CN1328159C - Equipment and technological process for preparing nitrogen trifluoride by using ammonia and hydrogen fluoride as raw material - Google Patents

Abstract

The invention relates to equipment and a process method for preparing nitrogen trifluoride with ammonia and hydrogen fluoride as raw materials. The ammonia in the ammonia storage tank first passes through an activated alumina adsorption tower to remove most of the sulfides, and then passes through an activated carbon adsorption tower to remove most of them. organic matter; then pass through a rectification tower to remove most of the dust and water and part of the remaining organic matter; then pass through a buffer tank; finally, ammonia, high-purity nitrogen and hydrogen fluoride after dehydration are passed into the reactor at a certain ratio and rate and A violent chemical reaction occurs in the reactor to generate ammonium fluoride, and the material in the reactor is finally a mixture of ammonium fluoride and hydrogen fluoride, thereby forming an electrolyte system of NH ₄ F-xHF, and then the mixture is input into conventional electrolysis tank, electrolytic preparation of nitrogen trifluoride. When the electrolytic raw material obtained by this method is used to produce nitrogen trifluoride, the current density of the electrolytic cell is high, the equipment is simple, the operability is strong, and the operation of the equipment is safe and stable. In particular, the cost of the raw material can be reduced to 30%- 50%.

Description

Equipment and process for preparing nitrogen trifluoride from ammonia and hydrogen fluoride

(1) Technical field

The invention belongs to a device and a process method for preparing nitrogen trifluoride by using ammonia and hydrogen fluoride as raw materials, and is suitable for synthesizing nitrogen trifluoride gas by using NH ₃ -xHF as raw materials.

(two), background technology

Nitrogen trifluoride is a colorless, odorless, stable gas at room temperature, with a boiling point of -129°C and a melting point of -208°C. In addition, it is a strong oxidizing agent. As an excellent plasma etching gas, nitrogen trifluoride has excellent etching rate and selectivity during ion etching, and does not leave any residue on the surface of the etched object, and is a very good cleaning agent. Therefore, it is used in semiconductors and The microelectronics industry has very broad prospects. In addition, it has also been widely used in the field of high-energy lasers. There are usually two methods for preparing nitrogen trifluoride: the chemical synthesis method represented by the preparation of nitrogen trifluoride using NH ₃ and F ₂ as raw materials, and the preparation of nitrogen trifluoride by using NH ₄ F-xHF as raw materials through an electrolytic cell. Nitrogen electrolysis. The advantage of the electrolysis method is that the production operation is relatively safe and stable, and the purity and yield of the gas are high. Therefore, this method is widely adopted by many companies, but its biggest disadvantage is that the cost of electrolysis raw materials is too high.

(3) Contents of the invention:

In order to overcome the shortcomings of the prior art, the present invention provides a kind of equipment and process method for preparing nitrogen trifluoride with ammonia and hydrogen fluoride as raw materials. When the electrolytic raw material obtained by this method is producing nitrogen trifluoride, the current density High, simple equipment, strong operability, safe and stable equipment operation, especially can reduce the cost of production raw materials to 30%-50% of the original.

The equipment for preparing nitrogen trifluoride from ammonia and hydrogen fluoride includes ammonia storage tank, activated alumina adsorption tower, activated carbon adsorption tower, rectification tower, buffer tank, reactor, electrolyzer, ammonia storage tank, hydrogen fluoride water removal tower, buffer Tanks, high-purity nitrogen storage tanks, characterized in that: the ammonia storage tank is connected to the activated alumina adsorption tower through pipelines, regulating valves and mass flow meters, the activated alumina adsorption tower is connected to the activated carbon adsorption tower through pipelines and regulating valves, and the activated carbon adsorption The tower is connected to the rectification tower through pipes and regulating valves, the rectification tower is connected to the buffer tank through pipes and regulating valves, the buffer tank is connected to the reactor through pipes and regulating valves; the hydrogen fluoride storage tank is connected to the reactor through pipes, regulating valves and mass flowmeters Potassium bifluoride water removal tower is connected, potassium bifluoride water removal tower is connected with buffer tank through pipeline and regulating valve, buffer tank is connected with reactor through pipeline and regulating valve; high-purity nitrogen storage tank is connected with reaction tank through pipeline, regulating valve and mass flow meter The reactor is connected to the electrolytic cell through pipelines and regulating valves, and the electrolytic cell is connected to subsequent equipment through pipelines and regulating valves. The inner cylinder of the reactor and all parts in contact with the raw materials are made of Monel alloy material , The piping and equipment between the liquid ammonia storage tank and the reactor shall not use copper materials.

