Microchannel process for the production of cyclic carbonates with reaction heat integration

Abstract

The present application relates to a kind of microchannel preparation cyclic carbonate reaction heat integration device and method, the device includes reaction unit, heat integration unit and catalyst separation unit.To realize reaction heat integration utilization, the reaction unit includes bubble bed reactor, microchannel reactor and heat integration system, raw material CO2 and alkylene oxide are reacted in the bubble bed reactor, reaction heat is absorbed by the heat extraction medium of the microchannel reactor and heat integration unit, after temperature and pressure are increased, heat supply for the evaporator of the catalyst separation unit, so that the reaction efficiency is ensured while realizing cyclic carbonate reaction heat integration utilization, the preparation energy consumption of cyclic carbonate is greatly reduced, and the reaction heat integration utilization efficiency is improved, an efficient low-carbon preparation technology is provided for industrial production.

Description

Technical Field

[0001] The invention belongs to the field of carbonate preparation and separation, and relates to a device and method for synthesizing cyclic carbonate by using alkylene oxide through microchannel thermal integration. Background Art

[0002] Cyclic carbonate is a heterocyclic ketone with the molecular formula shown below. It is widely used in printing and dyeing, plastics, gas separation, polymer synthesis and electrochemistry. It can replace ethylene oxide (EO) in ethoxylation reactions. Aliphatic bio-based polycarbonates with carbonate as the basic structural unit are used as biodegradable materials. It also has a high dielectric constant and is a key solvent in lithium battery electrolytes. It is mainly prepared by cycloaddition of CO2 and alkylene oxide and has significant low-carbon properties. At the same time, its downstream various carbonates are key components of current new energy electrolyte solvents, including dimethyl carbonate (DMC), ethyl methyl carbonate, diethyl carbonate, fluoroethylene carbonate, vinylene carbonate, etc., and the market is developing rapidly.

[0003]

[0004] The CO2 cycloaddition method for preparing carbonates exhibits a typical chemical carbon fixation effect, theoretically achieving 100% chemical carbon fixation. The annual demand growth rate is >30%, and it is expected to reach 4 million tons by 2025. To date, extensive research has been conducted domestically and internationally on the CO2 cycloaddition method for preparing carbonates, but it continues to face technical challenges related to the flammability and explosiveness of alkylene oxides, the risk of runaway reaction at high temperatures, and the difficulty in utilizing reaction heat. To address the issue of complete conversion of alkylene oxides, patent CN 105777543 A discloses a method and process system for preparing linear carbonates from epoxides and CO2, with the co-production of diols. This process system utilizes a fixed-bed or bubbling-bed tubular reactor loaded with a heterogeneous solid catalyst, resulting in highly continuous and stable production. However, after a certain degree of alkylene oxide conversion, the reaction rate drops sharply, requiring a long residence time and a low reaction space velocity for complete conversion, resulting in low production efficiency. Patent CN 106478586 A discloses a process for synthesizing ethylene carbonate. After the reactants, ethylene oxide and CO2, react in a synthesis reactor (fixed bed, bubbling bed, or fluidized bed), a portion of the liquid phase (50%-99%) is recycled to the synthesis reactor for further reaction. This process addresses issues such as incomplete ethylene oxide reaction and difficulty in recovering the ethylene oxide, but it also involves high energy consumption due to the large amount of liquid phase recycled.

[0005] To promote the mild conversion of alkylene oxides, CN 102464521B and CN 103724315 A both disclosed devices and methods for the enhanced synthesis of cyclic carbonates using microreactors. These devices leverage the rapid mass and heat transfer rates of microchannel reaction systems to significantly improve the space-time yield and selectivity of cyclic carbonates. However, because the process utilizes a system combination of a micromixer and a microchannel reactor, the reaction design and manufacturing are complex, resulting in high pressure drop. Furthermore, the reactor's volumetric efficiency has not been significantly improved, limiting its potential for industrial application. Similarly, CN 114478462A, CN 115960071B and CN117777087 A have respectively improved a device and method for preparing cyclic carbonates by microchannel reaction. By using low eutectic ionic liquids and microchannel reactors with different tube diameters, they successfully broke through the rate limitations of the cycloaddition reaction and gas-liquid mass transfer, and achieved a mild conversion of CO2 and alkylene oxide. However, the reaction heat was not utilized and the energy utilization efficiency still needs to be improved. At the same time, the flux of the microchannel reactor is low, and it cannot be used for large-scale industrial applications, and is not suitable for the preparation of bulk chemical carbonates.

[0006] Regarding the integrated utilization of carbonate reaction heat, CN217872958U provides a carbonate unit steam recovery device that can recycle excess steam generated in the carbonate unit, but does not address methods for transferring and converting reaction heat. CN112142599B provides a low-energy, green carbonate product production method and system that uses two series-connected reactors to produce ethylene carbonate (EC), and then utilizes heat pump distillation technology to achieve the preparation and separation of DMC reactive distillation. However, it does not address the integrated utilization of cyclic carbonate (ethylene carbonate) reaction heat.

[0007] In summary, in order to further improve the preparation efficiency and energy utilization of cyclic carbonates, how to achieve efficient integrated utilization of reaction heat in the preparation process of cyclic carbonates while stably achieving complete conversion of alkylene oxides is a key technical problem that needs to be solved in this field. Summary of the Invention

[0008] To address the challenges of existing technologies, the present invention provides a microchannel heat-integrated device and method for preparing cyclic carbonates. This method utilizes a microchannel reactor to deepen cycloaddition while simultaneously integrating reaction heat. This method enables the continuous and efficient stable conversion of alkylene oxides, removal of reaction heat, and reuse of reaction heat. This approach addresses both the requirements for reaction control and heat integration, simplifies the cyclic carbonate preparation process, and significantly improves the device's integration and the efficiency of the method.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In the first aspect, the present invention provides a microchannel heat-integrated device for preparing cyclic carbonate reactions, which mainly includes a reaction unit, a heat-integrated unit, and a catalyst separation unit connected in sequence, wherein the reaction unit includes a bubbling bed reactor and a microchannel reactor connected to each other; the heat-integrated unit includes a gas-liquid separation tank and at least one compressor connected to each other; the catalyst separation unit includes a flash tank and an evaporator connected in series, and the evaporator is provided with a heater for vaporization. The evaporator heaters are two in series or in parallel, one of which uses steam heating as a backup and is used for thermal compensation when there is insufficient reaction heat during start-up and when the reaction fluctuates and is unstable; the air inlet of the other is connected to the compressor outlet of the heat-integrated unit through a pipeline, and heat is supplied to the heater via a heat exchange medium; to ensure the efficiency of the reaction heat integration, at least two compressors are connected in series.

