A method for preparing high-purity ammonia water and high-purity ammonia gas

Abstract

This invention discloses a method for preparing high-purity ammonia water and high-purity ammonia gas, comprising: using industrial-grade urea as raw material, sequentially performing a first recrystallization, polar organic solvent treatment, a second recrystallization, filter cartridge filtration, chelating resin treatment, ion exchange treatment, a third recrystallization, and drying to obtain urea crystals; heating the prepared urea crystals to obtain a mixed gas of ammonia gas and other impurity gases; cooling the mixed gas to convert the ammonia gas in the mixed gas into a solid, separating it from some or all of the other impurity gases; then heating the solid ammonia gas to obtain primary purified ammonia gas; sequentially subjecting the primary purified ammonia gas to dehydration treatment, removing carbon dioxide gas using a polyimide membrane and / or modified polyimide membrane, and nanofiltration; and passing the obtained ammonia gas into ultrapure water to produce high-purity ammonia water. This invention features a simple process, is environmentally friendly, easily scalable, safe to operate, produces stable product quality, and is suitable for industrialization.

Description

Technical Field

[0001] This invention relates to the field of ultra-high purity reagent purification technology, specifically to a method for preparing high-purity ammonia water and high-purity ammonia gas. Background Technology

[0002] As wafer sizes continue to increase and chip integration becomes increasingly sophisticated in semiconductor manufacturing, the demand for high-purity solvents is also rising. Ultra-high purity reagents are crucial raw materials in integrated circuit production. Ultra-high purity ammonia, as an important solvent, is primarily used in cleaning processes in the panel and semiconductor industries to remove residues from wafer surfaces and reduce residual metal impurities. The effectiveness of ammonia cleaning directly impacts the performance of subsequent semiconductor devices, and this effectiveness is in turn affected by the purity of the ammonia solution. Therefore, obtaining ultra-high purity ammonia is a pressing issue that needs to be addressed.

[0003] Currently, ultra-high purity ammonia water is usually prepared using industrial-grade liquid ammonia, for example, through the following process, including the following steps:

[0004] (1) Liquid ammonia preparation: Prepare a sufficient amount of liquid ammonia in steel cylinders for use according to the required amount of high-purity ammonia water; (2) Pressure reduction evaporation: The industrial-grade liquid ammonia prepared in step (1) is subjected to pressure reduction evaporation through a pressure reduction evaporator to obtain ammonia gas; (3) Secondary purification: The ammonia gas extracted in step (2) is passed into the interior of a washing and purification tower for further purification, so that the ammonia gas is returned to the interior of the storage tank after washing and purification; (4) Gas washing: Prepare two tanks, put potassium permanganate and sodium hydroxide suspension into the interior of the two tanks respectively, and pass the purified ammonia gas into the two tanks in sequence. Inside the tank, two wash bottles filled with pure water are prepared to perform final purification of ammonia gas; (5) Blending: Ammonia gas treated in step (4) is absorbed by circulation using ultrapure water with a resistivity greater than or equal to 18 MΩ·cm to obtain semi-finished ammonia water; (6) Circulation filtration: The semi-finished ammonia water treated in step (5) is filtered by circulation through a liquid filter; However, this method uses industrial-grade liquid ammonia as the initial raw material, which has stringent requirements for the storage of raw materials. The storage of liquid ammonia is very dangerous, and the storage equipment is expensive. In particular, the purity of the ammonia water produced by this method is relatively insufficient and needs to be further improved.

[0005] In addition, there is a method of preparing ammonia water by making ammonia gas. However, in the process of making ammonia gas, a lot of organic by-products are inevitably present in the ammonia gas. In this case, it is difficult to remove the organic matter from the gas. Although it is possible to do so without considering the cost, it is not conducive to industrial application. Summary of the Invention

[0006] The purpose of this invention is to overcome one or more shortcomings of the prior art and provide an improved method for preparing high-purity ammonia water that uses industrial-grade urea as raw material and can meet high standards.

[0007] The present invention also provides a method for preparing high-purity ammonia.

