A method for removing 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile using an elimination reaction

Abstract

The present application relates to a method for removing 1,1,1,2,3,3,3-heptafluoropropane in heptafluoroisobutyronitrile by elimination reaction, the method comprising: adding an alkali metal or alkaline earth metal salt solution to a carrier material at room temperature, filtering after standing to obtain a catalyst precursor; drying the catalyst precursor, loading into a fixed bed reactor, calcining at 300-500 DEG C under a nitrogen atmosphere until constant weight to obtain a dehydrofluorination catalyst; adjusting the reactor temperature to 100-300 DEG C, passing in heptafluoroisobutyronitrile crude product at a certain flow rate, controlling the volume space velocity to be 10-500 h-1, collecting the reaction product in a cold trap after removing hydrogen fluoride by alkali absorption and removing hexafluoropropylene by rectification treatment, to obtain purified heptafluoroisobutyronitrile. ‑1 ~500 h ‑1 The method can remove 98% of 1,1,1,2,3,3,3-heptafluoropropane impurities in heptafluoroisobutyronitrile in a single pass, the product hexafluoropropylene is easily separated from heptafluoroisobutyronitrile, the purity of heptafluoroisobutyronitrile after final purification is increased to above 99.9%, and the overall purity of heptafluoroisobutyronitrile gas is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of gas separation and purification, and in particular relates to a method for removing 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile by utilizing an elimination reaction. Background Art

[0002] The insulation performance of heptafluoroisobutyronitrile is 2.2 times that of sulfur hexafluoride, and its greenhouse effect potential is only 1 / 10 of that of sulfur hexafluoride. It is a new generation of environmentally friendly sulfur hexafluoride substitute and has been used in electrical insulation equipment.

[0003] Due to differences in production processes, currently available heptafluoroisobutyronitrile gas contains numerous impurities and boasts a purity of only around 99.2%, significantly lower than the purity of sulfur hexafluoride gas used in power equipment (≥99.9%). Analysis of commercial heptafluoroisobutyronitrile products reveals that 1,1,1,2,3,3,3-heptafluoropropane is the most abundant impurity in heptafluoroisobutyronitrile, making it difficult to remove using conventional methods and a key constraint on improving the purity of heptafluoroisobutyronitrile. While patents CN110526834A and CN112979499A describe methods for separating and purifying heptafluoroisobutyronitrile, they do not specifically address the removal of the 1,1,1,2,3,3,3-heptafluoropropane impurity. Furthermore, as a fire extinguishing agent, 1,1,1,2,3,3,3-heptafluoropropane is inherently thermally stable and resistant to chemical reactions, making its removal a significant technical challenge.

[0004] Therefore, how to effectively further improve the purity of heptafluoroisobutyronitrile gas and remove the 1,1,1,2,3,3,3-heptafluoropropane impurity therein is a problem that needs to be solved. Summary of the Invention

[0005] To overcome the problems of the prior art, the present invention proposes a method for removing 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile using an elimination reaction. The method utilizes a dehydrofluorination catalyst to cause the 1,1,1,2,3,3,3-heptafluoropropane impurity to undergo a dehydrofluorination reaction to produce hexafluoropropylene, thereby effectively removing the 1,1,1,2,3,3,3-heptafluoropropane impurity from heptafluoroisobutyronitrile and improving the overall purity of the heptafluoroisobutyronitrile gas.

[0006] 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 from heptafluoroisobutyronitrile by elimination reaction, comprising the following steps:

[0007] 1) adding an alkali metal or alkaline earth metal salt solution to a support material at room temperature, allowing it to stand and then filtering to obtain a catalyst precursor;

[0008] 2) After drying the catalyst precursor, loading it into a fixed bed reactor, and calcining it at 300° C. to 500° C. under a nitrogen atmosphere to constant weight to obtain a dehydrofluorination catalyst;

[0009] 3) Adjust the reactor temperature to 100℃~300℃, introduce the crude heptafluoroisobutyronitrile at a certain flow rate, and control the volumetric space velocity to 10h -1 ~500h -1 The reaction product is absorbed by alkaline solution to remove hydrogen fluoride, distilled to remove hexafluoropropylene, and then collected by a cold trap to obtain purified heptafluoroisobutyronitrile.

[0010] Furthermore, the alkali metal is lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium or barium; and the alkaline earth metal salt is nitrate, carbonate, oxide or hydroxide of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium or barium.

[0011] Furthermore, the carrier material is aluminum fluoride, magnesium fluoride, barium fluoride, type A molecular sieve, type X molecular sieve, type Y molecular sieve, ZSM-5 molecular sieve or mesoporous carbon molecular sieve.

