Preparation method of high-purity cyclododecanone

Abstract

The application discloses a preparation method of high-purity cyclododecanone, and steps of the method comprise the following steps: 1) cyclododecanol is subjected to a dehydrogenation reaction under the action of a dehydrogenation catalyst to obtain a dehydrogenation reaction liquid rich in cyclododecanone; 2) the dehydrogenation reaction liquid is introduced into cyclopentyl methyl ether, cyclododecanone solid is precipitated, then solid-liquid separation is carried out, and the solid is subjected to vacuum rectification after being melted to obtain high-purity cyclododecanone. The method can prepare a cyclododecanone product with a purity of greater than or equal to 99.998%, impurities cyclododecane and cyclododecene can be controlled at an extremely low level, and the anti-yellowing capacity of the product is significantly enhanced.

Description

Technical Field

[0001] This invention relates to a method for preparing high-purity cyclododecanone, belonging to the fields of fine chemicals and fragrances. Background Technology

[0002] Cyclododecane (CDON) is a very important chemical product in the fragrance industry and engineering plastics field. It is an important intermediate in the Nylon 12 industrial chain. Its preparation can use cyclododecane, cyclododecene, epoxycyclododecane, epoxycyclododecadiene, cyclododecyl alcohol, cyclododecanetriene, etc. as starting materials.

[0003] Patent CN 114874085 B uses cyclododecanetriene as raw material to prepare a mixture of cyclododecones. After primary separation, primary distillation, dehydrogenation, secondary separation, and secondary distillation, a high-purity cyclododecone product is obtained. The primary and secondary distillation processes also involve multiple separation towers, making the actual separation process complex. Moreover, the separated light components, cyclododecane and cyclododecene, still need to be oxidized before being used as raw materials for the preparation of cyclododecones, resulting in a more lengthy overall process.

[0004] Patent CN 116730809 A uses cyclododecyl alcohol as a raw material to prepare cyclododecylone through dehydrogenation under the action of a copper-zinc catalyst. This method has a long catalyst lifetime, high cyclododecylone yield, and good safety. Furthermore, the raw material cyclododecyl alcohol can be prepared using the catalyst and process route in patent CN110882724B. Patent CN 110882724B uses polyamide-amine supramolecular grafted modified graphene foam as a carrier and platinum as the active component to selectively hydrogenate 9,10-epoxy-1,5-cyclododecadiene to cyclododecyl alcohol. The prepared cyclododecyl alcohol product has higher purity and fewer metal impurities, making it more suitable for dehydrogenation to prepare cyclododecylone. Patent CN 117623886 A uses 9,10-epoxy-1,5-cyclododecadiene as a raw material, and obtains cyclododecane through hydrogenation, distillation to remove solvent, stripping to remove solvent, and dehydrogenation. The process route is rationally designed, with high product yield, low tail gas volume, and avoids the risk of material solidification and blockage in the gas phase pipeline, making it a green and environmentally friendly process. However, this process, using 9,10-epoxy-1,5-cyclododecadiene as the initial raw material and hydrogenating before dehydrogenation, does not disclose the purity of the product, which is often the most important indicator determining the downstream application of the product. Furthermore, the above process generates intermediates with boiling points close to cyclododecane during production. If these intermediates cannot be controlled within a very low content range, it will seriously affect the downstream applications of cyclododecane. In addition, cyclododecane is a white solid at room temperature and needs to be melted at 70℃~110℃ for use. If the impurity content in the product is high, it is prone to yellowing, causing the color number of cyclododecane to increase and affecting product quality.

[0005] Therefore, it is necessary to develop a new process for preparing high-purity cyclododecanone products from cyclododecanol via dehydrogenation. Summary of the Invention

[0006] To address the problems of difficulty in preparing high-purity cyclododecanone products and their tendency to yellow in existing technologies, this invention provides a method for preparing high-purity cyclododecanone. The method involves using cyclododecanol as a raw material to prepare a dehydrogenation reaction solution, followed by absorption and precipitation of solids, solid-liquid separation, and product purification to produce cyclododecanone. This method can produce cyclododecanone products with a purity ≥99.998%, where impurities such as cyclododecane and cyclododecene can be controlled at extremely low levels, significantly enhancing the product's resistance to yellowing.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for preparing high-purity cyclododecanone, the method comprising the following steps:

[0009] 1) Cyclododecyl alcohol undergoes a dehydrogenation reaction under the action of a dehydrogenation catalyst to obtain a dehydrogenation reaction solution rich in cyclododecylone;

[0010] 2) The dehydrogenation reaction solution was passed into cyclopentyl methyl ether, and cyclododecanone solid was precipitated. Then, solid-liquid separation was performed, and the solid was melted and then distilled under reduced pressure to obtain high-purity cyclododecanone.

