Hexafluoropropylene oxide continuous production process and device

Abstract

The present invention belongs to the technical field of preparation of fluorine-containing fine chemicals, and specifically relates to a continuous production process and device of hexafluoropropylene oxide. The steps are as follows: Step 1, fully mix hexafluoropropylene and a solvent to obtain a mixed liquid, and add the mixed liquid to a tubular reactor; Step 2, the mixed liquid fully stays in contact with oxygen in the tubular reactor to react to obtain a gas-liquid mixture, the reaction temperature is 100-130°C, the reaction pressure is 1.3-1.8Mpa, and the gas-liquid mixture is discharged from the outlet of the tubular reactor after the reaction is completed; Step 3, the gas-liquid mixture discharged from step 2 is separated into gas and liquid through a condenser to obtain a gas phase and a solvent, the gas phase is discharged from the gas phase outlet, and the solvent is returned to the solvent storage tank through a solvent loop. The operation is simple, the production efficiency is high, the reaction conditions are mild, and the conversion rate and selectivity of the obtained product are high; the device used has a small footprint and is easy to control.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of fluorine-containing fine chemicals, and specifically relates to a continuous production process and a device for hexafluoropropylene oxide. Background Art

[0002] Hexafluoropropylene oxide (HFPO for short) is an important organic fluoride intermediate. It has special chemical activity and can be used in important new fluorine-containing materials such as polytetrafluoroethylene, fluorinated surfactants, and fluororubber, and is widely used in microelectronics, new energy, flexible displays, medicine and other fields. In 1962, DuPont published a patent for the preparation of HFPO from hexafluoropropylene (HFP). Since then, HFPO has developed rapidly, and with the continuous research on hexafluoropropylene oxide at home and abroad, the application field of this product has been continuously broadened. Fine chemicals using HFPO as raw materials are emerging in an endless stream, so HFPO has become an important intermediate in the field of new materials.

[0003] Most of the methods reported so far for synthesizing hexafluoropropylene oxide are carried out under high temperature and high pressure, and the reaction mode is mainly intermittent. When oxygen is used as an oxidant, the choice of reactor is very important. The current existing technologies are as follows:

[0004] (1) Chinese patent CN101157669 introduces a process for the continuous preparation of hexafluoropropylene oxide. In a fully mixed flow autoclave reaction, hexafluoropropylene and oxygen are introduced into a reactor containing a solvent, and the resulting reactants are continuously accumulated in the upper gas phase space of the reactor and then continuously discharged. Although this method can achieve continuous operation, due to the limited heat exchange area and large volume of the reactor, heat dissipation is difficult and there is a risk of explosion.

[0005] (2) Chinese patent CN201692802 introduces a process for continuously preparing hexafluoropropylene oxide in a tubular continuous reactor. The process uses an oxygen liquid phase oxidation method, where hexafluoropropylene and a solvent are premixed and heated to a specified temperature, and then oxygen is introduced to form a gas-liquid mixture. The mixture enters a tubular reactor to react. This method is limited by the solubility of oxygen and hexafluoropropylene in the solvent, and the reaction yield and conversion rate are not high.

[0006] (3) Chinese patent CN104672177B introduces a process for continuous production of hexafluoropropylene oxide using a microchannel reactor, which can avoid temperature runaway and oxygen explosion, achieve stable temperature control, and has high reaction conversion rate and good selectivity. However, the microchannel reactor has low liquid holding capacity and slow feed rate, which leads to low production efficiency; and the reaction temperature and pressure in this process are both high, the reaction conditions are harsh and dangerous, and the high temperature and high pressure can easily damage the reaction equipment, shortening its service life.

[0007] The use of oxygen to oxidize hexafluoropropylene to produce HFPO has been widely used. However, most of them are currently intermittent methods, that is, kettle reactions, in which hexafluoropropylene and oxygen are added to a reactor with a solvent in proportion, and oxygen and hexafluoropropylene are oxidized to produce HFPO through solvent mass transfer and heat transfer at a certain pressure and temperature. The disadvantage of this method is that the temperature needs to be slowly raised in the process of reaching the reaction conditions, and the temperature needs to be lowered after the reaction is completed, and then the material is slowly discharged into the condenser for gas-liquid separation. Therefore, the reactor cannot be used during the heating, cooling and discharging process, and the equipment efficiency and production capacity are low. Large-scale production requires large or many reactors of the same size, which occupies a large area, requires a large number of personnel, and uses a large amount of energy, which is very uneconomical. Summary of the invention

[0008] In view of the shortcomings of the prior art, the object of the present invention is to provide a continuous production process of hexafluoropropylene oxide, which is simple to operate, has high production efficiency, mild reaction conditions, and has high conversion rate and selectivity of the obtained product;

[0009] Another object of the present invention is to provide a device used in the continuous production process of hexafluoropropylene oxide, which occupies a small area and is easy to operate and control.

