CN1267391C - Method for preparing alpha, omega diiodo perfluo-alkane - Google Patents

Abstract

The invention discloses a preparation method of α, ω-diiodoperfluoroalkane. The method comprises adding copper powder or its alloy powder catalyst, solvent 1,2-diiodoperfluoroethane and solid iodine into a closed container, feeding _C2F4 gas under _sufficient stirring, and Temperature 140-200°C, pressure 0.6-1.2MPa, react for 40-60 minutes; then heat up the reaction product to continue the reaction; then lower the material to 140-200°C, and continue to pass C ₂ F ₄ gas and matter into the system The iodine is reacted until all the iodine is converted into 1,2-diiodoperfluoroethane. The present invention has the advantages of rationally adjusting the degree of telomerization and deiodination polymerization, overcoming the tendency of conversion and selectivity of simple deiodination polymerization or telomerization to overemphasize one side, and making the reaction The conversion rate and selectivity are reasonably balanced, so that the reaction raw material conversion rate and the selectivity to the target product both reach the level of 75%, the total yield of the process reaches 57%, and the product preparation cost is low.

Description

α, the preparation method of ω-diiodoperfluoroalkane

technical field

The present invention relates to a preparation method of α, ω-diiodoperfluoroalkane. In more detail, in the presence of a catalyst, α, ω-diiodoperfluoroethylene of medium chain length is prepared from 1,2-diiodoperfluoroethane, ethylene and iodine through telomerization and deiodination polymerization. alkanes method.

Background of the invention

Medium-chain α, ω-diiodoperfluoroalkanes are widely used chemical intermediates, which can be used to synthesize a variety of useful fluorine-containing compounds and as monomers for the production of various fluorine-containing polymers.

For example: the acylate obtained by the reaction of α, ω-diiodoperfluoroalkanes and oleum, and then hydrolyzed to obtain perfluoro fatty diacids.

Perfluoro fatty diacids can be used as monomers for the synthesis of fluorine-containing polyesters. Another example: react α, ω-diiodoperfluoroalkane with ethylene, the intermediate product can form two alkene groups at the end of the molecular formula after removing HI,

CH ₂ ═CH(C ₂ F ₄ ) _n CH═CH ₂ can be used as a monomer for synthesizing fluorine-containing polyolefin, and can also be further prepared into other useful fluorine-containing compounds.

Since α, ω-diiodoperfluoroalkane is widely used in chemical production, there are continuous reports on the preparation method and improvement of α, ω-diiodoperfluoroalkane. According to comprehensive literature reports, the preparation methods of medium-chain-length α, ω-diiodoperfluoroalkanes can be classified into two categories:

1. Using 1,2-diiodoperfluoroethane as the telogen and tetrafluoroethylene as the main chain, produce medium-chain α, ω-diiodoperfluoroalkane through telomerization.

2. Using 1,2-diiodoperfluoroethane as raw material, produce medium-chain α, ω-diiodoperfluoroalkane through heating deiodination polymerization reaction:

1,2-Diiodoperfluoroethane is prepared by reacting iodine with tetrafluoroethylene.

In 1951, Haszeldine first proposed the method of preparing α, ω-diiodoperfluoroalkanes from iodine and tetrafluoroethylene, or 1,2-diiodoperfluoroethane and tetrafluoroethylene through telomerization. But the article did not describe the details of the experiment and the yield of the reaction in detail.

In 1961, Knunyants et al tried to repeat the work of Haszeldine, but the yield of the target telomer product was extremely low. Afterwards, many researchers systematically investigated the reaction conditions for the preparation of α, ω-diiodoperfluoroalkanes by telomerization, including reaction temperature, pressure, reaction time, stirring method and speed, telomer/main chain material ratio, etc. The results show that: in the process of preparing α, ω-diiodoperfluoroalkane by tetrafluoroethylene and iodine, or by tetrafluoroethylene and 1,2-diiodoperfluoroethane, in order to achieve reasonable conversion and yield, High reaction temperature (>260°C) and high reaction pressure (>3.1MPa) are required.

