Preparation method of 1, 4-butanediol with low acetal content and low methyl butanediol content

Abstract

The invention belongs to the field of chemical production, and particularly relates to a production method of 1, 4-butanediol with low acetal content and low methyl butanediol content. The method comprises the following steps: (1) under the action of a first catalyst, acetylene reacts with a formaldehyde aqueous solution to generate a first reaction solution containing butynediol; (2) rectifying the first reaction solution to remove formaldehyde to obtain a first rectified reaction solution; (3) under the action of a second catalyst, carrying out a first hydrogenation reaction on the first rectification reaction liquid and first hydrogen to obtain a second reaction liquid containing 1, 4-butanediol; and (4) under the action of a third catalyst, carrying out a second hydrogenation reaction on the second reaction liquid and second hydrogen to prepare a third reaction liquid containing 1, 4-butanediol. The BDO product prepared by the method disclosed by the invention not only can meet the field of polymers with special requirements on color values, but also can be used in the field of lithium ion batteries with requirements on low methyl BDO content.

Description

Technical Field

[0001] The invention belongs to the field of chemical production, and specifically relates to a method for producing 1,4-butanediol with low acetal content and low methyl butanediol content. Background Art

[0002] 1, 4-Butanediol (BDO) is an important organic compound. Due to its special structure, 1, 4-Butanediol can be widely used in organic synthesis, industrial solvents and intermediates of polymer raw materials. Through different reactions, it can generate tetrahydrofuran (THF), γ-butyrolactone (GBL), polybutylene terephthalate (PBT), polytetramethylene ether glycol (PTMEG), N-methylpyrrolidone (NMP), etc. It can be widely used in automobile manufacturing, electronics and electrical, instrumentation, home appliances and textiles, pesticides, lithium-ion batteries, plasticizers, pharmaceutical intermediates, chain extenders and adhesives.

[0003] BDO has a variety of production routes, and the main industrial production processes include the Reppe process, maleic anhydride hydrogenation process, butadiene process, and propylene oxide process. Among the numerous BDO production processes, the Reppe process using formaldehyde and acetylene as raw materials has become the mainstream process in the world due to its cost advantage.

[0004] There are two representative routes for the existing acetylene aldehyde process. The first type is: the acetylene aldehyde is reacted in the first stage to generate butynediol, and the butynediol is then hydrogenated in two stages (the same catalyst and reaction conditions are used for the two-stage hydrogenation reaction) to generate BDO. Due to the early development time of this process, there are problems such as frequent replacement of catalysts and large fluctuations in product indicators due to different catalyst life cycles. The second type is: the acetylene aldehyde reaction uses a three-stage slurry bed reaction to generate butynediol, and then undergoes two steps of hydrogenation to generate BDO, and the two steps of hydrogenation use different catalysts and reaction conditions. This type of device operates continuously, does not require frequent shutdown to replace catalysts, and is simple to operate, but the main defect is the large number of reactors. Both process routes are representatives of the improved acetylene aldehyde BDO process, and also represent two different BDO quality characteristics. The most notable feature of the BDO product quality of the first type of process is the high acetal content, and the acetal is affected by acidic and high temperature conditions in the downstream polymerization reaction, which will affect the color value of the product and limit the use of this type of BDO product in the polymerization field. The BDO products of the second process are the opposite. They have a very low acetal content and can be widely used in polymer fields such as PBT, PU / TPU, etc. However, the methyl BDO content is relatively high, which limits the use of this type of BDO products in the electronic grade GBL and NMP industries.

[0005] Patent application CN109851477A believes that the production of methyl BDO is caused by formaldehyde contained in butynediol, so a certain amount of methanol is added to the butynediol distillation section to reduce the formaldehyde content in butynediol. This method not only increases steam consumption and distillation load, but also introduces methanol, which needs to be removed secondary in the BDO distillation process, so this method is not suitable for industrialization. Patent application CN101284762A discloses a method for preparing high-purity 1, 4-butanediol. The content of methyl BDO can be controlled below 0.07wt% through multi-stage distillation, but this method has the defects of high energy consumption and complex process. Patent application CN101284762A also adopts physical separation means: melt crystallization method is used to obtain high-purity BDO. Although the above physical separation method can reduce the content of methyl BDO, the cost is too high, the energy consumption is large, and it does not match the benefits.

[0006] In summary, the existing process for producing BDO by the acetylene aldehyde process mainly includes the following defects: (1) It is difficult to simultaneously reduce the contents of acetal and methyl BDO in the BDO product to a low level, which affects the overall quality of the BDO product by the acetylene aldehyde process; (2) The existing production method can only remove acetal or methyl BDO separately, and the existing multi-stage distillation, melt crystallization and other methods have high energy consumption and large equipment investment. Therefore, there is an urgent need in the art to provide a method for producing 1,4-butanediol with low acetal content and low 2-methyl-1, 4-butanediol content. Summary of the invention

[0007] The object of the present invention is to provide a method for producing 1,4-butanediol with low acetal content and low methyl butanediol content.

[0008] The first aspect of the present invention provides a method for preparing 1,4-butanediol, the method comprising the steps of:

[0009] (1) Under the action of a first catalyst, acetylene reacts with a formaldehyde aqueous solution to generate a first reaction liquid containing butynediol;

[0010] (2) distilling the first reaction liquid to remove formaldehyde, thereby obtaining a first distillation reaction liquid;

[0011] (3) Under the action of a second catalyst, subjecting the first distillation reaction liquid to a first hydrogenation reaction with a first hydrogen gas to obtain a second reaction liquid containing 1,4-butanediol;

[0012] (4) Under the action of a third catalyst, subjecting the second reaction liquid to a second hydrogenation reaction to obtain a third reaction liquid containing 1,4-butanediol;

[0013] In step (1), the molar ratio of acetylene to formaldehyde is (2-10):1;

[0014] In step (1), the reaction pressure is 140-200 kPa;

[0015] In step (3), the molar ratio of the first hydrogen to butynediol is (5-200):1;

[0016] In step (4), the molar ratio of the second hydrogen gas to the 1,4-butanediol in the second reaction liquid is (0.5-100):1.

[0017] In one or more embodiments, step (1) has one or more of the following features:

[0018] In the formaldehyde aqueous solution, the concentration of formaldehyde is 40-45wt%;

[0019] The acetylene is recycled for use in step (1);

[0020] The first catalyst is a supported copper catalyst;

[0021] The reaction temperature is 80-120°C;

[0022] The reaction residence time is 0.5-200h;

[0023] Step (1) reacts at a pH between 3.0 and 5.5;

[0024] In the first reaction solution, the content of propargyl alcohol is ≤0.5wt%;

[0025] In the first reaction liquid, the content of formaldehyde is ≤1.0wt%;

[0026] In the first reaction solution, the content of butynediol is 40-45wt%.

[0027] In one or more embodiments, the pH of step (1) is adjusted by a buffer comprising a strong base, a weak acid salt and an organic acid.

[0028] In one or more embodiments, step (2) has one or more of the following features:

[0029] The operating pressure of the formaldehyde removal tower used to implement the rectification formaldehyde removal is 250-300 kPaG;

[0030] The operating temperature of the formaldehyde removal tower used for implementing the rectification formaldehyde removal is 100-180°C;

[0031] The formaldehyde removal tower used for implementing the rectification and formaldehyde removal is a plate tower, and the number of trays of the formaldehyde removal tower is 25-35 layers;

[0032] The reflux ratio of the formaldehyde removal tower used for implementing the rectification formaldehyde removal is 5-10;

[0033] In the first distillation reaction liquid, the content of formaldehyde is ≤0.1wt%;

[0034] In the first distillation reaction liquid, the content of propargyl alcohol is ≤500ppmw;

[0035] In the first distillation reaction liquid, the content of butynediol is 40-45wt%.

[0036] In one or more embodiments, step (3) has one or more of the following features:

[0037] The concentration of butynediol in the first distillation reaction liquid is adjusted to 35-40wt%, and then subjected to a first hydrogenation reaction with the first hydrogen;

[0038] Step (3) is carried out in a slurry bed reactor;

[0039] The reaction pressure is 2.0-3.0MPaG;

[0040] The reaction temperature is 40-60°C;

[0041] The first hydrogen is recycled for use in step (3);

[0042] Step (3) reacting at a pH between 7 and 11;

[0043] The second catalyst is a nickel catalyst;

[0044] In step (3), the conversion rate of butynediol is ≥95%;

[0045] Reaction time is 10-240 min;

[0046] In the second reaction liquid, the content of butene glycol is ≤1.0wt%;

[0047] In the second reaction solution, the content of 2-methyl-1,4-butanediol is 10-2000 ppmw;

[0048] In the second reaction liquid, the content of acetal is ≤600 ppmw.

[0049] In one or more embodiments, step (4) has one or more of the following features:

[0050] The second reaction solution is directly applied to step (4);

[0051] The reaction pressure is 20.0-30.0MPaG;

[0052] The reaction temperature is 90-130°C;

[0053] The second hydrogen is recycled for use in step (4);

[0054] Step (4) is carried out in a trickle bed reactor;

[0055] The third catalyst is a supported nickel catalyst;

[0056] The reaction time is 1-8h;

[0057] In the third reaction liquid, the content of 2-methyl-1, 4-butanediol is ≤5000ppmw;

[0058] In the third reaction liquid, the content of acetal is ≤200 ppmw.

