), a propylene synthesis step (7), a propylene separation step (8), an acrylic acid synthesis step (9), an acrylic acid absorption step (10), and an acrylic acid purification step (11).

Description

Acrylic acid manufacturing method

[0001] The present invention relates to a method for producing acrylic acid. More specifically, the present invention relates to a method for producing acrylic acid using ethanol as a raw material.

[0002] Acrylic acid is an important industrial substance used as a raw material for water-absorbent resins, acrylic esters, fiber modifiers, and flocculants, and its global demand is expected to continue to expand. Currently, the production process for acrylic acid is a two-stage gas-phase oxidation process in which propylene is oxidized to acrylic acid via acrolein. Propylene is primarily produced as a by-product of petroleum cracking, but from the perspective of carbon neutrality, technologies for producing acrylic acid from raw materials not derived from fossil fuels (e.g., biomass raw materials) have been proposed.

[0003] For example, Japanese Patent Application Laid-Open Nos. 2015-160806 and 2015-160807 disclose methods for producing acrylic acid or acrolein by using isopropanol obtained by fermentation as a raw material, vaporizing the gas by heating, and then partially oxidizing the gas in the presence of oxygen using a partial oxidation catalyst.

[0004] In recent years, the problem of fossil fuel depletion has become more serious, and the prices of fossil fuels have been rising sharply. For this reason, there has been a growing demand for reducing production costs in the production of acrylic acid. Furthermore, from the perspective of carbon neutrality, studies have been promoted to convert the raw materials for industrial products such as acrylic acid from fossil fuels to bioethanol. However, when producing acrylic acid using bioethanol as a raw material, there are still problems such as the high cost of the raw material bioethanol, as well as the high production cost of the process from ethanol to acrylic acid.

[0005] Therefore, an object of the present invention is to provide a novel method for producing acrylic acid using ethanol as a raw material, which can reduce the production cost.

[0006] The above-mentioned object of the present invention is achieved by the following means: [1] A method for producing acrylic acid, comprising the following steps (1) to (11): an acetone synthesis step (1) of reacting ethanol with water (a) to obtain a mixed gas (A) containing acetone, water vapor, carbon dioxide, and hydrogen; an acetone separation step (2) of separating an acetone-containing aqueous solution and a mixed gas (B) containing carbon dioxide and hydrogen from the mixed gas (A); an acetone distillation step (3) of distilling the acetone-containing aqueous solution to separate acetone and water (c); a hydrogen separation step (4) of separating hydrogen from the mixed gas (B); an isopropanol synthesis step (5) of reacting the acetone obtained in the acetone distillation step (3) with the hydrogen obtained in the hydrogen separation step (4) to obtain a mixed gas (C) containing isopropanol; and an isopropanol separation step (6) of separating isopropanol from the mixed gas (C).

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0029]

[0031]

[0029]

[0032]

[0029]

[0033]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0034]

[0029]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0031]

[0029]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0041]

[0039]

[0042]

[0039]

[0043]

[0039]

[0044]

[0039]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060] [ [3] The method for producing acrylic acid according to the above [1] or [2], wherein the acetone separation step (2) comprises bringing the mixed gas (A) into contact with water (b) to separate an acetone-containing aqueous solution from a mixed gas (B) containing carbon dioxide and hydrogen, and at least one selected from the water (c) and the water (d) is reused as at least one selected from the water (a), the water (b), and the water (e).[4] The method for producing acrylic acid according to [3] above, wherein the acrylic acid purification step (11) includes an acrylic acid distillation step (11A) of distilling the acrylic acid-containing aqueous solution to separate acrylic acid and water (f), and at least one selected from the water (c), the water (d), and the water (f) is reused as at least one selected from the water (a), the water (b), and the water (e). [5] The method for producing acrylic acid according to any of [1] to [4] above, wherein the steps (1) to (11) are carried out in a continuous flow. [6] The method for producing acrylic acid according to [3] or [4] above, wherein the water (c) is reused as the water (a) and / or the water (b). [7] The method for producing acrylic acid according to [3] or [4] above, wherein the water (d) is reused as at least one selected from the water (a), the water (b), and the water (e). [8] The method for producing acrylic acid according to [4] above, wherein the water (f) is reused as the water (e). [9] The method for producing acrylic acid according to any one of [1] to [8] above, wherein the water (c) has a methyl propyl ketone content of 5,000 ppm or less and a methyl isobutyl ketone content of 500 ppm or less.

[10] The method for producing acrylic acid according to any one of [1] to [9] above, wherein the water (d) has an isopropanol content of 10,000 ppm or less.

[11] The method for producing acrylic acid according to [4] or [8] above, wherein the acrylic acid purification step (11) comprises an acrylic acid distillation step (11A) of azeotropically distilling the acrylic acid-containing aqueous solution with an azeotropic solvent to separate acrylic acid and water (f), and wherein the content of the azeotropic solvent component in the water (f) is 1,000 ppm or less.

[12] The method for producing acrylic acid according to any one of [1] to

[11] above, wherein the ethanol is bioethanol.

[13] Acrylic acid obtained by the method for producing acrylic acid according to any one of [1] to

[12] above.

[14] A method for producing polyacrylic acid (salt), comprising: obtaining acrylic acid by the method for producing acrylic acid according to any one of [1] to

[12] above; and polymerizing the acrylic acid after neutralization or in an unneutralized state.

[15] A polyacrylic acid (salt) obtained by the method for producing polyacrylic acid (salt) according to the above item

[14] .

[16] A process for producing acrylic acid according to any one of the above items [1] to

[12] , and a process for producing a polyacrylic acid (salt) from the acrylic acid and an alcohol (preferably at least one selected from alcohols having 1 to 30 carbon atoms; more preferably, methanol, ethanol, 1-propanol, isopropanol, 1-butanol, isobutanol, 1-pentanol, 1-hexanol, 1-octanol, 2-ethylhexyl alcohol, 2-octanol, isononyl alcohol, isoborneol, isoamyl alcohol, 2-methoxyethanol, 2-ethoxyethanol, tetrahydrofurfuryl alcohol, lauryl alcohol, stearyl alcohol, behenyl alcohol, cyclohexyl alcohol, 2-hydroxyethanol, 2-hydroxypropanol, 4-hydroxybutanol, 1,3-propanol, 2-hydroxybut ...

[17] A method for producing an acrylic ester, comprising: subjecting a hydroxybenzoate to a dehydration reaction with at least one selected from the group consisting of 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, glycerin, polyethylene glycol, and polypropylene glycol, as well as their ethylene oxide and propylene oxide addition polymers; more preferably at least one selected from 1-butanol, methanol, ethanol, isobutanol, 2-octanol, isononyl alcohol, isoborneol, 2-methoxyethanol, 2-hydroxyethanol, 2-hydroxypropanol, trimethylolpropane, and polyethylene glycol; particularly preferably 1-butanol.

[18] A method for producing a polymer, comprising: obtaining acrylic acid by the method for producing acrylic acid according to any one of the above [1] to

[12] and / or obtaining an acrylic ester by the method for producing an acrylic ester according to the above

[16] ; and polymerizing the acrylic acid and / or the acrylic ester.

[19] A polymer obtained by the method for producing a polymer according to

[18] above.

[20] A method for producing an acrylic acid copolymer, comprising: obtaining acrylic acid by the method for producing acrylic acid according to any one of [1] to

[12] above; and copolymerizing the acrylic acid and a monomer copolymerizable with the acrylic acid.

[21] A method for producing an acrylic ester copolymer, comprising: obtaining an acrylic ester by the method for producing an acrylic ester according to

[16] above; and copolymerizing the acrylic ester and a monomer copolymerizable with the acrylic ester.

[0007] 1 is a flow sheet showing steps (1) to (8) in a method for producing acrylic acid according to one embodiment of the present invention. FIG. 2 is a flow sheet showing steps (9) to (11) in a method for producing acrylic acid according to one embodiment of the present invention.

[0008] Hereinafter, embodiments of the present invention will be described, but the technical scope of the present invention should be defined based on the claims and is not limited to the following embodiments. In this specification, the numerical range "A to B" means "greater than or equal to A and less than or equal to B." "A and / or B" means "either A or B" or "both A and B."

[0009] <Method for producing acrylic acid> According to one aspect of the present invention, there is provided a method for producing acrylic acid, comprising the above steps (1) to (11). The production method according to this aspect can reduce the cost of producing acrylic acid using ethanol as a raw material. The overall flow of steps (1) to (11) will be explained below with reference to the drawings. Note that in the explanation of the drawings, identical elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, the dimensional proportions in the drawings have been exaggerated for the convenience of explanation and may differ from the actual proportions.

[0010] 1 and 2 are flow sheets showing steps (1) to (8) and steps (9) to (11), respectively, in a method for producing acrylic acid according to one embodiment of the present invention. For the sake of simplicity, only one apparatus and step are depicted in FIGS. 1 and 2 , but multiple apparatuses and steps may be connected in series or parallel. Furthermore, the reaction and purification in each step may be carried out continuously or batchwise, but a continuous system is preferred.

[0011] As shown in FIGS. 1 and 2 , the following are connected by pipes: an acetone synthesis reactor 1 in which step (1) is performed, an acetone separation column 2 in which step (2) is performed, an acetone distillation column 3 in which step (3) is performed, a hydrogen separation unit 4 in which step (4) is performed, an isopropanol synthesis reactor 5 in which step (5) is performed, an isopropanol separation unit 6 in which step (6) is performed, a propylene synthesis reactor 7 in which step (7) is performed, a propylene separation unit 8 in which step (8) is performed, an acrylic acid synthesis reactor 9 in which step (9) is performed, an acrylic acid absorption column 10 in which step (10) is performed, an acrylic acid distillation column 11A in which step (11A) is performed, and an acrylic acid crystallization unit 11B in which step (11B) is performed. Here, the pipe 90 shown in FIG. 1 and the pipe 90 shown in FIG. 2 are the same pipe, and therefore the propylene separation unit 8 and the acrylic acid synthesis reactor 9 are connected to each other. As a result, the acetone synthesis reactor 1 to the acrylic acid crystallization unit 11B are continuously connected. As a result, steps (1) to (11) can be performed in a continuous flow.

