Method and device for preparing high-purity molybdenum hexafluoride

Abstract

The invention discloses a method and a device for preparing high-purity molybdenum hexafluoride. The preparation method comprises the following steps: (1) preheating nitrogen trifluoride; (2) carrying out contact reaction on nitrogen trifluoride and metal molybdenum in the reactor; (3) settling the gas product through a settling tank to remove particulate matters, and collecting crude molybdenum hexafluoride gas; (4) introducing the molybdenum hexafluoride crude gas into an adsorption tower, and adsorbing to remove hydrogen fluoride; and (5) collecting a molybdenum hexafluoride finished product, and repeatedly heating, freezing and vacuumizing to remove low-boiling-point impurities to obtain the molybdenum hexafluoride product with the purity not lower than 99.996%. A nitrogen trifluoride steel cylinder, a mass flow controller, a nitrogen trifluoride preheater, a first reactor, a second reactor, a third reactor, a settling tank, a crude product storage tank, an adsorption tower and a finished product storage tank are sequentially connected, wherein the third reactor is formed by connecting three reaction containers in series; the adsorption tower is formed by connecting two stages of towers in series, and the adsorption tower is filled with sodium fluoride.

Description

Technical Field

[0001] The invention relates to electronic chemicals, and in particular to a method and a device for preparing high-purity molybdenum hexafluoride gas. Background Art

[0002] Molybdenum (Mo) has the advantages of high thermal conductivity, high electrical conductivity, and low thermal expansion coefficient, and is widely used in the electronic information industry and nuclear power sources. In the electronic information industry, molybdenum is mainly used as a target material for sputtering thin films, which usually requires molybdenum to have a high purity. Traditional molybdenum metallurgical technology can only purify molybdenum to 4N, and cannot reach 5N or above. Chemical vapor deposition (CVD) technology must be used. Molybdenum hexafluoride (MoF 6 ) is the only fluoride of Mo that can exist stably. It has low melting and boiling points and is suitable for chemical vapor deposition processes. Molybdenum hexafluoride (MoF6) is used in the microelectronics industry for chemical vapor deposition of molybdenum silicide or molybdenum to make low-resistance, high-melting-point interconnects. It can also be used as a strong fluorinating agent, film-forming material, ion doping, and isotope separation of molybdenum. Molybdenum has better conductivity than tungsten and can be used as a substitute for tungsten hexafluoride in logic chips with a process of more than 3nm and 3D NAND memories with more than 256 layers. At present, there are several methods for preparing tungsten hexafluoride: Patent document CN103449525A discloses a method for preparing molybdenum hexafluoride, which uses fluorine gas to react with molybdenum after purification to prepare molybdenum hexafluoride. Fluorine gas is active in nature and contains a large amount of hydrogen fluoride. The reaction conditions are difficult to control, the equipment requirements are high, and the product purity is low; Patent document CN111918839A discloses a method and a manufacturing device for molybdenum hexafluoride, which uses fluorine gas and molybdenum powder to continue to react, and then the molybdenum hexafluoride is automatically removed to separate the gas and liquid phases. However, the reactor preparation process is complicated and not easy to industrialize, and the product purity is 99.9347%; Patent document CN115 974157A discloses a method for preparing and purifying molybdenum hexafluoride, which uses nitrogen trifluoride to crack and then react with molybdenum powder, and collects and evacuates through a low-temperature collector to prepare a molybdenum hexafluoride product with a purity of 99.5%. This method does not solve the problem of insufficient reaction of fluorine gas and molybdenum powder to produce intermediates, which leads to system blockage, and the product purity is relatively low, only 99.5%; Patent document CN116920441A discloses a purification device and purification method for molybdenum hexafluoride, which prepares high-purity molybdenum hexafluoride from crude molybdenum hexafluoride by adsorption and distillation. The preparation method is complicated and the purification cost is relatively high. Summary of the invention

[0003] The first technical problem to be solved by the present invention is to provide a method for preparing high-purity molybdenum hexafluoride in view of the shortcomings of the prior art. The preparation method adopts nitrogen trifluoride and molybdenum powder to react to prepare molybdenum hexafluoride. The method is simple, the product purity is high, and it can be applied industrially.

[0004] The second technical problem to be solved by the present invention is to provide a device used in the preparation method.

