Method for increasing yield of 1, 4-cyclohexanedimethanol and increasing trans-isomer content

Abstract

The invention belongs to the technical field of 1, 4-cyclohexanedimethanol production, and discloses a method for increasing the yield of 1, 4-cyclohexanedimethanol and increasing the trans-isomer content. According to the invention, 1, 4-dimethyl cyclohexanedicarboxylate or 1, 4-cyclohexanedimethanol or tower top liquid or tower bottom liquid generated in the production process of 1, 4-cyclohexanedimethanol is adopted as a raw material, hydrogenation reaction is carried out in the presence of a catalyst, the yield of 1, 4-cyclohexanedimethanol in the production process can be increased, the yield of 1, 4-cyclohexanedimethanol can be increased, and the yield of 1, 4-cyclohexanedimethanol can be increased. The trans-isomer content in the 1, 4-cyclohexanedimethanol product is high, and the raw materials can be recycled. The 1, 4-cyclohexanedimethanol obtained by the method has good storage resistance, the trans-isomer content and the cis-isomer content in the 1, 4-cyclohexanedimethanol can be adjusted according to different needs, each index is qualified and stable, and downstream use of the 1, 4-cyclohexanedimethanol can be well met.

Description

Technical Field

[0001] The invention belongs to the technical field of 1,4-cyclohexanedimethanol production, and the invention relates to a method for producing 1,4-cyclohexanedimethanol, and specifically to a method for increasing the production of 1,4-cyclohexanedimethanol and improving the content of trans isomers. Background Art

[0002] 1,4-cyclohexanedimethanol (CHDM) is one of the important raw materials for high-performance, new environmentally friendly engineering plastics and packaging materials that have attracted great attention in the market in recent years. It is also an important polyester raw material monomer in industry. PETG copolyester chips produced by using 1,4-cyclohexanedimethanol as a monomer to partially replace ethylene glycol and polymerize with terephthalic acid are a high-end specialty polyester. PETG containing 30% to 40% CHDM and more than 50% CHDM as PCTG. Its products are highly transparent and have excellent impact resistance. They are particularly suitable for molding thick-walled transparent products, and their processing and molding performance is excellent. CHDM is increasingly widely used in new saturated and unsaturated polyesters, high-grade polyurethanes, environmentally friendly coatings and other fields. CHDM products with high trans-isomer content can also be used to produce high-precision liquid crystal materials, and the products also have greater added value and production benefits.

[0003] The widely used existing technology is the two-step hydrogenation technology of dimethyl terephthalate (DMT), in which the 1,4-cyclohexanedicarboxylic acid dimethyl ester (DMCD) obtained by the first step of hydrogenation of dimethyl terephthalate is further hydrogenated in the second step to obtain the crude product of 1,4-cyclohexanedimethanol (CHDM) ester-based hydrogenation technology. In recent years, there has been a new trend in the production technology of CHDM, and the reaction raw materials have been expanded from esters to acids, aldehydes, etc. In addition to the target product 1,4-cyclohexanedimethanol (CHDM), the crude hydrogenation product contains unreacted 1,4-cyclohexanedicarboxylic acid dimethyl ester (DMCD) and its partially hydrogenated products, as well as various by-product light components such as methanol and other various by-product heavy components.

[0004] Chinese patent CN201710482903.1 discloses a method for preparing 1,4-cyclohexanedimethanol by hydrogenating dimethyl 1,4-cyclohexanedicarboxylate, wherein liquid DMCD is used as a raw material and hydrogen is used as a reducing agent, and a gas-liquid-solid three-phase reaction is carried out in sequence through a first single-tube reactor and a second single-tube reactor loaded with a catalyst to obtain a 1,4-cyclohexanedimethanol product; the catalysts loaded in the two single-tube reactors are both Cu-Zn-Al catalysts; the reaction temperature of the two single-tube reactors is 150-240°C and the reaction temperature of the second single-tube reactor is greater than or equal to the reaction temperature of the first single-tube reactor; the pressures in the two single-tube reactors are equal and are both 4.0-12.0MPa; the hydrogen-to-oil molar ratio in the second single-tube reactor is greater than the hydrogen-to-oil molar ratio in the first single-tube reactor; the space velocity of DMCD relative to the total amount of the catalyst loaded in the first single-tube reactor and the second single-tube reactor is 0.1-1.5h -1 Compared with the prior art, the reaction energy consumption can be significantly reduced, the production capacity can be increased, and the conversion rate and selectivity of the DMCD hydrogenation to CHDM reaction process can be improved. As can be seen from Example 10, the maximum ratio of trans:cis CHDM (1,4-cyclohexanedimethanol) in the patent is 2.94. After removing the CHDM high boiling products and the unmentioned low boiling products, it is estimated that the content of trans CHDM is not higher than 73%.

