阅读说明：本技术 一种工业级硝酸的提纯方法 (Purification method of industrial-grade nitric acid ) 是由 杨华春 李云峰 王建萍 刘海霞 周小平 李凌云 王泽国 韩建军 于 2021-10-28 设计创作，主要内容包括：本发明涉及一种工业级硝酸的提纯方法,属于硝酸提纯的技术领域。本发明的工业级硝酸的提纯方法,包括以下步骤：对工业级硝酸进行预处理；所述预处理是在工业级硝酸中通入氟氮混合气进行氧化反应；所述工业级硝酸的浓度在98％以上。本发明的工业级硝酸的提纯方法,开发F-(2)气除杂工艺,深度去除HNO-(2)杂质,提升氮资源利用率和除杂效率,降低工业硝酸中脱色吹白的难度,并且能在后期通过加入金属硝酸盐沉淀PO-(4)～(3-)、SO-(4)～(2-)、Cl～(-)杂质离子时一并将生成氟离子去除。(The invention relates to a purification method of industrial nitric acid, belonging to the technical field of nitric acid purification. The purification method of industrial nitric acid comprises the following steps: pretreating industrial-grade nitric acid; the pretreatment is to introduce fluorine-nitrogen mixed gas into industrial nitric acid for oxidation reaction; the concentration of the industrial grade nitric acid is more than 98 percent. The invention relates to a method for purifying industrial nitric acid, and develops F 2 Gas impurity removal process for deeply removing HNO 2 Impurities, improves the utilization rate of nitrogen resources and the impurity removal efficiency, reduces the difficulty of decoloring and white blowing in industrial nitric acid, and can precipitate PO by adding metal nitrate in the later stage 4 3‑ 、SO 4 2‑ 、Cl ‑ And removing the generated fluorine ions when the impurity ions are generated.)

1. The method for purifying the industrial-grade nitric acid is characterized by comprising the following steps of: pretreating industrial-grade nitric acid; the pretreatment is to introduce fluorine-nitrogen mixed gas into industrial nitric acid for oxidation reaction; the concentration of the industrial grade nitric acid is more than 98 percent.

2. The method of claim 1, wherein the industrial nitric acid comprises: the fluorine-nitrogen mixed gas is F₂And N₂Mixed gas of (2), F in a fluorine-nitrogen mixed gas₂The mass fraction of (A) is 5-20%.

3. The method of purifying industrial-grade nitric acid according to claim 1 or 2, wherein: the introduction amount of the fluorine-nitrogen mixed gas is that F₂And HNO in industrial nitric acid₂The molar ratio of (A) to (B) is 1-1.5: 1.

4. The method of claim 1, wherein the industrial nitric acid comprises: the temperature of the oxidation reaction is-20-10 ℃, and the time is 10-30 min.

5. The method of purifying industrial-grade nitric acid according to claim 1 or 2, wherein: adding metal nitrate into the pretreated industrial nitric acid to precipitate impurity anions; the metal nitrate contains metal ions capable of precipitating fluoride ions.

6. The method of claim 5, wherein the industrial nitric acid comprises: the metal nitrate comprises a first nitrate and a second nitrate; adding a first nitrate into the pretreated industrial nitric acid to generate a precipitate, performing solid-liquid separation, adding a second nitrate into the obtained liquid to generate a precipitate, and filtering again; the first nitrate is selected from one or any combination of lithium nitrate, aluminum nitrate and ferric nitrate; the second nitrate is barium nitrate.

7. The method of claim 6, wherein the industrial nitric acid comprises: the amount of metal ion substances in the added first nitrate is 1-1.5 times of the theoretical reaction amount of metal ions needed by fluoride ions and phosphate ions in the industrial nitric acid after the precipitation pretreatment; the amount of barium ions in the added barium nitrate is 1-1.05 times of the amount of metal ions needed by sulfate radicals and chloride ions in the industrial-grade nitric acid after the precipitation pretreatment.

8. The method of claim 6, wherein the industrial nitric acid comprises: filtering treatment is carried out on the solid-liquid separation twice; the aperture of the filtering membrane adopted for filtering treatment is 1-5 mu m.

9. The method of claim 6, wherein the industrial nitric acid comprises: diluting the liquid obtained by the second solid-liquid separation to HNO with ultrapure water₃The concentration of the obtained product is 65-75%, and then sub-boiling distillation is carried out; the sub-boiling distillation temperature is 105-110 ℃, and the pressure is-0.1 to-0.3 KPa.