[0005] In order to solve the above-mentioned first technical problem, the technical solution adopted by the present invention is: a method for preparing high-purity molybdenum hexafluoride, comprising the following steps: (1) preheating nitrogen trifluoride; (2) nitrogen trifluoride and metal molybdenum are contacted and reacted in a reactor; (3) the gas product is precipitated in a sedimentation tank to remove particulate matter and collect molybdenum hexafluoride crude gas; (4) the molybdenum hexafluoride crude gas is passed into an adsorption tower to remove hydrogen fluoride by adsorption; (5) the molybdenum hexafluoride product is collected, and the low-boiling impurities are removed by repeated heating, freezing and vacuuming to obtain a molybdenum hexafluoride product with a purity of not less than 99.996%. The operation method of the present invention is simple, safe and economical, and has a high conversion rate and purity.

[0006] A method for preparing high-purity molybdenum hexafluoride further comprises the following steps: (1) Pass nitrogen trifluoride into a preheater and preheat it to 200~350℃; (2) Adding metallic molybdenum powder to the first reactor and the second reactor respectively, and leaving the third reactor empty, the third reactor is composed of three reaction vessels connected in series; first preheating all the reactors to 200-350°C, replacing the air in the reactors with nitrogen, and then evacuating to -0.095-0.085MPa; introducing preheated nitrogen trifluoride into the first reactor, the nitrogen trifluoride and the molybdenum powder are contacted and reacted, and molybdenum hexafluoride is generated through the three-stage reactor; (3) The reacted gas is passed into a settling tank to remove particulate impurities. The temperature of the settling tank is 50-80°C. (4) The crude molybdenum hexafluoride gaseous product coming out of the settling tank is frozen and collected in a crude product storage tank, and the temperature of the crude product storage tank is maintained at -60~-20℃; (5) Raise the temperature of the crude product storage tank to -5~-15℃, discharge the light component impurities in the crude product storage tank to the alkali washing tower for washing until the pressure of the crude product storage tank is 5~20Kpa; continue to raise the temperature of the crude product storage tank to 30~60℃, and remove HF and part of WF from the molybdenum hexafluoride crude gas through the adsorption tower. 6 After that, it passes through the filter and enters the finished product storage tank for collection, and the temperature of the finished product storage tank is maintained at -40~-10℃; the adsorption tower is filled with sodium fluoride; (6) Evacuate the finished product storage tank and reduce the pressure to -70~-30Kpa to remove the uncondensed light component impurities in the system; then heat the finished product storage tank to 40~80℃ and the pressure to 100~200Kpa; then cool the finished product storage tank to below 0℃, the material becomes solid, and vent the light component impurities in the finished product storage tank until the finished product storage tank is 5~20Kpa; repeatedly heat up, cool down and vent to obtain a molybdenum hexafluoride product with a purity of not less than 99.996%.

[0007] In step (1) of the method of the present invention, the feeding rate of nitrogen trifluoride is generally 2-20 L / min, and the pressure is generally 0.2-0.6 MPa.

[0008] In step (2) of the method of the present invention, the metallic molybdenum is preferably in powder form, with a particle size of preferably 5 to 50 μm and a purity of not less than 99.95%.

[0009] In step (2) of the method of the present invention, the temperature of the first reactor and the second reactor after the introduction of nitrogen trifluoride is 400-500°C, and the temperature of the third reactor is 300-400°C.

[0010] In step (5) of the method of the present invention, the diameter of the sodium fluoride in the adsorption tower is preferably 20-30 mm, and the gas flow rate is preferably 1-5 L / min.

[0011] In step (6) of the method of the present invention, the preheater, the first reactor, the second reactor and the third reactor are made of nickel or monel alloy, and the other equipment are all made of stainless steel.

[0012] In order to solve the above-mentioned second technical problem, the present invention provides a device used in the preparation method: a nitrogen trifluoride cylinder, a mass flow controller, a nitrogen trifluoride preheater, a first reactor, a second reactor, a third reactor, a settling tank, a crude product storage tank, an adsorption tower, and a finished product storage tank are connected in sequence, wherein the third reactor is composed of three reaction containers connected in series; the adsorption tower is composed of two-stage towers connected in series, and sodium fluoride is filled in the adsorption tower.

