System and method for preparing crotonyl alcohol through crotonaldehyde hydrogenation

Abstract

The invention discloses a system and a method for preparing crotonyl alcohol through selective hydrogenation of crotonaldehyde. The system comprises a reaction unit, a circulation unit and a rectification unit which are connected in sequence, the reaction unit is used for preheating, mixing and reacting raw materials crotonaldehyde and hydrogen, the circulation unit is used for carrying out gas-liquid separation and compression circulation of the raw material hydrogen on a product obtained after the reaction of the reaction unit, part of unreacted raw materials are recycled, and the rectification unit is used for further rectifying and separating the reaction product of the reaction unit. And different products are separated out. The method has the characteristics of wide raw material sources, mild reaction conditions, simple separation of the product and the catalyst, and small environmental pollution.

Description

Technical Field

[0001] The present invention belongs to the technical field of crotyl alcohol preparation, and particularly relates to a system and method for hydrogenating crotonaldehyde to crotyl alcohol. Background Art

[0002] Industrially, crotonaldehyde is usually used as a raw material, and it is reduced by metal hydrides such as LiAlH4 and NaBH4 to obtain crotyl alcohol. However, this process has problems such as harsh reaction conditions, complex process flow, difficult product separation, high cost of metal hydrides, and generation of a large amount of saline wastewater.

[0003] Patent CN111215093A discloses a novel nano-catalyst Ba 0.6 Ni 0.4 MnO3 to enhance the selectivity of synthesizing crotyl alcohol by hydrogenating crotonaldehyde, so that the hydrogenation reaction is concentrated on the C=O bond as much as possible, and the conversion rate of crotonaldehyde and the selectivity of crotyl alcohol are improved. However, its defect is that the separation and recovery of reaction process products and unreacted raw materials are insufficient.

[0004] Patent CN104368360B discloses a catalyst for gas-phase selective hydrogenation of crotonaldehyde to crotyl alcohol, which has the advantages of high efficiency, good reaction selectivity and reaction stability when used for selective hydrogenation of crotonaldehyde to prepare crotyl alcohol. However, its defect is that the description of product refining separation and continuous industrial process flow is insufficient.

[0005] In summary, the defects of the prior art are that the reaction process of selective hydrogenation of crotonaldehyde to crotyl alcohol and the recycling of raw materials are not considered enough, and the continuous industrial production process of product refining separation is not systematically considered. Summary of the Invention

[0006] In order to overcome the above defects of the prior art, the purpose of the present invention is to provide a system and method for hydrogenating crotonaldehyde to crotyl alcohol, which have the characteristics of wide raw material sources, mild reaction conditions, simple separation of products and catalysts, and little environmental pollution.

[0007] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0008] A system for selective hydrogenation of crotonaldehyde to crotyl alcohol includes a reaction unit 1, a circulation unit 2, and a rectification unit 3 connected in sequence.

[0009] The reaction unit 1 is used for preheating, mixing and reacting raw materials crotonaldehyde and hydrogen. The circulation unit 2 performs gas-liquid separation on the products after the reaction of the reaction unit 1, compresses and circulates raw material hydrogen, and circulates and uses part of the unreacted raw materials. The rectification unit 3 further rectifies and separates the reaction products of the reaction unit 1 to separate out different products.

[0010] The reaction unit 1 includes a crotonaldehyde storage tank 1-1, a reactor feed pump 1-2, a crotonaldehyde vaporizer 1-3, a hydrogen preheater 1-4, a raw material mixer 1-5, and a hydrogenation reactor 1-6;

[0011] The inlet of the crotonaldehyde storage tank 1-1 is connected to the outlet pipeline of the circulating crotonaldehyde pump 3-18, and another inlet is connected to the fresh crotonaldehyde pipeline. The outlet is successively connected to the reactor feed pump 1-2, the crotonaldehyde vaporizer 1-3, the raw material mixer 1-5, and the hydrogenation reactor 1-6 through pipelines. The inlet of the hydrogen preheater 1-4 is connected to the hydrogen outlet pipeline of the hydrogen membrane separation device 2-8, and the outlet is connected to the raw material mixer 1-5 through a pipeline.

[0012] The circulation unit 2 includes a gas-liquid separation tank 2-1, a gas-phase condenser 2-2, a pre-compressor liquid separation tank 2-3, a hydrogen compressor 2-4, a compressed gas condenser 2-5, a pre-membrane separation liquid separation tank 2-6, a gas-phase heater 2-7, and a hydrogen membrane separation device 2-8.

[0013] The inlet of the gas-liquid separation tank 2-1 is respectively connected to the outlet of the hydrogenation reactor 1-6, the liquid-phase outlet of the pre-compressor liquid separation tank 2-3, and the liquid-phase outlet of the pre-membrane separation liquid separation tank 2-6 through pipelines. The top gas-phase outlet is connected to the inlet pipeline of the gas-phase condenser 2-2, and the bottom liquid-phase outlet is connected to the inlet pipeline of the bottom liquid-phase pump 3-1. The outlet of the gas-phase condenser 2-2 is connected to the inlet pipeline of the pre-compressor liquid separation tank 2-3; the gas-phase outlet of the pre-compressor liquid separation tank 2-3 is successively connected to the hydrogen compressor 2-4, the compressed gas condenser 2-5, and the inlet of the pre-membrane separation liquid separation tank 2-6 through pipelines; the gas-phase outlet of the pre-membrane separation liquid separation tank 2-6 is successively connected to the gas-phase heater 2-7 and the inlet of the hydrogen membrane separation device 2-8 through pipelines; one outlet of the hydrogen membrane separation device 2-8 discharges the propane and propylene mixture and is connected to the off-site flare gas pipeline, and the hydrogen from the other outlet is connected to the inlet pipeline of the hydrogen preheater 1-4.

[0014] The rectification unit 3 includes a bottom liquid pump 3-1, molecular sieve drying tanks 3-2A / B, a butyraldehyde tower feed pump 3-3, a butyraldehyde tower 3-4, a butyraldehyde tower reflux tank 3-5, a butyraldehyde tower condenser 3-6, a butyraldehyde tower reboiler 3-7, a crotyl alcohol tower feed pump 3-8, a crotyl alcohol tower 3-9, a crotyl alcohol tower reflux tank 3-10, a crotyl alcohol tower condenser 3-11, a crotyl alcohol tower reboiler 3-12, a crotonaldehyde tower feed pump 3-13, a crotonaldehyde tower 3-14, a crotonaldehyde tower reflux tank 3-15, a crotonaldehyde tower condenser 3-16, a crotonaldehyde tower reboiler 3-17, a recycled crotonaldehyde pump 3-18, a heavy component tower feed pump 3-19, a heavy component tower 3-20, a heavy component tower reflux tank 3-21, a heavy component tower condenser 3-22, and a heavy component tower reboiler 3-23;

[0015] The inlet of the bottom liquid pump 3-1 is connected to the liquid phase outlet pipeline of the gas-liquid separation tank 2-1, and the outlets are respectively connected to the inlet pipelines of the molecular sieve drying tank 3-2A and the molecular sieve drying tank 3-2B; the liquid phase outlets after dehydration of the molecular sieve drying tank 3-2A and the molecular sieve drying tank 3-2B are both connected to the inlet pipeline of the butyraldehyde tower feed pump 3-3, and the removed water outlets are all discharged out of the boundary area; the outlet of the butyraldehyde tower feed pump 3-3 is connected to the feed port pipeline of the butyraldehyde tower 3-4; the top gas phase outlet of the butyraldehyde tower 3-4 is connected to the inlet pipeline of the butyraldehyde tower condenser 3-6, and the bottom liquid phase outlet is connected to the inlet pipeline of the crotyl alcohol tower feed pump 3-8, and a butyraldehyde tower reboiler 3-7 is arranged at the bottom of the tower to heat the liquid phase raw material in the tower; the gas-liquid mixed inlet of the butyraldehyde tower reflux tank 3-5 is connected to the outlet pipeline of the butyraldehyde tower condenser 3-6, one branch of the bottom liquid phase outlet is connected to the reflux port pipeline of the butyraldehyde tower 3-4, and the other branch is connected to the off-site butyraldehyde collection tank pipeline, and the top gas phase outlet is connected to the off-site flare gas pipeline;

