A kind of synthetic method of propylene carbonate
By using a combination catalyst of metal oxide and potassium iodide in the reaction distillation tower, high-purity propylene carbonate is efficiently synthesized under low energy consumption conditions, and the problems of high energy consumption and difficult catalyst separation in the prior art are solved, thereby achieving process stability and economicality.
Patent Information
- Application Number
- CN202510187559.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-20
- Publication Date
- 2025-05-16
- Estimated Expiration
- 2045-02-20
AI Technical Summary
The existing industrial synthesis route of propylene carbonate requires high temperature and high pressure conditions, resulting in high energy consumption and high operating costs, and at the same time, it is difficult to separate the catalyst, affecting process stability.
Using a reaction distillation tower, a combined catalyst is used to mix metal oxides and potassium iodide, and propylene carbonate is synthesized under low energy consumption through a continuous reaction process to achieve the recycling of the catalyst and the high purity production of the product.
Highly efficient synthesis of high-purity propylene carbonate under low energy consumption and low cost process conditions, achieving continuous preparation and synthesis of propylene carbonate, avoiding the cumbersome steps of catalyst separation and subsequent distillation treatment.
Smart Images
Figure CN119661493B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of preparation of propylene carbonate, and particularly relates to a method for synthesizing propylene carbonate. Background Art
[0002] Propylene carbonate (PC) is an important organic compound with a wide range of applications. For example, it is used as a raw material for the preparation of polycarbonate, polyurethane, pharmaceuticals, battery electrolytes and other products. It can also be used directly as a green and environmentally friendly solvent.
[0003] The current industrial synthesis route of propylene carbonate is usually in a reactor device, under the condition of a catalyst, propylene oxide and carbon dioxide undergo a cycloaddition reaction to obtain propylene carbonate. Since the reaction is an exothermic reaction, lowering the temperature can promote the positive reaction, but too low a temperature is not conducive to the activation of propylene oxide and carbon dioxide. In order to speed up the reaction rate, it is necessary to set a higher reaction temperature (usually not less than 150°C) and pressure (usually not less than 5MPa), resulting in high energy consumption and harsh operating conditions, resulting in high operating costs of the synthesis process; in addition, the catalyst in the current industrial synthesis route usually uses a homogeneous catalyst, and after the completion of the synthesis of propylene carbonate, it will face the problem of difficulty in separating the catalyst and the propylene carbonate product.
[0004] In order to solve the above problems, many new catalysts have emerged to improve the reaction activity between propylene oxide and carbon dioxide under the basic conditions of lowering the reaction temperature and pressure, and at the same time, it is necessary to ensure that the catalyst can be easily recovered later. Although these new catalysts have produced positive effects, from the perspective of industrial application, their preparation process is complicated, the scope of application is limited, and they are not easy to obtain, resulting in high raw material costs. In addition, the reaction conditions required when using new catalysts are relatively harsh, which also leads to the unstable implementation effect of the process of catalytic synthesis of propylene carbonate.
[0005] In addition, although the reaction distillation tower can be used as a device for catalytic reactions, since the catalyst is loaded in the distillation tower, the reaction efficiency is significantly slower than that of the reactor, and it is still necessary to select a catalyst with a complicated preparation process and difficult to obtain, and the purity and yield of the obtained product are low, and a relatively cumbersome purification and refining process is required later. Therefore, in the prior art, the reaction distillation tower is not a suitable device for preparing synthetic propylene carbonate.
[0006] Therefore, the applicant hopes to seek technical solutions to solve the above technical problems. Summary of the invention
[0007] In view of this, the object of the present invention is to provide a method for synthesizing propylene carbonate, which can efficiently synthesize high-purity propylene carbonate under low-energy consumption and low-cost process conditions, and realize the continuous preparation and synthesis of propylene carbonate, without the need for cumbersome catalyst separation and subsequent distillation of propylene carbonate.
