1,4-Cyclohexanedimethanol composition and method for purifying the same

Abstract

The present invention relates to a 1,4-cyclohexanedimethanol (CHDM) composition and a method for purifying the same, and more particularly to a 1,4-cyclohexanedimethanol composition that has a high purity due to a low content of by-products and a high ratio of trans isomers, and a method for purifying the same.

Description

Technical Field

[0001] Cross-reference to related applications This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0015384 filed on February 3, 2021 and Korean Patent Application No. 10-2021-0015385 filed on February 3, 2021, and all the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a method for purifying a 1,4-cyclohexanedimethanol (CHDM) composition. More specifically, the present invention relates to a 1,4-cyclohexanedimethanol composition having a high purity due to a low content of by-products and a high ratio of trans isomers, and a method for purifying the same.

Background Art

[0003] 1,4-Cyclohexanedimethanol (CHDM) is widely used as a raw material for pharmaceuticals, synthetic resins, synthetic fibers, dyes, etc., and is particularly used as a raw material for polyethylene terephthalate, a polyester that is environmentally friendly.

[0004] 1,4-Cyclohexanedimethanol exists as stereoisomers in cis and trans forms, but for higher quality products, a higher ratio of trans 1,4-cyclohexanedimethanol (trans CHDM) than cis is required.

[0005] Among the methods for producing 1,4 - cyclohexanedimethanol, the method by the hydrogenation reaction of dimethyl terephthalate (DMT) is commercially widely used. This method is a process in which phthalate reacts with methanol to produce DMT, and then 1,4 - cyclohexanedimethanol is generated by a two - step hydrogenation reaction. The first hydrogenation reaction is the reaction to convert DMT to diester dimethyl 1,4 - cyclohexanedicarboxylate (DMCD), and in the second hydrogenation reaction, DMCD is converted to CHDM. At this time, the ratio of cis - CHDM and trans - CHDM is determined by the type of catalyst. When using a copper chromite catalyst, which is mainly commercially used, the ratio of cis - CHDM and trans - CHDM is produced at about 3:7. Such a method uses DMT and the trans - esterification reaction using methanol, so the reaction and separation processes are complex, and additives must be used for isomerization, which may affect the quality of the final product.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to solve the above - mentioned problems, and to provide 1,4 - cyclohexanedimethanol with a high purity because the crude composition of 1,4 - cyclohexanedimethanol is purified to have a low content of by - products and water, and a high ratio of trans - isomers.

Means for Solving the Problems

[0007] To solve the above problems, One aspect of the present invention is 1,4 - cyclohexanedimethanol (CHDM) having a purity of 99.7% by weight or more measured by gas chromatography (GC) analysis and containing cis - isomers and trans - isomers; and Provided is a 1,4-cyclohexanedimethanol composition containing 0.15 wt% or less of a low molecular weight (light) by-product having a molecular weight of less than 144.21 g / mol.

[0008] Another aspect of the present invention is a water removal step of removing water from a crude composition of 1,4-cyclohexanedimethanol; a primary by-product removal step of removing a by-product having a boiling point lower than that of 1,4-cyclohexanedimethanol from the 1,4-cyclohexanedimethanol composition that has undergone the water removal step; and

[0009] a secondary by-product removal step of removing a by-product having a boiling point higher than that of 1,4-cyclohexanedimethanol from the 1,4-cyclohexanedimethanol composition that has undergone the primary by-product removal step and recovering a purified 1,4-cyclohexanedimethanol composition; including a method for purifying a 1,4-cyclohexanedimethanol composition is provided.

Advantages of the Invention

[0010] According to the 1,4-cyclohexanedimethanol composition and the purification method thereof of the present invention, since the contents of by-products and water are very low, 1,4-cyclohexanedimethanol with high purity can be provided, and improvement in physical properties can be expected when used as a high molecular raw material.

[0011] In addition, the purification method of 1,4-cyclohexanedimethanol of the present invention consumes less energy, has a simple process step, and has a high by-product removal efficiency, so high-quality 1,4-cyclohexanedimethanol can be produced at low cost.

Modes for Carrying Out the Invention

[0012] The terms used in this specification are used merely for the purpose of explaining exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "including", "comprising", or "having" are intended to specify the presence of implemented features, steps, components, or combinations thereof, and should not be construed as precluding the presence or addition possibility of one or more other features, steps, components, or combinations thereof.

[0013] While the present invention can be subjected to various modifications and can have various forms, specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood to include all modifications, equivalents, and alternatives included in the spirit and technical scope of the present invention.

[0014] Hereinafter, a method for purifying a 1,4 - cyclohexanedimethanol composition will be described in more detail according to specific embodiments of the invention.

[0015] The method for purifying 1,4 - cyclohexanedimethanol of the present invention includes a water removal step of removing water from a crude composition of 1,4 - cyclohexanedimethanol (1,4 - cyclohexanedimethanol, CHDM); a primary by - product removal step of removing by - products having a boiling point lower than that of 1,4 - cyclohexanedimethanol from the 1,4 - cyclohexanedimethanol composition that has undergone the water removal step; and a secondary by - product removal step of removing by - products having a boiling point higher than that of 1,4 - cyclohexanedimethanol from the 1,4 - cyclohexanedimethanol composition that has undergone the primary by - product removal step and recovering the purified 1,4 - cyclohexanedimethanol composition.