[0016] The outlet of the crotyl alcohol tower feed pump 3-8 is connected to the feed port pipeline of the crotyl alcohol tower 3-9; the top gas phase outlet of the crotyl alcohol tower 3-9 is connected to the inlet pipeline of the crotyl alcohol tower condenser 3-11, and the bottom liquid phase outlet is connected to the inlet pipeline of the crotonaldehyde tower feed pump 3-13, and a crotyl alcohol tower reboiler 3-12 is arranged at the bottom of the tower to heat the liquid phase raw material in the tower; the inlet of the crotyl alcohol tower reflux tank 3-10 is connected to the outlet pipeline of the crotyl alcohol tower condenser 3-11, one branch of the bottom liquid phase outlet is connected to the reflux port pipeline of the crotyl alcohol tower 3-9, and the other branch is connected to the off-site crotyl alcohol collection tank pipeline;

[0017] The outlet of the crotonaldehyde column feed pump 3-13 is connected to the inlet of the crotonaldehyde column 3-14 through a pipeline; the top gas-phase outlet of the crotonaldehyde column 3-14 is connected to the inlet of the crotonaldehyde column condenser 3-16 through a pipeline, and the bottom liquid-phase outlet is connected to the inlet of the heavy component column feed pump 3-19 through a pipeline. The crotonaldehyde column reboiler 3-17 is provided at the bottom of the column to heat the liquid-phase raw material in the column. The inlet of the crotonaldehyde column reflux drum 3-15 is connected to the outlet of the crotonaldehyde column condenser 3-16 through a pipeline. One branch of the bottom liquid-phase outlet is connected to the reflux port of the crotonaldehyde column 3-14 through a pipeline, and the other branch is connected to the inlet of the circulating crotonaldehyde pump 3-18 through a pipeline.

[0018] The outlet of the heavy component column feed pump 3-19 is connected to the inlet of the heavy component column 3-20 through a pipeline; the top gas-phase outlet of the heavy component column 3-20 is connected to the inlet of the heavy component column condenser 3-22 through a pipeline, and the bottom liquid-phase outlet is connected to the pipeline of the off-site 2,4,6-octatriene aldehyde collection tank. The heavy component column reboiler 3-23 is provided at the bottom of the column to heat the liquid-phase raw material in the column. The inlet of the heavy component column reflux drum 3-21 is connected to the outlet of the heavy component column condenser 3-22 through a pipeline. One branch of the bottom liquid-phase outlet is connected to the reflux port of the heavy component column 3-20 through a pipeline, and the other branch is connected to the off-site n-butanol collection tank through a pipeline.

[0019] A method for the selective hydrogenation of crotonaldehyde to crotyl alcohol includes the following steps:

[0020] 1. Selective hydrogenation reaction: Fresh crotonaldehyde and recycled crotonaldehyde enter the crotonaldehyde storage tank 1-1. The bottom of the crotonaldehyde storage tank is connected to the reactor feed pump 1-2. Crotonaldehyde is transported to the crotonaldehyde vaporizer 1-3 by the reactor feed pump 1-2 for vaporization, that is, converting liquid crotonaldehyde into gaseous crotonaldehyde, and then enters the raw material mixer 1-5.

[0021] Fresh hydrogen and recycled hydrogen are heated to 80-100 °C in the hydrogen preheater 1-4 and then enter the raw material mixer 1-5. In the raw material mixer 1-5, gaseous crotonaldehyde and hydrogen are uniformly mixed and then enter the hydrogenation reactor 1-6. Crotonaldehyde undergoes a selective hydrogenation reaction in the hydrogenation reactor 1-6. The reaction temperature is 80-90 °C, and the reaction pressure is 10-50 KPa.

[0022] The products mainly include the main product crotyl alcohol, unreacted crotonaldehyde and hydrogen, as well as by-products such as n-butyraldehyde, n-butanol, propane, propylene, 2,4,6-octatriene aldehyde and water.

[0023] 2. Gas-liquid separation of reaction products: The reaction products coming out of the hydrogenation reactors 1-6 enter the gas-liquid separation tank 2-1. The gas-phase components such as hydrogen, propane, and propylene carry some liquid-phase heavy components and are discharged from the top of the tank into the gas-phase condenser 2-2. After being cooled to -20 to -25 °C, they enter the pre-compressor liquid separation tank 2-3. The liquid-phase heavy components are discharged from the bottom of the tank and refluxed to the gas-liquid separation tank 2-1. The gas-phase components are discharged from the top of the tank and enter the hydrogen compressor 2-4. The gas-phase components are successively compressed by the hydrogen compressor to 1.2 to 1.5 MPa, cooled to -20 to -25 °C by the compressed gas condenser 2-5, and then enter the pre-membrane separation device liquid separation tank 2-6; The liquid-phase components are discharged from the bottom of the tank and refluxed to the gas-liquid separation tank 2-1. The gas-phase components are discharged from the top of the tank, heated to 60 to 80 °C by the gas-phase heater 2-7, and then enter the hydrogen membrane separation device 2-8;

[0024] The gas-phase components mainly composed of hydrogen, propane, and propylene are separated by the hydrogen membrane separation device 2-8 to obtain hydrogen with a purity greater than 99%. The hydrogen is mixed with fresh hydrogen as recycled hydrogen and participates in the reaction again. The mixture of propane and propylene is discharged from the membrane separation device out of the boundary area;

[0025] 3. Butyraldehyde rectification: The liquid-phase heavy components in the gas-liquid separation tank 2-1 are transported by the bottom liquid pump 3-1 to the common molecular sieve drying tank 3-2A / B in the market to remove moisture; The dehydrated liquid-phase product is sent to the butyraldehyde tower 3-4 by the butyraldehyde tower feed pump 3-3. The butyraldehyde tower 3-4 has 150 trays, and the feed tray is 28. The temperature of the butyraldehyde tower condenser 3-6 is 58 to 62 °C, the temperature of the butyraldehyde tower reboiler 3-7 is 121 to 125 °C, the pressure inside the butyraldehyde tower 3-4 is 0.1 to 0.15 MPa, and the reflux ratio is 55 to 60. The light component n-butyraldehyde is discharged from the top of the butyraldehyde tower 3-4, cooled by the butyraldehyde tower condenser 3-6 and then enters the butyraldehyde tower reflux tank 3-5; The non-condensable gas at the top of the butyraldehyde tower 3-4 is discharged from the top of the butyraldehyde tower reflux tank 3-5. Part of the n-butyraldehyde in the butyraldehyde tower reflux tank 3-5 is refluxed to the butyraldehyde tower 3-4, and the other part of the n-butyraldehyde is discharged to obtain n-butyraldehyde with a purity greater than 98 wt%. The heavy components are discharged from the bottom of the butyraldehyde tower 3-4;

[0026] 4. Crotonol rectification: The heavy components at the bottom of the butyraldehyde column 3-4 are sent to the crotonol column 3-9 by the crotonol column feed pump 3-8. The crotonol column 3-9 has 86 trays, and the feed tray is 44. The temperature of the crotonol column condenser 3-11 is 90-95 °C, the temperature of the crotonol column reboiler 3-12 is 120-125 °C, the pressure inside the crotonol column 3-9 is 0.1-0.15 MPa, and the reflux ratio is 4.67-4.8. Crotonol is discharged from the top of the crotonol column 3-9, and after being cooled by the crotonol column condenser 3-11, it enters the crotonol column reflux drum 3-10. Part of the crotonol in the crotonol column reflux drum 3-10 refluxes to the inside of the crotonol column 3-9, and the other part of the crotonol is discharged as a product to obtain crotonol with a purity greater than 99 wt%. The heavy components are discharged from the bottom of the crotonol column 3-9.