In 2004, Dindi Hasan and Hagedorn J. (EP1422211) prepared α, ω-diiodoperfluoroalkane through the telomerization method of tetrafluoroethylene and 1,2-diiodoperfluoroethane, at a reaction temperature of 245°C and a pressure of 3.65-3.86MPa, the reaction time is 12-20 hours, when the mol ratio of 1,2-diiodoperfluoroethane/ethylene is 1/1.5, the reaction conversion rate of 1,2-diiodoperfluoroethane reaches 96.0%, the selectivity to α,ω-diiodoperfluoroalkane I(C ₂ F ₄ ) _n I (n=2-5) is 53.0%, and the overall yield of the process is 50.1%.

Iodine is generated during the preparation of medium-chain-length α, ω-diiodoperfluoroalkanes by thermal deiodination polymerization of 1,2-diiodoperfluoroethane. Iodine can be recovered from the reaction mixture by filtration or reduction treatment, but this increases the complexity of the operation and the loss of iodine. In 1976, JP51-133206 adopted the method of introducing tetrafluoroethylene into the iodine-containing reaction mixture obtained by the heating deiodination polymerization reaction to convert free iodine into 1,2-diiodoperfluoroethane, and recover α, ω by distillation - After diiodoperfluoroalkane, 1,2-diiodoperfluoroethane can be returned to the reactor for recycling.

In the process of preparing medium-chain-length α, ω-diiodoperfluoroalkanes by thermal deiodination polymerization of 1,2-diiodoperfluoroethane, perfluorocyclobutane is the main by-product affecting the yield of the process one. JP53-144507 proposed in 1978 that pre-adding free iodine to the raw material 1,2-diiodoperfluoroethane can reduce the amount of perfluorocyclobutane produced. Document JP53-144507 is under 250 ℃, carries out deiodination polymerization reaction with 1,2-diiodoperfluoroethane, and the conversion rate of the reaction of 1,2-diiodoperfluoroethane is 70.0%, to I(C The selectivities of ₂ F ₄ ) _n I (n=2, 3, 4) are 56.7%, 13.8%, 1.06%, respectively, the total selectivity is 71.6%, and the total yield of the process is 50.1%.

Comparing two methods of preparing medium-chain length α, ω-diiodoperfluoroalkane by telomerization reaction and deiodination polymerization reaction, 1,2-diiodoperfluoroethane has a high conversion rate in telomerization reaction, but The selectivity of the reaction is low. In contrast, the conversion rate of 1,2-diiodoperfluoroethane in the deiodination polymerization reaction was significantly lower than that in the telomerization reaction, but the selectivity of the reaction was significantly improved. The overall process yields of the two preparation methods are almost the same.

Contents of the invention

The object of the present invention is to provide a method for the preparation of medium chain length α, ω-diiodoperfluoroalkane I(C ₂ F ₄ ) _n I (n=2, 3, 4 or 5), the reaction conditions of the method Mild, the conversion rate of the raw material and the selectivity to the target product are high, and the molecular weight distribution of the target product is concentrated.

The present invention is achieved through the following technical scheme, a preparation method of α, ω-diiodoperfluoroalkane I(C ₂ F ₄ ) _n I (n=2, 3, 4 or 5), which is characterized by the following process :

1. Add copper, tin, rhenium, ruthenium, rhodium, platinum, vanadium, or silver metal powder or its alloy powder, or a mixture of their metal powders, or their alloy powder in a closed container with a particle size of 5-500 mesh Mixture catalyst, and solvent 1,2-diiodoperfluoroethane IC ₂ F ₄ I and solid iodine, pass C ₂ F ₄ gas under full stirring to react; the reaction temperature is 140-200°C, and the reaction pressure is The process is 0.6-1.2MPa, and the reaction time is controlled at 40-60 minutes. The amount of iodine added is 0.1-3 times the mass of the solvent 1,2-diiodoperfluoroethane, the amount of catalyst added is 0.1-10% of the mass of iodine, and the amount of _C2F4 gas introduced is 0.1-10% of the mass of iodine _. 2-3 times the molar weight.

2. Heat the reaction product obtained in step 1 to 180-260° C., the reaction pressure rises to 1.0-2.0 MPa with the temperature, and continue the reaction for 3-5 hours.

