Preparation method of musk-T

Abstract

The invention discloses a preparation method of musk-T. The musk-T is prepared from two raw materials including brazil acid and ethylene glycol through the steps of polycondensation and depolymerization cyclization. After polycondensation is completed, excessive ethylene glycol is recovered through reduced pressure distillation, musk T is taken out with ethylene glycol in the depolymerization process, a mixed crude product of ethylene glycol and musk T is obtained, and a crude product of musk T is obtained through static layering; ethylene glycol is recycled and reused for a next batch of polycondensation reaction raw material or a next batch of depolymerization; meanwhile, the obtained crude musk T product is washed with water and a sodium sulfate solution and then rectified to obtain a finished musk-T product. The depolymerized residual liquid and the rectified residual liquid contain dimers and trimers with large molecular weights, and return to the depolymerization kettle to be depolymerized again. According to the method, closed circulation is integrally formed, three wastes are not generated, a large amount of high-viscosity high polymers are not generated, resource waste is avoided, the method conforms to the green and environment-friendly development concept, and industrial production of musk-T.

Description

Technical Field

[0001] The invention relates to the technical field of musk macrocyclic ester compounds, and in particular to a method for preparing musk-T. Background Art

[0002] Musk-T, also known as Kunlun Musk, has a chemical name of 1,4-dioxacycloheptadecane-5,17-dione. It is a colorless or slightly yellow viscous liquid and belongs to the macrocyclic lactone musk fragrance. Musk-T is a high-grade fixative, and its aroma type is close to that of natural musk, with stable aroma and good diffusion. It is non-toxic, pure and lasting. It has good roundness and fragrance-enhancing effects in blending spices. It is an indispensable raw material for blending high-grade flavors, and is particularly suitable for preparing various high-grade perfumes, shampoos and cosmetics. At present, the demand for Musk-T at home and abroad is increasing, and the price is also rising. The global demand is increasing at a rate of about 5% per year, and the supply is in short supply. It has broad application prospects and huge market demand. Therefore, researching and developing the production process of Musk-T is of great significance for seizing the international market and improving the new economic benefits of enterprises.

[0003] Musk-T is synthesized from tridecanedioic acid (brazil acid) and ethylene glycol through polycondensation to form a high-viscosity linear polyester, which is then depolymerized and cyclized by a catalyst to generate a crude product, which is then distilled and purified to obtain the final product. This is the currently commonly used industrial route, as follows.

[0004]

[0005] Patent CN1172928C discloses a method for synthesizing a macrolide compound, wherein tridecanedioic acid and ethylene glycol are first subjected to a polycondensation reaction, and then a depolymerization and cyclization reaction is carried out under the catalysis of dibutyltin oxide to produce tridecanedioic acid cycloethylene ester (musk-T). However, after the polycondensation reaction, the excess ethylene glycol is recovered, then adsorbed, filtered and regenerated, and the process is relatively cumbersome.

[0006] US4803288A discloses a method for preparing brazilic acid ethylene glycol ester (Musk-T), wherein brazilic acid and ethylene glycol are subjected to depolymerization and cyclization reaction in the presence of dibutyltin oxide to obtain a crude Musk T. However, it does not involve the recycling of the still residue or the purification of the crude Musk T.

[0007] Patent CN103508997A discloses a method for preparing 1,4-dioxahedodecane-5,17-dione (Musk-T) by catalyzing the reaction of brazilic acid (tridecanedioic acid) and ethylene glycol in the presence of isopropyl titanate (IPT) catalyst, but does not involve the treatment of the still residue from distillation and rectification.

[0008] Patent CN105884742B discloses a method for preparing musk-T, wherein α,ω-tridecanedioic acid and 1,2-ethylene glycol are polymerized under nitrogen protection by adding a polymerization inhibitor, and then depolymerized and cyclized under a composite catalyst composed of aluminum carbonate, p-toluenesulfonic acid, silicotungstomolybdic acid, anhydrous copper sulfate, water, and silicon dioxide to obtain crude ethylene tridecane dibasic acid (musk T), and then distilled, rectified, and redistilled to obtain the finished product. The polymerization yield is 87% and the depolymerization time is 24h, but there are certain difficulties in the preparation, recovery, and activation of the composite catalyst.

