Method for preparing allyl acetate and recovering propene
By using the synergistic operation of equipment such as reactors, absorption towers, condensers, compressors, and distillation towers in the allyl acetate production process, the problem of low single-pass conversion rate of propylene has been solved, enabling the recovery and recycling of propylene and reducing production costs.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ZHEJIANG HUANGMA TECH CO LTD
- Filing Date
- 2025-11-06
- Publication Date
- 2026-05-21
Smart Images
Figure CN2025132903_21052026_PF_FP_ABST
Abstract
Description
Method for preparing allyl acetate and recovering propylene Technical Field
[0001] This invention relates to the field of allyl acetate preparation technology, and more specifically to a method for preparing allyl acetate and recovering propylene. Background Technology
[0002] Allyl acetate is an important fine chemical with a wide range of applications. Currently, the main method for producing allyl acetate worldwide uses propylene, acetic acid, and oxygen as raw materials, catalyzed by a metal Pd catalyst. However, the single-pass conversion rate of propylene in the allyl acetate production process is low (<20%), and a certain amount of unreacted propylene dissolves in the crude allyl acetate, resulting in low utilization of the reactants and consequently increased production costs. Summary of the Invention
[0003] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing allyl acetate and recovering propylene. The method provided in this application is beneficial to improving the utilization rate of raw materials and reducing production costs.
[0004] To solve the above problems, the technical solution adopted by the present invention is as follows:
[0005] A method for preparing allyl acetate and recovering propylene includes the following steps:
[0006] A gaseous feedstock is introduced into a reactor to react and generate allyl acetate. The gaseous feedstock includes propylene, acetic acid, oxygen, and an inert gas.
[0007] The material discharged from the bottom of the reactor is condensed using a condenser, so that the condensed material is discharged into the bottom of the absorption tower.
[0008] The first compressor is used to pump the gas in the material from the top of the absorption tower back into the reactor, and the liquid in the material is discharged from the bottom of the absorption tower into the crude product storage tank.
[0009] The second compressor is used to pump the gas in the material from the crude product storage tank back to the bottom of the absorption tower, and the liquid in the material is discharged from the crude product storage tank into the distillation tower for separation.
[0010] The gas separated by the gas-liquid separator connected to the top of the distillation column is introduced into the crude product storage tank, and the second compressor also pumps the gas recovered from the gas-liquid separator into the crude product storage tank.
[0011] In some possible implementations, the reaction temperature inside the reactor is 140-220°C, and the reaction pressure is 0.6-1.0 MPa.
[0012] In some possible embodiments, the volume ratio of propylene, acetic acid, and oxygen in the gaseous feedstock is 1:0.1-0.3:0.1-0.3, the volume of the inert gas accounts for less than or equal to 50% of the total volume of the gaseous feedstock, and the volume hourly space velocity of the gaseous feedstock is 1500-2500 h⁻¹. -1 .
[0013] In some possible implementations, the operating pressure of the absorption tower is 0.5-0.9 MPa, and the temperature of the material discharged from the bottom of the absorption tower is controlled at 30-60°C.
[0014] In some possible implementations, the gas-liquid separator operates at atmospheric pressure and the separation temperature is controlled at 60-90°C.
[0015] In some possible implementations, the following steps are also included:
[0016] An absorbent liquid is introduced from the top of the absorption tower to absorb uncondensed allyl acetate vapor.
[0017] In some possible implementations, the distillation column operates at atmospheric pressure.
[0018] In some possible implementations, the first compressor is a centrifugal compressor or an axial compressor.
[0019] In some possible implementations, the second compressor is one of a liquid ring compressor, a reciprocating compressor, or a screw compressor.
[0020] In some possible implementations, the reactor is a tubular reactor.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0022] In this application, through the coordinated operation of the reactor, absorption tower, condenser, first compressor, crude product storage tank, second compressor, distillation tower and gas-liquid separator, the gas discharged along with allyl acetate is condensed, separated and pumped, and the flash-distilled propylene can be pumped back into the reactor for reaction, thereby improving the utilization rate of raw materials and reducing production costs.
