A process for the preparation of dibutyl adipate

Abstract

The application provides a preparation method of dibutyl adipate, belongs to the technical field of organic compound preparation, and can solve the problems of low catalytic efficiency, low raw material conversion rate, and the problems of the obtained product after treatment, such as the presence of catalyst residues, flocculent turbid substances in the obtained product, and the significant influence on product quality. The technical scheme comprises the following steps: taking adipic acid and monohydric alcohol as raw materials, fully reacting in a reactor filled with an organotin salt supported catalyst to obtain crude dibutyl adipate, and then performing vacuum distillation, adsorption impurity removal and rectification stripping on the crude dibutyl adipate to obtain dibutyl adipate product, wherein the monohydric alcohol is n-butanol or isobutanol. The preparation method has the advantages of high raw material conversion rate, fast reaction rate, high product yield, product purity ≥ 99.5% after refining treatment, low impurity content, and compliance with the cosmetic product standard, and can be applied to cosmetics.

Description

Technical Field

[0001] This invention belongs to the field of organic compound preparation technology, and particularly relates to a method for preparing dibutyl adipate. Background Technology

[0002] Dibutyl adipate is a fatty acid ester organic compound commonly used as a plasticizer in vinyl resins, fiber resins, and synthetic rubber, as well as in nitrocellulose coatings. Due to its refreshing feel and good compatibility, dibutyl adipate is also widely used in high-end cosmetics, sunscreens, and skincare products. In sunscreens, dibutyl adipate exhibits excellent dissolving and dispersing effects on crystalline organic sunscreens and inorganic sunscreens such as zinc oxide / titanium dioxide, stabilizing the SPF / PA value and reducing greasiness. In cosmetics, dibutyl adipate improves application smoothness, reduces the coefficient of friction, prevents patchiness and caking, and enhances pigment dispersion and stability, improving color payoff and longevity. In skincare products, dibutyl adipate aids in moisturizing and water retention, is suitable for oily / combination skin, enhances formula solubility, and adjusts the viscosity of oil systems, resulting in a finer texture for lotions and creams.

[0003] Currently, the preparation methods of dibutyl adipate have the following problems: (1) slow reaction efficiency and low product yield; (2) low catalytic efficiency, many side reactions, and the catalyst cannot be reused; (3) high feed ratio and high production cost; (4) large wastewater volume and high treatment cost; (5) low product purity and poor quality.

[0004] Strong acid catalysis is a commonly used method for the preparation of dibutyl adipate. The synthetic route involves using adipic acid and n-butanol / isobutanol as raw materials, employing a strong acid catalyst, and undergoing an esterification reaction to synthesize dibutyl adipate. Although this reaction process is simple, it suffers from low catalyst selectivity, low product yield, and numerous reaction byproducts, resulting in poor product quality that, even after purification, fails to meet the requirements for cosmetic use.

[0005] Chinese invention patent CN104058964A discloses a method for preparing dibutyl adipate, using FeCl3·6H2O as a catalyst and adipic acid and n-butanol as raw materials, to synthesize dibutyl adipate under microwave conditions. However, this method has drawbacks such as excessively high feed ratios and difficulty in industrializing the microwave process.

[0006] Chinese invention patent CN121270385A discloses a dibutyl adipate, its preparation method, and its application. The raw materials for preparation include adipic acid, n-butanol, and a catalyst. However, this method has the disadvantages of slow reaction rate, many impurities in the product, and poor product stability.

[0007] Therefore, there is a need to provide a method for preparing dibutyl adipate to improve the above-mentioned problems. Summary of the Invention

[0008] This invention addresses the technical problems of existing methods for preparing dibutyl adipate, such as low catalytic efficiency, low raw material conversion rate, easy presence of catalyst residue after post-processing, and the presence of flocculent turbidity in the product, which significantly affects product quality. The invention proposes a method for preparing dibutyl adipate with high raw material conversion rate, fast reaction rate, and high product yield. After purification, the product purity is ≥99.5%, with low impurity content and excellent product quality, making it suitable for the cosmetics industry.

