Method for efficiently purifying nitric acid

Abstract

The invention relates to a method for efficiently purifying nitric acid and belongs to the technical field of nitric acid preparation. The method comprises the following steps: diluting 98% industrial-grade nitric acid into 68% nitric acid by adding deionized water; the method comprises the following steps: adding a metal ion stabilizer and a stabilizing synergist into 68% nitric acid, feeding into a heat exchanger, and heating by steam to gasify; purifying the gasified nitric acid steam through a rectifying tower, feeding the purified nitric acid steam into a condenser, continuously introducing nitrogen into the condenser, and dehydrating and decoloring; after the decoloration is qualified, obtaining high-purity nitric acid; the disqualified decolorized product is returned to the heat exchanger for re-purification; the stabilizing synergist is prepared by adopting 3-mercaptoquinoline, 4, 4 '-divinyl-2, 2'-dipyridyl, tetra (4-boric acid phenyl) ethylene, N-methyl pyrrolidone and a photoinitiator, stirring at normal temperature, irradiating with an ultraviolet lamp to react, and performing reduced pressure distillation to remove the N-methyl pyrrolidone; the stable synergist prepared by the invention has higher metal impurity adsorption capacity and chelating effect, and can efficiently purify nitric acid.

Description

Technical Field

[0001] The invention relates to the technical field of nitric acid preparation, in particular to a method for efficiently purifying nitric acid. Background Art

[0002] Nitric acid is a strong oxidizing and corrosive acid. Nitric acid is easily soluble in water, and its solution is colorless and transparent at room temperature. Its aqueous solutions of different concentrations have different properties. Commercially available concentrated nitric acid is a constant boiling mixture with a mass fraction of 65-68%. The one with a sufficiently large mass fraction (commercial concentration of more than 95%) is called fuming nitric acid. Nitric acid has a wide range of uses. It is used in organic synthesis for nitration reactions and the preparation of ammonium nitrate (both fertilizer and explosive). Nitric acid is widely used in the pharmaceutical chemical industry and chemical fiber industry, and is one of the three acids and two alkalis that are important basic raw materials for the chemical industry.

[0003] Chinese patent CN109835877A discloses a method for purifying electronic-grade high-purity nitric acid, comprising a distillation tower, a heating coil is arranged in the distillation tower, the material of the heating coil is metallic nickel, the distillation tower is filled with polypropylene Raschig ring filler, the distillation tower has a tower diameter of 150-280 mm, and a tower height of 3-15 m; also discloses a process for preparing electronic-grade 68% nitric acid from industrial-grade 98% nitric acid, wherein the tower diameter of the distillation tower is set to 150-280 mm, the tower height is set to 3-15 m, the reflux ratio is controlled to be 1:2-1:5, the material of the heating coil in the distillation tower is set to metallic nickel, and the distillation tower is filled with polypropylene Raschig ring filler.

[0004] Chinese patent CN109835924A adopts calcium nitrate solution and potassium chloride double decomposition method to produce potassium nitrate by freezing, and produces calcium chloride as a byproduct. Calcium nitrate is produced by the reaction of dilute nitric acid and ground limestone (high-purity limestone or ordinary limestone) powder, which is low in cost; the reaction is carried out under normal temperature and pressure conditions, with low energy consumption and easy control of process conditions. Other calcium sources (such as heavy calcium, light calcium, quicklime, slaked lime, carbide slag, or calcium carbonate converted from phosphogypsum, etc.) can be used to replace limestone powder.

[0005] Chinese patent CN103601163B discloses a method for preparing high-purity nitric acid, which uses industrial-grade nitric acid as a raw material, adds metal nitrate to react, filters through a microfiltration membrane to remove impure anions in the nitric acid, filters through a melamine-formaldehyde-thiourea resin / polyacrylic acid resin composite membrane to remove impure cations in the nitric acid, and obtains the target product by distillation, high-purity water preparation, white blowing, and microfiltration.

[0006] The above patents and prior art processes for purifying nitric acid have disadvantages such as complex processes, high energy consumption, and high content of metal ion impurities. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a method for efficiently purifying nitric acid, and the operating steps are as follows: S1: Add deionized water to dilute industrial grade nitric acid with a mass concentration of 98% to a nitric acid with a mass concentration of 68%; S2: adding 0.1-1 parts of metal ion stabilizer and 0.001-0.06 parts of stabilizing synergist to 80-100 parts of nitric acid with a mass concentration of 68%, and then sending the mixture to a heat exchanger and gasifying it by steam heating; S3: The vaporized nitric acid vapor is purified by a distillation tower and then enters a condenser, into which nitrogen is continuously introduced for dehydration and decolorization; S4: After qualified decolorization, high-purity nitric acid is obtained; those that fail to meet the decolorization standards are returned to the heat exchanger for re-purification.

