Preparation method of phosphorus trifluoride

Abstract

The invention relates to the technical field of preparation of phosphorus compounds, and particularly discloses a preparation method of phosphorus trifluoride. The preparation method of phosphorus trifluoride comprises the following steps: blending phosphorus trichloride and anhydrous hydrogen fluoride in a molar ratio of 1: (3.0-3.2), adding a catalytic amount of a chromium catalyst, reacting at the reaction temperature of 25-45 DEG C, and collecting by a secondary cold trap to obtain phosphorus trifluoride. According to the preparation technology, the yield of phosphorus trifluoride can be increased to 98% or above, and therefore the preparation technology has the multiple advantages that conditions are convenient to control, the reaction speed is moderate, and the product yield is high.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of phosphorus compound preparation, in particular to a preparation method of phosphorus trifluoride. BACKGROUND

[0002] Phosphorus trifluoride (PF3) is an important inorganic compound and is widely applied in the fields of semiconductor industry, pesticide manufacturing, metal smelting and the like. Previously, phosphorus trifluoride is mainly prepared through direct fluorination or indirect fluorination, that is, phosphorus is directly reacted with fluorine gas under high temperature and high pressure, or indirect fluorination is carried out through an intermediate product. Although these methods can prepare phosphorus trifluoride, there are many problems such as high energy consumption, serious environmental pollution, large equipment investment, harsh reaction conditions, serious equipment corrosion and low product purity, which limit the wide application of phosphorus trifluoride.

[0003] At present, the widely applied preparation method is to bubble anhydrous hydrogen fluoride in phosphorus trichloride liquid to generate phosphorus trifluoride and hydrogen chloride through gas-liquid contact reaction, and the product gas is collected through two-stage cold traps to obtain the crude product of phosphorus trifluoride. The advantages of this reaction process are simple process and short technological process. The disadvantages are complex reaction control, that is, the temperature of the reactor needs to be controlled, and the temperature of the raw material hydrogen fluoride also needs to be controlled; and the reaction process is unbalanced before and after the reaction, in the reaction, the liquid level of phosphorus trichloride is gradually lowered, the reaction time of anhydrous hydrogen fluoride is shortened when it is bubbled, and part of the unreacted anhydrous hydrogen fluoride will escape into the product, causing the blockage of solid hydrogen fluoride at the pipe opening of the cold trap for recovering hydrogen chloride, affecting the smooth progress of the reaction, and causing large consumption of hydrogen fluoride raw material. SUMMARY

[0004] In order to solve the above technical problems, the application provides a preparation method of phosphorus trifluoride.

[0005] The preparation method of phosphorus trifluoride provided by the application comprises the following steps: mixing phosphorus trichloride and anhydrous hydrogen fluoride with a molar ratio of 1: (3.0-3.2), adding a catalytic amount of chromium catalyst, reacting at a reaction temperature of 25-45 DEG C, collecting through a secondary cold trap, and obtaining phosphorus trifluoride.

[0006] Preferably, the reaction time is 18-48 h.

[0007] Preferably, the reaction pressure is 4.5-6.0 MPa.

[0008] By adopting the technical scheme, the hydrogen fluoride is used as a fluorinating agent, and reacts with the phosphorus trichloride under the action of a catalyst, the reaction temperature is low, and the pressure is moderate, the corrosion of equipment and energy consumption are reduced, high-temperature and high-pressure equipment and a complex fluorine gas treatment system are not needed, the production process is simplified, and equipment investment is reduced, the reaction condition is mild, and energy consumption is low, the production cost is reduced, the hydrogen fluoride is used to avoid environmental pollution caused by direct use of fluorine gas, the secondary cold trap is used for collection, the generated phosphorus trifluoride is separated from water, and high-purity products are obtained.

[0009] Preferably, the molar ratio of the phosphorus trichloride to the anhydrous hydrogen fluoride is 1:3.05.

