Electrolyte and electrolysis method for electrolysis of acrylonitrile to adiponitrile

Abstract

The application discloses electrolyte for electrolysis of acrylonitrile to adiponitrile, which comprises acrylonitrile, modified quaternary ammonium salt and water, wherein the modified quaternary ammonium salt comprises functional groups shown in formula (a), formula (b) and formula (c) simultaneously, the functional group shown in formula (a) is R1-R9-C-N+<, the functional group shown in formula (b) is R1-R9-C-N+<, and the functional group shown in formula (c) is R1-R9-C-N+<, or wherein R1-R9 in formula (a) are alkyl groups with carbon number of 0-6 respectively; R1-R9 in formula (b) are alkyl groups with carbon number of 1-6 respectively; formula (c) is an alkyl group with carbon number of n, and n=1-20; the structure of the modified quaternary ammonium salt contains at least 1-3 functional groups shown in formula (a), at least one functional group shown in formula (b) and at least one functional group shown in formula (c); and the functional group shown in formula (a) or (b) can be connected to the functional group shown in formula (c) only. The application also discloses a method for electrolysis of acrylonitrile to adiponitrile by using the electrolyte. The electrolyte for electrolysis of acrylonitrile to adiponitrile contains the modified quaternary ammonium salt, thereby improving the conversion rate and selectivity of electrolysis of acrylonitrile to adiponitrile. 10 12 ​​

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemical synthesis, in particular to an electrolyte and an electrolysis method for synthesizing adiponitrile from acrylonitrile. BACKGROUND

[0002] Adiponitrile (ADN) is an important organic chemical intermediate, mainly used in the production of polyhexamethylene adipamide (nylon 66), 1,6-hexamethylene diisocyanate (HDI) and nylon 610 materials. According to statistics, about 90% of the global adiponitrile is used for the production of nylon 66 every year. The process is that adiponitrile is hydrogenated to produce hexamethylene diamine, and hexamethylene diamine is polycondensed with adipic acid to produce a translucent or opaque milky white synthetic resin (nylon 66).

[0003] The technical barrier and investment threshold of adiponitrile are high, and the industry concentration is extremely high. Adiponitrile manufacturers all have supporting hexamethylene diamine production devices, and most of the capacity is used for the production of adiponitrile and nylon 66 of the company. Only a few companies have some surplus adiponitrile for sale. Yingweida almost monopolizes the global supply of adiponitrile, and the global adiponitrile market is in a state of tension.

[0004] The industrial production process of adiponitrile includes adipic acid catalytic ammoniation (ADA), acrylonitrile electrolysis dimerization (AN) and butadiene cyanation (BD). The process technology is mainly monopolized by a few enterprises such as Yingweida, BASF and Asahi Kasei. There is no adiponitrile production device in China at present, and the product is entirely dependent on import.

[0005] The acrylonitrile electrolysis dimerization method was initially industrialized by Monsanto Company. This process uses acrylonitrile as raw material and uses electrochemical method to dimerize to adiponitrile. The acrylonitrile electrolysis dimerization method for producing adiponitrile has the characteristics of short process and high product quality. However, the existing process has the disadvantages of low current density and low product selectivity, therefore, it is necessary to develop a more efficient synthesis method. SUMMARY

[0006] In order to overcome the above-mentioned defects, the present application provides an electrolyte for electrolyzing acrylonitrile to produce adiponitrile and a preparation method thereof.

[0007] The present application provides an electrolyte for electrolyzing acrylonitrile to produce adiponitrile, which comprises acrylonitrile, modified quaternary ammonium salt and water, and simultaneously comprises functional groups shown in formula (a), formula (b) and formula (c):

[0008] The functional group shown in formula (a) is

[0009] The functional group shown in formula (b) is

[0010] The functional group shown in formula (c) is

[0011] wherein R1-R9 in formula (a) are each alkyl having a carbon number of 0-6; R 10 -R 12 in formula (b) are each alkyl having a carbon number of 1-6; formula (c) is alkyl having a carbon number of n, n = 1-20;

[0012] The modified quaternary ammonium salt contains at least 1-3 functional groups represented by formula (a), at least one functional group represented by formula (b), and at least one functional group represented by formula (c); and the functional groups represented by formula (a) or (b) can only be connected to the functional group represented by formula (c).

