Method for producing 1,3-butylene glycol

Abstract

To provide a method for producing high-purity 1,3-butylene glycol, which has a high potassium permanganate test value, an extremely low content of a low-boiling component and a high initial boiling point, with a high recovery rate.SOLUTION: There is provided a method for producing purified 1,3-butylene glycol from a crude reaction solution containing 1,3-butylene glycol, which comprises: in a dehydration column used in the dehydration step, distilling a feed liquid containing 1,3-butylene glycol and water and having an acetaldehyde content of 1000 ppm or less and a crotonaldehyde content of 400 ppm or less; distilling a liquid concentrated with low-boiling-point components containing water from the top of the feed stage; and in a product column used in the product distillation step, distilling a 1,3-butylene feed liquid having an acetaldehyde content of 500 ppm or less and a crotonaldehyde content of 200 ppm or less under conditions of a reflux ratio of more than 0.1.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a method for producing 1,3-butylene glycol. This application claims priority to Japanese Patent Application Nos. 2019-239974, 2019-239975, 2019-239976, 2019-239977, 2019-239978, and 2019-239979, filed in Japan on December 28, 2019, Japanese Patent Application No. 2020-006660, filed in Japan on January 20, 2020, and Japanese Patent Application No. 2020-018910, filed in Japan on February 6, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] 1,3-Butylene glycol is a colorless, transparent, odorless liquid with properties such as low volatility, low toxicity, and high hygroscopicity, and has excellent chemical stability. Therefore, its uses are diverse, including as a raw material for various synthetic resins and surfactants, as well as cosmetics, moisture absorbents, high-boiling-point solvents, and antifreeze materials. In recent years, 1,3-butylene glycol has particularly attracted attention for its excellent properties as a moisturizer, and demand for it in the cosmetics industry is expanding.

[0003] The crude reaction liquid produced during the production of 1,3-butylene glycol contains numerous low-boiling impurities, such as ethanol, butanol, acetaldehyde, crotonaldehyde, and esters. Among these, acetaldehyde and crotonaldehyde, when dimerized or further polymerized, produce high-boiling impurities. Furthermore, during the purification process of 1,3-butylene glycol, low-boiling and high-boiling impurities are produced due to heat and other factors. It is desirable to minimize the amount of such impurities in the 1,3-butylene glycol product. Japanese Patent Application Laid-Open No. 6-329664 discloses a method for controlling impurities derived from crotonaldehyde, a low-boiling impurity. Japanese Patent Application Laid-Open No. 2001-213828 discloses that highly pure 1,3-butylene glycol can be produced in high yield and economically by basifying the crude reaction liquid of 1,3-butylene glycol synthesized by hydrogenating acetaldols, distilling off the alcohol, and then distilling the resulting product. This document also describes removing low boiling impurities such as ethanol, isopropyl alcohol, and butanol by distillation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-329664 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-213828 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional methods have not been able to sufficiently remove low-boiling and high-boiling components from 1,3-butylene glycol. Cosmetics, an important use of 1,3-butylene glycol, generally contain water, and a long period of time is required between production and actual use by consumers. In addition, the liquid properties of cosmetics are strictly controlled to ensure storage stability, etc. When 1,3-butylene glycol, which contains low-boiling and high-boiling components, is used in cosmetics, the increased acid concentration can disrupt the liquid balance of the cosmetics, potentially resulting in a loss of the intended effects.In addition, the increased acid concentration in cosmetics can cause skin irritation and other problems for the user. Furthermore, cosmetics are exposed to air when used and when stored after use. Cosmetics are generally manufactured under an air atmosphere, and may also be heated for sterilization purposes. When 1,3-butylene glycol, which contains low-boiling and high-boiling components, is used in cosmetics, discoloration can occur due to the presence of air or heat. To solve these problems, it has been necessary to remove by-products from crude 1,3-butylene glycol and to highly purify the 1,3-butylene glycol.

[0006] Meanwhile, one of the quality standards for 1,3-butylene glycol is the initial boiling point. The higher the initial boiling point, the better the quality. However, to date, little technical research has been conducted to improve the initial boiling point. Another quality standard for 1,3-butylene glycol is the dry point. The lower the dry point, the better the quality. If high-boiling-point impurities produced during the reaction or purification process are mixed into the product, they not only reduce the purity of the product but also cause the dry point to rise, resulting in a product that does not meet quality standards. However, to date, little research has been done on methods for separating and removing high-boiling-point impurities. Furthermore, one of the product standards for 1,3-butylene glycol is the potassium permanganate test value (abbreviated as PMT), but the potassium permanganate test values of 1,3-butylene glycol products obtained using conventional methods have not always been fully satisfactory. Furthermore, the substances that cause the potassium permanganate test values of 1,3-butylene glycol products to decrease have not been identified. That is, until now, there has been no method for industrially and efficiently producing a 1,3-butylene glycol product that is excellent in two properties, namely, initial boiling point and dry point, two properties, namely, initial boiling point and potassium permanganate test value, or all three properties, namely, initial boiling point, dry point and potassium permanganate test value.

[0007] Therefore, an object of the present disclosure is to provide a method for industrially and efficiently producing high-purity 1,3-butylene glycol that has an extremely low content of low-boiling point components and high-boiling point components, a high initial boiling point, and a low dry point. Another object of the present disclosure is to provide a method for industrially and efficiently producing high-purity 1,3-butylene glycol that has an extremely low content of low-boiling point components, a high initial boiling point, and a high potassium permanganate test value. Another object of the present disclosure is to provide a method for industrially and efficiently producing high-purity 1,3-butylene glycol that exhibits a high potassium permanganate test value, has extremely low contents of low-boiling point components and high-boiling point components, and has a high initial boiling point and a low dry point. [Means for solving the problem]

[0008] As a result of intensive research to achieve the above-mentioned object, the inventors of the present disclosure have found that by specifying the contents of acetaldehyde and crotonaldehyde in the feed liquid to a dehydrating tower and distilling the feed liquid, whose contents of acetaldehyde and crotonaldehyde are not more than a specific value, at a specific reflux ratio in a product tower, high-purity 1,3-butylene glycol with extremely low contents of low-boiling and high-boiling components can be obtained from below the feed stage. Furthermore, they have found that by specifying the contents of acetaldehyde and crotonaldehyde in the feed liquid to a dehydrating tower and distilling a feed liquid containing 1,3-butylene glycol at a specific reflux ratio in a high-boiling separation tower, high-purity 1,3-butylene glycol with extremely low contents of low-boiling and high-boiling components can be obtained from above the feed stage. The present disclosure was completed based on these findings and further research.

[0009] That is, the present disclosure provides a method for producing 1,3-butylene glycol, which obtains purified 1,3-butylene glycol from a reaction crude liquid containing 1,3-butylene glycol, comprising: The process includes a dehydration process for removing water by distillation, a high boiling point removal process for removing high boiling point components by distillation, and a product distillation process for obtaining purified 1,3-butylene glycol. In the dehydration tower used in the dehydration step, a feed liquid containing 1,3-butylene glycol and water and having an acetaldehyde content of 1000 ppm or less and a crotonaldehyde content of 400 ppm or less is distilled, and a liquid containing concentrated low-boiling components including water is distilled from above the feed tray; The present invention provides a method for producing 1,3-butylene glycol (hereinafter, sometimes referred to as "Production Method 1 of the present disclosure"), in which a 1,3-butylene glycol feed solution having an acetaldehyde content of 500 ppm or less and a crotonaldehyde content of 200 ppm or less is distilled in a product column used in the product distillation step under conditions of a reflux ratio of more than 0.1, a liquid concentrated with low boiling point components is distilled from above the feed stage, and 1,3-butylene glycol is withdrawn from below the feed stage.

[0010] In the production method, it is preferable that in the high boiling point removal tower used in the high boiling point removal step, a feed liquid containing 1,3-butylene glycol is distilled under conditions of a reflux ratio of 0.02 or more, 1,3-butylene glycol with improved purity is distilled from above the feed stage, and a liquid in which high boiling point components are concentrated is withdrawn from below the feed stage.

[0011] It is also preferred that the concentration of 1,3-butylene glycol in the liquid charged to the product column is 90 GC area % or more, and the content of water in the liquid charged is 3 wt % or less.

[0012] The present disclosure also provides a method for producing 1,3-butylene glycol, which comprises obtaining purified 1,3-butylene glycol from a reaction crude liquid containing 1,3-butylene glycol, the method comprising the steps of: The method includes a dehydration step for removing water by distillation and a high boiling point removal step for removing high boiling point components by distillation, In the dehydration tower used in the dehydration step, a feed liquid containing 1,3-butylene glycol and water and having an acetaldehyde content of 1000 ppm or less and a crotonaldehyde content of 400 ppm or less is distilled, and a liquid containing concentrated low-boiling components including water is distilled from above the feed tray; The present invention provides a method for producing 1,3-butylene glycol (hereinafter, sometimes referred to as "Production Method 2 of the present disclosure"), in which a feed liquid containing 1,3-butylene glycol is distilled at a reflux ratio of more than 0.02 in a high boiling point removal tower used in the high boiling point removal step, and 1,3-butylene glycol with improved purity is distilled from above the feed stage, and a liquid in which high boiling point components are concentrated is withdrawn from below the feed stage.

[0013] In each of the above production methods, the reflux ratio in the dehydration tower is preferably 0.03 or more.

[0014] The reaction crude liquid containing 1,3-butylene glycol may be a reaction crude liquid obtained by hydrogen reduction of acetaldols.

[0015] Each of the above production methods may further include at least one of an alkali treatment step of treating a process stream containing 1,3-butylene glycol with a base, a desalting step of removing salts in the process stream containing 1,3-butylene glycol, and a dealcoholization step of removing low boiling points including alcohol in the process stream containing 1,3-butylene glycol.

[0016] In the present disclosure, "1,3-butylene glycol product" refers to a composition in which 1,3-butylene glycol accounts for the majority of the constituent components (for example, the 1,3-butylene glycol content is 95% by weight or more, preferably 98% by weight or more). [Effects of the Invention]

[0017] According to the production method of the present disclosure, it is possible to industrially efficiently produce high-purity 1,3-butylene glycol having an extremely low content of low-boiling point components and high-boiling point components, a high initial boiling point and a low dry point, high-purity 1,3-butylene glycol having an extremely low content of low-boiling point components, a high initial boiling point and a high potassium permanganate test value, and further high-purity 1,3-butylene glycol having a high potassium permanganate test value, an extremely low content of low-boiling point components and high-boiling point components, a high initial boiling point and a low dry point. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a flowchart showing an example of a method for producing (purifying) 1,3-butylene glycol according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] [Method of producing 1,3-butylene glycol] Production method 1 of the present disclosure is a method for producing 1,3-butylene glycol (1,3BG) from a crude reaction liquid containing 1,3-butylene glycol (1,3BG) (hereinafter, may be referred to as "crude 1,3-butylene glycol"), and includes a dehydration step for removing water by distillation, a high-boiling point removal step for removing high-boiling components by distillation, and a product distillation step for obtaining purified 1,3-butylene glycol. In the dehydration tower used in the dehydration step, a feed solution containing 1,3-butylene glycol and water and having an acetaldehyde (AD) content of 1,000 ppm or less and a crotonaldehyde (CR) content of 400 ppm or less is distilled, and a liquid concentrated with low-boiling-point components including water is distilled from above the feed stage. In the product tower used in the product distillation step, a 1,3-butylene glycol feed solution having an acetaldehyde content of 500 ppm or less and a crotonaldehyde content of 200 ppm or less is distilled under conditions of a reflux ratio of more than 0.1, and a liquid concentrated with low-boiling-point components is distilled from above the feed stage. The 1,3-butylene glycol obtained in this manner has a high potassium permanganate test value, very low contents of low-boiling-point components and high-boiling-point components, a high initial boiling point, and a low dry point, and can be used as a 1,3-butylene glycol product.

[0020] In Production Method 2 of the present disclosure, a method for producing 1,3-butylene glycol is provided, in which purified 1,3-butylene glycol is obtained from a crude reaction liquid (crude 1,3-butylene glycol) containing 1,3-butylene glycol, and the method includes a dehydration step for removing water by distillation and a high-boiling component removal step for removing high-boiling components by distillation. In the dehydration step, a feed liquid containing 1,3-butylene glycol and water and having an acetaldehyde content of 1,000 ppm or less and a crotonaldehyde content of 400 ppm or less is distilled to distill a liquid concentrated with low-boiling components containing water from above the feed stage. In the high-boiling component removal tower used in the high-boiling component removal step, the feed liquid containing 1,3-butylene glycol is distilled under conditions of a reflux ratio of more than 0.02 to distill 1,3-butylene glycol with improved purity from above the feed stage, and a liquid concentrated with high-boiling components is withdrawn from below the feed stage. The 1,3-butylene glycol thus obtained has an extremely low content of low-boiling point components and high-boiling point components, and can be converted into a 1,3-butylene glycol product by treating it with an alkali as needed.

[0021] The "Manufacturing Method 1 of the Present Disclosure" and the "Manufacturing Method 2 of the Present Disclosure" may be collectively referred to as the "Manufacturing Method of the Present Disclosure."

[0022] In this specification, the term "GC area %" refers to the ratio of the peak area of a component to the total peak area in gas chromatography analysis, which will be described later.

[0023] [Crude 1,3-butylene glycol] Examples of crude 1,3-butylene glycol include (1) a reaction crude liquid obtained by the reduction (hydrogenation) of acetaldols, (2) a reaction crude liquid obtained by the hydrolysis of 1,3-butylene oxide, (3) a reaction crude liquid obtained by the selective hydrogenolysis of erythritol, (4) a reaction crude liquid obtained by the selective addition of water to butadiene, (5) a reaction crude liquid obtained by the hydrogenation of n-butanal-3-one, (6) a reaction crude liquid obtained by the hydrogenation of 1-butanol-3-one, (7) a reaction crude liquid obtained by the hydrogenation of 3-hydroxy-1-butanoic acid, (8) a reaction crude liquid obtained by the hydrogenation of β-butyrolactone, and (9) a reaction crude liquid obtained by the hydrogenation of diketene. In the present disclosure, crude 1,3-butylene glycol may be one or a mixture of two or more of the above (1) to (9). The crude 1,3-butylene glycol is preferably a crude reaction liquid obtained by the reduction (particularly, liquid phase reduction) of acetaldols (1) above.

