Method for co-producing 1, 4-butanediol and alkyl-1, 4-butanediol

Abstract

The invention discloses a method for co-producing 1, 4-butanediol and alkyl-1, 4-butanediol, which creatively realizes the production of BDO and BDO containing alkyl-1, 4-butanediol by using an alkyne-aldehyde method BDO device, that is, the respective efficient production of BDO and BDO containing 0-25% wt of alkyl-1, 4-butanediol is completed in the same device, the product differentiation of a single device is realized, and the method has higher economic value.

Description

Technical Field

[0001] The present invention belongs to the field of fine chemical industry, and particularly relates to a method for co-producing 1,4-butanediol (BDO) and alkyl-1,4-butanediol. Background Art

[0002] At present, the production process of the acetylene aldehyde method BDO device is as follows: Formaldehyde reacts with excessive acetylene to produce 1,4-butynediol (BYD). The excessive acetylene needs to be separated and then recycled back to the BYD synthesis reactor for continuous reaction; the generated BYD enters the hydrogenation reactor after concentration and aldehyde removal, methanol removal, and reacts with hydrogen to produce crude BDO; the crude BDO is separated by distillation to obtain the BDO product. However, at present, the BDO industry has a serious overcapacity, and most enterprises are below the break-even point.

[0003] As a modified BDO product, alkyl-1,4-butanediol has more excellent properties. However, at present, it has not been industrially produced and is still in the laboratory research stage. The patent document US4590312A discloses that methyl-1,4-butanediol (MBDO) can be synthesized by using BYD and formaldehyde, but it belongs to an intermittent reaction process, cannot be produced on a large scale, and cannot be coupled with the existing acetylene aldehyde method device process. The patent document CN1037701A discloses a preparation method of a butanol mixture, which uses BYD and 4-hydroxybutyraldehyde / cyclic hemiacetal, hydrogen, and formaldehyde to generate 2-MBDO under a Raney nickel catalyst. The raw material 4-hydroxybutyraldehyde / cyclic hemiacetal is not easily obtained and cannot be produced on a large scale. The patent document CN 219232322 U discloses a two-stage hydrogenation device using a stirred tank in series with a fixed bed to inhibit the by-product MBDO in the BDO device. The mentioned conventional two-stage hydrogenation reactor is a trickle bed, the bed layer flow rate is slow, and the local high temperature affects the service life of the catalyst. In addition, at present, the patent literature reports that the maximum production of BDO products containing 16 wt% MBDO, and BDO products with a higher concentration of MBDO cannot be produced.

[0004] Therefore, there is an urgent need for a method for synthesizing highly efficient, low-cost, and capable of co-producing high-concentration MBDO by the acetylene aldehyde method BDO. Summary of the Invention

[0005] In order to improve the above technical problems, the present invention provides a method for co-producing 1,4-butanediol and alkyl-1,4-butanediol, including the following steps: (1) Formaldehyde reacts with acetylene to generate a 1,4-butynediol stream; (2) The 1,4-butynediol stream undergoes two-stage hydrogenation reaction to co-produce 1,4-butanediol and alkyl-1,4-butanediol; (2-1) When the target product is only 1,4-butanediol, the unreacted formaldehyde in step (1) needs to be recovered; (2-2) When the target product is 1,4-butanediol containing alkyl-1,4-butanediol, there is no need to recover the unreacted formaldehyde in the recovery step (1). Aldehyde is supplemented to the starting materials in step (1), the 1,4-butynediol stream in step (1), and / or the hydrogenation reaction process, and a promoter is added to the hydrogenation reaction process.

[0006] According to an embodiment of the present invention, the alkyl-1,4-butanediol is an alkyl-substituted 1,4-butanediol, for example, C 1~20 alkyl, C 1~10 alkyl or C 1~4 alkyl (methyl, ethyl, propyl, isopropyl, butyl, isobutyl)-substituted 1,4-butanediol.

[0007] According to an embodiment of the present invention, in step (1), the feed ratio of formaldehyde to acetylene is not particularly limited, and it is preferred that acetylene is completely converted as much as possible. For example, the acetylene conversion rate is not less than 95%, preferably not less than 98%.

[0008] In some embodiments, in step (1), the mass ratio of the formaldehyde stream to the acetylene stream is (2 to 10):1, for example (3 to 8):1, and exemplary values are 4:1, 5:1, 6:1, 6.5:1, 7:1.