[0059] In one or more embodiments, the method further comprises performing post-distillation treatment on the 1,4-butanediol in the third reaction liquid, wherein the post-distillation treatment comprises a dehydration process, a residue removal process, a 1,4-butanediol refining process and a 1,4-butanediol recovery process.

[0060] In one or more embodiments, the method has one or more of the following features:

[0061] Implementing the dehydration process through a dehydration system, wherein the dehydration system comprises a vacuum tower and an atmospheric pressure tower;

[0062] The deslagging process is implemented by a deslagging system, wherein the deslagging system includes a rising film evaporator, a falling film evaporator and a thin film evaporator;

[0063] Implementing the 1,4-butanediol refining process through a refining system, wherein the refining system includes an intermediate tower and a finished product tower;

[0064] The 1,4-butanediol recovery process is implemented through a recovery system, and the recovery system includes a light component recovery tower and a heavy component recovery tower.

[0065] In one or more embodiments, the method has one or more of the following features:

[0066] The operating pressure of the vacuum tower is 20-40 kPaA;

[0067] The operating temperature of the vacuum tower is 70-80°C;

[0068] The vacuum tower is a plate tower with 25-35 plates;

[0069] The reflux ratio of the vacuum tower is 0.5-1.0;

[0070] The operating pressure of the atmospheric tower is 35-50 kPaG;

[0071] The operating temperature of the atmospheric tower is 130-150°C;

[0072] The atmospheric pressure tower is a plate tower with 25-35 plates;

[0073] The reflux ratio of the atmospheric pressure tower is 1.0-1.5;

[0074] The operating pressure of the rising film evaporator is 5-15 kPaA;

[0075] The operating temperature of the rising film evaporator is 160-170°C;

[0076] The operation time of the rising film evaporator is 5-20min;

[0077] The operating pressure of the falling film evaporator is 5-15 kPaA;

[0078] The operating temperature of the falling film evaporator is 160-170°C;

[0079] The operation time of the falling film evaporator is 5-20min;

[0080] The operating pressure of the thin film evaporator is 1-10 kPaA;

[0081] The operating temperature of the thin film evaporator is 160-170°C;

[0082] The operation time of the thin film evaporator is 2-10min;

[0083] The operating pressure of the intermediate tower is 3-10 kPaA;

[0084] The operating temperature of the intermediate tower is 150-170°C;

[0085] The intermediate tower is a two-stage packed tower, and the height of the two-stage packing is independently 4800-5000mm;

[0086] The reflux ratio of the intermediate tower is 25-30;

[0087] The operating pressure of the finished product tower is 1-5 kPaA;

[0088] The operating temperature of the finished product tower is 150-170°C;

[0089] The finished product tower is a two-stage packed tower, and the height of the two-stage packing is independently 5400-5600mm;

[0090] The reflux ratio of the finished product tower is 20-25;

[0091] The operating pressure of the light component recovery tower is 1-10 kPaA;

[0092] The operating temperature of the light component recovery tower is 160-170°C;

[0093] The light component recovery tower is a two-stage packed tower, and the height of the two-stage packing is independently 3500-3700 mm;

[0094] The reflux ratio of the light component recovery tower is 5-15;

[0095] The operating pressure of the heavy component recovery tower is 1-5 kPaA;

[0096] The operating temperature of the heavy component recovery tower is 160-180°C;

[0097] The heavy component recovery tower is a three-stage packed tower, and the height of the three-stage packing is independently 3500-4500 mm;

[0098] The reflux ratio of the heavy component recovery tower is 5-15.

[0099] In one or more embodiments, the method has one or more of the following features:

[0100] The content of 2-(4-hydroxybutoxy)-tetrahydrofuran in 1,4-butanediol obtained by post-distillation treatment is ≤150ppmw;

[0101] The content of 2-methyl-1, 4-butanediol in the 1, 4-butanediol obtained by post-distillation treatment is ≤900ppmw;

[0102] The purity of 1, 4-butanediol obtained after distillation treatment is ≥99.85%;

[0103] The color number of 1, 4-butanediol obtained after distillation treatment is ≤8;

[0104] The water content of 1,4-butanediol obtained after distillation treatment is ≤80ppmw.

[0105] The present invention has the following beneficial effects:

[0106] (1) The present invention controls the conditions of each reaction unit (acetylation reaction, low-pressure hydrogenation reaction, high-pressure hydrogenation reaction) to ensure that the content of acetal entering the distillation unit (for example, the distillation post-treatment process of Example 4) is ≤200 ppmw, and the content of methyl BDO entering the distillation unit is ≤950 ppmw. The acetal content in the BDO product finally obtained after distillation is ≤150 ppmw, the methyl BDO content is ≤900 ppmw, and the purity of BDO is ≥99.85%.

[0107] (2) The BDO product prepared by the method of the present invention can meet the polymer fields such as PU / TPU, PBT, PBAT, etc. that have special requirements on color value (requiring low acetal content in the BDO product), and can also enter the lithium ion battery field that requires low methyl BDO content.

[0108] (3) The method of the present invention only needs to control the reaction conditions, does not require additional energy consumption, does not need to modify the distillation scheme, is simple to operate, easy to control, suitable for large-scale industrial production, and has good industrial application prospects. DETAILED DESCRIPTION

[0109] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0110] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0111] Herein, “comprising”, “including”, “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of”. For example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to be disclosed herein.

[0112] In this document, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions).

[0113] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0114] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0115] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0116] As used herein, "acetal" refers to 2-(4-hydroxybutoxy)-tetrahydrofuran, ie, HB-THF.

[0117] As used herein, "methyl butanediol" and "methyl BDO" both refer to 2-methyl-1,4-butanediol.

[0118] As used herein, "butanediol" and "BDO" both refer to 1,4-butanediol.

[0119] Herein, those skilled in the art can select the reflux ratio of each distillation tower according to conventional methods. Since acetal and methyl BDO cannot be separated by conventional distillation, changing the reflux ratio of each distillation tower has almost no effect on the separation effect of acetal and methyl BDO.

[0120] The inventors have found that by controlling the amount of circulating acetylene in the acetylation reaction, the amount of circulating hydrogen in the low-pressure hydrogenation reaction, the amount of circulating hydrogen in the high-pressure hydrogenation reaction, and the content of formaldehyde and propargyl alcohol in the reaction solution at each reaction stage, acetylene and formaldehyde can undergo an acetylation reaction, followed by low-pressure hydrogenation and high-pressure hydrogenation, to produce butanediol with low acetal and low methyl BDO content. On this basis, the present invention provides a method for preparing 1, 4-butanediol, the method comprising the steps of:

[0121] (1) Under the action of a first catalyst, acetylene reacts with a formaldehyde aqueous solution to generate a first reaction liquid containing butynediol;

[0122] (2) distilling the first reaction liquid to remove formaldehyde, thereby obtaining a first distillation reaction liquid;

[0123] (3) Under the action of a second catalyst, subjecting the first distillation reaction liquid to a first hydrogenation reaction with a first hydrogen gas to obtain a second reaction liquid containing 1,4-butanediol;

[0124] (4) Under the action of a third catalyst, the second reaction liquid and a second hydrogen gas are subjected to a second hydrogenation reaction to obtain a third reaction liquid containing 1,4-butanediol.

[0125] In step (1), the concentration of formaldehyde in the aqueous formaldehyde solution is 40-45 wt%, for example, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, preferably 43-45 wt%. By controlling the concentration of formaldehyde in the aqueous formaldehyde solution within the range defined herein, the contents of formaldehyde and propargyl alcohol in the first reaction liquid of the acetylation reaction can be effectively controlled within the range defined herein, and the contents of formaldehyde and propargyl alcohol in the first distillation reaction liquid can be further controlled within the range defined herein, which is conducive to the preparation of butanediol with low acetal content and low methyl BDO content.

[0126] The excess acetylene after the reaction with formaldehyde in step (1) is recycled to step (1).

[0127] In step (1), the molar ratio of acetylene to formaldehyde is (2-10):1, for example, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, preferably (2-5):1 or (5-10):1. By controlling the molar ratio of acetylene to formaldehyde within the range defined herein, the content of formaldehyde and propargyl alcohol in the first reaction liquid of the acetylation reaction can be effectively controlled within the range defined herein, and the content of formaldehyde and propargyl alcohol in the first distillation reaction liquid can be further controlled within the range defined herein, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0128] In step (1), the first catalyst is a supported copper catalyst.

[0129] Step (1) can be carried out in a conventional reactor in the art, preferably in a slurry bed reactor.

