Preparation method for improving purity of BDO

Abstract

The invention discloses a preparation method for improving the purity of BDO, which comprises the following steps: S1, putting sulfonic acid type ion exchange resin into a vacuum drying oven, and then cooling to room temperature to form a solid acid catalyst; s2, filling a reaction section of a catalytic distillation reactor with a solid acid catalyst, and introducing reaction raw materials into the reactor; s3, sequentially carrying out high-temperature, medium-temperature and low-temperature stepped cooling catalytic distillation by using a catalytic distillation reactor, adding an inhibitor at a low-temperature stage, and forming a reaction mixture when the temperature fluctuates within a range of + / -1 DEG C; s4, discharging the reaction mixture to a gas-liquid separator, recovering unreacted hydrogen through a recovery device, and collecting low-boiling-point byproducts through a condensing device to obtain residual liquid; s5, enabling the residual liquid to enter a rectifying tower for rectification; by adopting a stepped cooling catalytic distillation mode, the BDO purity can be improved, the impurity content can be reduced, the physical property can be optimized, and the stability can be enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of BDO purification, and particularly to a preparation method for improving the purity of BDO. Background Art

[0002] 1,4 - Butanediol (BDO) is an important organic chemical and fine chemical raw material, with wide and key applications in multiple fields. In the polyurethane industry, it is an important raw material for producing polyurethane elastomers and polyurethane fibers (spandex), endowing products with excellent elasticity, wear resistance, and chemical corrosion resistance. In the polyester industry, BDO is used to synthesize polybutylene terephthalate (PBT) resin, which has good mechanical properties, electrical properties, and processing properties, and is widely used in fields such as electronics and electrical appliances, and automotive parts.

[0003] Currently, the main preparation methods of BDO include the alkynal method, maleic anhydride hydrogenation method, butadiene acetoxylation method, etc. The alkynal method is the earliest industrialized production method, which uses acetylene and formaldehyde as raw materials, reacts under the action of a catalyst to generate 1,4 - butynediol, and then obtains BDO through hydrogenation.

[0004] In the traditional BDO preparation process, due to the complexity of the reaction and the occurrence of side reactions, the obtained BDO products often contain various impurities, such as unreacted raw materials, intermediate products, by - products, etc. The presence of these impurities will not only affect the quality and performance of BDO, but also have an adverse impact on the production and application of its downstream products.

[0005] Therefore, it is necessary to provide a preparation method for improving the purity of BDO to solve the above - mentioned technical problems. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a preparation method for improving the purity of BDO.

[0007] To achieve the above - mentioned purpose, the technical solution adopted by the present invention is: a preparation method for improving the purity of BDO, comprising the following steps:

[0008] S1: Place the sulfonic acid - type ion - exchange resin in a vacuum drying oven, and then cool it to room temperature to form a solid - acid catalyst;

[0009] S2: Load the solid - acid catalyst into the reaction section of a catalytic distillation reactor, and introduce the reaction raw materials into the reactor;

[0010] S3: Use the catalytic distillation reactor to carry out step - by - step cooling catalytic distillation at high temperature, medium temperature, and low temperature in sequence, and add an inhibitor in the low - temperature stage, with the temperature fluctuation within the range of ±1°C, and the stirring speed controlled at 100 - 300 r / min to form a reaction mixture;

[0011] S4: Discharge the reaction mixture into a gas-liquid separator, and recover the unreacted hydrogen through a recovery device.

[0012] The liquid remaining after collecting the low-boiling by-products through a condensing device;

[0013] S5: Feed the remaining liquid into a distillation column for rectification.

[0014] In a preferred embodiment of the present invention, in the step S1, the temperature range of the vacuum drying oven is 100 - 120 °C, and the drying time range is 4 - 6 h.

[0015] In a preferred embodiment of the present invention, in the step S2, the mass ratio of the solid acid catalyst to the reaction raw materials is 1:1.

[0016] In a preferred embodiment of the present invention, in the step S2, the reaction raw materials are maleic anhydride and hydrogen, the molar ratio of maleic anhydride to hydrogen is 1:4 - 6, the feed flow rate range of maleic anhydride is 0.1 - 1 L / h, and the feed flow rate range of hydrogen is 100 - 300 L / h.