[0008] To achieve the above objectives, the present invention provides a technical solution: a method for preparing high-purity ammonia water, which uses industrial-grade urea as raw material, and the steps include:

[0009] (1) Preparation of urea crystals:

[0010] Using industrial-grade urea as raw material, the process proceeds sequentially as follows: first recrystallization, polar organic solvent treatment, second recrystallization, filter cartridge filtration, chelating resin treatment, ion exchange treatment, third recrystallization, and drying.

[0011] (2) Preparation of ammonia:

[0012] The urea crystals prepared in step (1) are heated to obtain a mixture of ammonia and other impurity gases;

[0013] The mixed gas is cooled to below -76°C to convert the ammonia in the mixed gas into a solid, separating it from some or all of the other impurity gases; then the solid ammonia is heated to -42°C to -32°C to obtain primary purified ammonia.

[0014] The primary purified ammonia gas is subjected to the following steps in sequence: water removal, removal of carbon dioxide gas using a polyimide membrane and / or a modified polyimide membrane, and nanofiltration.

[0015] (3) Pass the ammonia gas obtained in step (2) into ultrapure water to produce high-purity ammonia water.

[0016] According to some preferred aspects of the present invention, in the preparation of urea crystals, the first recrystallization and the second recrystallization are carried out independently using ultrapure water as solvent, with a dissolution temperature of 70-76°C and a recrystallization temperature of 36-42°C, and the third recrystallization is carried out under reduced pressure at room temperature based on the solution obtained by ion exchange treatment.

[0017] According to some preferred aspects of the present invention, in the preparation of urea crystals, the polar organic solvent treatment is carried out using chloroform and / or chlorobenzene, and the crystals obtained from the first recrystallization are pulverized into powder and then mixed with chloroform and / or chlorobenzene.

[0018] According to some preferred aspects of the present invention, in the process of preparing urea crystals, the filter element filtration adopts multi-stage filtration, which sequentially uses polypropylene filter elements of 35-45μm, 15-25μm, 6-14μm, and 1-5μm.

[0019] According to some preferred aspects of the present invention, in the preparation of urea crystals, the chelating resin used for chelating resin treatment is Hydrolite D851 chelating resin and / or Lewatit Monoplus TP260 chelating resin.

[0020] According to some preferred aspects of the present invention, in the process of preparing urea crystals, the ion exchange treatment includes sequential treatment with anion exchange resin and cation exchange resin respectively.

[0021] Furthermore, the anion exchange resin is Zhengguang D201 anion resin, and the cation exchange resin is Zhengguang D001 cation resin.

[0022] According to some preferred aspects of the present invention, in the process of preparing urea crystals, the drying is carried out by vacuum distillation at a drying pressure of 0.002-0.004 MPa and a drying temperature of 36-42°C.

[0023] According to some preferred aspects of the present invention, in the process of preparing ammonia, the urea crystals prepared in step (1) are heated to 300-350°C.

[0024] According to some preferred aspects of the present invention, in the preparation of primary purified ammonia, the mixed gas is cooled to -86°C to -76°C to convert the ammonia in the mixed gas into a solid, separating it from some or all of the other impurity gases; then the solid ammonia is heated to -42°C to -32°C to obtain primary purified ammonia.

[0025] According to some preferred aspects of the present invention, in the process of preparing ammonia, water removal is performed using molecular sieves or alkaline compounds.

[0026] In some embodiments of the present invention, the filter membrane for removing carbon dioxide is made of Evonik sepuran@NG material.

[0027] According to some preferred aspects of the present invention, in the process of preparing ammonia, the nanofiltration membrane used is made of polytetrafluoroethylene and is processed in a multi-stage manner, with pore sizes of 15-25nm, 8-14nm, 4-7nm, 2-3nm, and 0.5-1.5nm respectively.

[0028] In this invention, ultrapure water, also known as UP water, refers to water with a resistivity of 18 MΩ·cm (25℃).

[0029] Another technical solution provided by this invention: a method for preparing high-purity ammonia gas, which uses industrial-grade urea as raw material, and the steps include:

[0030] (1) Preparation of urea crystals:

[0031] Using industrial-grade urea as raw material, the process proceeds sequentially as follows: first recrystallization, polar organic solvent treatment, second recrystallization, filter cartridge filtration, chelating resin treatment, ion exchange treatment, third recrystallization, and drying.