[0008] The technical solution adopted by the present invention is as follows:
[0009] A method for synthesizing propylene carbonate comprises the following steps:
[0010] S1. The propylene oxide and carbon dioxide gases are continuously fed into a reaction distillation tower; wherein the reaction distillation tower is filled with a combined catalyst, the combined catalyst is a mixture of metal oxides and potassium iodide;
[0011] S2. continuously feeding a liquid light component raw material into a reaction distillation tower, wherein propylene oxide and carbon dioxide gas undergo a cycloaddition reaction in the reaction distillation tower to obtain a propylene carbonate product; wherein the top temperature of the reaction distillation tower is set to 35-80°C, the bottom temperature is set to 75-110°C, and the tower pressure is set to 0.2-1.5MPa;
[0012] S3. The gas phase is continuously extracted from the top of the reaction distillation tower and condensed, and the liquid propylene carbonate product is continuously extracted from the bottom of the reaction distillation tower;
[0013] S4. The condensed liquid phase obtained after the gas phase is condensed is connected to the feeding pipeline of the liquid phase light component raw material to achieve the recycling of the liquid phase light component raw material.
[0014] Preferably, the feed molar ratio of propylene oxide to carbon dioxide gas is 1:2-5, and the feed mass ratio of propylene oxide to liquid phase light component raw material is 1:4-7.
[0015] Preferably, the feed rate of propylene oxide is 10-100 mol / hour.
[0016] Preferably, the metal oxide is aluminum oxide and / or zinc oxide; wherein the mass fraction of potassium iodide in the combined catalyst is 5-25%.
[0017] Preferably, the liquid phase light component raw material is chloroform and / or dichloromethane.
[0018] Preferably, the reaction distillation tower comprises a distillation section located at the top, a catalytic reaction section located in the middle and a stripping section located at the bottom; wherein the catalytic reaction section is respectively provided with a propylene oxide feed inlet and a carbon dioxide gas feed inlet, and the stripping section is provided with a liquid phase light component feed inlet; the combined catalyst is loaded in the catalytic reaction section.
[0019] Preferably, the number of plates of the reactive distillation tower ranges from 55 to 80; wherein the number of plates of the catalytic reaction section ranges from 25 to 45, and the propylene oxide feed port is located below the carbon dioxide gas feed port.
[0020] Preferably, the step S1 specifically includes the following steps:
[0021] S11. Continuously feeding propylene oxide to the reaction distillation tower so that propylene oxide is fully contacted with the transition combination catalyst;
[0022] S12. After the continuous feeding time of propylene oxide reaches 15-30 minutes, carbon dioxide gas is continuously introduced into the reaction distillation tower, and propylene oxide reacts with carbon dioxide gas to initially generate propylene carbonate.
[0023] Preferably, in step S11, the temperature of the reaction distillation tower is set at 40-70°C.
[0024] Preferably, the purity of the liquid propylene carbonate product extracted in step S3 is not less than 99%.
[0025] The present invention adopts a reactive distillation tower to prepare synthetic propylene carbonate, and introduces a recyclable liquid light component raw material as a gas phase for extraction in the process of generating propylene carbonate by cycloaddition reaction of propylene oxide and carbon dioxide gas. At the same time, it is particularly critical that the applicant has found that under the low-energy consumption distillation process operation conditions of reactive distillation not higher than 110° C. and not higher than 1.5 MPa, a combined catalyst (widely available and easy to obtain) composed of a mixture of metal oxides and potassium iodide is specially combined and applied to achieve efficient cycloaddition reaction, and the liquid phase propylene carbonate product is extracted as a continuous phase in the bottom of the tower, and basically no side reaction occurs; therefore, the present invention efficiently synthesizes high-purity propylene carbonate under low-energy consumption and low-cost process conditions, and realizes the continuous preparation and synthesis of propylene carbonate, without the need for cumbersome catalyst separation and subsequent distillation treatment of propylene carbonate. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 It is a flowchart of the operation steps of the method for synthesizing propylene carbonate according to a specific embodiment of the present invention;
[0027] Figure 2 It is a block diagram of specific operation steps of step S1 in a specific implementation mode of the present invention;
