A system and method for the multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst

Abstract

The application discloses a kind of multi-stage continuous synthesis perfluoroiodoalkane systems based on structured catalyst, including at least two reaction sections connected in series, raw material feeding device, tetrafluoroethylene supplement device, independent temperature control system;Each reaction section includes reactor, porous copper alloy catalyst, heat conducting oil jacket;The temperature of first reaction section is higher than the temperature of subsequent reaction section connected in series.One aspect, by the process of multi-stage series and tetrafluoroethylene segmented addition, the concentration distribution of reactants in each reaction section is effectively controlled, the generation of long-chain byproducts is significantly inhibited, and the selectivity of target product is improved.Meanwhile, control the temperature of first reaction section to be higher than the temperature of subsequent reaction section connected in series, form the best temperature gradient, further optimize reaction rate and selectivity.On the other hand, use porous copper alloy as catalyst, its three-dimensional network structure provides fixed catalytic bed, fundamentally avoids the blockage and high pressure drop of powder catalyst.

Description

Technical Field

[0001] This invention relates to the field of organofluorine chemical synthesis technology, specifically to a system and method for multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst. Background Technology

[0002] Perfluoroiodoalkanes (general formula X(CF2)) n I, where X = F, I, n = 1~8) are key intermediates in the synthesis of fluorinated surfactants, water- and oil-repellent finishing agents, and other fluorinated fine chemicals. Among them, medium-chain perfluoroiodoalkanes with 6 to 12 carbon atoms (such as perfluorohexyl iodide and perfluorooctyl iodide) have the highest application value.

[0003] Currently, the main industrial method for synthesizing perfluoroalkyl iodides is catalytic polymerization, which involves the polymerization of short-chain perfluoroalkyl iodides (such as pentafluoroalkyl iodide CF3CF2I) with tetrafluoroethylene (TFE) in the presence of a metal catalyst. This method mainly includes the following sub-methods: (1) Thermal initiation method: Chinese patent document CN1099023A discloses a method for continuously producing perfluoroalkyl iodine by thermal telomerization of pentafluoroethyl iodine or heptafluoroisopropyl iodine and tetrafluoroethylene in the gas phase in a tubular reactor. In order to improve the selectivity for the desired grade of telomer, the lower grade of telomer is recycled to at least one point on the reactor located at 1 / 20 to 3 / 4 of the tube length, and the reaction temperature is controlled at 300~360 °C. This method does not require a catalyst and can improve selectivity by recycling the telomer, but the higher reaction temperature will lead to the self-polymerization of tetrafluoroethylene, more by-products, and a wide molecular weight distribution.

[0004] (2) Catalytic initiation method: Chinese patent document CN1535258A discloses a method for continuous production of products using general formula R f (CF2CF2) n The method for perfluoroalkyl iodides represented by I, wherein R f The method comprises continuously providing perfluoroalkyl iodides as derived from general formula R, where n is an integer from C1 to C6 perfluoroalkyl and n is an integer from 1 to 4. f I represents the telomer, where R... f As defined above, tetrafluoroethylene is added as the main chain compound to a tubular reactor, which is packed with a metal catalyst including powdered spherical metal or sintered metal; and a telomerization reaction is carried out at a temperature of 60~160 °C and a pressure of 0.1~5 MPa (gauge pressure). This method has mild reaction conditions, good selectivity, and can be continuously operated. However, because a powdered metal catalyst is used, it is prone to clogging the reactor, resulting in problems such as high bed pressure drop and the need for product separation.

[0005] (3) Photoinitiation method: Chinese patent document CN1379008A discloses a method for photochemical synthesis of perfluoroalkyl iodides under pressure, including the following steps: a mixture of C2F5I and C2F4 is added to different positions of a reactor using a low-pressure light source as the photochemical reaction initiator. After cooling, the product enters a circulation pipe and then a gas-liquid separator. The separated gas is circulated back to the reactor by an axial flow fan, and the liquid product is released from the bottom of the gas-liquid separator. The reaction pressure is 130~300 kPa. The product obtained by this method has extremely high selectivity and high purity, but because the light source used as the initiation condition is easily contaminated and the reaction rate is slow, it is difficult to scale up industrially.