[0008] The metal ion stabilizer is one of acetic acid, tartaric acid, citric acid and EDTA.

[0009] The temperature of the heat exchanger is 115-125°C.

[0010] The reflux ratio of the distillation tower is 1:2-3.

[0011] The heating coil of the heat exchanger is made of metal tantalum.

[0012] The preparation method of the stabilizing synergist is as follows: The stirred kettle is kept under nitrogen condition and nitrogen is flushed for 10-30 minutes. 15-30 parts of 3-mercaptoquinoline, 0.05-0.5 parts of 4,4'-divinyl-2,2'-bipyridine, 5-10 parts of tetrakis(4-boronic acid phenyl)ethylene CAS: 1905395-21-2, 200-260 parts of N-methylpyrrolidone and 0.05-0.3 parts of photoinitiator are irradiated with ultraviolet light for 30-60 minutes under stirring condition at room temperature. After the reaction is completed, N-methylpyrrolidone is removed by reduced pressure distillation to obtain a stable synergist.

[0013] The photoinitiator is benzoin dimethyl ether or 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0014] Reaction mechanism The mechanism of the mercapto-olefin addition reaction between 3-mercaptoquinoline and 4,4'-divinyl-2,2'-bipyridine is as follows: 1. First, the thiol (SH) in 3-mercaptoquinoline reacts with the double bond (C=C) in 4,4'-divinyl-2,2'-bipyridine to form an intermediate; 2. Then, the sulfur atom in the intermediate forms a new covalent bond with the carbon atom on the double bond, and the hydrogen atom on the double bond is transferred to the sulfur atom to generate the product; 3. Finally, the bipyridine part and the tetraboric acid functional group part in the product are linked together by covalent bonds to form quinoline containing bipyridine and tetraboric acid functional groups. Technical Effects The present invention provides a method for efficiently purifying nitric acid. Compared with the prior art, the present invention has the following significant effects: The adsorption and chelation effects of quinoline containing bipyridine and tetraboric acid functional groups on trace impurities in nitric acid are as follows: 1. Quinoline containing bipyridine and tetraboric acid functional groups has a large surface area and abundant functional groups, which can provide more adsorption sites and increase the adsorption capacity for trace impurities.

[0015] 2. The bipyridine part has a strong coordination ability and can form a stable complex with metal ions, thereby removing metal impurities from nitric acid.

[0016] 3. The tetraboric acid functional group has multiple hydroxyl groups, which can form hydrogen bonds or electrostatic interactions with metal ions to enhance the adsorption capacity of metal impurities.

[0017] In summary, quinoline containing bipyridine and tetraboric acid functional groups as a stable enhancer for nitric acid purification to remove metal impurities has high adsorption capacity and chelating effect. DETAILED DESCRIPTION

[0018] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in combination with embodiments and comparative examples: Detection of nitric acid content and metal ion impurities: The test was performed using an inductively coupled plasma emission spectrometer (ICP), brand Agilent, model 5100VDV.

[0019] Example 1 A method for efficiently purifying nitric acid, the operating steps are: S1: Add deionized water to dilute industrial grade nitric acid with a mass concentration of 98% to a nitric acid with a mass concentration of 68%; S2: Add 0.1 g of metal ion stabilizer and 0.001 g of stabilizing synergist to 80 g of nitric acid with a mass concentration of 68%, and then send it to a heat exchanger and use steam heating to gasify it; S3: The vaporized nitric acid vapor is purified by a distillation tower and then enters a condenser, into which nitrogen is continuously introduced for dehydration and decolorization; S4: After qualified decolorization, high-purity nitric acid is obtained; those that fail to meet the decolorization standards are returned to the heat exchanger for re-purification.

[0020] The metal ion stabilizer is acetic acid.

[0021] The temperature of the heat exchanger is 115°C.

[0022] The reflux ratio of the distillation tower is 1:2.

[0023] The heating coil of the heat exchanger is made of metal tantalum.

[0024] The preparation method of the stabilizing synergist is as follows: The stirred kettle was kept under nitrogen conditions and nitrogen was flushed for 10 minutes. 15g of 3-mercaptoquinoline, 0.05g of 4,4'-divinyl-2,2'-bipyridine, 5g of tetrakis(4-boronic acid phenyl)ethylene CAS: 1905395-21-2, 200g of N-methylpyrrolidone and 0.05g of photoinitiator were irradiated with ultraviolet light for 30 minutes under stirring conditions at room temperature. After the reaction was completed, N-methylpyrrolidone was removed by reduced pressure distillation to obtain a stable synergist.

[0025] The photoinitiator is benzoin dimethyl ether.

