A system for preparing carbonate ester and a method for preparing carbonate ester

Abstract

The present invention belongs to the technical field of organic synthesis, and specifically relates to a system for preparing carbonate and a method for preparing carbonate, wherein the system for preparing carbonate comprises a main reactor, a light component flash tank, a tail gas recovery reactor, a dilute phase catalyst recovery tank, a dense phase catalyst recovery tank, a crude product condenser and a crude product tank; a liquid phase formed by mixing alkylene oxide and a dilute phase catalyst continuously flows into the main reactor to react with carbon dioxide, and the generated reaction heat is continuously transferred by a heat transfer tray, and the crude product of the main reactor enters the light component flash tank, and the flash gas and the pressure-stabilized tail gas of the main reactor are passed into the tail gas recovery reactor to react under the action of a dense phase catalyst to achieve tail gas recovery. In the present invention, a multi-layer heat transfer tray is arranged in the main reactor, so as to avoid problems such as excessive local reaction heat, increase the concentration of the catalyst in the tail gas recovery reactor, convert low-concentration reactants into carbonate products, and increase the raw material conversion rate and target carbonate product yield of the entire device.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a system for preparing carbonate ester and a method for preparing carbonate ester. Background Art

[0002] The direct catalytic addition reaction of carbon dioxide with ethylene oxide or propylene oxide is the main method for preparing ethylene carbonate or propylene carbonate. The main reaction equation is:

[0003] C2H4O (ethylene oxide) + CO2 (carbon dioxide) → C3H4O3 (ethylene carbonate)

[0004] C3H6O (propylene oxide) + CO2 (carbon dioxide) → C4H6O3 (propylene carbonate)

[0005] The above reaction process mostly uses homogeneous catalysts, and carbon dioxide and alkylene oxide are dissolved in the corresponding carbonate solution with the catalyst to react. The industrial device has the following characteristics, which must be considered in the industrial process:

[0006] (1) The reaction is a highly exothermic process, and the reaction heat needs to be removed in time, otherwise it is very easy to cause overheating of the reaction liquid and catalyst, overpressure of the reactor, and loss of control of the reaction process;

[0007] (2) The reaction raw materials alkylene oxide and carbon dioxide have low boiling points and high vapor pressures, and are easily vaporized when the reaction liquid is overheated, causing the reaction liquid to be mixed and the reactor to be overpressured. At the same time, the overpressure venting will lead to the loss of the raw materials alkylene oxide and carbon dioxide, increasing the unit consumption of the product.

[0008] (3) Reaction intensity is closely related to the concentration of catalyst and reactants in the reaction liquid, and is a parameter that needs to be strictly controlled during the reaction process. Taking a vertical reactor as an example, alkylene oxide and catalyst solution enter from the top of the reactor and flow from top to bottom, and carbon dioxide gas enters from the bottom of the reactor and flows from bottom to top; under the action of the catalyst, carbon dioxide gas contacts alkylene oxide to form carbonate. From top to bottom in the reactor: With the continuous generation of carbonate, the mass of the reaction liquid continues to increase, and the mass of alkylene oxide is gradually consumed and reduced, so the mass concentration of alkylene oxide and catalyst in the reaction liquid gradually decreases; the mass of carbon dioxide dissolved in the reaction liquid in the upper part of the reactor is less, and the mass of carbon dioxide dissolved in the reaction liquid in the lower part is more. Correspondingly, the mass concentration of carbon dioxide in the reaction liquid gradually increases, which is exactly the opposite of the concentration change trend of the other reactants, namely alkylene oxide and catalyst. The actual phenomenon on site caused by this situation is: from top to bottom in the reactor, the reaction intensity is uneven and the difference is large, and the change in reaction intensity is not simply a gradual decay or increase, but a wave-like fluctuation. In this way, timely and sufficient removal of reaction heat in areas with higher reaction intensity and reducing heat removal in areas with lower reaction intensity are the key to controlling the temperature uniformity in the entire reactor and maintaining it within a narrow window range to avoid local overheating, overtemperature and overpressure. This is an issue that must be considered in the device.

