Method for preparing allyl acetate and recovering propylene

Abstract

The invention provides a method for preparing allyl acetate and recovering propylene, which comprises the following steps: gas raw materials are introduced into a reactor for reaction to generate allyl acetate, and the gas raw materials comprise propylene, acetic acid, oxygen and inert gas; condensing the material discharged from the bottom of the reactor by using a condenser, so that the condensed material is discharged into the bottom in the absorption tower; pumping gas in the material back into the reactor from the top of the absorption tower by using a first compressor, and discharging liquid in the material into a crude product storage tank from the bottom of the absorption tower; pumping gas in the material back to the bottom in the absorption tower from the crude product storage tank by using a second compressor, and discharging liquid in the material from the crude product storage tank into a downstream rectifying tower for separation; gas separated by a gas-liquid separation tank communicated with the top of the rectifying tower is introduced into a crude product storage tank, and the second compressor also pumps gas recovered from the gas-liquid separation tank into the crude product storage tank. The method provided by the invention is beneficial to improving the raw material utilization rate so as to reduce the production cost.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of allyl acetate, and in particular to a method for preparing allyl acetate and recovering propylene. Background Art

[0002] Allyl acetate is an important fine chemical with a wide range of uses. The main method for producing allyl acetate in the world today is to use propylene, acetic acid and oxygen as raw materials to obtain allyl acetate under the catalysis of metal Pd. Since the single-pass conversion rate of propylene in the allyl acetate production process is low (<20%), and a certain amount of unreacted propylene will be dissolved in the obtained crude allyl acetate, resulting in low utilization of reaction raw materials and increased production costs. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a method for preparing allyl acetate and recovering propylene. The method provided in the present application is conducive to improving the utilization rate of raw materials to reduce 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 comprises the following steps:

[0006] Passing a gas raw material into a reactor to react and generate allyl acetate, wherein the gas raw material comprises propylene, acetic acid, oxygen and an inert gas;

[0007] Using a condenser to condense the material discharged from the bottom of the reactor, so that the condensed material is discharged into the bottom of the absorption tower;

[0008] Using a first compressor to pump the gas in the material from the top of the absorption tower back into the reactor, and discharging the liquid in the material from the bottom of the absorption tower into a crude product storage tank;

[0009] Using a second compressor to pump the gas in the material from the crude product storage tank back to the bottom of the absorption tower, and discharging the liquid in the material from the crude product storage tank into the distillation tower for separation;

[0010] The gas separated by the gas-liquid separation tank connected to the top of the distillation tower is introduced into the crude product storage tank, and the second compressor also pumps the gas recovered from the gas-liquid separation tank to the crude product storage tank.

[0011] In some possible implementations, the reaction temperature in the reactor is 140-220° C., and the reaction pressure is 0.6-1.0 MPa.

[0012] In some possible embodiments, in the gas raw material, the volume ratio of the propylene, the acetic acid and the oxygen 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 .

[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 operating pressure of the gas-liquid separation tank is normal pressure, and the separation temperature is controlled at 60-90°C.

[0015] In some possible implementations, the steps are further included:

[0016] An absorption liquid is introduced from the top of the absorption tower, and the absorption liquid is used to absorb the uncondensed allyl acetate vapor.

[0017] In some possible implementations, the operating pressure of the distillation tower is normal pressure.

[0018] In some possible implementations, the first compressor is a centrifugal compressor or an axial flow compressor.

[0019] In some possible implementations, the second compressor is a liquid ring compressor, a reciprocating compressor or a screw compressor.

[0020] In some possible implementations, the reactor is a shell-and-tube reactor.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] In the present application, through the coordinated cooperation among the reactor, the absorption tower, the condenser, the first compressor, the crude product storage tank, the second compressor, the distillation tower and the gas-liquid separation tank, the propylene discharged along with the gas of allyl acetate is condensed, separated and pumped, and the flashed propylene can be pumped back into the reactor for reaction, thereby facilitating the improvement of raw material utilization and reducing production costs.

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart of a method for preparing allyl acetate and recovering propylene provided in one embodiment of the present application;

[0025] Figure 2A connection diagram of a system corresponding to the method of the present application;

[0026] Figure 3 It is a connection diagram of the system corresponding to Comparative Example 1;

[0027] Figure 4 Schematic diagram of the connection of the system corresponding to Comparative Example 2.

