Method and device for producing crotonaldehyde by catalyzing gaseous acetaldehyde with Zr-beta molecular sieve

Abstract

The present application relates to a method and device for producing crotonaldehyde by Zr-beta molecular sieve catalytic gas phase acetaldehyde, and the process is used for producing crotonaldehyde by Zr-beta molecular sieve catalytic gas phase acetaldehyde. Through condensation reaction, heat exchange system, acetaldehyde recovery system, crotonaldehyde refining system and azeotrope separation system, the production of high-purity crotonaldehyde is realized, replacing the traditional homogeneous method using strong acid and strong base catalyst, avoiding the corrosion of the equipment, greatly increasing the service life of the equipment, and reducing the investment cost. The present application uses a packed fixed bed reactor, completely solves the problem of using sodium hydroxide catalyst in the traditional process, and the wastewater contains a large amount of sodium salt, which is not friendly to the environment. The steam out MCP process is proposed, the process is optimized, and the energy consumption is reduced. The selectivity of the main product crotonaldehyde is maintained between 90% and 95%.

Description

Technical Field

[0001] This invention belongs to the field of crotonaldehyde production, specifically relating to a method and apparatus for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis. Background Technology

[0002] Crotonaldehyde, also known as trans-2-crotonaldehyde, is an important fine chemical raw material with a wide range of applications, mainly including the preparation of crotonic acid, butyraldehyde, butanol, butyric acid, C8 compounds, and sorbic acid. Due to the excellent safety profile of sorbic acid as a food additive, and with increasing public awareness of food safety in recent years, sorbic acid is showing a strong trend of replacing sodium benzoate as the most important food additive. In the foreseeable future, the demand for crotonaldehyde from sorbic acid is expected to show a steady growth trend. The preparation of sorbic acid has become the largest consumption area for crotonaldehyde, making it imperative to strengthen crotonaldehyde production.

[0003] The liquid-phase condensation of acetaldehyde to prepare crotonaldehyde is currently the most mature industrial route. The production process mainly consists of a condensation tower, a dehydration tower, and a crotonaldehyde refining section. In the condensation tower, two molecules of acetaldehyde undergo an aldol condensation reaction under the action of an alkaline catalyst to produce 3-hydroxybutyraldehyde. After neutralization with acetic acid, 3-hydroxybutyraldehyde is sent to the dehydration tower for dehydration. Further dehydration is carried out under acidic conditions to produce crotonaldehyde. The crude crotonaldehyde product obtained includes water, 3-hydroxybutyraldehyde, sodium acetate, and other high-boiling-point byproducts in addition to crotonaldehyde. After initial distillation in a crotonaldehyde distillation tower, the crude crotonaldehyde product is distilled off from the top of the tower as an azeotrope with water. After separation by a decanter at the top of the tower, the secondary crotonaldehyde phase is sent to the refining tower for further distillation, and the product crotonaldehyde is collected as a gas from the side stream of the tower. The homogeneous method for producing crotonaldehyde has drawbacks such as low single-pass conversion rate, high requirements for raw material purity, strong corrosiveness of equipment by acidic and alkaline solutions, difficulty in separating the catalyst and product, and the generation of large amounts of saline wastewater. To address these issues, patent 200610016599 discloses a method and apparatus for producing crotonaldehyde. Compared to the traditional method, this method adds a distillation column, feeding wastewater from the bottom of the dehydration column and the distillation column into the bottom of the distillation column. The top of the column is refluxed, and the material collected from the side stream is sent to the dehydration column and further recovered through the distillation column. This method increases the crotonaldehyde yield by 1% and reduces the COD content of the wastewater discharged from the system by 50%. Patent 200610001278 discloses an improved crotonaldehyde production process, which involves condensing acetaldehyde to 2-hydroxybutyraldehyde under the catalysis of an organic amine, followed by dehydration under acidic conditions to produce crotonaldehyde. By using an organic amine instead of the traditional strong base as the catalyst for the aldol condensation reaction, the corrosiveness to the equipment is reduced. However, the problem of generating large amounts of saline wastewater still exists, which does not meet the increasingly stringent environmental protection requirements.

[0004] Regarding the research on molecular sieve catalysts, our research group's patent 202210567638.8 discloses a hierarchical porous β-zeolite with an ordered mesoporous structure, its preparation method, and its application. It proposes a one-step method to obtain a hierarchical porous β-zeolite with an ordered mesoporous structure using quaternary ammonium bases and long-chain quaternary ammonium salts as template agents. Our research group's patent 202211258742.5 discloses a heteroatom β-zeolite for low-carbon aldol condensation and its preparation method. This molecular sieve has a *BEA structure, and the heteroatoms it contains are one or more combinations of Ti, Sn, Zr, Ta, Ce, Hf, Y, Nb, V, Zn, Sc, and Fe. Its metal content, calculated as the molar ratio of silicon to metal (Si / M), is 10:1 to 1000:1, and the metal exists in the form of molecular sieve framework sites. This lays the foundation for inventing a molecular sieve-catalyzed process for the production of crotonaldehyde. Summary of the Invention

[0005] In order to completely solve the many problems existing in the homogeneous catalytic acetaldehyde to crotonaldehyde production process, this invention proposes a method and apparatus for the Zr-β molecular sieve catalytic gas-phase acetaldehyde to crotonaldehyde condensation reaction based on in-depth research on Zr-β molecular sieve catalytic gas-phase acetaldehyde to crotonaldehyde production.

[0006] This invention provides a method and apparatus for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis.

[0007] The technical solution of the present invention is as follows:

[0008] Based on previous research on Zr-β molecular sieve catalysts, this invention conducts a 100-hour long-term evaluation of the acetaldehyde condensation reaction catalyzed by the modified catalyst at 200℃ and 1 bar. The results show that within 100 hours of reaction, the selectivity of butadiene is between 0.1% and 0.15%, the selectivity of ethyl acetate is between 0.75% and 0.9%, the selectivity of ethanol is maintained between 0.7% and 0.9%, the selectivity of acetic acid is between 0.5% and 0.6%, the selectivity of methylcyclopentenone (MCP) is between 4% and 5% (hereinafter referred to as MCP), and the selectivity of the main product crotonaldehyde is maintained between 90% and 95%. This catalyst has preliminary industrialization potential, and a method and apparatus for the Zr-β molecular sieve-catalyzed acetaldehyde-to-crotonaldehyde production were designed.

[0009] The method for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis employs a Zr-β molecular sieve catalytic process for producing crotonaldehyde from gas-phase acetaldehyde.

