A high-purity electronic-grade ammonia refining production process

Abstract

This application relates to the field of gas refining production, specifically disclosing a refining process for high-purity electronic-grade ammonia, comprising the following steps: S1, pretreatment: the raw material liquid ammonia is sequentially vaporized, filtered, and adsorbed to obtain crude ammonia; S2, ultrafiltration: the crude ammonia obtained in step S1 is ultrafiltered under conditions of pressure 0.4-0.8 MPa, temperature 25-45℃, and flow rate 1.5-3.5 m / s to obtain high-purity ammonia; S3, distillation and condensation liquefaction: the high-purity ammonia obtained in step S2 is sequentially distilled and condensed to obtain electronic-grade ammonia with a purity of 5N. The refining process of this application simultaneously meets the requirements of high purity, low cost, and high efficiency, improves the removal efficiency of trace impurities, and can obtain electronic-grade ammonia with a purity of 5N, solving the problems of insufficient purity, high impurity content, and high production costs in existing ammonia refining processes.

Description

Technical Field

[0001] This application relates to the technical field of gas refining production, and in particular to a refining process for high-purity electronic-grade ammonia. Background Technology

[0002] In recent years, with the rapid development of global technology, the semiconductor and optoelectronic industries have ushered in an unprecedented golden age. As the core component of modern electronic devices, the performance improvement of semiconductor chips plays a decisive role in the overall performance of electronic products. Whether it's smartphones, computers, smart home devices, or automotive electronic systems, increasingly higher demands are being placed on the processing speed, storage capacity, and stability of chips. Meanwhile, optoelectronic devices are increasingly widely used in communication, lighting, and display fields, providing strong support for high-speed information transmission, energy-saving lighting, and high-definition displays. Against this backdrop, high-purity electronic-grade ammonia, as an important raw material in the manufacture of semiconductors and optoelectronic devices, is playing an increasingly prominent role. It participates in the key nitriding process in chip manufacturing, effectively improving the electrical performance and stability of chips; in the fabrication of optoelectronic devices, high-purity electronic-grade ammonia helps to precisely control the crystal structure and optical properties of materials, thereby improving the luminous efficiency and color quality of products such as light-emitting diodes. Therefore, with the booming development of the semiconductor and optoelectronic industries, the market demand for high-purity electronic-grade ammonia is experiencing explosive growth. This has not only boosted the prosperity of related industrial chains but also posed more severe challenges to ammonia refining processes. Many emerging technology companies have sprung up like mushrooms after rain, increasing their procurement of high-purity electronic-grade ammonia, further exacerbating the supply-demand imbalance in the market. At the same time, the industry's quality requirements for high-purity electronic-grade ammonia are constantly increasing, driving researchers and companies to continuously explore more advanced refining processes.

[0003] In existing technologies, the mainstream purification methods for improving ammonia purity include adsorption, distillation, and chemical purification. Adsorption is a relatively mature and widely used purification method. It mainly utilizes the special physical and chemical properties of selective adsorbents to enable them to interact with impurities in ammonia. This interaction can be physical adsorption, where impurity molecules are adsorbed onto the surface of the adsorbent through van der Waals forces; or chemical adsorption, where impurity molecules react chemically with the active sites on the adsorbent surface to form chemical bonds. Different adsorbents have different adsorption selectivity for different types of impurities. For example, activated carbon has a good adsorption effect on some organic impurities, while molecular sieves have a high adsorption affinity for moisture and certain small molecule impurities. In practical applications, a suitable adsorbent is usually selected based on the type and content of impurities in the ammonia and filled into an adsorption column. When ammonia passes through the adsorption column, impurities are adsorbed onto the adsorbent, thereby purifying the ammonia. The advantage of adsorption is that it can selectively remove specific impurities, thus improving the purity of ammonia to a certain extent. Moreover, the adsorption process is relatively simple and requires less equipment investment, making it suitable for small-scale ammonia refining production.

[0004] Distillation separates ammonia from impurities based on the difference in their boiling points. First, the ammonia containing impurities is heated to an evaporative state. Due to the difference in boiling points, ammonia and impurities evaporate at different rates. Ammonia, with its lower boiling point, evaporates first, while impurities with higher boiling points remain in the liquid phase. The evaporated ammonia is then condensed back into a liquid state, yielding relatively pure ammonia. Distillation can be divided into simple distillation and rectification. Simple distillation is suitable for situations where the boiling points of impurities and ammonia differ significantly; it is relatively simple to operate, but its separation effect is limited. Rectification is a more precise separation method. It uses a multi-stage distillation column to achieve a more thorough separation of ammonia and impurities through multiple evaporation and condensation processes. The rectification column has multiple trays or packing layers, allowing the ammonia vapor to come into full contact with the descending liquid as it rises within the column, resulting in heat and mass transfer, thus gradually separating the ammonia and impurities. Distillation is a highly effective method for separating ammonia and is widely used in industrial production. It can process ammonia on a large scale, and the separation effect is relatively stable. It also has a good removal effect on some common impurities.

