A process for co-producing tungsten halide and carbon tetrafluoride

Abstract

The present invention relates to a process for the co-production of tungsten halides and carbon tetrafluoride. Tungsten carbide or a mixture of tungsten carbide and carbon is added to a reactor, chlorine trifluoride gas is introduced into the reactor, the reactor temperature is controlled at 340-400°C, the reaction pressure is 0.01-0.15 MPa, and a reaction is carried out to obtain a mixture comprising tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride, and carbon tetrafluoride. After the reaction is completed, the reaction products are sequentially collected through a four-stage cold trap, with the first stage collecting tungsten hexachloride, the second stage collecting tungsten pentachloride, the third stage collecting tungsten hexafluoride, and the fourth stage collecting carbon tetrafluoride. The present invention has relatively mild reaction conditions, a reaction temperature below 400°C, higher safety, low raw material cost, high atom economy, higher safety, lower energy consumption, no by-products, and great economic benefits and development prospects. It meets the production requirements of chemical enterprises for safety, environmental protection, high efficiency, and circular economy.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorine chemical industry, and in particular to a process for co-producing tungsten halide and carbon tetrafluoride. Background Art

[0002] Tungsten hexachloride is a bluish-purple black crystal. It is used in vapor deposition tungsten plating, producing single-crystal tungsten filaments, conductive coatings on glass surfaces, and as a catalyst for olefin polymerization. It is primarily used for tungsten purification and organic synthesis. It is also widely used in new materials applications such as the automotive and glass industries. It is typically produced by reacting metallic tungsten powder with dry chlorine gas at 500-600°C.

[0003] Tungsten pentachloride is a shimmering dark green crystal. As a rare compound with a tungsten-to-chlorine ratio of 1:5, it exhibits unique characteristics of tungsten valence change and chlorine atomic decomposition. Its valence change pattern and the released chlorine free radicals offer the advantages of highly controllable timing and location. It is considered a promising material for future semiconductor, solar energy, catalysis, and advanced technologies. Its conventional preparation method involves heating tungsten hexachloride at 410-425°C in a quartz tube and introducing hydrogen for reduction.

[0004] Tungsten hexafluoride, a colorless gas or pale yellow liquid, and its solid form is a deliquescent white crystal. It is primarily used in integrated circuit manufacturing. Specifically, in the chemical vapor deposition process, it is deposited and stacked to form conductive films and metal wiring materials for large-scale integrated circuits. Currently, there are two main methods for industrially synthesizing tungsten hexafluoride: one is the direct reaction of tungsten powder with fluorine gas at 300-400°C; the other is the reaction of tungsten powder with nitrogen trifluoride at 300-500°C, where the nitrogen trifluoride decomposes to produce fluorine free radicals. These fluorine free radicals then react with tungsten powder to synthesize tungsten hexafluoride. This method requires a high moisture content in the nitrogen trifluoride raw material, which directly affects the purity of the tungsten hexafluoride product.

[0005] Carbon tetrafluoride (CF4) is a colorless, non-flammable, and easily compressed gas. It is primarily used in plasma etching processes for various integrated circuits and is also used as a laser gas and refrigerant. It is synthesized primarily by the direct reaction of fluorine gas and carbon.

[0006] All four products have important uses in the integrated circuit industry. The synthesis temperature of tungsten hexachloride is above 500°C, and the reaction temperature of tungsten pentachloride is above 400°C, and H2 reduction is involved, which poses a high safety risk. The synthesis of tungsten hexafluoride requires high purity of the fluorination raw materials. Nitrogen trifluoride is used as the raw material for synthesis, and N2 tail gas is produced, resulting in a low atomic utilization rate. The synthetic tungsten raw materials for the three tungsten halides all require high-purity tungsten powder, resulting in high raw material costs. External heating is required in the initial stage of the tungsten halide synthesis reaction, which consumes energy, and the temperature of the heating reactor wall can reach above 500°C, causing serious corrosion to the reactor by the raw gas. Summary of the Invention

[0007] In view of the above background technology, the present invention provides a process for co-producing tungsten halide and carbon tetrafluoride to solve the problems of high reaction temperature and high safety risks in the existing process.