[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description
[0024] Figure 1 is a flowchart of a method for preparing allyl acetate and recovering propylene according to an embodiment of this application;
[0025] Figure 2 is a connection diagram of the system corresponding to the method of this application;
[0026] Figure 3 is a schematic diagram of the system corresponding to Comparative Example 1;
[0027] Figure 4 is a schematic diagram of the system corresponding to Comparative Example 2.
[0028] Explanation of reference numerals: 10-Reactor; 11-Second Pipeline; 12-First Pipeline; 20-Absorber; 21-Third Pipeline; 22-Fourth Pipeline; 23-Eleventh Pipeline; 30-Condenser; 40-First Compressor; 50-Crude Product Storage Tank; 51-Fifth Pipeline; 52-Sixth Pipeline; 60-Second Compressor; 70-Distillation Column; 71-Eighth Pipeline; 72-Seventh Pipeline; 80-Gas-Liquid Separator; 81-Ninth Pipeline; 83-Tenth Pipeline. Detailed Implementation
[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0030] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. It should be noted that when an element is referred to as "fixed to" another element, it may be directly on the other element or there may be an intervening element. When an element is referred to as "connected to" another element, it may be directly connected to the other element or there may be an intervening element. When an element is referred to as "disposed on" another element, it may be disposed on the other element or there may be an intervening element.
[0031] Referring to Figures 1 and 2, an embodiment of this application provides a method for preparing allyl acetate and recovering propylene, comprising the following steps.
[0032] Step S101: A gaseous feedstock is introduced into reactor 10 to react and generate allyl acetate. The gaseous feedstock includes propylene, acetic acid, oxygen, and an inert gas. For example, the inert gas may include either carbon dioxide or nitrogen. Reactor 10 may be equipped with a suitable catalyst, such as Pd.
[0033] In some embodiments, the reaction temperature inside the reactor 10 is 140-220°C, and the reaction pressure is 0.6-1.0 MPa.
[0034] In some embodiments, the volume ratio of propylene, acetic acid, and oxygen in the gaseous feedstock is 1:0.1-0.3:0.1-0.3, the volume of inert gas accounts for less than or equal to 50% of the total volume of the gaseous feedstock, and the volume hourly space velocity of the gaseous feedstock is 1500-2500 h⁻¹. -1 The process parameters set within reactor 10 are beneficial for increasing the yield of allyl acetate.
[0035] Specifically, the top of the reactor 10 is connected to a first pipe 12, through which gaseous raw materials can be introduced into the reactor 10.
[0036] In step S102, the material discharged from the bottom of the reactor 10 is condensed using the condenser 30, so that the condensed material is discharged into the bottom of the absorption tower 20. At this time, the material entering the absorption tower 20 includes at least allyl acetate and propylene, and may also include inert gas.
[0037] Specifically, the bottom of the absorption tower 20 is connected to the bottom of the reactor 10 via the second pipe 11, and the condenser 30 is installed on the second pipe 11. The condenser 30 is used to condense the material discharged from the reactor 10.
[0038] In some embodiments, an absorbent is introduced from the top of the absorption tower 20. The absorbent is used to absorb uncondensed allyl acetate vapor. Exemplarily, the absorbent can be an aqueous acetic acid solution or acetic acid. The mass fraction of acetic acid in the aqueous acetic acid solution is greater than or equal to 50%.
[0039] Specifically, the top of the absorption tower 20 is also connected to an eleventh pipe 23 for feeding the absorbent liquid. The absorbent liquid is used to absorb uncondensed product vapor, thereby improving the process yield. At the same time, it reduces the possibility of product vapor being pumped into the reactor 10, which in turn helps to improve the lifespan of the catalyst in the reactor 10.
