A process system and method for the synthesis of medium and low molecular weight perfluoropolyethers

Abstract

The application provides a process system and method for synthesizing low-molecular-weight perfluoropolyether, which comprises oxidative polymerization, crude product phase separation, stabilization treatment and rectification separation. The raw material of mixed gas of hexafluoropropylene and fluorine oxygen is subjected to oxidative polymerization reaction in an oxidative polymerization reactor, the gas is fully dispersed by using high-speed mechanical shearing and liquid collision mixing, and the reactor is subjected to temperature control by coupling an integrated heat exchange structure. A phase separator collects perfluoropolyether crude product, which is preheated and then introduced into a fluorination reactor for fluorination stabilization treatment. The stabilized perfluoropolyether is subjected to rectification tower to obtain products with different molecular weight distributions. The application can continuously and controllably prepare perfluoropolyether products with various low-molecular-weight distributions, and has the following advantages: the bubble distribution and heat distribution in the oxidative polymerization reactor are uniform, hot spot areas are prevented, and the industrial operation safety is high; the oxidative polymerization reactor is coupled with the integrated heat exchange structure.

Description

Technical Field

[0001] The invention relates to a process system and method for synthesizing medium and low molecular weight perfluoropolyether, and belongs to the fields of chemical technology and chemical engineering. Background Art

[0002] The general formula of perfluoropolyether is [CF(CF3)CF2O] x (CF2O) y Medium and low molecular weight perfluoropolyethers have the characteristics of low viscosity, good fluidity and strong compatibility with electronic equipment. They have been explored as immersion liquid cooling materials for large data centers and have great development potential.

[0003] Perfluoropolyethers can be produced by photopolymerization, anionic polymerization, or chemical polymerization. Photopolymerization involves the polymerization of perfluoroolefins and oxygen under ultraviolet light to produce perfluoropolyethers. For example, patent US20060370042A uses a mixed solvent of heptafluoropropane, pentafluoroethane, and perfluoropropane. Tetrafluoroethylene and oxygen undergo photooxidation under ultraviolet light at temperatures between -80°C and -40°C, yielding perfluoropolyethers with a number-average molecular weight of 35,000-45,000. This method offers the advantage of mild reaction conditions, but the industrial equipment required for photopolymerization is complex and reaction control is difficult. Anionic polymerization involves the anionic polymerization of perfluoroalkylene oxides in the presence of catalysts such as cesium fluoride and potassium fluoride to produce perfluoropolyethers. While this method offers the advantage of low byproducts, it also offers the disadvantages of high raw material costs, long reaction times, and the resulting perfluoropolyethers having a high molecular weight. Chemical polymerization involves the polymerization of perfluoroolefins and oxygen under the action of a chemical initiator to produce perfluoropolyethers. Compared with the above two processes, this process has low raw material cost, simple industrial process and short reaction time, but it has the following two technical difficulties:

[0004] (1) High temperature control requirements. Hexafluoropropylene reacts differently with fluorine and oxygen in the gas phase and in the liquid phase. In the liquid phase, hexafluoropropylene undergoes an oxidative polymerization reaction with fluorine and oxygen to form perfluoropolyether; in the gas phase, hexafluoropropylene undergoes an oxidative reaction with fluorine and oxygen to form gaseous small molecular products such as fluorophosgene and trifluoroacetyl fluoride, and the gas volume expands rapidly. In the production process of perfluoropolyether, oxidative polymerization will generate a large amount of heat, and the boiling point of hexafluoropropylene is -28°C (normal pressure). Once there is a hot spot area or the temperature control performance of the reactor is poor, hexafluoropropylene will vaporize into gas. When gaseous hexafluoropropylene contacts fluorine and oxygen and undergoes gas-phase oxidation, there is a risk of rapid expansion of the gas volume, and the reaction will proceed in an uncontrolled direction, causing harm. Therefore, oxidative polymerization reactions require a reactor with good heat transfer performance, which needs to prevent the generation of hot spots and be able to remove heat in time.

