A method for the large-scale production of nitriles by electrocatalytic oxidation of primary amines

Abstract

The application discloses a method for large-scale production of nitrile by primary amine electrocatalytic oxidation. The method adopts a three-electrode system and carries out catalytic oxidation in an H-type electrolytic tank. A working electrode, a counter electrode and a reference electrode jointly form an electrocatalytic reactor. Primary amine is added into an alkaline solution, and the reaction is carried out for a certain time under constant voltage. Nitrile can be obtained through simple separation after the reaction process is completed. Compared with traditional processes, the method has the advantages of high efficiency, high selectivity, greenness, low cost, simple operation and the like, is suitable for industrial implementation and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic organic synthesis technology, and specifically to a method for preparing nitriles by electrocatalytic oxidation of primary amines. Background Technology

[0002] Nitriles are important chemical raw materials, widely used in the manufacture of pharmaceuticals, synthetic fibers, and plastics, as well as in industries such as electroplating, steel quenching, and mineral processing. Hydrogen cyanide and its salts are mainly used in the electroplating and mining industries (for extracting precious metals such as gold and silver), and in the manufacture of various resins and synthetic nitrile compounds. They are also sometimes used for rodent control through fumigation in warehouses and ship cabins. Acrylonitrile, methacrylonitrile, and other nitrile compounds are important raw materials for synthetic fibers, synthetic rubber, and plastics.

[0003] The main methods for synthesizing nitrile compounds include: ammonia oxidation, haloalkanes substitution, aryl diazonium salt substitution, and amide and aldehyde oxime dehydration. Traditional nitrile synthesis reactions involve highly toxic metallic cyanide reagents, which present the following major problems: (1) severe environmental pollution and harsh reaction conditions; (2) the high-temperature and high-pressure reaction process poses a huge threat to equipment, reaction condition control, and large-scale production safety; (3) low product yield, difficulty in material separation, and low product purity, which cannot meet user requirements and greatly limit the application of nitrile compounds. From the perspective of green chemistry, there is an urgent need for a mild and easy-to-operate preparation method.

[0004] Organic electrocatalytic synthesis is a new technology that uses electrons as reagents to synthesize organic chemicals through the gain and loss of electrons. It holds promise for fundamentally eliminating the pollution problems associated with traditional organic synthesis and has wide applications in the fine chemical industry, including pharmaceuticals, fragrances, auxiliaries, and dye intermediates. Organic electrosynthesis enables many conventional chemical reactions that require high temperatures, high pressures, special catalysts, and cause pollution to be carried out at room temperature and pressure, making it a highly selective, efficient, and environmentally friendly technology. Furthermore, primary amine substrates are inexpensive and readily available, and can be directly obtained from many chemical products. Therefore, large-scale production of nitrile chemicals based on electrocatalytic synthesis technology using primary amines as raw materials has excellent industrial application prospects. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the existing technology, the purpose of this invention is to overcome the problems of using highly toxic metal cyanide source reagents, heavy environmental pollution, and harsh reaction conditions in the current synthesis process of nitrile compounds, and to provide a method for large-scale production of nitrile by electrocatalytic oxidation of primary amines. The process has outstanding features such as being green and environmentally friendly, simple in production process, low in catalyst cost, high in reaction efficiency, and simple in product separation.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] 1. The present invention provides a method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, comprising: using a three-electrode system to carry out catalytic oxidation in an H-type electrolytic cell; the working electrode, the counter electrode, and the reference electrode together constitute an electrocatalytic reactor; adding primary amines to a KOH solution, reacting for a certain time under a constant potential voltage, and obtaining nitriles by simple separation after the reaction process is completed.