[0010] The technical solution adopted by the present invention is as follows:

[0011] The continuous production process of hexafluoropropylene oxide comprises the following steps:

[0012] Step 1, fully mixing hexafluoropropylene and a solvent to obtain a mixed solution, and adding the mixed solution into a tubular reactor;

[0013] Step 2: The mixed liquid is fully contacted with oxygen in a tubular reactor to react to obtain a gas-liquid mixture. The reaction temperature is 100-130° C. and the reaction pressure is 1.3-1.8 MPa. After the reaction is completed, the gas-liquid mixture is discharged from the outlet of the tubular reactor.

[0014] Step 3, the gas-liquid mixture discharged from step 2 is separated into gas and liquid through a condenser to obtain a gas phase and a solvent, the gas phase is discharged from the gas phase outlet, and the solvent is returned to the solvent storage tank through a solvent loop;

[0015] The device used includes an oxygen cylinder, a hexafluoropropylene storage tank and a solvent storage tank. The outlet of the oxygen cylinder is connected to the inlet of a tubular reactor through a pipeline, and a mass flow meter is arranged on the pipeline; the hexafluoropropylene storage tank and the solvent storage tank are respectively connected to the inlet of a mixer through pipelines, and a first metering pump and a second metering pump are respectively arranged on the pipelines; the outlet of the mixer is connected to the inlet of the tubular reactor through a pipeline, and the outlet of the tubular reactor is connected to the inlet of a condenser through a pipeline, and a back pressure valve is arranged on the pipeline; a gas phase outlet is arranged on the top of the condenser, and the liquid phase outlet on the top of the condenser is connected to the solvent storage tank through a solvent loop.

[0016] In the step 1, the volume ratio of hexafluoropropylene to the solvent is 1:(3-9), and the feed rates of the solvent and hexafluoropropylene are controlled by adjusting the first metering pump and the second metering pump.

[0017] In the step 1, the solvent is a fluorocarbon solvent, and no other catalyst is added; preferably, the solvent is hexafluoropropylene trimer, which has good solubility for hexafluoropropylene and hexafluoropropylene oxide, so the reaction pressure is lower and safer.

[0018] In the step 2, the molar ratio of hexafluoropropylene to oxygen in the mixed solution is (1.5-2):1, and the flow rate of oxygen is controlled by a mass flow meter to make hexafluoropropylene and oxygen reach a specific ratio.

[0019] In the step 2, the residence contact time is 16 to 40 minutes.

[0020] The device used in the hexafluoropropylene oxide continuous production process comprises an oxygen cylinder, a hexafluoropropylene storage tank and a solvent storage tank. The outlet of the oxygen cylinder is connected to the inlet of a tubular reactor through a pipeline, and a mass flowmeter is arranged on the pipeline; the hexafluoropropylene storage tank and the solvent storage tank are respectively connected to the inlet of a mixer through pipelines for fully mixing hexafluoropropylene with the solvent, and a first metering pump and a second metering pump are respectively arranged on the pipeline; the outlet of the mixer is connected to the inlet of the tubular reactor through a pipeline for stirring and reacting a mixed liquid of hexafluoropropylene and the solvent with oxygen, the outlet of the tubular reactor is connected to the inlet of a condenser through a pipeline for gas-liquid separation of the product after the reaction of the tubular reactor, and a back pressure valve is arranged on the pipeline; a gas phase outlet is arranged at the top of the condenser, and the liquid phase outlet at the top of the condenser is connected to the solvent storage tank through a solvent loop.

[0021] The tubular reactor is provided with a stirring shaft.

[0022] The tubular reactor is externally connected with a motor.

[0023] The bottom and top of the tubular reactor are respectively provided with a heat exchange liquid inlet and a heat exchange liquid outlet.

