Preparation process of 2, 2, 4-trimethyl-1, 3-pentanediol di-n-butyrate

Abstract

The invention belongs to the technical field of chemical materials, and particularly relates to a preparation process of 2, 2, 4-trimethyl-1, 3-pentanediol di-n-butyrate, which comprises the following steps: by adopting a specific acid catalyst, controlling the molar ratio of 2, 2, 4-trimethyl-1, 3-pentanediol to n-butyric acid to be (1: 2)-(1: 2.5), reacting at 120-170 DEG C for 5-10 hours, filtering, washing and drying to obtain 2, 2, 4-trimethyl-1, 3-pentanediol di-n-butyrate. The method comprises the steps of reaction in a reaction kettle, separation in a first rectifying tower, neutralization and extraction in an alkaline tower, refining in a second rectifying tower and the like. The process has the advantages of small catalyst dosage, strong selectivity, reusability, unique rectification and neutralization flow combination, reaction condition optimization, mild alkali liquor neutralization and effective waste treatment. According to the technology, the product purity reaches 98-99.5%, the conversion rate is 90-95%, and the technology has the advantages of being low in cost, environmentally friendly, efficient and the like and is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of chemical materials engineering technology, specifically relating to a preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate. Background Technology

[0002] Hexadecane diesters are widely used in many industries due to their diverse functions. Among them, 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate has been particularly prominent in the coatings field due to its excellent performance.

[0003] However, existing preparation processes for 2,2,4-trimethyl-1,3-pentanediol dibutyrate have many drawbacks. For example, Chinese patent CN111393288A discloses a synthesis process for 2,2,4-trimethyl-1,3-pentanediol dibutyrate and its application in interior wall latex paint. It uses 2,2,4-trimethyl-1,3-pentanediol and butyric acid as raw materials, reacting them in the presence of a catalyst to prepare 2,2,4-trimethyl-1,3-pentanediol dibutyrate. The catalyst is an inorganic salt catalyst, such as one of NaHSO4·H2O-NaH2PO4, NaHSO4·H2O-KH2PO4, NaHSO4·H2O-NH4H2PO4, NaHSO4·H2O-CuSO4·5H2O, or NaHSO4·H2O-Al2(SO4)3·18H2O. This reaction has many drawbacks, such as high catalyst cost and short lifespan, requiring frequent replacement and increasing production costs; the reaction easily generates a large amount of waste, increasing the environmental burden and not conforming to the concept of green chemistry; and the traditional process has complicated reaction steps and difficult to control conditions precisely, which can easily lead to low product purity and many by-products, affecting production efficiency and economic benefits, and making it difficult to meet the demand for high-quality and low-cost production.

[0004] Based on this, this application was developed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a process for preparing 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate. This process uses a novel acid catalyst that can be reused multiple times, reducing waste generation, simplifying the process flow, lowering production costs, and achieving a product purity of 98-99.5%, which meets the requirements of green chemistry development.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A process for preparing 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate involves reacting 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid at 120-170°C for 5-10 hours in the presence of an acid catalyst. After the reaction is complete, the product is obtained through post-treatment.

[0007] Specifically, the acid catalyst can be Nafion-H perfluorosulfonic acid resin, ion exchange resin with RF-SO3H functional group, or titanium dioxide supported phosphotungstic acid catalyst (PW@TiO2), etc.

[0008] Furthermore, the titanium dioxide-supported phosphotungstic acid catalyst (PW@TiO2) can be prepared via the following steps: Add titanium dioxide powder to an aqueous solution of phosphotungstic acid, stir at room temperature for 2-4 hours, let stand for 12-36 hours, heat to evaporate moisture, dry, grind into powder, and calcine at 500-600 ℃ for 3-5 hours to obtain the final product.

[0009] Furthermore, the ratio of titanium dioxide to phosphotungstic acid is 5-10 g: 8-45 mmol. For example, 5-10 g of titanium dioxide powder can be added to 80-150 mL of an aqueous solution of phosphotungstic acid with a concentration of 0.1-0.3 mol / L.