[0012] When steps (1) to (11) are carried out in a continuous flow, it is preferable that the devices used in each step are connected by piping. However, when piping is difficult due to restrictions on the topography or location of the production facilities, a transportation method may be used.

[0013] As shown in FIG. 1, raw materials ethanol and water (a) are supplied to an acetone synthesis reactor 1 through a pipe 12. In the acetone synthesis reactor 1, an acetone synthesis reaction "2CH ３ CH ２ OH+H ２ O → CH ３ C(=O)CH ３ +CO ２ +4H２ " produces a mixed gas (A) containing acetone, water vapor, carbon dioxide and hydrogen as products.

[0014] The mixed gas (A) obtained in the acetone synthesis reactor 1 is supplied to the acetone separation column 2 via a pipe 20. In the acetone separation column 2, an acetone-containing aqueous solution and a mixed gas (B) containing carbon dioxide and hydrogen are separated from the mixed gas (A). If necessary, water (b) may be supplied to the acetone separation column 2 via a pipe 21, and the mixed gas (A) may be brought into contact with the water (b) to form an acetone-containing aqueous solution.

[0015] The acetone-containing aqueous solution obtained in the acetone separation column 2 is supplied to the acetone distillation column 3 via a pipe 30. In the acetone distillation column 3, the acetone-containing aqueous solution is distilled to separate acetone and water (c). The water (c) can be supplied (reused) via a pipe 31 to at least one selected from the acetone synthesis reactor 1, the acetone separation column 2, and the acrylic acid absorption column 10. Here, reuse means that the water is reused in a process other than the process in which the water is generated. Before being reused, the water may be subjected to other treatments, such as removing impurities, or may not be subjected to other treatments. In addition, reuse also refers to the case where water generated in a process subsequent to the process in which the reused water is used is reused in a further process.

[0016] The mixed gas (B) obtained in the acetone separation column 2 is supplied to the hydrogen separation device 4 via a pipe 40. In the hydrogen separation device 4, hydrogen is separated from the mixed gas (B).

[0017] The acetone obtained in the acetone distillation column 3 is supplied to the isopropanol synthesis reactor 5 via a pipe 50, and the hydrogen obtained in the hydrogen separation unit 4 is supplied to the isopropanol synthesis reactor 5 via a pipe 41. In addition, unreacted hydrogen that can be obtained in the isopropanol separation unit 6 described below can be supplied to the isopropanol synthesis reactor 5 via a pipe 61.

[0018] In the isopropanol synthesis reactor 5, the isopropanol synthesis reaction “CH ３ C(=O)CH ３ +H ２ →CH ３ CH(OH)CH３ " produces a mixed gas (C) containing the product isopropanol (also called 2-propanol or isopropyl alcohol) and unreacted hydrogen.

[0019] The mixed gas (C) obtained in the isopropanol synthesis reactor 5 is supplied to the isopropanol separation device 6 via a pipe 60. In the isopropanol separation device 6, isopropanol is separated from the mixed gas (C). In addition, in the isopropanol separation device 6, unreacted hydrogen can be separated from the mixed gas (C).

[0020] The isopropanol obtained in the isopropanol separation device 6 is supplied to the propylene synthesis reactor 7 via a pipe 70. In the propylene synthesis reactor 7, the isopropanol undergoes a dehydration reaction "CH ３ CH(OH)CH ３ →CH ２ =CHCH ３ +H ２ O” produces a mixed gas (D) containing the product propylene and water.

[0021] The mixed gas (D) obtained in the propylene synthesis reactor 7 is supplied to the propylene separation unit 8 via a pipe 80. In the propylene separation unit 8, propylene and water (d) are separated from the mixed gas (D). The water (d) can be recycled via a pipe 81 to at least one selected from the acetone synthesis reactor 1, the acetone separation column 2, and the acrylic acid absorption column 10.

[0022] As shown in FIG. 2, propylene obtained in the propylene separation device 8 is supplied to the acrylic acid synthesis reactor 9 via a pipe 90. Oxygen is also supplied to the acrylic acid synthesis reactor 9 via a pipe 91. In the acrylic acid synthesis reactor 9, the acrylic acid synthesis reaction "CH ２ =CHCH ３ +1.5O ２ →CH ２ =CHCOOH+H ２ O" produces a mixed gas (E) containing the product acrylic acid.

[0023] The mixed gas (E) obtained in the acrylic acid synthesis reactor 9 is supplied to the acrylic acid absorption tower 10 via a pipe 100. Furthermore, water is supplied to the acrylic acid absorption tower 10 via a pipe 101. In the acrylic acid absorption tower 10, the mixed gas (E) is brought into contact with water (e) to obtain an aqueous solution containing acrylic acid. The mixed gas (F) that has not been absorbed (dissolved) in water is discharged from a pipe 102. If necessary, the mixed gas (F) is cooled and separated into a condensate and gas components. The condensate may be returned to the acrylic acid absorption tower 10. The gas components may be returned to the acrylic acid synthesis reactor 9.

[0024] The aqueous solution containing acrylic acid obtained in the acrylic acid absorption tower 10 is supplied to an acrylic acid purification apparatus via a pipe 110. In an embodiment shown in FIG. 2, an acrylic acid distillation tower 11A and an acrylic acid crystallizer 11B are arranged in this order as an example of an acrylic acid purification apparatus. The acrylic acid purification apparatus may consist only of the acrylic acid distillation tower 11A. When the acrylic acid purification apparatus consists only of the acrylic acid distillation tower 11A, the aqueous solution containing acrylic acid obtained in the acrylic acid absorption tower 10 is supplied to the acrylic acid distillation tower 11A via a pipe 110, and the acrylic acid crystallizer 11B and the pipes 113, 114, and 120 are not included in the acrylic acid production system.

[0025] The acrylic acid purification apparatus may consist only of the acrylic acid crystallizer 11B. In this case, the acrylic acid-containing aqueous solution obtained in the acrylic acid absorption tower 10 is supplied to the acrylic acid crystallizer 11B through the pipe 114. When the acrylic acid purification apparatus consists only of the acrylic acid crystallizer 11B, the acrylic acid production system does not include the acrylic acid distillation tower 11A and the pipes 110, 111, and 112.

[0026] In the acrylic acid distillation column 11A, the acrylic acid-containing aqueous solution is distilled to separate roughly purified acrylic acid and water (f). The water (f) can be recycled via a pipe 112 to at least one selected from the acetone synthesis reactor 1, the acetone separation column 2, and the acrylic acid absorption column 10. The roughly purified acrylic acid is supplied to an acrylic acid crystallizer 11B via a pipe 111.

[0027] In the acrylic acid crystallizer 11B, the partially purified acrylic acid is separated into purified acrylic acid by crystallization and a mother liquor. The mother liquor may be returned to the acrylic acid distillation column 11A or the acrylic acid absorption column 10. As described above, acrylic acid is produced from the raw material ethanol through steps (1) to (11). Next, each of steps (1) to (11) will be described.

[0028] [Acetone synthesis step (1)] In the acetone synthesis step (1) (also referred to as "step (1)"), ethanol and water (a) are reacted to obtain a mixed gas (A) containing acetone, water vapor, carbon dioxide, and hydrogen.

[0029] The raw material ethanol may be derived from fossil fuels, may be ethanol obtained by a reduction reaction of carbon monoxide and / or carbon dioxide, or may be derived from biomass raw materials. However, from the viewpoint of carbon neutrality, it is preferable that the raw material contains bioethanol derived from biomass raw materials (biomass ethanol), and it is more preferable that the raw material is bioethanol.

[0030] The content of bioethanol relative to 100% by mass of raw material ethanol is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 90% by mass or more. Specifically, hydrous ethanol such as Traceable 95 manufactured by Japan Alcohol Industry Co., Ltd. is preferred. Whether ethanol is bioethanol or derived from fossil fuels is determined by radiocarbon dating. Specifically, this can be determined as follows: 1. The ethanol used in the raw material gas is burned and the entire amount is converted into carbon dioxide. 2. The carbon dioxide is separated and purified using a vacuum line. 3. The carbon dioxide produced from ethanol is completely reduced with hydrogen using iron as a catalyst to produce graphite. 4. NEC Corporation's Traceable 95 is used. １４ Using a C-AMS measurement device, the graphite derived from ethanol １４ C concentration and １３ C concentration ratio ( １４ C / １３5. The same method as above 1 to 4 was also used to measure oxalic acid (hereinafter also referred to as the standard sample) from the same year that the raw material ethanol was produced, provided by the National Institute of Standards (NIST). １４ C concentration and １３ C concentration ratio ( １４ C / １３ C) is measured. 6. Graphite derived from raw material ethanol １４ C / １３ The value of C is １４ C / １３ The value divided by the C value is multiplied by 100 to obtain the bioethanol content.

[0031] The water (a) is not particularly limited, and may be tap water, industrial water, pure water (RO water, ion-exchanged water, distilled water), etc. The water obtained in the method for producing acrylic acid according to the present embodiment (at least one selected from the group consisting of water (c) in the step (3), water (d) in the step (8), and water (f) in the step (11a)) may be reused as the water (a).

[0032] Acetone synthesis reaction "2CH ３ CH ２ OH+H ２ O → CH ３ C(=O)CH ３ +CO ２ +4H ２ The catalyst used in " is not particularly limited, but preferably contains at least one metal (Me) selected from the group consisting of magnesium, calcium, manganese, copper, and zinc, iron, and zirconium. The state of these metal elements (metal (Me), iron, and zirconium) is not particularly limited, and for example, a metal oxide containing the metal element, a metal oxide supported on a carrier, a carrier containing the metal element, or a metal element supported on a carrier can be used as the catalyst.