[0005] Chinese patent CN201910233184.9 provides a method for preparing 1,4-cyclohexanedimethanol using a highly dispersed rhenium-based catalyst, which uses a continuous stirred tank reactor to effectively catalyze the liquid phase hydrogenation of 1,4-cyclohexanedicarboxylic acid dimethyl ester to prepare 1,4-cyclohexanedimethanol. The selective hydrogenation reaction is carried out in the pressure range of 6-14MPa and the reaction temperature is in the range of 150-230℃. The reaction time is 4-10 hours, and the conversion rate of 1,4-cyclohexanedicarboxylic acid dimethyl ester can reach 98.9%, and the selectivity of the target product 1,4-cyclohexanedimethanol can reach 66.4%. The selectivity of the target product 1,4-cyclohexanedimethanol of this patent is relatively low.

[0006] Chinese patent CN201110136368.7 provides a method for preparing 1,4-cyclohexanedimethanol from terephthalic acid, which is divided into three steps. In the first step, terephthalic acid and methanol generate dimethyl terephthalate, in the second step, dimethyl terephthalate is hydrogenated to generate dimethyl 1,4-cyclohexanedicarboxylate, and in the third step, the generated dimethyl 1,4-cyclohexanedicarboxylate is hydrogenated to generate the product 1,4-cyclohexanedimethanol.

[0007] Chinese patent CN113056446A discloses a method for preparing 1,4-cyclohexanedimethanol, using terephthalic acid as a starting material to carry out a two-step reduction reaction, and introducing an isomerization process for increasing the ratio of the trans isomer of CHDA (1,4-cyclohexanedicarboxylic acid) during the reduction reaction, thereby providing a method capable of stably preparing a product with a high ratio of trans isomers. As can be seen from the examples, the patent uses a batch reactor that is a device capable of stirring the reaction to carry out the hydrogenation reaction of CHDA, and the ratio of trans CHDM (trans 1,4-cyclohexanedimethanol) is about 70%.

[0008] There are many factors that affect the cis-trans ratio of CHDM. Experiments have shown that the main factors affecting the cis-trans ratio are the catalyst and the reaction temperature. By controlling a certain temperature range, an ideal cis-trans ratio can be obtained, and the trans isomer content can reach 70%. However, it is difficult to further increase the trans isomer content in the 1,4-cyclohexanedimethanol product. Summary of the invention

[0009] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for increasing the production of 1,4-cyclohexanedimethanol and improving the content of trans isomers, which can achieve the increase in the production of 1,4-cyclohexanedimethanol in the production process and improve the content of trans isomers in the 1,4-cyclohexanedimethanol product, so as to solve the problems of low raw material utilization and relatively low content of trans isomers in the production process of 1,4-cyclohexanedimethanol, and the content of trans isomers in the finally obtained 1,4-cyclohexanedimethanol can be adjusted according to different needs.

[0010] The above object of the present invention is achieved through the following technical solutions:

[0011] A method for increasing the production of 1,4-cyclohexanedimethanol and improving the content of trans isomers, wherein the top liquid or bottom liquid of a distillation tower related to 1,4-cyclohexanedimethanol produced during the production or use of 1,4-cyclohexanedimethanol is contacted with hydrogen in the presence of a catalyst, and the hydrogenation reaction conditions are: a reaction temperature of 150 to 250° C., a reaction pressure of 5.0 to 12.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.05 to 1 h -1, under the condition of hydrogen-to-oil ratio of 80-250 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor, and the obtained hydrogenation reaction product is 1,4-cyclohexanedimethanol containing impurities; a distillation tower is used to intermittently or continuously distill the 1,4-cyclohexanedimethanol containing impurities to remove low-boiling impurities such as water, methanol, and low-carbon alcohols; intermittent or continuous vacuum distillation is continued to remove colorless or colored impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol from the top of the tower, and the front fraction containing such impurities is the top liquid; intermittent or continuous vacuum distillation is continued, and the vacuum distillation operation conditions are: the bottom temperature of the tower is 165-220°C, the top temperature of the tower is 130-165°C, and the vacuum degree is - 0.0980~-0.1005Mpa (gauge pressure, the same below), reflux ratio is 20:1~5:1, tower top cooling water temperature is 61~80℃, and a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of>99.8% is obtained, and the trans-isomer content of 1,4-cyclohexanedimethanol can reach 75~92%. Impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the kettle residue, and the kettle residue material containing the impurities is the bottom liquid; the top liquid or the bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and improve the trans-isomer content, and the trans-isomer content in 1,4-cyclohexanedimethanol can be adjusted.