[0005] (2) High gas-liquid dispersion performance requirements. Hexafluoropropylene is used as a polymerization raw material and liquid phase solvent. Fluorine and nitrogen gas need to be dissolved in hexafluoropropylene before they can undergo chain growth reactions with the polymer chain or chain initiation reactions with hexafluoropropylene. Therefore, high gas-liquid dispersion performance requirements are placed on the reactor.

[0006] Patent CN115364875A prepares a perfluoropolyether end-capping catalyst that caps perfluoropolyethers containing acyl fluoride groups to form inert end groups. However, this catalyst cannot simultaneously remove peroxides, requiring an external thermal stabilization step, which increases operating costs. The present invention combines the peroxide removal and end-group stabilization steps into the same reactor, reducing operational complexity and saving production costs. Summary of the Invention

[0007] (1) Technical problems solved

[0008] In view of the shortcomings of the existing technology, the present invention provides a process system and method for synthesizing medium and low molecular weight perfluoropolyethers, which have the excellent characteristics of strong temperature control ability, good gas-liquid dispersibility, high production efficiency and good selectivity.

[0009] (2) Technical solution

[0010] A process system for synthesizing medium and low molecular weight perfluoropolyethers, characterized by comprising:

[0011] Hexafluoropropylene inlet (1), fluorine-oxygen mixed gas inlet (2), fluorine-nitrogen gas inlet (3), low-pressure steam inlet (4), perfluoropolyether product outlet (5), oxidative polymerization reactor (6), crude product extraction pump (7), phase separator (8), fluorination preheater (9), fluorination reactor (10), distillation feed pump (11), distillation tower (12); the connection order is:

[0012] An oxidative polymerization reactor, wherein the liquid feed pipe is connected to the hexafluoropropylene feed pipe, the gas feed pipe is connected to the fluorine-oxygen mixed gas pipe, the gas outlet is connected to the tail gas treatment device, and the liquid outlet is connected to the phase separator inlet via a crude product extraction pump;

[0013] A phase separator, whose inlet is connected to the liquid outlet of the oxidative polymerization reactor through a crude product extraction pump, whose gas outlet is connected to the tail gas treatment device, and whose liquid outlet is connected to the inlet of the fluorination preheater;

[0014] a fluorination preheater, the inlet of which is connected to the liquid outlet of the phase separator, and the outlet of which is connected to the liquid inlet of the fluorination reactor;

[0015] A fluorination reactor, whose gas inlet is connected to the fluorine and nitrogen pipeline, whose liquid inlet is connected to the outlet of the fluorination preheater, whose gas outlet is connected to the tail gas treatment device, and whose liquid outlet is connected to the liquid inlet of the distillation tower through a distillation feed pump;

[0016] a distillation tower, wherein the liquid inlet is connected to the liquid outlet of the fluorination reactor through a distillation feed pump, the liquid outlet is connected to a product collecting device, the gas inlet is connected to a low-pressure steam pipeline, and the gas outlet is connected to the product collecting device;

[0017] Specifically, the oxidative polymerization reactor comprises:

[0018] (1) Gas outlet (6-1);

[0019] (2) Two sets of integrated heat exchange structures that are symmetrical on both sides, including a heat exchange medium outlet (6-2), a heat exchange medium flow channel (6-10), and a heat exchange medium inlet (6-12);

[0020] (3) Two symmetrical liquid feed pipes (6-3);

[0021] (4) Mixing channel (6-4);

[0022] (5) Two symmetrical guide tubes (6-5);

[0023] (6) Two symmetrically arranged motors (6-6);

[0024] (7) Two sets of bilaterally symmetrical high-speed shear crushing components (6-7), both extending into the guide tube, including but not limited to propulsion type, screw type, and fan type components;

[0025] (8) Two symmetrical gas feed pipes (6-8), both extending to the inner edge of the guide tube and the outer edge of the high-speed shear crushing component;

[0026] (9) Multiple return pipes (6-9);

[0027] (10) Two sets of bilaterally symmetrical reflux channels (6-11) located between the integrated heat exchange structure and the reactor shell;

[0028] (11) Liquid outlet (6-13).