[0024] Hereinafter, the case where a crude reaction liquid obtained by reduction (hydrogenation) of acetaldols is used as crude 1,3-butylene glycol will be mainly described. The step of reducing (hydrogenating) acetaldols may also be referred to as the "hydrogenation step."

[0025] The acetaldol used as a raw material in the hydrogenation step is not particularly limited as long as it is a compound that can be converted to 1,3-butylene glycol by hydrogen reduction. Examples of the raw material acetaldol include acetaldol, its cyclized dimer, para-aldol, aldoxane, a cyclic trimer of acetaldehyde, and mixtures thereof.

[0026] The method for producing acetaldols (e.g., acetaldol and para-aldol) is not particularly limited, but may be, for example, those obtained by an aldol condensation reaction of acetaldehyde in the presence of a basic catalyst, or those obtained by thermal decomposition of aldoxane, etc. The process for producing acetaldols may be referred to as an "acetaldol production process" or an "acetaldehyde polymerization process."

[0027] The reaction crude liquid containing acetaldols obtained by the above reaction may be neutralized with an acid and used to produce 1,3-butylene glycol. In addition to acetaldols, such a reaction crude liquid may contain acetaldehyde (AD), crotonaldehyde (CR), other aldehyde components, low-boiling substances, high-boiling substances such as aldehyde dimers and trimers, water, salts, etc. In this specification, compounds having a boiling point lower than that of 1,3-butylene glycol may be referred to as "low-boiling substances" or "low-boiling products," and compounds having a boiling point higher than that of 1,3-butylene glycol may be referred to as "high-boiling substances" or "high-boiling products."

[0028] The reaction crude liquid containing the acetaldols may be subjected to pretreatment such as dealcoholization distillation, dehydration distillation, desalting, alkali treatment, dealkalization treatment, and impurity removal, as necessary, to remove by-products such as unreacted acetaldehyde and crotonaldehyde, and may be used after that. Pretreatment methods include distillation, adsorption, ion exchange, heating to convert to high boiling point substances, and decomposition. Various distillation methods can be used for distillation, such as reduced pressure, normal pressure, increased pressure, azeotropy, extraction, and reaction. In particular, it is preferred to subject the reaction crude liquid containing acetaldols to simple evaporation, distillation, or hydrogenation to remove aldehydes such as acetaldehyde and crotonaldehyde, and then subject the resulting product to a hydrogenation step.

[0029] The content of acetaldols in the hydrogenation raw material is not particularly limited, but is, for example, 30% by weight or more (e.g., 30 to 99% by weight), more preferably 40% by weight or more (e.g., 40 to 98% by weight), 50% by weight or more (e.g., 50 to 97% by weight), or 60% by weight or more (e.g., 60 to 95% by weight), even more preferably 65 to 90% by weight, particularly preferably 70 to 90% by weight, and most preferably 75 to 90% by weight. When the content of acetaldols is within the above range, impurities contained in the reaction crude liquid containing 1,3-butylene glycol (crude 1,3-butylene glycol) tend to be reduced.

[0030] The hydrogenation raw material may or may not contain water, but preferably does so from the viewpoint of the purity of the 1,3-butylene glycol product. The water content of the hydrogenation raw material is not particularly limited, but is preferably, for example, 2% by weight or more, more preferably 5% by weight or more, even more preferably 10% by weight or more, and particularly preferably 15% by weight or more. The upper limit may be, for example, 90% by weight, 80% by weight, 70% by weight, 60% by weight, 50% by weight, 40% by weight, 30% by weight, or 20% by weight. When the water content is within the above range, the amount of acetal compounds between 1,3-butylene glycol and acetaldol contained in the obtained crude 1,3-butylene glycol is reduced, and therefore the purity of the finally obtained 1,3-butylene glycol product tends to be higher. This is because the presence of a certain amount of water in the hydrogenation raw material causes the acetal compounds to be hydrolyzed to 1,3-butylene glycol, and the co-produced acetaldol is reduced to 1,3-butylene glycol.

[0031] Examples of hydrogenation catalysts include Raney nickel. The hydrogenation catalyst can be used in a suspended state or packed in a reaction vessel. The amount of hydrogenation catalyst used is not particularly limited, but is preferably 1 to 30 parts by weight, more preferably 4 to 25 parts by weight, even more preferably 8 to 20 parts by weight, and particularly preferably 12 to 18 parts by weight, per 100 parts by weight of the hydrogenation raw material. The amount of hydrogen used in the reduction reaction is not particularly limited, but is preferably 0.5 to 40 parts by weight, more preferably 1 to 30 parts by weight, even more preferably 4 to 20 parts by weight, and particularly preferably 8 to 12 parts by weight, per 100 parts by weight of the hydrogenation raw material. The pressure in the reaction system (total pressure; gauge pressure) in the reduction reaction is not particularly limited, but is, for example, 9 to 70 MPa, preferably 10 to 40 MPa. The hydrogen pressure (hydrogen partial pressure) in the reaction system is not particularly limited, but is, for example, 7 to 60 MPa, preferably 10 to 30 MPa. From the viewpoint of reducing reducing substances such as acetaldehyde and crotonaldehyde, it is advisable to increase the hydrogen pressure in the reaction system, preferably to 10 MPa or more, and may be 100 MPa. Increasing the hydrogen pressure in the reaction system can render acetaldehyde, crotonaldehyde, and other reducing substances harmless, and can also reduce the concentrations of acetaldehyde, crotonaldehyde, and other reducing substances in the dehydrating tower feed liquid described below, as well as trace amounts of other impurities such as acetals. This provides the advantage that product quality can be maintained even if the reflux ratios and distillate amounts of the dehydrating tower, high boiling removal tower, and product tower in the 1,3-butylene glycol purification step are relatively reduced.

[0032] The reaction temperature in the reduction reaction is not particularly limited, but is, for example, 40 to 150°C, preferably 50 to 140°C, and more preferably 60 to 130°C. The reaction time (residence time) in the reduction reaction is not particularly limited, but is, for example, 10 to 500 minutes, preferably 20 to 400 minutes, more preferably 30 to 300 minutes, even more preferably 50 to 280 minutes, and particularly preferably 80 to 250 minutes. This reaction can be carried out in any of a batch system, a semi-batch system, and a continuous system.

[0033] The crude 1,3-butylene glycol thus obtained contains low-boiling substances (low-boiling compounds) having unsaturated bonds, such as acetaldehyde (AD), butylaldehyde, crotonaldehyde (CR), acetone, and methyl vinyl ketone, as well as condensates thereof, condensates of 1,3-butylene glycol with the above-mentioned low-boiling substances (for example, acetals formed from 1,3-butylene glycol and acetaldol), alcohols such as ethanol, isopropyl alcohol, and butanol, water (solvent), salts produced by neutralization treatment, and catalysts (when used in suspension). By removing these impurities in a purification step, a 1,3-butylene glycol product (purified 1,3-butylene glycol) can be obtained.

[0034] [Purification of crude 1,3-butylene glycol] Production method 1 of the present disclosure includes at least a dehydration step of removing water by distillation, a high boiling point removal step of removing high boiling point components by distillation (high boiling point removal distillation step), and a product distillation step for obtaining purified 1,3-butylene glycol. Production method 2 of the present disclosure includes at least a dehydration step of removing water by distillation and a high boiling point removal step of removing high boiling point components by distillation (high boiling point removal distillation step).

[0035] In the production method of the present disclosure, the order of the dehydration step and the high-boiling point removal step does not matter. In Production Method 1 of the present disclosure, both the dehydration step and the high-boiling point removal step are performed before the product distillation step. In addition to these steps, the production method of the present disclosure may also include a desalting step, an alkali reaction step (alkali treatment step), and a dealkalization step. Furthermore, a catalyst separation step, an alkali neutralization step, and a dealcoholization step (low-boiling point removal step) may also be performed before the dehydration step. The above steps may be performed in the order described above, but the order of the steps may be changed as appropriate, except that the dealcoholization step is performed after the alkali reaction step. For example, the dealcoholization step (low-boiling point removal step), desalting step, alkali reaction step, and dealkalization step may be performed at any appropriate location, but are typically performed after the hydrogenation step. Among the above steps, the catalyst separation step, alkali neutralization step, dealcoholization step (low-boiling point removal step), desalting step, alkali reaction step, and dealkalization step may be performed as needed, but are not necessarily required.

[0036] FIG. 1 is a flow sheet of an apparatus showing an example of an embodiment of the method for producing 1,3-butylene glycol of the present disclosure. A is a dehydrating tower and is related to the dehydration step. B is a demineralizing tower and is related to the demineralizing step. C is a high boiler removal distillation tower (high boiler removal tower) and is related to the high boiler removal distillation step (high boiler removal step). D is an alkali reactor and is related to the alkali reaction step. E is a dealkalizing tower and is related to the dealkalizing step. F is a product distillation tower (product tower) and is related to the product distillation step. A-1, B-1, C-1, E-1, and F-1 are condensers. A-2, C-2, and F-2 are reboilers. Hereinafter, an example of an embodiment of the method for producing 1,3-butylene glycol of the present disclosure will be described using this flow sheet.

[0037] Crude 1,3-butylene glycol (corresponding to "X-1") obtained by hydrogen reduction of the hydrogenated raw material is supplied to the dehydration tower A. The crude 1,3-butylene glycol (corresponding to "X-1") may be supplied to the dehydration tower A after undergoing a dealcoholization step (distillation step using a dealcoholization tower) for removing alcohols such as ethanol and low boiling points.

[0038] In the production method of the present disclosure, in a dehydration tower A used in the dehydration step, a feed liquid containing 1,3-butylene glycol and water and having an acetaldehyde content of 1000 ppm or less and a crotonaldehyde content of 400 ppm or less is distilled, and a liquid concentrated with low boiling point components including water is distilled from above the feed stage (preferably the top of the tower) (corresponding to "X-2" in FIG. 1). Also, a crude 1,3-butylene glycol stream containing 1,3-butylene glycol is obtained from below the feed stage (preferably the bottom of the tower).

[0039] Dehydration column A and other distillation columns for separating 1,3-butylene glycol can be, for example, perforated plate columns or bubble cap columns. However, packed columns with low pressure loss, such as Sulzer Packing or Melapak (both trade names of Sumitomo Heavy Industries, Ltd.), are preferred. This is because 1,3-butylene glycol and trace impurities contained therein undergo thermal decomposition at high temperatures (e.g., 150°C or higher) to produce low-boiling substances that cause coloration, and therefore the distillation temperature must be low. Furthermore, a long thermal history (residence time) of 1,3-butylene glycol can have a similar effect. Therefore, the reboiler used should be one with a short residence time for the process fluid, such as a gravity-flow thin-film evaporator or a forced-agitation thin-film evaporator.

[0040] The number of theoretical plates in the dehydrating column A is, for example, 1 to 100, preferably 2 to 80, 3 to 80, 4 to 60, 5 to 40, 6 to 30, or 7 to 20, and more preferably 8 to 15. The feed position of the charge liquid is, for example, 10 to 90%, preferably 20 to 80%, more preferably 30 to 70%, and even more preferably 40 to 60% of the height of the column downward from the top of the column. In the distillation in the dehydrating column A, the pressure (absolute pressure) at the top of the column is, for example, 101 kPa or less, preferably 0.1 to 90 kPa, more preferably 0.5 to 70 kPa, even more preferably 1 to 50 kPa, 2 to 30 kPa, or 3 to 20 kPa, and particularly preferably 4 to 10 kPa. The distillation in the dehydration column A may be carried out under pressure, and in that case, the pressure (gauge pressure) at the top of the column may be, for example, 0.2 MPaG or less, or 0.1 MPaG or less.

[0041] The concentration of 1,3-butylene glycol in the liquid fed to dehydrating tower A is, for example, 9% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, even more preferably 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, 55% by weight or more, or 60% by weight or more, and particularly preferably 70% or more. The upper limit of the concentration of 1,3-butylene glycol in the liquid fed to dehydrating tower A is, for example, 90% by weight, 85% by weight, or 80% by weight. However, in consideration of the hydrogenation reaction in the step before the dehydration step, etc., a higher water concentration in the liquid fed to dehydrating tower A may be preferable. Taking all of this into consideration, the concentration of 1,3-butylene glycol in the feed liquid to dehydration column A may be, for example, 1% by weight or more, 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. In addition, the concentration of 1,3-butylene glycol in the feed liquid to dehydration column A may be, for example, 99% by weight or less, 95% by weight or more, 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, or 45% by weight or less. The concentration of 1,3-butylene glycol in the liquid charged to the dehydrating tower A can be adjusted to the above range by, for example, adjusting the reaction conditions in the hydrogenation step (e.g., the concentration of acetaldols used as a raw material) and the distillation conditions of a dealcoholization tower (low boiling point removal tower) that is installed as needed before the dehydrating tower.

[0042] The concentration (wt%) of 1,3-butylene glycol was determined by calculating the ratio of the area of the 1,3-butylene glycol peak to the total peak area (GC area%) in gas chromatography analysis under the following conditions, and then calculating it using the following formula: The concentration (wt%) of water in the liquid charged to dehydration tower A was measured by the method described below (Karl Fischer method). Concentration of 1,3-butylene glycol in the feed liquid to dehydration tower A (wt%) = (1 - water concentration in the feed liquid to dehydration tower A (wt%) / 100) x GC area % of the above 1,3-butylene glycol (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0043] In the production method of the present disclosure, the acetaldehyde content in the feed liquid to dehydration column A is set to 1000 ppm or less, and the crotonaldehyde content is set to 400 ppm or less. The acetaldehyde content in the feed liquid to dehydration column A is preferably 900 ppm or less, more preferably 800 ppm or less, 700 ppm or less, 600 ppm or less, or 500 ppm or less, and even more preferably 400 ppm or less, 300 ppm or less, 200 ppm or less, 155 ppm or less, or 140 ppm or less, and may be 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or 1 ppm or less.