[0012] The hydrogenation reaction conditions are preferably: reaction temperature 180-240°C, reaction pressure 6.0-11.0 MPa (gauge pressure, the same below), liquid hourly space velocity 0.08-0.5 h -1 , hydrogen-to-oil ratio is 100-200 mol / mol.

[0013] The vacuum distillation operation conditions are preferably: the bottom temperature is 170-200°C, the top temperature is 135-160°C, the vacuum degree is -0.0990--0.1005Mpa, the reflux ratio is 12:1-6:1, and the top cooling water temperature is 61-75°C, so as to obtain a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8%, the trans-isomer content of 1,4-cyclohexanedimethanol can reach 75-92%, and impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the bottom residue.

[0014] In the presence of a catalyst, the 1,4-cyclohexanedimethanol that contacts with hydrogen has a trans isomer content that is lower than the trans isomer content calculated by summing the cis isomer and the trans isomer after the hydrogenation reaction is balanced. That is, in the presence of a catalyst, an isomerization reaction of the cis and trans isomers of 1,4-cyclohexanedimethanol occurs when it contacts with hydrogen, and a portion of the cis isomer isomerized to the trans isomer, thereby increasing the production of 1,4-cyclohexanedimethanol and improving the trans isomer content.

[0015] In the presence of a catalyst, the 1,4-cyclohexanedimethanol that contacts with hydrogen has a cis-isomer content that is lower than the cis-isomer content calculated by summing the cis-isomer and the trans-isomer after the hydrogenation reaction is balanced. That is, in the presence of a catalyst, the 1,4-cyclohexanedimethanol can undergo an isomerization reaction of the cis- and trans-isomers of the 1,4-cyclohexanedimethanol when in contact with hydrogen, and can also partially isomerize the trans-isomer into the cis-isomer, thereby increasing the yield of 1,4-cyclohexanedimethanol and improving the cis-isomer content.

[0016] The top liquid or bottom liquid of the distillation tower related to 1,4-cyclohexanedimethanol produced in the production process of 1,4-cyclohexanedimethanol is a material containing 1,4-cyclohexanedicarboxylic acid dimethyl ester or 1,4-cyclohexanedimethanol or a partial hydrogenation product component of 1,4-cyclohexanedicarboxylic acid dimethyl ester.

[0017] The distillation tower top liquid or tower bottom liquid related to 1,4-cyclohexanedimethanol generated during the use of the 1,4-cyclohexanedimethanol is a by-product liquid material obtained by polymerization and other reactions using 1,4-cyclohexanedimethanol and mainly containing 1,4-cyclohexanedimethanol as a main component or its dimerization and polymer components.

[0018] The trans-isomer content of the 1,4-cyclohexanedimethanol can reach 80-90%, and the trans-isomer content and cis-isomer content in the finally obtained 1,4-cyclohexanedimethanol can be adjusted according to different needs.

[0019] When the distillation tower overhead liquid or tower bottom liquid related to 1,4-cyclohexanedimethanol generated during the production or use of the 1,4-cyclohexanedimethanol contains a variety of light components, a distillation tower can be used to intermittently or continuously distill the impurity-containing 1,4-cyclohexanedimethanol to remove low-boiling impurities such as water, methanol, and low-carbon alcohols, and then distilled into the distillation tower overhead liquid or tower bottom liquid, which is then used as a raw material for the hydrogenation reaction.

[0020] The top liquid or bottom liquid of the distillation tower can be recycled as a raw material for hydrogenation reaction. The top liquid or bottom liquid of the distillation tower can be recycled as a raw material for hydrogenation reaction alone, or the two can be mixed and recycled as a raw material for hydrogenation reaction.

[0021] The catalyst is an effective catalyst active substance including: one or more of the oxides or salts of Cu, Ni, and Co; the effective promoter substance includes oxides or salts or complexes of transition metals, alkali metals, and alkaline earth metals, and one or more of organic acids and bases, etc.; preferably, one or more of chromium oxide, zinc oxide, alkali metal oxides, aluminum oxide, etc. are selected as promoters, and the catalyst is used after being reduced after preparation.

