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CN-116854577-B - Method and device for producing crotonaldehyde by catalyzing gas-phase acetaldehyde through Zr-beta molecular sieve

CN116854577BCN 116854577 BCN116854577 BCN 116854577BCN-116854577-B

Abstract

The invention relates to a method and a device for producing crotonaldehyde by catalyzing gas-phase acetaldehyde by using a Zr-beta molecular sieve, and a process for producing crotonaldehyde by catalyzing gas-phase acetaldehyde by using the Zr-beta molecular sieve. The production of high-purity crotonaldehyde is realized through the condensation reaction and heat exchange system, the acetaldehyde recovery system, the crotonaldehyde refining system and the azeotrope separation system, the strong acid and strong alkali catalyst used in the traditional homogeneous phase method is replaced, the corrosion to equipment is avoided, the service life of the equipment is greatly prolonged, and the investment cost is reduced. The invention adopts the filling type fixed bed reactor, thoroughly solves the problems that sodium hydroxide is used for catalysis in the traditional process, and the wastewater contains a large amount of sodium salt, which is not friendly to the environment. The MCP stripping process is provided, the process is optimized, and the energy consumption is reduced. The selectivity of the main product crotonaldehyde is maintained between 90% and 95%.

Inventors

  • GENG ZHONGFENG
  • WANG LINGTAO
  • YANG GUOCHAO
  • JIANG HAOXI
  • ZHANG MINHUA

Assignees

  • 天津大学

Dates

Publication Date
20260512
Application Date
20230621

Claims (9)

