System for preparing cyclic carbonate by catalyzing cycloaddition of carbon dioxide

Abstract

The utility model provides a system for preparing cyclic carbonate by catalyzing cycloaddition of carbon dioxide. The system comprises a cycloaddition reactor, a flash tank and a rectifying tower, a product outlet of the cycloaddition reactor is connected with a material inlet of the flash tank, a gas phase outlet of the flash tank is connected with a material inlet of the rectifying tower, and a liquid phase outlet of the flash tank is connected with the cycloaddition reactor; an enhanced mass transfer unit is arranged inside the cycloaddition reactor, the side wall of the cycloaddition reactor is sequentially connected with a first feeding pipeline for introducing an epoxy compound and a second feeding pipeline for introducing carbon dioxide from top to bottom, and the second feeding pipeline is connected with the enhanced mass transfer unit; carbon dioxide in the second feeding pipeline is treated by the enhanced mass transfer unit and then enters the cycloaddition reactor; a material inlet of the rectifying tower is lower than the middle position of the rectifying tower in the height direction of the rectifying tower, and a plurality of tower plates are arranged in the rectifying tower and staggered from top to bottom in the height direction of the rectifying tower. The system is favorable for improving the reaction efficiency.

Description

Technical Field

[0001] The utility model relates to the technical field of cyclic carbonate preparation, in particular to a system for preparing cyclic carbonate by catalyzing carbon dioxide cycloaddition. Background Art

[0002] Cyclic carbonates are an important class of chemical products, which have wide applications and prospects in the fields of lithium-ion battery electrolytes, degradable polymer monomers, and organic synthesis intermediates. The industrial synthesis of cyclic carbonates is a cycloaddition reaction of carbon dioxide and epoxy compounds. The existing process uses metal halides and ammonium salts as catalysts, and is prepared under the conditions of a reaction temperature of 100-150°C and a reaction operating pressure of 2.0-5.0MPa. However, both metal halides and ammonium salts contain halogen anions, which cause serious corrosion to metal equipment under high temperature and high pressure reaction conditions, and place high demands on the material of the reactor. At the same time, the reactors used in the existing processes are mostly kettle reactors, and carbon dioxide and epoxy compounds cannot be fully mixed, and the gas / liquid interface area is small, resulting in the need for the reaction to be carried out at a higher operating pressure, and the reaction rate is low.

[0003] In view of this, the present utility model is proposed. Utility Model Content

[0004] The first purpose of the utility model is to provide a system for preparing cyclic carbonates by catalytic carbon dioxide cycloaddition. The system disperses and breaks carbon dioxide into microbubbles at the micron level by arranging an enhanced mass transfer unit in the cycloaddition reactor, which helps to increase the gas-liquid mass transfer area with the epoxy compound, thereby helping to improve the raw material conversion rate and product yield.

[0005] The second object of the utility model is to provide a method for preparing cyclic carbonate by catalytic carbon dioxide cycloaddition. On the one hand, the method is implemented by the above-mentioned system, which helps to increase the gas-liquid mass transfer area with the epoxy compound, thereby helping to improve the raw material conversion rate and product yield; on the other hand, the method uses Schiff alkali metal and imidazole bicarbonate as catalysts, which have good catalytic activity, help to reduce the reaction temperature, and improve the selectivity of cyclic carbonate. At the same time, the catalyst does not contain halogen anions, which helps to reduce corrosion to metal equipment and improve the service life of the equipment.

[0006] In order to achieve the above-mentioned purpose of the utility model, the following technical solutions are adopted:

[0007] The utility model provides a system for preparing cyclic carbonate by catalytic carbon dioxide cycloaddition, comprising: a cycloaddition reactor, a flash tank and a distillation tower; the product outlet of the cycloaddition reactor is connected to the material inlet of the flash tank, the gas phase outlet of the flash tank is connected to the material inlet of the distillation tower, and the liquid phase outlet of the flash tank is connected to the cycloaddition reactor; an enhanced mass transfer unit is arranged inside the cycloaddition reactor, a first feed pipeline for introducing an epoxy compound and a second feed pipeline for introducing carbon dioxide are sequentially connected to the side wall of the cycloaddition reactor from top to bottom, the second feed pipeline is connected to the enhanced mass transfer unit, and the carbon dioxide in the second feed pipeline enters the cycloaddition reactor after being processed by the enhanced mass transfer unit, so as to enhance the mass transfer effect between carbon dioxide and the epoxy compound; the material inlet of the distillation tower is lower than the middle position of the distillation tower along the height direction of the distillation tower, a plurality of tower plates are arranged in the distillation tower, and the plurality of tower plates are staggered from top to bottom along the height direction of the distillation tower.

[0008] In the prior art, the reactors used for cycloaddition reactions are mostly kettle reactors, in which carbon dioxide and epoxy compounds cannot be fully mixed, and the gas / liquid interface area is small, resulting in the need for the reaction to be carried out at a higher operating pressure, and a lower reaction rate. The utility model provides an enhanced mass transfer unit in the cycloaddition reactor, which can disperse and break carbon dioxide into micro-bubbles at the micron level, and mix them with the epoxy compound to form a gas-liquid emulsion, thereby helping to increase the gas-liquid mass transfer area between carbon dioxide and the epoxy compound, thereby helping to reduce the operating temperature and pressure, reduce the energy consumption required for the reaction, and help to increase the reaction rate; in addition, the enhanced mass transfer unit of the utility model is provided inside the cycloaddition reactor, which occupies a small area and has high intrinsic safety.

