Process for producing carbonates

Abstract

The present application relates to a process for producing carbonates, and belongs to the technical field of carbonates production. The process for producing carbonates uses equipment including 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 connected to the second reactor; the gas phase outlet of the first reactor is provided with a pressure regulating valve; the normal pressure range in the first reactor is 2.5-3.0 MPAG; when the pressure is not more than 3% of the normal pressure range, the pressure regulating valve is closed; when the pressure is greater than 3% and not more than 8% of the normal pressure range, the pressure regulating valve is opened; when the pressure is more than 8% of the normal pressure range, the pressure regulating valve is opened, and non-active gas is supplemented into the first reactor, and the flow rate of the non-active gas to the fresh carbon dioxide is 1-2. The process is simple to operate, has low equipment investment, has good economic and social benefits, can be applied to industrial production, the conversion rate of alkylene oxide in the reaction product is not less than 95%, and the purity of carbonates is not less than 99%.

Description

Technical Field

[0001] This invention relates to a process for producing carbonates, belonging to the field of carbonate production technology. Background Technology

[0002] With the overuse of energy and the dwindling reserves of oil, electric drive devices are gradually appearing in people's lives and becoming increasingly commonplace. As the production of electric vehicles increases, the market for carbonates, used as electrolytes, is expanding. The preparation of carbonates through the reaction of carbon dioxide and epoxides shows promising application prospects.

[0003] Chinese invention patent publication CN102482407A discloses a continuous method for preparing aliphatic polycarbonate from carbon dioxide and epoxy compounds. This method mainly involves continuously feeding carbon dioxide, one or more epoxy compounds, and a catalyst into a reactor to prepare aliphatic polycarbonate, separating unreacted carbon dioxide and epoxy compounds, and recovering them as raw materials. This recovery process first requires separating the catalyst from the gaseous carbon dioxide and epoxy compounds, then separating the gaseous carbon dioxide and epoxy compounds separately, and finally mixing the carbon dioxide and epoxy compounds as a fully liquid-phase feed for reaction. This separation and recovery process is complex, and since carbon dioxide itself is relatively inexpensive, the excessive investment in equipment and other resources for recovering only a small portion of the raw materials results in low practical applicability and is not conducive to industrial application.

[0004] Chinese invention patent publication CN112705124A discloses a reactor, system, and method for synthesizing carbonates, in which the top gas of the main reactor is directly discharged after cooling. The process involves the reaction of carbon dioxide and alkylene oxides in equal proportions. The feed ratio of carbon dioxide to alkylene oxides has different effects on the process. When the amount of carbon dioxide is excessive or insufficient, the amount of gas at the top of the reactor is small, the pressure regulation within the reactor is insensitive, and the carbon dioxide feed is easily unstable, affecting the reaction. When excessive carbon dioxide is used, the tail gas will carry more unreacted alkylene oxide raw materials and the product carbonate, placing higher demands on the subsequent tail gas treatment capacity.

[0005] CN213286231U discloses a system for extracting and purifying carbon dioxide and propylene oxide from carbonate production tail gas. The system consists of a compression unit, a carbon dioxide purification unit, a propylene oxide purification unit, and an emission system connected in series. This process primarily recovers carbon dioxide and propylene oxide from the tail gas. According to its embodiments, nearly 90% of the tail gas is carbon dioxide, with only a small amount of propylene oxide present. While carbon dioxide has a low market price, the equipment investment for this process is substantial, and the subsequent extraction and purification process requires significant operational investment. Compared to the small amount of propylene oxide recovered, its economic viability is low, hindering the industrial-scale implementation of this process.