  1. A method for producing crotonaldehyde by catalyzing gas-phase acetaldehyde by using a Zr-beta molecular sieve is characterized in that the technology for producing crotonaldehyde by catalyzing gas-phase acetaldehyde by using the Zr-beta molecular sieve; the process flow comprises the steps of mixing an acetaldehyde raw material with circulating recycle water after evaporating by an acetaldehyde evaporator (E-101), heating by a reactor feed heater (E-103), feeding the mixture into a condensation reactor (R-101), loading Zr-beta molecular sieve catalyst by using a fixed bed filling reactor, wherein the mass space velocity is 0.25h -1 , feeding an outlet flow of the condensation reactor (R-101) into a crotonaldehyde concentrating tower (C-301) after recovering acetaldehyde by using an acetaldehyde recovery tower (C-201), feeding the mixture into the crotonaldehyde concentrating tower (C-401) for refining, extracting crotonaldehyde product from a tower kettle, feeding a gas part at the top of the acetaldehyde recovery tower (C-201) for condensing butadiene in a side line discharging flow, feeding a flow containing ethyl acetate extracted from the acetaldehyde recovery tower (C-201) into an ethyl acetate recovery tower (C-202) for extracting flow, extracting an oil phase part from the crotonaldehyde refining tower (C-401) for extracting ethanol as a flow after condensing and phase separation, feeding methyl cyclopentenone (C-502) into a water tower top for extracting water, and a methyl cyclopentenone (C-501) after condensing part of water gas and methyl cyclopentenone, and feeding the mixture into a flash evaporation tower (C-502), mixing and heating the steam at the top of the tank and the acetaldehyde raw material, then entering a condensation reactor (R-101) for reaction, and discharging wastewater containing acetic acid and sorbic acid at the bottom of the tank.
  2. 2. The apparatus for realizing the method for producing crotonaldehyde by using Zr-beta molecular sieve to catalyze gas-phase acetaldehyde according to claim 1, which is characterized by comprising a condensation reaction and heat exchange system, an acetaldehyde recovery system, a crotonaldehyde refining system and an azeotrope separation system, wherein the condensation reaction and heat exchange system mainly comprises a raw material 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 comprises an acetaldehyde recovery tower (C-201) and an ethyl acetate recovery tower (C-202), the crotonaldehyde refining system comprises a crotonaldehyde concentration tower (C-301), a crotonaldehyde refining tower (C-401) and a dehydration tower (C-501), the azeotrope separation system comprises a demethylcyclopentenone tower (C-501), the discharging of the condensation reactor (R-101) is connected with the acetaldehyde recovery tower (C-201), the side line of the acetaldehyde recovery tower (C-201) is connected with the ethyl acetate recovery tower (C-202), the acetaldehyde recovery tower (C-201) is connected with the crotonaldehyde concentration tower (C-301), the crotonaldehyde concentration tower (C-301) is connected with the crotonaldehyde refining tower (C-401), the tower bottom pipeline is connected with a demethyl cyclopentenone tower (C-502), the tower top pipeline of a crotonaldehyde refining tower (C-401) is connected with a dehydration tower (C-501), a mixed water flash tank (EV-101) is used for mixing gas phase and acetaldehyde raw materials, heating the mixture by a reactor feeding heater E-103, then feeding the mixture into a condensation reactor (R-101), recycling acetaldehyde from an outlet stream of the condensation reactor (R-101) by an acetaldehyde recycling tower (C-201), feeding the mixture into a crotonaldehyde concentrating tower (C-301) for concentrating, and then feeding the mixture into the crotonaldehyde refining tower (C-401) for refining, and the crotonaldehyde product is extracted from the tower bottom.
  3. 3. The method of claim 1, wherein the process is provided with recycling of raw materials acetaldehyde and water, an outlet stream of the condensation reactor (R-101) enters an acetaldehyde recovery compressor (CP-101) to lift stream pressure and then enters an acetaldehyde recovery tower (C-201) to be rectified, overhead gas-phase acetaldehyde is returned to the condensation reactor (R-101) to react, wherein the outlet pressure of the acetaldehyde recovery compressor (CP-101) is 2-5.5 bar, the acetaldehyde recovery tower (C-201) is provided with 27-34 theoretical plates, water is recycled through a dehydration tower (C-501) and a demethylated cyclopentenone tower (C-502) tower kettle stream and is mixed and then enters a mixed water flash tank (EV-101), and mixed water flash steam phase discharge returns to the condensation reactor (R-101) to be used as a diluent.
  4. 4. The method of claim 1, wherein water produced by the system is recycled as a diluent to inhibit carbon deposition on the catalyst, improve process selectivity and extend catalyst life, and the ratio of acetaldehyde to water in the reactor feed is 1:9 to 9:1.
  5. 5. The method of claim 1, wherein the crotonaldehyde refining system comprises a crotonaldehyde concentrating tower (C-301), a crotonaldehyde refining tower (C-401) and a dehydrating tower (C-501), wherein an acetaldehyde recovery tower (C-201) tower bottom stream sequentially passes through the crotonaldehyde concentrating tower (C-301) and the crotonaldehyde refining tower (C-401) for rectification, the crotonaldehyde product is extracted from the crotonaldehyde refining tower (C-401) tower bottom, a concentrating tower separator (SP-301) and a refining tower separator (SP-401) are respectively arranged at the two tower tops, oil phase reflux is adopted, water phase enters the dehydrating tower (C-501) for treatment, 22-28 theoretical plates are arranged in the crotonaldehyde concentrating tower (C-301), 40-45 theoretical plates are arranged in the crotonaldehyde refining tower (C-401), and 18-25 theoretical plates are arranged in the dehydrating tower (C-501).
  6. 6. The method according to claim 1, wherein the impurity butadiene is discharged from a gas phase of the acetaldehyde recovery column (C-201) after partial vapor is condensed in the butadiene condenser (E-202), a stream containing ethyl acetate impurity is withdrawn from the side line of the acetaldehyde recovery column (C-201), after the acetaldehyde is recovered in the top of the ethyl acetate recovery column (C-202), crude ethyl acetate is discharged through a column bottom, and the number of trays of the ethyl acetate recovery column (C-202) is set to 6-10 theoretical plates.
  7. 7. The process of claim 1 wherein methylcyclopentenone is partially withdrawn after reflux by vapor phase condensation at the top of the demethylcyclopentenone column (C-502) while a portion of the acetic acid impurities is withdrawn.
  8. 8. The method according to claim 1, characterized in that the impurity sorbic acid is discharged through a mixed water flash tank (EV-101) tank bottom liquid phase stream.
  9. 9. The method according to claim 1, wherein heat coupling is used to save public works, specifically, the top steam of the crotonaldehyde concentrating tower (C-301) is used as a reboiling heat source at the bottom of the acetaldehyde raw material evaporator (E-101) and the ethyl acetate recovery tower (C-202), the outlet stream of the acetaldehyde recovery compressor (CP-101) is used as a heat source of a reactor feeding heater (E-103) and a heat source of a remixing water preheater (E-102), and the top steam of the demethylcyclopentenone tower (C-502) is used as a heat source of an acetaldehyde recovery tower reboiler (E-201).