The process for preparing nitrogen trifluoride using ammonia and hydrogen fluoride as raw materials is as follows: the present invention uses NH ₃ -xHF as raw material to first synthesize NH ₄ F-yHF liquid system through a series of processes, and uses this liquid as electrolyte to electrolyze to prepare trifluoride Nitrogen gas, characterized in that: the molar ratio of NH ₃ and HF in the reactor x=2.0-4, the reaction temperature is 70°C-180°C, the reaction pressure is 0.0MPa-0.6Mpa, and the final NH ₄ F-yHF system y=1.3-2.0, the liquid ammonia in the ammonia storage tank is vaporized and reaches the adsorption tower equipped with activated alumina through the valve and mass flow meter. The operating pressure in the adsorption tower is 0.3MPa-0.7Mpa, and the operating temperature is 0 ℃-80℃, in the adsorption tower, most of the sulfides in the ammonia gas are absorbed. After the ammonia gas flows out of the adsorption tower, it flows into the adsorption tower with activated carbon through the valve. The operating pressure of the adsorption tower is 0.3MPa-0.6 Mpa, the operating temperature is -20°C-70°C, in the adsorption tower, most of the organic matter in the raw ammonia gas is absorbed, the ammonia gas flows out of the adsorption tower and flows into the rectification tower through the control valve, the operation of the rectification tower The temperature is: top temperature -30°C-10°C, kettle temperature -20°C-50°C; the ammonia gas flows out of the rectification tower and flows into the reactor through the check valve and the buffer tank. In the reactor, the ammonia gas and the hydrogen fluoride storage The gaseous hydrogen fluoride in the tank and the high-purity nitrogen from the storage tank meet, and a violent chemical reaction occurs here to generate ammonium bifluoride. The present invention is equipped with a stirring device and a circulating water cooling device on the reactor. The material in the reactor is finally ammonium bifluoride A liquid mixture of hydrogen fluoride and hydrogen fluoride, which flows through a valve into a conventional electrolyzer, where it is electrolyzed to synthesize nitrogen trifluoride.

When the electrolytic raw material obtained by using the equipment and method is used to produce nitrogen trifluoride, the current density of the electrolytic cell is high, the equipment is simple, the operability is strong, the operation of the equipment is safe and stable, especially the cost of the raw material can be reduced to the original 30 %-50%.

(4) Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Accompanying drawing is schematic diagram of the present invention.

(5), specific implementation

As shown in the attached figure, 1—ammonia storage tank, 2, 5, 7, 13, 15, 16, 19, 25, 27, 30—control valve, 3, 26, 29—mass flow meter, 4— —Activated alumina adsorption tower, 6—activated carbon adsorption tower, 8—rectification tower, 9, 23—one-way valve, 10, 22—buffer tank, 11—stirrer motor, 12—reactor , 14—electrolyzer, 17—anode, 18—cathode, 21—circulating cooling water jacket, 22—buffer tank, 24—potassium bifluoride water removal tower.

The required equipment for realizing the technical purpose of the present invention includes: ammonia storage tank 1, activated alumina adsorption tower 4, activated carbon adsorption tower 6, rectification tower 8, buffer tank 10, reactor 12, electrolyzer 10, ammonia storage tank 20, Potassium bifluoride water removal tower 24, buffer tank 22, high-purity nitrogen storage tank 23. It is characterized in that: the ammonia storage tank 1 is connected to the activated alumina adsorption tower 4 through the pipeline, the regulating valve 2 and the mass flow meter 3, the activated alumina adsorption tower 4 is connected to the activated carbon adsorption tower 6 through the pipeline and the regulating valve 5, and the activated carbon adsorption tower 6 is connected to the rectification tower 8 through pipelines and regulating valves, the rectification tower 8 is connected to the buffer tank 10 through pipelines and regulating valves, and the buffer tank 10 is connected to the reactor 12 through pipelines and regulating valves; The valve 25, the regulating valve 27 and the mass flow meter 26 are connected to the potassium bifluoride dewatering tower 24, the potassium bifluoride dewatering tower 24 is connected to the buffer tank 22 through the pipeline and the regulating valve, and the buffer tank 22 is connected to the reactor 12 through the pipeline and the regulating valve ; The high-purity nitrogen storage tank 23 is connected to the reactor 12 through a pipeline, a regulating valve 30 and a mass flow meter 29 . The reactor 12 is connected to the electrolytic cell 14 through a pipeline and a regulating valve 19 , and the electrolytic cell is connected to subsequent equipment through a pipeline, a regulating valve 15 and a regulating valve 16 . The inner cylinder of the reactor 12 and all parts in contact with the raw materials are made of monel alloy material, and the pipeline and equipment between the liquid ammonia storage tank 1 and the reactor 12 shall not be made of copper material.