[0005] Chemical purification removes impurities from ammonia through chemical reactions. It typically utilizes specific chemical reagents to react with the impurities in the ammonia, transforming them into other easily separable substances. For example, for impurities containing metal ions, a precipitating agent can be used to form a precipitate, which is then removed by filtration. For impurities with reducing or oxidizing properties, oxidizing or reducing agents can be used to oxidize or reduce them into other substances, which are then separated. Chemical purification can treat impurities that are difficult to remove by physical methods, thereby improving the purity of ammonia. It has unique advantages in treating certain special impurities and can meet the needs of applications requiring extremely high ammonia purity.

[0006] However, these existing refining processes have significant drawbacks. Firstly, they struggle to simultaneously meet the requirements of high purity, low cost, and high efficiency. In today's highly competitive market, companies not only need to produce high-purity electronic-grade ammonia to meet customer demands but also need to control production costs and improve efficiency to maintain market competitiveness. Existing adsorption, distillation, and chemical purification methods are all inadequate in these areas. Low removal efficiency for trace impurities is a prominent problem with existing processes. In the semiconductor and optoelectronic industries, even minute amounts of trace impurities can severely impact product performance. For example, some metal ion impurities can increase chip leakage current, reducing chip reliability; while certain organic impurities can affect the luminous efficiency and lifespan of optoelectronic devices. However, existing refining processes are ineffective at removing these trace impurities, failing to meet the stringent purity standards for ammonia in the high-end electronics industry.

[0007] In summary, the shortcomings of existing ammonia refining processes make the development of a new refining process that can simultaneously meet the requirements of high purity, low cost, and high efficiency an urgent problem to be solved in the current semiconductor and optoelectronic industries. Summary of the Invention

[0008] To address the aforementioned technical problems, this application provides a refining process for high-purity electronic-grade ammonia.

[0009] This application provides a refining process for high-purity electronic-grade ammonia, comprising the following steps: S1, pretreatment: the raw liquid ammonia is sequentially vaporized, filtered, and adsorbed to obtain crude ammonia; S2, ultrafiltration: the crude ammonia obtained in step S1 is subjected to ultrafiltration under conditions of pressure 0.4-0.8 MPa, temperature 25-45℃, and flow rate 1.5-3.5 m / s to obtain high-purity ammonia; S3, distillation and condensation liquefaction: the high-purity ammonia obtained in step S2 is sequentially distilled and condensed to obtain electronic-grade ammonia with a purity of 5N.

[0010] Preferably, step S1 specifically involves: vaporizing the raw material liquid ammonia at a pressure of 1.2-1.5 MPa and a temperature of 40-60°C, filtering it through 0.2-0.22 μm micropores, and then adsorbing it in series with activated alumina and molecular sieves under a pressure of 0.8-1.0 MPa and a flow rate of 0.2-0.3 m / s for 4-6 hours. The operating temperature for adsorption by activated alumina is 50-80°C, and the operating temperature for adsorption by molecular sieves is 70-100°C.

[0011] By adopting the above technical solution, this application first vaporizes and filters the raw material liquid ammonia to remove suspended particulate impurities and mechanical impurities such as oil mist particles. The filtered gaseous substance enters an adsorption tower, where activated alumina and molecular sieves are adsorbed alternately in series. The entire process takes place in the adsorption tower, with the two towers used alternately. When one tower becomes saturated, the process switches to the other tower to continue adsorption. Simultaneously, the saturated tower is regenerated (regeneration is achieved by heating and desorbing with high-purity nitrogen gas treated with deoxygenation at 250-300℃ for 4-5 hours). After 4-6 hours of adsorption, this application has initially removed some impurities, obtaining crude ammonia gas. The crude ammonia gas is then subjected to ultrafiltration under specific pressure, temperature, and flow rate conditions. Under the action of pressure difference, ammonia gas preferentially permeates through the ultrafiltration membrane, while larger impurity molecules such as water and alcohols are preferentially retained, achieving further purification of ammonia gas to obtain high-purity ammonia. After separation by the ultrafiltration membrane, the water content in the ammonia gas is further reduced to below 10 ng / g, and the alcohol content is reduced to below 50 ng / g, which is conducive to subsequent processing. The distillation process provides high-quality raw materials. Compared with traditional adsorption processes, ultrafiltration membrane separation has advantages such as simple operation, low energy consumption, and no phase change. Moreover, the membrane module can be reused, which greatly saves production costs. Finally, this application uses distillation and condensation liquefaction to process high-purity ammonia. In the distillation environment, the relative volatility of ammonia is much greater than that of impurities. Therefore, impurities are mainly concentrated in the liquid phase at the bottom of the column and separated, while pure ammonia is purified in the gas phase at the top of the column. Compared with traditional distillation processes, distillation processes have advantages such as high tray efficiency, low energy consumption, and high product purity. Condensation liquefaction can achieve high-purity separation. The boiling points of ammonia and other gases (such as N2 and H2) are significantly different. Ammonia is preferentially liquefied and accumulates at the bottom of the column, while other gases remain in a gaseous state. Impurities can be gradually removed through staged cooling, and finally electronic-grade ammonia with a purity of 5N can be obtained. This solves the problems of insufficient purity, high impurity content, and high production costs in existing ammonia refining processes. It can simultaneously meet the requirements of high purity, low cost, and high efficiency, and improve the removal efficiency of trace impurities.

