A method for preparing electronic-grade nitric acid without yellow smoke

Abstract

The present invention relates to the technical field of electronic-grade nitric acid preparation, and more particularly to a method for preparing electronic-grade nitric acid without yellow smoke. The method uses industrial-grade nitric acid as a raw material to produce electronic-grade nitric acid. A relatively low-temperature azeotropic distillation is employed to avoid thermal decomposition of the nitric acid during high-temperature heating and distillation. Nitric acid is generated by oxidizing and removing nitrogen oxides from the nitric acid using inexpensive oxygen. This solves the problem of yellowing of industrial nitric acid solutions and the generation of yellow smoke. It also reduces the difficulty of waste gas treatment associated with traditional electronic-grade nitric acid production methods. The method is simple to operate, allows for stable content control, and, after microfiltration in a microfiltration unit, reduces the metal content of the nitric acid, meeting electronic-grade requirements.

Description

Technical Field

[0001] The invention relates to the technical field of electronic-grade nitric acid preparation, in particular to a method for preparing yellow-smoke-free electronic-grade nitric acid. Background Art

[0002] Electronic chemicals are a crucial supporting sector for the electronic information industry and the fastest-growing sector within the fine chemical sector. Their downstream applications are extensive, including integrated circuits, flat panel displays, printed circuit boards (PCBs), and photovoltaic solar energy. Due to the high level of technological integration and complexity in the downstream electronics sector, the quality requirements for upstream electronic chemicals are stringent. Electronic-grade nitric acid is a fine chemical with high purity requirements, with impurity levels below 109 (ppb).

[0003] Patent application number CN201110041529.4 discloses a method for producing electronic-grade nitric acid, which comprises the following steps in sequence: a) providing a chemically pure reagent-grade nitric acid raw material with a concentration of approximately 70%; b) subjecting the nitric acid raw material to microfiltration and preheating in a preheater before entering a reboiler; c) heating the reboiler with saturated steam, and the nitric acid vapor generated by the heating is passed through a steam condenser to obtain a semi-finished product; d) purging the semi-finished product with high-purity compressed air to remove any residues in the semi-finished product, and the resulting finished product is cooled again in a finished product cooler and then enters a finished product storage tank; e) removing particles through ultrafiltration to obtain the final nitric acid used in the electronics industry.

[0004] Patent application number CN202310698711.X discloses a method for preparing electronic-grade nitric acid, comprising the following steps: first mixing industrial concentrated nitric acid, a first impurity remover solution, and a second impurity remover solution to remove impurities, followed by distillation, and second mixing the obtained condensate with ultrapure deionized water to obtain a standard nitric acid solution; vacuum whitening the standard nitric acid solution to obtain the electronic-grade nitric acid; the first impurity remover in the first impurity remover solution is one or more of ammonium nitrate, silver nitrate, and sodium nitrate; and the second impurity remover in the second impurity remover solution is barium nitrate and / or a precious metal nitrate.

[0005] Patent application number CN201410626572.0 discloses a process for synthesizing electronic-grade nitric acid. The method of the present invention comprises the following steps: removing nitric acid obtained by condensing nitrogen oxide gas obtained by ammonia oxidation in a reactor of a double-pressurized nitric acid synthesis process through a polytetrafluoroethylene wire mesh demister, reacting the remaining nitrogen oxide gas with deionized water and bleaching it to become colorless nitric acid, and filtering the colorless nitric acid through a precision filter to obtain electronic-grade nitric acid. The precision filter is a polytetrafluoroethylene nanofiltration membrane filter with an accuracy of 0.9 μm to 2.0 μm.