[0130] In step (1), the reaction temperature is 80-120° C., for example, 80° C., 90° C., 100° C., 110° C., 120° C., preferably 80-90° C. or 90-120° C. Controlling the reaction temperature of step (1) within the range defined herein can effectively control the contents of formaldehyde and propargyl alcohol in the first reaction liquid of the acetylation reaction within the range defined herein, and can further achieve the contents of formaldehyde and propargyl alcohol in the first distillation reaction liquid within the range defined herein, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0131] In step (1), the reaction pressure is 140-200 kPa, for example, 140 kPa, 150 kPa, 160 kPa, 170 kPa, 180 kPa, 190 kPa, preferably 140-180 kPa, 140-160 kPa or 160-200 kPa. Controlling the reaction pressure of step (1) within the range defined herein can effectively control the contents of formaldehyde and propargyl alcohol in the first reaction liquid of the acetylation reaction within the range defined herein, and can further achieve the contents of formaldehyde and propargyl alcohol in the first distillation reaction liquid within the range defined herein, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0132] In step (1), the reaction residence time may be 0.5-200 h, for example, 1 h, 2 h, 4 h, 8 h, 15 h, 30 h, 50 h, 80 h, 100 h, 150 h, preferably 0.5-4 h, 4-100 h or 4-24 h.

[0133] Step (1) is reacted at a pH of 3.0-5.5, for example, 3.2, 3.4, 3.6, 4.0, 4.3, 4.5, 4.7, 5.0, 5.1, 5.3, preferably 4.3-4.7, 3.5-5.0 or 4.0-5.0. Herein, the pH of the reaction system of step (1) can be adjusted by using a buffer. A commonly used buffer in the art can be selected according to the pH required for the acetylation reaction of step (1). The buffer can be purchased directly or prepared by itself. The prepared buffer can include a strong base weak acid salt and an organic acid. Preferably, the buffer pair that plays a role in adjusting the pH of the solution consists of a strong base weak acid salt and an organic acid. Exemplary strong base weak acid salts include, but are not limited to, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, sodium acetate, etc. Exemplary organic acids include, but are not limited to, formic acid, acetic acid, oxalic acid, citric acid, etc. A person skilled in the art can configure a buffer solution of a specific pH according to the ionization properties of the strong base, weak acid salt and organic acid. For example, the molar ratio of the strong base, weak acid salt and organic acid can be (1-5):1, such as 1:1, 2:1, 3:1, 4:1, 5:1, preferably (1-2):1, (2-5):1 or (2-3):1. The pH of the reaction system of step (1) can be controlled within the range defined herein by using the buffer solution configured as defined in the present invention. By controlling the pH of the reaction solution of step (1) within the range defined herein, the content of formaldehyde and propargyl alcohol in the first reaction solution of the acetylation reaction can be effectively controlled within the range defined herein, and the content of formaldehyde and propargyl alcohol in the first distillation reaction solution can be further controlled within the range defined herein, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0134] In some embodiments, in step (1), the content of propargyl alcohol in the first reaction liquid is ≤0.5 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, preferably 0.1-0.5 wt%, 0.2-0.5 wt%. Controlling the content of propargyl alcohol in the first reaction liquid within the range defined herein can further achieve the content of propargyl alcohol in the first distillation reaction liquid within the range defined herein, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0135] In some embodiments, in step (1), the content of formaldehyde in the first reaction liquid is ≤1.0 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, such as 0.1-1.0 wt%, 0.3-1.0 wt% or 0.5-1.0 wt%. Controlling the content of formaldehyde in the first reaction liquid within the range defined herein can further achieve the content of formaldehyde in the first distillation reaction liquid within the range defined herein, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0136] In some embodiments, in step (1), the content of butynediol in the first reaction solution is 40-45 wt%, for example, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, preferably 42-44 wt%, 43-45 wt%.

[0137] In some embodiments, the first reaction liquid includes impurities, and the impurities include propargyl alcohol, methanol, and unreacted formaldehyde.

[0138] In step (2), the operating pressure of the formaldehyde removal tower used for implementing the distillation formaldehyde removal is 250-300 kPaG, such as 250 kPaG, 260 kPaG, 270 kPaG, 280 kPaG, 290 kPaG, 3000 kPaG, preferably 260-280 kPaG, 270-300 kPaG. By controlling the operating pressure of step (2) within the range defined herein, the contents of formaldehyde and propargyl alcohol in the first distillation reaction liquid can be effectively controlled within the range defined herein, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0139] In step (2), the operating temperature of the formaldehyde removal tower for implementing the distillation formaldehyde removal is 100-180° C., for example, 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., preferably 100-140° C. or 140-180° C. By controlling the operating temperature of step (2) within the range defined herein, the contents of formaldehyde and propargyl alcohol in the first distillation reaction liquid can be effectively controlled within the range defined herein, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0140] In step (2), the formaldehyde removal tower used for implementing the distillation formaldehyde removal is a plate tower, and the number of trays of the formaldehyde removal tower is 25-35 layers, for example, 25 layers, 26 layers, 27 layers, 28 layers, 29 layers, 30 layers, 31 layers, 32 layers, 33 layers, 34 layers, 35 layers, preferably 25-30 layers, 30-35 layers.

[0141] In step (2), the reflux ratio of the formaldehyde removal tower used for implementing the distillation formaldehyde removal is 5-10, for example, 5.5, 6.0, 6.5, 7.0, 8.0, 9.0, preferably 5.5-10, 5.5-8.0.

[0142] In step (2), the content of formaldehyde in the first distillation reaction liquid is ≤0.1 wt%, for example, 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, preferably 0.01-0.1 wt%. The content of formaldehyde in the first distillation reaction liquid is controlled within the range defined herein so that butanediol that meets the product index requirements can be obtained through subsequent low-pressure hydrogenation reaction and high-pressure hydrogenation reaction.

[0143] In step (2), the propargyl alcohol content in the first distillation reaction liquid is ≤500ppmw, for example, 50ppmw, 100ppmw, 200ppmw, 300ppmw, 400ppmw, 500ppmw, preferably 100-500ppmw, 200-500ppmw. The propargyl alcohol content in the first distillation reaction liquid is controlled within the range defined herein so that butanediol that meets the product index requirements can be obtained through subsequent low-pressure hydrogenation reaction and high-pressure hydrogenation reaction.

[0144] In step (2), the content of butynediol in the first distillation reaction liquid is 40-45 wt%, for example, 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, preferably 42-44 wt%, 43-45 wt%. The distillation in step (2) mainly removes formaldehyde and has little effect on the content of butynediol in the reaction liquid.

[0145] The inventors have found that under the working conditions defined in step (2), the formaldehyde removal tower can not only effectively reduce the content of formaldehyde in the first reaction liquid, but also reduce the content of other impurities (especially propargyl alcohol), but has almost no effect on the content of butynediol in the first reaction liquid.

[0146] Carrying out the acetylation reaction of step (1) under the conditions defined herein, and carrying out the formaldehyde removal distillation of the reaction liquid after the acetylation reaction under the conditions defined herein, can effectively prevent impurities such as formaldehyde and propargyl alcohol from entering the subsequent hydrogenation reaction and causing side reactions to produce methyl BDO. Controlling the content of formaldehyde and propargyl alcohol in the first reaction liquid within the range defined herein, and then carrying out the formaldehyde removal distillation defined in step (2) can effectively prevent impurities such as formaldehyde and propargyl alcohol from entering the subsequent hydrogenation reaction. If the content of impurities (formaldehyde, propargyl alcohol, etc.) in the first reaction liquid is not controlled within the range defined herein, the formaldehyde removal distillation of step (2) will lose its effect, resulting in the content of impurities (formaldehyde, propargyl alcohol, etc.) entering the subsequent hydrogenation reaction exceeding the standard.

[0147] Preferably, the butynediol in the first reaction solution is distilled to remove formaldehyde, and the removed formaldehyde is recovered. The recovery of formaldehyde is carried out by a formaldehyde recovery tower. Those skilled in the art can select the working conditions of the formaldehyde recovery tower according to conventional chemical knowledge. In some embodiments, the operating pressure of the formaldehyde recovery tower is 5-20 kPaG, such as 5-10 kPaG, 10-20 kPaG, 8-15 kPaG. In some embodiments, the operating temperature of the formaldehyde recovery tower is 90-120°C, such as 90-105°C, 105-120°C, 100-110°C. The formaldehyde recovery tower is a plate tower with 35-45 layers of trays, such as 35-40 layers and 40-45 layers. The reflux ratio of the formaldehyde recovery tower is 10-15, such as 10-12, 12-15.

[0148] In step (3), the concentration of butynediol in the first distillation reaction liquid is adjusted to 35-40wt%, for example, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt%, preferably 36-40wt%, 35-36wt%, and then subjected to a first hydrogenation reaction with the first hydrogen. The concentration of butynediol in the first distillation reaction liquid is adjusted to 35-40wt% and then subjected to a low-pressure hydrogenation reaction to obtain a second reaction liquid with a low acetal and low methyl BDO content, which is conducive to the preparation of butanediol with a low acetal and low methyl BDO content.

[0149] Those skilled in the art can select a reactor commonly used in the art according to the reaction conditions and reaction characteristics of step (3). In some embodiments, step (3) is carried out in a slurry bed reactor.

[0150] In some embodiments, the second catalyst is a nickel catalyst, such as a Raney nickel catalyst.