[0011] In the present invention, described micro channel reactor is any one of plate type, tubular type and spiral structure, and described micro channel reactor is provided with hot material channel and cold material channel, and described hot material channel and cold material channel are respectively provided with a liquid inlet and a liquid outlet.In order to realize the integrated utilization of reaction and reaction heat, described bubbling bed reactor top is provided with at least one liquid inlet, at least one air inlet and at least one liquid outlet, wherein the liquid outlet of described bubbling bed reactor is connected with the liquid inlet of the hot material channel of described micro channel reactor by pipeline, and described air inlet is connected with the gas distributor in described bubbling bed reactor.The liquid outlet of the hot material channel of described micro channel reactor is connected with the upper liquid inlet of described bubbling bed reactor, the liquid inlet of described gas-liquid knockout tank respectively by pipeline.The liquid outlet of the hot material channel of described micro channel reactor is provided with a mechanical pump and a cooler on the upper liquid inlet connecting pipeline of described bubbling bed reactor.

[0012] In the connection method between the heat integration unit and the reaction unit and the catalyst separation unit, the liquid inlet of the gas-liquid separation tank is connected to the liquid outlet of the cold material channel of the microchannel reactor through a pipeline, the heater is connected to the compressor outlet of the heat integration unit through a pipeline, and the liquid outlet of the heater is connected to the liquid inlet of the cold material channel of the microchannel reactor through a pipeline.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] As a preferred technical scheme of the present application, the bubble bed reactor is the main equipment for the cycloaddition reaction of CO2 and alkylene oxide, in order to ensure that the alkylene oxide is completely converted after passing through the bubble bed reactor and the micro-channel reactor, the bubble bed reactor is provided with two liquid inlets, which are an upper liquid inlet and a middle liquid inlet, wherein the upper liquid inlet is connected with the liquid outlet of the cooler through a pipeline, and the middle liquid inlet is connected with the liquid outlet of the evaporator through a pipeline; a mechanical pump is arranged on the connecting pipeline between the liquid outlet of the bubble bed reactor and the liquid inlet of the hot material channel of the micro-channel reactor.

[0015] The present application utilizes the bubble bed reactor to realize the conversion of most of the alkylene oxide, and the remaining small amount of alkylene oxide is mass transfer enhanced through the micro-channel reactor to realize complete conversion, and the heat released in the reaction is absorbed by the heat exchange medium of the cold material channel of the micro-channel reactor and taken out, and then the heat exchange medium is separated and pressurized through the flash tank and compressor device of the heat integration unit, and then provides heat supply for the evaporator, so that the heat integration efficiency of the reaction is greatly improved. In order to ensure the conversion efficiency of the alkylene oxide, the gas distributor in the bubble bed reactor is connected with the gas inlet of the bubble bed reactor, and the installation height of the gas distributor of the bubble bed reactor is at least 0.3 m from the liquid outlet of the bubble bed reactor. In order to further realize the utilization efficiency of the reaction heat integration, no additional heat exchange device is arranged in the interior and exterior of the reaction unit except the device system, and the liquid outlet at the bottom of the bubble bed reactor is pressurized by the mechanical pump on the pipeline and then directly enters the micro-channel reactor for deep reaction and heat exchange removal.

[0016] As a preferred technical scheme of the present application, the material of the micro-channel reactor is selected from any one or a combination of at least two of stainless steel, alloy, ceramic, polyester or silicon carbide glass; and the equivalent inner diameter of the hot material channel of the micro-channel reactor is 10 um to 19 mm.

[0017] As a preferred technical scheme of the present application, in order to ensure the bubble bed reaction efficiency and the stability of the bed temperature, the two liquid inlets at the upper part of the bubble bed reactor in the present application are arranged at different positions, wherein the upper liquid inlet is arranged at the uppermost part of the bubble bed reactor and is connected with the liquid outlet of the hot material channel of the micro-channel reactor through a pipeline; and the middle liquid inlet is arranged at the upper middle part of the bubble bed reactor and is connected with the bottom liquid outlet of the evaporator through a pipeline.

[0018] In the second aspect, the present application provides a processing method for realizing the reaction heat integration of cyclic carbonate by using the device, and the method comprises the following steps:

[0019] (a) Raw materials CO2 and alkylene oxide are introduced into the bubbling bed reactor through the bottom air inlet and the middle liquid inlet, respectively, and a cycloaddition reaction occurs under the action of a catalyst; to ensure the conversion efficiency of alkylene oxide, the catalyst is any one of ionic liquid imidazolium bromide, pyridinium bromide, quaternary phosphonium bromide, and quaternary ammonium bromide, or a combination of any one of these and any one or more of ZnBr2, CuBr2, NiBr2, and KI metal salts. To improve the utilization efficiency of the raw materials, the feed ratio of CO2 to alkylene oxide is controlled at (1.01 to 1.5) / 1;

[0020] (b) the liquid phase discharge of the unreacted alkylene oxide and dissolved CO2 at the bottom of the bubbling bed reactor is pressurized and introduced into the microchannel reactor to further undergo a cycloaddition reaction, wherein the equivalent inner diameter of the hot material channel of the microchannel reactor is 10 μm-19 mm;

[0021] (c) After passing through the microchannel reactor, 70% to 90% of the liquid phase is pressurized by a mechanical pump and cooled by a cooler, and then sent to the upper liquid inlet of the bubbling bed reactor for recycling, and the remaining 10% to 30% is pressurized by the mechanical pump and then extracted and sent to the catalyst separation unit; wherein the cooling medium of the cooler is hot water at 20-40° C., and the temperature of the bubbling bed reactor is controlled by the flow rate of the hot water;

[0022] (d) In order to realize the integrated utilization of reaction heat, a heat exchange medium at 60-80°C is introduced into the cold material channel of the microchannel reactor, and the reaction temperature of the microchannel reactor is controlled by the flow rate of the heat exchange medium; the heated heat exchange medium passes through the gas-liquid separation tank and the compressor of the heat integration unit, and is then sent to the heater of the evaporator of the catalyst separation unit for use.