[0009] (4) The raw material carbon dioxide is a gas phase feed, and the alkylene oxide is a low boiling point substance. The uniform and sufficient dissolution of both in the reaction liquid is the key to fully proceeding with the reaction, improving the conversion rate of the reactants, and reducing the consumption of raw materials;

[0010] (5) The reaction raw material alkylene oxide inevitably contains a small amount of water, which will produce a small amount of by-products. Taking ethylene oxide and carbon dioxide as raw materials to prepare ethylene carbonate as an example, the side reaction equation is:

[0011] C2H4O(ethylene oxide)+H2O(water)→C2H6O2(ethylene glycol)

[0012] C2H4O(ethylene oxide)+C2H6O2(ethylene glycol)→C4H 10 O3(Diethylene glycol)

[0013] C2H4O(ethylene oxide)+C4H 10 O3(diethylene glycol)→C6H 14 O4(Triethylene glycol)

[0014] C3H4O3 (ethylene carbonate) + H2O (water) → C2H6O2 (ethylene glycol) + CO2 (carbon dioxide)

[0015] Among them, the boiling points of the by-product diethylene glycol and ethylene carbonate are quite close, with a difference of only 3°C, which can easily lead to substandard high-purity ethylene carbonate products. This requires that the temperature of the reaction process be controlled within a very narrow window range to avoid the active range of side reactions as much as possible.

[0016] The patent document with Chinese invention patent application number 201810293831.0, authorization announcement number CN 108484565 B, and authorization announcement date 2021.03.19 discloses a system for producing carbonates and a method for producing carbonates using the system. The invention is provided with a first bubbling tower, a second bubbling tower and a heat exchanger, and the reaction circulating material is cooled by the heat exchanger to remove the reaction heat and control the reaction temperature in the bubbling tower. However, the invention has the following shortcomings: in order to control the temperature of the reaction material at the outlet of the bubbling tower from overheating, the circulating material can only be cooled by the heat exchanger, the circulating material temperature at the outlet of the heat exchanger is low, and the reaction temperature at the inlet of the bubbling tower is low. There is a large temperature difference from the inlet to the outlet in the first bubbling tower and the second bubbling tower, and the reaction temperature range is wide. The temperature of the entire reaction process cannot be controlled within the optimal reaction temperature range, which will lead to a decrease in the yield of ethylene carbonate or propylene carbonate, a large number of reaction by-products, rapid catalyst deactivation, and large catalyst loss; at the same time, the first bubbling tower and the second bubbling tower are only cooled by gas. The distributor distributes the carbon dioxide gas, which may easily lead to the deviation of the carbon dioxide gas in the reaction liquid, insufficient dissolution, and even the lifting of the ethylene oxide or propylene oxide gas dissolved in the reaction liquid to the gas phase. In order to maintain the stable pressure at the top of the first bubbling tower during the production process, it is inevitable that part of the tail gas containing carbon dioxide and ethylene oxide or propylene oxide will be discharged from the top thereof. When the carbonate is sent to the gas-liquid separator for pressure relief and gas-liquid separation, unreacted carbon dioxide and ethylene oxide or propylene oxide tail gas will also be discharged. However, the invention fails to recycle these tail gases, which will lead to higher raw material consumption and low yield of the target product.

[0017] The Chinese utility model patent application No. 201822116060.6, the authorization announcement No. CN 209456353 U, and the patent document with the authorization announcement date of October 1, 2019 discloses a ethylene carbonate synthesis reaction device. The utility model is provided with a reaction circulation pump, a circulating liquid cooler, and a circulating liquid heater. The bottom of the first reactor is connected to the bottom of the second reactor through the circulating liquid cooler, and the lower end of the circulating liquid heater is connected to the circulating liquid cooler through the reaction circulation pump. The shortcomings of the utility model are as follows: the circulating liquid of the first reactor is forced to circulate through the reaction circulation pump. Once the reaction circulation pump fails, the reaction heat cannot be removed from the reaction system in time, which will cause the first reactor and the second reactor to overheat and overpressure, and the device will be shut down; when the device is large-scale and the reactor size is high, the temperature difference between the top of the first reactor and the bottom of the first reactor is large, which is not conducive to controlling the reaction temperature within a narrow catalyst optimal reaction temperature window, reducing reaction by-products, increasing the yield of ethylene carbonate, and extending the service life of the catalyst; the vented gas phase at the top of the first reactor is collected in the overpressure vent tank and then sent to the thin film evaporator, and the entrained carbon dioxide and ethylene oxide cannot re-enter the reaction system for recovery and conversion into ethylene carbonate products, and the yield of ethylene carbonate products is low.

[0018] Therefore, providing a carbonate synthesis system and method that can remove reaction heat in time, control the reaction within a narrow temperature range, easily control the reaction process, produce fewer side reaction products, easily purify the crude product, evenly distribute and dissolve the reactants in the reaction solution, and effectively recover the reaction tail gas will have broad application prospects. Summary of the invention

[0019] The purpose of the present invention is to provide a system and method for preparing carbonate esters, which solve the problems of untimely heat transfer, wide reaction temperature range, easy over-temperature and over-pressure of the reactor, large number of reaction by-products, difficulty in refining crude products to meet the standards, uneven dissolution and distribution of reactants in the reaction solution, and failure to effectively recover the reaction tail gas.

