A fixed bed reaction system and method for synthesizing 3-hexyn-2,5-diol

Abstract

The present application relates to a kind of fixed bed reaction system and method of synthesizing 3-hexyne-2,5-diol, including gas mixer, fixed bed reactor, finished product receiving tank, reaction monitoring device and compression device;Wherein, the gas inlet of gas mixer is connected with aldehyde supply device and alkynyl supply device, for obtaining acetaldehyde and acetylene raw materials and carrying out uniform mixing;The gas outlet of gas mixer is connected with the inlet of fixed bed reactor, and catalyst layer is arranged in fixed bed reactor;The outlet of fixed bed reactor is connected with finished product receiving tank by reaction monitoring device;Reaction monitoring device is used to control the single-pass conversion rate of raw material in 60~80%;Finished product receiving tank is connected with the gas inlet of gas mixer by compression device, and forms circulation loop.The reaction system of the present application uses fixed bed reactor, realizes the continuous production of 3-hexyne-2,5-diol, and the operation process is simple and stable and controllable, suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic synthesis, and particularly relates to a fixed bed reaction system and method for synthesizing 3-hexyne-2,5-diol. BACKGROUND

[0002] The production of acetylene alcohol raw materials is cheap and has low production cost, so the development of such products has good market prospects, but due to the limitation of catalyst activity, only 1,4-butynediol (malachite catalysis) and decyne diol (potassium hydroxide catalysis) have realized industrialized production, and other acetylene alcohol products are not much, such as 3-hexyne-2,5-diol, molecular formula: C6H 10 O2, molecular weight: 114.14, CAS number: 3031-66-1; is a light yellow liquid, because it contains a triple bond and a hydroxyl group, it has special excellent performance, can be used as a brightener additive for nickel plating in electroplating industry, and as an inhibitor for aluminum anodization, can form semi-bright plating layer in a wide range, is a semi-bright nickel additive with excellent performance. It also has good wetting and defoaming properties, and can be used in water-based coatings to improve the performance of paint film. It can also be used as an important additive for corrosion inhibitors in oil and gas wells, which can significantly enhance the corrosion inhibition effect. In view of the excellent performance of the product in some fields, its research and development are particularly important.

[0003] At present, the industrial production method of 3-hexyne-2,5-diol mainly uses acetaldehyde and acetylene or propargyl chloride and acetylene as raw materials to react under the catalysis of catalyst to obtain the product, which is obtained by distillation after reaction in organic solvent or water system. There is also a method of synthesizing by Grignard reaction, but the water resistance of Grignard reagent and the flammability of acetylene make this process route have great safety hidden danger. The conventional kettle type has problems of great safety hidden danger, long reaction time, many by-products and environmental pollution.

[0004] Patent CN 113698274 A discloses a method for synthesizing 3-butyn-2-ol with high yield, which uses acetaldehyde and acetylene as raw materials, potassium hydroxide as catalyst, and obtains 3-butyn-2-ol through a tubular reactor, but the product obtained is mainly single-sided, it is difficult to convert into double-sided product, and there are many polymerization by-products. Using powder potassium hydroxide, potassium tert-butoxide and other alkalis as catalysts, the actual reaction process is difficult to control, and the product is easy to polymerize to form black tar.

[0005] Patent CN 102875332 A discloses a process for synthesizing 3-hexyne-2,5-diol by slurry bed low pressure method: acetaldehyde aqueous solution and catalyst are mixed and stirred in a slurry bed reactor to form a slurry liquid, acetylene is introduced into the slurry system from the lower part of the slurry liquid for reaction, and 3-hexyne-2,5-diol is prepared by concentration separation and reduced pressure distillation. The separation of the slurry liquid after reaction and the recovery of the catalyst are difficult in industrialization and the process is complicated.