[0028] Description of Figure Numbers:

[0029] 10 - reactor; 11 - second pipeline; 12 - first pipeline; 20 - absorption tower; 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 tower; 71 - eighth pipeline; 72 - seventh pipeline; 80 - gas-liquid separation tank; 81 - ninth pipeline; 83 - tenth pipeline. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. It should be noted that when an element is referred to as "fixed to" another element, it can be directly on the other element or there can be a centered element. When an element is referred to as "connected to" another element, it can be directly connected to the other element or there can be a centered element. When an element is referred to as "arranged on" another element, it can be arranged on the other element or there can be a centered element.

[0032] Reference Figure 1 and Figure 2 An embodiment of the present application provides a method for preparing allyl acetate and recovering propylene, comprising the following steps.

[0033] Step S101, introducing a gas raw material into a reactor 10 to react and generate allyl acetate, the gas raw material comprising propylene, acetic acid, oxygen and an inert gas. Exemplarily, the inert gas may comprise one of carbon dioxide or nitrogen. A corresponding catalyst, such as PD, may be provided in the reactor 10.

[0034] In some embodiments, the reaction temperature in the reactor 10 is 140-220° C., and the reaction pressure is 0.6-1.0 MPa.

[0035] In some embodiments, the volume ratio of propylene, acetic acid and 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 The setting of the process parameters in the reactor 10 is conducive to improving the yield of allyl acetate.

[0036] Specifically, the top of the reactor 10 is connected to a first pipeline 12 , and the gaseous raw material can be introduced into the reactor 10 through the first pipeline 12 .

[0037] Step S102, using the condenser 30 to condense the material discharged from the bottom of the reactor 10, 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 the material entering the absorption tower 20 may also include inert gas.

[0038] Specifically, the bottom of the absorption tower 20 is connected to the bottom of the reactor 10 through the second pipeline 11 , and the condenser 30 is installed on the second pipeline 11 . The condenser 30 is used to condense the materials discharged from the reactor 10 .

[0039] In some embodiments, an absorption liquid is introduced from the top of the absorption tower 20 to absorb the uncondensed allyl acetate vapor. For example, the absorption liquid can be an acetic acid aqueous solution or acetic acid. The mass fraction of acetic acid in the acetic acid aqueous solution is greater than or equal to 50%.

[0040] Specifically, the top of the absorption tower 20 is also connected to an eleventh pipeline 23 for feeding absorption liquid. The absorption 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 is beneficial to increasing the life of the catalyst in the reactor 10.

[0041] Step S103 , using the first compressor 40 to pump the gas in the material from the top of the absorption tower 20 back into the reactor 10 , and discharge the liquid in the material from the bottom of the absorption tower 20 into the crude product storage tank 50 .

[0042] 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 processing volume, thereby reducing the number of plates and the tower diameter of the absorption tower 20, thereby reducing the investment cost of the process equipment. In addition, reducing the gas processing volume is also conducive to reducing the pumping power of the first compressor 40, thereby further reducing the recovery cost.

[0043] Specifically, the top of the absorption tower 20 is connected to the first pipeline 12 through the third pipeline 21. The first compressor 40 is installed on the third pipeline 21, and the first compressor 40 is used to pump the gas in the absorption tower 20 into the reactor 10 for reaction, thereby realizing gas recovery, and the recovered gas includes propylene. The crude product storage tank 50 is connected to the bottom of the absorption tower 20 through the fourth pipeline 22.

[0044] Step S104, using the second compressor 60 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.

[0045] Specifically, the crude product storage tank 50 is connected to the bottom of the absorption tower 20 through the fifth pipeline 51. When observing the absorption tower 20, the access point of the fifth pipeline 51 is higher than the access point of the fourth pipeline 22. The access point of the fifth pipeline 51 can be above the liquid phase space at the bottom of the tower and below the filler in the absorption tower. Exemplarily, both the fourth pipeline 22 and the fifth pipeline 51 can be connected to the top of the crude product storage tank 50. The second compressor 60 is installed on the fifth pipeline 51. The second compressor 60 is used to pump the gas in the crude product storage tank 50 into the absorption tower 20. This part of the gas is also pumped by the first compressor 40 to react in the reactor 10, thereby further recovering the gas. The middle part of the distillation tower 70 is connected to the crude product storage tank 50 through the sixth pipeline 52. The bottom of the distillation tower 70 is provided with a seventh pipeline 72 for draining liquid. Part of the condensed liquid in the distillation tower 70 can be discharged from the seventh pipeline 72. Exemplarily, the condensed absorption liquid can be discharged from the seventh pipeline 72. The gas-liquid separation tank 80 is connected to the distillation tower 70 through at least two eighth pipelines 71 to separate the distilled materials and realize the reflux of the distillation tower 70 .