The invention uses NH ₃ -xHF as a raw material to electrolyze and synthesize nitrogen trifluoride gas through a series of processes. Because the price of liquid ammonia is far lower than the price of ammonium bifluoride equivalent to its purity, in addition, on the further purification problem, liquid ammonia is also much easier and more convenient than ammonium bifluoride, therefore, the technical purpose of the present invention (reduce raw material cost) A more perfect realization has been obtained. The molar ratio of _NH3 and HF raw material system in the reactor 12 is x=2.0-4, the reaction temperature is 70°C-180°C, and the reaction pressure is 0.0MPa-0.6Mpa. The specific reaction rate depends on the adsorption tower and rectification tower. It is determined by the processing capacity and the reaction capacity of the reactor.

When the liquid ammonia in the ammonia storage tank is vaporized and passes through the adsorption tower 4 equipped with activated alumina, since the activated alumina has a fairly good selectivity in the adsorption of NH3 _and sulfide, most of the sulfide in the ammonia gas The substances will be completely adsorbed here, the operating pressure in the adsorption tower 4 is 0.3MPa-0.7Mpa, and the operating temperature is 20°C-80°C.

When ammonia gas passes through the adsorption tower 6 with built-in activated carbon, because the selectivity of activated carbon to ammonia and organic matter is obvious, most of the organic matter in the ammonia gas is adsorbed here, and the operating pressure of the adsorption tower 6 is 0.3MPa-0.6Mpa. The temperature is 10°C-70°C.

When the ammonia gas passes through the rectification tower 8, since the boiling points of ammonia gas and water differ greatly, ammonia and water can be separated here. The operating temperature of the rectification tower 8 is: top temperature -30°C- 10°C, kettle temperature -20°C-50°C.

When hydrogen fluoride passes through potassium bifluoride water removal tower 24, water reacts with potassium bifluoride to generate hydrogen fluoride and potassium hydroxide, thereby, the water in hydrogen fluoride is relatively thoroughly removed, and the operating pressure of potassium bifluoride water removal tower 24 is 0.2MPa-0.6 Mpa, the operating temperature is 20°C-70°C.

After a series of treatments, the ammonia gas meets the gaseous hydrogen fluoride from the hydrogen fluoride storage tank and dehydrated by potassium bifluoride in the reactor, and a violent chemical reaction occurs here to form ammonium bifluoride. Because the reaction between ammonia and hydrogen fluoride is very violent, there is A large amount of heat of reaction is generated, therefore, the present invention configures a stirring device and a circulating water cooling device on the reactor to further control the reaction temperature.

Since we set the molar ratio of _NH3 to HF raw material system as x=2.0-4, the reaction temperature is 70°C-180°C, and the reaction pressure is 0.0MPa-0.6Mpa, therefore, the material in the reactor is finally liquid A mixture of ammonium bifluoride and hydrogen fluoride, the mixture flows into a conventional electrolytic cell through a valve, and is electrolyzed in the electrolytic cell to synthesize nitrogen trifluoride. Enter the follow-up section for further purification treatment.

The electrolytic solution prepared through the above process, in the process of normal electrolysis in the conventional electrolyzer 14, is analyzed from the outlet of the anode chamber, and the results are as shown in Table 1:

Table 1, the composition of the nitrogen trifluoride product gas that method of the present invention produces synthesis

Substance name O ₂ +N ₂ CF ₄ NF ₃ N _x F _y CO ₂ N ₂ O content 22.209% 0 73.707% 0.8% 1.2% 0.23%

Table 1 illustrates: in the nitrogen trifluoride product synthesized by the method of the present invention, O ₂ and _N The sum of the concentration and N ₂ O, N _x F _y etc. are slightly lower than the conventional method compared with the conventional method , CF ₄ was not detected here, and the concentration of NF ₃ was slightly higher compared with the traditional method.

