Process method for producing carbonic ester

Abstract

The invention relates to a process method for producing carbonic ester, and belongs to the technical field of carbonic ester production. The invention discloses a process method for producing carbonic ester. Equipment used in the process comprises an alkylene oxide source, a carbon dioxide source, a first reactor, a first heat exchanger, a second reactor and a second heat exchanger, a product II branch II-1 is communicated with the second reactor; a gas phase outlet of the first reactor is provided with a pressure regulating valve; the normal pressure in the first reactor ranges from 2.5 MPAG to 3.0 MPAG; when the pressure does not exceed 3% of the normal pressure range, the pressure regulating valve is closed; when the pressure is larger than 3% and not larger than 8% of the normal pressure range, the pressure adjusting valve is opened; when the pressure exceeds 8% of the normal pressure range, a pressure adjusting valve is opened, inert gas is supplemented into the first reactor, and the ratio of the flow of the inert gas to the flow of fresh carbon dioxide is 1-2. According to the present invention, the process operation is simple, the equipment investment is low, the good economic and social benefits are provided, the method can be used in the industrial production, in the reaction product, the conversion rate of the alkylene oxide is not less than 95%, and the purity of the carbonate is not less than 99%.

Description

Technical Field

[0001] The invention relates to a process for producing carbonate esters, and belongs to the technical field of carbonate ester production. Background Art

[0002] With the overuse of energy, the storage of oil is decreasing. At present, electric drive equipment is gradually appearing in people's vision and becoming a daily routine. Nowadays, the production of electric drive vehicles is gradually increasing, and the market of carbonate as electrolyte is gradually expanding. The preparation of carbonate by the reaction of carbon dioxide and alkylene oxide has a good application prospect.

[0003] Chinese invention patent disclosure CN102482407A discloses a continuous method for preparing aliphatic polycarbonate from carbon dioxide and epoxy compounds, which is mainly to continuously supply carbon dioxide, one or more epoxy compounds and catalysts into a reactor to prepare aliphatic polycarbonate, separate unreacted carbon dioxide and epoxy compounds and recycle them as raw materials. In this recovery process, it is first necessary to separate the catalyst from gaseous carbon dioxide and epoxy compounds, and then separate the gaseous carbon dioxide and epoxy compounds respectively, and finally mix carbon dioxide and epoxy compounds into a full liquid phase feed reaction. This separation and recovery process is complicated to operate, and carbon dioxide itself is relatively cheap, and only excessive equipment and other investments are added to recover a small part of the raw materials, and its practical application is low, which is not conducive to industrial application.

[0004] China invention patent disclosure CN112705124A discloses a reactor, system and method for synthesizing carbonate, wherein the gas at the top of the main reactor is directly discharged after cooling. Carbon dioxide reacts with alkylene oxide in equal proportions, and the feed ratio of carbon dioxide to alkylene oxide has different effects on the process. When the excess carbon dioxide is small, the gas volume at the top of the reactor is small, and the pressure regulation in the reactor is not sensitive, which easily causes unstable carbon dioxide feed and affects the reaction; when excessive carbon dioxide is used, more unreacted alkylene oxide raw materials and product carbonate will be entrained in the tail gas, which puts higher requirements on the subsequent tail gas processing capacity.

[0005] CN213286231U discloses a system for extracting and refining carbon dioxide and propylene oxide from tail gas of carbonate production. The system is connected in series with compression, carbon dioxide refining, propylene oxide refining and discharge systems. The process is mainly for recovering carbon dioxide and propylene oxide from tail gas. According to its embodiment, it can be known that nearly 90% of the tail gas is carbon dioxide, and only a small amount of propylene oxide exists. The market price of carbon dioxide is relatively low, and the equipment investment of this process is relatively large. The subsequent extraction and refining process requires a large amount of operation investment. Compared with the small amount of propylene oxide recovered, its economic efficiency is relatively low, which is not conducive to the industrial implementation of this process.

[0006] In the current heterogeneous carbonate production process, carbon dioxide and alkylene oxide react in nearly equal proportions, so the gas emission from the top of the reactor is small or non-existent, resulting in unstable pressure in the reaction system and instability in carbon dioxide feed. When the unstable pressure regulation causes a reduction in carbon dioxide feed, a large amount of alkylene oxide remains in the reactor, which can easily cause excessive local temperature rise in the catalyst bed and cause catalyst deactivation. Summary of the invention

[0007] The problems to be solved by the present invention are as follows: 1) unstable carbon dioxide feed; 2) excessive temperature rise in the catalyst bed; 3) unstable pressure control of the reaction system. In view of these problems, a process for preparing carbonate ester is provided, which can realize stable control of reactor pressure and ensure safe and stable reaction.

