A kind of preparation method of adiponitrile

Abstract

The present invention discloses a method for preparing adiponitrile, comprising the following steps: adding acrylonitrile, an ionic liquid, and water to an electrolytic cell, and generating adiponitrile by a reduction reaction at the cathode; wherein the cathode material comprises a substrate, an intermediate layer, and a surface layer, the substrate being selected from one of graphite, carbon steel, and titanium; the intermediate layer comprising a metal material selected from one of cadmium, lead, silver, and tin, and being connected to the substrate by supersonic flame spraying, magnetron sputtering, or plasma spraying; and the surface layer comprising two types of metals, the first type of metal being selected from one of metallic cadmium, lead, tin, and silver, and the second type of metal element being selected from one of rare earth metals. The present invention provides a green and efficient method for preparing adiponitrile, solving the problems of complex reaction processes, difficult product separation, and high safety risks associated with existing production technologies.

Description

Technical Field

[0001] The invention belongs to the field of organic electrochemical synthesis, and particularly relates to a method for preparing adiponitrile. Background Art

[0002] Adiponitrile is an important basic chemical raw material, primarily used to produce hexamethylenediamine, a key raw material in the production of materials such as nylon 66 and HDI. Adiponitrile also has broad applications in electronics, light industry, and other organic synthesis fields.

[0003] Currently, there are three main routes for the industrial production of adiponitrile. The first uses butadiene and HCN as raw materials and produces adiponitrile through a three-step reaction of selective cyanidation, isomerization, and cyanation. This route is long, complex, and difficult to recover the catalyst. It also requires the use of highly toxic substances such as HCN, posing a high safety risk. The second route uses acrylonitrile as raw material and produces adiponitrile through electrolytic dimerization. This route has simple reaction steps and the product is easy to separate, making it an ideal production route. The key to this route lies in controlling the electrolytic reaction.

[0004] Patent CN201010573038.X reports a method for electrosynthesizing adiponitrile using a dimensionally stable anode. This method uses acrylonitrile as the starting material and produces adiponitrile at the cathode. To improve the reaction selectivity, a quaternary ammonium base additive is added to the reaction aqueous phase. However, the quaternary ammonium base is unstable and easily decomposed and lost during subsequent reuse. Furthermore, the product selectivity is only 80%, and other by-products increase the difficulty of separation.

[0005] Therefore, it can be seen that the existing synthesis process still has problems such as complex reaction process, difficult product separation and high safety risks. The electrochemical preparation of adiponitrile also has problems such as low product selectivity and poor additive stability. A clean, safe and stable production method is needed. Summary of the Invention

[0006] In view of this, the main purpose of the present invention is to provide a method for electrochemically preparing adiponitrile using acrylonitrile as raw material, which solves the problems of complex existing reaction process, difficult product separation and high safety risks.

[0007] To achieve the above object of the invention, the present invention adopts the following technical solution: a method for preparing adiponitrile, comprising the following steps:

[0008] Acrylonitrile, an ionic liquid containing imidazole groups and water are added to an electrolytic cell, and a reduction reaction occurs at the cathode to generate adiponitrile;

[0009] Among them, the cathode material includes a substrate, an intermediate layer and a surface layer, and the substrate is selected from one of graphite, carbon steel, and titanium; the intermediate layer contains a metal material selected from one of cadmium, lead, silver, and tin, and the intermediate layer is connected to the substrate by supersonic flame spraying, magnetron sputtering or plasma spraying; the surface layer includes a first type of metal and a second type of metal, the first type of metal is selected from one of metal cadmium, lead, tin, and silver, and the second type of metal is selected from one of rare earth metals.

[0010] The first type of metal has a high hydrogen evolution overpotential and is used to obtain the target product. If other metals are used, hydrogen or other products will be produced. The second type of metal can improve the selectivity of the target product.

[0011] In the present invention, the ionic liquid is selected from one or more of [DEMIM]Y and [DOMIM]Y, wherein Y is one of trifluoromethanesulfonate (OTf), trifluoroacetate (CF3COO), and p-toluenesulfonate (OTs), and the structural formulas of [DEMIN] and [DOMIM] are as follows:

[0012]

[0013] In the present invention, preferably, the mass ratio of the added amount of ionic liquid to acrylonitrile is 1:100-1:50. The ionic liquid can serve as a supporting electrolyte to improve the yield and current efficiency of adiponitrile.

[0014] In the present invention, the mass ratio of the second type of metal in the surface layer to the mass ratio of all metals in the surface layer is 0.1-10% by weight, preferably 1-5% by weight, such as 0.1%, 1%, 3%, 5%, 10%, etc., and the best effect can be achieved within the above mass ratio range. The rare earth metal is preferably selected from cerium, scandium, yttrium, samarium, praseodymium, neodymium, etc.