[0017] In a preferred embodiment of the present invention, in the step S3, the high-temperature catalytic distillation step includes a cooling stage and a reaction stage. In the high-temperature stage, the temperature inside the reactor is increased to 150 - 200 °C at a heating rate of 5 - 10 °C / min; in the reaction stage, the reaction is carried out at a temperature of 150 - 200 °C for 2 - 3 h.

[0018] In a preferred embodiment of the present invention, in the step S3, the medium-temperature catalytic distillation step includes a cooling stage and a reaction stage. In the cooling stage, the temperature is decreased to 100 - 150 °C at a cooling rate of 3 - 5 °C / min; in the reaction stage, the reaction is carried out at a temperature of 100 - 150 °C for 3 - 4 h.

[0019] In a preferred embodiment of the present invention, in the step S3, the low-temperature catalytic distillation step includes a cooling stage and a reaction stage. In the cooling stage, the temperature is decreased to 50 - 100 °C at a cooling rate of 2 - 3 °C / min; in the reaction stage, the reaction is carried out at a temperature of 50 - 100 °C for 4 - 6 h.

[0020] In a preferred embodiment of the present invention, in the step S3, the inhibitor is hydroquinone, and the inhibitor accounts for 0.1 - 0.5% of the total mass of the reactants.

[0021] In a preferred embodiment of the present invention, in the step S4, the pressure of the gas-liquid separator is controlled at 0 - 500 kPa, and the temperature is controlled at 20 - 80 °C.

[0022] In a preferred embodiment of the present invention, in the step S5, the reflux ratio of the distillation column is controlled at 2 - 5, the top temperature of the column is controlled at 50 - 100 °C, and the bottom temperature of the column is controlled at 230 - 250 °C.

[0023] The present invention solves the defects existing in the background art and has the following beneficial effects:

[0024] (1) The present invention provides a preparation method for improving the purity of BDO. By adopting a stepped cooling catalytic distillation method at high temperature, medium temperature, and low temperature, the high-temperature stage can quickly initiate the reaction, accelerate the reaction rate, and promote the preliminary reaction of maleic anhydride and hydrogen. The medium-temperature stage helps the further conversion of reaction intermediates and reduces the occurrence of side reactions. The low-temperature stage is conducive to improving the selectivity of the reaction, making the reaction more inclined to produce BDO, thereby improving the purity of BDO. And hydroquinone is added as an inhibitor in the low-temperature stage, and the addition of the inhibitor can effectively inhibit some unnecessary side reactions.

[0025] (2) The present invention provides a preparation method for improving the purity of BDO. Through the setting of sulfonic acid-type ion exchange resin, it can effectively remove surface moisture and impurities, forming a solid acid catalyst with excellent performance. This can ensure that the active centers of the catalyst are fully exposed and improve the catalytic efficiency. By controlling the feed flow rate in terms of reaction raw materials, the concentration and ratio of various substances in the reaction system reach the optimal state, which is conducive to the reaction proceeding in the direction of producing BDO, laying a foundation for improving the purity of BDO from the source.

[0026] (3) The present invention provides a preparation method for improving the purity of BDO. The reaction mixture is treated by a gas-liquid separator, which can effectively separate unreacted hydrogen and low-boiling by-products. The unreacted hydrogen is recycled through a recycling device, which can realize the recycling of resources and reduce production costs; the low-boiling by-products are collected through a condensing device, reducing the impurity content in the subsequent rectification process. The remaining liquid enters the rectification tower for rectification, and according to the boiling point differences of different substances, BDO can be further separated from other impurities, thereby significantly improving the purity of BDO and obtaining a high-quality BDO product. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0028] Figure 1 It is the step flow structure diagram of the preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0030] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0031] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Therefore, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "plurality" is two or more.

[0032] In the description of the present application, it should be noted that, unless otherwise clearly defined and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific situations.