[0046] At this time, the absorption liquid and the product enter the distillation tower 70 together for distillation separation. The absorption liquid of the heavy component is enriched at the bottom of the distillation tower 70, and the product of the light component (dissolved propylene) is enriched at the top of the distillation tower 70. At this time, the absorption liquid can be separated while the concentration of propylene is increased, which is also conducive to increasing the recovery ratio of propylene.

[0047] In some embodiments, the operating pressure of the distillation column 70 is atmospheric pressure.

[0048] Step S105 , the gas separated by the gas-liquid separation tank 80 connected to the top of the distillation tower 70 is introduced into the crude product storage tank 50 , and the second compressor 60 also pumps the gas recovered from the gas-liquid separation tank 80 to the crude product storage tank 50 .

[0049] In some embodiments, the operating pressure of the gas-liquid separation tank 80 is normal pressure, and the separation temperature is controlled at 60-90° C. The process parameters of the gas-liquid separation tank 80 are conducive to reducing the solubility of propylene in the material, thereby further improving the recovery ratio of propylene.

[0050] Specifically, the gas-liquid separator 80 is connected to the crude product storage tank 50 through the ninth pipeline 81 for introducing the separated gas into the crude product storage tank 50. Exemplarily, the gas-liquid separator 80 can be connected to the top of the crude product storage tank 50 through the ninth pipeline 81, so that the gas separated by the gas-liquid separator 80 is pumped into the reactor 10 through the first compressor 40 and the second compressor 60, thereby realizing further recovery of the gas. The bottom of the gas-liquid separator 80 is connected to the tenth pipeline 83 to discharge part of the separated materials. At this time, the liquid discharged from the gas-liquid separator 80 is sent to the downstream separation tower to further purify allyl acetate.

[0051] In some embodiments, the reactor 10, the absorption tower 20, the crude product storage tank 50, the distillation tower 70 and the gas-liquid separation tank 80 can be arranged in sequence, so as to help reduce the layout space of the system.

[0052] In some embodiments, the first compressor 40 is a centrifugal compressor or an axial compressor, and the second compressor 60 is a liquid ring compressor, a reciprocating compressor or a screw compressor. The types of the first compressor 40 and the second compressor 60 are selected to have the advantages of low equipment cost and high pumping efficiency, thereby further reducing production costs.

[0053] In some embodiments, the reactor 10 is a shell-and-tube reactor, which has the advantages of good heat transfer performance and good mixing performance.

[0054] In other embodiments, a tank reactor, a tower reactor or a jet reactor can be selected according to the reaction type.

[0055] Illustratively, the absorption tower 20 may be a packed tower, a plate tower or a floating valve tower.

[0056] In the present application, through the coordinated cooperation among the reactor 10, the absorption tower 20, the condenser 30, the first compressor 40, the crude product storage tank 50, the second compressor 60, the distillation tower 70 and the gas-liquid separation tank 80, the propylene discharged along with the gas of allyl acetate is condensed, separated and pumped, and the flashed propylene can be pumped back into the reactor 10 for reaction, thereby facilitating the improvement of raw material utilization and reducing production costs.

[0057] Specific:

[0058] Embodiment 1:

[0059] The gas raw materials are introduced into the reactor 10, and the gas raw materials include propylene, acetic acid, oxygen and inert gas. The reactor 10 is equipped with a Pd catalyst. The reactor 10 is a tube reactor. The ratio of propylene: acetic acid: oxygen: inert gas is 1: 0.23: 0.15: 0.88 (volume ratio). The inert gas can be carbon dioxide. The operating conditions of the reactor 10 are: the reaction temperature is 146°C, the reaction pressure is 0.68MPa, and the volume space velocity of the gas raw materials is 2000h －1 . The material discharged from the bottom of the reactor 10 is condensed by a condenser 30, so that the condensed material is discharged into the bottom of the absorption tower 20. An acetic acid aqueous solution (absorption liquid) with an acetic acid mass fraction of 50% is introduced into the top of the absorption tower 20 to absorb the uncondensed allyl acetate vapor. The gas from the top of the absorption tower 20 is mixed with the gas raw material by a first compressor 40 (centrifugal compressor) and then enters the reactor 10, and the liquid at the bottom of the absorption tower flows into the crude product storage tank 50. The operating pressure of the absorption tower 20 is 0.5Mpa; the temperature of the material discharged from the bottom of the absorption tower 20 is 30°C. The crude product in the crude product storage tank 50 is then pumped into a distillation tower 70 (operating pressure is normal pressure). After distillation and separation, the acetic acid aqueous solution is discharged from the bottom of the distillation tower 70, and the material at the top of the distillation tower 70 is sent to the gas-liquid separation tank 80 to further purify the allyl acetate. The operating pressure of the gas-liquid separation tank 80 is normal pressure, and the temperature of the material in the gas-liquid separation tank 80 is 90°C. The second compressor 60 (liquid ring compressor) is then used to transport the propylene gas discharged from the crude product storage tank 50 and the gas-liquid separation tank 80 to the bottom gas phase space of the absorption tower 20, thereby achieving the recovery and reuse of propylene. The mass fraction of the circulating gas propylene in the pipeline 51 is 88%, and the amount of propylene recovered by this process accounts for 1.37% of the amount of allyl acetate in the crude product storage tank 50.

[0060] Embodiment 2:

[0061] The difference from Example 1 is that the volume ratio of propylene: acetic acid: oxygen: inert gas is 1: 0.21: 0.18: 0.96. The operating conditions of the reactor 10 are: the reaction temperature is 164°C, the reaction pressure is 0.75 MPa, the volume space velocity of the gas raw material is 1500 h －1The first compressor 40 is an axial flow compressor, and an acetic acid aqueous solution with a mass fraction of 60% acetic acid is introduced into the top of the absorption tower 20 to absorb the uncondensed allyl acetate vapor. The operating pressure of the absorption tower 20 is 0.66Mpa; the temperature of the material discharged from the bottom of the absorption tower 20 is 40°C. The material temperature in the gas-liquid separation tank 80 is 60°C. The second compressor 60 is a reciprocating compressor. The mass fraction of circulating gas propylene in the pipeline 51 is 84%, and the amount of propylene recovered by this process accounts for 1.18% of the amount of allyl acetate in the crude product storage tank 50.

[0062] Embodiment 3:

[0063] The difference from Example 1 is that the volume ratio of propylene: acetic acid: oxygen: other inert gases is 1: 0.28: 0.24: 1.04; the operating conditions of the reactor 10 are: the reaction temperature is 189°C, the reaction pressure is 0.88 MPa, and the volume space velocity of the gas raw material is 2500 h －1 . An acetic acid aqueous solution with an acetic acid mass fraction of 70% is introduced into the top of the absorption tower 20 to absorb the uncondensed allyl acetate vapor, wherein 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 temperature of the material in the gas-liquid separation tank 80 is 70°C. The second compressor 60 is a screw compressor. The mass fraction of circulating gas propylene in the 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.

[0064] Embodiment 4:

[0065] The difference from Example 1 is that the volume ratio of propylene: acetic acid: oxygen: inert gas is 1: 0.17: 0.12: 1.26; the operating conditions of the reactor 10 are: the reaction temperature is 214°C, the reaction pressure is 0.94 MPa, and the volume space velocity of the gas raw material is 2200 h －1 . An acetic acid aqueous solution with a mass fraction of 60% acetic acid is introduced into the top of the absorption tower 20 to absorb the uncondensed allyl acetate vapor. The first compressor 40 adopts an axial flow compressor, wherein the operating pressure of the absorption tower 20 is 0.88Mpa; the temperature of the material discharged from the bottom of the absorption tower 20 is 60°C. The temperature of the material in the gas-liquid separation tank 80 is 80°C. The mass fraction of circulating gas propylene in the pipeline 51 is 72%, and 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.

[0066] Comparative Example 1:

[0067] The difference from Example 1 is that, in combination with reference Figure 2 and Figure 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, so as to achieve the recovery and reuse of propylene. The mass fraction of the circulating gas propylene in the pipeline 51 is 89%, and the amount of propylene recovered by this process accounts for 0.87% of the amount of allyl acetate in the crude product storage tank 50.