[0010] Specifically, the amount of acid catalyst added is 0.5-5% of the sum of the mass of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid.

[0011] Specifically, the molar ratio of 2,2,4-trimethyl-1,3-pentanediol to n-butyric acid can be 1:2-2.5. During the reaction, by controlling the molar ratio of 2,2,4-trimethyl-1,3-pentanediol to n-butyric acid and the reaction temperature, the content of the byproduct 2,2,4-trimethyl-1,3-pentanediol monobutyrate is controlled to be below 5%.

[0012] As a preferred embodiment, the preparation process of the above-mentioned 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate includes the following steps: S1 adds 2,2,4-trimethyl-1,3-pentanediol, n-butyric acid, and acid catalyst to a reactor. A water separator is used to discharge the water generated during the reaction into a recovery tower, and a filter is installed at the bottom outlet of the reactor to retain the acid catalyst. After the reaction is completed, the product is sent to the first distillation tower. In the first distillation column, S2 undergoes partial reflux operation. Part of the material is collected, condensed, and separated into phases by the first phase separator. The lower aqueous phase is discharged into the recovery column, and the upper organic phase is pumped into the mixing vessel as raw material for reuse. The bottom product of the column is a weakly acidic solution containing 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate, which is pumped into the alkaline column. The S3 alkaline tower is filled with alkaline solution, which is used to backwash, extract and neutralize the material. After that, the material is allowed to stand and separate into layers. The aqueous phase is discharged to the wastewater treatment plant, and the organic phase, which is crude ester, is fed into the second distillation tower. In the second distillation column of S4, the top product is high-purity 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate, which is then sent to the condenser. The final product, 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate, is collected and stored. The purity of the final product, 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate, can reach 98.5%-99.5%, and the conversion rate of 2,2,4-trimethyl-1,3-pentanediol is between 90% and 95%.

[0013] Furthermore, the filtration device installed at the bottom outlet of the reactor in step S1 can be a filter element, filter screen, or pipeline filter, etc., used to retain the acid catalyst for reuse. The process removes the water generated in the reaction in a timely manner through a water separator and discharges it into a recovery tower, promoting the forward reaction and achieving water resource recovery and utilization, thus reducing wastewater discharge.

[0014] Specifically, the first and second distillation columns achieve precise separation of each component by accurately controlling the vacuum level, reflux ratio, and the temperature at the top and bottom of the columns.

[0015] Furthermore, in step S2, the first distillation column is maintained at a vacuum of -0.092 to -0.098 MPa for distillation, with the reflux ratio controlled between 3:1 and 5:1, the top temperature at 140-165°C, and the bottom temperature at 160-185°C. The top product from the first distillation column contains unreacted n-butyric acid, 2,2,4-trimethyl-1,3-pentanediol, the byproduct 2,2,4-trimethyl-1,3-pentanediol monobutyrate, and residual water, etc.

[0016] Furthermore, the alkaline solution mentioned in step S3 is selected from one or more combinations of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate; the concentration of the alkaline solution is preferably 5-15% (mass percentage), which neutralizes and removes acidic impurities through backflushing extraction and avoids product loss or quality degradation.

[0017] Furthermore, in step S4, the vacuum degree in the second distillation column is controlled at -0.092 to -0.098 MPa for distillation, the reflux ratio is controlled at 3:1 to 5:1, the top temperature is 160-180℃, the bottom temperature is 180-200℃, and partial top reflux is carried out.

[0018] This invention utilizes a low-catalyst dosage, exhibits high selectivity, and allows for reusability. Its unique combination of distillation and neutralization optimizes reaction conditions, employs a mild alkaline solution for neutralization, and effectively treats waste. This process achieves a product purity of 98-99.5% and a conversion rate of 90-95%, offering advantages such as low cost, environmental friendliness, and high efficiency, making it suitable for large-scale production.

[0019] Compared with the prior art, the advantages and beneficial effects of the process of the present invention are as follows: 1) The process of this invention effectively reduces the formation of by-products by precisely controlling the raw material ratio, reaction temperature, and time, resulting in a final product purity of 98-99.5%, far exceeding the 90-95% of traditional processes. This high-purity 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate product better meets the stringent quality requirements of high-end coatings and other fields, enhancing product application performance and market competitiveness.