[0028] Figure 3 Schematic diagram of the device connection structure used in the method for synthesizing propylene carbonate in Example 1 of the present invention;
[0029] Figure 4This is a sample photo of the liquid-phase propylene carbonate product produced in Example 5 of the present invention;
[0030] Figure 5 This is a chromatogram of the liquid phase propylene carbonate product extracted in Example 5 of the present invention (specifically using probe chromatography with an injection volume of 0.5 μL). DETAILED DESCRIPTION
[0031] Please refer to Figure 1 and Figure 2 As shown, this embodiment provides a method for synthesizing propylene carbonate, comprising the following steps:
[0032] S1. Propylene oxide and carbon dioxide gas are continuously fed into a reaction distillation tower respectively; wherein the reaction distillation tower is filled with a combined catalyst, which is a mixture of metal oxides and potassium iodide; preferably, in this step S1, the feed molar ratio of propylene oxide to carbon dioxide gas is 1:2-5, more preferably 1:2.5-4; the feed flow rate of propylene oxide is 10-100 mol / hour, more preferably 30-80 mol / hour; preferably, in this step S1, the metal oxide is aluminum oxide and / or zinc oxide, which are widely available and easy to obtain; wherein the mass fraction of potassium iodide in the combined catalyst is 5-25%, more preferably 10-20%; it should be noted that, in other embodiments of the present application, the metal oxide may also be copper oxide or zirconium dioxide, but due to the high cost, it is not recommended;
[0033] Preferably, this step S1 specifically includes the following steps:
[0034] S11. Continuously feeding propylene oxide to the reaction distillation tower so that propylene oxide is fully contacted with the metal combination catalyst; preferably, in this step S11, the temperature of the reaction distillation tower is set at 40-70°C;
[0035] S12. After the continuous feeding time of propylene oxide reaches 15-30 minutes, carbon dioxide gas is continuously introduced into the reaction distillation tower, and propylene oxide reacts with carbon dioxide gas to initially generate propylene carbonate;
[0036] S2. Continuously feeding a liquid-phase light component raw material into a reaction distillation tower, wherein propylene oxide and carbon dioxide gas undergo a cycloaddition reaction in the reaction distillation tower to obtain a propylene carbonate product; wherein the top temperature of the reaction distillation tower is set to 35-80°C, the bottom temperature is set to 75-110°C, and the tower pressure is set to 0.2-1.5MPa; preferably, in this step S2, the feed mass ratio of propylene oxide to the liquid-phase light component raw material is 1:4-7, more preferably 1:5-7; preferably, in this step S2, the liquid-phase light component raw material is chloroform and / or dichloromethane (more preferably chloroform); preferably, in this step S2, the liquid-phase light component raw material is continuously fed into the reaction distillation tower 5-15 minutes (more preferably 6-12 minutes) after the carbon dioxide gas is introduced;
[0037] S3. The gas phase is continuously extracted from the top of the reaction distillation tower and condensed, and the liquid propylene carbonate product is continuously extracted from the bottom of the reaction distillation tower; preferably, the purity of the liquid propylene carbonate product extracted in step S3 is not less than 99%;
[0038] S4. The condensed liquid phase obtained after the gas phase is condensed is connected to the feeding pipeline of the liquid phase light component raw material to realize the recycling of the liquid phase light component raw material.
[0039] Preferably, in this embodiment, the reaction distillation tower comprises a distillation section located at the top, a catalytic reaction section located in the middle and a stripping section located at the bottom; wherein the catalytic reaction section is respectively provided with a propylene oxide feed port and a carbon dioxide gas feed port, and the stripping section is provided with a liquid phase light component feed port; the combined catalyst is loaded in the catalytic reaction section; further preferably, in this embodiment, the number of tower plates of the reaction distillation tower ranges from 55 to 80 (all using CY wire mesh type structured packing); wherein the number of tower plates of the catalytic reaction section is 25 to 45, and the propylene oxide feed port is located below the carbon dioxide gas feed port.
[0040] It should be noted that the present application has cited various preferred range parameters for the above embodiments through a large number of trial and error experiments. Those skilled in the art can choose within these preferred parameter ranges (including endpoint values and intermediate values) according to actual conditions. In order to save space in the specification, the present embodiments will not be expanded one by one.
[0041] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.
