Method for electrochemical reduction of nitro T acid

Abstract

The invention discloses a method for electrochemical reduction of nitro T acid. The method is characterized in that electrochemical reduction is carried out in a separated electrolysis device, the separated electrolysis device comprises an electrolytic tank body, a cathode, an anode and an ionic membrane, the ionic membrane divides the electrolytic tank body into an anode tank and a cathode tank, a catholyte is an acid solution containing nitro T acid and having a pH value of 1-6, and an anolyte is an acid solution; direct current is applied between the cathode and the anode for electrolysis, nitro T acid is reduced to generate amino T acid, and meanwhile the anode releases oxygen. The nitro T acid reduction process is simple and convenient, the electrolyte can be recycled, the problem that'three wastes' generated in the nitro T acid reduction process are difficult to treat is solved, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of dye intermediate synthesis, and in particular to a method for electrochemically reducing nitro-T acid. Background Art

[0002] There are several main methods for reducing aromatic nitro compounds: (1) Iron powder reduction method. In an acidic aqueous medium, iron powder is used to reduce the nitro group to an amino group, producing water-insoluble Fe3O4 (commonly known as iron mud). This method is suitable for synthesizing water-soluble amino compounds with sulfonic acid groups. After the reaction is completed, the water-insoluble iron mud can be filtered out; iron powder reduction has been used in industry for many years, but the iron mud produced is difficult to handle and the production environment is harsh. (2) Catalytic hydrogenation reduction method. This method requires the use of expensive platinum / palladium / nickel and other catalysts, and there are problems with the recovery and deactivation of precious metal catalysts. There are also disadvantages such as easy poisoning and high loss of catalysts. In addition, the use of high pressure conditions and flammable and explosive hydrogen also places stringent requirements on the equipment and strict operating requirements, which limits its application in industry.

[0003] 1-amino-8-naphthol-3,6-disulfonic acid (H acid for short) is an important intermediate for producing reactive dyes. Azo dyes synthesized with it as raw material have been widely used in dyeing cotton, wool, silk fabrics, etc., and have a large market application volume. The existing H acid production method uses naphthalene as raw material, first undergoes sulfonation and nitration to obtain 1-nitronaphthalene-3,6,8-trisulfonic acid (nitro T acid for short), then undergoes alkali neutralization, hydrogenation reduction or iron powder reduction to obtain 1-aminonaphthalene-3,6,8-trisulfonate, then, undergoes acidification and filtration to obtain 1-aminonaphthalene-3,6,8-trisulfonic acid (amino T acid for short), and the obtained amino T acid is then subjected to alkali fusion, acidification and other steps to obtain the target product H acid. It can be seen from this that the existing H acid production method has a long process, and a large amount of by-products will be produced during the production process, causing environmental pollution and three wastes. At present, the reduction reaction in the H acid production process generally adopts iron powder reduction, and a large amount of wastewater and iron mud will be produced during the reaction process, which has serious environmental pollution problems.

[0004] Regarding the catalyst hydrogenation preparation method of H acid, the early Japanese patent JP49127956 disclosed the use of Raney nickel as a catalyst to reduce nitro T acid to amino T acid. Japanese patent JP50101349 disclosed the use of palladium carbon as a catalyst, but the catalysts disclosed in the above patents all have the disadvantages of poor stability, easy poisoning or high price. In Chinese patents CN1911907A, CN1810779A, CN103739524B, CN101381331B and CN100574877C, modified skeleton nickel is used as a catalyst, and hydrogenation reaction is carried out in an autoclave with a stirring device at a suitable temperature and pressure. The reaction time is generally 2 to 10 hours, and amino T acid with a yield of 95%-96% can be obtained (there are oily byproducts, which affect product quality); but during the reaction process, the catalyst will undergo mechanical wear, resulting in the loss of the catalyst into powder and the catalyst deactivation. In addition, in order to improve the mass transfer effect of the reaction process, strong stirring is required, which causes a strong collision between the catalyst and the stirrer, deforming the catalyst skeleton, reducing the specific surface area, and reducing the activity of the chemical agent, resulting in the need to continuously add catalyst to maintain the normal progress of the reaction during the intermittent production process. In Chinese patent CN108129361A, a continuous hydrogenation reduction process of H acid monosodium salt is disclosed, using powdered molecular sieve as a catalyst, introducing hydrogen into a stirred reactor, and completing the continuous hydrogenation reaction of nitro T acid in a manner of feeding below and discharging above at 140-160°C and 2.8-3.5MPa, with a yield of up to 99%. Although a continuous reaction process is adopted in this patent, the entire catalytic hydrogenation reaction is still carried out in a reactor; during the reaction, in order to fully react and achieve effective mass transfer and heat transfer effects, strong stirring is required, which will inevitably cause the catalyst particles or catalyst powder to collide and wear each other, and cause loss during the subsequent filtration process; due to the loss and deactivation of the catalyst, fresh catalyst needs to be continuously added to maintain a high yield; the entire reaction process not only consumes a lot of catalyst, but also has a long reaction time, which is not suitable for large-scale industrial production. Summary of the invention

