Recovery method for improving decomposition rate of methyl acetate
By combining hydrolysis reaction and distillation separation technology, the decomposition process of methyl acetate was optimized, solving the problems of complex methyl acetate recovery process and high energy consumption, achieving efficient decomposition and recovery of methyl acetate, and reducing energy consumption and cost.
Patent Information
- Application Number
- CN202511251882.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-03
- Publication Date
- 2025-12-02
AI Technical Summary
Existing methyl acetate recovery processes are complex and energy-intensive, making it difficult to achieve effective energy conservation and consumption reduction.
A method combining hydrolysis reaction and distillation separation technology was adopted. By combining multi-stage distillation columns and hydrolysis reactors, the decomposition process of methyl acetate was optimized, including steps such as separation, extraction, dealdehyde removal and hydrolysis reaction of alcoholysis mother liquor, thereby improving the decomposition rate and recovery efficiency of methyl acetate.
It significantly improves the decomposition and recycling rate of methyl acetate, reduces energy consumption, simplifies the process, and lowers recycling costs.
Smart Images
Figure CN121044985A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of methyl acetate recovery technology, and more specifically to a recovery method for improving the decomposition rate of methyl acetate. Background Technology
[0002] Acetylene synthesis is currently the main method for polyvinyl alcohol (PVA) production in my country. However, the existing domestic processes for methyl acetate recovery involve long routes, complex operations, and huge energy consumption. Data shows that 50%-60% of the total energy consumption in a PVA plant is used in the recovery section, and the energy required for methyl acetate recovery accounts for about 70% of the recovery section's energy consumption. Therefore, improving the energy-saving and consumption-reducing level of alcoholysis mother liquor recovery technology is particularly necessary.
[0003] Currently, industrial methods for recovering methyl acetate mainly include extractive distillation, azeotropic distillation, membrane separation, and catalytic hydrolysis. Among these, extractive distillation and azeotropic distillation are the most widely used traditional processes. Extractive distillation separates methyl acetate from other components by adding a specific extractant to a methyl acetate-containing mixture, thereby altering the relative volatility of the components. Azeotropic distillation utilizes the property of methyl acetate forming azeotropes with other components in the system; by adding an azeotropic agent, the original azeotropic equilibrium is broken, thus achieving separation and recovery. However, these two distillation methods have significant drawbacks in practical applications: on the one hand, achieving ideal separation often requires multiple distillation operations, leading to complex processes and high equipment investment costs; on the other hand, the distillation process continuously consumes a large amount of steam to maintain the high-temperature separation conditions, resulting in persistently high energy consumption during the recovery process. In some companies, the energy consumption for methyl acetate recovery even accounts for more than 20% of their total production energy consumption, severely hindering the achievement of energy conservation and emission reduction goals. Summary of the Invention
[0004] The purpose of this invention is to provide a method for improving the decomposition rate of methyl acetate and to solve the following technical problems: How to improve the decomposition efficiency of methyl acetate and reduce the energy consumption cost of recycling.
[0005] The objective of this invention can be achieved through the following technical solutions: A method for improving the decomposition rate of methyl acetate recovery includes the following steps: Step 1: Send the alcoholysis mother liquor to column A. Send the first crude methyl acetate obtained from the top of column A to the top of column F for condensation and reflux. Then send the uncondensed gas phase to column B for extraction. Send the crude methanol obtained from the bottom of column B to the methanol refining column. Step 2: The second crude methyl acetate obtained from the top of column B is sent to column C for aldehyde removal, and the dilute methanol obtained from the bottom of the column is sent to the methanol refining column. Step 3: The acetaldehyde stream obtained from the top of column C is sent to column D for purification, and the dealdehyde methyl acetate obtained from the bottom of column C is sent to column E. Step 4: Collect the acetaldehyde product obtained from the top of column D, and send the methyl acetate stream obtained from the bottom of column D to column E; Step 5: The dealdehyde methyl acetate and methyl acetate stream in tower E are sent to the hydrolysis reactor for hydrolysis reaction. The reaction liquid is refluxed back to tower E. Part of the gas phase obtained at the top of the tower is condensed and refluxed back to the bottom of the tower, and the other part of the uncondensed gas phase is sent to tower C for circulation. The mixture in the bottom of the tower is sent to tower F for separation. Step 6: The gas phase obtained from the top of column F is sent to column B for circulation, and the liquid phase obtained from the bottom of column F is sent to the acetic acid purification column. Towers A, B, C, D, E, and F are all distillation towers.
