A method and system for synthesizing 1,4-butanediol

Abstract

The application discloses a synthesis method and a synthesis system of 1,4-butanediol. The synthesis method of 1,4-butanediol comprises the following steps: a) ethylene glycol steam and an oxygen-containing mixed gas stream are contacted with a first catalyst to perform an oxidation reaction, and glyoxal is obtained through separation and purification; b) the glyoxal obtained in the step a) is subjected to a condensation reaction with acetaldehyde under the action of a second catalyst aqueous solution, and butenedial is obtained through separation and purification; and c) the butenedial obtained in the step b) is subjected to a hydrogenation reaction with hydrogen under the action of a hydrogenation catalyst, and 1,4-butanediol is obtained through separation and purification. The method has the advantages of stable raw material source, small investment, large operation flexibility and the like, can effectively simplify a traditional route, reduce investment, utilize the raw material advantages of an existing coal-to-ethylene glycol device, and has good economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method and system for synthesizing 1,4-butanediol. Background Technology

[0002] 1,4-Butanediol is an important raw material for organic and fine chemicals, and a fundamental raw material for the production of polybutylene terephthalate (PBT) engineering plastics and PBT fibers; PBT plastic is one of the five most promising engineering plastics. In addition, it is also a major raw material for the production of tetrahydrofuran and γ-butyrolactone, possessing high economic value.

[0003] Currently, there are four industrialized routes for the synthesis of 1,4-butanediol. 1. The Reppe method: Acetylene and formaldehyde are first reacted in the presence of a Cu-Bi catalyst to produce 1,4-butynediol, which is then hydrogenated to 1,4-butenediate via nickel skeletal catalysis, followed by further hydrogenation to 1,4-butanediol via Ni-Cu-Mn / Al₂O₃ catalysis. This method suffers from high acetylene costs and transportation and safety issues. 2. Maleic anhydride hydrogenation method: This is further divided into maleic anhydride esterification hydrogenation and direct maleic anhydride hydrogenation. The source of maleic anhydride for this method is unstable. 3. The butadiene method: 1,3-butadiene undergoes acetyloxidation with acetic acid and oxygen to produce 1,4-diacetoxy-2-butene, which is then hydrogenated and hydrolyzed. This method involves high investment and severe equipment corrosion. 4. Propylene oxide method (allyl alcohol method): This process was developed by Kuraray in Japan. Propylene oxide is used as raw material, and is catalytically isomerized into allyl alcohol. Under the action of organophosphorus ligand catalyst, hydroformylation reaction is carried out to generate the main product γ-hydroxypropanal. Then, it is extracted, hydrogenated, and purified to obtain 1,4-butanediol. However, the price of propylene oxide fluctuates greatly, and the selectivity and yield are low.

[0004] Developing and researching new technical routes suitable for the industrial production of 1,4-butanediol has always been a research hotspot in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and system for synthesizing 1,4-butanediol. The inventors have discovered that utilizing existing coal-to-ethylene glycol plants to further utilize ethylene glycol to produce high-value-added 1,4-butanediol offers advantages such as stable raw material sources, low investment, and high operational flexibility. Furthermore, it effectively simplifies traditional routes, reduces investment, and leverages the raw material advantages of existing coal-to-ethylene glycol plants, resulting in significant economic benefits.

[0006] The first aspect of this invention provides a method for synthesizing 1,4-butanediol, comprising:

[0007] a) Ethylene glycol vapor and an oxygen-containing gas mixture are contacted with the first catalyst to carry out an oxidation reaction, and glyoxal is obtained by separation and purification.

[0008] b) The glyoxal obtained in step a) and acetaldehyde are subjected to a condensation reaction in the presence of an aqueous solution of the second catalyst, and the resulting product is separated and purified to obtain butenedialdehyde.

[0009] c) The butenaldehyde obtained in step b) and hydrogen are subjected to a hydrogenation reaction in the presence of a hydrogenation catalyst, and then separated and purified to obtain 1,4-butanediol.

[0010] Further, in step a), the aldehyde content in the ethylene glycol vapor is below 20 ppm, and the weight hourly space velocity (WHSV) of the ethylene glycol vapor is 0.5–10 h⁻¹. -1 Preferably 1 to 5 hours -1 .

[0011] Further, in step a), the oxygen content of the oxygen-containing mixed gas is preferably 5% to 9% by volume. For example, the oxygen-containing mixed gas is air and / or a mixture of oxygen with nitrogen and water vapor. The molar ratio of ethylene glycol vapor to oxygen is 1:1 to 5, preferably 1:1.2 to 3.