10. The method of purifying industrial grade nitric acid according to claim 9, wherein: condensing, decoloring and blowing white nitric acid obtained by sub-boiling distillation, and then performing three-stage membrane filtration by adopting a microporous membrane, wherein the aperture of a first-stage membrane is 0.5-1 mu m, the aperture of a second-stage membrane is 0.2-0.4 mu m, and the aperture of a third-stage membrane is 0.05-0.1 mu m.

Technical Field

The invention relates to a purification method of industrial nitric acid, belonging to the technical field of nitric acid purification.

Background

Nitric acid (HNO)₃) The nitric acid is strong acid with strong oxidizing property and corrosivity, belongs to unitary inorganic strong acid, is one of six inorganic strong acids, is also an important chemical raw material, and the aqueous solution of the nitric acid is commonly called nitric acid or ammonia nitrogen water. Nitric acid is industrially used for preparing chemical fertilizers, pesticides, explosives, dyes, salts and the like; in organic chemistry, a mixed solution of concentrated nitric acid and concentrated sulfuric acid is an important nitrating agent. As an important electronic chemical, the ultra-clean high-purity nitric acid can be used in combination with hydrofluoric acid, glacial acetic acid, hydrogen peroxide and the like, and is widely applied to the links of cleaning, corrosion and the like in the processes of semiconductor element production, integrated circuit assembly and processing. Therefore, the purity and cleanliness of ultra-clean high-purity nitric acid directly limit the yield, electrical performance and reliability of integrated circuits.

At present, a continuous rectification method is mainly adopted for preparing the ultra-clean high-purity nitric acid, but impurities with the volatility similar to that of the nitric acid are difficult to remove by the continuous rectification method, and the content of the impurities after rectification can not meet the use requirement of a semiconductor. Chinese patent document CN102001635A discloses a process for preparing ultra-pure nitric acid: adding metal nitrate into industrial nitric acid serving as a raw material, reacting with impurity anions in the industrial nitric acid to precipitate, performing membrane filtration and purification, rectifying to remove inorganic salts, blending the rectified liquid into nitric acid with the concentration of 69-70 wt% by using ultrapure water, blowing white by using purified air in a white blowing tower, absorbing the nitrogen oxides removed by blowing by using a saturated sodium hydroxide aqueous solution, feeding the white blowing liquid into a crude product tank, and performing membrane filtration to obtain a target product. The preparation process can not remove nitrous acid impurities in the raw materials, the nitrous acid impurities can be decomposed into nitric oxides in the rectification process, the subsequent decolorization and white blowing difficulty is increased, and the efficient utilization of nitrogen resources can not be realized.

Disclosure of Invention

The invention aims to provide a purification method of industrial nitric acid, which can effectively reduce the difficulty of decoloring and white blowing in the industrial nitric acid.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for purifying industrial-grade nitric acid comprises the following steps: pretreating industrial-grade nitric acid; the pretreatment is to introduce fluorine-nitrogen mixed gas into industrial nitric acid for oxidation reaction; the concentration of the industrial grade nitric acid is more than 98 percent.

The method for purifying industrial nitric acid deeply removes HNO₂Impurities, improves the utilization rate of nitrogen resources and the impurity removal efficiency, reduces the difficulty of decoloring and white blowing in industrial nitric acid, and can precipitate PO by adding metal nitrate in the later stage₄ ^3-、SO₄ ^2-、Cl^-And removing the generated fluorine ions when the impurity ions are generated.

To reduce cost, further, the mixed gas of fluorine and nitrogen is F₂And N₂In which F is₂The mass fraction of (A) is 5-20%.

F₂Too high introduction leads to an increase in purification cost, and too low cannot completely remove HNO₂Impurities. Further, the mixed gas of fluorine and nitrogen is introduced into the industrial nitric acid in an amount which is enough to ensure that HNO in the industrial nitric acid is added₂Is completely oxidized into HNO₃. In order to further reduce the cost, it is preferable that the amount of the mixed fluorine-nitrogen gas is such that F₂And HNO₂The molar ratio of (A) to (B) is 1-1.5: 1.

The oxidation reaction is exothermic reaction, the volatilization of nitric acid can be reduced at low temperature, and in order to ensure that the reaction is more complete, the temperature of the oxidation reaction is-20-10 ℃. Further preferably, the oxidation reaction time is 10-30 min.

