A method for removing n2o and no2 from no

Abstract

The application discloses a method for removing N2O and NO2 in NO, and the NO sample containing N2O and NO2 is sequentially passed through a first absorption tower, a second absorption tower and an adsorption tower to obtain NO products meeting product technical requirements. In the purification process, the application does not produce condensed NO, and is high in safety. Meanwhile, the application overcomes the defects of the prior art alkali absorption method that produces a large amount of nitrogen-containing wastewater, and overcomes the defect of low-temperature rectification that consumes a large amount of energy, so that the application is low in energy consumption and small in three-waste production.

Description

Technical Field

[0001] This invention belongs to the field of specialty gas technology, specifically relating to a method for removing nitrous oxide and nitrogen dioxide from nitric oxide (removing N2O and NO2 from NO). Background Technology

[0002] Nitric oxide is widely used in the chemical, electronics, aerospace, metrology, life sciences, and medical industries. It also plays a crucial role in the semiconductor field. The applications of nitric oxide in semiconductors primarily involve two aspects: surface treatment and nitride materials.

[0003] Nitric oxide can be used for semiconductor surface treatment. During semiconductor manufacturing, surface treatment is necessary to improve the quality and performance of semiconductor materials. Nitric oxide can react with the semiconductor surface to form a nitride film. This nitride film exhibits good chemical and thermal stability, which can improve the performance of semiconductor materials. Furthermore, nitric oxide can alter the band structure of the semiconductor surface, enhancing electron transport properties and thus improving the performance of semiconductor devices.

[0004] Nitric oxide also plays a crucial role in nitride materials. Nitride materials are a class of semiconductor materials with excellent properties, widely used in high-power electronic devices, optoelectronic devices, and other fields. Nitric oxide can be used as a growth aid gas for nitride materials, reacting with other gases to form nitride materials. These nitride materials possess excellent electrical and optical properties, meeting the requirements of high-performance semiconductor devices.

[0005] Besides the two aspects mentioned above, nitric oxide has other applications in semiconductors. For example, nitric oxide can be used in the annealing and oxidation processes of semiconductor devices. During annealing, nitric oxide can alter the crystal structure of semiconductor materials, improving their electrical properties. During oxidation, nitric oxide can react with semiconductor materials to form nitride thin films, thereby improving the performance of semiconductor devices.

[0006] With the rise and rapid development of the semiconductor industry, the demand for nitric oxide (NO) is increasing, and the requirements for its purity are also becoming higher.

[0007] Due to its unique chemical properties, nitric oxide undergoes a disproportionation reaction at room temperature, producing nitrous oxide (N₂O) and nitrogen dioxide (NO₂). Therefore, NO typically has a very short shelf life. For example, a steel cylinder filled with NO at a pressure of 3.5 MPa will, after six months of storage, fail to meet the national standard technical requirements for N₂O and NO₂ (<500 ppm, GB / T42721-2023 Electronic Specialty Gas Nitric Oxide). The high levels of impurities N₂O and NO₂ in NO products can negatively impact its application in semiconductors, leading to a significant decrease in yield.

[0008] Existing technologies primarily employ alkaline absorption to remove NO2 from NO, and cryogenic distillation to remove N2O from NO. The main drawbacks and limitations of these technologies are:

[0009] 1) The alkaline absorption method will generate a large amount of nitrogen-containing wastewater, which is not environmentally friendly;

[0010] 2) Low-temperature distillation consumes a lot of energy, and a large amount of liquid NO will be present during the distillation process. NO has poor stability in liquid or solid states and is very easy to explode, which is highly dangerous.

[0011] Therefore, it is both necessary and urgent to provide a safe, low-energy-consumption, and environmentally friendly method for removing N2O and NO2 from NO, which can purify substandard NO products containing high levels of N2O and NO2 into qualified products. Summary of the Invention

[0012] To overcome the shortcomings of existing technologies, this invention discloses a method for removing N2O and NO2 from NO (removing nitrous oxide and nitrogen dioxide from nitric oxide), which can purify NO products with excessive N2O and NO2 content to obtain NO products that meet product technical requirements, thus avoiding the waste of large amounts of NO.