[0009] The preparation methods of musk-T reported in the above literature all use brazil acid as raw material, first polycondense with 1,2-ethylene glycol to obtain polyesters with different polymerization degrees, and then depolymerize and lactonize at high temperature under reduced pressure to obtain the product. The main difference between the processes lies in the catalyst selection and process conditions control during the polymerization and depolymerization processes.

[0010] The main reason restricting the production of Musk-T is the depolymerization process in the synthesis process. Since the reactants are polymerized to obtain high-viscosity polyester, the viscosity of the polyester increases further during the depolymerization process as the reaction proceeds, thereby reducing the heat transfer efficiency. In the later stage of the reaction, the polyester in the system becomes semi-solid or solid, making heat transfer difficult. If the depolymerization reaction temperature is increased, the material near the kettle wall will be carbonized, affecting the product quality and yield. The larger the reactor, the smaller the heat transfer area per unit polyester, and the more obvious this effect is. Therefore, the amplification of the synthesis process has become a key point restricting large-scale production.

[0011] The catalysts used in domestic technology are generally alkyl tin [dibutyltin dilaurate, dibutyltin acetate (salt)], aluminum alkoxide and lead oxide. The total yield is generally between 75-81%, and the polymerization and depolymerization time takes about 30 hours. This type of catalyst is prone to heavy metal residues, and trace heavy metal residues may also cause the product to change color and deteriorate during storage and transportation. Considering that the product is often used in personal care cosmetics, some heavy metal residues must be eliminated to avoid unnecessary damage to human skin.

[0012] Therefore, the key technical point of synthesizing musk-T is to develop a highly active depolymerization and cyclization catalyst and transfer musk-T to the interface in time to reduce cross-linking during polyester depolymerization, increase viscosity, and promote the reaction equilibrium to move towards the direction of musk-T formation.

[0013] In summary, it is crucial to develop an efficient catalyst that can overcome the above defects. Summary of the invention

[0014] In order to solve the technical problems mentioned in the above background technology, the present invention provides a method for preparing musk-T, which has advanced technology, high efficiency, stable quality, no pollution and is suitable for industrial production of musk-T.

[0015] In order to achieve the above object, the present invention adopts the following technical solutions:

[0016] A method for preparing musk-T comprises the following steps:

[0017] S1 polycondensation reaction: under nitrogen protection, add brazil acid and ethylene glycol into the polymerization reaction vessel, start heating, when the kettle temperature rises to 160℃, water droplets condense at the condenser mouth, keep at this temperature for 3h, the condensed fraction enters the polymerization receiving kettle, when the gas phase temperature drops significantly and no gas is generated, the normal pressure polymerization is completed, then, carry out vacuum distillation to evaporate the excess ethylene glycol, until the polyester acid value is less than 2.0KOH mg / g, the polymerization reaction is finished;

[0018] Preferably, the molar ratio of the brazilic acid and ethylene glycol is 1:1 to 1.5;

[0019] Preferably, the polycondensation temperature is 150-180°C. ;

[0020] Preferably, the excess ethylene glycol is evaporated under reduced pressure, the vacuum degree is 200 Pa, and the temperature is controlled at 165°C to 180°C.

[0021] S2 depolymerization and cyclization: After the polymerization reaction is completed, a depolymerization catalyst is added under nitrogen protection. After stirring evenly, a vacuum pump is used to evacuate the mixture. The vacuum degree is controlled at 200-800Pa. The depolymerization reaction is carried out under reduced pressure. When the temperature rises to 220°C, ethylene glycol is added dropwise. The rate of ethylene glycol addition is basically consistent with the outflow rate of the fraction.

[0022] The crude mixture of musk-T and ethylene glycol generated by the reaction overflows from the top of the kettle and enters the crude product receiving tank after condensation. The condensed mixture will be layered in the receiving tank, and the ethylene glycol obtained in the lower layer can be put back and continue to be added dropwise to the depolymerization kettle for use. The depolymerization reaction is completed to obtain the crude musk-T product;

[0023] Preferably, the vacuum degree of depolymerization in S2 depolymerization cyclization is controlled at 200-800 Pa

[0024] Preferably, the depolymerization catalyst in S2 depolymerization and cyclization is at least one of isopropyl titanate, calcium chloride, magnesium chloride, magnesium acetate, manganese chloride, dibutyl tin oxide, and tetrabutyl titanate.