[0006] (4) One-step method: Chinese patent document CN102241561A discloses a one-step method for preparing perfluoroalkyl iodine. Iodine, iodine pentafluoride and a composite catalyst are added to a reaction vessel, the vacuum is evacuated to -0.095 MPa, and high-purity nitrogen is used to replace the water content in the vessel multiple times to make the water content ≤100 ppm and the oxygen content ≤30 ppm. The temperature inside the vessel is kept at 60~80 ℃, and tetrafluoroethylene is added to maintain the pressure at 0.5~0.7 MPa for the reaction. When the pressure does not decrease after the addition of tetrafluoroethylene, the reaction temperature is raised to 130~150 ℃, tetrafluoroethylene is continued to be introduced, and the pressure is controlled at 2.8 MPa for the reaction to obtain perfluoroalkyl iodine. However, the composite reaction catalytic system of this method is complex and the reaction conditions are harsh.

[0007] (5) Continuous Tower Method: Chinese patent document CN103524294A discloses a continuous synthesis method for low-carbon chain perfluoroalkyl iodides: (a) adding a heat transfer medium and a catalyst to a packed tower, wherein the mass ratio of the heat transfer medium to the catalyst is 1:0.005~0.1; (b) drawing the mixture of heat transfer medium and catalyst from the bottom of the packed tower, heating it through a heater via a circulating pump, and returning it to the circulating liquid inlet of the packed tower, so that the heat transfer medium containing the catalyst circulates from top to bottom in the packed tower, while pentafluoroiodoethane and tetrafluoroethylene are continuously introduced into the packed tower from the bottom at a volume ratio of 5~20:1 for reaction, and the reaction temperature is 200~370 ℃; (c) continuously drawing the reaction product from the top of the packed tower, cooling it through a condenser to obtain low-carbon chain perfluoroalkyl iodides. This method has high heat transfer efficiency and online catalyst circulation, but the reaction system is complex and the equipment investment is large.

[0008] (6) Suspension catalysis method: Chinese patent document CN101805240A discloses a method for synthesizing perfluoroalkyl iodides via telomerization reaction, wherein the telomerization reaction is carried out by R f I is a telomer, using tetrafluoroethylene as the telomer, and the polymerization is carried out in the presence of a metal catalyst, wherein R fThe tetrafluoroethylene is a perfluoroalkyl group with 1 to 6 carbon atoms and a straight-chain or branched structure. The molar ratio of tetrafluoroethylene to RfI is 1:1 to 6. The metal catalyst is a metal powder with an average particle size of 50 nm to 50 μm, and its usage is [amount missing from original text]. f The amount of feed material is 0.1% to 5% of the total feed mass, but this method requires high control over the stability of the suspension.

[0009] The above-mentioned methods in the prior art still have many shortcomings: (1) Catalyst morphology problem: widely used powder catalysts such as copper powder and tin powder (such as those disclosed in CN1535258A and CN101219924A) are prone to bed pressure drop increase due to scouring and aggregation in continuously operating tubular reactors, and even block the pipeline. Moreover, the products need subsequent separation steps, which increases the complexity of the process; (2) Reaction selectivity control problem: in a single reactor or single-point feeding mode (such as CN1927787A), the reactant concentration distribution is not ideal, and it is difficult to accurately control the degree of polymerization (n). The local tetrafluoroethylene concentration is too high, which can easily lead to "over-reaction" and generate too many long-chain by-products with carbon chain length greater than 8, which reduces the selectivity of the target medium-length products; (3) Process control precision problem: traditional tubular reactors mostly use external heating furnaces for overall heating, which makes it difficult to achieve precise control of the reaction axial temperature (such as CN1099023A). Temperature is a key factor affecting the reaction rate and selectivity. Uneven temperature field will aggravate the occurrence of side reactions.