[0006] Preferably, in step one, the alcoholysis mother liquor comes from the alcoholysis section of the acetylene synthesis process.
[0007] Preferably, in step one, the first crude methyl acetate is an azeotrope containing methyl acetate and methanol, wherein the mass fraction of methyl acetate in the azeotrope is 70-85% and the mass fraction of methanol is 20-30%.
[0008] Preferably, in step one, the crude methanol is a liquid phase containing methanol, sodium acetate and water.
[0009] Preferably, in step one, the extractant in column B is water, which can break the azeotropic reaction between methyl acetate and methanol, causing methyl acetate to move towards the top of the column, while methanol and water move together towards the bottom of the column.
[0010] Preferably, in step two, the mass fraction of methyl acetate in the second crude methyl acetate is 90-95%.
[0011] Preferably, in step two, the dilute methanol is a liquid phase containing methanol and water.
[0012] Preferably, the heat source for the reboiler of column C is provided by the overhead steam of the acetic acid refining column, which can achieve a significant energy-saving effect; it saves both steam consumption and the cooling energy required for condensing the gas phase.
[0013] Preferably, in step five, the operation method for sending the dealdehyde methyl acetate and methyl acetate streams in tower E to the hydrolysis reactor for hydrolysis reaction is as follows: the dealdehyde methyl acetate and methyl acetate streams are drawn from the upper side stream of tower E, pressurized by the side-drawing pump and mixed with water, and then sent to the hydrolysis liquid preheater for heating, and then enter the hydrolysis reactor for hydrolysis reaction.
[0014] Preferably, the hydrolysis reactor is a fixed-bed reactor.
[0015] Specifically, in the hydrolysis reactor, the hydrolysis reaction refers to the hydrolysis of methyl acetate in a strongly acidic cation exchange resin to produce acetic acid and methanol. The reaction equation is as follows: CH3COOCH3+ H2O ←→CH3OH+CH3COOH Since this reaction is a chemically reversible equilibrium reaction, in order to improve the hydrolysis rate of methyl acetate, a process combining reaction and distillation is adopted to continuously remove the products from the fixed-bed reactor to tower E, promoting the reaction to move in the forward direction. At the same time, since this reaction involves two substances, in order to ensure that the two substances are fully and uniformly mixed, a hydrolysis preheater is added before entering the fixed-bed reactor to mix and heat the materials, so as to achieve the effect of thorough mixing.
[0016] Research was conducted through software simulation, pilot testing, and trial production, ultimately determining that the above-mentioned feeding and discharging methods could improve the decomposition rate of methyl acetate.
[0017] Preferably, in step five, the bottom mixture is a mixture of acetic acid and methanol generated from the hydrolysis of methyl acetate, as well as unreacted water and methyl acetate.
[0018] The beneficial effects of this invention are: The present invention provides a method for improving the decomposition rate of methyl acetate. By combining hydrolysis reaction with distillation separation technology, the hydrolysis rate of methyl acetate can be significantly improved, the amount of methyl acetate recycled can be reduced, and the energy consumption of the process can be lowered. During the recovery process, methyl acetate, methanol, and acetaldehyde products are all recovered, which can improve the recovery and utilization rate, while also improving the hydrolysis efficiency of methyl acetate and the product yield. The recovery method is simple, has low energy consumption, and can greatly reduce the recovery cost. Attached Figure Description
[0019] The invention will now be further described with reference to the accompanying drawings.