[0033] The metal oxide may be a composite metal oxide. Examples of the crystal structure of the composite metal oxide include spinel, perovskite, magnetoplumbite, and garnet types, with the spinel type being preferred.

[0034] The composite metal oxide may be a metal oxide represented by the general formula: MeO.nFe ２ O ３ (Me represents at least one metal selected from the group consisting of magnesium, calcium, manganese, and zinc, and n represents an integer of 1 to 6), and specifically, iron composite oxides (also called ferrites) represented by the formula MgO.Fe ２ O ３ (MgFe ２ O ４ ), ZnO.Fe ２ O ３ (ZnFe ２ O ４ ) etc.

[0035] The carrier may be activated carbon, silica (SiO ２ ), alumina (Al ２ O ３ ), zeolite, silica-calcia, zirconia (ZrO ２ ), ceria (CeO ２ ), magnesia (MgO), etc. Among these, activated carbon, silica-calcia, zirconia, ceria, and magnesia are more preferred, and zirconia is particularly preferred. The shape of the carrier is not particularly limited, and examples include spherical, pellet, and honeycomb shapes. The BET specific surface area of ​​the carrier is 20 to 200 m ２ / g, and more preferably 40 to 200m ２ The use of a carrier having a large specific surface area is preferred because it makes it easier for the catalyst components to be supported in a dispersed state, thereby increasing the catalytic activity.

[0036] The state of zirconium element contained in the catalyst is not particularly limited, and may be contained as a compound containing zirconium alone as a metal, as an element of a composite metal oxide containing other metal elements, or as a carrier. Examples of compounds containing zirconium alone as a metal include zirconium oxide (ZrO ２ Examples of composite metal oxides containing other metal elements include composite metal oxides of zirconium and Sn, Pb, Zn, Cu, Fe, Mn, In, etc. Among these, zirconium oxide (ZrO ２); a composite metal oxide of zirconium, Zn, and Fe is preferred, and from the viewpoint of catalytic performance, zirconium oxide (ZrO ２ ) is more preferable.

[0037] The amount of metal (Me) in the catalyst is preferably 0.4 to 0.7 mol, more preferably 0.4 to 0.6 mol, and even more preferably 0.45 to 0.55 mol per mol of iron. When the amount of metal (Me) is within the above range, good catalytic activity can be obtained.

[0038] The amount of zirconium in the catalyst is preferably 0.01 to 0.5 mol, more preferably 0.05 to 0.5 mol, and even more preferably 0.1 to 0.4 mol, per mol of iron. When the amount of zirconium is within the above range, the durability of the catalyst can be improved.

[0039] The total amount of the metal (Me), iron and zirconium in the catalyst is preferably 50 to 100 mass %, more preferably 80 to 100 mass %, based on 100 mass % of the catalyst.

[0040] The acetone synthesis reaction can be carried out in either a batch system or a continuous system, but from the viewpoint of productivity, a continuous system is preferred. The acetone synthesis reaction is preferably carried out as a gas phase reaction. Examples of the gas phase reaction include a fixed bed, a moving bed, and a fluidized bed, but the simpler fixed bed system is preferred.

[0041] In the case of a fixed-bed reactor, ethanol gas and water vapor may be mixed and then supplied to the acetone synthesis reactor to contact the catalyst, or ethanol gas and water vapor may be supplied separately to the acetone synthesis reactor to contact the catalyst. Ethanol gas and water vapor can be obtained by heating ethanol and water, respectively, in a vaporizer. In addition to ethanol gas and water vapor, an inert gas such as nitrogen or helium may also be supplied to the acetone synthesis reactor.

[0042] The concentration of ethanol gas is preferably 3 to 66 mol %, more preferably 5 to 50 mol %, relative to 100 mol % of the total amount of gas supplied to the acetone synthesis reactor. The molar ratio of water vapor to ethanol gas (water vapor / ethanol gas) is preferably 0.5 to 10, more preferably 1 to 5.

[0043] The reaction pressure in the acetone synthesis reaction may be reduced pressure, normal pressure, or increased pressure, but is preferably 0.07 to 2 MPa, and more preferably 0.1 to 1 MPa. The reaction temperature in the acetone synthesis reaction is preferably 250 to 600°C, more preferably 300 to 550°C, and even more preferably 330 to 500°C. The space velocity in the acetone synthesis reaction is preferably 300 to 10,000 (1 / h), more preferably 400 to 8,000 (1 / h), and even more preferably 500 to 6,000 (1 / h).

[0044] [Acetone Separation Step (2)] In the acetone separation step (2) (also referred to as "step (2)"), an acetone-containing aqueous solution and a mixed gas (B) containing carbon dioxide and hydrogen are separated from the mixed gas (A) obtained in the above step (1). As a result, water vapor and acetone gas are condensed, and the acetone aqueous solution and the mixed gas (B) are separated (gas-liquid separation). In this case, it is preferable to bring the liquid component obtained by condensation into contact with the gas component by stirring or the like, because the acetone gas remaining in the gas component dissolves in water and the recovery rate of acetone can be improved.

[0045] Water (b) may be supplied to the acetone separation device as needed, separate from the water vapor in the mixed gas (A). Supplying water (b) can improve the acetone absorption efficiency in the acetone separation device. The water (b), together with condensed water from the water vapor, serves as a solvent for the acetone-containing aqueous solution. The water (b) is not particularly limited, and tap water, industrial water, pure water (RO water, ion-exchanged water, distilled water), etc. may be used. Water obtained in the method for producing acrylic acid according to this embodiment (at least one selected from water (c) in step (3), water (d) in step (8), and water (f) in step (11a)) may be reused as water (b).

[0046] The pressure in the separation operation is preferably 0.1 to 2 MPa, more preferably 0.2 to 1 MPa. The temperature in the separation operation is preferably 0 to 90°C, more preferably 0 to 50°C, and even more preferably 5 to 40°C.

[0047] [Acetone Distillation Step (3)] In the acetone distillation step (3) (also referred to as "step (3)"), the acetone-containing aqueous solution obtained in the step (2) is distilled to separate acetone and water (c).

[0048] The distillation can be carried out by a known method. Examples of the distillation method include thin film distillation and rectification. The distillation can be carried out either batchwise or continuously, but from the viewpoint of productivity, the continuous method is preferred.

[0049] The distillation is carried out one or more times until a desired purity of acetone is obtained. The purity of acetone obtained in step (3) is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, from the viewpoint of improving the yield of isopropanol in the isopropanol synthesis step (5) described below and the purity of isopropanol in the isopropanol separation step (6).

[0050] The water (c) can be reused as water (at least one selected from the water (a) in the step (1), the water (b) in the step (2), and the water (e) in the step (10)) used in the method for producing acrylic acid according to the present embodiment.

[0051] [Hydrogen Separation Step (4)] In the hydrogen separation step (4) (also referred to as "step (4)"), hydrogen is separated from the mixed gas (B) containing carbon dioxide and hydrogen obtained in the above step (2). The method used for separation (hydrogen purification) is not particularly limited, and known methods such as physical adsorption, chemical absorption, membrane separation, cryogenic separation, and compression liquefaction can be appropriately adopted.

[0052] The physical adsorption method is a method of separating and recovering carbon dioxide from a mixed gas without chemical reaction by physical action such as adsorption (for example, adsorption onto an adsorbent such as activated carbon) or dissolution (for example, dissolution into an organic solvent). A preferred example of the physical adsorption method is pressure swing adsorption (PSA).

[0053] Chemical absorption is a method in which carbon dioxide is reacted (absorbed) with a basic substance, mainly an amine or alkali, and converted into a form such as bicarbonate, which is then separated and recovered from the mixed gas. Carbon dioxide can be recovered by heating or reducing the pressure of the absorption liquid after absorbing the carbon dioxide.

[0054] Membrane separation is a method for separating and recovering hydrogen or carbon dioxide from a mixed gas by selectively allowing the hydrogen or carbon dioxide to permeate through a separation membrane. Examples of separation membranes include inorganic membranes such as polymer membranes, dendrimer membranes, amine group-containing membranes, and zeolite membranes. The separation membrane may contain metal atoms. Examples of metal atoms include Pd.

[0055] The purity of the hydrogen obtained in the step (4) is preferably 90 mol % or more, more preferably 95 mol % or more, and even more preferably 98 mol % or more, from the viewpoint of improving the catalytic activity of the catalyst in the isopropanol synthesis step (5) described below.

[0056] [Isopropanol Synthesis Step (5)] In the isopropanol synthesis step (5) (also referred to as "step (5)"), the acetone obtained in the step (3) above is reacted with hydrogen (preferably the hydrogen obtained in the step (4) above) to obtain an isopropanol-containing mixed gas (C).

[0057] Isopropanol synthesis reaction (acetone hydrogenation reaction) "CH ３ C(=O)CH ３ +H ２ →CH ３ CH(OH)CH ３The catalyst used in " is not particularly limited, and examples thereof include Raney catalysts. Other catalysts include, for example, solid catalysts containing metal elements such as Ba, Co, Cr, Cu, Fe, Mn, Ni, Pd, Pt, Zn, Zr, Ru, and Rh. Among these, solid catalysts containing at least one metal element selected from the group consisting of Pt, Ru, Ni, Fe, and Co are preferred, and it is more preferred to use at least one solid catalyst selected from the group consisting of Ru catalysts, Ni—Pt catalysts, Ru—Pt catalysts, and Ni—Ru catalysts. By using a solid catalyst containing such a metal element, the activity inhibitory effect of carbon dioxide in the isopropanol synthesis reaction is suppressed, and acetone hydrogenation can proceed efficiently.

[0058] The catalyst may be in the form of a metal element, alloy, oxide, etc. The catalyst may also be in the form of a mixture of metal elements, a mixture of metal elements and metal oxides, a mixture of metal oxides, or a mixed metal oxide.