[0013] Compared with the prior art, the present invention has the following advantages: The invention provides a new route for preparing molybdenum hexafluoride. Crude molybdenum hexafluoride is prepared by reacting nitrogen trifluoride with molybdenum powder. A large amount of low-boiling impurities are removed by preliminary venting. Hydrogen fluoride is removed by adsorption with sodium fluoride. Finally, the low-boiling impurities are removed by repeated heating and cooling to obtain a molybdenum hexafluoride product with a purity of more than 99.996%. The method is simple, the purification difficulty is low, the product purity is high, and industrial application can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attached Figure 1 The present invention is a flow chart of the preparation method of molybdenum hexafluoride.

[0015] Among them: 1—nitrogen trifluoride cylinder; 2—mass flow controller; 3—nitrogen trifluoride preheater; 4—first reactor; 5—second reactor; 6—third reactor; 7—sedimentation tank; 8—crude product storage tank; 9—adsorption tower; 10—finished product storage tank. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with specific implementation methods, wherein the methods described are conventional methods unless otherwise specified, and the present invention is not limited by the specific implementations disclosed below.

[0017] like Figure 1 As shown, a device for preparing high-purity molybdenum hexafluoride: a nitrogen trifluoride cylinder, a mass flow controller, a nitrogen trifluoride preheater, a first reactor, a second reactor, a third reactor, a settling tank, a crude product storage tank, a sodium fluoride adsorption tower, and a finished product storage tank are connected in sequence, wherein the third reactor is composed of three reaction vessels connected in series; the adsorption tower is composed of two-stage towers connected in series, and the adsorption tower is filled with sodium fluoride.

[0018] Example 1

[0019] A method for preparing high-purity molybdenum hexafluoride comprises the following steps: Step (1) After the nitrogen trifluoride cylinder is fed through a mass flow controller at a rate of 5 L / min and a pressure of 0.2-0.25 MPa, it is passed into a preheater and preheated at 200-250° C.; Step (2) adding metal molybdenum powder from the feed port into the first reactor and the second reactor, the metal molybdenum powder is in powder form, has a particle size of 5 μm, and a purity of 99.95%, and the third reactor is vacant. Before nitrogen trifluoride is passed through, all reactors are preheated to 250° C., the air in the reactor is replaced with nitrogen, and then vacuumed to -0.089 MPa, and then the preheated nitrogen trifluoride is slowly passed through. The nitrogen trifluoride and the molybdenum powder are contacted and reacted at 350° C. in the first reactor and the second reactor, and the temperature of the third reactor is 300° C. to generate molybdenum hexafluoride; Step (3) The settling tank is heated to 50-60° C. The prepared molybdenum hexafluoride enters the settling tank from the rear end of the third reactor to remove particulate impurities; Step (4) The crude molybdenum hexafluoride gaseous product coming out of the settling tank is collected in a crude product storage tank by freezing, and the temperature of the crude product storage tank is maintained at -60~-50°C and the pressure is 15~20KPa; Step (5) raising the temperature of the crude product storage tank to -10~-5°C, discharging the light component impurities in the crude product storage tank to the alkali washing tower for washing until the pressure reaches 10~15KPa; continuing to raise the temperature of the crude product storage tank to 30~40°C, and passing the molybdenum hexafluoride crude gas through the sodium fluoride adsorption tower to remove HF and part of WF 6 After that, it passes through the filter and enters the finished product storage tank for collection, keeping the temperature of the finished product storage tank at -40~-30℃; Step (6) evacuate the finished product storage tank to -50 KPa to remove uncondensed light component impurities in the system; heat the finished product storage tank to a temperature of 40-50°C and a pressure of 50-100 KPa, then continue to cool it to -25-15°C, and vent the light component impurities in the finished product storage tank to 5-10 KPa; repeat heating and cooling and venting 5 times to obtain a molybdenum hexafluoride product with a purity of 99.997%. The various indicators are shown in Table 1.