[0029] In conjunction with the above system, the present invention proposes a method for synthesizing medium and low molecular weight perfluoropolyethers, which is characterized by comprising the following steps:

[0030] (1) Oxidative polymerization: Freshly fed hexafluoropropylene liquid enters and fills the reactor through two symmetrical liquid feed pipes respectively. Freshly fed oxygen and fluorine mixed gas are respectively introduced into the outer edges of the high-speed shear crushing components inside the two symmetrical guide tubes in the oxidative polymerization reactor. The mechanical energy generated by the high-speed shear crushing components of the guide tubes is concentrated. The linear velocity of the hexafluoropropylene liquid flow is the largest at the outer edges of the high-speed shear crushing components, which can produce a good initial dispersion effect on the fluorine-oxygen mixed gas. Under the action of the two high-speed shear crushing components in opposite directions, the fluorine-oxygen mixed gas is mechanically sheared into small bubbles and dispersed into the hexafluoropropylene liquid phase, and then entrained by the two hexafluoropropylene fluids flowing in opposite directions into the middle mixing channel. In the mixing channel, Two streams of hexafluoropropylene liquid flowing in opposite directions collide and mix, and the fluorine and oxygen bubbles therein oscillate and squeeze due to inertia, breaking and dispersing into smaller bubbles, achieving gas discretization and increasing the gas-liquid contact area; at the same time, the heat generated by the reaction is also evenly distributed in the hexafluoropropylene convection; the fully mixed liquid leaves the mixing flow channel under the action of the pressure difference and enters the reflux pipe, where it exchanges heat with the heat exchange medium; after flowing out of the reflux pipe, the liquid flows back to the guide tube through the reflux flow channels on both sides of the oxidative polymerization reactor, and the fluorine and oxygen consumed during the flow process are replenished in the guide tube, and oxidative polymerization continues to form a cycle; after the reaction continues for a period of time, the crude perfluoropolyether product is extracted from the liquid outlet at the bottom of the reactor, and the small molecular by-products are extracted from the gas outlet at the top;

[0031] (2) Phase separation of crude perfluoropolyether product: The crude perfluoropolyether product extracted from the oxidative polymerization reactor is introduced into the inlet of the phase separator through the crude product extraction pump, and gas-liquid separation occurs in the phase separator. Small molecular by-products, oxygen, and hexafluoropropylene are extracted from the gas outlet at the top of the phase separator, and the crude perfluoropolyether product is extracted from the liquid outlet at the bottom of the phase separator;

[0032] (3) Stabilization treatment of the fluorination reactor: The crude perfluoropolyether product extracted from the liquid outlet at the bottom of the phase separator passes through a fluorination preheater and is introduced into the liquid inlet of the fluorination reactor. The liquid covers the reactor stirring paddle and half fills the reactor; the fluorine-nitrogen mixed gas is introduced into the gas inlet of the fluorination reactor and is fully contacted with the crude perfluoropolyether product under the action of the stirring paddle to cause a fluorination reaction; the small molecular by-products produced by the fluorination reaction, nitrogen and unreacted fluorine gas are extracted from the gas outlet at the top of the fluorination reactor; the stabilized perfluoropolyether product is extracted from the bottom liquid outlet;

[0033] (4) Distillation Separation The perfluoropolyether product extracted from the liquid outlet of the fluorination reactor is introduced into the liquid inlet of the distillation tower, and the fresh low-pressure water vapor is introduced into the gas inlet at the bottom of the distillation tower. The perfluoropolyether product is distilled and separated in the distillation tower; a mixture of liquid perfluoropolyether and water with various molecular weight distributions is extracted from the corresponding distillation tower measurement line, and a mixture of gaseous perfluoropolyether and water vapor is extracted from the top of the distillation tower.