[0006] Patent CN 102285867 A discloses a method for synthesizing 3-hexyne-2,5-diol, which includes the following steps: 1) preparing an alumina-supported catalyst; 2) using acetaldehyde aqueous solution and acetylene as raw materials, reacting in a high-pressure reactor under the catalysis of the alumina-supported catalyst, controlling the reaction pressure by introducing nitrogen gas, and then obtaining the target product by filtration and distillation. In this process, there is a large excess of acetylene, and the treatment of the tail gas poses a great safety hazard. At the same time, too much excess acetylene will also form polymers and single-sided products, which greatly reduces the reaction selectivity and yield. In addition, the supported catalyst is easily lost in the aqueous system. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a fixed-bed reaction system and method for synthesizing 3-hexyne-2,5-diol, thereby solving the technical problems of high by-products and low yield in the synthesis of 3-hexyne-2,5-diol in the prior art.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a fixed-bed reaction system for synthesizing 3-hexyne-2,5-diol, comprising a gas mixer, a fixed-bed reactor, a finished product receiving tank, a reaction monitoring device, and a compression device; wherein, the gas inlet of the gas mixer is connected to an aldehyde supply device and an acetylene supply device for obtaining acetaldehyde and acetylene raw materials and mixing them uniformly; the gas outlet of the gas mixer is connected to the inlet of the fixed-bed reactor, which contains a catalyst layer; the outlet of the fixed-bed reactor is connected to the finished product receiving tank via the reaction monitoring device; the reaction monitoring device is used to control the single-pass conversion rate of the raw materials to be between 60% and 80%; the finished product receiving tank is connected to the gas inlet of the gas mixer via the compression device, forming a circulation loop.

[0009] Furthermore, the aldehyde supply device includes an acetaldehyde depolymerization vessel, which is connected to the gas inlet of a gas mixer via a first high-pressure plunger pump and a first gas flow meter.

[0010] Furthermore, the acetylene supply device includes an acetylene storage tank and an acetylene purification tower connected in sequence. The acetylene purification tower is connected to the gas inlet of the gas mixer via a second high-pressure plunger pump and a second gas flow meter.

[0011] Furthermore, the gas mixer is made of stainless steel; the interior of the gas mixer is equipped with alternating first and second baffles to form a wedge-shaped guide channel.

[0012] Furthermore, the fixed-bed reactor is vertically positioned with the inlet located at the top.

[0013] Furthermore, the compression device uses a variable frequency compressor.

[0014] The present invention also provides a method for synthesizing 3-hexyne-2,5-diol using the above-mentioned fixed-bed reaction system, comprising the following steps:

[0015] (1) Gas acetaldehyde and acetylene are simultaneously introduced into a gas mixer and mixed evenly to obtain a mixed gas;

[0016] (2) The mixed gas passes through a fixed-bed reactor and reacts under the action of a catalyst. The single-pass conversion rate of acetaldehyde is detected and controlled at 60-80% by a reaction monitoring device.

[0017] (3) The reaction liquid is collected by the finished product receiving tank and distilled to obtain 3-hexyne-2,5-diol. The tail gas is pressurized by the compression device and then introduced into the gas mixer to participate in the reaction.

[0018] Furthermore, the molar ratio of acetaldehyde to acetylene is 1:(0.5 to 0.6).

[0019] Furthermore, the catalyst is a mixture of copper salt, bismuth salt and co-catalyst supported on coarse-porous microsphere silica gel; wherein the molar ratio of copper salt, bismuth salt and co-catalyst is 1:(0.01~0.05):(0.06~0.2); the co-catalyst is a combination of at least two substances selected from alkali metal salt, alkaline earth metal salt, lanthanide metal salt and transition metal salt.

[0020] Furthermore, during the reaction, the pressure is controlled at 1.0 MPa to 2.0 MPa, and the reaction temperature is controlled at 90 to 120 °C.

[0021] Compared with the prior art, the beneficial effects of the present invention include:

[0022] 1. The reaction system of this invention adopts a fixed-bed reactor to realize the continuous production of 3-hexyne-2,5-diol. The contact time of the raw gas on the catalyst surface is short, which is different from the disadvantage of the long reaction time in the conventional batch reaction, which leads to an increase in by-product polymers. The whole operation process is simple, stable and controllable, and suitable for industrial production.

[0023] 2. This invention employs a gas mixer to premix the raw material gases acetaldehyde and acetylene before introducing them into a fixed bed for reaction in the catalyst bed, thereby enhancing the mass transfer and mixing process.