[0027] 5. Crotonaldehyde rectification: The heavy components discharged from the bottom of the crotonol column 3-9 are sent to the crotonaldehyde column 3-14 by the crotonaldehyde column feed pump 3-13. The crotonaldehyde column 3-14 has 54 trays, and the feed tray is 25. The temperature of the crotonaldehyde column condenser 3-16 is 102-105 °C, the temperature of the crotonaldehyde column reboiler 3-17 is 135-140 °C, the pressure inside the column is 0.1-0.15 MPa, and the reflux ratio is 2.15-2.3. The light component crotonaldehyde is discharged from the top of the crotonaldehyde column 3-14, and after being cooled by the crotonaldehyde column condenser 3-16, it enters the crotonaldehyde column reflux drum 3-15. Part of the crotonaldehyde in the crotonaldehyde column reflux drum 3-15 refluxes to the inside of the crotonaldehyde column 3-14, and the other part of the crotonaldehyde is discharged from the bottom of the crotonaldehyde column reflux drum 3-15 as recycled crotonaldehyde, and is sent to the crotonaldehyde storage tank 1-1 by the recycled crotonaldehyde pump 3-18. The purity of the recycled crotonaldehyde is greater than 99 wt%. The heavy components are discharged from the bottom of the crotonaldehyde column 3-14.

[0028] 6. Rectification of other reactants: The heavy components discharged from the crotonaldehyde column 3-14 are sent to the heavy components column 3-20 by the heavy components column feed pump 3-19. The heavy components column 3-20 has 26 trays, and the feed tray is 13. The temperature of the heavy components column condenser 3-22 is 117-120 °C, the temperature of the heavy components column reboiler 3-23 is 173-176 °C, the pressure inside the heavy components column 3-20 is 0.1-0.15 MPa, and the reflux ratio is 0.54-0.6. The light component n-butanol is discharged from the top of the heavy components column 3-20, and after being cooled by the heavy components column condenser 3-22, it enters the heavy components column reflux drum 3-21. Part of the n-butanol refluxes to the inside of the heavy components column 3-20, and the other part is taken out to obtain n-butanol with a purity greater than 96 wt%. 2,4,6-octatrienealdehyde with a purity greater than 99 wt% is obtained at the bottom of the heavy components column 3-20.

[0029] Advantages of the present invention:

[0030] 1. The present invention uses a solid catalyst in the hydrogenation reactor, making the reaction conditions mild and the separation of the product from the catalyst simple.

[0031] 2. The reaction raw materials of the present invention are crotonaldehyde and hydrogen. Using hydrogen as the hydrogen source, compared with metal hydrides, it has the advantages of low cost and wide source.

[0032] 3. The reaction unit, recycling unit, and rectification unit of the present invention do not produce a large amount of salty wastewater, so it can significantly reduce environmental pollution and the process is safer and more environmentally friendly.

[0033] 4. The present invention uses a molecular sieve drying tank to remove water from the liquid-phase product, avoiding the separation problems caused by the azeotropy of water with n-butyraldehyde and n-butanol respectively, and has the advantages of reasonable process design, simple process flow, and high separation efficiency. Description of the Drawings

[0034] Figure 1 is a schematic structural diagram of the present invention.

[0035] Among them, 1 - reaction unit; 2 - recycling unit; 3 - rectification unit; 1-1 crotonaldehyde storage tank; 1-2 reactor feed pump; 1-3 crotonaldehyde vaporizer; 1-4 hydrogen preheater; 1-5 raw material mixer; 1-6 hydrogenation reactor; 2-1 gas-liquid separation tank; 2-2 gas-phase condenser; 2-3 pre-separator before compressor; 2-4 hydrogen compressor; 2-5 compressed gas condenser; 2-6 pre-separator before membrane separation device; 2-7 gas-phase heater; 2-8 hydrogen membrane separation device; 3-1 bottom liquid-phase pump; 3-2 A / B molecular sieve drying tank; 3-3 n-butyraldehyde tower feed pump; 3-4 n-butyraldehyde tower; 3-5 n-butyraldehyde tower reflux tank; 3-6 n-butyraldehyde tower condenser; 3-7 n-butyraldehyde tower reboiler; 3-8 crotyl alcohol tower feed pump; 3-9 crotyl alcohol tower; 3-10 crotyl alcohol tower reflux tank; 3-11 crotyl alcohol tower condenser; 3-12 crotyl alcohol tower reboiler; 3-13 crotonaldehyde tower feed pump; 3-14 crotonaldehyde tower; 3-15 crotonaldehyde tower reflux tank; 3-16 crotonaldehyde tower condenser; 3-17 crotonaldehyde tower reboiler; 3-18 recycled crotonaldehyde pump; 3-19 heavy component tower feed pump; 3-20 heavy component tower; 3-21 heavy component tower reflux tank; 3-22 heavy component tower condenser; 3-23 heavy component tower reboiler. Detailed Embodiments

[0036] The present invention will be further described in detail below with reference to the drawings.

[0037] As Figure 1 shown, a system for selective hydrogenation of crotonaldehyde to crotyl alcohol according to the present invention includes a reaction unit 1, a recycling unit 2, and a rectification unit 3 connected in sequence.

[0038] The reaction unit 1 is used for preheating, mixing, and reacting the raw materials crotonaldehyde and hydrogen. The circulation unit 2 is used for gas-liquid separation of the reaction products and compression and circulation of the raw material hydrogen. The rectification unit 3 is used for rectification and separation of the reaction products butyraldehyde, crotyl alcohol, crotonaldehyde, n-butanol, and 2,4,6-octatriene aldehyde.

[0039] The reaction unit 1 is used for preheating, mixing, and reacting the raw materials. The circulation unit 2 performs gas-liquid separation on the products after the reaction in the reaction unit 1 and circulates and uses some of the unreacted raw materials. The rectification unit 3 further rectifies and separates the reaction products of the reaction unit 1 to separate out different products.

[0040] The reaction unit 1 includes a crotonaldehyde storage tank 1-1, a reactor feed pump 1-2, a crotonaldehyde vaporizer 1-3, a hydrogen preheater 1-4, a raw material mixer 1-5, and a hydrogenation reactor 1-6.

[0041] The inlet of the crotonaldehyde storage tank 1-1 is connected to the outlet pipeline of the circulating crotonaldehyde pump 3-18, and the other inlet is connected to the fresh crotonaldehyde pipeline. The outlet is sequentially connected to the reactor feed pump 1-2, the crotonaldehyde vaporizer 1-3, the raw material mixer 1-5, and the hydrogenation reactor 1-6 through pipelines. The inlet of the hydrogen preheater 1-4 is connected to the hydrogen outlet pipeline of the hydrogen membrane separation device 2-8, and the outlet is connected to the raw material mixer 1-5 through a pipeline.

[0042] The connection relationship of the innovative parts in this part of the components brings the effect of preheating the reactants and the circulating reactants, improving the reaction efficiency.