[0008] The technical solution of the present invention includes a reaction system and a pressure control solution.

[0009] The process for producing carbonate esters includes an alkylene oxide source, a carbon dioxide source, a first reactor, a first heat exchanger, a second reactor, and a second heat exchanger; the carbon dioxide source is connected to a carbon dioxide source branch P1 and a carbon dioxide source branch P2 in parallel; the alkylene oxide source and the carbon dioxide source branch P1 are respectively connected to the first reactor; the product outlet of the first reactor flows through the first heat exchanger and then connects to a product I branch I-1 and a product I branch I-2 in parallel; the product I branch I-1 is connected to the first reactor; the product I branch I-2 and the carbon dioxide source branch P2 are respectively connected to the second reactor; the product outlet of the second reactor flows through the second heat exchanger and then connects to a product II branch II-1 and a product II branch II-2 in parallel; the product II branch II-1 is connected to the second reactor. A pressure regulating valve is provided at the gas phase outlet of the first reactor.

[0010] Optionally, the normal pressure range in the first reactor is 2.5-3.0 MPAG; when the pressure in the first reactor does not exceed 3% of the normal pressure range, the pressure regulating valve is closed. According to a preferred embodiment of the present invention, when the overpressure at the top of the first reactor does not exceed 3%, the pressure regulating valve is closed, and the reaction can be carried out safely and effectively within this pressure range; when the pressure in the first reactor is greater than 3% of the normal pressure range and does not exceed 8%, the pressure regulating valve is opened. According to a preferred embodiment of the present invention, when the carbon dioxide feed flow rate is reduced and / or the pressure at the top of the reactor does not exceed 8%, the valve at the top of the reactor is opened, which can promote the feeding of carbon dioxide and ensure the normal progress of the reaction; When the pressure in the first reactor exceeds 8% of the normal pressure range, the pressure regulating valve is opened to supplement inert gas into the first reactor, and the ratio of the flow rate of the inert gas to the fresh carbon dioxide is 1 to 2; preferably, the feed flow rate of the alkylene oxide is reduced at the same time, and the feed flow rate is not higher than 80% of the normal production condition; according to a preferred embodiment of the present invention, when the reactor pressure overpressure exceeds 8%, the supplementary inert gas is mixed with the fresh carbon dioxide and enters the reactor, and the feed flow rate of the alkylene oxide is reduced at the same time. This method can reduce the concentration of carbon dioxide entering the reactor and prevent a large amount of carbon dioxide from entering, which causes the catalyst bed temperature to rise too high; the inert gas is selected from at least one of nitrogen, helium and argon.

[0011] Optionally, the device further comprises a cooler and a supercharger, and the gas phase outlet of the first reactor is connected to the cooler and the supercharger in sequence, and then connected to the gas phase branch C1 and the gas phase branch C2 in parallel; the gas phase branch C2 is connected to the lower part of the first reactor. According to a preferred embodiment of the present invention, the cooling gas at the top of the first reactor is divided into two streams, one of which is pressurized by the supercharger unit and circulated to the first reactor, and the other is treated in the absorption tower.

[0012] Optionally, the gas phase outlet of the first reactor is located at the top of the first reactor.

[0013] Optionally, the alkylene oxide source and the carbon dioxide source branch P1 are connected to the first reactor in a countercurrent manner; preferably, the alkylene oxide source is connected to the upper part of the first reactor, and the carbon dioxide source branch P1 is connected to the lower part of the first reactor.

[0014] Optionally, the product I branch I-2 and the carbon dioxide source branch P2 are connected to the second reactor in a countercurrent manner; preferably, the product I branch I-2 is connected to the upper part of the second reactor, and the carbon dioxide source branch P2 is connected to the lower part of the second reactor.

[0015] Optionally, the product II branch II-1 is connected to the upper part of the second reactor.

[0016] A process for producing carbonate esters, wherein the equipment used in the process comprises any of the above-mentioned equipment for producing carbonate esters, wherein a pressure regulating valve is provided at the gas phase outlet of the first reactor;

[0017] Optionally, when the pressure regulating valve is opened, the feed rate of the carbon dioxide source is increased at the same time, and the feed rate is 1.2 to 2 times that under normal operating conditions.