[0008] 2. The method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, wherein the primary amine is one of aromatic primary amines, heterocyclic primary amines, or aliphatic primary amines;

[0009] 3. In the method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, the working electrode is a metal oxide / hydroxide supported on porous nickel foam, the reference electrode is Hg / HgO, and the counter electrode is a platinum wire;

[0010] 4. In the method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, the molar concentration of the primary amine substrate is 10–500 mM, and the alkaline solution is a 0.1–6.0 M KOH or NaOH solution;

[0011] 5. The method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, wherein the operating voltage is 1.2V to 1.6V and the reaction time is 1 to 40 min;

[0012] 6. In the method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, the support thickness is 0.5-2 mm and the size is (1-5) cm × (1-5) cm;

[0013] 7. The method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, wherein the method for preparing the porous nickel foam-supported metal oxide / hydroxide comprises: (1) preparing a hydrogen peroxide reaction solution containing 3 mM metal salt; (2) ultrasonically washing a metal foam with a thickness of 0.5 mm to 2 mm with anhydrous ethanol, analytical grade acetone and deionized water for 15 min each, and then immersing it in the above solution for 2 to 15 min; (3) after the reaction is completed, removing it, rinsing the surface with deionized water and drying it at 60 °C to obtain the porous nickel foam-supported metal oxide / hydroxide.

[0014] In step 1), the metal salt is Fe. 2+ Co 2+ Mn 2+ Cu 2+ The mass fraction of the hydrogen peroxide reaction solution is 1% to 10%.

[0015] 8. In the method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, the metal oxide / hydroxide is a nickel, iron, manganese, cobalt, or copper oxide / hydroxide;

[0016] 9. In the method for large-scale production of nitriles by electrocatalytic oxidation of primary amines, after the electrocatalytic reaction is completed, the nitriles float on the surface of the electrolyte and can be obtained by simple oil-water separation, thus enabling continuous large-scale production of nitriles.

[0017] Compared with existing technologies, the advantages of this invention include:

[0018] (1) This invention uses metal oxides / hydroxides supported on porous nickel foam as catalysts to catalyze the conversion of primary amines into nitrile, without the need for highly toxic metal cyanide source reagents, and has the characteristics of being green and environmentally friendly.

[0019] (2) This invention can be carried out at room temperature and pressure without the harsh reaction conditions of traditional processes. It has high product selectivity and conversion rate. A large amount of nitrile products can be obtained through simple separation. It is suitable for industrial implementation and has broad application prospects. Attached Figure Description

[0020] Figure 1 This is the linear sweep voltammetric curve of the benzylamine electrocatalytic process in Example 2 of this invention.

[0021] Figure 2 These are images of the benzylamine electro-oxidation reaction in Example 2 of this invention and the color change after the addition of Oil Red O.

[0022] Figure 3 This is the linear sweep voltammetric curve of the 1,6-diaminohexane electrocatalytic process in Example 3 of the present invention.

[0023] Figure 4 This is the linear sweep voltammetric curve of the electrocatalytic process of 3-phenylprop-1-amine in Example 4 of the present invention.

[0024] Figure 5 This is the linear sweep voltammetric curve of the cyclohexylmethylamine electrocatalytic process in Example 5 of the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] Example 1

[0027] Prepare 50 mL of a reaction solution containing 3 mM cobalt chloride and 5% hydrogen peroxide. Then, a 1.5 mm thick nickel foam with a size of 2 cm × 2 cm is ultrasonically washed for 15 min each with anhydrous ethanol, analytical grade acetone, and deionized water. After that, it is immersed in the above solution for 15 min. After the reaction, it is taken out, the surface is rinsed with deionized water, and dried at 60 °C to obtain a porous nickel foam loaded with nickel and cobalt oxide / hydroxide.

[0028] A three-electrode system was used for catalytic oxidation in an H-type electrolytic cell; the working electrode was nickel and cobalt oxides / hydroxides supported on porous nickel foam, the reference electrode was Hg / HgO, and the counter electrode was platinum wire, forming an electrocatalytic reactor.

[0029] In the cathode electrolysis chamber, a 0.5M NaOH solution was used as the cathode electrolyte, and in the anolyte chamber, 50mM benzylamine was dissolved in a 0.5M NaOH solution as the anolyte. The mixture was magnetically stirred.