3. After the reaction in step 2 is completed, lower the temperature of the material to 140-200°C, and continue to introduce C ₂ F ₄ gas to react with iodine in the system until all iodine is converted into 1,2-diiodoperfluoroethyl Alkanes, the corresponding reaction pressure is 0.6-1.2MPa.

The catalyst mentioned above is copper metal powder or copper alloy powder.

Compared with the existing α, ω-diiodoperfluoroalkane preparation process, the main advantages of the present invention are as follows:

1. Prepare α, ω-diiodoperfluoroalkane through this technical scheme, and there are telomerization reactions of tetrafluoroethylene and 1,2-diiodoperfluoroethane and 1,2-diiodoperfluoroethane in the process The deiodination polymerization reaction, wherein said 1,2-diiodoperfluoroethane includes 1,2-diiodoperfluoroethane and tetrafluoroethylene reacting with iodine to generate 1, 2-Diiodoperfluoroethane. Selecting an appropriate feeding ratio can reasonably adjust the degree of telomerization reaction and deiodination polymerization reaction, so that the advantages and disadvantages of the two types of reactions complement each other, and overcome the simple deiodination polymerization reaction or telomerization reaction in terms of raw material conversion rate and target product. The tendency of the selectivity to overemphasize one side to the detriment of the other can reasonably balance the conversion rate of raw materials and the selectivity of the target product in the reaction, which is conducive to taking further measures to increase the conversion rate of raw materials and the selectivity to the target product. to a higher level.

2. Prepare α, ω-diiodoperfluoroalkane through this technical scheme. The iodine added at the beginning of the reaction can reduce the generation of by-product perfluorocyclobutane in the deiodination polymerization reaction, and it is also the formation of ethylene in the telomerization reaction. The raw material of 1,2-diiodoperfluoroethane and α, ω-diiodoperfluoroalkane, the addition of iodine has double effect.

3. Adding a suitable catalyst is the key of this technical solution. On the basis of the above-mentioned advantages 1 and 2, by adding a suitable catalyst, the reaction conditions for the preparation of α by this technical scheme, ω-diiodoperfluoroalkane are milder, and compared with the preparation process without catalyst, it can be used at a lower Under the reaction temperature, the reaction pressure and the shorter reaction time, the raw material conversion rate of the reaction and the selectivity to the target product all reach the level of 75%, and the total yield of the process reaches 57%, which is higher than the deiodination in the literature. Polymerization or telomerization 50% overall process yield.

4. Many substances can be used as catalysts for the preparation reaction of α, ω-diiodoperfluoroalkanes. Some liquid compounds and metal salts also have catalytic effects. The choice of solid metal powder is to consider the liquid reaction product after the reaction and the catalyst. separate. Among the many metal catalysts that can be used for this reaction, such as copper, tin, rhenium, ruthenium, rhodium, platinum, vanadium, silver, etc., copper is the most suitable because it not only has good catalytic activity, but also is cheap and easy to obtain. . The powdered metal has a large contact surface and is easy to disperse evenly in the liquid system when stirring, which is beneficial to reduce the amount of catalyst used. Therefore, the preparation of α, ω-diiodoperfluoroalkane by this catalytic technology has low catalyst cost and relatively simple process.

Detailed ways

Example 1:

Add 3900g of IC ₂ F ₄ I and 60g of copper powder into a closed autoclave with a volume of 5 liters. After vacuuming, heat the materials in the reactor to 220°C while stirring, and the pressure in the kettle rises to 0.6MPa. The reaction was continued for 4 hours with full stirring. After the reaction, quickly lower the temperature of the material in the kettle to 160°C, and then continuously and smoothly feed _C2F4 gas into the reactor under sufficient stirring _. The feeding speed of _C2F4 gas should ensure that the temperature of the _reactor is lower The temperature was maintained stably at 160°C. When the pressure in the kettle began to rise, the introduction of gas C ₂ F ₄ was stopped, and the amount of C ₂ F ₄ gas introduced during the process was 534g. After the reactor is cooled to room temperature, the pressure is removed, and the liquid product in the still is 4253g. Through liquid chromatography analysis, the product is composed of 2C: 4C: 6C: 8C=72.83: 24.78: 2.24: 0.15 (mol%).