[0010] The apparatus for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis includes a condensation reaction and heat exchange system, an acetaldehyde recovery system, a crotonaldehyde purification system, and an azeotropic separation system. The condensation reaction system includes a condensation reactor (R-101); the acetaldehyde recovery system includes an acetaldehyde recovery tower (C-201) and an ethyl acetate recovery tower (C-202); the crotonaldehyde purification system includes a crotonaldehyde concentration tower (C-301), a crotonaldehyde purification tower (C-401), and a dehydration tower (C-501); and the azeotropic separation system includes a demethylation cyclopentenone tower (C-501). The discharge from the condensation reactor (R-101) is connected to the acetaldehyde recovery tower (C-201), and the side pipeline of the acetaldehyde recovery tower (C-201) is connected to the ethyl acetate recovery tower (C-202). The bottom pipeline of the acetaldehyde recovery tower (C-201) is connected to the crotonaldehyde concentration tower (C-301), the top pipeline of the crotonaldehyde concentration tower (C-301) is connected to the crotonaldehyde refining tower (C-401), and the bottom pipeline is connected to the demethylated cyclopentenone tower (C-502). The top pipeline of the crotonaldehyde refining tower (C-401) is connected to the dehydration tower (C-501).

[0011] The method for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis involves evaporating the acetaldehyde feedstock in an acetaldehyde evaporator (E-101), mixing it with recycled water, and then heating it via a reactor feed heater (E-103) before it enters a condensation reactor (R-101). The condensation reactor is a fixed-bed packed reactor loaded with Zr-β molecular sieve catalyst, with a mass hourly space velocity (WHSV) of 0.25 h⁻¹. -1 The effluent stream from the condensation reactor (R-101) passes through the acetaldehyde recovery tower (C-201) to recover acetaldehyde, then enters the crotonaldehyde concentration tower (C-301) for concentration, and finally enters the crotonaldehyde refining tower (C-401) for refining. Crotonaldehyde product is collected from the bottom of the tower. Part of the gas from the top of the acetaldehyde recovery tower (C-201) is condensed and discharged from the butadiene in the process. The ethyl acetate-containing stream collected from the side of the acetaldehyde recovery tower (C-201) is sent to the ethyl acetate recovery tower (C-202) to remove ethyl acetate from the process. The crotonaldehyde refining tower (C-401)... -401) After the gas at the top of the tower is condensed and separated, the oil phase is collected as the ethanol discharge in the process; after the gas at the top of the demethylcyclopentenone tower (C-502) is condensed, water, methylcyclopentenone and acetic acid are discharged; the bottom water of the dehydration tower (C-501) and the bottom water of the demethylcyclopentenone tower (C-502) are mixed and preheated and then enter the mixed water flash tank (EV-101). The top steam is mixed with the acetaldehyde feedstock and heated and then enters the condensation reactor (R-101) for reaction. The bottom of the tank discharges wastewater containing acetic acid and sorbic acid.

[0012] The process of this invention includes the recycling of raw materials acetaldehyde and water; the outlet stream of the condensation reactor (R-101) enters the acetaldehyde recovery compressor (CP-101) to increase the stream pressure and then enters the acetaldehyde recovery tower (C-201) for distillation, and the gaseous acetaldehyde at the top of the tower is returned to the condensation reactor (R-101) for reaction; wherein the outlet pressure of the acetaldehyde recovery compressor (CP-101) is 2 to 5.5 bar, and the acetaldehyde recovery tower (C-201) is equipped with 27 to 34 theoretical plates; the water is circulated through the bottom stream of the dehydration tower (C-501) and the demethylcyclopentenone tower (C-502) and mixed with the water before entering the mixed water flash tank (EV-101), and the mixed water flash vapor is returned to the condensation reactor (R-101) as a diluent.

[0013] This invention uses water generated by the system as a diluent to inhibit carbon buildup on the catalyst, improve process selectivity, and extend catalyst life. The ratio of acetaldehyde to water in the reactor feed is 1:9 to 9:1, with a preferred ratio of 6:4.

[0014] The crotonaldehyde refining system of this invention consists of a crotonaldehyde concentration tower (C-301), a crotonaldehyde refining tower (C-401), and a dehydration tower (C-501). The bottom stream of the acetaldehyde recovery tower (C-201) passes sequentially through the crotonaldehyde concentration tower (C-301) and the crotonaldehyde refining tower (C-401) for distillation, and the crotonaldehyde product is collected from the bottom of the crotonaldehyde refining tower (C-401). A concentration tower separator (SP-301) and a refining tower separator (SP-401) are respectively installed at the top of the two towers, both of which use oil phase reflux, and the aqueous phase enters the dehydration tower (C-501) for treatment. The crotonaldehyde concentration tower (C-301) is equipped with 22 to 28 theoretical plates, the crotonaldehyde refining tower (C-401) is equipped with 40 to 45 theoretical plates, and the dehydration tower (C-501) is equipped with 18 to 25 theoretical plates.

[0015] In this invention, the impurity butadiene is discharged from the gas phase after partial condensation of the top vapor of the acetaldehyde recovery tower (C-201) by the butadiene condenser (E-202), with the partial condensation gas phase fraction controlled at 10% to 20%. The stream containing ethyl acetate impurities is taken from the side stream of the acetaldehyde recovery tower (C-201). After acetaldehyde is recovered at the top of the ethyl acetate recovery tower (C-202), the crude ethyl acetate is discharged through the bottom of the tower. The ethyl acetate recovery tower (C-202) is set with 6 to 10 theoretical plates.

[0016] The methylcyclopentenone of this invention is partially discharged after being refluxed from the top of the demethylcyclopentenone tower (C-502), along with some acetic acid impurities. The crude methylcyclopentenone flow fraction is 40-60%.

[0017] The impurity sorbic acid of this invention is discharged through the liquid phase stream at the bottom of the mixed water flash evaporator (EV-101).

[0018] This invention employs heat coupling to save on utilities. Specifically, the overhead steam from the crotonaldehyde concentration tower (C-301) is used as the reboiling heat source for the acetaldehyde feed evaporator (E-101) and the ethyl acetate recovery tower (C-202); the outlet stream of the acetaldehyde recovery compressor (CP-101) is first used as the heat source for the reactor feed heater (E-103), and then as the heat source for the mixing water preheater (E-102); the overhead steam from the demethylcyclopentenone tower (C-502) is used as the heat source for the reboiler (E-201) of the acetaldehyde recovery tower.