[0040] In step S103, the first compressor 40 is used to pump the gas in the material from the top of the absorption tower 20 back into the reactor 10, and the liquid in the material is discharged from the bottom of the absorption tower 20 into the crude product storage tank 50.
[0041] In some embodiments, the operating pressure of the absorption tower 20 is 0.5-0.9 MPa, and the temperature of the material discharged from the bottom of the absorption tower 20 is controlled at 30-60°C. The process parameters of the absorption tower 20 are conducive to reducing the gas throughput, thereby reducing the number of trays and the tower diameter, which in turn helps to reduce the investment cost of the process equipment. In addition, reducing the gas throughput also helps to reduce the pumping power of the first compressor 40, which also helps to further reduce the recovery cost.
[0042] Specifically, the top of the absorption tower 20 is connected to the first pipe 12 via a third pipe 21. A first compressor 40 is installed on the third pipe 21 and is used to pump the gas in the absorption tower 20 into the reactor 10 for reaction, thereby realizing the recovery of the gas, including propylene. The crude product storage tank 50 is connected to the bottom of the absorption tower 20 via a fourth pipe 22.
[0043] In step S104, the second compressor 60 is used to pump the gas in the material from the crude product storage tank 50 back to the bottom of the absorption tower 20, and the liquid in the material is discharged from the crude product storage tank 50 into the distillation tower 70 for separation.
[0044] Specifically, the crude product storage tank 50 is connected to the bottom of the absorption tower 20 via a fifth pipe 51. Observing the absorption tower 20, the access point of the fifth pipe 51 is higher than the access point of the fourth pipe 22. The access point of the fifth pipe 51 can be above the liquid phase space at the bottom of the tower and below the packing inside the absorption tower. For example, both the fourth pipe 22 and the fifth pipe 51 can be connected to the top of the crude product storage tank 50. The second compressor 60 is installed on the fifth pipe 51. The second compressor 60 is used to pump the gas in the crude product storage tank 50 into the absorption tower 20. This gas is also pumped by the first compressor 40 into the reactor 10 for reaction, thereby further recovering the gas. The middle part of the distillation column 70 is connected to the crude product storage tank 50 via a sixth pipe 52. The bottom of the distillation column 70 is provided with a seventh pipe 72 for draining liquid. Some of the condensate in the distillation column 70 can be discharged from the seventh pipe 72. For example, the condensed absorbent can be discharged from the seventh pipe 72. The gas-liquid separator 80 is connected to the distillation column 70 via at least two eighth pipes 71 for separating the distilled material and for reflux of the distillation column 70.
[0045] At this point, the absorbent and the product enter the distillation column 70 together for distillation separation. The heavy components of the absorbent are concentrated at the bottom of the distillation column 70, while the light components of the product (containing dissolved propylene) are concentrated at the top of the distillation column 70. This process not only separates the absorbent but also increases the concentration of propylene, thereby increasing the propylene recovery rate.
[0046] In some embodiments, the operating pressure of the distillation column 70 is atmospheric pressure.
[0047] In step S105, the gas separated by the gas-liquid separator 80 connected to the top of the distillation column 70 is introduced into the crude product storage tank 50, and the second compressor 60 also pumps the gas recovered from the gas-liquid separator 80 into the crude product storage tank 50.
[0048] In some embodiments, the gas-liquid separator 80 operates at atmospheric pressure and the separation temperature is controlled between 60-90°C. The process parameters of the gas-liquid separator 80 are conducive to reducing the solubility of propylene in the material, thereby facilitating a further increase in the propylene recovery rate.
[0049] Specifically, the gas-liquid separator 80 is connected to the crude product storage tank 50 via a ninth pipe 81 to introduce the separated gas into the crude product storage tank 50. For example, the gas-liquid separator 80 can be connected to the top of the crude product storage tank 50 via the ninth pipe 81, allowing the gas separated by the gas-liquid separator 80 to be pumped into the reactor 10 via the first compressor 40 and the second compressor 60, thereby achieving further gas recovery. The bottom of the gas-liquid separator 80 is connected to a tenth pipe 83 to discharge a portion of the separated material. At this time, the liquid discharged from the gas-liquid separator 80 is sent to a downstream separation tower for further purification of allyl acetate.