[0008] The object of the present invention is to provide a process for the co-production of tungsten halide and carbon tetrafluoride. The specific technical solution is as follows:

[0009] A process for co-producing tungsten halide and carbon tetrafluoride comprises the following steps:

[0010] S1, a reaction step of adding tungsten carbide or a mixture of tungsten carbide and carbon into a reactor, then introducing chlorine trifluoride gas into the reactor, controlling the temperature of the reactor to 340-400° C. and the reaction pressure to 0.01-0.15 MPa, and reacting to obtain a mixture comprising tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride;

[0011] S2, collection process: after the reaction is completed, the reaction products are sequentially collected through four-stage cold traps, with the first stage collecting tungsten hexachloride, the second stage collecting tungsten pentachloride, the third stage collecting tungsten hexafluoride, and the fourth stage collecting carbon tetrafluoride.

[0012] Preferably, in step S1, the ratio of carbon in the mixture of tungsten carbide and carbon is 0-10 wt%, the residence time of chlorine trifluoride in the reactor is 10-120 s, and the particle size of tungsten carbide and carbon powder is less than or equal to 20 μm.

[0013] Preferably, the charcoal in step S1 is one of wood charcoal powder, fruit shell charcoal powder, coal charcoal powder and petroleum charcoal powder.

[0014] Preferably, the purity of chlorine trifluoride in step S1 is between 70.0% and 99.9%, and the remaining components are one or more of F2, Cl2 or ClF.

[0015] Preferably, the reactor in step S1 is a horizontal reactor, and the material of the reactor is monel or pure nickel.

[0016] Preferably, in step S2, the temperature of the first-stage collection cold trap is 280-320° C., and the collected product is liquid crude tungsten hexachloride; the temperature of the second-stage collection cold trap is 215-240° C., and the collected product is solid crude tungsten pentachloride; the temperature of the third-stage collection cold trap is -30--10° C., and the collected product is solid crude tungsten hexafluoride; the collection temperature of the fourth-stage cold trap is -180--150° C., and the collected product is liquid crude carbon tetrafluoride.

[0017] Preferably, the mixture generated by the reaction passes through the third-stage collection cold trap, and then goes through alkali washing, low-temperature water removal and adsorption processes before entering the fourth-stage collection process.

[0018] Preferably, the product collected in step S2 is purified, and the purification method of the products collected in the first and second stages is cooling and vacuuming to obtain high-purity tungsten hexachloride and tungsten pentachloride; the purification method of the product collected in the third stage is atmospheric distillation combined with adsorption to obtain high-purity tungsten hexafluoride, and the purification method of the product collected in the fourth stage is pressure distillation to obtain a high-purity carbon tetrafluoride product.

[0019] The process of the present invention for co-producing tungsten halide and carbon tetrafluoride has the following beneficial effects:

[0020] 1. Chlorine trifluoride is used as the oxidizing raw material, and tungsten carbide and carbon powder are used as the starting raw materials, which replaces the heating step in the initial stage of the reaction, reduces the corrosion of the reactor wall by the raw gas, and reduces energy consumption.

[0021] 2. Tungsten carbide as raw material greatly reduces the cost of synthesizing tungsten halide compared to high-purity tungsten powder.

[0022] 3. The present invention has a low requirement on the purity of the oxidation raw material chlorine trifluoride. The fluorine gas, chlorine gas and part of the chlorine monofluoride that are not completely reacted in the chlorine trifluoride synthesis experiment can all participate in the reaction, and the synthetic products can all be purified into high-purity products, with high atom economy.

[0023] 4. The reaction conditions of the present invention are relatively mild, the reaction temperature is lower than 400°C, and the safety is higher. The technology has low raw material cost, high atom economy, higher safety, lower energy consumption, and no by-products. It has great economic benefits and development prospects; it meets the production requirements of chemical companies for safety, environmental protection, high efficiency, and circular economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic flow diagram of the production process of the present invention. DETAILED DESCRIPTION

[0025] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0026] Example 1

[0027] like Figure 1 Shown is a schematic flow chart of the production process of the present invention.