The experimental results are shown in Table 1: mixture ingredients Reaction raw material (g) reaction product Mol score weight fraction Weight (g) I(C ₂ F ₄ )I 3900 0.7283 0.6718 2857 I(C ₂ F ₄ ) ₂ I 0.2478 0.2932 1247 I(C ₂ F ₄ ) ₃ I 0.0224 0.0324 138 I(C ₂ F ₄ ) ₄ I 0.0015 0.0026 11 total 1.00 1.00 4253

The total yield of the process calculated by I(C ₂ F ₄ )I is 57.26%

Comparative Example 1:

Add 3900g of IC ₂ F ₄ I into a closed autoclave with a volume of 5 liters, heat the material in the reactor to 250°C while stirring after vacuuming, and the pressure in the autoclave rises to 0.8MPa. Thereafter, the operation is the same as in Example 1. In the process, the amount of C ₂ F ₄ gas is introduced to be 527g, and the liquid product obtained is 4241g. Through liquid chromatography analysis, the product is composed of 2C: 4C: 6C: 8C=76.81: 19.60: 3.18 : 0.41 (mol%).

The experimental results are shown in Table 2: mixture ingredients Reaction raw material (g) reaction product Mol score weight fraction Weight (g) I(C ₂ F ₄ )I 3900 0.7681 0.7133 3025 I(C ₂ F ₄ ) ₂ I 0.1960 0.2334 990 I(C ₂ F ₄ ) ₃ I 0.0318 0.0462 196 I(C ₂ F ₄ ) ₄ I 0.0041 0.0071 30 total 1.00 1.00 4253

The overall process yield calculated as I(C ₂ F ₄ )I was 50.88%.

Example 2:

The process consists of three stages.

1. Add 700g I(C ₂ F ₄ )I, 1524g iodine, and 20g copper powder into a closed autoclave with a volume of 5 liters. After vacuuming, heat the materials in the reactor to 160°C while stirring, and continuously Feed C ₂ F ₄ gas into the reactor smoothly, and the feeding speed of C ₂ F ₄ gas should ensure that the temperature and pressure of the reactor are relatively stable at 160°C and 0.7MPa. When the pressure in the reactor starts to rise , the feeding of gas C ₂ F ₄ was stopped, and the amount of C ₂ F ₄ gas feeding in stage 1 was 602 g.

2. Continue to heat the materials in the reactor to 220° C. under full stirring, the pressure in the reactor at this temperature is 1.6 MPa, and react at this temperature and pressure for 4 hours.

3. After the reaction, quickly lower the temperature of the material in the kettle to 160°C, and then, as in stage 1, continuously and steadily feed C ₂ F ₄ gas into the reactor under full stirring until the pressure no longer drops. The amount of C ₂ F ₄ gas introduced during the process was 384g. After the reaction kettle is cooled to room temperature, the pressure is released, and the liquid product in the kettle is 3080g. Through liquid chromatography analysis, the product composition is 2C: 4C: 6C: 8C=72.82: 24.78: 2.25: 0.15

The experimental results are shown in Table 3: mixture ingredients Reaction raw material (g) reaction product Mol score weight fraction Weight (g) free iodine 1524 I(C ₂ F ₄ )I 700 0.7282 0.6717 2069 I(C ₂ F ₄ ) ₂ I 0.2478 0.2932 903 I(C ₂ F ₄ ) ₃ I 0.0225 0.0325 100

I(C ₂ F ₄ ) ₄ I 0.0015 0.0026 8 Total 1.00 1.00 3080

The overall process yield calculated as I(C ₂ F ₄ )I was 57.27%.

Comparative Example 2

Except following difference, all are identical with embodiment 2:

In stage 1, the material added to the autoclave does not include copper powder, and the amount of C ₂ F ₄ gas introduced in this stage is 604g.

In stage 2, the kettle temperature was 260 °C and the pressure was 2.0 MPa.

In stage 3, the amount of C ₂ F ₄ gas introduced was 379 g.