[0024] 3. This invention controls the single-pass conversion rate at 60-80% through a reaction monitoring device and a compression device, effectively reducing the occurrence of side reactions and greatly reducing the generation of waste during the production process. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the fixed-bed reaction system for synthesizing 3-hexyne-2,5-diol according to the present invention;

[0026] Figure 2 This is a schematic diagram of the gas mixer in this invention;

[0027] Figure 3 This is a spectrum of the product obtained in Example 1 of the present invention;

[0028] Figure 4 This is a spectrum of the product obtained in Example 2 of the present invention;

[0029] Figure 5 This is a spectrum of the product obtained in Example 3 of the present invention;

[0030] Figure 6 The spectrum of the product obtained in Comparative Example 1 is shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] This invention proposes a fixed-bed reaction system and method for synthesizing 3-hexyne-2,5-diol. The synthesis of 3-hexyne-2,5-diol using this fixed-bed reaction system results in fewer byproducts, recycling of tail gas, and high product yield, making it a green and environmentally friendly preparation system and method.

[0033] See Figure 1 and Figure 2 The fixed-bed reaction system of the present invention includes an acetaldehyde depolymerization vessel 1, an acetylene storage tank 2, a gas mixer 3, a fixed-bed reactor 4, a finished product receiving tank 5, an acetylene purification tower 6, a first high-pressure plunger pump 7, a first gas flow meter 8, a second high-pressure plunger pump 9, a second gas flow meter 10, a compressor 11, a motor 12, and an online gas chromatograph detection device 13.

[0034] The acetaldehyde depolymerization reactor 1 is used to depolymerize triacetaldehyde and provide acetaldehyde as the reaction raw material; the acetylene storage tank 2 is used to store acetylene as the raw material, preferably in a steel cylinder; the acetaldehyde depolymerization reactor 1 is connected to the gas inlet 301 of the gas mixer 3 through a first high-pressure plunger pump 7 and a first gas flow meter 8; the acetylene storage tank 2 is connected to the acetylene purification tower 6, and the acetylene purification tower 6 is connected to the gas inlet 301 of the gas mixer 3 through a second high-pressure plunger pump 9 and a second gas flow meter 10.

[0035] Preferably, a motor 12 is installed on the acetaldehyde depolymerization reactor 1 to drive the stirrer and stir during the depolymerization of trimaldehyde.

[0036] Preferably, the gas mixer 3 is made of stainless steel and has alternating first baffles 302 and second baffles 303 inside to form a wedge-shaped guide channel, which is conducive to the full and uniform mixing of the reaction raw materials.

[0037] The gas outlet 304 of the gas mixer 3 is connected to the inlet of the fixed bed reactor 4, and the outlet of the fixed bed reactor 4 is connected to the finished product receiving tank 5.

[0038] Preferably, the present invention involves vertically setting the fixed-bed reactor 4 with the inlet located at the top, and setting a catalyst chamber on the bed of the fixed-bed reactor 4, which is filled with catalyst to form a catalyst layer; after the gaseous acetaldehyde and acetylene gas are fully mixed by the gas mixer 3, they enter the bed from the top of the fixed-bed reactor 4 and react from top to bottom through the catalyst layer.

[0039] Preferably, the present invention provides an online gas chromatography detection device 13 between the outlet of the fixed bed reactor 4 and the finished product receiving tank 5, which facilitates real-time monitoring and control of the single-pass conversion rate of the system raw materials and helps to suppress the occurrence of side reactions.

[0040] The top of the finished product receiving tank 5 is connected to the gas inlet 301 of the gas mixer 3 via the compressor 11. After acetaldehyde and acetylene gases react through the fixed bed catalyst layer, the products are discharged from the bottom of the fixed bed reactor 4 to the finished product receiving tank 5. The unreacted gases are pressurized by the compressor 11 and enter the gas mixer 3, and then enter the fixed bed catalyst layer again to react, forming a cycle.

[0041] Preferably, compressor 11 is a variable frequency compressor for better control of the reaction.

[0042] Preferably, the finished product receiving tank is purged with nitrogen before the reaction and controlled by a back pressure valve to maintain the nitrogen pressure of the reaction system at 1.0 MPa to 2.0 MPa.