[0009] In some embodiments, the flow rate of the formaldehyde stream in step (1) is 5000 to 7000 kg / h, for example 5500 to 6500 kg / h, and exemplary values are 6000 kg / h, 6500 kg / h.

[0010] In some embodiments, the flow rate of the acetylene stream in step (1) is 500 to 1500 kg / h, for example 800 to 1200 kg / h, and an exemplary value is 1000 kg / h.

[0011] According to an embodiment of the present invention, the reaction conditions of formaldehyde and acetylene include: The operating pressure is 0 to 0.3 MPaG, for example 0.05 to 0.2 MPaG; The reaction temperature is 80 to 100 °C, for example 85 to 95 °C; And / or, the catalyst is a Cu-Bi complex catalyst.

[0012] According to an embodiment of the present invention, the conditions of the first-stage hydrogenation reaction include: The operating pressure is 3 to 30 MPaG, for example 6 to 20 MPaG; The reaction temperature is 60 to 180 °C, for example 100 to 160 °C or 100 to 180 °C; The catalyst is a nickel-based catalyst; And / or, the molar ratio of the inlet hydrogen to 1,4-butynediol is 1 to 20, such as 2 to 16, and exemplary values are 2, 5, 8, 10, 13, 15.

[0013] According to an embodiment of the present invention, the conditions for the second-stage hydrogenation reaction include: The operating pressure is 10 to 30 MPaG, such as 20 to 30 MPaG or 24 to 34 MPaG; The reaction temperature is 100 to 180 °C, such as 100 to 160 °C or 120 to 180 °C; The catalyst is a nickel-based catalyst; And / or, the molar ratio of the inlet hydrogen to 1,4-butynediol is 1 to 20, such as 2 to 16, and exemplary values are 2, 5, 8, 10, 13, 15.

[0014] According to an embodiment of the present invention, the nickel-based catalyst includes, but is not limited to, one or more of Raney nickel, supported nickel, precipitated nickel, etc.

[0015] According to an embodiment of the present invention, the two-stage hydrogenation reaction is carried out in a bubble bed hydrogenation reactor.

[0016] According to an embodiment of the present invention, the operation of recovering the unreacted formaldehyde in step (1) includes: The operating pressure is 20 to 100 KPaA, such as 30 to 80 KPaA; The reflux ratio is 0.2 to 2, such as 0.5 to 1; And / or, the number of theoretical plates is 5 to 60, such as 10 to 50, and exemplary values are 20, 30, 40 or 45.

[0017] According to an embodiment of the present invention, the addition of aldehyde to the hydrogenation reaction process can add aldehyde to the first-stage hydrogenation reaction process, for example, adding aldehyde from the top, upper part, middle part and / or bottom of the first hydrogenation reactor. The tower body of the first hydrogenation reactor is divided into three equal parts. The part far from the ground is denoted as the upper part, the part close to the ground is denoted as the lower part, and the part between the upper part and the lower part is denoted as the middle part.

[0018] According to an embodiment of the present invention, the added aldehyde in step (2-2) is the aldehyde required to produce the alkyl-1,4-butanediol, for example, it is C 1~20 aldehyde, C 1~10 aldehyde or C 1~4 aldehyde, and exemplary values are formaldehyde, acetaldehyde, propionaldehyde, isopropyl aldehyde, butyraldehyde, isobutyraldehyde.

[0019] According to an embodiment of the present invention, in step (2), the mass ratio of the aldehyde supplemented in any process to the formaldehyde stream in step (1) is 1:(1 - 50), such as 1:(5 - 40), and exemplarily 1:6, 1:8, 1:8.5, 1:9, 1:10, 1:15, 1:20, 1:25, 1:30, 1:31, 1:32, 1:35.

[0020] In some embodiments, the flow rate of the aldehyde supplemented in any process is 100 - 1000 kg / h, such as 200 - 800 kg / h, and exemplarily 400 kg / h, 500 kg / h, 600 kg / h, 700 kg / h.

[0021] According to an embodiment of the present invention, the cocatalyst is selected from organic bases and / or inorganic bases, such as selected from n-butylamine, trimethylamine, ethylene glycol amine, ammonia water, and one or more of oxides or hydroxides of lithium, sodium, potassium, magnesium, calcium; for example, the cocatalyst is sodium hydroxide and / or potassium hydroxide.