[0059] The catalyst also contains metal elements in activated carbon, silica (SiO ２ ), alumina (Al ２ O ３ ), titania (TiO ２ ), zirconia (ZrO ２ ), ceria (CeO ２ The catalyst may be supported on a carrier such as silica (SiO ２ ), zirconia (ZrO ２ ) is preferred.

[0060] The above catalysts may be used alone or in combination of two or more.

[0061] The isopropanol synthesis reaction can be carried out in either a batch system or a continuous system, but from the viewpoint of productivity, a continuous system is preferred. The isopropanol synthesis reaction is preferably carried out as a gas phase reaction. Examples of the gas phase reaction include a fixed bed, a moving bed, and a fluidized bed, but the simpler fixed bed system is preferred.

[0062] In the case of a fixed-bed reactor, acetone gas and hydrogen may be mixed and then supplied to the isopropanol synthesis reactor to contact with the catalyst, or acetone gas and hydrogen may be supplied separately to the isopropanol synthesis reactor to contact with the catalyst. Acetone gas can be obtained by heating acetone in a vaporizer. In addition to acetone and hydrogen, an inert gas such as nitrogen or helium may be supplied to the isopropanol synthesis reactor.

[0063] The molar ratio of hydrogen to acetone gas (hydrogen / acetone gas) supplied to the isopropanol synthesis reactor is preferably 1 to 10, more preferably 1 to 5.

[0064] The reaction pressure in the isopropanol synthesis reaction may be reduced pressure, normal pressure, or increased pressure, but is preferably 0.1 to 2 MPa, more preferably 0.1 to 1 MPa. The reaction temperature in the isopropanol synthesis reaction is preferably 20 to 200°C, more preferably 25 to 150°C. A lower reaction temperature is advantageous in terms of equilibrium, but tends to make hydrogenation less likely to proceed. On the other hand, a higher reaction temperature tends to prevent an increase in the acetone hydrogenation conversion rate due to equilibrium constraints, and in addition, hydrogenolysis of acetone and isopropyl alcohol occurs simultaneously, resulting in a decrease in yield. The space velocity in the acetone synthesis reaction is preferably 200 to 50,000 (1 / h), more preferably 1,000 to 20,000 (1 / h), and even more preferably 2,000 to 10,000 (1 / h).

[0065] [Isopropanol Separation Step (6)] In the acetone separation step (6) (also referred to as "step (6)"), isopropanol is separated from the mixed gas (C) obtained in the step (5). The mixed gas (C) may contain hydrogen used in the step (5) in addition to isopropanol. More specifically, in the step (6), the mixed gas (C) is supplied to an isopropanol separation apparatus, and the mixed gas (C) is cooled in the apparatus. This condenses the isopropanol, and isopropanol (liquid) is separated from gas components such as hydrogen (gas-liquid separation). The hydrogen contained in the gas components may be reused in the isopropanol synthesis step (5).

[0066] The pressure in the separation operation is preferably 0.1 to 2 MPa, more preferably 0.2 to 1 MPa. The temperature in the separation operation is preferably 0 to 50°C, more preferably 5 to 40°C.

[0067] The isopropanol obtained by the separation (gas-liquid separation) may be supplied to the next step (7) as is, or may be further purified by distillation as necessary and then supplied to the next step (7). The purity of the isopropanol obtained in step (6) is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 93% by mass or more, from the viewpoint of improving the propylene yield in the propylene synthesis step (7) described below and the propylene purity in the propylene separation step (8).

[0068] [Propylene Synthesis Step (7)] In the propylene synthesis step (7) (also referred to as "step (7)"), the isopropanol obtained in the step (6) is subjected to a dehydration reaction to obtain a mixed gas (D) containing propylene and water.

[0069] Propylene synthesis reaction (isopropanol dehydration reaction) "CH ３ CH(OH)CH ３ →CH ２ =CHCH ３ +H ２ Examples of catalysts used in "O" include alumina catalysts, silica-alumina catalysts, zeolite catalysts, activated clay, etc., and titanium oxide (TiO ２ ), tungsten oxide, zirconium oxide (ZrO ２ ) or the like. Among these, alumina catalysts are preferred, γ-alumina catalysts are more preferred, and specifically, catalysts in which tungsten oxide is supported on γ-alumina are even more preferred. These catalysts may be used alone or in combination of two or more.

[0070] The catalyst may be any of the above-mentioned catalysts that have been subjected to an acid treatment and / or a calcination treatment, as necessary. The acid treatment is carried out by immersing the catalyst (e.g., a γ-alumina catalyst) in an acid to adjust the acid strength of the catalyst. Examples of acids used in the acid treatment include aqueous solutions of hydrochloric acid, nitric acid, boric acid, etc., and carboxylic acids such as acetic acid, formic acid, and oxalic acid.

[0071] The form of the catalyst used is not particularly limited, and examples thereof include tablet type, ring type, spherical type, cylindrical extrusion type, trilobe extrusion type, granule type, etc. Among these, the spherical type, tablet type, and cylindrical extrusion type are preferred in that they have high catalyst strength and can be uniformly packed into a reaction tube.

[0072] When the catalyst is a γ-alumina catalyst, a catalyst having an average pore diameter of 30 to 150 Å and a standard deviation of 10 to 40 Å, which is determined by statistical calculation based on the relationship between pore diameter and pore volume, is preferably used.

[0073] The propylene synthesis reaction can be carried out in either a batch system or a continuous system, but from the viewpoint of productivity, a continuous system is preferred. The propylene synthesis reaction is preferably carried out as a gas phase reaction. Examples of the gas phase reaction include a fixed bed, a moving bed, and a fluidized bed, but the simpler fixed bed system is preferred.

[0074] In the case of a gas-phase reaction, isopropanol can be heated in a vaporizer and supplied as isopropanol gas to the propylene synthesis reaction. In addition to isopropanol gas, an inert gas (e.g., nitrogen, helium, argon) may be supplied to the propylene synthesis reactor.

[0075] The reaction temperature in the propylene synthesis reaction is preferably 150 to 500° C., more preferably 180 to 400° C. The reaction pressure in the propylene synthesis reaction may be any of reduced pressure, normal pressure, and increased pressure, but is preferably a pressure at which a gas phase reaction can be maintained.

[0076] [Propylene Separation Step (8)] In the propylene separation step (8) (also referred to as "step (8)"), propylene and water (d) are separated from the mixed gas (D) obtained in the above step (7). More specifically, the mixed gas (D) is supplied to a propylene separation apparatus, and water is condensed by pressurization and cooling. This allows separation into a gas phase mainly consisting of propylene and an aqueous phase mainly consisting of water (d). The water (d) can be reused as water (at least one selected from water (a) in step (1), water (b) in step (2), and water (e) in step (10)) used in the production method for acrylic acid according to this embodiment.

[0077] The pressure when the pressurized state is established is preferably 5 to 50 kg / cm from the viewpoint of separation and purification costs. ２ G. The reaction product (gaseous) can be easily liquefied by simply cooling it to 20 to 50°C.

[0078] The propylene obtained by the separation (gas-liquid separation) may be supplied to the next step (9) as it is, or may be further purified by distillation, as necessary, and then supplied to the next step (9). The purity of the propylene obtained in step (8) is preferably 90% by mass or more, more preferably 93% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of improving the yield of acrylic acid in the acrylic acid synthesis step (9) described below and the purity of acrylic acid in the acrylic acid separation step (11).

[0079] [Acrylic Acid Synthesis Step (9)] In the acrylic acid synthesis step (9) (also referred to as "step (9)"), the propylene obtained in the step (8) is subjected to an oxidation reaction to obtain a mixed gas (E) containing acrylic acid. ２ =CHCH ３ +1.5O ２ →CH ２ =CHCOOH+H ２ For "O", known methods (for example, the methods described in Japanese Patent Nos. 3,948,837 and 3,938,646) can be appropriately adopted.

[0080] In the acrylic acid synthesis reaction, propylene is oxidized by contacting it with a molecular oxygen-containing gas such as oxygen or air in the presence of a known catalyst. Usually, the oxidation reaction is carried out in two stages. The catalyst used in the first stage reaction is one that can produce acrolein through the gas phase oxidation of propylene gas, and the catalyst used in the second stage reaction is not particularly limited as long as it can produce acrylic acid through the gas phase oxidation of acrolein gas.

[0081] The catalyst used in the first-stage reaction may be a solid catalyst containing at least one element selected from Fe, Co, Ni, Mo, Bi, Al, and Si, preferably containing at least one element selected from Fe, Mo, and Bi, and more preferably containing a composite oxide containing Fe, Mo, and Bi.

[0082] The catalyst used in the second-stage reaction may be a solid catalyst containing at least one element selected from V, Mo, Cu, W, Sb, Al, and Si, and preferably contains at least one element selected from Mo, V, and W, and more preferably contains Mo or V.

[0083] The acrylic acid synthesis reaction can be carried out either batchwise or continuously, but from the viewpoint of productivity, the continuous method is preferred. The reaction temperature in the acrylic acid synthesis reaction is usually in the range of 200 to 400°C.

[0084] [Acrylic Acid Absorption Step (10)] In the acrylic acid absorption step (10) (also referred to as "step (10)"), the mixed gas (E) obtained in the above step (9) is contacted with water (e) to obtain an aqueous solution containing acrylic acid. The mixed gas (E) may contain acrylic acid, the molecular oxygen-containing gas used in the above step (9), unreacted components (propylene, acrolein), and by-products (e.g., acetone, acrolein, furfural, formaldehyde, etc.).

[0085] The water (e) as a solvent for absorbing acrylic acid is not particularly limited, and may be tap water, industrial water, pure water (RO water, ion-exchanged water, distilled water), etc. The water obtained in the method for producing acrylic acid according to this embodiment (at least one selected from the group consisting of the water (c) in the step (3), the water (d) in the step (8), and the water (f) in the step (11a)) may be reused as the water (e).