[0042] Example 1: The operation process is as follows:
[0043] Preparation of a combined catalyst: preparing aluminum oxide and potassium iodide in a mass ratio of 4:1, respectively, and mixing them under stirring to obtain a combined catalyst for use;
[0044] Please refer to Figure 3 As shown, the operating conditions of the reaction distillation tower 1 are: 65 plates, and the spacing between each plate (all using CY wire mesh type structured packing, not shown in the figure) is: 320 mm; it includes a distillation section 1a located at the top (the number of plates is 10), a catalytic reaction section 1b located in the middle (the number of plates is 35) and a stripping section 1c located at the bottom (the number of plates is 20); the catalytic reaction section 1b is respectively provided with a propylene oxide feed port 11 (located at the 40th plate) and a carbon dioxide gas feed port 12 (located at the 20th plate), and the stripping section 1c is provided with a liquid phase light component feed port 13 (located at the 50th plate); the prepared combined catalyst is loaded in the catalytic reaction section 1b;
[0045] Continuously feed propylene oxide to the propylene oxide feed port 11 (initial temperature is set to 55°C) of the reaction distillation tower 1 at a feed rate of 60 mol / hour; after the continuous feeding time of propylene oxide reaches 20 minutes, start to continuously introduce excess carbon dioxide gas (200 mol / hour) to the carbon dioxide gas feed port 12 of the reaction distillation tower 1; 10 minutes after the carbon dioxide gas is introduced, start to continuously introduce dichloromethane to the liquid phase light component feed port 13 of the reaction distillation tower 1 (the feed mass ratio of dichloromethane to propylene oxide is 5:1); at this time, the top temperature of the reaction distillation tower 1 is set to 45°C, the bottom temperature is set to 90°C, and the tower pressure is set to 0.8MPa; after reacting for 45 minutes, the liquid phase propylene carbonate product is continuously produced from the bottom of the reaction distillation tower 1 and enters the product collecting tank 2; the gas phase (including dichloromethane and excess carbon dioxide gas) is continuously produced from the top of the reaction distillation tower 1 and condensed, and the tail gas after condensation treatment by the condenser 3 is directly discharged (in other embodiments, it can also be recycled), and the condensed liquid phase obtained after condensation treatment by the condenser 3 is connected to the dichloromethane feeding pipeline 4 to realize the recycling of the liquid phase dichloromethane.
[0046] Example 2: The operation process is as follows:
[0047] Preparation of a combined catalyst: preparing zinc oxide and potassium iodide in a mass ratio of 9:1, respectively, and mixing them under stirring to obtain a combined catalyst for use;
[0048] The operating conditions of the reaction distillation tower are: 60 plates, and the spacing between each plate is 320 mm; it includes a distillation section located at the top (the number of plates is 10), a catalytic reaction section located in the middle (the number of plates is 30) and a stripping section located at the bottom (the number of plates is 20); the catalytic reaction section is provided with a propylene oxide feed port (located at the 38th plate) and a carbon dioxide gas feed port (located at the 15th plate), and the stripping section is provided with a liquid phase light component feed port (located at the 50th plate); the prepared combined catalyst is loaded in the catalytic reaction section;
[0049] The propylene oxide feed port of the reactive distillation tower (initial temperature set at 60°C) was fed at 50 mol / h.
[0050] After the continuous feeding time of propylene oxide reaches 20 minutes, excessive carbon dioxide gas (200 mol / hour) is continuously introduced into the carbon dioxide gas feed port of the reaction distillation tower; 10 minutes after the carbon dioxide gas is introduced, dichloromethane is continuously introduced into the liquid phase light component feed port of the reaction distillation tower (the feed mass ratio of dichloromethane to propylene oxide is 6:1); at this time, the top temperature of the reaction distillation tower is set to 45°C, the bottom temperature is set to 80°C, and the tower pressure is set to 0.5MPa; after 45 minutes of reaction, the liquid phase propylene carbonate product is continuously produced in the bottom of the reaction distillation tower; the gas phase (including dichloromethane and excess carbon dioxide gas) continuously produced from the top of the reaction distillation tower is condensed, and the tail gas after condensation treatment in the condenser is directly discharged, and the condensed liquid phase obtained after condensation treatment in the condenser is connected to the feeding pipeline of dichloromethane to realize the recycling of liquid phase dichloromethane.