[0028] Pure tungsten carbide is added into the reactor, the particle size of the tungsten carbide is less than or equal to 20 μm, and the purity of the tungsten carbide is greater than 99.9%. The reactor is a horizontal reactor made of monel material. Chlorine trifluoride gas with a purity of 99.9% is introduced into the reactor for reaction. The residence time of chlorine trifluoride in the reactor is 120 s. The temperature of the reactor is controlled at 340° C. The reaction pressure is 0.01 MPa. The reaction obtains a mixture containing tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride.

[0029] After the reaction is completed, the products are collected in stages using cold traps. The temperature of the first-stage cold trap is 280°C to collect the liquid crude tungsten hexachloride, the temperature of the second-stage cold trap is 215°C to collect the solid crude tungsten pentachloride, the temperature of the third-stage cold trap is -10°C to collect the solid crude tungsten hexafluoride, and the temperature of the fourth-stage cold trap is -150°C to collect the liquid crude carbon tetrafluoride. An alkali washing tower, a low-temperature water removal tower and an adsorption tower are connected between the fourth-stage cold trap and the third-stage cold trap. The purpose of the alkali washing tower is to remove acidic gases such as chlorine trifluoride and tungsten hexafluoride in carbon tetrafluoride, and the purpose of the adsorption tower is to further remove moisture brought out of the alkali washing tower.

[0030] The products collected by the four-stage cold trap are purified to obtain high-purity tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride. The purification method is a conventional method in the art, and the products are purified by adjusting different purification conditions.

[0031] The products collected in the first and second stages are purified by cooling and vacuuming. The crude tungsten hexachloride is cooled and vacuumed to remove light impurities such as tungsten pentachloride and carbon tetrafluoride, resulting in a high-purity tungsten hexachloride product with a purity of 99.8%. The tungsten hexachloride and tungsten pentachloride are cooled and vacuumed to remove light impurities such as tungsten hexafluoride and carbon tetrafluoride, resulting in a high-purity tungsten pentachloride product with a purity of 99.9%. The crude tungsten hexafluoride is purified by atmospheric distillation combined with adsorption to remove trace impurities of oxygen, nitrogen and hydrogen fluoride, resulting in a high-purity tungsten hexafluoride product with a purity of 99.995%. The crude carbon tetrafluoride is purified by pressurized distillation to remove trace impurities of oxygen, nitrogen and hydrogen fluoride, resulting in a high-purity carbon tetrafluoride product with a purity of 99.992%.

[0032] Example 2

[0033] A mixture of tungsten carbide and 2 wt% carbon powder is added to a reactor, wherein the purity of the tungsten carbide is greater than 99.9%, the particle size of the tungsten carbide and the carbon powder is 20 μm, the carbon powder is wooden carbon powder with a purity of 99%, and the reactor is made of pure nickel. Chlorine trifluoride gas with a purity of 90.0% is introduced into the reactor for reaction. The residence time of chlorine trifluoride in the reactor is 60 s. The temperature of the reactor is controlled at 360° C. and the reaction pressure is 0.05 MPa. The reaction obtains a mixture containing tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride.

[0034] After the reaction is completed, the products are collected in stages using cold traps. The temperature of the first-stage cold trap is 290°C to collect the liquid crude tungsten hexachloride, the temperature of the second-stage cold trap is 220°C to collect the solid crude tungsten pentachloride, the temperature of the third-stage cold trap is -15°C to collect the solid crude tungsten hexafluoride, and the temperature of the fourth-stage cold trap is -160°C to collect the liquid crude carbon tetrafluoride. An alkali washing tower, a low-temperature water removal tower and an adsorption tower are connected between the fourth-stage cold trap and the third-stage cold trap.

