Iron-based composite anode preparation method and application thereof in electrochemical synthesis of adiponitrile

Abstract

The application discloses a preparation method of an iron-based composite anode for electrochemical synthesis of adiponitrile, and the iron-based composite anode comprises an iron base material which can be pure iron, carbon steel, 304, 316L, 904L, 2204 and the like, and a tungsten carbide bottom layer and a doped active layer are sequentially arranged on the surface of the iron base material from inside to outside. The tungsten carbide bottom layer is sprayed on the surface of the iron base material, and the doped active layer is prepared on the tungsten carbide bottom layer. In the electrochemical synthesis of adiponitrile, the iron-based composite anode is used as an anode. The iron-based composite anode improves the adhesion between the doped active layer and the base material, improves the electric conductivity, and improves the corrosion resistance. In the electrochemical synthesis of adiponitrile, the problem of easy corrosion of the anode in electrolysis is solved, the service life is prolonged, and the yield of adiponitrile and the electrolytic current efficiency are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of iron-based composite anode preparation method and its application in electrochemical synthesis adiponitrile, belong to chemical technology field. BACKGROUND

[0002] Adiponitrile (ADN) is a very important organic chemical raw material. About 90% of the world's production of adiponitrile is used for the synthesis of adiponitrile hydrogenation adiponitrile, and then for the production of nylon 66 salt, which is the most important industrial use of adiponitrile so far. In addition, adiponitrile can be generated by photochemical reaction of hexamethylene diamine 1,6-hexamethylene diisocyanate (HDI), HDI is an important raw material for the production of high-end environmentally friendly coatings. Therefore, it is of great significance to study the synthesis method of adiponitrile.

[0003] The current production process of adiponitrile mainly includes butadiene hydrocyanation method, acrylonitrile electrolysis dimerization method and adipic acid ammoniation dehydration method. Acrylonitrile electrolysis method is one of the three main methods for synthesizing adiponitrile. This method has a simple process route and can obtain adiponitrile in one step. It is relatively easy to overcome in technology. The raw material acrylonitrile used in this method has less toxicity than hydrocyanic acid used in butadiene method, and the safety risk is relatively small. However, there are still some problems in the synthesis of adiponitrile by acrylonitrile electrolysis method, such as serious anode corrosion, high electrolyte resistivity, high energy consumption and other problems.

[0004] In view of the above-mentioned problems in the process, it is urgent to develop a new type of anode material for synthesizing adiponitrile to overcome the problems of easy corrosion of the anode, hydrogen evolution caused by anode dissolution and poor product quality existing in the current production. SUMMARY

[0005] The purpose of the present application is to provide an iron-based composite anode and a preparation method, which can be used as an anode for electrochemical synthesis of adiponitrile. By adding a tungsten carbide bottom layer, the adhesion between the Fe3O4 plating layer and the substrate is improved, the conductivity is improved, the anode operating tank pressure is reduced, and the service life is improved.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] An iron-based composite anode, comprising an iron-based material, and a tungsten carbide bottom layer and a doped active layer on the surface of the iron-based material from inside to outside;

[0008] The iron-based material can be pure iron, carbon steel, 304, 316L, 904L, 2204, etc.

[0009] Preferably, the doped active layer is manganese ferrite doped magnetite (Fe3O4-MnFe2O4); preferably, the thickness of the doped active layer is 1-5 μm.

[0010] Preferably, the tungsten carbide primer has a thickness of 10-50 μm.

[0011] The present application also provides a method for preparing the iron-based composite anode as described above, comprising the following steps:

[0012] 1) optionally, surface treatment of the iron-based substrate;

[0013] 2) spraying a tungsten carbide primer on the surface of the iron-based substrate;

[0014] 3) using the iron-based substrate prepared in step 2) as an anode and a carbon steel plate as a cathode, an active layer is prepared by an anodic oxidation electrodeposition method in a MnFe2O4-containing nitric acid deposition solution system.