Obtain liquid product 3071g after reaction, through liquid chromatography analysis, product composition is 2C: 4C: 6C: 8C=76.76: 19.61: 3.18: 0.42

The experimental results are shown in Table 4: mixture ingredients Reaction raw material (g) reaction product Mol score weight fraction Weight (g) free iodine 1524 I(C ₂ F ₄ )I 700 0.7676 0.7131 2190 I(C ₂ F ₄ ) ₂ I 0.1961 0.2335 717 I(C ₂ F ₄ ) ₃ I 0.0318 0.0462 142 I(C ₂ F ₄ ) ₄ I 0.0042 0.0072 twenty two total 1.00 1.00 3071

The overall process yield calculated as I(C ₂ F ₄ )I was 50.92%.

Example 3:

The process consists of three stages.

1. Add 1600gI(C ₂ F ₄ )I, 1000g iodine, and 20g copper powder into a closed autoclave with a volume of 5 liters. After vacuuming, heat the materials in the reactor to 160°C while stirring, and continuously Feed C ₂ F ₄ gas into the reactor smoothly, and the feeding speed of C ₂ F ₄ gas should ensure that the temperature and pressure of the reactor are relatively stable at 160°C and 0.7MPa. When the pressure in the reactor starts to rise , the feeding of gas C ₂ F ₄ was stopped, and the amount of C ₂ F ₄ gas feeding in stage 1 was 464g.

2. Continue to heat the material in the reactor to 260° C. under sufficient stirring, and the pressure in the reactor at this temperature is 2.0 MPa, and react at this temperature and pressure for 3 hours.

3. After the reaction, quickly lower the temperature _of the material in the kettle to 160°C, and then, as in stage 1, continuously and steadily feed _C2F4 gas into the reactor under full stirring until the pressure does not drop any more. The amount of C ₂ F ₄ gas introduced was 402g. After the reaction kettle is cooled to room temperature, the pressure is released, and the liquid product in the kettle is 3120g. Through liquid chromatography analysis, the product composition is 2C: 4C: 6C: 8C=65.89: 30.46: 3.07: 0.67

The experimental results are shown in Table 5: mixture ingredients Reaction raw material (g) reaction product Mol score weight fraction Weight (g) free iodine 1000 I(C ₂ F ₄ )I 1600 0.6589 0.5945 1855 I(C ₂ F ₄ ) ₂ I 0.3046 0.3525 1100 I(C ₂ F ₄ ) ₃ I 0.0307 0.0420 130 I(C ₂ F ₄ ) ₄ I 0.0067 0.0112 35 total 1.0000 1.0000 3120

The overall process yield calculated as I(C ₂ F ₄ )I was 68.15%.

Claims (2)

1. A method for preparing α represented by the following general formula, ω-diiodoperfluoroalkane, I(C ₂ F ₄ ) _n I where n=2, 3, 4 or 5; Its characteristics include the following processes: 1). Add copper, tin, rhenium, nail, rhodium, platinum, vanadium, or silver metal powder or its alloy powder, or their mixture of metal powder, or their alloy powder in a closed container with a particle size of 5-500 mesh The mixture catalyst, and the solvent 1,2-diiodoperfluoroethane IC ₂ F ₄ I and solid iodine, under full stirring, feed C ₂ F ₄ gas to react; the reaction temperature is 140-200 ° C, the reaction pressure In the process, it is 0.6-1.2MPa, the reaction time is controlled at 40-60 minutes, the addition of the iodine is 0.1-3 times of the mass of the solvent 1,2-diiodoperfluoroethane, and the addition of the catalyst is the mass of iodine 0.1-10% of the C ₂ F ₄ gas is 2-3 times the molar amount of iodine; 2). Heat the reaction product obtained in step 1) to 180-260°C, the reaction pressure rises to 1.0-2.0MPa with the temperature, and continue the reaction for 3-5 hours; 3). Step 2) After the reaction is completed, lower the temperature of the material to 140-200°C, and continue to introduce C ₂ F ₄ gas to react with iodine in the system until all iodine is converted into 1,2-diiodo-all Fluoroethane, the corresponding reaction pressure is 0.6-1.2MPa. 2. by the described α of claim 1, the preparation method of ω-diiodine perfluoroalkane is characterized in that, catalyst is copper metal powder or copper alloy powder.