[0012] Preferably, in step S2, ultrafiltration is performed using a PVSQ / SiO2 / PVDF ultrafiltration membrane.

[0013] Preferably, the PVSQ / SiO2 / PVDF ultrafiltration membrane is made of PVSQ / SiO2 alcohol sol and PVDF membrane.

[0014] Preferably, the PVSQ / SiO2 alcohol sol is prepared from SiO2 and vinyltrimethoxysilane, and the weight ratio of SiO2 to vinyltrimethoxysilane in the PVSQ / SiO2 alcohol sol is 1:(4-4.5).

[0015] By adopting the above technical solution, this application utilizes vinyltrimethoxysilane to hydrophobically modify SiO2, and vinyltrimethoxysilane generates regular spherical polyvinylsilsesquioxane (PVSQ) particles through its own hydrolysis and condensation reaction, forming a structure in which nano-sized SiO2 is distributed on the surface of micron-sized PVSQ. The ethanol sol formed by dispersing in ethanol is then used to soak PVDF, forming a multi-layered micro / nano rough surface on its membrane surface. Under the combined action of low surface energy hydrophobic groups vinyl and methoxy groups, the superhydrophobic modification of PVDF ultrafiltration membrane is successfully achieved. Due to its significantly improved hydrophobicity, it exhibits a more stable flux than commercial PVDF membranes and has excellent antifouling properties. It can not only more effectively retain water molecules in crude ammonia, but also show superior stability in use, reduce replacement frequency, and improve ultrafiltration quality. Experimental demonstration shows that the various process steps in this application, together with the PVSQ / SiO2 / PVDF ultrafiltration membrane, form a whole with good and tight scheme coordination, ultimately achieving a purity of 7N for electronic-grade ammonia.

[0016] Preferably, in step S2, the pressure is 0.6-0.7 MPa and the flow rate is 2.5 m / s.

[0017] By adopting the above technical solution, controlling the pressure at 0.6-0.7 MPa and setting the flow rate to 2.5 m / s in the ultrafiltration step can further optimize the mass transfer effect of the ultrafiltration process, remove impurities from crude ammonia more efficiently, help improve the quality of high-purity ammonia, reduce production costs, and provide high-quality raw materials for subsequent distillation and condensation liquefaction processes, thereby more effectively realizing the refined production of high-purity electronic-grade ammonia.

[0018] Preferably, in step S3, the specific operation of distillation is as follows: distillation is carried out under the conditions of feed pressure of 1-1.2 MPa, feed temperature of 60-70℃, column top temperature of -35~-30℃, and column bottom temperature of 10-15℃.

[0019] By adopting the above technical solution, high-purity ammonia can be distilled under specific feed pressure, feed temperature, top temperature and bottom temperature conditions. This can further and effectively remove impurities and ensure that the final electronic-grade ammonia gas has a high purity of 5N or higher. This helps to solve the problem that existing refining processes cannot meet the stringent purity standards of ammonia gas in the high-end electronics industry.

[0020] Preferably, in the distillation process, the feed pressure is 1.1 MPa, the feed temperature is 65°C, the top temperature is -34°C, and the bottom temperature is 12°C.

[0021] By adopting the above technical solution, this application can further and effectively remove impurities by distilling high-purity ammonia under specific feed pressure, feed temperature, top temperature and bottom temperature conditions, ensuring that the final electronic-grade ammonia gas has a high purity of 6N or higher. This helps to solve the problem that existing refining processes cannot meet the stringent purity standards of ammonia gas in the high-end electronics industry.

[0022] Preferably, in step S3, the condensation liquefaction includes pre-cooling, main cooling, and final cooling performed sequentially.

[0023] Preferably, the temperatures of the pre-cooling, main cooling, and final cooling are set to decrease sequentially, with each decrease being 20-25°C, wherein the pre-cooling temperature is -30°C.

[0024] By adopting the above technical solution, this application uses a condensation and liquefaction method of pre-cooling, main cooling and final cooling of the high-purity ammonia after distillation. This allows the high-purity ammonia to be cooled gradually, more effectively converting gaseous ammonia into liquid electronic-grade ammonia with a purity of 5N or higher. This solves the problems of insufficient purity, high impurity content and high production cost in existing ammonia refining processes, and avoids the limitations of difficult adsorbent regeneration, huge energy consumption and large chemical reagent consumption, thus achieving economical and efficient large-scale production.