[0010] Therefore, developing a continuous synthesis method and apparatus for perfluoroiodoalkanes that can achieve efficient, highly selective, long-term stable operation and has a simple process flow has become an urgent technical problem to be solved in this field. Summary of the Invention

[0011] To address the aforementioned technical problems, this invention provides a system for the multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst. By employing a multi-stage tandem process with the segmented addition of tetrafluoroethylene (TFE), the concentration distribution of reactants in each reaction stage is effectively controlled. This avoids uncontrolled chain growth caused by excessively high initial TFE concentrations in single-stage reactions, significantly inhibits the formation of long-chain byproducts, and improves the selectivity of medium-chain-length target products.

[0012] A system for multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst includes at least two reaction stages connected in series, a feedstock device connected to the first reaction stage, a tetrafluoroethylene replenishment device connected to at least one subsequent reaction stage, and an independent temperature control system. Each reaction section includes a reactor, a porous copper alloy catalyst packed inside the reactor, and a heat transfer oil jacket wrapped around the outer wall of the tubular reactor. The temperature of the first reaction section is higher than the temperature of the subsequent reaction sections connected in series.

[0013] In this invention, the concentration distribution of reactants in each reaction stage is effectively controlled through a multi-stage series process and segmented addition of TFE. This strategy avoids uncontrolled chain growth caused by excessively high initial TFE concentration in single-stage reactions, significantly inhibits the formation of long-chain byproducts, and improves the selectivity of the target product. Furthermore, the multi-stage reaction process allows for the addition of TFE in each stage (except the first stage), maintaining a constant and low pressure in each reaction stage and reducing equipment requirements.

[0014] Furthermore, by setting the temperature of the first reaction stage to a higher initiation temperature and the subsequent series reaction stages to lower chain growth control temperatures, an optimal temperature gradient is formed, further optimizing the reaction rate and selectivity. Simultaneously, the use of a heat-conducting oil jacket and an independent temperature control system allows for the setting and maintenance of the optimal reaction temperature for each reaction stage. This system has a rational structure, continuous operation, long catalyst life, and stable operation, making it highly suitable for the large-scale industrial continuous production of perfluoroalkyl iodoalkanes.

[0015] Preferably, the temperature difference between the first reaction section and the subsequent reaction sections connected in series is 1~5℃.

[0016] Preferably, the porous copper alloy catalyst is pure copper, or an alloy of copper with one or more metals selected from tin, zinc, lead, aluminum, iron, and manganese.

[0017] In existing technologies, powdered metal catalysts are commonly used. These catalysts initially cause relatively low resistance, but as the catalyst wears down and corrodes (iodine in perfluoroiodoalkane compounds is highly reactive and reacts with the catalyst to form iodinated salts, causing the catalyst to become powdery), the powdered catalyst, worn catalyst, and the generated iodinated salts clog these pores due to the catalyst's low porosity, leading to increased resistance. Therefore, the service life of such catalysts is limited to no more than 200 hours.

[0018] In this invention, a porous copper alloy is used as the catalyst. Its three-dimensional network structure provides a fixed catalytic bed. Each catalytic point is firmly locked by the three-dimensional network structure, which will not cause a large amount of pulverization and loss. This fundamentally avoids the problems of clogging and high pressure drop of powdered catalyst, realizes the natural separation of catalyst and product, and simplifies the post-processing process.

[0019] Preferably, the porous copper alloy catalyst has a pore size of 30~133 PPI.

[0020] Preferably, the independent temperature control system includes a heat transfer oil circulation pump, a heater, and a cooler, for independently controlling the temperature of each reaction section.

[0021] Preferably, the reactor is a tubular reactor or a batch reactor.

[0022] The present invention also provides a method for the continuous synthesis of perfluoroiodoalkanes using the above system, comprising the following steps: (1) After mixing low molecular weight perfluoroiodoalkane with a portion of tetrafluoroethylene, the mixture is continuously introduced into the first reaction section containing a porous copper alloy catalyst for a preliminary telomerization reaction. The portion of tetrafluoroethylene accounts for 60-80% of the total tetrafluoroethylene. (2) After the reaction, the product is passed through the next series reaction section and tetrafluoroethylene is added at the inlet of the reaction section. The amount of tetrafluoroethylene added accounts for 20-40% of the total amount of tetrafluoroethylene. The perfluoroiodoalkane product is collected.