[0030] The reaction was carried out under constant voltage (1.4V vs. RHE) for 20 min at room temperature and pressure with continuous stirring. After the reaction, the product floated on the surface of the solution and was easily separated. High-performance liquid chromatography (HPLC) analysis of the reaction product showed a nitrile yield of 86%.

[0031] Example 2

[0032] Prepare 50 mL of a reaction solution containing 3 mM cobalt nitrate and 5% hydrogen peroxide. Then, a 1.5 mm thick nickel foam with a size of 2 cm × 2 cm is ultrasonically washed for 15 min each with anhydrous ethanol, analytical grade acetone, and deionized water. After that, it is immersed in the above solution for 15 min. After the reaction, it is taken out, the surface is rinsed with deionized water, and dried at 60 °C to obtain a porous nickel foam loaded with nickel and cobalt oxide / hydroxide.

[0033] A three-electrode system was used for catalytic oxidation in an H-type electrolytic cell; the working electrode was nickel and cobalt oxides / hydroxides supported on porous nickel foam, the reference electrode was Hg / HgO, and the counter electrode was platinum wire, forming an electrocatalytic reactor.

[0034] In the cathode electrolysis chamber, a 1M NaOH solution was used as the cathode electrolyte, and in the anolyte chamber, 100mM benzylamine was dissolved in a 1M NaOH solution as the anolyte, and the mixture was magnetically stirred.

[0035] The reaction was carried out under constant voltage (1.5V vs. RHE) at room temperature and pressure for 30 min with continuous stirring. After the reaction, the product floated on the surface of the solution and was easily separated. High-performance liquid chromatography (HPLC) analysis of the reaction product showed a nitrile yield of 94%.

[0036] Example 3

[0037] Prepare 50 mL of a hydrogen peroxide reaction solution containing 3 mM manganese chloride and 5% by mass. Then, a 1 mm thick nickel foam with dimensions of 1.5 cm × 1.5 cm is ultrasonically washed for 15 min each with anhydrous ethanol, analytical grade acetone, and deionized water. After that, it is immersed in the above solution for 15 min. After the reaction, it is taken out, the surface is rinsed with deionized water, and dried at 60 °C to obtain a porous nickel foam loaded with nickel and manganese oxide / hydroxide.

[0038] A three-electrode system was used for catalytic oxidation in an H-type electrolytic cell; the working electrode was nickel and cobalt oxides / hydroxides supported on porous nickel foam, the reference electrode was Hg / HgO, and the counter electrode was platinum wire, forming an electrocatalytic reactor.

[0039] In the cathode electrolysis chamber, a 1M KOH solution was used as the cathode electrolyte, and in the anolyte chamber, 100mM 1,6-diaminohexane dissolved in a 1M KOH solution was used as the anolyte. The mixture was magnetically stirred.

[0040] The reaction was carried out under constant voltage (1.5V vs. RHE) for 30 min at room temperature and pressure with continuous stirring. After the reaction, the product floated on the surface of the solution and was easily separated. High-performance liquid chromatography (HPLC) analysis of the reaction product showed a nitrile yield of 89%.

[0041] Example 4

[0042] Prepare 50 mL of a reaction solution containing 3 mM manganese nitrate and 5% hydrogen peroxide. Then, a 1 mm thick nickel foam with a size of 1 cm × 1 cm is ultrasonically washed for 15 min each with anhydrous ethanol, analytical grade acetone, and deionized water. After that, it is immersed in the above solution for 15 min. After the reaction, it is taken out, the surface is rinsed with deionized water, and dried at 60 °C to obtain a porous nickel foam loaded with nickel and manganese oxide / hydroxide.

[0043] A three-electrode system was used for catalytic oxidation in an H-type electrolytic cell; the working electrode was nickel and cobalt oxides / hydroxides supported on porous nickel foam, the reference electrode was Hg / HgO, and the counter electrode was platinum wire, forming an electrocatalytic reactor.

