Electrolytic tank for preparing nitrogen trifluoride

Abstract

The utility model relates to the technical field of electronic special gas, in particular to an electrolytic bath for preparing nitrogen trifluoride, which comprises an electrolytic bath, a cathode plate support rib is mounted in the electrolytic bath, a plurality of cathode plates are mounted on the inner wall of the cathode plate support rib at equal intervals, a horizontal grating is mounted on the inner wall of the front end of an ionic membrane, and a plurality of cathode plates are mounted on the inner wall of the front end of the ionic membrane. An overflow groove is formed in the upper portion of the inner wall of the electrolytic bath, and overflow observation openings are formed in the two sides of the overflow groove. Through cooperation of the anode plate, the electrolytic bath, the cathode plate, the ionic membrane and the inclined grating, the cathode assembly and the anode plate are completely immersed and suspended in electrolyte, laminar flow of the electrolyte is guaranteed through the horizontal grating at the front end of the ionic membrane, gas entrained in flowing of the electrolyte is isolated, and the stability of the electrolyte is improved. Meanwhile, the precipitation direction of solid impurities in the electrolysis process is controlled, so that the internal structure of the electrolytic bath for producing nitrogen trifluoride through the molten salt electrolysis method is effectively improved, and efficient nitrogen trifluoride production and product purity are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic special gases, in particular to an electrolytic cell for preparing nitrogen trifluoride. Background Art

[0002] In the microelectronics industry, nitrogen trifluoride is an excellent plasma etching gas. When etching silicon and silicon oxide materials, it does not pollute the circuit surface. Especially in the etching of integrated circuits with a thickness of less than 1.5μm, nitrogen trifluoride shows very excellent etching rate and selectivity. These characteristics of nitrogen trifluoride make it an essential material in the manufacturing process of contemporary semiconductor and liquid crystal display (LCD) industries. In recent years, with the widespread popularity and use of computers, the Internet, communications and radio consumer products, the global semiconductor and LCD industries have been showing a trend of rapid development in the past decade, and the demand for nitrogen trifluoride has also risen sharply. There are many methods for the industrial large-scale production of nitrogen trifluoride, including direct chemical method, molten salt method and electrolysis method. In the direct chemical method, gas-liquid reaction and gas-solid reaction are mostly used. However, in the production process, the gas-liquid reaction is difficult to control and is prone to corrosion. In the molten salt method, not only is it difficult to improve the conversion rate of fluorine gas, but also the process is complicated, with more purification and reaction devices, and it is also necessary to remove carbon impurities in molten salt, hydrogen fluoride and ammonia. If the carbon tetrafluoride in the fluorine gas is not completely removed, the nitrogen trifluoride gas will inevitably be contaminated by carbon tetrafluoride. In the electrolysis method, ammonium hydrogen fluoride salt is currently used as the electrolyte raw material for direct electrolysis preparation. The electrolysis method synthesizes nitrogen trifluoride gas in an electrolytic cell in one step, eliminating the electrolytic cell for preparing fluorine gas and the device for storing and purifying fluorine gas and complex subsequent reaction equipment. It is relatively simple in terms of preparation method and equipment. Compared with the chemical method, the most obvious advantage of the electrolysis method is that nitrogen trifluoride gas can be prepared with a higher yield in one step, and very little carbon tetrafluoride can be generated in the synthesis process, so it is easy to obtain high-purity nitrogen trifluoride gas.