[0035] The products collected by the four-stage cold trap are purified to obtain high-purity tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride;

[0036] The products collected in the first and second stages are purified by cooling and vacuuming. The crude tungsten hexachloride is cooled and vacuumed to remove impurities, obtaining a high-purity tungsten hexachloride product with a purity of 99.7%. The tungsten hexachloride and tungsten pentachloride are cooled and vacuumed to remove impurities, obtaining a high-purity tungsten pentachloride product with a purity of 99.7%. The crude tungsten hexafluoride is purified by atmospheric distillation combined with adsorption to remove impurities, obtaining a high-purity tungsten hexafluoride product with a purity of 99.994%. The crude carbon tetrafluoride is purified by pressurized distillation to remove impurities, obtaining a high-purity carbon tetrafluoride product with a purity of 99.994%.

[0037] Example 3

[0038] A mixture of tungsten carbide and 5wt% carbon powder is added to a reactor, the purity of tungsten carbide is greater than 99.9%, the particle size of tungsten carbide and carbon powder is 20μm, the carbon powder is coal-based carbon powder with a purity of 99%, and the reactor is made of monel. Chlorine trifluoride gas with a purity of 80.0% is introduced into the reactor for reaction. The residence time of chlorine trifluoride in the reactor is 30s. The temperature of the reactor is controlled at 380°C and the reaction pressure is 0.10MPa. The reaction obtains a mixture containing tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride.

[0039] After the reaction is completed, the products are collected in stages using cold traps. The temperature of the first-stage cold trap is 310°C to collect the liquid crude tungsten hexachloride, the temperature of the second-stage cold trap is 230°C to collect the solid crude tungsten pentachloride, the temperature of the third-stage cold trap is -20°C to collect the solid crude tungsten hexafluoride, and the temperature of the fourth-stage cold trap is -170°C to collect the liquid crude carbon tetrafluoride. An alkali washing tower, a low-temperature water removal tower and an adsorption tower are connected between the fourth-stage cold trap and the third-stage cold trap.

[0040] The products collected by the four-stage cold trap are purified to obtain high-purity tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride;

[0041] The products collected in the first and second stages are purified by cooling and vacuuming. The crude tungsten hexachloride is cooled and vacuumed to remove impurities, obtaining a high-purity tungsten hexachloride product with a purity of 99.7%. The tungsten hexachloride and tungsten pentachloride are cooled and vacuumed to remove impurities, obtaining a high-purity tungsten pentachloride product with a purity of 99.6%. The crude tungsten hexafluoride is purified by atmospheric distillation combined with adsorption to remove impurities, obtaining a high-purity tungsten hexafluoride product with a purity of 99.996%. The crude carbon tetrafluoride is purified by pressurized distillation to remove impurities, obtaining a high-purity carbon tetrafluoride product with a purity of 99.997%.

[0042] Example 4

[0043] A mixture of tungsten carbide and 10wt% carbon powder is added to a reactor, the purity of tungsten carbide is greater than 99.9%, the particle size of tungsten carbide and carbon powder is 20μm, the carbon powder is 99% pure carbon powder made from fruit shells, the reactor is made of pure nickel, and 70.0% pure chlorine trifluoride gas is introduced into the reactor for reaction. The residence time of chlorine trifluoride in the reactor is 10s, the temperature of the reactor is controlled at 400°C, and the reaction pressure is 0.15MPa. The reaction obtains a mixture containing tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride.

[0044] After the reaction is completed, the products are collected in stages using cold traps. The temperature of the first-stage cold trap is 320°C to collect the liquid crude tungsten hexachloride, the temperature of the second-stage cold trap is 240°C to collect the solid crude tungsten pentachloride, the temperature of the third-stage cold trap is -30°C to collect the solid crude tungsten hexafluoride, and the temperature of the fourth-stage cold trap is -180°C to collect the liquid crude carbon tetrafluoride. An alkali washing tower, a low-temperature water removal tower and an adsorption tower are connected between the fourth-stage cold trap and the third-stage cold trap.

