A method for preparing 1-aminoanthraquinone by electrocatalytic hydrogenation

Abstract

The invention discloses an application of using a carbon nanotube (CNT) film electrode as a cathode to electrocatalytically reduce 1-nitroanthraquinone to generate 1-aminoanthraquinone. An N-methylpyrrolidone (NMP) solution and a dissolved Na2SO4 electrolyte dispersed in 1-nitroanthraquinone are added to a reaction vessel, and an appropriate amount of palladium nanoclusters are added as a catalyst. With a titanium sheet as an anode and a CNT film as a cathode, 1-nitroanthraquinone is reduced to 1-aminoanthraquinone by direct electron transfer and hydrogen action at a certain applied voltage through the cathode. The 1-aminoanthraquinone preparation method proposed in the present invention is simple, has a short preparation cycle, mild preparation conditions, and is environmentally friendly. Using this method to prepare 1-aminoanthraquinone, the cathode further reduces the dual effects of the reactant through direct electron transfer and catalyst-enhanced hydrogen production, thereby achieving rapid preparation of 1-aminoanthraquinone. The CNT film electrode used has a richer active site, provides more reaction surface area, and significantly improves the generation rate of 1-aminoanthraquinone compared to traditional metal electrodes.

Description

Technical Field

[0001] The invention relates to the technical field of chemical production, and in particular to a method for preparing 1-aminoanthraquinone by electrocatalytic hydrogenation. Background Art

[0002] my country has a huge demand for anthraquinone dyes, and the main intermediate in the production of anthraquinone dyes is 1-aminoanthraquinone. Therefore, high-quality synthetic 1-aminoanthraquinone undoubtedly has huge economic value and market prospects. The synthesis methods of 1-aminoanthraquinone mainly include sulfonation ammonolysis, nitration reduction, naphthoquinone butadiene method, etc. Among them, the production process of sulfonation ammonolysis to prepare 1-aminoanthraquinone requires the use of highly toxic mercuric sulfate, so this method has gradually been eliminated by the market. The naphthoquinone butadiene method uses refined naphthalene as a raw material, and nitrates, oxidizes, nitrates and reacts with electrophilic addition to obtain 1-aminoanthraquinone. The product has high purity but the reaction process is complicated and not suitable for practical application. The nitration reduction method is currently commonly used in my country. Anthraquinone is used as a raw material to nitrate to obtain 1-nitroanthraquinone, and then reduced to prepare 1-aminoanthraquinone. The mainstream reduction methods include ammonolysis, alkali sulfide reduction, liquid phase catalytic hydrogenation and electrochemical reduction. The production process of the ammonolysis method produces ammonium nitrite due to the use of ammonium hydroxide, which has a potential risk of explosion; the alkali sulfide reduction method is a common method used by dye companies at home and abroad to produce 1-aminoanthraquinone. The main alkali sulfides used are sodium sulfide and sodium hydrosulfide, which have the advantages of mild reaction and easy collection of products, but the sulfate waste liquid produced will cause environmental pollution; the liquid phase catalytic hydrogenation method uses hydrogen as the hydrogen source, and Pt, Pd or Co is loaded on a carrier as a hydrogen production catalyst, and the 1-nitroanthraquinone reduction reaction is carried out under normal pressure or high pressure. This reaction is a multiphase reaction, and there is no requirement for the dissolution of reactants and products, but this method has high requirements for equipment, and the reaction conditions require a certain pressure or temperature.

[0003] The present application adopts an electrochemical reduction method to reduce 1-nitroanthraquinone by electron transfer. The method has a fast reaction rate, the product is easy to separate, and it is green and pollution-free. The key to the process is high efficiency, low cost, and the use of stable cathode materials. However, due to the problems of power utilization and reactant solubility, the 1-nitroanthraquinone electrochemical reduction method has not yet been reported for practical application. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for producing 1-aminoanthraquinone by electrochemical catalytic reduction of 1-nitroanthraquinone using a carbon nanotube (CNT) membrane electrode as a cathode, the method having a fast reaction rate, simple device operation and high product yield efficiency.

[0005] In order to solve the above problems, the technical solution provided by the present invention is as follows: a method for preparing 1-aminoanthraquinone by electrocatalytic hydrogenation, comprising the following steps: dissolving 1-nitroanthraquinone in N-methylpyrrolidone, adding Na2SO4 electrolyte solution, and then adding palladium nanoclusters as cathode hydrogen production catalysts, using CNT membrane electrode as cathode and titanium sheet as anode, and catalyzing hydrogenation reaction under a certain external voltage to obtain 1-aminoanthraquinone.