[0006] With the rapid development of the national economy, the use of electronic chemicals in related industries has also increased simultaneously. Simultaneously, with the advancement of science and technology, the requirements for the variety and quality of electronic chemicals have become increasingly stringent. In particular, electronic chemicals used in high-tech fields are generally of high purity, such as in large-scale integrated circuits, optical fiber materials, and related reagents, where impurity levels are limited to pb levels. Although my country's electronic chemical technology has reached a certain level, it still cannot fully meet the actual needs of scientific development and industrial requirements, and there is a considerable gap with the world's advanced level, requiring further development. Furthermore, under the new circumstances, environmental protection requirements are becoming increasingly stringent. Industrial-grade nitric acid solutions have the problem of yellowing and producing yellow smoke. The nitric acid solutions produced using traditional electronic-grade nitric acid preparation processes generate a large amount of waste gas that is difficult to dispose of, causing significant environmental pollution and low production efficiency. Summary of the Invention

[0007] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a method for preparing electronic-grade nitric acid without yellow smoke, which solves the problem of yellowing and yellow smoke generation of industrial-grade nitric acid solution, and at the same time reduces the difficulty of waste gas treatment in traditional electronic-grade nitric acid production methods. The operation is simple and the content control is stable.

[0008] Another object of the present invention is to provide the electronic grade nitric acid obtained by the above preparation method.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing electronic-grade nitric acid without yellow smoke, characterized by comprising the following steps:

[0011] (1) Distillation: Concentrated nitric acid is heated and distilled through a reboiler to obtain a vaporized acid gas solution;

[0012] (2) Reaction impurity removal: passing O3 into the nitric acid solution after distillation in step (1) to remove nitrogen oxide (NOx) impurities;

[0013] (3) Evaporation: The nitric acid solution obtained in step (2) is passed into an evaporator for evaporation, and O3 and unreacted NOx are gasified;

[0014] (4) impurity removal in a stripping tower: the nitric acid solution obtained in step (3) is pumped into a stripping tower to remove O3 and unreacted NOx in the nitric acid solution;

[0015] (5) Multi-stage filtration: The nitric acid solution obtained in step (4) is passed through a microfiltration unit for microfiltration treatment to obtain an electronic grade nitric acid solution.

[0016] Furthermore, the azeotropic distillation temperature in step (1) is 100-120°C

[0017] Furthermore, in step (2), the molar ratio of O3 to NOx is 1:2.6-3.4.

[0018] Furthermore, in step (3), the evaporator is an MVR evaporator, and the evaporation temperature is 50-90°C.

[0019] Furthermore, the stripping medium in step (4) is high-purity CDA.

[0020] Further, the microfiltration unit adopts a nitric acid filter lined with polytetrafluoroethylene (PTFE), and the filter element is a modified polytetrafluoroethylene filter element, which can adsorb metal ions in electronic grade nitric acid at the same time. The modification method of the modified polytetrafluoroethylene filter element is:

[0021] B1: Place a polytetrafluoroethylene filter element in a plasma surface treatment apparatus, turn on the radio frequency power supply of the low-temperature plasma treatment apparatus, adjust the discharge power of the radio frequency power supply, and introduce 6-mercapto-1-hexanol vapor into the reaction chamber of the plasma surface treatment apparatus for 10 to 30 minutes at a discharge power of 90 to 130 W to obtain a mercapto polytetrafluoroethylene filter element;

[0022] B2: To 600-700 parts of tetrahydrofuran, add 100-130 parts of mercapto polytetrafluoroethylene filter element, 4-7 parts of dimethylallyl diphosphoric acid, 0.5-2 parts of 3-(2-carboxyvinyl)phenylboric acid, 0.005-0.2 parts of 2,5-dimercaptothiazole, and 1-3 parts of photoinitiator benzoin dimethyl ether, by weight, and allow mercapto-ene click reaction to occur in a nitrogen atmosphere. Under ultraviolet light, react for 2-4 hours, filter, wash with tetrahydrofuran and ethanol, and dry to obtain a modified polytetrafluoroethylene filter element.

[0023] Furthermore, the air flow of the 6-mercapto-1-hexanol is 10-40 mL / min.