[0025] Preferably, the amount of the depolymerization catalyst used in S2 depolymerization and cyclization is 0.2%-0.5% (based on the molar amount of brazilic acid), and particularly preferably the amount of the depolymerization catalyst used is 0.2%.

[0026] Refining of crude S3: Wash with water and sodium sulfate solution, then distill under vacuum degree of 500 Pa, temperature of 180-225°C, and collect the distillate at top temperature of 145-165°C.

[0027] Preferably, in the refining of S3 crude product, based on the mass of the crude product, the amount of water is 10%, the amount of sodium sulfate solution is 10%; and the concentration of sodium sulfate is 10-15%.

[0028] S4 recovery depolymerization: The kettle liquid after depolymerization and the residual liquid after distillation contain dimers and trimers with larger molecular weight, which are returned to the depolymerization kettle for re-depolymerization.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention changes the conventional technology in which the process temperature of the depolymerization process starts from 280°C, the polyester is easily coked, and the viscosity of the polyester is further increased, thereby reducing the heat transfer efficiency. In the later stage of the reaction, the polyester in the system becomes semi-solid or solid, making heat transfer difficult.

[0031] The present invention maintains the depolymerization at 220°C from the aspects of high-efficiency catalyst and dripping ethylene glycol during depolymerization, reduces the generation of high-viscosity polymers as the reaction proceeds, and does not need to continuously increase the temperature to evaporate the product. The residual liquid contains dimers and trimers with large molecular weights, which are returned to the depolymerization kettle for re-depolymerization, forming a closed cycle, without the generation of "three wastes", and will not generate a large amount of high-viscosity polymers, thus avoiding waste of resources, conforming to the development concept of green environmental protection, and being conducive to the industrial production of Musk-T.

[0032] In addition, the catalyst used in the present invention is cheap and easily available, the reaction process only takes about 20 hours, and the yield is above 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 is the gas chromatography-mass spectrometry (GC-MS) diagram of the crude musk-T product obtained in Example 1;

[0035] Figure 2is a GC-MS graph of the Musk-T distillation product obtained in Example 1;

[0036] Figure 3a is the mass spectrometry result of the Musk-T distillation product obtained in Example 1;

[0037] Figure 3b This is the standard spectrum of Musk T. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] S1 polycondensation reaction

[0041] Weigh 280g of brazil acid and 78.24g of ethylene glycol respectively and add them into a 1L four-necked flask, then replace with nitrogen three times. Turn on the heating, raise the temperature to 170℃, keep warm for 3h, collect the water generated by polycondensation into the distillation bottle after condensation, when the gas phase temperature drops significantly and no gas is generated, the normal pressure polymerization ends, then vacuum decompression is used to recover the excess ethylene glycol, the vacuum degree is 200pa, and the temperature is 165℃. Then take a sample to measure the acid value, the acid value is 1.8KOH mg / g.

[0042] S2 depolymerization cyclization

[0043] Take 0.65g of depolymerization catalyst isopropyl titanate with a syringe, add it to the polymer reaction bottle in the previous step, stir evenly, start vacuuming, heat, and when it rises to 220°C, weigh 803g of ethylene glycol, add ethylene glycol to the depolymerization reaction liquid with a liquid phase pump, and add the ethylene glycol to the depolymerization reaction liquid with a drop rate of 4mL / min. While adding ethylene glycol, evaporate musk T. Use gas phase analysis to monitor whether the reaction is complete. The content of musk T in the received fraction is less than 1% to stop the reaction. The collected fractions are separated with a separatory funnel. The upper layer is the crude product of musk T (in the form of white oil), and the lower ethylene glycol layer is applied and continued to be added to the depolymerization reaction liquid with a liquid phase pump. Repeat the above operation 6-7 times. The total depolymerization time is 20h, and finally 340.32g of musk T crude product is obtained. The ethylene glycol layer is 700g, which can be used as the reactant or depolymerization reactant or solvent for the next polymerization.

[0044] S3 crude product refining

[0045] Wash three times with 34g water and 34g 10% sodium sulfate solution, and then collect fractions by rectification under vacuum degree 500pa, kettle temperature 195-215℃, top temperature 145-165℃ to obtain 287.71g of finished musk-T with a purity of 98%. The calculated yield is 91%;

[0046] S4 recycling depolymerization

[0047] The residual liquid after distillation contains dimers and trimers with larger molecular weight, which are returned to the depolymerization kettle for re-depolymerization.