[0010] By adopting the technical scheme, the molar ratio of the phosphorus trichloride to the anhydrous hydrogen fluoride is 2.98:1 in the preparation of the phosphorus trifluoride, the reaction is performed under the action of a catalytic amount of a chromium catalyst at a reaction temperature of 25-45 DEG C, and the process is collected through a secondary cold trap, so that the phosphorus trifluoride can be prepared under the conditions of mild reaction condition, simple equipment, low energy consumption, environmental friendliness and high product purity, and the yield of the phosphorus trifluoride is increased to more than 99%.

[0011] Preferably, the secondary cold trap is that: one cold trap is performed at a temperature of-85 DEG C, and then two cold traps are performed at a temperature of-150 DEG C.

[0012] By adopting the technical scheme, the one cold trap is performed at a temperature of-85 DEG C, and then the two cold traps are performed at a temperature of-150 DEG C, so that the secondary cold trap mode is used for collection, the phosphorus trifluoride can be more effectively collected, and the product collection effect is ensured.

[0013] Preferably, the chromium catalyst is prepared by the following method: chromium nitrate nine hydrate is precipitated in ammonia water, filtered, washed, dried, once calcined under the protection of an inert gas, heat preserved in hydrogen, then the obtained intermediate product is immersed in a chromic acid solution, the mass ratio of the chromic acid to the intermediate product in the system is controlled to be (11.5-12):100, and after being taken out, the chromium catalyst is obtained by drying, twice calcining under the protection of an inert gas at a temperature of 250-300 DEG C, washing and drying.

[0014] Preferably, the temperature of the once calcination is 400 DEG C, and the time is 2h.

[0015] Preferably, the time of the heat preservation is 2h.

[0016] Preferably, the concentration of the chromic acid solution is 50g / L.

[0017] By adopting the technical scheme, firstly, the chromium nitrate nonahydrate is precipitated in ammonia water, the obtained precipitate is once calcined and reduced (heat preservation in hydrogen), to obtain an intermediate product, the chromic acid and the intermediate product are mixed in water, the high-valence chromium ions in the chromic acid are impregnated on the intermediate product, and then secondary calcination is performed, and the temperature is strictly controlled, to form a chromium catalyst with high-valence chromium and low-valence chromium in the system. The high-valence chromium can greatly improve the fluorine-chlorine conversion activity in the system, and the low-valence chromium has more excellent catalytic stability. Therefore, the chromium catalyst of the application can greatly improve the reaction speed, promote the generation of phosphorus trifluoride, and maintain high catalytic stability within the reaction time of the preparation process of the application, to help the reaction proceed smoothly.

[0018] In summary, the application has the following beneficial technical effects: 1. The preparation method of the application is stable, does not need to control multiple temperature points, the raw materials can almost complete quantitative reaction, and has high reaction yield, and the subsequent treatment is simple and easy to operate, so that high-temperature and high-pressure equipment and a complex fluorine gas treatment system are not needed, the production process and equipment investment are simplified, and the production cost is reduced; 2. The preparation method of the application uses hydrogen fluoride to avoid environmental pollution problems caused by direct use of fluorine gas, and the secondary cold trap can separate the generated phosphorus trifluoride and water to obtain high-purity products; 3. The special chromium catalyst is added to greatly improve the reaction speed, and the yield of phosphorus trifluoride can be increased to more than 99.3%, which has the advantages of easy to control conditions, moderate reaction speed and high product yield. DETAILED DESCRIPTION

[0019] The application will be further described in detail below in combination with preparation examples, examples and comparative examples.

[0020] A preparation method of phosphorus trifluoride, comprising the following steps: mixing phosphorus trichloride and anhydrous hydrogen fluoride in a molar ratio of 1: (3.0-3.2), adding a catalytic amount of chromium catalyst, reacting at a reaction temperature of 25-45℃, collecting by a secondary cold trap, and obtaining phosphorus trifluoride.

[0021] In a preferred embodiment of the application, the reaction time is 18-48h.