[0024] Furthermore, the power of the controlled UV lamp is 400-500W, and the UV light intensity is 20-40mW / cm 2 .

[0025] The modification mechanism of modified polytetrafluoroethylene filter element is:

[0026] In this scheme, a polytetrafluoroethylene filter element is placed in plasma, and 6-mercapto-1-hexanol vapor is introduced to obtain a mercapto polytetrafluoroethylene filter element; the mercapto polytetrafluoroethylene filter element and 2,5-dimercaptothiazole respectively undergo a mercapto-ene click reaction with dimethylallyl diphosphoric acid and 3-(2-carboxyvinyl)phenylboronic acid, and under ultraviolet light irradiation, a modified polytetrafluoroethylene filter element containing diphosphoric acid, phenylboric acid, and thiazole is obtained; in the filtration of the nitric acid solution in step (5), trace metal ions therein can be retained on the membrane surface through the complexation of diphosphoric acid and phenylboric acid, thereby obtaining an electronic grade nitric acid solution.

[0027] The beneficial effects achieved by the present invention using the above technical solution are as follows:

[0028] In this solution, diphosphoric acid, phenylboronic acid, and thiazole on the modified polytetrafluoroethylene filter element react with trace metal ions, trapping them on the membrane surface and producing an electronic-grade nitric acid solution. The key to this reaction is that the ligands diphosphoric acid and phenylboronic acid donate one or more electrons to form complexes with the metal ions, trapping them on the membrane surface. This is primarily because the resulting complexes carry an electric charge, attracting them to the membrane surface, thereby trapping the metal ions. The resulting nitric acid solution has an extremely low metal ion content, meeting electronic-grade standards. DETAILED DESCRIPTION

[0029] To make the objects, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be described clearly and completely below in conjunction with the examples. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] Example 1

[0032] A method for preparing electronic-grade nitric acid without yellow smoke, characterized by comprising the following steps:

[0033] (1) Distillation: Concentrated nitric acid is heated and distilled through a reboiler to obtain a vaporized acid gas solution;

[0034] (2) Reaction impurity removal: passing O3 into the nitric acid solution after distillation in step (1) to remove nitrogen oxide (NOx) impurities;

[0035] (3) Evaporation: The nitric acid solution obtained in step (2) is passed into an evaporator for evaporation, and O3 and unreacted NOx are gasified;

[0036] (4) impurity removal in a stripping tower: the nitric acid solution obtained in step (3) is pumped into a stripping tower to remove O3 and unreacted NOx in the nitric acid solution;

[0037] (5) Multi-stage filtration: The nitric acid solution obtained in step (4) is passed through a microfiltration unit for microfiltration treatment to obtain an electronic grade nitric acid solution.

[0038] The azeotropic distillation temperature in step (1) is 100°C

[0039] The molar ratio of O3 to NOx in step (2) is 1:2.6.

[0040] The evaporator in step (3) is an MVR evaporator with an evaporation temperature of 50°C.

[0041] The stripping medium in step (4) is high-purity CDA.

[0042] The microfiltration unit adopts a nitric acid filter lined with polytetrafluoroethylene (PTFE), and the filter element is a modified polytetrafluoroethylene filter element, which can adsorb metal ions in electronic grade nitric acid. The modification method of the modified polytetrafluoroethylene filter element is as follows:

[0043] B1: Place a polytetrafluoroethylene filter element in a plasma surface treatment apparatus, turn on the radio frequency power supply of the low-temperature plasma treatment apparatus, adjust the discharge power of the radio frequency power supply, and introduce 6-mercapto-1-hexanol vapor into the reaction chamber of the plasma surface treatment apparatus for 10 minutes at a discharge power of 900 W to obtain a mercapto polytetrafluoroethylene filter element;

[0044] B2: To 600 g of tetrahydrofuran, 100 g of a mercapto polytetrafluoroethylene filter element, 4 g of dimethylallyl diphosphoric acid, 0.5 g of 3-(2-carboxyvinyl)phenylboric acid, 0.05 g of 2,5-dimercaptothiazole, and 1 g of a photoinitiator, benzoin dimethyl ether, were added. A mercapto-ene click reaction occurred in a nitrogen atmosphere. The reaction was carried out under ultraviolet light for 2 h, filtered, washed with tetrahydrofuran and ethanol, and dried to obtain a modified polytetrafluoroethylene filter element.