[0044] The content of crotonaldehyde in the feed liquid to dehydration column A is preferably 300 ppm or less, more preferably 200 ppm or less, even more preferably 150 ppm or less, 130 ppm or less, 117 ppm or less, or 100 ppm or less, and may be 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or 1 ppm or less.

[0045] The acetaldehyde and crotonaldehyde contents in the feed liquid to dehydrating tower A can be reduced, for example, by providing a dealcoholization tower (low boiling point removal tower) upstream of dehydrating tower A and adjusting the distillation conditions of the dealcoholization tower (low boiling point removal tower). For example, the acetaldehyde and crotonaldehyde contents in the feed liquid to dehydrating tower A can be reduced by increasing the reflux ratio, number of stages, and distillate yield of the dealcoholization tower (low boiling point removal tower). Furthermore, the acetaldehyde and crotonaldehyde contents can also be adjusted by the conditions of the hydrogenation reaction in the hydrogenation step. When hydrogenation is completed, the acetaldehyde and crotonaldehyde concentrations can be reduced to below the detection limit, but disadvantages such as an increase in reaction pressure and a larger reaction tank arise.

[0046] The acetaldehyde content and the crotonaldehyde content in the liquid fed to the dehydration tower A can be determined by GC-MS analysis (gas mass spectrometry) as described below.

[0047] In the production method of the present disclosure, the water content in the liquid fed to dehydration tower A is, for example, 90% by weight or less, 85% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, or 40% by weight or less, preferably 35% by weight or less, more preferably 30% by weight or less, and even more preferably 25% by weight or less. The lower limit of the water content in the liquid fed to dehydration tower A is, for example, 10% by weight or 15% by weight. In addition, when considering the hydrogenation reaction in the hydrogenation step, a high water concentration and low viscosity are advantageous for the hydrogenation reaction because they increase the solubility and dispersibility of hydrogen in the liquid. The water content in the liquid fed to dehydration tower A can be reduced, for example, by providing a dealcoholization tower (low boiling point removal tower) upstream of dehydration tower A and adjusting the distillation conditions of the dealcoholization tower (low boiling point removal tower). For example, the water content in the liquid charged to the dehydrating tower A can be reduced by increasing the reflux ratio, number of stages, and distillate rate of the dealcoholization tower (low boiling point removal tower). The water content in the liquid charged to the dehydrating tower A can be quantified using a Karl Fischer water content meter.

[0048] In the production method of the present disclosure, the content of low-boiling components (excluding water) in the feed liquid to dehydrating tower A is, for example, 20% or less, preferably 10% or less, more preferably 8% or less, even more preferably 5% or less, particularly preferably 3% or less or 2% or less, and may be 1% or less, 0.5% or less, or 0.1% or less. The content of low-boiling components excluding water (also referred to as "low boilers" or "low boilers") in the feed liquid to dehydrating tower A is the ratio (area %) of the total area of peaks having a shorter retention time than the peak of 1,3-butylene glycol to the total peak area in gas chromatography analysis under the above conditions. The content of low-boiling components (excluding water) in the feed liquid to dehydrating tower A can be reduced, for example, by providing a dealcoholization tower (low boiling tower) upstream of dehydrating tower A and adjusting the distillation conditions of the dealcoholization tower (low boiling tower). For example, by increasing the reflux ratio, number of stages, or distillate rate of the dealcoholization tower (low boiling point removal tower), it is possible to reduce the concentration of low boiling point components (excluding water) in the liquid fed to the dehydration tower A. In addition, the concentration of low boiling point components (excluding water) in the liquid fed to the dehydration tower A can also be reduced by, for example, the reaction conditions (e.g., reaction temperature) in the hydrogenation step.

[0049] The content of high-boiling components in the liquid fed to dehydrating column A is, for example, 20% or less, preferably 10% or less, more preferably 7% or less, 4% or less, 3% or less, or 2% or less, even more preferably 1% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, or 0.05% or less, and particularly preferably 0.01% or less. The content of high-boiling components in the liquid fed to dehydrating column A can be adjusted, for example, by the reaction conditions in the hydrogenation step (e.g., reaction temperature, etc.). The content of high-boiling components in the liquid fed to dehydrating column A is the ratio (area %) of the total area of peaks having a longer retention time than the 1,3BG peak to the total peak area in gas chromatography analysis under the above conditions.

[0050] In the production method of the present disclosure, the reflux ratio in dehydrating tower A [amount refluxed to dehydrating tower / amount distillate from dehydrating tower (amount discharged outside the distillation tower)] is, for example, 0.03 or more. In the reflux to dehydrating tower A, a condensate of the vapor from the top of the dehydrating tower is usually refluxed to the dehydrating tower, but part or all of the reflux may be replaced by feeding a water-containing liquid (e.g., pure water) to the dehydrating tower. In this case, the "amount refluxed to dehydrating tower" refers to the sum of the amount of the condensate of the vapor from the top of the dehydrating tower refluxed to the dehydrating tower and the amount of the water-containing liquid (e.g., pure water) fed to the dehydrating tower.

[0051] The reflux ratio in the dehydrating tower A is preferably 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.1 or more, 0.12 or more, 0.14 or more, 0.16 or more, 0.18 or more, 0.2 or more, 0.22 or more, 0.24 or more, 0.26 or more, from the viewpoint of reducing the content of low boiling points (including water) in the crude 1,3-butylene glycol stream containing 1,3-butylene glycol taken out from below the feed tray of the dehydrating tower A (preferably from the bottom of the tower). or more, 0.28 or more, 0.3 or more, 0.33 or more, 0.36 or more, 0.4 or more, 0.45 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more or 9 or more, and more preferably 10 or more (for example, 15 or more, 20 or more, 25 or more, 30 or more or 40 or more). In particular, in Production Method 2 of the present disclosure, the reflux ratio in dehydration tower A is preferably 0.2 or more, more preferably 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.5 or more, 2 or more, 3 or more, or 4 or more, even more preferably 5 or more, and particularly preferably 10 or more. From the viewpoint of energy costs, the upper limit of the reflux ratio is, for example, 50 (less than 50), preferably 20 (less than 20), more preferably 10 (less than 10). Note that when the number of theoretical plates in dehydration tower A is large, sufficient separation is possible even if the reflux ratio is about 0.03.

[0052] In the production method of the present disclosure, the distillation rate in dehydrating tower A can be appropriately set depending on the concentration of water in the feed liquid to dehydrating tower A. The distillation rate is desirably a rate sufficient to distill off all of the water in the feed liquid. For example, when the water concentration in the feed liquid to dehydrating tower A is X% by weight, the distillation rate in dehydrating tower A is preferably X% by weight or more. Therefore, the distillation rate in dehydrating tower A is, for example, 95% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 10% by weight or less, or 5% by weight or less. The distillate yield refers to the ratio (wt %) of the amount of liquid withdrawn from the dehydrating tower A above the feed tray (for example, the top of the tower) to the amount charged to the dehydrating tower A.

[0053] In the production method of the present disclosure, the 1,3BG recovery rate in the dehydration tower A is, for example, 99.3% or more. In this specification, the 1,3BG recovery rate in the dehydration tower A is a value (%) calculated by the following formula: {1 - [1,3BG concentration in distillate (wt%) x (distillate volume (parts) - recycled volume (parts))] / (1,3BG concentration in feed solution (wt%) x feed volume (parts))} x 100 Furthermore, low-boiling and high-boiling substances may be hydrolyzed with water to produce 1,3BG, while high-boiling substances may be produced by polymerization of 1,3BG. Furthermore, trace impurities may be produced or lost, so the material balance in the dehydration tower may not always be achieved. This also applies to other distillation towers, such as dealcoholization towers (low-boiling towers), high-boiling towers, and product towers.

[0054] Next, a crude 1,3-butylene glycol stream containing 1,3-butylene glycol withdrawn from the dehydrating tower A below the feed tray (preferably from the bottom) is supplied to a demineralizing tower B. In the demineralizing tower B, a crude 1,3-butylene glycol stream after desalting is obtained from the top of the tower by distillation, and salts, high boiling point substances, etc. are discharged as bottoms from the bottom of the tower. The bottoms rate (%) of the demineralizing tower B [(demineralizing tower bottoms amount (parts) / demineralizing tower charge amount (parts)) × 100] is, for example, 0.1 to 40 wt%, preferably 1 to 35 wt%, more preferably 2 to 30 wt%, even more preferably 3 to 25 wt%, particularly preferably 5 to 20 wt%, and may be 7 to 15 wt%. At least a portion of the bottoms from the demineralizing tower may be recycled to a process prior to the desalting step.

[0055] The crude 1,3-butylene glycol stream after the desalting is supplied to a high boiling removal column C. In the high boiling removal column C, high boiling components (high boilers) are discharged from below the feed tray (preferably from the bottom of the column). On the other hand, a crude 1,3-butylene glycol stream after the high boilers have been removed (1,3-butylene glycol with improved purity) is obtained from above the feed tray.

[0056] Although perforated plate columns, bubble cap columns, and the like can be used as the high-boiling column C, a packed column with low pressure loss, such as Sulzer Packing or Melapak (both trade names of Sumitomo Heavy Industries, Ltd.), is more preferred. This is because 1,3-butylene glycol and trace amounts of impurities contained therein undergo thermal decomposition at high temperatures (e.g., 150°C or higher), producing low-boiling substances that cause coloration, and therefore the distillation temperature must be low. Furthermore, a long thermal history (residence time) of 1,3-butylene glycol can have a similar effect. Therefore, the reboiler used is preferably one with a short residence time for the process fluid, such as a gravity-flow thin-film evaporator or a forced-agitation thin-film evaporator.

[0057] The number of theoretical plates in the high boiling removal column C is, for example, 1 to 100, preferably 2 to 90, more preferably 3 to 80, even more preferably 4 to 70, 5 to 60, 8 to 50, or 10 to 40, and particularly preferably 15 to 30. The feed position of the charge liquid is, from the top of the high boiling removal column downward, for example, 10 to 90%, preferably 20 to 80%, more preferably 30 to 70, and even more preferably 40 to 60% of the height of the column. In the distillation in the high boiling removal column C, the pressure (absolute pressure) at the top of the column is, for example, 0.01 to 50 kPa, preferably 0.1 to 30 kPa, more preferably 0.3 to 20 kPa, and even more preferably 0.5 to 10 kPa.

[0058] The concentration of 1,3BG in the liquid fed to high boiling desorption tower C is, for example, 95% or more, preferably 96% or more, more preferably 97% or more, even more preferably 98% or more, and particularly preferably 99% or more. In particular, in Production Method 2 of the present disclosure, the concentration of 1,3BG in the liquid fed to high boiling desorption tower C is preferably 97% or more, more preferably 98% or more, and even more preferably 99% or more. The concentration of 1,3BG in the liquid fed to high boiling desorption tower C can be improved by adjusting the distillation conditions of dehydrating tower A and demineralizing tower B. For example, the concentration of 1,3BG in the liquid fed to high boiling desorption tower C can be increased by increasing the reflux ratio of dehydrating tower A or the bottoms yield of demineralizing tower B. The above 1,3BG concentration is the ratio (area %) of the 1,3BG peak area to the total peak area in gas chromatography analysis (GC analysis) under the following conditions. (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0059] The content of high boiling point components in the feed liquid to high boiling desorption tower C is, for example, 4% or less, preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, or 0.05% or less, and particularly preferably 0.01% or less. In particular, in production method 2 of the present disclosure, the content of high boiling point components in the feed liquid to high boiling desorption tower C is preferably 3% or less, more preferably 2% or less, even more preferably 1.5% or less, 1% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, or 0.05% or less, and particularly preferably 0.01% or less. The content of high boiling point components in the feed liquid to high boiling desorption tower C can be reduced by adjusting the distillation conditions of the demineralization tower B. For example, the content of high boiling point components in the liquid fed to high boiling desorption column C can be reduced by increasing the bottoms rate of demineralization column B. The content of high boiling point components in the liquid fed to high boiling desorption column C is the ratio (area %) of the total area of peaks with longer retention times than the peak of 1,3BG to the total peak area in gas chromatography analysis under the above conditions.

[0060] In the production method of the present disclosure, the content of acetaldehyde in the feed liquid to high boiling removal column C is, for example, 500 ppm or less, preferably 205 ppm or less (e.g., 200 ppm or less), more preferably 100 ppm or less, even more preferably 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, or 10 ppm or less, and particularly preferably 5 ppm or less, and may be less than 2 ppm or less than 1 ppm. The crotonaldehyde content in the feed liquid to high boiling desorption column C is, for example, 200 ppm or less, preferably 110 ppm or less, more preferably 100 ppm or less, even more preferably 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, or 3 ppm or less, and particularly preferably 2 ppm or less, and may even be less than 1 ppm. The acetaldehyde content and crotonaldehyde content in the feed liquid to high boiling desorption column C can be reduced, for example, by providing a dealcoholization column (low boiling desorption column) or a dehydration column upstream of high boiling desorption column C and adjusting the distillation conditions of the dealcoholization column (low boiling desorption column) or the dehydration column. For example, by increasing the reflux ratio, number of stages, and distillate yield of the dealcoholization tower (low boiling removal tower) and the dehydration tower, it is possible to reduce the acetaldehyde content and the crotonaldehyde content in the liquid fed to the high boiling removal tower C. The acetaldehyde content and the crotonaldehyde content in the liquid fed to the high boiling removal tower C can be quantified by GC-MS analysis (gas mass spectrometry), as described below.