[0016] Hereinafter, a 1,4 - cyclohexanedimethanol composition and a method for purifying the same according to an embodiment of the present invention will be described in detail for each step.

[0017] The 1,4-cyclohexanedimethanol composition of the present invention has a purity of 99.7% by weight or more as measured by gas chromatography (GC) analysis, and contains 1,4-cyclohexanedimethanol (CHDM) including cis isomers and trans isomers; and low molecular weight (light) by-products having a molecular weight of less than 144.21 g / mol in an amount of 0.15% by weight or less.

[0018] More specifically, in the 1,4-cyclohexanedimethanol composition according to an embodiment of the present invention, a low molecular weight (light) by-product having a molecular weight of less than 144.21 g / mol, which is the molecular weight (Mw) of 1,4-cyclohexanedimethanol, can be contained in an amount of 0.15% by weight or less, or 0.14% by weight or less, or 0.12% by weight or less, or 0.10% by weight or less, or 0.09% by weight or less, based on the total weight of the 1,4-cyclohexanedimethanol composition. Since the lower the content of the low molecular weight by-product, the more preferable, the lower limit is 0% by weight, but it can be 0.001% by weight as an example.

[0019] When producing other polymers using a 1,4-cyclohexanedimethanol composition containing more than 0.15% by weight (more than 0.15% by weight) of the low molecular weight by-product, it may be difficult to produce high molecular weight and high quality products by interfering with the polymerization of the polymer.

[0020] Examples of the low molecular weight by-products include cyclohexylmethanol, 4-methyl-1-cyclohexanemethanol, cyclohexane carboxylic acid, 4-methyl-3-cyclohexene-1-methanol, 4-methyl cyclohexane carboxylic acid, 4-hydroxymethyl cyclohexane carboxylic acid, 4-hydroxymethyl-4-cyclohexanemethanol, 3-hydroxymethyl-4-cyclohexanemethanol, and the like.

[0021] Among the low molecular weight by-products, when cyclohexylmethanol (CHM) is contained in a large amount in the final product, the distribution of low molecular weight polymers becomes high during polymer production, which affects the intrinsic physical properties of polymers such as molecular weight distribution and intrinsic viscosity. Therefore, it is preferable to remove cyclohexylmethanol as much as possible and substantially not contain it.

[0022] The 1,4-cyclohexanedimethanol composition according to an embodiment of the present invention contains only a very small content of 0.01% by weight or less, or 0.005% by weight or less of the cyclohexylmethanol, or is contained only at a non-detectable level and can be used as a raw material for high-quality polymer products.

[0023] Also, in a 1,4 - cyclohexanedimethanol composition according to an embodiment of the present invention, a high - molecular - weight by - product having a molecular weight exceeding (more than) 144.21 g / mol, which is the molecular weight (Mw) of 1,4 - cyclohexanedimethanol, can be contained in an amount of 0.15 wt% or less, or 0.14 wt% or less, or 0.12 wt% or less, or 0.10 wt% or less, or 0.09 wt% or less, based on the total weight of the purified 1,4 - cyclohexanedimethanol composition. Since it is more preferable that the content of the high - molecular - weight by - product is lower, the lower limit value is 0 wt%, but it can be 0.01 wt% as an example.

[0024] When the high - molecular - weight by - product is contained in an amount exceeding 0.15 wt%, when using the 1,4 - cyclohexanedimethanol composition to produce other polymers, the carboxyl group at the end of the high - molecular - weight by - product hinders the polymerization of the polymer, making it difficult to produce a polymer with a desired molecular weight, and yellowing may occur, making it difficult to produce high - quality products in some cases.

[0025] Examples of the high - molecular - weight by - product include 1,4 - cyclohexane - hydroxymethyl - carboxylic acid, mono - ester - based compounds, or mono - ether - based compounds.

[0026] Also, a 1,4 - cyclohexanedimethanol composition according to an embodiment of the present invention can exhibit excellent color with an APHA value measured by ASTM D1209 of 10 or less, or 8 or less, or 6 or less, or 4 or less, or 2 or less.

[0027] Also, in a 1,4 - cyclohexanedimethanol composition according to an embodiment of the present invention, the content of the trans isomer, that is, trans - 1,4 - cyclohexanedimethanol in 1,4 - cyclohexanedimethanol can be 63% by weight or more, or 65% by weight or more, or 67% by weight or more, or 69% by weight or more, or 70% by weight or more, and can have a very high trans isomer content. Also, although there is no upper limit to the ratio of the trans isomer, as an example, it can be 99% by weight or less, or 95% by weight or less, or 90% by weight or less, or 85% by weight or less.

[0028] Also, in a 1,4 - cyclohexanedimethanol composition according to an embodiment of the present invention, the content of 1,4 - cyclohexanedimethanol, that is, the purity can be 99.5% by weight or more, or 99.6% by weight or more, or 99.7% by weight or more, or 99.75% by weight or more. Since the higher the purity is, the more preferable it is, although the theoretical purity is 100% by weight, it can be substantially 99.9% by weight or less.