[0045] The gas flow of 6-mercapto-1-hexanol was 10 mL / min.

[0046] The power of the UV lamp is controlled to be 400W, and the UV light intensity is 20mW / cm 2 .

[0047] Example 2

[0048] A method for preparing electronic-grade nitric acid without yellow smoke, characterized by comprising the following steps:

[0049] (1) Distillation: Concentrated nitric acid is heated and distilled through a reboiler to obtain a vaporized acid gas solution;

[0050] (2) Reaction impurity removal: passing O3 into the nitric acid solution after distillation in step (1) to remove nitrogen oxide (NOx) impurities;

[0051] (3) Evaporation: The nitric acid solution obtained in step (2) is passed into an evaporator for evaporation, and O3 and unreacted NOx are gasified;

[0052] (4) impurity removal in a stripping tower: the nitric acid solution obtained in step (3) is pumped into a stripping tower to remove O3 and unreacted NOx in the nitric acid solution;

[0053] (5) Multi-stage filtration: The nitric acid solution obtained in step (4) is passed through a microfiltration unit for microfiltration treatment to obtain an electronic grade nitric acid solution.

[0054] The azeotropic distillation temperature in step (1) is 110°C

[0055] The molar ratio of O3 to NOx in step (2) is 1:3.0.

[0056] The evaporator in step (3) is an MVR evaporator with an evaporation temperature of 70°C.

[0057] The stripping medium in step (4) is high-purity CDA.

[0058] The microfiltration unit adopts a nitric acid filter lined with polytetrafluoroethylene (PTFE), and the filter element is a modified polytetrafluoroethylene filter element, which can adsorb metal ions in electronic grade nitric acid. The modification method of the modified polytetrafluoroethylene filter element is as follows:

[0059] B1: Place a polytetrafluoroethylene filter element in a plasma surface treatment apparatus, turn on the radio frequency power supply of the low-temperature plasma treatment apparatus, adjust the discharge power of the radio frequency power supply, and introduce 6-mercapto-1-hexanol vapor into the reaction chamber of the plasma surface treatment apparatus for 20 minutes at a discharge power of 110 W to obtain a mercapto polytetrafluoroethylene filter element;

[0060] B2: To 650 g of tetrahydrofuran, 115 g of a mercapto polytetrafluoroethylene filter element, 5.5 g of dimethylallyl diphosphoric acid, 1.2 g of 3-(2-carboxyvinyl)phenylboronic acid, 0.1 g of 2,5-dimercaptothiazole, and 2 g of a photoinitiator, benzoin dimethyl ether, were added. A mercapto-ene click reaction occurred in a nitrogen atmosphere. The reaction was carried out under ultraviolet light for 3 h, filtered, washed with tetrahydrofuran and ethanol, and dried to obtain a modified polytetrafluoroethylene filter element.

[0061] The gas flow of 6-mercapto-1-hexanol was 25 mL / min.

[0062] The power of the UV lamp is controlled to be 450W, and the UV light intensity is 30mW / cm 2 .