[0061] In the production method of the present disclosure, the water content in the feed liquid to high boiling desorption column C is, for example, 1.2 wt% or less, preferably 1.1 wt% or less, more preferably 1.0 wt% or less, even more preferably 0.95 wt% or less, 0.9 wt% or less, 0.8 wt% or less, 0.7 wt% or less, 0.6 wt% or less, 0.5 wt% or less, 0.4 wt% or less, 0.3 wt% or less, or 0.2 wt% or less, and particularly preferably 0.1 wt% or less. The water content in the feed liquid to high boiling desorption column C can be reduced by adjusting the distillation conditions of the dehydrating column A. For example, the water concentration in the feed liquid to high boiling desorption column C can be reduced by increasing the reflux ratio, number of stages, or distillate rate of the dehydrating column A. The water content in the feed liquid to high boiling desorption column CF can be quantified using a Karl Fischer water content meter.

[0062] In the production method of the present disclosure, the content of low-boiling components (excluding water) in the liquid fed to high boiling removal column C is, for example, 1.8% or less, preferably 1.6% or less, more preferably 1.4% or less, even more preferably 1.2% or less, 1.1% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.2% or less, and particularly preferably 0.1% or less. The content of low-boiling components excluding water (also referred to as "low boilers" or "low boilers") in the liquid fed to high boiling removal column C is the ratio (area %) of the total area of peaks having a shorter retention time than the peak of 1,3-butylene glycol to the total peak area in gas chromatography analysis under the above conditions. The content of low boiling point components (excluding water) in the liquid fed to the high boiling decoupling tower C can be reduced, for example, by providing a dealcoholization tower (low boiling decoupling tower) upstream of the high boiling decoupling tower C and adjusting the distillation conditions of the dealcoholization tower (low boiling decoupling tower). For example, the concentration of low boiling point components (excluding water) in the liquid fed to the high boiling decoupling tower C can be reduced by increasing the reflux ratio, number of stages, or distillate yield of the dealcoholization tower (low boiling decoupling tower).

[0063] In Production Method 1 of the present disclosure, the reflux ratio in high boiling removal column C [amount refluxed to high boiling removal column / amount distilled from high boiling removal column (amount discharged outside the distillation column)] is, for example, 0.02 or more. From the viewpoint of lowering the dry point of the 1,3-butylene glycol product, the reflux ratio is preferably 0.03 or more, more preferably 0.04 or more, even more preferably 0.05 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.2 or more, 1.5 or more, 2 or more, 3 or more, 4 or more, 5 or more, or 10 or more, and particularly preferably 20 or more. In particular, in Production Method 2 of the present disclosure, the reflux ratio in high boiling removal tower C is greater than 0.02, preferably 0.03 or greater, more preferably 0.04 or greater, 0.05 or greater, 0.06 or greater, 0.07 or greater, 0.08 or greater, or 0.09 or greater, and even more preferably 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, 0.9 or greater, 1 or greater, 1.2 or greater, 1.5 or greater, 2 or greater, 3 or greater, 4 or greater, 5 or greater, or 10 or greater, and particularly preferably 20 or greater. From the viewpoint of energy costs, the upper limit of the reflux ratio is, for example, 100, preferably 50. When the number of theoretical plates in high boiling removal tower C is large, sufficient separation is possible even if the reflux ratio in high boiling removal tower C is about 0.02.

[0064] In the production method of the present disclosure, by setting the reflux ratio in high boiling point desorber C within the above-mentioned specific range, high-purity 1,3BG with an extremely low content of high-boiling point components and a low dry point can be produced with a high recovery rate.

[0065] In the production method of the present disclosure, the bottoms yield of the high boiling removal tower C is, for example, less than 30% by weight. However, this is not the case when the bottoms of the high boiling removal tower are distilled in an additional distillation tower to remove high boiling components and then commercialize the resulting 1,3BG. 1,3BG can be obtained in high yield by limiting the final amount of high boiling components withdrawn from the system to less than 30% by weight of the amount charged to the high boiling removal tower C. The bottoms yield refers to the ratio (by weight) of the amount of liquid withdrawn from below the feed tray of the high boiling removal tower C (for example, from the bottom of the tower) to the amount charged to the high boiling removal tower C (including the recycled amount if this liquid is recycled to the previous process described below). When this liquid is recycled to the previous process described below, the lower the outflow rate, the higher the recovery rate of 1,3BG.

[0066] The bottoms rate of the high boiling removal column C is preferably 25% by weight or less, more preferably 20% by weight or less, even more preferably 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, or 2% by weight or less, and can be 1% by weight or less, from the viewpoint of improving the recovery rate of 1,3BG. Furthermore, the bottoms rate of the high boiling removal column C is, for example, 0.01% by weight or more, preferably 0.1% by weight or more, 0.5% by weight or more, or 1% by weight or more, more preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 6% by weight or more, 7% by weight or more, 8% by weight or more, 9% by weight or more, 10% by weight or more, or 15% by weight or more, and particularly preferably 20% by weight or more, from the viewpoint of lowering the dry point of the 1,3-butylene glycol product.

[0067] At least a portion of the liquid containing concentrated high-boiling components withdrawn from below the feed tray of high-boiling column C (hereinafter, sometimes referred to as "bottom liquid") may be recycled to a step preceding the high-boiling component removal step (dashed arrow shown below high-boiling column C in Figure 1). By recycling at least a portion of the bottom liquid to a step preceding the high-boiling component removal step, the recovery rate of 1,3BG can be improved. In this specification, the recovery rate of 1,3BG in high-boiling column C is a value (%) calculated by the following formula: {1 - [GC area % of 1,3BG in bottoms × (bottoms amount (parts) - recycled amount (parts))] / (GC area % of 1,3BG in feed solution × feed amount (parts))} × 100 Note that low-boiling and high-boiling substances may be hydrolyzed with water to produce 1,3BG, while high-boiling substances may be produced by polymerization of 1,3BG. Furthermore, trace impurities may be produced or lost, so that a material balance in the high-boiling removal tower may not always be obtained.

[0068] The recovery rate of 1,3BG in high boiler removal column C is, for example, more than 80%, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 99% or more.

[0069] Examples of processes preceding the high-boiling point removal process include an acetaldehyde polymerization process (an aldol condensation process of acetaldehyde), a reaction process (a hydrogenation process), a dealcoholization process (a low-boiling point removal process), a dehydration process, and a desalination process. Among these, since 1,3BG is produced by hydrolysis of high-boiling points, it is preferable to recycle the acetaldehyde to the acetaldehyde polymerization process (an aldol condensation process of acetaldehyde). Furthermore, 1,3BG may also be produced by hydrogenation reduction, and from this perspective, the acetaldehyde may be recycled to the hydrogenation process.

[0070] The amount of the bottoms recycled to the process prior to the high boiling point removal step can be appropriately selected within the range of the amount of the bottoms. The amount of the bottoms recycled to the process prior to the high boiling point removal step is, for example, less than 30% by weight, preferably 25% by weight or less, based on the amount charged to high boiling point removal column C. The recycled amount may be 20% by weight or less, 15% by weight or less, 10% by weight or less, 7% by weight or less, 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less, based on the amount charged to high boiling point removal column C. From the viewpoint of improving the 1,3BG recovery rate in the high boiling removal tower and the yield throughout the 1,3BG production process, the amount of the bottoms recycled to the steps preceding the high boiling removal tower is, for example, 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 7% by weight or more, or 10% by weight or more, and particularly preferably 20% by weight or more, relative to the amount charged to high boiling removal tower C. Note that when the amount of bottoms is minimized, 1,3BG can be recovered at a high yield without recycling to the preceding steps.

[0071] In Production Method 2 of the present disclosure, the crude 1,3-butylene glycol stream withdrawn from above the feed tray of the high boiling removal tower C can be used as a 1,3-butylene glycol product as is. Alternatively, the crude 1,3-butylene glycol stream withdrawn from above the feed tray of the high boiling removal tower C can be subjected to an alkali treatment in an alkali reactor D described below and evaporated (or distilled) in a dealkalizer E, and the overhead distillate of the dealkalizer E can be used as a 1,3-butylene glycol product.

[0072] In Production Method 2 of the present disclosure, by setting the acetaldehyde content and the crotonaldehyde content in the feed liquid to dehydrating tower A within specific ranges and setting the reflux ratio of high-boiling tower C to a specific value or more, it is possible to industrially and efficiently produce high-purity 1,3-butylene glycol that has a high potassium permanganate test value, very low contents of low-boiling point components and high-boiling point components, a high initial boiling point, and a low dry point.

[0073] In Production Method 1 of the present disclosure, the crude 1,3-butylene glycol stream withdrawn from the high boiler removal column C above the feed stage is supplied to, for example, an alkali reactor (e.g., a flow-type tubular reactor) D and subjected to a base treatment (alkali treatment). By base treatment, by-products contained in the crude 1,3-butylene glycol can be decomposed. The base is added to the alkali reactor D or to a pipe upstream thereof. The amount of base added is, for example, 0.05 to 10 wt %, preferably 0.1 to 1.0 wt %, based on the crude 1,3-butylene glycol stream to be subjected to the alkali treatment. If the amount of base added exceeds 10 wt %, the base may precipitate in the distillation column, pipes, etc., and cause blockage. Furthermore, a decomposition reaction of high-boiling compounds may occur, which may result in the generation of by-products. If the amount of base added is less than 0.05 wt %, the effect of decomposing by-products is small.

[0074] The base added to the alkaline reactor D or the piping upstream thereof is not particularly limited, but is preferably, for example, an alkali metal compound. Examples of alkali metal compounds include sodium hydroxide, potassium hydroxide, sodium (bi)carbonate, and potassium (bi)carbonate. A basic ion exchange resin can also be used as the base. From the viewpoint of reducing by-products contained in the finally obtained 1,3-butylene glycol product, sodium hydroxide and potassium hydroxide are preferred as the base. The base may be added as a solid as is, but is preferably added as an aqueous solution for operational reasons and to promote contact with the liquid to be treated. The above bases may be used alone or in combination of two or more.

[0075] The reaction temperature in the alkali reactor D is not particularly limited, but is preferably 90 to 140°C, more preferably 110 to 130°C, for example. If the reaction temperature is less than 90°C, a long reaction residence time is required, which increases the reactor capacity and is uneconomical. If the reaction temperature exceeds 140°C, the coloration of the final 1,3-butylene glycol product may increase. The reaction residence time is preferably 5 to 120 minutes, more preferably 10 to 30 minutes, for example. If the reaction residence time is less than 5 minutes, the reaction may be insufficient, and the quality of the final 1,3-butylene glycol product may deteriorate. If the reaction residence time exceeds 120 minutes, a large reactor is required, which increases the equipment cost and is therefore disadvantageous from an economic standpoint.

[0076] After leaving the alkali reactor D, the crude reaction liquid stream is optionally supplied to a dealkalizer (e.g., a thin-film evaporator) E, where the base and other components are removed from the bottom of the column by evaporation. Meanwhile, a crude 1,3-butylene glycol stream (which becomes the 1,3-butylene glycol product in Production Method 2 of the present disclosure) after debasing is obtained from the top of the dealkalizer E. The evaporator used in the dealkalizer E is preferably a gravity-flow thin-film evaporator or a forced-agitation thin-film evaporator with a short residence time, in order to minimize the thermal history of the process fluid. A demister may be installed in the space above the charge position of the dealkalizer (e.g., thin-film evaporator) E to remove droplets of the base and other components. This prevents the base and high-boiling substances from being mixed into the 1,3-butylene glycol product.

[0077] In the evaporator used in the dealkalizer E, evaporation is carried out at the top of the column under reduced pressure, for example, an absolute pressure of 20 kPa or less, preferably an absolute pressure of 0.5 to 10 kPa. The temperature of the evaporator is preferably, for example, 90 to 120°C. The crude 1,3-butylene glycol stream containing low boiling point substances distilled from the top of the column is supplied to a product distillation column (product column) F. As described above, in Production Method 2 of the present disclosure, the distillate (corresponding to E-1) from the top of the dealkalizer E can be used as the 1,3-butylene glycol product.

[0078] The alkali reactor D and the dealkalizer E may be installed between the demineralizer B and the high boiling demineralizer C, between the demineralizer A and the demineralizer B (in this case, the demineralizer may also serve as the dealkalizer), or before the dehydrator A. Alternatively, the alkali treatment can be performed without installing the alkali reactor D and the dealkalizer E by feeding a base into the high boiling demineralizer feed line, feeding into the dehydrator feed line, or adding it to the reaction liquid after hydrogenation [and then feeding it into the dealcoholizer (low boiling demineralizer)].

[0079] In production method 1 of the present disclosure, in product column F used in the product distillation step, a 1,3-butylene glycol feed solution having an acetaldehyde content of 500 ppm or less and a crotonaldehyde content of 200 ppm or less is distilled under conditions of a reflux ratio of more than 0.1, and a liquid concentrated with low boiling point components is distilled from above the feed stage (corresponding to "X-6" in FIG. 1), and 1,3-butylene glycol is withdrawn from below the feed stage (corresponding to "Y" in FIG. 1). The withdrawn 1,3-butylene glycol can be used as a 1,3-butylene glycol product.

[0080] For example, a perforated plate column or a bubble cap column can be used as product column F. However, a packed column with low pressure drop, such as Sulzer Packing or Melapak (both trade names of Sumitomo Heavy Industries, Ltd.), is more preferable. This is because 1,3-butylene glycol and trace amounts of impurities contained therein undergo thermal decomposition at high temperatures (e.g., 150°C or higher), producing low-boiling substances that cause coloration, and therefore the distillation temperature must be low. Furthermore, a long thermal history (residence time) of 1,3-butylene glycol can have a similar effect. Therefore, the reboiler used should be one with a short residence time for the process fluid, such as a gravity-flow thin-film evaporator or a forced-agitation thin-film evaporator.