[0029] As described above, the 1,4 - cyclohexanedimethanol composition according to an embodiment of the present invention has a high purity of 1,4 - cyclohexanedimethanol, a high trans content, and a very low content of residual by - products, and thus can be usefully used as a raw material for manufacturing high - quality products such as pharmaceuticals, synthetic resins, synthetic fibers, or dyes.

[0030] The 1,4-cyclohexanedimethanol composition of the present invention having the foregoing characteristics is obtained by a purification method including, as an example, a water removal step of removing water from a crude composition of 1,4-cyclohexanedimethanol (1,4-cyclohexanedimethanol, CHDM); a primary by-product removal step of removing by-products having a boiling point lower than that of 1,4-cyclohexanedimethanol from the 1,4-cyclohexanedimethanol composition that has undergone the water removal step; and a secondary by-product removal step of removing by-products having a boiling point higher than that of 1,4-cyclohexanedimethanol from the 1,4-cyclohexanedimethanol composition that has undergone the primary by-product removal step to recover a purified 1,4-cyclohexanedimethanol composition.

[0031] Hereinafter, a method for purifying a 1,4-cyclohexanedimethanol composition according to an embodiment of the present invention will be described in detail for each step.

[0032] First, a step of removing water from a crude composition of 1,4-cyclohexanedimethanol containing 1,4-cyclohexanedimethanol (1,4-cyclohexanedimethanol, CHDM), water, and by-products is performed.

[0033] The crude composition of 1,4-cyclohexanedimethanol to be purified by the purification method of the present invention is, but not limited to, obtained by a two-step hydrogenation reaction with respect to terephthalic acid. Since the first reactant, terephthalic acid, undergoes a hydrogenation reaction in a state dissolved in water, the crude composition of 1,4-cyclohexanedimethanol contains a large amount of water.

[0034] As an example, the crude composition of 1,4-cyclohexanedimethanol contains 10 to 40% by weight of 1,4-cyclohexanedimethanol, 60 to 90% by weight of water, and by-products with respect to the total weight. A substantial portion of the remaining components excluding the 10 to 40% by weight of 1,4-cyclohexanedimethanol is occupied by water.

[0035] Therefore, in order to recover highly purified 1,4 - cyclohexanedimethanol, it is first necessary to remove water. However, since the crude composition of 1,4 - cyclohexanedimethanol contains a large amount of water as described above, if water is removed together during the by - product removal step, a large amount of energy is consumed.

[0036] Therefore, in one embodiment of the present invention, first, a water removal step of removing a large amount of water at a low temperature and in a high - vacuum state is performed.

[0037] As an example, the water removal step can be performed on the crude composition of 1,4 - cyclohexanedimethanol at a temperature of 50 to 110 °C and a pressure of - 0.1 to 0.1 barg. More preferably, it can be performed at a temperature of 55 to 105 °C and a pressure of 0 to 0.01 barg.

[0038] When deviating from the above - mentioned temperature and pressure conditions, water cannot be sufficiently removed, additional water removal is required in the subsequent process, and the energy consumption required for purification may increase.

[0039] The water removal step can be performed using a device such as an evaporator, a multi - stage evaporator, or a distillation column, but the present invention is not limited thereto.

[0040] By the water removal step as described above, 80% by weight or more, preferably 90% by weight or more, more preferably 97% by weight or more of the water contained in the initial crude composition of 1,4 - cyclohexanedimethanol can be removed.

[0041] Next, a primary by - product removal step is performed.

[0042] The primary by - product removal step is a step of removing by - products (hereinafter referred to as low - boiling by - products) having a boiling point lower than that of 1,4 - cyclohexanedimethanol from the 1,4 - cyclohexanedimethanol composition that has undergone the water removal step.

[0043] The low-boiling by-products are compounds with a boiling point lower than 286°C, which is the boiling point of 1,4-cyclohexanedimethanol. For example, cyclohexylmethanol (boiling point of about 181°C), 4-methyl-1-cyclohexanemethanol (boiling point of about 197°C), 4-methyl cyclohexane carboxylic acid (boiling point of about 134°C), 4-methyl-3-cyclohexene-1-methanol (boiling point of about 197°C), 4-hydroxymethyl cyclohexane carboxylic acid (boiling point of about 278 - 282°C), 4-hydroxymethyl-4-cyclohexanemethanol (boiling point of about 278 - 282°C), 3-hydroxymethyl-4-cyclohexanemethanol (boiling point of about 278 - 282°C), etc. can be mentioned.

[0044] As an example, the primary by-product removal step is a step of distilling the 1,4-cyclohexanedimethanol composition that has undergone the water removal step in a low-boiling distillation column to separate the low-boiling by-products at the bottom and 1,4-cyclohexanedimethanol at the top.

[0045] At this time, the primary by-product removal step can be carried out such that the temperature at the top of the low-boiling distillation column is 40 to 55°C, the pressure is -1 to 1 barg, the temperature at the bottom of the column is 200 to 220°C, and the pressure is -1 to 1 barg.

[0046] When deviating from the above temperature and pressure conditions, the removal rate of the low-boiling by-products may decrease.

[0047] By means of the primary by-product removal step as described above, 99% by weight or more, preferably 99.5% by weight or more, of the total weight of the low-boiling by-products contained in the crude composition of the first 1,4-cyclohexanedimethanol can be removed.