[0011] The method for preparing cyclododecanone from cyclododecanol via dehydrogenation reaction in step 1) of this invention is an existing process. The operations, process conditions, and apparatus involved can all be conventionally selected in the art, and there are no particular limitations. Those skilled in the art can optimize the process based on existing technology and known processes according to actual needs. Specifically, for example, step 1) of this invention can adopt the conditions listed in the following embodiments:

[0012] In one embodiment, the content of 1,2-epoxycyclododecane in the cyclododecyl raw material in step 1) is ≤0.01wt%, for example, 0.01wt%, 0.009wt%, 0.008wt%, 0.006wt%, 0.004wt%, 0.002wt%, 0.001wt%, etc.;

[0013] The cyclododecyl alcohol is a solid at room temperature, and is preferably fed after being melted into a liquid state.

[0014] The existing process for preparing cyclododecyl alcohol typically produces 1,2-epoxycyclododecane impurities, which have a boiling point very close to that of cyclododecone and are difficult to completely remove from the cyclododecone product. Therefore, the 1,2-epoxycyclododecane remaining in the raw material cyclododecyl alcohol will enter the reaction solution along with the dehydrogenation of cyclododecyl alcohol and cannot be completely separated from cyclododecone, which will reduce the purity of the cyclododecone product and affect downstream applications.

[0015] Currently, there are no industry requirements regarding the content of 1,2-epoxycyclododecane in cyclododecyl alcohol products. The content of commonly available products is usually in the range of 0.001 to 1.0 wt%. Cyclododecyl alcohol raw materials that meet the requirement of 1,2-epoxycyclododecane content ≤ 0.01 wt% can be directly used in this invention. However, for cyclododecyl alcohol raw materials with 1,2-epoxycyclododecane content > 0.01 wt%, epoxycyclododecane needs to be removed before use to bring its content to ≤ 0.01 wt%. This invention does not specify the method for removing epoxycyclododecane; for example, conventional separation methods such as vacuum distillation can be used.

[0016] The type of dehydrogenation catalyst mentioned in step 1) of this invention is not particularly required. It can be a dehydrogenation catalyst commonly used in the field. For example, the dehydrogenation catalyst is selected from copper-based catalysts, preferably supported copper catalysts.

[0017] The copper-based catalyst used in this invention is a product already disclosed in the prior art. It can be a commercially available product that can be purchased through commercial channels, such as the copper-based catalyst of Nanjing Zunlong New Material Technology Co., Ltd., or the TC-1 copper catalyst of Japan High Chemical Co., Ltd.; it can also be a dehydrogenation catalyst product prepared by technicians based on existing processes, for example, by referring to the methods disclosed in patents CN 116730809 A and CN 118767991 A.

[0018] In one embodiment, the dehydrogenation reaction in step 1) is carried out at a temperature of 190–290°C and a pressure of 80–125 kPaA; for example, reaction temperatures of 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, etc., and reaction pressures of 80 kPaA, 85 kPaA, 90 kPaA, 95 kPaA, 100 kPaA, 105 kPaA, 110 kPaA, 115 kPaA, 120 kPaA, 125 kPaA, etc.

[0019] The dehydrogenation reaction is carried out in a fixed-bed reactor, and the dehydrogenation catalyst is packed in the reactor with a mass hourly space velocity (WHSV) of 0.1–1 h⁻¹ (based on cyclododecyl alcohol). -1 For example, 0.1h -1 0.3h -1 0.5h -1 0.7h -1 0.9h -1 1h -1In one embodiment, the mass ratio of the dehydrogenation reaction solution to cyclopentyl methyl ether in step 2) is 1:1.5 to 3.0, for example, 1:1.5, 1:1.7, 1:2.0, 1:2.2, 1:2.5, 1:2.8, 1:3.0, etc., preferably 1:1.8 to 2.0.