[0022] In a preferred embodiment of the application, the reaction pressure is 4.5-6.0MPa.

[0023] In a preferred embodiment of the application, the molar ratio of the phosphorus trichloride and the anhydrous hydrogen fluoride is 1:3.05.

[0024] In a preferred embodiment of the present application, the secondary cold trap is specifically: a primary cold trap at a temperature of -85°C, followed by a secondary cold trap at a temperature of -150°C.

[0025] In a preferred embodiment of the present application, the chromium catalyst is prepared by the following method: chromium nitrate nonahydrate is precipitated in ammonia water, filtered, washed, dried, once calcined under inert gas protection, incubated in hydrogen, and then the obtained intermediate product is immersed in a chromic acid solution, the mass ratio of chromic acid to the intermediate product in the system is controlled to be (11.5-12):100, dried after taking out, twice calcined under inert gas protection at a temperature of 250-300°C, washed, and dried to obtain the chromium catalyst.

[0026] In a preferred embodiment of the present application, the temperature of the primary calcination is 400°C, and the time is 2h.

[0027] In a preferred embodiment of the present application, the incubation time is 2h.

[0028] In a preferred embodiment of the present application, the concentration of the chromic acid solution is 50g / L.

[0029] <Preparation Example 1> A preparation method of a chromium catalyst, comprising the following steps: Chromium nitrate nonahydrate is dispersed in water, stirred until completely dissolved, and then precipitated by dropping ammonia water until no precipitate is generated, and the dropping of ammonia water is stopped. The precipitate is filtered, washed, dried, once calcined under nitrogen protection at a temperature of 400°C for 2h, and then the substance is incubated in a hydrogen atmosphere at 400°C for 2h to obtain an intermediate product. The intermediate product is immersed in a chromic acid solution with a concentration of 50g / L, the mass ratio of chromic acid to the intermediate product in the system is controlled to be 11.5:100, and the water is evaporated under stirring in a water bath at 80°C after taking out. The intermediate product is twice calcined under nitrogen protection at a temperature of 300°C for 4h, washed, and dried to obtain the chromium catalyst.

[0030] <Preparation Example 2> A preparation method of a chromium catalyst, comprising the following steps: The chromium nitrate nine hydrate is dispersed in water, stirred until completely dissolved, then ammonia water is added dropwise for precipitation, until no precipitate is produced, then stop adding ammonia water, filter, wash, dry, and perform first calcination under nitrogen protection at a temperature of 400℃ for 2h, then immerse the intermediate product in a chromium acid solution with a concentration of 50g / L, control the mass ratio of chromium acid to intermediate product in the system to be 12:100, remove and evaporate water under stirring in a water bath at 80℃, perform second calcination under nitrogen protection at a temperature of 250℃ for 4h, wash, dry, and obtain the chromium catalyst.

[0031] <Preparation Example 3> The preparation method of the chromium catalyst is different from that in Preparation Example 1 in that the temperature during the second calcination is 150℃, and the rest is the same as in Preparation Example 1.

[0032] <Example 1> A preparation method of phosphorus trifluoride, comprising the following steps: The chromium catalyst prepared in Preparation Example 1 is placed at the bottom of a high-pressure container with a pressure of 6.0MPa, then phosphorus trichloride is poured in, then anhydrous hydrogen fluoride is introduced from the bottom of the high-pressure container, the molar ratio of phosphorus trichloride to anhydrous hydrogen fluoride is 1:3.0, the addition amount of the chromium catalyst is 15wt% of the amount of phosphorus trichloride, the temperature of the system is controlled to be 35℃, after 30h of reaction, the obtained product is subjected to first cold trapping at a temperature of -85℃, and second cold trapping at a temperature of -150℃, and then purified by rectification to obtain phosphorus trifluoride, with a yield of 98.1%.