[0063] Example 3

[0064] A method for preparing electronic-grade nitric acid without yellow smoke, characterized by comprising the following steps:

[0065] (1) Distillation: Concentrated nitric acid is heated and distilled through a reboiler to obtain a vaporized acid gas solution;

[0066] (2) Reaction impurity removal: passing O3 into the nitric acid solution after distillation in step (1) to remove nitrogen oxide (NOx) impurities;

[0067] (3) Evaporation: The nitric acid solution obtained in step (2) is passed into an evaporator for evaporation, and O3 and unreacted NOx are gasified;

[0068] (4) impurity removal in a stripping tower: the nitric acid solution obtained in step (3) is pumped into a stripping tower to remove O3 and unreacted NOx in the nitric acid solution;

[0069] (5) Multi-stage filtration: The nitric acid solution obtained in step (4) is passed through a microfiltration unit for microfiltration treatment to obtain an electronic grade nitric acid solution.

[0070] The azeotropic distillation temperature in step (1) is 120°C

[0071] The molar ratio of O3 to NOx in step (2) is 1:3.4.

[0072] The evaporator in step (3) is an MVR evaporator with an evaporation temperature of 90°C.

[0073] The stripping medium in step (4) is high-purity CDA.

[0074] The microfiltration unit adopts a nitric acid filter lined with polytetrafluoroethylene (PTFE), and the filter element is a modified polytetrafluoroethylene filter element, which can adsorb metal ions in electronic grade nitric acid. The modification method of the modified polytetrafluoroethylene filter element is as follows:

[0075] B1: Place a polytetrafluoroethylene filter element in a plasma surface treatment apparatus, turn on the radio frequency power supply of the low-temperature plasma treatment apparatus, adjust the discharge power of the radio frequency power supply, and introduce 6-mercapto-1-hexanol vapor into the reaction chamber of the plasma surface treatment apparatus for 30 minutes at a discharge power of 130 W to obtain a mercapto polytetrafluoroethylene filter element;

[0076] B2: To 700 g of tetrahydrofuran, 130 g of a mercapto polytetrafluoroethylene filter element, 7 g of dimethylallyl diphosphoric acid, 2 g of 3-(2-carboxyvinyl)phenylboric acid, 0.2 g of 2,5-dimercaptothiazole, and 3 g of a photoinitiator, benzoin dimethyl ether, were added. A mercapto-ene click reaction occurred in a nitrogen atmosphere. The reaction was carried out under ultraviolet light for 4 h, filtered, washed with tetrahydrofuran and ethanol, and dried to obtain a modified polytetrafluoroethylene filter element.

[0077] The gas flow of 6-mercapto-1-hexanol was 40 mL / min.

[0078] The power of the UV lamp is controlled to be 500W, and the UV light intensity is 40mW / cm 2 .

[0079] Comparative Example 1

[0080] A method for preparing electronic-grade nitric acid without yellow smoke, characterized by comprising the following steps:

[0081] (1) Distillation: Concentrated nitric acid is heated and distilled through a reboiler to obtain a vaporized acid gas solution;

[0082] (2) Reaction impurity removal: passing O3 into the nitric acid solution after distillation in step (1) to remove nitrogen oxide (NOx) impurities;

[0083] (3) Evaporation: The nitric acid solution obtained in step (2) is passed into an evaporator for evaporation, and O3 and unreacted NOx are gasified;

[0084] (4) impurity removal in a stripping tower: the nitric acid solution obtained in step (3) is pumped into a stripping tower to remove O3 and unreacted NOx in the nitric acid solution;

[0085] (5) Multi-stage filtration: The nitric acid solution obtained in step (4) is passed through a microfiltration unit for microfiltration treatment to obtain an electronic grade nitric acid solution.

[0086] The azeotropic distillation temperature in step (1) is 100°C

[0087] The molar ratio of O3 to NOx in step (2) is 1:2.6.

[0088] The evaporator in step (3) is an MVR evaporator with an evaporation temperature of 50°C.

[0089] The stripping medium in step (4) is high-purity CDA.