[0018] Optionally, when the pressure regulating valve is opened, the gas is cooled by the heat exchanger at the top of the reactor, and the cooling temperature of the cooler is 50-100°C, preferably 50-80°C., to prevent the temperature of the gas from being too high during the compression process of the booster, thereby affecting the feed stability.

[0019] Optionally, the material flow ratio of the product I branch I-1 and the product I branch I-2 is 5-10; the material flow ratio of the product II branch II-1 and the product II branch II-2 is 3-10.

[0020] Optionally, the alkylene oxide is selected from at least one of ethylene oxide and propylene oxide.

[0021] Optionally, the total flow rate of the carbon dioxide source (fresh raw carbon dioxide) and the total flow rate of the alkylene oxide source are fed in a ratio of 1.05 to 1.2. Less carbon dioxide feed can reduce the amount of tail gas treatment.

[0022] Optionally, the flow ratio between the carbon dioxide source branch P1 and the carbon dioxide source branch P2 is 0.02-0.2.

[0023] Optionally, the reaction conditions in the first reactor include: resin-type catalyst, temperature 50-200° C., and pressure 2.0-4.0 MPAG.

[0024] Optionally, the temperature of the product I of the first reactor after heat exchange in the first heat exchanger is 50-100°C, preferably 50-80°C.

[0025] Optionally, the reaction conditions in the second reactor include: resin-type catalyst, temperature 50-200° C., and pressure 2.0-4.0 MPAG.

[0026] Optionally, the temperature of the second heat exchanger product II after heat exchange in the first heat exchanger is 80-120°C, preferably 80-100°C.

[0027] The process of the present invention is simple to operate and has low equipment investment. The process method of producing carbonate esters of the present invention adopts a pressure regulation control method at the top of the reactor to ensure stable pressure control. It has good economic and social benefits and can be applied to industrial production. In the reaction product, the conversion rate of alkylene oxide is not less than 95%, and the purity of carbonate ester is not less than 99%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The process diagram for synthesizing carbonate esters of the present invention is as follows:

[0029] Figure 1 In the figure, 1 is the first reactor, 2 is the first circulation pump, 3 is the first heat exchanger, 4 is the second reactor, 5 is the second circulation pump, 6 is the second heat exchanger, 7 is the cooler, and 8 is the booster.

[0030] Reactant Flow:

[0031] 101 is propylene oxide, 100, 102, 201 are fresh carbon dioxide, 103 is product I, 104, 202 are product I after heat exchange; 105 is the tail gas after heat exchange, and 106 is the non-condensable gas discharge;

[0032] 203 is product II, 204 and 301 are product II after heat exchange, and 205 is gas phase II (residual carbon dioxide). DETAILED DESCRIPTION

[0033] The equipment for producing carbonate esters of the present invention mainly comprises a first reactor, a first heat exchanger, a second reactor, a second heat exchanger, a circulation pump, an absorption tower, a booster, a cooler, a first circulation pump, and a second circulation pump;

[0034] A first circulation pump is connected to the bottom of the first reactor;

[0035] The first heat exchanger is connected to the first circulation pump, and the outlet is connected to the upper part of the first reactor and the second reactor respectively;

[0036] A second circulation pump is connected to the bottom of the second reactor;

[0037] The second heat exchanger is connected to the second circulation pump, and the outlet is respectively to the upper part of the second reactor, and the final product of the reaction is taken out.

[0038] A cooler has one end connected to the top of the first reactor and the other end connected to the booster.

[0039] The booster has one end connected to the cooler and the other end connected to the lower part of the first reactor.

[0040] The first reactor and the second reactor are filled with solid catalysts, and the raw material ethylene oxide or propylene oxide 101 and the gas phase II 205 of the second reactor enter the first reactor 1 in countercurrent (101 enters at the upper part of the first reactor, and 205 enters at the lower part of the first reactor), and the product I 103 of the first reactor is cooled by the first heat exchanger 3, and a part 202 enters the second reactor 4, and the other part 104 is circulated to the first reactor 1 (enters the upper part of the first reactor); 202 and fresh carbon dioxide 201 enter the second reactor in countercurrent to react (202 enters at the upper part of the second reactor, and 201 enters at the lower part of the second reactor). The flow rate of the reaction feed alkylene oxide 101 is nearly proportional to the flow rate of the carbon dioxide 100. Under normal operating conditions, the top valve of the first reactor is closed, and the pressure in the first reactor is stable. Under abnormal operating conditions, the top valve is opened, and the gas phase at the top of the first reactor is cooled after flowing out. A part 106 is connected to the absorption tower (not shown in the figure), and the other part 105 is increased by the booster and circulated to the first reactor (enters at the lower part of the first reactor) to mix with the carbon dioxide 102, so as to effectively control the pressure of the first reactor.