[0020] 2) Significantly reduced costs: Raw materials are widely available and highly utilized; unreacted materials can be recycled and reused, reducing material costs. Acid catalysts can be reused multiple times; for example, PW@TiO2 maintains high activity even after 10 cycles, significantly reducing the cost per use compared to traditional single-use inorganic salt catalysts. The simplified process reduces process costs, resulting in an overall production cost reduction of approximately 25%-30%, facilitating large-scale industrial production.

[0021] 3) Outstanding environmental benefits: The new acid catalyst reduces waste generation, the water produced by the reaction can be recycled, and the small amount of saline wastewater generated by alkali neutralization can be effectively treated, reducing environmental pollution and resource waste, meeting the requirements of green chemistry development, reducing the environmental pressure and costs of enterprises, and promoting sustainable development.

[0022] 4) Improved production efficiency: The unique catalyst system accelerates the reaction rate, shortening the reaction time to 5-10 hours, significantly improving reaction efficiency compared to the 15-20 hours of traditional processes. Simultaneously, the rationally designed distillation column and precisely controlled operating parameters enhance raw material utilization and product separation efficiency, further increasing production efficiency and boosting enterprise capacity and economic benefits. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0024] In the following examples, all raw materials used are common commercially available products that can be purchased directly, or can be prepared using conventional techniques in the art.

[0025] In the examples, the acid catalyst, titanium dioxide-supported phosphotungstic acid catalyst (PW@TiO2), was prepared via the following steps: Weigh 10g of titanium dioxide and add it to 100 mL of 0.2mol / L phosphotungstic acid aqueous solution. Stir at room temperature for 3 hours and let stand for 24 hours. Heat at 100℃ to evaporate the water, dry in a drying oven at 120℃ for 3 hours, grind into powder, and calcine in a muffle furnace at 550℃ for 4 hours to obtain the final product.

[0026] Room temperature refers to 23±2℃.

[0027] Example 1 A process for preparing 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate, comprising the following steps: In step S1, 2,2,4-trimethyl-1,3-pentanediol, n-butyric acid, and titanium dioxide-supported phosphotungstic acid catalyst (catalyst addition amount: 5% of the sum of the mass of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid, with a molar ratio of 2,2,4-trimethyl-1,3-pentanediol to n-butyric acid of 1:2) are added to the reactor. The reaction temperature is controlled at 120℃, and the reaction time is 5 hours. During the reaction, the water generated is discharged into a recovery tower using a water separator, and the acid catalyst is retained by a filter installed at the bottom outlet of the reactor. After the reaction is completed, the product is pumped to the first distillation column. In the first distillation column, S2 is subjected to vacuum distillation and partial reflux operation with a controlled vacuum of -0.095 MPa and a reflux ratio of 4:1. The top temperature is 149°C and the bottom temperature is 178°C. A portion of the material (i.e., unreacted material and byproducts from the top of the column) is collected, condensed, and separated into phases by the first phase separator. The lower aqueous phase is discharged into the recovery column, while the upper organic phase is pumped into the mixing vessel for reuse as feedstock. The bottom product is a weakly acidic solution containing 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate and is pumped into the alkaline column. The S3 alkaline tower is filled with a 10% sodium hydroxide alkaline solution. The alkaline solution is used to backwash, extract and neutralize the material. After that, the material is allowed to stand and separate into layers. The aqueous phase is discharged to the wastewater treatment plant, and the organic phase, which is crude ester, is fed into the second distillation tower. In the second distillation column S4, distillation was carried out under reduced vacuum of -0.095 MPa and a reflux ratio of 4:1. The top temperature was 169°C and the bottom temperature was 195°C. The high-purity 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate from the top of the column was then sent to a condenser. After partial reflux in the condenser, the final product, 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate, was pumped into a warehouse.