[0006] In current heterogeneous carbonate production processes, carbon dioxide and alkyl epoxides react in nearly equal proportions. Therefore, the gas emission from the top of the reactor is small or nonexistent, leading to pressure instability in the reaction system and consequently, instability in the carbon dioxide feed. When pressure regulation instability reduces the carbon dioxide feed rate, a large amount of alkyl epoxides remain in the reactor, easily causing excessively high local temperatures in the catalyst bed and resulting in catalyst deactivation. Summary of the Invention

[0007] The problems to be solved by this invention are as follows: 1) unstable carbon dioxide feed; 2) excessively high local temperature rise in the catalyst bed; 3) unstable pressure control of the reaction system. To address these problems, a process for preparing carbonates is provided, which can achieve stable pressure control in the reactor and ensure the safe and stable progress of the reaction.

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

[0009] A process for producing carbonates 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 parallel carbon dioxide source branches P1 and P2. The alkylene oxide source and 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 is then connected to parallel product I branches I-1 and I-2. Product I branch I-1 is connected to the first reactor. Product I branch I-2 and 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 is then connected to parallel product II branches II-1 and II-2. 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 proceed safely and effectively within this pressure range. When the pressure in the first reactor is greater than 3% of the normal pressure range but 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 decreases 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 inside the first reactor exceeds 8% of the normal pressure range, the pressure regulating valve is opened to supplement the first reactor with an inactive gas. The flow rate of the inactive gas is in a ratio of 1 to 2 with that of fresh carbon dioxide. Preferably, the feed flow rate of alkyl epoxides is reduced simultaneously, 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 exceeds 8%, an inactive gas is added and mixed with fresh carbon dioxide before entering the reactor, while the feed flow rate of alkyl epoxides is reduced. This method can reduce the concentration of carbon dioxide entering the reactor and prevent a large amount of carbon dioxide from entering, which would cause the catalyst bed temperature to rise too high. Preferably, the inactive gas is selected from at least one of nitrogen, helium, and argon.

[0011] Optionally, the device further includes a cooler and a booster compressor. The gas phase outlet of the first reactor is sequentially connected to the cooler and the booster compressor, and then connected to parallel gas phase branches C1 and C2. Gas phase branch C2 connects 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 stream is pressurized by the booster compressor and circulated back to the first reactor, while the other stream is sent to the absorption tower for treatment.

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

[0013] Optionally, the alkyl oxidant source and the carbon dioxide source branch P1 are connected to the first reactor in a countercurrent manner; preferably, the alkyl oxidant 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, product branch I-2 and carbon dioxide source branch P2 are connected to the second reactor in a countercurrent manner; preferably, product branch I-2 is connected to the upper part of the second reactor, and carbon dioxide source branch P2 is connected to the lower part of the second reactor.

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

[0016] A process for producing carbonates, wherein the equipment used in the process includes any of the above-mentioned equipment for producing carbonates, and 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 simultaneously, to 1.2 to 2 times that under normal operating conditions.

[0018] Optionally, when the pressure regulating valve is opened, the gas is cooled by a heat exchanger at the top of the reactor. The cooling temperature of the heat exchanger is 50–100°C, preferably 50–80°C, to prevent the gas temperature from becoming too high during the compression process of the booster compressor, which could affect the stability of the feed.

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

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

[0021] Optionally, the total feed flow rate of carbon dioxide source (fresh feed carbon dioxide) and the total feed flow rate of epoxide source are 1.05 to 1.2. Less carbon dioxide feed can reduce the amount of exhaust gas to be treated.

[0022] Optionally, the flow ratio of carbon dioxide source branch P1 to carbon dioxide source branch P2 is 0.02 to 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 MPa.

[0024] Optionally, the temperature of product I from 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 product II after heat exchange in the second heat exchanger is 80–120°C, preferably 80–100°C.

[0027] The process of this invention is simple to operate and requires low equipment investment. The method for producing carbonates uses a reactor top pressure regulation control, ensuring stable pressure control. It offers good economic and social benefits and can be applied to industrial production. The conversion rate of epoxides in the reaction products is not less than 95%, and the purity of the carbonates is not less than 99%. Attached Figure Description

[0028] Figure 1 This is a process diagram for synthesizing carbonates according to the present invention:

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

[0030] Reaction logistics:

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

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

[0033] The equipment for producing carbonates according to this invention mainly includes a first reactor, a first heat exchanger, a second reactor, a second heat exchanger, a circulating pump, an absorption tower, a booster compressor, a cooler, a first circulating pump, and a second circulating pump.