[0025] In summary, this application has the following beneficial technical effects: This application first involves the sequential vaporization, filtration, and adsorption of raw liquid ammonia. Filtration removes suspended particulate impurities and mechanical impurities such as oil mist particles from the liquid ammonia. The filtered gaseous substance enters an adsorption tower, where activated alumina and molecular sieves undergo alternating adsorption in series. The entire process takes place within the adsorption tower, yielding crude ammonia. A PVSQ / SiO2 alcohol sol is prepared using a specific ratio of SiO2 and vinyltrimethoxysilane. A PVSQ / SiO2 / PVDF ultrafiltration membrane is then fabricated using the PVSQ / SiO2 alcohol sol and a PVDF membrane. Under specific pressure, temperature, and flow rate conditions, this ultrafiltration membrane is used to ultrafilter the crude ammonia. Ammonia preferentially permeates through the ultrafiltration membrane under pressure difference, while larger impurity molecules such as water and alcohols are preferentially retained, achieving further purification of ammonia to obtain high-purity ammonia. After ultrafiltration, the water content in the ammonia is further reduced. The ammonia content is reduced to below 10 ng / g and the alcohol content is reduced to below 50 ng / g, providing high-quality raw materials for subsequent distillation processes to obtain high-purity ammonia. Finally, the high-purity ammonia is sequentially distilled and condensed and liquefied. In the distillation environment, the relative volatility of ammonia is much greater than that of impurities. Therefore, impurities are mainly concentrated in the liquid phase at the bottom of the column and separated, while pure ammonia is purified in the gas phase at the top of the column. Condensation and liquefaction can achieve high-purity separation. The boiling points of ammonia and other gases (such as N2 and H2) are significantly different. Ammonia is preferentially liquefied and accumulates at the bottom of the column, while other gases remain in a gaseous state. Impurities can be gradually removed through staged cooling, and finally electronic-grade ammonia with a purity of over 5N can be obtained. This solves the problems of insufficient purity, high impurity content, high production cost, and low efficiency in removing trace impurities in existing ammonia refining processes, and realizes high-purity, low-cost, and high-efficiency ammonia refining production. Detailed Implementation

[0026] Material source Unless otherwise specified, all raw materials used in this application are commercially available products, specifically: The PVDF ultrafiltration membrane has an average pore size of 40 μm. The SiO2 was purchased from Shanghai Maclean Company, with an average particle size of 10 μm and a purity of 99.99%. Vinyltrimethoxysilane was purchased from Shanghai Maclean Company, with a purity of 98%. The distillation column is a packed column with a specific surface area of ​​700 m². 2 / m 3 The tower is 50m high and 1.5m in diameter, with 50 theoretical trays, a reflux ratio of 0.8, and is packed with θ-ring Dixon packing.

[0027] The present application will be further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0028] Preparation Example 1 The preparation method of PVSQ / SiO2 alcohol sol includes the following steps: SiO2 was added to anhydrous ethanol and magnetically stirred for 30 min, then ultrasonically dispersed for 30 min to ensure full dispersion of SiO2. Ammonia was then added to adjust the pH of the system to 10, and vinyltrimethoxysilane was added to control the SiO2 to vinyltrimethoxysilane ratio to 1:4 to obtain an alcohol sol. The sol was then ultrasonically dispersed at 40 °C for 2 h, and then stirred at room temperature for another 10 h to obtain a PVSQ / SiO2 alcohol sol with a SiO2 concentration of 2 wt%.

[0029] Preparation Example 2 The preparation method of PVSQ / SiO2 alcohol sol includes the following steps: SiO2 was added to anhydrous ethanol and magnetically stirred for 30 min, then ultrasonically dispersed for 30 min to ensure full dispersion of SiO2. Ammonia was then added to adjust the pH of the system to 10, and vinyltrimethoxysilane was added to control the SiO2 to vinyltrimethoxysilane ratio at 1:4.5 to obtain an alcohol sol. The sol was then ultrasonically dispersed at 40 °C for 2 h, and then stirred at room temperature for another 10 h to obtain a PVSQ / SiO2 alcohol sol with a SiO2 concentration of 2 wt%.

[0030] Preparation Example 3 The preparation method of PVSQ / SiO2 / PVDF ultrafiltration membrane includes the following steps: The PVDF membrane was immersed in 2 mol·L⁻¹ water. -1 The alkali-treated PVDF membrane was obtained by immersing it in NaOH solution at 60°C for 2 hours. Then, the alkali-treated PVDF membrane was immersed in the PVSQ / SiO2 alcohol sol obtained in Preparation Example 1 at 40°C for 40 minutes. The alkali-treated PVDF membrane was then removed and placed at room temperature until the anhydrous ethanol completely evaporated, thus obtaining the PVSQ / SiO2 / PVDF ultrafiltration membrane.

[0031] Preparation Example 4 The preparation method of PVSQ / SiO2 / PVDF ultrafiltration membrane includes the following steps: The PVDF membrane was immersed in 2 mol·L⁻¹ water. -1 The alkali-treated PVDF membrane was obtained by immersing the alkali-treated PVDF membrane in NaOH solution at 60°C for 2 hours. Then, the alkali-treated PVDF membrane was immersed in the PVSQ / SiO2 alcohol sol obtained in Preparation Example 1 at 40°C for 30 minutes. The alkali-treated PVDF membrane was then removed and placed at room temperature until the anhydrous ethanol completely evaporated, thus obtaining the PVSQ / SiO2 / PVDF ultrafiltration membrane.