[0022] According to an embodiment of the present invention, the addition amount of the cocatalyst needs to control the pH value of the effluent from the second-stage hydrogenation reaction at 7 - 14, such as 8 - 12.

[0023] According to an embodiment of the present invention, the cocatalyst is added in the form of an aqueous solution. For example, the concentration of the cocatalyst aqueous solution is 10 - 40 wt% (such as 15 - 30 wt%), and the addition amount does not exceed 1 wt% of the mass of the formaldehyde stream in step (1).

[0024] According to an embodiment of the present invention, the cocatalyst is added to the first-stage hydrogenation reaction process or the second-stage hydrogenation reaction process.

[0025] According to some embodiments of the present invention, in step (2-2), aldehyde is supplemented to the initial raw material in step (1), the 1,4-butyne diol stream in step (1), the top, upper part, middle part or bottom of the first hydrogenation reactor, and the cocatalyst is added to the first-stage hydrogenation reaction process.

[0026] According to some embodiments of the present invention, in step (2-2), aldehyde is supplemented to the initial raw material in step (1), the 1,4-butyne diol stream in step (1), the top, upper part, middle part or bottom of the first hydrogenation reactor, and the cocatalyst is added to the second-stage hydrogenation reaction process.

[0027] According to an embodiment of the present invention, the method further includes step (3) distillation process: deweighting, recovering methanol and light component removal from the effluent of the second-stage hydrogenation reaction.

[0028] According to an embodiment of the present invention, the deweighting includes the following operations: The operating pressure is 0 to 20 KPaA, such as 3 to 8 KPaA; The number of theoretical plates is 5 to 30, such as 10 to 20; And / or, the reflux ratio is 0.2 to 5, such as 0.5 to 2.

[0029] According to an embodiment of the present invention, the recovered methanol includes the following operations: The operating pressure is 0 to 20 KPaA, such as 5 to 10 KPaA; The number of theoretical plates is 10 to 50, such as 20 to 40; And / or, the reflux ratio is 1 to 5, such as 1 to 3.

[0030] According to an embodiment of the present invention, the light component removal includes the following operations: The operating pressure is 0 to 20 KPaA, such as 5 to 10 KPaA; The number of theoretical plates is 10 to 50, such as 20 to 40; And / or, the reflux ratio is 1 to 10, such as 2 to 5.

[0031] According to an embodiment of the present invention, the method can be carried out in the following system, which includes: 1,4 - butynediol synthesis reactor; A formaldehyde recycle column located downstream of the 1,4 - butynediol synthesis reactor; A first hydrogenation reactor and a second hydrogenation reactor located downstream of the formaldehyde recycle column. The first hydrogenation reactor and the second hydrogenation reactor are in series. The first hydrogenation reactor and the second hydrogenation reactor are bubble - bed hydrogenation reactors, and a nickel - based catalyst layer is provided inside. The first hydrogenation reactor and / or the second hydrogenation reactor is also provided with a promoter feed end; An aldehyde make - up feed end, which is used to provide more aldehyde to the 1,4 - butynediol synthesis reactor and / or the first hydrogenation reactor; the aldehyde make - up feed end is provided at the feed port of the 1,4 - butynediol synthesis reactor, and / or, is provided at the top, upper part, middle part and / or bottom of the first hydrogenation reactor; preferably, it is provided in the middle part of the first hydrogenation reactor; And a rectification unit located downstream of the hydrogenation reactor. The rectification unit includes a heavy - component removal column, a methanol recovery column located downstream of the heavy - component removal column, and a light - component removal column located downstream of the methanol recovery column.

[0032] Beneficial effects The co - production method provided by the present invention realizes the efficient production of BDO and BDO products containing 0 to 25% wt alkyl - 1,4 - butanediol respectively in the same device, realizes product differentiation of a single device, and has high economic value.

[0033] (1)Creatively realize the production of two products, BDO and BDO containing alkyl-1,4-butanediol, in the alkynal method BDO plant, improving the plant efficiency.

[0034] (2)According to the needs of the enterprise and the market, the content of alkyl-1,4-butanediol can be adjusted between 0 and 25 wt%, and even up to 30 wt%, improving the operating flexibility of the plant.

[0035] (3)By adjusting the ratio of raw materials formaldehyde and acetylene, the emissions of acetylene tail gas are reduced. During the production process of alkyl-1,4-butanediol, the secondary recovery of acetylene and formaldehyde is avoided, reducing the production energy consumption of the plant and the production cost.