[0013] To achieve the above-mentioned technical objectives, the technical solution of the present invention is a method for removing N2O and NO2 from NO, wherein NO product containing N2O and NO2 is passed sequentially through a primary absorption tower, a secondary absorption tower, and an adsorption tower to remove N2O and NO2 from NO; wherein the absorbent in the primary absorption tower is a mixed solution of ethanol, water, and NaOH, the absorbent in the secondary absorption tower is low-temperature ethanol, and the adsorbent packed in the adsorption tower is activated carbon.

[0014] Preferably, the composition (mass fraction) of the absorbent in the primary absorption tower is: ethanol: 75%–90%, H2O: 5%–20%, NaOH: 2%–10%. The used absorbent can be distilled to separate the generated salts. The dissolved N2O released during distillation can be collected, purified, and used as a byproduct. The aqueous ethanol solution can be recycled after adding NaOH.

[0015] The absorbent in the secondary absorption tower is ethanol, which is cooled to -40 to -30°C by a low-temperature refrigerant. The used absorbent in the secondary absorption tower can be recycled by distillation or used to prepare the absorbent in the primary absorption tower.

[0016] After the activated carbon adsorbent in the adsorption tower becomes saturated, it can be regenerated by heating. The desorbed ethanol can be condensed and used as the absorbent in the secondary absorption tower or for the preparation of the absorbent in the primary absorption tower.

[0017] During the regeneration process of the absorbent and adsorbent, the residual heat energy from adsorbent regeneration can be used for distillation of the absorbent in the primary and secondary absorption towers, thus reducing energy consumption.

[0018] The principle of this invention is as follows: When NO containing N2O and NO2 passes through the primary absorption tower, NO2 reacts with NaOH to produce NaNO2, NaNO3, and H2O. Since N2O has good solubility in ethanol, it will dissolve in the solution. The gas exiting the primary absorption tower contains a small amount of water and a small amount of unabsorbed N2O. After entering the secondary absorption tower, N2O and water are dissolved and absorbed by low-temperature ethanol. The gas exiting the secondary absorption tower contains a small amount of ethanol, which is adsorbed by the adsorbent in the adsorption tower to obtain purified NO.

[0019] Traditional methods for removing NO2 from NO involve absorption with an alkaline aqueous solution, which generates a large amount of nitrogen-containing wastewater. The method of this invention uses a mixed solution of ethanol, water, and NaOH to remove NO2. Ethanol has a low boiling point and can be recycled through distillation, thus greatly reducing the amount of wastewater generated, producing only a small amount of wastewater, and significantly reducing energy consumption and costs.

[0020] Existing methods for removing N2O involve low-temperature distillation (below -130°C). This process is energy-intensive, and NO exists in a gas-liquid two-phase state during distillation, posing a significant risk as it is prone to explosion in its liquid state. The method of this invention utilizes the property that N2O is soluble in ethanol. N2O has high solubility at low temperatures and low solubility at high temperatures. This property is used to regenerate ethanol by increasing the temperature, enabling recycling.

[0021] The beneficial effects of this invention are as follows:

[0022] I. The method provided by this invention can purify NO products with excessive N2O and NO2 content to obtain NO products that meet the product technical requirements, thus avoiding the waste of a large amount of NO.

[0023] Second, the safety of this invention is high: NO has a boiling point of -151.771℃ and a melting point of -163.6℃ under normal pressure. The temperature in this invention will not reach this level, so NO will not liquefy or solidify during the production process. Therefore, the solution provided by this invention will not produce condensed NO (liquid or solid) in the actual production process, and has high safety.

[0024] Third, the absorbent used in this invention can be recycled and reused, and the nitrogen-containing salts generated during the primary absorption process can be separated in solid form. Therefore, this invention overcomes the defect of existing alkaline absorption methods that generate a large amount of nitrogen-containing wastewater. At the same time, this invention does not consume a large amount of energy like traditional low-temperature distillation, because low-temperature distillation requires the NO temperature to be lowered to below approximately -130°C, while the technical solution of this invention only requires the temperature to be lowered to around -40 to -30°C. Therefore, the technical solution provided by this invention has low energy consumption, generates less waste, and is green and environmentally friendly.