[0019] The specific explanation is as follows:

[0020] The apparatus for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis includes a condensation reaction and heat exchange system, an acetaldehyde recovery system, a crotonaldehyde purification system, and an azeotropic separation system. The condensation reaction and heat exchange system mainly comprises an acetaldehyde evaporator (E-101), a mixed water preheater (E-102), a mixed water flash tank (EV-101), a reactor feed heater (E-103), a wastewater cooler (E-104), a condensation reactor (R-101), an acetaldehyde recovery compressor (CP-101), an acetaldehyde recovery tower feed heat exchanger (E-105), an acetaldehyde recovery tower feed condenser (E-106), and a reactor discharge flash tank (EV-102). The condensation reactor (R-101) is a fixed-bed packed reactor loaded with Zr-β molecular sieve catalyst and has a mass hourly space velocity (MSV) of 0.The acetaldehyde recovery system consists of an acetaldehyde recovery tower (C-201), an acetaldehyde recovery tower feed heat exchanger (E-105), an acetaldehyde recovery tower feed condenser (E-106), a reactor outlet flash tank (EV-102), and an acetaldehyde recovery tower (C-201). The system comprises an acetaldehyde recovery tower (C-201), an ethyl acetate recovery tower (C-202), an acetaldehyde recovery tower reboiler (E-201), a butadiene condenser (E-202), an acetaldehyde recovery tower heat exchanger (E-203), an acetaldehyde recovery tower condenser (E-204), and an acetaldehyde recovery tower. The system comprises a reflux tank (V-201), an acetaldehyde recovery gas-liquid separator (EV-201), an ethyl acetate recovery tower reflux tank (V-202), an ethyl acetate recovery tower reboiler (E-205), and an ethyl acetate recovery tower condenser (E-206). The side stream of the acetaldehyde recovery tower (C-201) is connected to the ethyl acetate recovery tower (C-202). The top of the acetaldehyde recovery tower (C-201) is connected sequentially to the acetaldehyde recovery tower heat exchanger (E-203), the butadiene condenser (E-202), the acetaldehyde recovery tower reflux tank (V-201), and the acetaldehyde recovery gas-liquid separator (EV-201). The acetaldehyde recovery tower (C-201) bottom pipeline is connected to the crotonaldehyde concentration tower (C-301); the crotonaldehyde refining system includes the crotonaldehyde concentration tower (C-301), crotonaldehyde concentration tower reboiler (E-301), concentration tower condenser (E-302), concentration tower cooler (E-303), concentration tower separator (SP-301), crotonaldehyde refining tower (C-401), crotonaldehyde refining tower reboiler (E-401), refining tower condenser (E-402), refining tower cooler (E-403), refining tower separator (SP-401), and dehydration tower (C-5). 01) and the dehydration tower reboiler (E-501), wherein the top pipeline of the crotonaldehyde concentration tower (C-301) is connected in sequence to the concentration tower condenser (E-302), the concentration tower cooler (E-303) and the concentration tower separator (SP-301). One branch of the organic phase pipeline of the concentration tower separator (SP-301) enters the top reflux of the crotonaldehyde concentration tower (C-301), and the other branch is connected to the crotonaldehyde refining tower (C-401). The aqueous phase pipeline is connected to the dehydration tower (C-501), and the bottom pipeline of the crotonaldehyde concentration tower (C-301) is connected to the deMCP removal tower (C-502). The crotonaldehyde refining tower (C-401) discharges crotonaldehyde product via its bottom pipeline. The top pipeline sequentially connects to the refining tower condenser (E-402), refining tower cooler (E-403), refining tower separator (SP-401), and dehydration tower (C-501). The azeotropic separation system includes a MCP removal tower (C-502), a MCP removal tower reboiler (E-502), a MCP removal tower condenser (E-503), and a MCP removal tower reflux tank (V-501). The bottom pipeline of the MCP removal tower (C-502) is connected to the mixed water flash tank (EV-101).

[0021] The method for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis involves a condensation reaction and heat exchange system that includes a mixed feed of two raw materials. Part of the acetaldehyde feed is new material, and the remainder comes from acetaldehyde recovered from the acetaldehyde recovery system. The dilution steam used in the reaction process is generated water that is recycled within the system. Drainage from the bottom of the dehydration tower (C-501) and the MCP removal tower (C-502) is preheated by the mixed water preheater (E-102) and then enters the mixed water flash tank (EV-101). The liquid phase discharges process wastewater containing sorbic acid. The gas phase is mixed with the acetaldehyde raw material and heated by the reactor feed heater E-103 before entering the condensation reactor (R-101). The products include butadiene, crotonaldehyde, MCP, ethyl acetate, ethanol, acetic acid, sorbic acid, and unreacted acetaldehyde and water.

[0022] The reactor product is pressurized by the acetaldehyde recovery compressor (CP-101) and then passes through the acetaldehyde recovery tower feed heat exchanger (E-105) and the acetaldehyde recovery tower feed condenser (E-106) for heat exchange before flowing into the reactor outlet flash tank (EV-102). The gas stream from the reactor outlet flash tank (EV-102) serves as the feed to the acetaldehyde recovery tower (C-201), while the liquid stream from the reactor outlet flash tank (EV-102) is fed from the bottom of the acetaldehyde recovery tower (C-201). A large amount of vapor is collected from the top of the acetaldehyde recovery tower (C-201), and a small portion is condensed and discharged as vapor in the butadiene condenser (E-202). The remaining portion is condensed by the acetaldehyde recovery tower heat exchanger (E-203) and then enters the acetaldehyde recovery tower reflux tank (V-201). The top of the tank contains a large amount of water. After the residual acetaldehyde is recovered by the acetaldehyde recovery gas-liquid separator (EV-201), the liquid phase enters the top of the tower for reflux. The side stream from the recovery tower is pumped by the acetaldehyde recovery tower side stream pump (P-201) into the ethyl acetate recovery tower (C-202). Similarly, the acetaldehyde-rich stream from the top of the ethyl acetate recovery tower is sent back to the feed circulation. The crotonaldehyde-rich stream from the bottom of the acetaldehyde recovery tower (C-201) is sent to the purification section by the acetaldehyde recovery tower bottom discharge pump (P-301).