[0090] The microfiltration unit adopts a nitric acid filter lined with polytetrafluoroethylene (PTFE), and the filter element is a modified polytetrafluoroethylene filter element, which can adsorb metal ions in electronic grade nitric acid. The modification method of the modified polytetrafluoroethylene filter element is as follows:

[0091] B1: Place a polytetrafluoroethylene filter element in a plasma surface treatment apparatus, turn on the radio frequency power supply of the low-temperature plasma treatment apparatus, adjust the discharge power of the radio frequency power supply, and introduce 6-mercapto-1-hexanol vapor into the reaction chamber of the plasma surface treatment apparatus for 10 minutes at a discharge power of 900 W to obtain a mercapto polytetrafluoroethylene filter element;

[0092] B2: To 600 g of tetrahydrofuran, 100 g of a mercaptopolytetrafluoroethylene filter element, 0.5 g of 3-(2-carboxyvinyl)phenylboronic acid, 0.05 g of 2,5-dimercaptothiazole, and 1 g of photoinitiator benzoin dimethyl ether were added. A mercaptoene click reaction occurred in a nitrogen atmosphere. The reaction was carried out under ultraviolet light for 2 h, filtered, washed with tetrahydrofuran and ethanol, and dried to obtain a modified polytetrafluoroethylene filter element.

[0093] The gas flow of 6-mercapto-1-hexanol was 10 mL / min.

[0094] The power of the UV lamp is controlled to be 400W, and the UV light intensity is 20mW / cm 2 .

[0095] Comparative Example 2

[0096] A method for preparing electronic-grade nitric acid without yellow smoke, characterized by comprising the following steps:

[0097] (1) Distillation: Concentrated nitric acid is heated and distilled through a reboiler to obtain a vaporized acid gas solution;

[0098] (2) Reaction impurity removal: passing O3 into the nitric acid solution after distillation in step (1) to remove nitrogen oxide (NOx) impurities;

[0099] (3) Evaporation: The nitric acid solution obtained in step (2) is passed into an evaporator for evaporation, and O3 and unreacted NOx are gasified;

[0100] (4) impurity removal in a stripping tower: the nitric acid solution obtained in step (3) is pumped into a stripping tower to remove O3 and unreacted NOx in the nitric acid solution;

[0101] (5) Multi-stage filtration: The nitric acid solution obtained in step (4) is passed through a microfiltration unit for microfiltration treatment to obtain an electronic grade nitric acid solution.

[0102] The azeotropic distillation temperature in step (1) is 100°C

[0103] The molar ratio of O3 to NOx in step (2) is 1:2.6.

[0104] The evaporator in step (3) is an MVR evaporator with an evaporation temperature of 50°C.

[0105] The stripping medium in step (4) is high-purity CDA.

[0106] The microfiltration unit adopts a nitric acid filter lined with polytetrafluoroethylene (PTFE), and the filter element is a modified polytetrafluoroethylene filter element, which can adsorb metal ions in electronic grade nitric acid. The modification method of the modified polytetrafluoroethylene filter element is as follows:

[0107] B1: Place a polytetrafluoroethylene filter element in a plasma surface treatment apparatus, turn on the radio frequency power supply of the low-temperature plasma treatment apparatus, adjust the discharge power of the radio frequency power supply, and introduce 6-mercapto-1-hexanol vapor into the reaction chamber of the plasma surface treatment apparatus for 10 minutes at a discharge power of 900 W to obtain a mercapto polytetrafluoroethylene filter element;

[0108] B2: To 600 g of tetrahydrofuran, 100 g of a mercaptopolytetrafluoroethylene filter element, 4 g of dimethylallyl diphosphoric acid, 0.05 g of 2,5-dimercaptothiazole, and 1 g of a photoinitiator, benzoin dimethyl ether, were added. A mercapto-ene click reaction occurred in a nitrogen atmosphere. The reaction was carried out under ultraviolet light for 2 h, filtered, washed with tetrahydrofuran and ethanol, and dried to obtain a modified polytetrafluoroethylene filter element.

[0109] The gas flow of 6-mercapto-1-hexanol was 10 mL / min.

[0110] The power of the UV lamp is controlled to be 400W, and the UV light intensity is 20mW / cm 2 .