[0003] CN104962946A discloses an electrolytic cell for preparing nitrogen trifluoride gas and its application, which is mainly composed of a diaphragm, an anode, a cathode, an anode chamber, a cathode chamber, an anode gas outlet, a cathode gas outlet, an anode nitrogen scavenging and electrolyte inlet, and a cathode nitrogen scavenging and electrolyte inlet. The diaphragm isolates the electrolytic cell into a completely independent anode chamber and cathode chamber; the anode chamber is composed of an anode, an anode gas outlet, and an anode nitrogen scavenging and electrolyte inlet, wherein one end of the anode is located in the anode chamber, and the other end is connected to a conductive rod, which extends out of the anode chamber and is connected to a power supply, and the anode gas outlet, the anode nitrogen scavenging and electrolyte inlet are respectively located on both sides of the anode, and the anode gas outlet is close to the diaphragm side; the cathode chamber is composed of a cathode, a cathode gas outlet, and a cathode nitrogen scavenging and electrolyte inlet, wherein one end of the cathode is located in the cathode chamber, and the other end is connected to a conductive rod, which extends out of the cathode chamber and is connected to a power supply, and the cathode gas outlet, the cathode nitrogen scavenging and electrolyte inlet are respectively located on both sides of the cathode, and the cathode gas outlet is close to the diaphragm side. The main technical principle is to use the treated Nafion membrane produced by DuPont in the diaphragm electrolyzer. The Nafion membrane itself is a fluorine resin membrane that can withstand the corrosion of high-temperature NH4F·xHF molten salt. The ionized ions in the NH4F·xHF molten salt are NH4 + , H + and F - NH4 + and F - At the anode, NF3 and N2 are generated. + H2 is generated at the cathode. The treated Nafion membrane divides the electrolyzer into completely independent cathode and anode chambers, which can pass cations H + At the same time, F- ions migrate to the anode chamber under the action of the electric field, thus forming a current loop. The electrolyzer uses an ion exchange membrane that is airtight but allows the electrolyte to flow, which can prevent the mixing of the cathode and cathode gases and reduce the distance between the anode and cathode, thereby stably producing NF3 gas.

[0004] Indeed, the ion exchange membrane greatly ensures the safety of production. However, as the electrolysis proceeds, the electrolyte concentration will decrease and the electrolyte will decrease. In order to avoid the decrease of electrolyte and the decrease of electrolysis efficiency due to the decrease of electrolyte concentration, new anhydrous electrolyte is added to the cathode chamber of the electrolytic cell through the electrolyte inlet to replenish the electrolyte, and then the electrolyte is circulated in the cathode chamber and the anode chamber through the ion exchange membrane, that is, the electrolyte is circulated through the ion exchange membrane diffusion method. In this way, the electrolyte flow rate is slow, thereby limiting the further efficient preparation of NF3 gas. Utility Model Content

[0005] The utility model aims to solve the problem that the efficiency of preparing NF3 gas is low, and thus an electrolytic cell for preparing nitrogen trifluoride is proposed to solve the problems caused by the above electrolysis method.

[0006] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0007] An anode plate, a cathode plate and an ion membrane are arranged in the electrolytic cell. The ion membrane is arranged between the anode plate and the cathode plate. The ion membrane is located on one side of the anode plate to form an anode chamber. The ion membrane is located on the cathode plate to form a cathode chamber. The electrolytic cell is also provided with a gas-liquid separator connected with the cathode chamber and the anode chamber. The electrolytic cell is provided with a liquid inlet, and the liquid inlet is used to input the electrolyte to be electrolyzed into the electrolytic cell. The electrolytic cell is also provided with an overflow trough, and the overflow trough is higher than the anode plate and the cathode plate, and the overflow trough is connected with the anode chamber. The overflow trough transports the electrolyte after the electrolysis reaction to the outside of the electrolytic cell.

[0008] Preferably, the plurality of cathode plates are spaced apart in the left-right direction, the anode plates are installed in sequence on the inner sides of adjacent cathode plates, the ion membranes are distributed on the inner sides of the anode plates and cathode plates, the gas-liquid separator is an inclined grid, the left and right ends of the inclined grid are respectively connected to two adjacent ion membranes, and the inclined grid covers the gaps between the front and rear ends of the two adjacent ion membranes.

[0009] Preferably, the inclined grid covers the gap before and after two adjacent ion membranes, and flat grids are installed before and after two adjacent ion membranes. The anode plate is located in the area enclosed by the ion membranes, the inclined grids and the flat grids, and this area is the anode chamber.

[0010] Preferably, a flat grid is disposed at the front end of two adjacent ion membranes, the liquid inlet is multiple and disposed at the front end of the electrolytic cell, and the liquid inlet is disposed in a one-to-one correspondence with the flat grid.