[0050] In some embodiments, the reactor 10, the absorption tower 20, the crude product storage tank 50, the distillation tower 70, and the gas-liquid separator 80 can be arranged in sequence, thereby reducing the system's layout space.
[0051] In some embodiments, the first compressor 40 is a centrifugal compressor or an axial compressor, and the second compressor 60 is one of a liquid ring compressor, a reciprocating compressor, or a screw compressor. The selection of the types of the first compressor 40 and the second compressor 60 can take into account the advantages of low equipment cost and high pumping efficiency, thereby also helping to further reduce production costs.
[0052] In some embodiments, reactor 10 is a tubular reactor, which has the advantages of good heat transfer performance and good mixing performance.
[0053] In another embodiment, a batch reactor, a tower reactor, or a jet reactor may be selected depending on the reaction type.
[0054] For example, the absorption tower 20 can be one of a packed tower, a plate tower, or a valve tower.
[0055] In this application, through the coordinated operation of reactor 10, absorption tower 20, condenser 30, first compressor 40, crude product storage tank 50, second compressor 60, distillation tower 70 and gas-liquid separator 80, the gas discharged along with propylene acetate is condensed, separated and pumped, and the flash-distilled propylene can be pumped back into reactor 10 for reaction, thereby improving the utilization rate of raw materials and reducing production costs.
[0056] Specifically:
[0057] Example 1:
[0058] A gaseous feedstock, comprising propylene, acetic acid, oxygen, and an inert gas, is introduced into reactor 10. Reactor 10 contains a Pd catalyst. Reactor 10 is a tubular reactor. The propylene:acetic acid:oxygen:inert gas ratio is 1:0.23:0.15:0.88 (volume ratio). The inert gas can be carbon dioxide. The operating conditions of reactor 10 are: reaction temperature 146℃, reaction pressure 0.68MPa, and gas hourly space velocity (VHSV) of the gaseous feedstock 2000 h⁻¹. -1 The material discharged from the bottom of reactor 10 is condensed using condenser 30, and the condensed material is then discharged into the bottom of absorption tower 20. A 50% acetic acid aqueous solution (absorbent) is introduced into the top of absorption tower 20 to absorb uncondensed allyl acetate vapor. The gas from the top of absorption tower 20 is mixed with the gaseous feedstock using a first compressor 40 before entering reactor 10. The liquid at the bottom of absorption tower flows into crude product storage tank 50. The operating pressure of absorption tower 20 is 0.5 MPa; the temperature of the material discharged from the bottom of absorption tower 20 is 30°C. The crude product in crude product storage tank 50 is then pumped into distillation tower 70 (operating pressure: atmospheric pressure). After distillation separation, the acetic acid aqueous solution is discharged from the bottom of distillation tower 70, and the material at the top of distillation tower 70 is sent to gas-liquid separator 80 for further purification of allyl acetate. The operating pressure of gas-liquid separator 80 is atmospheric pressure, and the temperature of the material inside gas-liquid separator 80 is 90°C. The propylene gas discharged from the crude product storage tank 50 and the gas-liquid separator 80 is then transported to the bottom gas phase space of the absorption tower 20 using a second compressor 60 (liquid ring compressor), thereby achieving propylene recovery and reuse. The mass fraction of propylene in the circulating gas in pipeline 51 is 88%, and the amount of propylene recovered by this process accounts for 1.37% of the allyl acetate content in the crude product storage tank 50.