[0015] Preferably, in step 1), the iron-based substrate is surface treated by an electrochemical method and polished with sandpaper to make the surface of the iron-based substrate uniform and free of oxide scale; in a specific embodiment, the electrochemical method is, for example, adding 1 L of water and then 110 g of NaHCO3 in a plastic box, stirring uniformly, using a carbon rod as an anode and clamping an iron plate as a cathode, immersing the cathode and anode in the water without contact, passing a current of 1-5 A, a voltage of 12-36 V, and a time of 3-8 h.

[0016] Preferably, in step 2), the tungsten carbide primer is prepared by a spraying method, and the spraying method is a flame spraying method. In some specific embodiments, the flame spraying method process is: drying the tungsten carbide powder used for spraying in an oven at 80-100 °C for 1-2 hours, and then flame spraying at a flame temperature of 2000-3000 °C.

[0017] Preferably, the operation of the anodic oxidation electrodeposition method in step 3) comprises: using a MnFe2O4-containing nitric acid deposition solution system as an electrolyte, using the iron-based substrate prepared in step 2) as an anode and a carbon steel plate as a cathode, and passing a current to deposit under ultrasonic (for example, 40 kHz) at a temperature of 30-70 °C for 2-8 h, and the electrodeposition current density is 150-300 A / m 2 ;

[0018] Preferably, the MnFe2O4-containing nitric acid deposition solution system is a mixed solution of ferrous acetate and titanium nitrate containing MnFe2O4, and more preferably, the MnFe2O4-containing nitric acid deposition solution system is prepared using deionized water, which contains 140-180 g / L of Fe 2 + , 15-30 g / L of Ti 2+ , and 4-10 g / L of MnFe2O4.

[0019] The present application also provides the use of the iron-based composite anode as an anode in the electrochemical synthesis of adiponitrile.

[0020] Preferably, when the iron-based composite anode is used as an anode for electrochemical synthesis of adiponitrile, the cadmium-plated carbon steel plate is used as a cathode, and the current density for electrochemical synthesis of adiponitrile is 1000-2000 A / m 2 ;

[0021] Preferably, in the system for electrochemical synthesis of adiponitrile, the electrolyte contains 1-5% of acrylonitrile, 7%-20% of dipotassium hydrogen phosphate as a supporting electrolyte, 0.5-3% of EDTA sodium salt as a buffer for pH value of the electrolyte, 1-3% of borax and 0.5%-6% of a quaternary amine salt as a source of guiding ions, and the rest is water; the pH value of the electrolyte is adjusted to be in the range of 7-10 by using phosphoric acid or a strong base; and the concentration of each substance in the electrolyte is a mass percentage concentration.

[0022] The quaternary amine salt can be tetrabutylammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tributylmethylammonium hydroxide, tetrabutylammonium bisulfate, tetrabutylammonium dihydrogen phosphate, etc.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The iron-based composite anode for electrochemical synthesis of adiponitrile comprises, from inside to outside, an iron base material (Fe), a tungsten carbide bottom layer (WC), and a doped active layer (Fe3O4-MnFe2O4). The tungsten carbide bottom layer has two main functions: excellent electrical conductivity and improved adhesion and corrosion resistance of the iron base material. The doped active layer is mainly used to improve the oxygen evolution activity of the anode active layer, thereby reducing the operating cell voltage of the anode.

[0025] The iron-based composite anode improves the electrical conductivity and service life of the anode product.

[0026] The electrochemical method is used to treat the oxide scale of the iron base material, replacing the traditional sand blasting and pickling processes, and the process is simple and practical. The WC bottom layer is prepared by flame spraying in the electrode, and the electrical conductivity is greatly improved. The prepared iron-based composite anode is applied to electrochemical synthesis of adiponitrile, solving the problem of easy corrosion of the anode in electrolysis, improving the service life, and improving the yield of adiponitrile and the electrolysis current efficiency. DETAILED DESCRIPTION

[0027] The present application is further described in conjunction with the following examples, but the scope of the present application is not limited to these examples.

