CN116003296A - Method for removing 1,2, 3-heptafluoropropane from perfluoroisobutyronitrile - Google Patents

Abstract

The invention relates to a method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, comprising: 1) an adsorbent is filled in an adsorption column, and the adsorbed The adsorbent is calcined at 250-500°C to constant weight. The adsorbent is an aluminum phosphate molecular sieve with the structural formula (El _{x Aly} P _z )O ₂ ; 2) stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to absolute The pressure reaches 0.01 MPa, and the adsorbent is cooled to room temperature for use; 3) The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column, and the absolute pressure in the adsorption column is controlled to reach 0.1 MPa and kept constant; 4) Turn on the diaphragm compressor Press the gas in the adsorption column into the gas cylinder, and stop when the pressure in the adsorption column reaches 0.01 MPa. The single-pass adsorption rate of 1,1,1,2,3,3,3-heptafluoropropane in this method can reach 90.4%, and it can be completely removed after the second adsorption, and the regeneration effect is good. The impurity removal method of the invention has the advantages of simple operation, mild conditions, high product yield, large adsorption capacity, good regeneration effect and the like.

Description

A method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile

technical field

The invention belongs to the technical field of gas separation and purification, in particular to a method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile.

Background technique

Perfluoroisobutyronitrile is a new type of environmentally friendly insulating gas with excellent insulation performance and environmental friendliness. It is considered to be an ideal substitute for SF ₆ at this stage. The new generation of insulating medium developed on this basis has been successfully applied in gas insulated switchgear (GIS) and gas insulated pipeline (GIL), and has received extensive attention from researchers at home and abroad.

Due to the many synthetic routes of perfluoroisobutyronitrile, the types and contents of various impurities in the products of different manufacturers are also quite different. Although the technical routes of various manufacturers are different, the synthesis process of perfluoroisobutyronitrile requires the dehydration reaction of heptafluoroisobutyramide, so impurities are common in commercially available perfluoroisobutyronitrile products1,1,1 , 2,3,3,3-heptafluoropropane, the product purity range is concentrated between 99.2 and 99.9%.

Patent CN110526834A discloses a method for preparing high-purity perfluoroisobutyronitrile based on adsorption and low-temperature distillation. This method removes most of the water and a small amount of acidic substances through adsorption, and then uses low-temperature distillation to remove non-condensable gases and halogenated hydrocarbons. And fluorocarbons, and finally obtain high-purity perfluoroisobutyronitrile gas with a purity of 99.99%.

Patent CN112979499A discloses a method for separating a mixed gas of perfluoroisobutyronitrile and carbon dioxide, which uses a modified adsorbent to remove pentafluoropropionitrile, trifluoroethylene, ethanedinitrile and Saturated fluorocarbons, and then perfluoroisobutyronitrile is further purified by rectification to finally obtain perfluoroisobutyronitrile gas with a purity higher than 99.3%.

Although these methods can increase the purity of perfluoroisobutyronitrile to more than 99%, or even 99.99%, they all need to use a combination of multiple unit operations to refine, such as adsorption and rectification, and low-temperature rectification usually consumes more energy. high. In addition, there is no detailed description on the removal effect of the key impurity 1,1,1,2,3,3,3-heptafluoropropane.

Therefore, how to further improve the quality of perfluoroisobutyronitrile, realize the deep removal of the key impurity 1,1,1,2,3,3,3-heptafluoropropane, simplify the operation process and reduce energy consumption, is a problem that needs to be solved The problem.

Contents of the invention

In order to overcome the problems of the prior art, the present invention proposes a method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, which further improves the quality of perfluoroisobutyronitrile , while simplifying the operation process and reducing energy consumption.