[0009] To achieve the above objectives, the technical solution adopted by this invention is as follows: a method for preparing dibutyl adipate, comprising the following steps: using adipic acid and a monohydric alcohol as raw materials, reacting them fully in a reactor filled with an organotin salt supported catalyst to obtain crude dibutyl adipate; then subjecting the crude dibutyl adipate to vacuum distillation for alcohol removal, adsorption for impurity removal, and distillation stripping to obtain the dibutyl adipate product; wherein the molar ratio of monohydric alcohol to adipic acid is 3-6:1; the feeding time is 1-3 hours; and the reaction temperature during the feeding process is gradually increased from 110±10℃ to 190℃. ±20℃; the mass ratio of the organotin salt supported catalyst m1 to the total mass of the raw materials m2 satisfies m1:m2=0.3-0.7wt%:1; the reaction temperature in the reactor is 170-210℃, and the reaction time is 6-10h; the temperature for de-alcoholization by vacuum distillation is 130-190℃, and the vacuum degree is 10-50mbar; the adsorption temperature for impurity removal is 50-80℃, and the adsorption time is 1-2h; the temperature for stripping by distillation is 150-210℃, and the vacuum degree is 1-10mbar; the monohydric alcohol is n-butanol or isobutanol.

[0010] It is understood that, based on actual circumstances, those skilled in the art can adjust the molar ratio of monohydric alcohol to adipic acid within the above range. For example, the molar ratio of monohydric alcohol to adipic acid can also be 3:1, 4:1, 5:1, 6:1, or any value within the above range. Similarly, those skilled in the art can adjust the ratio of the mass m1 of the organotin salt supported catalyst to the mass m2 of the total raw materials within the above range. For example, the ratio of the mass m1 of the organotin salt supported catalyst to the mass m2 of the total raw materials can also be 0.3wt%:1, 0.4wt%:1, or 0.5wt%. wt%: 1, 0.6wt%: 1, 0.7wt%: 1, or any value within the above range; those skilled in the art can adjust the reaction temperature and reaction time in the reactor within the above range according to actual conditions. For example, the reaction temperature can also be 170℃, 180℃, 190℃, 200℃, 210℃, or any value within the above range, and the reaction time can also be 6h, 7h, 8h, 9h, 10h, or any value within the above range; those skilled in the art can adjust the temperature and vacuum degree of vacuum distillation deethanolination within the above range according to actual conditions. For example, the temperature for vacuum distillation dehydrogenation can be 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, or any value within the above range; the vacuum degree can also be 10mba, 20mba, 30mba, 40mba, 50mba, or any value within the above range. Those skilled in the art can adjust the adsorption temperature and adsorption time within the above range according to actual conditions. For example, the adsorption temperature can also be 50℃, 60℃, 70℃, 80℃, or any value within the above range, and the adsorption time can also be adjusted accordingly. The temperature and vacuum level can be set to 1h, 2h, or any value within the above range. Those skilled in the art can adjust the temperature and vacuum level within the above range according to actual conditions. For example, the temperature of the distillation stripping can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, or any value within the above range, and the vacuum level can be 1mbar, 2mbar, 3mbar, 4mbar, 5mbar, 6mbar, 7mbar, 8mbar, 9mbar, 10mbar, or any value within the above range.

[0011] In one embodiment, the organotin salt supported catalyst has an organotin salt loading of 3-8 wt%. The use of this organotin salt supported catalyst in this invention is beneficial for improving catalytic efficiency.

[0012] It is understood that, depending on the actual situation, those skilled in the art can adjust the loading of the active precursor in the organotin salt supported catalyst within the above range. For example, the loading of organotin salt in the organotin salt supported catalyst can also be 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, or any point value within the above range.

[0013] In one embodiment, the organotin salt supported catalyst includes an active precursor and a support, wherein the active precursor is selected from at least one of dibutyltin dilaurate, dibutyltin dioctanoate, dibutyltin oxide, and butyltin chloride; and the support is selected from at least one of inorganic oxides, carbon materials, and molecular sieves.

[0014] In one embodiment, the reaction ends when the concentration of adipic acid in the reaction system is <0.3wt%.

