Method for preparing phosphorus trifluoride

Abstract

The invention discloses a method for preparing phosphorus trifluoride, which comprises the following steps: by taking phosphorus trichloride as a raw material, firstly heating and vaporizing, then carrying out gas-phase fluorination continuous preparation through a fixed bed reactor filled with a supported fluorination reagent, pre-cooling the reacted mixed gas, cooling the gas phase, and collecting a liquid-phase phosphorus trifluoride product; the active component of the supported fluorinating reagent is one or more of cobalt fluoride, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, silver fluoride and lead fluoride; the carrier is active carbon, active oxygen aluminum or a molecular sieve with a high silica-alumina ratio; the mass percentage ratio of the active component to the carrier of the load type fluorinating reagent is (20-40%): (60-80%); the reaction temperature is 50-200 DEG C; the reaction pressure is 0 to 100 KPa; the standing time is 0.05 to 20 seconds; the molecular sieve with the high silica-alumina ratio refers to a molecular sieve with the SiO2 / Al2O3 molar ratio being greater than or equal to 8. The method can realize continuous preparation of phosphorus trifluoride through gas phase fluorination, and is simple and safe to operate, free of solvent reaction, low in cost, low in equipment requirement and easy for industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing phosphorus trifluoride. Background Art

[0002] Phosphorus trifluoride is an inorganic compound with the chemical formula PF3 and a boiling point of -101.2°C. It is a colorless, odorless, toxic gas at room temperature and pressure. It is relatively stable in the air. When heated, it reacts with hydrogen to form PH3 and can react with water to form phosphorous acid and hydrogen fluoride. It can also decompose in alkali and is soluble in ethanol.

[0003] Phosphorus trifluoride is an important chemical reagent. In the semiconductor manufacturing process, phosphorus trifluoride can be used as a dopant to dope semiconductor materials such as silicon, thereby changing their electronic properties.

[0004] At present, the production process of phosphorus trifluoride is less public. CN101955173A discloses a technology for preparing phosphorus trifluoride by reacting phosphorus trichloride and zinc fluoride. Phosphorus trichloride and zinc fluoride react in a reactor at 140-150°C. This scheme has low reaction activity, long reaction time, requires the use of hydrogen fluoride, has high requirements for reaction equipment, and is not easy to scale production. CN117163925A discloses a method for preparing phosphorus trifluoride, using phosphorus triiodide organic solution and fluoride metal salt, with a high reaction temperature of 270-400°C, using a large amount of organic solvent, generating a large amount of three wastes, and high production cost. CN117228643A discloses a method for preparing electronic grade phosphorus trifluoride, adding phosphorus trichloride to a reactor, heating it, passing anhydrous hydrogen fluoride at the bottom of the reactor, and generating phosphorus trifluoride for direct collection. This method uses hydrogen fluoride, the equipment is easily corroded, and the operation is difficult. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing phosphorus trifluoride. The present invention can realize gas-phase catalytic continuous preparation, has simple and safe operation, solvent-free reaction, low cost, low equipment requirements, and is easy for industrial production.

[0006] The purpose of the present invention is achieved by the following technical scheme: a method for preparing phosphorus trifluoride, using phosphorus trichloride as a raw material, first heating and vaporizing, and then continuously preparing by gas phase catalysis in a fixed bed reactor equipped with a supported fluorination agent, and collecting liquid phase phosphorus trifluoride products by cooling the gas phase after the reaction after precooling the mixed gas; the active component of the supported fluorination agent is one or more of cobalt fluoride, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, silver fluoride, lead fluoride, etc.; the carrier is activated carbon, activated aluminum oxide or high silicon aluminum ratio molecular sieve, etc.; the mass percentage of the active component of the supported fluorination agent and the carrier is 20%~40%: 60%~80%; the reaction temperature is generally carried out at 50~200℃; the reaction pressure is generally 0~100KPa; the residence time is generally 0.05~20s. The high silicon aluminum ratio molecular sieve refers to a molecular sieve with a molar ratio of SiO2 / Al2O3≥8.

[0007] Furthermore, the reaction temperature is preferably 100-150°C, and is particularly preferably carried out above the boiling point of phosphorus trichloride to ensure that the phosphorus trichloride is in a vaporized state. To avoid decomposition of phosphorus trichloride, the upper limit is preferably 150°C.

[0008] Furthermore, the reaction pressure is preferably 0-50 KPa, and the residence time is preferably 0.05-10 s.

[0009] Phosphorus trichloride reacts with a fluorination agent, and products with different yields and purities can be obtained by controlling the reaction temperature and residence time of the phosphorus trichloride and the fluorination agent. Excess phosphorus trichloride is reused after being liquefied by precooling.

[0010] Furthermore, the supported fluorination agent is preferably dried under nitrogen flow at 100 to 300° C. before use.

[0011] Furthermore, the vaporization temperature is generally 70~150°C, preferably 100~150°C; the precooling temperature is generally -10~-50°C; and the cooling collection is generally -180~-120°C.