[0059] Example 2:
[0060] The difference from Example 1 is that the propylene:acetic acid:oxygen:inert gas ratio is 1:0.21:0.18:0.96 (volume ratio). The operating conditions of reactor 10 are: reaction temperature 164°C, reaction pressure 0.75 MPa, and gas hourly space velocity (HSV) of the gaseous feedstock 1500 h⁻¹. -1 The first compressor 40 is an axial flow compressor. A 60% acetic acid aqueous solution is introduced into the top of the absorption tower 20 to absorb uncondensed allyl acetate vapor. The operating pressure of the absorption tower 20 is 0.66 MPa; the temperature of the material discharged from the bottom of the absorption tower 20 is 40°C. The material temperature in the gas-liquid separator 80 is 60°C. The second compressor 60 is a reciprocating compressor. The propylene mass fraction in the circulating gas in pipeline 51 is 84%, and the amount of propylene recovered by this process accounts for 1.18% of the allyl acetate content in the crude product storage tank 50.
[0061] Example 3:
[0062] The difference from Example 1 is that the ratio of propylene:acetic acid:oxygen:other inert gases is 1:0.28:0.24:1.04 (volume ratio); the operating conditions of reactor 10 are: reaction temperature of 189°C, reaction pressure of 0.88 MPa, and gas hourly space velocity of the feedstock of 2500 h⁻¹. -1 An acetic acid aqueous solution with a mass fraction of 70% is introduced into the top of the absorption tower 20 to absorb uncondensed allyl acetate vapor. The operating pressure of the absorption tower 20 is 0.8 MPa; the temperature of the material discharged from the bottom of the absorption tower 20 is 50°C. The material temperature in the gas-liquid separator 80 is 70°C. The second compressor 60 is a screw compressor. The mass fraction of propylene in the circulating gas in pipeline 51 is 79%, and the amount of propylene recovered by this process accounts for 1.09% of the amount of allyl acetate in the crude product storage tank 50.
[0063] Example 4:
[0064] The difference from Example 1 is that the propylene:acetic acid:oxygen:inert gas ratio is 1:0.17:0.12:1.26 (volume ratio); the operating conditions of reactor 10 are: reaction temperature of 214°C, reaction pressure of 0.94 MPa, and gas hourly space velocity of the gaseous feedstock of 2200 h⁻¹. -1 An acetic acid aqueous solution with a mass fraction of 60% is introduced into the top of the absorption tower 20 to absorb uncondensed allyl acetate vapor. The first compressor 40 is an axial flow compressor. The operating pressure of the absorption tower 20 is 0.88 MPa; the temperature of the material discharged from the bottom of the absorption tower 20 is 60°C. The material temperature in the gas-liquid separator 80 is 80°C. The mass fraction of propylene in the circulating gas in pipeline 51 is 72%. The amount of propylene recovered by this process accounts for 1.46% of the amount of allyl acetate in the crude product storage tank 50.
[0065] Comparative Example 1:
[0066] The difference from Example 1 is that, referring to Figures 2 and 3, the second compressor 60 is used to transport only the propylene gas discharged from the crude product storage tank 50 to the bottom gas phase space of the absorption tower 20, thereby achieving propylene recovery and reuse. The mass fraction of propylene in the circulating gas in pipeline 51 is 89%, and the amount of propylene recovered by this process accounts for 0.87% of the allyl acetate content in the crude product storage tank 50.
[0067] Comparative Example 2:
[0068] The difference from Example 3 is that the gas exiting from the top of the absorption tower 20 is mixed with the reactant gas by a set of two series-connected first compressors 40 (centrifugal compressors) before entering the reactor 10. The operating pressure of the absorption tower 20 is atmospheric pressure. Referring to Figures 2 and 4, the small amount of propylene gas emitted from the crude product storage tank 50 and the gas-liquid separator 80 is transported to the tail gas treatment system of the unit and is not recovered.