[0033] <Example 2> A preparation method of phosphorus trifluoride, comprising the following steps: The chromium catalyst prepared in Preparation Example 2 is placed at the bottom of a high-pressure container with a pressure of 4.5MPa, then phosphorus trichloride is poured in, then anhydrous hydrogen fluoride is introduced from the bottom of the high-pressure container, the molar ratio of phosphorus trichloride to anhydrous hydrogen fluoride is 1:3.2, the addition amount of the chromium catalyst is 15wt% of the amount of phosphorus trichloride, the temperature of the system is controlled to be 45℃, after 18h of reaction, the obtained product is subjected to first cold trapping at a temperature of -85℃, and second cold trapping at a temperature of -150℃, and then purified by rectification to obtain phosphorus trifluoride, with a yield of 98.8%.

[0034] <Example 3> A preparation method of phosphorus trifluoride, comprising the following steps: The chromium catalyst prepared in Preparation Example 1 was placed at the bottom of a high-pressure container with a pressure of 5.5 MPa, and then phosphorus trichloride was poured in. Anhydrous hydrogen fluoride was then introduced from the bottom of the high-pressure container, with the molar ratio of phosphorus trichloride to anhydrous hydrogen fluoride being 1:3.05. The amount of chromium catalyst added was 15 wt% of the amount of phosphorus trichloride used. The temperature of the system was controlled at 25°C. After 48 h of reaction, the obtained product was subjected to a first cold trap at a temperature of -85°C and a second cold trap at a temperature of -150°C. Purification by rectification was performed, and phosphorus trifluoride was obtained, with a yield of 99.4%.

[0035] <Example 4> A method for preparing phosphorus trifluoride, comprising the following steps: The chromium catalyst prepared in Preparation Example 3 was placed at the bottom of a high-pressure container with a pressure of 5.5 MPa, and then phosphorus trichloride was poured in. Anhydrous hydrogen fluoride was then introduced from the bottom of the high-pressure container, with the molar ratio of phosphorus trichloride to anhydrous hydrogen fluoride being 1:3.05. The amount of chromium catalyst added was 15 wt% of the amount of phosphorus trichloride used. The temperature of the system was controlled at 25°C. After 48 h of reaction, the obtained product was subjected to a first cold trap at a temperature of -85°C and a second cold trap at a temperature of -150°C. Purification by rectification was performed, and phosphorus trifluoride was obtained, with a yield of 98.3%.

[0036] <Comparative Example 1> The difference from Example 1 is that the chromium catalyst prepared in Preparation Example 1 was removed, and the rest was the same as Example 1. Phosphorus trifluoride was obtained, with a yield of 85.8%.

[0037] <Comparative Example 2> The difference from Example 1 is that the chromium catalyst prepared in Preparation Example 1 was removed, and the reaction time was 72 h. The rest was the same as Example 1. Phosphorus trifluoride was obtained, with a yield of 97.4%.

[0038] <Comparative Example 3> Phosphorus trichloride was poured into a container under nitrogen protection at a temperature of 50°C. Anhydrous hydrogen fluoride was then introduced from the bottom of the container, with the molar ratio of phosphorus trichloride to anhydrous hydrogen fluoride being 4:1. The temperature of the system was controlled at 50°C. After 30 min of reaction, the obtained product was subjected to a first cold trap at a temperature of -85°C and a second cold trap at a temperature of -150°C. Purification by rectification was performed, and phosphorus trifluoride was obtained, with a yield of 95.0%.

[0039] Table 1 Data Summary

[0040] Data Analysis: As can be seen from the data in Table 1, the phosphorus trifluoride yield of Examples 1-4 is as high as 98.1%, which proves that the present application has low reaction temperature and moderate pressure by using hydrogen fluoride as fluorinating agent and reacting with phosphorus trichloride under the action of catalyst, thereby reducing the corrosion of equipment and energy consumption, without the need for high-temperature and high-pressure equipment and complex fluorine gas treatment system, simplifying the production process and equipment investment, and being conducive to reducing production cost due to mild reaction conditions and low energy consumption, and avoiding environmental pollution problems caused by direct use of fluorine gas by using hydrogen fluoride, and high-purity product can be obtained by separating the generated phosphorus trifluoride and water through the secondary cold trap. More importantly, the present application adds a special chromium catalyst, which greatly improves the reaction speed and increases the yield of phosphorus trifluoride to more than 98%, and the preparation process has multiple advantages of easy-to-control conditions, moderate reaction speed, and high product yield.