[0025] Fourth, the process of this invention is simple, requires little equipment investment, and has low cost, so it will not impose a cost burden on manufacturing enterprises. Detailed Implementation

[0026] The technical solutions of this application will be further described below with reference to specific embodiments, but this application is not limited to these embodiments.

[0027] A method for removing N2O and NO2 from NO involves passing an NO sample containing N2O and NO2 sequentially through a primary absorption tower, a secondary absorption tower, and an adsorption tower. The absorbent in the primary absorption tower is a mixed solution of ethanol, water, and NaOH; the absorbent in the secondary absorption tower is low-temperature ethanol; and the adsorbent in the adsorption tower is activated carbon.

[0028] Example 1:

[0029] A NO sample containing N2O and NO2 was sequentially passed through a primary absorption tower, a secondary absorption tower, and an adsorption tower. The composition (mass fraction) of the absorbent in the primary absorption tower was: ethanol: 90%, H2O: 5%, NaOH: 5%; the absorbent in the secondary absorption tower was ethanol, cooled to -40°C using a low-temperature refrigerant; finally, the sample was adsorbed by activated carbon to obtain high-purity NO.

[0030] Example 2:

[0031] A NO sample containing N2O and NO2 was sequentially passed through a primary absorption tower, a secondary absorption tower, and an adsorption tower. The composition (mass fraction) of the absorbent in the primary absorption tower was: ethanol: 85%, H2O: 13%, NaOH: 2%; the absorbent in the secondary absorption tower was ethanol, cooled to -35°C using a low-temperature refrigerant; finally, the sample was adsorbed by activated carbon to obtain high-purity NO.

[0032] Example 3:

[0033] A NO sample containing N2O and NO2 was sequentially passed through a primary absorption tower, a secondary absorption tower, and an adsorption tower. The composition (mass fraction) of the absorbent in the primary absorption tower was: ethanol: 80%, H2O: 10%, NaOH: 10%; the absorbent in the secondary absorption tower was ethanol, cooled to -35°C using a low-temperature refrigerant; finally, the sample was adsorbed by activated carbon to obtain high-purity NO.

[0034] Example 4:

[0035] A NO sample containing N2O and NO2 was sequentially passed through a primary absorption tower, a secondary absorption tower, and an adsorption tower. The composition (mass fraction) of the absorbent in the primary absorption tower was: ethanol: 75%, H2O: 20%, NaOH: 5%; the absorbent in the secondary absorption tower was ethanol, cooled to -30°C using a low-temperature refrigerant; finally, the sample was adsorbed by activated carbon to obtain high-purity NO.

[0036] The N2O and NO2 component contents of NO samples before and after purification according to the examples were analyzed, and the results are shown in Table 1 below:

[0037] Table 1. NO2 and N2O content of NO samples purified by the examples.

[0038]

[0039] As can be seen from Table 1, the NO containing N2O and NO2 purified by the method of the present invention has almost completely removed NO2, leaving only trace amounts of N2O, which fully meets the requirements of most industrial applications.

[0040] This invention purifies NO products with excessive N2O and NO2 content to obtain NO products that meet product technical requirements, avoiding the waste of large amounts of NO. This invention does not produce condensed NO during the purification process, ensuring high safety; it also overcomes the shortcomings of existing alkaline absorption methods, which generate large amounts of nitrogen-containing wastewater; and it overcomes the drawback of low-temperature distillation, which consumes a large amount of energy, resulting in low energy consumption and minimal waste generation.

[0041] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of this application, and these all fall within the protection scope of this application.

Claims

1. A method for removing N2O and NO2 from NO, characterized in that, The method is as follows: NO product containing N2O and NO2 is passed sequentially through a primary absorption tower, a secondary absorption tower, and an adsorption tower to remove N2O and NO2 from NO; wherein, the absorbent in the primary absorption tower is a mixed solution of ethanol, water, and NaOH, the absorbent in the secondary absorption tower is low-temperature ethanol, and the adsorbent packed in the adsorption tower is activated carbon. According to mass fraction, the composition of the absorbent in the primary absorption tower is: ethanol: 75%~90%, H2O: 5%~20%, NaOH: 2%~10%; The absorbent in the secondary absorption tower is ethanol, and the temperature of the ethanol is -40~-30℃.

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