[0044] In the cathodic electrolysis chamber, a 1M KOH solution was used as the cathodic electrolyte, and in the anodic electrolysis chamber, 100mM 3-phenylprop-1-amine was dissolved in a 1M KOH solution as the anodic electrolyte, and the mixture was magnetically stirred.

[0045] The reaction was carried out under constant voltage (1.5V vs. RHE) for 30 min at room temperature and pressure with continuous stirring. After the reaction, the product floated on the surface of the solution and was easily separated. High-performance liquid chromatography (HPLC) analysis of the reaction product showed a nitrile yield of 87%.

[0046] Example 5

[0047] Prepare 50 mL of a reaction solution containing 3 mM ferrous chloride and 5% hydrogen peroxide. Then, a 0.5 mm thick nickel foam with a size of 1 cm × 1 cm is ultrasonically washed for 15 min each with anhydrous ethanol, analytical grade acetone, and deionized water. After that, it is immersed in the above solution for 15 min. After the reaction, it is taken out, the surface is rinsed with deionized water, and dried at 60 °C to obtain a porous nickel foam loaded with nickel and iron oxide / hydroxide.

[0048] A three-electrode system was used for catalytic oxidation in an H-type electrolytic cell; the working electrode was nickel and cobalt oxides / hydroxides supported on porous nickel foam, the reference electrode was Hg / HgO, and the counter electrode was platinum wire, forming an electrocatalytic reactor.

[0049] In the cathode electrolysis chamber, 1M KOH solution was used as the cathode electrolyte, and in the anolyte electrolysis chamber, 100mM cyclohexylmethylamine was dissolved in 1M KOH solution as the anolyte, and the mixture was magnetically stirred.

[0050] The reaction was carried out under constant voltage (1.5V vs. RHE) at room temperature and pressure for 30 min with continuous stirring. After the reaction, the product floated on the surface of the solution and was easily separated. High-performance liquid chromatography (HPLC) analysis of the reaction product showed a nitrile yield of 88%.

[0051] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for the large-scale production of nitriles by the electrocatalytic oxidation of primary amines, characterized in that: The catalytic oxidation is carried out in an H-type electrolytic cell by using a three-electrode system, wherein the working electrode, the counter electrode and the reference electrode jointly form an electro-catalytic reactor; the molar concentration of the primary amine is 100-500 mM, and the alkaline solution is a 1M KOH or NaOH solution; the primary amine is added to the KOH or NaOH solution, and after the reaction is carried out at a working voltage of 1.4-1.6 V for 20-40 min, the nitrile is obtained by separation; the working electrode is a porous nickel foam loaded metal oxide / metal hydroxide, and the metal oxide / metal hydroxide is a composite oxide or composite hydroxide of nickel and a second metal, and the second metal is iron, manganese, cobalt or copper; The primary amine is one of an aromatic primary amine, a heterocyclic primary amine or an aliphatic primary amine. The preparation method of the porous nickel foam loaded metal oxide / hydroxide comprises the following steps: (1) preparing a hydrogen peroxide reaction solution containing 3 mM metal salt, (2) ultrasonically washing a foam metal with a thickness of 0.5-2 mm with anhydrous ethanol, analytical pure acetone and deionized water for 15 min, and then immersing the foam metal in the above solution for 2-15 min, and (3) after the reaction is completed, taking out the foam metal, rinsing the surface with deionized water, and drying at 60℃ to obtain the porous nickel foam loaded metal oxide / hydroxide. The metal ion in the metal salt is Fe 2+ , Co 2+ , Mn 2+ or Cu 2+ , and the mass fraction of the reaction solution of the hydrogen peroxide is 1% to 10%.

2. A method for the large-scale production of nitriles by the electrocatalytic oxidation of primary amines according to claim 1, characterized in that, The reference electrode is Hg / HgO, and the counter electrode is a platinum wire.

3. A process for the large scale production of nitriles by the electrocatalytic oxidation of primary amines according to claim 2, characterized in that The thickness of the porous nickel foam is 0.5-2 mm, and the size is (1-5) cm × (1-5) cm.

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