[0009] In the technical solution of the utility model, the material inlet of the distillation tower is lower than the middle position of the distillation tower along the height direction of the distillation tower, and a plurality of trays are arranged in the distillation tower, and the plurality of trays are arranged staggered from top to bottom along the height direction of the distillation tower. This arrangement helps to extend the distillation path of the gas phase material sent from the flash tank to the distillation tower, prolong the distillation time, and thus help to improve the separation efficiency.

[0010] Preferably, the enhanced mass transfer unit comprises a first enhanced mass transfer reactor and a second enhanced mass transfer reactor, the first enhanced mass transfer reactor is arranged above the second enhanced mass transfer reactor, and the outlets of the first enhanced mass transfer reactor and the second enhanced mass transfer reactor are opposite.

[0011] In this scheme, the enhanced mass transfer unit consists of a first enhanced mass transfer reactor and a second enhanced mass transfer reactor. The reason for using two enhanced mass transfer reactors is to disperse and crush the carbon dioxide at the same time to improve the dispersion and crushing efficiency; at the same time, when the two enhanced mass transfer reactors are arranged, the first enhanced mass transfer reactor is arranged above the second enhanced mass transfer reactor, and the outlets of the two enhanced mass transfer reactors are opposite to each other. This is to allow the two microbubbles to offset each other, so that the microbubbles can be further broken, and it helps to promote the uniform distribution of microbubbles, which in turn helps to further increase the gas-liquid mass transfer area.

[0012] Preferably, a connecting pipe is provided between the outlets of the first enhanced mass transfer reactor and the second enhanced mass transfer reactor, and a plurality of output holes for outputting the internal materials are provided on the side wall of the connecting pipe. In this scheme, the connecting pipe can guide the two streams of microbubbles to collide along the connecting pipe, thereby further promoting the breakage of the microbubbles. The output holes on the side wall of the connecting pipe can provide an outlet for the broken microbubbles, and the broken microbubbles can be discharged from the connecting pipe along the output holes.

[0013] Preferably, a circulating fan blade is provided in the connecting pipe, and the circulating fan blade is used to rotate under the drive of the microbubbles output by the first enhanced mass transfer reactor and / or the second enhanced mass transfer reactor to stir the internal materials in the connecting pipe. In this scheme, the microbubbles output by the two enhanced mass transfer reactors can provide power for the rotation of the circulating fan blades, so that the circulating fan blades can stir the microbubbles during the collision of the two microbubbles, thereby helping to make the distribution of the microbubbles more uniform and helping to further cut and break the microbubbles using the circulating fan blades.

[0014] Preferably, the tower plate is tilted from top to bottom in a direction away from the side wall of the distillation tower; preferably, the tilt angle of the tower plate is in the range of [30°, 60°], wherein the tilt angle of the tower plate is the angle between the tower plate and the side wall of the distillation tower. This tilted arrangement helps to further extend the distillation path and improve the separation efficiency. The tilted tower plate can also play a drainage role, so that the liquid phase material (i.e., cyclic carbonate) on the wall of the distillation tower can be drained along the tower plate to the central part of the distillation tower, thereby helping to make the heat exchange in the distillation tower proceed in an orderly manner and improve the separation efficiency of the distillation tower.

[0015] Preferably, a first heat exchanger is provided on the second feed pipeline, and the gas phase outlet of the flash tank is connected to the material inlet of the distillation tower via the first heat exchanger. The gas phase material discharged from the gas phase outlet of the flash tank can be heat exchanged with the carbon dioxide in the second feed pipeline in the first heat exchanger, so that the waste heat of the gas phase material discharged from the gas phase outlet of the flash tank can be fully utilized to preheat the carbon dioxide, so that the carbon dioxide has a certain temperature before entering the cycloaddition reactor, which helps to improve the reaction efficiency of the raw materials. On the other hand, this heat exchange method can reduce the temperature of the gas phase material discharged from the gas phase outlet of the flash tank, so that the epoxy compounds and cyclic carbonates in the gas phase materials are initially separated and then enter the distillation tower for further separation, which helps to improve the separation efficiency of epoxy compounds and cyclic carbonates.

[0016] Preferably, a second heat exchanger is also included, the product outlet of the cycloaddition reactor is connected to the material inlet of the flash tank via the second heat exchanger, and the material outlet at the top of the distillation tower is connected to the first feed pipeline via the second heat exchanger, so that the epoxy compound obtained by distillation of the distillation tower can be directly transported to the cycloaddition reactor to continue to participate in the reaction, which helps to improve the utilization rate of raw materials. On the other hand, this method of using the waste heat of the epoxy compound obtained by distillation of the distillation tower to exchange heat with the material output from the cycloaddition reactor can pre-heat the material output from the cycloaddition reactor, which helps to shorten the heating time of the flash tank for the material output from the cycloaddition reactor and reduce the energy consumption of the flash tank; and this heat exchange method can reduce the temperature of the epoxy compound obtained by distillation of the distillation tower to avoid its excessive temperature affecting the reaction efficiency in the cycloaddition reactor. At the same time, the epoxy compound obtained by distillation in the distillation tower in this scheme is transported to the cycloaddition reactor via the first feed pipeline. The epoxy compound obtained by distillation in the distillation tower can be mixed with the epoxy compound in the first feed pipeline to preheat the epoxy compound, which helps to improve the reaction efficiency of the raw materials.