[0024] The device used works as follows:

[0025] The method comprises the following steps: adding hexafluoropropylene and a solvent into a mixer and mixing them fully to obtain a mixed liquid; adjusting the feed rates of the solvent and hexafluoropropylene by adjusting the flow rates of a first metering pump and a second metering pump; adding the mixed liquid into a continuously dynamically stirred tubular reactor; controlling the temperature of the tubular reactor by a heat exchange liquid; adjusting the reaction pressure by a back pressure valve; introducing oxygen; controlling the flow rate of oxygen by a mass flow meter to keep a specific ratio of hexafluoropropylene and oxygen; fully contacting hexafluoropropylene and oxygen through the solvent in the continuously stirred tubular reactor to react; discharging the material from the tubular reactor after a period of reaction; condensing the discharged material by a condenser to separate the gas from the liquid; reusing the separated liquid phase solvent; and collecting and detecting the gas phase.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The continuous production process of hexafluoropropylene oxide described in the present invention significantly improves production efficiency through a carefully designed continuous production process; the entire process is easy to operate, the reaction conditions are mild, and harsh temperature and pressure conditions are not required, which not only reduces energy consumption but also greatly improves production safety; at the same time, the solvent used in the present invention has good solubility for hexafluoropropylene and hexafluoropropylene oxide, so that the reaction pressure can be reduced, further improving production safety;

[0028] (2) The continuous production process of hexafluoropropylene oxide described in the present invention has also achieved significant improvements in product quality and selectivity; by accurately controlling the molar ratio of hexafluoropropylene to oxygen and the reaction residence time, the reaction can be carried out efficiently and fully, thereby greatly improving the conversion rate and selectivity of the product, which not only reduces the production cost but also effectively ensures the product quality;

[0029] (3) The device used in the continuous production process of hexafluoropropylene oxide described in the present invention has a compact structure and occupies a small area, which not only saves production space but also reduces equipment investment costs; at the same time, the device is simple to operate and easy to control, making the production process more stable and reliable; by accurately controlling each metering pump and mass flow meter, accurate adjustment of raw material feed can be achieved, thereby ensuring the smooth progress of the reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of the device used in the continuous production process of hexafluoropropylene oxide according to the present invention;

[0031] In the figure: 1. oxygen cylinder; 2. hexafluoropropylene storage tank; 3. solvent storage tank; 4. mass flow meter; 5. mixer; 6. heat exchange liquid inlet; 7. heat exchange liquid outlet; 8. motor; 9. condenser; 10. tubular reactor; 11. stirring shaft; 12. gas phase outlet; 13. back pressure valve; 14. first metering pump; 15. second metering pump; 16. solvent loop. DETAILED DESCRIPTION

[0032] The present invention is further described below with reference to the embodiments, but they do not limit the implementation of the present invention.

[0033] The raw materials used in the examples and comparative examples are conventional commercially available raw materials unless otherwise specified, and the process methods used in the examples and comparative examples are conventional methods in the art unless otherwise specified.

[0034] like Figure 1 As shown, the continuous production process of hexafluoropropylene oxide described in the embodiment of the present invention, the device used therein includes an oxygen cylinder 1, a hexafluoropropylene storage tank 2 and a solvent storage tank 3, the outlet of the oxygen cylinder 1 is connected to the inlet of the tubular reactor 10 through a pipeline, and a mass flowmeter 4 is provided on the pipeline; the hexafluoropropylene storage tank 2 and the solvent storage tank 3 are respectively connected to the inlet of the mixer 5 through pipelines, and a first metering pump 14 and a second metering pump 15 are respectively provided on the pipeline; the outlet of the mixer 5 is connected to the inlet of the tubular reactor 10 through a pipeline, and the outlet of the tubular reactor 10 is connected to the inlet of the condenser 9 through a pipeline, and a back pressure valve 13 is provided on the pipeline; a gas phase outlet 12 is provided at the top of the condenser 9, and a liquid phase outlet at the top of the condenser 9 is connected to the solvent storage tank 3 through a solvent loop 16;

[0035] The tubular reactor 10 is provided with a stirring shaft 11 .

[0036] The tubular reactor 10 is externally connected to a motor 8 .

[0037] The bottom and top of the tubular reactor 10 are respectively provided with a heat exchange liquid inlet 6 and a heat exchange liquid outlet 7 .