[0036] (4)Through the two-stage bubble bed hydrogenation process, the plant capacity can be improved and the service life of the catalyst can be extended.

[0037] (5)By changing the material ratio and feeding process, BED is generated in the first-stage hydrogenation reaction process, and the reaction between BED and aldehyde occurs in the second-stage hydrogenation reaction process, and a 30 wt% alkyl-1,4-butanediol product can be produced. Description of the Drawings

[0038] Figure 1 It is a schematic process flow diagram for co-producing 1,4-butanediol and methyl-1,4-butanediol; The reference numerals are as follows: R1 - BYD synthesis reactor; T1 - formaldehyde circulation tower; R2 - first hydrogenation reactor; R2 - first hydrogenation reactor; R3 - first hydrogenation reactor; C1 - heavy component removal tower; C2 - methanol recovery loop tower; C3 - light component removal tower; Logistics code: 1 - formaldehyde from methanol oxidation plant; 2 - acetylene; 3 - formaldehyde pipeline; 4 - tail gas from alkynylation reactor; 5 - R1 discharge; 6 - 9 - formaldehyde; 10 - promoter; 11 - hydrogen; 12 - R2 discharge; 13 - R3 feed; 14 - R3 discharge; 15 - heavy components; 16 - methanol, returned to methanol oxidation to formaldehyde plant; 17 - aqueous solution of mixed alcohols (propanol, butanol); 18 - BDO product or BDO product containing MBDO; Detailed Embodiments

[0039] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only for illustrative and explanatory purposes of the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0040] Unless otherwise specified, the raw materials and reagents used in the following embodiments are commercially available products, or can be prepared by known methods.

[0041] Figure 1 The process flow diagram of the method of the present invention, and the adopted device system includes: 1,4 - butynediol synthesis reactor R1; Formaldehyde recycle tower T1 located downstream of the 1,4 - butynediol synthesis reactor; The first hydrogenation reactor R2 and the second hydrogenation reactor R3 located downstream of the formaldehyde recycle tower T1, the first hydrogenation reactor R2 and the second hydrogenation reactor R3 are in series, the first hydrogenation reactor R2 and the second hydrogenation reactor R3 are bubble - bed hydrogenation reactors, and a nickel - based catalyst layer is provided inside both of them. The first hydrogenation reactor R2 and / or the second hydrogenation reactor R3 are also provided with a promoter feed end F; One or more than two (for example, two, three, four or five) aldehyde feed ends, and the aldehyde feed ends are used to provide more aldehydes to the 1,4 - butenediol synthesis reactor and / or the first hydrogenation reactor; And a rectification unit located downstream of the hydrogenation reactor, and the rectification unit includes: a heavy - component removal tower C1, a methanol recovery tower C2 located downstream of the heavy - component removal tower C1, and a light - component removal tower C3 located downstream of the methanol recovery tower C2.

[0042] The 1,4 - butynediol synthesis reactor R1 is provided with a feed port (such as a formaldehyde feed port, an acetylene feed port), a discharge port, a formaldehyde recycle inlet and a tail gas outlet; The formaldehyde recycle tower T1 is provided with a feed port and a discharge port, the first hydrogenation reactor R2 is provided with a feed port and a discharge port, and the second hydrogenation reactor R3 is provided with a feed port and a discharge port; When only 1,4 - butanediol is produced, the discharge port of the 1,4 - butynediol synthesis reactor R1 is connected to the feed port of the formaldehyde recycle tower T1, and the discharge port of the formaldehyde recycle tower T1 is connected to the feed port or the formaldehyde recycle inlet of the 1,4 - butynediol synthesis reactor R1.

[0043] When alkyl - 1,4 - butanediol is also produced, the valve on the connecting pipeline between the discharge port of the 1,4 - butynediol synthesis reactor R1 and the feed port of the formaldehyde recycle tower T1 is closed, and the discharge port of the 1,4 - butynediol synthesis reactor R1 is connected to the feed port of the first hydrogenation reactor; The discharge port of the first hydrogenation reactor R2 is connected to the feed port of the second hydrogenation reactor R3, and the discharge port of the second hydrogenation reactor R3 is connected to the rectification unit; The feed port of the first hydrogenation reactor R2 includes a feed port for the reaction product of the 1,4 - butynediol synthesis reactor and a hydrogen feed port.