[0068] Comparative Example 2:

[0069] The difference from Example 3 is that the gas coming out of the top of the absorption tower 20 passes through a set of two first compressors 40 (centrifugal compressors) connected in series and is mixed with the reaction raw gas before entering the reactor 10, wherein the operating pressure of the absorption tower 20 is atmospheric pressure. Figure 2 and Figure 4 The small amount of propylene gas discharged from the crude product storage tank 50 and the gas-liquid separation tank 80 is transported to the tail gas treatment system of the device without being recovered.

[0070] By comparing Comparative Example 1 with Example 1, it can be found that after the connecting pipeline between the gas phase space of the gas-liquid separation tank 80 and the crude product storage tank 50 is removed, the proportion of recovered propylene is significantly reduced; this is mainly due to the low temperature of the material in the crude product storage tank 50 and the short residence time of the material in the storage tank, and some propylene is still dissolved in the material entering the distillation tower 70. Example 1 enriches the light components to the top of the tower through the distillation tower 70, further improving the concentration of propylene, while maintaining the high temperature of the material in the gas-liquid separation tank 80 at the top of the tower, thereby reducing the solubility of propylene in the material, thereby achieving a large amount of propylene recovery.

[0071] By comparing Comparative Example 2 with Example 3, it can be found that in Comparative Example 2, by changing the absorption tower 20 to a normal pressure operation tower, the propylene dissolved in the crude allyl acetate product is flashed out in the absorption tower 20, thereby realizing the recovery of propylene. However, this process will greatly increase the energy consumption of the first compressor 40 and the number of plates of the absorption tower 20.

[0072] Since the propylene per-pass conversion rate of the oxidation reaction in this process is relatively low (<20%), the amount of propylene gas recovered through the second compressor 60 in Example 3 can be ignored relative to the amount of circulating gas through the first compressor 40. In Comparative Example 2, an atmospheric pressure absorption tower 20 is used. It is calculated 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.

[0073] At the same time, since Comparative Example 2 changes the absorption tower 20 into a normal pressure operation tower, its gas processing capacity increases by about 8 times compared with the absorption tower 20 of Example 3. The theoretical number of plates and the tower diameter of the absorption tower 20 need to be greatly increased, which will also greatly increase the equipment investment cost of the process.

[0074] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for preparing allyl acetate and recovering propylene, characterized in that: The steps include: Passing a gas raw material into a reactor to react and generate allyl acetate, wherein the gas raw material comprises propylene, acetic acid, oxygen and an inert gas; Using a condenser to condense the material discharged from the bottom of the reactor, so that the condensed material is discharged into the bottom of the absorption tower; Using a first compressor to pump the gas in the material from the top of the absorption tower back into the reactor, and discharging the liquid in the material from the bottom of the absorption tower into a crude product storage tank; Using a second compressor to pump the gas in the material from the crude product storage tank back to the bottom of the absorption tower, and discharging the liquid in the material from the crude product storage tank into the distillation tower for separation; The gas separated by the gas-liquid separation tank connected to the top of the distillation tower is introduced into the crude product storage tank, and the second compressor also pumps the gas recovered from the gas-liquid separation tank to the crude product storage tank.

2. The method according to claim 1, characterized in that The reaction temperature in the reactor is 140-220° C., and the reaction pressure is 0.6-1.0 MPa.

3. The method according to claim 1, characterized in that In the gas raw material, the volume ratio of the propylene, the acetic acid and the oxygen 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 according to claim 1, characterized in that The operating pressure of the absorption tower is 0.5-0.9Mpa, and the temperature of the material discharged from the bottom of the absorption tower is controlled at 30-60°C.

5. The method according to claim 1, characterized in that The operating pressure of the gas-liquid separation tank is normal pressure, and the separation temperature is controlled at 60-90°C.

6. The method according to any one of claims 1 to 5, characterized in that Also includes the steps: An absorption liquid is introduced from the top of the absorption tower, and the absorption liquid is used to absorb the uncondensed allyl acetate vapor.

7. The method according to claim 1, characterized in that The operating pressure of the distillation tower is normal pressure.

8. The method according to claim 1, characterized in that The first compressor is a centrifugal compressor or an axial compressor.

9. The method according to claim 1, characterized in that The second compressor is one of a liquid ring compressor, a reciprocating compressor or a screw compressor.

10. The method according to claim 1, characterized in that The reactor is a tube-in-tube reactor.

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