[0017] Those skilled in the art can understand that the enhanced mass transfer reactor adopted in the present invention has been embodied in the prior patents of the present invention, such as patents with application numbers CN201610641119.6, CN201610641251.7, CN201710766435.0, CN106187660, CN105903425A, CN109437390A, CN205833127U and CN207581700U. The prior patent CN201610641119.6 describes in detail the specific product structure and working principle of the micron bubble generator (i.e., bubble breaker). The application document states that "the micron bubble generator includes a main body and a secondary crushing member, a cavity is provided in the main body, an inlet connected to the cavity is provided on the main body, the first and second opposite ends of the cavity are open, wherein the cross-sectional area of ​​the cavity decreases from the middle of the cavity to the first and second ends of the cavity; the secondary crushing member is provided at at least one of the first and second ends of the cavity, a part of the secondary crushing member is provided in the cavity, and an annular channel is formed between the secondary crushing member and the through holes open at both ends of the cavity. The micron bubble generator also includes an air inlet pipe and a liquid inlet pipe." From the specific structure disclosed in the application document, it can be known that its specific working principle is: the liquid enters the micron bubble generator tangentially through the liquid inlet pipe, rotates at ultra-high speed and cuts the gas, so that the gas bubbles are broken into micron-level microbubbles, thereby increasing the mass transfer area between the liquid phase and the gas phase, and the micron bubble generator in the patent is a pneumatic bubble breaker.

[0018] In addition, the prior patent 201610641251.7 records that the primary bubble breaker has a circulating liquid inlet, a circulating gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker connects the feed port with the gas-liquid mixture outlet, indicating that the bubble breaker requires gas-liquid mixture to enter. In addition, it can be seen from the following figures that the primary bubble breaker mainly uses circulating liquid as power, so the primary bubble breaker actually belongs to a hydraulic enhanced reactor, and the secondary bubble breaker simultaneously passes the gas-liquid mixture into an elliptical rotating ball for rotation, thereby achieving bubble breaking during the rotation process, so the secondary bubble breaker actually belongs to a gas-liquid linkage type bubble breaker. In fact, whether it is a hydraulic bubble breaker or a gas-liquid linkage type bubble breaker, it is a specific form of a bubble breaker. However, the enhanced mass transfer reactor adopted by the utility model is not limited to the above-mentioned forms. The specific structure of the bubble breaker recorded in the prior patent is only one of the forms that can be adopted by the utility model.

[0019] In addition, the prior patent 201710766435.0 records that "the principle of the bubble breaker is a high-speed jet to achieve mutual collision of gases"; and the prior patent CN106187660 also has relevant records on the specific structure of the bubble breaker, see paragraphs

[0031] -

[0041] in the specification, and the drawings, which explain in detail the specific working principle of the bubble breaker S-2. The top of the bubble breaker is a liquid phase inlet, and the side is a gas phase inlet. The liquid phase coming in from the top provides suction power, thereby achieving the effect of crushing into ultrafine bubbles. It can also be seen in the drawings that the bubble breaker has a conical structure, and the diameter of the upper part is larger than the diameter of the lower part, so that the liquid phase can better provide suction power.

[0020] Since the bubble breaker was just developed in the early stage of the prior patent application, it was named micron bubble generator (CN201610641119.6) in the early stage. With the continuous technical improvement, it was renamed as bubble breaker in the later stage. Now the enhanced mass transfer reactor in the utility model is equivalent to the previous micron bubble generator, micro interface generator, etc., but the name is different. In summary, the enhanced mass transfer reactor of the utility model belongs to the prior art.

[0021] The utility model also provides a method for preparing cyclic carbonate by catalytic carbon dioxide cycloaddition, which is implemented by the above-mentioned system, and comprises the following steps: using Schiff alkali metal and imidazole bicarbonate as catalysts, carbon dioxide and epoxy compounds as raw materials, and performing cycloaddition reaction to generate cyclic carbonate, wherein the structural formula of the Schiff alkali metal catalyst is:

[0022]

[0023] Wherein, R is ethyl, phenyl, cyclohexyl or naphthyl, M is copper, manganese, zinc or aluminum, and X is Cl, Br, CH3, CH3CO2, BF4 or PF6;

[0024] The structural formula of imidazole bicarbonate is:

[0025]

[0026] Wherein, R1 is methyl, ethyl, propyl, n-butyl, n-pentyl or n-hexyl.