In order to achieve the above object, the first aspect of the present invention provides a method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, comprising the following steps:

1) The adsorption column is filled with adsorbent, and under nitrogen atmosphere, the adsorbent is roasted at 250-500°C to constant weight;

The adsorbent is an aluminum phosphate molecular sieve whose structural formula is (El _{x Aly} P _z ) _O2 ; wherein, x, y, and z are all mole fractions, and the value range is: x≥0.001, y≥0.01, z≥0.01 , and x+y+z=1.

2) stop feeding nitrogen, use a vacuum pump to evacuate the adsorption column until the absolute pressure reaches 0.01MPa, and cool the adsorbent to room temperature for use;

3) Pass the perfluoroisobutyronitrile raw material to be treated into the adsorption column, control the absolute pressure in the adsorption column to reach 0.1MPa, and keep it constant;

4) Turn on the diaphragm compressor to press the gas in the adsorption column into the gas cylinder, stop when the pressure in the adsorption column reaches 0.01MPa, use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content;

5) Repeat step 4) until 1,1,1,2,3,3,3-heptafluoropropane is not detected.

Further, in step 1), the pore diameter of the aluminum phosphate molecular sieve is 0.3-1.2 nm, preferably 0.7-0.9 nm. More preferred aluminum phosphate molecular sieves are: AlPO-5, AlPO-8 and VPI-5, all of which are three-dimensional channel structures formed by aluminum-oxygen tetrahedrons and phosphorus-oxygen tetrahedrons, belonging to the hexagonal crystal system, and the channel systems are respectively 12, 14 and 18.

Further, in step 2), the vacuuming process needs to be carried out at a calcination temperature of 250-500°C.

Further, in step 3), the content of 1,1,1,2,3,3,3-heptafluoropropane in the perfluoroisobutyronitrile raw material to be treated is at least 552.5ppm.

Further, in step 4), the filling coefficient of perfluoroisobutyronitrile in the gas cylinder is 0.5-1.5.

Further, in step 5, the content of 1,1,1,2,3,3,3-heptafluoropropane is detected by using a hydrogen flame ionization detector.

The second aspect of the present invention provides the application of aluminum phosphate molecular sieve in removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, wherein the structural formula of the aluminum phosphate molecular sieve is (El _{x AlyPz} ) _{O2 .}

Further, the pore diameter of the aluminum phosphate molecular sieve is 0.3-1.2 nm, preferably 0.7-0.9 nm. More preferred aluminum phosphate molecular sieves are: AlPO-5, AlPO-8 and VPI-5, all of which are three-dimensional channel structures formed by aluminum-oxygen tetrahedrons and phosphorus-oxygen tetrahedrons, belonging to the hexagonal crystal system, and the channel systems are respectively 12, 14 and 18.

Advantage and beneficial effect of the present invention compared with prior art are:

1. In the method of the present invention, aluminum phosphate molecular sieve is used as the adsorbent, which has excellent adsorption effect and large adsorption capacity for 1,1,1,2,3,3,3-heptafluoropropane, and can realize perfluoroisobutyric acid The deep removal of 1,1,1,2,3,3,3-heptafluoropropane in nitrile also has a certain adsorption effect on other organic and inorganic impurities in perfluoroisobutyronitrile; Nitrile, 1,1,1,2,3,3,3-heptafluoropropane can reach undetected levels, which will help to further improve the quality of perfluoroisobutyronitrile;

2. The method of the present invention for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile has simple operation, mild conditions and high product yield;

3. In the present invention, aluminum phosphate molecular sieve is applied to remove 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile for the first time. Aluminum phosphate molecular sieve has good regeneration performance, and heptafluoropropane will Desorb from the adsorbent, and then replace the control of the adsorbent with nitrogen to complete regeneration and recycling.

Description of drawings

The present invention will be further described below in conjunction with drawings and embodiments.

Fig. 1 is that each embodiment of the present invention, comparative example carry out the device structural representation of removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile;

Fig. 2 is the gas chromatography result figure of the perfluoroisobutyronitrile raw material to be processed;

Fig. 3 is the result figure of the gas chromatography after removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile by the method described in Example 1.