[0012] Furthermore, it is characterized in that the weight ratio of the alkali metal or alkaline earth metal salt to the carrier material is (1-5):100.

[0013] Furthermore, in step 2), the calcination temperature of the catalyst precursor is preferably 330°C to 400°C.

[0014] Furthermore, in step 3), the reactor temperature is preferably 180°C to 250°C; the volume space velocity is preferably 30h -1 ~150h -1 The alkali solution is preferably potassium hydroxide solution, the mass percentage is 1% to 20%; the distillation treatment conditions are: tower bottom heating temperature 35 ° C, condensing temperature -5 ° C, operating pressure 0.02MPa.

[0015] The second aspect of the present invention provides a new use of a dehydrofluorination catalyst, wherein the dehydrofluorination catalyst is used to remove 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile, and the dehydrofluorination catalyst is prepared by loading an alkali metal or alkaline earth metal salt onto a carrier material;

[0016] The alkali metal is lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium or barium; the alkaline earth metal salt is nitrate, carbonate, oxide or hydroxide of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium or barium; the carrier material is aluminum fluoride, magnesium fluoride, barium fluoride, type A molecular sieve, type X molecular sieve, type Y molecular sieve, ZSM-5 molecular sieve or mesoporous carbon molecular sieve.

[0017] Furthermore, the weight ratio of the alkali metal or alkaline earth metal salt to the carrier material is (1-5):100.

[0018] Furthermore, the preparation method of the dehydrofluorination catalyst is:

[0019] 1) adding an alkali metal or alkaline earth metal salt solution to a support material at room temperature, allowing it to stand and then filtering to obtain a catalyst precursor;

[0020] 2) After drying the catalyst precursor, the catalyst precursor is loaded into a fixed bed reactor and calcined at 300° C. to 500° C. under a nitrogen atmosphere to a constant weight, thereby obtaining the dehydrofluorination catalyst.

[0021] Furthermore, the calcination temperature of the catalyst precursor is preferably 330°C to 400°C.

[0022] The advantages and beneficial effects of the present invention are:

[0023] (1) In the method of removing 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile by elimination reaction according to the present invention, the 1,1,1,2,3,3,3-heptafluoropropane impurity in heptafluoroisobutyronitrile is converted into hexafluoropropylene and hydrogen fluoride by catalytic dehydrofluorination, the hydrogen fluoride generated by the reaction is absorbed by alkaline solution, the reaction product after alkaline washing is collected and then purified by distillation, the purity of heptafluoroisobutyronitrile is increased to more than 99.9%, and the overall purity of heptafluoroisobutyronitrile gas is effectively improved;

[0024] (2) The method of removing 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile by elimination reaction of the present invention has simple operation, mild conditions, and high conversion rate of 1,1,1,2,3,3,3-heptafluoropropane;

[0025] (3) The present invention proposes for the first time the application of a dehydrofluorination catalyst to the removal of 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile. It is found that the dehydrofluorination catalyst obtained under the calcination temperature of 300°C to 500°C has a high conversion rate for 1,1,1,2,3,3,3-heptafluoropropane, thereby achieving the best removal effect.

[0026] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings and examples.

[0028] Figure 1 This is a diagram showing the results of gas chromatography analysis of heptafluoroisobutyronitrile after purification in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In the following examples, the experimental instruments and raw materials involved are commercially available unless otherwise specified.

[0030] Experimental instruments are shown in Table 1.

[0031] Table 1

[0032] instrument model source Gas chromatograph GC 9560 Shanghai Huaai Chromatography Analysis Technology Co., Ltd. Fixed bed reactor Inconal 600 1 / 2 inch outer diameter, 30 cm long Tianjin Disheng Technology Co., Ltd. Cold trap 30cm Kangbo Experimental Equipment Co., Ltd.

[0033] Raw materials are shown in Table 2.

[0034] Table 2

[0035] raw material source Aluminum fluoride Beijing Yuji Technology Development Co., Ltd. 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. Mesoporous carbon molecular sieves Henan Shengwei Desiccant Co., Ltd. Heptafluoroisobutyronitrile crude product Beijing Yuji Technology Development Co., Ltd.