[0032] Preparation Example 5 The method for preparing alkali-treated PVDF membranes includes the following steps: The PVDF membrane was immersed in 2 mol·L⁻¹ water. -1The PVDF membrane was prepared by treating it in NaOH solution at 60°C for 2 hours and then left at room temperature until the water completely evaporated.

[0033] Example 1 A refining process for high-purity electronic-grade ammonia includes the following steps: S1. Pretreatment: The raw material liquid ammonia is pressurized to 1.5MPa by an ammonia pump and heated to 40℃. Under these conditions, it is vaporized and then filtered through a 0.22μm microporous membrane filter to remove suspended particulate impurities and mechanical impurities such as oil mist particles. The filtered gaseous ammonia enters the adsorption tower and continues to be adsorbed in series by an activated alumina adsorption tower and a molecular sieve adsorption tower at a pressure of 1.0MPa and a flow rate of 0.2m / s. When one tower is saturated, it is switched to the other tower to continue adsorption. At the same time, the saturated tower is regenerated. The regeneration is carried out by heating and desorbing with high-purity nitrogen gas treated by deoxygenation at 250℃ for 5 hours. After regeneration, the activated alumina adsorption tower is preheated to the operating temperature for later use. After regeneration, the molecular sieve adsorption tower is cooled to room temperature and sealed with high-purity nitrogen for 4 hours. The operating temperature for adsorption by activated alumina is 80℃, and the operating temperature for adsorption by molecular sieve is 100℃. The two towers are used alternately to obtain crude ammonia gas. S2. Ultrafiltration: The crude ammonia gas obtained in step S1 is passed into the ultrafiltration membrane separation unit and further purified by a tubular PVDF ultrafiltration membrane. The membrane separation operation is carried out at a temperature of 25°C, a pressure of 0.4 MPa, and a flow rate of 3.5 m / s. Ultrafiltration is carried out under these process conditions to obtain high-purity ammonia. S3. Distillation and Liquefaction: The high-purity ammonia obtained in step S2 is fed into a distillation column for final purification to remove residual trace impurities. The distillation column is a packed column with a specific surface area of ​​700 m². 2 / m 3 The column is 50m high and 1.5m in diameter, with 50 theoretical trays and a reflux ratio of 0.8. Distillation is carried out under the conditions of feed pressure of 1.2MPa, feed temperature of 60℃, top temperature of -30℃, and bottom temperature of 15℃. Impurities are concentrated in the liquid phase at the bottom of the column and separated, while pure ammonia is purified in the gas phase at the top of the column. It is then condensed and liquefied, and successively subjected to pre-cooling at -30℃, main cooling at -55℃, and final cooling at -75℃ to obtain electronic grade ammonia.

[0034] Example 2 A refining process for high-purity electronic-grade ammonia includes the following steps: S1. Pretreatment: The raw material liquid ammonia is pressurized to 1.2 MPa by an ammonia pump and heated to 60°C. Under these conditions, it is vaporized and then filtered through a 0.2 μm microporous membrane filter to remove suspended particulate impurities and mechanical impurities such as oil mist particles. The filtered gaseous ammonia enters the adsorption tower and continues to be adsorbed in series by an activated alumina adsorption tower and a molecular sieve adsorption tower at a pressure of 0.8 MPa and a flow rate of 0.3 m / s. When one tower is saturated, it is switched to the other tower to continue adsorption. At the same time, the saturated tower is regenerated. The regeneration is carried out by heating and desorbing with high-purity nitrogen gas treated by deoxygenation at 300°C for 4 hours. After regeneration, the activated alumina adsorption tower is preheated to the operating temperature for later use. After regeneration, the molecular sieve adsorption tower is cooled to room temperature and sealed with high-purity nitrogen for 6 hours. The operating temperature for adsorption by activated alumina is 50°C, and the operating temperature for adsorption by molecular sieve is 70°C. The two towers are used alternately to obtain crude ammonia gas. S2. Ultrafiltration: The crude ammonia gas obtained in step S1 is passed into the ultrafiltration membrane separation unit and further purified by a tubular PVDF ultrafiltration membrane. The membrane separation operation is carried out at a temperature of 45℃, a pressure of 0.8MPa, and a flow rate of 1.5m / s. Ultrafiltration is carried out under these process conditions to obtain high-purity ammonia. S3. Distillation and Liquefaction: The high-purity ammonia obtained in step S2 is fed into a distillation column for final purification to remove residual trace impurities. The distillation column is a packed column with a specific surface area of ​​700 m². 2 / m 3 The column is 50m high and 1.5m in diameter, with 50 theoretical trays and a reflux ratio of 0.8. Distillation is carried out under the conditions of feed pressure of 1MPa, feed temperature of 70℃, top temperature of -35℃, and bottom temperature of 10℃. Impurities are concentrated in the liquid phase at the bottom of the column and separated, while pure ammonia is purified in the gas phase at the top of the column. Then, it is condensed and liquefied, and successively subjected to pre-cooling at -30℃, main cooling at -50℃, and final cooling at -75℃ to obtain electronic grade ammonia.

