Method for preparing p-aminophenol by electrolytic reduction of p-nitrophenol

Abstract

The invention discloses a method for preparing p-aminophenol by electroreduction of p-nitrophenol. Electrolytic reduction is carried out in a double-chamber electrolytic cell, an anode chamber and a cathode chamber are separated by a proton membrane, an acidic aqueous solution is added into the anode chamber and the cathode chamber, and p-nitrophenol is added into the cathode chamber. According to the method, p-aminophenol can be obtained in a cathode chamber under a certain reaction condition through electrifying electrolysis, additional reducing agents and catalysts do not need to be added, the yield of p-aminophenol generated through reaction is high and can reach 94.87%, the product purity is high, the technological process is environmentally friendly, and the method has good application value.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic preparation technology, and specifically relates to a method for preparing p-aminophenol from p-nitrophenol. Background Technology

[0002] p-Aminophenol is an important organic chemical raw material and pharmaceutical intermediate, widely used in industries such as pharmaceuticals, dyes, rubber, and photography. Therefore, the active exploration of preparation methods for p-aminophenol is of great significance.

[0003] The main methods for synthesizing p-aminophenol are: (1) Iron powder reduction method: This production process is relatively simple and technically skilled, and the equipment requirements are not high. However, the yield is low, the raw material input is large, and the environment is polluted and difficult to treat. (2) Catalytic hydrogenation reduction method: The production method uses nitrobenzene as a substrate and carries out hydrogenation reduction under suitable catalyst conditions to obtain p-aminophenol. Using noble metals as catalysts, the reaction conditions are relatively mild and the selectivity of p-aminophenol is high. However, the cost of catalysts in this process is high, the purity of reactants is required, and it is easy to cause catalyst deactivation. (3) Electrolytic reduction method: Generally, titanium dioxide / titanium or titanium oxide coated electrodes are used, with nitrobenzene as raw material, and the reaction is carried out under appropriate current density, acid concentration, and reaction temperature conditions. Publication number CN117867532A reports a method to improve the conversion rate of nitrobenzene and the purity of p-aminophenol by adding emulsifiers and using tungsten carbide modified sponge-like metallic nickel as cathode. However, the electrode preparation process is complicated and various additives need to be added, making the process cumbersome. Therefore, there is a need for a method that is low-cost, simple in process, mild in reaction conditions, environmentally friendly, and has a high yield. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing p-aminophenol by electrolytic reduction of p-nitrophenol and the electrode used therein. This method addresses the problems of low yield, severe environmental pollution, and high production costs in the synthesis of p-aminophenol, as well as the complexity of electrode preparation in electrolytic reduction methods. The invention provides a high-yield, high-purity, high-current-efficiency, and low-cost method for synthesizing p-aminophenol.

[0006] (2) Technical solution

[0007] To address the aforementioned technical problems, this invention provides a method for preparing p-aminophenol by electrolytic reduction of p-nitrophenol.

[0008] Apparatus: An H-type electrolytic cell is used, with the cathode chamber and anode chamber separated by a proton exchange membrane. The electrolytic cell is connected to constant-temperature water, and electrolysis is carried out under constant current.

[0009] Method: Acidic aqueous solutions were added to a dual-chamber electrolytic cell. The concentration of the acidic aqueous solution in the anode chamber was 0.1–5.0 mol / L, and the concentration in the cathode chamber was also 0.1–5.0 mol / L. p-Nitrophenol, a raw material, was added to the cathode chamber at a concentration of 10–50 g / L in the acidic aqueous solution. Electrolysis was performed, with the reaction temperature and current density kept constant. After a period of electrolysis, an electrolyte containing p-aminophenol was obtained.

[0010] The acidic aqueous solution is selected from sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, and perchloric acid; the reaction temperature is 20–100℃; and the current density is 100–1500 A / m. 2 .

[0011] The anode plate of the anode chamber is one of iridium-plated titanium electrode, ruthenium-iridium-titanium plate electrode, ruthenium-titanium electrode, graphite electrode, and lead dioxide electrode, and the cathode plate of the cathode chamber is one of stainless steel electrode, lead electrode, copper electrode, and titanium electrode.