[0011] Preferably, the inclined grid is arranged at the rear ends of two adjacent ion membranes, the liquid inlets are multiple and arranged at the front end of the electrolytic cell, and the liquid inlets are arranged one-to-one with the flat grids. A sewage outlet is arranged at the rear side of the electrolytic cell near the flat grids.

[0012] Preferably, cathode plate support ribs are installed inside the electrolytic cell, a plurality of cathode plates are installed at intervals on the inner wall of the cathode plate support ribs, and the cathode chamber is formed by the interval area between the cathode plates and the inner wall of the electrolytic cell.

[0013] Preferably, the overflow trough is arranged above the inner wall of the electrolytic cell, and overflow observation ports are installed on both sides of the overflow trough; and a U-shaped liquid sealing tube is installed on the outer wall of the overflow observation port.

[0014] Preferably, cathode plate support ribs are installed inside the electrolytic cell, and multiple cathode plates are equidistantly installed on the inner wall of the cathode plate support ribs. A cell cover is detachably provided on the top of the electrolytic cell, and the upper ends of the anode plate and the cathode plate are fixedly connected to the cell cover of the electrolytic cell through nuts and insulating seals.

[0015] Preferably, both sides of the upper end of the cell cover of the electrolytic cell are fixedly connected with nitrogen trifluoride outlets; and the upper sides of the outer wall of the electrolytic cell are fixedly connected with hydrogen outlets.

[0016] Preferably, the electrolytic cell is an electrolytic cell for continuously producing nitrogen trifluoride, and the electrolytic cell also includes a circulation device and a filtering device, the overflow tank transports the electrolyte in the electrolytic cell to the filtering device, the filtering device filters the electrolyte, and the circulation device transports the filtered electrolyte to the electrolytic cell through the liquid inlet.

[0017] The utility model provides an electrolytic cell for preparing nitrogen trifluoride, which has the following beneficial effects:

[0018] The ion membrane between the cathode and the anode strictly isolates the gases produced by the two electrodes to prevent gas mixing. When power is turned on, the ions in the cathode chamber and the anode chamber on both sides of the ion membrane are exchanged through the ion membrane, and then nitrogen trifluoride and hydrogen are generated on the anode plate and the cathode plate respectively. The gas-liquid separators in the cathode chamber and the anode chamber circulate the electrolyte (an inclined grid can be used) to avoid gas mixing in the cathode chamber and the anode chamber while ensuring the flow and flow rate of the electrolyte. The liquid inlet inputs the electrolyte into the electrolytic cell to play a role in replenishment and recirculation. The overflow tank outputs the electrolyte from the electrolytic cell and maintains the liquid level so that the anode plate and the cathode plate are always in an immersed state. The anode plate, the electrolytic cell, the cathode plate, the ion membrane, the liquid inlet, the overflow tank and the gas-liquid separator cooperate with each other to achieve stable, efficient and continuous production and preparation of nitrogen trifluoride. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Electrolysis for preparing nitrogen trifluoride in the prior art;

[0020] Figure 2 This is a schematic diagram of the main structure of the utility model;

[0021] Figure 3 For this utility model Figure 2 The structural diagram of the middle A direction;

[0022] Figure 4 For this utility model Figure 2 Schematic diagram of the structure in the middle B direction;

[0023] Figure 5 For this utility model Figure 2The local schematic diagram at I in the middle;

[0024] Figure 6 It is a schematic diagram of the structure of the inclined grille.

