Device and process for green synthesis of high-purity nitric acid

Abstract

The invention discloses a device and a process for green synthesis of high-purity nitric acid. A first reaction gas component and a second reaction gas component in the device are both communicated with a gas coupler, an outlet pipeline of the gas coupler is communicated with a thermal plasma reactor, an outlet pipeline of the thermal plasma reactor is communicated with a reaction tower, and a bottom outlet of the reaction tower is communicated with a liquid storage tank; wherein the first reaction gas component comprises a high-purity oxygen pipeline and a cold plasma reactor, high-purity oxygen enters the cold plasma reactor through the high-purity oxygen pipeline, and ozone-containing gas obtained after ozone is generated from part of oxygen in the cold plasma reactor enters the gas coupler; the second reaction gas component comprises a high-purity nitrogen pipeline, and high-purity nitrogen enters the gas coupler through the high-purity nitrogen pipeline. According to the method, high-purity nitrogen, oxygen and water are taken as raw materials, and the ultra-high-purity (electronic-grade) nitric acid is directly and greenly synthesized by adopting renewable electric power to drive plasma.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to an apparatus and process for the green synthesis of high-purity nitric acid. Background Technology

[0002] Ultra-high purity nitric acid is mainly used in high-tech fields such as semiconductor manufacturing, display panel production, and photovoltaic cell processing. Its high purity makes it an indispensable cleaning and etching material in the electronics industry.

[0003] The main processes for preparing ultra-high purity nitric acid include sub-boiling distillation and continuous distillation. Currently, the most common method is to distill industrial concentrated nitric acid (95% or higher) to obtain a nitric acid product with a purity of about 95%, then dilute it with ultrapure water to the required concentration of about 70%. Using this as raw material, further distillation yields electronic-grade nitric acid.

[0004] Patent CN103072962A discloses a method for preparing electronic-grade nitric acid, which uses a 0.1μm-1μm polytetrafluoroethylene nanofiltration membrane filter to precisely filter low-purity nitric acid to generate electronic-grade nitric acid.

[0005] Patent CN116490458A provides a method for synthesizing nitrogen oxides by heating a gas mixture to a temperature of at least 2300 K in a thermal reactor at a pressure of 10-100 bar to form a gas mixture comprising nitrogen oxides, and also provides a method for producing nitric acid.

[0006] Patent CN118949440A discloses a high-purity nitric acid purification system that can continuously purify low-concentration nitric acid. At the same time, it can generate a low pressure in the evaporator, thereby improving the evaporation effect of nitric acid and effectively increasing the production efficiency of high-purity nitric acid.

[0007] Patent CN120154923A provides a purification device for producing electronic-grade industrial nitric acid. The heated barrel is divided into a heating zone and a feeding zone by an arc-shaped tube, so that the acid vapor on the inner wall of the arc-shaped tube exchanges heat with the reagent-grade nitric acid in the feeding zone. The heat released during condensation is absorbed by the reagent-grade nitric acid inside the feeding zone.

[0008] Patent CN118987661B discloses a preparation device and method for preparing electronic-grade nitric acid from raw materials. By setting up a homogenizing device, the stirring blade, rotating ring, spiral blade, preparation device body, and heating device work together to drive the spiral blade to stir the nitric acid solution and transport it to the inside of the filter cylinder. The stirring action of the spiral blade can effectively stir the heated nitric acid solution evenly, ensuring a uniform temperature distribution of the nitric acid solution, which in turn helps in the purification of nitric acid.

[0009] In summary, the main technological innovations in the preparation of electronic-grade nitric acid are concentrated in nitric acid purification technology and equipment, while there is a lack of green synthesis technologies and equipment for electronic-grade nitric acid. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a green apparatus and process for synthesizing high-purity nitric acid. The high-purity nitric acid obtained by this invention is ultra-high purity electronic-grade nitric acid. This invention uses high-purity nitrogen, oxygen, and water as raw materials, and employs renewable electricity to drive plasma for the direct and green synthesis of ultra-high purity (electronic-grade) nitric acid.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A green apparatus for synthesizing high-purity nitric acid includes a first reactive gas component, a second reactive gas component, a gas coupler, a thermal plasma reactor, a reaction tower, and a storage tank; wherein the first reactive gas component and the second reactive gas component are both connected to the gas coupler, the outlet pipe of the gas coupler is connected to the thermal plasma reactor, the outlet pipe of the thermal plasma reactor is connected to the reaction tower, and the bottom outlet of the reaction tower is connected to the storage tank;