[0012] Further, in step a), the first catalyst is an oxidation catalyst, preferably a CuO / alumina catalyst.

[0013] Furthermore, the CuO content in the CuO / alumina catalyst is 3% to 15% by mass. The CuO / alumina catalyst can be prepared using conventional methods in the art.

[0014] Further, in step a), the temperature of the oxidation reaction is 200–450°C, preferably 250–350°C; the pressure of the oxidation reaction is 0.1–1.0 MPa, preferably 0.4–0.8 MPa.

[0015] Further, in step b), the molar ratio of glyoxal to acetaldehyde is 2–6:1, preferably 2–4:1. The weight hourly space velocity (WHSV) of the glyoxal is 0.5–10 h⁻¹. -1 Preferably 1 to 5 hours -1 The condensation reaction is carried out under a protective atmosphere, preferably a nitrogen atmosphere. The acetaldehyde may be derived from industrial ethylene oxidation.

[0016] Further, in step b), the second catalyst is an aqueous solution of at least one or more of ethylenediamine, ethanolamine, KOH, K2CO3, potassium oxalate, and Cs2CO3. The pH value of the aqueous solution of the second catalyst is 11-14, preferably 11.5-13.5.

[0017] Further, in step b), the reaction temperature of the condensation reaction is 70–130°C, and the reaction pressure is 0.1–0.5 MPa, preferably 0.1–0.3 MPa.

[0018] Further, in step b), the condensation reaction is preferably carried out in a distillation column reactor. The temperature of the reaction section of the distillation column reactor is 70–130°C, preferably 80–110°C, the top temperature is 50–70°C, and the bottom temperature is 120–160°C, preferably 135–145°C; the pressure is 0.1–0.5 MPa, preferably 0.1–0.3 MPa.

[0019] Furthermore, in step c), the hydrogenation catalyst includes a catalyst containing trace amounts of noble metals, preferably a Ni-Pd / C catalyst.

[0020] Furthermore, based on the weight of the Ni-Pd / C catalyst, the Ni content is 1 wt% to 30 wt%, and the Pd content is 0.001 wt% to 2 wt%. The Ni-Pd / C catalyst can be prepared using methods conventional in the art.

[0021] Furthermore, in step c), the weight hourly space velocity (WHSV) of butenedialdehyde is 0.5–10 h⁻¹. -1 Preferably 1 to 5 hours -1 The molar ratio of butenedialdehyde to hydrogen is 1:1 to 20, preferably 1:3 to 10.

[0022] Further, in step c), the temperature of the hydrogenation reaction is 150–300°C, preferably 180–250°C; the reaction pressure is 1–15 MPa, preferably 4–10 MPa.

[0023] Furthermore, the specific reaction process of the synthesis method of the present invention is shown in formula (1):

[0024]

[0025] A second aspect of the present invention provides a synthesis system for 1,4-butanediol, comprising: an oxidation reactor, a condensation reactor, and a hydrogenation reactor; wherein,

[0026] An oxidation reactor is used for the oxidation reaction of ethylene glycol to produce glyoxal;

[0027] A condensation reactor is used for the condensation reaction of glyoxal and acetaldehyde to produce butenedialdehyde.

[0028] A hydrogenation reactor is used for the hydrogenation reaction of butenedialdehyde and hydrogen to produce 1,4-butanediol.

[0029] Furthermore, the condensation reactor is a distillation column reactor.

[0030] Furthermore, the synthesis system also includes a low-temperature flash evaporation unit, a separation and processing unit, and a purification unit.

[0031] The separation processing unit includes a first separation processing unit, a second separation processing unit, and a third separation processing unit.

[0032] Furthermore, the low-temperature flash evaporation unit is used to receive the products obtained from the oxidation reactor, thereby recycling the separated oxygen-containing mixed gas back to the oxidation reactor.

[0033] Furthermore, the first separation and processing unit is used to receive the material separated by the low-temperature flash evaporation unit, and the separated glyoxal enters the condensation reactor.

[0034] Furthermore, the second separation and processing unit is used to receive the product obtained from the condensation reactor, separate out glyoxal, and recycle the separated glyoxal and the second catalyst back to the condensation reactor.

[0035] Furthermore, the third separation and processing unit is used to receive the product obtained from the hydrogenation reactor. The separated hydrogen can be recycled back to the hydrogenation reactor, and the separated crude 1,4-butanediol enters the purification unit.

[0036] Furthermore, the refining unit is used to receive crude 1,4-butanediol from the third separation and processing unit to obtain the product 1,4-butanediol.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. This invention is the first to use ethylene glycol to produce high-value-added 1,4-butanediol. Ethylene glycol can be obtained from coal-based synthesis routes, with stable raw material sources and low costs.