[0043] The main working process and principle of the reaction system of this invention are as follows: The composite catalyst is loaded into the catalyst chamber of the fixed-bed reactor 4. Under certain temperature and pressure, a mixture of acetylene gas and acetaldehyde gas is introduced into the fixed-bed reactor 4. The temperature and pressure are controlled to allow for a full reaction. The reaction is sampled and detected by the online gas chromatograph 13. The frequency of the tail gas compressor 11 is adjusted to control the single-pass conversion rate of acetaldehyde. The reaction liquid is collected and distilled to obtain 3-hexyne-2,5-diol as the finished product. The unreacted gaseous mixture is pressurized by the compressor 11 and then enters the gas mixer 3, which is then fed into the fixed-bed reactor 4 for further reaction, thereby realizing the continuous production of 3-hexyne-2,5-diol. The entire operation process is simple, stable and controllable, and suitable for industrial production.

[0044] The synthesis method of this invention includes the following steps:

[0045] (1) The depolymerized gaseous acetaldehyde and the purified acetylene gas are thoroughly mixed together in a gas mixer to obtain a mixed gas.

[0046] (2) The mixed gas is fully reacted in a fixed-bed reactor filled with coarse-porous microspheres and silica gel supported by copper-based catalyst. The temperature and pressure of the fixed-bed reactor are controlled by online sampling gas chromatography to ensure that the single-pass conversion rate of acetaldehyde is 60-80%.

[0047] (3) The reaction liquid is collected in the finished product receiving tank and distilled to obtain 3-hexyne-2,5-diol. The tail gas is pressurized by the compressor and then introduced into the gas mixer to participate in the reaction.

[0048] In some preferred embodiments, the molar ratio of acetaldehyde to acetylene is 1:0.5 to 1:0.6.

[0049] In some preferred embodiments, the single-pass conversion rate of the system feedstock acetaldehyde is controlled at 60-80% by online gas chromatography detection, which effectively suppresses the occurrence of side reactions. If the single-pass conversion rate is too low, the system capacity will be low; if the single-pass conversion rate is too high, there will be more by-products, and the tar produced by polymerization will easily coat the catalyst, leading to catalyst deactivation.

[0050] The single-pass conversion rate refers to the conversion rate of the total feed (including fresh raw materials and recycle gas) passing through the reactor in one pass. Simply put, the single-pass conversion rate is the conversion rate of the reaction without recirculation; for the recycle reaction of this invention, the total conversion rate is necessarily higher than the single-pass conversion rate.

[0051] In some preferred embodiments, unreacted acetaldehyde and acetylene are pressurized by a compressor and then participate in the reaction again through the catalyst bed. The flow rate of the return gas is controlled by controlling the frequency of the compressor.

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the fixed-bed system for the synthesis of 3-hexyne-2,5-diol provided by this invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Unless otherwise specified, the experimental methods in this invention are conventional methods. Unless otherwise specified, the experimental materials used in this invention are commercially available.

[0053] The catalyst used in this invention is a copper-based catalyst described in the applicant's prior patent application ZL202211605390.6, which describes an acetylene-aldehyde reaction catalyst, its preparation method, and its application. This catalyst uses coarse-porous microsphere silica gel as a support, supporting a mixture of copper salt, bismuth salt, and a co-catalyst. The molar ratio of the copper salt, bismuth salt, and co-catalyst is 1:(0.01–0.05):(0.06–0.2). The co-catalyst is a combination of at least two substances selected from alkali metal salts, alkaline earth metal salts, lanthanide metal salts, and transition metal salts. The specific preparation steps of the catalyst used in the following examples are as follows:

[0054] (1) Add 100g of deionized water to a 500ml three-necked flask;

[0055] (2) Add 5g of bismuth nitrate pentahydrate, 5g of potassium nitrate and 5g of lanthanum nitrate hexahydrate in sequence while stirring at room temperature;

[0056] (3) Heat to 60℃ and add a few drops of nitric acid until bismuth nitrate is completely dissolved;

[0057] (4) Add 100g of copper nitrate trihydrate and keep warm to dissolve for 2 hours;

[0058] (5) Add 250g of coarse-pore silica gel that has been calcined in a muffle furnace at 400℃ for 4h to expand the pores;

[0059] (6) Stop stirring and allow the silica gel to fully soak and age in the salt solution for more than 24 hours;

[0060] (7) The aged coarse-pore silica microspheres were centrifuged and spray-dried, and then calcined in a muffle furnace at 500°C for 5 hours.