[0023] Preferably, the low molecular weight perfluoroiodoalkane is pentafluoroiodoethane (CF3CF2I), heptafluoroisopropyl iodide, or octafluorodiiodobutane (ICF2CF2CF2CF2I).

[0024] Preferably, the molar ratio of the total amount of low molecular weight perfluoroiodoalkane to tetrafluoroethylene is 0.1~0.4:1.

[0025] Preferably, the temperature of the first reaction section containing the porous copper alloy catalyst is 110~130℃, and the temperature of the series reaction sections is 105~129℃.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, on the one hand, the concentration distribution of reactants in each reaction stage is effectively controlled through a multi-stage series reaction process and the segmented addition of tetrafluoroethylene (TFE). This strategy avoids uncontrolled chain growth caused by excessively high initial TFE concentrations in single-stage reactions, significantly inhibits the formation of long-chain byproducts, and improves the selectivity of the target product. Simultaneously, controlling the temperature of the first reaction stage higher than that of subsequent series reaction stages creates an optimal temperature gradient, further optimizing the reaction rate and selectivity. On the other hand, using a porous copper alloy as the catalyst, its three-dimensional network structure provides a fixed catalytic bed, fundamentally avoiding the clogging and high pressure drop problems of powdered catalysts, achieving natural separation of the catalyst and product, and simplifying the post-processing steps. Attached Figure Description

[0027] Figure 1 The system used in Example 1 includes: 1, raw material storage tank; 2, tetrafluoroethylene storage tank; 3, preheater; 4, first tubular reaction section; 5, second tubular reaction section; 6, Nth tubular reaction section; 7, porous metal catalyst; 8, heat transfer oil jacket; 9, tetrafluoroethylene replenishment pipeline; 10, independent temperature control system; 11, product collection tank; 12, filter; and 13, liquid inlet pump.

[0028] Figure 2The system used in Example 10 includes: 1, raw material storage tank; 2, tetrafluoroethylene storage tank; 3, first reaction vessel; 4, second reaction vessel; 7, porous metal catalyst; 8, heat transfer oil jacket; 9, tetrafluoroethylene replenishment pipeline; 10, independent temperature control system; 11, product collection tank; 12, filter; and 13, liquid inlet pump.

[0029] Figure 3 The system used in Example 11 includes: 1, raw material storage tank; 2, tetrafluoroethylene storage tank; 3, first tubular reaction section; 4, second reaction vessel; 5 and 7, porous metal catalysts; 8, heat transfer oil jacket; 9, tetrafluoroethylene replenishment pipeline; 10, independent temperature control system; 11, product collection tank; 12, filter; and 13, liquid inlet pump.

[0030] Figure 4 The system used in Comparative Example 1 is as follows: 1 is the raw material storage tank, 2 is the tetrafluoroethylene storage tank, 3 is the first reaction vessel, 7 is the porous metal catalyst, 8 is the heat transfer oil jacket, 9 is the tetrafluoroethylene replenishment pipeline, 10 is the independent temperature control system, 11 is the product collection tank, 12 is the filter, and 13 is the liquid inlet pump. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited to the following embodiments.

[0032] All raw materials used in this invention are commercially available.

[0033] Calculation explanation in the examples: 1. Calculation of raw material conversion rate Assume the product contains five components: A (A is unreacted raw material), B, C, D, and E, with molecular weights of MA, MB, MC, MD, and ME, respectively, and the contents of each component are a, b, c, d, and e (mass percentage; all component contents in the product mentioned in this article are mass percentages).

[0034] The formula for calculating the conversion rate of raw material A is: ; 2. Calculation of selectivity of key products Assume the product contains five components: A (A is the unreacted raw material), B (B is the key product), C, D, and E, with molecular weights of MA, MB, MC, MD, and ME, respectively, and the contents of each component are a, b, c, d, and e (mass percentage; all component contents in the product mentioned in this article are mass percentages).

[0035] The formula for calculating the selectivity of key product B is: .