[0025] In the figure: 1, liquid inlet, 2, flat grid, 3, nitrogen trifluoride outlet, 4, ion membrane, 5, cathode plate, 6, anode plate, 7, hydrogen outlet, 8, U-shaped liquid seal pipe, 9, inclined grid, 10, sewage outlet, 11, overflow observation port, 12, cathode plate support rib, 13, overflow trough, 14, electrolytic cell, 15, nut insulation seal, 16, hanger plate, 17, cathode chamber, 18, anode chamber. DETAILED DESCRIPTION

[0026] The utility model is further described below in conjunction with the accompanying drawings:

[0027] See attached Figure 2-4 In the present embodiment, an electrolytic cell for preparing nitrogen trifluoride includes an electrolytic cell 14, wherein a cathode plate support rib 12 is installed inside the electrolytic cell 14, and a plurality of cathode plates 5 are installed equidistantly on the inner wall of the cathode plate support rib 12, and anode plates 6 are installed on the inner sides of adjacent cathode plates 5, and the upper ends of the anode plates 6 and the cathode plates 5 are fixedly connected to the cell cover of the electrolytic cell 14 through nuts and insulating seals, and an ion membrane 4 is distributed on the inner sides of the anode plates 6 and the cathode plates 5, and a flat grid 2 is installed on the inner wall of the front end of the ion membrane 4, and An inclined grid 9 is installed on the inner wall of the rear end of the ion membrane 4, an overflow groove 13 is installed on the upper part of the inner wall of the electrolytic cell 14, and overflow observation ports 11 are installed on both sides of the overflow groove 13. A plurality of liquid inlets 1 are equidistantly installed at the front end of the electrolytic cell 14, a sewage outlet 10 is installed on the right side of the lower end of the electrolytic cell 14, and nitrogen trifluoride outlets 3 are fixedly connected to both sides of the upper end of the cell cover of the electrolytic cell 14, a U-shaped liquid sealing tube 8 is installed on the outer wall of the overflow observation port 11 on the right side, and hydrogen outlets 7 are fixedly connected to the upper part of both sides of the outer wall of the electrolytic cell 14.

[0028] In a preferred embodiment, the electrolytic cell 14 is an electrolytic cell 14 for continuously producing nitrogen trifluoride, and the electrolytic cell 14 further includes a circulation device (not shown in the figure) and a filtering device (not shown in the figure), and the circulation device and the filtering device can adopt existing technologies and are not limited here. The overflow tank 13 transports the electrolyte in the electrolytic cell 14 to the filtering device, the filtering device filters the electrolyte, and the circulation device transports the filtered electrolyte to the electrolytic cell 14 through the liquid inlet 1.

[0029] In a preferred embodiment, the cathode plate 5 and the anode plate 6 are both fixed to the cover of the electrolytic cell 14 by means of a hanger plate 16 and a nut insulating seal 15 .

[0030] 1. The plates are used as anodes and cathodes, the cathode and anode are arranged in parallel, and the electrolytic cell 14 is made into a removable top cover to facilitate the removal of the plates and the ion membrane 4;

[0031] 2. The anode plate 6 is a nickel anode plate, which is connected to the anode column through a copper hanger, and the anode column is fixed to the cover of the electrolytic cell 14 by nuts and insulating seals;

[0032] 3. The cathode assembly is a plate cathode, the cathode plate 5 is composed of supporting ribs to form a cathode assembly, the cathode assembly is connected to the cathode column through a hanger plate, and the cathode column is fixed to the cover of the electrolytic cell 14 by a nut insulation seal;

[0033] 4. The distance between the anode plate 6 and the oblique grid on the electrolyte outlet side is 200-500mm to prevent the electrolyte flow from carrying the gas generated by electrolysis to the cathode outside the grid;

[0034] 5. The cathode assembly and the anode plate 6 are completely immersed and suspended in the electrolyte, and the distance between the cathode plate 5 and the anode plate 6 is less than 80 mm; the gas generated by the two electrodes is strictly isolated by the ion membrane between the cathode and the anode to prevent gas mixing;

[0035] 6. A nitrogen trifluoride outlet 3 is provided at the top of the electrolytic cell 14, and a hydrogen outlet 7 is provided at the side wall of the electrolytic cell 14;

[0036] 7. The electrolyte enters the electrolytic cell 14 through multiple nozzles for uniform feeding, and the flat grid 2 at the front end of the ion membrane 4 is used to ensure the laminar flow of the electrolyte, and its flow rate is controlled to achieve temperature stability during the electrolysis process;

[0037] 8. An inclined grid 9 is used at the rear end of the ion membrane 4. The gas in the cathode chamber 17 and the anode chamber 18 on both sides of the inclined grid 9 has a lower density, and the generated gas floats upward in the cathode chamber 17 and the anode chamber 18. The inclined grid 9 isolates the gas entrained in the flow of the electrolyte and controls the precipitation direction of the solid impurities in the electrolysis process. The sewage outlet 10 is set at the precipitated solid impurities for discharging them.