[0151] In some embodiments, in step (3), the reaction pressure is 2.0-3.0 MPaG, such as 2.0 MPaG, 2.1 MPaG, 2.2 MPaG, 2.3 MPaG, 2.4 MPaG, 2.5 MPaG, 2.6 MPaG, 2.7 MPaG, 2.8 MPaG, 2.9 MPaG, 3.0 MPaG, preferably 2.0-2.5 MPaG, 2.0-2.1 MPaG. By controlling the reaction pressure of step (3) within the range defined herein, a second reaction liquid with low acetal and low methyl BDO content can be obtained, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0152] In some embodiments, in step (3), the reaction temperature is 40-60° C., such as 40° C., 45° C., 50° C., 55° C., 60° C., preferably 40-50, 45-60° C. By controlling the reaction temperature of step (3) within the range defined herein, a second reaction liquid with low acetal and low methyl BDO content can be obtained, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0153] In some embodiments, in step (3), the reaction time is 10-240 min, for example, 20 min, 30 min, 60 min, 80 min, 120 min, 150 min, 180 min, 220 min, preferably 30-60 min.

[0154] In some embodiments, step (3) is reacted at a pH between 7 and 11, for example, pH 7, 8, 9, 10, preferably 7-9. A person skilled in the art can adjust the pH of the low-pressure hydrogenation reaction in step (3) according to common methods, for example, by adding an alkaline agent (sodium hydroxide, potassium hydroxide, etc.) to the reaction solution in step (3). The amount of alkaline agent added can be calculated according to the required pH. In some embodiments, 10-30 wt% (for example, 20 wt%) of an aqueous sodium hydroxide solution is added to the low-pressure hydrogenation reaction solution in step (3). By controlling the pH of the reaction solution in step (3) within the range defined herein, a second reaction solution with low acetal and low methyl BDO content can be obtained, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0155] In some embodiments, in step (3), the molar ratio of the first hydrogen to butynediol is (5-200):1, such as 5:1, 10:1, 30:1, 50:1, 80:1, 100:1, 130:1, 150:1, 180:1, preferably 10-150:1, 100-200:1, 5-150:1. Preferably, the first hydrogen is recycled to step (3). By controlling the molar ratio of the first hydrogen to butynediol in step (3) within the range defined herein, a second reaction liquid with low acetal and low methyl BDO content can be obtained, which is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0156] In step (3), the conversion rate of butynediol is ≥95%, preferably ≥96%, ≥97%, ≥98%, ≥99%. In the low-pressure hydrogenation reaction unit, in addition to the production of butanediol, side reactions also occur to produce various impurities such as butenediol, acetal, tetrahydroxybutyraldehyde, n-butanol, and 2-(4-hydroxybutoxy)-tetrahydrofuran. Except for butynediol (BYD), the content of other organic impurity components does not exceed 5wt%.

[0157] In the second reaction liquid, the content of butenediol is ≤1.0wt%, preferably 0.01-1.0wt%, 0.01-0.5wt%, 0.01-0.3wt%. Controlling the content of butenediol in the second reaction liquid within the range defined herein is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0158] In the second reaction solution, the content of 2-methyl-1, 4-butanediol is 10-2000 ppmw, such as 10 ppmw, 50 ppmw, 100 ppmw, 200 ppmw, 300 ppmw, 400 ppmw, 500 ppmw, 800 ppmw, 1000 ppmw, 1500 ppmw, preferably 100-1500 ppmw, 50-500 ppmw, 80-300 ppmw. Controlling the content of 2-methyl-1, 4-butanediol in the second reaction solution within the range defined herein is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0159] In the second reaction liquid, the content of acetal is ≤600 ppmw, for example, 50 ppmw, 100 ppmw, 200 ppmw, 300 ppmw, 400 ppmw, 500 ppmw, 600 ppmw, preferably 100-600 ppmw, 200-500 ppmw, 250-500 ppmw. Controlling the content of acetal in the second reaction liquid within the range defined herein is conducive to the preparation of butanediol with low acetal and low methyl BDO content.

[0160] Preferably, in the second reaction liquid, the content of 1,4-butanediol is 30-35wt%, for example, 30 wt%, 31wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, preferably 31-35wt%, 31-33wt%.

[0161] The second reaction liquid is directly used in step (4). In the high-pressure hydrogenation unit, the second reaction liquid from the low-pressure hydrogenation is hydrogenated with the third catalyst to remove unreacted unsaturated organic matter.

[0162] In some embodiments, in step (4), the reaction pressure is 20.0-30.0 MPaG, such as 21 MPaG, 22 MPaG, 23 MPaG, 25 MPaG, 28 MPaG, preferably 20-25 MPaG, 20-23 MPaG. By controlling the reaction pressure of step (4) within the range defined herein, butanediol with low acetal content and low methyl BDO content can be obtained.

[0163] In some embodiments, in step (4), the reaction temperature is 90-130° C., such as 95° C., 100° C., 105° C., 110° C., 115° C., 120° C., 125° C., 130° C., preferably 105-115° C. By controlling the reaction temperature of step (4) within the range defined herein, butanediol with low acetal content and low methyl BDO content can be obtained.

[0164] In some embodiments, in step (4), the reaction time is 1-8 h, for example, 2 h, 3 h, 5 h, 6 h, 8 h, preferably 2-5 h.

[0165] In some embodiments, in step (4), the molar ratio of the second hydrogen to the 1, 4-butanediol in the second reaction liquid is (0.5-100):1, such as 1:1, 2:1, 5:1, 10:1, 15:1, 30:1, 50:1, 80:1, 90:1, preferably 1-50:1, 5-30:1, 30-50:1. Preferably, the second hydrogen is recycled to step (4). By controlling the molar ratio of the second hydrogen to 1, 4-butanediol within the range defined herein, butanediol with low acetal content and low methyl BDO content can be produced.

[0166] Those skilled in the art can select a suitable reactor according to the reaction requirements. Preferably, step (4) is carried out in a trickle bed reactor. By carrying out step (4) in the reactor defined herein, butanediol with low acetal content and low methyl BDO content can be produced.

[0167] In some embodiments, the third catalyst is a supported nickel catalyst.

[0168] In the third reaction liquid, the content of 2-methyl-1, 4-butanediol is ≤5000ppmw, for example, 50ppmw, 100ppmw, 200ppmw, 300ppmw, 400ppmw, 500ppmw, 600ppmw, 800ppmw, 1000ppmw, 2000ppmw, 3000ppmw, 4000ppmw, preferably 50-5000ppmw, 100-3000ppmw, 150-2000ppmw, 100-1000ppmw, 150-600ppmw. Ensure that the content of 2-methyl-1, 4-butanediol entering the distillation post-treatment unit is ≤950ppmw. Controlling the content of 2-methyl-1, 4-butanediol in the third reaction liquid within the range defined herein can produce butanediol with low acetal and low methyl BDO content.

[0169] In the third reaction liquid, the content of acetal is ≤200 ppmw, for example, 10 ppmw, 20 ppmw, 50 ppmw, 80 ppmw, 100 ppmw, 120 ppmw, 150 ppmw, 180 ppmw, 200 ppmw, preferably 10-200 ppmw, 50-190 ppmw, 80-185 ppmw. By controlling the content of acetal in the third reaction liquid within the range defined herein, butanediol with low acetal and low methyl BDO content can be obtained.

[0170] Preferably, in the third reaction liquid, the content of 1,4-butanediol is 30.1-38wt%, for example, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, preferably 31-35wt%, 32-34wt%, 31.1-38wt%.

[0171] The method of the present invention also includes distillation post-treatment of 1,4-butanediol in the third reaction solution, and the distillation post-treatment includes a dehydration process, a residue removal process, a 1,4-butanediol refining process and a 1,4-butanediol recovery process. Preferably, the method also includes a by-product purification and recovery process. Those skilled in the art can select the operating conditions of each distillation post-treatment process according to conventional knowledge in the chemical industry. Exemplary operating conditions of each process are described below.

[0172] The dehydration process is implemented by a dehydration system, and the dehydration system includes a vacuum tower and an atmospheric pressure tower; preferably, the dehydration process controls the water content in the third reaction liquid to 1-3wt%, preferably 1-1.5wt%. The operating pressure of the vacuum tower is 20-40kPaA, such as 23 kPaA, 25 kPaA, 27 kPaA, 30 kPaA, 35 kPaA, 37 kPaA, preferably 23-30kPaA, 25-30 kPaA. The operating temperature of the vacuum tower is 70-80°C, such as 72°C, 74°C, 76°C, 78°C, preferably 74-76°C. The vacuum tower is a plate tower with 25-35 plates, such as 26 layers, 28 layers, 30 layers, 32 layers, 34 layers, preferably 30-35 layers. The reflux ratio of the vacuum tower is 0.5-1.0, such as 0.6, 0.7, 0.8, 0.9, preferably 0.8-1.0. The operating pressure of the atmospheric tower is 35-50 kPaG, such as 36 kPaG, 38 kPaG, 40 kPaG, 42 kPaG, 45 kPaG, 48 kPaG, preferably 35-40 kPaG, 40-50 kPaG, 35-45 kPaG. The operating temperature of the atmospheric tower is 130-150°C, such as 135°C, 140°C, 145°C, 150°C, preferably 130-140°C, 140-150°C, 135-145°C. The atmospheric tower is a plate tower with 25-35 plates, such as 26, 28, 30, 32, 34, preferably 30-35. The reflux ratio of the atmospheric pressure tower is 1.0-1.5, for example, 1.1, 1.2, 1.3, 1.4, preferably 1.2-1.5, 1.0-1.2.

