Process for preparing 1,4-butanediol with low acetal content and low methylbutanediol content

Abstract

The present invention belongs to the field of chemical production, and particularly relates to a method for producing 1,4-butanediol with low acetal content and low methyl butanediol content. The method comprises the steps of: (1) reacting acetylene with an aqueous formaldehyde solution under the action of a first catalyst to generate a first reaction solution containing butynediol; (2) subjecting the first reaction solution to rectification to remove formaldehyde to obtain a first rectified reaction solution; (3) carrying out a first hydrogenation reaction on the first rectified reaction solution and a first hydrogen to obtain a second reaction solution containing 1,4-butanediol under the action of a second catalyst; (4) carrying out a second hydrogenation reaction on the second reaction solution and a second hydrogen under the action of a third catalyst to prepare a third reaction solution containing 1,4-butanediol. The BDO product prepared by the method of the present invention can not only meet the polymer field with special requirements for color value, but also enter the lithium-ion battery field requiring low methyl BDO content.

Description

Technical Field

[0001] The present invention belongs to the field of chemical production, and particularly 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 as an intermediate for organic synthesis, industrial solvents, and polymer raw materials. Through different reactions, it can produce tetrahydrofuran (THF), γ-butyrolactone (GBL), polybutylene terephthalate (PBT), polytetramethylene ether glycol (PTMEG), N-methylpyrrolidone (NMP), etc., and can be widely applied in fields such as automobile manufacturing, electronics and electrical appliances, instrumentation, household appliances and textiles, pesticides, lithium-ion batteries, plasticizers, pharmaceutical intermediates, chain extenders, and adhesives.

[0003] BDO has multiple production routes, and the main industrial production processes include the Reppe process (using acetylene and formaldehyde), 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 existing Reppe process plants. The first type is: acetylene and formaldehyde react in the first stage to form butynediol, and then butynediol undergoes two-stage hydrogenation (the same catalyst and reaction conditions are used in the two-stage hydrogenation reaction) to produce BDO. Since this process was developed earlier, there are problems such as the need to frequently replace the catalyst and significant fluctuations in product indicators during different life cycles of the catalyst. The second type is: the acetylene and formaldehyde reaction uses a three-stage slurry bed reaction to form butynediol, and then undergoes two-step hydrogenation to produce BDO, with different catalysts and reaction conditions used in the two-step hydrogenation. Such a device operates continuously and does not require frequent shutdowns to replace the catalyst, and the operation is simple, but it mainly has the defect of a large number of reactors. Both process routes are representatives of the improved Reppe process BDO process and also represent two different BDO quality characteristics. The most significant characteristic of the BDO product of the first type of process is its high acetal content. Acetal is affected by acidic and high-temperature conditions during 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. On the contrary, the BDO product of the second type of process has a very low acetal content and can be widely used in fields such as PBT, PU / TPU polymers, but has a high methyl BDO content, which limits the use of this type of BDO product in the electronic grade GBL and NMP industries.

[0005] Patent application CN109851477 believes that the generation of methyl BDO is caused by formaldehyde contained in butynediol. Therefore, by adding a certain amount of methanol to the rectification section of butynediol, the content of formaldehyde in butynediol is reduced. This method not only increases steam consumption and rectification load, but also introduces methanol, which needs to be removed twice in the BDO rectification process. Therefore, this method is not suitable for industrialization. Patent application CN101284762 discloses a method for preparing high-purity 1,4-butanediol. The content of methyl BDO can be controlled below 0.07 wt% through multi-stage rectification, but this method has the defects of high energy consumption and complex process. Patent application CN101284762 also uses physical separation means: using the method of melt crystallization to obtain high-purity BDO. Although the above method of physical separation can reduce the content of methyl BDO, the cost is too high and the energy consumption is large, which does not match the benefits.

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

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

[0008] In the first aspect of the present invention, a method for preparing 1,4-butanediol is provided, and the method includes the steps of:

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

[0010] (2) Rectifying and removing formaldehyde from the first reaction solution to obtain a first rectified reaction solution;

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

[0012] (4) Under the action of a third catalyst, the second reaction solution reacts with a second hydrogen gas to perform a second hydrogenation reaction to obtain a third reaction solution 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 to 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 aqueous formaldehyde solution, the concentration of formaldehyde is 40 - 45 wt%;

[0019] The acetylene is recycled to 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 - 200 h;

[0023] Step (1) is carried out at a pH between 3.0 and 5.5;

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

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

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

[0027] In one or more embodiments, the pH of step (1) is adjusted by a buffer solution, and the buffer solution includes a strong base 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 - removing tower for carrying out the rectification of formaldehyde removal is 250 - 300 kPaG;

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

[0031] The formaldehyde - removing tower for carrying out the rectification of formaldehyde removal is a plate tower, and the number of trays of the formaldehyde - removing tower is 25 - 35;

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

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

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

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

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

[0037] Adjust the concentration of butynediol in the first rectification reaction liquid to 35 - 40 wt%, and then carry out the 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 - 3.0 MPaG;

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

[0041] The first hydrogen is recycled and used in step (3);

[0042] Step (3) reacts 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] The reaction time is 10 - 240 min;

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

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

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

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

[0050] Take the second reaction liquid and directly apply it to step (4);

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

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

[0053] The second hydrogen recycle is reused 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 - 8 h;

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

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

[0059] In one or more embodiments, the method further includes subjecting 1,4 - butanediol in the third reaction liquid to rectification post - treatment, and the rectification post - treatment includes 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] The dehydration process is implemented by a dehydration system, and the dehydration system includes a vacuum column and an atmospheric column;

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

[0063] The 1,4 - butanediol refining process is implemented by a refining system, and the refining system includes an intermediate column and a product column;

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

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

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

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

[0068] The vacuum column is a plate column, and the number of trays is 25 - 35;

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

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

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

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

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

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

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

[0076] The operating time of the climbing - film evaporator is 5 - 20 min;

[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 operating time of the falling - film evaporator is 5 - 20 min;

[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 operating time of the thin - film evaporator is 2 - 10 min;

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0100] In the 1,4-butanediol prepared by rectification post-treatment, the content of 2-(4-hydroxybutoxy)-tetrahydrofuran is ≤ 150 ppmw;

[0101] In the 1,4-butanediol prepared by rectification post-treatment, the content of 2-methyl-1,4-butanediol is ≤ 900 ppmw;

[0102] In the 1,4-butanediol prepared by rectification post-treatment, the purity of 1,4-butanediol is ≥ 99.85%;

[0103] The color number of the 1,4-butanediol prepared by rectification post-treatment is ≤ 8;

[0104] In the 1,4-butanediol prepared by rectification post-treatment, the water content is ≤ 80 ppmw.