[0048] Next, a secondary by-product removal step is carried out.

[0049] The secondary by-product removal step is a step of removing by-products (hereinafter referred to as high-boiling by-products) having a boiling point higher than that of 1,4-cyclohexanedimethanol from the 1,4-cyclohexanedimethanol composition that has undergone the primary by-product removal step and recovering purified 1,4-cyclohexanedimethanol.

[0050] The high-boiling by-products are compounds having a boiling point higher than 286°C, which is the boiling point of 1,4-cyclohexanedimethanol, and examples include 1,4-cyclohexane-hydroxylmethyl-carboxylic acid (boiling point about 316°C), monoester compounds, or monoether compounds.

[0051] As an example, the secondary by-product removal step is a step of distilling the 1,4-cyclohexanedimethanol composition that has undergone the primary by-product removal step in a high-boiling distillation column to separate high-boiling by-products at the top and 1,4-cyclohexanedimethanol at the bottom.

[0052] At this time, the secondary by-product removal step can be carried out such that the temperature at the top of the high-boiling distillation column is 200 to 220°C, the pressure is -1 to 1 barg, the temperature at the bottom is 240 to 260°C, and the pressure is -1 to 1 barg.

[0053] If the temperature and pressure conditions deviate from the above, the removal rate of high-boiling by-products may decrease.

[0054] By means of the secondary by-product removal step as described above, 99% by weight or more, preferably 99.5% by weight or more, of the total weight of the high-boiling by-products contained in the crude composition of the initial 1,4-cyclohexanedimethanol can be removed.

[0055] The 1,4-cyclohexanedimethanol composition obtained by the purification method of the present invention including the water removal step, the primary by-product removal step, and the secondary by-product removal step as described above can have a purity of 1,4-cyclohexanedimethanol calculated based on the content of 1,4-cyclohexanedimethanol measured by gas chromatography (GC) analysis of 99.5% by weight or more.

[0056] More specifically, in the purified 1,4-cyclohexanedimethanol composition, the content of 1,4-cyclohexanedimethanol, that is, the purity, can be 99.5% by weight or more, or 99.7% by weight or more, or 99.75% by weight or more, or 99.8% by weight or more, or 99.9% by weight or more.

[0057] Also, the water content remaining in the purified 1,4-cyclohexanedimethanol composition can be 0.15% by weight or less, or 0.13% by weight or less, or 0.12% by weight or less, or 0.10% by weight or less, or 0.09% by weight or less, or 0.08% by weight or less, or 0.07% by weight or less with respect to the total weight of the purified 1,4-cyclohexanedimethanol composition, and the water content can be very low.

[0058] When water is contained in an amount exceeding 0.15% by weight, the low-boiling components may not be sufficiently removed, and the purity of the final 1,4-cyclohexanedimethanol may be lowered.

[0059] In addition, the 1,4-cyclohexanedimethanol composition obtained by the purification method of the present invention may contain a low molecular weight (light) by-product having a molecular weight of less than 144.21 g / mol, which is the molecular weight (Mw) of 1,4-cyclohexanedimethanol, in an amount of 0.15% by weight or less, or 0.14% by weight or less, or 0.12% by weight or less, or 0.10% by weight or less, or 0.09% by weight or less, based on the total weight of the purified 1,4-cyclohexanedimethanol composition. Since the lower the content of the low molecular weight by-product, the more preferable, the lower limit is 0% by weight, but it can be 0.01% by weight as an example.

[0060] When using a 1,4-cyclohexanedimethanol composition containing more than 0.15% by weight of the low molecular weight by-product to produce other polymers, it may be difficult to produce high molecular weight and high quality products due to interference with the polymerization of the polymer.

[0061] Examples of the low molecular weight by-products include cyclohexylmethanol, 4-methyl-1-cyclohexanemethanol, cyclohexane carboxylic acid, 4-methyl-3-cyclohexene-1-methanol, 4-methyl cyclohexane carboxylic acid, 4-hydroxymethyl cyclohexane carboxylic acid, 4-hydroxymethyl-4-cyclohexanemethanol, 3-hydroxymethyl-4-cyclohexanemethanol, and the like.

[0062] Among the low molecular weight by-products, when cyclohexylmethanol (CHM) is contained in a large amount in the final product, the distribution of low molecular weight polymers becomes high during polymer production, which affects the intrinsic physical properties of polymers such as molecular weight distribution and intrinsic viscosity. Therefore, it is preferable to remove cyclohexylmethanol as much as possible and substantially not contain it.

[0063] The 1,4-cyclohexanedimethanol composition obtained by the purification method of the present invention contains cyclohexylmethanol in a very small content of 0.01% by weight or less, or 0.005% by weight or less, or only at a non-detectable level, and can be used as a raw material for high-quality polymer products.

[0064] In addition, the 1,4-cyclohexanedimethanol composition obtained by the purification method of the present invention contains high molecular weight (heavy) by-products having a molecular weight exceeding 144.21 g / mol, which is the molecular weight (Mw) of 1,4-cyclohexanedimethanol, in an amount of 0.15% by weight or less, or 0.14% by weight or less, or 0.12% by weight or less, or 0.10% by weight or less, or 0.09% by weight or less based on the total weight of the purified 1,4-cyclohexanedimethanol composition. Since it is more preferable that the content of the high molecular weight by-product is lower, the lower limit is 0% by weight, but it can be 0.01% by weight as an example.