[0006] Preferably, the method for preparing the CNT membrane electrode comprises: firstly uniformly dispersing a small amount of CNT powder in an NMP solution by ultrasonic treatment, and then vacuum filtering the dispersion onto a polytetrafluoroethylene (PTFE) based membrane to obtain the CNT membrane electrode.

[0007] Preferably, the preparation method of the palladium nanocluster catalyst comprises: mixing and stirring a Na2PdCl4 solution and a 2-hydroxy-4-methylthiobutyric acid solution, then adding a NaOH solution and a NaBH4 solution, and magnetically stirring to obtain the catalyst.

[0008] Preferably, the mass ratio of the amount of CNT used to 1-nitroanthraquinone is 0.6 to 2:1.

[0009] Preferably, the mass ratio of the catalyst volume to 1-nitroanthraquinone (ml:mg) is 0-0.4:1.

[0010] Preferably, the voltage is 0-10V, and direct current is used.

[0011] Preferably, the Na2SO4 electrolyte solution is prepared by dissolving Na2SO4 in ultrapure water, wherein the mass ratio of Na2SO4 to ultrapure water (mg:ml) is 14.2-42.6:40, and the preferred ratio is 25-30:40.

[0012] Preferably, the mass ratio of the volume of N-methylpyrrolidone to 1-nitroanthraquinone (ml:mg) is 10-30:25, and the mass ratio of the volume of Na2SO4 electrolyte solution to 1-nitroanthraquinone (ml:mg) is 35-45:25.

[0013] Preferably, in the palladium nanocluster catalyst: the Na2PdCl4 solution is a 1.5mM-2.5mM aqueous solution, the 2-hydroxy-4-methylthiobutyric acid solution is a 4mM-6mM aqueous solution, the NaOH solution is a 0.5M-1.5M aqueous solution, and the NaBH4 solution is a 105mM-125mM aqueous solution; the volume ratio of Na2PdCl4 solution: 2-hydroxy-4-methylthiobutyric acid solution: NaOH solution: NaBH4 solution is 26:20:3:1.

[0014] Preferably, the volume ratio of the CNT powder mass to the NMP (mg:ml) is 1:0.4-1.3, and the ratio of the CNT powder mass to the amount of the polytetrafluoroethylene (PTFE) base film used (mg:cm 2 ) is 2.6~0.8:1.

[0015] The principle of the present invention is as follows:

[0016] Under the action of the auxiliary electric field, 1-nitroanthraquinone near the CNT membrane electrode receives electrons and is reduced to 1-aminoanthraquinone, while part of the 1-nitroanthraquinone precipitated in the solution forms flocs with Na2SO4 in a suspended state, which can also undergo reduction reaction through contact with the CNT membrane electrode. The addition of palladium nanocluster catalyst is intended to accelerate the rate at which the cathode produces hydrogen through electrolysis of water, and to produce 1-nitroanthraquinone by hydrogen reduction.

[0017] The advantages of the present invention are:

[0018] (1) The method for preparing 1-aminoanthraquinone proposed in the present invention has a simple device structure, a short preparation cycle, mild preparation conditions, and is environmentally friendly, thus solving the practical application problem of preparing 1-aminoanthraquinone by electrochemical method.

[0019] (2) The present invention proposes to use CNT membrane as cathode for electrochemical preparation of 1-aminoanthraquinone. The specific surface area (cm 2 / g) is 60-120, which is comparable to the specific surface area (cm 2 / g)4-15, it can provide more 1-nitroanthraquinone reaction and hydrogen adsorption sites, and at the same time has a certain catalytic effect on reduction hydrogen production. The cathode further reduces the reactants through direct electron transfer and catalyst-enhanced hydrogen production, achieving the rapid preparation of 1-aminoanthraquinone. The CNT film electrode used has more active sites and provides more reaction surface area. Compared with traditional metal electrodes, it significantly increases the generation rate of 1-aminoanthraquinone and effectively improves the reaction rate of the system.