[0036] In the following examples, the specific parameters of gas chromatography analysis are shown in Table 3:

[0037] Table 3

[0038]

[0039] Example 1

[0040] Prepare 100 g of a 2.5% by mass potassium nitrate solution, add 20 g of an aluminum fluoride carrier, and stand for impregnation at room temperature for 12 h. After filtration, dry at 150°C for 12 h to obtain a catalyst precursor. Load 30 mL of the catalyst precursor into a fixed bed reactor, and calcine at 350°C under a nitrogen atmosphere until the weight is constant to obtain a 5% K / AlF3 catalyst with a loading amount of 5%. Adjust the reaction temperature to 200°C, and pass in 50 mL / min of crude heptafluoroisobutyl cyanide to obtain a volume space velocity of 100 h-1. The reaction product is absorbed by 10% KOH solution to remove hydrogen fluoride, and is treated by rectification to remove hexafluoropropylene. The rectification conditions are: column still heating temperature 35°C, condensation temperature -5°C, and operating pressure 0.02 MPa. Collect the product in a cold trap to obtain purified heptafluoroisobutyl cyanide. As shown in the following table, the purified heptafluoroisobutyl cyanide is analyzed by gas chromatography. -1 Figure 1

[0041] Example 2

[0042] Prepare 100 g of a 2.5% by mass potassium nitrate solution, add 20 g of a 5A molecular sieve carrier (pore size 5 angstroms), and stand for impregnation at room temperature for 12 h. After filtration, dry at 150°C for 12 h to obtain a catalyst precursor. Load 30 mL of the catalyst precursor into a fixed bed reactor, and calcine at 350°C under a nitrogen atmosphere until the weight is constant to obtain a 5% K / 5A catalyst with a loading amount of 5%. Adjust the reaction temperature to 200°C, and pass in 50 mL / min of crude heptafluoroisobutyl cyanide to obtain a volume space velocity of 100 h-1. The reaction product is absorbed by 10% KOH solution to remove hydrogen fluoride, and is treated by rectification to remove hexafluoropropylene. The rectification conditions are: column still heating temperature 35°C, condensation temperature -5°C, and operating pressure 0.02 MPa. Collect the product in a cold trap to obtain purified heptafluoroisobutyl cyanide. As shown in the following table, the purified heptafluoroisobutyl cyanide is analyzed by gas chromatography. -1 ​​The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0043] Example 3

[0044] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of 10X molecular sieve carrier (zeolite molecular sieve, pore size of 10 angstroms), and let it stand and soak at room temperature for 12 hours. After filtering, dry at 150°C for 12 hours to obtain a catalyst precursor. Take 30mL of the catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350°C to constant weight to obtain a catalyst with a loading of 5% K / 10X. Adjust the reaction temperature to 200°C, and introduce the crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0045] Example 4

[0046] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of NaY molecular sieve carrier (high silicon-aluminum ratio zeolite molecular sieve), and let it stand and soak at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a K / NaY catalyst with a loading of 5%. Adjust the reaction temperature to 200℃, and pass the crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0047] Example 5

[0048] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of ZSM-5 molecular sieve carrier, and let it stand and soak at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a K / ZSM-5 catalyst with a loading of 5%. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0049] Example 6

[0050] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of mesoporous carbon molecular sieve carrier, and let it stand and soak at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / carbon molecular sieve. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0051] Example 7

[0052] Prepare 100g of sodium nitrate solution with a mass fraction of 3.7%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% Na / AlF3. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0053] Example 8

[0054] Prepare 100g of cesium nitrate solution with a mass fraction of 1.5%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% Cs / AlF3. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0055] Example 9

[0056] Prepare 100g of magnesium nitrate solution with a mass fraction of 6.2%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under nitrogen atmosphere, bake at 350℃ to constant weight to obtain a catalyst with a loading of 5% Mg / AlF3. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0057] Example 10

[0058] Prepare 100g of calcium nitrate solution with a mass fraction of 4.1%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a Ca / AlF3 catalyst with a loading of 5%. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0059] Example 11

[0060] Prepare 100g of 1.9% barium nitrate solution, add 20g of aluminum fluoride carrier, and let it stand at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under nitrogen atmosphere, bake at 350℃ to constant weight to obtain a Ba / AlF3 catalyst with a loading of 5%. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0061] Example 12

[0062] Prepare 100g of potassium nitrate solution with a mass fraction of 0.5%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 1% K / AlF3. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0063] Example 13

[0064] Prepare 100g of potassium nitrate solution with a mass fraction of 1.25%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and fill it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 2.5%. Adjust the reaction temperature to 200℃, and introduce the crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0065] Example 14

[0066] Prepare 100g of potassium nitrate solution with a mass fraction of 3.75%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 300℃ to constant weight to obtain a K / AlF3 catalyst with a loading of 7.5%. Adjust the reaction temperature to 200℃, and introduce the crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0067] Example 15