[0041] The present invention will be further described below by way of examples, but are not limited thereto.

[0042] In the embodiment, the reaction product testing method is chromatographic analysis, and the calculation formula is as follows:

[0043]

[0044] Where:

[0045] f i — volume correction factor for component i;

[0046] m i —Content of component i in the standard sample, % (volume fraction);

[0047] A i —Peak area of ​​component i in the standard sample;

[0048] The content of each component in the sample is calculated by the corrected area normalization method. The calculation formula is as follows:

[0049]

[0050] Where:

[0051] X i : The content of component i in the sample, % (volume fraction);

[0052] A i : The peak area of ​​component i in the sample;

[0053] f i: Volume correction factor for component i in the sample.

[0054] In summary, the carbonate content is calculated as:

[0055] M 碳酸酯 =M 出口总量 ×X 碳酸酯

[0056] The conversion of alkylene oxide is calculated as:

[0057] η 环氧烷烃 =(M 出口总量 × X环氧烷烃 -M 新鲜环氧烷烃量 ) / M 新鲜环氧烷烃量 .

[0058] Example 1 Method for producing carbonate

[0059] like Figure 1 As shown, the equipment for producing carbonate includes an alkylene oxide source 101, a carbon dioxide source 100, a first reactor 1, a first heat exchanger 3, a second reactor 4, a second heat exchanger 6, a cooler 7 and a supercharger 8; the first reactor 1 and the second reactor 4 are filled with a solid halogen-type complex hydroxyimidazole resin catalyst (using the preparation method in Example 1 in patent document CN105503608B). The carbon dioxide source 100 is connected to the parallel carbon dioxide source branch 102 and the carbon dioxide source branch 201; the alkylene oxide source 101 and the carbon dioxide source branch 102 are respectively connected to the first reactor; the product outlet of the first reactor flows through the first heat exchanger 3 and then connects to the parallel product I branch 104 and product I branch 202; the product I branch 104 is connected to the first reactor; the product I branch 202 and the carbon dioxide source branch 201 are respectively connected to the second reactor; the product outlet of the second reactor flows through the second heat exchanger 6 and then connects to the parallel product II branch 204 and product II branch 301; the product II branch 204 is connected to the upper part of the second reactor. The gas phase outlet of the first reactor is connected to the cooler 7 and the supercharger 8 in sequence, and then connected to the parallel gas phase branch 105 and gas phase branch 106; the gas phase branch 105 is connected to the lower part of the first reactor; the gas phase outlet of the first reactor is located at the top of the first reactor, and is provided with a pressure regulating valve. The alkylene oxide source is connected to the upper part of the first reactor, and the carbon dioxide source branch 102 is connected to the lower part of the first reactor; the product I branch 202 is connected to the upper part of the second reactor, and the carbon dioxide source branch 201 is connected to the lower part of the second reactor.

[0060] The process for producing carbonate esters using equipment for producing carbonate esters is as follows:

[0061] Alkylene oxide 101 (ethylene oxide) enters the first reactor 1 at the upper portion of the first reactor 1 .

[0062] The fresh carbon dioxide is divided into two streams, namely, fresh carbon dioxide 102 and fresh carbon dioxide 201 . The fresh carbon dioxide 102 enters the first reactor 1 at the lower portion of the first reactor 1 , and the fresh carbon dioxide 201 enters the second reactor 4 at the lower portion of the second reactor 4 .

[0063] In the first reactor 1, the reaction temperature is 100°C; the reaction pressure is 2.8 MPAG; the flow rate of alkylene oxide 101 is 1000 kg / h; and the flow rate of fresh carbon dioxide 102 is 50 kg / h.

[0064] In the second reactor 4, the reaction temperature is 110°C; the reaction pressure is 2.9 MPAG; and the flow rate of the fresh carbon dioxide 201 is 1050 kg / h.