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

[0106] (1) By controlling the conditions of each reaction unit (alkynylation reaction, low-pressure hydrogenation reaction, high-pressure hydrogenation reaction), the present invention ensures that the content of acetal entering the rectification unit (such as the rectification post-treatment process in Example 4) is ≤ 200 ppmw, ensures that the content of methyl BDO entering the rectification unit is ≤ 950 ppmw, and the content of acetal in the finally obtained BDO product after rectification is ≤ 150 ppmw, the content of methyl BDO 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 not only meet the polymer fields such as PU / TPU, PBT, PBAT, etc. which have special requirements for color value (requiring low acetal content in the BDO product), but also enter the lithium-ion battery field with requirements for 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 rectification scheme, is simple to operate and easy to control, is suitable for large-scale industrial production, and has good industrial application prospects. Specific embodiments

[0109] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

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

[0111] In this article, "comprising", "including", "containing" and similar terms cover the meanings of "consisting essentially of" and "consisting of". For example, when it is disclosed herein that "A comprises B and C", it should be considered that "A consists essentially of B and C" and "A consists of B and C" have been disclosed herein.

[0112] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the ranges (including integers and fractions).

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

[0114] In this article, when describing the embodiments or examples, it should be understood that it is not used to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the methods and materials described in the present invention can be covered within the scope defined by the claims.

[0115] In this text, for the sake of brevity in description, not all possible combinations of all technical features in each implementation or embodiment are described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation or embodiment can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0116] In this text, "acetal" refers to 2-(4-hydroxybutoxy)-tetrahydrofuran, namely HB-THF.

[0117] In this text, both "methyl butanediol" and "methyl BDO" refer to 2-methyl-1,4-butanediol.

[0118] In this text, both "butanediol" and "BDO" refer to 1,4-butanediol.

[0119] In this text, those skilled in the art can select the reflux ratio of each distillation column according to conventional methods. Since acetal and methyl BDO cannot be separated by conventional distillation methods, changing the reflux ratio of each distillation column has little effect on the separation effect of acetal and methyl BDO.

[0120] The inventors found that by controlling the amount of recycled acetylene in the alkynylation reaction, the amount of recycled hydrogen in the low-pressure hydrogenation reaction, the amount of recycled hydrogen in the high-pressure hydrogenation reaction, and the contents of formaldehyde and propargyl alcohol in the reaction liquid at each reaction stage, 1,4-butanediol with low acetal and low methyl BDO contents can be prepared by subjecting acetylene to an alkynylation reaction with formaldehyde and then performing low-pressure hydrogenation and high-pressure hydrogenation. On this basis, the present invention provides a method for preparing 1,4-butanediol, and the method includes the steps of:

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

[0122] (2) The first reaction liquid is subjected to rectification to remove formaldehyde to obtain a first rectified reaction liquid;

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

[0124] (4) Under the action of a third catalyst, the second reaction liquid reacts with a second hydrogen to perform a second hydrogenation reaction to obtain a third reaction liquid containing 1,4-butanediol.

[0125] In step (1), in the aqueous formaldehyde solution, the concentration of formaldehyde is 40-45 wt%, such as 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 solution of the alkynylation reaction can be effectively controlled within the range defined herein, and further, the contents of formaldehyde and propargyl alcohol in the first rectification reaction solution can be realized within the range defined herein, which is beneficial to preparing butanediol with low acetal and low methyl BDO contents.

[0126] The excessive acetylene remaining 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, such as 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 contents of formaldehyde and propargyl alcohol in the first reaction solution of the alkynylation reaction can be effectively controlled within the range defined herein, and further, the contents of formaldehyde and propargyl alcohol in the first rectification reaction solution can be realized within the range defined herein, which is beneficial to preparing butanediol with low acetal and low methyl BDO contents.

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

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

[0130] In step (1), the reaction temperature is 80-120 °C, such as 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, preferably 80-90 °C or 90-120 °C. By controlling the reaction temperature of step (1) within the range defined herein, the contents of formaldehyde and propargyl alcohol in the first reaction solution of the alkynylation reaction can be effectively controlled within the range defined herein, and further, the contents of formaldehyde and propargyl alcohol in the first rectification reaction solution can be realized within the range defined herein, which is beneficial to preparing butanediol with low acetal and low methyl BDO contents.

[0131] In step (1), the reaction pressure is 140 - 200 kPa, such as 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 in step (1) within the range defined herein can effectively control the contents of formaldehyde and propargyl alcohol in the first reaction liquid of the alkynylation reaction within the range defined herein, and further enable the contents of formaldehyde and propargyl alcohol in the first rectification reaction liquid to be within the range defined herein, which is beneficial to obtaining butanediol with low acetal and low methyl BDO contents.

[0132] In step (1), the reaction residence time can be 0.5 - 200 h, such as 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 carried out at a pH between 3.0 and 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. In this article, the pH of the reaction system in step (1) can be adjusted by using a buffer solution. A commonly used buffer solution in the art can be selected according to the pH required for the alkynylation reaction in step (1). The buffer solution can be directly commercially available or prepared by oneself. The prepared buffer solution may 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 is composed 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. Those skilled in the art can prepare a buffer solution with a specific pH according to the ionization properties of the strong base weak acid salt and the organic acid. For example, the molar ratio of the strong base weak acid salt to the 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. Using the prepared buffer solution defined in the present invention can control the pH of the reaction system in step (1) within the range defined herein. Controlling the pH of the reaction liquid in step (1) within the range defined herein can effectively control the contents of formaldehyde and propargyl alcohol in the first reaction liquid of the alkynylation reaction within the range defined herein, and further enable the contents of formaldehyde and propargyl alcohol in the first rectification reaction liquid to be within the range defined herein, which is beneficial to obtaining butanediol with low acetal and low methyl BDO contents.

[0134] In some embodiments, in step (1), in the first reaction solution, the content of propargyl alcohol 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 solution within the range defined herein can further achieve that the content of propargyl alcohol in the first rectification reaction solution is within the range defined herein, which is beneficial to obtaining butanediol with low acetal and low methyl BDO content.