[0038] 9. At the bottom of the electrolytic cell 14, an electrolytic cell drain port 10 is arranged outside the inclined grid 9 to regularly drain solid impurities generated during the electrolysis process.

[0039] 10. The electrolyte outlet is arranged at the periphery of the anode, and an electrolyte overflow tank 13 is arranged at a certain height. Both ends of the overflow pipe extend to the outside of the electrolytic tank 14. Sight glass assemblies are arranged at both ends to facilitate observation of the electrolyte level and flow state, and a U-shaped liquid seal tube 8 is arranged at one end to prevent gas from entering the downstream electrolyte system.

[0040] Through the coordination among the anode plate 6, the electrolytic cell 14, the cathode plate 5, the ion membrane 4, the flat grid 2 and the inclined grid 9, the cathode assembly and the anode plate 6 are completely immersed and suspended in the electrolyte, the distance between the cathode plate 5 and the anode plate 6 is less than 80 mm, the gas generated by the two electrodes is strictly isolated by the ion membrane 4 between the cathode and the anode to prevent gas mixing, the electrolyte enters the electrolytic cell 14 as a multi-tube uniform feed, the flat grid 2 at the front end of the ion membrane 4 is used to ensure the laminar flow of the electrolyte, and its flow rate is controlled to achieve temperature stability during the electrolysis process, and the inclined grid 9 is used at the rear end of the ion membrane 4 to isolate the gas entrained in the electrolyte flow, and at the same time control the precipitation direction of solid impurities during the electrolysis process, so that the internal structure of the electrolytic cell for producing nitrogen trifluoride by molten salt electrolysis is effectively improved, and the high efficiency of nitrogen trifluoride production and the purity of the product are achieved.

[0041] Working principle:

[0042] When the electrolytic cell for preparing nitrogen trifluoride is needed, the electrolyte outlet is arranged outside the anode plate 6 in this case, and an electrolyte overflow tank 13 is arranged at a certain height. Both ends of the overflow tank 13 extend outside the electrolytic cell 14. Sightglass assemblies are arranged at both ends to facilitate observation of the electrolyte level and flow state, and a U-shaped liquid seal tube 8 is arranged at one end to prevent gas from entering the downstream electrolyte system. When in use, the cathode assembly and the anode plate 6 are completely immersed and suspended in the electrolyte, and the distance between the cathode plate 5 and the anode plate 6 is less than 80 mm. Through the ion membrane 4 between the cathode and the anode, The gases generated by the two electrodes are strictly isolated to prevent gas mixing. The electrolyte enters the electrolytic cell 14 through multiple nozzles for uniform feeding. The flat grid 2 at the front end of the ion membrane 4 is used to ensure the laminar flow of the electrolyte, and its flow rate is controlled to achieve temperature stability during the electrolysis process. An inclined grid 9 is used at the rear end of the ion membrane 4 to isolate the gas entrained in the electrolyte flow and control the precipitation direction of solid impurities during the electrolysis process. In this way, the internal structure of the electrolytic cell for producing nitrogen trifluoride by molten salt electrolysis is effectively improved, and the high efficiency of nitrogen trifluoride production and the purity of the product are achieved.

[0043] Although the present invention has been shown and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein within the scope of the claims.