[0086] The method for contacting the mixed gas (E) with water (e) is not particularly limited, and any known contact method can be appropriately adopted. Specific examples of the contact method include cross-current contact using a bubble cap tray, a uniflat tray, a perforated plate tray, a jet tray, a bubble tray, or a Venturi tray; and countercurrent contact using a turbogrid tray, a dual flow tray, a ripple tray, a Kittel tray, or a gauze-type, sheet-type, or grit-type structured packing or a random packing.

[0087] [Acrylic acid purification step (11)] In the acrylic acid purification step (11) (also referred to as "step (11)"), the acrylic acid-containing aqueous solution obtained in the step (10) is purified to obtain acrylic acid. The acrylic acid-containing aqueous solution may contain acrylic acid, acetic acid, water, and other impurities (maleic acid, propionic acid, furfural, formaldehyde, etc.).

[0088] The method for purifying acrylic acid is not particularly limited, and known techniques such as distillation and crystallization can be appropriately employed. The purification may involve only distillation (acrylic acid distillation step (11A)), only crystallization (acrylic acid crystallization step (11B)), or a combination of distillation (acrylic acid distillation step (11A)) and crystallization (acrylic acid crystallization step (11B)). In the embodiment shown in FIG. 2, the acrylic acid distillation step (11A) and the acrylic acid crystallization step (11B) are combined in this order. Furthermore, distillation may be performed only once, or multiple times in combination. Furthermore, crystallization may be performed only once, or multiple times in combination.

[0089] When distillation is included as a purification method, water (f) is preferably separated from the aqueous acrylic acid solution by azeotropic distillation. Examples of the azeotropic solvent components used in the azeotropic distillation include heptane, toluene, ethyl methacrylate, methyl isobutyl ketone, n-propyl acrylate, methyl acetate, and n-butyl acetate. Preferred are toluene, methyl isobutyl ketone, methyl acetate, and n-butyl acetate, more preferred are toluene and methyl isobutyl ketone, and even more preferred is toluene. When multiple azeotropic solvents are used, they may be used as a mixture.

[0090] The water (f) can be reused as water (at least one selected from the water (a) in the step (1), the water (b) in the step (2), and the water (e) in the step (10)) used in the method for producing acrylic acid according to the present embodiment.

[0091] In the method for producing acrylic acid according to this embodiment, it is preferable to reuse the water obtained by the method as the water used in the method. That is, it is preferable to reuse at least one selected from water (c) and water (d) as at least one selected from water (a) and water (e). When the mixed gas (A) is contacted with water (b) (water (b) is supplied) in the acetone separation step (2), it is preferable to reuse at least one selected from water (c) and water (d) as at least one selected from water (a), water (b), and water (e). When the acrylic acid purification step (11) includes an acrylic acid distillation step (11A), it is preferable to reuse at least one selected from water (c), water (d), and water (f) as at least one selected from water (a), water (b), and water (e).

[0092] The reuse described above not only reduces the cost of water procurement, but also reduces the total amount of wastewater discharged from the production process, thereby reducing the environmental burden and the cost of wastewater treatment, thereby providing an acrylic acid production method that is excellent in both environmental and economic terms. In the present specification, "reusing water (X) as water (Y)" encompasses both "a form in which water (Y) is only water (X)" and "a form in which water (Y) is composed of water (X) and water other than water (X) (for example, tap water, industrial water, pure water)." "Reusing water (X) as water (Y)" preferably means "a form in which water (Y) is only water (X)." In the present specification, water (a) to water (f) are each H ２ Impurities other than O may be contained in an amount of 25% by mass or less (preferably 20% by mass or less, more preferably 18% by mass or less).

[0093] Water (c) is preferably reused as water (a) and / or water (b), and more preferably reused as water (a). This reduces the amount of wastewater, and when unreacted ethanol remains in water (c) from the acetone synthesis step (1), the unreacted ethanol can be reused again for acetone synthesis without being discarded, thereby improving the yield of acetone synthesis from raw material ethanol. It is preferable that the content of methyl propyl ketone in water (c) is 5000 ppm or less and the content of methyl isobutyl ketone is 500 ppm or less; more preferably, the content of methyl propyl ketone in water (c) is 3000 ppm or less and the content of methyl isobutyl ketone is 200 ppm or less. When the contents of methyl propyl ketone and methyl isobutyl ketone are within the above ranges, the water can be suitably reused as water (a) and / or water (b).

[0094] Water (d) is preferably reused as at least one selected from water (a), water (b), and water (e), more preferably reused as water (a) and / or water (b), and even more preferably reused as water (a). This reduces the amount of wastewater and enables the reuse of acetone, a small amount of by-product produced during the isopropanol dehydration reaction, without being discarded together with the wastewater. The isopropanol content in water (d) is preferably 10,000 ppm or less, more preferably 5,000 ppm or less. When the isopropanol content is within the above range, the water can be suitably reused as at least one selected from water (a), water (b), and water (e).

[0095] It is preferable to reuse water (f) as water (e). This reduces the amount of wastewater and enables recovery of acrylic acid remaining in water (f), thereby improving the production efficiency of acrylic acid. When the water (f) is reused as water (e), the impurities contained in the water (f) preferably include components used in distillation step 11(A), and the amount of these components is preferably not more than a predetermined amount. For example, when the distillation step is azeotropic distillation using an azeotropic solvent, the content of the azeotropic solvent component in the water (f) is preferably 1000 ppm or less, more preferably 500 ppm or less. When the content of the azeotropic solvent component is within the above range, the water can be suitably reused as water (e).

[0096] As described above, in order to reuse water, it is important to appropriately determine the process to which the water will be reused depending on the type and amount of impurities contained in the water. By appropriately determining the process to which the water will be reused, problems such as a decrease in the yield of the target product and an increase in the load on the purification process can be prevented. As a result, production costs can be further reduced, which is preferable.

[0097] In the method for producing acrylic acid according to this embodiment, steps (1) to (11) are preferably carried out in a continuous flow. This eliminates the need for ancillary equipment such as an intermediate tank, allowing for a simpler production facility, thereby shortening production time and reducing facility costs. Furthermore, wastewater generated in the process can be utilized in other steps within the process, thereby reducing the overall amount of wastewater in the process, resulting in an effect of reducing wastewater treatment costs.

[0098] According to another embodiment of the present invention, there is provided a system for producing acrylic acid, which comprises an acetone reactor, an acetone separation column, an acetone distillation column, a hydrogen separation unit, an isopropanol synthesis reactor, an isopropanol separation unit, a propylene synthesis reactor, a propylene separation unit, an acrylic acid synthesis reactor, an acrylic acid absorption column, and an acrylic acid distillation column and / or an acrylic crystallizer.

[0099] According to yet another aspect of the present invention, there is provided acrylic acid obtained by the above-mentioned method for producing acrylic acid. The acrylic acid produced by the present invention can be used for various acrylic acid derivatives that can use acrylic acid as a raw material or an intermediate product.

[0100] For example, the acrylic acid produced by the present invention can be suitably used as a raw material for a water-absorbent resin. Therefore, according to another aspect of the present invention, there can be provided a method for producing polyacrylic acid (salt), the method comprising: obtaining acrylic acid by the method for producing acrylic acid; and polymerizing the acrylic acid after neutralization or in an unneutralized state; and polyacrylic acid (salt) obtained by the method for producing polyacrylic acid (salt).

[0101] For example, the acrylic acid produced by the present invention can be suitably used as a raw material for an acrylic ester. Therefore, according to another aspect of the present invention, there can be provided a method for producing an acrylic ester, the method comprising the steps of obtaining acrylic acid by the above-mentioned method for producing acrylic acid and subjecting the acrylic acid to a dehydration reaction with an alcohol (hereinafter also referred to as a "dehydration reaction step"); and an acrylic ester obtained by the method for producing an acrylic ester.

[0102] Specific examples of acrylic acid esters include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, 2-ethylhexyl, 1-octyl, 2-octyl, isononyl, isobornyl, isoamyl, 2-methoxyethyl, 2-ethoxyethyl, tetrahydrofurfuryl, lauryl, stearyl, cyclohexyl, 2-hydroxyethyl, 2-hydroxypropyl, 4-hydroxybutyl, and other esters of acrylic acid, and esters of polyhydric alcohols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, glycerin, polyethylene glycol, and polypropylene glycol, in which some or all of the alcohol groups therein are esterified with acrylic acid. Additionally, examples include esters of alcohols modified with ethylene oxide and / or propylene oxide in which some or all of the alcohol groups therein are esterified with acrylic acid.

[0103] The dehydration reaction step in the method for producing an acrylic ester according to this embodiment will be described below.

[0104] In the dehydration reaction step, the acrylic acid obtained by the above-mentioned method for producing acrylic acid (i.e., acrylic acid derived from ethanol (preferably bioethanol)) and an alcohol are subjected to a dehydration reaction (esterification).

[0105] The alcohol may be appropriately selected depending on the acrylic acid ester and is not particularly limited, but is preferably at least one selected from alcohols having 1 to 30 carbon atoms; more preferably, methanol, ethanol, 1-propanol, isopropanol, 1-butanol, isobutanol, 1-pentanol, 1-hexanol, 1-octanol, 2-ethylhexyl alcohol, 2-octanol, isononyl alcohol, isoborneol, isoamyl alcohol, 2-methoxyethanol, 2-ethoxyethanol, tetrahydrofurfuryl alcohol, lauryl alcohol, stearyl alcohol, behenyl alcohol, cyclohexyl alcohol, 2-hydroxyethanol, 2-hydroxypropanol, 4-hydroxyethanol, 4-hydroxypropyl methyl ... and at least one selected from 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, glycerin, polyethylene glycol, polypropylene glycol, and ethylene oxide addition polymers and propylene oxide addition polymers thereof; more preferably at least one selected from 1-butanol, methanol, ethanol, isobutanol, 2-octanol, isononyl alcohol, isoborneol, 2-methoxyethanol, 2-hydroxyethanol, 2-hydroxypropanol, trimethylolpropane, and polyethylene glycol, and particularly preferably 1-butanol.