[0045] The products collected by the four-stage cold trap are purified to obtain high-purity tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride;

[0046] The products collected in the first and second stages are purified by cooling and vacuuming. The crude tungsten hexachloride is cooled and vacuumed to remove impurities, obtaining a high-purity tungsten hexachloride product with a purity of 99.8%; the tungsten hexachloride and tungsten pentachloride are cooled and vacuumed to remove impurities, obtaining a high-purity tungsten pentachloride product with a purity of 99.8%; the crude tungsten hexafluoride is purified by atmospheric distillation combined with adsorption to remove impurities, obtaining a high-purity tungsten hexafluoride product with a purity of 99.994%; the crude carbon tetrafluoride is purified by pressurized distillation to remove impurities, obtaining a high-purity carbon tetrafluoride product with a purity of 99.994%.

[0047] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A process for the co-production of tungsten halide and carbon tetrafluoride, characterized in that: The following steps are involved: S1, a reaction process, adding tungsten carbide or a mixture of tungsten carbide and carbon into a reactor, then introducing chlorine trifluoride gas into the reactor, controlling the temperature of the reactor to 340-400° C. and the reaction pressure to 0.01-0.15 MPa, and reacting to obtain a mixture comprising tungsten hexachloride, tungsten pentachloride, tungsten hexafluoride and carbon tetrafluoride; S2, collection process: after the reaction is completed, the reaction products are sequentially collected through four-stage cold traps, with the first stage collecting tungsten hexachloride, the second stage collecting tungsten pentachloride, the third stage collecting tungsten hexafluoride, and the fourth stage collecting carbon tetrafluoride.

2. The process for co-producing tungsten halide and carbon tetrafluoride according to claim 1, characterized in that: In step S1, the ratio of carbon in the mixture of tungsten carbide and carbon is 2-10 wt %, the residence time of chlorine trifluoride in the reactor is 10-120 s, and the particle size of tungsten carbide and carbon powder is less than or equal to 20 μm.

3. The process for co-producing tungsten halide and carbon tetrafluoride according to claim 1, characterized in that: In step S1, the charcoal is one of wood charcoal powder, fruit shell charcoal powder, coal charcoal powder and petroleum charcoal powder.

4. The process for co-producing tungsten halide and carbon tetrafluoride according to claim 1, characterized in that: The purity of chlorine trifluoride in step S1 is between 70.0% and 99.9%, and the remaining components are one or more of F2, Cl2 or ClF.

5. The process for co-producing tungsten halide and carbon tetrafluoride according to claim 1, characterized in that: The reactor in step S1 is a horizontal reactor, and the material of the reactor is one of monel or pure nickel.

6. The process for co-producing tungsten halide and carbon tetrafluoride according to claim 1, characterized in that: In step S2, the temperature of the first-stage collection cold trap is 280~320°C, and the collected product is liquid crude tungsten hexachloride; the temperature of the second-stage collection cold trap is 215~240°C, and the collected product is solid crude tungsten pentachloride; the temperature of the third-stage collection cold trap is -30~-10°C, and the collected product is solid crude tungsten hexafluoride; the collection temperature of the fourth-stage cold trap is -180~-150°C, and the collected product is liquid crude carbon tetrafluoride.

7. The process for co-producing tungsten halide and carbon tetrafluoride according to claim 1, characterized in that: The mixture generated by the reaction passes through the third-stage collection cold trap, and then goes through alkaline washing, low-temperature water removal and adsorption processes before entering the fourth-stage collection process.

8. The process for co-producing tungsten halide and carbon tetrafluoride according to claim 1, characterized in that: The product collected in step S2 is purified. The purification method for the products collected in the first and second stages is cooling and vacuuming to obtain high-purity tungsten hexachloride and tungsten pentachloride. The purification method for the product collected in the third stage is atmospheric distillation combined with adsorption to obtain high-purity tungsten hexafluoride. The purification method for the product collected in the fourth stage is pressure distillation to obtain a high-purity carbon tetrafluoride product.

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