[0020] Figure 1 This is a process flow diagram of the recovery method for improving the decomposition rate of methyl acetate according to the present invention. Detailed Implementation
[0021] This invention discloses a method for improving the decomposition rate of methyl acetate, comprising the following steps: Step 1: Send the alcoholysis mother liquor to column A. Send the first crude methyl acetate obtained from the top of column A to the top of column F for condensation and reflux. Then send the uncondensed gas phase to column B for extraction. Send the crude methanol obtained from the bottom of column B to the methanol refining column. Preferably, the mother liquor from the alcoholysis stage of the acetylene synthesis process is from the alcoholysis stage; the first crude methyl acetate is an azeotrope containing methyl acetate and methanol, wherein the mass fraction of methyl acetate in the azeotrope is 70-85% and the mass fraction of methanol is 20-30%; the crude methanol is a liquid phase containing methanol, sodium acetate and water; the extractant in column B is water, which can break the azeotropic effect of methyl acetate and methanol, causing methyl acetate to move to the top of the column, while methanol and water move together to the bottom of the column.
[0022] Step 2: The second crude methyl acetate obtained from the top of column B is sent to column C for aldehyde removal, and the dilute methanol obtained from the bottom of the column is sent to the methanol refining column. Preferably, the mass fraction of methyl acetate in the second crude methyl acetate is 90-95%; the dilute methanol is a liquid phase containing methanol and water.
[0023] Step 3: The acetaldehyde stream obtained from the top of column C is sent to column D for purification, and the dealdehyde methyl acetate obtained from the bottom of column C is sent to column E. Preferably, the heat source for the reboiler of column C is provided by the overhead steam from the acetic acid refining column.
[0024] Step 4: Collect the acetaldehyde product obtained from the top of column D, and send the methyl acetate stream obtained from the bottom of column D to column E; Step 5: The dealdehyde methyl acetate and methyl acetate stream in tower E are sent to the hydrolysis reactor for hydrolysis reaction. The reaction liquid is refluxed back to tower E. Part of the gas phase obtained at the top of the tower is condensed and refluxed back to the bottom of the tower, and the other part of the uncondensed gas phase is sent to tower C for circulation. The mixture in the bottom of the tower is sent to tower F for separation. Preferably, the operation method for sending the dealdehyde methyl acetate and methyl acetate stream in tower E to the hydrolysis reactor for hydrolysis reaction is as follows: the dealdehyde methyl acetate and methyl acetate stream are drawn from the upper side stream of tower E, pressurized by the side-drawing pump and mixed with water, and then sent to the hydrolysis liquid preheater for heating, and then enter the hydrolysis reactor for hydrolysis reaction. Preferably, the bottom mixture is a mixture of acetic acid and methanol generated from the hydrolysis of methyl acetate, as well as unreacted water and methyl acetate.
[0025] Step 6: The gas phase obtained from the top of column F is sent to column B for circulation, and the liquid phase obtained from the bottom of column F is sent to the acetic acid purification column. Towers A, B, C, D, E, and F mentioned above are all distillation towers.
[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.
[0028] Example 1
[0029] Please see Figure 1 This embodiment provides a method for improving the decomposition rate of methyl acetate. Taking the recovery within 24 hours as an example, the method includes the following steps.
[0030] Step 1: Starting at 8:00 AM the previous day, the mother liquor from the alcoholysis section of the acetylene synthesis process is discharged at 88.0 m³ / min. 3 The feed is sent to distillation column A at a rate of / h. Column A has a pressure of 53.6 kPa, a top temperature of 52°C, a middle temperature of 58°C, a bottom temperature of 73°C, and a reflux flow rate of 45.0 m³ / h. 3 / h; The mass fractions of the components in the alcoholysis mother liquor were determined to be: methanol 69.85%, methyl acetate 27.82%, sodium acetate 0.29%, acetaldehyde 0.01%, and water 0.53%; The top of column A yields an azeotrope containing methyl acetate and methanol, namely the first crude methyl acetate; the bottom of column A yields crude methanol; the first crude methyl acetate obtained from the top of column A is first sent to the top of column F for condensation and reflux, and then the uncondensed gas phase is sent to column B for extraction; the crude methanol obtained from the bottom of column A is sent to the methanol refining column.