[0036] Example 1: Continuous tubular reaction using pentafluoroiodoethane (C2F5I) Reference Figure 1 A device with a three-stage series tubular reactor was constructed, including three reaction stages connected in series, a raw material feeding device connected to the first reaction stage, a tetrafluoroethylene replenishment device connected to at least one subsequent reaction stage, and an independent temperature control system. Low-molecular-weight perfluoroalkyl iodoalkane flows out from raw material storage tank 1, is filtered by filter 12, and then pumped into preheater 3 by inlet pump 13. After preheating, it mixes with tetrafluoroethylene flowing out from tetrafluoroethylene storage tank 2, and is then sequentially introduced into the first tubular reaction section 4, the second tubular reaction section 5, and the Nth tubular reaction section 6, which contain porous metal catalyst 7. After the reaction is completed, the product is introduced into product collection tank 11. Each reaction section is wrapped with a heat transfer oil jacket 8. The tetrafluoroethylene is introduced into each tubular reaction section through a tetrafluoroethylene replenishment pipeline 9, and each tubular reaction section is connected to an independent temperature control system 10.

[0037] Pentafluoroiodoethane (C2F5I) and tetrafluoroethylene were introduced into the first tubular reaction section at average flow rates of 20 kg / h and 2.5 kg / h, respectively. The first tubular reaction section was filled with pure copper (copper content ≥99.5%, 30 PPI) as a catalyst. The temperature of the first tubular reaction section was controlled at 110 °C using an independent temperature control system for the initial telomerization reaction. The inlet pressure of the first tubular reaction section was 0.6 MPa, and the outlet pressure was 0.53 MPa. The reaction solution was continuously introduced into the second and third tubular reaction sections, while the temperature of the second and third tubular reaction sections was controlled at 105 °C. The flow rate of tetrafluoroethylene added to the second tubular reaction section was controlled at 1.5 kg / h, resulting in an inlet pressure of 0.55 MPa and an outlet pressure of 0.48 MPa. The flow rate of tetrafluoroethylene added to the third tubular reaction section was controlled at 0.825 kg / h, resulting in an inlet pressure of 0.48 MPa. At an outlet pressure of 0.40 MPa, after 1500 hours of stable operation, no significant increase in bed pressure drop was observed. The contents of each component in the reaction solution were obtained by GC analysis, as shown in Table 1.

[0038] Table 1: Content of each component in the reaction solution of Example 1 As can be seen from Table 1, the conversion rate of raw material F(CF2)2I is 30%, of which the selectivity of F(CF2)4I is 33.67% and the selectivity of F(CF2)6I is 28.07%.

[0039] Examples 2-6 The system of Example 1 was used, and the preparation method was the same as in Example 1, except that the type of porous copper catalyst was changed, as shown in the table below.

[0040] Table 2: Preparation differences and conversion rate and selectivity test results of Examples 1-6 Example 7 Using the system of Example 1, pentafluoroiodoethane (C2F5I) and tetrafluoroethylene were introduced into the first tubular reaction section at average flow rates of 20 kg / h and 3.0 kg / h, respectively. The first tubular reaction section was filled with pure copper (copper content ≥99.5%, 133 PPI) as a catalyst. The temperature of the first tubular reaction section was controlled at 110 °C using an independent temperature control system for preliminary polymerization. The inlet pressure of the first tubular reaction section was 0.58~0.6 MPa, and the outlet pressure was 0.52~0.56 MPa. The reaction solution was continuously introduced into the second and third tubular reaction sections, while the temperature of the second and third tubular reaction sections was controlled at 105 °C. The flow rate of tetrafluoroethylene added to the second tubular reaction section was controlled at 1.2 kg / h, resulting in an inlet pressure of 0.50~0.52 MPa and an outlet pressure of 0.48~0.5 MPa. The flow rate of tetrafluoroethylene added to the third tubular reaction section was controlled at 0.581 kg / h, resulting in an inlet pressure of 0.44–0.48 MPa and an outlet pressure of 0.44–0.46 MPa for the third tubular reaction section. After 1500 hours of stable operation, no significant increase in bed pressure drop was observed. The content of each component in the reaction solution was obtained by GC analysis, as shown in Table 3.

[0041] Table 3: Content of each component in the reaction solution of Example 7 As can be seen from Table 3, the conversion rate of raw material F(CF2)2I is 30%, of which the selectivity of F(CF2)4I is 47.89% and the selectivity of F(CF2)6I is 21.36%.