[0034] The first circulating pump is connected to the bottom of the first reactor;

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

[0036] The second circulating pump is connected to the bottom of the second reactor;

[0037] The second heat exchanger is connected to the second circulating pump, and its outlet is located at the top of the second reactor, where the final reaction product is collected.

[0038] The cooler is connected at one end to the top of the first reactor and at the other end to the booster.

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

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

[0041] The present invention will be further illustrated by the following embodiments, but is not limited to these embodiments.

[0042] In this embodiment, the reaction product was tested using chromatographic analysis, and the calculation formula is as follows:

[0043]

[0044] In the formula:

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

[0046] m i —The 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 using the corrected area normalization method. The calculation formula is as follows:

[0049]

[0050] In the formula:

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

[0052] A i : 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 follows:

[0055] M 碳酸酯 =M 出口总量 ×X 碳酸酯

[0056] The conversion rate of epoxides is calculated as follows:

[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 carbonates

[0059] like Figure 1 As shown, the equipment for producing carbonates 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 booster 8; the first reactor 1 and the second reactor 4 are filled with a solid halogen-type complex hydroxyimidazolium resin catalyst (prepared using the method in Example 1 of patent document CN105503608B). Carbon dioxide source 100 is connected to parallel carbon dioxide source branches 102 and 201; epoxide alkane source 101 and 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 parallel product I branch 104 and product I branch 202; product I branch 104 is connected to the first reactor; product I branch 202 and 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 parallel product II branch 204 and product II branch 301; product II branch 204 is connected to the upper part of the second reactor. The gas phase outlet of the first reactor is sequentially connected to the cooler 7 and the booster 8, and then connected to parallel gas phase branches 105 and 106; 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 equipped with a pressure regulating valve. The epoxide alkane 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 carbonates using equipment for producing carbonates is as follows:

[0061] Epoxyalkane 101 (ethylene oxide) enters the first reactor 1 from the upper part.

[0062] Fresh carbon dioxide is divided into two streams, fresh carbon dioxide 102 and fresh carbon dioxide 201. Fresh carbon dioxide 102 enters the first reactor 1 from the lower part, and fresh carbon dioxide 201 enters the second reactor 4 from the lower part.

[0063] Inside the first reactor 1, the reaction temperature is 100℃; the reaction pressure is 2.8 MPaG; the flow rate of epoxide 101 is 1000 kg / h; and the flow rate of fresh carbon dioxide 102 is 50 kg / h.

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

[0065] Product I 103, after reacting in the first reactor 1, flows out from the bottom of the first reactor and is cooled to 80°C by the first heat exchanger 3 using circulating cooling water as the cooling medium. After cooling, it splits into two streams: product I 104 and 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. Product II 203 flows out from the bottom of the second reactor and is cooled to 100°C by the second heat exchanger 6 using circulating cooling water as the cooling medium. After cooling, it splits into two streams: product II 204 and product II 202 after heat exchange. The flow rates of reactors 301 and 204 are 8000 kg / h and 1980 kg / h, respectively. Reactor 204 is returned to the second reactor 4. The overall temperature rise in the second reactor 4 is also reduced by circulating cooling water. The second reaction product 203 was tested, showing a 95.2% conversion rate of ethylene oxide and a 99.1% content of carbonates.

[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 enters the first reactor 1 from the bottom with a small amount of replenished fresh carbon dioxide 102, where it reacts with the epoxides in the first reactor 1.

[0067] The top part of the first reactor 1 is equipped with a pressure regulating valve. The pressure in the first reactor 1 and the second reactor 4 is stable. When the pressure does not exceed 3% of the reaction pressure, the pressure regulating valve is closed.