[0023] The concentration of the catalyst is 0.5% to 12% of the mass of the feed alkylene oxide, and the catalyst is preferably an imidazolium bromide, pyridinium bromide, quaternary phosphine bromide, or quaternary ammonium bromide type ionic liquid, and the catalyst concentration is preferably 3% to 12%; the catalyst can also be at least two combinations of imidazolium bromide, pyridinium bromide, quaternary phosphine bromide, or quaternary ammonium bromide type ionic liquid and any one of ZnBr2, CuBr2, NiBr2 and KI metal salts, for example, it can be a binary composite catalyst of imidazolium bromide / ZnBr2, pyridinium bromide / CuBr2, or quaternary phosphine bromide / KI, or a ternary or multi-compound catalyst of quaternary phosphine bromide / ZnBr2 / KI. When the catalyst is a binary or multi-compound catalyst, the catalyst concentration is controlled at 0.5 to 3%.

[0024] The following takes the preparation of ethylene carbonate (EC) by cycloaddition of CO2 and ethylene oxide (EO) as an example, focusing on the unit composition and connection relationship of the above-mentioned device, and introducing the conditions and methods for synthesizing cyclic ethylene carbonate using this device.

[0025] In the bubbling bed reactor described in step (a), the reaction temperature is 0.05~10wt% at 100 ℃~150 ℃ of ethylene oxide contents, such as 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃ and 150 ℃, but is not limited only to the numerical value enumerated, and other unenumerated numerical values ​​in this numerical range are equally applicable; The pressure is 2.0~4.0MPa, such as 2.0MPa, 2.2MPa, 2.5MPa, 2.7MPa, 3.0MPa, 3.5MPa and 4.0MPa, but is not limited only to the numerical value enumerated, and other unenumerated numerical values ​​in this numerical range are equally applicable; The residence time is 2~30min, such as 2min, 5min, 10min, 15min, 20min, 25min and 30min, but is not limited only to the numerical value enumerated, and other unenumerated numerical values ​​in this numerical range are equally applicable.

[0026] The raw material CO2 and ethylene oxide are respectively introduced by the bottom air inlet and the middle liquid inlet of the bubbling bed reactor, and the bottom air inlet is connected to the gas distributor in the bubbling bed reactor. The raw material CO2 is introduced into the bubbling bed reactor by the gas distributor, and under the action of the catalyst of the filling, the ethylene oxide feeding generation cycloaddition reaction generates cyclic ethylene carbonate with the ethylene oxide feeding of the middle liquid inlet, and releases a large amount of heat. Under the effect of reaction heat, the material in the bubbling bed reactor is heated and temperature is controlled by the circulating feed flow and temperature of the bubbling bed reactor at the upper liquid inlet of the bubbling bed reactor. The ethylene carbonate solution heated by the absorption reaction heat is extracted at the bottom liquid outlet of the reactor, and enters the microchannel reactor after being pressurized by the mechanical pump to further deepen the reaction and realize the removal of reaction heat.

[0027] In order to achieve the withdrawal of the bubbling bed reaction temperature and the reaction heat, the temperature of the microchannel reactor and the temperature of the bubbling bed reactor are controlled to have a certain temperature difference, wherein the reaction temperature in the microchannel reactor in the step (b) is 80°C to 120°C, for example, 80°C, 85°C, 90°C, 100°C, 110°C and 120°C, but is not limited to the enumerated numerical values, and other unenumerated numerical values ​​within this numerical range are equally applicable; the pressure of the microchannel reactor is controlled to be 0.5 to 2.0 MPa, for example, 0.5 MPa, 0.8 MPa, 1.0 MPa, 1.2 MPa, 1.5 MPa, 1.8 MPa and 2.0 MPa, but is not limited to the enumerated numerical values, and other unenumerated numerical values ​​within this numerical range are equally applicable; the residence time of the microchannel reactor is 10s-10min, for example, 10s, 30s, 1min, 2min, 3min, 5min, 8min and 10min, but is not limited to the enumerated numerical values, and other unenumerated numerical values ​​within this numerical range are equally applicable.

[0028] In order to control the bed temperature of the bubbling bed reactor, the material after deep reaction in the microchannel reactor is pressurized by a mechanical pump and further cooled by a cooler, and then circulated back to the bubbling bed reactor, wherein the proportion of the feed circulated to the upper part of the bubbling bed reactor in the step (c) is 70% to 90%, preferably 90%; the remaining part is used as a crude cyclic ethylene carbonate product, still containing a small amount of dissolved CO2 and catalyst, and enters a catalyst separation unit through a pipeline for further separation and recovery, and the proportion of the material entering the catalyst separation unit is controlled to be 10% to 30%, preferably 10%.