[0081] The number of theoretical plates in product column F is, for example, 1 to 100, preferably 2 to 90, 3 to 80, 4 to 70, 5 to 60, 8 to 50, or 10 to 40, and more preferably 15 to 30. The feed position of the charge liquid is, for example, 10 to 90%, preferably 20 to 80%, more preferably 30 to 70%, and even more preferably 40 to 60% of the height of the column downward from the top of the column. In the distillation in product distillation column F, the pressure (absolute pressure) at the top of the column is, for example, 20 kPa or less, preferably 0.1 to 10 kPa, more preferably 0.3 to 8 kPa, and even more preferably 0.5 to 5 kPa.

[0082] In Figure 1, the feed to product tower F is the liquid obtained by condensing the top vapor of dealkalization tower E in condenser E-1, but the top vapor from dealkalization tower E may also be fed directly to product tower F.

[0083] The concentration of 1,3-butylene glycol in the feed liquid (1,3-butylene glycol feed liquid) to the product column F is, for example, 90% or more, preferably 92% or more, more preferably 95% or more, still more preferably 97% or more, 97.1% or more, 97.2% or more, 97.3% or more, 97.4% or more, 97.5% or more, 97.6% or more, 97.7% or more, 97.8% or more, 97.9% or more, 98% or more, 98.1% or more, 98.2% or more, 98.3% or more, 98.4% or more, 98.5% or more, 98.6% or more, 98.7% or more, 98.8% or more or 98.9% or more, particularly preferably 99% or more. If the theoretical number of plates, reflux amount, and reflux ratio of the product column F are sufficient, it is possible to produce a product even if the concentration of 1,3-butylene glycol in the feed liquid to the product column F is less than 90%.

[0084] The concentration of 1,3-butylene glycol in the liquid charged to product column F can be improved, for example, by adjusting the distillation conditions of dehydrating column A, by providing a dealcoholization column (low boiling column) upstream of dehydrating column A and adjusting the distillation conditions therefor, or by adjusting the distillation conditions of high boiling column C. For example, the purity of 1,3-butylene glycol in the liquid charged to product column F can be increased by increasing the reflux ratio of the dealcoholization column (low boiling column), dehydrating column A, and / or high boiling column C, or by increasing the number of plates.

[0085] The concentration of 1,3-butylene glycol in the liquid charged to the product column F is the ratio (area %) of the area of the 1,3-butylene glycol peak to the total peak area in gas chromatography analysis under the following conditions. (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0086] In Production Method 1 of the present disclosure, the acetaldehyde content in the feed liquid to product column F is set to 500 ppm or less, and the crotonaldehyde content is set to 200 ppm or less. The acetaldehyde content in the feed liquid to product column F is preferably 205 ppm or less (e.g., 200 ppm or less), more preferably 150 ppm or less, even more preferably 120 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, or 10 ppm or less, and particularly preferably 5 ppm or less, and may be less than 2 ppm. The crotonaldehyde content in the feed liquid to product column F is preferably 150 ppm or less, more preferably 130 ppm or less, even more preferably 110 ppm or less, 100 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, or 3 ppm or less, and particularly preferably 2 ppm or less, and may even be less than 1 ppm. The acetaldehyde content and crotonaldehyde content in the feed liquid to product column F can be reduced, for example, by providing a dealcoholization column (low boiling point removal column) or a dehydration column upstream of product column F and adjusting the distillation conditions of the dealcoholization column (low boiling point removal column) or the dehydration column. For example, the acetaldehyde content and crotonaldehyde content in the feed liquid to product column F can be reduced by increasing the reflux ratio, number of stages, and distillate rate of the dealcoholization column (low boiling point removal column) and the dehydration column. The acetaldehyde content and crotonaldehyde content in the feed liquid to product column F can be reduced by increasing the reaction temperature, the residence time, or the amount of base added in the alkali reaction step. The acetaldehyde content and crotonaldehyde content in the feed liquid to product column F can be quantified by GC-MS analysis (gas mass spectrometry), as described below.

[0087] In Production Method 1 of the present disclosure, the water content in the feed liquid to product column F is, for example, 1.2 wt% or less, preferably 1.1 wt% or less, more preferably 1.0 wt% or less, even more preferably 0.95 wt% or less, 0.9 wt% or less, 0.8 wt% or less, 0.7 wt% or less, 0.6 wt% or less, 0.5 wt% or less, 0.4 wt% or less, 0.3 wt% or less, or 0.2 wt% or less, and particularly preferably 0.1 wt% or less. The water content in the feed liquid to product column F can be reduced by adjusting the distillation conditions of dehydrating column A. For example, the water concentration in the feed liquid to product column F can be reduced by increasing the reflux ratio, number of stages, or distillate rate of dehydrating column A. The water content in the feed liquid to product column F can be quantified using a Karl Fischer moisture meter.

[0088] The content of low-boiling components (excluding water) in the liquid fed to product column F is, for example, 1.8% or less, preferably 1.6% or less, more preferably 1.4% or less, even more preferably 1.2% or less, 1.1% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.2% or less, and particularly preferably 0.1% or less. The content of low-boiling components (excluding water) in the liquid fed to product column F is the ratio (area %) of the total area of peaks having a shorter retention time than the peak of 1,3-butylene glycol to the total peak area in gas chromatography analysis under the above conditions. The content of low-boiling components (excluding water) in the liquid fed to product column F can be reduced, for example, by providing a dealcoholization column (low-boiling column) upstream of product column F and adjusting the distillation conditions of the dealcoholization column (low-boiling column). For example, by increasing the reflux ratio, number of stages, and distillate rate of the dealcoholization tower (low boiling point removal tower), the concentration of low boiling point components (excluding water) in the feed liquid to product tower F can be reduced.

[0089] The content of high-boiling components (excluding water) in the liquid fed to product column F is, for example, 1.8% or less, preferably 1.6% or less, more preferably 1.4% or less, even more preferably 1.2% or less, 1.1% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.2% or less, and particularly preferably 0.1% or less. The content of high-boiling components excluding water (also referred to as "high boilers" or "high boilers") in the liquid fed to product column F is the ratio (area %) of the total area of peaks having a longer retention time than the peak of 1,3-butylene glycol to the total peak area in gas chromatography analysis under the above conditions. The content of high-boiling components (excluding water) in the liquid fed to product column F can be reduced, for example, by adjusting the distillation conditions of the high-boiling separation column. For example, the concentration of high boiling point components (excluding water) in the liquid fed to the product column F can be reduced by increasing the reflux ratio, number of stages, and bottoms rate of the high boiling separation column.

[0090] In Production Method 1 of the present disclosure, the reflux ratio in product column F [amount refluxed to product column / amount distilled from product column (amount discharged outside the distillation column)] is set to a value greater than 0.1. From the viewpoint of increasing the initial boiling point of the 1,3-butylene glycol product, the reflux ratio is preferably 0.2 or more, more preferably 0.3 or more, even more preferably 0.4 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 20 or more, or 50 or more, and particularly preferably 400 or more (e.g., 500 or more). The upper limit of the reflux ratio in product column F is, for example, 700 or 1000 from the viewpoint of energy costs.

[0091] In Production Method 1 of the present disclosure, the distillate rate from product column F is, for example, less than 30% by weight, preferably 29% by weight or less, more preferably 28% by weight or less, even more preferably 27% by weight or less, 26% by weight or less, 25% by weight or less, 24% by weight or less, 23% by weight or less, 22% by weight or less, 21% by weight or less, 20% by weight or less, 19% by weight or less, 18% by weight or less, 17% by weight or less, 16% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, or 0.6% by weight or less, and particularly preferably 0.4% by weight or less, from the viewpoint of improving the recovery rate of 1,3-butylene glycol. The distillate yield refers to the ratio (by weight) of the amount of liquid extracted from above the feed tray of product column F (e.g., from the top of the column) to the amount charged to product column F (including the recycled amount if recycled to the previous process described below).

[0092] At least a portion of the liquid (hereinafter sometimes referred to as "distillate") in which low boiling components are concentrated and which is withdrawn from above the feed tray of product column F may be recycled to a step preceding the product distillation step (the dashed arrow shown to the right of product column F in FIG. 1). By recycling at least a portion of the distillate to a step preceding the product distillation step, the recovery rate of 1,3-butylene glycol can be improved.

[0093] Examples of the process prior to the product distillation process include a dehydration process, a dealcoholization process (low boiling point removal process), etc. The dealcoholization process (low boiling point removal process) is preferably performed before the dehydration process.

[0094] The amount of the distillate recycled to the process prior to the product distillation step can be appropriately selected within the range of the amount of the distillate. The amount of the distillate recycled to the process prior to the product distillation step is, for example, less than 30% by weight relative to the amount charged to the product column F. From the viewpoint of improving the 1,3BG recovery rate in the product column and the yield throughout the process, the amount of the distillate recycled to the process prior to the product distillation step is, for example, 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 1.5% by weight or more, 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 7% by weight or more, or 10% by weight or more, and particularly preferably 20% by weight or more.

[0095] In production method 1 of the present disclosure, the acetaldehyde content and the crotonaldehyde content in the feed liquid to dehydration column A are set within specific ranges, the acetaldehyde and crotonaldehyde contents in the feed liquid to product column F are set to specific values or less, and the reflux ratio in product column F is set within a specific range, thereby making it possible to produce high-purity 1,3-butylene glycol that has a high potassium permanganate test value, very low contents of low-boiling point components and high-boiling point components, a high initial boiling point, and a low dry point, generally at a high recovery rate.

[0096] The recovery rate of 1,3BG in product column F is, for example, more than 80%, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 99% or more.

[0097] In this specification, the recovery rate of 1,3BG in product tower F is a value (%) calculated by the following formula. {1 - [GC area % of 1,3BG in the distillate × (distillate amount (parts) - recycled amount (parts))] / (GC area % of 1,3BG in the feed solution × feed amount (parts))} × 100 As mentioned above, low-boiling and high-boiling substances may be hydrolyzed with water to produce 1,3BG, while high-boiling substances may be produced by polymerization of 1,3BG. Therefore, the material balance in the product column may not always be achieved.

[0098] [1,3-butylene glycol products] According to the method for producing 1,3-butylene glycol of the present disclosure, it is possible to obtain a 1,3-butylene glycol product having an initial boiling point greater than 203°C and a potassium permanganate test value (PMT) of 30 minutes or more, a 1,3-butylene glycol product having an initial boiling point greater than 203°C and a dry point of 209°C or less, and further a 1,3-butylene glycol product having an initial boiling point greater than 203°C, a dry point of 209°C or less, and a potassium permanganate test value (PMT) of 30 minutes or more. The initial boiling point is preferably 204°C or more, more preferably 205°C or more, even more preferably 206°C or more or 207°C or more, and particularly preferably 208°C or more. The potassium permanganate test value (PMT) is more preferably greater than 30 minutes (e.g., 32 minutes or more), even more preferably 35 minutes or more (e.g., 40 minutes or more), and particularly preferably 50 minutes or more (especially 60 minutes or more).

[0099] Furthermore, according to the method for producing 1,3-butylene glycol of the present disclosure, in addition to the above properties, a 1,3-butylene glycol product can be obtained in which, in gas chromatography analysis (GC analysis) under the following conditions, the area ratio of the 1,3-butylene glycol peak is higher than 98.7%. Furthermore, according to the method for producing 1,3-butylene glycol of the present disclosure, in addition to the above properties, a 1,3-butylene glycol product can be obtained in which the total area ratio of peaks having shorter retention times than the 1,3-butylene glycol peak is lower than 0.3%. Furthermore, according to the method for producing 1,3-butylene glycol of the present disclosure, in addition to the above properties, a 1,3-butylene glycol product can be obtained in which the total area ratio of peaks having longer retention times than the 1,3-butylene glycol peak is lower than 1.2%. (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[0100] The area ratio of the peak of the 1,3-butylene glycol is preferably 98.8% or more, more preferably 98.9% or more, even more preferably 99% or more, 99.1% or more, 99.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, or 99.7% or more, and particularly preferably 99.8% or more.

[0101] The total area ratio of peaks having retention times shorter than that of the 1,3-butylene glycol peak is preferably 0.28% or less, more preferably 0.25% or less, even more preferably 0.23% or less, 0.2% or less, 0.17% or less, 0.15% or less, 0.12% or less, 0.1% or less, 0.07% or less, 0.04% or less, 0.03% or less, 0.02% or less, 0.01% or less, or 0.007% or less, and particularly preferably 0.005% or less (e.g., 0.002% or less).

[0102] The total area ratio of peaks having a longer retention time than the peak of 1,3-butylene glycol is preferably 1% or less, more preferably 0.9% or less, even more preferably 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.2% or less, and particularly preferably 0.1% or less.

[0103] In the present disclosure, the "area ratio" of a peak refers to the ratio (area %) of the area of a specific peak to the sum of the areas of all peaks appearing in a chart. Furthermore, "all peaks" refers to all peaks that appear when the analysis is continued until the relative retention time reaches 7.8, assuming that the relative retention time of the peak of 1,3-butylene glycol is 1.0, and then stopped.

[0104] The method for producing 1,3-butylene glycol of the present disclosure can produce a 1,3-butylene glycol product having a water content of less than 0.4 wt%. The water content is preferably 0.3 wt% or less, more preferably 0.2 wt% or less, even more preferably 0.1 wt% or less, 0.07 wt% or less, 0.05 wt% or less, 0.03 wt% or less, 0.02 wt% or less, or 0.01 wt% or less, and particularly preferably 0.005 wt% or less. The water content can be quantified using a Karl Fischer moisture analyzer.