[0173] The deslagging process is implemented by a deslagging system, and the deslagging system includes a rising film evaporator, a falling film evaporator and a thin film evaporator. The operating pressure of the rising film evaporator is 5-15 kPaA, such as 6 kPaA, 8 kPaA, 10 kPaA, 12 kPaA, 14 kPaA, preferably 5-10 kPaA, 10-15 kPaA. The operating temperature of the rising film evaporator is 160-170°C, such as 162°C, 164°C, 166°C, 168°C, preferably 164-166°C. The operating time of the rising film evaporator is 5-20min, such as 8 min, 10 min, 12 min, 15 min, 18 min, preferably 5-10 min, 10-20 min, 5-15 min. The operating pressure of the falling film evaporator is 5-15 kPaA, such as 6 kPaA, 8 kPaA, 10 kPaA, 12 kPaA, 14 kPaA, preferably 5-10 kPaA, 10-15 kPaA. The operating temperature of the falling film evaporator is 160-170°C, such as 162°C, 164°C, 166°C, 168°C, preferably 164-166°C. The operating time of the falling film evaporator is 5-20min, such as 8 min, 10 min, 12 min, 15 min, 18 min, preferably 5-10 min, 10-20 min, 5-15 min. The operating pressure of the thin film evaporator is 1-10 kPaA, such as 3 kPaA, 5 kPaA, 8 kPaA, 10 kPaA, preferably 5-10kPaA, 1-5 kPaA. The operating temperature of the thin film evaporator is 160-170° C., such as 162° C., 164° C., 166° C., 168° C., preferably 164-166° C. The operating time of the thin film evaporator is 2-10 min, such as 3 min, 5 min, 8 min, 10 min, preferably 2-5 min, 5-10 min.

[0174] The 1, 4-butanediol refining process is implemented by a refining system, and the refining system includes an intermediate tower and a finished product tower. The operating pressure of the intermediate tower is 3-10 kPaA, such as 4 kPaA, 5 kPaA, 6 kPaA, 7 kPaA, 8 kPaA, preferably 3-5 kPaA, 5-10 kPaA, 4-6 kPaA. The operating temperature of the intermediate tower is 150-170°C, such as 155°C, 160°C, 165°C, 170°C, preferably 150-160°C, 160-170°C, 155-165°C. The intermediate tower is a two-stage packed tower, and the height of the two-stage packing is independently 4800-5000mm, such as 4850mm, 4900mm, 4950mm, 5000mm, preferably 4800-4900mm, 4900-5000mm, 4850-4950mm. The reflux ratio of the intermediate tower is 25-30, for example, 25, 26, 27, 28, preferably 25-27. The operating pressure of the finished product tower is 1-5 kPaA, for example, 1 kPaA, 2 kPaA, 3 kPaA, 4 kPaA, 5 kPaA, preferably 1-3 kPaA, 3-5 kPaA, 2-4 kPaA. The operating temperature of the finished product tower is 150-170°C, for example, 155°C, 160°C, 165°C, 170°C, preferably 150-160°C, 160-170°C, 155-165°C. The finished product tower is a two-stage packed tower, and the height of the two-stage packing is independently 5400-5600 mm, for example, 5450 mm, 5500 mm, 5550 mm, 5600 mm, preferably 5500-5600 mm, 5400-5500 mm. The reflux ratio of the finished product tower is 20-25, for example, 21, 22, 23, 24, 25, preferably 22-25, 20-22.

[0175] The 1,4-butanediol recovery process is implemented by a recovery system, and the recovery system includes a light component recovery tower and a heavy component recovery tower. The operating pressure of the light component recovery tower is 1-10kPaA, such as 2 kPaA, 3 kPaA, 5 kPaA, 8 kPaA, 10 kPaA, such as 1-3 kPaA, 3-10 kPaA, 3-5 kPaA. The operating temperature of the light component recovery tower is 160-170°C, such as 162°C, 165°C, 168°C, preferably 160-165°C, 165-170°C. The light component recovery tower is a two-stage packed tower, and the height of the two-stage packing is independently 3500-3700mm, such as 3550 mm, 3600 mm, 3650 mm, 3700 mm, preferably 3500-3600 mm, 3600-3700 mm. The reflux ratio of the light component recovery tower is 5-15, for example, 6, 8, 10, 12, 14, preferably 5-10, 10-15. The operating pressure of the heavy component recovery tower is 1-5 kPaA, for example, 1 kPaA, 2 kPaA, 3 kPaA, 4 kPaA, 5 kPaA, preferably 1-2 kPaA, 2-5 kPaA. The operating temperature of the heavy component recovery tower is 160-180°C, for example, 163°C, 165°C, 167°C, 168°C, 169°C, 170°C, 175°C, 180°C, preferably 165-170°C, 167-169°C. The heavy component recovery tower is a three-stage packed tower, and the height of the three-stage packed tower is independently 3500-4500 mm, such as 3600 mm, 3700 mm, 3800 mm, 3900 mm, 4000 mm, 4100 mm, 4200 mm, 4300 mm, 4400 mm, 4450 mm, preferably 3600-4500 mm. The reflux ratio of the heavy component recovery tower is 5-15, such as 7, 8, 10, 12, 14, preferably 5-10, 10-15.

[0176] The by-product purification and recovery process is implemented by a by-product purification and recovery system, and the by-product purification and recovery system includes a n-butanol dehydration tower and a n-butanol refining tower. The operating pressure of the n-butanol dehydration tower is 2-5 kPaG, such as 2-3 kPaG, 3-5 kPaG. The operating temperature of the n-butanol dehydration tower is 95-110°C, such as 95-105°C, 105-110°C. The n-butanol dehydration tower is a plate tower with 20-30 layers, such as 20-25 layers, 25-30 layers. The reflux ratio of the n-butanol dehydration tower is 10-20, such as 10-15, 15-20. The operating pressure of the n-butanol refining tower is 3-8 kPaG, and the inflow is 3-5 kPaG, 5-8 kPaG. The operating temperature of the n-butanol refining tower is 110-130°C, such as 110-120°C, 120-130°C. The n-butanol refining tower is a two-stage packed tower, and the heights of the two-stage packed towers are independently 3500-4000 mm, such as 3500-3760 mm and 3760-4000 mm. The reflux ratio of the n-butanol refining tower is 1.0-3.0, such as 1.0-1.5 and 1.5-3.0.

[0177] In some embodiments, the content of 2-(4-hydroxybutoxy)-tetrahydrofuran in 1,4-butanediol obtained by post-distillation treatment is ≤150 ppmw, for example, 20 ppmw, 50 ppmw, 80 ppmw, 100 ppmw, 120 ppmw, 130 ppmw, 140 ppmw, 150 ppmw, preferably 50-150 ppmw, 80-150 ppmw.

[0178] In some embodiments, the content of 2-methyl-1, 4-butanediol in the 1, 4-butanediol obtained by post-distillation treatment is ≤900 ppmw, for example, 20 ppmw, 50 ppmw, 80 ppmw, 100 ppmw, 120 ppmw, 150 ppmw, 300 ppmw, 400 ppmw, 500 ppmw, 600 ppmw, 700 ppmw, 800 ppmw, 900 ppmw, preferably 50-900 ppmw, 80-800 ppmw, 100-700 ppmw, 120-650 ppmw.

[0179] In some embodiments, the purity of 1, 4-butanediol obtained by post-distillation treatment is ≥99.85%, for example, ≥99.86%, ≥99.87%, ≥99.88%, ≥99.89%, ≥99.90%, ≥99.91%, ≥99.92%, ≥99.93%, ≥99.94%, ≥99.95%.

[0180] In some embodiments, the color number of 1,4-butanediol obtained after distillation is ≤8, for example, 2-8, 3-6, 4-5, 4.5-5.5.

[0181] In some embodiments, the water content of 1,4-butanediol obtained by post-distillation treatment is ≤80 ppmw, for example ≤70 ppmw, ≤60 ppmw, ≤50 ppmw, ≤40 ppmw, preferably 10-80 ppmw, 20-70 ppmw, 30-60 ppmw.

[0182] The present invention also provides a butanediol with low acetal and low methyl BDO content, wherein the acetal, the methyl BDO and the butanediol are as described in any embodiment of the present invention.

[0183] The acetylene-aldehyde BDO process has long been criticized for its inferior product quality compared to the maleic anhydride process, butadiene process and other process routes. Among the products of different acetylene-aldehyde BDO process routes, the defects of acetal and methyl BDO in their quality are difficult to solve at the same time. At the same time, with the continuous development of downstream application fields and the continuous expansion of emerging products, the requirements for the quality of BDO products are becoming increasingly diversified, strict and refined, and higher requirements are put forward for the quality control of acetylene-aldehyde BDO products. The technical solution of the present invention targets the quality defects of acetylene-aldehyde BDO products, can achieve low acetal content and low methyl BDO content in BDO products, improve the overall level of acetylene-aldehyde BDO products, and reach or even exceed the products of maleic anhydride process, butadiene process and other process routes.

[0184] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by weight.