[0048] Example 2

[0049] The difference between this embodiment and embodiment 1 is that the ratio of the two raw materials, brazilic acid and ethylene glycol, is 1:1.2.

[0050] S1 polycondensation reaction

[0051] Weigh 280g of brazil acid and 85.36g of ethylene glycol respectively and add them into a 1L four-necked flask, then replace with nitrogen three times. Turn on the heating, raise the temperature to 170℃, keep warm for 3h, collect the water generated by polycondensation into the distillation bottle after condensation, when the gas phase temperature drops significantly and no gas is generated, the normal pressure polymerization is completed, and then vacuum decompression is used to recover the excess ethylene glycol, the vacuum degree is 200pa, and the temperature is 165℃. Then take a sample to measure the acid value, which is 1.85KOH mg / g.

[0052] S2 depolymerization cyclization

[0053] Take 0.65g of depolymerization catalyst isopropyl titanate with a syringe and add it to the polymer reaction bottle in the previous step. After stirring evenly, start vacuuming and heating. When it rises to 220°C, weigh 803g of ethylene glycol and add ethylene glycol to the depolymerization reaction liquid with a liquid phase pump. The drop rate is 4mL / min. While adding ethylene glycol, evaporate musk T. Use gas phase analysis to monitor whether the reaction is complete. The content of musk T in the received fraction is less than 1%, stop the reaction. The depolymerization time is 19.8h. The collected fractions are separated with a separatory funnel. The upper layer is the crude musk T (white oily), and the lower ethylene glycol layer is applied and continued to be added to the depolymerization reaction liquid with a liquid phase pump. Repeat the above operation 6-7 times. The total depolymerization time is 20.2h, and finally 342.32g of musk T crude product is obtained. The ethylene glycol layer is 702g, which can be used as a reactant for the next polymerization or a solvent for depolymerization.

[0054] S3 crude product refining

[0055] Wash three times with 34g water and 34g 10% sodium sulfate solution, and then collect the fractions by rectification under the conditions of vacuum degree 500pa, kettle temperature 195-215℃, top temperature 145-165℃ to obtain 288.70g finished musk-T with a purity of 98.2%. The calculated yield is 91.5%;

[0056] S4 recycling depolymerization

[0057] The residual liquid after distillation contains dimers and trimers with larger molecular weight, which are returned to the depolymerization kettle for re-depolymerization.

[0058] For other structures not described, refer to Example 1.

[0059] Example 3

[0060] The difference between this embodiment and embodiment 1 is that the ratio of the two raw materials of brazilic acid and ethylene glycol is 1:1.3, the polycondensation temperature is 180° C., and the depolymerizing agent is a mixture of magnesium chloride and magnesium acetate.

[0061] S1 polycondensation reaction

[0062] Weigh 280g of brazil acid and 92.47g of ethylene glycol respectively and add them into a 1L four-necked flask, then replace with nitrogen three times. Turn on the heating, raise the temperature to 180℃, keep warm for 3h, collect the water generated by polycondensation into the distillation bottle after condensation, when the gas phase temperature drops significantly, the normal pressure polymerization ends, then vacuum decompression is used to recover the excess ethylene glycol, the vacuum degree is 200pa, and the temperature is 165℃. Then take a sample to measure the acid value, the acid value is 1.84KOH mg / g.

[0063] S2 depolymerization cyclization

[0064] Weigh 0.65g of a mixture of magnesium chloride and acetic acid (molar ratio of 1:1) as a depolymerization catalyst, add it to the polymer reaction bottle in the previous step, stir evenly, start vacuuming, heat, and when it rises to 220°C, weigh 803g of ethylene glycol, add ethylene glycol to the depolymerization reaction liquid with a liquid phase pump, and add the ethylene glycol to the depolymerization reaction liquid at a drop rate of 4mL / min. While adding ethylene glycol, evaporate musk T. Use gas phase analysis to monitor whether the reaction is complete. The reaction is stopped when the content of musk T in the received fraction is less than 1%. The collected fractions are separated with a separatory funnel, the upper layer is the crude musk T (in the form of white oil), and the lower ethylene glycol layer is applied and continued to be added to the depolymerization reaction liquid with a liquid phase pump. Repeat the above operation 6-7 times, the total depolymerization time is 20.1h, and finally 345.32g of crude musk T is obtained. The ethylene glycol layer is 705g, which can be used as a reactant or depolymerization reactant or solvent for the next polymerization.