[0012] The cathode has dimensions of 1mm × 45mm × 50mm, a porosity of 96.7%–98%, a pore size of 95–110 PPI, and an areal density of 280–350 g / m³. 2 .

[0013] Preferably, the acidic aqueous solution is sulfuric acid, with the sulfuric acid concentration in the anode chamber being 1.5–3 mol / L and the sulfuric acid concentration in the cathode chamber being 1.5–3 mol / L.

[0014] Preferably, the reaction temperature is 50–80°C and the current density is 750–1500 A / m. 2 .

[0015] Preferably, the concentration of p-nitrophenol in the acidic aqueous solution is 20–50 g / L.

[0016] By adopting the above technical solution, the present invention has the following advantages and beneficial effects:

[0017] ① The yield of p-aminophenol produced by the reaction is high, reaching 94.87%. ② Apart from the hydrogen evolution reaction, there are no other side reactions in this process, and the product has high purity. ③ The electrochemical synthesis method uses electrons as a reducing agent, making the process green and environmentally friendly, in line with the concept of sustainable development. ④ A simple electrode is used, avoiding the problem of complex electrode preparation and difficulty in scale-up in electroreduction methods. Attached Figure Description

[0018] Figure 1 The relationship between current density and p-aminophenol yield is shown.

[0019] Figure 2The relationship between temperature and the yield of p-aminophenol.

[0020] Figure 3 This represents the relationship between sulfuric acid concentration and the yield of p-aminophenol.

[0021] Figure 4 The relationship between raw material concentration and p-aminophenol yield is shown.

[0022] Figure 5 This is a schematic diagram of the device of the present invention.

[0023] Wherein: 1-Power line; 2-Power supply; 3-Cathode; 4-Cathode chamber; 5-Proton membrane; 6-Anode chamber; 7-Anode. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific content described below is illustrative and not restrictive, and should not be used to limit the scope of protection of the present invention.

[0025] Example 1

[0026] 250 mL of 2.0 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a copper foam. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 40℃ and a current density of 750 A / m. 2 After the reaction solution reached the set temperature, the power was turned on to begin electrolysis. The electrolysis reaction was terminated when the flux reached 6 F / mol. The yield of p-aminophenol in the resulting cathode solution was 72.31%.

[0027] Example 2

[0028] 250 mL of 2.0 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a copper foam. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 40℃ and a current density of 1000 A / m. 2 After the reaction solution reaches the set temperature, the power is turned on to initiate electrolysis. The electrolysis reaction is terminated when the flux reaches 6 F / mol. The yield of p-aminophenol in the resulting cathode solution is 89.57%.

[0029] Example 3

[0030] 250 mL of 2.0 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a copper foam. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 40℃ and a current density of 1250 A / m. 2 After the reaction solution reaches the set temperature, the power is turned on to initiate electrolysis. The electrolysis reaction is terminated when the flux reaches 6 F / mol. The yield of p-aminophenol in the resulting cathode solution is 77.79%.

[0031] As can be seen from the results of Examples 1-3, the yield of p-aminophenol obtained in Example 2 is higher than that in Examples 1 and 3.

[0032] Example 4

[0033] 250 mL of 2.0 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a foamed copper electrode. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 50℃ and a current density of 1000 A / m. 2 After the reaction solution reaches the set temperature, the power is turned on to initiate electrolysis. The electrolysis reaction is terminated when the flux reaches 6 F / mol. The yield of p-aminophenol in the resulting cathode solution is 89.75%.

[0034] Example 5

[0035] 250 mL of 2.0 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a copper foam. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 60℃ and a current density of 1000 A / m. 2 After the reaction solution reaches the set temperature, the power is turned on to initiate electrolysis. The electrolysis reaction is terminated when the flux reaches 6 F / mol. The yield of p-aminophenol in the resulting cathode solution is 90.32%.

[0036] As can be seen from the results of Examples 2, 4 and 5, the yield of p-aminophenol obtained in Example 5 is higher than that in Examples 2 and 4.