[0022] The beneficial effects of the present invention compared with the prior art are:

[0023] The present invention uses dimethyl 1,4-cyclohexanedicarboxylate or 1,4-cyclohexanedimethanol or a distillation tower top liquid or a tower bottom liquid related to 1,4-cyclohexanedimethanol generated during the production or use of 1,4-cyclohexanedimethanol, contacts the top liquid or the bottom liquid with hydrogen in the presence of a catalyst, and performs a hydrogenation reaction in a catalyst bed section of a fixed bed hydrogenation reactor, so that the obtained hydrogenation reaction product is 1,4-cyclohexanedimethanol containing impurities. By using a distillation tower to intermittently or continuously distill the impurity-containing 1,4-cyclohexanedimethanol, a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8% can be obtained, and the trans-isomer content of 1,4-cyclohexanedimethanol can reach 75-92%. The top liquid or bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and improve the trans-isomer content, and the trans-isomer content and cis-isomer content in 1,4-cyclohexanedimethanol can be adjusted. The present invention can achieve the increase of 1,4-cyclohexanedimethanol production in the production process, and can increase the trans-isomer content in the 1,4-cyclohexanedimethanol product, and the raw materials can be recycled. The 1,4-cyclohexanedimethanol obtained by the present invention has good storage stability, and the trans-isomer content and cis-isomer content in the finally obtained 1,4-cyclohexanedimethanol can be adjusted according to different needs. All indicators are qualified and stable, and can well meet the downstream use of 1,4-cyclohexanedimethanol. DETAILED DESCRIPTION

[0024] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels. All percentages involved in the embodiments are weight percentages.

[0025] The catalyst selected in the embodiment is any one or more of the oxides or salts containing active substances Cu, Ni, Co; effective promoter substances include oxides or salts or complexes of transition metals, alkali metals, alkaline earth metals, and any one or more of organic acids, bases, etc.; preferably, any one or more of chromium oxide, zinc oxide, alkali metal oxides, aluminum oxide, etc. are selected as promoters, and the catalyst is prepared and used after reduction.

[0026] The specific implementation is further described by examples:

[0027] Examples 1 to 6 were prepared by the following method: dimethyl 1,4-cyclohexanedicarboxylate (DMCD) was contacted with hydrogen in the presence of a catalyst at a reaction temperature of 180 to 240° C., a reaction pressure of 6.0 to 11.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.08 to 0.5 h-1 Under the condition of hydrogen-to-oil ratio of 100-200 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor to obtain a hydrogenation reaction product, and a sample is taken for gas chromatography analysis.

[0028] Example 1

[0029] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) is contacted with hydrogen in the presence of a catalyst at a reaction temperature of 185°C, a reaction pressure of 11.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.08 to 0.5 h -1 Under the condition of hydrogen-to-oil ratio of 100-200 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor to obtain a hydrogenation reaction product, and a sample is taken for gas chromatography analysis.

[0030] Example 2

[0031] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) is contacted with hydrogen in the presence of a catalyst at a reaction temperature of 190°C, a reaction pressure of 11.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.08 to 0.5 h -1 Under the condition of hydrogen-to-oil ratio of 100-200 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor to obtain a hydrogenation reaction product, and a sample is taken for gas chromatography analysis.

[0032] Example 3

[0033] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) is contacted with hydrogen in the presence of a catalyst at a reaction temperature of 210°C, a reaction pressure of 10.5 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.08 to 0.5 h -1 Under the condition of hydrogen-to-oil ratio of 100-200 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor to obtain a hydrogenation reaction product, and a sample is taken for gas chromatography analysis.

[0034] Example 4

[0035] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) is contacted with hydrogen in the presence of a catalyst at a reaction temperature of 230°C, a reaction pressure of 10.5 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.08 to 0.5 h -1 Under the condition of hydrogen-to-oil ratio of 100-200 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor to obtain a hydrogenation reaction product, and a sample is taken for gas chromatography analysis.

[0036] Example 5

[0037] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) is contacted with hydrogen in the presence of a catalyst at a reaction temperature of 230°C, a reaction pressure of 6.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.08 to 0.5 h -1 Under the condition of hydrogen-to-oil ratio of 100-200 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor to obtain a hydrogenation reaction product, and a sample is taken for gas chromatography analysis.

[0038] Example 6

[0039] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) is contacted with hydrogen in the presence of a catalyst at a reaction temperature of 240°C, a reaction pressure of 8.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.08 to 0.5 h -1 Under the condition of hydrogen-to-oil ratio of 100-200 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor to obtain a hydrogenation reaction product, and a sample is taken for gas chromatography analysis.

[0040] The operating conditions of the DMCD hydrogenation reaction and the contents of cis and trans isomers of 1,4-cyclohexanedimethanol in the products of Examples 1, 2, 3, 4, 5 and 6 are shown in Table 1.