[0020] In one embodiment, the precipitation temperature of the cyclododecanone solid in step 2) is 60–70°C, the operating pressure is 100–120 kPaA, and the precipitation time is 1–5 h; for example, reaction temperatures of 60°C, 62°C, 65°C, 68°C, 70°C, etc., reaction pressures of 100 kPaA, 102 kPaA, 105 kPaA, 108 kPaA, 110 kPaA, 112 kPaA, 115 kPaA, 118 kPaA, 120 kPaA, etc., and precipitation times of 1 h, 2 h, 3 h, 4 h, 5 h, etc. After the dehydrogenation reaction is completed, the reaction solution obtained is in a molten solution state due to its high temperature. During the process of mixing with cyclopentyl methyl ether and cooling, cyclododecanone and other substances will gradually precipitate to obtain a white solid.

[0021] In one embodiment, the solid-liquid separation in step 2) can be performed using conventional separation operations in the art, such as filtration, centrifugation, etc., preferably centrifugation; the centrifugation speed is preferably 1000-1300 rpm.

[0022] In one embodiment, the solid melting temperature in step 2) is 78-85°C, and the white solid obtained by solid-liquid separation is heated to melt and then sent to the product refining tower.

[0023] In one embodiment, the reduced pressure distillation in step 2) is carried out at an operating pressure of -(20~0.1) kPaG, such as -20 kPaG, -15 kPaG, -10 kPaG, -5 kPaG, -0.1 kPaG, etc., and the bottom temperature of the column is 120~150℃, such as 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, etc. Through this operation, the molten solid is deweighted and the cyclododecanone product is obtained from the top side of the product refining column.

[0024] The high-purity cyclododecane product obtained by the method of the present invention can have a purity of up to 99.998 wt% or more, wherein the impurity content of cyclododecene is ≤0.001 wt% and the content of cyclododecane is ≤0.001 wt%.

[0025] In one implementation, the remaining liquid phase after solid-liquid separation in step 2) is mainly cyclopentyl methyl ether, which can be recycled.

[0026] Specifically, the liquid phase is distilled in a recovery tower to recover cyclopentyl methyl ether. The operating pressure is 40-80 kPaA, the bottom temperature is 110-125°C, and the purity of the cyclopentyl methyl ether obtained by distillation is ≥99.4 wt%.

[0027] Compared with the prior art, the positive effects of the present invention are as follows:

[0028] (1) The contents of the impurities cyclododecane and cyclododecene produced by the dehydrogenation reaction can be controlled to within 0.001 wt%, respectively, to obtain a high-purity cyclododecone product with a purity ≥ 99.998 wt%.

[0029] (2) It effectively enhances the anti-yellowing ability of cyclododecanone products in the molten state and when not completely isolated from air, thus extending the yellowing time of the product by at least 100%.

[0030] (3) By selecting a suitable cyclopentyl methyl ether as the absorbent to remove key impurities, the separation difficulty of impurities with similar boiling points to the product is reduced, thus reducing distillation investment and energy consumption. Detailed Implementation

[0031] To better understand the technical solution of this application, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Unless otherwise specified, the reagents, materials, and instruments used in the following examples are all conventional reagents, materials, and instruments in the art, and are commercially available. The reagents involved can also be synthesized by conventional methods in the art.

[0033] The sources of the main raw materials used in the various embodiments and comparative examples of this invention are as follows:

[0034] Cyclododecyl alcohol: purity 99.3-99.9 wt%, Wanhua Chemical; before use, adjust its 1,2-epoxycyclododecyl content to be within the range of 0.001-0.01 wt%.

[0035] Dehydrogenation catalyst A: Modified Cu-Zn catalyst-C prepared using Example 3 of CN 116730809 A;

[0036] Dehydrogenation catalyst B: Modified Cu-Zn-Si catalyst-C prepared using Example 3 of CN 118767991 A.