[0027] In the prior art, epoxy carbonate is generally reacted by carbon dioxide and epoxy compounds under the catalytic action of metal halides and ammonium salts, but the reaction has the following problems: the catalyst metal halides and ammonium salts used contain halogen anions, and under high temperature and high pressure conditions, halogen anions can cause corrosion to metal equipment, seriously affecting the service life of the equipment. For this reason, the utility model provides a method for preparing cyclic carbonate by catalytic carbon dioxide cycloaddition, the method adopts Schiff alkali metal and imidazole bicarbonate as catalysts, has good catalytic activity, helps to fully reduce the reaction temperature, improves the selectivity of cyclic carbonate, and the catalyst does not contain halogen anions, helps to reduce the corrosion of metal equipment, and improves the service life of the equipment. In addition, the method is implemented by the system in the above embodiment, which helps to improve the gas-liquid mass transfer area with the epoxy compound, thereby helping to reduce the operating temperature and pressure, and improve the raw material conversion rate and product yield.

[0028] Preferably, the cycloaddition reaction comprises: breaking carbon dioxide into microbubbles of micrometer level through a microinterface, and then mixing with an epoxy compound to carry out a cycloaddition reaction under the catalysis of a catalyst; preferably, the epoxy compound is ethylene oxide, propylene oxide, epichlorohydrin, butyl ethylene oxide, styrene oxide, isopropyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether or cyclohexene oxide. By combining microinterface breaking with the carbon dioxide cycloaddition reaction, the gas-liquid mass transfer area between carbon dioxide and the epoxy compound is increased, which is conducive to increasing the reaction rate and reducing energy consumption.

[0029] Preferably, the temperature of the cycloaddition reaction is 25-80°C, preferably 40°C; the reaction temperature can be 25°C, 30°C, 35°C, 40°C, 45°C, etc.

[0030] Preferably, the pressure of the cycloaddition reaction is 0.1-0.3 MPa, preferably 0.2 MPa. The reaction pressure can be 0.1 MPa, 0.2 MPa, 0.3 MPa, etc.

[0031] Compared with the prior art, the beneficial effects of the utility model are:

[0032] 1. The utility model provides an enhanced mass transfer unit in the cycloaddition reactor, so that the carbon dioxide can be dispersed and broken into micro-bubbles of micron level, and mixed with the epoxy compound to form a gas-liquid emulsion, thereby helping to increase the gas-liquid mass transfer area between the carbon dioxide and the epoxy compound, thereby helping to reduce the operating temperature and pressure, reduce the energy consumption required for the reaction, and at the same time help to increase the reaction rate.

[0033] 2. The enhanced mass transfer unit of the utility model is arranged inside the cycloaddition reactor, which occupies a small area and has high intrinsic safety.

[0034] 3. In the technical solution of the utility model, the material inlet of the distillation tower is lower than the middle position of the distillation tower along the height direction of the distillation tower, and a plurality of trays are arranged in the distillation tower, and the plurality of trays are arranged staggered from top to bottom along the height direction of the distillation tower. This arrangement helps to extend the distillation path of the gas phase material sent from the flash tank to the distillation tower, extend the distillation time, and thus help to improve the separation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limiting of the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0036] Figure 1 A schematic diagram showing a system for preparing cyclic carbonate by catalytic carbon dioxide cycloaddition according to one embodiment of the utility model;

[0037] Figure 2 The nuclear magnetic hydrogen spectrum of the catalyst SH4-Al(Cl) provided in Example 1 of the utility model;

[0038] Figure 3 The NMR carbon spectrum of the catalyst SH4-Al(Cl) provided in Example 1 of the present utility model;

[0039] Figure 4 The NMR hydrogen spectrum of the catalyst [C1C6Im[HCO3] provided in Example 1 of the present utility model;

[0040] Figure 5 The NMR carbon spectrum of the catalyst [C1C6Im[HCO3] provided in Example 1 of the present invention.

[0041] in:

[0042] 10-epoxide storage tank; 20-carbon dioxide storage tank;

[0043] 30-first feed pipeline; 40-second feed pipeline;

[0044] 50-cycloaddition reactor; 501-first enhanced mass transfer reactor;

[0045] 502-connecting pipe; 503-circulating fan blade;

[0046] 504-second enhanced mass transfer reactor; 60-second heat exchanger;

[0047] 70-flash tank; 80-first heat exchanger;

[0048] 90-distillation tower; 901-tower plate. DETAILED DESCRIPTION

[0049] The technical solution of the utility model will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but those skilled in the art will understand that the embodiments described below are part of the embodiments of the utility model, rather than all of the embodiments, and are only used to illustrate the utility model, and should not be considered as limiting the scope of the utility model. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the utility model. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0050] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0051] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] According to one aspect of the utility model, a system for preparing cyclic carbonate by catalytic carbon dioxide cycloaddition is provided. Figure 1 A schematic diagram of a system for preparing cyclic carbonate by catalytic carbon dioxide cycloaddition according to an embodiment of the present invention is shown. Figure 1As shown, the system comprises: a cycloaddition reactor 50, a flash tank 70 and a distillation tower 90; the product outlet of the cycloaddition reactor 50 is connected to the material inlet of the flash tank 70, the gas phase outlet of the flash tank 70 is connected to the material inlet of the distillation tower 90, and the liquid phase outlet of the flash tank 70 is connected to the cycloaddition reactor 50; an enhanced mass transfer unit is arranged inside the cycloaddition reactor 50, and the side wall of the cycloaddition reactor 50 is sequentially connected with a first feed pipeline 30 for introducing an epoxy compound and a first feed pipeline 30 for introducing a dioxygen compound from top to bottom. A second feed pipeline 40 for carbon dioxide is connected to the enhanced mass transfer unit. The carbon dioxide in the second feed pipeline 40 enters the cycloaddition reactor 50 after being processed by the enhanced mass transfer unit to enhance the mass transfer effect between carbon dioxide and epoxides; the material inlet of the distillation tower 90 is lower than the middle position of the distillation tower 90 along the height direction of the distillation tower 90, and a plurality of tower plates 901 are arranged in the distillation tower 90, and the plurality of tower plates 901 are staggered from top to bottom along the height direction of the distillation tower 90.

