Electrolyte and electrolysis method for electrocatalytic production of adiponitrile from acrylonitrile
By modifying quaternary phosphonium salts and optimizing electrolyte composition and reaction conditions, the problem of high cost of quaternary ammonium salts in traditional electrolytes was solved, and adiponitrile was produced with high selectivity and economy through the electrolytic dimerization of acrylonitrile.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2022-01-27
- Publication Date
- 2026-06-16
AI Technical Summary
The quaternary ammonium salts used in the traditional acrylonitrile electrolytic dimerization process are expensive, which increases the cost of acrylonitrile electrolytic dimerization and results in low reaction selectivity.
By using modified quaternary phosphonium salt as the main component of the electrolyte, combined with appropriate cathode and anode materials, controlling the electrolysis reaction conditions, optimizing the electrolyte composition and pH value, and improving the selectivity of adiponitrile.
The use of modified quaternary phosphonium salts improved the selectivity and economic efficiency of adiponitrile and reduced electrolysis costs.
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Figure CN116555789B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical synthesis and discloses a method for synthesizing adiponitrile from acrylonitrile. Background Technology
[0002] Adiponitrile (ADN) is an important organic chemical intermediate, mainly used in the production of materials such as polyhexamethylene adipamide (Nylon 66), 1,6-hexamethylene diisocyanate (HDI), and Nylon 610. It is estimated that approximately 90% of the world's adiponitrile is used to produce Nylon 66 annually. The process involves hydrogenating adiponitrile to produce hexamethylenediamine, which is then polycondensed with adipic acid to obtain a translucent or opaque milky-white synthetic resin (Nylon 66).
[0003] Adiponitrile has high technological barriers and investment thresholds, resulting in extremely high industry concentration. Industrial production technologies for adiponitrile include adipic acid catalytic amination (ADA), acrylonitrile electrolytic dimerization (AN), and butadiene cyanidation (BD).
[0004] Acrylonitrile electrolytic dimerization uses acrylonitrile as a raw material and electrochemically dimers it to produce adiponitrile. This method offers advantages such as a short process and high product quality. However, the main component used in traditional electrolytes to adjust reaction selectivity is quaternary ammonium salt. The large quantity of quaternary ammonium salt used and its high cost contribute to the increased cost of acrylonitrile electrolytic dimerization. Summary of the Invention
[0005] To address the aforementioned problems, this invention provides an electrolyte for the electrolysis of acrylonitrile to produce adiponitrile and a method for its preparation.
[0006] The present invention provides an electrolyte for the electrocatalytic production of adiponitrile from acrylonitrile, comprising acrylonitrile, a modified quaternary phosphonium salt and water, wherein the cation of the modified quaternary phosphonium salt is a structure of formula (f) with one end connected to a group shown in formula (a1) or formula (b1) and the other end connected to a group of formula (a1), (b1), (c), (d) or (e).
[0007]
[0008] Among them, R2~R 22 Each is an alkyl group, C1 to C5, and n = 1 to 6.
[0009] According to one embodiment of the present invention, the content of the modified quaternary phosphonium salt in the electrolyte is 0.01 to 3 wt%, preferably 0.01 to 1 wt%.
[0010] According to another embodiment of the present invention, the anion of the modified quaternary phosphonium salt is one or more of hydroxide, hydrogen sulfate, sulfate, phosphate, hydrogen phosphate, dihydrogen phosphate, acetate, nitrate, and bis(trifluoromethanesulfonyl)imide anion.
[0011] According to another embodiment of the present invention, the electrolyte further contains 0.1 to 10 wt% EDTA or its sodium or potassium salt, and 0.01 to 5 wt% borax.
[0012] According to another embodiment of the present invention, the electrolyte further comprises 1 to 20 wt% of phosphate, wherein the phosphate is at least one selected from potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.
[0013] According to another embodiment of the present invention, the content of acrylonitrile in the electrolyte is 4 to 7 wt%.
[0014] According to another embodiment of the present invention, n is 4 to 6, R2 to R 12 Each is an alkyl group, which is independently C2 to C4.
[0015] Another aspect of the present invention provides a method for producing adiponitrile by electrolysis of acrylonitrile, wherein the above-mentioned electrolyte is used for the electrolysis reaction.
[0016] According to one embodiment of the present invention, the cathode of the electrolytic reaction is Cd or Pb or their alloy, and the anode is carbon steel or stainless steel or PbO2.
[0017] According to another embodiment of the present invention, the reaction temperature of the electrolysis reaction is 30–70°C, and the current density is 200–5000 A / m. 2 .
[0018] The electrolyte for the electrolytic production of adiponitrile from acrylonitrile in this invention contains a modified quaternary phosphonium salt. Compared with traditional quaternary ammonium salts, the use of quaternary phosphonium salts improves the selectivity of the target product adiponitrile, thus resulting in better economic benefits. Detailed Implementation
[0019] The present invention will now be described in detail with reference to specific embodiments.