[0037] The main analytical methods used in the embodiments and comparative examples of this invention are as follows:

[0038] Gas chromatography analysis: The reaction solution sample was diluted with chromatographic ethanol, shaken thoroughly, and then analyzed by GC on an Agilent 7820 using an HP-5 capillary column (5% Phenyl Methyl Siloxan, 30m × 0.32mm × 0.25μm) and an FID detector. Injector temperature: 280℃, pressure: 8.5868psi, split ratio: 30:1; detector temperature: 300℃, hydrogen flow rate: 30mL / min; column temperature was programmed: initial column temperature 100℃, hold for 3 minutes, increase to 200℃ at 10℃ / min, hold for 2 minutes, then increase to 280℃ at 20℃ / min, hold for 5 minutes. Column pressure: 8.5868psi, flow rate: 1.5mL / min, residence time: 1.6837 minutes. Injection volume: 0.2μL.

[0039] Anti-yellowing performance test: The 1L aluminum bottle containing the cyclododecanone product was opened and placed in a 90℃ oven to melt. Every 2 hours, a sample of the molten cyclododecanone was taken and the color number was determined according to the provisions of GB / T 6324.7-2014. The anti-yellowing performance of the cyclododecanone product was evaluated based on the increase in color number per unit time.

[0040] Example 1

[0041] 1) Preparation of dehydrogenation reaction solution: 100g of dehydrogenation catalyst A was loaded into the reaction tube. The feedstock cyclododecyl alcohol (1,2-epoxycyclododecane content 0.01wt%) was melted at 90℃ and pumped into the reaction tube. The reaction temperature was set to 290℃, the reaction pressure to 80kPaA, the cyclododecyl alcohol feed rate to 100g / h, and the mass hourly space velocity (WHSV) based on cyclododecyl alcohol to be 1h. -1 The dehydrogenation reaction solution obtained at the reactor outlet was sampled and tested. The conversion rate of cyclododecyl alcohol was 99.27%, the selectivity of cyclododecone was 99.85%, the selectivity of cyclododecane was 0.08%, and the selectivity of cyclododecene was 0.06%.

[0042] 2) Post-processing: The dehydrogenation reaction solution was passed into cyclopentyl methyl ether to precipitate cyclododecanone solid. The mass ratio of the dehydrogenation reaction solution to cyclopentyl methyl ether was 1:1.8. The precipitation operation temperature was 60℃, the operation pressure was 120 kPaA, and the operation time was 5 h. Then, solid-liquid separation was performed by centrifugation at 1000 rpm. A white solid was obtained by centrifugation. The white solid was heated to 85℃ to melt and then sent to the product purification tower. The operation pressure was -20 kPaG, and the bottom temperature of the tower was 120℃. High-purity cyclododecanone product was collected from the top of the product purification tower.

[0043] This high-purity cyclododecane product has a purity of 99.998 wt%, a cyclododecene content of 1.4 ppm, a cyclododecane content of 1.7 ppm, and a cyclododecyl alcohol content of 16 ppm.

[0044] The liquid phase obtained from the aforementioned solid-liquid separation is sent to the recovery tower for distillation at an operating pressure of 40 kPaA and a bottom temperature of 110°C to obtain recovered cyclopentyl methyl ether with a purity of 99.4 wt%, which is then returned to the cyclopentyl methyl ether absorption step in step 2).

[0045] Example 2

[0046] 1) Preparation of dehydrogenation reaction solution: 100g of dehydrogenation catalyst B was loaded into the reaction tube. The feedstock cyclododecyl alcohol (1,2-epoxycyclododecane content 0.005wt%) was melted at 90℃ and pumped into the reaction tube. The reaction temperature was set to 190℃, the reaction pressure to 125kPaA, the cyclododecyl alcohol feed rate to 10g / h, and the mass hourly space velocity (WHSV) based on cyclododecyl alcohol to be 0.1h. -1 The dehydrogenation reaction solution obtained at the reactor outlet was sampled and tested. The conversion rate of cyclododecyl alcohol was 99.77%, the selectivity of cyclododecone was 99.92%, the selectivity of cyclododecane was 0.05%, and the selectivity of cyclododecene was 0.03%.