[0013] According to an embodiment of the present application, R1-R9 in the functional group represented by formula (a) are each alkyl having a carbon number of 0-4; R 10 -R 12 in formula (b) are each alkyl having a carbon number of 1-4; and n in the functional group represented by formula (c) is 4-6.

[0014] According to another embodiment of the present application, the anion of the modified quaternary ammonium salt is one or more of hydroxide, hydrogen sulfate, dihydrogen phosphate, acetate, nitrate.

[0015] According to another embodiment of the present application, the content of the modified quaternary ammonium salt is 0.1-10 wt%, preferably 0.5-5 wt%.

[0016] According to another embodiment of the present application, the electrolyte further contains 0.1-10 wt% of EDTA or its sodium salt or potassium salt, and 0.01-5 wt% of borax.

[0017] According to another embodiment of the present application, the electrolyte further contains 1-20 wt% of phosphate, which is at least one of potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate.

[0018] According to another embodiment of the present application, the content of the acrylonitrile is 3-7 wt%.

[0019] The present application also provides a method for electrolyzing acrylonitrile to produce adiponitrile, which uses the electrolyte described above for electrolysis.

[0020] According to an embodiment of the present application, the cathode of the electrolysis reaction is Cd or Pb or an alloy thereof, and the anode is carbon steel or stainless steel.

[0021] According to another embodiment of the present application, the reaction temperature of the electrolysis reaction is 30-70℃, and the current density is 200-5000 A / m 2 .

[0022] The electrolyte for electrolyzing propylene nitrile into adiponitrile of the present application comprises modified quaternary ammonium salt, thereby improving the conversion rate of propylene nitrile and the selectivity of adiponitrile. DETAILED DESCRIPTION

[0023] The present application will be described in detail below with specific embodiments.

[0024] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The endpoints of the ranges and any values are understood to be approximate values. The approximate values allow for variation based on the precision of the equipment used to measure the values and the inherent variability of the equipment. The approximate values are understood to be within 10% of the value.

[0025] The electrolyte for electrolyzing propylene nitrile into adiponitrile of the present application comprises propylene nitrile, modified quaternary ammonium salt and water, and the modified quaternary ammonium salt comprises functional groups represented by formula (a), formula (b) and formula (c) at the same time.

[0026] The functional group represented by formula (a) is

[0027] The functional group represented by formula (b) is

[0028] The functional group represented by formula (c) is

[0029] wherein R1-R9 in formula (a) are alkyl groups with carbon number of 0-6; R 10 -R 12 in formula (b) are alkyl groups with carbon number of 1-6; n in formula (c) is 1-20.

[0030] The structure of the modified quaternary ammonium salt contains at least 1-3 functional groups represented by formula (a), at least 1 functional group represented by formula (b) and at least 1 functional group represented by formula (c); and the functional groups represented by formula (a) or (b) can only be connected to the functional group represented by formula (c). The structure of the alkyl group in formula (c) is not limited to the form in the schematic diagram, but is an alkyl group with different carbon combinations such as primary carbon, secondary carbon, quaternary carbon and tertiary carbon, and the alkyl group has 2-4 free ends in whole, and the free ends are connected to the free ends of (a) or (b).

[0031] The functional group represented by formula (a) in the structure of the modified quaternary ammonium salt has a 4-valent N + structure unit, which is an "inducer" for the electrolytic dimerization reaction of propylene nitrile, and can form a hydrophobic layer on the electrode surface and increase the solubility of propylene nitrile on the electrode surface. R1-R9 are alkyl groups with carbon number of 0-6, and when the carbon number of R1-R9 is greater than 6, the steric hindrance is large, which is not conducive to the formation of the hydrophobic layer on the electrode surface.