[0034] Specifically, the method proposed in the present invention is supplemented with the following process parameters: the molar ratio of fluorine gas used in the oxidative polymerization is 0.5%-2%, preferably 1%-1.5%; the temperature in the oxidative polymerization reactor is controlled at -50°C to -25°C, preferably -40°C to -30°C; the pressure is controlled at 200kPa to 600kPa, preferably 500kPa; the reaction time is controlled at 2 hours to 10 hours; the speed of the high-speed shear crushing component in the oxidative polymerization reactor is 200r / min-800r / min; the temperature of the fluorination preheater is controlled at 200°C to 300°C, preferably 250°C to 300°C; the molar ratio of fluorine gas used in the fluorination is 1% to 20%, preferably 5 to 10%; the speed of the stirring paddle in the fluorination reactor is 400r / min-1000r / min; the temperature in the fluorination reactor is controlled at 225°C to 350°C, preferably 300°C to 350°C; the pressure is controlled at 150kPa to 250kPa, preferably 200kPa to 250kPa; the reaction time is controlled at 8 hours to 20 hours; the temperature of the low-pressure water vapor introduced into the distillation tower is controlled at 150°C to 250°C.

[0035] (3) Beneficial technical effects

[0036] (1) The oxidative polymerization reactor has strong temperature control capabilities. Oxidative polymerization reactions release a large amount of heat and are prone to generating hot spots. The present invention utilizes liquid collision mixing to evenly disperse the heat generated by the reaction, and couples the reactor with an integrated heat exchange structure. Without affecting the flow field inside the reactor, the oxidative polymerization fluid is fully in contact with the heat exchange medium, thereby promptly removing the heat generated by the reaction, controlling the reaction temperature, and improving production safety.

[0037] (2) The oxidative polymerization reactor has good gas-liquid dispersion. The present invention utilizes high-speed mechanical shearing and fluid collision mixing to disperse the fluorine-oxygen mixed gas into the hexafluoropropylene liquid phase in the form of small bubbles. The good dispersion enables the reaction to proceed quickly, shortening the reaction time.

[0038] (3) The synthesis system operates continuously, resulting in high production efficiency. As previously mentioned, the oxidative polymerization and fluorination reactions are semi-batch operations, with gases continuously extracted and perfluoropolyethers extracted uniformly after the reaction time. The oxidative polymerization and fluorination reactors are set up in a group of two to ensure the overall continuity of perfluoropolyether synthesis and processing. The distillation tower and phase separator are always in operation, improving production efficiency and reducing operating costs.

[0039] (4) High selectivity for medium and low molecular weight perfluoropolyethers. Perfluoropolyether products with a number average molecular weight of <3000 are suitable for use as liquid cooling materials in data centers, and the higher the proportion of -CF2O- segments in the molecular chain, the better the fluidity. The perfluoropolyether produced by the present invention is fluorinated and distilled to obtain multi-segment products with a molecular weight distribution of 220 to 6000, among which the selectivity of perfluoropolyether with a number average molecular weight of <3000 is above 60%, and the proportion of -CF2O- segments in the product can reach 10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 A schematic diagram of a process system for synthesizing medium- and low-molecular-weight perfluoropolyethers according to an embodiment of the present invention is shown; 1—hexafluoropropylene inlet, 2—fluorine-nitrogen-oxygen mixed gas inlet, 3—fluorine-nitrogen inlet, 4—low-pressure water vapor inlet, 5—perfluoropolyether product outlet, 6—oxidative polymerization reactor, 7—crude product extraction pump, 8—phase separator, 9—fluorination preheater, 10—fluorination reactor, 11—distillation feed pump, and 12—distillation tower.

[0042] Figure 2 The overall structure diagram of the oxidative polymerization reactor of the present invention is shown; 6-1 - gas outlet, 6-2 - heat exchange medium outlet, 6-3 - liquid feed pipe, 6-4 - mixing flow channel, 6-5 - guide tube, 6-6 - motor, 6-7 - high-speed shear crushing component, 6-8 - gas feed pipe, 6-9 - reflux pipe, 6-10 - heat exchange medium flow channel, 6-11 - reflux flow channel, 6-12 - heat exchange medium inlet, 6-13 - liquid outlet. DETAILED DESCRIPTION