Claims (4)

1. Equipment for preparing nitrogen trifluoride with ammonia and hydrogen fluoride as raw materials, including ammonia storage tanks (1, 20), activated alumina adsorption tower (4), activated carbon adsorption tower (6), rectification tower (8), buffer tank (10, 22), reactor (12), electrolyzer (14), potassium bifluoride water removal tower (24), high-purity nitrogen storage tank (23), it is characterized in that: ammonia storage tank (1) passes pipeline, The regulating valve (2) and the mass flow meter (3) are connected with the activated alumina adsorption tower (4), and the activated alumina adsorption tower (4) is connected with the activated carbon adsorption tower (6) through the pipeline and the regulating valve (5). The tower (6) is connected to the rectification tower (8) through a pipeline and a regulating valve, the rectification tower (8) is connected to the buffer tank (10) through a pipeline and a regulating valve, and the buffer tank (10) is connected to the reactor through a pipeline and a regulating valve (12) links to each other; Hydrogen fluoride storage tank (28) links to each other with potassium bifluoride dewatering tower (24) by pipeline, control valve (25,27) and mass flowmeter (26), and potassium bifluoride dewatering tower (24) is through pipeline and The regulating valve is connected with the buffer tank (22), and the buffer tank (22) is connected with the reactor (12) through the pipeline and the regulating valve; the high-purity nitrogen storage tank (23) is connected through the pipeline, the regulating valve (30) and the mass flow meter (29 ) is connected with the reactor (12), and the reactor (12) is connected with the electrolyzer (14) through the pipeline and the regulating valve (19), and the electrolyzer is connected with the follow-up equipment through the pipeline and the regulating valve (15,16), and the reaction The inner cylinder of the device (12) and all parts in contact with the raw materials are made of Monel alloy material, and the pipeline and equipment between the liquid ammonia storage tank (1) and the reactor (12) must not be made of copper material. 2. The equipment for preparing nitrogen trifluoride using ammonia and hydrogen fluoride as raw materials according to claim 1, characterized in that potassium bifluoride particles are installed in the potassium bifluoride water removal tower (24). 3. The process for preparing nitrogen trifluoride using ammonia and hydrogen fluoride as raw materials using the equipment described in claim 1, which is characterized in that: NH ₄ F-yHF liquid system is first synthesized through a series of processes using NH ₃ -xHF as raw material, And use this liquid as the electrolytic solution to prepare nitrogen trifluoride gas, the molar ratio x=2.0-4 of _NH3 and HF in the reactor (8), the reaction temperature is 70°C-180°C, and the reaction pressure is 0.0MPa- 0.6MPa, y=1.3-2.0 in the final NH ₄ F-yHF system, the liquid ammonia in the ammonia storage tank (1) is vaporized and then passes through the valve (2) and the mass flow meter (3) to reach the adsorbent with activated alumina Tower (4), the operating pressure in the adsorption tower (4) is 0.3MPa-0.7MPa, and the operating temperature is 0 ℃-80 ℃, and in the adsorption tower (4), most of the sulfides in the ammonia are adsorbed, After the ammonia gas flows out from the adsorption tower (4), it flows into the adsorption tower (6) with activated carbon inside through the valve (5). The operating pressure of the adsorption tower (6) is 0.3MPa-0.6MPa, and the operating temperature is -20°C-70 ℃, in the adsorption tower (6), most of the organic matter in the raw ammonia gas is adsorbed, and the ammonia gas flows into the rectification tower (8) through the control valve (7) after flowing out from the adsorption tower (6), and the rectification tower The operating temperature of (8) is: top temperature-30 DEG C-10 DEG C, still temperature-20 DEG C-50 DEG C; After the ammonia gas flows out of the rectifying tower (8), it flows through the check valve (9) and the buffer tank (10). Into the reactor (12), in the reactor (12), the ammonia meets the gaseous hydrogen fluoride from the hydrogen fluoride storage tank (28) and the high-purity nitrogen from the storage tank (31), and a violent chemical reaction occurs here to generate hydrogen fluoride Ammonium, the present invention is equipped with stirring device (11) and circulating water cooling device (21) on reactor (12), and the material in the reactor finally is the liquid mixture of ammonium bifluoride and hydrogen fluoride, and this mixture flows into through valve (19) Conventional electrolyzer (14), and nitrogen trifluoride is electrolytically synthesized in electrolyzer (14). 4. The process for preparing nitrogen trifluoride using ammonia and hydrogen fluoride as raw materials according to claim 2, characterized in that: the reactants in the reactor (12) are NH ₃ and HF.