A process for separating cis and trans 2,2,4,4-tetramethyl-1,3-cyclobutanediol

Abstract

The application provides a method for separating cis and trans 2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising the following steps: cooling a mixed solution containing a solvent, cis and trans 2,2,4,4-tetramethyl-1,3-cyclobutanediol to a first temperature at a first cooling rate, then cooling to a second temperature at a second cooling rate, and performing solid-liquid separation to obtain mixed crystals; performing screening treatment on the mixed crystals to obtain cis and trans 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals; wherein the first cooling rate is less than or equal to 10 DEG C / h, and the second cooling rate is greater than or equal to 30 DEG C / h; the first temperature is higher than the second temperature, the temperature of the mixed solution is greater than the first temperature, the first temperature is less than or equal to 70 DEG C, and the second temperature is less than or equal to 30 DEG C. The method can efficiently and simply separate cis and trans 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals.

Description

Technical Field

[0001] This invention relates to a separation method, and more particularly to a method for separating cis- and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol, belonging to the field of organic matter separation and purification technology. Background Technology

[0002] 2,2,4,4-Tetramethyl-1,3-cyclobutanediol is an important alicyclic diol with two stereoisomers, cis and trans. These two isomers differ significantly in their physicochemical properties and the properties they impart to the final product as polymer monomers (such as thermal stability, mechanical strength, and optical properties). Therefore, obtaining high-purity single cis or trans isomers efficiently and economically is of key significance for the refined synthesis and performance control of high-performance polyesters, polyurethanes, and other polymer materials.

[0003] Currently, common separation methods in existing technologies mainly include precision distillation, chromatographic separation, and solvent-based recrystallization. Among them, precision distillation usually requires a sufficient boiling point difference between isomers, but the boiling points of such diol isomers are often very close, resulting in low separation efficiency, high energy consumption, and easy degradation of heat-sensitive substances. Although chromatographic separation methods (such as column chromatography) can obtain high-purity products, their throughput is small, solvent consumption is large, and the operation cycle is long, making it difficult to meet the economic requirements of large-scale industrial production. Traditional recrystallization methods rely heavily on finding specific solvents with high selectivity for a certain isomer, which involves a complex screening process and insufficient process stability. Summary of the Invention

[0004] This invention provides a method for separating cis- and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol. This method combines staged temperature-controlled crystallization with physical sieving technology, which can more efficiently and conveniently separate cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals.

[0005] In detail, the present invention provides a method for separating cis- and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising the following steps:

[0006] A mixture containing a solvent, cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is cooled to a first temperature at a first cooling rate and then cooled to a second temperature at a second cooling rate, and solid-liquid separation is performed to obtain mixed crystals.

[0007] The mixed crystals were sieved to obtain cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals.

[0008] Wherein, the first cooling rate is less than or equal to 10℃ / h, and the second cooling rate is greater than or equal to 30℃ / h; the first temperature is higher than the second temperature, and the temperature of the mixture is greater than the first temperature, wherein the first temperature is less than or equal to 70℃, and the second temperature is less than or equal to 30℃.

[0009] In some embodiments, the first temperature is 55°C-70°C;

[0010] And / or, the second temperature is 5°C-30°C.

[0011] In some embodiments, the first cooling rate is 2°C / h-10°C / h;

[0012] And / or, the second cooling rate is 30℃ / h-60℃ / h.

[0013] In some embodiments, the solvent includes at least one of alkyl acetate with 3-8 carbon atoms, alkyl propionate with 4-8 carbon atoms, alkyl carbonate with 2-8 carbon atoms, and alcohol with 1-8 carbon atoms.

[0014] In some embodiments, the solvent includes at least one selected from methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, n-propyl propionate, n-butyl propionate, dimethyl carbonate, methanol, ethanol, and ethylene glycol.

[0015] In some embodiments, the sieving process includes using a sieve with a mesh size of 20-250.

[0016] In some embodiments, the screening process includes a first screening process and a second screening process, wherein the first screening process uses a first screen with a mesh size of 20-40 mesh; and the second screening process uses a second screen with a mesh size of 200-250 mesh.