[0061] (8) After calcination, the catalyst is sealed and stored for later use. The molar ratio of copper salt: bismuth salt: co-catalyst is 1:0.0249:0.1474; it is referred to as ZR catalyst.

[0062] Example 1:

[0063] Example 1 of the present invention provides an operating procedure for a fixed-bed reaction system for the synthesis of 3-hexyne-2,5-diol, comprising the following steps:

[0064] (1) To 50g of powdered quartz sand, 100g of ZR catalyst, and 50g of powdered quartz sand were added sequentially to a fixed-bed reactor.

[0065] (2) The reaction system is purged with 1.0 MPa nitrogen gas to check for leaks. If no leaks are found, the system is purged with nitrogen gas twice.

[0066] (3) Adjust the back pressure valve of the receiving tank to maintain the nitrogen pressure of the system at 1.0 MPa and raise the temperature of the fixed bed to 120°C;

[0067] (4) Add metaldehyde and 0.5% sulfuric acid by weight to the depolymerization reactor, and slowly raise the temperature to 50°C to maintain a slight positive pressure inside the reactor and ensure sufficient acetaldehyde gas supply to the high-pressure plunger pump.

[0068] (5) Turn on the acetylene and acetaldehyde high-pressure plunger pumps, adjust the flow meter to a certain flow rate, so that the molar ratio of acetaldehyde to acetylene is 1:0.5, and then enter the fixed bed reaction after passing through the gas mixer;

[0069] (6) By analyzing the reaction liquid through online gas chromatography, the single-pass conversion rate of acetaldehyde is controlled at 60%. The compressor frequency converter is turned on to pressurize the unreacted mixed gas and then send it to the gas mixer for reaction through the catalyst layer again.

[0070] (7) Collect the reaction liquid, and after distillation, obtain 3-hexyne-2,5-diol as the final product. See [link to product description]. Figure 3 Its content is 98.305%, and the total yield is 93.14%.

[0071] Example 2:

[0072] Example 2 of the present invention provides an operating procedure for a fixed-bed reaction system for the synthesis of 3-hexyne-2,5-diol, comprising the following steps:

[0073] (1) To 50g of powdered quartz sand, 100g of ZR catalyst, and 50g of powdered quartz sand were added sequentially to a fixed-bed reactor.

[0074] (2) The reaction system is purged with 1.0 MPa nitrogen gas to check for leaks. If no leaks are found, the system is purged with nitrogen gas twice.

[0075] (3) Adjust the back pressure valve of the receiving tank to maintain the nitrogen pressure of the system at 1.2 MPa and raise the temperature of the fixed bed to 100°C;

[0076] (4) Add metaldehyde and 0.5% sulfuric acid by weight to the depolymerization reactor, and slowly raise the temperature to 50°C to maintain a slight positive pressure inside the reactor and ensure sufficient acetaldehyde gas supply to the high-pressure plunger pump.

[0077] (5) Turn on the acetylene and acetaldehyde high-pressure plunger pumps, adjust the flow meter to a certain flow rate, so that the molar ratio of acetaldehyde to acetylene is 1:0.5, and then enter the fixed bed reaction after passing through the gas mixer;

[0078] (6) By analyzing the reaction liquid through online gas chromatography, the single-pass conversion rate of acetaldehyde is controlled at 70%. The compressor frequency converter is turned on to pressurize the unreacted mixed gas and then send it to the gas mixer for reaction through the catalyst layer again.

[0079] (7) Collect the reaction liquid, and after distillation, obtain 3-hexyne-2,5-diol as the final product. See [link to product description].Figure 4 Its content is 98.491%, and the total yield is 90.68%.

[0080] Example 3:

[0081] Example 3 of the present invention provides an operating procedure for a fixed-bed reaction system for the synthesis of 3-hexyne-2,5-diol, comprising the following steps:

[0082] (1) To 50g of powdered quartz sand, 100g of ZR catalyst, and 50g of powdered quartz sand were added sequentially to a fixed-bed reactor.