[0023] The main equipment of the crotonaldehyde refining system consists of a crotonaldehyde concentration tower (C-301), a crotonaldehyde refining tower (C-401), and a dehydration tower (C-501). The raw material comes from the recovered acetaldehyde stream taken from the bottom of the acetaldehyde recovery tower (C-201). It mainly contains crotonaldehyde, MCP, ethyl acetate, ethanol, acetic acid, sorbic acid, water, and a small amount of butadiene, acetaldehyde, and ethyl acetate that have not been completely removed. After separation in the crotonaldehyde concentration tower (C-301), the high-water-content stream from the bottom of the crotonaldehyde concentration tower is sent to the deMCP tower (C-502) for further processing by the feed pump (P-502). The components rich in crotonaldehyde and water are distilled off from the top of the tower and condensed into a liquid stream by the condenser (E-302) of the concentration tower. The liquid stream then enters the cooler (E-303) of the concentration tower for further cooling to 45°C. The cooled liquid phase enters the separator (SP-301) of the concentration tower for separation, with the aqueous phase at the bottom and the organic crotonaldehyde phase at the top. The lower aqueous phase is sent to the dehydration tower (C-501) by the feed pump (P-501) to recover the crotonaldehyde. The upper crotonaldehyde phase is partially refluxed by the crotonaldehyde concentration tower condenser reflux pump (P-302) and partially sent to the crotonaldehyde refining tower (C-401) for further refining. The steam from the top of the crotonaldehyde refining tower (C-401) first enters the refining tower condenser (E-402) for condensation, then enters the refining tower cooler (E-403) for further cooling to 45°C, and then enters the refining tower separator (SP-401). A portion of the upper organic phase is drawn out by the crotonaldehyde refining tower condensate reflux pump (P-402) and returned to the top of the tower for reflux, while a small portion is drawn out as an ethanol impurity discharge stream. The aqueous phase in the refining tower separator (SP-401) mixes with the aqueous phase in the concentration tower separator (SP-301) and is sent to the top of the dehydration tower (C-501) by the dehydration tower feed pump (P-501) for dehydration treatment. The aqueous phase separated by the separator enters the dehydration tower (C-501) from the top of the tower. The dehydration tower and the crotonaldehyde refining tower (C-401) share a set of top condensation and reflux system. The vapor phase from the top of the dehydration tower (C-501) is mixed with the crotonaldehyde refining tower and enters the refining tower condenser (E-402) for condensation. The bottom water stream is sent by the dehydration tower discharge pump (P-503) to be mixed with the bottom water of the MCP removal tower and then enters the mixed water flash tank (EV-101).

[0024] The main equipment of the azeotropic separation system is the MCP removal tower (C-502). MCP has a higher boiling point than water, and all the water needs to be evaporated to remove MCP. However, this invention discovered the azeotropic effect between MCP and water and fitted the parameters, so that the MCP generated during the condensation reaction can be removed by the MCP removal tower (C-502). The feed to the MCP removal tower comes from the bottom of the crotonaldehyde concentration tower (C-301). The top fraction of the MCP removal tower is condensed by the MCP removal tower condenser (E-503) and enters the MCP removal tower reflux tank (V-501). Part of it is sent back to the top of the tower for reflux by the MCP removal tower condenser reflux pump (P-504), and part of it is discharged to remove MCP. The bottom stream of the MCP removal tower is sent by the bottom pump (P-505) to mix with the feed water and the bottom stream of the dehydration tower and then enters the mixed water flash tank (EV-101) to complete the water circulation process. After flash evaporation, the liquid containing sorbic acid is discharged.

[0025] This invention relates to a method and apparatus for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis; the process employs Zr-β molecular sieve catalysis for the production of crotonaldehyde from gas-phase acetaldehyde. Through a condensation reaction and heat exchange system, an acetaldehyde recovery system, a crotonaldehyde purification system, and an azeotropic separation system, high-purity crotonaldehyde production is achieved, replacing the traditional homogeneous method using strong acid and strong base catalysts, avoiding equipment corrosion, greatly increasing equipment lifespan, and reducing investment costs. This invention uses a packed fixed-bed reactor, completely solving the problem of traditional processes using sodium hydroxide catalysis, resulting in wastewater containing large amounts of sodium salts, which is environmentally unfriendly. A distillation-to-MCP removal process is proposed, optimizing the process and reducing energy consumption. The selectivity of the main product, crotonaldehyde, is maintained between 90% and 95%.

[0026] The beneficial technical effects of this invention are as follows:

[0027] 1. Compared with the traditional homogeneous crotonaldehyde production process, the process of this invention innovatively adopts a Zr-β molecular sieve heterogeneous process, which replaces the traditional homogeneous method using strong acid and strong base catalysts, avoids equipment corrosion, greatly increases equipment service life, and reduces investment costs.

[0028] 2. This invention uses a packed fixed-bed reactor, which is environmentally friendly to wastewater, has low energy consumption, and is economical. It can completely solve the problem of traditional processes using sodium hydroxide catalysis, which results in wastewater containing a large amount of sodium salt, making it environmentally unfriendly.

[0029] 3. This invention discovers and proposes a distillation process for removing MCP. This invention discovers the azeotropic effect between methylcyclopentenone and water, which allows for the removal of MCP without completely distilling out all the water. The parameters were successfully fitted, the process was optimized, and energy consumption was reduced. Attached Figure Description

[0030] Figure 1This invention relates to the condensation reaction and heat exchange system and the acetaldehyde recovery system in the Zr-β molecular sieve catalytic process for the production of crotonaldehyde from acetaldehyde.

[0031] Among them, R-101 is the condensation reactor, C-201 is the acetaldehyde recovery tower, and C-202 is the ethyl acetate recovery tower;

[0032] EV-102 – Reactor discharge flash tank; EV-201 – Acetaldehyde recovery gas-liquid separator; V-201 – Acetaldehyde recovery tower reflux tank; V-202 – Ethyl acetate recovery tower reflux tank;

[0033] E-101 – Acetaldehyde Evaporator, E-103 – Reactor Feed Heater, E-105 – Acetaldehyde Recovery Tower Feed Heat Exchanger, E-106 – Acetaldehyde Recovery Tower Feed Condenser, E-201 – Acetaldehyde Recovery Tower Reboiler, E-202 – Butadiene Condenser, E-203 – Acetaldehyde Recovery Tower Heat Exchanger, E-205 – Ethyl Acetate Recovery Tower Reboiler, E-206 – Ethyl Acetate Recovery Tower Condenser;

[0034] CP-101 – Acetaldehyde recovery compressor; P-201 – Acetaldehyde recovery tower side-stream pump; P-202 – Acetaldehyde recovery tower condenser reflux pump; P-203 – Ethyl acetate pump; P-204 – Ethyl acetate recovery tower condenser reflux pump.

[0035] Figure 2 This refers to the crotonaldehyde refining system and azeotropic separation system in the Zr-β molecular sieve catalytic process for the production of crotonaldehyde from acetaldehyde according to the present invention.