[0041] The phosphorus trifluoride yield of Example 4 is slightly lower than that of Example 3, and the difference between them is that the selection of chromium catalyst is different. In the chromium catalyst of Preparation Example 3, the amount of high-valence chromium is lower than that of the chromium catalyst of Preparation Example 1, so the catalytic activity is lacking, which leads to a decrease in the generation speed of phosphorus trifluoride.

[0042] The difference between Comparative Example 1 is that the chromium catalyst is removed, and the phosphorus trifluoride yield is much lower than that of Example 1. Comparative Example 2 also removes the chromium catalyst, and the reaction time is 72 h, and the phosphorus trifluoride yield is still slightly lower than that of Example 1, which proves that the present application adds a special chromium catalyst, which greatly improves the reaction speed.

[0043] The phosphorus trifluoride yield of Comparative Example 3 is also lower than that of Example 1, which proves that the preparation method of the present application overcomes the problem that the contact between phosphorus trichloride and anhydrous hydrogen fluoride is not sufficient, which leads to the escape of anhydrous hydrogen fluoride into the product phosphorus trifluoride and the blockage of the hydrogen chloride pipe during the cold trap process, thereby effectively improving the utilization rate of anhydrous hydrogen fluoride raw materials and the overall reaction yield.

[0044] The examples of the specific embodiment are the preferred embodiments of the present application, but do not limit the protection scope of the present application, so that: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A process for the preparation of phosphorus trifluoride, characterized in that, The method comprises the following steps: The phosphorus trichloride and anhydrous hydrogen fluoride with a molar ratio of 1: (3.0-3.2) are blended, a catalytic amount of chromium catalyst is added, and the reaction is carried out at a reaction temperature of 25-45 DEG C, and a secondary cold trap is used for collection, so as to obtain phosphorus trifluoride.

2. The method of claim 1, wherein the phosphorus trifluoride is prepared by the process of: The reaction time is 18-48 h. ​ 3. The method of claim 1, wherein the phosphorus trifluoride is prepared by the steps of: The reaction pressure is 4.5-6.0 MPa. ​ 4. The method of claim 1, wherein the phosphorus trifluoride is prepared by the process of: The molar ratio of the phosphorus trichloride and the anhydrous hydrogen fluoride is 1:3.

05. ​ 5. The method of claim 1, wherein the phosphorus trifluoride is prepared by the process of: The secondary cold trap is specifically: a primary cold trap is carried out at a temperature of -85 DEG C, and then a secondary cold trap is carried out at a temperature of -150 DEG C. ​ 6. The method of claim 1, wherein the phosphorus trifluoride is prepared by the process of: The chromium catalyst is prepared by the following method: ​ The chromium nitrate nonahydrate is precipitated in ammonia water, filtered, washed, dried, once calcined under the protection of inert gas, heat preserved in hydrogen, and then the obtained intermediate product is immersed in a chromic acid solution, the mass ratio of the chromic acid in the system to the intermediate product is controlled to be (11.5-12):100, taken out and dried, twice calcined under the protection of inert gas at a temperature of 250-300 DEG C, washed, and dried, so as to obtain the chromium catalyst.

7. A process for the preparation of phosphorus trifluoride according to claim 6, characterized in that, The temperature of the once calcination is 400 DEG C, and the time is 2 h.

8. The method of claim 6, wherein the phosphorus trifluoride is prepared by the process of: The heat preservation time is 2 h. ​ 9. The method of claim 6, wherein the phosphorus trifluoride is prepared by the process of: The concentration of the chromic acid solution is 50 g / L. ​

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