[0043] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] (1) Fresh hexafluoropropylene liquid fed in oxidative polymerization enters and fills the reactor through two symmetrical liquid feed pipes respectively, and fresh oxygen and fluorine mixed gas are respectively introduced into the outer edges of the high-speed shear crushing components inside the two symmetrical guide tubes in the oxidative polymerization reactor, wherein the molar ratio of fluorine gas used in oxidative polymerization is 0.5%-2%, and the mechanical energy generated by the high-speed shear crushing components of the guide tubes is concentrated; the linear velocity of the hexafluoropropylene liquid flow is the largest at the outer edges of the high-speed shear crushing components, and the rotation speed of the high-speed shear crushing components in the oxidative polymerization reactor is 200r / min-800r / min, which can produce a good initial dispersion effect on the fluorine-oxygen mixed gas; under the action of the two high-speed shear crushing components in opposite directions, the fluorine-oxygen mixed gas is mechanically sheared into small bubbles and dispersed into the hexafluoropropylene liquid phase, and then entrained by two hexafluoropropylene fluids flowing in opposite directions into the middle mixing channel; in the mixing channel , two streams of hexafluoropropylene liquids with opposite flow directions collide and mix, and the fluorine and oxygen bubbles therein oscillate and squeeze due to inertia, break and disperse into smaller bubbles, thereby realizing gas discretization and increasing the gas-liquid contact area; at the same time, the heat generated by the reaction is also evenly distributed in the hexafluoropropylene convection; the fully mixed liquid leaves the mixing flow channel under the action of the pressure difference and enters the reflux pipe, where it exchanges heat with the heat exchange medium; after the liquid flows out of the reflux pipe, it flows back to the guide tube through the reflux flow channels on both sides of the oxidative polymerization reactor, and the fluorine and oxygen consumed during the flow process are replenished in the guide tube, and oxidative polymerization continues. The temperature in the oxidative polymerization reactor is controlled at -50℃~-25℃; the pressure is controlled at 200kPa~600kPa; the reaction time is controlled at 2 hours~10 hours, forming a cycle; after a period of continuous reaction, the crude perfluoropolyether product is extracted from the liquid outlet at the bottom of the reactor, and the small molecular by-products are extracted from the gas outlet at the top;

[0045] (2) Phase separation of crude perfluoropolyether product: The crude perfluoropolyether product extracted from the oxidative polymerization reactor is introduced into the inlet of the phase separator through the crude product extraction pump, and gas-liquid separation occurs in the phase separator. Small molecular by-products, oxygen, and hexafluoropropylene are extracted from the gas outlet at the top of the phase separator, and the crude perfluoropolyether product is extracted from the liquid outlet at the bottom of the phase separator;

[0046] (3) Stabilization treatment of the fluorination reactor The crude perfluoropolyether product extracted from the liquid outlet at the bottom of the phase separator is passed through a fluorination preheater and introduced into the liquid inlet of the fluorination reactor. The liquid covers the reactor stirring paddle and half fills the reactor. The temperature of the fluorination preheater is controlled at 200°C to 300°C; the molar ratio of fluorine gas used for fluorination is 1% to 20%; the speed of the stirring paddle in the fluorination reactor is 400r / min-1000r / min; the temperature in the fluorination reactor is controlled at 225°C to 350°C, the pressure is controlled at 150kPa to 250kPa, and the reaction time is controlled at 8 hours to 20 hours; the fluorine-nitrogen mixed gas is introduced into the gas inlet of the fluorination reactor and is fully contacted with the crude perfluoropolyether product under the action of the stirring paddle to undergo fluorination reaction; the small molecular by-products produced by the fluorination reaction, nitrogen and incompletely reacted fluorine gas are extracted from the gas outlet at the top of the fluorination reactor; the stabilized perfluoropolyether product is extracted from the bottom liquid outlet;

[0047] (4) Distillation and separation The perfluoropolyether product extracted from the liquid outlet of the fluorination reactor is introduced into the liquid inlet of the distillation tower, and the fresh low-pressure water vapor is introduced into the gas inlet at the bottom of the distillation tower. The perfluoropolyether product is distilled and separated in the distillation tower; the temperature of the low-pressure water vapor introduced into the distillation tower is controlled at 150°C to 250°C; a mixture of liquid perfluoropolyether and water with various molecular weight distributions is extracted from the corresponding distillation tower measuring line, and a mixture of gaseous perfluoropolyether and water vapor is extracted from the top of the distillation tower.