[0020] To achieve the above object, the technical solution adopted by the present invention is:

[0021] A system for preparing carbonate, comprising a main reactor, a light component flash tank, a tail gas recovery reactor, a dilute phase catalyst recovery tank, a dense phase catalyst recovery tank, a crude product condenser and a crude product tank;

[0022] The main reactor is respectively provided with a pressure-stabilized tail gas discharge port, a liquid phase feed port, a gas phase feed port and a main reactor crude product discharge port, the liquid phase feed port is connected with a liquid phase feed pipe for introducing alkylene oxide, supplementary catalyst and dilute phase catalyst into the main reactor, and the gas phase feed port is connected with a gas phase feed pipe for introducing carbon dioxide gas into the main reactor;

[0023] The light component flash tank is respectively provided with a light component output port, a main reactor crude product input port and a main reactor crude product discharge port after flash evaporation, and the main reactor crude product input port is connected to the main reactor crude product discharge port;

[0024] The dilute phase catalyst recovery tank is respectively provided with a crude product gas discharge port A, a dilute phase catalyst discharge port, a crude product input port of the post-flash main reactor and a crude product input port of the tail gas recovery reactor, and the crude product input port of the post-flash main reactor is connected to the crude product discharge port of the post-flash main reactor;

[0025] The dense phase catalyst recovery tank is respectively provided with a crude product gas discharge port B, a dense phase catalyst discharge port and a dilute phase catalyst input port, and the dilute phase catalyst input port is connected to the dilute phase catalyst discharge port;

[0026] The input end of the crude product condenser is respectively connected to the crude product gas outlet A and the crude product gas outlet B;

[0027] The crude product tank is provided with a crude product input port and a crude product output port, respectively. The crude product input port is connected to the output end of the crude product condenser, and the crude product output port is connected to the product refining process;

[0028] The tail gas recovery reactor is respectively provided with a tail gas output port at the top of the tail gas recovery reactor, a crude product discharge port of the tail gas recovery reactor, an input port for a dense phase catalyst, a pressure-stabilized tail gas input port and a light component input port; the crude product discharge port of the tail gas recovery reactor is connected with the crude product input port of the tail gas recovery reactor, the pressure-stabilized tail gas input port is connected with the pressure-stabilized tail gas discharge port, the light component input port is connected with the light component output port, and the dense phase catalyst input port is connected with the dense phase catalyst discharge port.

[0029] The dilute phase catalyst discharge port is also communicated with the liquid phase feed pipe.

[0030] The main reactor is provided with a plurality of layers of heat transfer trays from top to bottom, each layer of the heat transfer tray is provided with a heat transfer pipe, one end of the heat transfer pipe is a heat transfer medium inlet, and the other end is a heat transfer medium outlet, and the heat transfer medium inlet and the heat transfer medium outlet both extend to the outside of the main reactor;

[0031] A plurality of gas lifting channels are provided on the heat transfer tray outside the heat transfer pipe.

[0032] The heat transfer tray is provided with a plurality of rows of gas-raising passages arranged in parallel, and the heat transfer pipes bypass the gas-raising passages in each row in sequence.

[0033] A gap is formed between the heat transfer tray and the inner wall of the main reactor, an overflow weir is arranged on one side of the heat transfer tray close to the gap, and a downcomer is formed between the overflow weir and the inner wall of the main reactor.

[0034] The main reactor is provided with multiple layers of heat transfer trays from top to bottom, and the notches of each layer are arranged at positions opposite to the notches of the adjacent layer in the main reactor.

[0035] The air-raising channel may be in the form of a bubble cap, a float valve, etc.;

[0036] The heat transfer tube can be a plain tube, a finned tube, etc.

[0037] The heat transfer medium is thermal oil or cooling water;

[0038] The main reactor may have multiple gas phase feed pipes.

[0039] A method for preparing carbonate esters by using the carbonate preparation system, wherein a liquid phase formed by mixing alkylene oxide and a dilute phase catalyst continuously flows into a main reactor to react with carbon dioxide to generate carbonate esters, the generated reaction heat is continuously transferred by a heat transfer tray, a crude product of the main reactor enters a light component flash tank, and the flash gas and the pressure-stabilized tail gas of the main reactor are introduced into a tail gas recovery reactor to react under the action of a dense phase catalyst to generate carbonate esters, thereby realizing tail gas recovery.