[0026] Example 2 A method for efficiently purifying nitric acid, the operating steps are: S1: Add deionized water to dilute industrial grade nitric acid with a mass concentration of 98% to a nitric acid with a mass concentration of 68%; S2: Add 0.5g of metal ion stabilizer and 0.02g of stabilizing synergist to 85g of nitric acid with a mass concentration of 68%, and then send it to a heat exchanger and use steam heating to gasify it; S3: The vaporized nitric acid vapor is purified by a distillation tower and then enters a condenser, into which nitrogen is continuously introduced for dehydration and decolorization; S4: After qualified decolorization, high-purity nitric acid is obtained; those that fail to meet the decolorization standards are returned to the heat exchanger for re-purification.

[0027] The metal ion stabilizer is tartaric acid.

[0028] The temperature of the heat exchanger is 118°C.

[0029] The reflux ratio of the distillation tower is 1:2.

[0030] The heating coil of the heat exchanger is made of metal tantalum.

[0031] The preparation method of the stabilizing synergist is as follows: The stirred kettle was kept under nitrogen conditions and nitrogen was flushed for 15 minutes. 20g of 3-mercaptoquinoline, 0.2g of 4,4'-divinyl-2,2'-bipyridine, 6g of tetrakis(4-boronic acid phenyl)ethylene CAS: 1905395-21-2, 220g of N-methylpyrrolidone and 0.1g of photoinitiator were irradiated with ultraviolet light for 40 minutes under stirring conditions at room temperature. After the reaction was completed, N-methylpyrrolidone was removed by reduced pressure distillation to obtain a stable synergist.

[0032] The photoinitiator is benzoin dimethyl ether.

[0033] Example 3 A method for efficiently purifying nitric acid, the operating steps are: S1: Add deionized water to dilute industrial grade nitric acid with a mass concentration of 98% to a nitric acid with a mass concentration of 68%; S2: Add 0.8g of metal ion stabilizer and 0.04g of stabilizing synergist to 95g of nitric acid with a mass concentration of 68%, and then send it to a heat exchanger and use steam heating to gasify it; S3: The vaporized nitric acid vapor is purified by a distillation tower and then enters a condenser, into which nitrogen is continuously introduced for dehydration and decolorization; S4: After qualified decolorization, high-purity nitric acid is obtained; those that fail to meet the decolorization standards are returned to the heat exchanger for re-purification.

[0034] The metal ion stabilizer is citric acid.

[0035] The temperature of the heat exchanger is 123°C.

[0036] The reflux ratio of the distillation tower is 1:3.

[0037] The heating coil of the heat exchanger is made of metal tantalum.

[0038] The preparation method of the stabilizing synergist is as follows: The stirred kettle was kept under nitrogen conditions and nitrogen was flushed for 25 minutes. 25g of 3-mercaptoquinoline, 0.4g of 4,4'-divinyl-2,2'-bipyridine, 8g of tetrakis(4-boronic acid phenyl)ethylene CAS: 1905395-21-2, 240g of N-methylpyrrolidone and 0.2g of photoinitiator were irradiated with ultraviolet light for 50 minutes under stirring conditions at room temperature. After the reaction was completed, N-methylpyrrolidone was removed by reduced pressure distillation to obtain a stable synergist.

[0039] The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0040] Example 4 A method for efficiently purifying nitric acid, the operating steps are: S1: Add deionized water to dilute industrial grade nitric acid with a mass concentration of 98% to a nitric acid with a mass concentration of 68%; S2: Add 1g of metal ion stabilizer and 0.06g of stabilizing synergist to 100g of nitric acid with a mass concentration of 68%, and then send it to a heat exchanger and use steam heating to gasify it; S3: The vaporized nitric acid vapor is purified by a distillation tower and then enters a condenser, into which nitrogen is continuously introduced for dehydration and decolorization; S4: After qualified decolorization, high-purity nitric acid is obtained; those that fail to meet the decolorization standards are returned to the heat exchanger for re-purification.

[0041] The metal ion stabilizer is EDTA.

[0042] The temperature of the heat exchanger is 125°C.

[0043] The reflux ratio of the distillation tower is 1:3.

[0044] The heating coil of the heat exchanger is made of metal tantalum.

[0045] The preparation method of the stabilizing synergist is as follows: The stirred kettle was kept under nitrogen conditions and nitrogen was flushed for 30 minutes. 30g of 3-mercaptoquinoline, 0.5g of 4,4'-divinyl-2,2'-bipyridine, 10g of tetrakis(4-boronic acid phenyl)ethylene CAS: 1905395-21-2, 260g of N-methylpyrrolidone and 0.3g of photoinitiator were irradiated with ultraviolet light for 60 minutes under stirring conditions at room temperature. After the reaction was completed, N-methylpyrrolidone was removed by reduced pressure distillation to obtain a stable synergist.