[0036] C-301 – Crotonaldehyde Concentration Tower, C-401 – Crotonaldehyde Refining Tower, C-501 – Dehydration Tower, C-502 – MCP Removal Tower;

[0037] EV-101 – Mixed Water Flash Tank, SP-301 – Concentration Tower Separator, SP-401 – Refining Tower Separator, V-501 – MCP Removal Tower Reflux Tank;

[0038] E-102 – Mixed water preheater, E-104 – Wastewater cooler, E-301 – Crotonaldehyde concentration tower reboiler, E-302 – Concentration tower condenser, E-303 – Concentration tower cooler, E-401 – Crotonaldehyde refining tower reboiler, E-402 – Refining tower condenser, E-403 – Refining tower cooler, E-501 – Dehydration tower reboiler, E-502 – MCP removal tower reboiler, E-503 – MCP removal tower condenser;

[0039] P-301 – Acetaldehyde recovery tower bottom discharge pump; P-302 – Crotonaldehyde concentration tower condenser reflux pump; P-401 – Crotonaldehyde collection pump; P-402 – Crotonaldehyde refining tower condenser reflux pump; P-501 – Dehydration tower feed pump; P-502 – MCP removal tower feed pump; P-503 – Dehydration tower discharge pump; P-504 – MCP removal tower condenser reflux pump; P-505 – MCP removal tower bottom discharge pump. Specific implementation methods

[0040] This invention provides a process and apparatus for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis. The following is a description of the method and apparatus of this invention in conjunction with the accompanying drawings.

[0041] This invention is achieved through Figure 1 and Figure 2 The method shown is implemented as follows:

[0042] The apparatus for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis according to the present invention includes a condensation reaction and heat exchanger system, an acetaldehyde recovery system, a crotonaldehyde purification system, and an azeotropic separation system.

[0043] The condensation reaction and heat exchange system mainly includes a condensation reactor (R-101) for the feed section, a flash tank for mixed water (EV-101), and a flash tank for reactor discharge (EV-102). The heat exchange system mainly includes an acetaldehyde evaporator (E-101), a mixed water preheater (E-102), a reactor feed heater (E-103), a wastewater cooler (E-104), an acetaldehyde recovery tower feed heat exchanger (E-105), and an acetaldehyde recovery tower feed condenser (E-106). The condensation reactor (R-101) is sequentially connected to its auxiliary equipment, the acetaldehyde recovery tower feed heat exchanger (E-105), the acetaldehyde recovery tower feed condenser (E-106), and the reactor discharge flash tank (EV-102). The mixed water flash tank (EV-101) is connected to its auxiliary equipment, the wastewater cooler (E-104).

[0044] The acetaldehyde recovery system mainly includes an acetaldehyde recovery tower (C-201) and an ethyl acetate recovery tower (C-202) connected in sequence. The acetaldehyde recovery tower (C-201) is connected to its auxiliary equipment, including an acetaldehyde recovery tower reboiler (E-201), a butadiene condenser (E-202), an acetaldehyde recovery tower heat exchanger (E-203), an acetaldehyde recovery tower reflux tank (V-201), an acetaldehyde gas-liquid separator (EV-201), an acetaldehyde recovery tower condensation reflux pump (P-202), and an acetaldehyde recovery tower side-stream discharge pump (P-201). The ethyl acetate recovery tower (C-202) is connected to its auxiliary equipment, including an ethyl acetate recovery tower reflux tank (V-202), an ethyl acetate recovery tower condenser (E-206), an ethyl acetate recovery tower reboiler (E-205), an ethyl acetate discharge pump (P-203), and an ethyl acetate recovery tower condensation reflux pump (P-204).

[0045] The crotonaldehyde refining system includes a crotonaldehyde concentration tower (C-301), a crotonaldehyde refining tower (C-401), and a dehydration tower (C-501). The crotonaldehyde concentration tower (C-301) is connected to its auxiliary equipment, including a crotonaldehyde concentration tower reboiler (E-301), a deMCP removal tower feed pump (P-502), a concentration tower condenser (E-302), a crotonaldehyde concentration tower (C-301), a concentration tower separator (SP-301), a crotonaldehyde concentration tower condenser reflux pump (P-302), and the crotonaldehyde refining tower (C-401) and dehydration tower (C-501). The crotonaldehyde refining tower (C-401) is connected to its auxiliary equipment, including the crotonaldehyde refining tower reboiler (E-401), crotonaldehyde discharge pump (P-401), refining tower condenser (E-402), refining tower cooler (E-403), refining tower separator (SP-401), crotonaldehyde refining tower condensate reflux pump (P-402), and dehydration tower feed pump (P-501). The dehydration tower (C-501) is connected to its auxiliary equipment, including the dehydration tower reboiler (E-501) and dehydration tower discharge pump (P-503).

[0046] The azeotropic separation system mainly consists of an MCP removal tower (C-502), which is connected to its auxiliary equipment, including an MCP removal tower reboiler (E-502), an MCP removal tower bottom discharge pump (P-505), an MCP removal tower condenser (E-503), an MCP removal tower reflux tank (V-501), and an MCP removal tower condenser reflux pump (P-504).

[0047] The method for producing crotonaldehyde according to the present invention is as follows:

[0048] The condensation reactor (R-101) is used for the reaction of acetaldehyde and water to produce crotonaldehyde, while the mixed water flash tank (EV-101) handles the discharge of water, sorbic acid, and acetic acid. Circulating acetaldehyde is mixed with the acetaldehyde feedstock, and supplementary water is mixed with the circulating water. Both are heated to the reaction temperature (set at 200°C) by the reactor feed heater (E-103). The reaction stream passes through the acetaldehyde recovery tower feed heat exchanger (E-105) and the acetaldehyde recovery tower feed condenser (E-106) before entering the reactor discharge flash tank (EV-102).