[0029] The catalyst separation unit comprises a flash tank and an evaporator connected in series. The evaporator includes at least one heater, with two heaters connected in series or in parallel. To ensure efficient separation of the product and catalyst, the two evaporators are preferably connected in parallel. To ensure heat integration efficiency, at least two heaters are arranged in series within each evaporator. One heater is interconnected with the compressor of the heat integration unit and the microchannel reactor of the reaction unit, and the other heater is heated by steam or thermal oil. To ensure heat integration efficiency, the heater in the evaporator primarily provides the vaporization energy required for separation of the catalyst and cyclic ethylene carbonate. With the heat supplied by the heater, the vaporization rate of the evaporator is controlled within a range of 50% to 90%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and 90%. These values ​​are not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0030] Through the connection and control of the above-described reaction units, the reaction heat from the CO2 cycloaddition process to synthesize ethylene carbonate is transferred to the heat exchange medium in the cold material channel of the microchannel reactor. The heat exchange medium is then separated from the gas and liquid and pressurized by the compressor to provide heat to the heater of the evaporator. To ensure heat integration efficiency and effectiveness, the heat exchange medium in step (d) is at least one of a lithium bromide aqueous solution, an ammonia aqueous solution, a fluorocarbon, and an ammonium carbamate solution. For example, it can be a 45% to 55% lithium bromide aqueous solution, a 20% to 30% ammonia aqueous solution, or a combination of one or two of R245fa, R365mfc, R1233zd(E), or R365mfc fluorocarbons. It can also be an ammonium carbamate-based reaction medium. Due to the relatively low reaction temperature of the CO2 cycloaddition reaction, to ensure reaction heat integration efficiency, the heat exchange medium is preferably a binary mixed fluorocarbon, for example, a combination of R245fa and R365mfc, or a combination of R1233zd(E) and R365mfc.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention utilizes a microchannel reactor integrated with a bubbling bed reactor. While ensuring production efficiency, the microchannel reactor can be used to further enhance the depth of the cycloaddition reaction, significantly reducing the reaction residence time, reducing the equipment volume, and improving the production efficiency of the cyclic carbonate device;

[0033] (2) The present invention utilizes a microchannel reactor integrated with a heat pump system to efficiently recover and improve the quality of the reaction heat during the reaction of CO2 and alkylene oxide, further improving the system integration and achieving efficient transfer and conversion of cycloaddition reaction heat, significantly improving preparation efficiency and energy utilization, and reducing the energy consumption of the device. When the alkylene oxide conversion rate exceeds 99%, the energy consumption level of cyclic carbonate preparation can be reduced by at least 50%;

[0034] (3) By adopting a scheme of coupling a bubbling bed reactor with a microchannel reactor, the traditional inefficient second-stage deepening reactor is replaced, ensuring high-throughput and efficient preparation of synthetic cyclic carbonates, which is suitable for large-scale production of 10,000 tons and 100,000 tons, and promotes the application of microchannels in the manufacture of bulk chemicals. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the unit connections of the microchannel carbonate synthesis device according to an embodiment of the present invention;

[0036] Among them, 1-bubbling bed reactor, 2-microchannel reactor, 3-gas-liquid separation tank, 4-compressor, 5-flash tank, 6-evaporator, S1~S11 are material pipelines, and U1~U7 are heat exchange medium pipelines.

[0037] Figure 2 This is a connection diagram of the process system for preparing cyclic carbonate in a conventional industry provided in Comparative Example 1;

[0038] Among them, 1-first stage bubbling bed reactor, 2-second stage bubbling bed reactor, 3-cooler, 4-evaporator, 5A / 5B-gas-liquid separation tank, S1~S13 are material pipelines.

[0039] Figure 3 This is a diagram comparing the energy consumption of Examples 5 to 7 and Comparative Example 2. DETAILED DESCRIPTION

[0040] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0041] The specific embodiment of the present invention provides a microchannel heat-integrated device for preparing cyclic carbonate reactions. This device includes a reaction unit, a heat-integrated unit, a catalyst separation unit, and its attached unit devices. The reaction unit is a bubbling bed reactor and a microchannel reactor connected in series, wherein the microchannel reactor is any one of a plate type, a tubular type, and a spiral structure, and the microchannel reactor is provided with a hot material channel and a cold material channel, and the hot material channel and the cold material channel are respectively provided with a liquid inlet and a liquid outlet. The catalyst separation unit includes a flash tank and an evaporator connected in series, and the evaporator is provided with at least one heater for vaporization. The liquid inlet of the flash tank is connected to the hot material channel liquid outlet of the microchannel reactor through a pipeline, and the liquid outlet of the evaporator is connected to the liquid inlet of the bubbling bed reactor through a pipeline. The heat integration unit includes an interconnected gas-liquid separation tank and at least one compressor, wherein the liquid inlet of the gas-liquid separation tank is connected to the liquid outlet of the cold material channel of the microchannel reactor, the gas outlet of the compressor is connected to the heater in the evaporator through a pipeline, and the liquid outlet of the heater is connected to the liquid inlet of the cold material channel of the microchannel reactor through a pipeline.

[0042] Implementation Case 1:

[0043] This embodiment includes a reaction unit, a heat integration unit, a catalyst separation unit and their associated device systems, wherein:

[0044] The reaction unit is a bubbling bed reactor and a microchannel reactor connected in series, wherein the bubbling bed reactor is provided with two liquid inlets, the liquid inlet of the upper portion is connected to the hot material channel liquid outlet of the microchannel reaction by a pipeline; the lower portion is provided with an air inlet connected to the gas distributor in the bubbling bed reactor, and the gas distributor is installed at a height of 0.3m from the bottom liquid outlet; a liquid outlet is provided at the bottom, which is connected to the tube-side liquid inlet of the microchannel reactor by a pipeline; the microchannel reactor is a stainless steel spiral jacketed shell and tube type, the hot material channel is a smooth round tube with an equivalent diameter of 15mm, and the cold material channel is a 19mm sleeve. At the same time, for the convenience of material transfer and transportation, a mechanical pump is provided between the bottom liquid outlet of the bubbling bed reactor and the hot material channel liquid inlet of the microchannel reactor. The material is pressurized by the mechanical pump and then passed through the hot material channel liquid inlet of the microchannel reactor. After continuing to deepen the reaction in the microchannel reactor, it enters the catalyst separation unit for separation of product and catalyst.

[0045] The catalyst separation unit comprises a flash tank and an evaporator connected in series, wherein the outlet of the hot material passage of the micro-channel reactor is connected to the inlet of the flash tank through a pipeline, and a mechanical pump is arranged on the pipeline; in order to ensure the separation efficiency, two heaters connected in series are arranged in the evaporator, one of which is connected to the outlet of the heat integration unit and the inlet of the cold material passage of the micro-channel reactor through pipelines, and is the main place for reaction heat utilization; the other heater is standby and heated by steam or heat conducting oil, and is used as an external heat compensation source during the start-up process of the device and reaction fluctuation, so as to ensure the normal operation of the evaporator.