[0020] (3) The present invention proposes to use palladium nanoclusters to catalyze the reduction of 1-nitroanthraquinone to produce hydrogen. The prepared nanoclusters can not only effectively accelerate the generation of hydrogen but also play a role in storing hydrogen, preventing the generated hydrogen from escaping the solution without reacting, thereby improving the reaction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a comparison diagram of the generation of 1-aminoanthraquinone in the system when the reaction system uses different cathodes in Example 1 and Comparative Example 1;

[0022] Figure 2This is a diagram showing the generation rate of 1-aminoanthraquinone in the system under different applied voltage conditions in the reaction system in Example 1 and Comparative Example 2;

[0023] Figure 3 This is a comparison chart of the generation of 1-aminoanthraquinone in the system under the condition of adding different amounts of catalyst in the reaction system in Example 1 and Comparative Example 3. DETAILED DESCRIPTION

[0024] The present invention is described below with reference to examples, but the present invention is not limited thereto. In the art, simple replacement or improvement made by technicians in the field to the present invention belongs to the technical solution protected by the present invention.

[0025] Embodiment 1:

[0026] An electrochemical method for catalytic reduction of 1-nitroanthraquinone to prepare 1-aminoanthraquinone is implemented as follows:

[0027] (1) Take a 100 mL beaker as a reactor, add 25 mg of 1-nitroanthraquinone and 20 mL of NMP solution as a solvent, and stir to dissolve. Take another beaker, add 40 mL of ultrapure water and 28.4 mg of Na2SO4 as an electrolyte solution, and stir to dissolve.

[0028] (2) Add 4 mL of palladium nanocluster catalyst, pour the prepared electrolyte solution into the reactor, stir and mix, and then insert electrodes, with the anode being a titanium sheet and the cathode being a CNT film, and apply an external voltage of 4 V.

[0029] The preparation method of palladium nanocluster catalyst is as follows: 260 ml of 2.5 mM Na2PdCl4 aqueous solution and 200 ml of 5 mM 2-hydroxy-4-methylthiobutyric acid (MHA) solution are mixed and stirred for 5 minutes, and then 30 mL of 1 M NaOH solution and 10 mL of 105 mM NaBH4 solution are added, and magnetic stirring is performed for 3 hours.

[0030] The preparation method of CNT membrane electrode is as follows: firstly, a small amount of CNT powder is uniformly dispersed in NMP solution by ultrasonic treatment, and then the dispersion is vacuum filtered onto a polytetrafluoroethylene (PTFE) base membrane to obtain a CNT membrane electrode with a specific surface area of ​​60 to 120 cm 2 / g.

[0031] (3) A zero sample was taken before power was turned on, and samples were taken every 20 minutes thereafter. The 1-aminoanthraquinone content in the sample was determined by high performance liquid chromatography. At the end of the reaction, the 1-aminoanthraquinone conversion rate was 99.6%.

[0032] Comparative Example 1:

[0033] The difference between this comparative example and Example 1 is that the electrode used as the cathode is a gold-loaded molybdenum disulfide CNT film, and the other experimental conditions are the same.

[0034] Comparative Example 2:

[0035] The difference between this comparative example and Example 1 is that the applied voltages are: 0V, 3V, 5V and 10V respectively.

[0036] Comparative Example 3:

[0037] The difference between this comparative example and Example 1 is that the amounts of palladium nanocluster catalyst added are: 0 mL, 2 mL, 5 mL and 10 mL respectively.

[0038] The experimental data of Example 1 and Comparative Example 1 are as follows Figure 1 As shown in the figure, the loading of elemental gold and molybdenum disulfide materials did not have a positive effect on the experiment. On the contrary, the yield of 1-aminoanthraquinone was very low compared with the pure CNT membrane electrode. The yield of using CNT cathode at 60 minutes was calculated by measuring the content of 1-aminoanthraquinone, which was 6.3 mg / h. The relative yield of loaded gold CNT was only 3.1 mg / h. The main reason is that the loading of gold and molybdenum disulfide reduced the content of CNT, and CNT was directly related to the cathode reduction reaction of hydrogen production and 1-nitroanthraquinone reduction. Therefore, the cathode should directly use a pure CNT membrane electrode.

[0039] The experimental data of Example 1 and Comparative Example 2 are as follows Figure 2 As shown, when there is no applied voltage, no 1-aminoanthraquinone is generated in the system. When the applied voltage is 3V, a small amount of 1-aminoanthraquinone is generated in the system. It is speculated that the generation of the product at this time depends on the reduction reaction of 1-nitroanthraquinone by hydrogen after the cathode electroreduction produces hydrogen; when the applied voltage reaches 4V, the product generation rate increases significantly, so it can be inferred that the threshold voltage of the direct electroreduction of 1-nitroanthraquinone by the cathode is around 4V; when the applied voltage continues to rise to 5V, the generation rate of 1-aminoanthraquinone increases slightly; when the applied voltage is increased to 10V, the generation of 1-aminoanthraquinone drops sharply and only a very small amount is detected. At the same time, green substances are observed near the cathode in the reactor. The reason is that the excessively high voltage triggers side reactions, resulting in a reduction in the yield of 1-aminoanthraquinone. When the applied voltage was 5V, the final yield of 1-aminoanthraquinone reached 99.3%, and the reaction was considered to be complete, with an average production rate of 1-aminoanthraquinone of 6.5mg / h; and when the applied voltage was 4V, the final yield of 1-aminoanthraquinone reached 99.6%, and the reaction was considered to be complete, with an average production rate of 1-aminoanthraquinone of 6.3mg / h. Considering the overall efficiency and energy consumption, 4V is the most suitable voltage for practical applications.