[0068] Example 2

[0069] The operating conditions in this embodiment are the same as in Embodiment 1. The difference is that when the overpressure in the first reactor is within the range of 3-8%, the carbon dioxide feed decreases due to the excessive pressure. Under this abnormal condition, the pressure regulating valve at the top of the first reactor is opened to release some gas and reduce the pressure in the first reactor to 2.8 MPaG, while simultaneously replenishing carbon dioxide at a rate of 300 kg / h. The gas at the top of the first reactor is cooled to 60°C by cooler 7, with a small amount discharged and the majority recycled and compressed to mix with the bottom gas feed. This makes reasonable use of the carbon dioxide-rich tail gas, reducing the amount of tail gas to be treated. After the reaction stabilizes, the valve at the top of the first reactor is gradually closed.

[0070] Example 3

[0071] The operating conditions in this embodiment are the same as in Embodiment 1, except that the operating pressure is 8% or higher overpressure. At this point, the pressure inside the first reactor was not stabilized in time as described in Embodiment 2, and a large amount of epoxides had accumulated inside the reactor. To prevent a large amount of high-concentration carbon dioxide from entering the reactor and reacting with the epoxides, causing a temperature runaway, the regulating valve at the top of the first reactor is opened, and 1200 kg / h of nitrogen gas is introduced from 102 to mix with the fresh carbon dioxide entering from 102, fully agitating the catalyst bed, lowering the temperature inside the first reactor, and consuming the epoxides. At this point, the epoxide feed rate needs to be promptly reduced to 500 kg / h. As the reaction proceeds, the proportion of inert gas feed is gradually reduced until the temperature and pressure inside the reactor are relatively stable. Once the reaction gradually returns to normal, the epoxide feed rate is increased to the normal operating rate, and finally, the valve at the top of the first reactor is closed.

[0072] Comparative Example

[0073] The operating conditions in this comparative example are the same as in Example 1, except that no pressure regulation mechanism is installed in the reactor. Since the carbon dioxide feed rate is controlled by the reactor pressure, as the reactor pressure gradually increases, the carbon dioxide feed rate decreases accordingly. However, the feeding of alkyl epoxides does not stop, leading to the accumulation of alkyl epoxides in the reactor. Through manual intervention, the process operation exhibits a lag, and the operating pressure easily exceeds 8%. At this point, the accumulated amount of alkyl epoxides is greater than that using the process method in Example 2. To address this overpressure condition, nitrogen is used to purge the bed to reduce the concentration of alkyl epoxides. The increased content of alkyl epoxides in the tail gas affects tail gas treatment. When the operational lag is severe, the concentration of alkyl epoxides continues to increase. To prevent carbon dioxide from entering the system and causing problems such as overheating and catalyst deactivation, a shutdown is necessary.

[0074] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically 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 for explaining the present invention and do not constitute any limitation on 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 terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A process for producing carbonates, characterized in that, 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 parallel carbon dioxide source branches P1 and P2. The epoxy alkane source and 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 is connected to the parallel product I branch I-1 and product I branch I-2. Product I branch I-1 is connected to the first reactor; Product I branch I-2 and 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 is connected to the parallel product II branch II-1 and product II branch II-2. Product II branch II-1 connects to the second reactor; The gas phase outlet of the first reactor is equipped with a pressure regulating valve; The first and second reactors are filled with solid catalysts; Carbon dioxide and raw material epoxide alkane enter the first reactor and react to obtain product I. The product in branch I-1 is recycled to the first reactor, and carbon dioxide and the product in branch I-2 enter the second reactor to react. The normal pressure range within the first reactor is 2.5–3.0 MPa. When the pressure inside the first reactor does not exceed 3% of the normal pressure range, close the pressure regulating valve; When the pressure inside the first reactor is 3% greater than the normal pressure range but does not exceed 8%, open the pressure regulating valve. When the pressure inside the first reactor exceeds 8% of the normal pressure range, open the pressure regulating valve to replenish the first reactor with inactive gas.