[0041] Table 1 DMCD hydrogenation reaction operating conditions and the content of cis-trans isomers of 1,4-cyclohexanedimethanol in the product

[0042]

[0043] Example 7

[0044] The top liquid of the distillation tower related to 1,4-cyclohexanedimethanol is generated during the production or use of 1,4-cyclohexanedimethanol, wherein the methanol content is 0.21%, the DMCD content is 14.84%, the CHDM trans-isomer content is 58.47%, the CHDM cis-isomer content is 14.40%, and the rest are other colorless or colored impurities with a boiling point lower or higher than the boiling point of 1,4-cyclohexanedimethanol.

[0045] The top liquid of the distillation tower related to 1,4-cyclohexanedimethanol is contacted with hydrogen in the presence of a catalyst, at a reaction temperature of 150-250°C, a reaction pressure of 5.0-12.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.1-1 h -1 , hydrogenation reaction was carried out in the catalyst bed section of the fixed bed hydrogenation reactor under the condition of hydrogen-to-oil molar ratio of 80 to 250 to obtain hydrogenation reaction products, which were sampled for gas chromatography analysis. The contents of cis- and trans-isomers of 1,4-cyclohexanedimethanol in the hydrogenation products of the tower top liquid are shown in Table 2.

[0046] Table 2 Content of cis-trans isomers of 1,4-cyclohexanedimethanol in the hydrogenation product of the overhead liquid

[0047]

[0048] Example 8

[0049] The bottom liquid of the distillation tower related to 1,4-cyclohexanedimethanol is generated during the production or use of 1,4-cyclohexanedimethanol, of which the content of CHDM trans isomer is 27.35%, the content of CHDM cis isomer is 47.29%, and the rest are other colorless or colored impurities with a boiling point lower or higher than the boiling point of 1,4-cyclohexanedimethanol.

[0050] The bottom liquid of the distillation tower related to 1,4-cyclohexanedimethanol is contacted with hydrogen in the presence of a catalyst, at a reaction temperature of 150-250°C, a reaction pressure of 5.0-12.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.1-1 h -1 , hydrogenation reaction was carried out in the catalyst bed section of the fixed bed hydrogenation reactor under the condition of hydrogen-oil molar ratio of 80 to 250 to obtain hydrogenation reaction products, which were sampled for gas chromatography analysis. The contents of cis- and trans-isomers of 1,4-cyclohexanedimethanol in the hydrogenation products of the bottom liquid are shown in Table 3.

[0051] Example 9

[0052] First, the distillation tower bottom liquid related to 1,4-cyclohexanedimethanol produced during the production or use of 1,4-cyclohexanedimethanol in this embodiment is used, and the rest is the same as in Example 8.

[0053] Table 3 Content of cis-trans isomers of 1,4-cyclohexanedimethanol in the hydrogenation product of the bottom liquid

[0054]

[0055] Example 10

[0056] A mixed material of distillation tower overhead liquid and tower bottom liquid related to 1,4-cyclohexanedimethanol generated during the production or use of 1,4-cyclohexanedimethanol, wherein the methanol content is 0.10%, the DMCD content is 15.97%, the CHDM trans-isomer content is 42.25%, the CHDM cis-isomer content is 16.30%, and the rest are other colorless or colored impurities with a boiling point lower than or higher than the boiling point of 1,4-cyclohexanedimethanol.

[0057] The bottom liquid of the distillation tower related to 1,4-cyclohexanedimethanol is contacted with hydrogen in the presence of a catalyst, at a reaction temperature of 150-250°C, a reaction pressure of 5.0-12.0 MPa (gauge pressure, the same below), and a liquid hourly space velocity of 0.1-1 h -1, hydrogenation reaction was carried out in the catalyst bed section of the fixed bed hydrogenation reactor under the condition of hydrogen-oil molar ratio of 80 to 250 to obtain hydrogenation reaction products, and samples were taken for gas chromatography analysis. The contents of cis- and trans-isomers of 1,4-cyclohexanedimethanol in the hydrogenation products of the mixture of the top liquid and the bottom liquid are shown in Table 4.

[0058] Embodiment 11

[0059] First, the mixed material of the top liquid and bottom liquid of the distillation tower related to 1,4-cyclohexanedimethanol generated during the production or use of 1,4-cyclohexanedimethanol in the embodiment is used, and the rest is the same as in Example 11.