[0065] When producing other polymers using a 1,4-cyclohexanedimethanol composition containing more than 0.15% by weight of the high molecular weight by-product, it may interfere with the polymerization of the polymer, affect the color, viscosity, etc., and make it difficult to produce high-quality products.

[0066] Examples of the high molecular weight by-products include 1,4-cyclohexane-hydroxylmethyl-carboxylic acid, monoester compounds, or monoether compounds.

[0067] In addition, the 1,4 - cyclohexanedimethanol composition obtained by the purification method of the present invention can exhibit excellent color with an APHA value measured by ASTM D1209 of 10 or less, or 8 or less, or 6 or less, or 4 or less, or 2 or less.

[0068] In addition, in the 1,4 - cyclohexanedimethanol composition obtained by the purification method of the present invention, the content of the trans isomer, that is, trans - 1,4 - cyclohexanedimethanol in 1,4 - cyclohexanedimethanol can be 63% by weight or more, or 65% by weight or more, or 67% by weight or more, or 69% by weight or more, or 70% by weight or more, having a very high trans isomer content. Also, although there is no upper limit to the ratio of the trans isomer, as an example, it can be 99% by weight or less, or 95% by weight or less, or 90% by weight or less, or 85% by weight or less.

[0069] As described above, the 1,4 - cyclohexanedimethanol obtained by the purification method of the present invention has high purity and very low contents of residual water and by - products, and thus can be usefully used as a raw material for manufacturing high - quality products such as pharmaceuticals, synthetic resins, synthetic fibers, or dyes.

[0070] The crude composition of 1,4 - cyclohexanedimethanol, which is the subject of the purification method of the present invention described above, can be produced by a one - step hydrogenation reaction of terephthalic acid as a starting material to 1,4 - cyclohexane dicarboxylic acid (CHDA), and a two - step hydrogenation reaction from 1,4 - cyclohexane dicarboxylic acid to 1,4 - cyclohexanedimethanol.

[0071] As an example, it may be produced by a production method including: a first step of supplying a reaction solution containing terephthalic acid, a first hydrogenation catalyst, and water, and hydrogen gas to a first reactor equipped with a stirrer to perform a hydrogenation reaction to produce 1,4-cyclohexane dicarboxylic acid (CHDA) containing cis and trans isomers; and a second step of supplying the reaction product of the first step, a second hydrogenation catalyst, and a reaction solution containing water, and hydrogen gas to a second reactor equipped with a stirrer to perform a hydrogenation reaction to produce 1,4-cyclohexanedimethanol (CHDM) containing cis and trans isomers.

[0072] The first step is a step of supplying a reaction solution containing terephthalic acid, a first hydrogenation catalyst, and water, and hydrogen gas to a first reactor equipped with a stirrer to perform a hydrogenation reaction to produce 1,4-cyclohexane dicarboxylic acid containing cis and trans isomers.

[0073] More specifically, a reaction solution containing terephthalic acid, a first hydrogenation catalyst, and water is supplied to a first reactor equipped with a stirrer.

[0074] The terephthalic acid is 5 to 25% by weight based on the total amount of terephthalic acid and water. More specifically, the terephthalic acid may be 5% by weight or more, or 10% by weight or more, or 15% by weight or more, or 18% by weight or more, and 25% by weight or less, or 24% by weight or less, or 22% by weight or less based on the total amount of terephthalic acid and water.

[0075] When the terephthalic acid is less than 5% by weight based on the total amount of terephthalic acid and water, there is a problem that the time for the ratio of trans / cis isomers to reach equilibrium is very long and the ratio of trans isomers in the produced CHDA is low. When it exceeds 25% by weight, there is a problem that it is difficult to dissolve due to the low solubility of terephthalic acid, and the reaction temperature has to be set high. When the reaction temperature increases, a large amount of low-boiling by-products are generated, resulting in a low yield, and the catalytic activity decreases due to thermal fatigue.

[0076] According to an embodiment of the present invention, as the first hydrogenation catalyst, a catalyst known to be usable for the hydrogenation reaction of terephthalic acid can be used.

[0077] According to an embodiment of the present invention, the first hydrogenation catalyst may include one or more metals selected from the group consisting of palladium (Pd), rhodium (Rh), ruthenium (Ru), and platinum (Pt) as active components. Preferably, the first hydrogenation catalyst may include palladium (Pd) as an active component.

[0078] Such a first hydrogenation catalyst can be used by being supported on a carrier. At this time, as the carrier, carriers known in the art can be used without limitation. Specifically, carriers such as carbon, zirconia (ZrO2), titania (TiO2), alumina (Al2O3), or silica (SiO2) can be used.

[0079] Next, hydrogen gas is supplied to the first reactor into which the reaction solution is introduced.

[0080] The hydrogenation reaction can be carried out in a liquid state or a gaseous state. According to an embodiment of the present invention, the terephthalic acid can be in a liquid state dissolved in a solvent such as water, and hydrogenation reaction can be carried out with hydrogen in a gaseous state.