[0068] Prepare 100g of 5% potassium nitrate solution, add 20g of aluminum fluoride carrier, and let it stand at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under nitrogen atmosphere, bake at 400℃ to constant weight to obtain a catalyst with a loading of 10%. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0069] Example 16

[0070] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / AlF3. Adjust the reaction temperature to 100℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0071] Example 17

[0072] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of aluminum fluoride carrier, and let it stand at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and fill it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / AlF3. Adjust the reaction temperature to 150℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0073] Example 18

[0074] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of aluminum fluoride carrier, and let it stand at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / AlF3. Adjust the reaction temperature to 250℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0075] Example 19

[0076] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of aluminum fluoride carrier, and let it stand at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / AlF3. Adjust the reaction temperature to 300℃, and introduce the crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 100h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0077] Example 20

[0078] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of aluminum fluoride carrier, and let it stand at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and fill it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / AlF3. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 50h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0079] Example 21

[0080] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and load it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / AlF3. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 150h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0081] Example 22

[0082] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and fill it into a fixed bed reactor. Under nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / AlF3. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 200h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0083] Example 23

[0084] Prepare 100g of potassium nitrate solution with a mass fraction of 2.5%, add 20g of aluminum fluoride carrier, and let it stand and soak at room temperature for 12h. After filtering, dry it at 150℃ for 12h to obtain a catalyst precursor. Take 30mL of catalyst precursor and fill it into a fixed bed reactor. Under a nitrogen atmosphere, bake it at 350℃ to constant weight to obtain a catalyst with a loading of 5% K / AlF3. Adjust the reaction temperature to 200℃, and introduce crude heptafluoroisobutyronitrile at a flow rate of 50mL / min, with a volume space velocity of 250h -1 The reaction product was absorbed in a 10% KOH solution to remove hydrogen fluoride and distilled to remove hexafluoropropylene. The distillation conditions were: a bottom heating temperature of 35°C, a condensing temperature of -5°C, and an operating pressure of 0.02 MPa. The product was then collected in a cold trap to obtain purified heptafluoroisobutyronitrile. The purified heptafluoroisobutyronitrile was analyzed by gas chromatography.

[0085] Test Example 1

[0086] In order to compare the effects of dehydrofluorination catalysts prepared from different support materials on the removal of 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile, this test example compared the 1,1,1,2,3,3,3-heptafluoropropane content before and after the reaction of Examples 1 to 6. The results are shown in Table 4.

[0087] Table 4 Comparison of catalyst effects of different carrier materials

[0088]

[0089] As can be seen from Table 4, the catalysts prepared with different support materials have significant differences in the elimination reaction of heptafluoropropane. Among them, the 5% K / AlF3 catalyst prepared with aluminum fluoride support in Example 1 has the best reaction effect. The content of heptafluoropropane in the reaction product is only 0.0014%, which is a decrease of 98.2% compared with the content before the reaction.

[0090] Test Example 2

[0091] In order to compare the effects of different active metals on the dehydrofluorination catalyst and the removal of 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile, this test example compared the 1,1,1,2,3,3,3-heptafluoropropane content before and after the reaction of Example 1 and Examples 7 to 11. The results are shown in Table 5.

[0092] Table 5 Comparison of the effects of different active metal catalysts

[0093]

[0094] As can be seen from Table 5, the catalysts prepared with different active elements have obvious differences in the elimination reaction of heptafluoropropane. Among them, the catalysts loaded with metallic potassium and cesium have better reaction effects, and the contents of heptafluoropropane in the products are 0.0014% and 0.0018%, respectively. However, the catalysts prepared with metallic sodium, magnesium, calcium, and barium as active components have poor reaction effects.

[0095] Test Example 3

[0096] In order to compare the effects of different active metals on the dehydrofluorination catalyst and the removal of 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile, this test example compared the 1,1,1,2,3,3,3-heptafluoropropane content before and after the reaction of Example 1 and Examples 7 to 11. The results are shown in Table 6.

[0097] Table 6 Comparison of catalyst effects with different loading amounts

[0098]

[0099] As can be seen from Table 6, the dehydrofluorination reaction effect of heptafluoropropane gradually improves with increasing loading. When the loading is greater than 5%, the reaction effect tends to stabilize as the loading continues to increase. Therefore, the optimal loading is preferably 5%.

[0100] Test Example 4

[0101] In order to compare the effects of different active metals on the dehydrofluorination catalyst and the removal of 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile, this test example compared the 1,1,1,2,3,3,3-heptafluoropropane content before and after the reaction of Example 1 and Examples 16 to 19. The results are shown in Table 7.