[0053] In the scheme of this example, the carbon dioxide in the second feed pipeline 40 is processed by the enhanced mass transfer unit and then enters the cycloaddition reactor 50. In other words, the carbon dioxide in the second feed pipeline 40 can be dispersed and broken into micron-level microbubbles by the enhanced mass transfer unit. The micron-level microbubbles herein refer to microbubbles with a diameter greater than or equal to 1 μm and less than 1 mm.

[0054] Optionally, the enhanced mass transfer unit can be composed of one or more enhanced mass transfer reactors. The specific type of the enhanced mass transfer reactor may include but is not limited to one or a combination of a pneumatic enhanced mass transfer reactor, a hydraulic enhanced mass transfer reactor, and a gas-liquid linkage enhanced mass transfer reactor. When the enhanced mass transfer unit is composed of multiple enhanced mass transfer reactors, the arrangement of multiple enhanced mass transfer reactors can be arranged according to actual needs. For example, the enhanced mass transfer unit may include two enhanced mass transfer reactors. In some implementation schemes, the two enhanced mass transfer reactors may be arranged at the same height, and the outlet directions of the two enhanced mass transfer reactors may be the same, for example, they may all face upward. Of course, the outlet directions of the two enhanced mass transfer reactors may also be different, for example, the outlet of one of the enhanced mass transfer reactors may face upward, and the outlet of the other enhanced mass transfer reactor may face downward. In other implementation schemes, the two enhanced mass transfer reactors may also be arranged at different heights. For example, one of the enhanced mass transfer reactors may be located above another enhanced mass transfer reactor.

[0055] Optionally, the tower plate 901 can be horizontally arranged in the distillation tower 90, or can be inclinedly arranged in the distillation tower 90, for example, it can be inclined from bottom to top along the direction away from the side wall of the distillation tower 90, or it can be inclined from top to bottom along the direction away from the side wall of the distillation tower 90.

[0056] Optionally, a pump may be provided on both the first feed pipeline 30 and the second feed pipeline 40. Figure 1 In the illustrated embodiment, an inlet of the first feed line 30 may be connected to the epoxy compound storage tank 10 , and an inlet of the second feed line 40 may be connected to the carbon dioxide storage tank 20 .

[0057] Preferably, if Figure 1 As shown, the enhanced mass transfer unit includes a first enhanced mass transfer reactor 501 and a second enhanced mass transfer reactor 504. The first enhanced mass transfer reactor 501 is arranged above the second enhanced mass transfer reactor 504, and the outlets of the first enhanced mass transfer reactor 501 and the second enhanced mass transfer reactor 504 are opposite. Figure 1 In the illustrated embodiment, the first enhanced mass transfer reactor 501 and the second enhanced mass transfer reactor 504 are both pneumatic enhanced mass transfer reactors.

[0058] Preferably, if Figure 1 As shown, a connecting pipe 502 is provided between the outlets of the first enhanced mass transfer reactor 501 and the second enhanced mass transfer reactor 504, and a plurality of output holes for outputting the internal materials are provided on the side wall of the connecting pipe 502. The plurality of output holes have different directions, respectively, thereby facilitating the output of the broken microbubbles in the connecting pipe 502 along the output holes to different positions in the cycloaddition reactor 50, thereby facilitating the distribution of the microbubbles to be more uniform.

[0059] Preferably, if Figure 1 As shown, a circulation fan blade 503 is provided in the connecting pipe 502 , and the circulation fan blade 503 is used to rotate under the drive of the microbubbles output by the first enhanced mass transfer reactor 501 and / or the second enhanced mass transfer reactor 504 to stir the internal material in the connecting pipe 502 .

[0060] Preferably, if Figure 1 As shown, the tray 901 is tilted from top to bottom in a direction away from the side wall of the distillation tower 90. Preferably, the tilt angle of the tray 901 is in the range of [30°, 60°], wherein the tilt angle of the tray 901 is the angle between the tray 901 and the side wall of the distillation tower 90. Figure 1 In the illustrated embodiment, the inclination angle of the tray 901 is 60°.

[0061] Preferably, if Figure 1 As shown, a first heat exchanger 80 is disposed on the second feed pipeline 40 , and the gas phase outlet of the flash tank 70 is connected to the material inlet of the distillation tower 90 via the first heat exchanger 80 .