[0013] The first reaction gas component includes a high-purity oxygen pipeline and a cold plasma reactor. The high-purity oxygen enters the cold plasma reactor through the high-purity oxygen pipeline. In the cold plasma reactor, some of the oxygen is converted into ozone, and the resulting ozone-containing gas enters the gas coupler.

[0014] The second reaction gas component includes a high-purity nitrogen pipeline, through which the high-purity nitrogen enters the gas coupler.

[0015] Gas control components are provided on the high-purity oxygen pipeline, the high-purity nitrogen pipeline, and the outlet pipeline of the gas coupler. The gas control components include control valves and mass flow controllers.

[0016] The tail gas outlet of the reaction tower is connected to the gas coupler via a gas circulation pump.

[0017] A dehydrator is installed on the pipeline connecting the tail gas outlet of the reaction tower to the gas coupler.

[0018] The cold plasma reactor is a dielectric barrier discharge plasma reactor; the voltage of the dielectric barrier discharge plasma reactor is 5-25 kV and the frequency is less than 100 kHz.

[0019] The thermal plasma reactor is a plasma reactor using metal electrodes, and the voltage of the thermal plasma reactor is 5-25 kV and the frequency is less than 100 kHz.

[0020] A green process for synthesizing high-purity nitric acid, employing the aforementioned apparatus for green synthesis of high-purity nitric acid, includes the following steps:

[0021] S1: To generate ozone from high-purity oxygen in a cold plasma reactor;

[0022] S2: Mix the ozone-containing mixed gas obtained in step S1 with high-purity nitrogen gas;

[0023] S3: The mixed reaction gas obtained in step S2 is used to generate nitrogen oxides in a thermal plasma reactor;

[0024] S4: High-purity nitric acid can be generated by dissolving the mixed product gas containing nitrogen oxides obtained in step S3 in water.

[0025] In step S2, the volume percentage concentration of ozone in the mixed reaction gas is 5%-10%.

[0026] In step S3, the flow rate of the mixed reaction gas entering the thermal plasma reactor is 100 ml / min - 1 L / min.

[0027] In step S1, the gas temperature of the cold plasma reactor is 350K-450K, and in step S3, the gas temperature of the hot plasma reactor is 1500K-2000K.

[0028] The beneficial effects of this invention are as follows:

[0029] (1) This invention uses high-purity nitrogen, high-purity oxygen and water as raw materials and adopts a new technology for direct and green synthesis of ultra-high purity (electronic grade) nitric acid by using renewable electricity to drive plasma. This avoids catalysts and additional heating measures, and the generated nitric acid has high purity. The overall process has less pollution and low carbon emissions.

[0030] (2) The present invention proposes a scheme to synthesize part of ozone from high-purity oxygen through plasma in advance, and then to convert high-purity nitrogen and oxygen containing ozone through plasma, which significantly improves the concentration of nitrogen dioxide in nitrogen oxide products and the synthesis rate of high-purity nitric acid. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the apparatus for the green synthesis of high-purity nitric acid according to the present invention.

[0032] The attached figures are labeled as follows: 1-High-purity oxygen; 2-High-purity nitrogen; 3-Control valve; 4-Mass flow controller; 5-Cold plasma reactor; 6-First high-voltage power supply; 7-Gas coupler; 8-Hot plasma reactor; 9-Second high-voltage power supply; 10-Reaction tower; 11-Storage tank; 12-High-purity water storage tank; 13-Atomizing water sprayer; 14-Dehydrator; 15-Gas circulation pump. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] See Figure 1 This invention provides a green apparatus for synthesizing high-purity nitric acid, comprising a first reactive gas component, a second reactive gas component, a gas coupler 7, a thermal plasma reactor 8, a reaction tower 10, and a storage tank 11; wherein the first and second reactive gas components are both connected to the gas coupler 7, the outlet pipe of the gas coupler 7 is connected to the thermal plasma reactor 8, the outlet pipe of the thermal plasma reactor 8 is connected to the reaction tower 10, and the bottom outlet of the reaction tower 10 is connected to the storage tank 11.