[0044] The feed port of the second hydrogenation reactor R3 includes a feed port for the product of the first hydrogenation reactor and a hydrogen feed port.

[0045] The heavy component removal column C1, the methanol recovery column C2, and the light component removal column C3 are plate rectification columns.

[0046] The heavy component removal column C1, the methanol recovery column C2, and the light component removal column C3 are all provided with a feed inlet, a gas-phase discharge outlet, and a liquid-phase discharge outlet; The discharge outlet of the second hydrogenation reactor R3 is connected to the feed inlet of the heavy component removal column C1, the gas-phase discharge outlet of the heavy component removal column C1 is connected to the feed inlet of the methanol recovery column C2, and the liquid-phase discharge outlet of the methanol recovery column C2 is connected to the feed inlet of the light component removal column C3; The liquid-phase discharge outlet of the heavy component removal column C1 extracts heavy components; The gas-phase discharge outlet of the methanol recovery column C2 extracts methanol and is connected to the methanol oxidation to formaldehyde unit; The liquid-phase discharge outlet of the light component removal column C3 extracts 1,4-butanediol and alkyl-1,4-butanediol, and the gas-phase discharge outlet of the light component removal column C3 extracts other alcohols except methanol.

[0047] The excess hydrogen in the hydrogenation reactor is separated by gas-liquid separation in a known manner and then recycled through a compressor to the feed inlets of the first hydrogenation reactor R2 and the second hydrogenation reactor R3 (not shown in the figure).

[0048] Examples 1 to 3 Using the system as Figure 1 shown, formaldehyde 1 from the methanol oxidation unit and acetylene 2 react in the 1,4-butynediol synthesis reactor R1 to convert acetylene as much as possible. The discharge 5 of the 1,4-butynediol synthesis reactor R1 passes through the formaldehyde recycle tower T1 to recover formaldehyde and returns to the 1,4-butynediol synthesis reactor R1 for continuous reaction. The tail gas 4 of the R1 reactor is discharged. The non-formaldehyde-containing material stream at the bottom of the formaldehyde recycle tower T1, that is, the feed to R2, reacts with hydrogen 11 in the first hydrogenation reactor R2. The discharge of R2 reacts with hydrogen 11 in the second hydrogenation reactor R3. The discharge of R3 first passes through the heavy component removal column C1 to remove salts and heavy components 15, and then passes through the methanol recovery column C2 to complete the recovery of methanol 16. The bottom stream of the methanol recovery column C2 enters the light component removal column C3 to complete the separation of the impurity alcohol (propanol, butanol) aqueous solution 17, and the BDO product is obtained at the bottom of the light component removal column C3.

[0049] The specific parameters are shown in Table 1 below. In addition, the liquid hourly space velocity of R2 / R3 is 0.3 h -1 , and the molar ratio of hydrogen to BYD in R2 / R3 is 13 (the molar ratio of hydrogen to BYD refers to the molar ratio of hydrogen and BYD at the inlet of the reactor R2 / R3). The results show that the acetylene conversion rate can be increased by increasing the formaldehyde feed amount.

[0050] Table 1

[0051] Examples 4 to 7 Formaldehyde 1 from the methanol oxidation unit reacts with acetylene 2 in the 1,4 - butynediol synthesis reactor R1, and the effluent 5 from the 1,4 - butenediol synthesis reactor R1 directly enters the first hydrogenation reactor R2. Fresh formaldehyde is supplemented through the aldehyde feed end to the 1,4 - butenediol synthesis reactor R1 or the first hydrogenation reactor R2 to adjust the material ratio and increase the proportion of MBDO. The effluent 5 from R1 and hydrogen 11 enter the first hydrogenation reactor R2, and undergo a hydrogenation reaction under the action of a catalyst and a promoter 10. The resulting effluent 12 from R2 and hydrogen 11 enter the second hydrogenation reactor R3 for hydrogenation reaction. 1,4 - Butynediol (BYD), formaldehyde, and hydrogen are converted into the effluent 14 from R3 under the combined action of a nickel - based catalyst and a promoter, that is, a stream containing 1,4 - butanediol (BDO), methyl - 1,4 - butanediol (MBDO), methanol, impurity alcohols (such as butanol, propanol, etc.), and heavy components. The effluent 14 from R3 first passes through the heavy - removal tower C1 to remove salts and heavy components 15, and then passes through the methanol recovery tower C2 to complete the recovery of methanol 16. The methanol recovered at the top of the tower is directly sent to the methanol oxidation unit and can be converted into formaldehyde and re - enter the system. The bottom stream of the methanol recovery tower C2 enters the light - removal tower C3 to complete the separation of the aqueous solution of impurity alcohols (propanol, butanol) 17, and a BDO product 18 containing MBDO is obtained at the bottom of the light - removal tower C3.