The method for purifying the industrial-grade nitric acid further comprises the following steps: adding metal nitrate into the pretreated industrial nitric acid to precipitate impurity anions; the metal nitrate contains metal ions capable of precipitating fluoride ions.

The metal nitrate includes a first nitrate and a second nitrate. Adding a first nitrate into the pretreated industrial nitric acid raw material to generate a precipitate, carrying out solid-liquid separation, adding a second nitrate into the obtained liquid to generate a precipitate, and filtering again. The first nitrate is selected from one or any combination of lithium nitrate, aluminum nitrate and ferric nitrate. The second nitrate is barium nitrate.

Preferably, the amount of the metal ion species in the first nitrate salt added is (1-1.5) times the theoretical reaction amount of the metal ion required for the fluoride ion and phosphate ion. The reaction time for generating the precipitate after the first nitrate is added is 10-30 min.

Preferably, the amount of barium ions in the added barium nitrate is (1-1.05) times of the amount of substances of metal ions required for precipitating sulfate and chloride ions in the industrial-grade nitric acid after pretreatment.

Preferably, the reaction time for generating the precipitate after adding the second nitrate is 10-30 min.

Preferably, both solid-liquid separations are carried out by filtration. Preferably, the aperture of the filtering membrane used for the filtering treatment is 1-5 μm. More preferably, the pore diameter of the filter membrane is 1 to 3 μm.

The method for purifying the industrial nitric acid further comprises the step of using ultrapure water to separate HNO in the liquid obtained by the second solid-liquid separation₃The concentration of (b) is adjusted to 65 to 75%, and then sub-boiling distillation is performed. The concentration is adjusted in a reactor, and the material of the reactor is 316 stainless steel, silicon carbide, Hastelloy, Monel alloy or nickel alloy. The reactor is adopted to dilute and prepare the nitric acid, so that the mass transfer efficiency and the heat transfer efficiency are high, the mixing is more uniform, the decomposition side reaction of the nitric acid is inhibited, and the product quality and the yield are improved. The reactor may be one of a pipeline mixer and a microchannel reactor. The equivalent diameter of the micro-channel of the pipeline mixer or the micro-channel reactor is 1-3 mm. Preferably, the temperature of the solution is controlled to be 30-50 ℃ in the preparation process.

The sub-boiling distillation temperature is 105-110 ℃, and the pressure is-0.1 to-0.3 KPa.

The purification method of the industrial-grade nitric acid further comprises the steps of condensing, decoloring and blowing white the nitric acid obtained by sub-boiling distillation, and then carrying out tertiary membrane filtration by adopting a microporous membrane, wherein the aperture of the primary membrane is 0.5-1 mu m, the aperture of the secondary membrane is 0.2-0.4 mu m, and the aperture of the tertiary membrane is 0.05-0.1 mu m.

The decoloring and white blowing process is carried out in a stripping tower, and dry air (CDA) prepared by a clean compressed air supply system is adopted, and the pressure is 0.3-1 kg. In the decoloring and white blowing process, dry air is introduced from the bottom of the stripping tower and counter-current flows with nitric acid flowing down from the top to remove nitrogen oxides. The gas stripping tower is filled with pall rings made of PTFE, FEP, PVDF, PFA and other materials. The discharged gas of the gas stripping tower is subjected to two-stage washing treatment and then discharged, wherein the first stage is an acid washing tower, generates dilute nitric acid after absorbing nitrogen dioxide, and returns to the reactor for continuous utilization after gradually concentrating; the second level is an alkaline washing tower which absorbs the acid gases such as nitric oxide, carbon dioxide and the like which are not absorbed by the acid washing tower.

Preferably, the decolorization and whitening is realized by adopting a counter-current mode. The countercurrent decoloring and white blowing can ensure that the chromaticity of the nitric acid meets the standard requirement, and the discharged nitric oxide gas is absorbed by acid and alkali in two stages in the white blowing process, so that the cyclic utilization of nitrogen resources and the standard discharge of the discharged gas are realized.

The equipment in the method for purifying the industrial-grade nitric acid adopts ultrapure water for cleaning, and the resistivity of the ultrapure water is more than 16M omega cm; the equipment and the pipeline used except the reactor for concentration adjustment are made of one of Polytetrafluoroethylene (PTFE), poly (perfluoroalkoxy) (PFA), perfluoro (ethylene propylene) copolymer (FEP) and polyvinylidene fluoride (PVDF), and the lining is one of Polytetrafluoroethylene (PTFE), poly (perfluoroalkoxy) (PFA), perfluoro (ethylene propylene) copolymer (FEP) and polyvinylidene fluoride (PVDF).