[0069] A comparison of Example 1 and Example 1 reveals that eliminating the connecting pipe between the gas phase space of the gas-liquid separator 80 and the crude product storage tank 50 significantly reduces the propylene recovery rate. This is mainly because the material temperature in the crude product storage tank 50 is low, and the material's residence time within the tank is short, resulting in some dissolved propylene remaining in the material entering the distillation column 70. Example 1, by enriching the light components at the top of the distillation column 70, further increases the propylene concentration while maintaining a high temperature in the gas-liquid separator 80 at the top, thereby reducing the solubility of propylene in the material and achieving a large-scale propylene recovery.
[0070] A comparison of Comparative Example 2 and Example 3 reveals that Comparative Example 2, by changing the absorption tower 20 to an atmospheric pressure operating tower, allows propylene dissolved in crude allyl acetate to flash out in the absorption tower 20, thus achieving propylene recovery. However, this process significantly increases the energy consumption of the first compressor 40 and the number of trays in the absorption tower 20.
[0071] Because the single-pass conversion rate of propylene in the oxidation reaction of this process is low (<20%), the amount of recovered propylene gas after passing through the second compressor 60 in Example 3 is negligible compared to the amount of circulating gas after passing through the first compressor 40. Comparative Example 2 used an atmospheric pressure absorption tower 20, and calculations show that the power of the unit composed of the first compressor 40 selected in Comparative Example 2 will be more than 10 times the power of the first compressor selected in Example 3.
[0072] Meanwhile, since Comparative Example 2 changed the absorption tower 20 to an atmospheric pressure operating tower, its gas processing capacity increased by about 8 times compared to the absorption tower 20 in Example 3. The theoretical number of plates and the tower diameter of the absorption tower 20 need to be increased significantly, which will also greatly increase the equipment investment cost of the process.
[0073] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.
Claims
1. A process for the production of allyl acetate and recovery of propylene, characterized by, Includes the following steps: A gaseous feedstock is introduced into a reactor to react and generate allyl acetate. The gaseous feedstock includes propylene, acetic acid, oxygen, and an inert gas. The material discharged from the bottom of the reactor is condensed using a condenser, so that the condensed material is discharged into the bottom of the absorption tower. The first compressor is used to pump the gas in the material from the top of the absorption tower back into the reactor, and the liquid in the material is discharged from the bottom of the absorption tower into the crude product storage tank. The second compressor is used to pump the gas in the material from the crude product storage tank back to the bottom of the absorption tower, and the liquid in the material is discharged from the crude product storage tank into the distillation tower for separation. The gas separated by the gas-liquid separator connected to the top of the distillation column is introduced into the crude product storage tank, and the second compressor also pumps the gas recovered from the gas-liquid separator into the crude product storage tank.
2. The method of claim 1, wherein, The reaction temperature inside the reactor is 140-220℃, and the reaction pressure is 0.6-1.0 MPa.
3. The method of claim 1, wherein, The volume ratio of the propylene, the acetic acid and the oxygen in the gas raw material is 1:0.1-0.3:0.1-0.3, the volume of the inert gas accounts for less than or equal to 50% of the total volume of the gas raw material, and the volume space velocity of the gas raw material is 1500-2500h -1 .
4. The method of claim 1, wherein, The operating pressure of the absorption tower is 0.5-0.9 MPa, and the temperature of the material discharged from the bottom of the absorption tower is controlled at 30-60℃.
5. The method of claim 1, wherein, The gas-liquid separator operates at atmospheric pressure and the separation temperature is controlled between 60-90℃.
6. The method according to any one of claims 1 to 5, characterized in that, It also includes the following steps: An absorbent liquid is introduced from the top of the absorption tower to absorb uncondensed allyl acetate vapor.
7. The method of claim 1, wherein, The distillation column operates at atmospheric pressure.
8. The method of claim 1, wherein, The first compressor is a centrifugal compressor or an axial compressor.
9. The method of claim 1, wherein, The second compressor is one of a liquid ring compressor, a reciprocating compressor, or a screw compressor.
10. The method of claim 1, wherein, The reactor is a tubular reactor.