[0135] In some embodiments, in step (1), in the first reaction solution, the content of formaldehyde 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 solution within the range defined herein can further achieve that the content of formaldehyde in the first rectification reaction solution is within the range defined herein, which is beneficial to obtaining butanediol with low acetal and low methyl BDO content.

[0136] In some embodiments, in step (1), in the first reaction solution, the content of butynediol is 40-45 wt%, such as 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 solution contains impurities, and the impurities include propargyl alcohol, methanol, and unreacted formaldehyde, etc.

[0138] In step (2), the operating pressure of the formaldehyde removal tower for carrying out the rectification to remove formaldehyde 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. Controlling the operating pressure of step (2) within the range defined herein can effectively control the contents of formaldehyde and propargyl alcohol in the first rectification reaction solution within the range defined herein, which is beneficial to obtaining butanediol with low acetal and low methyl BDO content.

[0139] In step (2), the operating temperature of the formaldehyde removal column for carrying out the rectifying formaldehyde removal is 100-180°C, such as 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. Controlling the operating temperature of step (2) within the range defined herein can effectively control the contents of formaldehyde and propargyl alcohol in the first rectification reaction solution within the range defined herein, which is beneficial to obtaining butanediol with low acetal and low methyl BDO contents.

[0140] In step (2), the formaldehyde removal column for carrying out the rectifying formaldehyde removal is a plate column, and the number of trays of the formaldehyde removal column is 25-35 trays, such as 25 trays, 26 trays, 27 trays, 28 trays, 29 trays, 30 trays, 31 trays, 32 trays, 33 trays, 34 trays, 35 trays, preferably 25-30 trays, 30-35 trays.

[0141] In step (2), the reflux ratio of the formaldehyde removal column for carrying out the rectifying formaldehyde removal is 5-10, such as 5.5, 6.0, 6.5, 7.0, 8.0, 9.0, preferably 5.5-10, 5.5-8.0.

[0142] In step (2), in the first rectification reaction solution, the content of formaldehyde ≤ 0.1 wt%, such as 0.01 wt%, 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, preferably 0.01-0.1 wt%. Only by controlling the content of formaldehyde in the first rectification reaction solution within the range defined herein can butanediol meeting the product index requirements be obtained through subsequent low-pressure hydrogenation reaction and high-pressure hydrogenation reaction.

[0143] In step (2), in the first rectification reaction solution, the content of propargyl alcohol ≤ 500 ppmw, such as 50 ppmw, 100 ppmw, 200 ppmw, 300 ppmw, 400 ppmw, 500 ppmw, preferably 100-500 ppmw, 200-500 ppmw. Only by controlling the content of propargyl alcohol in the first rectification reaction solution within the range defined herein can butanediol meeting the product index requirements be obtained through subsequent low-pressure hydrogenation reaction and high-pressure hydrogenation reaction.

[0144] In step (2), in the first rectification reaction solution, the content of butynediol is 40-45 wt%, such as 40 wt%, 41 wt%, 42 wt%, 43 wt%, 44 wt%, 45 wt%, preferably 42-44 wt%, 43-45 wt%. The rectification in step (2) mainly serves to remove formaldehyde and has little effect on the content of butynediol in the reaction solution.

[0145] The inventors found that under the working conditions defined in step (2), in addition to effectively reducing the content of formaldehyde in the first reaction liquid, the formaldehyde removal tower can also reduce the content of other impurities (especially propargyl alcohol), but has little effect on the content of butynediol in the first reaction liquid.

[0146] Under the conditions defined herein, the alkynylation reaction of step (1) is carried out, and the reaction liquid after the alkynylation reaction is subjected to the formaldehyde removal rectification of step (2) under the conditions defined herein, which 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 contents of formaldehyde and propargyl alcohol in the first reaction liquid within the ranges defined herein, and then carrying out the formaldehyde removal rectification defined in step (2), can effectively prevent impurities such as formaldehyde and propargyl alcohol from entering the subsequent hydrogenation reaction. If the contents of impurities (such as formaldehyde and propargyl alcohol) in the first reaction liquid are not controlled within the ranges defined herein, the formaldehyde removal rectification in step (2) will lose its effect, resulting in the excessive content of impurities (such as formaldehyde and propargyl alcohol) entering the subsequent hydrogenation reaction.

[0147] Preferably, the butynediol in the first reaction liquid is subjected to rectification to remove formaldehyde, and the removed formaldehyde is recovered. The formaldehyde recovery is carried out through a formaldehyde recovery tower. Those skilled in the art can select the working conditions of the formaldehyde recovery tower according to conventional chemical engineering 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 trays, such as 35 - 40 trays, 40 - 45 trays. 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 rectification reaction liquid is adjusted to 35 - 40 wt%, such as 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, 40 wt%, preferably 36 - 40 wt%, 35 - 36 wt%, and then it is subjected to the first hydrogenation reaction with the first hydrogen. Adjusting the concentration of butynediol in the first rectification reaction liquid to 35 - 40 wt% and then carrying out the low-pressure hydrogenation reaction can produce a second reaction liquid with low acetal and low methyl BDO contents, which is beneficial to producing butanediol with low acetal and low methyl BDO contents.

[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 Raney nickel catalyst.

[0151] In some embodiments, in step (3), the reaction pressure is 2.0 - 3.0 MPaG, for example, 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. Controlling the reaction pressure of step (3) within the range defined herein can produce a second reaction solution with low acetal and low methyl BDO content, which is beneficial to obtaining butanediol with low acetal and low methyl BDO content.

[0152] In some embodiments, in step (3), the reaction temperature is 40 - 60 °C, for example, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, preferably 40 - 50 °C, 45 - 60 °C. Controlling the reaction temperature of step (3) within the range defined herein can produce a second reaction solution with low acetal and low methyl BDO content, which is beneficial to obtaining 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 carried out at a pH between 7 and 11, for example, pH 7, 8, 9, 10, preferably 7 - 9. Those skilled in the art can adjust the pH of the low-pressure hydrogenation reaction in step (3) according to common methods. For example, an alkaline reagent (such as sodium hydroxide, potassium hydroxide, etc.) is added to the reaction solution in step (3). The addition amount of the alkaline reagent can be calculated according to the required pH. In some embodiments, an aqueous sodium hydroxide solution with a concentration of 10 - 30 wt% (for example, 20 wt%) is added to the low-pressure hydrogenation reaction solution in step (3). Controlling the pH of the reaction solution in step (3) within the range defined herein can produce a second reaction solution with low acetal and low methyl BDO content, which is beneficial to obtaining 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 and used in step (3). Controlling the molar ratio of the first hydrogen to butynediol within the range defined herein can produce a second reaction solution with low acetal and low methyl BDO content, which is beneficial to producing 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 producing butanediol, side reactions will also occur simultaneously to produce various impurities such as butenediol, acetal, tetrahydroxybutyraldehyde, n-butanol, 2-(4-hydroxybutoxy)-tetrahydrofuran, etc. Except for butynediol (BYD), the content of other organic impurity components does not exceed 5 wt%.