[0043] The circulation unit 2 includes a gas-liquid separation tank 2-1, a gas-phase condenser 2-2, a pre-compressor liquid separation tank 2-3, a hydrogen compressor 2-4, a compressed gas condenser 2-5, a pre-membrane separation liquid separation tank 2-6, a gas-phase heater 2-7, and a hydrogen membrane separation device 2-8.

[0044] The inlet of the gas-liquid separation tank 2-1 is respectively connected to the outlet of the hydrogenation reactor 1-6, the liquid phase outlet of the knockout drum 2-3 before the compressor, and the liquid phase outlet of the knockout drum 2-6 before the membrane separation device through pipelines. The gas phase outlet at the top is connected to the inlet of the gas condenser 2-2 through a pipeline. The liquid phase outlet at the bottom is connected to the inlet of the bottom liquid phase pump 3-1 through a pipeline. The outlet of the gas condenser 2-2 is connected to the inlet of the knockout drum 2-3 before the compressor through a pipeline. The gas phase outlet of the knockout drum 2-3 before the compressor is sequentially connected to the hydrogen compressor 2-4, the compressed gas condenser 2-5, and the inlet of the knockout drum 2-6 before the membrane separation device through pipelines. The gas phase outlet of the knockout drum 2-6 before the membrane separation device is sequentially connected to the gas heater 2-7 and the inlet of the hydrogen membrane separation device 2-8 through pipelines. One outlet of the hydrogen membrane separation device 2-8 discharges the propane and propylene mixture and is connected to the off-site flare gas pipeline. The hydrogen at the other outlet is connected to the inlet of the hydrogen preheater 1-4 through a pipeline.

[0045] The connection relationship of the innovative parts in this section of components brings the effect of gas-liquid separation of the reaction products, recycling the unreacted reactants, and improving the resource utilization rate.

[0046] The rectification unit 3 includes a bottom liquid phase pump 3-1, molecular sieve drying tanks 3-2A / B, a butyraldehyde tower feed pump 3-3, a butyraldehyde tower 3-4, a butyraldehyde tower reflux drum 3-5, a butyraldehyde tower condenser 3-6, a butyraldehyde tower reboiler 3-7, a crotyl alcohol tower feed pump 3-8, a crotyl alcohol tower 3-9, a crotyl alcohol tower reflux drum 3-10, a crotyl alcohol tower condenser 3-11, a crotyl alcohol tower reboiler 3-12, a crotonaldehyde tower feed pump 3-13, a crotonaldehyde tower 3-14, a crotonaldehyde tower reflux drum 3-15, a crotonaldehyde tower condenser 3-16, a crotonaldehyde tower reboiler 3-17, a circulating crotonaldehyde pump 3-18, a heavy component tower feed pump 3-19, a heavy component tower 3-20, a heavy component tower reflux drum 3-21, a heavy component tower condenser 3-22, and a heavy component tower reboiler 3-23;

[0047] The inlet of the bottom liquid pump 3-1 of the tank is connected to the liquid phase outlet pipeline of the gas-liquid separation tank 2-1, and the outlets are respectively connected to the inlet pipelines of the molecular sieve drying tank 3-2A and the molecular sieve drying tank 3-2B. The liquid phase outlets after dehydration of the molecular sieve drying tank 3-2A and the molecular sieve drying tank 3-2B are both connected to the inlet pipeline of the butyraldehyde tower feed pump 3-3, and the water removal outlets are both discharged out of the boundary area. The outlet of the butyraldehyde tower feed pump 3-3 is connected to the feed port pipeline of the butyraldehyde tower 3-4. The top gas phase outlet of the butyraldehyde tower 3-4 is connected to the inlet pipeline of the butyraldehyde tower condenser 3-6, and the bottom liquid phase outlet is connected to the inlet pipeline of the crotyl alcohol tower feed pump 3-8, and a butyraldehyde tower reboiler 3-7 is arranged at the bottom of the tower to heat the liquid phase raw material in the tower. The gas-liquid mixing inlet of the butyraldehyde tower reflux tank 3-5 is connected to the outlet pipeline of the butyraldehyde tower condenser 3-6. One branch of the bottom liquid phase outlet is connected to the reflux port pipeline of the butyraldehyde tower 3-4, and the other branch is connected to the off-site butyraldehyde collection tank pipeline. The top gas phase outlet is connected to the off-site flare gas pipeline.

[0048] The outlet of the crotyl alcohol tower feed pump 3-8 is connected to the feed port pipeline of the crotyl alcohol tower 3-9. The top gas phase outlet of the crotyl alcohol tower 3-9 is connected to the inlet pipeline of the crotyl alcohol tower condenser 3-11, and the bottom liquid phase outlet is connected to the inlet pipeline of the crotonaldehyde tower feed pump 3-13. A crotyl alcohol tower reboiler 3-12 is arranged at the bottom of the tower to heat the liquid phase raw material in the tower. The inlet of the crotyl alcohol tower reflux tank 3-10 is connected to the outlet pipeline of the crotyl alcohol tower condenser 3-11. One branch of the bottom liquid phase outlet is connected to the reflux port pipeline of the crotyl alcohol tower 3-9, and the other branch is connected to the off-site crotyl alcohol collection tank pipeline.

[0049] The outlet of the crotonaldehyde tower feed pump 3-13 is connected to the feed port pipeline of the crotonaldehyde tower 3-14. The top gas phase outlet of the crotonaldehyde tower 3-14 is connected to the inlet pipeline of the crotonaldehyde tower condenser 3-16, and the bottom liquid phase outlet is connected to the inlet pipeline of the heavy component tower feed pump 3-19. A crotonaldehyde tower reboiler 3-17 is arranged at the bottom of the tower to heat the liquid phase raw material in the tower. The inlet of the crotonaldehyde tower reflux tank 3-15 is connected to the outlet pipeline of the crotonaldehyde tower condenser 3-16. One branch of the bottom liquid phase outlet is connected to the reflux port pipeline of the crotonaldehyde tower 3-14, and the other branch is connected to the inlet of the circulating crotonaldehyde pump 3-18.

[0050] The outlet of the heavy component tower feed pump 3-19 is connected to the inlet pipeline of the heavy component tower 3-20. The gas-phase outlet at the top of the heavy component tower 3-20 is connected to the inlet pipeline of the heavy component tower condenser 3-22, and the liquid-phase outlet at the bottom is connected to the pipeline of the off-site 2,4,6-octatriene aldehyde collection tank. A reboiler 3-23 of the heavy component tower is arranged at the bottom of the tower to heat the liquid-phase raw materials in the tower. The inlet of the heavy component tower reflux drum 3-21 is connected to the outlet pipeline of the heavy component tower condenser 3-22. One branch of the liquid-phase outlet at the bottom is connected to the reflux port pipeline of the heavy component tower 3-20, and the other branch is connected to the off-site n-butanol collection tank pipeline.

[0051] The connection relationships of the innovative parts in this section of components bring the effect of using multiple distillation towers to separately separate and extract various reaction products, and utilize resources in a hierarchical manner, which not only improves the energy utilization rate but also reduces environmental pollution.