Claims

1. An electrolytic cell for preparing nitrogen trifluoride, characterized in that: The electrolytic cell (14) is provided with an anode plate (6), a cathode plate (5) and an ion membrane (4). The ion membrane (4) is provided between the anode plate (6) and the cathode plate (5). The ion membrane (4) is located on one side of the anode plate (6) to form an anode chamber. The ion membrane (4) is located on the cathode plate (5) to form a cathode chamber. The electrolytic cell is also provided with a gas-liquid separator connected to the cathode chamber and the anode chamber. The electrolytic cell (14) is provided with a liquid inlet (1). The liquid inlet (1) is used to input an electrolyte to be electrolyzed into the electrolytic cell (14). The electrolytic cell (14) is also provided with an overflow trough (13). The overflow trough (13) is higher than the anode plate (6) and the cathode plate (5). The overflow trough (13) is connected to the anode chamber. The overflow trough transports the electrolyte after the electrolysis reaction to the outside of the electrolytic cell.

2. The electrolytic cell for preparing nitrogen trifluoride according to claim 1, characterized in that: A plurality of cathode plates (5) are arranged at intervals in the left-right direction, the anode plates (6) are sequentially installed on the inner sides of adjacent cathode plates (5), the ion membranes (4) are distributed on the inner sides of the anode plates (6) and the cathode plates (5), the gas-liquid separator is an inclined grid (9), the left and right ends of the inclined grid (9) are respectively connected to two adjacent ion membranes (4), and the inclined grid (9) covers the gaps between the front and rear ends of the two adjacent ion membranes.

3. The electrolytic cell for preparing nitrogen trifluoride according to claim 2, characterized in that: The inclined grid (9) covers a gap at a position in front and behind two adjacent ion membranes (4), and a flat grid (2) is installed in front and behind the two adjacent ion membranes (4). The anode plate (6) is located in an area enclosed by the ion membranes (4), the inclined grid (9) and the flat grid (2), and the area is the anode chamber.

4. The electrolytic cell for preparing nitrogen trifluoride according to claim 2, characterized in that: A flat grid (2) is arranged at the front ends of two adjacent ion membranes. The liquid inlets (1) are multiple and arranged at the front ends of the electrolytic cells (14). The liquid inlets (1) and the flat grids (2) are arranged in a one-to-one correspondence.

5. The electrolytic cell for preparing nitrogen trifluoride according to claim 2, characterized in that: The electrolytic cell (14) is provided with cathode plate support ribs (12), and a plurality of cathode plates (5) are installed at intervals on the inner wall of the cathode plate support ribs (12), and the cathode chamber is formed in the interval area between the cathode plates (5) and the inner wall of the electrolytic cell (14).

6. The electrolytic cell for preparing nitrogen trifluoride according to claim 2, characterized in that: The overflow trough (13) is arranged above the inner wall of the electrolytic cell (14), and overflow observation ports (11) are installed on both sides of the overflow trough (13); and a U-shaped liquid sealing pipe (8) is installed on the outer wall of the overflow observation port (11).

7. The electrolytic cell for preparing nitrogen trifluoride according to claim 2, characterized in that: The electrolytic cell (14) is provided with cathode plate support ribs (12) inside, and a plurality of cathode plates (5) are equidistantly installed on the inner wall of the cathode plate support ribs (12). A detachable cell cover is provided on the top of the electrolytic cell (14), and the upper ends of the anode plate (6) and the cathode plate (5) are fixedly connected to the cell cover of the electrolytic cell (14) via nuts and insulating seals.

8. The electrolytic cell for preparing nitrogen trifluoride according to claim 1, characterized in that: Both sides of the upper end of the tank cover of the electrolytic tank (14) are fixedly connected to nitrogen trifluoride outlets (3); and both sides of the upper part of the outer wall of the electrolytic tank (14) are fixedly connected to hydrogen outlets (7).

9. The electrolytic cell for preparing nitrogen trifluoride according to claim 1, characterized in that: The electrolytic cell (14) is an electrolytic cell (14) for continuously producing nitrogen trifluoride. The electrolytic cell (14) further comprises a circulation device and a filtering device. The overflow tank (13) transports the electrolyte in the electrolytic cell (14) to the filtering device. The filtering device filters the electrolyte. The circulation device transports the filtered electrolyte into the electrolytic cell (14) through the liquid inlet (1).

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