[0051] Embodiment 3: The operation process is as follows:
[0052] Preparation of a combined catalyst: preparing aluminum oxide and potassium iodide in a mass ratio of 3:1, respectively, and mixing them under stirring to obtain a combined catalyst for use;
[0053] The operating conditions of the reaction distillation tower are: 80 plates, and the spacing between each plate is 320 mm; it includes a distillation section located at the top (the number of plates is 15), a catalytic reaction section located in the middle (the number of plates is 45) and a stripping section located at the bottom (the number of plates is 20); the catalytic reaction section is provided with a propylene oxide feed port (located at the 55th plate) and a carbon dioxide gas feed port (located at the 25th plate), and the stripping section is provided with a liquid phase light component feed port (located at the 70th plate); the prepared combined catalyst is loaded in the catalytic reaction section;
[0054] The propylene oxide feed port of the reactive distillation tower (initial temperature set at 70°C) was fed at 80 mol / h.
[0055] After the continuous feeding time of propylene oxide reaches 20 minutes, excessive carbon dioxide gas (320 mol / hour) is continuously introduced into the carbon dioxide gas feed port of the reaction distillation tower; 10 minutes after the carbon dioxide gas is introduced, dichloromethane is continuously introduced into the liquid phase light component feed port of the reaction distillation tower (the feed mass ratio of dichloromethane to propylene oxide is 7:1); at this time, the top temperature of the reaction distillation tower is set to 45°C, the bottom temperature is set to 90°C, and the tower pressure is set to 0.8MPa; after 45 minutes of reaction, the liquid phase propylene carbonate product is continuously produced in the bottom of the reaction distillation tower; the gas phase (including dichloromethane and excess carbon dioxide gas) continuously produced from the top of the reaction distillation tower is condensed, and the tail gas after condensation treatment in the condenser is directly discharged, and the condensed liquid phase obtained after condensation treatment in the condenser is connected to the feeding pipeline of dichloromethane to realize the recycling of liquid phase dichloromethane.
[0056] Embodiment 4: The operation process is as follows:
[0057] Preparation of a combined catalyst: preparing aluminum oxide and potassium iodide in a mass ratio of 95:5 respectively, and mixing them under stirring to obtain a combined catalyst for use;
[0058] The operating conditions of the reaction distillation tower are: 55 plates, and the spacing between each plate is 320 mm; it includes a distillation section located at the top (the number of plates is 15), a catalytic reaction section located in the middle (the number of plates is 25) and a stripping section located at the bottom (the number of plates is 15); the catalytic reaction section is provided with a propylene oxide feed port (located at the 35th plate) and a carbon dioxide gas feed port (located at the 20th plate), and the stripping section is provided with a liquid phase light component feed port (located at the 50th plate); the prepared combined catalyst is loaded in the catalytic reaction section;
[0059] The propylene oxide feed port of the reactive distillation tower (initial temperature set at 45°C) was fed at 30 mol / h.
[0060] After the continuous feeding time of propylene oxide reaches 15 minutes, excessive carbon dioxide gas (150 mol / hour) is continuously introduced into the carbon dioxide gas feed port of the reaction distillation tower; 10 minutes after the carbon dioxide gas is introduced, dichloromethane is continuously introduced into the liquid phase light component feed port of the reaction distillation tower (the feed mass ratio of dichloromethane to propylene oxide is 4:1); at this time, the top temperature of the reaction distillation tower is set to 45°C, the bottom temperature is set to 75°C, and the tower pressure is set to 0.4MPa; after 45 minutes of reaction, the liquid phase propylene carbonate product is continuously produced in the bottom of the reaction distillation tower; the gas phase (including dichloromethane and excess carbon dioxide gas) continuously produced from the top of the reaction distillation tower is condensed, and the tail gas after condensation treatment in the condenser is directly discharged, and the condensed liquid phase obtained after condensation treatment in the condenser is connected to the feeding pipeline of dichloromethane to realize the recycling of liquid phase dichloromethane.
[0061] Example 5: The operation process is as follows:
[0062] Preparation of a combined catalyst: preparing aluminum oxide and potassium iodide in a mass ratio of 4:1, respectively, and mixing them under stirring to obtain a combined catalyst for use;
[0063] The operating conditions of the reaction distillation tower are: 65 plates, and the spacing between each plate is 320 mm; it includes a distillation section located at the top (the number of plates is 10), a catalytic reaction section located in the middle (the number of plates is 35) and a stripping section located at the bottom (the number of plates is 20); the catalytic reaction section is provided with a propylene oxide feed port (located at the 40th plate) and a carbon dioxide gas feed port (located at the 20th plate), and the stripping section is provided with a liquid phase light component feed port (located at the 50th plate); the prepared combined catalyst is loaded in the catalytic reaction section;
[0064] The propylene oxide feed port of the reactive distillation tower (initial temperature set at 55°C) was fed at 60 mol / h.