[0028] Preparation of MnFe2O4: MnSO4·H2O and FeCl3·6H2O were weighed according to the molar ratio of Mn 2+ / Fe 3+ = 1:2, dissolved in deionized water to prepare a mixed solution. The mixed solution was stirred, and 3 mol·L-1 The pH value was adjusted to 11 with NaOH. After stirring uniformly, the mixture was transferred to a Teflon-lined autoclave (filling degree of 75%) and heated at 200°C for 12 h. The impurities were removed by washing with deionized water and anhydrous ethanol for several times until neutral. After drying in an electric thermostatic oven at 80°C and sintering at 400°C for 5 h, the product was obtained.

[0029] Example 1

[0030] The preparation method of the iron-based composite anode comprises the following steps:

[0031] 1) The surface of the carbon steel substrate was treated by an electrochemical method (1 L of deionized water was added to a plastic box, then 110 g of NaHCO3 was added and stirred to dissolve, a carbon rod was inserted into the water as the anode, and a carbon steel was immersed below the liquid surface as the cathode to ensure that the anode and cathode did not contact, the voltage was 12 V, the current was 1.5 A, and the power-on time was 3 h) to remove the surface oxide scale, and the carbon steel substrate surface was polished with 200 mesh sandpaper to make the carbon steel substrate surface uniform.

[0032] 2) The carbon steel substrate treated by the electrochemical method in step 1) was prepared by flame spraying to form a tungsten carbide bottom layer: the tungsten carbide powder was dried in an oven at 80°C for 2 hours, then flame spraying was performed at a flame temperature of 2500°C to prepare a WC bottom layer with a thickness of 10 μm.

[0033] 3) The carbon steel substrate prepared in step 2) was used as the anode, and a carbon steel plate was used as the cathode to form a doped active layer (Fe3O4-MnFe2O4) by anodic oxidation electrodeposition in a MnFe2O4-containing nitric acid deposition solution system:

[0034] The MnFe2O4-containing nitric acid deposition solution system was a mixed solution of ferrous acetate and titanium nitrate containing MnFe2O4 prepared in an electrolytic cell, which contained 180 g / L Fe 2+ , 20 g / L Ti 2+ , 6 g / L MnFe2O4, and was heated to 30°C and stirred uniformly;

[0035] Then the carbon steel substrate anode prepared in step 2) and the carbon steel plate cathode were fixed in the electrolytic cell respectively, and ultrasonic electrodeposition was performed for 3 h at an electrodeposition current density of 200 A / m 2 . The Fe3O4-MnFe2O4 doped active layer was formed on the carbon steel substrate prepared in step 2) with a thickness of 2 μm.

[0036] The iron-based composite anode (Fe / WC / Fe3O4-MnFe2O4) prepared by the above steps 1) to 3) was used to prepare electrochemical synthesis adiponitrile. The specific operation method is as follows:

[0037] Iron-based composite anode and carbon steel cadmium plating cathode are fixed in electrolytic cell respectively, and power is supplied, and electrochemical synthesis current density is 1500A / m 2 ;

[0038] Electrolyte in electrochemical synthesis adiponitrile system contains 3% acrylonitrile, 10% dipotassium hydrogen phosphate, 1% EDTA sodium salt, 3% borax, 0.5% tetrabutylammonium hydroxide, and the rest is water, and pH value of electrolyte is 7.

[0039] After running for 3000h, Fe ion content in water phase is 186ppm, yield of adiponitrile reaches more than 90%, and current efficiency is more than 80%.

[0040] Adopting the above Fe / WC / Fe3O4-MnFe2O4 anode to electrochemically synthesize adiponitrile solves the defect that anode is easy to corrode in electrolysis, and service life is prolonged by 1 time.

[0041] Example 2

[0042] Preparation method of iron-based composite anode, comprising the following steps:

[0043] 1) The surface of the carbon steel substrate is treated by the same electrochemical method as in Example 1, the surface oxide scale is removed, and the iron substrate surface is polished using 200 mesh sandpaper.

[0044] 2) The carbon steel substrate treated by the electrochemical method in step 1) is prepared by flame spraying to form a tungsten carbide bottom layer: the tungsten carbide powder is dried in an oven at 100℃ for 1 hour, then flame spraying is carried out at a flame temperature of 2000℃ to form a WC bottom layer with a thickness of 15μm.