[0105] Furthermore, the method for producing 1,3-butylene glycol disclosed herein can produce a 1,3-butylene glycol product having an acetaldehyde content of less than 2 ppm. Furthermore, the method for producing 1,3-butylene glycol disclosed herein can produce a 1,3-butylene glycol product having a crotonaldehyde content of less than 1.2 ppm. The acetaldehyde and crotonaldehyde contents in a 1,3-butylene glycol product can be quantified by GC-MS analysis (gas mass spectrometry), for example, under the following conditions: In GC-MS analysis, even very small peaks are subjected to mass spectrometry to quantify each component. Because analysis is performed for specific masses, substances with different masses are not detected even if other impurities overlap the peaks, resulting in higher sensitivity than GC analysis. In this specification, the unit "ppm" used to express the content of each component in GC-MS analysis means "ppm by weight." (GC-MS analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Ion source temperature: EI 230℃, CI 250℃ Q pole temperature: 150℃ Sample: Ready for analysis

[0106] Under the above GC-MS analysis conditions, when the relative retention time of the peak of 1,3-butylene glycol is taken as 1.0, the relative retention time of the peak of acetaldehyde is 0.3 to 0.5, and the relative retention time of the peak of crotonaldehyde is 0.3 to 0.5.

[0107] The acetaldehyde content in the 1,3-butylene glycol product obtained by the production method of the present disclosure is more preferably 1.8 ppm or less, even more preferably 1.7 ppm or less, 1.5 ppm or less, 1.4 ppm or less, 1.3 ppm or less, 1.2 ppm or less, 1.1 ppm or less, 1.0 ppm or less, 0.9 ppm or less, 0.8 ppm or less, 0.7 ppm or less, 0.6 ppm or less, or 0.5 ppm or less, and particularly preferably 0.3 ppm or less (e.g., 0.2 ppm or less).Furthermore, the crotonaldehyde content in the 1,3-butylene glycol product obtained by the production method of the present disclosure is more preferably 1.0 ppm or less, even more preferably 0.9 ppm or less, 0.8 ppm or less, 0.7 ppm or less, 0.6 ppm or less, 0.5 ppm or less, 0.4 ppm or less, or 0.3 ppm or less, and particularly preferably 0.2 ppm or less (e.g., 0.1 ppm or less).

[0108] Thus, according to the method for producing 1,3-butylene glycol of the present disclosure, it is possible to obtain a high-purity, high-quality 1,3-butylene glycol product that has excellent initial boiling point and dry point, a large potassium permanganate test value, a high area ratio of the 1,3-butylene glycol peak, a low total area ratio of peaks having shorter retention times than the 1,3-butylene glycol peak, a low total area ratio of peaks having longer retention times than the 1,3-butylene glycol peak, a low acetaldehyde content, and a low crotonaldehyde content.

[0109] [Moisturizers and cosmetics] Therefore, the 1,3-butylene glycol product obtained by the manufacturing method of the present disclosure can be suitably used as a moisturizer or a raw material for cosmetics. The moisturizer may contain components other than the above-mentioned 1,3-butylene glycol product, for example, moisturizer components other than the above-mentioned 1,3-butylene glycol product. In such a moisturizer, the content of the above-mentioned 1,3-butylene glycol product is, for example, 10 wt % or more, preferably 30 wt % or more, more preferably 50 wt % or more, even more preferably 80 wt % or more, and particularly preferably 90 wt % or more, and the moisturizer may be composed solely of the above-mentioned 1,3-butylene glycol product.

[0110] The amount of the 1,3-butylene glycol product in the cosmetic may be any amount that can exhibit moisturizing properties, depending on the type and form of the cosmetic. The amount of the 1,3-butylene glycol product in such a cosmetic is, for example, 0.01 to 40% by weight, preferably 0.1 to 30% by weight, more preferably 0.2 to 20% by weight, even more preferably 0.5 to 15% by weight, and particularly preferably 1 to 10% by weight.

[0111] In addition to the above-mentioned 1,3-butylene glycol product, the cosmetic may contain, for example, other moisturizers; oils such as vegetable oils, hydrocarbon oils, higher fatty acids, higher alcohols, and silicones; surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants; preservatives, sequestering agents, thickeners, powders, UV absorbers, UV blockers, fragrances, pH adjusters; medicinal ingredients or physiologically active ingredients such as vitamins, skin activators, blood circulation promoters, whitening agents, antibacterial agents, and anti-inflammatory agents.

[0112] The cosmetic may be a skin cosmetic such as a lotion, emulsion, cream, gel, pack, or mask, or a hair cosmetic such as a shampoo, rinse, or hair growth agent. It may also be a sunscreen cosmetic or a makeup cosmetic. It may also be a pharmaceutical or quasi-drug containing a medical ingredient. The cosmetic may be produced by a method known per se.

[0113] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, each configuration and their combinations in each embodiment are merely examples, and additions, omissions, and other modifications of configurations are possible as appropriate within the scope of the gist of this disclosure. The present disclosure is not limited by the embodiments, but is limited only by the scope of the claims. [Example]

[0114] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples. Note that "parts" used in the examples refer to "parts by weight" unless otherwise specified. Gas chromatography analysis (GC analysis), measurement of initial boiling point, and measurement of water content were performed by the methods described below.

[0115] [Example 1] The method for producing 1,3-butylene glycol will be described with reference to FIG. 100 parts of an acetaldol solution containing 30% by weight of water as a raw material (a mixed solution of 69 parts of acetaldol and 29 parts of water, containing a total of 2 parts of low-boiling and high-boiling impurities, and less than 0.1 parts of Na salt) were charged into a liquid-phase hydrogen reduction reactor with 10 parts of hydrogen, and 15 parts of Raney nickel were added as a catalyst. The reactor was maintained at 120°C and 10 MPa (gauge pressure) to carry out liquid-phase hydrogen reduction. After separating the catalyst from the liquid after the reaction, the liquid was neutralized with caustic soda to obtain crude 1,3-butylene glycol (1) containing low-boiling impurities and water.

[0116] The acetaldehyde solution containing 30% by weight of water used as a raw material was produced by stirring acetaldehyde and water in the presence of 100 ppm by weight of NaOH at 30°C for a residence time of 10 hours to dimerize acetaldehyde [acetaldehyde polymerization process (acetaldehyde aldol condensation process)].

[0117] Crude 1,3-butylene glycol (1) (corresponding to "X-1" in Figure 1) was charged to dehydration column A. The concentration of 1,3-butylene glycol in the charge to dehydration column A was 56 wt%, the concentration of water was 40 wt%, the content of acetaldehyde (AD) was 130 ppm, the content of crotonaldehyde (CR) was 89 ppm, and in the GC analysis described below, the total area ratio of impurity peaks with a shorter retention time (RT) than 1,3-butylene glycol was 3%, and the total area ratio of impurity peaks with a longer retention time than the 1,3-butylene glycol peak was 1%. In dehydration column A, distillation was performed under conditions of a column top pressure of 10 kPa (absolute pressure) and a reflux ratio of 0.05. Water was extracted from the top of the column, and 43 parts (distillate) per 100 parts of the charge was discharged and removed outside the system (corresponding to "X-2" in Figure 1). From the bottom of the column, crude 1,3-butylene glycol (2) was obtained, which had a 1,3-butylene glycol concentration of 96.9 GC area %, water of 0.9 wt %, a total area ratio of impurity peaks having shorter retention times than 1,3-butylene glycol of 0.8%, a total area ratio of peaks having longer retention times than 1,3-butylene glycol peaks of 2.3%, an acetaldehyde content of 18 ppm, and a crotonaldehyde content of 17 ppm in a GC analysis described below.

[0118] Next, crude 1,3-butylene glycol (2) was charged into demineralizer B. In demineralizer B, salts, high boiling point materials, and a portion of 1,3-butylene glycol were discharged as evaporation residue from the bottom of the column (corresponding to "X-3" in Figure 1). The amount of evaporation residue discharged was 5 parts per 100 parts of the charged liquid. Meanwhile, crude 1,3-butylene glycol (3) containing 1,3-butylene glycol, low boiling point materials, and a portion of the high boiling point materials was obtained from the top of the column.

[0119] Next, the crude 1,3-butylene glycol (3) was charged into high boiling separation column C. In high boiling separation column C, distillation was carried out under conditions of a column top pressure of 5 kPa (absolute pressure) and a reflux ratio of 0.05, and high boiling point materials and a portion of 1,3-butylene glycol were discharged from the column bottom (corresponding to "X-4" in Figure 1). The amount of the discharged material from the column bottom was 20 parts per 100 parts of the charged liquid. Meanwhile, 80 parts of crude 1,3-butylene glycol (4) containing low boiling point materials was obtained as a distillate from the column top.

[0120] Next, the crude 1,3-butylene glycol (4) was charged into an alkaline reactor D. At this time, a 20 wt % aqueous solution of caustic soda was added so that the concentration of caustic soda in the charged liquid was 0.1 wt %. The reaction temperature in the alkaline reactor D was maintained at 120°C, and the reaction was carried out for a residence time of 20 minutes.

[0121] Next, the crude reaction liquid discharged from the alkali reactor D was charged into a dealkalizer E. In the dealkalizer E, caustic soda, high boiling point substances, and a portion of 1,3-butylene glycol were discharged from the bottom of the column (corresponding to "X-5" in Figure 1). The amount of the liquid discharged from the bottom of the column was 10 parts per 100 parts of the charged liquid. Meanwhile, 90 parts of crude 1,3-butylene glycol (5) containing 1,3-butylene glycol and low boiling point substances was obtained from the top of the column. The crude 1,3-butylene glycol (5) containing 1,3-butylene glycol and low boiling point substances was subjected to water content measurement, GC analysis, and GC-MS analysis. As a result, the water concentration was 1.1% by weight, the area ratio of 1,3-butylene glycol was 99%, the total area ratio of impurity peaks having a shorter retention time than 1,3-butylene glycol was 0.4%, the total area ratio of impurity peaks having a longer retention time than 1,3-butylene glycol was 0.6%, the acetaldehyde content was 21 ppm, and the crotonaldehyde content was 10 ppm.

[0122] Next, crude 1,3-butylene glycol (5) was charged into product column F. In product column F, 10 parts of low boiling point materials and a portion of 1,3-butylene glycol were distilled from the top of the column relative to 100 parts of the charged liquid (corresponding to "X-6" in Figure 1), and the entire amount was discharged outside the system. The column was operated at a reflux ratio (reflux amount / distillate amount) of 0.5, and 90 parts of 1,3-butylene glycol product were obtained from the bottom of the column (distillate amount: 10 parts) (corresponding to "Y" in Figure 1).

[0123] The resulting 1,3-butylene glycol product was subjected to measurement of the initial boiling point, moisture content, GC analysis, and GC-MS analysis. The initial boiling point was 203.3°C, the dry point was 209°C, the moisture content was 0.2% by weight, the area ratio of 1,3-butylene glycol was 99.2%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.08%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 0.7%, the acetaldehyde content was 1.6 ppm, and the crotonaldehyde content was 1.0 ppm. The potassium permanganate test value was 35 minutes. The recovery rate of 1,3-butylene glycol in product column F was 90%.

[0124] [Example 2] The same operation as in Example 1 was carried out, except that the reflux ratio of dehydrating tower A was changed to 10. 1,3-butylene glycol product was obtained from the bottom of product tower F. Note that, due to the change in the conditions of dehydrating tower A, the composition of the dehydrating tower bottoms changed, and the compositions of the charged liquids of high boiling removal tower C and product tower F each changed, resulting in a change in the quality of the product. The resulting 1,3-butylene glycol product was subjected to measurement of the initial boiling point, moisture content, GC analysis, and GC-MS analysis. The initial boiling point was 206.5°C, the dry point was 208.9°C, the moisture content was 0.1% by weight, the area ratio of 1,3-butylene glycol was 99.2%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.06%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 0.7%, the acetaldehyde content was 0.8 ppm, and the crotonaldehyde content was 0.8 ppm. The potassium permanganate test value was 45 minutes. The recovery rate of 1,3-butylene glycol in product column F was 90%.

[0125] [Examples 3 to 28] Dehydration column A, high-boiling column C, and product column F were operated under the conditions shown in Tables 1 to 3. In Examples 4 to 22 and 24 to 26, the distillate from product column F was recycled in its entirety to the hydrogen reduction reactor. In Examples 23 and 28, product column F was not used, and the overhead distillate from dealkalization column E (a demister was installed in the space above the charging position) was used as the 1,3-butylene glycol product. The concentration of the aqueous caustic soda solution in alkali reactor D was increased by 1.5 times, and the amount of aqueous caustic soda solution added was half that of Example 1, thereby minimizing the increase in moisture content due to the alkali treatment. If the alkali concentration of the aqueous caustic soda solution is too high, crystals will precipitate, so it is preferable to heat it to 40°C or higher. In Table 3, the column for "Product column F bottoms" for Examples 23 and 28 lists the composition and physical properties of the overhead distillate from dealkalization column E. In Example 16, 8 parts of the 10 parts of the high boiling column bottoms were recycled to the hydrogenation step, and 2 parts were discharged outside the system. In Example 25, the pressure of the hydrogenation reaction was reduced to 7 MPaG (gauge pressure). Therefore, the acetaldehyde and crotonaldehyde contents in the dehydration column feed liquid were high. In Example 26, the pressure of the hydrogenation reaction was increased to 40 MPaG (gauge pressure) (the remaining conditions were the same as in Example 18).

[0126] [Comparative Example 1] The reflux ratio of dehydration tower A was changed to 0.03, the distillate volume was changed to 42 parts, the reflux ratio of high boiling tower C was changed to 0.02, the reflux ratio of product tower F was changed to 0.05, and the distillate volume was changed to 20 parts. 80 parts of 1,3-butylene glycol product was obtained from the bottom of product tower F in the same manner as in Example 1. The initial boiling point of the obtained 1,3-butylene glycol product was 193.1 ° C., the dry point was 210.2 ° C., the water concentration was 0.6 wt%, the area ratio of 1,3-butylene glycol was 98.2%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.3%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 1.5%, the acetaldehyde content was 5 ppm, and the crotonaldehyde content was 4 ppm. The potassium permanganate test value was 0 min. The recovery rate of 1,3-butylene glycol in product column F was 81%.