[0052] Aldehyde feed end: Formaldehyde is supplemented to the formaldehyde from the methanol oxidation unit in stream 1. Formaldehyde stream 7 is supplemented to the upper part of the first hydrogenation reactor R2, formaldehyde stream 8 is supplemented to the middle part of the first hydrogenation reactor R2, or formaldehyde stream 9 is supplemented to the bottom of the first hydrogenation reactor R2 through the formaldehyde pipeline 3.

[0053] The specific parameters are shown in Table 2 below. In addition, the liquid hourly space velocity of R2 / R3 is 0.3 h -1 , the molar ratio of hydrogen to BYD in R2 / R3 is 13 (the molar ratio of hydrogen to BYD refers to the molar ratio of hydrogen and BYD at the inlet of reactors R2 / R3), and the reaction conditions of R1, R2, and R3 are the same as those in Examples 1 - 3. The addition amount of the promoter 25% sodium hydroxide is 30 kg / h. The results show that adding formaldehyde from different positions 1, 7, 8, 9 has different effects, and the highest MBDO of 25% can be obtained.

[0054] Example 8 Other conditions are the same as in Example 4, except that the promoter does not enter R2 but is sent to R3, and the aldehyde feed end: formaldehyde stream 6 at the top of the first hydrogenation reactor R2. The molar ratio of hydrogen to BYD in R2 is 2, and the molar ratio of hydrogen to BYD in R3 is 13. The results show that the highest MBDO of 30 wt% can be obtained.

[0055] Table 2

[0056] The present invention surprisingly discovers that 1,4-butynediol can generate 1,4-butenediol (BED) during the hydrogenation process, and BED and formaldehyde are more likely to generate MBDO in a hydrogen atmosphere. By controlling the ratio of hydrogen to BYD in reactor R2, the BED content in the effluent of R2 can be regulated. Through the newly added process, in reactor R3, formaldehyde is added from stream 6, and the cocatalyst enters R3 along stream 10, realizing the synthesis of BED in R2 and the hydrogenation reaction of BED, formaldehyde, and hydrogen in R3, and a BDO product containing 30%wt MBDO can be generated.

[0057] If 2-ethyl-1,4-butanediol is to be generated, the formaldehyde in streams 6-9 needs to be replaced with an equimolar amount of acetaldehyde. By analogy, in the known manner, if 2-propyl-1,4-butanediol is to be generated, the formaldehyde in streams 6-9 is replaced with propionaldehyde. This patent is also applicable to the generation of all alkyl-substituted alkyl-1,4-butanediols such as butyl, isopropyl, and isobutyl, and only the formaldehyde in the raw materials of the hydrogenation reactor needs to be replaced with the corresponding alkyl aldehydes.

[0058] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A process for co-producing 1,4-butanediol and alkyl-1,4-butanediol, characterized in that, The method comprises the following steps: (1) Formaldehyde reacts with acetylene to produce a 1,4-butynediol stream; (2) The 1,4-butynediol stream undergoes two-stage hydrogenation reaction to co-produce 1,4-butanediol and alkyl-1,4-butanediol; (2-1) When the target product is only 1,4-butanediol, the unreacted formaldehyde in step (1) needs to be recovered; (2-2) When the target product is 1,4-butanediol containing alkyl-1,4-butanediol, the unreacted formaldehyde in step (1) does not need to be recovered, aldehyde is supplemented to the initial raw materials in step (1), the 1,4-butynediol stream in step (1) and / or the hydrogenation reaction process, and a cocatalyst is added to the hydrogenation reaction process.

2. The method according to claim 1, wherein In step (1), the mass ratio of the formaldehyde stream to the acetylene stream is (2-10):

1.