Description

Method and device for producing crotonaldehyde by catalyzing gas-phase acetaldehyde through Zr-beta molecular sieve Technical Field The invention belongs to the field of crotonaldehyde production, and particularly relates to a method and a device for producing crotonaldehyde by catalyzing gas phase acetaldehyde through a Zr-beta molecular sieve. Background Crotonaldehyde, also known as trans-2-crotonaldehyde, is an important fine chemical raw material and has very wide application, and mainly comprises the preparation of crotonic acid, butyraldehyde, butanol, butyric acid, C8 compounds, sorbic acid and the like. Because sorbic acid has excellent safety as a food additive, with the improvement of food safety consciousness in recent years, sorbic acid has a trend of replacing sodium benzoate to become the most important food additive, and in the foreseeable future, the demand of sorbic acid for crotonaldehyde has a steadily increasing development trend, so that the preparation of sorbic acid has become the largest consumption field of crotonaldehyde, and the production force of crotonaldehyde is imperative to be enhanced. The production process mainly comprises a condensation tower, a dehydration tower and a crotonaldehyde refining section, wherein two molecules of acetaldehyde are subjected to aldol condensation reaction in the condensation tower under the action of an alkaline catalyst to generate 3-hydroxybutanal, the 3-hydroxybutanal is neutralized by acetic acid and then is sent to the dehydration tower to be subjected to dehydration reaction, and further, the dehydration is performed under acidic conditions by heating to generate crotonaldehyde, the obtained crotonaldehyde crude product also comprises water, 3-hydroxybutanal, sodium acetate and other high-boiling-point byproducts, the crotonaldehyde crude product is distilled from the top of the tower in the form of azeotrope after being primarily distilled from the crotonaldehyde rectifying tower, separated by a decanter at the top of the tower, and the secondary crotonaldehyde phase is sent to the rectifying tower to be rectified, and the product crotonaldehyde is extracted from the side line of the tower in the form of gas phase. The homogeneous process for producing crotonaldehyde has the disadvantages of low single pass conversion rate, high requirement on raw material purity, strong equipment corrosion property of acid-base solution on equipment, difficult separation of catalyst and product, large amount of salt-containing wastewater production, etc. Aiming at the problems, patent 200610016599 discloses a crotonaldehyde production method and a crotonaldehyde production device, compared with the traditional production method, a distillation tower is added, dehydration tower kettle waste water and rectification tower kettle waste water are sent into the distillation tower kettle, total reflux is carried out on the tower top, and materials extracted from the side line of the tower are sent into the dehydration tower and are further recovered through the rectification tower. The method improves the crotonaldehyde yield by 1%, and reduces the COD content of the wastewater discharged by the system by 50%. Patent 200610001278 discloses an improved process for producing crotonaldehyde, which comprises condensing acetaldehyde under the catalysis of organic amine to generate 2-hydroxy butyraldehyde, dehydrating under acidic condition to generate crotonaldehyde, and reducing corrosiveness to equipment by using organic amine instead of traditional strong base as catalyst for aldol condensation reaction. However, the problem of generating a large amount of salt-containing wastewater still exists, and the increasingly improved environmental protection requirements are not met. For the research of molecular sieve catalysts, patent 202210567638.8 of the subject group discloses a hierarchical pore beta molecular sieve with an ordered mesoporous structure, a preparation method and application thereof, and provides a hierarchical pore beta molecular sieve with an ordered mesoporous structure, which is obtained by taking quaternary ammonium base and long-chain quaternary ammonium salt as templates in one step. The patent 202211258742.5 discloses a heteroatom beta molecular sieve for low-carbon aldol condensation and a preparation method thereof, wherein the molecular sieve has a BEA structure, the heteroatom contained in the molecular sieve is one or a combination of a plurality of types of Ti, sn, zr, ta, ce, hf, Y, nb, V, zn, sc, fe, the metal content is 10:1-1000:1 in terms of the molar ratio (Si/M) of silicon to metal, and the metal exists in the form of molecular sieve skeleton sites. The method creates a foundation for the process of preparing crotonaldehyde by catalyzing the molecular sieve. Disclosure of Invention In order to thoroughly solve a plurality of problems existing in the production process of preparing crotonaldehyde by homogeneously catalyzing ace