[0102] Table 7 Comparison of reaction effects at different temperatures

[0103]

[0104] It can be seen from Table 7 that as the reaction temperature increases, the reaction effect of heptafluoropropane becomes better. When the reaction temperature reaches 250°C, heptafluoroisobutyronitrile undergoes a large amount of decomposition to generate more heptafluoropropane. Therefore, the optimal reaction temperature should not be higher than 250°C, and is preferably 150°C to 250°C.

[0105] Test Example 5

[0106] In order to compare the effects of different active metals on the dehydrofluorination catalyst and the removal of 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile, this test example compared the 1,1,1,2,3,3,3-heptafluoropropane content before and after the reaction of Example 1 and Examples 20 to 23. The results are shown in Table 8.

[0107] Table 8 Comparison of reaction effects at different volumetric space velocities

[0108]

[0109] From Table 8, we can see that the reaction effect of heptafluoropropane becomes worse when the volume space velocity increases. When the space velocity reaches 200h -1 When the volume space velocity is above 50 h, it is difficult for heptafluoropropane to undergo dehydrofluorination reaction in a short time, and the content of heptafluoropropane in the product does not decrease significantly. Therefore, the volume space velocity is preferably 50 h -1 ~150h -1 .

[0110] Finally, it should be noted that the above is only used to illustrate the technical solution of the present invention and is not limiting. Although the present invention is described in detail with reference to the preferred arrangement scheme, ordinary technicians in this field should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for removing 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile by elimination reaction, characterized in that: The method comprises the following steps: 1) Adding an alkali metal or alkaline earth metal to a carrier material at room temperature, allowing the mixture to stand and then filtering to obtain a catalyst precursor; The alkali metal or alkaline earth metal is sodium, potassium, cesium, calcium or barium; the carrier material is aluminum fluoride, 5A molecular sieve, 10X molecular sieve, NaY molecular sieve carrier, ZSM-5 molecular sieve or mesoporous carbon molecular sieve; The weight ratio of the alkali metal or alkaline earth metal to the carrier material is (1-5):100; 2) drying the catalyst precursor, loading it into a fixed-bed reactor, and calcining it at 300° C. to 500° C. under a nitrogen atmosphere to a constant weight, thereby obtaining a dehydrofluorination catalyst; 3) Adjust the reactor temperature to 100 ℃~250 ℃, introduce the crude heptafluoroisobutyronitrile at a certain flow rate, and control the volumetric space velocity to 10 h -1 ~500 h -1 The reaction product is absorbed by alkaline solution to remove hydrogen fluoride, distilled to remove hexafluoropropylene, and then collected by a cold trap to obtain purified heptafluoroisobutyronitrile.

2. The method for removing 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile by elimination reaction according to claim 1, characterized in that In step 3), the reactor temperature is 180°C to 250°C; the volume space velocity is 30 h -1 ~150 h -1 The alkali solution is a potassium hydroxide solution with a mass percentage of 1% to 20%; the conditions for the distillation treatment are: the tower bottom heating temperature is 35°C, the condensation temperature is -5°C, and the operating pressure is 0.02 MPa.

3. A use of a dehydrofluorination catalyst, characterized in that: The dehydrofluorination catalyst is used to remove 1,1,1,2,3,3,3-heptafluoropropane from heptafluoroisobutyronitrile, and the dehydrofluorination catalyst is prepared by loading an alkali metal or an alkaline earth metal onto a carrier material; The alkali metal or alkaline earth metal is sodium, potassium, cesium, calcium or barium; the carrier material is aluminum fluoride, type A molecular sieve, type X molecular sieve, type Y molecular sieve, ZSM-5 molecular sieve or mesoporous carbon molecular sieve; The preparation method of the dehydrofluorination catalyst is: 1) Adding an alkali metal or alkaline earth metal to a carrier material at room temperature, allowing the mixture to stand and then filtering to obtain a catalyst precursor; 2) After drying the catalyst precursor, the catalyst precursor is loaded into a fixed bed reactor and calcined at 300° C. to 500° C. under a nitrogen atmosphere to a constant weight, thereby obtaining the dehydrofluorination catalyst.

4. The use of the dehydrofluorination catalyst according to claim 3, characterized in that The weight ratio of the alkali metal or alkaline earth metal to the carrier material is (1-5):

100.

5. The use of the dehydrofluorination catalyst according to claim 3, characterized in that The calcination temperature of the catalyst precursor is 330°C to 400°C.

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