[0020] Table 1 Product indicators of Example 1

[0021] Example 2 A method for preparing high-purity molybdenum hexafluoride comprises the following steps: Step (1) After the nitrogen trifluoride cylinder is fed through a mass flow controller at a rate of 10 L / min and a pressure of 0.3-0.4 MPa, it is passed into a preheater and preheated at 300-350° C.; Step (2) adding metal molybdenum powder into the first reactor and the second reactor from the feeding port, the metal molybdenum powder is in powder form, has a particle size of 20 μm, and a purity of 99.95%, and the third reactor is vacant. Before nitrogen trifluoride is passed through, all reactors are preheated to 300-350° C., the reactors are replaced with nitrogen, and then evacuated to -0.095 MPa, and then the preheated nitrogen trifluoride is slowly passed through. The nitrogen trifluoride and the molybdenum powder are contacted and reacted at 350-400° C. in the first reactor and the second reactor, and the temperature of the third reactor is 300-350° C. to generate molybdenum hexafluoride; Step (3) The settling tank is heated to 65-75°C, and the prepared molybdenum hexafluoride enters the settling tank from the rear end of the reactor to remove particulate impurities; Step (4) The crude molybdenum hexafluoride gaseous product coming out of the settling tank is collected in a crude product storage tank by freezing, and the temperature of the crude product storage tank is maintained at -30 to -20°C and the pressure is maintained at 25 to 30 KPa; Step (5) raising the temperature of the crude product storage tank to -10~-5°C, discharging the light component impurities in the crude product storage tank to the alkali washing tower for washing until the pressure reaches 15~20KPa; continuing to raise the temperature of the crude product storage tank to 40~45°C, and passing the molybdenum hexafluoride crude gas through the sodium fluoride adsorption tower to remove HF and part of WF 6 After that, it passes through the filter and enters the finished product storage tank for collection, and the temperature of the finished product storage tank is kept at -30~-20℃; Step (6) evacuate the finished product storage tank to -40 KPa to remove uncondensed light component impurities in the system; heat the finished product storage tank to a temperature of 50-60°C and a pressure of 100-150 KPa, then continue to cool it to -15--20°C, and vent the light component impurities in the finished product storage tank to 10-15 KPa; repeat heating, cooling and venting 5 times to obtain a molybdenum hexafluoride product with a purity of 99.997%. The various indicators are shown in Table 2.

[0022] Table 2 Product indicators of Example 2

[0023] Example 3 A method for preparing high-purity molybdenum hexafluoride comprises the following steps: Step (1) After the nitrogen trifluoride cylinder is fed through a mass flow controller at a rate of 20 L / min and a pressure of 0.5-0.6 MPa, it is passed into a preheater and preheated at 300-350° C.; Step (2) adding metal molybdenum powder from the feed port into the first reactor and the second reactor, the metal molybdenum powder is in powder form, has a particle size of 50 μm, and a purity of 99.95%, and the third reactor is vacant. Before nitrogen trifluoride is passed through, all reactors are preheated to 300-350° C., the reactors are replaced with nitrogen, and then evacuated to -0.090 MPa, and then the preheated nitrogen trifluoride is slowly passed through. The nitrogen trifluoride and the molybdenum powder are contacted and reacted at 400-450° C. in the first reactor and the second reactor, and the temperature of the third reactor is 350-400° C. to generate molybdenum hexafluoride; Step (3) The settling tank is heated to 70-80°C, and the prepared molybdenum hexafluoride enters the settling tank from the rear end of the reactor to remove particulate impurities; Step (4) The crude molybdenum hexafluoride gaseous product coming out of the settling tank is collected in a crude product storage tank by freezing, and the temperature of the crude product storage tank is maintained at -50 to -40°C and the pressure is 20 to 25 KPa; Step (5) raising the temperature of the crude product storage tank to -10~-5°C, discharging the light component impurities in the crude product storage tank to the alkali washing tower for washing until the pressure reaches 10~15KPa; continuing to raise the temperature of the crude product storage tank to 50~60°C, passing the molybdenum hexafluoride crude gas through a sodium fluoride adsorption column to remove HF and part of WF 6 After that, it passes through the filter and enters the finished product storage tank for collection, keeping the temperature of the finished product storage tank at -40~-30℃; Step (6) evacuate the finished product storage tank to -50 KPa to remove uncondensed light component impurities in the system; heat the finished product storage tank to a temperature of 65~75°C and a pressure of 150~200 KPa, then continue to cool to -30~-20°C, and vent the light component impurities in the finished product storage tank to 15~20 KPa; repeatedly heat and cool and vent 5 times to obtain a molybdenum hexafluoride product with a purity of 99.996%. The various indicators are shown in Table 3.