[0039] 2. The synthesis method of 1,4-butanediol of the present invention is simple and only requires three steps: oxidation, condensation and hydrogenation, to obtain high-value-added 1,4-butanediol from ethylene glycol.

[0040] 3. The 1,4-butanediol synthesis system of the present invention greatly improves the selectivity of the target product and increases the utilization rate of raw materials through the coordination of various reaction units, especially the distillation column reactor module.

[0041] 4. The condensation reaction of glyoxal and acetaldehyde in this invention, that is, acetaldehyde containing α-hydrogen can undergo aldol condensation with glyoxal without α-hydrogen to generate butenedialdehyde, and the short residence time of the reaction raw materials and catalyst in the distillation column reactor can effectively prevent the deep condensation reaction of glyoxal. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the production process of 1,4-butanediol according to the present invention;

[0043] Figure 2 This is a schematic diagram of a distillation column reactor;

[0044] in, Figure 1 The numbers in the diagram are: A - Oxidation reactor, B - Low-temperature flash evaporation unit, C - First separation and processing unit, D - Distillation column reactor, E - Second separation and processing unit, F - Hydrogenation reactor, G - Third processing and separation unit, H - Purification unit;

[0045] Figure 2 The numbers in the table are: 1-glyoxal / acetaldehyde, 2-aqueous solution of the second catalyst, 3-glyoxal, 4-butenedialdehyde / aqueous solution of the second catalyst. Detailed Implementation

[0046] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0047] Combination Figure 1 The specific process and system for synthesizing 1,4-butanediol according to the present invention are described below:

[0048] The synthesis system for 1,4-butanediol includes: an oxidation reactor, a low-temperature flash evaporation unit, a first separation and processing unit, a distillation column reactor, a second separation and processing unit, a hydrogenation reactor, a third separation and processing unit, and a purification unit.

[0049] Ethylene glycol vapor and an oxygen-containing mixture are fed into an oxidation reactor. Under the action of a first catalyst, an oxidation reaction occurs, yielding an oxidation product containing glyoxal. The product enters a low-temperature flash evaporation unit. The separated oxygen-containing mixture is recycled back to the oxidation reactor. The remainder is processed by a first separation unit to obtain glyoxal, which is then mixed with acetaldehyde and fed from the bottom of the reaction section of a distillation column reactor. A second catalyst aqueous solution is fed from the top of the reaction section. The two streams come into countercurrent contact and undergo an aldol condensation reaction to produce a condensation product mainly containing butenedialdehyde. Unreacted glyoxal is recovered from the top of the column and recycled. The second catalyst aqueous solution and butenedialdehyde are collected from the bottom of the column and processed by a second separation unit. The second catalyst aqueous solution is recycled back into the distillation column reactor, while butenedialdehyde enters a hydrogenation reactor. Butenedialdehyde and hydrogen react in the hydrogenation reactor to obtain a product mainly composed of 1,4-butanediol. Unreacted hydrogen is recycled. The product is processed by a third separation unit to obtain crude 1,4-butanediol, which is then purified to obtain the final product, 1,4-butanediol.

[0050] Example 1

[0051] use Figure 1The process shown involves feeding a stream containing ethylene glycol vapor, oxygen, nitrogen, and water vapor in a molar ratio of 1:1.5:15:2 into an oxidation reactor for oxidation. The aldehyde content in the ethylene glycol is below 20 ppm, and the weight hourly space velocity (WHSV) of the ethylene glycol is 1.5 h⁻¹. -1 The reactor is loaded with a CuO / alumina catalyst containing 5% CuO by mass. The reaction pressure is 0.2 MPa, and the reaction temperature is controlled at 280℃ to obtain an oxidation product containing glyoxal. After passing through a low-temperature flash evaporation unit and a first separation unit, the separated glyoxal and acetaldehyde streams are mixed at a molar ratio of 3:1 and fed into a distillation column reactor. Acetaldehyde and glyoxal react countercurrently with a KOH aqueous solution at pH=12. The reaction section temperature is 90℃, the top temperature is 60℃, and the bottom temperature is 110℃. Unreacted glyoxal is recovered from the top of the column and recycled. The product and catalyst aqueous solution are collected from the bottom of the column and processed by a second separation unit. The KOH aqueous solution is reused, and butenedialdehyde enters a hydrogenation reactor pre-loaded with a Ni-Pd / C catalyst, wherein the Ni content is 10 wt% and the Pd content is 0.2 wt%. The reaction pressure is 5 MPa, the reaction temperature is 200℃, and the weight hourly space velocity of butenedialdehyde is 3 h⁻¹. -1 The molar ratio of butenaldehyde and hydrogen is 1:8. The reaction yields a product mainly composed of 1,4-butanediol. Unreacted hydrogen is recycled. The product is processed by the third separation unit to obtain crude 1,4-butanediol, and then purified to obtain the final product 1,4-butanediol.