[0065] After the reaction in the first reactor 1, the product I 103 flows out from the bottom of the first reactor, and is cooled to 80°C by the first heat exchanger 3. The cooling medium is circulating cooling water. After cooling, it is divided into two streams, namely, the product I 104 after heat exchange and the product I 202 after heat exchange; the flow rate of 104 is 12000 kg / h, and the flow rate of 202 is 2000 kg / h; 104 returns to the first reactor 1 to control the overall temperature rise of the first reactor 1, 202 enters the upper part of the second reactor, and reacts with the fresh carbon dioxide 201 entering from the bottom. The product II 203 flows out from the bottom of the second reactor, and is cooled to 100°C by the second heat exchanger 6. The cooling medium is circulating cooling water. After cooling, it is divided into two streams, namely, the product II 204 after heat exchange and the product II after heat exchange. 301; 204 flow rate is 8000kg / h, 301 flow rate is 1980kg / h; 204 returns to the second reactor 4, and the overall temperature rise in the second reactor 4 is also cooled and removed by circulating cooling water. The second reaction product 203 is tested, and the conversion rate of ethylene oxide is 95.2%, and the content of carbonate is 99.1%.

[0066] After the reaction in the second reactor 4 , the residual carbon dioxide 205 is discharged from the top of the second reactor 4 , and then enters the first reactor 1 from the bottom of the first reactor 1 with a small amount of fresh carbon dioxide 102 added, and reacts with the alkylene oxide in the first reactor 1 .

[0067] A pressure regulating valve is provided at the top of the first reactor 1. When the pressure in the first reactor 1 and the second reactor 4 is kept stable and does not exceed 3% of the reaction pressure, the pressure regulating valve is closed.

[0068] Example 2

[0069] The operating conditions of this embodiment are the same as those of embodiment 1, except that when the overpressure in the first reactor is within the range of 3-8%, the carbon dioxide feed is reduced due to the excessive pressure. Under this abnormal condition, the pressure regulating valve at the top of the first reactor is opened to reduce the pressure in the first reactor to 2.8MPAG by releasing a portion of the gas, and 300kg / h of carbon dioxide can be replenished in time. The gas at the top of the first reactor is cooled to 60°C by the cooler 7, a small amount is discharged, and most of it is mixed with the bottom gas feed in a circulating compression method, so as to reasonably utilize the carbon dioxide rich in the tail gas and reduce the processing amount of the tail gas. After the reaction is stable, the valve at the top of the first reactor is gradually closed.

[0070] Example 3

[0071] The operating conditions of this embodiment are the same as those of embodiment 1, except that the operating overpressure is 8% or more. At this time, the pressure in the first reactor is not controlled to be stable in time through the operation of embodiment 2. At this time, a large amount of alkylene oxide has accumulated inside the reactor. In order to prevent a large amount of high-concentration carbon dioxide from entering the reactor and reacting with alkylene oxide to cause temperature runaway, the regulating valve at the top of the first reactor is opened at this time, and 1200kg / h of nitrogen is introduced from 102 to mix with the fresh carbon dioxide entering 102, fully disturbing the catalyst bed, reducing the temperature in the first reactor and consuming alkylene oxide. At this time, it is necessary to reduce the feed amount of alkylene oxide to 500kg / h in time. As the reaction proceeds, the feed ratio of inert gas is gradually reduced until the temperature and pressure in the reactor are relatively stable, and the reaction gradually returns to normal, the feed amount of alkylene oxide is increased to the normal operating condition, and finally the valve at the top of the first reactor is closed.

[0072] Comparative Example

[0073] The operating conditions of this comparative example are the same as those of Example 1, except that no pressure regulating means is provided in the reactor. Since the carbon dioxide feed amount is controlled by the reactor pressure, when the reactor pressure gradually increases, the carbon dioxide feed amount decreases accordingly, but the alkylene oxide feed does not stop, which will cause the accumulation of alkylene oxide in the reactor. Through manual intervention, the process operation has hysteresis, and the operating pressure is very likely to exceed 8%. At this time, the accumulated amount of alkylene oxide is greater than that of the process method using Example 2. In view of this overpressure condition, nitrogen is used to purge the bed to reduce the concentration of alkylene oxide, and the content of alkylene oxide in the tail gas increases, which affects the tail gas treatment. When the operation hysteresis is more serious, the concentration of alkylene oxide continues to increase. In order to prevent carbon dioxide from entering the system and causing problems such as temperature runaway and catalyst deactivation, it is necessary to shut down the process.