[0049] The acetaldehyde recovery tower (C-201) is used to recover most of the unreacted acetaldehyde feedstock from the shrinkage reactor (R-101), while simultaneously discharging butadiene from the system. The ethyl acetate recovery tower (C-202) is used to discharge ethyl acetate from the system. The vapor from the top of the acetaldehyde recovery tower (C-201) is cooled below the boiling point of acetaldehyde by the butadiene condenser (E-202). Part of it is discharged as butadiene gas, and the remainder returns to the acetaldehyde recovery tower reflux tank (V-201) for reflux. The steam from the acetaldehyde recovery tower reflux tank (V-201) is cooled by the acetaldehyde recovery tower condenser (E-204) and enters the acetaldehyde recovery gas-liquid separator (EV-201). It is then sent back to the top of the tower for reflux by the acetaldehyde recovery tower condenser reflux pump (P-202). The liquid in the bottom of the acetaldehyde recovery tower (C-201) is sent to the crotonaldehyde concentration tower (C-301) for concentration by the acetaldehyde recovery tower bottom discharge pump (P-301). The heat required for the reboiling of the acetaldehyde recovery tower (C-201) is provided by the steam from the top of the MCP removal tower (C-502). The side stream is drawn from the acetaldehyde recovery tower side stream pump (P-201) and fed into the ethyl acetate recovery tower (C-202). The vapor from the top of the ethyl acetate recovery tower (C-202) is condensed in the ethyl acetate recovery tower condenser (E-206) and returned to the acetaldehyde recovery tower (C-201) in vapor phase, while the liquid phase is refluxed through the ethyl acetate recovery tower reflux tank (V-202). The bottom portion of the ethyl acetate recovery tower (C-202) is drawn from the ethyl acetate discharge pump (P-203) and discharged as ethyl acetate. The heat required for the reboiling of the ethyl acetate recovery tower (C-202) is provided by the vapor from the top of the crotonaldehyde concentration tower (C-301).

[0050] The crotonaldehyde concentration tower (C-301) is used to concentrate crotonaldehyde in the product stream; the crotonaldehyde refining tower (C-401) is used to refine the steam at the top of the crotonaldehyde concentration tower (C-301) into crotonaldehyde product; and the dehydration tower (C-501) is used for the reuse of circulating water. The bottom stream of the crotonaldehyde concentration tower (C-301) is fed into the MCP removal tower (C-502) via the feed pump (P-502) to remove MCP. The top vapor of the crotonaldehyde concentration tower (C-301) passes through the condenser (E-302) and cooler (E-303) of the concentration tower and enters the separator (SP-301) of the concentration tower for phase separation. The heat from the condenser (E-302) of the concentration tower is coupled with the acetaldehyde evaporator (E-101) and the reboiler (E-205) of the ethyl acetate recovery tower. The aqueous phase after phase separation in the separator (SP-301) is sent to the dehydration tower for treatment by the feed pump (P-501) of the dehydration tower. The oil phase is partially returned to the tower for reflux by the crotonaldehyde concentration tower condenser reflux pump (P-302), and part of it enters the crotonaldehyde refining tower (C-401) for crotonaldehyde refining. The overhead vapor from the crotonaldehyde refining tower (C-401) passes through the refining tower condenser (E-402) and refining tower cooler (E-403) before entering the refining tower separator (SP-401) for phase separation. The aqueous phase is fed into the dehydration tower for treatment by the dehydration tower feed pump (P-501), while the oil phase is refluxed into the tower by the crotonaldehyde refining tower condenser reflux pump (P-402), which also serves as the ethanol discharge point. The crotonaldehyde product from the bottom of the crotonaldehyde refining tower (C-401) is collected by the crotonaldehyde collection pump (P-401). The dehydration tower (C-501) receives feed from the top, and its overhead vapor is mixed with that of the crotonaldehyde refining tower (C-401) using a shared condensation unit. The bottom stream from the dehydration tower (C-501) is sent by the dehydration tower discharge pump (P-503) to be mixed with the feed water.

[0051] The bottom stream of the MCP stripping tower (C-502) is sent by the bottom pump (P-505) to mix with the bottom water of the dehydration tower. The top steam of the MCP stripping tower (C-502) is cooled by the condenser (E-503) and enters the reflux tank (V-501). It is then refluxed by the condenser reflux pump (P-504). The heat from the top steam is used to heat the bottom of the acetaldehyde recovery tower (C-201) for reboiling. At the same time, this area serves as the discharge outlet for byproducts such as MCP and acetic acid.

[0052] Preferably, the acetaldehyde recovery tower (C-201) has 25 to 36 theoretical plates, the ethyl acetate recovery tower (C-202) has 10 to 29 theoretical plates, the crotonaldehyde concentration tower (C-301) has 22 to 28 theoretical plates, the crotonaldehyde refining tower (C-401) has 40 to 45 theoretical plates, the dehydration tower (C-501) has 17 to 25 theoretical plates, and the MCP removal tower (C-502) has 27 to 33 theoretical plates.

[0053] Preferably, the gas phase fraction of the butadiene condenser (E-204) is set to 10% to 20%, and the condensate recovery fraction from the top of the MCP removal tower (C-502) is set to 40% to 60%.

[0054] Preferably, the condensation reactor (R-101) is a packed fixed-bed reactor, the reaction temperature is set to 200°C, and it is loaded with a Zr-β molecular sieve catalyst with a mass space velocity of 0.25 h⁻¹. -1 The cooling temperature at the top of the crotonaldehyde concentration tower (C-301) is set to 38–52℃, and the cooling temperature at the top of the crotonaldehyde refining tower is set to 38–52℃.

[0055] The ratio of acetaldehyde to water in the reactor feed is 1:9 to 9:1, with a preferred ratio of 6:4.

[0056] In the first embodiment of the present invention, the feed temperature of acetaldehyde is 20°C, the feed temperature of makeup water is 70°C, and the feed mass flow rate ratio of acetaldehyde:water is 20%:80%. The reaction temperature of the condensation reactor (R-101) is 200°C, and it is loaded with Zr-β molecular sieve catalyst with a total catalyst mass of 250,244 kg. The acetaldehyde recovery tower (C-201) is equipped with 30 theoretical plates, and the mass flow rate of butadiene collected from the top of the tower is 2000 kg / h, with a mass fraction of 0.06974. In the acetaldehyde recovery section, the feed pipe of the acetaldehyde recovery compressor (CP-101) is connected to the discharge pipe of the condensation reactor (R-101), and the discharge pipe of the acetaldehyde recovery compressor (CP-101) is connected to the acetaldehyde recovery tower (C-201). The discharge pressure of the acetaldehyde recovery compressor is set at 2.2 bar. The ethyl acetate recovery tower (C-202) is equipped with 10 theoretical plates, and the ethyl acetate collection rate is 100 kg / h, with a mass fraction of 0.7348. The crotonaldehyde concentration tower (C-301) has 40 theoretical plates, and the crotonaldehyde refining tower (C-401) has 42 theoretical plates. Ethanol is collected from the top vapor phase condensation of the crotonaldehyde refining tower at a flow rate of 107.5036 kg / h and a mass fraction of 0.1960. The crotonaldehyde product mass flow rate collected from the bottom of the crotonaldehyde refining tower (C-401) is 6320 kg / h, with a mass fraction of 0.9792. The dehydration tower (C-501) has 20 theoretical plates, and the MCP removal tower (C-502) has 30 theoretical plates. The mass flow rate collected from the top vapor phase condensation of the MCP removal tower (C-502) is 1132.00 kg / h, of which the acetic acid mass content is 0.001567% and the MCP mass fraction is 0.2497%. The mixed water flash tank (EV-101) discharges wastewater at a flow rate of 1093 kg / h, with an MCP mass fraction of 0.002953 and a sorbic acid mass fraction of 0.1033.