[0127] Comparative Example 2 The feed composition of the dehydration tower A was changed, the reflux ratio was changed to 0.03, the distillate amount was changed to 32 parts, the reflux ratio of the high boiling tower C was changed to 0.02, the reflux ratio of the product tower F was changed to 0.05, and the distillate amount was changed to 20 parts. Except for this, 80 parts of 1,3-butylene glycol product was obtained from the bottom of the product tower F in the same manner as in Example 1. The initial boiling point of the obtained 1,3-butylene glycol product was 198.9 ° C, the dry point was 210.1 ° C, the water concentration was 0.4 wt%, the area ratio of 1,3-butylene glycol was 98.5%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.1%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 1.4%, the acetaldehyde content was 4 ppm, and the crotonaldehyde content was 2 ppm. The potassium permanganate test value was 5 minutes. The recovery rate of 1,3-butylene glycol in product column F was 80%.

[0128] Comparative Example 3 The feed composition of dehydration tower A was changed, the reflux ratio was changed to 0.03, the distillate amount was changed to 32 parts, the reflux ratio of high boiling tower C was changed to 0.02, the reflux ratio of product tower F was changed to 0.05, and the distillate amount was changed to 30 parts. Except for this, 70 parts of 1,3-butylene glycol product was obtained from the bottom of product tower F in the same manner as in Example 1. The initial boiling point of the obtained 1,3-butylene glycol product was 203.0 ° C, the dry point was 210.2 ° C, the water concentration was 0.2 wt%, the area ratio of 1,3-butylene glycol was 98.4%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.1%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 1.5%, the acetaldehyde content was 2 ppm, and the crotonaldehyde content was 1.4 ppm. The potassium permanganate test value was 30 minutes. The recovery rate of 1,3-butylene glycol in product column F was 70%.

[0129] Comparative Example 4 The feed composition of the dehydration tower A was changed, the reflux ratio was changed to 0.03, the distillate amount was changed to 23 parts, the reflux ratio of the high boiling tower C was changed to 0.02, the reflux ratio of the product tower F was changed to 0.1, and the distillate amount was changed to 20 parts. Except for this, 80 parts of 1,3-butylene glycol product was obtained from the bottom of the product tower F in the same manner as in Example 1. The initial boiling point of the obtained 1,3-butylene glycol product was 203.1 ° C, the dry point was 209.5 ° C, the water concentration was 0.2 wt%, the area ratio of 1,3-butylene glycol was 98.8%, the total area ratio of impurity peaks with shorter retention times than 1,3-butylene glycol was 0.1%, the total area ratio of impurity peaks with longer retention times than 1,3-butylene glycol was 1.1%, the acetaldehyde content was 2 ppm, and the crotonaldehyde content was 1.4 ppm. The potassium permanganate test value was 30 minutes. The recovery rate of 1,3-butylene glycol in product column F was 80%.

[0130] [Gas Chromatography Analysis] Gas chromatography analysis of the target 1,3-butylene glycol product was carried out under the following conditions. (Gas chromatographic analysis conditions) Analytical equipment: Shimadzu GC2010 Analytical column: A column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) ("Agilent J&W GC Column - DB-1," manufactured by Agilent Technologies, Inc.) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction and temperature: Split sample introduction, 250°C Split gas flow rate and carrier gas: 23 mL / min, helium Column gas flow rate and carrier gas: 1 mL / min, helium Detector and temperature: Flame ionization detector (FID), 280°C Injected sample: 0.2 μL of 80 wt% 1,3-butylene glycol product aqueous solution

[0131] [Initial boiling point and dry point measurement] The test was carried out in accordance with the test method specified in the atmospheric distillation test method of JIS K2254 "Petroleum products - Distillation test method."

[0132] [Moisture measurement] The measurement was carried out using a Karl Fischer moisture content analyzer.

[0133] [GC-MS analysis] Analyzer: Agilent 6890A-GC / 5973A-MSD Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Ion source temperature: EI 230℃, CI 250℃ Q pole temperature: 150℃ Sample: Ready for analysis

[0134] [Potassium permanganate test] In this specification, the potassium permanganate test value (PMT) is a value measured in accordance with the procedure of the visual colorimetric method of JIS K1351 (1993).

[0135] [Discussion of results] The results of the above comparative examples and examples are shown in Tables 1 to 3.

[0136] [Table 1]

[0137] [Table 2]

[0138] [Table 3]

[0139] Comparative Examples 1 to 4 show that even if the dehydrating tower feed composition is changed, the product quality is poor when the reflux ratio and distillate volume of each distillation tower are low. Comparative Examples 3 and 4 are cases in which the amount of water discharged from the product tower to the distillation system is increased or the water content of the dehydrating tower feed is reduced. Although the initial boiling point and PMT are satisfactory, the dry point is high. In addition, the recovery rate of 1,3BG is low, making this uneconomical. Furthermore, separation of acetaldehyde and crotonaldehyde in the dehydrating tower appears to be more difficult than usual, and there is a possibility that acetaldehyde and crotonaldehyde are being generated in the tower.

[0140] From Comparative Example 1 and Examples 1 and 27, it can be seen that if the feed composition to the dehydrating tower is the same and the reflux ratio of at least the product tower among the dehydrating tower, high boiling tower, and product tower is set to a specific value or higher, the initial boiling point, PMT, and dry point can be simultaneously satisfied, and the 1,3BG recovery rates of the dehydrating tower, high boiling tower, and product tower can also be maintained at an acceptably high level.

[0141] From Examples 1 and 2, it can be seen that by increasing the reflux ratio of the dehydration tower to a specific value or more, the contents of water, acetaldehyde, and crotonaldehyde decrease, and in particular the initial boiling point and PMT improve.

[0142] As shown in Examples 2 and 3, when the reflux ratio of the product tower is increased above a certain value and the distillate volume is reduced, the increase in low-boiling impurities due to the reduced distillate volume is offset by the improved separation of low-boiling impurities due to the increased reflux ratio, and the BG recovery rate of product towers 1 and 3 can be improved without changing the product quality.

[0143] From Comparative Example 2 and Example 4, and Comparative Example 4 and Example 11, it can be seen that the quality can be improved by setting the distillation conditions for the dehydrating tower, high boiling tower, and product tower within the ranges specified in this disclosure, even when the feed composition for the dehydrating tower is the same.

[0144] From Examples 4 and 5, it can be seen that the initial boiling point and PMT can be further improved by further increasing the reflux ratio of the dehydration tower.

[0145] From Examples 5 and 6, when the reflux ratio of the dehydration tower was increased and the distillate amount of the product tower was decreased, the initial boiling point decreased but was within the specifications, and the 1,3BG recovery rate improved.

[0146] From Examples 6 to 8, it can be seen that when the reflux ratio of the product column is increased drastically, the initial boiling point and PMT are improved to the limit. However, when the reflux ratio is about 500, the quality reaches a plateau.

[0147] Examples 6, 9, and 10 show that increasing the dehydrating tower reflux ratio improves the initial boiling point and PMT. However, if treatment with an alkaline aqueous solution is performed between the dehydrating tower and the product tower, the moisture content increases in this process, making extreme moisture removal in the dehydrating tower less effective, so the reflux ratio in the dehydrating tower does not need to be very high. However, since the alkaline reactor can be moved upstream of the dehydrating tower, in that case, it is effective to increase the reflux ratio of the dehydrating tower to a certain extent.

[0148] In Examples 11 to 13, the water concentration in the dehydrating tower feed liquid was reduced, the dehydrating tower reflux ratio was increased, and the reflux and distillate amounts in the product tower were changed. As explained above, the effects and influences of each of these methods result in satisfying the initial boiling point and PMT.

[0149] Examples 14 to 21 show that increasing the reflux ratio of the high boiling column reduces the content of high boiling impurities in the product and improves the dry point. In addition, Example 16 shows conditions in which 8 parts of 10 parts of the high boiling column bottoms are recycled to the hydrogenation step and 2 parts are discharged outside the system, thereby lowering the boiling point of the impurities by hydrogenation. This improves the 1,3BG recovery rate of the high boiling column, but slightly increases the amount of high boiling impurities in the product and raises the dry point. However, it can be seen that this remains within the specifications.

[0150] From Examples 1 and 22, it can be seen that even if the reflux ratio of the dehydration tower is 0.05, a high quality product can be maintained by increasing the reflux ratio of the product tower.

[0151] Comparative Example 4 and Examples 13, 23, and 28 show that by significantly increasing the reflux ratio of the dehydrating tower, the contents of acetaldehyde, crotonaldehyde, and water can be reduced and commercialized even without a product tower. Furthermore, by performing alkali treatment before distillation in the dehydrating tower, the water concentration in the product can be further reduced.

[0152] Example 24 is an example in which the water concentration in the dehydrating tower feed liquid is extremely high. Although the water content in the dehydrating tower bottoms and the high boiling tower feed liquid increases significantly, product quality can be maintained by adjusting the distillate flow rate and reflux ratio of the product tower.

[0153] Examples 4 and 25 show that even if the acetaldehyde and crotonaldehyde contents in the dehydrating tower feed liquid are quite high, the high quality of the product can be maintained by increasing the distillate volume and reflux ratio in the product tower to remove acetaldehyde and crotonaldehyde.

[0154] Example 26 shows that by increasing the pressure of the hydrogenation reaction and detoxifying acetaldehyde, crotonaldehyde, and other reducing substances through hydrogenation, thereby reducing the concentrations of acetaldehyde, crotonaldehyde, and other reducing substances in the dehydrating tower charge, as well as trace amounts of other impurities such as acetals, product quality can be maintained even if the reflux ratios and distillate volumes of the dehydrating tower, high-boiling removal tower, and product tower are relatively low.

[0155] Furthermore, among the 1,3-butylene glycol products obtained by conventional methods, there have been no high-quality products having an initial boiling point higher than 203°C and a potassium permanganate test value of 30 minutes or more, or an initial boiling point higher than 203°C and a dry point of 209°C or less, or an initial boiling point higher than 203°C, a dry point of 209°C or less, and a potassium permanganate test value of 30 minutes or more.

[0156] To summarize the above, the configurations and variations of the present disclosure are noted below. [1] A method for producing 1,3-butylene glycol, in which purified 1,3-butylene glycol is obtained from a reaction crude liquid containing 1,3-butylene glycol, The process includes a dehydration process for removing water by distillation, a high boiling point removal process for removing high boiling point components by distillation, and a product distillation process for obtaining purified 1,3-butylene glycol. In the dehydration tower used in the dehydration step, the acetaldehyde content contains 1,3-butylene glycol and water and is 1000 ppm or less (or 900 ppm or less, 800 ppm or less, 700 ppm or less, 600 ppm or less, 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, 155 ppm or less, 140 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less , 3 ppm or less, 2 ppm or less, or 1 ppm or less), and a crotonaldehyde content of 400 ppm or less (or 200 ppm or less, 150 ppm or less, 130 ppm or less, 117 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or 1 ppm or less), and a liquid in which low-boiling point components including water are concentrated is distilled from above the feed stage, In the product column used in the product distillation step, the acetaldehyde content is 500 ppm or less (or 205 ppm or less, 200 ppm or less, 150 ppm or less, 120 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, or less than 2 ppm), and the crotonaldehyde content is 200 ppm or less (or 205 ppm or less, 200 ppm or less, 150 ppm or less, 120 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less). a reflux ratio of more than 0.1 (or 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 20 or more, 50 or more, 400 or more, or 500 or more), to distill a liquid in which low-boiling point components are concentrated from above the feed stage, and to withdraw 1,3-butylene glycol from below the feed stage. [2] The method for producing 1,3-butylene glycol according to [1] above, wherein in the high boiling point removal tower used in the high boiling point removal step, a feed liquid containing 1,3-butylene glycol is distilled under conditions of a reflux ratio of 0.02 or more (or 0.03 or more, 0.04 or more, 0.05 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.2 or more, 1.5 or more, 2 or more, 3 or more, 4 or more, 5 or more, 10 or more, or 20 or more), and 1,3-butylene glycol with improved purity is distilled from above the feed stage, and a liquid in which high boiling point components are concentrated is withdrawn from below the feed stage. [3] The concentration of 1,3-butylene glycol in the feed liquid to the product column is 90 GC area% or more (or 92 GC area% or more, 95 GC area% or more, more preferably 97 GC area% or more, 97.1 GC area% or more, 97.2 GC area% or more, 97.3 GC area% or more, 97.4 GC area% or more, 97.5 GC area% or more, 97.6 GC area% or more, 97.7 GC area% or more, 97.8 GC area% or more, 97.9 GC area% or more, 98 GC area% or more, 98.1 GC area% or more, 98.2 GC area% or more, 98.3 GC area% or more, 98.4 GC area% or more, 98. 5% or more, 98.6% or more, 98.7% or more, 98.8% or more, 98.9% or more, or 99% or more), and the water content in the feed solution is 3% or less by weight (or 1.2% or less, 1.1% or less, 1.0% or less, 0.95% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less by weight). [4] The method for producing 1,3-butylene glycol according to any one of [1] to [3], wherein the content of low-boiling components other than water in the feed liquid to the product column is 1.8 GC area% or less (or 1.6 GC area% or less, 1.4 GC area% or less, 1.2 GC area% or less, 1.1 GC area% or less, 1 GC area% or less, 0.9 GC area% or less, 0.8 GC area% or less, 0.7 GC area% or less, 0.6 GC area% or less, 0.5 GC area% or less, 0.4 GC area% or less, 0.3 GC area% or less, 0.2 GC area% or less, or 0.1 GC area% or less). [5] The method for producing 1,3-butylene glycol according to any one of [1] to [4], wherein the acetaldehyde content in the feed liquid to the product column is 205 ppm or less (or 200 ppm or less, 150 ppm or less, 120 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, or less than 2 ppm), and the crotonaldehyde content in the feed liquid is 110 ppm or less (100 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or less than 1 ppm). [6] The method for producing 1,3-butylene glycol according to any one of [1] to [5], wherein the product column has 1 to 100 theoretical plates. [7] The method for producing 1,3-butylene glycol according to any one of [1] to [6], wherein at least a portion of the distillate from the product column is recycled to a dehydration step, a dealcoholization step, a low-boiling point removal step, or a step preceding these steps, which are steps preceding the product distillation step. [8] A method for producing 1,3-butylene glycol, in which purified 1,3-butylene glycol is obtained from a reaction crude liquid containing 1,3-butylene glycol, The method includes a dehydration step for removing water by distillation and a high boiling point removal step for removing high boiling point components by distillation, In the dehydration tower used in the dehydration step, the acetaldehyde content contains 1,3-butylene glycol and water and is 1000 ppm or less (or 900 ppm or less, 800 ppm or less, 700 ppm or less, 600 ppm or less, 500 ppm or less, 400 ppm or less, 300 ppm or less, 200 ppm or less, 155 ppm or less, 140 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less , 3 ppm or less, 2 ppm or less, or 1 ppm or less), and a crotonaldehyde content of 400 ppm or less (or 200 ppm or less, 150 ppm or less, 130 ppm or less, 117 ppm or less, 100 ppm or less, 90 ppm or less, 80 ppm or less, 70 ppm or less, 60 ppm or less, 50 ppm or less, 40 ppm or less, 30 ppm or less, 20 ppm or less, 10 ppm or less, 5 ppm or less, 3 ppm or less, 2 ppm or less, or 1 ppm or less), and a liquid in which low-boiling point components including water are concentrated is distilled from above the feed stage, In the high boiling point removal tower used in the high boiling point removal step, a feed liquid containing 1,3-butylene glycol is distilled under conditions where the reflux ratio is greater than 0.02 (or 0.1 or greater, more preferably 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, 0.9 or greater, 1 or greater, 1.2 or greater, 1.5 or greater, 2 or greater, 3 or greater, 4 or greater, 5 or greater, 10 or greater, or 20 or greater), thereby distilling out 1,3-butylene glycol with improved purity from above the feed stage, and withdrawing a liquid in which high boiling point components are concentrated from below the feed stage. [9] The reflux ratio in the dehydration tower is 0.03 or more (or 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.1 or more, 0.12 or more, 0.14 or more, 0.16 or more, 0.18 or more, 0.2 or more, 0.22 or more, 0.24 or more, 0.26 or more, 0.28 or more, 0.3 or more, 0.33 or more, 0.36 or more, 0.4 or more, 0.45 or more, 0.5 or more, 0.6 or more, The method for producing 1,3-butylene glycol according to any one of [1] to [8] above, wherein the β-glucan group is 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, or 40 or more.