[0015] In the present invention, the intermediate layer preferably has a thickness of 5-20 μm. Within this range, the bonding strength with the adjacent layers is enhanced, which can be reflected in a specific embodiment by measuring the metal content through ICP.

[0016] In the present invention, the anode material is selected from one of carbon steel, titanium plated with ruthenium dioxide, and titanium plated with iridium oxide.

[0017] In the present invention, the current density of the cathode is 500-3000A / m 2 , preferably 1000-2000A / m 2 .

[0018] In the present invention, the reduction reaction temperature range is 40-60°C.

[0019] The reaction of the present invention is carried out in an electrolytic cell, which can be a conventional non-diaphragm electrolytic cell, and can be equipped with a stirrer, a thermometer and other accessories in addition to the electrodes. In a specific embodiment, the anode and cathode are rectangular electrodes, and the anode electrode area is 1-10 cm 2 , cathode electrode area is 1-10cm 2 The two electrodes are placed in parallel, and the distance between the cathode and anode is 2-5mm.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention uses supersonic flame spraying, magnetron sputtering, plasma spraying and other technologies to form a metallurgical bond between the substrate and the spraying element. This bond can significantly increase the bonding force between the substrate and the spraying element and extend the service life of the electrode.

[0022] (2) The present invention introduces rare earth metals into the surface layer of the cathode material, thereby improving the selectivity and current density of the reaction and increasing the output per unit electrode area.

[0023] In summary, the present invention provides a green and efficient method for preparing adiponitrile, which solves the problems of complex reaction process, difficult product separation and high safety risks in existing production technologies. DETAILED DESCRIPTION

[0024] The present invention is further described below with reference to the embodiments. However, the present invention is not limited to the listed embodiments but also includes equivalent improvements and variations of the technical solutions defined in the claims attached to the present application.

[0025] The raw materials and equipment in the examples are described as follows:

[0026] Acrylonitrile purchasing manufacturer: Xilong Reagent, purity>99.5%.

[0027] Ionic liquids [DEMIM][OTs], [DEMIM][OTf], [DEMIM][CF3COO], [DOMIM][OTs], [DOMIM][OTf], [DOMIM][CF3COO] purchased from: Sinochem Reagent Company, purity >99%.

[0028] Anode material: Xi'an Taijin Materials Co., Ltd.

[0029] Cathode material substrate and intermediate layer purchasing manufacturer: Xi'an Taijin Materials Co., Ltd.

[0030] Gas chromatography analysis conditions: instrument model: Shimadzu 2010 Plus, carrier gas: helium; flow rate: 1.0 ml / min; injection volume: 0.2 ul; injection port temperature: 300°C; split ratio: 30:1; chromatographic column: DB-5 (30 m×0.25 mm×0.25 μm); column temperature: 50°C for 2 min, heated to 80°C at 5°C / min, held for 0 min, heated to 300°C at 15°C / min, held for 10 min; detector: FID, temperature: 300°C.

[0031] Example 1

[0032] Cathode preparation method:

[0033] An electrode material containing a carbon steel substrate and a cadmium intermediate layer was placed in an electroplating solution containing 10 wt% cadmium sulfate and 0.1 wt% cerium sulfate. The electrode was used as a cathode and a platinum sheet as an anode. Constant current electroplating was performed at room temperature for 30 minutes with a current of 0.4 A. After the electrode was taken out, it was washed three times with distilled water and allowed to dry naturally.

[0034] 20g acrylonitrile, 0.2g [DEMIM][OTf], and 100g water were added to the electrolytic cell. The cathode material base material was carbon steel, with a cadmium intermediate layer connected to the base material using supersonic flame spraying technology. The intermediate layer was 5 microns thick, and the surface metals were cadmium and cerium, with a cadmium content of 99wt% and a cerium content of 1wt%. The anode material was carbon steel, and the cathode current density was controlled to 1000A / m 2 , electrolysis was carried out at 40°C for 10 hours. The product yield was determined by gas chromatography to be 96% of adiponitrile, with a current efficiency of 94%. The cadmium content of the reaction solution was determined by ICP-OES to be 3 ppm. The reduction reaction formula is:

[0035]

[0036] The anode and cathode are both rectangular electrodes, and the anode electrode area is 10cm 2 , the cathode electrode area is 10cm 2 The two electrodes are placed in parallel, and the distance between the cathode and anode is 5 mm.

[0037] Example 2

[0038] The preparation method of the cathode material is similar to that of Example 1.