[0052] Results: 0.78 tons of 1,4-butanediol product can be produced from 1 ton of ethylene glycol raw material, with a purity of 99.6% and an aldehyde content of <12 ppm. The color was tested by the Pt-Co method and the color was <10 APHA.

[0053] Examples 2-4

[0054] Compared with Example 1, Examples 2-4 differ in the molar ratio of glyoxal to acetaldehyde, as shown in Table 1.

[0055] Table 1. Effect of different molar ratios of glyoxal and acetaldehyde on the yield of 1,4-butanediol.

[0056]

[0057] Examples 5-7

[0058] Compared with Example 1, Examples 5-7 differ in that the pH value of the KOH aqueous solution in the distillation column reactor is different, as shown in Table 2.

[0059] Table 2 Effect of pH value on the yield of 1,4-butanediol by different catalysts.

[0060]

[0061] Example 8

[0062] A stream containing ethylene glycol vapor, oxygen, nitrogen, and water vapor in a molar ratio of 1:2:20:3 is fed into an oxidation reactor for oxidation. The aldehyde content in the ethylene glycol is below 20 ppm, and the space velocity of the ethylene glycol is 2 h⁻¹. -1 The reactor is loaded with a CuO / alumina catalyst containing 8% CuO. The reaction pressure is 0.3 MPa, and the reaction temperature is controlled at 270℃ to obtain an oxidation product containing glyoxal. After passing through a low-temperature flash evaporation unit and a first separation unit, the separated glyoxal and acetaldehyde streams are mixed at a molar ratio of 2:1 and fed into a distillation column reactor. Acetaldehyde and glyoxal react countercurrently with a Cs₂CO₃ aqueous solution at pH=13. The reaction section temperature is 100℃, the top temperature is 70℃, and the bottom temperature is 120℃. Unreacted glyoxal is recovered from the top of the column and recycled. The product and catalyst aqueous solution are collected from the bottom of the column and processed by a second separation unit. The Cs₂CO₃ aqueous solution is reused, and butenedialdehyde enters a hydrogenation reactor pre-loaded with a Ni-Pd / C catalyst, containing 11 wt% Ni and 0.25 wt% Pd. The reaction pressure is 4 MPa, the reaction temperature is 200℃, and the weight hourly space velocity (WHSV) of butenedialdehyde is 2 h⁻¹. -1 The molar ratio of butenaldehyde and hydrogen is 1:6. The reaction yields a product mainly composed of 1,4-butanediol. Unreacted hydrogen is recycled. The product is processed by the third separation unit to obtain crude 1,4-butanediol, and then purified by the purification unit to obtain the final product 1,4-butanediol.

[0063] Results: 0.74 tons of 1,4-butanediol product can be produced from 1 ton of ethylene glycol raw material, with a purity of 99.7% and an aldehyde content of <10 ppm. The color was tested by the Pt-Co method and the color was <10 APHA.

[0064] Comparative Example 1

[0065] use Figure 1 The process shown is the same as in Example 1, with the catalyst and reaction conditions controlled as in Example 1, except that the pH of the KOH aqueous solution in the distillation column reactor is controlled to be 10.

[0066] Results: 0.26 tons of 1,4-butanediol product can be produced from 1 ton of ethylene glycol raw material, with a purity of 98.8% and an aldehyde content of <15ppm. The color was tested by the Pt-Co method and the color was <10APHA.

[0067] Comparative Example 2

[0068] use Figure 1 The process shown is the same as in Example 1, with the catalyst and reaction conditions controlled as in Example 1, and the molar ratio of glyoxal to acetaldehyde controlled at 1:1.

[0069] Results: 0.32 tons of 1,4-butanediol product can be produced from 1 ton of ethylene glycol raw material, with a purity of 98.6% and an aldehyde content of <15ppm. The color was tested by the Pt-Co method and the color was <10APHA.

[0070] Comparative Example 3

[0071] use Figure 1 The process shown is the same as in Example 1, except that the distillation column reactor is replaced with a traditional batch reactor.

[0072] Results: 0.4 tons of 1,4-butanediol product can be produced from 1 ton of ethylene glycol raw material, with a purity of 98.2% and an aldehyde content of <15 ppm. The color was tested by the Pt-Co method and the color was <10 APHA.