[0012] The supported fluorination reagent is filled in a fixed bed reactor, and the reactor is made of high temperature resistant stainless steel, monel or nickel.

[0013] Compared with the prior art, the invention has the following beneficial effects: phosphorus trichloride is used for gas phase reaction with a fluorination agent, the use of an organic solvent is avoided, the reaction conditions are mild, the equipment is simple, the production cost is low, the operation is simple, and it is easy to industrialize. DETAILED DESCRIPTION

[0014] The present invention will be further described in detail below in conjunction with the examples, but the present invention is not limited to the following examples.

[0015] Example 1

[0016] Phosphorus trichloride is heated to 100°C, and after vaporization, is passed into a fixed bed reactor filled with activated carbon loaded with 20% potassium fluoride. The reaction temperature is 100°C, the residence time is 1s, and the reaction pressure is 10Kpa. The gas phase product after the reaction is passed through a precooler to cool the phosphorus trichloride at -20°C and collect it, and then the subsequent gas phase product is cooled and collected at -120°C to obtain a phosphorus trifluoride liquid product with a product yield of 70% and a purity of 82%.

[0017] Example 2

[0018] Phosphorus trichloride is heated to 120°C, and after vaporization, is passed into a fixed bed reactor filled with molecular sieve loaded with 30% cesium fluoride, the reaction temperature is 150°C, the residence time is 0.5s, the reaction pressure is 20Kpa, the gas phase product after the reaction is passed through a precooler to cool the phosphorus trichloride at -30°C and collect it, and then the subsequent gas phase product is cooled and collected at -140°C to obtain a phosphorus trifluoride liquid product, the product yield is 80%, and the purity is 85%.

[0019] Example 3

[0020] Phosphorus trichloride is heated to 150°C, and after vaporization, is passed into a fixed bed reactor filled with active oxygen aluminum loaded with 25% silver fluoride. The reaction temperature is 130°C, the residence time is 10s, and the reaction pressure is 30Kpa. The gas phase product after the reaction is cooled and collected at -50°C in a precooler, and the subsequent gas phase product is cooled and collected at -145°C to obtain a phosphorus trifluoride liquid product with a product yield of 85% and a purity of 60%.

[0021] Example 4

[0022] Phosphorus trichloride is heated to 50°C, and after vaporization, is passed into a fixed bed reactor filled with active oxygen aluminum loaded with 30% cobalt fluoride. The reaction temperature is 140°C, the residence time is 20s, and the reaction pressure is 40Kpa. The gas phase product after the reaction is passed through a precooler to cool the phosphorus trichloride at -40°C and collect it, and then the subsequent gas phase product is cooled and collected at -145°C to obtain a phosphorus trifluoride liquid product with a product yield of 87.2% and a purity of 75%.

[0023] Example 5

[0024] Phosphorus trichloride is heated to 200°C, and after vaporization, is passed into a fixed bed reactor filled with active oxygen aluminum loaded with 35% sodium fluoride. The reaction temperature is 120°C, the residence time is 15s, and the reaction pressure is 100Kpa. The gas phase product after the reaction is passed through a precooler to cool the phosphorus trichloride at -50°C and collect it, and then the subsequent gas phase product is cooled and collected at -150°C to obtain a phosphorus trifluoride liquid product with a product yield of 88% and a purity of 68%.

Claims

1. A method for preparing phosphorus trifluoride, which uses phosphorus trichloride as a raw material, first heats and vaporizes it, and then continuously prepares it by gas phase fluorination in a fixed bed reactor equipped with a supported fluorination agent, and the mixed gas after the reaction is precooled and the gas phase is cooled to collect the liquid phase phosphorus trifluoride product; the active component of the supported fluorination agent is one or more of cobalt fluoride, lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, silver fluoride, and lead fluoride; the carrier is activated carbon, activated aluminum oxide or a molecular sieve with a high silicon-aluminum ratio; the mass percentage of the active component of the supported fluorination agent to the carrier is 20%-40%: 60%-80%; the reaction temperature is 50-200°C; the reaction pressure is 0-100KPa; the residence time is 0.05-20s; the molecular sieve with a high silicon-aluminum ratio refers to a molecular sieve with a molar ratio of SiO2 / Al2O3≥8.

2. The method according to claim 1, characterized in that The reaction temperature is 100~150℃.

3. The method according to claim 1, characterized in that: The reaction pressure is 0~50KPa.

4. The method according to claim 1, characterized in that The residence time is 0.05~10s.

5. The method according to claim 1, characterized in that The vaporization temperature is 70~150℃.

6. The method according to claim 1, characterized in that The precooling temperature is -10~-50℃.

7. The method according to claim 1, characterized in that The cooling temperature is -180~-120℃.

8. The method according to claim 1, characterized in that The supported fluorination reagent was dried under nitrogen flow at 100-300°C before use.