[0035] The first reaction gas component includes a high-purity oxygen pipeline and a cold plasma reactor 5. High-purity oxygen 1 enters the cold plasma reactor 5 through the high-purity oxygen pipeline. After some of the oxygen in the cold plasma reactor 5 is converted into ozone, the resulting ozone-containing gas enters the gas coupler 7.

[0036] The second reaction gas component includes a high-purity nitrogen pipeline, through which the high-purity nitrogen 2 enters the gas coupler 7.

[0037] See Figure 1 The cold plasma reactor 5 is connected to the first high-voltage power supply 6, and the hot plasma reactor 8 is connected to the second high-voltage power supply 9. The first high-voltage power supply 6 and the second high-voltage power supply 9 can be DC, AC, pulse, or other high-voltage power supplies.

[0038] The reaction tower 10 is equipped with an atomizing water sprayer 13, which is connected to a high-purity water storage tank 12. The atomizing water sprayer 13 sprays atomized high-purity water, which comes into countercurrent contact with the mixed product gas containing nitrogen oxides entering the reaction tower 10 to generate ultra-high-purity nitric acid. The ultra-high-purity nitric acid flows out from the bottom of the reaction tower 10 and into the storage tank 11.

[0039] Preferred, see Figure 1 Gas control components are provided on the high-purity oxygen pipeline, the high-purity nitrogen pipeline, and the outlet pipeline of the gas coupler 7. These gas control components include a control valve 3 and a mass flow controller 4. In this embodiment, the control valve 3 is preferably a ball valve.

[0040] The high-purity oxygen pipeline is connected to high-purity oxygen 1, and the high-purity nitrogen pipeline is connected to high-purity nitrogen 2.

[0041] Preferably, the exhaust gas outlet of the reaction tower 10 is connected to the gas coupler 7 via a gas circulation pump 15. The purpose is to reuse the exhaust gas of the reaction tower 10, eliminating the need for an exhaust gas treatment device and enabling the reuse of nitrogen oxides in the exhaust gas.

[0042] Furthermore, in order to prevent water vapor in the exhaust gas from affecting the thermal plasma reactor 8, a dehydrator 14 is installed on the pipeline connecting the exhaust gas outlet of the reaction tower 10 to the gas coupler 7.

[0043] In one embodiment, the cold plasma reactor 5 is a dielectric barrier discharge plasma reactor with a coaxial circular or parallel plate electrode structure; the voltage of the dielectric barrier discharge plasma reactor is 5-25 kV, and the frequency is less than 100 kHz. In this embodiment, the dielectric barrier discharge plasma reactor uses a high-purity quartz plate covering a metal electrode, and the two metal electrodes are respectively connected to a high-voltage power supply and ground.

[0044] In one embodiment, the thermal plasma reactor 8 is a plasma reactor employing a metal electrode discharge electrode structure. The voltage of the thermal plasma reactor 8 is 5-25 kV, and the frequency is less than 100 kHz. The thermal plasma reactor 8 uses high-temperature resistant metals as metal electrode materials, including titanium alloys, nickel-based high-temperature alloys, tungsten, molybdenum, niobium, hafnium, etc., preferably alloy electrodes. The two metal electrodes are respectively connected to a high-voltage power supply and grounded.

[0045] More preferably, the thermal plasma reactor 8 is a plasma reactor employing electrode structures such as spark discharge or sliding arc discharge.

[0046] Based on the above-mentioned green synthesis of high-purity nitric acid apparatus, the present invention also provides a green synthesis process for high-purity nitric acid. Specifically, the process of the present invention involves first converting high-purity oxygen 1 into partial ozone through cold plasma, then converting a mixture of high-purity nitrogen gas containing ozone and oxygen gas into nitrogen oxides through plasma, and finally generating ultra-high-purity nitric acid by spraying with high-purity water and collecting and storing it.