[0032] The functional group shown as formula (b) in the structure of the modified quaternary ammonium salt has a four-valent N + The structural unit is an "inducer" for the acrylonitrile electrolytic dimerization reaction, which can form a hydrophobic layer on the electrode surface and increase the solubility of acrylonitrile on the electrode surface. R 10 ~R 12 in formula (b) are alkyl groups with a carbon number of 1-6. When n is greater than 6, the steric hindrance is large, which is not conducive to the formation of a hydrophobic layer on the electrode surface.

[0033] The functional group shown as formula (c) in the structure of the modified quaternary ammonium salt is to connect multiple functional groups of (a) and (b) in one molecular structure. n in formula (c) is 1-20, and when n is greater than 20, the steric hindrance is large, which is not conducive to the formation of a hydrophobic layer on the electrode surface.

[0034] The modified quaternary ammonium salt contains at least 1-3 functional groups shown as formula (a), at least one functional group shown as formula (b), and at least one functional group shown as formula (c); and the functional groups shown as formula (a) or (b) can only be connected to the functional group shown as formula (c).

[0035] In optional embodiments, the anions (A - , B - ) of the modified quaternary ammonium salt are one or more of hydroxide, hydrogen sulfate, dihydrogen phosphate, acetate, and nitrate.

[0036] In optional embodiments, the content of the modified quaternary ammonium salt is 0.1-10 wt%. When the content of the modified quaternary ammonium salt in the electrolyte is less than 0.1 wt%, the content of the modified quaternary ammonium salt is low, which is not sufficient to significantly affect the conversion rate and selectivity of the acrylonitrile electrolytic dimerization reaction; and when the content is greater than 10 wt%, the content of the modified quaternary ammonium salt is too high, which causes high use cost. A person skilled in the art can select any value in the above range, for example but not limited to, 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%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc. Preferably, the content of the modified quaternary ammonium salt in the electrolyte is 0.5-5 wt%.

[0037] In optional embodiments, in order to improve the electrolysis efficiency, the electrolyte can also contain 0.1-10 wt% of EDTA or its sodium salt or potassium salt, and 0.01-5 wt% of borax.

[0038] In an optional embodiment, the electrolyte can further contain 1-20 wt% of phosphate, the phosphate being at least one of 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 the content of the phosphate can be selected according to the actual need to achieve the desired pH value, for example, the concentration of the phosphate can be, but is not limited to, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, etc.

[0039] In an optional embodiment, the content of acrylonitrile is 3-7 wt%. When the content of acrylonitrile in the electrolyte is less than 3 wt%, the production efficiency is relatively low; and the saturated solubility of acrylonitrile in the electrolyte is 7 wt%. Therefore, the content of acrylonitrile is preferably 3-7 wt%.

[0040] The present application also provides a method for electrolyzing acrylonitrile to produce adiponitrile, which comprises electrolyzing the electrolyte as described above.

[0041] In an optional embodiment, the cathode of the electrolysis reaction is Cd or Pb or an alloy thereof, and the anode is carbon steel or stainless steel.

[0042] In an optional embodiment, the reaction temperature of the electrolysis reaction is 30-70℃, and the current density is 200-5000 A / m 2 . When the current density is less than 200 A / m 2 , the production efficiency is too low, and more electrolytic cells need to be invested to achieve the same production capacity; when the current density is greater than 5000 A / m 2 , the current heat production is relatively large, and the side reactions increase.

[0043] After the electrolysis reaction is completed, the electrolyte after electrolysis is mixed with the crude adiponitrile to absorb the acrylonitrile that has not been reacted, and the mixture is subjected to oil-water separation to obtain an oil phase containing acrylonitrile, adiponitrile, and organic by-products, and a water phase, and the oil phase is subjected to distillation to obtain acrylonitrile, crude adiponitrile, and organic by-products.

[0044] The present application will be further described by specific examples. However, these examples are merely exemplary and do not constitute any limitation on the scope of protection of the present application. In the following examples and comparative examples, the reagents, materials, and instruments used are commercially available unless otherwise specified.