[0015] In one embodiment, the adsorption and impurity removal includes a first-stage adsorption and a second-stage adsorption. After each stage of adsorption, the particles are filtered out. The filter membrane has a pore size of 1-10 μm. The first-stage adsorbent is a mixture of activated clay, activated carbon, diatomaceous earth, and bentonite, and the second-stage adsorbent is a macroporous adsorption resin.

[0016] In one embodiment, the product yield of dibutyl adipate is >95wt%, and the purity of dibutyl adipate is ≥99.5wt%.

[0017] In one embodiment, the step of adding an oil antioxidant to the dibutyl adipic acid product is further included, wherein the oil antioxidant is selected from at least one of tocopherol, tocopherol acetate, rosemary extract, and 2,6-di-tert-butyl-p-cresol.

[0018] Compared with the prior art, the advantages and positive effects of the present invention are as follows: The preparation method of dibutyl adipic acid provided by the present invention improves the reaction efficiency and product yield, and the obtained product has high purity and good quality, which can be applied in cosmetics; the present invention uses an organotin salt supported catalyst, which has high catalytic efficiency, reduces side reactions, and the catalyst can be reused; the molar ratio of monohydric alcohol to adipic acid in the present invention is 3-6:1, which reduces the feeding ratio and raw material loss, and reduces production costs; the crude product obtained by the present invention is treated by vacuum distillation for alcohol removal, adsorption for impurity removal, and distillation stripping, without the need for a water washing step, reducing wastewater discharge, and the product meets the national standard GB 4806.1-2016 (tin ≤50mg / kg). Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the preparation method of dibutyl adipate provided in the embodiments of the present invention;

[0020] In the diagram, 1 is the adipic acid feed tank, 2 is the monohydric alcohol feed tank, 3 is the fixed-bed reactor, 4 is the condenser, and 5 is the reaction vessel. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a method for preparing dibutyl adipic acid, see attached figure. Figure 1 As shown, this invention uses adipic acid and a monohydric alcohol as raw materials, and carries out an esterification reaction in a fixed-bed reactor 3 filled with an organotin salt supported catalyst to obtain crude dibutyl adipate. The crude dibutyl adipate is then subjected to vacuum distillation for alcohol removal, adsorption for impurity removal, and distillation stripping to obtain the final dibutyl adipate product. The monohydric alcohol is either n-butanol or isobutanol. This invention improves catalytic selectivity and product yield by optimizing the synthesis process and post-refining steps, further refining the product to obtain high-quality dibutyl adipate that meets cosmetic-grade standards and can be used in cosmetics. In actual production applications, it has gained widespread recognition from downstream cosmetic customers.

[0023] The present invention provides a method for preparing dibutyl adipate, comprising: melting adipic acid and feeding it from the top of a fixed-bed reactor 3 loaded with an organotin salt supported catalyst; feeding a monohydric alcohol from the bottom of the fixed-bed reactor 3; after sufficient reaction, removing alcohol by vacuum distillation to obtain crude dibutyl adipate; and then obtaining the dibutyl adipate product by adsorption filtration and distillation stripping.

[0024] In the preparation method steps of the present invention, the mass ratio of the organotin salt supported catalyst m1 to the total mass m2 of the raw materials is m1:m2 = 0.3-0.7wt%:1; the organotin salt supported catalyst includes an active precursor and a support, and the loading of the active precursor in the organotin salt supported catalyst is 3-8wt%; wherein, the active precursor is selected from at least one of dibutyltin dilaurate (DBTDL), dibutyltin dioctanoate (DBTO), dibutyltin oxide (DBTO2), and butyltin chloride (MBTC); the support is selected from at least one of inorganic oxides, carbon materials, and molecular sieves, preferably, the support is SBA-15 molecular sieve.

[0025] Preferably, the organotin salt supported catalyst is prepared by co-precipitation.

[0026] In one embodiment, the organotin salt supported catalyst uses SBA-15 molecular sieve as a support and dibutyltin oxide as an active precursor. The preparation method includes the following steps: after the SBA-15 molecular sieve is activated by calcination at 100-130℃ for 4-6 hours, it is dispersed in anhydrous ethanol and dissolved by adding dibutyltin oxide; deionized water is added dropwise to precipitate, and ammonia is added dropwise to adjust the pH to neutral. The precipitation loading time is 4-12 hours; after the precipitate is washed by centrifugation, it is dried at 80-100℃ for 2-6 hours and then calcined at 200-400℃ in a nitrogen atmosphere for 1-5 hours to solidify, thereby obtaining the organotin salt supported catalyst.