[0062] Preferably, if Figure 1As shown, the system also includes a second heat exchanger 60, and the product outlet of the cycloaddition reactor 50 is connected to the material inlet of the flash tank 70 via the second heat exchanger 60, and the material outlet at the top of the distillation tower 90 is connected to the first feed pipeline 30 via the second heat exchanger 60, so as to transport the epoxide compound obtained by distillation in the distillation tower 90 to the cycloaddition reactor 50 via the first feed pipeline 30.

[0063] According to another aspect of the utility model, a method for preparing cyclic carbonate by catalytic carbon dioxide cycloaddition is provided. The method is implemented by the system in any of the above embodiments. The method comprises the following steps: using Schiff alkali metal and imidazole bicarbonate as catalysts, carbon dioxide and epoxy compounds as raw materials, and performing cycloaddition reaction to generate cyclic carbonate. The structural formula of the Schiff alkali metal catalyst is:

[0064]

[0065] Wherein, R is ethyl, phenyl, cyclohexyl or naphthyl, M is copper, manganese, zinc or aluminum, and X is Cl, Br, CH3, CH3CO2, BF4 or PF6;

[0066] The structural formula of imidazole bicarbonate is:

[0067]

[0068] Wherein, R1 is methyl, ethyl, propyl, n-butyl, n-pentyl or n-hexyl.

[0069] Preferably, the cycloaddition reaction comprises: breaking carbon dioxide into microbubbles of micrometer level through a microinterface, and then mixing the carbon dioxide with an epoxy compound to carry out a cycloaddition reaction under the catalysis of a catalyst.

[0070] Preferably, the epoxy compound is ethylene oxide, propylene oxide, epichlorohydrin, butylethylene oxide, styrene oxide, isopropyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether or cyclohexene oxide.

[0071] Preferably, the temperature of the cycloaddition reaction is 25-80°C, preferably 40°C.

[0072] Preferably, the pressure of the cycloaddition reaction is 0.1-0.3 MPa, preferably 0.2 MPa.

[0073] In order to more clearly explain the technical solution of the present invention, it is described in the form of specific embodiments below.

[0074] Example 1

[0075] In this embodiment, the Figure 1 The system shown prepares cyclic carbonates.

[0076] In this embodiment, the epoxy compound is propylene oxide.

[0077] The method for preparing cyclic carbonate in this embodiment is as follows: Schiff alkali metal and imidazole bicarbonate catalyst are loaded into the cycloaddition reactor 50, propylene oxide and carbon dioxide are introduced into the cycloaddition reactor 50, and react under the conditions of pressure of 0.2 MPa and reaction temperature of 40° C. The reaction product enters the flash tank 70, and the propylene oxide and cyclic carbonate carried therein are vaporized in the flash tank 70 and enter the distillation tower 90, and the catalyst at the bottom is transported back to the cycloaddition reactor 50.

[0078] Propylene oxide and cyclic carbonate are separated in the distillation tower 90 , propylene oxide is discharged from the material outlet at the top of the distillation tower 90 , and is transported to the cycloaddition reactor 50 via the first feed pipeline 30 , and the product cyclic carbonate flows out at the bottom of the distillation tower 90 .

[0079] In this embodiment, the central metal element M of the Schiff base metal compound is aluminum, the bridging group R is naphthyl, R1 of the imidazole bicarbonate is methyl, and R2 is n-hexyl.

[0080] The production intensity of cyclic carbonate is 580kg / m 3 ·h, its nuclear magnetic hydrogen spectrum is as follows Figure 2 shown.

[0081] According to the test, the separation efficiency of the distillation tower is 83%.

[0082] Embodiment 2-4

[0083] The system and method for preparing carbonate ester by reacting propylene oxide with carbon dioxide in Example 1 were used, and the central metal element M of the Schiff alkali metal compound was changed. The results are shown in Table 1:

[0084] Table 1

[0085]

[0086] According to the data of Examples 1-4, it can be seen that when preparing cyclic carbonates, the system can be guaranteed to have good production intensity when using Schiff base metal compounds with different central metal elements M as catalysts. Among them, the production intensity of the system is the best when the central metal element M is zinc.

[0087] Embodiment 5-7

[0088] The system and method for preparing cyclic carbonate by reacting propylene oxide with carbon dioxide in Example 1 were used, and the bridging group R of the Schiff base aluminum compound was changed. The results are shown in Table 2:

[0089] Table 2

[0090] Example R <![CDATA[Production intensity of cyclic carbonate (kg / m 3 ·h)]]> 5 <![CDATA[Ethyl SH1 - Al(Cl)]]> 482 6 <![CDATA[Cyclohexyl SH2 - Al(Cl)]]> 511 7 <![CDATA[Phenyl SH3 - Al(Cl)]]> 542

[0091] According to the data of Example 1 and Examples 5-7, it can be seen that when preparing cyclic carbonates, the use of Schiff alkali metal compounds with different bridging groups R as catalysts can ensure that the system has good production intensity. Among them, the production intensity of the system is the best when the bridging group R is phenyl.