[0046] The heat integration unit comprises a gas-liquid separation tank and a compressor, wherein the outlet of the heat integration unit is the outlet of the compressor, and the inlet of the gas-liquid separation tank is connected to the outlet of the cold material passage of the micro-channel reactor through a pipeline.

[0047] In order to control the temperature stability of the bubble bed reactor bed, the outlet of the hot material passage of the micro-channel reactor is connected to the upper inlet of the bubble bed reactor through a pipeline, and a mechanical pump and a cooler are arranged on the pipeline. At the same time, in order to ensure the recycling of the catalyst, the outlet of the evaporator is connected to the middle inlet of the bubble bed reactor through a pipeline.

[0048] Comparative Example 1:

[0049] The comparative example provides a traditional two-stage bubble bed device for synthesizing cyclic carbonate, and the device and the connection relationship thereof are as shown in Figure 2 The difference between the example 1 and the comparative example is that: there is no reaction heat integration unit; the reactor in the system is a traditional two-stage bubble bed reactor connected in series, and an external circulation cooler is arranged outside the first-stage bubble bed reactor, and the reaction temperature is controlled by the outlet temperature circulation of the external circulation cooler; the positions and modes of the inlet and outlet are different, and the specific performance is that the inlet of the first-stage bubble bed reactor is located at the bottom of the reactor, and the outlet is located at the top of the reactor; the top outlet of the first-stage bubble bed reactor is separated and then respectively introduced into the second-stage bubble bed reactor.

[0050] Example 2:

[0051] The difference between the example 1 and the comparative example is that: there is no reaction heat integration unit; the reactor in the system is a traditional two-stage bubble bed reactor connected in series, and an external circulation cooler is arranged outside the first-stage bubble bed reactor, and the reaction temperature is controlled by the outlet temperature circulation of the external circulation cooler; the positions and modes of the inlet and outlet are different, and the specific performance is that the inlet of the first-stage bubble bed reactor is located at the bottom of the reactor, and the outlet is located at the top of the reactor; the top outlet of the first-stage bubble bed reactor is separated and then respectively introduced into the second-stage bubble bed reactor. The micro-channel reactor in the device is a stainless steel tube type micro-channel reactor, and the inner diameter of the single tube is 19 mm; the catalyst separation unit comprises a flash tank and an evaporator, and a heater is arranged in the evaporator; the inlet and outlet of the heater are connected to the outlet of the compressor of the heat integration unit and the inlet of the cold material passage of the micro-channel reactor through pipelines; in order to ensure the reaction heat integration efficiency, the heat integration unit comprises three gas-liquid separation tanks and three compressors arranged at intervals, and the outlet of the heat integration unit is the outlet of the last compressor.

[0052] Implementation Case 3:

[0053] The difference from Example 2 is that the microchannel reactor in this device is two groups of 10-layer silicon carbide plate and shell reactors connected in series, wherein the single-layer main channel is a heart-shaped structure with an inner diameter of 3 mm, which is mainly used as a circulation channel for hot materials, and the plate and frame interlayer is used as a cold material channel, which is mainly used to pass heat exchange working fluid for reaction and heat exchange integrated temperature control; the catalyst separation unit is a flash tank and two parallel evaporators, each evaporator is equipped with a heater, and the inlet and outlet of one heater are respectively connected to the compressor outlet of the heat integration unit and the liquid inlet of the cold material channel of the microchannel reactor through a pipe; to meet the heat integration efficiency, the heat integration unit includes two compressors in series, and the outlet of the heat integration unit is the outlet of the last compressor.

[0054] Implementation Case 4:

[0055] The difference from Example 3 is that the microchannel reactor in this device is two groups of 50-layer stainless steel plate shell reactors connected in series, in which the single-layer main channel is a toothed structure with an inner diameter of 50um; the catalyst separation unit is a flash tank and two parallel evaporators, and two heaters are provided in each evaporator, wherein the inlet and outlet of each heater are respectively connected to the compressor outlet of the heat integration unit and the liquid inlet of the cold material channel of the microchannel reactor through a pipeline; to meet the heat integration efficiency, the heat integration unit includes two parallel compressors, and the outlet of the heat integration unit is the outlet of the last compressor.

[0056] Implementation Case 5:

[0057] This embodiment uses Example 1 to provide a microchannel heat-integrated device for preparing cyclic carbonate reaction, which includes a bubbling bed reactor 1, a microchannel reactor 2, a gas-liquid separation tank 3, a compressor 4, a flash tank 5 and an evaporator 6 connected in sequence.

[0058] The treatment method includes a cycloaddition reaction process, a catalyst separation process, and a heat exchange integration process. The process flow chart is as follows: Figure 1 As shown, the specific steps include:

[0059] (1) 1100 kg / h of raw CO2 and 1000 kg / h of ethylene oxide were introduced into the bubbling bed reactor 1 through the bottom air inlet and the upper liquid inlet, respectively, and a cycloaddition reaction occurred under the action of 10.2 wt% of 1-methyl-3-ethylimidazolium bromide ion liquid catalyst. The pressure of the bubbling bed reactor was controlled at 2.5 MPa, and the residence time was 25 min.

[0060] (2) The unreacted 0.4% alkylene oxide and 3.2% dissolved CO2 at the bottom of the bubble bed reactor 1 are discharged at a liquid rate of 11986 kg / h. After being pressurized to 2.6 MPa by a mechanical pump, they are introduced into the microchannel reactor 2 for further cycloaddition reaction. The temperature of the microchannel reactor 2 is controlled at 100°C, the pressure is at 2.4 MPa, and the residence time is 5 min.

