Electrolyte and electrolysis method for electrocatalytic production of adiponitrile from acrylonitrile
By modifying the quaternary phosphonium salt electrolyte and optimizing the electrolysis conditions, the problem of high cost of traditional electrolytes was solved, the selectivity and yield of adiponitrile were improved, and a highly efficient electrolysis process was achieved.
Patent Information
- Application Number
- CN202210101557.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-01-27
- Publication Date
- 2026-07-14
- Estimated Expiration
- 2042-01-27
AI Technical Summary
In the existing acrylonitrile electrolytic dimerization process, the quaternary ammonium salts used in the traditional electrolyte are expensive, which increases the cost of acrylonitrile electrolytic dimerization. There is a need to develop more efficient electrolytes to reduce costs and improve the selectivity and yield of adiponitrile.
An electrolyte with modified quaternary phosphonium salt as the main component is used, combined with appropriate electrolysis conditions, such as electrode materials and current density, to carry out an electrolysis reaction. The modified quaternary phosphonium salt is adsorbed on the electrode surface to reduce the formation of by-products and improve the selectivity and yield of adiponitrile.
The use of modified quaternary phosphonium salts improved the selectivity and yield of adiponitrile, reduced electrolysis costs, and enabled a highly efficient electrolysis process.
Smart Images
Figure CN116555786B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical synthesis, specifically to an electrolyte and electrolysis method for the electrochemical synthesis of 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 a quaternary ammonium salt. The large quantity of quaternary ammonium salt used and its high cost contribute to the increased cost of acrylonitrile electrolytic dimerization. Therefore, there is a need to develop more efficient synthesis methods. 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] This 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 comprises the structure shown in formula (a) and / or formula (b):
[0007]
[0008] Among them, R1~R 10 Each is an alkyl group, which is independently C1 to C6.
[0009] According to one embodiment of the present invention, the content of the modified quaternary phosphonium salt in the electrolyte is 0.05 to 5 wt%, preferably 0.1 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] Another aspect of the present invention provides a method for producing adiponitrile by electrolysis of acrylonitrile, wherein the electrolysis reaction is carried out using the above-mentioned electrolyte.
[0015] 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.
[0016] 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 .
[0017] The electrolyte for the electrolytic production of adiponitrile from acrylonitrile of the present invention contains a modified quaternary phosphonium salt, which can improve the selectivity of the target product adiponitrile and thus increase the yield. Detailed Implementation
[0018] The present invention will now be described in detail with reference to specific embodiments.
[0019] 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.
[0020] The electrolyte for the electrocatalytic production of adiponitrile from acrylonitrile according to the present invention comprises acrylonitrile, a modified quaternary phosphonium salt, and water, wherein the cation of the modified quaternary phosphonium salt comprises the structure shown in formula (a) and / or formula (b):
[0021]
[0022] Among them, R1~R 10 Each alkyl group is independently C1 to C6; preferably, it is a C2 to C4 alkyl group.
[0023] The inventors discovered that the presence of modified quaternary phosphonium salts in the electrolyte can improve the selectivity for adiponitrile. The mechanism is not yet fully understood, but a possible mechanism is that the quaternary phosphonium salts adsorb onto the electrode surface during electrolysis, reducing the probability of further hydrogenation of the activated acrylonitrile on the electrode surface to form the byproduct propionitrile, thus improving the selectivity for adiponitrile formation from acrylonitrile.
[0024] In an optional embodiment, the content of the modified quaternary phosphonium salt is 0.05–5 wt%. When the content of the modified quaternary phosphonium salt in the electrolyte is less than 0.05 wt%, the content is too low to significantly affect the conversion rate and selectivity of the acrylonitrile electrolytic dimerization reaction; when it is greater than 5 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, 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc. Preferably, the content of the modified quaternary phosphonium salt in the electrolyte is 0.1–1 wt%.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] The experimental conditions and results are calculated as follows:
[0036] Current = Electrode area × Current density;
[0037] Reaction time = (2 × mass of acrylonitrile × Faraday constant) / (molar mass of acrylonitrile × current);
[0038] Acrylonitrile conversion rate = (1 - mass of remaining acrylonitrile / mass of added acrylonitrile) × 100%;
[0039] Adiponitrile yield = (actual mass of adiponitrile received / theoretical mass of acrylonitrile completely converted to adiponitrile) × 100%.
[0040] The compounds of formulas (A) to (G) described in the examples and comparative examples are shown below:
[0041]
[0042] Example 1
[0043] 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 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 1.1 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1100 A / m. 2 .
[0044] Example 2
[0045] The electrolyte used contained 3 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 0.5 wt% borax, and 1.5 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 1200 A / m. 2 .
[0046] Example 3
[0047] The electrolyte used contained 3 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 0.5 wt% borax, and 1.7 wt% modified quaternary phosphonium salt E. The pH of the electrolyte was adjusted to 9 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 4
[0049] The electrolyte used contained 4 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 1.5 wt% borax, and 1.5 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 1.5 m / s, the cathode was Cd, the anode was PbO2, and the current density was 1000 A / m. 2 .
[0050] Example 5
[0051] The electrolyte used contained 3 wt% sodium EDTA, 7 wt% sodium dihydrogen phosphate, 0.5 wt% borax, and 1.7 wt% modified quaternary phosphonium salt G. 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 1500 A / m. 2 .
[0052] Comparative Example 1
[0053] 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 .
[0054] Comparative Example 2
[0055] 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 .
[0056] Table 1
[0057]
[0058] As can be seen from the results in Table 1, the adiponitrile yield obtained using the electrolytes of Examples 1-5 of this invention is higher. This demonstrates that using the electrolyte of this invention can improve the selectivity for the conversion of acrylonitrile to adiponitrile, thereby increasing the yield.
[0059] 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, The mixture comprises acrylonitrile, a modified quaternary phosphonium salt, and water, wherein the cation of the modified quaternary phosphonium salt comprises the structure shown in formula (a) and / or formula (b): 、 (a) (b); Among them, R1~R4 are simultaneously ethyl, propyl or butyl; R5~R 10 Each is an alkyl group that is independently formed from C1 to C6; 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.
2. The electrolyte according to claim 1, characterized in that, The modified quaternary phosphonium salt content in the electrolyte is 0.05~5wt%.
3. The electrolyte according to claim 1, characterized in that, The modified quaternary phosphonium salt content in the electrolyte is 0.1~1wt%.
4. 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.
5. 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.
6. The electrolyte according to claim 1, characterized in that, The content of acrylonitrile in the electrolyte is 4~7wt%.
7. 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 1-6.
8. The method according to claim 7, 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.
9. The method according to claim 7, characterized in that, The electrolysis reaction is carried out at a temperature of 30~70℃ and a current density of 200~5000A / m. 2 .