[0037] Example 6

[0038] 250 mL of 1.5 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a foamed copper electrode. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 60℃ and a current density of 1000 A / m. 2After the reaction solution reaches the set temperature, the power is turned on to initiate electrolysis. The electrolysis reaction is terminated when the flux reaches 6 F / mol. The yield of p-aminophenol in the resulting cathode solution is 81.97%.

[0039] Example 7

[0040] 250 mL of 2.5 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a copper foam. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 60℃ and a current density of 1000 A / m. 2 After the reaction solution reaches the set temperature, the power is turned on to initiate electrolysis. The electrolysis reaction is terminated when the flux reaches 6 F / mol. The yield of p-aminophenol in the resulting cathode solution is 92.40%.

[0041] As can be seen from the results of Examples 5, 6 and 7, the yield of p-aminophenol obtained in Example 7 is higher than that in Examples 5 and 6.

[0042] Example 8

[0043] 250 mL of 2.5 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 2.5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a copper foam. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 60℃ and a current density of 1000 A / m. 2 After the reaction solution reached the set temperature, the power was turned on to begin electrolysis. The electrolysis reaction was terminated when the flux reached 6 F / mol. The yield of p-aminophenol in the resulting cathode solution was 62.81%.

[0044] Example 9

[0045] 250 mL of 2.5 mol / L sulfuric acid aqueous solution was added to each of the two chambers of the electrolytic cell. 7.5 g of p-nitrophenol was added to the cathode chamber. The anode was an iridium-plated titanium mesh, and the cathode was a copper foam. The stirring device and the constant temperature water bath were turned on, maintaining a constant reaction temperature of 60℃ and a current density of 1000 A / m. 2 After the reaction solution reaches the set temperature, the power is turned on to initiate electrolysis. The electrolysis reaction is terminated when the flux reaches 6 F / mol. The yield of p-aminophenol in the resulting cathode solution is 94.87%.

[0046] As can be seen from the results of Examples 7, 8 and 9, the yield of p-aminophenol obtained in Example 9 is higher than that in Examples 7 and 8.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing p-aminophenol by electrolytic reduction of p-nitrophenol, characterized in that: The method comprises the following steps: adding an acidic aqueous solution into a double-chamber electrolytic cell, wherein the concentration of the acidic aqueous solution in the anode chamber is 0.1-4.0 mol / L, and the concentration in the cathode chamber is 0.1-4.0 mol / L; adding raw material p-nitrophenol into the cathode chamber, wherein the concentration of p-nitrophenol in the acidic aqueous solution is 1 g / L; -1 ~1000gL -1 , applying power for electrolysis, controlling the reaction temperature and current density to be constant, and obtaining an electrolyte containing the p-aminophenol after applying power for a period of time; The acidic aqueous solution is selected from sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, and perchloric acid aqueous solutions, the reaction temperature is 10 to 100°C, and the current density is 10 to 1000A / m 2 .

2. The method for preparing p-aminophenol as claimed in claim 1, wherein The anode chamber and cathode chamber are separated by a cation exchange membrane, which is one of a perfluorosulfonic acid cation exchange membrane, a carboxylic acid cation exchange membrane, a stearic acid cation exchange membrane, a brominated polyvinylidene fluoride cation exchange membrane, and a silicate-based cation exchange membrane.

3. The method for preparing p-aminophenol as claimed in claim 1, characterized in that, The anode plate of the anode chamber is one of iridium-plated titanium electrode, ruthenium-iridium-titanium plate electrode, ruthenium-titanium electrode, graphite electrode, and lead dioxide electrode, and the cathode plate of the cathode chamber is one of stainless steel electrode, lead electrode, copper electrode, and titanium electrode.

4. The method for preparing p-aminophenol as claimed in claim 1, wherein The acidic aqueous solution is sulfuric acid, the concentration of sulfuric acid in the anode chamber is 0.5-3 mol / L; the concentration of sulfuric acid in the cathode chamber is 0.5-3 mol / L.

5. The method for preparing p-aminophenol as claimed in claim 1, characterized in that, The reaction temperature is 30-80°C, and the current density is 200-1500A / m 2 .

6. The method for preparing p-aminophenol as claimed in claim 1, characterized in that: The concentration of p-aminophenol in the acidic aqueous solution is 1 g / L -1 ~50gL -1 .

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