[0033] As Figure 1 shown, the present invention provides a preparation method for improving the purity of BDO, including the following steps:

[0034] S1: Place the sulfonic acid type ion exchange resin in a vacuum drying oven. The temperature range of the vacuum drying oven is 100 - 120 °C, and the drying time range is 4 - 6 h to remove the surface moisture and impurities, and then cool to room temperature to form a solid acid catalyst;

[0035] Among them, drying the sulfonic acid type ion exchange resin in a vacuum drying oven at 100 - 120 °C for 4 - 6 hours can effectively remove the moisture and impurities on its surface. The removal of moisture avoids its interference with subsequent catalytic reactions;

[0036] S2: Load the solid acid catalyst into the reaction section of the catalytic distillation reactor, and introduce the reaction raw materials into the reactor. The reaction raw materials are maleic anhydride and hydrogen. The molar ratio of maleic anhydride to hydrogen is 1:4 - 6. The feeding flow rate range of maleic anhydride is 0.1 - 1 L / h, and the feeding flow rate range of hydrogen is 100 - 300 L / h. The mass ratio of the solid acid catalyst to the reaction raw materials is 1:1;

[0037] Among them, through the addition of the catalyst and the reaction raw materials, the reaction can proceed efficiently under the action of the catalyst, making full use of the active sites of the catalyst to promote the reaction between maleic anhydride and hydrogen;

[0038] S3: Use the catalytic distillation reactor to carry out stepwise cooling catalytic distillation at high temperature, medium temperature, and low temperature in sequence. The high-temperature catalytic distillation step includes a cooling stage and a reaction stage. The temperature fluctuation of the catalytic distillation reactor is within the range of ±1 °C, and the stirring speed is controlled at 100 - 300 r / min to form a reaction mixture;

[0039] In the high-temperature stage, the temperature in the reactor is raised to 150 - 200 °C at a heating rate of 5 - 10 °C / min, and in the reaction stage, the reaction is carried out at 150 - 200 °C for 2 - 3 h;

[0040] The medium-temperature catalytic distillation step includes a cooling stage and a reaction stage. In the cooling stage, the temperature is lowered to 100 - 150 °C at a cooling rate of 3 - 5 °C / min, and in the reaction stage, the reaction is carried out at 100 - 150 °C for 3 - 4 h;

[0041] The low-temperature catalytic distillation step includes a cooling stage and a reaction stage. In the cooling stage, the temperature is lowered to 50 - 100 °C at a cooling rate of 2 - 3 °C / min, and in the reaction stage, the reaction is carried out at 50 - 100 °C for 4 - 6 h, and an inhibitor is added in the low-temperature stage. The inhibitor is hydroquinone, and the inhibitor is 0.1 - 0.5% of the total mass of the reactants;

[0042] Among them, the stepwise cooling catalytic distillation method of high temperature, medium temperature, and low temperature, combined with the action of the catalyst, can carry out reactions at different temperatures according to the different stages and characteristics of the reaction. The high-temperature stage is conducive to quickly starting the reaction, promoting the activation of reactants and the initial progress of the reaction; the medium-temperature stage can further promote the progress of the reaction and improve the conversion rate of the reaction; at the low-temperature stage, hydroquinone is added as an inhibitor at the same time, which can inhibit the occurrence of side reactions, improve the selectivity of the reaction, and make the reaction proceed in the direction of generating the target product BDO; controlling the temperature fluctuation of the catalytic distillation reactor within the range of ±1°C helps to improve the uniformity and stability of the reaction, enables the catalyst to fully contact with the reactants, and improves the reaction efficiency;

[0043] S4: Discharge the reaction mixture to a gas-liquid separator, control the pressure at 0 - 500 kPa, control the temperature at 20 - 80°C, recover the unreacted hydrogen through a recovery device, and collect the remaining liquid after the low-boiling by-products are collected through a condensing device;

[0044] Among them, discharging the reaction mixture to a gas-liquid separator can effectively separate the unreacted hydrogen and low-boiling by-products. The unreacted hydrogen is recovered through a recovery device and can be recycled to reduce production costs; the low-boiling by-products are collected through a condensing device, reducing the impact of by-products on the subsequent rectification process, and improving the purity and quality of the product. The gas-liquid separation process further purifies the reaction system, removes the unreacted gas and low-boiling impurities, makes the liquid mixture entering the subsequent rectification step more pure, and is conducive to improving the rectification effect and the purity of BDO;