[0027] In the preparation method steps of the present invention, the purity of adipic acid is ≥99%, the purity of the monohydric alcohol is ≥99%, and the molar ratio of monohydric alcohol to adipic acid is 3-6:1; the melting temperature of adipic acid is 160℃, the feeding temperature of the monohydric alcohol is 100-120℃, the feeding time is 1-3h, and the reaction temperature during the feeding process is gradually increased from 110±10℃ to 190±20℃; the reaction ends when the concentration of adipic acid in the reaction system is <0.3wt%.

[0028] In the preparation method steps of the present invention, after the feeding is completed, the reaction temperature is 170-210℃ and the reaction time is 6-10h, that is, the residence time of the material in the fixed bed is 6-10h; the reaction is carried out under normal pressure or positive pressure conditions. During the reaction, the azeotrope of monohydric alcohol and water is discharged from the top of the fixed bed reactor 3. After being condensed and separated by the condenser 4, the recovered monohydric alcohol is returned to the reaction system from the bottom of the fixed bed reactor 3. The aqueous phase after condensation and separation is distilled to separate the dissolved monohydric alcohol. The recovered raw material is tested for purity and reused. During the reaction, the reaction product is discharged from the bottom of the fixed bed reactor 3 and returned to the reaction system from the top of the fixed bed reactor 3 after passing through the reaction vessel 5.

[0029] In the preparation method steps of the present invention, the vacuum distillation temperature is 130-190℃ and the vacuum degree is 10-50mbar; in the vacuum distillation step, water vapor or inert gas is introduced into the bottom of the distillation vessel to carry out the residual alcohol; after alcohol removal, the butanol content in dibutyl adipic acid is <0.1%, and the removed butanol can be reused.

[0030] In the above preparation method of the present invention, the adsorption temperature for adsorption and impurity removal is 50-80℃, and the residence time is 1-2h. The adsorption and impurity removal includes a first-stage adsorption and a second-stage adsorption. The first-stage adsorbent is a mixture of activated clay, activated carbon, diatomaceous earth, and bentonite to remove colored impurities, residual catalysts, and a small amount of colloids and suspended solids. Preferably, the mass ratio of activated clay, activated carbon, diatomaceous earth, and bentonite in the first-stage adsorbent is 1:1:1:1. The second-stage adsorbent is a macroporous adsorption resin to remove non-polar or weakly polar organic impurities and odorous substances. Preferably, the macroporous adsorption resin is a styrene-based or propionate-based resin. After each stage of adsorption and impurity removal, the particles are filtered to retain the filter membrane, and the pore size is 1-10μm.

[0031] In the preparation method steps of the present invention, the distillation stripping temperature is 150-210℃ and the vacuum degree is 1-10mbar to further remove impurities; after purification, the yield of dibutyl adipate product is >95wt%, the concentration of dibutyl adipate is >99.5wt%, and the purity of dibutyl adipate can be further improved according to requirements.

[0032] To ensure product stability, an oil antioxidant can be added to the dibutyl adipic acid product. The oil antioxidant is selected from at least one of tocopherol, tocopherol acetate, rosemary extract, and 2,6-di-tert-butyl-p-cresol.

[0033] The dibutyl adipate product prepared by this invention is colorless and odorless or has the special odor of the ester itself, meeting the requirements for high-quality raw materials in cosmetics.

[0034] To provide a clearer and more detailed description of the preparation method of dibutyl adipate provided in the embodiments of the present invention, specific examples will be described below.

[0035] Example 1

[0036] The preparation method of dibutyl adipate in this embodiment includes the following steps:

[0037] 4.54 g of organotin salt supported catalyst was loaded into fixed-bed reactor 3. The fixed-bed reactor 3 was preheated to 115 °C under a nitrogen atmosphere, adipic acid was preheated to 160 °C, and n-butanol was preheated to 115 °C. The addition ratio of organotin salt supported catalyst was 0.5 wt%. The active precursor of organotin salt supported catalyst was dibutyltin dioctanoate, and the loading of dibutyltin dioctanoate was 5 wt%. The support was SBA-15 molecular sieve.