[10] The method for producing 1,3-butylene glycol according to any one of [1] to [9], wherein the reaction crude liquid containing 1,3-butylene glycol is a reaction crude liquid obtained by hydrogen reduction of acetaldols.

[11] The method for producing 1,3-butylene glycol according to any one of [1] to

[10] above, further comprising an alkali treatment step of treating a process stream containing 1,3-butylene glycol with a base.

[12] The method for producing 1,3-butylene glycol according to any one of [1] to

[11] above, further comprising a desalting step for removing salts in a process stream containing 1,3-butylene glycol.

[13] The method for producing 1,3-butylene glycol according to any one of [1] to

[12] above, further comprising a dealcoholization step of removing low boiling points containing alcohol from a process stream containing 1,3-butylene glycol.

[14] The method for producing 1,3-butylene glycol according to any one of [1] to

[13] , wherein the water content in the liquid fed to the dehydration tower is 90% by weight or less (or 85% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 35% by weight or less, 30% by weight or less, or 25% by weight or less).

[15] The method for producing 1,3-butylene glycol according to any one of [1] to

[14] , wherein at least one of the dehydrating tower and the high boiling removal tower has a theoretical plate number of 1 to 100.

[16] The method for producing 1,3-butylene glycol according to any one of [1] to

[15] , wherein the concentration of 1,3-butylene glycol in the feed liquid to the high boiling removal tower is 95% or more (or 96% or more, 97% or more, 98% or more, or 99% or more).

[17] The method for producing 1,3-butylene glycol according to any one of [1] to

[16] , wherein the content of high-boiling components in the feed liquid to the high-boiling removal tower is 4% or less (or 3% or less, 2% or less, 1% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0.1% or less, 0.05% or less, or 0.01% or less).

[18] 1,3-butylene glycol products with an initial boiling point of more than 203°C (or 204°C or more, 205°C or more, 206°C or more, 207°C or more, or 208°C or more) and a potassium permanganate test value of 30 minutes or more (or more than 30 minutes, 32 minutes or more, 35 minutes or more, 40 minutes or more, 50 minutes or more, or 60 minutes or more).

[19] 1,3-butylene glycol products having an initial boiling point greater than 203°C (or 204°C or higher, 205°C or higher, 206°C or higher, 207°C or higher, or 208°C or higher) and a dry point of 209°C or lower.

[20] 1,3-butylene glycol products with an initial boiling point of more than 203°C (or 204°C or more, 205°C or more, 206°C or more, 207°C or more, or 208°C or more), a dry point of 209°C or less, and a potassium permanganate test value of 30 minutes or more (or more than 30 minutes, 32 minutes or more, 35 minutes or more, 40 minutes or more, 50 minutes or more, or 60 minutes or more).

[21] (a) In a gas chromatography analysis under the following conditions, the area ratio of the peak of 1,3-butylene glycol is higher than 98.7% (or 98.8% or more, 98.9% or more, 99% or more, 99.1% or more, 99.2% or more, 99.3% or more, 99.4% or more, 99.5% or more, 99.6% or more, 99.7% or more, or 99.8% or more), (b) In a gas chromatography analysis under the following conditions, the total area ratio of peaks having a shorter retention time than the peak of 1,3-butylene glycol is lower than 0.3% ( or 0.28% or less, 0.25% or less, 0.23% or less, 0.2% or less, 0.17% or less, 0.15% or less, 0.12% or less, 0.1% or less, 0.07% or less, 0.04% or less, 0.03% or less, 0.02% or less, 0.01% or less, 0.007% or less, 0.005% or less, or 0.002% or less), (c) in gas chromatography analysis under the following conditions, the total area ratio of peaks having a longer retention time than the peak of 1,3-butylene glycol is less than 1.2% (or 1% or less, 0.9% or less, 0.8% or less) (d) the water content is less than 0.4% by weight (or 0.3% by weight or less, 0.2% by weight or less, 0.1% by weight or less, 0.07% by weight or less, 0.05% by weight or less, 0.03% by weight or less, 0.02% by weight or less, 0.01% by weight or less, or 0.005% by weight or less), (e) the acetaldehyde content is less than 2 ppm (or 1.8 ppm or less, 1.7 ppm or less, 1.5 ppm or less, 1.4 ppn or less, 1.3 ppm or less, 1.2 ppm or less, 1.1 ppm or less, 1.0 ppm or less, 0.9 ppm or less, 0.8 ppm or less, 0.7 ppm or less, 0.6 ppm or less, 0.5 ppm or less, 0.3 ppm or less, or 0.2 ppm or less), (f) The content of crotonaldehyde is less than 1.2 ppm (or 1.0 ppm or less, 0.9 ppm or less, 0.8 ppm or less, 0.7 ppm or less, 0.6 ppm or less, 0.5 ppm or less, 0.4 ppm or less, 0.3 ppm or less, 0.2 ppm or less, or 0.The 1,3-butylene glycol product according to any one of the above

[18] to

[20] satisfies at least one (preferably two or more, more preferably three or more, even more preferably four or more, particularly preferably five or more, and especially all of the conditions) selected from the following six conditions: (Gas chromatographic analysis conditions) Analytical column: Column with a stationary phase of dimethylpolysiloxane (film thickness 1.0 μm × length 30 m × inner diameter 0.25 mm) Temperature increase conditions: Increase temperature from 80°C to 120°C at 5°C / min, then increase temperature to 160°C at 2°C / min and hold for 2 minutes. Further increase temperature to 230°C at 10°C / min and hold at 230°C for 18 minutes. Sample introduction temperature: 250℃ Carrier gas: Helium Column gas flow rate: 1 mL / min Detector and detection temperature: Hydrogen flame ionization detector (FID), 280°C

[22] A moisturizer containing the 1,3-butylene glycol product according to any one of

[18] to

[21] above.

[23] The moisturizing agent according to the above

[22] , wherein the content of the 1,3-butylene glycol product according to any one of the above

[18] to

[21] is 10% by weight or more (or 30% by weight or more, 50% by weight or more, 80% by weight or more, or 90% by weight or more).

[24] A cosmetic comprising the moisturizer according to

[22] or

[23] above.

[25] The cosmetic according to the above

[24] , wherein the content of the 1,3-butylene glycol product according to any one of the above

[18] to

[21] is 0.01 to 40% by weight (or 0.1 to 30% by weight, 0.2 to 20% by weight, 0.5 to 15% by weight, or 1 to 10% by weight).

[26] The cosmetic according to

[24] or

[25] above, which is a skin cosmetic, a hair cosmetic, a sunscreen cosmetic, or a makeup cosmetic. [Industrial Applicability]

[0157] According to the production method of the present disclosure, it is possible to industrially efficiently produce high-purity 1,3-butylene glycol having an extremely low content of low-boiling point components and high-boiling point components, a high initial boiling point and a low dry point, high-purity 1,3-butylene glycol having an extremely low content of low-boiling point components, a high initial boiling point and a high potassium permanganate test value, and further high-purity 1,3-butylene glycol having a high potassium permanganate test value, an extremely low content of low-boiling point components and high-boiling point components, a high initial boiling point and a low dry point. [Explanation of symbols]

[0158] A: Dehydration tower B: Desalination tower C: High boiling point removal distillation column (high boiling point removal column) D: Alkaline reactor E: Dealkalization tower F: Product distillation column (product column) A-1, B-1, C-1, E-1, F-1: Condenser A-2, C-2, F-2: Reboiler X-1: Crude 1,3-butylene glycol X-2: Water (drainage) X-3: Salt, high boiling point substances, and some 1,3-butylene glycol X-4: High boiling point substances and part of 1,3-butylene glycol X-5: Caustic soda, high boiling point substances, and some 1,3-butylene glycol X-6: Low boiling point substances and part of 1,3-butylene glycol Y: 1,3-butylene glycol products

Claims

1. A method for producing 1,3-butylene glycol, in which purified 1,3-butylene glycol is obtained from a reaction crude liquid containing 1,3-butylene glycol, comprising the steps of: The method includes a dehydration step for removing water by distillation, a high boiling point removal step for removing high boiling point components by distillation, and a product distillation step for obtaining purified 1,3-butylene glycol, In the dehydration tower used in the dehydration step, a feed liquid containing 1,3-butylene glycol and water and having an acetaldehyde content of 1000 ppm or less and a crotonaldehyde content of 400 ppm or less is distilled, and a liquid containing concentrated low-boiling components including water is distilled from above the feed stage; In the product column used in the product distillation step, a 1,3-butylene glycol feed solution having an acetaldehyde content of 500 ppm or less and a crotonaldehyde content of 200 ppm or less is distilled under conditions of a reflux ratio of more than 0.1, a liquid in which low-boiling point components are concentrated is distilled from above the feed stage, and 1,3-butylene glycol is withdrawn from below the feed stage.

2. The method for producing 1,3-butylene glycol according to claim 1, wherein in the high boiling point removal tower used in the high boiling point removal step, a feed liquid containing 1,3-butylene glycol is distilled under conditions of a reflux ratio of 0.02 or more, and 1,3-butylene glycol with improved purity is distilled from above the feed stage, and a liquid in which high boiling point components are concentrated is withdrawn from below the feed stage.

3. 3. The method for producing 1,3-butylene glycol according to claim 1, wherein the concentration of 1,3-butylene glycol in the feed liquid to the product column is 90 GC area % or more, and the content of water in the feed liquid is 3 wt % or less.

4. A method for producing 1,3-butylene glycol, in which purified 1,3-butylene glycol is obtained from a reaction crude liquid containing 1,3-butylene glycol, comprising the steps of: The method includes a dehydration step for removing water by distillation and a high boiling point removal step for removing high boiling point components by distillation, In the dehydration tower used in the dehydration step, a feed liquid containing 1,3-butylene glycol and water and having an acetaldehyde content of 1000 ppm or less and a crotonaldehyde content of 400 ppm or less is distilled, and a liquid containing concentrated low-boiling components including water is distilled from above the feed stage; In the high boiling point removal tower used in the high boiling point removal step, a feed liquid containing 1,3-butylene glycol is distilled under conditions where the reflux ratio is greater than 0.02, and 1,3-butylene glycol having an improved purity is distilled from above the feed stage, and a liquid in which high boiling point components are concentrated is withdrawn from below the feed stage.

5. The method for producing 1,3-butylene glycol according to any one of claims 1 to 4, wherein the reflux ratio in the dehydrating tower is 0.03 or more.

6. The method for producing 1,3-butylene glycol according to any one of claims 1 to 5, wherein the reaction crude liquid containing 1,3-butylene glycol is a reaction crude liquid obtained by hydrogen reduction of acetaldols.

7. The method for producing 1,3-butylene glycol according to any one of claims 1 to 6, further comprising an alkali treatment step of treating the process stream containing 1,3-butylene glycol with a base.

8. The method for producing 1,3-butylene glycol according to any one of claims 1 to 7, further comprising a desalting step for removing salts in a process stream containing 1,3-butylene glycol.

9. The method for producing 1,3-butylene glycol according to any one of claims 1 to 8, further comprising a dealcoholization step of removing low boiling points containing alcohol from a process stream containing 1,3-butylene glycol.

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