[0040] Specifically, the following steps are included:

[0041] (1) introducing alkylene oxide, supplementary catalyst and dilute phase catalyst into the liquid phase feed pipe of the main reactor and entering the main reactor;

[0042] (2) passing carbon dioxide gas into the gas phase feed pipe of the main reactor and entering the main reactor;

[0043] (3) passing the heat transfer medium into the heat transfer medium inlet of each heat transfer tray and into the heat transfer pipe;

[0044] (4) In the main reactor, the liquid phase formed by the mixture of alkylene oxide, supplementary catalyst and dilute phase catalyst is the continuous phase, which enters from the liquid phase feed pipe of the main reactor, flows through the heat transfer tray, overflow weir and downcomer to the lower heat transfer tray; carbon dioxide gas is the dispersed phase, which enters from the gas phase feed pipe of the main reactor, enters the upper heat transfer tray through the rising gas channel, contacts and dissolves with the liquid phase on the tray, and reacts with alkylene oxide under the action of the dilute phase catalyst to generate carbonate; the heat released by the reaction is continuously transferred by the heat transfer medium in the heat transfer tube;

[0045] (5) The crude product of the main reactor is discharged from the main reactor and passed into a light component flash tank to flash off the incompletely reacted alkylene oxide and carbon dioxide dissolved therein, and the flash gas is passed into a tail gas recovery reactor; the crude product of the main reactor after flashing is passed into a dilute phase catalyst recovery tank; in order to maintain the pressure of the main reactor stable, the stabilized tail gas containing alkylene oxide and carbon dioxide is discharged from the top of the main reactor and passed into a tail gas recovery reactor;

[0046] (6) The dilute phase catalyst discharged from the dilute phase catalyst recovery tank is divided into two streams, one of which is circulated back to the liquid phase feed pipe of the main reactor, and the other is passed into the dense phase catalyst recovery tank; the crude product gas discharged from the dilute phase catalyst recovery tank and the crude product gas discharged from the dense phase catalyst recovery tank are passed into the crude product condenser, and the crude product after cooling and condensation is passed into the crude product tank and finally sent to the product refining process;

[0047] (7) The dense phase catalyst discharged from the dense phase catalyst recovery tank is introduced into the tail gas recovery reactor, where it countercurrently contacts with the flash gas from the light component flash tank and the main reactor's pressure-stabilized tail gas and absorbs and dissolves it. Under the action of the dense phase catalyst, alkylene oxide and carbon dioxide react to form carbonates. The tail gas recovery reactor discharges the crude product of the recovery reactor and introduces it into the dilute phase catalyst recovery tank.

[0048] The temperature difference of each layer of heat transfer tray in the main reactor is less than 5°C.

[0049] The mass concentration of the dilute phase catalyst is 2-8%, and the mass concentration of the concentrated phase catalyst is 8-25%; the residence time of the reaction liquid in the main reactor is 0.3-2.0h.

[0050] The material mass ratio of carbon dioxide to alkylene oxide is (0.7-1.5):1;

[0051] The catalyst is a homogeneous catalyst;

[0052] The homogeneous catalyst is tetraethylammonium bromide, potassium iodide, tetrabutylammonium halide salt or hydroxyl functional group ionic liquid, etc.;

[0053] The alkylene oxide is ethylene oxide or propylene oxide;

[0054] The carbonate is ethylene carbonate or propylene carbonate;

[0055] The dilute phase catalyst introduced into the dense phase catalyst recovery tank in step (6) accounts for 30-90% of the total amount of the dilute phase catalyst discharged from the bottom of the dilute phase catalyst recovery tank;

[0056] The pressure of the main reactor is 2.0-6.0 MPaG;

[0057] The temperature of the main reactor is 110-160°C;

[0058] The tail gas recovery reactor pressure is 0.3-2.0 MPaG;

[0059] The temperature of the tail gas recovery reactor is 110-160°C;

[0060] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0061] 1. The liquid phase in the main reactor of the present invention is a continuous phase, which flows from the upper heat transfer tray to the lower tray through the overflow weir and the downcomer; the gas phase is a dispersed phase, which enters the upper tray from the lower tray through the gas riser, contacts with the liquid phase and dissolves in the liquid phase. Multiple layers of heat transfer trays are arranged in the main reactor, and the carbon dioxide gas is evenly distributed through the gas riser of the heat transfer tray and fully dissolved in the reaction liquid on the tray, and reacts with the alkylene oxide in the reaction liquid to form carbonate under the action of the catalyst, thereby avoiding the problems of uneven reaction caused by uneven distribution or biased flow of carbon dioxide gas, excessive local reaction heat, back mixing of the reaction liquid, and large amount of tail gas discharged from the top of the reactor.