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

The raw materials and equipment used in the invention are commonly sold in the market, or products which can be obtained by the technicians in the field through a public way; for further understanding of the present invention, the following examples are given for illustrating the present invention, and the scope of the present invention is not limited by the following examples.

The pipeline mixing reactor used in examples 1-3 was 316 stainless steel, and the remaining equipment and pipelines were Polytetrafluoroethylene (PTFE).

Example 1

The process flow of the purification method of industrial nitric acid disclosed by the invention is shown in figure 1, and the purification method comprises the following steps:

1) 100kg of 98.5% technical nitric acid (HNO) is weighed₂ 0.41％，SO₄ ^2-0.07％，PO₄ ^3-0.03％、Cl^-0.02%) first 6.62kg of 5% F are introduced₂And N₂The reaction is controlled to be carried out at minus 20 ℃ and stirred for 30min, then 1.28kg of lithium nitrate is added, the mixture is stirred and reacted for 10min at room temperature, after the mixture is filtered by a 3 mu m filtering membrane, 0.26kg of barium nitrate is added into the filtrate, the mixture is stirred and reacted for 20min at room temperature, and then the mixture is filtered by the 3 mu m filtering membrane to obtain 101kg of refined concentrated nitric acid;

2) introducing refined concentrated nitric acid and 39.9kg of ultrapure water into a pipeline mixing reactor simultaneously, mixing and blending to obtain 70% nitric acid, wherein the temperature of the solution is controlled to be 30 ℃ in the blending process;

3) and adding the prepared 70% nitric acid into a distillation kettle for sub-boiling distillation, and controlling the temperature of the distillation to be 105 ℃ and the pressure to be-0.1 KPa. Discharging azeotrope of nitric acid and water from the top of the distillation kettle; and discharging waste liquid containing high boiling point, heavy components, granular substances and the like from the bottom of the distillation kettle, and recovering the waste liquid.

The azeotropic mixture of nitric acid and water discharged from the top of the distillation still is condensed and then is introduced into a stripping tower, clean dry compressed air (CDA) is introduced from the bottom of the stripping tower, the gas pressure is 0.3kg, nitric oxide is removed by countercurrent with nitric acid flowing down from the top, and the nitric acid solution is discharged from the bottom of the distillation still after decoloration and whitening.

The discharged gas of the gas stripping tower is subjected to two-stage washing treatment and then discharged, wherein the first stage is an acid washing tower, generates dilute nitric acid after absorbing nitrogen dioxide, and returns to the pipeline mixing reactor for continuous utilization after being gradually concentrated; the second stage is an alkaline washing tower which absorbs the acid gases such as nitric oxide, carbon dioxide and the like which are not absorbed by the acid washing tower, and the residual gas reaches the standard and is discharged.

The nitric acid solution discharged from the bottom of the stripping tower is filtered by a primary membrane with the aperture of 1 mu m, a secondary membrane with the aperture of 0.4 mu m and a tertiary microporous membrane with the aperture of 0.1 mu m in sequence, and then the ultra-clean high-purity nitric acid product 126kg is obtained by filling.

Example 2

The purification method of industrial nitric acid comprises the following steps:

1) 150kg of 98.5% technical nitric acid (HNO) is weighed₂ 0.41％，SO₄ ^2-0.07％，PO₄ ^3-0.03％、Cl^-0.02%) and 5.07kg of 10% F was first introduced₂And N₂The reaction is controlled to be carried out at 10 ℃ and stirred for 20min, then 1.94kg of lithium nitrate is added and stirred for reaction for 20min at room temperature, after the mixture is filtered by a 2-micron filtering membrane, 0.39kg of barium nitrate is added into the filtrate and stirred for reaction for 30min at room temperature, and then the mixture is filtered by the 2-micron filtering membrane to obtain 152kg of refined concentrated nitric acid;

2) introducing refined concentrated nitric acid and 66kg of ultrapure water into a pipeline mixing reactor simultaneously, mixing and blending to obtain 69.5% nitric acid, and controlling the temperature of the solution to be 40 ℃ in the blending process;

3) and adding the prepared 70.5 percent nitric acid into a distillation kettle for sub-boiling distillation, and controlling the temperature of 108 ℃ of distillation and the pressure to be-0.2 KPa. Discharging azeotrope of nitric acid and water from the top of the distillation kettle; waste liquid containing high boiling point, heavy components, particulate matter, etc. is recovered.