[0061] (3) The liquid phase after passing through the microchannel reactor 2 contains 2.8% CO2 and 94% ethylene carbonate. In order to control the temperature stability of the bubbling bed reactor 1, 80% of the crude EC product (8390 kg / h) is pressurized by a mechanical pump, cooled to 60°C by a cooler, and then sent to the upper liquid inlet of the bubbling bed reactor 1 for recycling; the remaining 20% ​​of the crude EC (3596 kg / h) is pressurized by the mechanical pump and sent to the catalyst separation unit; wherein, the cooling medium of the cooler is 40°C hot water, and the temperature of the bubbling bed reactor 1 is maintained at 169°C by controlling the flow of hot water;

[0062] (4) To realize the integrated utilization of reaction heat, a 74°C heat exchange medium, a 3 / 7 mixed working medium mixture of 1,1,1,3,3-pentafluorobutane and 1-chloro-3,3,3-trifluoropropene (fluorocarbon), is introduced into the cold material channel of the microchannel reactor 2. The flow rate of the heat exchange medium is controlled to 30500 kg / h to realize the stable control of the reaction temperature of the microchannel reactor 2. After heat exchange, 95% of the fluorocarbon is vaporized. After passing through the gas-liquid separation tank 3, the liquid phase returns to the microchannel reactor 2. After the gas phase is compressed to 2.4 MPa by the compressor 4, the gas phase is heated to 150°C and sent to the evaporator 6 for use in the heater of the reboiler. The liquid phase is separated and recycled back to the microchannel reactor 2 for continued heat exchange.

[0063] (5) To remove dissolved CO2, the solution from microchannel reactor 2 first enters flash tank 5. After flash separation, the liquid phase is sent to evaporator 6 to separate the EC product from the catalyst. Under the action of the heat exchange medium mixed with fluorocarbons, the evaporator achieves a 60% vaporization rate. The remaining 1495 kg / h of catalyst solution containing 7.3% is pressurized by a pump and circulated to the liquid inlet in the middle of the bubbling bed reactor 1. After mixing with fresh ethylene oxide feed, it enters the bubbling bed reactor 1 for continued use.

[0064] In this example, the ethylene oxide conversion rate reached 99.997%, removing a total of 414 kW of reaction heat. After compression work, 732 kW of heat at 150°C was supplied. The evaporator heater only required 504 kW of heat, leaving a 31% surplus in thermal energy and achieving 100% reaction heat supply. After deducting compressor power consumption, the unit energy consumption was -4.8 kW per ton of ethylene carbonate, achieving both conversion efficiency and efficient utilization of reaction heat. The logistics data for this example is shown in Table 1.

[0065] Implementation Case 6:

[0066] This embodiment uses Example 2 to provide a microchannel heat-integrated device for preparing cyclic carbonate reaction. The device includes a bubbling bed reactor 1, a microchannel reactor 2, a gas-liquid separation tank 3, a primary compressor 4A, a secondary compressor 4B, a tertiary compressor 4C, a flash tank 5, and an evaporator 6 connected in sequence. Specifically, the device includes the following steps:

[0067] (1) 1100 kg / h of raw material CO2 and 1000 kg / h of ethylene oxide are introduced into the bubbling bed reactor 1 through the bottom air inlet and the upper liquid inlet, respectively, and a cycloaddition reaction occurs under the action of 0.75 wt% tetrabutylphosphonium bromide ionic liquid and ZnBr2 binary composite catalyst. The hot spot temperature in the bubbling bed reactor is controlled at 136°C, the pressure is controlled at 3.0 MPa, and the residence time is 30 min;

[0068] (2) The unreacted 0.3% alkylene oxide and 3.1% dissolved CO2 at the bottom of the bubble bed reactor 1 are discharged at a liquid rate of 17,687 kg / h and fed through a pipeline into the microchannel reactor 2 for further cycloaddition reaction. The temperature of the microchannel reactor 2 is controlled at 90°C, the pressure is 1.0 MPa, and the residence time is 5 min.

[0069] (3) The liquid phase after passing through the microchannel reactor 2 contains 2.8% CO2 and 97% ethylene carbonate. In order to control the temperature stability of the bubbling bed reactor 1, 80% of the crude EC product (14149 kg / h) is pressurized by a mechanical pump, cooled to 60°C by a cooler, and then sent to the upper liquid inlet of the bubbling bed reactor 1 for recycling; the remaining 20% ​​of the crude EC (3537 kg / h) is pressurized by the mechanical pump and sent to the catalyst separation unit; wherein, the cooling medium of the cooler is 30°C hot water, and the temperature of the bubbling bed reactor 1 is maintained at 136°C by controlling the flow of hot water;

[0070] (4) To achieve integrated utilization of reaction heat, a 70°C heat exchange medium consisting of a 3 / 7 ratio of 1,1,1,3,3-pentafluoropropane and 1,1,2,2,3-pentafluoropropane binary fluorocarbon solution was introduced into the cold material channel of the microchannel reactor 2. The flow rate of the binary fluorocarbon mixed solution was controlled to be 30500 kg / h to achieve stable control of the reaction temperature of the microchannel reactor 2. After heat exchange, 84% of the heat exchange medium was vaporized. After passing through the gas-liquid separation tank 3, the liquid phase returned to the microchannel reactor 2. The gas phase was compressed to 2.4 MPa by the three-stage compressor 4A / 4B / 4C, and then the gas phase was heated to 141°C and sent to the evaporator 6 for use in the reboiler heater. The liquid phase was separated and recycled back to the microchannel reactor 2 for continued heat exchange.

[0071] (5) To remove dissolved CO2, the solution from microchannel reactor 2 first enters flash tank 5. The liquid phase after flash separation is sent to evaporator 6 to separate the EC product and catalyst. Under the action of the heat exchange medium mixed with fluorocarbons, the evaporator achieves a 60% vaporization rate. The remaining 1437 kg / h of catalyst solution containing 1.3% is pressurized by a pump and circulated to the liquid inlet in the middle of bubbling bed reactor 1. After mixing with fresh ethylene oxide feed, it enters bubbling bed reactor 1 for continued use.

[0072] In this example, the ethylene oxide conversion rate reached 99.997%, removing a total of 404 kW of reaction heat. After compression work, 571 kW of heat at 149°C was supplied, while the evaporator heater required only 403 kW of heat, achieving 100% reaction heat supply. After deducting compressor power consumption, the unit energy consumption was 77 kW per ton of ethylene carbonate, achieving both conversion efficiency and efficient utilization of reaction heat. The logistics data for this example is shown in Table 2.