[0035] Example 3 A refining process for high-purity electronic-grade ammonia gas differs from Example 1 in that, in step S2, the pressure is 0.6 MPa and the flow rate is 2.5 m / s, while the rest is the same as in Example 1.

[0036] Example 4 A refining process for high-purity electronic-grade ammonia gas differs from Example 1 in that, in step S2, the pressure is 0.7 MPa and the flow rate is 2.5 m / s, while the rest is the same as in Example 1.

[0037] Example 5 A refining process for high-purity electronic-grade ammonia gas differs from Example 1 in that the pressure in step S2 is 0.6 MPa, while the rest is the same as in Example 1.

[0038] Example 6 A refining process for high-purity electronic-grade ammonia gas differs from Example 1 in that the pressure in step S2 is 0.7 MPa, while the rest is the same as in Example 1.

[0039] Example 7 A refining process for high-purity electronic-grade ammonia gas differs from Example 1 in that, in step S2, the flow rate is 2.5 m / s, while the rest is the same as in Example 1.

[0040] Example 8 A refining process for high-purity electronic-grade ammonia gas differs from Example 3 in that, in step S2, the PVDF ultrafiltration membrane in the tubular PVDF ultrafiltration membrane is replaced with the PVSQ / SiO2 / PVDF ultrafiltration membrane prepared in Example 3; all other steps are the same as in Example 3.

[0041] Example 9 A refining process for high-purity electronic-grade ammonia gas differs from Example 3 in that, in step S2, the PVDF ultrafiltration membrane in the tubular PVDF ultrafiltration membrane is replaced with the PVSQ / SiO2 / PVDF ultrafiltration membrane prepared in Preparation Example 4; all other steps are the same as in Example 3.

[0042] Example 10 A refining process for high-purity electronic-grade ammonia gas differs from Example 3 in that, in step S2, the PVDF ultrafiltration membrane in the tubular PVDF ultrafiltration membrane is replaced with the alkali-treated PVDF ultrafiltration membrane obtained in Preparation Example 5; otherwise, the process is the same as in Example 3.

[0043] Example 11 A refining process for high-purity electronic-grade ammonia differs from Example 1 in that the distillation in step S3 has a feed pressure of 1.1 MPa, a feed temperature of 65°C, a top temperature of -34°C, and a bottom temperature of 12°C, while the rest are the same as in Example 1.

[0044] Example 12 A refining process for high-purity electronic-grade ammonia differs from Example 1 in that the distillation in step S3 has a feed pressure of 1.05 MPa, a feed temperature of 68°C, a top temperature of -32°C, and a bottom temperature of 14°C, while the rest are the same as in Example 1.

[0045] Example 13 A refining process for high-purity electronic-grade ammonia differs from Example 1 in that the distillation in step S3 has a feed pressure of 1.15 MPa, a feed temperature of 62°C, a top temperature of -31°C, and a bottom temperature of 11°C, while the rest are the same as in Example 1.

[0046] Comparative Example 1 The difference from Example 1 is that step S2 is omitted, specifically: S1. Pretreatment: The raw material liquid ammonia is pressurized to 1.5MPa by an ammonia pump and heated to 40℃. Under these conditions, it is vaporized and then filtered through a 0.22μm microporous membrane filter to remove suspended particulate impurities and mechanical impurities such as oil mist particles. The filtered gaseous ammonia enters the adsorption tower and continues to be adsorbed in series by an activated alumina adsorption tower and a molecular sieve adsorption tower at a pressure of 1.0MPa and a flow rate of 0.2m / s. When one tower is saturated, it is switched to the other tower to continue adsorption. At the same time, the saturated tower is regenerated. The regeneration is carried out by heating and desorbing with high-purity nitrogen gas treated by deoxygenation at 250℃ for 5 hours. After regeneration, the activated alumina adsorption tower is preheated to the operating temperature for later use. After regeneration, the molecular sieve adsorption tower is cooled to room temperature and sealed with high-purity nitrogen for 4 hours. The operating temperature for adsorption by activated alumina is 80℃, and the operating temperature for adsorption by molecular sieve is 100℃. The two towers are used alternately to obtain crude ammonia gas. S2. Distillation and Liquefaction: The crude ammonia gas obtained in step S1 is fed into a distillation column for final purification to remove residual trace impurities. The distillation column is a packed column with a specific surface area of ​​700 m². 2 / m 3 The column is 50m high and 1.5m in diameter, with 50 theoretical trays and a reflux ratio of 0.8. Distillation is carried out under the conditions of feed pressure of 1.2MPa, feed temperature of 60℃, top temperature of -30℃, and bottom temperature of 15℃. Impurities are concentrated in the liquid phase at the bottom of the column and separated, while pure ammonia is purified in the gas phase at the top of the column. It is then condensed and liquefied, and successively subjected to pre-cooling at -30℃, main cooling at -55℃, and final cooling at -75℃ to obtain electronic grade ammonia.