[0083] (2) The reaction system is purged with 1.0 MPa nitrogen gas to check for leaks. If no leaks are found, the system is purged with nitrogen gas twice.

[0084] (3) Adjust the back pressure valve of the receiving tank to maintain the nitrogen pressure of the system at 1.5 MPa and raise the temperature of the fixed bed to 90°C;

[0085] (4) Add metaldehyde and 0.5% sulfuric acid by weight to the depolymerization reactor, and slowly raise the temperature to 50°C to maintain a slight positive pressure inside the reactor and ensure sufficient acetaldehyde gas supply to the high-pressure plunger pump.

[0086] (5) Turn on the acetylene and acetaldehyde high-pressure plunger pumps, adjust the flow meter to a certain flow rate, so that the molar ratio of acetaldehyde to acetylene is 1:0.5, and then enter the fixed bed reaction after passing through the gas mixer;

[0087] (6) By analyzing the reaction liquid through online gas chromatography, the single-pass conversion rate of acetaldehyde is controlled at 80%. The compressor frequency converter is turned on to pressurize the unreacted mixed gas and then send it to the gas mixer for reaction through the catalyst layer again.

[0088] (7) Collect the reaction liquid, and after distillation, obtain 3-hexyne-2,5-diol as the final product. See [link to product description]. Figure 5 Its content is 98.460%, and the total yield is 95.31%.

[0089] Comparative Example 1:

[0090] Comparative Example 1 provides an operating procedure for a fixed-bed reaction system for the synthesis of 3-hexyne-2,5-diol, including the following steps:

[0091] (1) To 50g of powdered quartz sand, 100g of malachite catalyst, and 50g of powdered quartz sand were added sequentially to the fixed-bed reactor.

[0092] (2) The reaction system is purged with 1.0 MPa nitrogen gas to check for leaks. If no leaks are found, the system is purged with nitrogen gas twice.

[0093] (3) Adjust the back pressure valve of the receiving tank to maintain the nitrogen pressure of the system at 1.0 MPa and raise the temperature of the fixed bed to 90°C;

[0094] (4) Add metaldehyde and 0.5% sulfuric acid by weight to the depolymerization reactor, and slowly raise the temperature to 50°C to maintain a slight positive pressure inside the reactor and ensure sufficient acetaldehyde gas supply to the high-pressure plunger pump.

[0095] (5) Turn on the acetylene and acetaldehyde high-pressure plunger pumps, adjust the flow meter to a certain flow rate, so that the molar ratio of acetaldehyde to acetylene is 1:0.5, and then enter the fixed bed reaction after passing through the gas mixer;

[0096] (6) By analyzing the reaction liquid through online gas chromatography, the single-pass conversion rate of acetaldehyde is controlled at 60%. The compressor frequency converter is turned on to pressurize the unreacted mixed gas and then send it to the gas mixer for reaction through the catalyst layer again.

[0097] (7) After the reaction proceeded for 8 hours, the total conversion rate decreased significantly and the catalyst was deactivated. However, in Examples 1, 2 and 3, the catalyst activity did not decrease significantly even after 36 hours of continuous operation.

[0098] (8) Collect the reaction liquid, and after distillation, obtain 3-hexyne-2,5-diol as the final product. See [link to product description]. Figure 6 Its content is 98.252%, and the total yield is 40.78%.

[0099] As can be seen from the above embodiments, the fixed-bed reaction system used in this invention can achieve continuous production of 3-hexyne-2,5-diol, and by controlling the single-pass conversion rate of acetaldehyde, the side reactions are suppressed, the product content is above 98%, and the total yield is above 90%. Combined with Examples 1-3, Comparative Example 1, and the prior patent application ZL202211605390.6, it can be seen that this invention, by using a specific fixed-bed reaction system and a specific catalyst, can produce a synergistic effect. That is, compared with the preparation of 3-hexyne-2,5-diol alone, the content and yield of the combined system are significantly improved.