[0081] Next, 1,4-cyclohexanedicarboxylic acid is produced by stirring the stirrer of the first reactor to carry out the hydrogenation reaction.

[0082] The reaction product obtained after the first-stage reaction contains CHDA including cis isomer and trans isomer, water as a solvent, a catalyst, etc., and this is used as a reactant for the subsequent second-stage hydrogenation reaction (hydrogenation reaction from CHDA to CHDM). If necessary, the catalyst contained in the reaction product can be removed by a catalyst filter or the like and then transferred to the reactant for the second-stage hydrogenation reaction.

[0083] According to one embodiment of the present invention, the total amount of 1,4-cyclohexanedicarboxylic acid including cis isomer and trans isomer in the reaction product of the first stage can be 5 to 30% by weight based on the total amount of 1,4-cyclohexanedicarboxylic acid and water. More specifically, it can be 5% by weight or more, or 7% by weight or more, or 10% by weight or more, and 30% by weight or less, or 25% by weight or less, or 23% by weight or less.

[0084] According to one embodiment of the present invention, when producing 1,4-cyclohexanedicarboxylic acid by subjecting a mixed solution containing terephthalic acid, a first hydrogenation catalyst, and water, where the terephthalic acid is contained in an amount of 5 to 25% by weight, preferably 10 to 25% by weight, more preferably 12 to 22% by weight based on the total amount of terephthalic acid and water, to a hydrogenation reaction, the ratio of the trans isomer in the total amount of the produced 1,4-cyclohexanedicarboxylic acid can be 60% by weight or more, or 62% by weight or more, or 65% by weight or more, or 67% by weight or more, or 70% by weight or more. There is no upper limit to the ratio of the trans isomer, but as an example, it can be 80% by weight or less, or 78% by weight or less, or 75% by weight or less.

[0085] In the second stage, a reaction solution containing the reaction product of the first stage, a second hydrogenation catalyst, and water, and hydrogen gas are supplied to a second reactor equipped with a stirrer to perform a hydrogenation reaction to produce 1,4-cyclohexanedimethanol (1,4-cyclohexanedimethanol, CHDM) including cis isomer and trans isomer.

[0086] More specifically, a reaction solution containing the reaction product of the first stage, the second hydrogenation catalyst, and water is supplied to the second reactor equipped with a stirrer.

[0087] The reaction product of the first stage reaction contains 1,4 - cyclohexanedicarboxylic acid, the first hydrogenation catalyst, and water as a solvent, and this can be used as a reactant for the second stage hydrogenation reaction. At this time, before performing the second stage, it is preferable to remove the first hydrogenation catalyst contained in the reaction product of the first stage reaction using a filter or the like.

[0088] In addition, since the reaction product of the first stage contains a solvent of water in addition to 1,4 - cyclohexanedicarboxylic acid, it can be directly used for the second stage reaction without adding additional water. Or, if necessary, in order to adjust the concentration of the reaction solution, a part of the water can be removed or additional water can be added.

[0089] The 1,4 - cyclohexanedicarboxylic acid is contained in an amount of 5 to 30% by weight based on the total amount of 1,4 - cyclohexanedicarboxylic acid and water. More specifically, it can be 5% by weight or more, or 7% by weight or more, or 10% by weight or more, and 30% by weight or less, or 25% by weight or less, or 23% by weight or less.

[0090] When the 1,4 - cyclohexanedicarboxylic acid is less than 5% by weight based on the total amount of 1,4 - cyclohexanedicarboxylic acid and water, there are problems such as a decrease in the contact between the reactant and the catalyst, a slow reaction rate, and a decrease in the ratio of the trans isomer in the produced CHDM. When it exceeds 30% by weight, the solubility of 1,4 - cyclohexanedicarboxylic acid decreases, productivity decreases, and as a result, the crystallization of the reactant and the amount of catalyst increase, making it difficult in the process of feeding the slurry.

[0091] At this time, the ratio of the cis isomer and the trans isomer of 1,4-cyclohexanedicarboxylic acid, which is the reaction raw material, is the same as the ratio of the cis isomer and the trans isomer of 1,4-cyclohexanedicarboxylic acid obtained in the first-stage hydrogenation reaction. Therefore, the 1,4-cyclohexanedicarboxylic acid may have a trans isomer ratio of 60% by weight or more, or 62% by weight or more, or 65% by weight or more, or 67% by weight or more, or 70% by weight or more. Although there is no upper limit to the ratio of the trans isomer, as an example, it may be 80% by weight or less, or 78% by weight or less, or 75% by weight or less.

[0092] According to an embodiment of the present invention, the second hydrogenation catalyst may contain, as active components, one or more metals selected from the group consisting of palladium (Pd), rhodium (Rh), and ruthenium (Ru), and one or more metals selected from the group consisting of tin (Sn), iron (Fe), rhenium (Re), and gallium (Ga).

[0093] Preferably, the second hydrogenation catalyst may contain ruthenium (Ru) and tin (Sn) as active components. More preferably, the active components of the hydrogenation catalyst may consist only of ruthenium (Ru) and tin (Sn), and may not contain other active components.