[0052] Based on the above device, a method for the selective hydrogenation of crotonaldehyde to crotyl alcohol according to the present invention includes the following steps:

[0053] 1. Selective hydrogenation reaction: Fresh crotonaldehyde and recycled crotonaldehyde enter the crotonaldehyde storage tank 1-1. The bottom of the crotonaldehyde storage tank is connected to the reactor feed pump 1-2. Crotonaldehyde is transported to the crotonaldehyde vaporizer 1-3 by the reactor feed pump 1-2 for vaporization, that is, converting liquid-phase crotonaldehyde into gas-phase crotonaldehyde, and then enters the raw material mixer 1-5;

[0054] Fresh hydrogen and recycled hydrogen are heated to 80-100 °C by the hydrogen preheater 1-4 and then enter the raw material mixer 1-5. In the raw material mixer 1-5, gas-phase crotonaldehyde and hydrogen are uniformly mixed and then enter the hydrogenation reactor 1-6. Crotonaldehyde undergoes a selective hydrogenation reaction in the hydrogenation reactor 1-6. The reaction temperature is 80-90 °C, and the reaction pressure is 10-50 KPa. The products mainly include the main product crotyl alcohol, unreacted crotonaldehyde and hydrogen, as well as by-products such as n-butyraldehyde, n-butanol, propane, propylene, 2,4,6-octatriene aldehyde and water.

[0055] 2 Reactor product gas-liquid separation: The reaction products coming out of the hydrogenation reactors 1-6 enter the gas-liquid separation tank 2-1. Gas-phase components such as hydrogen, propane, and propylene carry some liquid-phase heavy components and are discharged from the top of the tank into the gas-phase condenser 2-2. After being cooled to -20 to -25 °C, they enter the pre-compressor liquid separation tank 2-3. The liquid-phase heavy components are discharged from the bottom of the tank and refluxed to the gas-liquid separation tank 2-1, and the gas-phase components are discharged from the top of the tank and enter the hydrogen compressor 2-4. The gas-phase components are successively compressed by the hydrogen compressor to 1.2 to 1.5 MPa, cooled to -20 to -25 °C by the compressed gas condenser 2-5, and then enter the pre-membrane separation device liquid separation tank 2-6. The liquid-phase components are discharged from the bottom of the tank and refluxed to the gas-liquid separation tank 2-1, and the gas-phase components are discharged from the top of the tank, heated to 60 to 80 °C by the gas-phase heater 2-7, and then enter the hydrogen membrane separation device 2-8. The gas-phase components mainly composed of hydrogen, propane, and propylene are separated by the hydrogen membrane separation device 2-8 to obtain hydrogen with a purity greater than 99%, which is mixed with fresh hydrogen as recycled hydrogen and participates in the reaction again. The mixture of propane and propylene is discharged from the membrane separation device out of the boundary area.

[0056] 3 Butyraldehyde rectification: The liquid-phase heavy components in the gas-liquid separation tank 2-1 are transported by the bottom liquid pump 3-1 to the common molecular sieve drying tanks 3-2A / B in the market to remove moisture. The dehydrated liquid product is sent to the butyraldehyde tower 3-4 by the butyraldehyde tower feed pump 3-3. The butyraldehyde tower 3-4 has 150 trays, the feed tray is 28, the temperature of the butyraldehyde tower condenser 3-6 is 58 to 62 °C, the temperature of the butyraldehyde tower reboiler 3-7 is 121 to 125 °C, the pressure inside the butyraldehyde tower 3-4 is 0.1 to 0.15 MPa, the reflux ratio is 55 to 60, and the light component n-butyraldehyde is discharged from the top of the butyraldehyde tower 3-4. After being cooled by the butyraldehyde tower condenser 3-6, it enters the butyraldehyde tower reflux tank 3-5. The non-condensable gas at the top of the butyraldehyde tower 3-4 is discharged from the top of the butyraldehyde tower reflux tank 3-5. Part of the n-butyraldehyde in the butyraldehyde tower reflux tank 3-5 is refluxed to the butyraldehyde tower 3-4, and the other part of the n-butyraldehyde is discharged to obtain n-butyraldehyde with a purity greater than 98 wt%. The heavy components are discharged from the bottom of the butyraldehyde tower 3-4.

[0057] 4 Crotyl alcohol rectification: The bottom heavy components of the butyraldehyde tower 3-4 are sent to the crotyl alcohol tower 3-9 by the crotyl alcohol tower feed pump 3-8. The crotyl alcohol tower 3-9 has 86 trays, the feed tray is 44, the temperature of the crotyl alcohol tower condenser 3-11 is 90 to 95 °C, the temperature of the crotyl alcohol tower reboiler 3-12 is 120 to 125 °C, the pressure inside the crotyl alcohol tower 3-9 is 0.1 to 0.15 MPa, and the reflux ratio is 4.67 to 4.8. Crotyl alcohol is discharged from the top of the crotyl alcohol tower 3-9. After being cooled by the crotyl alcohol tower condenser 3-11, it enters the crotyl alcohol tower reflux tank 3-10. Part of the crotyl alcohol in the crotyl alcohol tower reflux tank 3-10 is refluxed into the crotyl alcohol tower 3-9, and the other part of the crotyl alcohol is discharged as a product to obtain crotyl alcohol with a purity greater than 99 wt%. The heavy components are discharged from the bottom of the crotyl alcohol tower 3-9.

[0058] 5 Crotonaldehyde rectification: The heavy components discharged from the bottom of the crotyl alcohol column 3-9 are sent to the crotonaldehyde column 3-14 by the crotonaldehyde column feed pump 3-13. The crotonaldehyde column 3-14 has 54 trays, and the feed tray is 25. The crotonaldehyde column condenser 3-16 is at 102-105 °C, the crotonaldehyde column reboiler 3-17 is at 135-140 °C, the pressure inside the column is 0.1-0.15 MPa, and the reflux ratio is 2.15-2.3. The light component crotonaldehyde is discharged from the top of the crotonaldehyde column 3-14, cooled by the crotonaldehyde column condenser 3-16 and then enters the crotonaldehyde column reflux drum 3-15. A part of the crotonaldehyde in the crotonaldehyde column reflux drum 3-15 refluxes into the crotonaldehyde column 3-14, and another part of the crotonaldehyde is discharged from the bottom of the crotonaldehyde column reflux drum 3-15 as recycled crotonaldehyde, and is sent to the crotonaldehyde storage tank 1-1 by the recycled crotonaldehyde pump 3-18. The purity of the recycled crotonaldehyde is greater than 99 wt%. The heavy components are discharged from the bottom of the crotonaldehyde column 3-14.

[0059] 6 Rectification of other reactants: The heavy components discharged from the crotonaldehyde column 3-14 are sent to the heavy component column 3-20 by the heavy component column feed pump 3-19. The heavy component column 3-20 has 26 trays, and the feed tray is 13. The heavy component column condenser 3-22 is at 117-120 °C, the heavy component column reboiler 3-23 is at 173-176 °C, the pressure inside the heavy component column 3-20 is 0.1-0.15 MPa, and the reflux ratio is 0.54-0.6. The light component n-butanol is discharged from the top of the heavy component column 3-20, cooled by the heavy component column condenser 3-22 and then enters the heavy component column reflux drum 3-21. A part of the n-butanol refluxes into the heavy component column 3-20, and another part is taken out to obtain n-butanol with a purity greater than 96 wt%. 2,4,6-Octatrienealdehyde with a purity greater than 99 wt% is obtained at the bottom of the heavy component column 3-20.

[0060] Example 1

[0061] In this example, crotonaldehyde is used as the raw material, and solid catalyst is adopted for direct catalytic hydrogenation to prepare crotyl alcohol.