[0031] Step 2: The feed rate for tower B is 15.3m³. 3 / h, extraction water is 29.0m 3 / h, tower pressure 13.6 kPa, top temperature 52℃, middle temperature 67℃, bottom temperature 83℃, reflux flow rate 5.0 m³ / h. 3 / h; The top of column B yields a second crude methyl acetate, and the bottom of column B yields dilute methanol; The second crude methyl acetate obtained from the top of column B is sent to column C for aldehyde removal; The dilute methanol obtained from the bottom of column B is sent to the methanol refining column, so the crude methanol obtained from the bottom of column A and the dilute methanol obtained from the bottom of column B are both sent to the methanol refining column for refining.
[0032] Step 3: The air blowing pressure of tower C is 25.0 kPa, and the air blowing rate is 4600 Nm³. 3 / h, feed temperature 54℃, tower pressure 22.0KPa, top temperature 54℃, middle temperature 58℃, bottom temperature 59℃; acetaldehyde stream is obtained at the top of tower C, and dealdehyde methyl acetate is obtained at the bottom of tower C; the acetaldehyde stream obtained at the top of tower C is sent to tower D for purification, and the dealdehyde methyl acetate obtained at the bottom of tower C is sent to tower E. Step 4: The feed rate for tower D is 0.6m³. 3 / h, tower pressure is 5.3KPa, top temperature is 20.3℃, middle temperature is 52.1℃, bottom temperature is 53.2℃; acetaldehyde product is obtained at the top of tower D, and methyl acetate stream is obtained at the bottom of tower D; the acetaldehyde product obtained at the top of tower D is collected, and the methyl acetate stream obtained at the bottom of tower D is sent to tower E. Step 5: The feed rate of the methyl acetate and methyl acetate streams in tower E is 45.0 m³. 3 / h, the amount of water decomposed is 10.0m 3 At a rate of 4.0 m / h, the deformed methyl acetate and methyl acetate streams in column E are sent to the hydrolysis reactor for hydrolysis. The reaction liquid is refluxed back to column E. The column pressure of column E is 5.3 kPa, the gas blowing pressure is 24.1 kPa, the top temperature is 20.3℃, the middle temperature is 52.1℃, and the bottom temperature is 53.2℃. A portion of the gas phase obtained from the top of column E is condensed and refluxed back to the bottom of the column at a rate of 4.0 m / h, while the other portion of the uncondensed gas phase is sent to column C for circulation. The mixture obtained from the bottom of column E is sent to column F for separation. Step 6: The feed rate for tower F is 55.2 m³. 3 / h, return flow rate is 50.3m 3 / h, gas blowing pressure is 33.1KPa, tower pressure is 55.6KPa, top temperature is 58.4℃, middle temperature is 104.1℃, bottom temperature is 107.2℃; the gas phase obtained from the top of tower F is sent to tower B for circulation, and the liquid phase obtained from the bottom of the tower is sent to the acetic acid refining tower.
[0033] Towers A, B, C, D, E, and F mentioned above are all distillation towers.
[0034] The recycling method in this embodiment runs from 8:00 AM the day before to 6:00 AM the next day. During the recycling process, samples are taken and tested at 10:00 AM and 4:00 PM the day before, as detailed below.