[0024] Table 3 Product indicators of Example 3

Claims

1. A method for preparing high-purity molybdenum hexafluoride, comprising the following steps: (1) Preheating nitrogen trifluoride; (2) Nitrogen trifluoride and metallic molybdenum are contacted and reacted in a reactor; (3) The gas product is precipitated in a settling tank to remove particulate matter and collect the molybdenum hexafluoride crude gas; (4) The molybdenum hexafluoride crude gas is passed into an adsorption tower to remove hydrogen fluoride by adsorption; (5) The molybdenum hexafluoride product is collected, repeatedly heated, frozen and vacuumed to remove low-boiling impurities, and a molybdenum hexafluoride product with a purity of not less than 99.996% is obtained.

2. The method according to claim 1, characterized in that The following steps are involved: (1) Pass nitrogen trifluoride into a preheater and preheat it to 200~350℃; (2) Adding metallic molybdenum powder to the first reactor and the second reactor respectively, and leaving the third reactor empty, the third reactor is composed of three reaction vessels connected in series; first preheating all the reactors to 200-350°C, replacing the air in the reactors with nitrogen, and then evacuating to -0.095-0.085MPa; introducing preheated nitrogen trifluoride into the first reactor, the nitrogen trifluoride and the molybdenum powder are contacted and reacted, and molybdenum hexafluoride is generated through the three-stage reactor; (3) The reacted gas is passed into a settling tank to remove particulate impurities. The temperature of the settling tank is 50-80°C. (4) The crude molybdenum hexafluoride gaseous product coming out of the settling tank is frozen and collected in a crude product storage tank, and the temperature of the crude product storage tank is maintained at -60~-20℃; (5) Raise the temperature of the crude product storage tank to -5~-15℃, and discharge the light component impurities in the crude product storage tank to the alkali washing tower for washing until the pressure of the crude product storage tank is 5~20Kpa; Continue to increase the crude product storage tank temperature to 30~60℃, and pass the molybdenum hexafluoride crude gas through the adsorption tower to remove HF and part of WF6, and then pass through the filter into the finished product storage tank for collection, and keep the finished product storage tank temperature at -40~-10℃; (6) Evacuate the finished product storage tank and reduce the pressure to -70~-30Kpa to remove the uncondensed light component impurities in the system; then heat the finished product storage tank to 40~80℃ and the pressure to 100~200Kpa; then cool the finished product storage tank to below 0℃, the material becomes solid, and vent the light component impurities in the finished product storage tank until the finished product storage tank is 5~20Kpa; repeatedly heat up, cool down and vent to obtain a molybdenum hexafluoride product with a purity of not less than 99.996%.

3. The method according to claim 2, characterized in that In step (1), the feeding rate of nitrogen trifluoride is 2-20 L / min, and the pressure is 0.2-0.6 MPa.

4. The method according to claim 2, characterized in that: In step (2), the metallic molybdenum is in powder form with a particle size of 5-50 μm and a purity of not less than 99.95%.

5. The method according to claim 2, characterized in that: In step (2), the temperature of the first reactor and the second reactor after the introduction of nitrogen trifluoride is 400-500°C, and the temperature of the third reactor is 300-400°C.

6. The method according to claim 2, characterized in that In step (5), the adsorption tower is filled with sodium fluoride, has a diameter of 20-30 mm, and a gas flow rate of 1-5 L / min.

7. The method according to claim 2, characterized in that In step (6), the preheater, the first reactor, the second reactor, and the third reactor are made of nickel or monel alloy, and the other equipment are made of stainless steel.

8. A device for use in the method for preparing high-purity molybdenum hexafluoride according to any one of claims 1 to 7, wherein a nitrogen trifluoride cylinder, a mass flow controller, a nitrogen trifluoride preheater, a first reactor, a second reactor, a third reactor, a settling tank, a crude product storage tank, an adsorption tower, and a finished product storage tank are connected in sequence, wherein the third reactor is composed of three reaction vessels connected in series; the adsorption tower is composed of two towers connected in series, and sodium fluoride is filled in the adsorption tower.

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