[0060] Table 4 Content of cis-trans isomers of 1,4-cyclohexanedimethanol in hydrogenation products of the mixture of overhead liquid and bottom liquid

[0061]

[0062] Example 12

[0063] The hydrogenation product, i.e., 1,4-cyclohexanedimethanol containing impurities, is subjected to intermittent or continuous distillation by a distillation tower to remove low-boiling impurities such as water, methanol, and low-carbon alcohols; intermittent or continuous vacuum distillation is continued to remove colorless or colored impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol from the top of the tower, and the front fraction containing the impurities is the top liquid; intermittent or continuous vacuum distillation is continued, and the vacuum distillation operation conditions are: the bottom temperature of the tower is 165-220°C, the top temperature of the tower is 130-165°C, the vacuum degree is -0.0998Mpa (gauge pressure, the same below), and the reflux ratio is 10:1 , the cooling water temperature at the top of the tower is 61-80°C, and a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8% is obtained. The trans isomer content of 1,4-cyclohexanedimethanol can reach 75-92%. Impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the kettle residue, and the kettle residue containing this impurity is the bottom liquid; the top liquid or the bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and increase the trans isomer content, and the trans isomer content in 1,4-cyclohexanedimethanol can be adjusted. The test results of the cis-trans isomer content and purity of the distillation product 1,4-cyclohexanedimethanol are shown in Table 5.

[0064] Embodiment 13

[0065] The hydrogenation product, i.e., 1,4-cyclohexanedimethanol containing impurities, is subjected to intermittent or continuous distillation by a distillation tower to remove low-boiling impurities such as water, methanol, and low-carbon alcohols; intermittent or continuous vacuum distillation is continued to remove colorless or colored impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol from the top of the tower, and the front fraction containing the impurities is the top liquid; intermittent or continuous vacuum distillation is continued, and the vacuum distillation operation conditions are: the bottom temperature of the tower is 165-220°C, the top temperature of the tower is 130-165°C, the vacuum degree is -0.0995Mpa (gauge pressure, the same below), and the reflux ratio is 15:1 , the cooling water temperature at the top of the tower is 61-80°C, and a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8% is obtained. The trans isomer content of 1,4-cyclohexanedimethanol can reach 75-92%. Impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the kettle residue, and the kettle residue containing this impurity is the bottom liquid; the top liquid or the bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and increase the trans isomer content, and the trans isomer content in 1,4-cyclohexanedimethanol can be adjusted. The test results of the cis-trans isomer content and purity of the distillation product 1,4-cyclohexanedimethanol are shown in Table 5.

[0066] Embodiment 14

[0067] The hydrogenation product, i.e., 1,4-cyclohexanedimethanol containing impurities, is subjected to intermittent or continuous distillation by a distillation tower to remove low-boiling impurities such as water, methanol, and low-carbon alcohols; intermittent or continuous vacuum distillation is continued to remove colorless or colored impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol from the top of the tower, and the front fraction containing the impurities is the top liquid; intermittent or continuous vacuum distillation is continued, and the vacuum distillation operation conditions are: the bottom temperature of the tower is 165-220°C, the top temperature of the tower is 130-165°C, the vacuum degree is -0.1000Mpa (gauge pressure, the same below), and the reflux ratio is 8:1. , the cooling water temperature at the top of the tower is 61-80°C, and a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8% is obtained. The trans isomer content of 1,4-cyclohexanedimethanol can reach 75-92%. Impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the kettle residue, and the kettle residue containing this impurity is the bottom liquid; the top liquid or the bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and increase the trans isomer content, and the trans isomer content in 1,4-cyclohexanedimethanol can be adjusted. The test results of the cis-trans isomer content and purity of the distillation product 1,4-cyclohexanedimethanol are shown in Table 5.

[0068] Embodiment 15

[0069] The hydrogenation product, i.e., 1,4-cyclohexanedimethanol containing impurities, is subjected to intermittent or continuous distillation by a distillation tower to remove low-boiling impurities such as water, methanol, and low-carbon alcohols; intermittent or continuous vacuum distillation is continued to remove colorless or colored impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol from the top of the tower, and the front fraction containing the impurities is the top liquid; intermittent or continuous vacuum distillation is continued, and the vacuum distillation operating conditions are: the bottom temperature of the tower is 165-220°C, the top temperature of the tower is 130-165°C, the vacuum degree is -0.1000Mpa (gauge pressure, the same below), and the reflux ratio is 6:1 , the cooling water temperature at the top of the tower is 61-80°C, and a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8% is obtained. The trans isomer content of 1,4-cyclohexanedimethanol can reach 75-92%. Impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the kettle residue, and the kettle residue containing this impurity is the bottom liquid; the top liquid or the bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and increase the trans isomer content, and the trans isomer content in 1,4-cyclohexanedimethanol can be adjusted. The test results of the cis-trans isomer content and purity of the distillation product 1,4-cyclohexanedimethanol are shown in Table 5.