[0042] Example 8: Using octafluorodiiodobutane (IC2F4C2F4C2F4C2F4I) as a raw material Using the system of Example 1, octafluorodiiodobutane (IC2F4C2F4C2F4C2F4I) and tetrafluoroethylene were introduced into the first tubular reaction section at average flow rates of 20 kg / h and 0.8 kg / h, respectively. The first tubular reaction section was filled with pure copper (copper content ≥99.5%, 30 PPI) as a catalyst. The temperature of the first tubular reaction section was controlled at 130 °C using an independent temperature control system for preliminary polymerization. The inlet pressure of the first tubular reaction section was 0.48~0.5 MPa, and the outlet pressure was 0.44~0.48 MPa. The reaction solution was continuously introduced into the second and third tubular reaction sections, while the temperatures of the second and third tubular reaction sections were controlled at 129 °C and 128 °C, respectively. The flow rate of tetrafluoroethylene added to the second tubular reaction section was controlled at 0.2 kg / h, resulting in an inlet pressure of 0.46~0.48 MPa and an outlet pressure of 0.46~0.47 MPa. The flow rate of tetrafluoroethylene added to the third tubular reaction section was controlled at 0.119 kg / h, resulting in an inlet pressure of 0.46–0.47 MPa and an outlet pressure of 0.44–0.46 MPa for the third tubular reaction section. After 1500 hours of stable operation, no significant increase in bed pressure drop was observed. The content of each component in the reaction solution was obtained by GC analysis, as shown in Table 4.

[0043] Table 4: Content of each component in the reaction solution of Example 8 As can be seen from Table 4, the conversion rate of raw material I(CF2)4I is 20%, of which the selectivity of I(CF2)6I is 77.43% and the selectivity of I(CF2)8I is 15.92%.

[0044] Example 9: Using heptafluoroisopropyl iodine (CF3CFICF3) as a raw material Using the system of Example 1, heptafluoroisopropyl iodine (CF3CFICF3) and tetrafluoroethylene were introduced into the first tubular reaction section at average flow rates of 20 kg / h and 1.4 kg / h, respectively. The first tubular reaction section was filled with pure copper (copper content ≥99.5%, 30 PPI) as a catalyst. The temperature of the first tubular reaction section was controlled at 110 °C using an independent temperature control system for preliminary polymerization. The inlet pressure of the first tubular reaction section was 0.58~0.6 MPa, and the outlet pressure was 0.55~0.57 MPa. The reaction solution was continuously introduced into the second and third tubular reaction sections, while the temperature of the second and third tubular reaction sections was controlled at 108 °C. The flow rate of tetrafluoroethylene added to the second tubular reaction section was controlled at 0.6 kg / h, resulting in an inlet pressure of 0.55~0.56 MPa and an outlet pressure of 0.52~0.53 MPa. The flow rate of tetrafluoroethylene added to the third tubular reaction section was controlled at 0.118 kg / h, resulting in an inlet pressure of 0.52–0.53 MPa and an outlet pressure of 0.50–0.51 MPa for the third tubular reaction section. After 1500 hours of stable operation, no significant increase in bed pressure drop was observed. The content of each component in the reaction solution was obtained by GC analysis, as shown in Table 5.

[0045] Table 5: Content of each component in the reaction solution of Example 9 As can be seen from Table 5, the conversion rate of raw material CF3CFFICF3 is 20%, of which the selectivity of CF3CF(CF3)(CF2)2I is 49.15% and the selectivity of CF3CF(CF3)(CF2)4I is 35.41%.

[0046] Example 10: Continuous reaction using pentafluoroiodoethane (C2F5I) Reference Figure 2 A reaction apparatus with two reactors connected in series is constructed. Low-molecular-weight perfluoroalkyl iodoalkane flows out from the raw material storage tank 1, is filtered by filter 12, and then pumped sequentially into the first reactor 3 and the second reactor 4 (both reactors are jacketed with jackets 8) containing porous metal catalyst 7 via the inlet pump 13. After the reaction is completed, the product is fed into the product collection tank 11. The tetrafluoroethylene is supplied from the tetrafluoroethylene storage tank 2 through the tetrafluoroethylene replenishment pipeline 9 into each reactor, and each reactor is connected to an independent temperature control system 10.