[0065] S3 crude product refining

[0066] Wash three times with 35g water and 35g 10% sodium sulfate solution, and then collect the distillate under the conditions of vacuum degree 500pa, kettle temperature 195-215℃, top temperature 145-165℃ to obtain 292.10g finished musk-T with a purity of 98.5%. The calculated yield is 92.86%;

[0067] S4 recycling depolymerization

[0068] The residual liquid after distillation contains dimers and trimers with larger molecular weight, which are returned to the depolymerization kettle for re-depolymerization.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that the ratio of the two raw materials of brazilic acid and ethylene glycol is 1:1.4, the polycondensation temperature is 180° C., and the depolymerization catalyst is dibutyltin oxide.

[0071] S1 polycondensation reaction

[0072] Weigh 280g of brazil acid and 99.58g of ethylene glycol respectively and add them into a 1L four-necked flask, then replace with nitrogen three times. Turn on the heating, raise the temperature to 180℃, keep warm for 3h, collect the water generated by polycondensation into the fraction bottle after condensation, when the gas phase temperature drops significantly, the normal pressure polymerization ends, then vacuum decompression is used to recover the excess ethylene glycol, the vacuum degree is 200pa, and the temperature is 165℃. Then take a sample to measure the acid value, the acid value is 1.80KOH mg / g.

[0073] S2 depolymerization cyclization

[0074] Take 0.65g of dibutyltin oxide, a depolymerization catalyst, with a weigher and add it to the polymer reaction bottle in the previous step. After stirring evenly, start vacuuming and heating. When it rises to 220°C, weigh 803g of ethylene glycol and add ethylene glycol to the depolymerization reaction liquid with a liquid phase pump. The drop rate is 4mL / min. While adding ethylene glycol, evaporate musk T. Use gas phase analysis to monitor whether the reaction is complete. The reaction is stopped when the content of musk T in the received fraction is less than 1%. The collected fractions are separated with a separatory funnel. The upper layer is the crude product of musk T (in the form of white oil). The lower ethylene glycol layer is applied and continued to be added to the depolymerization reaction liquid with a liquid phase pump. Repeat the above operation 6-7 times. The total depolymerization time is 20.1h, and finally 352.32g of crude musk T is obtained. The ethylene glycol layer is 708g, which can be used as a reactant for the next polymerization or a solvent for depolymerization.

[0075] S3 crude product refining

[0076] Wash three times with 35g water and 35g 10% sodium sulfate solution, and then collect the fractions by rectification under the conditions of vacuum degree 500pa, kettle temperature 195-215℃, top temperature 145-165℃ to obtain 289.67g finished musk-T with a purity of 98.8%. The calculated yield is 92.37%;

[0077] S4 recycling depolymerization

[0078] The residual liquid after distillation contains dimers and trimers with larger molecular weight, which are returned to the depolymerization kettle for re-depolymerization.

[0079] For other structures not described, refer to Example 1.

[0080] Example 5

[0081] The difference between this embodiment and embodiment 1 is that the ratio of the two raw materials of brazilic acid and ethylene glycol is 1:1.5, the polycondensation temperature is 175° C., and the depolymerizing agent is tetrabutyl titanate.

[0082] S1 polycondensation reaction

[0083] Weigh 280g of brazil acid and 106.69g of ethylene glycol respectively and add them into a 1L four-necked flask, then replace with nitrogen three times. Turn on the heating, raise the temperature to 175℃, keep warm for 3h, collect the water generated by polycondensation into the fraction bottle after condensation, when the gas phase temperature drops significantly, the normal pressure polymerization ends, then vacuum decompression is used to recover the excess ethylene glycol, the vacuum degree is 200pa, and the temperature is 165℃. Then take a sample to measure the acid value, the acid value is 1.75KOH mg / g.

[0084] S2 depolymerization cyclization

[0085] Take 0.65g of tetrabutyl titanate, a depolymerization catalyst, with a syringe and add it to the polymer reaction bottle in the previous step. After stirring evenly, start vacuuming and heating. When it rises to 220°C, weigh 803g of ethylene glycol and add ethylene glycol to the depolymerization reaction liquid with a liquid phase pump. The drop rate is 4mL / min. While adding ethylene glycol, evaporate musk T. Use gas phase analysis to monitor whether the reaction is complete. The content of musk T in the received fraction is less than 1%, so stop the reaction. The collected fractions are separated with a separatory funnel. The upper layer is the crude product of musk T (in the form of white oil), and the lower ethylene glycol layer is applied and continued to be added to the depolymerization reaction liquid with a liquid phase pump. Repeat the above operation 6-7 times. The total depolymerization time is 20.3h, and finally 360.82g of musk T crude product is obtained. The ethylene glycol layer is 712g, which can be used as a reactant for the next polymerization or a solvent for depolymerization.