[0045] S5: The remaining liquid enters a rectification column for rectification. The reflux ratio of the rectification column is controlled at 2 - 5, the top temperature of the column is controlled at 50 - 100°C, and the bottom temperature of the column is controlled at 230 - 250°C;

[0046] Among them, through rectification in the rectification column, different components in the remaining liquid mixture can be effectively separated. The low-boiling impurities are separated from the top of the column, and the high-boiling impurities remain at the bottom, thereby obtaining a high-purity BDO product;

[0047] Steps S1 - S5, from the treatment of the catalyst, the control of reaction conditions to the separation and purification of products, cooperate with each other and work synergistically, and finally achieve the purpose of improving the purity of BDO.

[0048] Example 1:

[0049] S1: Place the sulfonic acid-type ion exchange resin in a vacuum drying oven at a temperature of 110°C for a drying time of 5 h, and then cool it to room temperature to form a solid acid catalyst;

[0050] S2: Charge the solid acid catalyst into the reaction section of the catalytic distillation reactor, and feed the reaction raw materials into the reactor. The reaction raw materials are maleic anhydride and hydrogen. The molar ratio of maleic anhydride to hydrogen is 1:5. The feed flow rate of maleic anhydride is 0.5 L / h, and the feed flow rate range of hydrogen is 200 L / h. The mass ratio of the solid acid catalyst to the reaction raw materials is 1:1.

[0051] S3: Use the catalytic distillation reactor to carry out stepwise temperature reduction catalytic distillation at high temperature, medium temperature, and low temperature in sequence. The high-temperature catalytic distillation step includes a temperature reduction stage and a reaction stage. In the high-temperature stage, the temperature in the reactor is raised to 170 °C at a heating rate of 7 °C / min; in the reaction stage, the reaction is carried out at 170 °C for 2.5 h. The medium-temperature catalytic distillation step includes a temperature reduction stage and a reaction stage. In the temperature reduction stage, the temperature is reduced to 120 °C at a cooling rate of 4 °C / min; in the reaction stage, the reaction is carried out at 120 °C for 3.5 h. The low-temperature catalytic distillation step includes a temperature reduction stage and a reaction stage. In the temperature reduction stage, the temperature is reduced to 75 °C at a cooling rate of 2.5 °C / min; in the reaction stage, the reaction is carried out at 75 °C for 5 h, and an inhibitor is added in the low-temperature stage. The inhibitor is hydroquinone, and the inhibitor is 0.3% of the total mass of the reactants. The temperature fluctuation is within the range of ±1 °C, and the stirring speed is 200 r / min to form a reaction mixture.

[0052] S4: Drain the reaction mixture into a gas-liquid separator. The pressure is 250 kPa and the temperature is 50 °C. The unreacted hydrogen is recovered through a recovery device, and the low-boiling by-products are collected by a condensation device and the remaining liquid.

[0053] S5: The remaining liquid mixture enters a rectification column for rectification. The reflux ratio of the rectification column is 3, the top temperature of the column is 75 °C, and the bottom temperature of the column is 240 °C.

[0054] Example 2:

[0055] This example is basically the same as Example 1, except that: in the step of S3, no inhibitor is added in the low-temperature stage.

[0056] Example 3:

[0057] This example is basically the same as Example 1, except that: in the step of S3, use the catalytic distillation reactor for isothermal catalytic distillation at a temperature of 170 °C for 2.5 h, and the stirring speed is 200 r / min to form a reaction mixture.

[0058] Example 4:

[0059] This example is basically the same as Example 1, except that: in the step of S3, use the catalytic distillation reactor for isothermal catalytic distillation at a temperature of 120 °C for 3.5 h, and the stirring speed is 200 r / min to form a reaction mixture;

[0060] Example 5:

[0061] This example is basically the same as Example 1, except that in step S3, catalytic distillation reactor is used for isothermal catalytic distillation at a temperature of 75 °C for 5 h, and the stirring speed is 200 r / min to form a reaction mixture.