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

[0159] In the second reaction solution, the content of acetal is ≤600 ppmw, such as 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 solution within the range defined herein is beneficial to producing butanediol with low acetal and low methyl BDO content.

[0160] Preferably, in the second reaction solution, the content of 1,4-butanediol is 30-35 wt%, such as 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, preferably 31-35 wt% or 31-33 wt%.

[0161] Take the second reaction solution directly for use in step (4). In the high-pressure hydrogenation unit, the second reaction solution from low-pressure hydrogenation undergoes hydrogenation of the unreacted unsaturated organic matter under the action of the third catalyst.

[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 or 20-23 MPaG. Controlling the reaction pressure of step (4) within the range defined herein can produce butanediol with low acetal and low methyl BDO content.

[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. Controlling the reaction temperature of step (4) within the range defined herein can produce butanediol with low acetal and low methyl BDO content.

[0164] In some embodiments, in step (4), the reaction time is 1-8 h, such as 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 1,4-butanediol in the second reaction solution 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 for use in step (4). Controlling the molar ratio of the second hydrogen to 1,4-butanediol within the range defined herein can produce butanediol with low acetal and low methyl BDO content.

[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. Carrying out step (4) in the reactor defined herein can produce butanediol with low acetal and low methyl BDO content.

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

[0168] In the third reaction solution, the content of 2-methyl-1,4-butanediol is ≤5000 ppmw, such as 50 ppmw, 100 ppmw, 200 ppmw, 300 ppmw, 400 ppmw, 500 ppmw, 600 ppmw, 800 ppmw, 1000 ppmw, 2000 ppmw, 3000 ppmw, 4000 ppmw, preferably 50-5000 ppmw, 100-3000 ppmw, 150-2000 ppmw, 100-1000 ppmw, 150-600 ppmw. Ensure that the content of 2-methyl-1,4-butanediol entering the rectification post-treatment unit is ≤950 ppmw. By controlling the content of 2-methyl-1,4-butanediol in the third reaction solution within the range defined herein, butanediol with low acetal and low methyl BDO content can be obtained.

[0169] In the third reaction solution, the content of acetal is ≤200 ppmw, such as 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 solution within the range defined herein, butanediol with low acetal and low methyl BDO content can be obtained.

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

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

[0172] The dehydration process is implemented through a dehydration system, which includes a vacuum tower and an atmospheric tower; preferably, the dehydration process controls the water content in the third reaction liquid to be 1-3 wt%, preferably 1-1.5 wt%. The operating pressure of the vacuum tower is 20-40 kPaA, such as 23 kPaA, 25 kPaA, 27 kPaA, 30 kPaA, 35 kPaA, 37 kPaA, preferably 23-30 kPaA, 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, and the number of trays is 25-35, such as 26, 28, 30, 32, 34, preferably 30-35. 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, and the number of trays is 25-35, such as 26, 28, 30, 32, 34, preferably 30-35. The reflux ratio of the atmospheric tower is 1.0-1.5, such as 1.1, 1.2, 1.3, 1.4, preferably 1.2-1.5, 1.0-1.2.

[0173] The residue removal process is implemented through a residue removal system, which includes a climbing film evaporator, a falling film evaporator, and a thin film evaporator. The operating pressure of the climbing 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 climbing 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 climbing film evaporator is 5 - 20 min, 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 - 20 min, 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 - 10 kPaA, 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 through 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, and 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, and preferably 150 - 160 °C, 160 - 170 °C, 155 - 165 °C. The intermediate tower is a two-stage packed tower, and the height of each of the two stages of packing is independently 4800 - 5000 mm, such as 4850 mm, 4900 mm, 4950 mm, 5000 mm, and preferably 4800 - 4900 mm, 4900 - 5000 mm, 4850 - 4950 mm. The reflux ratio of the intermediate tower is 25 - 30, such as 25, 26, 27, 28, and preferably 25 - 27. The operating pressure of the finished product tower is 1 - 5 kPaA, such as 1 kPaA, 2 kPaA, 3 kPaA, 4 kPaA, 5 kPaA, and preferably 1 - 3 kPaA, 3 - 5 kPaA, 2 - 4 kPaA. The operating temperature of the finished product tower is 150 - 170 °C, such as 155 °C, 160 °C, 165 °C, 170 °C, and preferably 150 - 160 °C, 160 - 170 °C, 155 - 165 °C. The finished product tower is a two-stage packed tower, and the height of each of the two stages of packing is independently 5400 - 5600 mm, such as 5450 mm, 5500 mm, 5550 mm, 5600 mm, and preferably 5500 - 5600 mm, 5400 - 5500 mm. The reflux ratio of the finished product tower is 20 - 25, such as 21, 22, 23, 24, 25, and preferably 22 - 25, 20 - 22.

[0175] The 1,4-butanediol recovery process is implemented through a recovery system, which includes a light component recovery column and a heavy component recovery column. The operating pressure of the light component recovery column is 1-10 kPaA, such as 2 kPaA, 3 kPaA, 5 kPaA, 8 kPaA, 10 kPaA, for example 1-3 kPaA, 3-10 kPaA, 3-5 kPaA. The operating temperature of the light component recovery column is 160-170 °C, such as 162 °C, 165 °C, 168 °C, preferably 160-165 °C, 165-170 °C. The light component recovery column is a two-stage packed column, and the height of each of the two stages of packing is independently 3500-3700 mm, 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 column is 5-15, such as 6, 8, 10, 12, 14, preferably 5-10, 10-15. The operating pressure of the heavy component recovery column is 1-5 kPaA, such as 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 column is 160-180 °C, such as 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 column is a three-stage packed column, and the height of each of the three stages of packing 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 column 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 through a by-product purification and recovery system, which 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 column with 20 - 30 trays, such as 20 - 25 trays, 25 - 30 trays. 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, such as 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 column, and the height of each of the two packed sections is independently 3500 - 4000 mm, such as 3500 - 3760 mm, 3760 - 4000 mm. The reflux ratio of the n-butanol refining tower is 1.0 - 3.0, such as 1.0 - 1.5, 1.5 - 3.0.