[0038] 300g of molten adipic acid was added dropwise from the top of fixed-bed reactor 3, and 609g of n-butanol was added dropwise from the bottom of fixed-bed reactor 3. The molar ratio of n-butanol to adipic acid was 4:1, and the feeding time was 2h. During the feeding process, the reaction temperature was gradually increased from 115℃ to 190℃. After the feeding was completed, the reaction continued for 8h until the concentration of adipic acid in the reaction system was <0.3wt%, at which point the reaction ended. During the reaction, the azeotrope of n-butanol and water was discharged from the top of fixed-bed reactor 3. After being condensed and separated by condenser 4, the recovered n-butanol was returned to the reaction system from the bottom of fixed-bed reactor 3. During the reaction, the reaction product was discharged from the bottom of fixed-bed reactor 3, passed through reactor 5, and then returned to the reaction system from the top of fixed-bed reactor 3.

[0039] Under conditions of 160℃ and 15mbar vacuum, the reaction solution after complete reaction was subjected to vacuum distillation to remove excess butanol from the system, yielding crude dibutyl adipic acid. The butanol content in the dibutyl adipic acid after removal was <0.05%.

[0040] At 60℃, crude dibutyl adipate was sequentially subjected to a first-stage adsorption process using a mixture of activated clay, activated carbon, diatomaceous earth, and bentonite in a mass ratio of 1:1:1:1, followed by a second-stage adsorption process using macroporous adsorption resin to remove residual impurities. Then, it was subjected to distillation stripping at 180℃ and a vacuum of 1 mbar to obtain a colorless and odorless dibutyl adipate product with a purity of 99.6% and a calculated yield of 96.3 wt%.

[0041] Example 2

[0042] The preparation method of dibutyl adipate in this embodiment includes the following steps:

[0043] 6.23 g of organotin salt supported catalyst was loaded into fixed-bed reactor 3. The fixed-bed reactor 3 was preheated to 115 °C under a nitrogen atmosphere, adipic acid was preheated to 160 °C, and n-butanol was preheated to 115 °C. The addition ratio of organotin salt supported catalyst was 0.7 wt%. The active precursor of organotin salt supported catalyst was dibutyltin dioctanoate, and the loading of dibutyltin dioctanoate was 3 wt%. The support was SBA-15 molecular sieve.

[0044] 220g of molten adipic acid was added dropwise from the top of fixed-bed reactor 3, and 669g of n-butanol was added dropwise from the bottom of fixed-bed reactor 3. The molar ratio of n-butanol to adipic acid was 6:1, and the feeding time was 1 hour. During the feeding process, the reaction temperature was gradually increased from 115℃ to 170℃. After the feeding was completed, the reaction continued for 6 hours until the concentration of adipic acid in the reaction system was <0.3wt%, at which point the reaction ended. During the reaction, the azeotrope of n-butanol and water was discharged from the top of fixed-bed reactor 3. After being condensed and separated by condenser 4, the recovered n-butanol was returned to the reaction system from the bottom of fixed-bed reactor 3. During the reaction, the reaction product was discharged from the bottom of fixed-bed reactor 3, passed through reactor 5, and then returned to the reaction system from the top of fixed-bed reactor 3.

[0045] Under conditions of 160℃ and 15mbar vacuum, the reaction solution after complete reaction was subjected to vacuum distillation to remove excess butanol from the system, yielding crude dibutyl adipic acid. The butanol content in the dibutyl adipic acid after removal was <0.05%.

[0046] At 60℃, crude dibutyl adipate was sequentially subjected to a first-stage adsorption process using a mixture of activated clay, activated carbon, diatomaceous earth, and bentonite in a mass ratio of 1:1:1:1, followed by a second-stage adsorption process using macroporous adsorption resin to remove residual impurities. Then, it was subjected to distillation stripping at 180℃ and a vacuum of 1 mbar to obtain a colorless and odorless dibutyl adipate product with a purity of 99.6% and a calculated yield of 96.9 wt%.