[0038] When in use, set the parameters of the first metering pump 14 and the second metering pump 15, turn on the first metering pump 14 and the second metering pump 15, and the hexafluoropropylene and the solvent in the hexafluoropropylene storage tank 2 and the solvent storage tank 3 are mixed by the mixer 5 and enter the tubular reactor 10. Turn on the motor 8 connected to the stirring shaft 11 in the tubular reactor 10, stir under the action of the stirring shaft 11, and use the heat exchange liquid to flow between the heat exchange liquid inlet 6 and the heat exchange liquid outlet 7 to heat the tubular reactor 10. After reaching the set temperature, adjust the back pressure valve 13 to keep a constant pressure in the tubular reactor 10. Then open the oxygen cylinder 1, set the mass flow meter 4 to the specified value, pass oxygen to react, stay in the tubular reactor for a period of time, discharge the obtained gas-liquid mixture, separate the gas and liquid through the condenser, obtain the gas phase and the solvent, the gas phase is discharged from the gas phase outlet, sampled and tested, and the collected gas phase sample is analyzed by gas chromatography; the solvent returns to the solvent storage tank through the solvent loop.

[0039] Example 1

[0040] The continuous production process of hexafluoropropylene oxide comprises the following steps:

[0041] Step 1, fully mixing hexafluoropropylene and hexafluoropropylene trimer to obtain a mixed solution, and adding the mixed solution into a tubular reactor;

[0042] Step 2: The mixed liquid is fully contacted with oxygen in a tubular reactor to react to obtain a gas-liquid mixture. The reaction temperature is 130° C. and the reaction pressure is 1.8 MPa. After the reaction is completed, the gas-liquid mixture is discharged from the outlet of the tubular reactor.

[0043] Step three, the gas-liquid mixture discharged in step two is separated into gas and liquid through a condenser to obtain a gas phase and a hexafluoropropylene trimer solvent, the gas phase is discharged from the gas phase outlet, and the hexafluoropropylene trimer solvent is returned to the solvent storage tank through a solvent loop.

[0044] The continuous production process of hexafluoropropylene oxide, the device parameters used are set as follows:

[0045] The temperature of the tubular reactor 10 is set to 130° C., and it is heated by a heat exchange liquid. The feed rate parameters of the first metering pump 14 and the second metering pump 15 are set to 3 mL / min and 10 mL / min, respectively. The temperature of the mixer 5 is set to 100° C., the rotation speed of the stirring shaft 11 is set to 150 r / min, and the liquid holding capacity of the tubular reactor 10 is 400 mL. When the tubular reactor 10 is filled with a mixed liquid of the solvent and hexafluoropropylene, the pressure in the tubular reactor 10 is adjusted to 1.8 MPa by the back pressure valve 13. After the pressure is stable, oxygen is started to be passed, and the feed rate parameter of the mass flowmeter 4 is set to 32 g / h. After staying in contact in the tubular reactor 10 for 40 minutes, the gas-liquid mixture is discharged from the outlet of the tubular reactor 10 into the condenser 9, and the gas phase is collected from the gas phase outlet 12 for gas chromatography analysis to calculate the content of each component in the gas phase.

[0046] Example 2

[0047] The difference from Example 1 is that the feed rate parameter of the mass flow meter 4 is set to 36 g / h, and the rest is the same as Example 1.

[0048] Example 3

[0049] The difference from Example 1 is that the feed rate parameter of the mass flow meter 4 is set to 40 g / h, and the rest is the same as Example 1.

[0050] Example 4

[0051] The difference from Example 3 is that the feed rate parameter of the second metering pump 15 is set to 15 mL / min, the contact time in the tubular reactor 10 is 30 min, and the rest is the same as Example 3.

[0052] Example 5

[0053] The difference from Example 3 is that the feed rate parameter of the second metering pump 15 is set to 20 mL / min, the contact time in the tubular reactor 10 is 22 min, and the rest is the same as Example 3.

[0054] Example 6

[0055] The difference from Example 3 is that the feed rate parameter of the second metering pump 15 is set to 27 mL / min, the contact time in the tubular reactor 10 is 16 min, and the rest is the same as Example 3.

[0056] The gas phases collected in Examples 1 to 6 were analyzed by gas chromatography to calculate the volume percentage (%) of each component in the gas phase, and the hexafluoropropylene conversion rate (%) and the hexafluoropropylene oxide selectivity (%) were calculated at the same time. The test results are shown in Table 1;

[0057] Table 1

[0058]

[0059] It can be seen from Table 1 that in Examples 1 to 3, with the increase of oxygen dosage under the condition that other conditions remain unchanged, the conversion rate of hexafluoropropylene increases, but the selectivity of hexafluoropropylene oxide decreases. This is because some by-products are produced due to the long-term contact of oxygen with the materials in the reaction system. In Examples 4 to 5, an oxygen dosage with a higher conversion rate of hexafluoropropylene is selected. By increasing the flow rate of the solvent and reducing the contact time of oxygen with the system, although the conversion rate of hexafluoropropylene is slightly reduced, the selectivity of hexafluoropropylene oxide is significantly improved.