[0074] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0075] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A process for producing carbonate esters, wherein the equipment used in the process includes an alkylene oxide source, a carbon dioxide source, a first reactor, a first heat exchanger, a second reactor and a second heat exchanger; The carbon dioxide source is connected to the parallel carbon dioxide source branch P1 and the carbon dioxide source branch P2; The alkylene oxide source and carbon dioxide source branches P1 are respectively connected to the first reactor; The product outlet of the first reactor flows through the first heat exchanger and then connects to the parallel product I branch I-1 and product I branch I-2; The product I branch I-1 is connected to the first reactor; The product I branch I-2 and the carbon dioxide source branch P2 are respectively connected to the second reactor; The product outlet of the second reactor flows through the second heat exchanger and then connects to the parallel product II branch II-1 and product II branch II-2; The product II branch II-1 is connected to the second reactor; The gas phase outlet of the first reactor is provided with a pressure regulating valve.

2. The process according to claim 1, characterized in that: The normal pressure range in the first reactor is 2.5-3.0 MPAG; When the pressure in the first reactor does not exceed 3% of the normal pressure range, close the pressure regulating valve; When the pressure in the first reactor is greater than 3% of the normal pressure range and does not exceed 8%, open the pressure regulating valve; When the pressure in the first reactor exceeds 8% of the normal pressure range, the pressure regulating valve is opened to add inert gas into the first reactor, and the ratio of the flow rate of the inert gas to the fresh carbon dioxide is 1 to 2; and / or, when the pressure in the first reactor exceeds 8% of the normal pressure range, the pressure regulating valve is opened to add inert gas to the first reactor while reducing the feed flow rate of alkylene oxide, and the feed flow rate is not higher than 80% of the normal production condition; preferably, the inert gas is selected from at least one of nitrogen, helium and argon; And / or, the device further comprises a cooler and a supercharger, the gas phase outlet of the first reactor is connected to the cooler and the supercharger in sequence, and then connected to the gas phase branch C1 and the gas phase branch C2 in parallel; the gas phase branch C2 is connected to the lower part of the first reactor; And / or, the gas phase outlet of the first reactor is located at the top of the first reactor.

3. The process according to claim 1 or 2, characterized in that: The alkylene oxide source and the carbon dioxide source branch P1 are connected to the first reactor in a countercurrent manner; preferably, the alkylene oxide source is connected to the upper part of the first reactor, and the carbon dioxide source branch P1 is connected to the lower part of the first reactor; And / or, the product I branch I-2 and the carbon dioxide source branch P2 are connected to the second reactor in a countercurrent manner; preferably, the product I branch I-2 is connected to the upper part of the second reactor, and the carbon dioxide source branch P2 is connected to the lower part of the second reactor; And / or, the product II branch II-1 is connected to the upper part of the second reactor.

4. The process method according to claim 1, 2 or 3, wherein the material flow ratio of the product I branch I-1 and the product I branch I-2 is 5 to 10; And / or, the material flow ratio between the product II branch II-1 and the product II branch II-2 is 3 to 10.

5. The process according to any one of claims 1 to 4, characterized in that: The alkylene oxide is selected from at least one of ethylene oxide and propylene oxide.

6. The process according to any one of claims 1 to 5, characterized in that: The total flow rate of the carbon dioxide source and the total flow rate of the alkylene oxide source are fed in a ratio of 1.05 to 1.2; and / or, the flow ratio between the carbon dioxide source branch P1 and the carbon dioxide source branch P2 is 0.02 to 0.2; and / or, the reaction conditions in the first reactor include: resin-type catalyst, reaction temperature of 50 to 200° C., reaction pressure of 2.0 to 4.0 MPAG; And / or, the temperature of the product I of the first reactor after heat exchange in the first heat exchanger is 50-100°C, preferably 50-80°C.

7. The process according to any one of claims 1 to 6, characterized in that: The reaction conditions in the second reactor include: resin-type catalyst, reaction temperature of 50-200° C., and reaction pressure of 2.0-4.0 MPAG.

8. The process according to any one of claims 1 to 7, characterized in that: The temperature of the second heat exchanger product II after heat exchange in the first heat exchanger is 80-120°C, preferably 80-100°C.

9. The process according to any one of claims 1 to 8, characterized in that: When the pressure regulating valve is opened, the feed rate of the carbon dioxide source is increased at the same time, and the feed rate is 1.2 to 2 times that of the normal working condition; And / or, when the pressure regulating valve is opened, the cooling temperature of the cooler is 50-100°C, preferably 50-80°C.

10. The process according to any one of claims 1 to 9, characterized in that: In the process, the conversion rate of alkylene oxide is not less than 95%, and the purity of carbonate is not less than 99%.

Images