[0047] Example 3

[0048] The preparation method of dibutyl adipate in this embodiment includes the following steps:

[0049] 2.65 g of organotin salt supported catalyst was loaded into fixed-bed reactor 3. The fixed-bed reactor 3 was preheated to 115 °C under a nitrogen atmosphere, adipic acid was preheated to 160 °C, and n-butanol was preheated to 115 °C. The addition ratio of organotin salt supported catalyst was 0.3 wt%. The active precursor of organotin salt supported catalyst was dibutyltin dioctanoate, and the loading of dibutyltin dioctanoate was 8 wt%. The support was SBA-15 molecular sieve.

[0050] 350g of molten adipic acid was added dropwise from the top of fixed-bed reactor 3, and 533g of n-butanol was added dropwise from the bottom of fixed-bed reactor 3. The molar ratio of n-butanol to adipic acid was 3:1, and the feeding time was 3h. During the feeding process, the reaction temperature was gradually increased from 115℃ to 210℃. After the feeding was completed, the reaction continued for 10h until the concentration of adipic acid in the reaction system was <0.3wt%, at which point the reaction ended. During the reaction, the azeotrope of n-butanol and water was discharged from the top of fixed-bed reactor 3. After being condensed and separated by condenser 4, the recovered n-butanol was returned to the reaction system from the bottom of fixed-bed reactor 3. During the reaction, the reaction product was discharged from the bottom of fixed-bed reactor 3, passed through reactor 5, and then returned to the reaction system from the top of fixed-bed reactor 3.

[0051] Under conditions of 160℃ and 15mbar vacuum, the reaction solution after complete reaction was subjected to vacuum distillation to remove excess butanol from the system, yielding crude dibutyl adipic acid. The butanol content in the dibutyl adipic acid after removal was <0.05%.

[0052] At 60℃, crude dibutyl adipate was sequentially subjected to a first-stage adsorption process using a mixture of activated clay, activated carbon, diatomaceous earth, and bentonite in a mass ratio of 1:1:1:1, followed by a second-stage adsorption process using macroporous adsorption resin to remove residual impurities. Then, it was subjected to distillation stripping at 180℃ and a vacuum of 1 mbar to obtain a colorless and odorless dibutyl adipate product with a purity of 99.5% and a calculated yield of 95.5 wt%.

[0053] Example 4

[0054] The preparation method of dibutyl adipate in this embodiment includes the following steps:

[0055] 6.44 g of organotin salt supported catalyst was loaded into fixed-bed reactor 3. The fixed-bed reactor 3 was preheated to 115 °C under a nitrogen atmosphere, adipic acid was preheated to 160 °C, and isobutanol was preheated to 115 °C. The addition ratio of organotin salt supported catalyst was 0.7 wt%. The active precursor of organotin salt supported catalyst was dibutyltin oxide, and the loading of dibutyltin oxide was 6 wt%. The support was SBA-15 molecular sieve.

[0056] 260g of molten adipic acid was added dropwise from the top of fixed-bed reactor 3, and 659g of isobutanol was added dropwise from the bottom of fixed-bed reactor 3. The molar ratio of isobutanol to adipic acid was 5:1, and the feeding time was 2.5h. During the feeding process, the reaction temperature was gradually increased from 115℃ to 205℃. After the feeding was completed, the reaction continued for 9.5h until the concentration of adipic acid in the reaction system was <0.3wt%, at which point the reaction ended. During the reaction, the azeotrope of isobutanol and water was discharged from the top of fixed-bed reactor 3. After being condensed and separated by condenser 4, the recovered n-butanol was returned to the reaction system from the bottom of fixed-bed reactor 3. During the reaction, the reaction products were discharged from the bottom of fixed-bed reactor 3, passed through reactor 5, and then returned to the reaction system from the top of fixed-bed reactor 3.

[0057] Under conditions of 160℃ and 15mbar vacuum, the reaction solution after complete reaction was subjected to vacuum distillation to remove excess butanol from the system, yielding crude dibutyl adipic acid. The butanol content in the dibutyl adipic acid after removal was <0.05%.