[0070] Example 16

[0071] The hydrogenation product, i.e., 1,4-cyclohexanedimethanol containing impurities, is subjected to intermittent or continuous distillation by a distillation tower to remove low-boiling impurities such as water, methanol, and low-carbon alcohols; intermittent or continuous vacuum distillation is continued to remove colorless or colored impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol from the top of the tower, and the front fraction containing the impurities is the top liquid; intermittent or continuous vacuum distillation is continued, and the vacuum distillation operation conditions are: the bottom temperature of the tower is 165-220°C, the top temperature of the tower is 130-165°C, the vacuum degree is -0.1000Mpa (gauge pressure, the same below), and the reflux ratio is 5:1 , the cooling water temperature at the top of the tower is 61-80°C, and a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8% is obtained. The trans isomer content of 1,4-cyclohexanedimethanol can reach 75-92%. Impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the kettle residue, and the kettle residue containing this impurity is the bottom liquid; the top liquid or the bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and increase the trans isomer content, and the trans isomer content in 1,4-cyclohexanedimethanol can be adjusted. The test results of the cis-trans isomer content and purity of the distillation product 1,4-cyclohexanedimethanol are shown in Table 5.

[0072] Embodiment 17

[0073] The hydrogenation product, i.e., 1,4-cyclohexanedimethanol containing impurities, is subjected to intermittent or continuous distillation by a distillation tower to remove low-boiling impurities such as water, methanol, and low-carbon alcohols; intermittent or continuous vacuum distillation is continued to remove colorless or colored impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol from the top of the tower, and the front fraction containing the impurities is the top liquid; intermittent or continuous vacuum distillation is continued, and the vacuum distillation operating conditions are: the bottom temperature of the tower is 165-220°C, the top temperature of the tower is 130-165°C, the vacuum degree is -0.1000Mpa (gauge pressure, the same below), and the reflux ratio is 6:1 , the cooling water temperature at the top of the tower is 61-80°C, and a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8% is obtained. The trans isomer content of 1,4-cyclohexanedimethanol can reach 75-92%. Impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the kettle residue, and the kettle residue containing this impurity is the bottom liquid; the top liquid or the bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and increase the trans isomer content, and the trans isomer content in 1,4-cyclohexanedimethanol can be adjusted. The test results of the cis-trans isomer content and purity of the distillation product 1,4-cyclohexanedimethanol are shown in Table 5.

[0074] Table 5 Distillation product 1,4-cyclohexanedimethanol cis-trans isomer content and purity test

[0075]

[0076]

[0077] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for increasing the production of 1,4-cyclohexanedimethanol and the content of trans isomers, characterized in that: The top liquid or bottom liquid of a distillation tower related to 1,4-cyclohexanedimethanol produced during the production or use of 1,4-cyclohexanedimethanol is contacted with hydrogen in the presence of a catalyst. The hydrogenation reaction conditions are: a reaction temperature of 150 to 250° C., a reaction pressure of 5.0 to 12.0 MPa, and a liquid hourly space velocity of 0.05 to 1 h -1 , under the condition of hydrogen-to-oil ratio of 80-250 mol / mol, a hydrogenation reaction is carried out in the catalyst bed section of a fixed bed hydrogenation reactor, and the obtained hydrogenation reaction product is 1,4-cyclohexanedimethanol containing impurities; a distillation tower is used to intermittently or continuously distill the 1,4-cyclohexanedimethanol containing impurities to remove low-boiling impurities such as water, methanol, and low-carbon alcohols; intermittent or continuous vacuum distillation is continued to remove colorless or colored impurities with a boiling point lower than that of 1,4-cyclohexanedimethanol from the top of the tower, and the front fraction containing such impurities is the top liquid of the tower; intermittent or continuous vacuum distillation is continued, and the vacuum distillation operation conditions are: the bottom temperature of the tower is 165-220°C, the top temperature of the tower is 130-165°C, and the vacuum degree is The pressure is -0.0980 to -0.1005Mpa, the reflux ratio is 20:1 to 5:1, the cooling water temperature at the top of the tower is 61 to 80°C, and a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of more than 99.8% is obtained. The trans-isomer content of 1,4-cyclohexanedimethanol can reach 75 to 92%. Impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the kettle residue, and the kettle residue material containing the impurities is the bottom liquid; the top liquid or the bottom liquid can be recycled as a raw material for hydrogenation reaction to increase the production of 1,4-cyclohexanedimethanol and improve the trans-isomer content, and the trans-isomer content in the finally obtained 1,4-cyclohexanedimethanol can be adjusted.

2. A method for increasing the production of 1,4-cyclohexanedimethanol and the content of trans isomers as claimed in claim 1, characterized in that: The hydrogenation reaction conditions are: reaction temperature 180-240°C, reaction pressure 6.0-11.0 MPa, liquid hourly space velocity 0.08-0.5 h -1 , hydrogen-to-oil ratio is 100-200 mol / mol.