[0185] Herein, the content of each component in each reaction stage can be measured by chromatography, and those skilled in the art can select the test parameters of the chromatography according to the general knowledge in the art.

[0186] Herein, the abbreviations of various compounds are shown in Table a below.

[0187] Table a

[0188] Example 1, acetylation reaction In a slurry bed reactor, acetylene and 45 wt% formaldehyde aqueous solution are used to produce butynediol in the presence of a copper catalyst (BASF Cu6081P). The molar ratio of circulating acetylene to formaldehyde in the feed formaldehyde solution is 5:1. The reaction temperature is 90°C and the reaction pressure is 160 kPa. Sodium acetate and acetic acid are added to the reactor in a molar ratio of 2:1, and the pH of the reaction solution is controlled at 4.5±0.2.

[0189] The circulating acetylene is sent out from the top of the slurry bed reactor after condensation in the cooler, and after the organic matter is removed by the acetylene recovery unit, it continues to return to the slurry bed reactor to participate in the reaction. After 4 hours of reaction, the content of propargyl alcohol in the reaction liquid is monitored to be less than 0.5wt%, and the content of formaldehyde is ≤1.0wt%, and it can enter the butynediol distillation unit. A 43wt% butynediol (BYD) solution is extracted from the bottom of the slurry bed reactor, and then sent to the low-pressure hydrogenation reaction after subsequent butynediol distillation.

[0190] BYD distillation consists of a butynediol formaldehyde removal tower and a formaldehyde recovery tower, which are mainly used to remove impurities such as formaldehyde and methanol, and recover dilute formaldehyde for reuse.

[0191] The butynediol formaldehyde removal tower is a plate tower with 30 layers of tower plates, an operating pressure of 270±10kPaG, an operating temperature of 140±2°C, and a reflux ratio of 5.5. After formaldehyde removal distillation, the formaldehyde content in the solution is 0.05wt%, and the propargyl alcohol content in the solution is 200±20ppmw. According to the production results, when the content of residual formaldehyde in the reaction solution of the acetylation reaction is ≤1.0wt%, the content of formaldehyde and propargyl alcohol in the butynediol solution can be controlled at a lower level by formaldehyde removal distillation, which is beneficial to reduce the impurity content in the final product.

[0192] The light component impurities at the top of the butynediol formaldehyde removal tower enter the formaldehyde recovery tower. The formaldehyde recovery tower is a plate tower with 40 layers of trays, an operating pressure of 10±1kPaG, an operating temperature of 105±2℃, and a reflux ratio of 12.0, which is used to recover formaldehyde. The recovered formaldehyde can be recycled for acetylation reaction.

[0193] Example 2: Low-pressure hydrogenation reaction The low-pressure hydrogenation reaction converts most of BYD into BDO. In Example 1, the concentration of butynediol in the aqueous solution after the butynediol distillation to remove formaldehyde is about 43wt%. It is configured as a 36wt% butynediol aqueous solution according to the requirements of the low-pressure hydrogenation reaction. In a slurry bed reactor, Raney nickel (Dalian Zion Technology) is used as a catalyst, and the reaction occurs under the conditions of 45±5°C and 2.0MPaG, and the butynediol conversion rate reaches 99%. A 20wt% concentration of sodium hydroxide aqueous solution is added to the reactor, and the pH of the reactor is controlled at 8±1. The content of BYD in the feed liquid is determined by gas chromatography analysis, and the molar ratio of circulating hydrogen to feed BYD is 100:1. After the circulating hydrogen is condensed from the top of the low-pressure hydrogenation reactor through a cooler, it continues to return to the low-pressure hydrogenation reactor for recycling.

[0194] After 0.5 hours of reaction, the low-pressure hydrogenation reaction liquid is monitored. The methyl BDO content in the reaction liquid is less than 300 ppmw, the acetal content is ≤500 ppmw, and the butene glycol content is no more than 1.0 wt%. The low-pressure hydrogenation reaction is completed and can be fed to the high-pressure hydrogenation. The crude BDO solution extracted from the bottom of the low-pressure hydrogenation reactor is continuously sent to the high-pressure hydrogenation reactor.

[0195] Example 3, High-pressure hydrogenation reaction High-pressure hydrogenation is a refined hydrogenation reaction, which is a key step in controlling the content of methyl BDO and acetal. The high-pressure hydrogenation reactor is a trickle bed reactor, with carrier nickel (Shanxi Jiaocheng Kate New Materials) as the catalyst. The raw hydrogen from outside is usually 3.0MPaG. After the hydrogen is pressurized to 30.0MPaG by a compressor, it is added to the high-pressure hydrogenation reactor from the top and downstream at the same time as the crude BDO solution.

[0196] Under the conditions of reaction temperature of 110±5℃ and reaction pressure of 20.0MPaG, the acetal and other unsaturated substances in the crude BDO solution are completely reacted. The circulating hydrogen is extracted from below the catalyst bed of the high-pressure hydrogenation reactor, condensed in the cooler, and then circulated back to the high-pressure hydrogenation reactor. The molar ratio of the circulating hydrogen to the BDO in the feed liquid is 30:1.

[0197] After 2 hours of reaction, the content of methyl BDO in the high-pressure hydrogenation reaction liquid was monitored to be less than 600 ppm, and the content of acetal was ≤200 ppm, and the reaction was completed. The crude BDO solution extracted from the bottom of the high-pressure reactor was sent to the distillation post-processing unit.

[0198] Example 4, distillation post-treatment The crude BDO solution after high-pressure hydrogenation needs to go through five steps in the BDO distillation unit: dehydration, residue removal, product refining, BDO recovery process and by-product purification and recovery to obtain the BDO product.

[0199] The dehydration system of the dehydration process consists of a vacuum tower and an atmospheric pressure tower, which are used to control the water content in the crude BDO solution to ≤1.5wt%. The vacuum tower is a plate tower with 30 plates, the operating pressure is controlled at 25±1.0kPaA, the operating temperature is controlled at 75±1℃, and the reflux ratio is 0.8. The atmospheric pressure tower is a plate tower with 30 plates, the operating pressure is controlled at 40±1kPaG, the operating temperature is controlled at 140±1℃, and the reflux ratio is 1.2.

[0200] At 165±1℃ and high vacuum operating conditions, the dehydrated crude BDO product is sequentially subjected to three-stage evaporation separation in a rising film evaporator, a falling film evaporator and a thin film evaporator to remove the residue. The operating pressure of the falling film evaporator and the rising film evaporator is controlled at 10kPaA, and the operating time is 10min. The operating pressure of the thin film evaporator is controlled at 5kPaA, and the operating time is 5min.

[0201] The product refining process purifies the BDO after the residue is removed. The BDO refining system consists of an intermediate tower and a finished product tower. After refining, qualified BDO products are obtained. The intermediate tower is a packed tower with Sulzer Bxplus as the packing material. There are 2 sections with packing heights of 4900 / 4900mm, operating pressure of 5±0.5kPaA, operating temperature of 160±1℃, and reflux ratio of 25.0. The finished product tower is a packed tower with Sulzer Bxplus as the packing material. There are 2 sections with packing heights of 5500 / 5500mm, operating pressure of 3±0.5kPaA, operating temperature of 160±1℃, and reflux ratio of 22.0.

[0202] The BDO recovery process is to recover the BDO in the light components and heavy components discharged from the product refining process by secondary distillation to improve the yield. The light component recovery tower is used to recover the BDO in the light components. The tower is a packed tower with Sulzer Bxplus as the packing material. It is divided into 2 sections with packing heights of 3600 / 3600mm, operating pressure of 3±0.5kPaA, operating temperature of 165±1℃, and reflux ratio of 10.0. The heavy component is a packed tower with Sulzer Bxplus as the packing material. It has 3 sections with packing heights of 4472 / 3600 / 3600mm. The recovery tower is used to recover the BDO in the heavy components. The operating pressure is 2±0.2kPaA, the operating temperature is 168±1℃, and the reflux ratio is 10.0.

[0203] By-product purification and recovery is to purify and recover the n-butanol produced as a by-product during the hydrogenation process to obtain commercial-grade n-butanol that meets the requirements of GB / T6027-2023. In view of the special physical properties of n-butanol and water, it consists of an n-butanol dehydration tower and an n-butanol refining tower. The n-butanol dehydration tower is a plate tower with 25 layers, an operating pressure of 3±1 kPaG, an operating temperature of 105±2℃, and a reflux ratio of 15.0. The n-butanol refining tower is a two-stage packed tower, the packing is Sulzer M252Y, the packing height is 3760 / 3760mm, the operating pressure is 5±1 kPaG, the operating temperature is 120±2℃, and the reflux ratio is 1.5.

[0204] Example 5, Acetylation Reaction The only difference between Example 5 and Example 1 is that the molar ratio of circulating acetylene to feed formaldehyde is 2:1.

[0205] Example 6, acetylation reaction The only difference between Example 6 and Example 1 is that the molar ratio of circulating acetylene to feed formaldehyde is 10:1.

[0206] Example 7: Low-pressure hydrogenation reaction The only difference between Example 7 and Example 2 is that the molar ratio of circulating hydrogen to feed BYD is 5:1.