[0039] 10g acrylonitrile, 0.2g [DEMIM][CF3COO], and 100g water were added to the electrolytic cell. The cathode material base material was carbon steel, with an intermediate layer of silver, which was connected to the base material using magnetron sputtering technology. The intermediate layer thickness was 20 microns. The surface metal was silver and scandium, with a silver content of 95wt% and a scandium content of 5wt%. The anode material was titanium plated with ruthenium dioxide. The cathode current density was controlled at 2000A / m2 , electrolysis was carried out at 60° C. for 5 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 95% and the current efficiency was 92%.

[0040] Example 3

[0041] The preparation method of the cathode material is similar to that of Example 1.

[0042] 30g acrylonitrile, 0.4g [DEMIM][OTs], and 100g water were added to the electrolytic cell. The cathode material base material was titanium, with an intermediate layer of lead, connected to the base material using plasma jet technology. The intermediate layer thickness was 10 microns. The surface metal was lead and yttrium, with a lead content of 97wt% and a yttrium content of 3wt%. The anode material was titanium plated with iridium oxide. The cathode current density was controlled at 1500A / m 2 , electrolysis was carried out at 50° C. for 7.5 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 92% and the current efficiency was 90%.

[0043] Example 4

[0044] The preparation method of the cathode material is similar to that of Example 1.

[0045] 15g acrylonitrile, 0.25g [DOMIM][OTf], and 100g water were added to the electrolytic cell. The cathode material was graphite-based, with a tin interlayer, bonded to the substrate using supersonic sputtering technology. The interlayer thickness was 15 microns. The surface metal was tin and samarium, with a tin content of 99.9wt% and a samarium content of 0.1%. The anode material was carbon steel. The cathode current density was controlled at 500A / m 2 , electrolysis was carried out at 45° C. for 8 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 90% and the current efficiency was 86%.

[0046] Example 5

[0047] The preparation method of the cathode material is similar to that of Example 1.

[0048] 32g acrylonitrile, 0.4g [DOMIM][CF3COO], and 100g water were added to the electrolytic cell. The cathode material base material was graphite, and the middle layer was cadmium, which was connected to the base material using magnetron sputtering technology. The middle layer thickness was 8 microns. The surface metal was cadmium and praseodymium, with a cadmium content of 90wt% and a praseodymium content of 10%. The anode material was titanium plated with ruthenium dioxide. The cathode current density was controlled at 3000A / m 2 , electrolysis was carried out at 55° C. for 6 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 95% and the current efficiency was 92%.

[0049] Example 6

[0050] The preparation method of the cathode material is similar to that of Example 1.

[0051] 27g acrylonitrile, 0.3g [DOMIM][OTs], and 100g water were added to the electrolytic cell. The cathode material was titanium with a lead intermediate layer, connected to the substrate using plasma jet technology. The intermediate layer was 12 microns thick. The surface metal was lead and neodymium, with a lead content of 98wt% and a neodymium content of 2%. The anode material was titanium plated with iridium oxide. The cathode current density was controlled at 1750A / m 2 , electrolysis was carried out at 45° C. for 9 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 93% and the current efficiency was 91%.

[0052] Example 7

[0053] The preparation method of the cathode material is similar to that of Example 1.

[0054] 27g acrylonitrile, 0.3g [DOMIM] [methanesulfonate], and 100g water were added to the electrolytic cell. The cathode material base material was titanium, with an intermediate layer of lead, connected to the base material using plasma jet technology. The intermediate layer thickness was 12 microns. The surface metal was lead and neodymium, with a lead content of 98wt% and a neodymium content of 2%. The anode material was titanium plated with iridium oxide. The cathode current density was controlled at 1750A / m 2 The electrolysis was carried out at 45° C. for 9 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 73% and the current efficiency was 71%.

[0055] Comparative Example 1

[0056] 20g acrylonitrile, 0.2g [DEMIM][OTf] and 100g water were added to the electrolytic cell. The cathode material base material was carbon steel, and the middle layer was cadmium. It was connected to the base material using supersonic flame spraying technology and was used directly without the surface material. The anode material was carbon steel, and the cathode current density was controlled to 1000A / m 2 , electrolysis was carried out at 40°C for 10 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 26% and the current efficiency was 14%.

[0057] In Comparative Example 1, the cathode material does not use a surface layer containing a rare earth metal, and the selectivity and current efficiency of the reaction are greatly reduced, resulting in a decrease in the yield of adiponitrile.

[0058] Comparative Example 2

[0059] 20g acrylonitrile, 2.0g [BPY] [HSO4] and 100g water were added to the electrolytic cell. The cathode material base material was carbon steel, and the middle layer was cadmium. It was connected to the base material using supersonic flame spray technology. The surface metal was cadmium and cerium, with a cadmium content of 99wt% and a cerium content of 1wt%. The anode material was carbon steel. The cathode current density was controlled to 1000A / m 2, electrolysis was carried out at 40° C. for 10 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 16% and the current efficiency was 12%.