[0092] Examples 8-12

[0093] The system and method for preparing cyclic carbonate by reacting propylene oxide with carbon dioxide in Example 1 were used, and R1 and R2 of imidazole bicarbonate were changed. The results are shown in Table 3:

[0094] Table 3

[0095]

[0096] According to the data of Example 1 and Examples 8-12, it can be seen that when preparing cyclic carbonate, using imidazole bicarbonate with different R1 and R2 as catalyst can ensure that the system has good production intensity. Among them, the production intensity of the system is the best when R1 is n-hexyl and R2 is n-hexyl.

[0097] Examples 13-16

[0098] The system and method for preparing cyclic carbonate by reacting propylene oxide with carbon dioxide in Example 1 were used, and the reaction temperature was changed. The results are shown in Table 4:

[0099] Table 4

[0100]

[0101] According to the data of Example 1 and Examples 8-12, it can be seen that the system still has good production intensity even at a relatively low temperature (25°C-45°C) when the Schiff alkali metal and imidazole bicarbonate are used as catalysts to catalyze carbon dioxide cyclization to prepare cyclic carbonate. Therefore, the utility model helps to reduce the temperature required for preparing cyclic carbonate by using Schiff alkali metal and imidazole bicarbonate as catalysts.

[0102] Examples 17-18

[0103] The system and method for preparing cyclic carbonate by reacting propylene oxide with carbon dioxide in Example 1 were used, and the reaction pressure was changed. The results are shown in Table 5:

[0104] Table 5

[0105]

[0106] According to the data of Example 1 and Examples 8-12, it can be seen that the system still has good production intensity even under the condition of low pressure (0.1-0.3MPa) by using Schiff alkali metal and imidazole bicarbonate as catalysts to catalyze carbon dioxide cyclization to prepare cyclic carbonate. Therefore, the utility model helps to reduce the pressure required for preparing cyclic carbonate by using Schiff alkali metal and imidazole bicarbonate as catalysts.

[0107] In summary, it can be seen from the experimental data of Examples 1-21 that the use of Schiff alkali metals and imidazole bicarbonate as catalysts to catalyze the carbon dioxide cyclization to prepare cyclic carbonates still has good production intensity even under low temperature and low pressure conditions. Therefore, the utility model uses Schiff alkali metals and imidazole bicarbonate as catalysts to catalyze the carbon dioxide cyclization, and limits the reaction temperature and reaction pressure, thereby achieving a reaction under lower temperature and pressure conditions, reducing reaction energy consumption, and having a higher reaction efficiency.

[0108] Embodiment 19

[0109] The difference between this embodiment and embodiment 1 is that no circulation fan blades are provided.

[0110] The production intensity of cyclic carbonate is 552kg / m 3 ·h.

[0111] By comparing the production intensity of the cyclic carbonate obtained by each of Example 1 and Example 19, it can be found that the production intensity of the cyclic carbonate in Example 1 is significantly better than that in Example 19. This may be because the circulating fan blades can stir the microbubbles during the reaction, making the distribution of the microbubbles more uniform, and can cut and break the microbubbles, making the volume of the microbubbles smaller and the mass transfer area larger. In other words, the scheme of Example 1 significantly improves the reaction efficiency by setting the circulating fan blades.

[0112] Embodiment 20

[0113] The difference between this embodiment and embodiment 1 is that no connecting pipe is provided, and the circulation fan blades are provided between the two enhanced mass transfer reactors.

[0114] The production intensity of cyclic carbonate is 543kg / m 3 ·h.

[0115] By comparing the production intensities of the cyclic carbonates obtained in Example 19 and Example 20, it can be found that the production intensities of the cyclic carbonates in Example 19 and Example 20 are not much different. This may be because when no connecting pipe is set, the impact effect of the two microbubbles on the circulating fan blades is poor, resulting in poor stirring and cutting effects of the circulating fan blades.

[0116] By comparing the production intensity of cyclic carbonate measured in Example 1 and Example 20, it can be found that the production intensity of cyclic carbonate in Example 1 is significantly better than that in Example 20. This may be due to the following two reasons: on the one hand, the connecting pipe can guide the two streams of microbubbles, guide the two streams of microbubbles to collide along the connecting pipe, and promote the breakage of microbubbles; on the other hand, the microbubbles are more concentrated under the guidance of the connecting pipe, and the impact effect on the circulating fan blades is better, so that the circulating fan blades can achieve better stirring and cutting effects, thereby further increasing the mass transfer area of ​​the microbubbles, and facilitating a more uniform distribution of the microbubbles.

[0117] Combining the data of Example 1, Example 19 and Example 20, it can be seen that in the scheme of Example 1, by combining the connecting pipe and the circulating fan blade, the dispersion and crushing effect of the microbubbles can be significantly improved, and the phase boundary mass transfer area of ​​the reactants can be increased, which helps to further improve the reaction efficiency.

[0118] Embodiment 21

[0119] The difference between this embodiment and embodiment 1 is that the second enhanced mass transfer reactor is not provided.

[0120] The production intensity of cyclic carbonate is 467kg / m 3 ·h.