[0177] In some embodiments, in the 1,4-butanediol obtained after rectification post-treatment, the content of 2-(4-hydroxybutoxy)-tetrahydrofuran is ≤150 ppmw, such as 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, in the 1,4-butanediol obtained after rectification post-treatment, the content of 2-methyl-1,4-butanediol is ≤900 ppmw, such as 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, in the 1,4-butanediol obtained after rectification post-treatment, the purity of 1,4-butanediol is ≥99.85%, such as ≥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 rectification post - treatment is ≤8, such as 2 - 8, 3 - 6, 4 - 5, 4.5 - 5.5.

[0181] In some embodiments, in the 1,4 - butanediol obtained after rectification post - treatment, the water content is ≤80 ppmw, such as ≤70 ppmw, ≤60 ppmw, ≤50 ppmw, ≤40 ppmw, and 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 of the embodiments herein.

[0183] All along, the alkyne - aldehyde BDO process has been criticized because its product quality is inferior to those of the maleic anhydride method, the butadiene method and other process routes. Among the products of different alkyne - aldehyde BDO process routes, it is difficult to simultaneously solve the quality defects of acetal and methyl BDO. 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 diverse, strict and refined, which puts forward higher requirements for the quality control of alkyne - aldehyde BDO products. The technical solution of the present invention aims at the quality defects of alkyne - aldehyde BDO products, can achieve low acetal content and low methyl BDO content in BDO products, improves the overall level of alkyne - aldehyde BDO products, and reaches or even exceeds the products of process routes such as the maleic anhydride method and the butadiene method.

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

[0185] In this article, 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 chromatography according to the general knowledge in the art.

[0186] In this article, the abbreviations of each compound are as shown in Table a below.

[0187] Table a

[0188]

[0189] Example 1, Alkynylation reaction

[0190] In a slurry bed reactor, acetylene and 45 wt% aqueous formaldehyde solution react to form butynediol under the action of a copper catalyst (BASF Cu6081P). The molar ratio of recycled 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.

[0191] The recycled acetylene is sent out after being condensed by a cooler from the top of the slurry bed reactor. After removing organic substances through the acetylene recovery unit, it continues to return to the slurry bed reactor to participate in the reaction. After reacting for 4 h, when the content of propargyl alcohol in the reaction solution is less than 0.5 wt% and the content of formaldehyde is ≤ 1.0 wt%, it can enter the butynediol rectification unit. A 43 wt% butynediol (BYD) solution is withdrawn from the bottom of the slurry bed reactor and sent to low-pressure hydrogenation reaction after subsequent butynediol rectification.

[0192] The BYD rectification consists of a butynediol de-formaldehyde tower and a formaldehyde recovery tower, mainly to remove impurities such as formaldehyde and methanol, and at the same time recycle dilute formaldehyde for reuse.

[0193] The butynediol de-formaldehyde tower is a plate tower with a total of 30 trays. The operating pressure is 270 ± 10 kPaG, the operating temperature is 140 ± 2 °C, and the reflux ratio is 5.5. After the formaldehyde removal rectification, the content of formaldehyde in the solution is 0.05 wt%, and the content of propargyl alcohol in the solution is 200 ± 20 ppmw. According to the production results, when the content of residual formaldehyde in the reaction solution of the alkynylation reaction is ≤ 1.0 wt%, the contents of formaldehyde and propargyl alcohol in the butynediol solution can be controlled at a low level through formaldehyde removal rectification, which is beneficial to reducing the impurity content in the final product.

[0194] The light component impurities at the top of the butynediol de-formaldehyde tower enter the formaldehyde recovery tower. The formaldehyde recovery tower is a plate tower with a total of 40 trays. The operating pressure is 10 ± 1 kPaG, the operating temperature is 105 ± 2 °C, and the reflux ratio is 12.0, which is used to recover formaldehyde. The recovered formaldehyde can be recycled and reused in the alkynylation reaction.

[0195] Example 2. Low-pressure hydrogenation reaction

[0196] The low-pressure hydrogenation reaction converts most of the BYD into BDO. In Example 1, in the aqueous solution after removing formaldehyde by rectifying butynediol, the concentration of butynediol is about 43 wt%. It is configured into a 36 wt% aqueous solution of butynediol according to the requirements of the low-pressure hydrogenation reaction. In the slurry bed reactor, using Raney nickel (Dalian Zion Technology) as the catalyst, the reaction occurs under the conditions of 45 ± 5 °C and 2.0 MPaG, and the conversion rate of butynediol reaches 99%. An aqueous solution of sodium hydroxide with a concentration of 20 wt% is configured and added to the reactor to control the pH of the reactor at 8 ± 1. The content of BYD in the feed liquid is determined by gas chromatography analysis method, and the molar ratio of recycled hydrogen to feed BYD is 100:1. The recycled hydrogen is condensed by a cooler after passing through the top of the low-pressure hydrogenation reactor and then continues to be recycled back to the low-pressure hydrogenation reactor for use.

[0197] After reacting for 0.5 hours, the low-pressure hydrogenation reaction liquid is monitored. The content of methyl BDO in the reaction liquid is less than 300 ppmw, the content of acetal is ≤ 500 ppmw, and the content of butenediol does not exceed 1.0 wt%. After the low-pressure hydrogenation reaction ends, it can be fed to the high-pressure hydrogenation. The crude BDO solution drawn from the bottom of the low-pressure hydrogenation reactor is continuously sent to the high-pressure hydrogenation reactor.

[0198] Example 3. High-pressure hydrogenation reaction

[0199] The high-pressure hydrogenation reaction is a refining hydrogenation and is a key step in controlling the content of methyl BDO and acetal. The high-pressure hydrogenation reactor is a trickle bed reactor, using supported nickel (Shanxi Jiaocheng Kate New Materials) as the catalyst. The raw material hydrogen from outside the plant is usually 3.0 MPaG. After boosting the hydrogen pressure to 30.0 MPaG by a compressor, it is added to the high-pressure hydrogenation reactor from the top and in co-current with the crude BDO solution simultaneously.