[0045] 3) The carbon steel substrate prepared in step 2) is used as an anode, and a carbon steel plate is used as a cathode to electrodeposit an active layer in a nitric acid deposition liquid system containing MnFe2O4 to prepare an iron-based composite anode (Fe3O4-MnFe2O4):

[0046] The nitric acid deposition liquid system containing MnFe2O4 is a mixed solution of ferrous acetate and titanium nitrate containing MnFe2O4 prepared in an electrolytic cell, which contains 180g / L Fe 2+ , 30g / L Ti 2+ , 6g / L MnFe2O4, and is heated to 30℃ and stirred uniformly;

[0047] Subsequently, the carbon steel substrate anode prepared in step 2) and the carbon steel plate cathode are fixed in the electrolytic cell respectively, and power is supplied for ultrasonic electrodeposition for 4h, and the electrodeposition current density is 250A / m 2 . An Fe3O4-MnFe2O4 doped active layer is formed on the carbon steel substrate with a thickness of 3μm.

[0048] The carbon steel-based composite anode prepared in steps 1) to 3) above is used to prepare electrochemical synthesis of adiponitrile. The specific operation method is as follows:

[0049] The carbon steel-based composite anode and the cadmium-plated carbon steel plate cathode are respectively fixed in an electrolytic cell, and electricity is supplied, and the electrochemical synthesis current density is 1200 A / m 2 ;

[0050] The electrolyte in the electrochemical synthesis of adiponitrile system contains 2% of acrylonitrile, 10% of dipotassium hydrogen phosphate, 1.5% of EDTA sodium salt, 3% of borax, 2% of tetraethylammonium hydroxide, and the rest is water, and the pH value of the electrolyte is 7.5.

[0051] After running for 2000h, the content of Fe ions in the aqueous phase is 200ppm, and the yield of adiponitrile is more than 88%, and the current efficiency is more than 80%.

[0052] The electrochemical synthesis of adiponitrile using the above Fe / WC / Fe3O4-MnFe2O4 anode solves the problem of easy corrosion of the anode in electrolysis.

[0053] Example 3

[0054] The preparation method of the iron-based composite anode comprises the following steps:

[0055] 1) The surface of the iron-based material is treated by the same electrochemical method as in Example 1, the surface oxide scale is removed, and the surface of the iron-based material is polished with 200 mesh sandpaper to make it uniform.

[0056] 2) The iron-based material treated by the electrochemical method in step 1) is prepared by flame spraying to form a tungsten carbide bottom layer: The tungsten carbide powder is dried in an oven at 90°C for 1 hour, and then flame spraying is carried out at a flame temperature of 2000°C to prepare a WC bottom layer with a thickness of 30μm.

[0057] 3) The iron-based material prepared in step 2) is used as an anode, and a carbon steel plate is used as a cathode to electrodeposit an active layer in a nitric acid deposition liquid system containing MnFe2O4 to prepare an iron-based composite anode (Fe3O4-MnFe2O4):

[0058] The nitric acid deposition liquid system containing MnFe2O4 is a mixed solution of ferrous acetate and titanium nitrate containing MnFe2O4 prepared in an electrolytic cell, wherein it contains 140g / L Fe 2+ , 20g / L Ti 2+ , 5g / L MnFe2O4, and is heated to 40°C and stirred uniformly;

[0059] Subsequently, the iron-based material anode prepared in step 2) and the carbon steel plate cathode are respectively fixed in an electrolytic cell, and ultrasonic power deposition is carried out for 2h, and the electrodeposition current density is 300 A / m 2Fe3O4-MnFe2O4 doped active layer is formed on the iron base material with a thickness of 1 μm.

[0060] The iron base composite anode prepared by the above steps 1) to 3) is used to prepare electrochemical synthesis adiponitrile.

[0061] The iron base composite anode and the carbon steel cadmium-plated plate cathode are fixed in the electrolytic cell respectively, and electricity is conducted, and the electrochemical synthesis current density is 1800 A / m 2 ;

[0062] The electrolyte in the electrochemical synthesis adiponitrile system contains 5% acrylonitrile, 20% dipotassium hydrogen phosphate, 3% EDTA sodium salt, 2% borax, 3% tetramethylammonium hydroxide, and the rest is water, and the pH value of the electrolyte is 8.