[0062] 1 - Reaction unit; 2 - Circulation unit; 3 - Rectification unit; 1 - 1 Crotonaldehyde storage tank; 1 - 2 Reactor feed pump; 1 - 3 Crotonaldehyde vaporizer; 1 - 4 Hydrogen preheater; 1 - 5 Feed mixer; 1 - 6 Hydrogenation reactor; 2 - 1 Gas - liquid separation tank; 2 - 2 Gas - phase condenser; 2 - 3 Separator before compressor; 2 - 4 Hydrogen compressor; 2 - 5 Compressed gas condenser; 2 - 6 Separator before hydrogen membrane separation device; 2 - 7 Gas - phase heater; 2 - 8 Hydrogen membrane separation device; 3 - 1 Bottom liquid pump of tank; 3 - 2 A / B molecular sieve drying tank; 3 - 3 Butyraldehyde tower feed pump; 3 - 4 Butyraldehyde tower; 3 - 5 Butyraldehyde tower reflux tank; 3 - 6 Butyraldehyde tower condenser; 3 - 7 Butyraldehyde tower reboiler; 3 - 8 Crotyl alcohol tower feed pump; 3 - 9 Crotyl alcohol tower; 3 - 10 Crotyl alcohol tower reflux tank; 3 - 11 Crotyl alcohol tower condenser; 3 - 12 Crotyl alcohol tower reboiler; 3 - 13 Crotonaldehyde tower feed pump; 3 - 14 Crotonaldehyde tower; 3 - 15 Crotonaldehyde tower reflux tank; 3 - 16 Crotonaldehyde tower condenser; 3 - 17 Crotonaldehyde tower reboiler; 3 - 18 Recirculating crotonaldehyde pump; 3 - 19 Feed pump for heavy - component tower; 3 - 20 Heavy - component tower; 3 - 21 Heavy - component tower reflux tank; 3 - 22 Heavy - component tower condenser; 3 - 23 Heavy - component tower reboiler.

[0063] Fresh crotonaldehyde and recycled crotonaldehyde enter the crotonaldehyde storage tank 1 - 1. The bottom of the crotonaldehyde storage tank is connected to the reactor feed pump 1 - 2. The crotonaldehyde is transported by the reactor feed pump 1 - 2 to the crotonaldehyde vaporizer 1 - 3 for gasification, that is, converting liquid crotonaldehyde into gaseous crotonaldehyde, and then enters the feed mixer 1 - 5. Fresh hydrogen and recycled hydrogen are heated to 80 - 100 °C by the hydrogen preheater 1 - 4 and then enter the feed mixer 1 - 5. In the feed mixer 1 - 5, gaseous crotonaldehyde and hydrogen are evenly mixed and then enter the hydrogenation reactor 1 - 6. Crotonaldehyde undergoes a selective hydrogenation reaction in the hydrogenation reactor 1 - 6, with a reaction temperature of 80 - 90 °C and a reaction pressure of 10 - 50 KPa. The products mainly include the main product crotyl alcohol, unreacted crotonaldehyde and hydrogen, as well as by - products such as n - butyraldehyde, n - butanol, propane, propylene, 2,4,6 - octatriene aldehyde and water.

[0064] The reaction products exiting the hydrogenation reactors 1-6 enter the gas-liquid separation tank 2-1. Gas-phase components such as hydrogen, propane, and propylene, carrying some liquid-phase heavy components, are discharged from the top of the tank and enter the gas-phase condenser 2-2. After being cooled to -20 to -25 °C, they enter the pre-compressor liquid-separation tank 2-3. The liquid-phase heavy components are discharged from the bottom of the tank and refluxed to the gas-liquid separation tank 2-1, while the gas-phase components are discharged from the top of the tank and enter the hydrogen compressor 2-4. The gas-phase components are successively compressed by the hydrogen compressor to 1.2 to 1.5 MPa, cooled to -20 to 25 °C by the compressed-gas condenser 2-5, and then enter the pre-membrane-separation device liquid-separation tank 2-6. The liquid-phase components are discharged from the bottom of the tank and refluxed to the gas-liquid separation tank 2-1, and the gas-phase components are discharged from the top of the tank, heated to 60 to 80 °C by the gas-phase heater 2-7, and then enter the hydrogen-membrane separation device 2-8. The gas-phase components mainly composed of hydrogen, propane, and propylene are separated by the hydrogen-membrane separation device 2-8 to obtain hydrogen with a purity greater than 99%, which is mixed with fresh hydrogen as recycled hydrogen and participates in the reaction again. The mixture of propane and propylene is discharged from the membrane separation device out of the battery limits.

[0065] The liquid-phase heavy components in the gas-liquid separation tank 2-1 are transported by the bottom liquid pump 3-1 to the commonly available molecular sieve drying tanks 3-2A / B in the market to remove moisture. The dehydrated liquid-phase product is sent to the butyraldehyde tower 3-4 by the butyraldehyde tower feed pump 3-3. The butyraldehyde tower 3-4 has 150 trays, the feed tray is 28, the temperature of the butyraldehyde tower condenser 3-6 is 58 to 62 °C, the temperature of the butyraldehyde tower reboiler 3-7 is 121 to 125 °C, the pressure inside the butyraldehyde tower 3-4 is 0.1 to 0.15 MPa, the reflux ratio is 55 to 60, and the light component n-butyraldehyde is discharged from the top of the butyraldehyde tower 3-4. After being cooled by the butyraldehyde tower condenser 3-6, it enters the butyraldehyde tower reflux tank 3-5. The non-condensable gas at the top of the butyraldehyde tower 3-4 is discharged from the top of the butyraldehyde tower reflux tank 3-5. Part of the n-butyraldehyde in the butyraldehyde tower reflux tank 3-5 is refluxed to the butyraldehyde tower 3-4, and the other part of the n-butyraldehyde is discharged to obtain n-butyraldehyde with a purity greater than 98 wt%. The heavy components are discharged from the bottom of the butyraldehyde tower 3-4.

[0066] The heavy components at the bottom of the butyraldehyde tower 3-4 are sent to the crotyl alcohol tower 3-9 by the crotyl alcohol tower feed pump 3-8. The crotyl alcohol tower 3-9 has 86 trays, the feed tray is 44, the temperature of the crotyl alcohol tower condenser 3-11 is 90 to 95 °C, the temperature of the crotyl alcohol tower reboiler 3-12 is 120 to 125 °C, the pressure inside the crotyl alcohol tower 3-9 is 0.1 to 0.15 MPa, and the reflux ratio is 4.67 to 4.8. Crotyl alcohol is discharged from the top of the crotyl alcohol tower 3-9. After being cooled by the crotyl alcohol tower condenser 3-11, it enters the crotyl alcohol tower reflux tank 3-10. Part of the crotyl alcohol in the crotyl alcohol tower reflux tank 3-10 is refluxed into the crotyl alcohol tower 3-9, and the other part of the crotyl alcohol is discharged as a product to obtain crotyl alcohol with a purity greater than 99 wt%. The heavy components are discharged from the bottom of the crotyl alcohol tower 3-9.

[0067] The heavy components discharged from the bottom of Crotyl alcohol column 3-9 are sent to Crotonaldehyde column 3-14 by Crotonaldehyde column feed pump 3-13. Crotonaldehyde column 3-14 has 54 trays, and the feed tray is the 25th. The temperature of Crotonaldehyde column condenser 3-16 is 102-105°C, the temperature of Crotonaldehyde column reboiler 3-17 is 135-140°C, the pressure inside the column is 0.1-0.15 MPa, and the reflux ratio is 2.15-2.3. The light component crotonaldehyde is discharged from the top of Crotonaldehyde column 3-14, cooled by Crotonaldehyde column condenser 3-16 and then enters Crotonaldehyde column reflux drum 3-15. Part of the crotonaldehyde in Crotonaldehyde column reflux drum 3-15 flows back into Crotonaldehyde column 3-14, and the other part of the crotonaldehyde is discharged from the bottom of Crotonaldehyde column reflux drum 3-15 as recycled crotonaldehyde, and is sent to Crotonaldehyde storage tank 1-1 by recycled crotonaldehyde pump 3-18. The purity of the recycled crotonaldehyde is greater than 99 wt%. The heavy components are discharged from the bottom of Crotonaldehyde column 3-14.