[0020] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0021] The electrolyte for the electrocatalytic production of adiponitrile from acrylonitrile of the present invention comprises acrylonitrile, a modified quaternary phosphonium salt and water, wherein the cation of the modified quaternary phosphonium salt is a structure of formula (f) with one end connected to a group shown in formula (a1) or formula (b1) and the other end connected to a group of formula (a1), (b1), (c), (d) or (e).
[0022]
[0023] Among them, R2~R 22 Each is an alkyl group, C1 to C5, and n = 1 to 6.
[0024] The inventors discovered that modified quaternary phosphonium salts in the electrolyte can improve the selectivity of adiponitrile. The mechanism is not yet fully understood, but a possible mechanism is that the quaternary phosphonium salts adsorb onto the electrode surface, reducing the probability of further hydrogenation of activated acrylonitrile to form the byproduct propionitrile. Therefore, better selectivity for the target product can be obtained.
[0025] In an optional embodiment, the content of the modified quaternary phosphonium salt is 0.01–3 wt%. When the content of the modified quaternary phosphonium salt in the electrolyte is less than 0.01 wt%, the content is low and insufficient to significantly affect the conversion rate and selectivity of the acrylonitrile electrolytic dimerization reaction; when it is greater than 3 wt%, the content of the modified quaternary phosphonium salt is too high, resulting in high usage costs. Those skilled in the art can choose any value within the above range, such as, but not limited to, 0.0 wt%, 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, etc. Preferably, the content of the modified quaternary phosphonium salt in the electrolyte is 0.01–1 wt%.
[0026] In an optional embodiment, the anion of the modified quaternary phosphonium salt is one or more of hydroxide, hydrogen sulfate, sulfate, phosphate, hydrogen phosphate, dihydrogen phosphate, acetate, nitrate, and bis(trifluoromethanesulfonyl)imide anion.
[0027] In an optional embodiment, to improve electrolysis efficiency, the electrolyte may also contain 0.1 to 10 wt% EDTA or its sodium or potassium salt, and 0.01 to 5 wt% borax.
[0028] In an optional embodiment, the electrolyte may further contain 1-20 wt% phosphate, wherein the phosphate is at least one selected from potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate. The phosphate serves to adjust the pH value of the electrolyte, and an appropriate phosphate content can be selected according to actual needs to achieve the desired pH value. For example, the phosphate concentration may be, but is not limited to, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, etc.
[0029] In an optional embodiment, the acrylonitrile content is 4–7 wt%. When the acrylonitrile content in the electrolyte is less than 4 wt%, the preparation efficiency is low; and the saturated solubility of acrylonitrile in the electrolyte is 7 wt%. Therefore, an acrylonitrile content of 4–7 wt% is preferred.
[0030] The present invention also provides a method for producing adiponitrile by electrolysis of acrylonitrile, wherein the above-mentioned electrolyte is used for the electrolysis reaction.
[0031] In an optional embodiment, the cathode of the electrolysis reaction is Cd or Pb or their alloys, and the anode is carbon steel or stainless steel or PbO2.
[0032] In an optional embodiment, the electrolysis reaction temperature is 30–70°C, and the current density is 200–5000 A / m. 2 Current density less than 200 A / m 2 If the current density is greater than 5000 A / m, the production efficiency will be too low, requiring investment in more electrolytic cells to achieve the same production capacity; 2 If the current generates more heat, the side reactions will increase.
[0033] After the electrolysis reaction is completed, the electrolyte is mixed with crude adiponitrile to absorb the unreacted acrylonitrile. The mixture is then separated into an oil phase and an aqueous phase containing acrylonitrile, adiponitrile and organic by-products. The oil phase is then distilled to obtain acrylonitrile, crude adiponitrile and organic by-products.
[0034] The present invention is further described below through specific examples. However, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present invention. Unless otherwise specified, the reagents, materials, and instruments used in the following embodiments and comparative examples are commercially available.
[0035] In the following examples, all reactions were carried out in an electrolytic cell with electrode dimensions of 100mm*200mm*5mm, with the anode and cathode positioned parallel to each other and spaced 3mm apart. The electrolyte was pumped and circulated, with a linear velocity of 1m / s within the electrolytic cell. Current was applied based on the current density and electrode area, and the reaction time was calculated based on a Faraday efficiency of 100%. Electrolysis was then performed using the calculated current and reaction time. After the reaction was complete, the organic matter in the electrolyte was extracted with CH2Cl2 and weighed. The composition of the organic matter was analyzed chromatographically, and the acrylonitrile conversion and adiponitrile selectivity were calculated. All pressures used were gauge pressures. The test results are shown in Table 1.
[0036] The experimental conditions and results are calculated as follows:
[0037] Current = Electrode area × Current density;
[0038] Reaction time = (2 × mass of acrylonitrile × Faraday constant) / (molar mass of acrylonitrile × current);
[0039] Acrylonitrile conversion rate = (1 - mass of remaining acrylonitrile / mass of added acrylonitrile) × 100%;
[0040] Adiponitrile yield = (actual mass of adiponitrile received / theoretical mass of acrylonitrile completely converted to adiponitrile) × 100%.