2. The process method according to claim 1, characterized in that, The ratio of the flow rate of the inactive gas to the flow rate of fresh carbon dioxide is 1 to 2.

3. The process method according to claim 1, characterized in that, The inactive gas is selected from at least one of nitrogen, helium, and argon.

4. The process method according to claim 1, characterized in that, When the pressure inside the first reactor exceeds 8% of the normal pressure range, open the pressure regulating valve to replenish the first reactor with inactive gas while reducing the feed flow rate of epoxide alkane. The feed flow rate should not exceed 80% of the normal operating condition.

5. The process method according to claim 1, characterized in that, The equipment also includes a cooler and a booster. The gas phase outlet of the first reactor is connected to the cooler and the booster in sequence, and then connected to the parallel gas phase branch C1 and gas phase branch C2. The gas phase branch C2 is connected to the lower part of the first reactor.

6. The process method according to claim 1, characterized in that, The gas phase outlet of the first reactor is located at the top of the first reactor.

7. The process method according to claim 1, characterized in that, The epoxide alkane source and the carbon dioxide source branch P1 are connected to the first reactor in a countercurrent manner.

8. The process method according to claim 1, characterized in that, The epoxide alkane 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.

9. The process method according to claim 1, characterized in that, The product I branch I-2 is connected to the second reactor in a countercurrent manner with the carbon dioxide source branch P2.

10. The process method according to claim 1, characterized in that, Product I branch I-2 connects to the upper part of the second reactor, and carbon dioxide source branch P2 connects to the lower part of the second reactor.

11. The process method according to claim 1, characterized in that, Product II branch II-1 is connected to the upper part of the second reactor.

12. The process method according to claim 1, characterized in that, The material flow ratio between Product I branch I-1 and Product I branch I-2 is 5 to 10.

13. The process method according to claim 1, characterized in that, The material flow ratio between Product II Branch II-1 and Product II Branch II-2 is 3 to 10.

14. The process method according to claim 1, characterized in that, The epoxide alkane is selected from at least one of ethylene oxide and propylene oxide.

15. The process method according to claim 1, characterized in that, The feed ratio of the total flow rate of carbon dioxide source to the total flow rate of epoxide alkane source is 1.05 to 1.

2.

16. The process method according to claim 1, characterized in that, The flow ratio of the carbon dioxide source branch P1 and the carbon dioxide source branch P2 is 0.02 to 0.

2.

17. The process method according to claim 1, characterized in that, The reaction conditions in the first reactor include: resin-type catalyst, reaction temperature of 50–200°C, and reaction pressure of 2.0–4.0 MPa.

18. The process method according to claim 1, characterized in that, The product I from the first reactor is heated to a temperature of 50–100°C after passing through the first heat exchanger.

19. The process method according to claim 18, characterized in that, The product I from the first reactor is heated to a temperature of 50–80°C after passing through the first heat exchanger.

20. The process method according to claim 1, 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 MPa.

21. The process method according to claim 1, characterized in that, The temperature of product II after heat exchange in the second heat exchanger is 80-120℃.

22. The process method according to claim 21, characterized in that, The temperature of product II after heat exchange in the second heat exchanger is 80-100℃.

23. The process method according to claim 1, characterized in that, When the pressure regulating valve is opened, the feed rate of the carbon dioxide source is increased simultaneously, to 1.2 to 2 times that under normal operating conditions.

24. The process method according to claim 1, characterized in that, When the pressure regulating valve is open, the cooler temperature is 50–100°C. o C.

25. The process method according to claim 24, characterized in that, When the pressure regulating valve is open, the cooler temperature is 50-80°C. o C.

26. The process method according to claim 1, characterized in that, In the aforementioned process, the conversion rate of epoxides is not less than 95%, and the purity of carbonates is not less than 99%.

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