[0062] 2. The heat released by the reaction of the present invention is taken away in time by the heat transfer tube of the heat transfer tray, so as to avoid the accumulation and overheating of the reaction heat in the main reactor. At the same time, the temperature of each layer of the heat transfer tray is individually controlled by adjusting the amount of the heat transfer medium, so as to solve the problems of uneven reaction intensity and large fluctuation range and large difference in heat release in each local area caused by the change of the concentration of reactants and catalysts in the reaction liquid. Therefore, the temperature of each layer of the tray in the main reactor can be accurately controlled within a narrow optimal temperature window, effectively avoiding the catalytic activity range of the side reaction of the catalyst, maximizing the yield of the target carbonate product, and reducing the difficulty of subsequent product refining.

[0063] 3. The arrangement of the heat transfer tray of the present invention realizes the stable control of temperature and pressure in the whole reaction process and the orderly progress of the reaction, and effectively avoids the occurrence of over-temperature, over-pressure and even safety accidents in the reaction system.

[0064] 4. The present invention sets the reaction conditions such as the concentration of reactants, catalyst concentration, reaction temperature and pressure in the tail gas recovery reactor and the main reactor differently, and the target reaction is independently carried out in the main reactor and the tail gas recovery reactor, without interfering with each other and easy to control. In the tail gas recovery reactor, when the concentration of reactants carbon dioxide and alkylene oxide is low, the concentration of the catalyst in the tail gas recovery reactor is increased, so that the low-concentration reactants are converted into carbonate products, and the reaction tail gas is effectively recovered, thereby improving the raw material conversion rate and the target carbonate product yield of the entire device; because the tail gas recovery reactor can react at a pressure lower than that of the main reactor, there is no need to add a tail gas compressor or other boosting equipment, which has the advantage of saving energy consumption; at the same time, it also solves the problem of difficult treatment of tail gas caused by conventional processes without tail gas recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a structural schematic diagram of the present invention;

[0066] Figure 2 It is a structural schematic diagram of the present invention.

[0067] In the figure: 101 is a main reactor, 102 is a light component flash tank, 103 is a dilute phase catalyst recovery tank, 104 is a dense phase catalyst recovery tank, 105 is a crude product condenser, 106 is a crude product tank, 107 is a tail gas recovery reactor, 108 is a liquid phase feed pipe, 109 is a gas phase feed pipe, 110 is a heat transfer tray, 111 is a gas riser, 112 is a heat transfer pipe, and 113 is an overflow weir;

[0068] 201 is carbon dioxide gas, 202 is ethylene oxide or propylene oxide raw material, 203 is supplementary catalyst, 204 is crude product of main reactor, 205 is crude product of main reactor after flash evaporation, 206 is light component, 207 is dilute phase catalyst, 208 is crude product gas, 209 is dense phase catalyst, 210 is crude product, 211 is pressure stabilizing tail gas, 212 is crude product of tail gas recovery reactor, 213 is circulating dilute phase catalyst, 214 is dilute phase catalyst to dense phase catalyst recovery tank, and 215 is top tail gas of tail gas recovery reactor. DETAILED DESCRIPTION

[0069] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and through specific 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 are within the scope of protection of the present invention.

[0070] Example 1

[0071] This embodiment provides a system for preparing ethylene carbonate, including a main reactor 101, a light component flash tank 102, a tail gas recovery reactor 107, a dilute phase catalyst recovery tank 103, a dense phase catalyst recovery tank 104, a crude product condenser 105 and a crude product tank 106;

[0072] The main reactor 101 is provided with a pressure-stabilized tail gas discharge port at the top, a liquid phase feed port at the upper part, a gas phase feed port at the lower part, and a main reactor crude product discharge port at the bottom. The liquid phase feed port is connected to a liquid phase feed pipe 108 for introducing alkylene oxide, supplementary catalyst and dilute phase catalyst into the main reactor 101, and the gas phase feed port is connected to a gas phase feed pipe 109 for introducing carbon dioxide gas into the main reactor 101.