[0005] In order to solve the problems in the existing nitro-trifluoroacetic acid reduction process, the conventional iron powder reduction method will produce a large amount of "three wastes", increasing the post-processing cost; the precious metal catalyst of the catalytic hydrogenation reduction method is expensive and difficult to obtain, the reaction is carried out under high temperature and high pressure conditions, the process cost is high, and there are high safety risks; the present invention provides an electrochemical reduction method for preparing amino-trifluoroacetic acid from nitro-trifluoroacetic acid under acidic system conditions, the electrolysis reaction conditions are mild, and the equipment is simple and easy to operate; the method directly uses clean electrons as a reducing agent, effectively avoiding the addition of additional catalysts or reducing agents, and uses the active H* generated on the cathode surface to react with the reactants in the electrolyte, so as to efficiently reduce the nitro-trifluoroacetic acid to the target product amino-trifluoroacetic acid.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for electrochemically reducing nitro-T acid, the method comprising:

[0008] The electrochemical reduction is carried out in a separated electrolysis device, which includes an electrolytic cell body, a cathode, an anode and an ion membrane. The ion membrane separates the electrolytic cell body into an anode cell and a cathode cell. The cathode electrolyte is an acidic solution containing nitro-triamino acid with a pH between 1 and 6, and the anode electrolyte is an acid solution. Direct current is applied between the cathode and the anode for electrolysis to reduce the nitro-triamino acid to generate amino-triamino acid, while the anode releases oxygen.

[0009] In the above technical solution, further, the ion membrane is a cationic membrane.

[0010] In the above technical solution, further, the anode material is a platinum electrode, a titanium-coated electrode or a graphite electrode, and the cathode material is a foam copper electrode, a foam nickel electrode, a zinc electrode or a lead electrode.

[0011] In the above technical solution, further, the electrolysis is constant current electrolysis with a current density of 20 mA / cm 2 ~50mA / cm 2 The electrolysis reaction temperature is 30-70°C and the reaction time is 4-12h.

[0012] In the above technical solution, further, the pH of the cathode electrolyte is 1 to 6, preferably 2.8 to 3.2. Hydrochloric acid can be added to the cathode electrolyte to adjust the pH. Furthermore, in the cathode electrolyte, the mass fraction of nitro-T acid is 7 to 8%, and hydrochloric acid is added to adjust the pH of the cathode electrolyte to 2.8 to 3.2.

[0013] In the above technical solution, further, the anode electrolyte is a sulfuric acid solution; further, the concentration of the sulfuric acid solution is 1-3M, preferably 2M.

[0014] The cathode and anode reaction processes of the present invention are as follows:

[0015] Cathode reaction:

[0016]

[0017] Anode reaction: 6OH - →3 / 2O2+3H2O+6e -

[0018] Beneficial effects of the present invention:

[0019] 1. The present invention proposes for the first time a synthetic strategy for preparing amino T acid by electrochemical reduction of nitro T acid, which has not been reported in the prior art.

[0020] 2. The existing amino T acid synthesis method generally requires the presence of a reducing agent and high temperature or precious metal catalysis to proceed smoothly, and the reaction conditions are harsh and the catalyst cost is high. The present invention adopts mild and simple conditions, uses "electrons" as a reducing agent, and can make the reaction proceed to the predetermined target by changing the current density, reducing pollution and being green and environmentally friendly.

[0021] 3. Since amino T acid is an important intermediate for the synthesis of H acid, H acid is an important intermediate for the production of reactive dyes, azo dyes synthesized with amino T acid as raw materials have been widely used in dyeing cotton, wool, silk fabrics, etc., and have a large market application volume. Therefore, the present invention has great application value and social and economic effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the separated electrolysis device used in the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0024] The schematic diagram of the separated electrolysis device used in the embodiment of the present invention is as follows Figure 1 As shown, the membrane is a cationic membrane.

[0025] Example 1

[0026] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 3.02. The cathode electrolyte was added to the cathode chamber.

[0027] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0028] The cathode uses a foam copper electrode and the anode uses a platinum sheet electrode.

[0029] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2 , the temperature was 30°C, the stirring speed was 500r / min under normal pressure, and the power was turned on for 4.6 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 42.14%.

[0030] Example 2

[0031] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 3.08. The cathode electrolyte was added to the cathode chamber.

[0032] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0033] The cathode uses a foam copper electrode and the anode uses a platinum sheet electrode.

[0034] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2 , the temperature was 50°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 4.6 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 45.38%.

[0035] Example 3

[0036] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 3.04. The cathode electrolyte was added to the cathode chamber.

[0037] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0038] The cathode uses a foam copper electrode and the anode uses a platinum sheet electrode.

[0039] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2 , the temperature was 70°C, the stirring speed was 500r / min under normal pressure, and the power was turned on for 4.6 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 46.01%.

[0040] Example 4

[0041] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 3.12. The cathode electrolyte was added to the cathode chamber.

[0042] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0043] The cathode uses a nickel foam electrode and the anode uses a platinum sheet electrode.