[0047] It includes the following steps:

[0048] S1: High-purity oxygen 1 is used to generate ozone in the cold plasma reactor 5; high-purity oxygen 1 is introduced into the cold plasma reactor 5 through control valve 3 and mass flow controller 4, wherein the purity of high-purity oxygen 1 is not less than 99.999%; the first high-voltage power supply 6 is turned on, so that the cold plasma reactor 5 starts to operate and generate ozone, and the ozone-containing mixed gas is introduced into the gas coupler 7. The ozone concentration generated by the cold plasma reactor 5 can be adjusted by controlling power supply parameters (mainly voltage amplitude, frequency, etc.), plasma reactor parameters (mainly electrode gap distance), and gas flow rate.

[0049] S2: Mix the ozone-containing mixed gas obtained in step S1 with high-purity nitrogen 2; introduce high-purity nitrogen 2 into gas coupler 7 through gas control component, mix the ozone-containing mixed gas generated in step S1 with high-purity nitrogen in gas coupler 7, and then introduce it into thermal plasma reactor 8 through gas control system, wherein the purity of high-purity nitrogen 2 is not less than 99.999%.

[0050] S3: The mixed reaction gas obtained in step S2 is used to generate nitrogen oxides in the thermal plasma reactor 8; the second high-voltage power supply 9 is turned on so that the thermal plasma reactor 8 starts to run and generates nitrogen oxides;

[0051] S4: High-purity nitric acid can be generated by dissolving the mixed product gas containing nitrogen oxides obtained in step S3 in water. The mixed gas containing nitrogen oxides is passed into reaction tower 10; high-purity water in high-purity water storage tank 12 is sprayed into reaction tower 10 through atomizing water sprayer 13 to dissolve nitrogen oxides in water to generate nitric acid, which is then stored in storage tank 11.

[0052] The flow rates of high-purity oxygen 1 and high-purity nitrogen 2 are adjusted by mass flow controller 4, and the exhaust gas flow rate of gas circulation pump 15 is adjusted accordingly to maintain the gas pressure at around 1 bar. Then, the water spray volume of atomizing water sprayer 13 is adjusted according to the gas flow rate and nitrogen oxide generation rate in thermal plasma reactor 8.

[0053] In step S2, the volume percentage concentration of ozone in the mixed reaction gas is 5%-10%.

[0054] In step S3, the flow rate of the mixed reaction gas entering the thermal plasma reactor 8 is 100 ml / min - 1 L / min.

[0055] In step S1, the gas temperature of the cold plasma reactor 5 is 350K-450K, and in step S3, the gas temperature of the hot plasma reactor 8 is 1500K-2000K.

[0056] Example

[0057] (1) High-purity oxygen 1 with a purity of 99.999% is introduced into the dielectric barrier discharge cold plasma reactor 5 with a parallel plate electrode structure. The first high-voltage power supply 6 is a high-voltage pulse power supply (voltage is 10 kV, frequency is 5 kHz, gas pressure is 1 bar). The gas temperature of the cold plasma is measured to be about 350 K by spectroscopy. By controlling the flow rate of high-purity oxygen 1, the ozone concentration in the product generated by the cold plasma reactor 5 is controlled within the range of 5%-10%. The ozone-containing mixed gas is introduced into the gas coupler 7.

[0058] (2) High-purity nitrogen gas 2 with a purity of 99.999% is introduced into the gas coupler 7. The mixed reaction gas is introduced into the thermal plasma reactor 8 with a sliding arc discharge structure (metal material is tungsten) through the gas control system. The second high-voltage power supply 9 is a high-voltage AC power supply (voltage is 7kV, frequency is 10kHz, gas pressure is 1bar). The gas temperature of the thermal plasma is measured to be about 1800 K by the spectrometer. Nitrogen oxides are generated in the mixed reaction gas in the thermal plasma reactor 8 (the main nitrogen oxide is nitrogen dioxide, and it contains a small amount of nitric oxide).