Detailed ways

In the following examples, unless otherwise specified, the experimental instruments and raw materials involved are all commercially available.

For experimental equipment, see Table 1.

Table 1

instrument model source Gas Chromatograph GC9560 Shanghai Huaai Chromatographic Analysis Technology Co., Ltd. Adsorption column Φ3cm*60cm self made vacuum pump 2XZ-4 Shanghai Keneng Pump Industry diaphragm compressor N145AN.18 Kanfu Technology (Shanghai) Co., Ltd. gas cylinder 250mL Swagelok (Shanghai) Fluid System Technology Co., Ltd.

For raw materials, see Table 2.

Table 2

raw material source 5A molecular sieve Henan Shengwei Desiccant Co., Ltd. 10X molecular sieve Henan Shengwei Desiccant Co., Ltd. NaY molecular sieve Henan Shengwei Desiccant Co., Ltd. ZSM-5 molecular sieve Henan Shengwei Desiccant Co., Ltd. AlPO-5 molecular sieve Zoran Environmental Protection Technology (Dalian) Co., Ltd. AlPO-8 molecular sieve Zoran Environmental Protection Technology (Dalian) Co., Ltd. VPI-5 molecular sieve Zoran Environmental Protection Technology (Dalian) Co., Ltd. activated carbon Henan Shengwei Desiccant Co., Ltd. Crude heptafluoroisobutyronitrile Beijing Yuji Technology Development Co., Ltd.

In the following examples, the test methods involved are shown in Table 3:

table 3

In the following examples and comparative examples, the perfluoroisobutyronitrile raw materials to be treated are the crude heptafluoroisobutyronitrile purchased from Beijing Yuji Technology Development Co., Ltd., wherein 1,1,1,2,3,3, The content of 3-heptafluoropropane was 552.5 ppm.

Comparative example 1

Utilize the device as shown in Figure 1, carry out the processing that removes 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, comprise the following steps:

The adsorption column was filled with 1 L of 5A molecular sieve adsorbent, and the adsorbent was calcined at 350° C. to constant weight under nitrogen atmosphere. Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content.

Comparative example 2

The adsorption column was filled with 1 L of 10X molecular sieve adsorbent, and the adsorbent was calcined at 350° C. to constant weight under nitrogen atmosphere. Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content.

Comparative example 3

The adsorption column was filled with 1 L of NaY molecular sieve adsorbent, and the adsorbent was calcined at 350° C. to constant weight under nitrogen atmosphere. Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content.

Comparative example 4

The adsorption column was filled with 1 L of ZSM-5 molecular sieve adsorbent, and the adsorbent was calcined at 350° C. to constant weight under nitrogen atmosphere. Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content.

Comparative example 5

The adsorption column was filled with 1 L of activated carbon adsorbent, and the adsorbent was calcined at 250° C. to constant weight under nitrogen atmosphere. Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content.

Comparative example 6 (10X molecular sieve twice adsorption)

Adsorption was carried out twice continuously according to the conditions of Comparative Example 2, and the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas was analyzed by gas chromatography.

Example 1

The adsorption column was filled with 1 L of AlPO-5 molecular sieve adsorbent, and the adsorbent was calcined at 350° C. to constant weight under nitrogen atmosphere. Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content.

Fig. 2 and Fig. 3 are respectively before and after the removal treatment, the gas chromatograph results.

Example 2

The adsorption column was filled with 1 L of AlPO-8 molecular sieve adsorbent, and the adsorbent was calcined at 350° C. to constant weight under nitrogen atmosphere. Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content.

Example 3

The adsorption column was filled with 1 L of VPI-5 molecular sieve adsorbent, and the adsorbent was calcined at 350° C. to constant weight under nitrogen atmosphere. Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and use gas chromatography to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content.