[0028] In this embodiment, the conversion rate of 2,2,4-trimethyl-1,3-pentanediol was 90%, and the content of the final 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate was 99.5%.

[0029] Example 2 The differences between this embodiment and Embodiment 1 are as follows; other aspects are the same as in Embodiment 1: The molar ratio of 2,2,4-trimethyl-1,3-pentanediol to n-butyric acid was 1:2.5. Titanium dioxide supported phosphotungstic acid catalyst (catalyst addition amount was 3% of the sum of the mass of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid) was used. The reaction temperature was 120℃ and the reaction time was 10h. The first distillation column has a vacuum of -0.093 MPa, a reflux ratio of 4:1, a top temperature of 155℃, and a bottom temperature of 185℃. The alkaline solution is 12% potassium hydroxide; The second distillation column has a vacuum of -0.093 MPa, a reflux ratio of 3:1, a top temperature of 175℃, and a bottom temperature of 197℃.

[0030] In this embodiment, the conversion rate of 2,2,4-trimethyl-1,3-pentanediol was 95%, and the content of the final 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate was 98.8%.

[0031] Example 3 The differences between this embodiment and Embodiment 1 are as follows; other aspects are the same as in Embodiment 1: The molar ratio of 2,2,4-trimethyl-1,3-pentanediol to n-butyric acid was 1:2.3. Titanium dioxide supported phosphotungstic acid catalyst (catalyst addition amount was 1% of the sum of the mass of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid) was used. The reaction temperature was 140℃ and the reaction time was 7h. The first distillation column has a vacuum of -0.095 MPa, a reflux ratio of 5:1, a top temperature of 148°C, and a bottom temperature of 178°C. The alkaline solution is 5% sodium bicarbonate; The second distillation column has a vacuum of -0.095 MPa, a reflux ratio of 5:1, a top temperature of 169°C, and a bottom temperature of 195°C.

[0032] In this embodiment, the conversion rate of 2,2,4-trimethyl-1,3-pentanediol was 93%, and the content of the final 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate was 98.3%.

[0033] Example 4 The differences between this embodiment and Embodiment 1 are as follows; other aspects are the same as in Embodiment 1: The molar ratio of 2,2,4-trimethyl-1,3-pentanediol to n-butyric acid was 1:2.2. Titanium dioxide supported phosphotungstic acid catalyst (catalyst addition amount was 2.6% of the sum of the mass of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid) was used. The reaction temperature was 125℃ and the reaction time was 8h. The first distillation column has a vacuum of -0.092 MPa, a reflux ratio of 4:1, a top temperature of 160℃, and a bottom temperature of 185℃. The alkaline solution is 10% potassium carbonate; The second distillation column has a vacuum of -0.095 MPa, a reflux ratio of 4:1, a top temperature of 169°C, and a bottom temperature of 195°C.

[0034] In this embodiment, the conversion rate of 2,2,4-trimethyl-1,3-pentanediol was 94%, and the content of the final 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate was 98%.

[0035] Example 5 The differences between this embodiment and Embodiment 1 are as follows; other aspects are the same as in Embodiment 1: The molar ratio of 2,2,4-trimethyl-1,3-pentanediol to n-butyric acid was 1:2.4. Titanium dioxide supported phosphotungstic acid catalyst (catalyst addition amount was 3.4% of the sum of the mass of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid) was used. The reaction temperature was 150℃ and the reaction time was 6h. The first distillation column has a vacuum of -0.094 MPa, a reflux ratio of 4:1, a top temperature of 153℃, and a bottom temperature of 180℃. The alkaline solution is a mixed solution of potassium carbonate, sodium bicarbonate, and potassium bicarbonate (mass ratio 1:1:1), with a concentration of 12%. The second distillation column has a vacuum of -0.095 MPa, a reflux ratio of 4:1, a top temperature of 170°C, and a bottom temperature of 196°C.

[0036] In this embodiment, the conversion rate of 2,2,4-trimethyl-1,3-pentanediol was 92%, and the content of the final 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate was 98.2%.