The azeotropic mixture of nitric acid and water discharged from the top of the distillation still is condensed and then is introduced into a stripping tower, clean dry compressed air (CDA) is introduced from the bottom of the stripping tower, the gas pressure is 0.5kg, nitric oxide is removed by countercurrent with nitric acid flowing down from the top, and the nitric acid solution is discharged from the bottom of the distillation still after decoloration and whitening.

The discharged gas of the gas stripping tower is subjected to two-stage washing treatment and then discharged, wherein the first stage is an acid washing tower, generates dilute nitric acid after absorbing nitrogen dioxide, and returns to the pipeline mixing reactor for continuous utilization after being gradually concentrated; the second stage is an alkaline washing tower which absorbs the acid gases such as nitric oxide, carbon dioxide and the like which are not absorbed by the acid washing tower, and the residual gas reaches the standard and is discharged.

Filtering the nitric acid solution discharged from the bottom of the gas stripping tower by a primary membrane with the aperture of 0.8 mu m, a secondary membrane with the aperture of 0.3 mu m and a tertiary microporous membrane with the aperture of 0.1 mu m in sequence, and filling to obtain 195kg of ultra-clean high-purity nitric acid product.

Example 3

The purification method of industrial nitric acid comprises the following steps:

1) 200kg of 98.5% technical nitric acid (HNO) is weighed₂ 0.41％，SO₄ ^2-0.07％，PO₄ ^3-0.03％、Cl^-0.02%) first 3.48kg of 20% F are introduced₂And N₂The reaction is controlled to be carried out at minus 10 ℃ and stirred for 10min, then 2.78kg of lithium nitrate is added and stirred for reaction for 10min at room temperature, after the mixture is filtered by a filter membrane with the diameter of 1 mu m, 0.54kg of barium nitrate is added into the filtrate and stirred for reaction for 30min at room temperature, and then the mixture is filtered by the filter membrane with the diameter of 1 mu m to obtain 101kg of refined concentrated nitric acid;

2) introducing refined concentrated nitric acid and 87.9kg of ultrapure water into a pipeline mixing reactor simultaneously, mixing and blending to obtain 69% nitric acid, and controlling the temperature of the solution to be 50 ℃ in the blending process;

3) and adding the prepared 69% nitric acid into a distillation kettle for sub-boiling distillation, and controlling the temperature of the distillation to be 110 ℃ and the pressure to be-0.3 KPa. Discharging azeotrope of nitric acid and water from the top of the distillation kettle; waste liquid containing high boiling point, heavy components, particulate matter, etc. is recovered.

The azeotropic mixture of nitric acid and water discharged from the top of the distillation still is condensed and then is introduced into a stripping tower, clean dry compressed air (CDA) is introduced from the bottom of the stripping tower, the gas pressure is 0.8kg, nitric oxide is removed by countercurrent with nitric acid flowing down from the top, and the nitric acid solution is discharged from the bottom of the distillation still after decoloration and whitening.

The discharged gas of the gas stripping tower is subjected to two-stage washing treatment and then discharged, wherein the first stage is an acid washing tower, generates dilute nitric acid after absorbing nitrogen dioxide, and returns to the pipeline mixing reactor for continuous utilization after being gradually concentrated; the second stage is an alkaline washing tower which absorbs the acid gases such as nitric oxide, carbon dioxide and the like which are not absorbed by the acid washing tower, and the residual gas reaches the standard and is discharged.

The nitric acid solution discharged from the bottom of the stripping tower is filtered by a primary membrane with the aperture of 0.5 mu m, a secondary membrane with the aperture of 0.2 mu m and a tertiary microporous membrane with the aperture of 0.05 mu m in sequence, and then the mixture is filled to obtain 259kg of ultra-clean high-purity nitric acid product.

Examples of the experiments

In this experimental example, the high purity nitric acid products obtained in example 1, example 2, example 3 and comparative example were tested, and the results are shown in table 1.

TABLE 1 test results of ultra-clean high-purity nitric acid product obtained in example

Example 1-3 ultra-clean high purity nitric acid product F^-The contents (ppb) are respectively: 36. 31, 35.

As can be seen from the detection results in Table 1, the high-purity nitric acid product prepared by the method has high purity and low impurity content, and is obviously superior to the national industry standard index.