[0017] In some embodiments, with the total molar amount of the cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and the trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals being 100%, the molar percentage of the cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals is 0.5%-99.5%.

[0018] In some embodiments, the molar ratio of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol in the mixture is 1-50:1-50.

[0019] In some embodiments, the total mass percentage of the cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and the trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is 20wt%-40wt% based on the mass of the mixture.

[0020] The method provided by this invention first involves cooling a mixture containing cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol to a first temperature at a first cooling rate, and then cooling it to a second temperature at a second cooling rate. This method, based on the difference in temperature and kinetics of crystallization of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol in the solvent, induces the precipitation of the two isomers in different physical forms with high purity, thus achieving preliminary enrichment and purification at the source. Secondly, the introduced sieving process effectively separates the two isomers, improving the selectivity of the separation. This method features a simple process route and mild conditions, avoiding decomposition problems that may be caused by high-temperature fractionation. It also overcomes the limitations of chromatographic separation in terms of scale. The equipment requirements are low, the energy consumption is small, and it is easy to scale up and achieve continuous production. It provides an efficient, stable and economical new way to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol in a single configuration at low cost for industrialization. Attached Figure Description

[0021] Figure 1 Image of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals obtained in Example 1 of this invention;

[0022] Figure 2 This is an image of trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals obtained in Example 1 of this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] It should also be understood that the mention of one or more method steps in this invention does not preclude the presence of additional method steps before or after the combined steps, or intermediate method steps between those explicitly indicated steps. Furthermore, the letter symbols for method steps or components are a convenient means of identifying discrete activities or components, and should be understood to mean that, unless otherwise stated, the letter symbols may be arranged in any order.

[0025] To resolve the contradiction between the separation efficiency and industrial feasibility of existing technologies, the inventors, through in-depth research, discovered that cis- and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol not only differ in thermodynamic properties, but also exhibit significant differences in nucleation rates, crystal growth habits, and final macroscopic crystal morphologies (such as particle size distribution and crystal regularity) during controlled crystallization. Therefore, this invention creatively proposes a synergistic separation strategy: First, through a dynamic crystallization process involving staged cooling, the differences in solubility and crystallization kinetics between the two isomers are utilized to achieve preliminary enrichment and purification of the target isomer; then, by leveraging the differences in their physical morphology, efficient physical sieving methods are introduced for separation. This concept organically integrates and sequentially optimizes two physical processes based on different separation principles, aiming to synergistically overcome the challenge of isomer separation with a simple and low-cost process route.

[0026] Based on the above concept, the present invention provides a method for separating cis- and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol, comprising the following steps:

[0027] A mixture containing a solvent, cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is cooled to a first temperature at a first cooling rate and then cooled to a second temperature at a second cooling rate, and solid-liquid separation is performed to obtain mixed crystals.

[0028] The mixed crystals were sieved to obtain cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals.

[0029] Wherein, the first cooling rate is less than or equal to 10℃ / h, and the second cooling rate is greater than or equal to 30℃ / h; the first temperature is higher than the second temperature, the temperature of the mixed liquid is greater than the first temperature, the first temperature is less than or equal to 70℃, and the second temperature is less than or equal to 30℃.

[0030] Compared to existing technologies, this invention achieves stable, efficient, and scalable separation of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals by controlling cooling parameters and combining them with sieving. The main reasons are as follows: when the mixture is cooled to a first temperature at a relatively low first cooling rate, cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol grow into regular and uniform crystals at a slower cooling rate, effectively suppressing the inclusion of impurities. Then, when cooled to a second temperature at a second cooling rate, the two isomers that have already undergone preliminary crystallization rapidly establish a supersaturated driving force that is conducive to the precipitation of the target isomer, prompting it to preferentially and extensively form crystal nuclei, ultimately resulting in crystals with different particle size distributions and morphological characteristics. Combined with sieving, efficient separation can be achieved.