[0047] Comparative Example 2 The difference from Example 1 lies in the process parameters in step S2, specifically: S2. Ultrafiltration: The crude ammonia gas obtained in step S1 is passed into the ultrafiltration membrane separation unit and further purified by a tubular PVDF ultrafiltration membrane. The membrane separation operation is carried out at a temperature of 50℃, a pressure of 0.2MPa, and a flow rate of 1m / s. Ultrafiltration is carried out under these process conditions to obtain high-purity ammonia.

[0048] Comparative Example 3 The difference from Example 1 lies in the process parameters in step S2, specifically: S2. Ultrafiltration: The crude ammonia gas obtained in step S1 is passed into the ultrafiltration membrane separation unit and further purified by a tubular PVDF ultrafiltration membrane. The membrane separation operation is carried out at a temperature of 20°C, a pressure of 1 MPa, and a flow rate of 5 m / s. Ultrafiltration is carried out under these process conditions to obtain high-purity ammonia.

[0049] Performance testing The electronic-grade ammonia obtained in the examples and comparative examples was subjected to the following tests: its purity was comprehensively analyzed using analytical methods such as gas chromatography (GC), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma mass spectrometry (ICP-MS).

[0050] Table 1 Purity Record Sheet Group purity Example 1 5N Example 2 5N Example 3 6N Example 4 6N Example 5 5N Example 6 5N Example 7 5N Example 8 7N Example 9 7N Example 10 4N Example 11 6N Example 12 5N Example 13 5N Comparative Example 1 3N Comparative Example 2 4N Comparative Example 3 4N Data Analysis: As shown in Table 1, the purity of the electronic-grade ammonia in Examples 1-2 of this application can reach 5N, while the purity of the electronic-grade ammonia in Comparative Examples 1-3 is 3-4N. This proves that in this application, the raw material liquid ammonia is first vaporized, filtered, and adsorbed sequentially. Filtration can remove suspended particulate impurities and mechanical impurities such as oil mist particles from the liquid ammonia. The filtered gaseous substance enters the adsorption tower, where it is adsorbed alternately by activated alumina and molecular sieves in series. The entire process is carried out in the adsorption tower to obtain crude ammonia. PVSQ / SiO2 alcohol sol is prepared using a specific ratio of SiO2 and vinyltrimethoxysilane. Then, PVSQ / SiO2 / PVDF ultrafiltration membrane is prepared from PVSQ / SiO2 alcohol sol and PVDF membrane. Under the strict control of pressure, temperature, and flow rate in this application, the crude ammonia is ultrafiltered using this ultrafiltration membrane. Ammonia preferentially permeates through the ultrafiltration membrane under the action of pressure difference, while larger impurity molecules such as water and alcohols are preferentially retained, achieving... Further purification of ammonia yields high-purity ammonia. After ultrafiltration, the water content in the ammonia is further reduced to below 10 ng / g, and the alcohol content to below 50 ng / g, providing high-quality raw materials for subsequent distillation processes. High-purity ammonia is then obtained through a combination of distillation and condensation. During distillation, the relative volatility of ammonia is much higher than that of impurities. Therefore, impurities are mainly concentrated in the liquid phase at the bottom of the column and separated, while pure ammonia is purified in the gaseous phase at the top. Condensation achieves high-purity separation. Due to the significant difference in boiling points between ammonia and other gases (such as N2 and H2), ammonia preferentially liquefies and accumulates at the bottom of the column, while other gases remain in a gaseous state. Impurities can be gradually removed through staged cooling, ultimately yielding electronic-grade ammonia with a purity of over 5N. This process solves the problems of insufficient purity, high impurity content, high production costs, and low efficiency in removing trace impurities in existing ammonia refining processes, achieving high-purity, low-cost, and high-efficiency ammonia refining production.

[0051] The difference between Examples 3-4 and Example 1 is that this application simultaneously changed the pressure and flow rate during ultrafiltration. The results show that the electronic-grade ammonia concentration in Examples 3-4 can reach 6N. The difference between Examples 5-7 and Example 1 is that this application only changed the pressure or flow rate during ultrafiltration. The results show that the electronic-grade ammonia concentration in Examples 5-7 is no different from that in Example 1. This proves that by controlling the pressure at 0.6-0.7MPa and simultaneously setting the flow rate to 2.5m / s during the ultrafiltration step, this application can further optimize the mass transfer effect of the ultrafiltration process, remove impurities from the crude ammonia more efficiently, help improve the quality of high-purity ammonia, reduce production costs, and provide high-quality raw materials for subsequent distillation and condensation liquefaction processes, thereby more effectively realizing the refined production of high-purity electronic-grade ammonia.