[0065] propylene oxide was continuously fed at a feed rate of 100 mol / h; after the continuous feeding time of propylene oxide reached 20 minutes, excessive carbon dioxide gas (200 mol / h) was continuously introduced into the carbon dioxide gas feed port of the reaction distillation tower; 10 minutes after the carbon dioxide gas was introduced, chloroform was continuously introduced into the liquid phase light component feed port of the reaction distillation tower (the feed mass ratio of chloroform to propylene oxide was 5:1); at this time, the top temperature of the reaction distillation tower was set to 65°C, the bottom temperature was set to 95°C, and the tower pressure was set to 1 MPa; after 45 minutes of reaction, the liquid phase propylene carbonate product was continuously withdrawn from the bottom of the reaction distillation tower (please refer to Figure 4 Sample photos of the products shown and Figure 5The gas phase (including chloroform and excess carbon dioxide gas) continuously extracted from the top of the reaction distillation tower is condensed, and the tail gas after condensation treatment in the condenser is directly discharged, and the condensed liquid phase obtained after condensation treatment in the condenser is connected to the chloroform feed pipeline to realize the recycling of liquid chloroform.
[0066] Embodiment 6: The rest of the technical scheme of this embodiment 6 is the same as that of embodiment 5, except that, in this embodiment 6, the continuous feeding of excess carbon dioxide gas and chloroform into the reaction distillation tower is carried out simultaneously.
[0067] Comparative Example 1: The rest of the technical solutions of this comparative example 1 are the same as those of Example 1, except that, in this comparative example 1, the potassium iodide in Example 1 is replaced by aluminum oxide.
[0068] Comparative Example 2: The rest of the technical solutions of this comparative example 2 are the same as those of Example 1, except that, in this comparative example 2, the aluminum oxide in Example 1 is replaced by potassium iodide.
[0069] Comparative Example 3: The remaining technical solutions of this Comparative Example 3 are the same as those of Example 1, except that, in this Comparative Example 3, carbon dioxide gas and propylene oxide are continuously fed synchronously; 10 minutes after the continuous feeding of carbon dioxide gas and propylene oxide, dichloromethane is continuously fed into the liquid phase light component feed port of the reaction distillation tower.
[0070] Comparative Example 4: The rest of the technical solutions of this comparative example 4 are the same as those of Example 1, except that, in this comparative example 4, carbon dioxide gas, propylene oxide and dichloromethane are continuously fed simultaneously.
[0071] Comparative Example 5: The remaining technical solutions of this comparative example 5 are the same as those of Example 1, except that, in this comparative example 5, a reaction kettle (temperature set to 90° C., pressure set to 0.8 MPa) is used to replace the reaction distillation tower in Example 1; the specific operation steps are as follows:
[0072] Propylene oxide and the combined catalyst were fed into the reactor in advance, stirred and mixed, and then carbon dioxide gas was introduced into the reactor to react for 3.5 hours to obtain propylene carbonate product.
[0073] Comparative Example 6: The rest of the technical solutions of Comparative Example 6 are the same as those of Comparative Example 5, with the only difference being that, in Comparative Example 6, the potassium iodide in Comparative Example 5 is replaced by aluminum oxide.
[0074] Comparative Example 7: The rest of the technical solutions of Comparative Example 7 are the same as those of Comparative Example 5, with the only difference being that, in Comparative Example 7, the aluminum oxide in Comparative Example 5 is replaced by potassium iodide.
[0075] Comparative Example 8: The remaining technical solutions of Comparative Example 8 are the same as those of Example 5, except that, in Comparative Example 8, chloroform is not introduced into the reaction distillation tower.
[0076] Comparative Example 9: The rest of the technical solutions of this comparative example 9 are the same as those of Example 5, with the only difference being that, in this comparative example 9, the aluminum oxide in Example 5 is replaced by silicon dioxide.