[0047] 2) Post-processing: The dehydrogenation reaction solution was passed into cyclopentyl methyl ether to precipitate cyclododecanone solid. The mass ratio of the dehydrogenation reaction solution to cyclopentyl methyl ether was 1:1.5. The precipitation operation temperature was 70℃, the operation pressure was 100 kPaA, and the operation time was 1 h. Then, solid-liquid separation was performed by centrifugation at 1300 rpm. A white solid was obtained by centrifugation. The white solid was heated to 78℃ to melt and then sent to the product purification tower. The operation pressure was -0.1 kPaG, and the bottom temperature of the tower was 150℃. High-purity cyclododecanone product was collected from the top of the product purification tower.

[0048] This high-purity cyclododecane product has a purity of 99.998 wt%, a cyclododecene content of 0.9 ppm, a cyclododecane content of 0.3 ppm, and a cyclododecyl alcohol content of 12 ppm.

[0049] The liquid phase obtained from the aforementioned solid-liquid separation is sent to the recovery tower for distillation at an operating pressure of 80 kPaA and a bottom temperature of 125°C to obtain recovered cyclopentyl methyl ether with a purity of 99.4 wt%, which is then returned to the cyclopentyl methyl ether absorption step in step 2).

[0050] Example 3

[0051] 1) Preparation of dehydrogenation reaction solution: 100g of dehydrogenation catalyst B was loaded into the reaction tube. The feedstock cyclododecyl alcohol (1,2-epoxycyclododecane content 0.001wt%) was melted at 90℃ and pumped into the reaction tube. The reaction temperature was set to 220℃, the reaction pressure to 100kPaA, the cyclododecyl alcohol feed rate to 80g / h, and the mass hourly space velocity (WHSV) based on cyclododecyl alcohol to be 0.8h. -1The dehydrogenation reaction solution obtained at the reactor outlet was sampled and tested. The conversion rate of cyclododecyl alcohol was 99.79%, the selectivity of cyclododecone was 99.91%, the selectivity of cyclododecane was 0.04%, and the selectivity of cyclododecene was 0.04%.

[0052] 2) Post-processing: The dehydrogenation reaction solution was passed into cyclopentyl methyl ether to precipitate cyclododecanone solid. The mass ratio of the dehydrogenation reaction solution to cyclopentyl methyl ether was 1:2.0. The precipitation operation temperature was 70℃, the operation pressure was 110 kPaA, and the operation time was 3 h. Then, solid-liquid separation was performed by centrifugation at 1200 rpm. A white solid was obtained by centrifugation. The white solid was heated to 80℃ to melt and then sent to the product purification tower. The operation pressure was -10 kPaG, and the bottom temperature of the tower was 140℃. High-purity cyclododecanone product was collected from the top of the product purification tower.

[0053] This high-purity cyclododecane product has a purity of 99.999 wt%, a cyclododecene content of 0.6 ppm, a cyclododecane content of 0.4 ppm, and a cyclododecyl alcohol content of 8 ppm.

[0054] The liquid phase obtained from the aforementioned solid-liquid separation is sent to the recovery tower for distillation at an operating pressure of 60 kPaA and a bottom temperature of 130°C to obtain recovered cyclopentyl methyl ether with a purity of 99.5 wt%, which is then returned to the cyclopentyl methyl ether absorption step in step 2).

[0055] Example 4

[0056] 1) Preparation of dehydrogenation reaction solution: 100g of dehydrogenation catalyst A was loaded into the reaction tube. The feedstock cyclododecyl alcohol (1,2-epoxycyclododecane content 0.008wt%) was melted at 90℃ and pumped into the reaction tube. The reaction temperature was set to 240℃, the reaction pressure to 90kPaA, the cyclododecyl alcohol feed rate to 70g / h, and the mass hourly space velocity (WHSV) based on cyclododecyl alcohol to be 0.7h. -1 The dehydrogenation reaction solution obtained at the reactor outlet was sampled and tested. The conversion rate of cyclododecyl alcohol was 99.31%, the selectivity of cyclododecone was 99.84%, the selectivity of cyclododecane was 0.08%, and the selectivity of cyclododecene was 0.07%.

[0057] 2) Post-processing: The dehydrogenation reaction solution was passed into cyclopentyl methyl ether to precipitate cyclododecanone solid. The mass ratio of the dehydrogenation reaction solution to cyclopentyl methyl ether was 1:3.0. The precipitation operation temperature was 65℃, the operation pressure was 100 kPaA, and the operation time was 2 h. Then, solid-liquid separation was performed by centrifugation at 1300 rpm. A white solid was obtained by centrifugation. The white solid was heated to 82℃ to melt and then sent to the product purification tower. The operation pressure was -10 kPaG, and the bottom temperature of the tower was 135℃. High-purity cyclododecanone product was collected from the top of the product purification tower.