[0031] In summary, the above methods not only achieve an optimized match between crystallization thermodynamics and kinetics, but also maximize the efficiency of physical sieving, thereby significantly improving the separation efficiency and product yield of cis and trans isomers as a whole, while ensuring the stability and scalability of the process, overcoming the shortcomings of traditional methods such as low selectivity, difficulty in scaling up, or high energy consumption.

[0032] It is understandable that the initial temperature of the above mixture is in the range of 60-110℃. The mixture can be heated to 60-110℃ and then cooled as described above.

[0033] In some specific implementations, the first temperature is 55°C-70°C.

[0034] The first temperature within this range can further promote the orderly growth and purification of the target isomer crystals, effectively suppressing the inclusion of impurities, thereby further improving the crystal purity and regularity of the primary product. For example, the first temperature is any value or a range of any two of the following: 55℃, 57℃, 59℃, 60℃, 62℃, 65℃, 67℃, 69℃, and 70℃.

[0035] In some specific embodiments, the second temperature is 5°C-30°C. This range of second temperatures can further promote the formation of a large number of crystal nuclei in the target isomer, achieving preliminary separation of the isomers. Exemplarily, the first temperature is any value or a range of any combination of 5°C, 7°C, 9°C, 10°C, 20°C, 25°C, and 30°C.

[0036] In some specific embodiments, the first cooling rate is 2℃ / h-10℃ / h. This range of first cooling rates can further promote the orderly growth and purification of the target isomer crystals, thereby further improving the crystal purity and regularity of the primary product. Exemplarily, the first cooling rate is any value or a combination of any two of 2℃ / h, 7℃ / h, 9℃ / h, and 10℃ / h.

[0037] In some specific embodiments, the second cooling rate is 30°C / h to 60°C / h. This range of second cooling rates can further promote the rapid growth of different isomers into grains with a specific grain size distribution. Exemplarily, the second cooling rate is any value or a range of any combination of 30°C / h, 40°C / h, 50°C / h, 60°C / h, etc.

[0038] In some specific embodiments, the solvent includes at least one of the following: alkyl acetate with 3-8 carbon atoms, alkyl propionate with 4-8 carbon atoms, alkyl carbonate with 2-8 carbon atoms, and alcohol with 1-8 carbon atoms.

[0039] The solvents mentioned above exhibit excellent and controllable selective solubility for cis- and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol. Furthermore, during the cooling process, these solvents can precisely control the supersaturation of the system, allowing the target isomers to crystallize and precipitate in the desired order and morphology at the set first / second cooling rates. In addition, these ester solvents typically have low viscosity and surface tension, making it easy to separate the mother liquor from the crystals after crystallization. The obtained crystals have smooth surfaces, regular crystal shapes, and good flowability, which greatly facilitates subsequent sieving operations and significantly improves the separation efficiency based on particle size or morphological differences.

[0040] In some specific embodiments, the solvent includes at least one selected from methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, n-propyl propionate, n-butyl propionate, dimethyl carbonate, methanol, ethanol, and ethylene glycol.

[0041] The specific solvents mentioned above not only ensure stable, efficient, and scalable separation of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals, but also have the characteristics of being environmentally friendly, having low toxicity, and being easy to recycle and reuse, giving the entire process excellent industrial operability and economy.

[0042] In some specific implementations, the screening process includes using a sieve with a mesh size of 20-250.

[0043] By selecting a sieve with a mesh size of 20 to 250, cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals can be separated. Furthermore, by adjusting the specific mesh size, different ratios of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals can be obtained through sieving.

[0044] In some specific embodiments, the screening process includes a first screening process and a second screening process, wherein the first screening process uses a first screen with a mesh size of 20-40 mesh; and the second screening process uses a second screen with a mesh size of 200-250 mesh.

[0045] In the above embodiments, the first sieving process includes using a first sieve with a mesh size of 20-40, which preferentially traps large crystal particles to obtain a product rich in trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals; the second sieving process uses a second sieve with a mesh size of 200-250, which preferentially traps small crystal particles to obtain a product rich in cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals.

[0046] The method of the present invention can adjust the molar ratio of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals by controlling a first cooling rate, a first temperature, a second cooling rate, a second temperature, and a sieve mesh size. In some specific embodiments, with the total molar amount of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals being 100%, the molar percentage of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals is 0.5%-99.5%.