[0063] After running for 1000 h, the content of Fe ions in the water phase is 80 ppm, the yield of adiponitrile is more than 85%, and the current efficiency is more than 82%.

[0064] The above Fe / WC / Fe3O4-MnFe2O4 anode is used for electrochemical synthesis of adiponitrile, and the defect that the anode is easily corroded in electrolysis is solved.

[0065] Comparative Example 1

[0066] The carbon steel anode and the carbon steel cadmium-plated cathode are fixed in the electrolytic cell respectively, and electricity is conducted, and the electrochemical synthesis current density is 1500 A / m 2 ;

[0067] The electrolyte in the electrochemical synthesis adiponitrile system contains 3% acrylonitrile, 10% dipotassium hydrogen phosphate, 1% EDTA sodium salt, 3% borax, 0.5% tetrabutylammonium hydroxide, and the rest is water, and the pH value of the electrolyte is 7.

[0068] After running for 1000 h, the content of Fe ions in the water phase is 800 ppm, the yield of adiponitrile is 83%, and the current efficiency is 74%.

[0069] Compared with the iron base composite anode, directly using the carbon steel as the anode, the corrosion is serious, and the hydrogen evolution of the cathode causes the yield and current selectivity to decrease.

[0070] The iron base composite anode of the application increases the conductive performance and the binding force of the Fe3O4 plating layer and the base material by increasing the WC bottom layer, prevents the base material from being corroded and passivated, the doped active layer is mainly used to improve the oxygen evolution activity of the anode active layer, so as to reduce the anode working tank pressure. Therefore, the iron base composite anode has good conductive performance and high service life.

Claims

1. An iron-based composite anode, characterized in that, The iron-based composite anode comprises an iron base material, and a tungsten carbide bottom layer and a doped active layer are sequentially arranged on the surface of the iron base material from inside to outside. The preparation method of the iron-based composite anode comprises the following steps: 1) performing surface treatment on the iron base material; 2) spraying the tungsten carbide bottom layer on the surface of the iron base material; 3) using the iron base material prepared in step 2) as an anode and a carbon steel plate as a cathode, and preparing the doped active layer in a MnFe2O4-containing nitric acid deposition solution system by using an anodic oxidation electrodeposition method.

2. The iron-based composite anode according to claim 1, characterized in that The thickness of the doped active layer is 1-5 μm.

3. The iron-based composite anode according to claim 1 or 2, characterized in that The thickness of the tungsten carbide bottom layer is 10-50 μm.

4. The iron-based composite anode according to claim 1, characterized in that The operation of step 3) comprises: using the MnFe2O4-containing nitric acid deposition solution system as an electrolyte, using the iron base material prepared in step 2) as an anode, using a carbon steel plate as a cathode, and performing ultrasonic current deposition at a temperature of 30-70 ℃. 2 .

5. The iron-based composite anode according to claim 4, characterized in that The nitric acid deposition solution system containing MnFe2O4 is a mixed solution of ferrous acetate and titanium nitrate containing 140-180 g / L Fe 2+ , 15-30 g / L Ti 2+ , and 4-10 g / L MnFe2O4.

6. The iron-based composite anode according to any one of claims 1-5 is used as an anode in electrochemical synthesis of adiponitrile.

7. A method for electrochemical synthesis of adiponitrile, using the iron-based composite anode according to any one of claims 1-5 as an anode, a cadmium-plated carbon steel plate as a cathode, and a current density of 1000-2000 A / m 2 .

8. The method of claim 7, wherein, The electrolyte contains 1-5% of acrylonitrile, 7%-20% of dipotassium hydrogen phosphate, 0.5-3% of EDTA sodium salt, 1-3% of borax, 0.5%-6% of quaternary amine salt, and the pH value is in the range of 7-10; the concentration of each substance in the electrolyte is a mass percentage concentration.

9. The method of claim 8, wherein, The quaternary amine salt is selected from tetrabutylammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tributylmethylammonium hydroxide, tetrabutylammonium bisulfate and tetrabutylammonium dihydrogen phosphate.