[0058] This high-purity cyclododecane product has a purity of 99.999 wt%, a cyclododecene content of 1.9 ppm, a cyclododecane content of 2.0 ppm, and a cyclododecyl alcohol content of 5 ppm.

[0059] The liquid phase obtained from the aforementioned solid-liquid separation is sent to the recovery tower for distillation at an operating pressure of 50 kPaA and a bottom temperature of 120°C to obtain recovered cyclopentyl methyl ether with a purity of 99.6 wt%, which is then returned to the cyclopentyl methyl ether absorption step in step 2).

[0060] Comparative Example 1

[0061] The dehydrogenation reaction solution was prepared according to step 1) of Example 1 and directly fed into the product purification tower. The operating pressure was -20 kPaG and the bottom temperature of the tower was 120°C. The cyclododecanone product was collected from the top side of the product purification tower. The cyclododecanone product had a purity of 99.69 wt%, a cyclododecene content of 0.05 wt%, a cyclododecane content of 0.08 wt%, and a cyclododecyl alcohol content of 0.14 wt%.

[0062] Comparative Example 2

[0063] Referring to the method of Example 1, the difference is that in step 2), cyclopentyl methyl ether is replaced with cyclohexane, while other operations and conditions remain unchanged. The cyclododecanone product obtained by this method has a purity of 99.74%, a cyclododecene content of 0.03 wt%, a cyclododecane content of 0.04 wt%, and a cyclododecyl alcohol content of 0.09 wt%.

[0064] The cyclododecanone products obtained in Examples 1-4 and Comparative Examples 1-2 were used for anti-yellowing performance testing, and the results are shown in Table 1 below.

[0065] Table 1. Anti-yellowing performance test of cyclododecanone products

[0066]

[0067] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing high-purity cyclododecanone, characterized in that the steps include... include: 1) Cyclododecyl alcohol undergoes a dehydrogenation reaction in the presence of a dehydrogenation catalyst to obtain a dehydrogenation reaction solution rich in cyclododecylone; the dehydrogenation catalyst is selected from copper-based catalysts, and the dehydrogenation reaction is carried out at a reaction temperature of 190~290℃ and a reaction pressure of 80~125kPaA. 2) The dehydrogenation reaction solution was passed into cyclopentyl methyl ether, and cyclododecanone solid was precipitated. Then, solid-liquid separation was performed, and the solid was melted and then distilled under reduced pressure to obtain high-purity cyclododecanone. Step 2) The precipitation temperature of the cyclododecanone solid is 60~70℃, the operating pressure is 100~120kPaA, and the precipitation time is 1~5h.

2. The preparation method according to claim 1, characterized in that, Step 1) The content of 1,2-epoxycyclododecane in the cyclododecyl raw material is ≤0.01wt%.

3. The preparation method according to claim 1, characterized in that, The dehydrogenation catalyst mentioned in step 1) is selected from supported copper catalysts.

4. The preparation method according to claim 1, characterized in that, The dehydrogenation reaction described in step 1) has a mass hourly space velocity (WHSV) of 0.1–1 h⁻¹, based on cyclododecyl alcohol. -1 .

5. The preparation method according to claim 1, characterized in that, In step 2), the mass ratio of the dehydrogenation reaction solution to cyclopentyl methyl ether is 1:1.5~3.

0.

6. The preparation method according to claim 5, characterized in that, In step 2), the mass ratio of the dehydrogenation reaction solution to cyclopentyl methyl ether is 1:1.8~2.

0.

7. The preparation method according to claim 1, characterized in that, Step 2) The solid-liquid separation method is centrifugal separation.

8. The preparation method according to claim 7, characterized in that, The centrifugal speed is 1000~1300 rpm.

9. The preparation method according to claim 1, characterized in that, Step 2) The solid melting temperature is 78~85℃.

10. The preparation method according to claim 1, characterized in that, Step 2) describes vacuum distillation with an operating pressure of -20 to -0.1 kPaG and a bottom temperature of 120 to 150°C.

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