[0073] The light component flash tank 102 is provided with a light component output port at the top, a main reactor crude product input port at the middle, and a main reactor crude product discharge port after flash evaporation at the bottom, and the main reactor crude product input port is connected to the main reactor crude product discharge port;

[0074] The top of the dilute phase catalyst recovery tank 103 is provided with a crude product gas outlet A, the bottom is provided with a dilute phase catalyst outlet, the middle is provided with a crude product inlet of the post-flash main reactor and a crude product inlet of the tail gas recovery reactor, and the crude product inlet of the post-flash main reactor is connected to the crude product outlet of the post-flash main reactor;

[0075] The top of the dense phase catalyst recovery tank 104 is provided with a crude product gas discharge port B, the bottom is provided with a dense phase catalyst discharge port, and the middle is provided with a dilute phase catalyst input port, and the dilute phase catalyst input port is connected to the dilute phase catalyst discharge port;

[0076] The input end of the crude product condenser 105 is connected to the crude product gas outlet A and the crude product gas outlet B respectively;

[0077] The crude product tank 106 is provided with a crude product input port at the top and a crude product output port at the bottom, the crude product input port is connected to the output end of the crude product condenser 105, and the crude product output port is connected to the product refining process;

[0078] The top of the tail gas recovery reactor 107 is provided with a tail gas recovery reactor top tail gas output port, the bottom is provided with a tail gas recovery reactor crude product discharge port, the upper part is provided with a dense phase catalyst input port, and the lower part is provided with a stabilized pressure tail gas input port and a light component input port. The crude product discharge port of the tail gas recovery reactor is connected to the crude product input port of the tail gas recovery reactor, the stabilized pressure tail gas input port is connected to the stabilized pressure tail gas discharge port, the light component input port is connected to the light component output port, and the dense phase catalyst input port is connected to the dense phase catalyst discharge port.

[0079] The dilute phase catalyst discharge port is communicated with the liquid phase feed pipe 108 .

[0080] The main reactor 101 has a diameter of 0.9 m and a height of 30 m. There are 50 layers of heat transfer trays 110 from top to bottom inside the main reactor 101, and the distance between two adjacent layers of heat transfer trays is 0.5 m. A heat transfer pipe 112 is penetrated inside each layer of the heat transfer tray 110. The heat transfer pipe 112 adopts a light pipe type with a diameter of 25 mm, and the length of the heat transfer pipe 112 is 6.5 m / layer. One end of the heat transfer pipe 112 is a heat transfer medium inlet, and the other end is a heat transfer medium outlet. The heat transfer medium inlet and the heat transfer medium outlet both extend to the outside of the main reactor 101, and the heat transfer medium is heat transfer oil.

[0081] A plurality of air-raising channels 111 are provided on the heat transfer tray 110 outside the heat transfer pipe 112. The air-raising channels are in the form of bubbles with a diameter of 25 mm. From top to bottom, the number of bubbles on the 1st to 10th heat transfer trays is 60 per layer, the number of bubbles on the 11th to 20th heat transfer trays is 70 per layer, the number of bubbles on the 21st to 30th heat transfer trays is 80 per layer, the number of bubbles on the 31st to 40th heat transfer trays is 90 per layer, and the number of bubbles on the 41st to 50th heat transfer trays is 100 per layer.

[0082] The heat transfer tray 110 is provided with a plurality of rows of gas-raising channels 111 arranged in parallel, and the heat transfer pipe 112 bypasses the gas-raising channels 111 in each row in sequence;

[0083] A gap is formed between the heat transfer tray 110 and the inner wall of the main reactor 101, and an overflow weir 113 is provided on one side of the heat transfer tray 110 close to the gap, and a downcomer is formed between the overflow weir 113 and the inner wall of the main reactor 101; the setting position of the gap in each layer and the setting position of the gap in the adjacent layer are respectively located on opposite sides of the main reactor 101.

[0084] Example 2

[0085] The method for preparing ethylene carbonate by reacting ethylene oxide with carbon dioxide using the system of Example 1, wherein the catalyst is tetraethylammonium bromide, comprises the following steps:

[0086] (1) Ethylene oxide 202, supplementary catalyst 203 and dilute phase catalyst 213 are introduced into the liquid phase feed pipe 108 at the upper portion of the main reactor 101 and enter the main reactor 101;

[0087] (2) The carbon dioxide gas 201 is passed into the gas phase feed pipe 109 at the lower part of the main reactor 101 and enters the main reactor 101;

[0088] (3) passing the heat transfer medium into the heat transfer medium inlet of each heat transfer tray 110 and into the heat transfer pipe 112;