[0207] Example 8: Low-pressure hydrogenation reaction The only difference between Example 8 and Example 2 is that the molar ratio of circulating hydrogen to feed BYD is 200:1.

[0208] Example 9, Acetylation Reaction The only difference between Example 9 and Example 1 is that the reaction pressure is 140 kPa.

[0209] Example 10, Acetylation Reaction The only difference between Example 10 and Example 1 is that the reaction pressure is 200 kPa.

[0210] Example 11, High-pressure hydrogenation reaction The only difference between Example 11 and Example 3 is that the molar ratio of circulating hydrogen to feed BDO is 0.5:1.

[0211] Example 12: High-pressure hydrogenation reaction The only difference between Example 12 and Example 3 is that the molar ratio of circulating hydrogen to feed BDO is 100:1.

[0212] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the molar ratio of circulating acetylene to feed formaldehyde is 0.5:1.

[0213] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the reaction pressure is 1000 kPa.

[0214] Comparative Example 3 The only difference between Comparative Example 3 and Example 2 is that the molar ratio of circulating hydrogen to feed BYD is 2:1.

[0215] Comparative Example 4 The only difference between Comparative Example 4 and Example 3 is that the molar ratio of circulating hydrogen to feed BDO is 0.3:1.

[0216] Test methods in this article

[0217] 1. Determination of formaldehyde content.

[0218] The formaldehyde in the acetylation reaction solution was analyzed by titration using a potentiometric titrator (Mettler T70). The specific method is as follows.

[0219] The pH value of the prepared anhydrous sodium sulfite solution was adjusted to 9.5.

[0220] Weigh 50 mL of anhydrous sodium sulfite solution adjusted to pH value, and perform blank determination using sulfuric acid standard solution on T70 automatic potentiometric titrator using the method.

[0221] Add 50mL of sodium sulfite solution into a 100mL titration cup, use a Pasteur pipette to transfer the reaction solution (1.5±0.2g for first stage; 2.5±0.2g for second stage; 3±0.2g for third stage; 1.5±0.5g for distillation; 3±0.2g for V402) into the titration cup, and titrate to the endpoint with sulfuric acid standard solution on a T70 automatic potentiometric titrator using the method "JiaQuan-D", read the value, and record the result.

[0222] The formaldehyde content X expressed as a mass percentage is calculated as follows: , Where: C1: concentration of sulfuric acid standard solution, mol / L; V1: volume of sulfuric acid standard solution consumed in titration, mL; M1: mass of formaldehyde sample, g; 0.03003: Mass of formaldehyde per millimole, g.

[0223] 2. The contents of methanol, propargyl alcohol and BYD were analyzed using gas chromatography (Thermo Fisher Trace 1310).

[0224] 3. The contents of methanol, tetrahydrofuran, butanol, γ-butyrolactone, 4-hydroxybutyraldehyde, 1,4-pentanediol, butanediol, methylbutanediol, acetal, and methyl-pentanediol were analyzed using a gas chromatograph (Thermo Fisher Trace 1310).

[0225] 4. Chromaticity analysis.

[0226] Instrument: UV-Vis spectrophotometer, PFX-195.

[0227] Operation steps: Turn on the colorimeter and let it stabilize for 30 minutes. Run the baseline program. Use distilled water or an empty cuvette as a blank. Replace the same cuvette with the sample 1-3 times. Wipe the quartz window of the cuvette clean. Run the colorimeter reading program. Record the test results.

[0228] Test Example 1 According to the method defined in the test method of this article, the butynediol solution generated in the acetylation reaction step was tested, and the measured product indicators are shown in Table 1 below.

[0229] Table 1

[0230] In Table 1, "conversion rate" refers to the calculation based on formaldehyde, conversion rate = (feed formaldehyde - residual formaldehyde) / feed formaldehyde * 100%.

[0231] Methanol is brought into the reactor together with the feed formaldehyde solution, so the content of methanol does not change during the reaction. Comparing the data results of Examples 1, 5, and 6, it can be found that adjusting the molar ratio of circulating acetylene to feed formaldehyde has an effect on the contents of residual formaldehyde and propargyl alcohol. As the molar ratio of circulating acetylene to feed formaldehyde increases, the content of propargyl alcohol gradually decreases, thereby creating conditions for reducing the content of methyl BDO in the final product. Comparing the data results of Examples 1, 9, 10 and Comparative Example 2, it can be found that the content of propargyl alcohol is proportional to the pressure of the acetylation reaction. When the reaction pressure is further increased to 1000 kPa, the content of propargyl alcohol increases significantly by about 50 times. Therefore, carrying out the acetylation reaction under low pressure is more conducive to controlling the content of propargyl alcohol.

[0232] Test Example 2 According to the method defined in the test method of this article, the crude BDO solution generated in the low-pressure hydrogenation reaction step was tested, and the measured product indicators are shown in Table 2 below.

[0233] Table 2: Analysis of low pressure hydrogenation reaction liquid

[0234] In Examples 2, 7, and 8, the content of butynediol is relatively low, indicating that the low-pressure hydrogenation reaction has a high feed conversion rate. From the data in the table, it can be seen that adjusting the molar ratio of circulating hydrogen to feed BYD has an effect on the formation of acetal and methyl BDO. As the molar ratio of circulating hydrogen to feed BYD increases, the acetal content and methyl BDO content gradually decrease.

[0235] Test Example 3 According to the method defined in the test method of this article, the crude BDO solution generated by the high pressure hydrogenation reaction step was tested, and the measured product indicators are shown in Table 3 below.

[0236] Table 3: Analysis of high pressure hydrogenation reaction liquid

[0237] The present invention has found through the study of the reaction mechanism that the high-pressure hydrogenation reaction is a refined hydrogenation reaction, which can mainly eliminate the side reaction acetal generated during the low-pressure hydrogenation reaction, and can also avoid the generation of methyl BDO. From the data in Table 2 and Table 3, it can be seen that compared with Examples 2, 7, and 8, the acetal content in the reaction solution of Examples 3, 11, and 12 is significantly lower, and the BDO content is increased. Adjusting the molar ratio of circulating hydrogen to BDO has an effect on the generation of acetal and methyl BDO. As the molar ratio of circulating hydrogen to BDO increases, the generation of methyl BDO is suppressed.

[0238] Test Example 4 According to the method defined in the test method of this article, the product indicators are tested and the test results are shown in Table 4.

[0239] Example 1, Example 2, Example 3 and Example 4 were carried out in sequence to obtain Product 1. Example 1, Example 2, Example 11 and Example 4 were carried out in sequence to obtain Product 2. Example 1, Example 2, Example 12 and Example 4 were carried out in sequence to obtain Product 3.

[0240] Comparative Example 1, Example 2, Example 3 and Example 4 were carried out in sequence to obtain Product 4. Comparative Example 2, Example 2, Example 3 and Example 4 were carried out in sequence to obtain Product 5.

[0241] The butynediol solution obtained by the acetylation reaction in Example 1 is directly fed into Example 2 for low-pressure hydrogenation reaction without distillation (i.e., without formaldehyde removal distillation), and then Examples 3 and 4 are carried out to obtain Product 6.

[0242] Example 1, Comparative Example 3, Example 3 and Example 4 were carried out in sequence to obtain Product 7.

[0243] Example 1, Example 2, Comparative Example 4 and Example 4 were carried out in sequence to obtain Product 8.

[0244] Table 4 project Moisture Chroma Butanediol HB-THF Methyl Butanediol other unit ppmw APHA wt% ppmw ppmw wt% Product 1 46 4.9 99.88 118 429 0.056 Product 2 32 5.2 99.85 148 611 0.068 Product 3 52 5 99.9231 82 124 0.051 Product 4 48 4.6 99.58 596 2822 0.08 Product 5 52 4.5 99.43 689 3604 0.1428 Product 6 58 5 99.16 793 5061 0.26 Product 7 50 5.2 99.41 1277 1864 0.28 Product 8 55 5.5 99.63 312 1988 0.13

[0245] Analysis of the data in Table 1 (the data in Table 1 are data without distillation for formaldehyde removal after acetylation reaction; the formaldehyde content of Comparative Example 1 exceeds the standard; the propargyl alcohol content of Comparative Example 2 exceeds the standard) and the indicators of Product 1, Product 4, Product 5, and Product 6 shows that the content of formaldehyde and propargyl alcohol in the BYD solution entering the low-pressure hydrogenation reaction has a great influence on the content of acetal and methyl BDO in the final BDO product. For Product 4 and Product 5, the content of formaldehyde or propargyl alcohol in the reaction liquid obtained by the acetylation reaction exceeds the standard (see the data of Comparative Example 1 and Comparative Example 2 in Table 1), which exceeds the processing capacity of the formaldehyde removal distillation, resulting in the formaldehyde or propargyl alcohol in the reaction liquid entering the subsequent hydrogenation reaction not meeting the indicator requirements of the present invention, and ultimately resulting in the content of acetal and methyl BDO in the obtained products far exceeding the product indicators of the present invention. For product 6, since the reaction liquid obtained from the acetylation reaction in Example 1 was not distilled to remove formaldehyde, the formaldehyde and propargyl alcohol in the reaction liquid entering the low-pressure hydrogenation reaction exceeded the standard at the same time, resulting in a significant increase in acetal and methyl BDO in the final product, and the product quality was the worst.