[0121] By comparing the production intensity of the cyclic carbonate measured in Example 1 and Example 21, it can be found that the production intensity of the cyclic carbonate in Example 1 is significantly better than that in Example 21. It can be seen that the scheme of Example 1 significantly improves the reaction efficiency by adopting two enhanced mass transfer reactors and aligning the outlets of the two enhanced mass transfer reactors relative to each other.

[0122] Embodiment 22

[0123] The difference between this embodiment and embodiment 1 is that the plates in the distillation tower are arranged horizontally.

[0124] According to the test, the separation efficiency of the distillation tower is 80%.

[0125] By comparing the separation efficiency of the distillation towers obtained in Example 1 and Example 22, it can be seen that the separation efficiency of the distillation tower in Example 1 is better than that in Example 22. This may be because the inclined arrangement of the tower plates can further extend the distillation path, thereby improving the separation efficiency.

[0126] Comparative Example 1

[0127] The difference between this example and Example 1 is that the enhanced mass transfer unit is replaced by an annular bubbling tube.

[0128] After testing, the production intensity of cyclic carbonate is 398kg / m 3 ·h.

[0129] The structure of the reactor in Comparative Example 1 is a bubbling reactor commonly used in the relevant art. The production intensity of the cyclic carbonate obtained by measuring each of Comparative Example 1-21 and Comparative Example 1 can be found that the production intensity of the cyclic carbonate in Examples 1-21 is significantly better than that in Comparative Example 1. It can be seen that under the same reaction conditions and operating conditions, the technical scheme of the present application significantly improves the production intensity of the cyclic carbonate by applying the enhanced mass transfer unit. Among them, the improvement degree of the production intensity of the cyclic carbonate in the scheme of Example 1 is the most obvious, compared with Comparative Example 1, it has increased by about 46%.

[0130] Comparative Example 2

[0131] The difference between this example and Example 1 is that no trays are provided in the distillation tower.

[0132] According to the test, the separation efficiency of the distillation tower is 75%.

[0133] By comparing the separation efficiencies of the distillation towers obtained in Example 1, Example 22, and Comparative Example 2, it can be seen that the separation efficiencies of the distillation towers in Example 1 and Example 22 are significantly better than those in Comparative Example 2. This indicates that the present application significantly improves the separation efficiency of the distillation tower by arranging a tray in the distillation tower.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A system for preparing cyclic carbonates by catalytic carbon dioxide cycloaddition, characterized in that: include: A cycloaddition reactor, a flash tank and a distillation tower; the product outlet of the cycloaddition reactor is connected to the material inlet of the flash tank, the gas phase outlet of the flash tank is connected to the material inlet of the distillation tower, and the liquid phase outlet of the flash tank is connected to the cycloaddition reactor; The cycloaddition reactor is provided with an enhanced mass transfer unit inside, and the side wall of the cycloaddition reactor is connected with a first feed pipeline for introducing an epoxy compound and a second feed pipeline for introducing carbon dioxide in sequence from top to bottom, the second feed pipeline is connected to the enhanced mass transfer unit, and the carbon dioxide in the second feed pipeline enters the cycloaddition reactor after being processed by the enhanced mass transfer unit, so as to enhance the mass transfer effect between carbon dioxide and epoxy compounds; The material inlet of the distillation tower is lower than the middle position of the distillation tower along the height direction of the distillation tower. A plurality of tower plates are arranged in the distillation tower, and the plurality of tower plates are staggered from top to bottom along the height direction of the distillation tower.

2. The system according to claim 1, characterized in that The enhanced mass transfer unit includes a first enhanced mass transfer reactor and a second enhanced mass transfer reactor. The first enhanced mass transfer reactor is arranged above the second enhanced mass transfer reactor, and the outlets of the first enhanced mass transfer reactor and the second enhanced mass transfer reactor are opposite.

3. The system according to claim 2, characterized in that A connecting pipe is arranged between the outlets of the first enhanced mass transfer reactor and the outlet of the second enhanced mass transfer reactor, and a plurality of output holes for outputting internal materials are arranged on the side wall of the connecting pipe.

4. The system according to claim 3, characterized in that The communicating pipe is provided with a circulation blade, and the circulation blade is used to rotate under the drive of the microbubbles output by the first enhanced mass transfer reactor and / or the second enhanced mass transfer reactor to stir the internal material in the communicating pipe.

5. The system according to any one of claims 1 to 4, characterized in that: The tower plates are arranged to be inclined from top to bottom in a direction away from the side wall of the distillation tower.

6. The system according to claim 5, characterized in that The inclination angle of the tower plate is in the range of [30°, 60°], wherein the inclination angle of the tower plate is the angle between the tower plate and the side wall of the distillation tower.

7. The system according to any one of claims 1 to 4, characterized in that: The second feed pipeline is provided with a first heat exchanger, and the gas phase outlet of the flash tank is connected to the material inlet of the distillation tower via the first heat exchanger.

8. The system according to any one of claims 1 to 4, characterized in that: It also includes a second heat exchanger, and the product outlet of the cycloaddition reactor is connected to the material inlet of the flash tank via the second heat exchanger, and the material outlet at the top of the distillation tower is connected to the first feed pipeline via the second heat exchanger, so as to transport the epoxide obtained by distillation in the distillation tower to the cycloaddition reactor via the first feed pipeline.

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