[0047] Using the above system, pentafluoroiodoethane (C2F5I) and tetrafluoroethylene were introduced into the first reactor at average flow rates of 20 kg / h and 2.0 kg / h, respectively. The first reactor was filled with pure copper (copper content ≥99.5%, 133 PPI) as the catalyst. The temperature of the first reactor was controlled at 110 °C using an independent temperature control system for the initial polymerization reaction. The pressure inside the first reactor was controlled at 0.7–0.9 MPa, and the material residence time was 10 kg. The reaction solution was continuously introduced into the second reactor, while the temperature of the second reactor was controlled at 105 °C. The flow rate of tetrafluoroethylene added to the second reactor was controlled at 1.0 kg / h, so that the pressure inside the second reactor was controlled at 0.5–0.6 MPa, and the material residence time was 10 kg. After 1500 hours of stable operation, the catalyst activity remained stable, and the pressure in each reactor was relatively stable. After 4500 hours of operation, the catalyst activity decreased, and the pressure in each reactor began to rise. The contents of each component in the reaction solution (sampled within 4500 h) were obtained by GC analysis, as shown in Table 6.

[0048] Table 6: Content of each component in the reaction solution of Example 10 As can be seen from Table 6, the conversion rate of raw material F(CF2)2I is 13.29%, of which the selectivity of F(CF2)4I is 34.85% and the selectivity of F(CF2)6I is 27.26%.

[0049] Example 11: Continuous reaction using pentafluoroiodoethane (C2F5I) Reference Figure 3 A reaction apparatus consisting of a tubular reactor (first stage) and a batch reactor (second stage) connected in series is constructed. Low molecular weight perfluoroalkyl iodoalkane flows out from the raw material storage tank 1, is filtered by filter 12, and is then pumped sequentially by the inlet pump 13 into the first tubular reaction section 3 containing porous metal catalyst 5 and the second reaction vessel 4 containing porous metal catalyst 7. After the reaction is completed, the product is fed into the product collection tank 11. Each reaction section is wrapped with a heat transfer oil jacket 8. The tetrafluoroethylene is introduced into the two reactors from the tetrafluoroethylene storage tank 2 through the tetrafluoroethylene replenishment pipeline 9. Each reactor is connected to an independent temperature control system 10.

[0050] Using the above system, pentafluoroiodoethane (C2F5I) and tetrafluoroethylene were introduced into the first tubular reaction section at average flow rates of 20 kg / h and 2.0 kg / h, respectively. Pure copper (copper content ≥99.5%, 133 PPI) was used as the catalyst filling in the first tubular reaction section. The temperature of the first tubular reaction section was controlled at 110 °C by an independent temperature control system for preliminary polymerization. The pressure inside the first reactor was controlled at 0.56~0.58 MPa, and the outlet pressure was 0.53~0.54 MPa. The reaction liquid was continuously introduced into the second reactor, and the temperature of the second reactor was controlled at 105 °C. The flow rate of tetrafluoroethylene added to the second reactor was controlled at 0.8 kg / h, so that the pressure inside the second reactor was controlled at 0.53~0.54 MPa, and the material residence volume in the reactor was 10 kg. After the reaction was running stably for 1500 hours, the catalyst activity remained stable, and the pressure inside each reactor was relatively stable. After 2500 hours of operation, the catalyst activity decreased, and the pressure differential inside the primary reactor began to increase. The contents of each component in the reaction solution (samples taken within 2500 hours) were obtained by GC analysis, as shown in Table 7.

[0051] Table 7: Content of each component in the reaction solution of Example 11 As can be seen from Table 7, the conversion rate of raw material F(CF2)2I is 17.89%, of which the selectivity of F(CF2)4I is 41.29% and the selectivity of F(CF2)6I is 35.11%.