[0046] The photoinitiator is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0047] Comparative Example 1 No stabilizing agent was added, and the other steps were the same as in Example 1.

[0048] Comparative Example 2 The other steps were the same as in Example 1 except that 3-mercaptoquinoline was not added.

[0049] Comparative Example 3 The other steps were the same as in Example 1 except that 4,4'-divinyl-2,2'-bipyridine was not added.

[0050] Table 1 shows the test results.

[0051] Table 1 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Nitric acid content / % 67.5 67.8 68.3 68.7 65.1 66.6 66.9 Lithium / ppb 0.55 0.53 0.50 0.48 0.88 0.62 0.59 Sodium / ppb 0.29 0.27 0.26 0.25 0.45 0.35 0.33 Magnesium / ppb 0.17 0.14 0.13 0.11 0.34 0.22 0.21 Aluminum / ppb 0.51 0.47 0.43 0.39 0.89 0.65 0.62 Potassium / ppb 0.25 0.23 0.19 0.18 0.51 0.33 0.30 Calcium / ppb 0.57 0.55 0.51 0.49 0.91 0.66 0.64 Manganese / ppb 0.66 0.63 0.62 0.61 0.94 0.73 0.71 Nickel / ppb 0.47 0.46 0.44 0.43 0.63 0.53 0.52 Iron / ppb 0.25 0.24 0.22 0.21 0.46 0.32 0.31 Copper / ppb 0.14 0.12 0.12 0.11 0.22 0.18 0.17 Zinc / ppb 0.50 0.49 0.48 0.46 0.82 0.58 0.55 Titanium / ppb 0.16 0.15 0.13 0.12 0.59 0.23 0.21 Germanium / ppb 0.09 0.07 0.04 0.03 0.41 0.16 0.15 Strontium / ppb 0.02 0.01 0.01 0 0.13 0.08 0.06 Boron / ppb 0.19 0.17 0.15 0.14 0.39 0.27 0.25 Arsenic / ppb 0.03 0.02 0.01 0.01 0.15 0.09 0.08 Through the data analysis of the above examples and comparative examples, the stable synergist prepared by the present invention has a high metal impurity adsorption capacity and chelating effect, and can be used to purify nitric acid with high efficiency.

[0052] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for efficiently purifying nitric acid, the operating steps of which are: S1: Add deionized water to dilute industrial grade nitric acid with a mass concentration of 98% to a nitric acid with a mass concentration of 68%; S2: adding 0.1-1 parts of metal ion stabilizer and 0.001-0.06 parts of stabilizing synergist to 80-100 parts of nitric acid with a mass concentration of 68%, and then sending the mixture to a heat exchanger and heating it with steam to gasify it; S3: The vaporized nitric acid vapor is purified by a distillation tower and then enters a condenser, into which nitrogen is continuously introduced for dehydration and decolorization; S4: After qualified decolorization, high-purity nitric acid is obtained; unqualified decolorization is returned to the heat exchanger for re-purification; The stabilizing synergist is prepared by reacting 3-mercaptoquinoline, 4,4'-divinyl-2,2'-bipyridine and tetrakis(4-boronic acid phenyl)ethylene.

2. A method for efficiently purifying nitric acid according to claim 1, characterized in that: The metal ion stabilizer is one of acetic acid, tartaric acid, citric acid and EDTA.

3. A method for efficiently purifying nitric acid according to claim 1, characterized in that: The temperature of the heat exchanger is 115-125°C.

4. A method for efficiently purifying nitric acid according to claim 1, characterized in that: The reflux ratio of the distillation tower is 1:2-3.

5. A method for efficiently purifying nitric acid according to claim 1, characterized in that: The heating coil of the heat exchanger is made of metal tantalum.

6. A method for efficiently purifying nitric acid according to claim 1, characterized in that: The preparation method of the stabilizing synergist is as follows: The stirred kettle is kept under nitrogen condition and nitrogen is flushed for 10-30 minutes. 15-30 parts of 3-mercaptoquinoline, 0.05-0.5 parts of 4,4'-divinyl-2,2'-bipyridine, 5-10 parts of tetrakis(4-boronic acid phenyl)ethylene, 200-260 parts of N-methylpyrrolidone and 0.05-0.3 parts of photoinitiator are added and irradiated with ultraviolet light for 30-60 minutes under stirring condition at room temperature. After the reaction is completed, N-methylpyrrolidone is removed by reduced pressure distillation to obtain a stable synergist.

7. A method for efficiently purifying nitric acid according to claim 6, characterized in that: The photoinitiator is benzoin dimethyl ether or 2-hydroxy-2-methyl-1-phenyl-1-propanone.