[0077] Comparative Example 10: The rest of the technical solutions of Comparative Example 10 are the same as those of Example 5, with the only difference being that, in Comparative Example 10, the potassium iodide in Example 5 is replaced by silicon dioxide.
[0078] Comparative Example 11: The rest of the technical solutions of Comparative Example 11 are the same as those of Example 5, with the only difference being that, in Comparative Example 11, the potassium iodide in Example 5 is replaced by zirconium dioxide.
[0079] Comparative Example 12: The rest of the technical solutions of this Comparative Example 12 are the same as those of Example 5, with the only difference being that, in this Comparative Example 12, the potassium iodide in Example 5 is replaced by copper oxide.
[0080] In order to verify the technical effects achieved by the embodiments of the present application, the present application compares the implementation effects of embodiments 1-6 and comparative examples 1-12. The results are shown in Table 1 below:
[0081]
[0082] Through the above comparative implementation results, it can be seen that Examples 1-6 of the present application efficiently synthesized high-purity propylene carbonate under low-energy consumption and low-cost process conditions, and realized the continuous preparation and synthesis of propylene carbonate. The selected catalyst is widely available and easy to obtain, and there is no need for cumbersome catalyst separation or subsequent distillation of propylene carbonate.
[0083] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and range of equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.
[0084] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.
Claims
1. A method for synthesizing propylene carbonate, characterized in that: The steps are as follows: S1. Propylene oxide and carbon dioxide gas are continuously fed into a reaction distillation tower respectively; wherein the reaction distillation tower is filled with a combined catalyst, the combined catalyst is a mixture of metal oxides and potassium iodide; the metal oxide is aluminum oxide and / or zinc oxide; wherein the mass fraction of potassium iodide in the combined catalyst is 5-25%; The step S1 specifically includes the following steps: S11. Continuously feeding propylene oxide to the reaction distillation tower so that propylene oxide is fully in contact with the combined catalyst; the temperature of the reaction distillation tower is set at 40-70°C; S12. After the continuous feeding time of propylene oxide reaches 15-30 minutes, carbon dioxide gas is continuously introduced into the reaction distillation tower, and propylene oxide reacts with carbon dioxide gas to initially generate propylene carbonate; S2. continuously feeding a liquid light component raw material into a reaction distillation tower, wherein propylene oxide and carbon dioxide gas undergo a cycloaddition reaction in the reaction distillation tower to obtain a propylene carbonate product; wherein the top temperature of the reaction distillation tower is set to 35-80°C, the bottom temperature is set to 75-110°C, and the tower pressure is set to 0.2-1.5MPa; and the liquid light component raw material is chloroform and / or dichloromethane; S3. The gas phase is continuously extracted from the top of the reaction distillation tower and condensed, and the liquid propylene carbonate product is continuously extracted from the bottom of the reaction distillation tower; S4. The condensed liquid phase obtained after the gas phase is condensed is connected to the feeding pipeline of the liquid phase light component raw material to achieve the recycling of the liquid phase light component raw material.
2. The method for synthesizing propylene carbonate according to claim 1, characterized in that: The feed molar ratio of propylene oxide to carbon dioxide gas is 1:2-5, and the feed mass ratio of propylene oxide to liquid phase light component raw material is 1:4-7.
3. The method for synthesizing propylene carbonate according to claim 1, characterized in that: The feed flow rate of the propylene oxide is 10-100 mol / hour.
4. The method for synthesizing propylene carbonate according to claim 1, characterized in that: The reaction distillation tower comprises a distillation section at the top, a catalytic reaction section in the middle and a stripping section at the bottom; wherein the catalytic reaction section is provided with a propylene oxide feed port and a carbon dioxide gas feed port, and the stripping section is provided with a liquid phase light component feed port; the combined catalyst is loaded in the catalytic reaction section.
5. The method for synthesizing propylene carbonate according to claim 4, characterized in that: The number of plates of the reactive distillation tower ranges from 55 to 80; wherein the number of plates of the catalytic reaction section ranges from 25 to 45, and the propylene oxide feed port is located below the carbon dioxide gas feed port.
6. The method for synthesizing propylene carbonate according to claim 1, characterized in that: The purity of the liquid propylene carbonate product extracted in step S3 is not less than 99%.