[0037] Comparative experiment To more intuitively demonstrate the advantages of the preparation process of this invention compared to traditional processes, this application conducted a detailed comparative synergistic experiment. Using a traditional inorganic salt catalytic preparation process as a control, under the same initial raw material amounts and similar reaction equipment conditions, two processes were employed to prepare 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate. Key indicators such as product yield, purity, catalyst cost, waste generation, and energy consumption were compared and analyzed.

[0038] Experimental Group: Following the process method of this invention, 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid were added to the reactor at a molar ratio of 1:2.2. A PW@TiO2 catalyst, accounting for 2.6% of the sum of the mass of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid, was added. The reaction temperature was controlled at 130°C, and the reaction time was 8 hours. During the reaction, the generated water was discharged into a recovery tower using a water separator, and the catalyst was retained in the reactor through a pipeline filter at the bottom of the reactor. After the reaction, the product was purified sequentially through a first distillation column (vacuum -0.095 MPa, reflux ratio 4:1, top temperature 150℃, bottom temperature 180℃), an alkaline column, and a second distillation column (vacuum -0.095 MPa, reflux ratio 4:1, top temperature 170℃, bottom temperature 195℃). The organic phase from the top of the first distillation column was returned to the mixing vessel as raw material for reuse. The bottom product was neutralized in an alkaline column (filled with 10% potassium carbonate solution) and then entered the second distillation column, finally yielding 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate.

[0039] Control group: Following the method of patent CN111393288A, the same amount of raw materials were used, and an inorganic salt catalyst (NaHSO4·H2O-KH2PO4) was employed for esterification. The catalyst dosage was 8% (mass ratio) of the sum of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid. The reaction temperature was 140℃, and the reaction time was 8 hours. After the reaction, the product was purified by conventional distillation and separation methods, but no dedicated catalyst recovery and raw material recycling device was installed.

[0040] Experimental group: After repeated experiments, the average yield reached 94.5%, and under certain optimized conditions, the yield could be further increased to over 95%. Control group: The average yield was only about 85%, significantly lower than the experimental group. This is mainly due to the more reasonable raw material ratio of the present invention, the higher catalyst activity, and the ability to ensure a more complete reaction. At the same time, the efficient design of the distillation column and the recycling of raw materials also contribute to improving the overall product yield.

[0041] Experimental group: Through precise control and optimized operation of the two-stage distillation column, the product purity remained stable between 98.8% and 99.2%, meeting the requirements of high-quality products and satisfying the application needs of the high-end market. Control group: The product purity fluctuated between 90% and 92%, with a significant amount of impurities. This is because traditional purification methods are relatively simple and difficult to effectively remove byproducts and impurities. The distillation process of this invention can more accurately separate and purify the target product, thereby significantly improving product purity.

[0042] Experimental Group: The catalyst used in this invention, such as PW@TiO2, exhibits excellent reusability, maintaining high activity even after multiple cycles. The catalyst cost per use is significantly lower than that of the single-use inorganic salt catalyst in the control group. Calculated per single reaction, the catalyst cost of the experimental group is only about 30% of that of the control group. Raw Material Costs: Due to the high raw material utilization rate of this invention, unreacted raw materials can be recovered through distillation and reused in the reaction, reducing actual raw material consumption and lowering raw material costs by approximately 20% compared to the control group. Energy Costs: Although this invention employs a two-stage distillation column, through precise optimization of distillation parameters, energy consumption has not increased significantly while ensuring product quality, remaining essentially equivalent to the energy cost of the control group. This is attributed to the synergistic optimization of each stage of the process, such as the rational control of reaction temperature and time, reducing unnecessary energy consumption. Control Group: Traditional processes, due to longer reaction times and lower purification efficiency, increase energy consumption to some extent. Overall, the production cost of the experimental group is reduced by approximately 25%-30% compared to the control group. This gives the process of this invention a significant cost advantage in large-scale industrial production, bringing higher economic benefits to enterprises.