Claims

1. A continuous production process for hexafluoropropylene oxide, characterized in that: Here are the steps: Step 1, fully mixing hexafluoropropylene and hexafluoropropylene trimer to obtain a mixed solution, and adding the mixed solution into a tubular reactor; Step 2: The mixed liquid is fully contacted with oxygen in a tubular reactor to react to obtain a gas-liquid mixture. The reaction temperature is 130° C. and the reaction pressure is 1.8 MPa. After the reaction is completed, the gas-liquid mixture is discharged from the outlet of the tubular reactor. Step 3, the gas-liquid mixture discharged from step 2 is separated into gas and liquid through a condenser to obtain a gas phase and a hexafluoropropylene trimer solvent, the gas phase is discharged from the gas phase outlet, and the hexafluoropropylene trimer solvent is returned to the solvent storage tank through a solvent loop; The device used comprises an oxygen cylinder (1), a hexafluoropropylene storage tank (2) and a solvent storage tank (3); the outlet of the oxygen cylinder (1) is connected to the inlet of a tubular reactor (10) through a pipeline, and a mass flow meter (4) is provided on the pipeline; the hexafluoropropylene storage tank (2) and the solvent storage tank (3) are respectively connected to the inlet of a mixer (5) through pipelines, and a first metering pump (14) and a second metering pump (15) are respectively provided on the pipelines; the outlet of the mixer (5) is connected to the inlet of the tubular reactor (10) through a pipeline, and the outlet of the tubular reactor (10) is connected to the inlet of a condenser (9) through a pipeline, and a back pressure valve (13) is provided on the pipeline; a gas phase outlet (12) is provided at the top of the condenser (9), and a liquid phase outlet at the top of the condenser (9) is connected to the solvent storage tank (3) through a solvent loop (16); The tubular reactor (10) is provided with a stirring shaft (11); The tubular reactor (10) is externally connected to a motor (8); The bottom and top of the tubular reactor (10) are also provided with a heat exchange liquid inlet (6) and a heat exchange liquid outlet (7) respectively; The continuous production process of hexafluoropropylene oxide, the device parameters used are set as follows: The temperature of the tubular reactor (10) is set to 130° C. and the tubular reactor (10) is heated by a heat exchange liquid. The feed rate parameters of the first metering pump (14) and the second metering pump (15) are set to 3 mL / min and 27 mL / min, respectively. The temperature of the mixer (5) is set to 100° C. and the rotation speed of the stirring shaft (11) is set to 150 r / min. The liquid holding capacity of the tubular reactor (10) is 400 mL. When the tubular reactor (10) is filled with a mixed liquid of the solvent and hexafluoropropylene, the pressure in the tubular reactor (10) is adjusted to 1.8 MPa by a back pressure valve (13). After the pressure is stabilized, oxygen is introduced. The feed rate parameter of the mass flow meter (4) is set to 40 g / h. After the gas-liquid mixture stays in contact with the tubular reactor (10) for 16 minutes, it is discharged from the outlet of the tubular reactor (10) into the condenser (9). The gas phase is collected from the gas phase outlet (12) for gas chromatography analysis, and the content of each component in the gas phase is calculated.

2. A device used in the continuous production process of hexafluoropropylene oxide according to claim 1, characterized in that: The invention comprises an oxygen cylinder (1), a hexafluoropropylene storage tank (2) and a solvent storage tank (3); the outlet of the oxygen cylinder (1) is connected to the inlet of a tubular reactor (10) through a pipeline, and a mass flow meter (4) is provided on the pipeline; the hexafluoropropylene storage tank (2) and the solvent storage tank (3) are respectively connected to the inlet of a mixer (5) through pipelines, and a first metering pump (14) and a second metering pump (15) are respectively provided on the pipelines; the outlet of the mixer (5) is connected to the inlet of the tubular reactor (10) through a pipeline, and the outlet of the tubular reactor (10) is connected to the inlet of a condenser (9) through a pipeline, and a back pressure valve (13) is provided on the pipeline; a gas phase outlet (12) is provided at the top of the condenser (9), and a liquid phase outlet at the top of the condenser (9) is connected to the solvent storage tank (3) through a solvent loop (16); The tubular reactor (10) is provided with a stirring shaft (11); The tubular reactor (10) is externally connected to a motor (8); The bottom and top of the tubular reactor (10) are also provided with a heat exchange liquid inlet (6) and a heat exchange liquid outlet (7) respectively.

Images