[0047] For example, the molar percentage of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals is any value or a range of any two of the following: 0.5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 99.5%.

[0048] The proportion of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol in the mixture is not specifically limited in this invention. In some specific embodiments, the molar ratio of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol in the mixture is 1-50:1-50.

[0049] For example, in the mixture, the molar ratio of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is 1:1, 1:10, 1:20, 1:30, 1:40, 1:50, 10:1, 20:1, 30:1, 40:1, 50:1, etc.

[0050] In some specific embodiments, based on the mass of the mixture, the total mass percentage of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is 20wt%-40wt%.

[0051] The total mass ratio of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol in the mixture within the above-mentioned range can provide a more ideal crystallization kinetic environment for the staged cooling and ester solvent system, giving the solution a more suitable viscosity and supersaturation driving ability, which is more conducive to the subsequent effective separation of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol.

[0052] For example, based on the mass of the mixture, the total mass percentage of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is any one of 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, or any combination thereof.

[0053] For example, the mixture can be derived from the product of isobutyric anhydride after high-temperature cracking, dimerization or hydrogenation, or it can be prepared by using crude CBDO product.

[0054] The following specific embodiments illustrate the method for separating cis- and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol provided by the present invention.

[0055] Examples 1-6

[0056] A method for separating cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is provided, comprising the following steps:

[0057] cis- and trans-tetramethyl-1,3-cyclobutanediol (CBDO) were dissolved in butyl acetate at a molar ratio of 50:50 to prepare a mixed solution with a CBDO content of 30% wt.

[0058] The above mixed solution was heated to 100℃ and then added to a crystallizer for cooling and crystallization. The cooling rate was gradient cooling, specifically cooling to a first temperature at a first cooling rate and then cooling to a second temperature at a second cooling rate. Specific parameters are shown in Table 1. After solid-liquid separation, the solid phase was dried, and the dried solid was sieved through 20-40 and 200-250 mesh sieves to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystal products with different cis-trans ratios.

[0059] Figure 1 Image of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals isolated in Example 1; Figure 2 Image of trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals isolated in Example 1. From Figure 1 and Figure 2 It can be seen that the cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals obtained in Example 1 have different morphologies and sizes.

[0060] Comparative Examples 1-6

[0061] The only difference from Example 1 is that the temperature is lowered to a first temperature at a first cooling rate, and then lowered to a second temperature at a second cooling rate. Specific parameters are shown in Table 1.

[0062] The cis-trans ratios of 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals obtained in Examples 1-6 and Comparative Examples 1-6 were determined using gas chromatography. The specific method is as follows: the instrument was a Shimadzu 2030, the column was a PEG-20M 30m × 0.32mm × 0.5μm, the injection port temperature was 240℃, the column temperature was 60℃, and the injection volume was 0.6 μL. The results are shown in Table 1.

[0063] Table 1:

[0064]

[0065] As shown in Table 1, compared with Comparative Examples 1-6, the methods of Examples 1-6 can utilize physical separation to control the cis-trans ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals. Furthermore, by comparing Examples 1-6, it can be seen that by adjusting the specific values ​​of the first cooling rate, the second cooling rate, the first temperature, and the second temperature, the cis-trans ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals can be further controlled.

[0066] Example 7

[0067] A method for separating cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is provided, comprising the following steps:

[0068] cis- and trans-tetramethyl-1,3-cyclobutanediol (CBDO) were dissolved in butyl acetate at a molar ratio of 50:50 to prepare a mixed solution with a CBDO content of 30% wt.

[0069] The above mixed solution was added to a crystallizer and cooled for crystallization. The cooling rate was gradient cooling, specifically 2℃ / h to 70℃, then 50℃ / h to 25℃. Solid-liquid separation was then performed, and the solid phase was dried. The dried solid was sieved through sieves of different mesh sizes. The specific parameters are shown in Table 2, to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystal products with different cis-trans ratios.