Embodiment 4 (AlPO-5 molecular sieve is adsorbed twice)

This embodiment is a preferred scheme based on Example 1. According to the conditions of Example 1, the adsorption is carried out twice continuously, and gas chromatography is used to analyze the content of 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas. content.

Embodiment 5 (AlPO-5 molecular sieve regeneration effect)

The adsorption column was fed with nitrogen, and the saturated AlPO-5 molecular sieve adsorbent (that is, the AlPO-5 saturated with adsorption of 1,1,1,2,3,3,3-heptafluoropropane) was roasted at 350 ° C. After 12 hours, Stop feeding nitrogen, and use a vacuum pump to evacuate the adsorption column to 0.01 MPa (absolute pressure), and cool to room temperature. The perfluoroisobutyronitrile raw material to be treated is passed into the adsorption column at 200mL/min, and the pressure in the adsorption column reaches 0.1MPa (absolute pressure) and remains constant and then closes the perfluoroisobutyronitrile feed valve. Turn on the diaphragm compressor to press the gas in the adsorption column into the steel cylinder, stop when the pressure in the adsorption column reaches 0.01MPa (absolute pressure), and repeat the above conditions to perform the adsorption again, and use gas chromatography to analyze the gas in the cylinder after the second adsorption. ,1,1,2,3,3,3-Heptafluoropropane content.

test case 1

In order to compare the effects of different adsorbents on the removal effect of 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, this test example compared the reactions of Comparative Examples 1 to 5 and Example 1 Before and after, the content of 1,1,1,2,3,3,3-heptafluoropropane, the results are shown in Table 4.

Table 4 Comparison of different adsorbent effects

The data in Table 4 shows that each molecular sieve has a certain degree of adsorption effect on 1,1,1,2,3,3,3-heptafluoropropane, among which the adsorption effect of aluminum phosphate molecular sieve AlPO-5 is the most significant, for 1,1,1 , The one-way adsorption rate of 2,3,3,3-heptafluoropropane reaches 90.4%, much higher than other types of molecular sieves. This may be due to the regular pore structure and large specific surface area of aluminum phosphorus molecular sieves, which are more conducive to the adsorption of 1,1,1,2,3,3,3-heptafluoropropane.

test case 2

In order to compare the effects of different aluminum phosphate molecular sieves on the removal effect of 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, this test example compares the effects of Examples 1 to 3 before and after the reaction , the content of 1,1,1,2,3,3,3-heptafluoropropane, the results are shown in Table 5.

Table 5 Comparison of adsorption effects of different aluminum phosphate molecular sieves

The data in Table 5 shows that different aluminum phosphate molecular sieves have good adsorption effects on 1,1,1,2,3,3,3-heptafluoropropane, and the single-pass adsorption rate reaches more than 85%. The aperture of ALPO-8 is 7.9*8.7A, the aperture of VPI-5 is 12.7*12.7A, and the aperture of ALPO-5 is 7.3*7.3A. In contrast, the AlPO-5 molecular sieve with a pore size of about 7.3*7.3A has the best adsorption effect. This may be because the pore size of the adsorbent is too large to cause the adsorption of part of perfluoroisobutyronitrile, which affects the adsorption capacity and reduces the adsorption rate of heptafluoropropane. .

Test case 3

In order to compare the effects of multiple adsorption treatments on different adsorbents on the removal effect of 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, this test example compares Examples 1 and 4 , Comparative Examples 2 and 6, before and after the reaction, the content of 1,1,1,2,3,3,3-heptafluoropropane, the results are shown in Table 6.

Table 6 Comparison of multiple adsorption effects between AlPO-5 molecular sieve and 10X molecular sieve

From the data in Table 6, it can be seen that using AlPO-5 molecular sieve as the adsorbent, 1,1,1,2,3,3,3-heptafluoropropane can be completely removed after two adsorptions, while faujasite 10X molecular sieve with similar pore size , after two adsorptions, the adsorption rate of 1,1,1,2,3,3,3-heptafluoropropane was only 81.2%.