[0035] The first crude methyl acetate obtained from the top of column A and the crude methanol obtained from the bottom of column A were sampled and tested to determine the mass fraction of methyl acetate in the first crude methyl acetate and the mass fraction of methyl acetate in the crude methanol. The test results are listed in Table 1 below: Table 1 Sampling and testing results of Tower A
[0036] Samples were taken from the second crude methyl acetate obtained at the top of column B and the dilute methanol obtained at the bottom of the column for testing. The mass fraction of methyl acetate in the second crude methyl acetate and the mass fraction of methyl acetate in the dilute methanol were tested, and the test results are listed in Table 2 below: Table 2 Sampling and testing results of Tower B
[0037] The deformaldehyde methyl acetate obtained from the bottom of column C was sampled and tested to determine the mass fraction of methyl acetate and acetaldehyde. The test results are listed in Table 3 below: Table 3 Sampling and testing results of tower C
[0038] Samples were taken from the acetaldehyde product obtained at the top of column D and the ethyl acetate stream obtained from the bottom of column D for testing. The mass fraction of acetaldehyde in the acetaldehyde product and the mass fraction of acetaldehyde in the methyl acetate stream were tested, and the test results are listed in Table 4 below: Table 4 Sampling and testing results of tower D
[0039] The mixture obtained from the bottom of column E was sampled and tested to determine the decomposition rate of the hydrolysis reaction. The test results are listed in Table 5 below: Table 5 Sampling and testing results for Tower E
[0040] The gas phase obtained from the top of column F and the liquid phase obtained from the bottom of column F were sampled and tested to determine the mass fractions of acetic acid and methyl acetate in the gas phase and the mass fractions of acetic acid and methanol in the liquid phase. The test results are listed in Table 6 below: Table 6 Sampling and testing results of tower F
[0041] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.
Claims
1. A method for improving the decomposition rate of methyl acetate during recovery, characterized in that, Includes the following steps: Step 1: Send the alcoholysis mother liquor to column A. Send the first crude methyl acetate obtained from the top of column A to the top of column F for condensation and reflux. Then send the uncondensed gas phase to column B for extraction. Send the crude methanol obtained from the bottom of column B to the methanol refining column. Step 2: The second crude methyl acetate obtained from the top of column B is sent to column C for aldehyde removal, and the dilute methanol obtained from the bottom of the column is sent to the methanol refining column. Step 3: The acetaldehyde stream obtained from the top of column C is sent to column D for purification, and the dealdehyde methyl acetate obtained from the bottom of column C is sent to column E. Step 4: Collect the acetaldehyde product obtained from the top of column D, and send the methyl acetate stream obtained from the bottom of column D to column E; Step 5: The dealdehyde methyl acetate and methyl acetate stream in tower E are sent to the hydrolysis reactor for hydrolysis reaction. The reaction liquid is refluxed back to tower E. Part of the gas phase obtained at the top of the tower is condensed and refluxed back to the bottom of the tower, and the other part of the uncondensed gas phase is sent to tower C for circulation. The mixture in the bottom of the tower is sent to tower F for separation. Step 6: The gas phase obtained from the top of column F is sent to column B for circulation, and the liquid phase obtained from the bottom of column F is sent to the acetic acid purification column. Towers A, B, C, D, E, and F are all distillation towers.
2. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, In step one, the alcoholysis mother liquor comes from the alcoholysis section of the acetylene synthesis process.
3. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, In step one, the first crude methyl acetate is an azeotrope containing methyl acetate and methanol, wherein the mass fraction of methyl acetate in the azeotrope is 70-85% and the mass fraction of methanol is 20-30%.
4. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, In step one, the crude methanol is a liquid phase containing methanol, sodium acetate, and water.
5. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, In step one, the extractant in tower B is water.
6. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, In step two, the mass fraction of methyl acetate in the second crude methyl acetate is 90-95%.
7. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, In step two, the dilute methanol is a liquid phase containing methanol and water.
8. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, The heat source for the reboiler in column C is provided by the overhead steam from the acetic acid refining column.
9. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, In step five, the operation method for sending the dealdehyde methyl acetate and methyl acetate streams in tower E to the hydrolysis reactor for hydrolysis reaction is as follows: the dealdehyde methyl acetate and methyl acetate streams are drawn from the upper side stream of tower E, pressurized by the side-drawing pump and mixed with water, and then sent to the hydrolysis liquid preheater for heating, and then enter the hydrolysis reactor for hydrolysis reaction.
10. The method for improving the decomposition rate of methyl acetate according to claim 1, characterized in that, In step five, the bottom mixture is a mixture of acetic acid and methanol generated from the hydrolysis of methyl acetate, as well as unreacted water and methyl acetate.