[0200] Under the conditions of a reaction temperature within 110 ± 5 °C and a reaction pressure of 20.0 MPaG, the acetal and other unsaturated substances in the crude BDO solution are completely reacted. The recycled hydrogen is drawn from below the catalyst bed layer of the high-pressure hydrogenation reactor, condensed by a cooler, and then recycled back to the high-pressure hydrogenation reactor. The molar ratio of recycled hydrogen to BDO in the feed liquid is 30:1.

[0201] After reacting for 2 hours, the content of methyl BDO in the high-pressure hydrogenation reaction liquid is monitored to be less than 600 ppm, and the content of acetal is ≤ 200 ppm, and the reaction ends. The crude BDO solution drawn from the bottom of the high-pressure reactor is sent to the rectification and post-treatment unit.

[0202] Example 4. Rectification and post-treatment

[0203] The crude BDO solution after high-pressure hydrogenation needs to go through five steps of dehydration, de-residue, product refining, BDO recovery process, and by-product purification and recovery in the BDO rectification unit to obtain the BDO product.

[0204] The dehydration system in the dehydration process consists of a vacuum column and an atmospheric column, and is used to control the water content in the crude BDO solution to ≤1.5 wt%. The vacuum column is a plate column with 30 plates. The operating pressure is controlled at 25 ± 1.0 kPaA, the operating temperature is controlled at 75 ± 1 °C, and the reflux ratio is 0.8. The atmospheric column is a plate column with 30 plates. The operating pressure is controlled at 40 ± 1 kPaG, the operating temperature is controlled at 140 ± 1 °C, and the reflux ratio is 1.2.

[0205] Under the conditions of high vacuum operation at 165 ± 1 °C, the dehydrated crude BDO product is successively subjected to three-stage evaporation separation through a rising film evaporator, a falling film evaporator and a thin film evaporator to remove residues. The operating pressure of the falling film evaporator and the rising film evaporator is controlled at 10 kPaA, and the operating time is 10 min. The operating pressure of the thin film evaporator is controlled at 5 kPaA, and the operating time is 5 min.

[0206] The product refining process refines the BDO after removing residues. The BDO refining system consists of an intermediate column and a finished product column. After refining, qualified BDO products are obtained. The intermediate column is a packed column with Sulzer Bxplus packing, with a total of 2 sections, and the packing heights are 4900 / 4900 mm respectively. The operating pressure is 5 ± 0.5 kPaA, the operating temperature is 160 ± 1 °C, and the reflux ratio is 25.0. The finished product column is a packed column with Sulzer Bxplus packing, with a total of 2 sections, and the packing heights are 5500 / 5500 mm respectively. The operating pressure is 3 ± 0.5 kPaA, the operating temperature is 160 ± 1 °C, and the reflux ratio is 22.0.

[0207] The BDO recovery process is to perform secondary rectification recovery on the BDO in the light components and heavy components discharged from the product refining process to improve the recovery rate. The light component recovery column recovers the BDO in the light components. This column is a packed column with Sulzer Bxplus packing, divided into 2 sections, and the packing heights are 3600 / 3600 mm respectively. The operating pressure is 3 ± 0.5 kPaA, the operating temperature is 165 ± 1 °C, and the reflux ratio is 10.0. The heavy component recovery column is a packed column with Sulzer Bxplus packing, with a total of 3 sections, and the packing heights are 4472 / 3600 / 3600 mm respectively. This column recovers the BDO in the heavy components. The operating pressure is 2 ± 0.2 kPaA, the operating temperature is 168 ± 1 °C, and the reflux ratio is 10.0.

[0208] The purification and recovery of by-products is to refine 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. For the special physical property system 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 a total of 25 layers, an operating pressure of 3±1 kPaG, an operating temperature of 105±2°C, and a reflux ratio of 15.0. The n-butanol refining tower is a two-stage packed tower with Sulzer M252Y packing, packing heights of 3760 / 3760 mm respectively, an operating pressure of 5±1 kPaG, an operating temperature of 120±2°C, and a reflux ratio of 1.5.

[0209] Example 5, Alkynylation Reaction

[0210] The only difference between Example 5 and Example 1 is that the molar ratio of recycled acetylene to fed formaldehyde is 2:1.

[0211] Example 6, Alkynylation Reaction

[0212] The only difference between Example 6 and Example 1 is that the molar ratio of recycled acetylene to fed formaldehyde is 10:1.

[0213] Example 7, Low-Pressure Hydrogenation Reaction

[0214] The only difference between Example 7 and Example 2 is that the molar ratio of recycled hydrogen to fed BYD is 5:1.

[0215] Example 8, Low-Pressure Hydrogenation Reaction

[0216] The only difference between Example 8 and Example 2 is that the molar ratio of recycled hydrogen to fed BYD is 200:1.

[0217] Example 9, Alkynylation Reaction

[0218] The only difference between Example 9 and Example 1 is that the reaction pressure is 140 kPa.

[0219] Example 10, Alkynylation Reaction

[0220] The only difference between Example 10 and Example 1 is that the reaction pressure is 200 kPa.

[0221] Example 11, High-Pressure Hydrogenation Reaction

[0222] The only difference between Example 11 and Example 3 is that the molar ratio of recycled hydrogen to fed BDO is 0.5:1.

[0223] Example 12, High-Pressure Hydrogenation Reaction

[0224] The only difference between Example 12 and Example 3 is that the molar ratio of recycled hydrogen to fed BDO is 100:1.

[0225] Comparative Example 1

[0226] The only difference between Comparative Example 1 and Example 1 is that the molar ratio of recycled acetylene to fed formaldehyde is 0.5:1.

[0227] Comparative Example 2

[0228] The only difference between Comparative Example 2 and Example 1 is that the reaction pressure is 1000 kPa.

[0229] Comparative Example 3

[0230] The only difference between Comparative Example 3 and Example 2 is that the molar ratio of recycled hydrogen to fed BYD is 2:1.

[0231] Comparative Example 4

[0232] The only difference between Comparative Example 4 and Example 3 is that the molar ratio of recycled hydrogen to fed BDO is 0.3:1.

[0233] Testing methods in this article

[0234] 1. Determination of formaldehyde content.