[0068] The heavy components discharged from Crotonaldehyde column 3-14 are sent to Heavy components column 3-20 by Heavy components column feed pump 3-19. Heavy components column 3-20 has 26 trays, and the feed tray is the 13th. The temperature of Heavy components column condenser 3-22 is 117-120°C, the temperature of Heavy components column reboiler 3-23 is 173-176°C, the pressure inside Heavy components column 3-20 is 0.1-0.15 MPa, and the reflux ratio is 0.54-0.6. The light component n-butanol is discharged from the top of Heavy components column 3-20, cooled by Heavy components column condenser 3-22 and then enters Heavy components column reflux drum 3-21. Part of the n-butanol flows back into Heavy components column 3-20, and the other part is withdrawn to obtain n-butanol with a purity greater than 96 wt%. 2,4,6-Octatrienal with a purity greater than 99 wt% is obtained at the bottom of Heavy components column 3-20.

Claims

1. A system for the selective hydrogenation of crotonaldehyde to crotyl alcohol, characterized in that, It includes a reaction unit (1), a circulation unit (2), and a rectification unit (3) connected in sequence. The reaction unit (1) is used for preheating, mixing, and reacting raw materials crotonaldehyde and hydrogen. The circulation unit (2) performs gas-liquid separation on the products after the reaction in the reaction unit (1), compresses and circulates the raw material hydrogen, and recycles part of the unreacted raw materials. The rectification unit (3) further rectifies and separates the reaction products of the reaction unit (1) to separate out different products.

2. The system for the selective hydrogenation of crotonaldehyde to crotyl alcohol according to claim 1, wherein, The reaction unit (1) includes a crotonaldehyde storage tank (1-1), a reactor feed pump (1-2), a crotonaldehyde vaporizer (1-3), a hydrogen preheater (1-4), a raw material mixer (1-5), and a hydrogenation reactor (1-6). The inlet of the crotonaldehyde storage tank (1-1) is connected to the outlet pipeline of the circulating crotonaldehyde pump (3-18), and another inlet is connected to the fresh crotonaldehyde pipeline. The outlet is connected to the reactor feed pump (1-2), the crotonaldehyde vaporizer (1-3), the raw material mixer (1-5), and the hydrogenation reactor (1-6) in sequence through pipelines. The inlet of the hydrogen preheater (1-4) is connected to the hydrogen outlet pipeline of the hydrogen membrane separation device (2-8), and the outlet is connected to the raw material mixer (1-5) through a pipeline.

3. A system for the selective hydrogenation of crotonaldehyde to crotyl alcohol according to claim 1, characterized in that, The circulation unit (2) includes a gas-liquid separation tank (2-1), a gas-phase condenser (2-2), a pre-compressor liquid separation tank (2-3), a hydrogen compressor (2-4), a compressed gas condenser (2-5), a pre-membrane separation liquid separation tank (2-6), a gas-phase heater (2-7), and a hydrogen membrane separation device (2-8). The inlet of the gas-liquid separation tank (2-1) is connected to the outlet of the hydrogenation reactor (1-6), the liquid-phase outlet of the pre-compressor liquid separation tank (2-3), and the liquid-phase outlet of the pre-membrane separation liquid separation tank (2-6) through pipelines. The top gas-phase outlet is connected to the inlet of the gas-phase condenser (2-2) through a pipeline, and the bottom liquid-phase outlet is connected to the inlet of the bottom liquid-phase pump (3-1) through a pipeline. The outlet of the gas-phase condenser (2-2) is connected to the inlet of the pre-compressor liquid separation tank (2-3) through a pipeline. The gas-phase outlet of the pre-compressor liquid separation tank (2-3) is connected to the hydrogen compressor (2-4), the compressed gas condenser (2-5), and the inlet of the pre-membrane separation liquid separation tank (2-6) in sequence through pipelines. The gas-phase outlet of the pre-membrane separation liquid separation tank (2-6) is connected to the gas-phase heater (2-7) and the inlet of the hydrogen membrane separation device (2-8) in sequence through pipelines. One outlet of the hydrogen membrane separation device (2-8) discharges the propane and propylene mixture and is connected to the off-site flare gas pipeline, and the hydrogen at the other outlet is connected to the inlet pipeline of the hydrogen preheater (1-4).

4. A system for the selective hydrogenation of crotonaldehyde to crotyl alcohol according to claim 3, wherein The rectification unit (3) includes a bottom liquid pump (3-1). The inlet of the bottom liquid pump (3-1) is connected to the liquid phase outlet pipeline of the gas-liquid separation tank (2-1), and the outlet is respectively connected to the inlet pipelines of the molecular sieve drying tank (3-2A) and the molecular sieve drying tank (3-2B). The dehydrated liquid phase outlets of the molecular sieve drying tank (3-2A) and the molecular sieve drying tank (3-2B) are both connected to the inlet pipeline of the butyraldehyde tower feed pump (3-3), and the removed water outlets are both discharged out of the boundary area. The outlet of the butyraldehyde tower feed pump (3-3) is connected to the feed port pipeline of the butyraldehyde tower (3-4). The top gas phase outlet of the butyraldehyde tower (3-4) is connected to the inlet pipeline of the butyraldehyde tower condenser (3-6), and the bottom liquid phase outlet is connected to the inlet pipeline of the crotyl alcohol tower feed pump (3-8). And a butyraldehyde tower reboiler (3-7) is arranged at the bottom of the tower to heat the liquid phase raw material in the tower. The gas-liquid mixing inlet of the butyraldehyde tower reflux tank (3-5) is connected to the outlet pipeline of the butyraldehyde tower condenser (3-6). One branch of the bottom liquid phase outlet is connected to the reflux port pipeline of the butyraldehyde tower (3-4), and the other branch is connected to the off-site butyraldehyde collection tank pipeline. The top gas phase outlet is connected to the off-site flare gas pipeline; The outlet of the crotyl alcohol tower feed pump (3-8) is connected to the feed port pipeline of the crotyl alcohol tower (3-9). The top gas phase outlet of the crotyl alcohol tower (3-9) is connected to the inlet pipeline of the crotyl alcohol tower condenser (3-11), and the bottom liquid phase outlet is connected to the inlet pipeline of the crotonaldehyde tower feed pump (3-13). And a crotyl alcohol tower reboiler (3-12) is arranged at the bottom of the tower to heat the liquid phase raw material in the tower. The inlet of the crotyl alcohol tower reflux tank (3-10) is connected to the outlet pipeline of the crotyl alcohol tower condenser (3-11). One branch of the bottom liquid phase outlet is connected to the reflux port pipeline of the crotyl alcohol tower (3-9), and the other branch is connected to the off-site crotyl alcohol collection tank pipeline; The outlet of the crotonaldehyde tower feed pump (3-13) is connected to the feed port pipeline of the crotonaldehyde tower (3-14). The top gas phase outlet of the crotonaldehyde tower (3-14) is connected to the inlet pipeline of the crotonaldehyde tower condenser (3-16), and the bottom liquid phase outlet is connected to the inlet pipeline of the heavy component tower feed pump (3-19). And a crotonaldehyde tower reboiler (3-17) is arranged at the bottom of the tower to heat the liquid phase raw material in the tower. The inlet of the crotonaldehyde tower reflux tank (3-15) is connected to the outlet pipeline of the crotonaldehyde tower condenser (3-16). One branch of the bottom liquid phase outlet is connected to the reflux port pipeline of the crotonaldehyde tower (3-14), and the other branch is connected to the inlet pipeline of the circulating crotonaldehyde pump (3-18); The outlet of the heavy component tower feed pump (3-19) is connected to the inlet pipeline of the heavy component tower (3-20). The gas-phase outlet at the top of the heavy component tower (3-20) is connected to the inlet pipeline of the heavy component tower condenser (3-22), and the liquid-phase outlet at the bottom is connected to the pipeline of the off-site 2,4,6-octatriene aldehyde collection tank. A heavy component tower reboiler (3-23) is provided at the bottom of the tower to heat the liquid-phase raw materials in the tower. The inlet of the heavy component tower reflux tank (3-21) is connected to the outlet pipeline of the heavy component tower condenser (3-22). One branch of the liquid-phase outlet at the bottom is connected to the reflux port pipeline of the heavy component tower (3-20), and the other branch is connected to the off-site n-butanol collection tank.