[0070] The cis-trans ratio of the 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals obtained in Example 7 was determined using gas chromatography. The specific method is as follows: the instrument was a Shimadzu 2030, the column was a PEG-20M 30m×0.32mm×0.5μm, the injection port temperature was 240℃, the column temperature was 60℃, and the injection volume was 0.6 μL. The results are shown in Table 2.

[0071] Table 2:

[0072]

[0073] As shown in Table 2, the cis-trans ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals can be further controlled by using sieves with different mesh sizes.

[0074] Examples 8-12

[0075] A method for separating cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is provided, comprising the following steps:

[0076] The cis- and trans-tetramethyl-1,3-cyclobutanediols were dissolved in butyl acetate at a molar ratio of 50:50 to prepare mixed solutions with different CBDO contents (different total proportions of cis- and trans-tetramethyl-1,3-cyclobutanediols). Specific parameters are shown in Table 3.

[0077] The above mixed solution was added to a crystallizer and cooled for crystallization. The cooling rate was gradient cooling, specifically 2℃ / h to 70℃, and then 60℃ / h to 25℃. Solid-liquid separation was then performed, and the solid phase was dried. The dried solid was then sieved through 20-40 mesh and 200-250 mesh sieves to obtain 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystal products with different cis-trans ratios.

[0078] The cis-trans ratio of 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals obtained in Examples 8-12 was determined using gas chromatography. The specific method is as follows: the instrument was a Shimadzu 2030, the column was a PEG-20M 30m×0.32mm×0.5μm, the injection port temperature was 240℃, the column temperature was 60℃, and the injection volume was 0.6 μL. The results are shown in Table 3.

[0079] Table 3:

[0080]

[0081] As shown in Table 3, by controlling the initial content of 2,2,4,4-tetramethyl-1,3-cyclobutanediol in the mixed solution in Examples 8-12, the molar ratio of cis-trans isomers of 2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals can be further regulated.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separating cis- and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol, characterized in that, Includes the following steps: A mixture containing a solvent, cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol, and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is cooled to a first temperature at a first cooling rate and then cooled to a second temperature at a second cooling rate, resulting in solid-liquid separation to obtain mixed crystals. The mixed crystals were sieved to obtain cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals. Wherein, the first cooling rate is less than or equal to 10℃ / h, and the second cooling rate is greater than or equal to 30℃ / h; the first temperature is higher than the second temperature, and the temperature of the mixture is greater than the first temperature, wherein the first temperature is less than or equal to 70℃, and the second temperature is less than or equal to 30℃.

2. The method according to claim 1, characterized in that, The first temperature is 55℃-70℃; And / or, the second temperature is 5°C-30°C.

3. The method according to claim 1 or 2, characterized in that, The first cooling rate is 2℃ / h-10℃ / h; And / or, the second cooling rate is 30℃ / h-60℃ / h.

4. The method according to any one of claims 1-3, characterized in that, The solvent includes at least one of the following: alkyl acetate with 3-8 carbon atoms, alkyl propionate with 4-8 carbon atoms, alkyl carbonate with 2-8 carbon atoms, and alcohol with 1-8 carbon atoms.

5. The method according to claim 4, characterized in that, The solvent includes at least one of methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, n-propyl propionate, n-butyl propionate, dimethyl carbonate, methanol, ethanol, and ethylene glycol.

6. The method according to any one of claims 1-3, characterized in that, The screening process includes using a sieve with a mesh size of 20-250.

7. The method according to claim 6, characterized in that, The screening process includes a first screening process and a second screening process. The first screening process uses a first screen with a mesh size of 20-40 mesh; the second screening process uses a second screen with a mesh size of 200-250 mesh.

8. The method according to claim 6 or 7, characterized in that, With the total molar amount of the cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals and the trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals being 100%, the molar percentage of the cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol crystals is 0.5%-99.5%.

9. The method according to any one of claims 1-3, characterized in that, In the mixture, the molar ratio of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is 1-50:1-50.

10. The method according to claim 9, characterized in that, Based on the mass of the mixture, the total mass percentage of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol and trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol is 20wt%-40wt%.

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