[0073] Implementation Case 7:

[0074] This embodiment uses Example 3 to provide a microchannel heat-integrated device for preparing cyclic carbonate reaction. The device includes a bubbling bed reactor 1, a microchannel reactor 2, a gas-liquid separation tank 3, a primary compressor 4A, a secondary compressor 4B, a flash tank 5, and an evaporator 6 connected in sequence. Specifically, the device includes the following steps:

[0075] (1) 1100 kg / h of raw CO2 and 1000 kg / h of ethylene oxide were introduced into the bubbling bed reactor 1 through the bottom air inlet and the upper liquid inlet, respectively, and a cycloaddition reaction occurred under the action of 3.6 wt% of tetrabutylphosphonium bromide ionic liquid catalyst. The hot spot temperature in the bubbling bed reactor was controlled at 125°C, the pressure was controlled at 3.0 MPa, and the residence time was 20 min.

[0076] (2) The unreacted 0.3% alkylene oxide and 4.1% dissolved CO2 at the bottom of the bubble bed reactor 1 are discharged at a rate of 26529 kg / h and fed into the microchannel reactor 2 through a pressure control valve for further cycloaddition reaction. The temperature of the microchannel reactor 2 is controlled at 80°C, the pressure is 1.0 MPa, and the residence time is 10 min.

[0077] (3) The liquid phase after passing through the microchannel reactor 2 contains 3.8% CO2 and 94.8% ethylene carbonate. In order to control the temperature stability of the bubbling bed reactor 1, 90% of the crude EC product (23876 kg / h) is pressurized by a mechanical pump, cooled to 80°C by a cooler, and then sent to the upper liquid inlet of the bubbling bed reactor 1 for recycling; the remaining 10% of the crude EC (2653 kg / h) is pressurized by the mechanical pump and sent to the catalyst separation unit; wherein, the cooling medium of the cooler is 60°C hot water, and the temperature of the bubbling bed reactor 1 is maintained at 125°C by controlling the flow of hot water;

[0078] (4) To achieve integrated utilization of reaction heat, a 3 / 7 ratio binary fluorocarbon solution of 1,1,1,3,3-pentafluorobutane and 1-chloro-3,3,3-trifluoropropene at 70°C was introduced into the cold material channel of the microchannel reactor 2. The flow rate of the binary fluorocarbon mixed solution was controlled to 85500 kg / h to achieve stable control of the reaction temperature of the microchannel reactor 2. After heat exchange, 62% of the heat exchange medium was vaporized. After passing through the gas-liquid separation tank 3, the liquid phase returned to the microchannel reactor 2. The gas phase was compressed to 2.4 MPa by the secondary compressor 4A / 4B, and then the gas phase was heated to 151°C and sent to the evaporator 6 for use in the evaporator heater. The liquid phase was separated and recycled back to the microchannel reactor 2 for continued heat exchange.

[0079] (5) To remove dissolved CO2, the solution from the microchannel reactor 2 first enters the flash tank 5. After flash separation, the liquid phase is sent to the evaporator 6 to separate the EC product and the catalyst. Under the action of the heat exchange medium mixed with fluorocarbons, the evaporator achieves a vaporization rate of 78%. The remaining 553 kg / h of 6.5% catalyst solution is pressurized by a pump and circulated to the liquid inlet in the middle of the bubbling bed reactor 1. After mixing with the fresh feed of ethylene oxide, it enters the bubbling bed reactor 1 for continued use.

[0080] In this example, the ethylene oxide conversion rate reached 99.999%, removing a total of 567kW of reaction heat. After compression work, 1277kW of heat at 151°C was supplied. The evaporator heater only required 415kW of heat, leaving a 68% surplus of heat energy and achieving 100% reaction heat supply. After deducting compressor power consumption, the unit energy consumption was -81.4kW / ton of ethylene carbonate, achieving the conversion efficiency and efficient utilization of reaction heat. The logistics data for this example is shown in Table 3.

[0081] Comparative Example 2:

[0082] This comparative example provides a method for synthesizing cyclic carbonates using a conventional two-stage bubbling bed apparatus according to comparative example 1. The method differs from Example 5 only in that: to enhance gas-liquid mass transfer within the two-stage bubbling bed reactor, the gas-liquid ratio of the feed is controlled to 1.8 / 1, the 1-methyl-3-ethylimidazolium bromide ion liquid catalyst is controlled at 10.7 wt %, the external circulation cooler is cooled by 40°C hot water heat exchange, and the temperature of the first-stage bubbling bed reactor is controlled at 164°C; the reaction temperature of the second-stage bubbling bed reactor is controlled at 120°C, and the residence time is 2 hours; the evaporator is heated by steam, and the vaporization rate is controlled at 60%, and other operating conditions remain unchanged.

[0083] In this comparative example, after the system operation stabilized, the final ethylene oxide conversion rate of the first-stage bubbling bed reactor was 97%, the ethylene oxide conversion rate of the second-stage bubbling bed reactor was 70%, and the total ethylene oxide conversion rate was 99.1%. All the reaction heat was removed by the 40°C hot water in the external circulation cooler. The evaporator in the catalyst separation section required an additional 447kW of steam, and the energy consumption was 216.7kW / ton of ethylene carbonate. The logistics data table of this comparative example is shown in Table 4

[0084] From the above embodiments and comparative examples, it can be seen that the present invention adopts a microchannel reactor to replace the external circulation cooler and the second-stage bubbling bed reactor of the traditional first-stage bubbling bed reactor, and utilizes its advantages of efficient heat transfer and mass transfer to facilitate the rapid reaction of ethylene oxide and carbon dioxide, increase the reaction rate, and shorten the reaction residence time; at the same time, by utilizing low-boiling point heat exchange fluids such as fluorocarbons and lithium bromide aqueous solution, the integrated utilization of the reaction heat pump and the reaction heat is realized, breaking through the waste of low-temperature reaction heat of CO2 cycloaddition, and realizing the efficient preparation of cyclic ethylene carbonate.