Test case 4

In order to study the regenerative adsorption effect of AlPO-5 molecular sieve with the best adsorption effect, this test example compares Examples 1 and 4, Comparative Examples 2 and 6, before and after the reaction, 1,1,1,2,3,3 , the content of 3-heptafluoropropane, the results are shown in Table 7.

Table 7 AlPO-5 molecular sieve regeneration adsorption effect comparison

From the data in Table 7, it can be seen that the single-pass adsorption rate of the regenerated AlPO-5 molecular sieve is 88.8%, which is slightly lower than 90.4% of the fresh AlPO-5 molecular sieve. Heptafluoropropane can also be undetected, which is basically equivalent to the effect of fresh adsorbent.

Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that the technical solution of the present invention can be modified Or an equivalent replacement without departing from the spirit and scope of the technical solution of the present invention.

Claims (10)

1. a method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, it is characterized in that, described method comprises the following steps: 1) The adsorption column is filled with adsorbent, and under nitrogen atmosphere, the adsorbent is roasted at 250~500 °C to constant weight; The adsorbent is an aluminum phosphate molecular sieve whose structural formula is (El _{x Aly} P _z ) _O2 ; 2) Stop feeding nitrogen, use a vacuum pump to evacuate the adsorption column to an absolute pressure of 0.01 MPa, and cool the adsorbent to room temperature for use; 3) Pass the perfluoroisobutyronitrile raw material to be treated into the adsorption column, control the absolute pressure in the adsorption column to 0.1 MPa, and keep it constant; 4) Turn on the diaphragm compressor to press the gas in the adsorption column into the gas cylinder, stop when the pressure in the adsorption column reaches 0.01 MPa, and use a gas chromatograph to analyze the 1,1,1,2,3,3,3-heptafluoropropane in the cylinder gas content; 5) Repeat step 4) until 1,1,1,2,3,3,3-heptafluoropropane is not detected. 2. The method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile according to claim 1, characterized in that, in step 1), the pore size of the aluminum phosphate molecular sieve 0.3~1.2nm. 3. The method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile according to claim 2, characterized in that, in step 1), the aperture of the aluminum phosphate molecular sieve 0.7~0.9nm. 4. The method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile according to claim 1, characterized in that, in step 2), the vacuuming process needs to be Carry out at 250-500 ℃ calcination temperature. 5. The method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile according to claim 1, characterized in that, in step 3), the perfluoroisobutyronitrile to be treated The content of 1,1,1,2,3,3,3-heptafluoropropane in the isobutyronitrile raw material is at least 552.5 ppm. 6. The method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile according to claim 1, characterized in that, in step 4), the perfluorinated gas in the gas cylinder The filling coefficient of isobutyronitrile is 0.5~1.5. 7. according to the method for removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile according to claim 1, it is characterized in that, in step 5, utilize hydrogen flame ionization detector to detect 1,1,1,2,3,3,3-Heptafluoropropane content. 8. Application of aluminum phosphate molecular sieve in removing 1,1,1,2,3,3,3-heptafluoropropane in perfluoroisobutyronitrile, characterized in that, the structural formula of said aluminum phosphate molecular sieve is (El _x Al _y P _z ) O ₂ ; wherein, x≧0.001, y≧0.01, z≧0.01, and x+y+z=1. 9. according to the application of the aluminum phosphate molecular sieve of claim 8 in removing 1,1,1,2,3,3,3-heptafluoropropane, it is characterized in that the aperture of the aluminum phosphate molecular sieve is 0.3~1.2nm. 10. according to the application of the aluminum phosphate molecular sieve of claim 9 in removing 1,1,1,2,3,3,3-heptafluoropropane, it is characterized in that the aperture of the aluminum phosphate molecular sieve is 0.7~0.9nm.

Images