[0052] Comparative Example 1: A continuous reaction was carried out using pentafluoroiodoethane (C2F5I). Reference Figure 4 A reaction apparatus with only a single reactor is constructed. Low-molecular-weight perfluoroalkyl iodoalkane flows out from the raw material storage tank 1, is filtered by filter 12, and is then pumped sequentially into the first reactor 3 containing a porous metal catalyst 7 via the inlet pump 13. After the reaction is completed, the product is fed into the product collection tank 11. Each reaction section is wrapped with a heat-conducting oil jacket 8. The tetrafluoroethylene is introduced into the reactor from the tetrafluoroethylene storage tank 2 through the tetrafluoroethylene replenishment pipeline 9. The reactor jacket is connected to a temperature control system 10.

[0053] Using the above system, pentafluoroiodoethane (C2F5I) and tetrafluoroethylene were introduced into the first reactor at average flow rates of 20 kg / h and 3.5 kg / h, respectively. The first reactor was filled with pure copper (copper content ≥99.5%, 133 PPI) as the catalyst. The temperature of the first reactor was controlled at 110 °C using an independent temperature control system for the initial telomerization reaction. The pressure inside the first reactor was controlled at 1.1~1.2 MPa, and the material residence time was 15 kg. After 1500 hours of stable operation, the catalyst activity remained stable, and the pressure inside the reactor was relatively stable. After 1500 hours, the catalyst activity decreased, and the pressure inside the reactor began to increase. The content of each component in the reaction solution (samples taken within 1500 hours) was obtained by GC analysis, as shown in Table 6.

[0054] Table 8: Content of each component in the reaction solution of Comparative Example 1 As can be seen from Table 8, the conversion rate of raw material F(CF2)2I is 11.72%, of which the selectivity of F(CF2)4I is 31.87% and the selectivity of F(CF2)6I is 23.21%.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for the multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst, characterized in that, It includes at least two reaction sections connected in series, a raw material feeding device connected to the first reaction section, a tetrafluoroethylene replenishment device connected to at least one subsequent reaction section, and an independent temperature control system; Each reaction section includes a reactor, a porous copper alloy catalyst packed inside the reactor, and a heat transfer oil jacket wrapped around the outer wall of the tubular reactor. The temperature of the first reaction section is higher than the temperature of the subsequent reaction sections connected in series.

2. The system for multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst according to claim 1, characterized in that, The temperature difference between the first reaction section and the subsequent reaction sections connected in series is 1~5℃.

3. The system for multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst according to claim 1, characterized in that, The porous copper alloy catalyst is pure copper, or an alloy of copper with one or more metals selected from tin, zinc, lead, aluminum, iron, and manganese.

4. The system for multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst according to claim 1, characterized in that, The porous copper alloy catalyst has a pore size of 30~133 PPI.

5. The system for multi-stage continuous synthesis of perfluoroiodoalkanes based on a structured catalyst according to claim 1, characterized in that, The independent temperature control system includes a heat transfer oil circulation pump, a heater, and a cooler. The independent temperature control system is connected to the heat transfer oil jacket of each reaction section and is used to independently control the temperature of each reaction section.

6. A method for the continuous synthesis of perfluoroiodoalkanes using the system according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) After mixing low molecular weight perfluoroiodoalkane with a portion of tetrafluoroethylene, the mixture is continuously introduced into the first reaction section containing a porous copper alloy catalyst for a preliminary telomerization reaction. The portion of tetrafluoroethylene accounts for 60-80% of the total tetrafluoroethylene. (2) After the reaction, the product is passed through the next series reaction section and tetrafluoroethylene is added at the inlet of the reaction section. The amount of tetrafluoroethylene added accounts for 20-40% of the total amount of tetrafluoroethylene. The perfluoroiodoalkane product is collected.

7. The method according to claim 6, characterized in that, The low molecular weight perfluoroiodoalkane is pentafluoroiodoethane, heptafluoroisopropyl iodide, or octafluorodiiodobutane.

8. The method according to claim 6, characterized in that, The molar ratio of the total amount of low molecular weight perfluoroiodoalkane to tetrafluoroethylene is 0.1~0.4:

1.

9. The method according to claim 6, characterized in that, The temperature of the first reaction section containing the porous copper alloy catalyst is 110~130 ℃, and the temperature of the series reaction sections is 105~129 ℃.

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