[0086] S3 crude product refining

[0087] Wash three times with 36g water and 36g 10% sodium sulfate solution, and then collect the fractions by rectification under the conditions of vacuum degree 500pa, kettle temperature 195-215℃, top temperature 145-165℃ to obtain 289.57g finished musk-T with a purity of 98.9%. The calculated yield is 92.43%;

[0088] S4 recycling depolymerization

[0089] The residual liquid after distillation contains dimers and trimers with larger molecular weights, which are returned to the depolymerization kettle for re-depolymerization. For other structures not described, refer to Example 1.

[0090] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing musk-T, characterized in that: The following steps are involved: S1 polycondensation reaction Under nitrogen protection, brazil acid and ethylene glycol were added to the polymerization reaction vessel, and the temperature was raised. When the temperature reached 160°C, water droplets condensed at the condenser nozzle. The temperature was raised to 180°C and kept at this temperature for 3 hours. The condensed fraction entered the polymerization receiving kettle. After the normal pressure polymerization was completed, vacuum distillation was performed to evaporate the excess ethylene glycol until the polyester acid value was lower than 2.0KOHmg / g, and the polymerization reaction was terminated. S2 depolymerization cyclization After the polymerization reaction is completed, a depolymerization catalyst is added under nitrogen protection, and after stirring evenly, a vacuum pump is used to evacuate the mixture, and then a vacuum pump is used to evacuate the mixture, and the vacuum degree is controlled at 200-800Pa. The depolymerization reaction is carried out under reduced pressure, and when the temperature rises to 220°C, ethylene glycol is added dropwise, and the speed of adding ethylene glycol is kept consistent with the outflow speed of the fraction; The crude mixture of musk-T and ethylene glycol generated by the reaction overflows from the top of the kettle and enters the crude product receiving tank after condensation. The condensed mixture will be layered in the receiving tank, and the ethylene glycol obtained in the lower layer will be used back and continued to be added dropwise to the depolymerization kettle for use. The depolymerization reaction is completed to obtain the crude musk-T product. The ethylene glycol after the final layering is used in the next batch of polycondensation or depolymerization; S3 crude product refining The crude musk-T product is washed with water and sodium sulfate solution, and then distilled under the conditions of vacuum degree of 500 Pa and kettle temperature of 180-235°C, and the finished musk-T fraction is collected at a top temperature of 145-165°C; S4 recycling depolymerization The residual liquid after distillation contains dimers and trimers with larger molecular weight, which are returned to the depolymerization kettle for re-depolymerization.

2. The method for preparing musk-T according to claim 1, characterized in that: In the S1 polycondensation reaction, the molar ratio of the two raw materials, brazil acid and ethylene glycol, is 1:1-1.5, and the polycondensation temperature is 150-180°C.

3. The method for preparing musk-T according to claim 1, characterized in that: In the S1 polycondensation reaction, excess ethylene glycol is evaporated under reduced pressure, the pressure is 200 Pa, and the temperature is controlled at 165°C to 180°C.

4. The method for preparing musk-T according to claim 1, characterized in that: The depolymerization catalyst in S2 depolymerization and cyclization is at least one of isopropyl titanate, calcium chloride, magnesium chloride, magnesium acetate, manganese chloride, dibutyl tin oxide, and tetrabutyl titanate.

5. The method for preparing musk-T according to claim 1, characterized in that: The amount of the depolymerization catalyst used in S2 depolymerization cyclization is 0.2%-0.5%, based on the molar amount of brazil acid.

6. The method for preparing musk-T according to claim 1, characterized in that: The vacuum degree described in S2 depolymerization cyclization is 200-800Pa.

7. The method for preparing musk-T according to claim 1, characterized in that: In the refining of S3 crude product, based on the mass of the crude product, the amount of water is 10%, the amount of sodium sulfate solution is 10%; and the concentration of sodium sulfate is 10-15%.

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