[0106] The alcohol may be derived from a fossil fuel or a biomass material, or may be a mixture of these.

[0107] The molar ratio of alcohol to acrylic acid to be subjected to the dehydration reaction (alcohol / acrylic acid) is stoichiometrically 1, but from the viewpoint of accelerating the dehydration reaction, it is preferable to make one of the raw materials (e.g., a raw material having a lower boiling point) more than the other raw material (e.g., a raw material having a higher boiling point). Specifically, the molar ratio (alcohol / acrylic acid) is preferably 0.2 to 5.0, more preferably 0.3 to 3.0, even more preferably 0.5 to 2.0, and particularly preferably 0.7 to 1.5.

[0108] The dehydration reaction is preferably carried out in the presence of an acid catalyst from the viewpoint of rapidly progressing the reaction. Examples of acid catalysts include sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonic acid hydrate, xylenesulfonic acid, xylenesulfonic acid hydrate, naphthalenesulfonic acid, naphthalenesulfonic acid hydrate, trifluoromethanesulfonic acid, and a strongly acidic cation exchange resin. Among these, sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, and a strongly acidic cation exchange resin are preferred. One acid catalyst may be used alone, or two or more may be used in combination. The amount of acid catalyst added (when two or more types are used in combination, the total amount) is not particularly limited, but is preferably 0.0001 to 100 mol, more preferably 0.01 to 30 mol, and even more preferably 0.1 to 10 mol per 100 mol of the raw material acrylic acid.

[0109] The dehydration reaction is preferably carried out in the presence of a polymerization inhibitor to prevent polymerization of the raw material acrylic acid and / or the product acrylic acid ester. The polymerization inhibitor is not particularly limited, but examples include phenothiazine, hydroquinone, methoquinone, methylhydroquinone, benzoquinone, di(tert-butyl)-p-cresol (BHT), p-phenylenediamine, TEMPO (2,2,6,6-tetramethyl-1-piperazinyloxy), p-tert-butylcatechol, di(tert-butyl)catechol, TEMPO derivatives such as OH-TEMPO, 2,6-tert-butyl-4-methylphenol, and copper(II) dibutyldithiocarbamate. Among these, phenothiazine, hydroquinone, and methoquinone are preferred. One type of polymerization inhibitor may be used alone, or two or more types may be used in combination. The amount of polymerization inhibitor added (when two or more types are used in combination, the total amount of the polymerization inhibitors) is not particularly limited, but is preferably 0.0001 to 10 parts by mass, and more preferably 0.001 to 2 parts by mass, relative to 100 parts by mass of acrylic acid as a raw material.

[0110] The dehydration reaction is carried out, if necessary, in the presence of an azeotropic solvent that forms an azeotropic distillate with water. By carrying out the dehydration reaction in the presence of an azeotropic solvent, the water produced by the dehydration reaction can be efficiently discharged from the reaction system, shifting the reaction equilibrium and thereby increasing the production rate of the acrylic acid ester. Examples of azeotropic solvents include benzene, toluene, xylene, cyclohexane, dioxane, pentane, hexane, heptane, chlorobenzene, and isopropyl ether. Among these, toluene, xylene, and cyclohexane are preferred because of their low azeotropic temperatures with water. One azeotropic solvent may be used alone, or two or more may be used in combination. The amount of azeotropic solvent added (the total amount when two or more are used in combination) is not particularly limited, but is preferably 0.1 to 200 parts by mass, more preferably 0.1 to 150 parts by mass, even more preferably 0.1 to 10 parts by mass, and particularly preferably 0.2 to 5 parts by mass, per 100 parts by mass of the raw material acrylic acid.

[0111] The dehydration reaction may be carried out in either a batch or continuous manner, but is preferably carried out in a batch manner. The reaction conditions for the dehydration reaction are not particularly limited as long as the reaction proceeds smoothly, and can be appropriately set by one skilled in the art. The reaction temperature is preferably 40 to 160°C, more preferably 60 to 120°C. The pressure during the reaction can be appropriately selected from normal pressure, reduced pressure, or increased pressure depending on the reaction form, but is preferably normal pressure or reduced pressure, more preferably reduced pressure. The progress of the reaction can be confirmed by gas chromatography, and the reaction is terminated when it has progressed sufficiently.

[0112] In the method for producing an acrylic ester according to this embodiment, it is preferable to carry out a neutralization step after the dehydration step, in which the reaction solution obtained in the dehydration step is neutralized. By carrying out the neutralization step, unreacted acrylic acid and any added acid catalyst are neutralized and transferred to the aqueous phase, thereby obtaining an oil phase containing a crude acrylic ester. When a strongly acidic cation exchange resin is used as the catalyst, the acid catalyst can be easily separated by solid-liquid separation. In addition, in the method for producing an acrylic ester according to this embodiment, it is preferable to carry out a purification step after the neutralization step, in which the crude acrylic ester is purified. The purification in the purification step is preferably carried out by distillation. More specifically, the purification step may include a low-boiling-point substance removal step for removing substances having a boiling point lower than that of the target acrylic ester, and a high-boiling-point substance removal step for removing substances having a boiling point higher than that of the target acrylic ester. Furthermore, for example, the acrylic acid produced according to the present invention may also be suitably used as a raw material for acrylic acid salts. Examples of acrylates include sodium acrylate, potassium acrylate, magnesium acrylate, calcium acrylate, iron(II) acrylate, iron(III) acrylate, zinc acrylate, and ammonium acrylate.

[0113] The acrylic acid and / or acrylic acid esters produced by the present invention can be polymerized alone or in combination to produce various polymers. As the monomers used for the polymers, in addition to the acrylic acid and / or acrylic acid esters produced by the present invention, polymerizable monomers produced by other methods may also be used.

[0114] Examples of polymers obtainable by the present invention include polyacrylic acid esters, polyacrylic acid (sodium), and crosslinked products thereof, and examples of crosslinked products include water-absorbent resins, slightly crosslinked resins (commonly called carbomers), etc. The acrylic acid and / or acrylic acid esters produced by the present invention are useful as raw materials for synthesizing water-absorbent resins such as polyacrylic acid and sodium polyacrylate.

[0115] The polymerization method for the acrylic acid and / or acrylic acid ester produced by the present invention is not particularly limited, and any known or commonly used method can be employed, for example, bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. Furthermore, a composition containing the acrylic acid and / or acrylic acid ester produced by the present invention may be used as a curable resin composition, and the method for curing the curable resin composition may be thermal curing or photocuring.

[0116] Polymers using acrylic acid and / or acrylic acid esters produced by the present invention can be used in a wide range of applications, including building materials, optical applications, automobiles, detergents, disposable diapers, sanitary materials, food applications, cosmetics, and pharmaceuticals, and can be used as adhesives, pressure-sensitive adhesives, paints, coating agents, inks, highly water-absorbent resins, thickeners, water-retaining materials, vibration-damping materials, acrylic rubbers, acrylic fibers, acrylic resins, acrylic emulsions, molding resins, electronics materials, reactive diluents, pharmaceutical raw materials, etc.

[0117] Examples relating to acrylic acid, acrylic acid esters, and polymers using acrylic acid esters according to the present invention will be described. The present invention is not limited to these examples. In the following examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0118] Experimental Example 1: Reuse of Water (c) An oxide catalyst containing Fe, Zn, and Zr in a molar ratio of Fe / Zn / Zr = 1 / 0.5 / 0.5 was formed into a cylindrical shape with a diameter of 6 mm and a length of 6 mm and packed into a stainless steel U-shaped reactor tube with an inner diameter of 22.4 mm to a catalyst layer length of 930 mm. The reactor tube was immersed in a bath of molten nitrate salts, and a bioethanol gas mixture (traceable 95% bioethanol by mass, manufactured by Japan Alcohol Industry Co., Ltd.) with a molar ratio of bioethanol / water vapor / nitrogen = 2 / 8 / 1 was introduced into the stainless steel U-shaped reactor tube at 5100 mL / min (standard conditions equivalent) to carry out an acetone synthesis reaction. The molten salt bath temperature was 400 °C. Ethanol conversion was over 95% and acetone selectivity was 70%. Acetone was recovered from the reactor outlet gas by cooling the outlet gas to -15 °C and condensing the acetone-containing liquid.

[0119] The acetone aqueous solution recovered above was distilled using a glass Oldershaw distillation apparatus to obtain acetone with a purity of 95% or more. At this time, water (c), consisting mainly of water, was obtained from the bottom of the distillation column. This water (c) was analyzed by gas chromatography under the following conditions, and the composition was as shown in Table 1. Apparatus: Agilent Technology 7890B Column: HP-Plot Q (30 m) Column oven temperature: After holding at 150°C for 5 minutes, the temperature was increased to 270°C at 10°C / min and held at 270°C for 15 minutes Carrier gas: Nitrogen Gas flow rate: 5 mL / min Internal standard: 2-butanol

[0120]

[0121] Water (c) contained a small amount of acetone that could not be separated by distillation and ethanol, an unreacted raw material in the acetone synthesis process, but it also contained a small amount of by-products from the acetone synthesis process, and the concentrations of these by-products were not high. Therefore, it can be reused as water (a), water (b), and water (e).

[0122] Example 2: Reuse of Water (d) A catalyst containing 90% by mass of spherical silica (particle size 1.7-4 mm), 5% by mass of nickel, and 5% by mass of ruthenium was packed into a stainless steel U-shaped reactor tube with an inner diameter of 22.4 mm, 224 g. This stainless steel U-shaped reactor tube was immersed in a silicone oil bath, and hydrogen reduction was carried out for 30 minutes under a hydrogen stream at an oil bath temperature of 200°C. Next, the oil bath temperature was lowered to 100°C, and hydrogen / acetone gas of 2.7 / 1 (molar ratio) was introduced into the stainless steel U-shaped reactor tube at 1300 mL / min (standard state equivalent) to carry out an isopropanol synthesis reaction by acetone hydrogenation. At this time, the pressure was adjusted using a back pressure valve so that the reaction pressure was 4 atmospheres (gauge). Reaction results of approximately 99% acetone conversion and 98% isopropanol selectivity were obtained. Isopropanol was recovered from the gas at the outlet of the reaction tube by condensing the isopropanol by cooling the gas to −5° C. In this way, isopropanol with a purity of 98% was obtained.