[0048] Examples 1-10: The system and method of the present invention were used to produce low- and medium-molecular-weight perfluoropolyethers under the following operating conditions: pressure controlled at 500 kPa, high-speed shear crushing component speed controlled at 300 r / min, reaction time controlled at 3 hours; fluorination preheater temperature controlled at 250°C; fluorination reactor temperature controlled at 300°C, fluorine gas molar ratio controlled at 10%, pressure controlled at 225 kPa, impeller speed controlled at 600 r / min, reaction time controlled at 10 hours; and fresh feed ground-pressure steam temperature controlled at 250°C. Continuous production of perfluoropolyether was achieved after the system operated in steady state.

[0049] Table 1 Process conditions and experimental results of Examples 1 to 10

[0050]

[0051] Among all the examples, Examples 1 to 3 are within the process parameter range claimed by the present invention. From the results of the examples, it can be concluded that the number average molecular weight and molecular weight distribution of the perfluoropolyether are good.

[0052] In all the examples, some process parameter ranges of Examples 4 to 10 are not within the optimal range. It can be seen from the results of the examples that the improvement of the number average molecular weight and molecular weight distribution of the products is limited or not significant, and more material and energy consumption is caused.

[0053] The various embodiments in this specification are described in a progressive manner. Similar portions between the various embodiments can be referenced to each other. Each embodiment focuses on the differences between the other embodiments. In particular, the system embodiment is generally similar to the method embodiment, so the description is relatively simple. For relevant portions, refer to the description of the method embodiment.

[0054] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of this specification. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example.

[0055] In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, unless they are mutually inconsistent. The above description is merely an embodiment of the embodiment of this specification and is not intended to limit the embodiment of this specification. For those skilled in the art, various changes and modifications may be made to the embodiment of this specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiment of this specification shall be included within the scope of the claims of the embodiment of this specification.

Claims

1. A process system for synthesizing medium and low molecular weight perfluoropolyether, characterized in that: include: Hexafluoropropylene inlet (1), fluorine-oxygen mixed gas inlet (2), fluorine-nitrogen gas inlet (3), low-pressure steam inlet (4), perfluoropolyether product outlet (5), oxidative polymerization reactor (6), crude product extraction pump (7), phase separator (8), fluorination preheater (9), fluorination reactor (10), distillation feed pump (11), distillation tower (12); the connection order is: An oxidative polymerization reactor, wherein the liquid feed pipe is connected to the hexafluoropropylene feed pipe, the gas feed pipe is connected to the fluorine-oxygen mixed gas pipe, the gas outlet is connected to the tail gas treatment device, and the liquid outlet is connected to the phase separator inlet via a crude product extraction pump; A phase separator, whose inlet is connected to the liquid outlet of the oxidative polymerization reactor through a crude product extraction pump, whose gas outlet is connected to the tail gas treatment device, and whose liquid outlet is connected to the inlet of the fluorination preheater; a fluorination preheater, the inlet of which is connected to the liquid outlet of the phase separator, and the outlet of which is connected to the liquid inlet of the fluorination reactor; A fluorination reactor, whose gas inlet is connected to the fluorine and nitrogen pipeline, whose liquid inlet is connected to the outlet of the fluorination preheater, whose gas outlet is connected to the tail gas treatment device, and whose liquid outlet is connected to the liquid inlet of the distillation tower through a distillation feed pump; a distillation tower, wherein the liquid inlet is connected to the liquid outlet of the fluorination reactor through a distillation feed pump, the liquid outlet is connected to a product collecting device, the gas inlet is connected to a low-pressure steam pipeline, and the gas outlet is connected to the product collecting device; The oxidative polymerization reactor comprises: a gas outlet (6-1); two sets of bilaterally symmetrical integrated heat exchange structures, including a heat exchange medium outlet (6-2), a heat exchange medium flow channel (6-10), and a heat exchange medium inlet (6-12); two bilaterally symmetrical liquid feed pipes (6-3); a mixing flow channel (6-4); two bilaterally symmetrical guide tubes (6-5); two symmetrically arranged motors (6-6); two sets of bilaterally symmetrical high-speed shearing and crushing components (6-7), both extending into the guide tube, including but not limited to propulsion-type, screw-type, and fan-type components; two bilaterally symmetrical gas feed pipes (6-8), both extending to the inner edge of the guide tube and the outer edge of the high-speed shearing and crushing components; a plurality of return pipes (6-9); two sets of bilaterally symmetrical return flow channels (6-11), located between the integrated heat exchange structure and the reactor shell; and a liquid outlet (6-13).