[0043] Experimental Group: Throughout the preparation process, the amount of waste generated was significantly reduced due to the use of novel acid catalysts and optimized processes. The reuse of the catalyst reduced catalyst waste emissions, while precise reaction control and improved raw material utilization also reduced the generation of other byproducts and waste. Furthermore, through a rational distillation design, the water generated in the reaction and unreacted raw materials were effectively recovered and recycled, further reducing the environmental impact and aligning with the development concept of green chemistry. Using inorganic salt catalysts generates a large amount of waste containing metal ions after the reaction, requiring specialized treatment and increasing the environmental burden. Moreover, traditional processes have low raw material utilization rates, and the direct discharge or treatment of unreacted raw materials also leads to resource waste and environmental pollution.

[0044] The above comparative synergistic experiments clearly demonstrate that the preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate of the present invention has significant advantages in terms of product yield, purity, production cost, and environmental benefits. It overcomes many shortcomings of the prior art and provides a more efficient, environmentally friendly, and economical solution for the industrial production of this compound, with broad application prospects and important industrial value.

Claims

1. A process for preparing 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate, characterized in that, 2,2,4-Trimethyl-1,3-pentanediol and n-butyric acid are reacted at 120-170℃ for 5-10 hours in the presence of an acid catalyst. After the reaction is completed, the product is obtained after post-treatment.

2. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 1, characterized in that, The acid catalyst is a perfluorosulfonic acid resin Nafion-H, an ion exchange resin with RF-SO3H functional groups, or a titanium dioxide-supported phosphotungstic acid catalyst.

3. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 1, characterized in that, The titanium dioxide-supported phosphotungstic acid catalyst was prepared via the following steps: Add titanium dioxide to an aqueous solution of phosphotungstic acid, stir at room temperature for 2-4 hours, let stand, heat to evaporate the water, dry, grind into powder, and calcine at 500-600 ℃ for 3-5 hours to obtain the product.

4. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 3, characterized in that, The ratio of titanium dioxide to phosphotungstic acid is 5-10 g: 8-45 mmol.

5. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 1, characterized in that, The amount of acid catalyst added is 0.5-5% of the sum of the mass of 2,2,4-trimethyl-1,3-pentanediol and n-butyric acid.

6. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 1, characterized in that, The molar ratio of 2,2,4-trimethyl-1,3-pentanediol to n-butyric acid is 1:2-2.

5.

7. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 1, characterized in that, Includes the following steps: S1 adds 2,2,4-trimethyl-1,3-pentanediol, n-butyric acid, and acid catalyst to the reactor. The water generated during the reaction is discharged into the recovery tower using a water separator, and a filter device is installed at the bottom outlet of the reactor to retain the acid catalyst. After the reaction is completed, the product is sent to the first distillation tower. In the first distillation column, S2 undergoes partial reflux operation. Part of the material is collected, condensed, and separated into phases by the first phase separator. The lower aqueous phase is discharged into the recovery column, and the upper organic phase is pumped into the mixing vessel as raw material for reuse. The bottom product of the column is a weakly acidic solution containing 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate, which is pumped into the alkaline column. The S3 alkaline tower is filled with alkaline solution, which is used to backwash, extract and neutralize the material. After that, the material is allowed to stand and separate into layers. The aqueous phase is discharged to the wastewater treatment plant, and the organic phase, which is crude ester, is fed into the second distillation tower. In the second distillation column S4, the top product is sent to the condenser to obtain the product 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate.

8. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 1, characterized in that, In step S2, the vacuum level is maintained at -0.092 ~ -0.098 MPa for distillation, and the reflux ratio is controlled between 3:1 and 5:1, the top temperature is 140-165℃, and the bottom temperature is 160-185℃.

9. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 1, characterized in that, The alkaline solution mentioned in step S3 is selected from one or more combinations of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate; the concentration of the alkaline solution is 5-15%.

10. The preparation process of 2,2,4-trimethyl-1,3-pentanediol di-n-butyrate as described in claim 1, characterized in that, In step S4, the vacuum degree is controlled at -0.092 to -0.098 MPa for distillation, the reflux ratio is controlled at 3:1 to 5:1, the top temperature of the column is 160-180℃, and the bottom temperature of the column is 180-200℃.