[0057] In a second embodiment of the present invention, the feed temperature of acetaldehyde is 20°C, the feed temperature of makeup water is 70°C, and the feed mass flow rate ratio of acetaldehyde:water is 60%:40%. The reaction temperature of the condensation reactor (R-101) is 200°C, and it is loaded with Zr-β molecular sieve catalyst with a total catalyst mass of 247,544 kg. The acetaldehyde recovery tower (C-201) is equipped with 30 theoretical plates, and the mass flow rate of butadiene collected at the top of the tower is 201.29 kg / h, with a mass fraction of 0.06984. In the acetaldehyde recovery section, the feed pipe of the acetaldehyde recovery compressor (CP-101) is connected to the discharge pipe of the condensation reactor (R-101), and the discharge pipe of the acetaldehyde recovery compressor (CP-101) is connected to the acetaldehyde recovery tower (C-201). The discharge pressure of the acetaldehyde recovery compressor is set at 3.2 bar. The ethyl acetate recovery tower (C-202) is equipped with 10 theoretical plates, and the ethyl acetate collection rate is 100 kg / h, with a mass fraction of 0.7393. The crotonaldehyde concentration tower (C-301) has 25 theoretical plates, and the crotonaldehyde refining tower (C-401) has 42 theoretical plates. Ethanol is collected from the top vapor phase condensation of the crotonaldehyde refining tower at a flow rate of 171.57 kg / h and a mass fraction of 0.1975. The crotonaldehyde product mass flow rate collected from the bottom of the crotonaldehyde refining tower (C-401) is 6320 kg / h, with a mass fraction of 0.999. The dehydration tower (C-501) has 20 theoretical plates, and the MCP removal tower (C-502) has 30 theoretical plates. The mass flow rate collected from the top vapor phase condensation of the MCP removal tower (C-502) is 706.9283 kg / h, of which the acetic acid mass content is 0.0084% and the MCP mass fraction is 0.3613%. The mixed water flash tank (EV-101) discharges wastewater at a flow rate of 1400 kg / h, containing acetic acid at a mass fraction of 0.001 and sorbic acid at a mass fraction of 0.06487.

[0058] In the third embodiment of the present invention, the feed temperature of acetaldehyde is 20°C, the feed temperature of makeup water is 70°C, and the feed mass flow rate ratio of acetaldehyde:water is 90%:10%. The reaction temperature of the condensation reactor (R-101) is 200°C, and it is loaded with Zr-β molecular sieve catalyst with a total catalyst mass of 248,988 kg. The acetaldehyde recovery tower (C-201) is equipped with 30 theoretical plates, and the mass flow rate of butadiene collected at the top of the tower is 199.97 kg / h, with a mass fraction of 0.07106. In the acetaldehyde recovery section, the feed pipe of the acetaldehyde recovery compressor (CP-101) is connected to the discharge pipe of the condensation reactor (R-101), and the discharge pipe of the acetaldehyde recovery compressor (CP-101) is connected to the acetaldehyde recovery tower (C-201). The discharge pressure of the acetaldehyde recovery compressor is set at 5.2 bar. The ethyl acetate recovery tower (C-202) is equipped with 10 theoretical plates, and the ethyl acetate collection rate is 100 kg / h, with a mass fraction of 0.6064. The crotonaldehyde concentration tower (C-301) has 25 theoretical plates, and the crotonaldehyde refining tower (C-401) has 42 theoretical plates. Ethanol is collected from the top vapor phase condensation of the crotonaldehyde refining tower at a flow rate of 198.44 kg / h and a mass fraction of 0.17230. The crotonaldehyde product mass flow rate collected from the bottom of the crotonaldehyde refining tower (C-401) is 6321 kg / h, with a mass fraction of 0.9989. The dehydration tower (C-501) has 20 theoretical plates, and the MCP removal tower (C-502) has 30 theoretical plates. The mass flow rate collected from the top vapor phase condensation of the MCP removal tower (C-502) is 760.34 kg / h, with an MCP mass fraction of 0.4019. The mixed water flash tank (EV-101) discharges wastewater at a flow rate of 1319 kg / h, with an MCP mass fraction of 0.0022 and a sorbic acid mass fraction of 0.03239.

[0059] In one embodiment of the invention, the apparatus further includes a pump for conveying materials. As those skilled in the art will know, material conveying between the various distillation columns can utilize positional differences, relying on the gravity of the materials to achieve the conveying of raw materials within the distillation columns; however, when material conveying cannot be achieved by gravity, one or more material conveying pumps can be installed at appropriate pipeline locations to achieve material conveying.

[0060] Unless otherwise specified, the equipment used in this invention is conventional equipment, and can be implemented using methods and equipment known to those skilled in the art.

[0061] Although the invention has been described in conjunction with specific embodiments and accompanying drawings, it is not intended to be limited to the specific forms set forth herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, while individual features may be contained in different claims, these features may be advantageously combined, and inclusion in different claims does not imply that such combinations of features are not feasible and / or advantageous. References to "first," "second," etc., do not exclude the plural.