[0085] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

[0086] Table 1 Main flow balance data table of Example 5

[0087]

[0088] Table 2 Main flow balance data table of Example 6

[0089]

[0090] Table 3 Logistics balance data table of Example 7

[0091]

[0092] Table 4 Logistics balance data table of comparative example 2

[0093]

Claims

1. A microchannel heat integrated device for preparing cyclic carbonate reaction, characterized in that: The device comprises a reaction unit, a heat integration unit and a catalyst separation unit connected in sequence, wherein the reaction unit comprises a bubbling bed reactor and a microchannel reactor connected to each other, the microchannel reactor being any one of a plate type, a tubular type and a spiral structure, and the microchannel reactor being provided with a hot material channel and a cold material channel, each of the hot material channel and the cold material channel being provided with a liquid inlet and a liquid outlet; The heat integration unit comprises a gas-liquid separation tank and at least one compressor connected to each other, wherein the liquid inlet of the gas-liquid separation tank is connected to the liquid outlet of the cold material channel of the microchannel reactor through a pipeline; The catalyst separation unit includes a flash tank and an evaporator connected in series, the evaporator is provided with at least one heater for catalyst separation, the air inlet of the heater is connected to the air outlet of the compressor through a pipeline, and the liquid outlet of the heater is connected to the liquid inlet of the cold material of the microchannel reactor through a pipeline; The bubbling bed reactor is provided with at least one liquid inlet, an air inlet and a liquid outlet, wherein the liquid outlet of the bubbling bed reactor is connected to the liquid inlet of the hot material channel of the microchannel reactor through a pipeline; the air inlet is connected to the gas distributor in the bubbling bed reactor, and the installation height of the gas distributor is 0.2-1.5m from the liquid outlet; The upper liquid inlet of the bubbling bed reactor is connected to the liquid outlet of the hot material channel of the microchannel reactor through a pipeline; The liquid phase of the unreacted alkylene oxide and dissolved CO2 at the bottom of the bubbling bed reactor is discharged and, after being pressurized, is introduced into the microchannel reactor to further undergo a cycloaddition reaction.

2. The device according to claim 1, characterized in that The bubbling bed reactor is provided with two liquid inlets, namely an upper liquid inlet and a middle liquid inlet, an air inlet is provided at the lower part, and a liquid outlet is provided at the bottom, and the middle liquid inlet is connected to the liquid outlet of the evaporator through a pipeline; The equivalent inner diameter of the hot material channel of the microchannel reactor is 10 um-19 mm.

3. The device according to claim 1, characterized in that The liquid outlet of the hot material channel of the microchannel reactor is connected to the liquid inlet of the flash tank through a pipeline; A mechanical pump and a cooler are provided on the pipeline connecting the liquid outlet of the hot material channel of the microchannel reactor and the upper liquid inlet of the bubbling bed reactor.

4. The device according to claim 1, characterized in that The evaporator comprises two heaters connected in series or in parallel, the air inlet of one of the heaters is connected to the air outlet of the compressor of the heat integration unit through a pipeline, and the other heater is heated by steam as a standby; In order to ensure the reaction heat integration efficiency, there are at least two compressors connected in series.

5. The device according to claim 1, characterized in that A mechanical pump is provided on the connecting pipe between the liquid outlet of the bubbling bed reactor and the liquid inlet of the hot material channel of the microchannel reactor.

6. The device according to claim 1, characterized in that The evaporator includes a gas outlet and a liquid outlet, and the liquid outlet of the evaporator is connected to the middle liquid inlet of the bubbling bed reactor through a pipeline; A mechanical pump is provided on the pipeline connecting the liquid outlet of the evaporator and the middle liquid inlet of the bubbling bed reactor.

7. A method for realizing heat integration of cyclic carbonate reaction using the device according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: (a) raw materials CO2 and alkylene oxide are introduced into the gas inlet and the middle liquid inlet of the bubbling bed reactor respectively, and a cycloaddition reaction occurs under the action of a catalyst; the catalyst is any one of an ionic liquid imidazolium bromide, pyridinium bromide, quaternary phosphine bromide, and quaternary ammonium bromide, or a combination of any one of them and any one or more of ZnBr2, CuBr2, NiBr2 and KI metal salt; the feed ratio of CO2 to alkylene oxide is controlled at (1.01-1.5) / 1; (b) the liquid phase discharge of the unreacted alkylene oxide and dissolved CO2 at the bottom of the bubbling bed reactor is pressurized and introduced into the microchannel reactor for further cycloaddition reaction, and the temperature of the microchannel reactor is controlled at 80°C to 120°C, and the residence time is 10s to 10min; (c) After passing through the microchannel reactor, 70% to 90% of the liquid phase is pressurized by a mechanical pump and cooled by a cooler, and then sent to the upper liquid inlet of the bubbling bed reactor for recycling, and the remaining 10% to 30% is pressurized by the mechanical pump and then sent to the catalyst separation unit; wherein, the cooler performs heat exchange with a cooling medium at 20 to 40° C., and the temperature of the bubbling bed reactor is controlled by the cooler; (d) To achieve integrated utilization of reaction heat, a heat exchange medium at 60-80° C. is introduced into the cold material channel of the microchannel reactor, and the reaction temperature of the microchannel reactor is controlled by the flow rate of the heat exchange medium; the heated heat exchange medium is successively passed through a gas-liquid separation tank and a compressor, and then sent to the heater of the evaporator for use; In order to ensure the separation efficiency of the catalyst and the cyclic carbonate product in the evaporator, the vaporization rate of the evaporator is controlled at 50% to 90%.

8. The cyclic carbonate reaction heat integration method according to claim 7, characterized in that: In step (a), the reaction temperature in the bubbling bed reactor is 100° C. to 150° C., the pressure is 2.0 to 4.0 MPa, and the residence time is 2 to 30 min; and the catalyst concentration is 0.5% to 12% of the mass of the feed alkylene oxide.

9. The heat integration method for cyclic carbonate reaction according to claim 7, characterized in that: In the step (b), the outlet pressure of the microchannel reactor is 1.0-3.0 MPa; in the step (d), the heat exchange medium is at least one of lithium bromide aqueous solution, ammonia aqueous solution, fluorocarbon, and ammonium carbamate solution.

10. The heat integration method for cyclic carbonate reaction according to claim 7, characterized in that: The heat exchange medium in step (d) is a binary fluorocarbon.

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