[0246] It can be seen from the indicators of product 7 that when the acetal and methyl BDO in the low-pressure reaction exceed the standard (see the data of comparative example 3 in Table 2), although the acetal content in the product is reduced, it still does not meet the requirement of low acetal, and the content of methyl BDO exceeds the content of methyl BDO in product 1 by more than 2 times, indicating that although the high-pressure hydrogenation step can reduce the acetal content in the product, it has no effect on reducing the methyl BDO content. It can be seen from the indicators of product 8 (see the data of comparative example 4 in Table 3) that the acetal and methyl BDO in the reaction liquid obtained in the high-pressure hydrogenation stage exceed the standard, and there is no obvious decrease after distillation in Example 4, resulting in unqualified contents of acetal and methyl BDO in the product.

[0247] In summary, from the above comparison, it can be seen that the distillation post-treatment step has almost no effect on reducing the content of acetal and methyl BDO, which is consistent with the physical property system of acetal-BDO and methyl BDO-BDO azeotropy and boiling points. The indicators of the three reactions of acetylation reaction, low-pressure hydrogenation, and high-pressure hydrogenation are affected step by step. Only by controlling the indicators of each step of the reaction can the product quality of the final product be guaranteed. The present invention controls the content of acetal and methyl BDO before entering the distillation post-treatment step to a lower level by controlling the reaction conditions of the acetylation reaction, low-pressure hydrogenation, and high-pressure hydrogenation steps and the indicators of the reaction liquid, thereby obtaining a BDO product with low acetal content and low methyl BDO content.

Claims

1. A method for preparing 1,4-butanediol, characterized in that: The method comprises the steps of: (1) Under the action of a first catalyst, acetylene reacts with a formaldehyde aqueous solution to generate a first reaction liquid containing butynediol; (2) distilling the first reaction liquid to remove formaldehyde, thereby obtaining a first distillation reaction liquid; (3) Under the action of a second catalyst, subjecting the first distillation reaction liquid to a first hydrogenation reaction with a first hydrogen gas to obtain a second reaction liquid containing 1,4-butanediol; (4) Under the action of a third catalyst, subjecting the second reaction liquid to a second hydrogenation reaction to obtain a third reaction liquid containing 1,4-butanediol; In step (1), the molar ratio of acetylene to formaldehyde is (2-10):1; In step (1), the reaction pressure is 140-200 kPa; In step (3), the molar ratio of the first hydrogen to butynediol is (5-200):1; In step (4), the molar ratio of the second hydrogen gas to the 1,4-butanediol in the second reaction liquid is (0.5-100):

1.

2. The method according to claim 1, characterized in that Step (1) has one or more of the following characteristics: In the formaldehyde aqueous solution, the concentration of formaldehyde is 40-45wt%; The acetylene is recycled for use in step (1); The first catalyst is a supported copper catalyst; The reaction temperature is 80-120°C; The reaction residence time is 0.5-200h; Step (1) reacts at a pH between 3.0 and 5.5; In the first reaction solution, the content of propargyl alcohol is ≤0.5wt%; In the first reaction liquid, the content of formaldehyde is ≤1.0wt%; In the first reaction solution, the content of butynediol is 40-45wt%.

3. The method according to claim 2, characterized in that The pH of step (1) is adjusted by a buffer, wherein the buffer comprises a strong base, a weak acid salt and an organic acid.

4. The method according to claim 1, characterized in that: Step (2) has one or more of the following characteristics: The operating pressure of the formaldehyde removal tower used to implement the rectification formaldehyde removal is 250-300 kPaG; The operating temperature of the formaldehyde removal tower used for implementing the rectification formaldehyde removal is 100-180°C; The formaldehyde removal tower used for implementing the rectification and formaldehyde removal is a plate tower, and the number of trays of the formaldehyde removal tower is 25-35 layers; The reflux ratio of the formaldehyde removal tower used for implementing the rectification formaldehyde removal is 5-10; In the first distillation reaction liquid, the content of formaldehyde is ≤0.1wt%; In the first distillation reaction liquid, the content of propargyl alcohol is ≤500ppmw; In the first distillation reaction liquid, the content of butynediol is 40-45wt%.

5. The method according to claim 1, characterized in that Step (3) has one or more of the following characteristics: The concentration of butynediol in the first distillation reaction liquid is adjusted to 35-40wt%, and then subjected to a first hydrogenation reaction with the first hydrogen; Step (3) is carried out in a slurry bed reactor; The reaction pressure is 2.0-3.0MPaG; The reaction temperature is 40-60°C; The first hydrogen is recycled for use in step (3); Step (3) reacting at a pH between 7 and 11; The second catalyst is a nickel catalyst; In step (3), the conversion rate of butynediol is ≥95%; Reaction time is 10-240 min; In the second reaction liquid, the content of butene glycol is ≤1.0wt%; In the second reaction solution, the content of 2-methyl-1,4-butanediol is 10-2000 ppmw; In the second reaction liquid, the content of acetal is ≤600 ppmw.

6. The method according to claim 1, characterized in that Step (4) has one or more of the following characteristics: The second reaction solution is directly applied to step (4); The reaction pressure is 20.0-30.0MPaG; The reaction temperature is 90-130°C; The second hydrogen is recycled for use in step (4); Step (4) is carried out in a trickle bed reactor; The third catalyst is a supported nickel catalyst; The reaction time is 1-8h; In the third reaction liquid, the content of 2-methyl-1, 4-butanediol is ≤5000ppmw; In the third reaction liquid, the content of acetal is ≤200 ppmw.

7. The method according to claim 1, characterized in that The method further includes performing post-distillation treatment on the 1,4-butanediol in the third reaction liquid, wherein the post-distillation treatment includes a dehydration process, a residue removal process, a 1,4-butanediol refining process and a 1,4-butanediol recovery process.

8. The method according to claim 7, characterized in that The method has one or more of the following features: Implementing the dehydration process through a dehydration system, wherein the dehydration system comprises a vacuum tower and an atmospheric pressure tower; The deslagging process is implemented by a deslagging system, wherein the deslagging system includes a rising film evaporator, a falling film evaporator and a thin film evaporator; Implementing the 1,4-butanediol refining process through a refining system, wherein the refining system includes an intermediate tower and a finished product tower; The 1,4-butanediol recovery process is implemented through a recovery system, and the recovery system includes a light component recovery tower and a heavy component recovery tower.

9. The method according to claim 8, characterized in that The method has one or more of the following features: The operating pressure of the vacuum tower is 20-40 kPaA; The operating temperature of the vacuum tower is 70-80°C; The vacuum tower is a plate tower with 25-35 plates; The reflux ratio of the vacuum tower is 0.5-1.0; The operating pressure of the atmospheric tower is 35-50 kPaG; The operating temperature of the atmospheric tower is 130-150°C; The atmospheric pressure tower is a plate tower with 25-35 plates; The reflux ratio of the atmospheric pressure tower is 1.0-1.5; The operating pressure of the rising film evaporator is 5-15 kPaA; The operating temperature of the rising film evaporator is 160-170°C; The operation time of the rising film evaporator is 5-20min; The operating pressure of the falling film evaporator is 5-15 kPaA; The operating temperature of the falling film evaporator is 160-170°C; The operation time of the falling film evaporator is 5-20min; The operating pressure of the thin film evaporator is 1-10 kPaA; The operating temperature of the thin film evaporator is 160-170°C; The operation time of the thin film evaporator is 2-10min; The operating pressure of the intermediate tower is 3-10 kPaA; The operating temperature of the intermediate tower is 150-170°C; The intermediate tower is a two-stage packed tower, and the height of the two-stage packing is independently 4800-5000mm; The reflux ratio of the intermediate tower is 25-30; The operating pressure of the finished product tower is 1-5 kPaA; The operating temperature of the finished product tower is 150-170°C; The finished product tower is a two-stage packed tower, and the height of the two-stage packing is independently 5400-5600mm; The reflux ratio of the finished product tower is 20-25; The operating pressure of the light component recovery tower is 1-10 kPaA; The operating temperature of the light component recovery tower is 160-170°C; The light component recovery tower is a two-stage packed tower, and the height of the two-stage packing is independently 3500-3700 mm; The reflux ratio of the light component recovery tower is 5-15; The operating pressure of the heavy component recovery tower is 1-5 kPaA; The operating temperature of the heavy component recovery tower is 160-180°C; The heavy component recovery tower is a three-stage packed tower, and the height of the three-stage packing is independently 3500-4500 mm; The reflux ratio of the heavy component recovery tower is 5-15.

10. The method according to claim 7, characterized in that The method has one or more of the following features: The content of 2-(4-hydroxybutoxy)-tetrahydrofuran in 1,4-butanediol obtained by post-distillation treatment is ≤150ppmw; The content of 2-methyl-1, 4-butanediol in the 1, 4-butanediol obtained by post-distillation treatment is ≤900ppmw; The purity of 1, 4-butanediol obtained after distillation treatment is ≥99.85%; The color number of 1, 4-butanediol obtained after distillation treatment is ≤8; The water content of 1,4-butanediol obtained after distillation treatment is ≤80ppmw.

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