[0059] (3) The mixed product gas generated by the thermal plasma reactor 8 is fed into the reaction tower 10, and high-purity water is sprayed to generate nitric acid, which is then stored in the storage tank 11. The tail gas of the reaction tower (containing nitrogen, oxygen, ozone, a small amount of nitric oxide, etc.) is dehydrated and then recycled to the gas coupler 7.

[0060] The nitric acid solution in storage tank 11 was analyzed by inductively coupled plasma mass spectrometry (ICP-MS), and the results of the metal content analysis are shown in Table 1.

[0061] Table 1. Detection of impurity metals in synthetic nitric acid

[0062]

[0063] As can be seen from Table 1, the nitric acid synthesized in this embodiment meets the electronic grade nitric acid standard and is high-purity nitric acid.

[0064] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0065] The parts of this invention not described in detail are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. An apparatus for the green synthesis of high-purity nitric acid, characterized in that, It includes a first reacting gas component, a second reacting gas component, a gas coupler, a thermal plasma reactor, a reaction tower, and a storage tank; wherein the first reacting gas component and the second reacting gas component are both connected to the gas coupler, the outlet pipe of the gas coupler is connected to the thermal plasma reactor, the outlet pipe of the thermal plasma reactor is connected to the reaction tower, and the bottom outlet of the reaction tower is connected to the storage tank; The first reaction gas component includes a high-purity oxygen pipeline and a cold plasma reactor. The high-purity oxygen enters the cold plasma reactor through the high-purity oxygen pipeline. In the cold plasma reactor, some of the oxygen is converted into ozone, and the resulting ozone-containing gas enters the gas coupler. The second reaction gas component includes a high-purity nitrogen pipeline, through which the high-purity nitrogen enters the gas coupler.

2. The apparatus for green synthesis of high-purity nitric acid according to claim 1, characterized in that, Gas control components are provided on the high-purity oxygen pipeline, the high-purity nitrogen pipeline, and the outlet pipeline of the gas coupler. The gas control components include control valves and mass flow controllers.

3. The apparatus for green synthesis of high-purity nitric acid according to claim 1, characterized in that, The tail gas outlet of the reaction tower is connected to the gas coupler via a gas circulation pump.

4. The apparatus for green synthesis of high-purity nitric acid according to claim 3, characterized in that, A dehydrator is installed on the pipeline connecting the tail gas outlet of the reaction tower to the gas coupler.

5. The apparatus for the green synthesis of high-purity nitric acid according to any one of claims 1 to 4, characterized in that, The cold plasma reactor is a dielectric barrier discharge plasma reactor; the voltage of the dielectric barrier discharge plasma reactor is 5-25 kV and the frequency is less than 100 kHz.

6. The apparatus for the green synthesis of high-purity nitric acid according to any one of claims 1 to 4, characterized in that, The thermal plasma reactor is a plasma reactor using metal electrodes, and the voltage of the thermal plasma reactor is 5-25 kV, and the frequency is less than 100 kHz.

7. A green process for synthesizing high-purity nitric acid, characterized in that, The apparatus for the green synthesis of high-purity nitric acid according to any one of claims 1 to 6, wherein the process comprises the following steps: S1: To generate ozone from high-purity oxygen in a cold plasma reactor; S2: Mix the ozone-containing mixed gas obtained in step S1 with high-purity nitrogen gas; S3: The mixed reaction gas obtained in step S2 is used to generate nitrogen oxides in a thermal plasma reactor; S4: High-purity nitric acid can be generated by dissolving the mixed product gas containing nitrogen oxides obtained in step S3 in water.

8. The process for green synthesis of high-purity nitric acid according to claim 7, characterized in that, The volume percentage concentration of ozone in the mixed reaction gas obtained in step S2 is 5%-10%.

9. The process for green synthesis of high-purity nitric acid according to claim 7, characterized in that, In step S3, the flow rate of the mixed reaction gas entering the thermal plasma reactor is 100 ml / min - 1 L / min.

10. The process for green synthesis of high-purity nitric acid according to claim 7, characterized in that, The gas temperature of the cold plasma reactor in step S1 is 350K-450K, and the gas temperature of the hot plasma reactor in step S3 is 1500K-2000K.

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