[0235] The formaldehyde in the alkynylation reaction solution was analyzed by titration using a potentiometric titrator (Mettler T70). The specific method is as follows.

[0236] Adjust the pH value of the prepared anhydrous sodium sulfite solution to 9.5.

[0237] Weigh 50 mL of the anhydrous sodium sulfite solution with adjusted pH value, and perform a blank determination using a sulfuric acid standard solution on the T70 automatic potentiometric titrator using the method.

[0238] Add 50 mL of the sodium sulfite solution to a 100 mL titration cup. Use a Pasteur pipette to transfer the reaction solution (primary 1.5 ± 0.2 g; secondary 2.5 ± 0.2 g; tertiary 3 ± 0.2 g; rectification 1.5 ± 0.5 g; V402 3 ± 0.2 g) sample into the titration cup, and titrate to the end point with a sulfuric acid standard solution on the T70 automatic potentiometric titrator using the method "JiaQuan-D", read the value, and record the result.

[0239] The formaldehyde content X expressed in mass percentage is calculated by the following formula:

[0240] ,

[0241] In the formula:

[0242] C1: Concentration of sulfuric acid standard solution, mol / L;

[0243] V1: Volume of sulfuric acid standard solution consumed in titration, mL;

[0244] M1: Mass of formaldehyde sample, g;

[0245] 0.03003: Mass of each millimole of formaldehyde, g.

[0246] 2. The contents of methanol, propargyl alcohol, and BYD are analyzed using gas chromatography (Thermo Fisher Trace 1310).

[0247] 3. The contents of methanol, tetrahydrofuran, butanol, γ-butyrolactone, 4-hydroxybutyraldehyde, 1,4-pentanediol, butanediol, methylbutanediol, acetal, and methyl-pentanediol are analyzed using a gas chromatograph (Thermo Fisher Trace 1310).

[0248] 4. Chromaticity analysis.

[0249] Instrument: UV-visible spectrophotometer, PFX-195.

[0250] Operating procedure: Turn on the power of the chromaticity meter and stabilize for 30 min. Run the baseline program. Use distilled water or an empty cuvette as the blank. Replace the same cuvette with the sample 1 - 3 times. Wipe the quartz window of the cuvette clean. Run the reading program of the chromaticity meter. Record the test results.

[0251] Test Example 1

[0252] According to the method defined in the test method of this article, the butynediol solution generated in the acetylenation reaction step is tested, and the measured product indexes are shown in Table 1 below.

[0253] Table 1

[0254]

[0255] In Table 1, "conversion rate" is calculated based on formaldehyde, and the conversion rate = (feed formaldehyde - remaining formaldehyde) / feed formaldehyde * 100%.

[0256] Methanol is carried into the reactor together with the feed formaldehyde solution. Therefore, during the reaction process, the content of methanol does not change. By comparing the data results of Examples 1, 5, and 6, it can be found that adjusting the molar ratio of recycled acetylene to feed formaldehyde has an impact on the contents of both remaining formaldehyde and propargyl alcohol. As the molar ratio of recycled acetylene to feed formaldehyde increases, the content of propargyl alcohol gradually decreases, thus creating conditions for reducing the content of methyl BDO in the final product. By 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 acetylenation 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 acetylenation reaction at low pressure is more conducive to controlling the content of propargyl alcohol.

[0257] Test Example 2

[0258] 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 indexes are shown in Table 2 below.

[0259] Table 2: Analysis of low-pressure hydrogenation reaction liquid

[0260]

[0261] In Examples 2, 7, and 8, the content of butynediol is relatively low, indicating that the low-pressure hydrogenation reaction has a high raw material conversion rate. From the data in the table, it can be seen that adjusting the molar ratio of recycled hydrogen to fed BYD has an impact on the formation of both acetal and methyl BDO. As the molar ratio of recycled hydrogen to fed BYD increases, the acetal content and methyl BDO content gradually decrease.

[0262] Test Example 3

[0263] According to the method defined in the test method of this article, the crude BDO solution generated in the high-pressure hydrogenation reaction step was tested, and the measured product indexes are shown in Table 3 below.

[0264] Table 3: Analysis of high-pressure hydrogenation reaction liquid

[0265]

[0266] Through the research on the reaction mechanism, the present invention finds that the high-pressure hydrogenation reaction is a refining hydrogenation, which can mainly eliminate the side reaction acetal generated in the low-pressure hydrogenation reaction process and can also avoid the formation 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 liquid of Examples 3, 11, and 12 is significantly lower, and the BDO content increases. Adjusting the molar ratio of recycled hydrogen to BDO has an impact on the formation of both acetal and methyl BDO. As the molar ratio of recycled hydrogen to BDO increases, the formation of methyl BDO is inhibited.

[0267] Test Example 4

[0268] According to the method defined in the test method of this article, the product indexes were tested, and the test results are shown in Table 4.

[0269] Product 1 was prepared by successively carrying out Example 1, Example 2, Example 3, and Example 4. Product 2 was prepared by successively carrying out Example 1, Example 2, Example 11, and Example 4. Product 3 was prepared by successively carrying out Example 1, Example 2, Example 12, and Example 4.

[0270] Product 4 was prepared by successively carrying out Comparative Example 1, Example 2, Example 3, and Example 4. Product 5 was prepared by successively carrying out Comparative Example 2, Example 2, Example 3, and Example 4.

[0271] The butynediol solution obtained from the ethynylation reaction in Example 1 was directly fed into Example 2 for low-pressure hydrogenation reaction without rectification (i.e., without formaldehyde-removing rectification), and then Example 3 and Example 4 were carried out to obtain Product 6.

[0272] Example 1, Comparative Example 3, Example 3 and Example 4 were carried out in sequence to obtain Product 7.

[0273] Example 1, Example 2, Comparative Example 4 and Example 4 were carried out in sequence to obtain Product 8.