[0100] Unlike existing technologies, this invention provides a fixed-bed reaction system and method for synthesizing 3-hexyne-2,5-diol, comprising the following apparatus: a triacetaldehyde depolymerization section, a gas mixer, a fixed-bed reactor, a receiving tank, and an online gas chromatography detection and tail gas recovery section. The process flow is as follows: depolymerized acetaldehyde vapor and acetylene gas are simultaneously introduced into the gas mixer and thoroughly mixed before entering the fixed-bed reactor loaded with a copper-based catalyst supported on coarse-porous microsphere silica gel for full reaction. A specific reaction temperature and pressure are controlled, and by controlling the single-pass conversion rate, side reactions are effectively controlled. The resulting reaction liquid is distilled to obtain the 3-hexyne-2,5-diol product. Unreacted tail gas is returned to the gas mixer inlet via a compressor and re-enters the fixed-bed reactor to participate in the reaction. This fixed-bed reaction system enables continuous production of 3-hexyne-2,5-diol.

[0101] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for synthesizing 3-hexyne-2,5-diol, characterized in that, Includes the following steps: (1) Gas acetaldehyde and acetylene are simultaneously introduced into a gas mixer and mixed evenly to obtain a mixed gas; (2) The mixed gas is passed through a fixed-bed reactor and reacted under the action of a catalyst. The single-pass conversion rate of acetaldehyde is detected and controlled at 60-80% by a reaction monitoring device. The catalyst is a mixture of copper salt, bismuth salt and co-catalyst supported on coarse-porous microsphere silica gel. The molar ratio of copper salt, bismuth salt and co-catalyst is 1:(0.01-0.05):(0.06-0.2). The co-catalyst is a combination of at least two substances selected from alkali metal salt, alkaline earth metal salt, lanthanide metal salt and transition metal salt. (3) The reaction liquid is collected by the finished product receiving tank and distilled to obtain 3-hexyne-2,5-diol. The tail gas is pressurized by the compression device and then introduced into the gas mixer to participate in the reaction again. The method utilizes a fixed-bed reaction system, which includes a gas mixer, a fixed-bed reactor, a finished product receiving tank, a reaction monitoring device, and a compression device; wherein... The gas inlet of the gas mixer is connected to an aldehyde supply device and an acetylene supply device to obtain acetaldehyde and acetylene raw materials and mix them evenly. The gas outlet of the gas mixer is connected to the inlet of the fixed-bed reactor, which contains a catalyst bed. The outlet of the fixed-bed reactor is connected to the finished product receiving tank via a reaction monitoring device. The reaction monitoring device is used to control the single-pass conversion rate of the raw materials to 60-80%. The finished product receiving tank is connected to the gas inlet of the gas mixer via a compression device, forming a circulation loop.

2. The method for synthesizing 3-hexyne-2,5-diol according to claim 1, characterized in that, The aldehyde supply device includes an acetaldehyde depolymerization vessel, which is connected to the gas inlet of a gas mixer via a first high-pressure plunger pump and a first gas flow meter.

3. The method for synthesizing 3-hexyne-2,5-diol according to claim 1, characterized in that, The acetylene supply device includes an acetylene storage tank and an acetylene purification tower connected in sequence. The acetylene purification tower is connected to the gas inlet of the gas mixer via a second high-pressure plunger pump and a second gas flow meter.

4. The method for synthesizing 3-hexyne-2,5-diol according to claim 1, characterized in that, The gas mixer is made of stainless steel; the interior of the gas mixer is equipped with alternating first and second baffles to form a wedge-shaped guide channel.

5. The method for synthesizing 3-hexyne-2,5-diol according to claim 1, characterized in that, The fixed-bed reactor is set vertically with the inlet located at the top.

6. The method for synthesizing 3-hexyne-2,5-diol according to claim 1, characterized in that, The compression unit uses a variable frequency compressor.

7. The method for synthesizing 3-hexyne-2,5-diol according to claim 1, characterized in that, The molar ratio of acetaldehyde to acetylene is 1:(0.5 to 0.6).

8. The method for synthesizing 3-hexyne-2,5-diol according to claim 1, characterized in that, During the reaction, the pressure was controlled at 1.0 MPa to 2.0 MPa, and the reaction temperature was 90 to 120 °C.

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