[0123] A stainless steel reaction tube with an inner diameter of 22.4 mm was packed with a catalyst containing 90% by mass of spherical γ-alumina (particle size 2-4 mm) and 10% by mass of tungsten oxide, with the catalyst layer length being 5 cm. A packed bed filled with SUS DIXON PACKING was installed on the inlet side of the reaction tube and heated to 200°C from the outside using an electric heater. Nitrogen and isopropanol were supplied to the inlet side of this packed bed at 10 mL / min and 0.3334 g / min, respectively, to vaporize the isopropanol, which was then homogeneously mixed with the nitrogen and discharged from the packed bed. The gas discharged from the outlet of the packed bed, consisting primarily of isopropanol, was introduced into the stainless steel reaction tube. The stainless steel reaction tube was placed in a circular electric furnace heated to 300°C, where the isopropanol was dehydrated over the 10% by mass tungsten oxide-containing γ-alumina catalyst, with most of it being converted to propylene and water. The isopropanol conversion was 99.5% and the propylene selectivity was 98.4%.

[0124] The gas from the reactor outlet was introduced into a spiral metal tube immersed in an ice bath for cooling, condensing the water vapor in the gas. A gas consisting mainly of propylene and nitrogen as a carrier gas, and condensed water were discharged from the spiral metal tube outlet, and these could be easily separated into a gas consisting mainly of propylene and water (d) by conventional gas-liquid separation. When this water (d) was analyzed by gas chromatography under the same conditions as water (c), the composition was as shown in Table 2.

[0125]

[0126] The most common impurity in water (d) was isopropanol at 0.9% by mass, and a small amount of acetone, a by-product of the dehydrogenation of isopropanol, was also detected, but at a low concentration. Because water (d) contains few impurities, it can be reused as water (a), water (b), and water (e).

[0127] Example 3: Reuse of Water (f) A mixed gas of propylene / oxygen / water / nitrogen (6.5 / 12 / 4 / 77.5 vol.%) was prepared from propylene obtained by dehydration of isopropanol, nitrogen, air, and water. This mixed gas was supplied to a first reactor filled with a catalyst (particle size 5-7 mm) containing bismuth and molybdenum, and then to a second reactor containing a catalyst (particle size 5-7 mm) containing molybdenum and vanadium. The first and second reactors were arranged from the gas inlet side, immersed in separate molten nitrate baths, and operated at their respective reaction temperatures to carry out the synthesis of acrylic acid from propylene. The molten nitrate bath temperature in the first reactor was 325°C, and the molten nitrate bath temperature in the second reactor was 275°C. The reaction pressure was atmospheric. A propylene conversion of 100% and an acrylic acid yield of 87% were obtained. The reactor outlet gas containing acrylic acid was cooled, and condensed components containing acrylic acid were recovered as a liquid. The resulting aqueous acrylic acid solution was subjected to azeotropic distillation using toluene as the azeotropic solvent, to obtain acrylic acid and water (f) with increased purity. This water (f) was analyzed by gas chromatography under the following conditions, and the composition was as shown in Table 3. Apparatus: Shimadzu GC-2014 Column: DB-FFAP (60 m) Column oven temperature: After holding at 50°C for 5 minutes, the temperature was increased to 240°C at a rate of 10°C / min and held at 240°C for 10 minutes Carrier gas: Helium Gas flow rate: 5 mL / min Internal standard: Anisole

[0128]

[0129] A relatively large amount of the target acrylic acid remained in the water (f). Therefore, it is preferable to reuse the water (e) as absorption water and recover the acrylic acid.

[0130] As described above, water (c) can be reused as water (a), water (b), and water (e), water (d) can be reused as water (a), water (b), and water (e), and water (f) can be reused as water (a), water (b), and water (e), with water (e) being the most preferable.

[0131] The large amount of water generated in the process of producing acrylic acid from ethanol or polyacrylic acid (salt) using the acrylic acid is no longer required to be treated by recycling, which can significantly reduce water treatment costs. By producing acrylic acid from raw material ethanol in a continuous flow, the water can be reused in processes appropriate to the impurity components and amounts in the water, eliminating the need for water treatment processes for long-distance transportation and wastewater treatment processes.

[0132] Example 4: Production of butyl acrylate (dehydration reaction step) A 6 L round-bottom flask connected to a Dean-Stark column was charged with 1968 g of acrylic acid (produced by steps (1) to (11) using bioethanol as a raw material), 2692 g of 1-butanol derived from biomass, 47 g of p-toluenesulfonic acid, and 9.3 g of hydroquinone, and the mixture was heated to a reflux temperature. The reaction was carried out while removing the produced water using the Dean-Stark column. The empty column was packed with a 40 mm Dixon packing, and the column top pressure was set to 30 kPa. Hydroquinone was also continuously added from the column top during the reaction. The reaction solution was analyzed by gas chromatography to observe the conversion of acrylic acid, and heating was stopped when the conversion reached 98% or more.

[0133] (Neutralization step) 400 g of a 10% aqueous sodium hydroxide solution was added to the reaction solution obtained in the dehydration reaction step and stirred to neutralize p-toluenesulfonic acid and residual acrylic acid. After discarding the neutralized solution, extraction was further performed three times with 800 g of water to remove water-soluble components, and 3,980 g of crude butyl acrylate in the oil phase was recovered.

[0134] (Purification Step) The crude butyl acrylate obtained in the neutralization step was purified by distillation. A continuous distillation column having 20 gated sieve trays was used for the distillation. The distillation was carried out at a column top pressure of 30 kPa, a reflux ratio of 10, a feed flow rate:bottom flow rate = 1.2:1.0, with the feed starting from the 10th sieve tray, and while continuously feeding hydroquinone and phenothiazine from the column top, distillation was carried out. Low boiling point substances were separated from the column top, and the liquid from which the low boiling point substances had been separated was obtained from the column bottom. Thereafter, while bottom-feeding the liquid obtained in the same apparatus, distillation was carried out at a column top pressure of 15 kPa, a reflux ratio of 1, a feed flow rate:bottom flow rate = 10:1, and while continuously feeding hydroquinone from the column top. 2150 g of purified butyl acrylate was obtained from the column top. Hydroquinone was added to the obtained purified butyl acrylate immediately after collection to a concentration of 10 ppm. The obtained purified butyl acrylate was analyzed using a gas chromatograph (detector: FID) to confirm the peaks of the main components and impurities in the chromatogram. As a result of the analysis, the obtained purified butyl acrylate had the same main components and impurities as butyl acrylate obtained when acrylic acid derived from fossil fuels was used as the raw material, and therefore it was found to have equivalent quality.

[0135] Example 5 Production of Butyl Acrylate Butyl acrylate was produced in the same manner as in Example 4, except that the butanol raw material in Example 4 was changed to fossil fuel-derived 1-butanol. The obtained purified butyl acrylate was found to have the same quality as butyl acrylate produced from biomass.

[0136] <<Production Example of Adhesive Tape Containing Polymer Using Acrylic Ester>> <Measurement Method>> The physical properties of each polymer emulsion were evaluated by the following methods.

[0137] [Nonvolatile Content (Solid Content)] 1 g of the pressure-sensitive adhesive composition was weighed and dried in a hot air dryer at a temperature of 110° C. for 1 hour, and the resulting residue was taken as the nonvolatile content and calculated using the following formula.

[0138]

[0139] [Viscosity] Measurement was carried out using a B-type rotational viscometer ("VISCOMETER TVB-10" manufactured by Toki Sangyo Co., Ltd.) under conditions of 25°C and 30 rpm.

[0140] [pH] The value was measured at 25°C using a pH meter ("F-23" manufactured by Horiba Ltd.).

[0141] [Average Particle Diameter] The average particle diameter was measured using a particle size distribution measuring instrument (Otsuka Electronics Co., Ltd. FPAR-1000) using a dynamic light scattering method.

[0142] [Bio-based carbon content of polymer] According to ISO 16620-2, the bio-based carbon content of each monomer １４ C number, １３ From the C number, the obtained polymer １４ C / １３ The calculated proportion of C was calculated as the biobased carbon content. １４ C number, １３ The C numbers are shown in the table below. The abbreviations in the table represent the following compounds: Bio-BA: １４ C-derived butyl acrylate BA: butyl acrylate 2EHA: 2-ethylhexyl acrylate MMA: methyl methacrylate Bio-AA: １４ C-derived acrylic acid AA: Acrylic acid produced by two-stage oxidation of fossil fuel-derived propylene HEMA: 2-hydroxyethyl methacrylate

[0143]

[0144] <Evaluation Methods> The physical properties of the pressure-sensitive adhesive tapes obtained in Examples 6 to 8 and Comparative Example 1 were evaluated by the following methods.

[0145] [SUS Adhesion Strength] The adhesive tape was cut into a rectangle 100 mm long and 25 mm wide, and the release paper was peeled off and the adhesive tape was placed on a SUS304 steel plate whose surface had been polished with 280 grit sandpaper in an atmosphere of 23°C and 50% relative humidity. The adhesive tape was then pressed from above by rolling a 2 kg rubber roller back and forth once. After leaving the tape to stand for 25 minutes, the peel force (adhesion strength) was measured when peeled at a peel angle of 180° and a peel speed of 300 mm / min, and the adhesive strength to the SUS surface was evaluated. This measurement was performed using a tensile tester ("QC Tensile Tester" manufactured by Tester Sangyo Co., Ltd.).