[0094] Such a second hydrogenation catalyst can be used by being supported on a carrier. At this time, as the carrier, carriers known in the art can be used without limitation. Specifically, carriers such as carbon, zirconia (ZrO2), titania (TiO2), alumina (Al2O3), or silica (SiO2) can be used.

[0095] Next, hydrogen gas is supplied to the reactor into which the reaction solution has been charged.

[0096] The hydrogenation reaction can be carried out in a liquid state or a gaseous state. According to an embodiment of the present invention, the 1,4-cyclohexanedicarboxylic acid can be in a liquid state dissolved in a solvent such as water, and hydrogen can be in a gaseous state for the hydrogenation reaction to be carried out.

[0097] Next, the stirrer of the second reactor is stirred to carry out a hydrogenation reaction to produce 1,4 - cyclohexanedimethanol.

[0098] The crude composition of 1,4 - cyclohexanedimethanol, which is the reaction product obtained after the second - stage reaction, contains 1,4 - cyclohexanedimethanol including cis - isomer and trans - isomer, water as a solvent, and reaction by - products, etc. By purifying this by the purification method of the present application, high - purity 1,4 - cyclohexanedimethanol can be obtained.

[0099] According to one embodiment of the present invention, the content of 1,4 - cyclohexanedimethanol including cis - isomer and trans - isomer in the total weight of the step - reaction product can be 10 to 40% by weight, or 15 to 30% by weight.

[0100] Preferably, in the 1,4 - cyclohexanedimethanol which is the reaction product of the second stage, the content of the trans - isomer can be 63% by weight or more, or 65% by weight or more, or 67% by weight or more, or 69% by weight or more, or 70% by weight or more, having a very high trans - isomer content. Also, although there is no upper limit to the ratio of the trans - isomer, as an example, it can be 99% by weight or less, or 95% by weight or less, or 90% by weight or less, or 85% by weight or less.

[0101] As described above, since the 1,4 - cyclohexanedimethanol obtained after the hydrogenation reaction of the second stage has a high content of the trans - isomer, it can be usefully used as a raw material for producing higher - quality products even without an additional isomerization step, and high - purity 1,4 - cyclohexanedimethanol can be recovered by purifying it by the purification method according to one embodiment of the present invention.

[0102] The following will be described in more detail for the understanding of the present invention. However, the following examples are merely illustrative of the present invention, and the content of the present invention is not limited by the following examples.

Example

[0103] <Example> Production Example 1 First stage A first reactor including a gas-induced type stirrer was prepared.

[0104] 550 g of terephthalic acid (TPA) as a reactant, 92 g of 5 wt% hydrogenation catalyst Pd / C (containing 5 wt% Pd with respect to the carrier carbon), and 2,100 g of distilled water as a solvent were placed in the reactor. After replacing the internal atmosphere of the reactor with nitrogen, the temperature of the mixed solution was raised to 250 °C while stirring at 50 rpm.

[0105] After the temperature of the mixed solution reached 250 °C, it was stirred for 30 minutes while maintaining the temperature for the dissolution of TPA. Then, the stirring speed was increased so that the inside of the reactor was 120 bar and the surface area per unit volume of hydrogen gas was 300 to 500 m 2 / m 3 The hydrogenation reaction was carried out over 1 hour while supplying hydrogen gas into the reaction solution so as to maintain.

[0106] After completion of the reaction, a product containing 569 g of 1,4-cyclohexanedimethanol (CHDA) (trans-CHDA ratio in CHDA: 68 wt%) and 2,100 g of water was obtained. After removing only the hydrogenation catalyst with a metal filter, it was directly used as a reactant in the second-stage hydrogenation reaction step.

[0107] Second stage A second reactor including a gas-induced type stirrer was prepared.

[0108] 569 g of CHDA (trans-CHDA ratio in CHDA: 68% by weight), which is the product of the first-stage reaction, and 2,100 g of distilled water as a solvent were placed in the second reactor, and 152 g of a catalyst (ruthenium-tin / carbon catalyst, containing 5 parts by weight of ruthenium and 5.8 parts by weight of tin with respect to 100 parts by weight of the carbon carrier) was added. After purging twice with nitrogen at 5 bar and twice with hydrogen at 5 bar, the temperature was raised to 230 °C while stirring at 50 rpm in a hydrogen atmosphere (about 14 - 15 bar).

[0109] Once the reaction temperature was reached, hydrogen was injected up to a reaction pressure of 100 bar, and then the stirring speed was increased so that the surface area per unit volume of hydrogen gas bubbles was maintained at 300 to 450 m 2 / m 3 and the reaction was carried out for 6 hours.

[0110] After removing the hydrogenation catalyst from the product of the second-stage reaction with a metal filter, it was transferred to the purification stage of the example.

[0111] Example 1 The following steps were performed on the crude composition of 1,4-cyclohexanedimethanol of Production Example 1.

[0112] First, water was evaporated from the crude product in an evaporator under the conditions of an operating temperature of 103 °C and a pressure of 0 barg to remove it to 97.5% by weight with respect to the initial water content.

[0113] The 1,4-cyclohexanedimethanol composition that had undergone the water removal step was distilled in a distillation column apparatus under the conditions of an operating pressure at the top of the column of -0.91 barg, an operating temperature of 45 °C, an operating pressure at the bottom of the column of -0.9 barg, and an operating temperature of 213 °C to perform a primary by-product removal step of separating low-boiling by-products.