Claims

1. A method for producing crotonaldehyde from gas-phase acetaldehyde using Zr-β molecular sieve catalysis, characterized in that... A Zr-β molecular sieve catalytic process for the gas-phase production of crotonaldehyde from acetaldehyde was adopted. The process flow is as follows: acetaldehyde feedstock is evaporated in an acetaldehyde evaporator (E-101), mixed with recycled water, and then heated by a reactor feed heater (E-103) before entering a condensation reactor (R-101). The condensation reactor is a fixed-bed packed reactor loaded with Zr-β molecular sieve catalyst, with a mass hourly space velocity (HHSV) of 0.25 h⁻¹. -1 The effluent stream from the condensation reactor (R-101) passes through the acetaldehyde recovery tower (C-201) to recover acetaldehyde, then enters the crotonaldehyde concentration tower (C-301) for concentration, and finally enters the crotonaldehyde refining tower (C-401) for refining. Crotonaldehyde product is collected from the bottom of the tower. Part of the gas from the top of the acetaldehyde recovery tower (C-201) is condensed and discharged from the butadiene in the process. The ethyl acetate-containing stream collected from the side of the acetaldehyde recovery tower (C-201) is sent to the ethyl acetate recovery tower (C-202) to remove ethyl acetate from the process. The crotonaldehyde refining tower (C-401)... -401) After the gas at the top of the tower is condensed and separated, the oil phase is collected as the ethanol discharge in the process; after the gas at the top of the demethylcyclopentenone tower (C-502) is condensed, water, methylcyclopentenone and acetic acid are discharged; after the water at the bottom of the dehydration tower (C-501) and the water at the bottom of the demethylcyclopentenone tower (C-502) are mixed and preheated, they enter the mixed water flash tank (EV-101). The steam at the top of the tank is mixed with the acetaldehyde feedstock and heated before entering the condensation reactor (R-101) for reaction. Wastewater containing acetic acid and sorbic acid is discharged from the bottom of the tank.

2. An apparatus for implementing the Zr-β molecular sieve catalytic gas-phase acetaldehyde production method for crotonaldehyde according to claim 1, characterized in that, The system includes a condensation reaction and heat exchange system, an acetaldehyde recovery system, a crotonaldehyde refining system, and an azeotropic separation system. The condensation reaction and heat exchange system mainly includes an acetaldehyde evaporator (E-101), a mixed water flash tank (EV-101), a reactor feed heater (E-103), and a condensation reactor (R-101). The acetaldehyde recovery system includes an acetaldehyde recovery tower (C-201) and an ethyl acetate recovery tower (C-202). The crotonaldehyde refining system includes a crotonaldehyde concentration tower (C-301), a crotonaldehyde refining tower (C-401), and a dehydration tower (C-501). The azeotropic separation system includes a demethylation cyclopentenone tower (C-501). The discharge from the condensation reactor (R-101) is connected to the acetaldehyde recovery tower (C-201), and the side pipeline of the acetaldehyde recovery tower (C-201) is connected to the ethyl acetate return line. The acetaldehyde recovery tower (C-202) is connected to the acetaldehyde recovery tower (C-201). The bottom pipeline of the acetaldehyde recovery tower (C-201) is connected to the crotonaldehyde concentration tower (C-301). The top pipeline of the crotonaldehyde concentration tower (C-301) is connected to the crotonaldehyde refining tower (C-401). The bottom pipeline of the crotonaldehyde refining tower (C-401) is connected to the dehydration tower (C-501). The gas phase of the mixed water flash evaporator (EV-101) is mixed with the acetaldehyde raw material and heated by the reactor feed heater E-103 before entering the condensation reactor (R-101). The outlet stream of the condensation reactor (R-101) passes through the acetaldehyde recovery tower (C-201) to recover acetaldehyde and then enters the crotonaldehyde concentration tower (C-301) for concentration before entering the crotonaldehyde refining tower (C-401) for refining. The crotonaldehyde product is collected from the bottom of the tower.

3. The method as described in claim 1, characterized in that, The process includes the recycling of raw materials acetaldehyde and water. The outlet stream of the condensation reactor (R-101) enters the acetaldehyde recovery compressor (CP-101) to increase the stream pressure, and then enters the acetaldehyde recovery tower (C-201) for distillation. The vapor acetaldehyde at the top of the tower is returned to the condensation reactor (R-101) for further reaction. The outlet pressure of the acetaldehyde recovery compressor (CP-101) is 2~5.5 bar, and the acetaldehyde recovery tower (C-201) is equipped with 27~34 theoretical plates. The water is circulated through the bottom stream of the dehydration tower (C-501) and the demethylation cyclopentenone tower (C-502) and mixed with the water before entering the mixed water flash tank (EV-101). The vapor phase of the mixed water flash is returned to the condensation reactor (R-101) as a diluent.

4. The method as described in claim 1, characterized in that, The system uses recycled water as a diluent to suppress carbon buildup on the catalyst, improve process selectivity, and extend catalyst life. The ratio of acetaldehyde to water in the reactor feed is 1:9 to 9:

1.

5. The method as described in claim 1, characterized in that, The crotonaldehyde refining system consists of a crotonaldehyde concentration tower (C-301), a crotonaldehyde refining tower (C-401), and a dehydration tower (C-501). The bottom stream of the acetaldehyde recovery tower (C-201) passes sequentially through the crotonaldehyde concentration tower (C-301) and the crotonaldehyde refining tower (C-401) for distillation, and the crotonaldehyde product is collected from the bottom of the crotonaldehyde refining tower (C-401). The tops of the two towers are respectively equipped with a concentration tower separator (SP-301) and a refining tower separator (SP-401), both of which use oil phase reflux, and the aqueous phase enters the dehydration tower (C-501) for treatment. The crotonaldehyde concentration tower (C-301) is equipped with 22~28 theoretical plates, the crotonaldehyde refining tower (C-401) is equipped with 40~45 theoretical plates, and the dehydration tower (C-501) is equipped with 18~25 theoretical plates.

6. The method as described in claim 1, characterized in that the impurities... Butadiene is discharged from the gas phase after the top part of the vapor from the acetaldehyde recovery tower (C-201) is partially condensed by the butadiene condenser (E-202); the stream containing ethyl acetate impurities is collected from the side stream of the acetaldehyde recovery tower (C-201), and after acetaldehyde is recovered at the top of the ethyl acetate recovery tower (C-202), the crude ethyl acetate is discharged through the bottom of the tower. The number of theoretical plates in the ethyl acetate recovery tower (C-202) is set to 6~10.

7. The method as described in claim 1, characterized in that, Methylcyclopentenone is partially discharged after being refluxed from the top of the demethylcyclopentenone tower (C-502), along with some acetic acid impurities.

8. The method as described in claim 1, characterized in that, The impurity sorbic acid is discharged through the liquid phase stream at the bottom of the mixed water flash tank (EV-101).

9. The method as described in claim 1, characterized in that: The use of heat coupling saves on utilities. Specifically, the top steam of the crotonaldehyde concentration tower (C-301) is used as the reboiling heat source for the acetaldehyde feed evaporator (E-101) and the ethyl acetate recovery tower (C-202); the outlet stream of the acetaldehyde recovery compressor (CP-101) is first used as the heat source for the reactor feed heater (E-103), and then as the heat source for the mixing water preheater (E-102); the top steam of the demethylcyclopentenone tower (C-502) is used as the heat source for the reboiler (E-201) of the acetaldehyde recovery tower.

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