[0032] (2) Preparation of high-purity ammonia:

[0033] The urea crystals prepared in step (1) are heated to obtain a mixture of ammonia and other impurity gases;

[0034] The mixed gas is cooled to below -76°C to convert the ammonia in the mixed gas into a solid, separating it from some or all of the other impurity gases; then the solid ammonia is heated to -42°C to -32°C to obtain primary purified ammonia.

[0035] The primary purified ammonia gas is subjected to the following steps in sequence: water removal, removal of carbon dioxide gas using a polyimide membrane, and nanofiltration.

[0036] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0037] This invention uses industrial-grade urea as raw material. First, some impurities are removed by recrystallization and organic solvent cleaning. Then, it is recrystallized again, and the particles are controlled by a filter element. Chelating resin adsorbs large molecular particles, anions are removed by anion exchange resin, and cations are removed by cation exchange resin. After recrystallization and drying, dry urea crystals are obtained. Then, the urea crystals are decomposed by heating to obtain ammonia and other impurity gases. The generated gases are selectively treated at low temperature to obtain ammonia. Then, the water in the ammonia is removed, and the carbon dioxide gas is separated. Then, nanofiltration is used to control the particles, and finally, high-purity ammonia product is obtained. It can be dissolved in high-purity water to obtain high-purity ammonia water.

[0038] This invention, through the above-mentioned multi-stage processing, first removes impurities with high content, then removes impurities with relatively low content, and combines the interconversion between solids and between solids and gases to achieve step-by-step control of impurity content, thus meeting high standard requirements, such as SEMI Tier D.

[0039] The product prepared by this invention has a weight content of 28-30%, an APHA color of less than or equal to 1, carbon dioxide ≤10000 ppb, chloride, nitrate, phosphate, and sulfate ≤1 ppb, cobalt, molybdenum, tungsten, and other metal cations <5 ppt, and dust particles (>0.2 μm) <100 pcs / mL, meeting the requirements of semiconductor device fabrication processes. This invention features a simple, environmentally friendly process that is easily implemented continuously, safe to operate, and produces stable product quality, making it suitable for industrial production. Attached Figure Description

[0040] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention. Detailed Implementation

[0041] The above-mentioned solution will be further described below with reference to specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0042] Unless otherwise specified in the following examples, all raw materials can be obtained from commercial sources or prepared by conventional methods in the art.

[0043] The test results for industrial-grade urea are shown in Table 1 below:

[0044] Table 1

[0045] project standard Test results Urea content (mass fraction) / % 31.8-33.2 33.1 <![CDATA[Density (20 °C) / (kg / m 3 )]]> 1087.0-1093.0 1092.0 refractive index 1.3814-1.3843 1.3841 <![CDATA[Alkalinity (calculated as NH3) (mass fraction) / %]]> ≤0.2 0.01 Biuret (mass fraction) / % ≤0.3 0.04 Aldehydes (as HCHO) / ​​ppm ≤5 0.5 Insoluble matter / ppm ≤20 1 <![CDATA[Phosphate (calculated as PO4 3- ) / ppm]]> ≤0.5 0.05 Ca / ppm ≤0.5 0.03 Fe / ppm ≤0.5 0.03 Cu / ppm ≤0.2 0.01 Zn / ppm ≤0.2 0.01 Cr / ppm ≤0.2 0.01 Ni / ppm ≤0.2 0.01 Al / ppm ≤0.5 0.02 Mg / ppm ≤0.5 0.02 Na / ppm ≤0.5 0.03 K / ppm ≤0.5 0.03

[0046] Example 1

[0047] This example provides a method for preparing high-purity ammonia water, using... Figure 1 The process shown uses industrial-grade urea as raw material, and its steps include:

[0048] (1) Preparation of urea crystals:

[0049] First recrystallization: Industrial grade urea is dissolved in high-purity water and heated to 72°C to make a supersaturated solution. Then the temperature is lowered to 36°C and the precipitated solid is filtered using a filter screen.

[0050] Chlorobenzene treatment: The obtained solid urea is crushed into powder and then placed in chlorobenzene and stirred thoroughly to remove organic impurities from the urea;

[0051] Second recrystallization: The urea solid with some organic impurities removed is placed back into ultrapure water for recrystallization (the process is the same as the previous recrystallization). After recrystallization, the filtered solid urea is placed into ultrapure water and completely dissolved.