[0060] In Comparative Example 2, [BPY][HSO4] ionic liquid was used, and the selectivity and current efficiency of the reaction were greatly reduced, resulting in a decrease in the yield of adiponitrile.

[0061] Comparative Example 3

[0062] 20g acrylonitrile, 0.2g [DEMIM][OTf] and 100g water were added to the electrolytic cell. The cathode material base material was carbon steel, and the middle layer was cadmium. It was connected to the base material using supersonic flame spray technology. The surface metal was cadmium and cerium. The cadmium content was 99.95wt% and the cerium content was 0.05wt%. The anode material was carbon steel. The cathode current density was controlled to 1000A / m 2 , electrolysis was carried out at 40°C for 10 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 48% and the current efficiency was 42%.

[0063] In Comparative Example 3, the rare earth element content is 0.05 wt %, and the selectivity and current efficiency of the reaction are greatly reduced, resulting in a decrease in the yield of adiponitrile.

[0064] Comparative Example 4

[0065] 20g acrylonitrile, 0.2g [DEMIM][OTf] and 100g water were added to the electrolytic cell. The cathode material was cadmium-plated carbon steel with a cadmium content of 99wt% and a cerium content of 1wt%. The anode material was carbon steel. The cathode current density was controlled to 1000A / m 2 The electrolysis was carried out at 40° C. for 10 h. The yield of the product was determined by gas chromatography, and the yield of adiponitrile was 94%, the current efficiency was 91%, and the cadmium content of the reaction solution was determined by ICP-OES to be 12 ppm.

[0066] In Comparative Example 4, the cathode did not use supersonic flame spraying, magnetron sputtering, or plasma spraying technology to construct the intermediate layer. The cadmium content in the reaction solution was four times that in Example 1, and the cadmium loss rate was four times that in Example 1.

[0067] The supersonic flame spraying, magnetron sputtering, and plasma spraying technologies described herein may refer to conventional steps or parameters of corresponding methods in the prior art.

[0068] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing adiponitrile, characterized in that: The steps include: Acrylonitrile, an ionic liquid containing an imidazole group, and water are added to an electrolytic cell, and a reduction reaction occurs at the cathode to generate adiponitrile; The cathode material includes a substrate, an intermediate layer, and a surface layer, wherein the substrate is selected from one of graphite, carbon steel, and titanium; the intermediate layer comprises a metal material selected from one of cadmium, lead, silver, and tin, and the intermediate layer is connected to the substrate by supersonic flame spraying, magnetron sputtering, or plasma spraying; the surface layer comprises a first type of metal and a second type of metal, wherein the first type of metal is selected from one of cadmium, lead, tin, and silver, and the second type of metal is selected from one of rare earth metals; The ionic liquid is selected from one or more of [DEMIM]Y and [DOMIM]Y, wherein Y is one of trifluoromethanesulfonate, trifluoroacetate, and p-toluenesulfonate, and the structural formulas of [DEMIN] and [DOMIM] are as follows:

2. The method for preparing adiponitrile according to claim 1, wherein: The mass ratio of the added amount of ionic liquid to acrylonitrile is 1:100-1:

50.

3. The method for preparing adiponitrile according to claim 1, wherein: The thickness of the intermediate layer is 5-20 microns.

4. The method for preparing adiponitrile according to claim 1, wherein: The mass ratio of the second type of metal in the surface layer to the mass ratio of all metals in the surface layer is 0.1-10 wt %.

5. The method for preparing adiponitrile according to claim 4, wherein: The mass ratio of the second type of metal in the surface layer to the mass ratio of all metals in the surface layer is 1-5%wt.

6. The method for preparing adiponitrile according to claim 1, wherein: The rare earth metal is selected from one of cerium, scandium, yttrium, samarium, praseodymium and neodymium.

7. The method for preparing adiponitrile according to claim 1, wherein: The anode material is selected from one of carbon steel, titanium plated with ruthenium dioxide, and titanium plated with iridium oxide.

8. The method for preparing adiponitrile according to claim 1, wherein: The current density of the cathode is 500-3000A / m 2 .

9. The method for preparing adiponitrile according to claim 8, wherein: The current density of the cathode is 1000-2000A / m 2 .

10. The method for preparing adiponitrile according to claim 9, wherein: The reduction reaction temperature range is 40-60°C.

11. The method for preparing adiponitrile according to claim 1, wherein: The reduction reaction is carried out in a diaphragmless electrolytic cell, where both the anode and cathode are rectangular electrodes with an anode electrode area of ​​1-10 cm 2 , cathode electrode area is 1-10cm 2 The two electrodes are placed in parallel, and the distance between the cathode and the anode is 2-5mm.

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