Claims

1. A method for synthesizing 1,4-butanediol, characterized in that, include: a) Ethylene glycol vapor and an oxygen-containing gas mixture are contacted with the first catalyst to carry out an oxidation reaction, and glyoxal is obtained by separation and purification. b) The glyoxal obtained in step a) and acetaldehyde are subjected to a condensation reaction in the presence of an aqueous solution of the second catalyst, and the resulting product is separated and purified to obtain butenedialdehyde; c) The butenaldehyde obtained in step b) and hydrogen are subjected to a hydrogenation reaction in the presence of a hydrogenation catalyst, and then separated and purified to obtain 1,4-butanediol; In step b), the second catalyst aqueous solution is an aqueous solution of at least one or more of ethylenediamine, ethanolamine, KOH, K2CO3, potassium oxalate, and Cs2CO3; In step b), the condensation reaction is carried out at a temperature of 70-130°C and a pressure of 0.1-0.5 MPa.

2. The method according to claim 1, characterized in that, In step a), the volume content of oxygen in the oxygen-containing mixed gas is 5% to 9% based on the volume of the gas; the molar ratio of ethylene glycol vapor to oxygen is 1:1 to 5.

3. The method according to claim 2, characterized in that, In step a), the molar ratio of ethylene glycol vapor to oxygen is 1:1.2~3.

4. The method according to claim 1, characterized in that, In step a), the first catalyst is an oxidation catalyst.

5. The method according to claim 4, characterized in that, In step a), the first catalyst is a CuO / alumina catalyst.

6. The method according to claim 1, characterized in that, In step a), the temperature of the oxidation reaction is 200~450℃ and the pressure of the oxidation reaction is 0.1~1.0MPa.

7. The method according to claim 6, characterized in that, In step a), the temperature of the oxidation reaction is 250~350℃ and the pressure of the oxidation reaction is 0.4~0.8MPa.

8. The method according to claim 1, characterized in that, In step b), the molar ratio of glyoxal to acetaldehyde is 2~6:

1.

9. The method according to claim 8, characterized in that, In step b), the molar ratio of glyoxal to acetaldehyde is 2-4:

1.

10. The method according to claim 1, characterized in that, In step b), the pH value of the second catalyst aqueous solution is 11-14.

11. The method according to claim 10, characterized in that, In step b), the pH value of the second catalyst aqueous solution is 11.5~13.

5.

12. The method according to claim 1, characterized in that, In step b), the reaction pressure of the condensation reaction is 0.1~0.3 MPa.

13. The method according to claim 1, characterized in that, In step c), the temperature of the hydrogenation reaction is 150~300℃ and the reaction pressure is 1~15MPa.

14. The method according to claim 13, characterized in that, In step c), the temperature of the hydrogenation reaction is 180~250℃ and the reaction pressure is 4~10MPa.

15. A synthetic system for the method of synthesizing 1,4-butanediol according to any one of claims 1-14, characterized in that, include: Oxidation reactors, condensation reactors, and hydrogenation reactors; among them, An oxidation reactor is used for the oxidation reaction of ethylene glycol to produce glyoxal; A condensation reactor is used for the condensation reaction of glyoxal and acetaldehyde to produce butenedialdehyde. A hydrogenation reactor is used for the hydrogenation reaction of butenedialdehyde and hydrogen to produce 1,4-butanediol.

16. The synthesis system according to claim 15, characterized in that, The condensation reactor is a distillation column reactor.

17. The synthesis system according to claim 15, characterized in that, The synthesis system further includes a low-temperature flash evaporation unit, a separation processing unit, and a purification unit; the separation processing unit includes a first separation processing unit, a second separation processing unit, and a third separation processing unit.

18. The synthesis system according to claim 17, characterized in that, The low-temperature flash evaporation unit is used to receive the products obtained from the oxidation reactor, thereby recycling the separated oxygen-containing mixed gas back to the oxidation reactor; and / or, The first separation and processing unit is used to receive the material separated by the low-temperature flash evaporation unit, wherein the separated glyoxal enters the condensation reactor; and / or, The second separation and processing unit is used to receive the product obtained from the condensation reactor, separate ethylene glycol, and recycle the separated glyoxal and the second catalyst back to the condensation reactor; and / or, The third separation and processing unit is used to receive the product obtained from the hydrogenation reactor. The separated hydrogen can be recycled back to the hydrogenation reactor, and the crude 1,4-butanediol obtained from the separation enters the purification unit; and / or, The refining unit is used to receive crude 1,4-butanediol from the third separation and processing unit to obtain the product 1,4-butanediol.

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