[0052] Filter cartridge filtration: The solution is then filtered sequentially through polypropylene filter cartridges of 40μm, 20μm, 10μm, and 5μm to obtain a urea solution with some particulate impurities removed.

[0053] Chelating resin treatment, ion exchange treatment, third recrystallization and drying: The ions in the urea solution obtained above were removed sequentially using chelating resin (Zhengguang Hydrolite D851 chelating resin), anion exchange resin (Zhengguang D201 anion resin), and cation exchange resin (Zhengguang D001 cation resin). The resulting solution was then recrystallized under reduced pressure at room temperature, filtered, and the obtained solid was dried by reduced pressure distillation (pressure 0.003 MPa, temperature approximately 40°C) to obtain relatively pure urea crystals.

[0054] (2) Preparation of ammonia:

[0055] Urea crystals are heated and decomposed at 320℃ to obtain a mixture of ammonia and other gases. The mixture is then cooled to -86℃ and slowly heated to about -32℃ to obtain ammonia. This process can separate ammonia from other gases.

[0056] The obtained ammonia gas was passed through a molecular sieve (4A molecular sieve, purchased from Haixia (Shanghai) Environmental Protection Materials, brand name 4A) to remove moisture, and carbon dioxide was separated by a modified polyimide membrane (Evonik sepuran@NG) to obtain relatively pure ammonia gas. Then, the ammonia gas was passed through 40nm, 10nm, 5nm, 2nm and 1nm filter elements in sequence to remove particles and obtain high-purity ammonia gas.

[0057] (3) Preparation of high-purity ammonia water:

[0058] High-purity ammonia gas is passed into ultrapure water to obtain high-purity ammonia water.

[0059] Comparative Example 1

[0060] The process in Example 1 is identical except for the step of removing some organic impurities with chlorobenzene between the two recrystallizations.

[0061] Comparative Example 2

[0062] The step of achieving carbon dioxide separation using a modified polyimide membrane in Example 1 is removed; otherwise, it remains the same as in Example 1.

[0063] Comparative Example 3

[0064] The chelating resin, cation exchange resin, and anion exchange resin treatment steps in Example 1 were all removed, and everything else was the same as in Example 1.

[0065] Comparative Example 4

[0066] The order of chlorobenzene treatment and first recrystallization in Example 1 was reversed, while everything else remained the same as in Example 1.

[0067] Comparative Example 5

[0068] The order of chelating resin treatment and anion / cation resin treatment in Example 1 is reversed, and everything else is the same as in Example 1.

[0069] Comparative Example 6

[0070] The phrase "then the obtained mixed gas is cooled to -86°C and then slowly heated to about -32°C to obtain ammonia, and this process can separate ammonia from other gases" in Example 1 is omitted. After being heated into a gas, it is directly passed into the molecular sieve. Everything else is the same as in Example 1.

[0071] Example 2

[0072] The method is basically the same as in Example 1, except that chlorobenzene is replaced with chloroform.

[0073] Example 3

[0074] The process is basically the same as in Example 1, except that: Lanxess Lewatit Monoplus TP260 chelating resin is selected, and urea crystals are decomposed by heating at 350°C.

[0075] Performance testing

[0076] Tables 2-3 below show the detection results of ammonia water obtained in Examples 1-3 and Comparative Examples 1-6, respectively.

[0077] The product's mass content was measured using acid-base titration, anions were determined using liquid ion chromatography (IC), and the weight content of metal ions was analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Particle size was measured using a laser particle size analyzer, and colorimetry was determined using a colorimetric method.