[0111] Comparative Example 3

[0112] A method for preparing electronic-grade nitric acid without yellow smoke, characterized by comprising the following steps:

[0113] (1) Distillation: Concentrated nitric acid is heated and distilled through a reboiler to obtain a vaporized acid gas solution;

[0114] (2) Reaction impurity removal: passing O3 into the nitric acid solution after distillation in step (1) to remove nitrogen oxide (NOx) impurities;

[0115] (3) Evaporation: The nitric acid solution obtained in step (2) is passed into an evaporator for evaporation, and O3 and unreacted NOx are gasified;

[0116] (4) impurity removal in a stripping tower: the nitric acid solution obtained in step (3) is pumped into a stripping tower to remove O3 and unreacted NOx in the nitric acid solution;

[0117] (5) Multi-stage filtration: The nitric acid solution obtained in step (4) is passed through a microfiltration unit for microfiltration treatment to obtain an electronic grade nitric acid solution.

[0118] The azeotropic distillation temperature in step (1) is 100°C

[0119] The molar ratio of O3 to NOx in step (2) is 1:2.6.

[0120] The evaporator in step (3) is an MVR evaporator with an evaporation temperature of 50°C.

[0121] The stripping medium in step (4) is high-purity CDA.

[0122] O3 is passed into the nitric acid solution after distillation in step (1) to remove nitrogen oxides (NO x ) impurities, the principle is:

[0123] NO+O3==NO2+O2; NO2+O3==NO3+O2; NO3+NO2==N2O5;

[0124] N2O5+H2O==HNO3

[0125] The microfiltration unit adopts a nitric acid filter lined with polytetrafluoroethylene (PTFE), and the filter element is a modified polytetrafluoroethylene filter element, which can adsorb metal ions in electronic grade nitric acid. The modification method of the modified polytetrafluoroethylene filter element is as follows:

[0126] B1: Place a polytetrafluoroethylene filter element in a plasma surface treatment apparatus, turn on the radio frequency power supply of the low-temperature plasma treatment apparatus, adjust the discharge power of the radio frequency power supply, and introduce 6-mercapto-1-hexanol vapor into the reaction chamber of the plasma surface treatment apparatus for 10 minutes at a discharge power of 900 W to obtain a mercapto polytetrafluoroethylene filter element;

[0127] B2: To 600 g of tetrahydrofuran, 100 g of a mercapto polytetrafluoroethylene filter element, 4 g of dimethylallyl diphosphoric acid, 0.5 g of 3-(2-carboxyvinyl)phenylboric acid, and 1 g of a photoinitiator, benzoin dimethyl ether, were added. A mercapto-ene click reaction occurred in a nitrogen atmosphere. The reaction was carried out under ultraviolet light for 2 h, filtered, washed with tetrahydrofuran and ethanol, and dried to obtain a modified polytetrafluoroethylene filter element.

[0128] The gas flow of 6-mercapto-1-hexanol was 10 mL / min.

[0129] The power of the UV lamp is controlled to be 400W, and the UV light intensity is 20mW / cm 2 .

[0130] The content of metallic impurity elements in the nitric acid prepared in the above example was measured using an Agilent ICP-MS8900. The test parameters were: power 1.5 kW, pressure 0.7 MPa, hydrogen 0.05 MPa, helium 0.05 MPa, carrier gas flow rate 0.75 L / min, makeup gas flow rate 0.41 L / min, sampling depth 8 mm, and Millipore water as ultrapure water. The tuning mode was conventional, with the sample inlet line placed in the tuning solution. After stabilization for 15 seconds, the signal value cps of the mass number 7Li element was greater than 4000. Test method: standard addition method.