[0041] The compounds of formulas (A) to (F) described in the examples and comparative examples are shown below:
[0042]
[0043]
[0044] Example 1
[0045] The electrolyte used contained 3.5 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 1.5 wt% borax, and 2.5 wt% modified quaternary phosphonium salt C. The pH of the electrolyte was adjusted to 8 by adding H3PO4 and NaOH. The acrylonitrile concentration was 7 wt%, the solution linear velocity was 1 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1000 A / m. 2 .
[0046] Example 2
[0047] The electrolyte used contained 3.5 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 1.5 wt% borax, and 2.5 wt% modified quaternary phosphonium salt D. The pH of the electrolyte was adjusted to 8 by adding H3PO4 and NaOH. The acrylonitrile concentration was 7 wt%, the solution linear velocity was 1 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1000 A / m. 2 .
[0048] Example 3
[0049] The electrolyte used contained 3 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 0.5 wt% borax, and 0.5 wt% modified quaternary phosphonium salt E. The pH of the electrolyte was adjusted to 8 by adding H3PO4 and NaOH. The acrylonitrile concentration was 7 wt%, the solution linear velocity was 1.1 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1100 A / m. 2 .
[0050] Example 4
[0051] The electrolyte used contained 3 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 0.5 wt% borax, and 5 wt% modified quaternary phosphonium salt F. The pH of the electrolyte was adjusted to 8 by adding H3PO4 and NaOH. The acrylonitrile concentration was 7 wt%, the solution linear velocity was 1.1 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1100 A / m. 2 .
[0052] Example 5
[0053] The electrolyte used contained 3 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 0.5 wt% borax, and 5 wt% modified quaternary phosphonium salt F. The pH of the electrolyte was adjusted to 8 by adding H3PO4 and NaOH. The acrylonitrile concentration was 7 wt%, the solution linear velocity was 1.1 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1100 A / m. 2 .
[0054] Comparative Example 1
[0055] The electrolyte used contained 3.5 wt% potassium EDTA, 5 wt% sodium dihydrogen phosphate, 0.3 wt% borax, and 2 wt% ionic liquid A. The pH of the electrolyte was adjusted to 8 by adding H3PO4 and NaOH. The acrylonitrile concentration was 7 wt%, the solution linear velocity was 1.3 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1200 A / m. 2 .
[0056] Comparative Example 2
[0057] The electrolyte used contained 4 wt% sodium EDTA, 8 wt% sodium dihydrogen phosphate, 0.5 wt% borax, and 2 wt% modified quaternary ammonium salt B. The pH of the electrolyte was adjusted to 8 by adding H3PO4 and NaOH. The acrylonitrile concentration was 7 wt%, the solution linear velocity was 1.2 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1000 A / m. 2 .
[0058] Table 1
[0059]
[0060]
[0061] As can be seen from the results in Table 1, using the quaternary phosphonium salt employed in this invention yields higher selectivity for the target product. This is of great significance for the economic efficiency of the acrylonitrile dimerization process to adiponitrile.
[0062] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. An electrolyte for the electrocatalytic production of adiponitrile from acrylonitrile, characterized in that, It includes acrylonitrile, modified quaternary phosphonium salt and water, wherein the cation of the modified quaternary phosphonium salt is a structure shown in formula (f) with one end connected to a group shown in formula (a1) or formula (b1) and the other end connected to a group of formula (a1), (b1), (c), (d) or (e). ； Among them, R2~R 22 Each is an alkyl group, C1 to C5, and n = 1 to 6.
2. The electrolyte according to claim 1, characterized in that, The modified quaternary phosphonium salt content in the electrolyte is 0.01~3wt%.
3. The electrolyte according to claim 2, characterized in that, The modified quaternary phosphonium salt content in the electrolyte is 0.01~1wt%.
4. The electrolyte according to claim 1, characterized in that, The modified quaternary phosphonium salt has one or more of the following anions: hydroxide, hydrogen sulfate, sulfate, phosphate, hydrogen phosphate, dihydrogen phosphate, acetate, nitrate, and bis(trifluoromethanesulfonyl)imide anion.
5. The electrolyte according to claim 1, characterized in that, The electrolyte also contains 0.1-10 wt% EDTA or its sodium or potassium salt, and 0.01-5 wt% borax.
6. The electrolyte according to claim 1, characterized in that, The electrolyte also contains 1-20 wt% phosphate, wherein the phosphate is at least one of potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate.
7. The electrolyte according to claim 1, characterized in that, The content of acrylonitrile in the electrolyte is 4~7wt%.
8. The electrolyte according to claim 1, characterized in that, n is 4~6, R2~R 12 Each is an alkyl group that is independently C2 to C4.
9. A method for producing adiponitrile by electrolysis of acrylonitrile, characterized in that, The electrolysis reaction is carried out using the electrolyte described in any one of claims 1-8.
10. The method according to claim 9, characterized in that, The cathode of the electrolytic reaction is Cd or Pb or their alloys, and the anode is carbon steel or stainless steel or PbO2.
11. The method according to claim 9, characterized in that, The electrolysis reaction is carried out at a temperature of 30~70℃ and a current density of 200~5000A / m. 2 .