2. A method for synthesizing medium and low molecular weight perfluoropolyethers using the process system according to claim 1, characterized in that: The following steps are involved: (1) Fresh hexafluoropropylene liquid fed into the oxidative polymerization reactor is introduced into two symmetrical liquid feed pipes to fill the reactor. Fresh oxygen and fluorine gas mixture is introduced into the outer edges of the high-speed shear crushing components inside the two symmetrical guide tubes in the oxidative polymerization reactor through two symmetrical gas feed pipes respectively. The gas-liquid mixture is mechanically sheared by the two high-speed shear crushing components rotating in opposite directions and collides and mixes in the mixing channel. The evenly mixed liquid carries bubbles through the reflux pipe and reflux channel and circulates back into the guide tube. The generated small molecular by-products are extracted from the top gas outlet. The crude perfluoropolyether product is extracted from the bottom liquid outlet. (2) Phase separation of crude perfluoropolyether product The crude perfluoropolyether product extracted from the bottom liquid outlet of the oxidative polymerization reactor is introduced into the inlet of the phase separator through the crude product extraction pump, and gas-liquid separation occurs in the phase separator. Small molecular by-products, oxygen, and hexafluoropropylene are extracted from the gas outlet at the top of the phase separator, and the crude perfluoropolyether product is extracted from the liquid outlet at the bottom of the phase separator; (3) Stabilization treatment of the fluorination reactor: The crude perfluoropolyether product extracted from the liquid outlet at the bottom of the phase separator is passed through a fluorination preheater and introduced into the liquid inlet of the fluorination reactor. The liquid covers the stirring device of the reactor and half fills the reactor. The freshly fed fluorine and nitrogen mixed gas is introduced into the gas inlet of the fluorination reactor and is fully contacted with the crude perfluoropolyether product under the action of the stirring device to cause a fluorination reaction. The small molecular by-products produced by the fluorination reaction, nitrogen and incompletely reacted fluorine gas are extracted from the gas outlet at the top of the fluorination reactor. The stabilized perfluoropolyether product is extracted from the bottom liquid outlet. (4) Distillation separation: The perfluoropolyether product extracted from the liquid outlet of the fluorination reactor is introduced into the liquid inlet of the distillation tower, and the fresh low-pressure water vapor is introduced into the gas inlet at the bottom of the distillation tower. The perfluoropolyether product is distilled and separated in the distillation tower; a mixture of liquid perfluoropolyether and water with various molecular weight distributions is extracted from the corresponding distillation tower measurement line, and a mixture of water vapor and small molecular by-products is extracted from the top of the distillation tower; The temperature of the fluorination preheater is controlled at 200°C to 300°C.

3. The method for synthesizing medium and low molecular weight perfluoropolyether according to claim 2, characterized in that: The temperature in the oxidative polymerization reactor is controlled at -50°C to -25°C, the pressure is controlled at 200kPa to 600kPa, and the reaction time is controlled at 2 hours to 10 hours.

4. The method for synthesizing medium and low molecular weight perfluoropolyether according to claim 2, characterized in that: The rotation speed of the high-speed shearing and crushing component in the oxidative polymerization reactor is 200 r / min-800 r / min.

5. The method for synthesizing medium and low molecular weight perfluoropolyether according to claim 2, characterized in that: The temperature in the fluorination reactor is controlled at 225° C. to 350° C.; the pressure is controlled at 150 kPa to 250 kPa; and the reaction time is controlled at 8 hours to 20 hours.

Images