[0089] (4) In the main reactor 101, the liquid phase formed by the mixture of ethylene oxide 202, supplementary catalyst 203 and dilute phase catalyst 213 is the continuous phase, which enters from the liquid phase feed pipe 108 at the upper part of the main reactor 101, flows through the heat transfer tray 110, the overflow weir 113 and the downcomer to the lower tray; the carbon dioxide gas is the dispersed phase, which enters from the gas phase feed pipe 109 at the lower part of the main reactor 101, enters the upper heat transfer tray through the gas riser 111, fully contacts and dissolves with the liquid phase on the tray, and reacts with ethylene oxide 202 under the action of the dilute phase catalyst to generate ethylene carbonate; the heat released by the reaction is continuously taken away by the heat transfer medium in the heat transfer pipe 112

[0090] (5) The crude product 204 of the main reactor is discharged from the bottom of the main reactor 101 and passed into the light component flash tank 102 to flash out the unreacted ethylene oxide and carbon dioxide dissolved therein, and the flash gas is passed into the lower part of the tail gas recovery reactor 107; the crude product 205 of the main reactor after flashing is passed into the dilute phase catalyst recovery tank 103; in order to maintain the pressure of the main reactor 101 stable, the stabilized tail gas 211 containing ethylene oxide and carbon dioxide is discharged from the top of the main reactor 101 and passed into the lower part of the tail gas recovery reactor 107;

[0091] (6) The dilute phase catalyst 207 discharged from the bottom of the dilute phase catalyst recovery tank 103 is divided into two streams, one stream 213 is circulated back to the liquid phase feed pipe 108 at the top of the main reactor 101, and the other stream 214 is introduced into the dense phase catalyst recovery tank 104; the crude product gas 208 discharged from the top of the dilute phase catalyst recovery tank 103 and the crude product gas 208 discharged from the top of the dense phase catalyst recovery tank 104 are introduced into the crude product condenser 105, and the crude product after cooling and condensation is introduced into the crude product tank 106, and finally sent to the product refining process;

[0092] (7) The dense phase catalyst 209 discharged from the bottom of the dense phase catalyst recovery tank 104 is introduced into the upper part of the tail gas recovery reactor 107, countercurrently contacts with the flash gas 206 of the light component flash tank and the main reactor pressure-stabilized tail gas 211 introduced into the lower part thereof, and absorbs and dissolves them. Under the action of the dense phase catalyst, ethylene oxide and carbon dioxide generate ethylene carbonate; the recovery reactor crude product 212 is discharged from the bottom of the tail gas recovery reactor 107 and introduced into the dilute phase catalyst recovery tank 103;

[0093] Wherein, the catalyst mass concentration of the dilute phase catalyst 207 discharged from the bottom of the dilute phase catalyst tank 103 in step (6) is 4.5%;

[0094] The dilute phase catalyst 214 introduced into the dense phase catalyst recovery tank 104 in step (6) accounts for 50% of the total amount of the dilute phase catalyst 207 discharged from the bottom of the dilute phase catalyst recovery tank;

[0095] Wherein, the catalyst mass concentration of the dense phase catalyst 209 discharged from the bottom of the dense phase catalyst recovery tank 104 in step (7) is 16.78%;

[0096] The mass ratio of carbon dioxide introduced into the lower part of the main reactor 101 to ethylene oxide introduced into the upper part thereof is 1.05:1;

[0097] Wherein, the residence time of the reaction liquid in the main reactor 101 is 1.0h;

[0098] The key technical parameters of this embodiment are shown in Table 1.

[0099] Table 1 Key technical parameters of the system and method for preparing ethylene carbonate

[0100]

[0101]

[0102]

[0103]