[0062] Example 6:

[0063] This example is basically the same as Example 1, except that in step S3, catalytic distillation reactor is used for isothermal catalytic distillation and an inhibitor is added at a temperature of 75 °C for 5 h, the stirring speed is 200 r / min, the inhibitor is hydroquinone, and the inhibitor is 0.3% of the total mass of the reactants to form a reaction mixture.

[0064] Experimental detection:

[0065] Experiment 1:

[0066] Direct purity determination experiment: Analyzed by gas chromatography - mass spectrometry (GC - MS). GC - MS combines the high separation ability of gas chromatography and the high identification ability of mass spectrometry, and can accurately determine the content of BDO and its impurities.

[0067] Experimental steps: Appropriate amounts of BDO samples prepared in Examples 1 to 6 were taken respectively, and diluted with a solvent: methanol into a solution with a certain concentration. The diluted samples were injected into GC - MS, and the chromatographic conditions (column temperature) and mass spectrometry conditions (scanning range) were set for analysis. According to the chromatographic peak area and mass spectrometry identification results, the purity of BDO in each example was calculated.

[0068] Experiment 2:

[0069] Impurity content determination experiment: High performance liquid chromatography (HPLC). HPLC can effectively separate and quantitatively analyze various impurities in BDO.

[0070] Experimental steps: Prepare BDO samples of Examples 1 - 6, dissolve and filter them with a mobile phase (acetonitrile - water mixed solution). Inject the samples into the HPLC system, select a chromatographic column (C18 column) and a detection wavelength (210 nm) for analysis. According to the standard curve method, the content of each impurity was calculated.

[0071] Experiment 3:

[0072] Physical property comparison experiment: Measure physical properties such as density and boiling point. The physical properties of pure substances have fixed values, and the presence of impurities will change these physical properties.

[0073] Experimental steps:

[0074] Density measurement: The density of the BDO samples in each example was measured using a densitometer.

[0075] Boiling point measurement: The boiling point of the BDO samples in each example was determined by distillation.

[0076] Experiment 4:

[0077] Stability experiment: Equal amounts of the BDO samples in each example were taken and placed in sealed containers. The containers were placed in an incubator at 60 °C and exposed to light for 7 days. After 7 days, the purity of each sample was redetermined according to the purity measurement method of Experiment 1.

[0078] Table 1:

[0079]

[0080]

[0081] As can be seen from Table 1:

[0082] From Experiment 1, it was found that the BDO in Example 1 had the highest purity, reaching 98.8%, which was significantly higher than that of other examples. This indicates that the method of stepwise cooling catalytic distillation and adding inhibitors at low temperature can effectively improve the purity of BDO. In Example 2, no inhibitor was added, and in Examples 3 - 5, isothermal catalytic distillation was used, and their purities were all lower than that of Example 1, indicating that the addition of inhibitors and stepwise temperature control play a key role in improving purity.

[0083] From Experiment 2, it was found that the total impurity content in Example 1 was the lowest, only 1.2%, and the impurity content in other examples was significantly higher than that in Example 1. Among them, the impurity content in Example 5 was the highest, reaching 9.2%. This further proves that the preparation method in Example 1 can effectively inhibit side reactions, reduce impurity generation, and thus improve the purity of the product.

[0084] From Experiment 3, it was found that:

[0085] Density: The density of Example 1 was 1.017 g / cm 3 , which was closest to the theoretical density of pure BDO. The densities of other examples were relatively lower and decreased with the decrease in purity. This shows that the higher the purity, the closer the density of BDO is to the theoretical value, and the presence of impurities will reduce the density.

[0086] Boiling point: The boiling point range of Example 1 was 230 - 232 °C, which was closer to the boiling point of pure BDO. The boiling point ranges of other examples were relatively lower and narrower. This indicates that BDO with high purity has a more stable boiling point, and impurities will cause the boiling point to decrease and the boiling point range to narrow.