[0058] At 60℃, crude dibutyl adipate was sequentially subjected to a first-stage adsorption process using a mixture of activated clay, activated carbon, diatomaceous earth, and bentonite in a mass ratio of 1:1:1:1, followed by a second-stage adsorption process using macroporous adsorption resin to remove residual impurities. Then, it was subjected to distillation stripping at 180℃ and a vacuum of 1 mbar to obtain a colorless and odorless dibutyl adipate product with a purity of 99.5% and a calculated yield of 95.1 wt%.

[0059] Sensory evaluation of the dibutyl adipic acid obtained in Examples 1-4 showed that the product was colorless and odorless, with a slightly oily feel, obvious slipperiness, strong sealing properties, easy to spread, good moisturizing effect, and long-lasting slipperiness; no change was observed when the product was placed at 100℃ for 12 hours; no chromatography was observed when the product was centrifuged at 3000 rpm / 60 min; the product was completely miscible when mixed with silicone oil, mineral oil, vegetable oil, and sunscreen agent respectively.

[0060] As can be seen from the above, the dibutyl adipic acid obtained by the preparation method of the present invention has a high raw material conversion rate, a high product yield (>95wt%), a product purity (≥99.5wt%), and a low impurity content, which meets the cosmetic grade product standard and can be used in cosmetics.

[0061] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, alterations, evolutions, or improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing dibutyl adipate, characterized in that, The process includes the following steps: using adipic acid and monohydric alcohol as raw materials, the mixture is fully reacted in a reactor filled with an organotin salt supported catalyst to obtain crude dibutyl adipate. The crude dibutyl adipate is then subjected to vacuum distillation to remove alcohol, adsorption to remove impurities, and distillation stripping to obtain a dibutyl adipate product with a purity ≥99.5 wt%, meeting cosmetic-grade product standards and suitable for cosmetic applications. The molar ratio of monohydric alcohol to adipic acid is 3-6:1; the feeding time is 1-3 hours; and the reaction temperature is gradually increased from 110±10℃ to 190±20℃ during the feeding process. The organotin salt supported catalyst includes an active precursor and a support, wherein the active precursor is selected from dibutyltin dilaurate and dioctanoic acid. At least one of butyltin, dibutyltin oxide, and butyltin chloride; the support is SBA-15 molecular sieve; the mass ratio of the organotin salt supported catalyst m1 to the total mass of the raw materials m2 satisfies m1:m2=0.3-0.7wt%:1; the reaction temperature in the reactor is 170-210℃, the reaction time is 6-10h, and the reaction is carried out under normal or positive pressure conditions; the temperature for vacuum distillation de-alcoholization is 130-190℃, and the vacuum degree is 10-50mbar; the adsorption temperature for adsorption and impurity removal is 50-80℃, and the adsorption time is 1-2h; the temperature for distillation stripping is 150-210℃, and the vacuum degree is 1-10mbar; the monohydric alcohol is n-butanol or isobutanol.

2. The method for preparing dibutyl adipate according to claim 1, characterized in that, The loading of active precursor in organotin salt supported catalysts is 3-8 wt%.

3. The method for preparing dibutyl adipate according to claim 1, characterized in that, The reaction ends when the concentration of adipic acid in the reaction system is <0.3wt%.

4. The method for preparing dibutyl adipate according to claim 1, characterized in that, Adsorption and impurity removal includes primary adsorption and secondary adsorption. After each adsorption stage, the particles are filtered out. The filter membrane has a pore size of 1-10 μm. The primary adsorbent is a mixture of activated clay, activated carbon, diatomaceous earth, and bentonite, while the secondary adsorbent is a macroporous adsorption resin.

5. The method for preparing dibutyl adipate according to claim 1, characterized in that, The yield of dibutyl adipic acid is >95 wt%.

6. The method for preparing dibutyl adipate according to claim 1, characterized in that, It also includes the step of adding an oil antioxidant to the dibutyl adipic acid product, wherein the oil antioxidant is selected from at least one of tocopherol, tocopherol acetate, rosemary extract, and 2,6-di-tert-butyl-p-cresol.

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