[0114] The 1,4 - cyclohexanedimethanol composition that has undergone the primary by - product removal step is distilled in a distillation column apparatus under the conditions of an operating pressure of - 0.91 barg at the top of the column, an operating temperature of 210 °C, an operating pressure of - 0.9 barg at the bottom of the column, and an operating temperature of 250 °C to separate high - boiling by - products and obtain purified 1,4 - cyclohexanedimethanol.

[0115] Example 2 In the high - boiling by - product separation step of Example 1, the crude composition of 1,4 - cyclohexanedimethanol was purified in the same manner as in Example 1, except that the operating temperature at the top of the column was set to 205 °C.

[0116] Comparative Example 1 In Example 1, the 1,4 - cyclohexanedimethanol composition that only underwent the water removal step was used as Comparative Example 1.

[0117] Comparative Example 2 The crude composition of 1,4 - cyclohexanedimethanol in Production Example 1 was used as Comparative Example 2.

[0118] Comparative Example 3 The commercially available 1,4 - cyclohexanedimethanol (product name: SKY CHDM, manufacturer: SK Chemical Co., Ltd.) was used as Comparative Example 3.

[0119] Comparative Example 4 The commercially available 1,4 - cyclohexanedimethanol (product name: CHDM - D, manufacturer: Eastman Chemical Company) was used as Comparative Example 4.

[0120] <Experimental Example> For the 1,4 - cyclohexanedimethanol compositions of the above - mentioned Examples and Comparative Examples, the purity, the contents of Light by - products and Heavy by - products, the water content, the content of trans - CHDM in CHDM, and the APHA value were measured by the following method and are shown in Table 2.

[0121] 1) Purity (total content of CHDM), contents of low molecular weight (Light) by-products and high molecular weight (Heavy) by-products, and trans-CHDM content in CHDM Measured by gas chromatography, and the detailed conditions are as shown in Table 1 below.

[0122]

Table 1

[0123] 2) Water content Measured by ASTM D1364 (Karl Fischer).

[0124] 3) APHA value Measured by ASTM D1209.

[0125]

Table 2

[0126] Referring to Table 2 above, the 1,4-cyclohexanedimethanol compositions obtained by the purification methods of Examples 1 and 2 of the present invention showed very low by-product contents with both the contents of low molecular weight (Light) by-products and high molecular weight (Heavy) by-products being 0.15% by weight or less.

[0127] Also, since the content of CHM (cyclohexylmethanol), which is a by-product that has an adverse effect when used as a high molecular weight raw material, is as low as 0.001% by weight, high-quality 1,4-cyclohexanedimethanol can be provided.

Claims

1. A water removal step of removing water from a crude composition of 1,4 - cyclohexanedimethanol (1,4 - cyclohexanedimethanol, CHDM) using an evaporator; A primary by - product removal step of distilling the 1,4 - cyclohexanedimethanol composition that has undergone the water removal step in a first distillation column to remove by - products having a boiling point lower than that of 1,4 - cyclohexanedimethanol; and A secondary by - product removal step of distilling the 1,4 - cyclohexanedimethanol composition that has undergone the primary by - product removal step in a second column to remove by - products having a boiling point higher than that of 1,4 - cyclohexanedimethanol and recovering a purified 1,4 - cyclohexanedimethanol composition; comprising wherein the water removal step is carried out at a temperature of 50 to 110 °C and a pressure of - 0.1 to 0.1 barg until 80 wt% or more of the water contained in the crude composition of 1,4 - cyclohexanedimethanol is removed, a purified 1,4 - cyclohexanedimethanol composition, wherein the purity of 1,4 - cyclohexanedimethanol is 99.5 wt% or more, A method for purifying a 1,4 - cyclohexanedimethanol composition.

2. The crude composition of 1,4 - cyclohexanedimethanol contains 1,4 - cyclohexanedimethanol, water, and by - products, The method for purifying a 1,4 - cyclohexanedimethanol composition according to Claim 1.

3. The purified 1,4 - cyclohexanedimethanol composition contains 0.15 wt% or less of water, The method for purifying a 1,4 - cyclohexanedimethanol composition according to Claim 1.

4. The purified 1,4 - cyclohexanedimethanol composition contains 0.15 wt% or less of low molecular weight (light) by - products having a molecular weight of less than 144.21 g / mol. The method for purifying a 1,4 - cyclohexanedimethanol composition according to claim 1.

5. The purified 1,4 - cyclohexanedimethanol composition contains 0.15 wt% or less of high molecular weight (heavy) by - products having a molecular weight of more than 144.21 g / mol. The method for purifying a 1,4 - cyclohexanedimethanol composition according to claim 1.

6. The purified 1,4 - cyclohexanedimethanol composition has an APHA value of 10 or less as measured by ASTM D1209. The method for purifying a 1,4 - cyclohexanedimethanol composition according to claim 1.

7. The 1,4 - cyclohexanedimethanol contains 63 wt% or more of the trans isomer. The method for purifying a 1,4 - cyclohexanedimethanol composition according to claim 1.

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