[0052] In Examples 8-9, this application replaced the ordinary commercially available PVDF ultrafiltration membrane in the tubular PVDF ultrafiltration membrane with a PVSQ / SiO2 / PVDF ultrafiltration membrane. The results showed that the purity of the electronic-grade ammonia obtained in Examples 8-9 reached 7N. It can be seen that this application used vinyltrimethoxysilane to perform hydrophobic modification on SiO2, and vinyltrimethoxysilane generated regular spherical polyvinylsilsesquioxane (PVSQ) particles through its own hydrolysis and condensation reaction, forming a structure in which nano-sized SiO2 is distributed on the surface of micron-sized PVSQ. The ethanol sol formed by dispersing in ethanol was then used to soak PVDF, forming a multi-layered micro / nano rough surface on its membrane surface. Under the combined action of low surface energy hydrophobic groups vinyl and methoxy groups, the superhydrophobic modification of PVDF ultrafiltration membrane was successfully achieved. Due to its significantly improved hydrophobicity, it exhibits a more stable flux than commercial PVDF membranes and has excellent antifouling properties. It can not only more effectively retain water molecules in crude ammonia gas, but also show superior stability in use, reduce replacement frequency, and improve ultrafiltration quality.

[0053] In Example 10, this application replaced the ordinary commercially available PVDF ultrafiltration membrane in the tubular PVDF ultrafiltration membrane with an alkali-treated PVDF ultrafiltration membrane. At this time, the ultrafiltration membrane has a stronger hydrophilicity. The results showed that the purity of electronic-grade ammonia decreased to 4N. It can be seen that the superhydrophobicity of the PVSQ / SiO2 / PVDF ultrafiltration membrane can indeed more effectively retain water molecules in crude ammonia, improve the ultrafiltration quality, and more effectively realize the purification production of high-purity electronic-grade ammonia.

[0054] In Examples 11-13, the process parameters during distillation were adjusted. The results showed that the purity of the electronic-grade ammonia in Example 11 was improved compared to Example 1, while the purity in Examples 12-13 did not change significantly. It can be seen that by precisely controlling the feed pressure to 1.1 MPa, feed temperature to 65°C, top temperature to -34°C, and bottom temperature to 12°C during distillation, the present application can further and effectively remove impurities, ensuring that the final electronic-grade ammonia reaches a high purity of 6N or higher. This helps to solve the problem that existing refining processes cannot meet the stringent purity standards of ammonia in the high-end electronics industry.

[0055] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A refining process for high-purity electronic-grade ammonia, characterized in that, Includes the following steps: S1. Pretreatment: The raw liquid ammonia is successively vaporized, filtered, and adsorbed to obtain crude ammonia gas. S2, Ultrafiltration: The crude ammonia gas obtained in step S1 is subjected to ultrafiltration under conditions of pressure of 0.4-0.8 MPa, temperature of 25-45℃ and flow rate of 1.5-3.5 m / s to obtain high-purity ammonia; S3. Distillation and condensation liquefaction: The high-purity ammonia obtained in step S2 is successively distilled and condensed to obtain electronic-grade ammonia with a purity of 5N.

2. The refining process for high-purity electronic-grade ammonia according to claim 1, characterized in that, Step S1 specifically involves: The raw material liquid ammonia is vaporized at a pressure of 1.2-1.5 MPa and a temperature of 40-60℃, filtered through 0.2-0.22 μm micropores, and then adsorbed in series by activated alumina and molecular sieves at a pressure of 0.8-1.0 MPa and a flow rate of 0.2-0.3 m / s for 4-6 h. The operating temperature for adsorption by activated alumina is 50-80℃, and the operating temperature for adsorption by molecular sieves is 70-100℃.

3. The refining process for high-purity electronic-grade ammonia according to claim 1, characterized in that, In step S2, ultrafiltration is performed using a PVSQ / SiO2 / PVDF ultrafiltration membrane.

4. The refining process for high-purity electronic-grade ammonia according to claim 3, characterized in that, The PVSQ / SiO2 / PVDF ultrafiltration membrane is prepared from PVSQ / SiO2 alcohol sol and PVDF membrane.

5. The refining process for high-purity electronic-grade ammonia according to claim 4, characterized in that, The PVSQ / SiO2 alcohol sol is prepared from SiO2 and vinyltrimethoxysilane, and the weight ratio of SiO2 to vinyltrimethoxysilane in the PVSQ / SiO2 alcohol sol is 1:(4-4.5).

6. The refining process for high-purity electronic-grade ammonia according to claim 1, characterized in that, In step S2, the pressure is 0.6-0.7 MPa and the flow rate is 2.5 m / s.

7. The refining process for high-purity electronic-grade ammonia according to claim 1, characterized in that, In step S3, the specific operation of distillation is as follows: distillation is carried out under the conditions of feed pressure of 1-1.2 MPa, feed temperature of 60-70℃, column top temperature of -35~-30℃, and column bottom temperature of 10-15℃.

8. The refining process for high-purity electronic-grade ammonia according to claim 7, characterized in that, In the distillation process, the feed pressure is 1.1 MPa, the feed temperature is 65°C, the top temperature is -34°C, and the bottom temperature is 12°C.

9. The refining process for high-purity electronic-grade ammonia according to claim 1, characterized in that, In step S3, condensation and liquefaction include pre-cooling, main cooling, and final cooling performed sequentially.

10. The refining process for high-purity electronic-grade ammonia according to claim 9, characterized in that, The pre-cooling process involves setting the temperatures of the main cooling and final cooling to decrease sequentially, with each decrease ranging from 20 to 25°C. The pre-cooling temperature is -30°C.