5. A method for the selective hydrogenation of crotonaldehyde to crotyl alcohol, characterized in that, It includes the following steps: (1) Selective hydrogenation reaction: Fresh crotonaldehyde and recycled crotonaldehyde enter the crotonaldehyde storage tank (1-1). The bottom of the crotonaldehyde storage tank is connected to the reactor feed pump (1-2). Crotonaldehyde is vaporized in the crotonaldehyde vaporizer (1-3) through the reactor feed pump (1-2) and then enters the raw material mixer (1-5). Fresh hydrogen and recycled hydrogen are heated to 80-100 °C in the hydrogen preheater (1-4) and then enter the raw material mixer (1-5). In the raw material mixer (1-5), gaseous crotonaldehyde and hydrogen are evenly mixed and then enter the hydrogenation reactor (1-6). Crotonaldehyde undergoes a selective hydrogenation reaction in the hydrogenation reactor (1-6), with a reaction temperature of 80-90 °C and a reaction pressure of 10-50 KPa. (2) Gas-liquid separation of the reaction product: The reaction product coming out of the hydrogenation reactor (1-6) enters the gas-liquid separation tank (2-1). Gas-phase components such as hydrogen, propane, and propylene carry some liquid-phase heavy components and are discharged from the top of the tank into the gas-phase condenser (2-2). After being cooled to -20 to -25 °C, they enter the pre-separator before the compressor (2-3). The liquid-phase heavy components are discharged from the bottom of the tank and refluxed to the gas-liquid separation tank (2-1). The gas-phase components are discharged from the top of the tank and enter the hydrogen compressor (2-4). The gas-phase components are successively compressed to 1.2-1.5 MPa by the hydrogen compressor, cooled to -20 to -25 °C in the compressed gas condenser (2-5), and then enter the pre-separator before the membrane separation device (2-6). The liquid-phase components are discharged from the bottom of the tank and refluxed to the gas-liquid separation tank (2-1). The gas-phase components are discharged from the top of the tank, heated to 60-80 °C by the gas-phase heater (2-7), and then enter the hydrogen membrane separation device (2-8). The gas-phase components of hydrogen, propane, and propylene are separated by the hydrogen membrane separation device (2-8) to obtain hydrogen with a purity greater than 99%. It is mixed with fresh hydrogen as recycled hydrogen and participates in the reaction again. The mixture of propane and propylene is discharged from the membrane separation device out of the battery limit. (3) n-Butyraldehyde rectification: The liquid-phase heavy components in the gas-liquid separation tank (2-1) are transported by the bottom liquid pump (3-1) of the tank to the commonly used molecular sieve drying tank (3-2A / B) in the market to remove moisture. The dehydrated liquid-phase product is sent to the n-butyraldehyde tower (3-4) by the n-butyraldehyde tower feed pump (3-3). The temperature of the n-butyraldehyde tower condenser (3-6) is 58 - 62 °C, the temperature of the n-butyraldehyde tower reboiler (3-7) is 121 - 125 °C, the pressure inside the n-butyraldehyde tower (3-4) is 0.1 - 0.15 MPa, the reflux ratio is 55 - 60. The light component n-butyraldehyde is discharged from the top of the n-butyraldehyde tower (3-4), and after being cooled by the n-butyraldehyde tower condenser (3-6), it enters the n-butyraldehyde tower reflux tank (3-5). The non-condensable gas at the top of the n-butyraldehyde tower (3-4) is discharged from the top of the n-butyraldehyde tower reflux tank (3-5). Part of the n-butyraldehyde in the n-butyraldehyde tower reflux tank (3-5) is refluxed to the n-butyraldehyde tower (3-4), and the other part of the n-butyraldehyde is discharged to obtain n-butyraldehyde with a purity greater than 98 wt%. The heavy components are discharged from the bottom of the n-butyraldehyde tower (3-4); (4) Crotyl alcohol rectification: The heavy components at the bottom of the n-butyraldehyde tower (3-4) are sent to the crotyl alcohol tower (3-9) by the crotyl alcohol tower feed pump (3-8). The temperature of the crotyl alcohol tower condenser (3-11) is 90 - 95 °C, the temperature of the crotyl alcohol tower reboiler (3-12) is 120 - 125 °C, the pressure inside the crotyl alcohol tower (3-9) is 0.1 - 0.15 MPa, and the reflux ratio is 4.67 - 4.

8. Crotyl alcohol is discharged from the top of the crotyl alcohol tower (3-9), and after being cooled by the crotyl alcohol tower condenser (3-11), it enters the crotyl alcohol tower reflux tank (3-10). Part of the crotyl alcohol in the crotyl alcohol tower reflux tank (3-10) is refluxed into the crotyl alcohol tower (3-9), and the other part of the crotyl alcohol is discharged as a product to obtain crotyl alcohol with a purity greater than 99 wt%. The heavy components are discharged from the bottom of the crotyl alcohol tower (3-9); (5) Crotonaldehyde rectification: The heavy components discharged from the bottom of the crotyl alcohol tower (3-9) are sent to the crotonaldehyde tower (3-14) by the crotonaldehyde tower feed pump (3-13). The temperature of the crotonaldehyde tower condenser (3-16) is 102 - 105 °C, the temperature of the crotonaldehyde tower reboiler (3-17) is 135 - 140 °C, the pressure inside the tower is 0.1 - 0.15 MPa, and the reflux ratio is 2.15 - 2.

3. The light component crotonaldehyde is discharged from the top of the crotonaldehyde tower (3-14), and after being cooled by the crotonaldehyde tower condenser (3-16), it enters the crotonaldehyde tower reflux tank (3-15). Part of the crotonaldehyde in the crotonaldehyde tower reflux tank (3-15) is refluxed into the crotonaldehyde tower (3-14), and the other part of the crotonaldehyde is discharged as recycled crotonaldehyde from the bottom of the crotonaldehyde tower reflux tank (3-15), and is transported to the crotonaldehyde storage tank (1-1) by the recycled crotonaldehyde pump (3-18). The purity of the recycled crotonaldehyde is greater than 99 wt%. The heavy components are discharged from the bottom of the crotonaldehyde tower (3-14); (6) Rectification of other reactants: The heavy components discharged from the crotonaldehyde column (3-14) are sent to the heavy component column (3-20) by the heavy component column feed pump (3-19); the temperature of the heavy component column condenser (3-22) is 117-120°C, the temperature of the heavy component column reboiler (3-23) is 173-176°C, the pressure inside the heavy component column (3-20) is 0.1-0.15 MPa, the reflux ratio is 0.54-0.

6. The light component n-butanol is discharged from the top of the heavy component column (3-20), cooled by the heavy component column condenser (3-22) and then enters the heavy component column reflux drum (3-21). Part of the n-butanol is refluxed into the heavy component column (3-20), and the other part is withdrawn to obtain n-butanol with a purity greater than 96 wt%. 2,4,6-octatrienealdehyde with a purity greater than 99 wt% is obtained at the bottom of the heavy component column (3-20).

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