[0131] The test results of the above embodiment (unit: μg / L):

[0132]

[0133]

[0134] The particle impurity content in nitric acid was measured using a Rion KS-42AF. The particle analyzer was cleaned with high-purity water until the 0.2 μm particle content in the high-purity water was less than 1 particle / mL, meeting the nitric acid sample testing standard. The particle test results of the above example (unit: particles / mL) are as follows:

[0135]

[0136] The present invention has been described above through specific embodiments and examples, but these descriptions are merely illustrative and should not be construed as limiting the scope of protection of the present invention. Without departing from the spirit and scope of protection of the present invention, those skilled in the art may make various improvements, modifications, or equivalent substitutions to the technical solutions and implementations of the present invention, all of which should fall within the scope of protection of the present invention.

Claims

1. A method for preparing electronic-grade nitric acid without yellow smoke, characterized in that: The following steps are involved: (1) Distillation: Concentrated nitric acid is heated and distilled through a reboiler to obtain a vaporized acid gas solution; (2) Reaction impurity removal: passing O3 into the nitric acid solution after distillation in step (1) to remove nitrogen oxide (NOx) impurities; (3) Evaporation: The nitric acid solution obtained in step (2) is passed into an evaporator for evaporation, and O3 and unreacted NOx are gasified; (4) impurity removal in a stripping tower: the nitric acid solution obtained in step (3) is pumped into a stripping tower to remove O3 and unreacted NOx in the nitric acid solution; (5) multi-stage filtration: the nitric acid solution obtained in step (4) is passed through a microfiltration unit for microfiltration treatment to obtain an electronic grade nitric acid solution; The microfiltration unit adopts a nitric acid filter lined with polytetrafluoroethylene (PTFE), and the filter element is a modified polytetrafluoroethylene filter element, which can adsorb metal ions in electronic grade nitric acid. The modification method of the modified polytetrafluoroethylene filter element is as follows: B1: Place a polytetrafluoroethylene filter element in a plasma surface treatment apparatus, turn on the radio frequency power supply of the low-temperature plasma treatment apparatus, adjust the discharge power of the radio frequency power supply, and introduce 6-mercapto-1-hexanol vapor into the reaction chamber of the plasma surface treatment apparatus for 10 to 30 minutes at a discharge power of 90 to 130 W to obtain a mercapto polytetrafluoroethylene filter element; B2: To 600-700 parts of tetrahydrofuran, add 100-130 parts of mercapto polytetrafluoroethylene filter element, 4-7 parts of dimethylallyl diphosphoric acid, 0.5-2 parts of 3-(2-carboxyvinyl)phenylboric acid, 0.005-0.2 parts of 2,5-dimercaptothiazole, and 1-3 parts of photoinitiator benzoin dimethyl ether, by weight, and allow a mercapto-ene click reaction to occur in a nitrogen atmosphere. Under ultraviolet light, react for 2-4 hours, filter, wash with tetrahydrofuran and ethanol, and dry to obtain a modified polytetrafluoroethylene filter element.

2. The method for preparing electronic-grade nitric acid without yellow smoke according to claim 1, wherein: The azeotropic distillation temperature in step (1) is 100-120°C.

3. The method for preparing electronic-grade nitric acid without yellow smoke according to claim 1, wherein: The molar ratio of O3 to NOx in step (2) is 1:2.6-3.

4.

4. The method for preparing electronic-grade nitric acid without yellow smoke according to claim 1, wherein: In the step (3), the evaporator is an MVR evaporator, and the evaporation temperature is 50-90°C.

5. The method for preparing electronic-grade nitric acid without yellow smoke according to claim 1, wherein: The stripping medium in step (4) is high-purity CDA.

6. The method for preparing electronic-grade nitric acid without yellow smoke according to claim 1, characterized in that: The gas flow of the 6-mercapto-1-hexanol is 10-40 mL / min.

7. The method for preparing electronic-grade nitric acid without yellow smoke according to claim 1, characterized in that: The UV lamp power in B2 is controlled to be 400-500W, and the UV lamp intensity is 20-40mW / cm 2 .

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