[0274] Table 4

[0275] Item Moisture Chromaticity Butylene Glycol HB-THF Methylbutylene Glycol Others 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

[0276] Analysis of the data in Table 1 (the data in Table 1 are the data of the reaction solution after ethynylation reaction without formaldehyde-removing rectification; the formaldehyde content in Comparative Example 1 exceeded the standard; the propargyl alcohol content in Comparative Example 2 exceeded the standard) and the indicators of Product 1, Product 4, Product 5 and Product 6 shows that the contents of formaldehyde and propargyl alcohol in the BYD solution entering the low-pressure hydrogenation reaction have great influence on the contents 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 solution obtained from the ethynylation reaction exceeded the standard (see the data of Comparative Example 1 and Comparative Example 2 in Table 1), exceeding the treatment capacity of formaldehyde-removing rectification, resulting in the content of formaldehyde or propargyl alcohol in the reaction solution entering the subsequent hydrogenation reaction not meeting the index requirements of the present invention, and finally resulting in the contents of acetal and methyl BDO in the prepared product far exceeding the product indexes of the present invention. For Product 6, since the reaction solution obtained from the ethynylation reaction in Example 1 was not rectified to remove formaldehyde, the contents of formaldehyde and propargyl alcohol in the reaction solution entering the low-pressure hydrogenation reaction exceeded the standard at the same time, resulting in a significant increase in both acetal and methyl BDO in the finally prepared product, and the product quality was the worst.

[0277] From the indicators of Product 7, it can be seen that when the acetal and methyl BDO in the low-pressure reaction exceeded the standard (see the data of Comparative Example 3 in Table 2), although the acetal content in the product decreased, it still did not meet the requirement of low acetal, and the content of methyl BDO exceeded more than twice the content of methyl BDO in Product 1, 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. From the indicators of Product 8, it can be seen (see the data of Comparative Example 4 in Table 3) that both acetal and methyl BDO in the reaction solution prepared in the high-pressure hydrogenation stage exceeded the standard, and there was no obvious decrease after rectification in Example 4, resulting in the unqualified contents of acetal and methyl BDO in the product.

[0278] In summary, as can be seen from the above comparison, the post-treatment steps of rectification have little effect on reducing the contents of acetal and methyl BDO, which is also consistent with the physical property systems of acetal-BDO and methyl BDO-BDO azeotropes and close boiling points. The indicators of the three reactions of alkynylation reaction, low-pressure hydrogenation, and high-pressure hydrogenation affect each other step by step. Only by controlling the indicators of each step of the reaction can the product quality of the final product be ensured. By controlling the reaction conditions and reaction liquid indicators of each step of alkynylation reaction, low-pressure hydrogenation, and high-pressure hydrogenation, the present invention controls the contents of acetal and methyl BDO before entering the post-treatment steps of rectification to a relatively low level, 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 includes the steps: (1) Under the action of a first catalyst, acetylene reacts with an aqueous formaldehyde solution to form a first reaction solution containing butynediol; (2) The first reaction solution is subjected to rectification to remove formaldehyde to obtain a first rectified reaction solution; (3) Under the action of a second catalyst, the first rectified reaction solution reacts with first hydrogen gas in a first hydrogenation reaction to obtain a second reaction solution containing 1,4-butanediol; (4) Under the action of a third catalyst, the second reaction solution reacts with second hydrogen gas in a second hydrogenation reaction to obtain a third reaction solution 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 gas to butynediol is (5-200):1; In step (4), the molar ratio of the second hydrogen gas to 1,4-butanediol in the second reaction solution is (0.5-100):1; In the third reaction solution, the content of 2-methyl-1,4-butanediol is ≤5000 ppmw; In the third reaction solution, the content of acetal is ≤200 ppmw; In the first reaction solution, the content of propargyl alcohol is ≤0.5 wt%; In the first reaction solution, the content of formaldehyde is ≤1.0 wt%.

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

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

4. The method according to claim 1, wherein Step (2) has one or more of the following characteristics: The operating pressure of the formaldehyde removal tower for carrying out the rectification to remove formaldehyde is 250-300 kPaG; The operating temperature of the formaldehyde removal tower for carrying out the rectification to remove formaldehyde is 100-180 °C; The formaldehyde removal tower for carrying out the rectification to remove formaldehyde 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 for carrying out the rectification to remove formaldehyde is 5-10; In the first rectified reaction solution, the content of formaldehyde is ≤0.1 wt%; In the first rectified reaction solution, the content of propargyl alcohol is ≤500 ppmw; In the first rectified reaction solution, the content of butynediol is 40-45 wt%.

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

6. The method according to claim 1, wherein Step (4) has one or more of the following characteristics: Taking the second reaction solution directly for use in step (4); The reaction pressure is 20.0 - 30.0 MPaG; 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 - 8 h.

7. The method according to claim 1, wherein The method further includes subjecting 1,4 - butanediol in the third reaction solution to rectification post - treatment, and the rectification post - 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 characteristics: Implementing the dehydration process through a dehydration system, and the dehydration system includes a vacuum tower and an atmospheric tower; Implementing the residue removal process through a residue removal system, and the residue removal system includes a climbing - film evaporator, a falling - film evaporator, and a thin - film evaporator; Implementing the 1,4 - butanediol refining process through a refining system, and the refining system includes an intermediate tower and a product tower; Implementing the 1,4 - butanediol recovery process 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, wherein The method has one or more of the following characteristics: 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, and the number of tower plates is 25 - 35 layers; 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 tower is a plate tower, and the number of tower plates is 25 - 35 layers; The reflux ratio of the atmospheric tower is 1.0 - 1.5; The operating pressure of the climbing - film evaporator is 5 - 15 kPaA; The operating temperature of the climbing - film evaporator is 160 - 170 °C; The operating time of the climbing - film evaporator is 5 - 20 min; 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 operating time of the falling - film evaporator is 5 - 20 min; 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 operating time of the thin - film evaporator is 2 - 10 min; 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 each of the two stages of packing is independently 4800 - 5000 mm; The reflux ratio of the intermediate tower is 25 - 30; The operating pressure of the 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 each of the two packings is independently 5400 - 5600 mm; 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 each of the two packings 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 each of the three packings is independently 3500 - 4500 mm; The reflux ratio of the heavy component recovery tower is 5 - 15.

10. The method according to claim 7, wherein The method has one or more of the following features: In the 1,4-butanediol prepared through rectification post-treatment, the content of 2-(4-hydroxybutoxy)-tetrahydrofuran is ≤150 ppmw; In the 1,4-butanediol prepared through rectification post-treatment, the content of 2-methyl-1,4-butanediol is ≤900 ppmw; In the 1,4-butanediol prepared through rectification post-treatment, the purity of 1,4-butanediol is ≥99.85%; The color number of the 1,4-butanediol prepared through rectification post-treatment is ≤8; In the 1,4-butanediol prepared through rectification post-treatment, the water content is ≤80 ppmw.

Images