[0044] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2, the temperature was 70°C, the stirring speed was 500r / min under normal pressure, and the power was turned on for 7 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino acid yield of 44.16%.

[0045] Example 5

[0046] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 2.94. The cathode electrolyte was added to the cathode chamber.

[0047] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0048] The cathode is a zinc electrode and the anode is a platinum electrode.

[0049] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2 , the temperature was 50°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 7 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino acid yield of 39.59%.

[0050] Example 6

[0051] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 3.04. The cathode electrolyte was added to the cathode chamber.

[0052] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0053] The cathode uses a lead electrode and the anode uses a platinum electrode.

[0054] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2 , the temperature was 50°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 7 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 38.09%.

[0055] Example 7

[0056] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 3.01. The cathode electrolyte was added to the cathode chamber.

[0057] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0058] The cathode uses a foam copper electrode and the anode uses a platinum sheet electrode.

[0059] Start stirring, turn on the power supply, and energize at a current density of 20 mA / cm 2 , the temperature was 50°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 11.5 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 48.98%.

[0060] Example 8

[0061] 5 mL of 30% nitro-T-acid aqueous solution was added to 14 mL of water, and then 10 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte with a pH of 1.15. The cathode electrolyte was added to the cathode chamber.

[0062] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0063] The cathode uses a foam copper electrode and the anode uses a platinum sheet electrode.

[0064] Start stirring, turn on the power supply, and energize at a current density of 20 mA / cm 2 , the temperature was 50°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 9.2 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 42.14%.

[0065] Example 9

[0066] 5 mL of 30% nitro-T-acid aqueous solution was added to 25 mL of water as the cathode electrolyte, with a pH of 6.21. The cathode electrolyte was added to the cathode chamber.

[0067] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0068] The cathode uses a foam copper electrode and the anode uses a platinum sheet electrode.

[0069] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2 , the temperature was 50°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 7 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 39.74%.

[0070] Example 10

[0071] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte with a pH of 3.00. The cathode electrolyte was added to the cathode chamber.

[0072] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0073] The cathode uses a foam copper electrode and the anode uses a platinum sheet electrode.

[0074] Start stirring, turn on the power supply, and energize at a current density of 20 mA / cm 2 , the temperature was 70°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 11.5 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 49.68%.

[0075] Embodiment 11

[0076] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 3.07. The cathode electrolyte was added to the cathode chamber.

[0077] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0078] The cathode uses a foam copper electrode and the anode uses a titanium coated electrode.

[0079] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2 , the temperature was 50°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 7.7 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 46.57%.

[0080] Example 12

[0081] 5 mL of 30% nitro-T-acid aqueous solution was added to 24 mL of water, and then 1 mL of 3M dilute hydrochloric acid solution was added as the cathode electrolyte, with a pH of 3.03. The cathode electrolyte was added to the cathode chamber.

[0082] Add 30 mL of 2M dilute sulfuric acid solution into the anode chamber.

[0083] The cathode uses a foam copper electrode and the anode uses a graphite electrode.

[0084] Start stirring, turn on the power supply, and energize at a current density of 50 mA / cm 2 , the temperature was 50°C, the stirring speed was 500 r / min under normal pressure, and the power was turned on for 9.2 hours. The power was stopped, and the cathode electrolyte was diazotized and titrated to obtain an amino T acid yield of 33.83%.

Claims

1. A method for electrochemical reduction of nitro-T-acid, characterized in that: The method is: The electrochemical reduction is carried out in a separated electrolysis device, which includes an electrolytic cell body, a cathode, an anode and an ion membrane. The ion membrane separates the electrolytic cell body into an anode cell and a cathode cell. The cathode electrolyte is an acidic solution containing nitro-triamino acid with a pH between 1 and 6, and the anode electrolyte is an acid solution. Direct current is applied between the cathode and the anode for electrolysis to reduce the nitro-triamino acid to generate amino-triamino acid, while the anode releases oxygen.

2. The method according to claim 1, characterized in that: The anode material is a platinum electrode, a titanium coating electrode or a graphite electrode, and the cathode material is a foam copper electrode, a foam nickel electrode, a zinc electrode or a lead electrode.

3. The method according to claim 1, characterized in that: The electrolysis was performed with a constant current electrolysis, and the current density was 20 mA / cm 2 ~50mA / cm 2 The electrolysis reaction temperature is 30-70°C and the reaction time is 4-12h.

4. The method according to claim 1, characterized in that: The pH of the cathode electrolyte is 2.8-3.

2.

5. The method according to claim 4, characterized in that: In the cathode electrolyte, the mass fraction of nitro-T acid is 7-8%, and hydrochloric acid is added to adjust the pH of the cathode electrolyte to 2.8-3.

2.

6. The method according to claim 1, characterized in that: The anolyte is a sulfuric acid solution.

7. The method according to claim 6, characterized in that: The concentration of the sulfuric acid solution is 1-3M.

8. The method according to claim 1, characterized in that: The ion membrane is a cationic membrane.

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