3. The method according to claim 1, wherein The reaction conditions of the formaldehyde and acetylene include: The operating pressure is 0-0.3 MPaG; The reaction temperature is 80-100 °C; And / or, the catalyst is a Cu-Bi complex catalyst; The conditions of the first-stage hydrogenation reaction include: The operating pressure is 3-30 MPaG; The reaction temperature is 60-180 °C; The catalyst is a nickel-based catalyst; And / or, the molar ratio of the inlet hydrogen to 1,4-butynediol is 1-20; The conditions of the second-stage hydrogenation reaction include: The operating pressure is 10-30 MPaG; The reaction temperature is 100-180 °C; The catalyst is a nickel-based catalyst; And / or, the molar ratio of the inlet hydrogen to 1,4-butynediol is 1-20.

4. The method according to claim 1, wherein The operation of recovering the unreacted formaldehyde in step (1) includes: The operating pressure is 20-100 KPaA; The reflux ratio is 0.2-2; And / or, the number of theoretical plates is 5-60; And / or, the flow rate of the formaldehyde stream in step (1) is 5000-7000 kg / h, and / or, the flow rate of the acetylene stream in step (1) is 500-1500 kg / h.

5. The method according to claim 1, characterized in that, The supplement of aldehyde to the hydrogenation reaction process is to supplement aldehyde to the first-stage hydrogenation reaction process, including adding aldehyde from the top, upper part, middle part and / or bottom of the first hydrogenation reactor; The supplemented aldehyde in step (2-2) is the aldehyde required to produce the alkyl-1,4-butanediol.

6. The method according to claim 1, wherein In step (2-2), the mass ratio of the supplemented aldehyde in any process to the formaldehyde stream in step (1) is 1:(1-50); And / or, the cocatalyst is selected from organic bases and / or inorganic bases; And / or, the addition amount of the cocatalyst needs to control the pH value of the effluent of the second-stage hydrogenation reaction to be 7-14; And / or, the cocatalyst is added in the form of an aqueous solution, the concentration of the cocatalyst aqueous solution is 10-40 wt%, and the addition amount does not exceed 1 wt% of the mass of the formaldehyde stream in step (1); And / or, the cocatalyst is added to the first-stage hydrogenation reaction process or the second-stage hydrogenation reaction process.

7. The method according to claim 1, characterized in that, In step (2-2), aldehyde is supplemented to the initial raw materials in step (1), the 1,4-butynediol stream in step (1), the top, upper part, middle part or bottom of the first hydrogenation reactor, and a cocatalyst is added to the first-stage hydrogenation reaction process. Alternatively, in step (2-2), aldehyde is supplemented to the initial raw materials in step (1), the 1,4-butynediol stream in step (1), the top, upper part, middle part or bottom of the first hydrogenation reactor, and a cocatalyst is added to the second-stage hydrogenation reaction process.

8. The method according to claim 1, wherein The method further includes step (3) distillation process: removing heavy components, recovering methanol and removing light components from the effluent of the second-stage hydrogenation reaction.

9. The method according to claim 8, wherein The heavy component removal includes the following operations: Operating pressure 0~20KPaA; The number of theoretical plates is 5~30; And / or, reflux ratio 0.2~5; The methanol recovery includes the following operations: Operating pressure 0~20KPaA; The number of theoretical plates is 10~50; And / or, reflux ratio 1~5; The light component removal includes the following operations: Operating pressure 0~20KPaA; The number of theoretical plates is 10~50; And / or, reflux ratio 1~10.

10. The method according to any one of claims 1-9, characterized in that, The method can be carried out in the following system, and the system includes: 1,4-butynediol synthesis reactor; A formaldehyde recycle column located downstream of the 1,4-butynediol synthesis reactor; A first hydrogenation reactor and a second hydrogenation reactor located downstream of the formaldehyde recycle column, the first hydrogenation reactor and the second hydrogenation reactor are connected in series, the first hydrogenation reactor and the second hydrogenation reactor are bubble column hydrogenation reactors, and a nickel-based catalyst layer is provided inside both of them. The first hydrogenation reactor and / or the second hydrogenation reactor are also provided with a cocatalyst feed end; An aldehyde feed end, which is used to provide more aldehyde to the 1,4-butynediol synthesis reactor and / or the first hydrogenation reactor; the aldehyde feed end is arranged at the feed port of the 1,4-butynediol synthesis reactor, and / or, arranged at the top, upper part, middle part and / or bottom of the first hydrogenation reactor; preferably arranged in the middle part of the first hydrogenation reactor; And a distillation unit located downstream of the hydrogenation reactor, the distillation unit includes a heavy component removal column, a methanol recovery column located downstream of the heavy component removal column, and a light component removal column located downstream of the methanol recovery column.

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