[0040] The experimental data of Example 1 and Comparative Example 3 are as follows Figure 3As shown, when no catalyst is added to the system, the generation rate of 1-aminoanthraquinone is significantly lower than that of Example 1. The reason is that when no catalyst is added, the rate of hydrogen generation at the cathode is low, so the rate of reducing 1-nitroanthraquinone by hydrogen is slow. At this time, 1-nitroanthraquinone is mainly reduced by direct electron transfer at the cathode. Compared with Example 1, the effects of adding 2mL and 5mL of catalyst are slightly worse, indicating that the optimal amount of catalyst added is about 4mL. When the amount of catalyst added reaches 10mL, the yield of 1-aminoanthraquinone decreases significantly, even lower than the value when no catalyst is added. The reason is that too much catalyst affects the dissolution of 1-nitroanthraquinone in the original solution, causing more reactants to precipitate, which is not conducive to the reaction.

[0041] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, which all fall within the protection scope of the present invention.

Claims

1. A method for preparing 1-aminoanthraquinone by electrocatalytic hydrogenation, characterized in that: The method comprises the following steps: dissolving 1-nitroanthraquinone in N-methylpyrrolidone, adding a Na2SO4 electrolyte solution, and then adding a palladium nanocluster as a cathode hydrogen production catalyst, using a CNT membrane electrode as a cathode and a titanium sheet as an anode, and catalyzing a hydrogenation reaction under a certain applied voltage to obtain 1-aminoanthraquinone; the voltage is 4 to 5V, and direct current is used; the mass ratio of the catalyst volume to 1-nitroanthraquinone is 0.08 to 0.4 ml: 1 mg.

2. The method according to claim 1, characterized in that The preparation method of the CNT membrane electrode comprises: firstly uniformly dispersing a small amount of CNT powder in an N-methylpyrrolidone solution by ultrasonic treatment, and then vacuum filtering the dispersion onto a polytetrafluoroethylene (PTFE) base membrane to obtain the CNT membrane electrode.

3. The method according to claim 1, characterized in that The preparation method of the palladium nanocluster catalyst comprises: mixing and stirring a Na2PdCl4 solution and a 2-hydroxy-4-methylthiobutyric acid solution, then adding a NaOH solution and a NaBH4 solution, and magnetically stirring to obtain the catalyst.

4. The method according to claim 1, characterized in that The mass ratio of the amount of CNT used to 1-nitroanthraquinone is 0.6 to 2:

1.

5. The method according to claim 1, characterized in that The Na2SO4 electrolyte solution is prepared by dissolving Na2SO4 in ultrapure water, wherein the volume ratio of Na2SO4 mass to ultrapure water is 25-30 mg:40 ml.

6. The method according to claim 1, characterized in that The mass ratio of the volume of N-methylpyrrolidone to 1-nitroanthraquinone is 10-30 ml:25 mg, and the mass ratio of the volume of Na2SO4 electrolyte solution to 1-nitroanthraquinone is 35-45 ml:25 mg.

7. The method according to claim 3, characterized in that In the palladium nanocluster catalyst: the Na2PdCl4 solution is a 1.5mM-2.5mM aqueous solution, the 2-hydroxy-4-methylthiobutyric acid solution is a 4mM-6mM aqueous solution, the NaOH solution is a 0.5M-1.5M aqueous solution, and the NaBH4 solution is a 105mM-125mM aqueous solution; the volume ratio of Na2PdCl4 solution: 2-hydroxy-4-methylthiobutyric acid solution: NaOH solution: NaBH4 solution is 26:20:3:

1.

8. The method according to claim 2, characterized in that The volume ratio of the CNT powder mass to N-methylpyrrolidone is 1 mg: 0.4-1.3ml, the ratio of CNT powder mass to PTFE base film usage is 2.6-0.8mg:1cm 2 .

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