[0104] As can be seen from Table 1, when ethylene carbonate is prepared by the system of Example 1, the maximum temperature difference of each layer of heat transfer tray 110 in the main reactor 101 is only 2.8°C, the ethylene oxide conversion rate can reach 99.995%, and the ethylene carbonate yield can reach 99.867%. Therefore, the device system of the present invention solves the problems of uneven reaction intensity, large fluctuation range, and large difference in heat release in each local area caused by changes in the concentration of reactants and catalysts, realizes stable control of temperature and pressure in the whole reaction process, orderly reaction, and improves the raw material conversion rate and target carbonate product yield of the whole device.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for preparing carbonate, characterized in that: It comprises a main reactor (101), a light component flash tank (102), a tail gas recovery reactor (107), a dilute phase catalyst recovery tank (103), a dense phase catalyst recovery tank (104), a crude product condenser (105) and a crude product tank (106); The main reactor (101) is provided with a pressure-stabilized tail gas outlet, a liquid phase feed inlet, a gas phase feed inlet and a main reactor crude product outlet, respectively; the liquid phase feed inlet is connected to a liquid phase feed pipe (108) for introducing alkylene oxide, supplementary catalyst and dilute phase catalyst into the main reactor (101); the gas phase feed inlet is connected to a gas phase feed pipe (109) for introducing carbon dioxide into the main reactor (101); The light component flash tank (102) is provided with a light component output port, a main reactor crude product input port and a main reactor crude product discharge port after flashing, respectively, and the main reactor crude product input port is connected to the main reactor crude product discharge port; The dilute phase catalyst recovery tank (103) is respectively provided with a crude product gas outlet A, a dilute phase catalyst outlet, a crude product inlet of the post-flash main reactor, and a crude product inlet of the tail gas recovery reactor, wherein the crude product inlet of the post-flash main reactor is connected to the crude product outlet of the post-flash main reactor; The dense phase catalyst recovery tank (104) is respectively provided with a crude product gas discharge port B, a dense phase catalyst discharge port and a dilute phase catalyst input port, and the dilute phase catalyst input port is connected to the dilute phase catalyst discharge port; The input end of the crude product condenser (105) is respectively connected to the crude product gas outlet A and the crude product gas outlet B; The crude product tank (106) is provided with a crude product input port and a crude product output port, respectively. The crude product input port is connected to the output end of the crude product condenser (105), and the crude product output port is connected to the product refining process; The tail gas recovery reactor (107) is respectively provided with a tail gas output port at the top of the tail gas recovery reactor, a crude product discharge port of the tail gas recovery reactor, an input port for a dense phase catalyst, a pressure-stabilized tail gas input port and a light component input port. The crude product discharge port of the tail gas recovery reactor is connected to the crude product input port of the tail gas recovery reactor, the pressure-stabilized tail gas input port is connected to the pressure-stabilized tail gas output port, the light component input port is connected to the light component output port, and the dense phase catalyst input port is connected to the dense phase catalyst discharge port.

2. The system for preparing carbonate according to claim 1, characterized in that: The main reactor (101) is provided with a plurality of layers of heat transfer trays (110) from top to bottom, and each layer of the heat transfer trays (110) is provided with a heat transfer pipe (112). One end of the heat transfer pipe (112) is a heat transfer medium inlet, and the other end is a heat transfer medium outlet. Both the heat transfer medium inlet and the heat transfer medium outlet extend to the outside of the main reactor (101); A plurality of gas raising channels (111) are provided on the heat transfer tray (110) outside the heat transfer pipe (112).

3. The system for preparing carbonate according to claim 2, characterized in that: The heat transfer tray (110) is provided with a plurality of rows of gas-raising channels (111) arranged in parallel, and the heat transfer pipe (112) bypasses the gas-raising channels (111) in each row in sequence.

4. The system for preparing carbonate according to claim 2, characterized in that: A gap is formed between the heat transfer tray (110) and the inner wall of the main reactor (101), and an overflow weir (113) is provided on one side of the heat transfer tray (110) close to the gap, and a downcomer is formed between the overflow weir (113) and the inner wall of the main reactor (101).

5. The system for preparing carbonate according to claim 4, characterized in that: Multiple layers of heat transfer trays (110) are arranged inside the main reactor (101) from top to bottom, and the notches of each layer are arranged at positions opposite to the notches of the adjacent layer.

6. A method for preparing carbonate esters using the system for preparing carbonate esters according to claim 1, characterized in that: The liquid phase formed by the mixture of alkylene oxide and dilute phase catalyst continuously flows into the main reactor to react with carbon dioxide. The generated reaction heat is continuously transferred by the heat transfer tower plate. The crude product of the main reactor enters the light component flash tank. The flash gas and the pressure-stabilized tail gas of the main reactor are passed into the tail gas recovery reactor to react under the action of the dense phase catalyst to achieve tail gas recovery.

7. The method for preparing carbonate according to claim 6, characterized in that: The temperature difference of each layer of heat transfer tower tray is less than 5℃.

8. The method for preparing carbonate according to claim 6, characterized in that: The mass concentration of the dilute phase catalyst is 2-8%, and the mass concentration of the dense phase catalyst is 8-25%.

9. The method for preparing carbonate according to claim 6, characterized in that: The residence time of the reaction liquid in the main reactor is 0.3 to 2.0 h; the pressure of the tail gas recovery reactor is 0.3 to 2.0 MPaG.

10. The method for preparing carbonate according to claim 6, characterized in that: The material mass ratio of carbon dioxide to alkylene oxide is (0.7-1.5):1.

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