[0087] It can be concluded from Experiment 4 that the purity of Example 1 after the stability experiment is 98.2%, with the smallest decline, indicating its best stability. The purity decline of other examples is relatively large, especially for Example 5, where the purity drops to 90.0% after the stability experiment. This shows that the preparation method of Example 1 can not only improve the initial purity of BDO but also ensure its good stability under certain conditions.

[0088] In summary, the preparation method of Example 1 has obvious advantages in improving the purity of BDO, reducing the impurity content, optimizing the physical properties, and enhancing the stability.

[0089] Based on the ideal embodiments of the present invention as inspiration, through the above description, relevant personnel can make various changes and modifications completely within the scope of not deviating from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A preparation method for improving the purity of BDO, characterized in that, It includes the following steps: S1: Place the sulfonic acid type ion exchange resin in a vacuum drying oven, and then cool it to room temperature to form a solid acid catalyst; S2: Load the solid acid catalyst into the reaction section of the catalytic distillation reactor, and introduce the reaction raw materials into the reactor; S3: Use the catalytic distillation reactor to carry out stepwise temperature reduction catalytic distillation at high temperature, medium temperature, and low temperature in sequence, and add an inhibitor in the low temperature stage. The temperature fluctuation is within the range of ±1°C, and the stirring speed is controlled at 100 - 300 r / min to form a reaction mixture; S4: Discharge the reaction mixture into a gas-liquid separator. The unreacted hydrogen is recovered through a recovery device, and the low-boiling by-products are collected by a condensation device, and the remaining liquid; S5: The remaining liquid enters a rectification tower for rectification.

2. The preparation method for improving the purity of BDO according to claim 1, characterized in that: In the said S1, the temperature range of the vacuum drying oven is 100 - 120°C, and the drying time range is 4 - 6 h.

3. The preparation method for improving the purity of BDO according to claim 1, characterized in that: In the said S2, the mass ratio of the solid acid catalyst to the reaction raw materials is 1:

1.

4. The preparation method for improving the purity of BDO according to claim 1, wherein: In the said S2, the reaction raw materials are maleic anhydride and hydrogen. The molar ratio of maleic anhydride to hydrogen is 1:4 - 6. The maleic anhydride feed flow rate range is 0.1 - 1 L / h, and the hydrogen feed flow rate range is 100 - 300 L / h.

5. The preparation method for improving the purity of BDO according to claim 1, characterized in that: In the said S3, the high-temperature catalytic distillation step includes a temperature reduction stage and a reaction stage. In the high-temperature stage, the temperature in the reactor is raised to 150 - 200°C at a heating rate of 5 - 10°C / min; in the reaction stage, the reaction is carried out at a temperature of 150 - 200°C for 2 - 3 h.

6. The preparation method for improving the purity of BDO according to claim 1, wherein: In the said S3, the medium-temperature catalytic distillation step includes a temperature reduction stage and a reaction stage. In the temperature reduction stage, the temperature is reduced to 100 - 150°C at a temperature reduction rate of 3 - 5°C / min; in the reaction stage, the reaction is carried out at a temperature of 100 - 150°C for 3 - 4 h.

7. A preparation method for improving the purity of BDO according to claim 1, characterized in that: In the said S3, the low-temperature catalytic distillation step includes a temperature reduction stage and a reaction stage. In the temperature reduction stage, the temperature is reduced to 50 - 100°C at a temperature reduction rate of 2 - 3°C / min; in the reaction stage, the reaction is carried out at a temperature of 50 - 100°C for 4 - 6 h.

8. A preparation method for improving the purity of BDO according to claim 1, characterized in that: In the said S3, the inhibitor is hydroquinone, and the inhibitor is 0.1 - 0.5% of the total mass of the reactants.

9. The preparation method for improving the purity of BDO according to claim 1, characterized in that: In the said S4, the pressure of the gas-liquid separator is controlled at 0 - 500 kPa, and the temperature is controlled at 20 - 80°C.

10. The preparation method for improving the purity of BDO according to claim 1, characterized in that: In the said S5, the reflux ratio of the rectification tower is controlled at 2 - 5, the top temperature of the tower is controlled at 50 - 100°C, and the bottom temperature of the tower is controlled at 230 - 250°C.

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