3. A method for increasing the production of 1,4-cyclohexanedimethanol and improving the content of trans isomers as claimed in claim 1, characterized in that: The vacuum distillation operation conditions are preferably: the bottom temperature is 170-200°C, the top temperature is 135-160°C, the vacuum degree is -0.0990--0.1005Mpa, the reflux ratio is 12:1-6:1, and the top cooling water temperature is 61-75°C, so as to obtain a colorless or nearly colorless qualified 1,4-cyclohexanedimethanol product with a 1,4-cyclohexanedimethanol content of >99.8%, the trans-isomer content of 1,4-cyclohexanedimethanol can reach 75-92%, and impurities with a boiling point higher than that of 1,4-cyclohexanedimethanol are removed in the bottom residue.

4. A method for increasing the production of 1,4-cyclohexanedimethanol and improving the content of trans isomers as claimed in claim 1, characterized in that: In the presence of a catalyst, the 1,4-cyclohexanedimethanol that contacts with hydrogen has a trans isomer content that is lower than the trans isomer content calculated by summing the cis isomer and the trans isomer after the hydrogenation reaction is balanced. That is, in the presence of a catalyst, an isomerization reaction of the cis and trans isomers of 1,4-cyclohexanedimethanol occurs when it contacts with hydrogen, and a portion of the cis isomer isomerized to the trans isomer, thereby increasing the production of 1,4-cyclohexanedimethanol and improving the trans isomer content.

5. A method for increasing the production of 1,4-cyclohexanedimethanol and improving the content of trans isomers as claimed in claim 1, characterized in that: In the presence of a catalyst, the 1,4-cyclohexanedimethanol that contacts with hydrogen has a cis-isomer content that is lower than the cis-isomer content calculated by summing the cis-isomer and the trans-isomer after the hydrogenation reaction is balanced. That is, in the presence of a catalyst, the 1,4-cyclohexanedimethanol can undergo an isomerization reaction of the cis- and trans-isomers of the 1,4-cyclohexanedimethanol when in contact with hydrogen, and can also partially isomerize the trans-isomer into the cis-isomer, thereby increasing the yield of 1,4-cyclohexanedimethanol and improving the cis-isomer content.

6. A method for increasing the production of 1,4-cyclohexanedimethanol and improving the content of trans isomers as claimed in claim 1, characterized in that: The top liquid or bottom liquid of the distillation tower related to 1,4-cyclohexanedimethanol produced in the production process of 1,4-cyclohexanedimethanol is a material containing 1,4-cyclohexanedicarboxylic acid dimethyl ester or 1,4-cyclohexanedimethanol or a partial hydrogenation product component of 1,4-cyclohexanedicarboxylic acid dimethyl ester.

7. A method for increasing the production of 1,4-cyclohexanedimethanol and the content of trans isomers as claimed in claim 1, characterized in that: The distillation tower top liquid or tower bottom liquid related to 1,4-cyclohexanedimethanol generated during the use of the 1,4-cyclohexanedimethanol is a by-product liquid material obtained by polymerization and other reactions using 1,4-cyclohexanedimethanol and mainly containing 1,4-cyclohexanedimethanol as a main component or its dimerization and polymer components.

8. A method for increasing the production of 1,4-cyclohexanedimethanol and the content of trans isomers as claimed in any one of claim 1 or claim 3, characterized in that: The trans-isomer content of the 1,4-cyclohexanedimethanol can reach 80-90%, and the trans-isomer content and cis-isomer content in the finally obtained 1,4-cyclohexanedimethanol can be adjusted according to different needs.

9. A method for increasing the production of 1,4-cyclohexanedimethanol and the content of trans isomers as claimed in any one of claim 1, claim 6 or claim 7, characterized in that: When the distillation tower overhead liquid or tower bottom liquid related to 1,4-cyclohexanedimethanol generated during the production or use of the 1,4-cyclohexanedimethanol contains a variety of light components, a distillation tower can be used to intermittently or continuously distill the impurity-containing 1,4-cyclohexanedimethanol to remove low-boiling impurities such as water, methanol, and low-carbon alcohols, and then distilled into the distillation tower overhead liquid or tower bottom liquid, which is then used as a raw material for the hydrogenation reaction.

10. A method for increasing the production of 1,4-cyclohexanedimethanol and the content of trans isomers according to any one of claim 1, claim 6, claim 7 or claim 9, characterized in that: The top liquid or bottom liquid of the distillation tower can be recycled as a raw material for hydrogenation reaction, or the two can be mixed and recycled as a raw material for hydrogenation reaction.

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