[0146] [Holding Power] The adhesive tape was cut into a rectangle 50 mm long and 25 mm wide, and in an atmosphere of 23°C and 50% relative humidity, a test piece was placed on a SUS surface whose surface had been polished with sandpaper of 280 grit size so that the adhesive area was 25 mm x 25 mm, and the test piece was pressed against the SUS surface by rolling a 2 kg rubber roller back and forth once from above the test piece. The pressed test piece was left in an atmosphere of 70°C for 20 minutes, and then a 1 kg weight was attached to the end of the adhesive sheet and hung from it, and the test piece was left to stand in the same atmosphere for 1,440 minutes, and the time required for the adhesive sheet to peel off or the width of displacement on the stainless steel plate was measured.

[0147] [Example 6] In a beaker, 25.7 parts of deionized water (parts by weight, the same applies hereinafter), 44.4 parts of biobutyl acrylate (BiO-BA, obtained in Example 4), 45.0 parts of 2-ethylhexyl acrylate (2EHA), 5.1 parts of methyl methacrylate (MMA), 2.0 parts of bioacrylic acid (Bio-AA, produced by steps (1) to (11) using bioethanol as a raw material), 3.5 parts of 2-hydroxyethyl methacrylate (HEMA), 0.03 parts of normal dodecyl mercaptan (n-DM), and 7.3 parts of "New Coal 707-SF" (manufactured by Nippon Nyukazai Co., Ltd.) (active ingredient 30%) as an emulsifier were added and stirred well to prepare a pre-emulsion. Next, 42.1 parts of deionized water and 1% of the pre-emulsion were charged into a reaction vessel equipped with a condenser, a nitrogen gas inlet tube, a thermometer, a dropping funnel, and a stirrer, and the atmosphere was replaced with nitrogen and the temperature was raised to 75°C. Then, 0.04 parts of potassium persulfate dissolved in 1 part of deionized water was added to the reaction vessel, and the pre-emulsion was continuously added dropwise over approximately 4 hours. At the same time, 0.36 parts of potassium persulfate dissolved in 10 parts of deionized water was added dropwise to carry out a polymerization reaction. After completion of the addition, the mixture was aged for 3 hours at 80°C in a nitrogen gas atmosphere, yielding a pressure-sensitive adhesive composition A-1 containing polymer A-1 and having a non-volatile content of 55%. The pressure-sensitive adhesive composition A-1 was applied to a PET (polyethylene terephthalate) film substrate (thickness: 50 μm) using an applicator and then dried at a temperature of 100°C for 3 minutes. This resulted in the formation of a 25 μm-thick pressure-sensitive adhesive layer on the PET. A release paper (trade name: K-80HS, manufactured by San-A Kaken Co., Ltd.) was attached to the adhesive layer, followed by aging at 23° C. for 24 hours to obtain an adhesive tape with one adhesive surface.

[0148] Example 7 The same procedures as in Example 6 were carried out, except that in the preparation of the pre-emulsion in Example 6, bioacrylic acid (Bio-AA) was replaced with acrylic acid (AA, produced by two-stage oxidation of fossil fuel-derived propylene), to obtain a PSA composition A-2 with a non-volatile content of 55% and a PSA tape therefor.

[0149] Example 8 The same operations as in Example 6 were carried out, except that in the preparation of the pre-emulsion in Example 6, biobutyl acrylate (Bio-BA) was replaced with butyl acrylate (BA, obtained by the dehydration reaction of acrylic acid produced by the two-stage oxidation of fossil fuel-derived propylene and fossil fuel-derived 1-butanol), to obtain a PSA composition A-3 with a non-volatile content of 55% and a PSA tape therefor.

[0150] Comparative Example 1 The same operations as in Example 6 were carried out to obtain a PSA composition B-1 with a non-volatile content of 55% and a PSA tape therefor, except that in the preparation of the pre-emulsion in Example 6, biobutyl acrylate (Bio-BA) was changed to butyl acrylate (BA, an ester of acrylic acid produced by the two-stage oxidation of fossil fuel-derived propylene) and bioacrylic acid (Bio-AA) was changed to acrylic acid (AA, produced by the two-stage oxidation of fossil fuel-derived propylene).

[0151] The abbreviations in the table represent the following compounds: Bio-BA: １４ C-derived butyl acrylate BA: butyl acrylate 2EHA: 2-ethylhexyl acrylate MMA: methyl methacrylate Bio-AA: １４ C-derived acrylic acid AA: Acrylic acid produced by two-stage oxidation of fossil fuel-derived propylene HEMA: 2-hydroxyethyl methacrylate n-DM: normal dodecyl mercaptan

[0152]

[0153] This application is based on Japanese Patent Application No. 2023-198629 filed on November 22, 2023 and Japanese Patent Application No. 2023-223201 filed on December 28, 2023, the disclosures of which are incorporated by reference in their entirety.

[0154] 1 Acetone synthesis reactor, 2 Acetone separation tower, 3 Acetone distillation tower, 4 Hydrogen separation unit, 5 Isopropanol synthesis reactor, 6 Isopropanol separation unit, 7 Propylene synthesis reactor, 8 Propylene separation unit, 9 Acrylic acid synthesis reactor, 10 Acrylic acid absorption tower, 11A Acrylic acid distillation tower, 11B Acrylic crystallizer, 12, 20, 21, 30, 31, 41, 50, 60, 61, 70, 80, 81, 90, 91, 100, 101, 102, 110, 111, 112, 113, 114, 120 Piping.

Claims

1. A method for producing acrylic acid, comprising the following steps (1) to (11): an acetone synthesis step (1) of reacting ethanol with water (a) to obtain a mixed gas (A) containing acetone, water vapor, carbon dioxide and hydrogen; an acetone separation step (2) of separating an acetone-containing aqueous solution and a mixed gas (B) containing carbon dioxide and hydrogen from the mixed gas (A); an acetone distillation step (3) of distilling the acetone-containing aqueous solution to separate acetone and water (c); a hydrogen separation step (4) of separating hydrogen from the mixed gas (B); an isopropanol synthesis step (5) of reacting the acetone obtained in the acetone distillation step (3) with the hydrogen obtained in the hydrogen separation step (4) to obtain a mixed gas (C) containing isopropanol; an isopropanol separation step (6) of separating isopropanol from the mixed gas (C); a propylene synthesis step (7) of dehydrating the isopropanol obtained in the isopropanol separation step (6) to obtain a mixed gas (D) containing propylene and water; a propylene separation step (8) of separating propylene and water (d) from the mixed gas (D); an acrylic acid synthesis step (9) of oxidizing the propylene obtained in the propylene separation step (8) to obtain a mixed gas (E) containing acrylic acid; an acrylic acid absorption step (10) of contacting the mixed gas (E) with water (e) to obtain an aqueous solution containing acrylic acid; and an acrylic acid purification step (11) of purifying the aqueous solution containing acrylic acid to obtain acrylic acid.

2. The method for producing acrylic acid according to claim 1, wherein at least one selected from the water (c) and the water (d) is reused as at least one selected from the water (a) and the water (e).

3. The method for producing acrylic acid according to claim 2, wherein the acetone separation step (2) comprises contacting the mixed gas (A) with water (b) to separate an acetone-containing aqueous solution from a mixed gas (B) containing carbon dioxide and hydrogen, and at least one selected from the water (c) and the water (d) is reused as at least one selected from the water (a), the water (b) and the water (e).

4. The method for producing acrylic acid according to claim 3, wherein the acrylic acid purification step (11) includes an acrylic acid distillation step (11A) of distilling the acrylic acid-containing aqueous solution to separate acrylic acid and water (f), and at least one selected from the water (c), the water (d) and the water (f) is reused as at least one selected from the water (a), the water (b) and the water (e).

5. The method for producing acrylic acid according to claim 1 or 2, wherein steps (1) to (11) are carried out in a continuous flow.

6. The method for producing acrylic acid according to claim 3, wherein the water (c) is reused as the water (a) and / or the water (b).

7. The method for producing acrylic acid according to claim 3, wherein the water (d) is recycled as at least one selected from the water (a), the water (b) and the water (e).

8. The method for producing acrylic acid according to claim 4, wherein the water (f) is reused as the water (e).

9. The method for producing acrylic acid according to claim 6, wherein the water (c) contains 5,000 ppm or less of methyl propyl ketone and 500 ppm or less of methyl isobutyl ketone.

10. The method for producing acrylic acid according to claim 7, wherein the content of isopropanol in the water (d) is 10,000 ppm or less.

11. The method for producing acrylic acid according to claim 8, wherein the acrylic acid purification step (11) comprises an acrylic acid distillation step (11A) of azeotropically distilling the acrylic acid-containing aqueous solution with an azeotropic solvent to separate acrylic acid and water (f), and the content of the azeotropic solvent component in the water (f) is 1000 ppm or less.

12. The method for producing acrylic acid according to claim 1 or 2, wherein the ethanol is bioethanol.

13. Acrylic acid obtained by the method for producing acrylic acid according to claim 1 or 2.

14. A method for producing polyacrylic acid (salt), comprising: obtaining acrylic acid by the method for producing acrylic acid according to claim 1 or 2; and polymerizing the acrylic acid after neutralization or in an unneutralized state.

15. Polyacrylic acid (salt), obtained by the method for producing polyacrylic acid (salt) according to claim 14.

16. A method for producing an acrylic ester, comprising: obtaining acrylic acid by the method for producing acrylic acid according to claim 1 or 2; and subjecting the acrylic acid to a dehydration reaction with an alcohol.

17. An acrylic ester obtained by the method for producing an acrylic ester according to claim 16.

18. A method for producing a polymer, comprising: obtaining acrylic acid by the method for producing acrylic acid according to claim 1 or 2, and / or obtaining an acrylic ester by the method for producing an acrylic ester according to claim 16; and polymerizing the acrylic acid and / or the acrylic ester.

19. A polymer obtained by the method for producing a polymer according to claim 18.

Images