[0078] Table 2

[0079]

[0080]

[0081] Table 3

[0082]

[0083]

[0084] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

[0085] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A method for preparing high-purity ammonia water, characterized in that, This preparation method uses industrial-grade urea as raw material, and its steps include: (1) Preparation of urea crystals: Using industrial-grade urea as raw material, the process involves the following steps in sequence: first recrystallization, polar organic solvent treatment, second recrystallization, filter cartridge filtration, chelating resin treatment, ion exchange treatment, third recrystallization, and drying. The polar organic solvent treatment uses chloroform and / or chlorobenzene, and the crystals obtained from the first recrystallization are pulverized into powder and then mixed with chloroform and / or chlorobenzene. The ion exchange treatment includes sequential treatment with anion exchange resin and cation exchange resin. (2) Preparation of ammonia: The urea crystals prepared in step (1) are heated to obtain a mixture of ammonia and other impurity gases; The mixed gas is cooled to below -76°C to convert the ammonia in the mixed gas into a solid, separating it from some or all of the other impurity gases; then the solid ammonia is heated to -42°C to -32°C to obtain primary purified ammonia. The primary purified ammonia gas is subjected to the following steps in sequence: water removal, removal of carbon dioxide gas using a polyimide membrane and / or a modified polyimide membrane, and nanofiltration. (3) Pass the ammonia gas obtained in step (2) into ultrapure water to produce high-purity ammonia water.

2. The method for preparing high-purity ammonia water according to claim 1, characterized in that, In the preparation of urea crystals, the first and second recrystallizations were carried out independently using ultrapure water as the solvent, with a dissolution temperature of 70-76℃ and a recrystallization temperature of 36-42℃. The third recrystallization was carried out under reduced pressure at room temperature based on the solution obtained by ion exchange treatment.

3. The method for preparing high-purity ammonia water according to claim 1, characterized in that, In the preparation of urea crystals, the filter element uses multi-stage filtration, which sequentially uses polypropylene filter elements of 35-45μm, 15-25μm, 6-14μm, and 1-5μm.

4. The method for preparing high-purity ammonia water according to claim 1, characterized in that, In the preparation of urea crystals, the chelating resin used for chelation treatment is either Hydrolite D851 chelating resin or Lewatit Monoplus TP260 chelating resin.

5. The method for preparing high-purity ammonia water according to claim 1, characterized in that, In the preparation of urea crystals, the anion exchange resin includes Zhengguang D201 anion resin, and the cation exchange resin includes Zhengguang D001 cation resin.

6. The method for preparing high-purity ammonia water according to claim 1, characterized in that, In the preparation of urea crystals, the drying process adopts vacuum distillation, with a drying pressure of 0.002-0.004 MPa and a drying temperature of 36-42℃.

7. The method for preparing high-purity ammonia water according to claim 1, characterized in that, In the process of preparing ammonia, the urea crystals prepared in step (1) are heated to 300-350℃; In the preparation of primary purified ammonia, the mixed gas is cooled to -86℃ to -76℃ to convert the ammonia in the mixed gas into a solid, separating it from some or all of the other impurity gases; then the solid ammonia is heated to -42℃ to -32℃ to obtain primary purified ammonia.

8. The method for preparing high-purity ammonia water according to claim 1, characterized in that, Molecular sieves are used for water removal during the ammonia preparation process. In the process of ammonia preparation, the nanofiltration membrane used is made of polytetrafluoroethylene and adopts a multi-stage treatment method with pore sizes of 15-25nm, 8-14nm, 4-7nm, 2-3nm, and 0.5-1.5nm respectively.

9. A method for preparing high-purity ammonia, characterized in that, This preparation method uses industrial-grade urea as raw material, and its steps include: (1) Preparation of urea crystals: Using industrial-grade urea as raw material, the process is carried out in sequence as follows: first recrystallization, polar organic solvent treatment, second recrystallization, filter cartridge filtration, chelating resin treatment, ion exchange treatment, third recrystallization, and drying; wherein, the polar organic solvent treatment is carried out using chloroform and / or chlorobenzene, and the crystals obtained from the first recrystallization are crushed into powder and then mixed with chloroform and / or chlorobenzene. (2) Preparation of high-purity ammonia: The urea crystals prepared in step (1) are heated to obtain a mixture of ammonia and other impurity gases; The mixed gas is cooled to below -76°C to convert the ammonia in the mixed gas into a solid, separating it from some or all of the other impurity gases; then the solid ammonia is heated to -42°C to -32°C to obtain primary purified ammonia. The primary purified ammonia gas is subjected to the following steps in sequence: water removal, removal of carbon dioxide gas using a polyimide membrane, and nanofiltration.

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