[0045] In the following examples, all reactions were carried out in an electrolytic cell with an electrode size of 100 mm*200 mm, the anode and cathode being parallel and opposite, the distance between the anode and cathode being 3 mm. The electrolyte was pumped and circulated, the linear velocity of the electrolyte in the electrolytic cell being 1 m / s. The current was passed according to the current density and electrode area, the reaction time was calculated according to the Faraday efficiency of 100%, and the electrolysis reaction was carried out according to the calculated current and reaction time. After the reaction was completed, the organic matter in the electrolyte was extracted using CH2Cl2 and weighed, the composition of the organic matter was analyzed by chromatography, and the conversion rate of acrylonitrile and the selectivity of adiponitrile were calculated. The pressures involved are all gauge pressures. The test results are shown in Table 1.

[0046] In which, the test conditions and the calculation method of the results are as follows:

[0047] Current = electrode area x current density;

[0048] Reaction time = (2 x acrylonitrile mass x Faraday constant) / (molar mass of acrylonitrile x current);

[0049] Conversion rate of acrylonitrile = (1 - mass of residual acrylonitrile / mass of acrylonitrile added) x 100%;

[0050] Yield of adiponitrile = (mass of actual adiponitrile received / theoretical mass of acrylonitrile completely converted to adiponitrile) x 100%;

[0051] The compounds of formula (A) to (F) described in the examples are as follows:

[0052]

[0053]

[0054] Example 1

[0055] The electrolyte used contains 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, 1wt% of borax, and 2wt% of the modified quaternary ammonium salt of formula (C). The pH of the electrolyte is adjusted to 8 by adding NaOH. The concentration of acrylonitrile is 7wt%, the cathode used is Pb, the anode is carbon steel, and the current density is 1000 A / m 2 .

[0056] Example 2

[0057] The electrolyte used contains 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, 1wt% of borax, and 2wt% of the modified quaternary ammonium salt of formula (D). The pH of the electrolyte is adjusted to 8 by adding NaOH. The concentration of acrylonitrile is 7wt%, the cathode used is Pb, the anode is carbon steel, and the current density is 1000 A / m 2 .

[0058] Example 3

[0059] The electrolyte used contained 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, 1wt% of borax, and 2wt% of the modified quaternary ammonium salt shown in formula (E). The pH of the electrolyte was adjusted to 8 by adding NaOH. The concentration of acrylonitrile was 7wt%, the cathode used was Pb, the anode was carbon steel, and the current density was 1000 A / m 2 .

[0060] Example 4

[0061] The electrolyte used contained 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, 1wt% of borax, and 2wt% of the modified quaternary ammonium salt shown in formula (F). The pH of the electrolyte was adjusted to 8 by adding NaOH. The concentration of acrylonitrile was 7wt%, the cathode used was Pb, the anode was carbon steel, and the current density was 1000 A / m 2 .

[0062] Example 5

[0063] The electrolyte used contained 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, 1wt% of borax, and 0.1wt% of the modified quaternary ammonium salt shown in formula (F). The pH of the electrolyte was adjusted to 8 by adding NaOH. The concentration of acrylonitrile was 7wt%, the cathode used was Pb, the anode was carbon steel, and the current density was 1000 A / m 2 .

[0064] Example 6

[0065] The electrolyte used contained 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, 1wt% of borax, and 10wt% of the modified quaternary ammonium salt shown in formula (F). The pH of the electrolyte was adjusted to 8 by adding NaOH. The concentration of acrylonitrile was 7wt%, the cathode used was Pb, the anode was carbon steel, and the current density was 1000 A / m 2 .

[0066] Comparative Example 1

[0067] The electrolyte used contained 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, 1wt% of borax, and 2wt% of tetrabutylammonium hydroxide. The pH of the electrolyte was adjusted to 8 by adding NaOH. The concentration of acrylonitrile was 7wt%, the cathode used was Pb, the anode was carbon steel, and the current density was 1000 A / m 2 .

[0068] Comparative Example 2

[0069] The electrolyte used contains 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, and 1wt% of borax, 2wt% of modified quaternary ammonium salt shown in formula (A). The pH of the electrolyte is adjusted to 8 by adding NaOH. The concentration of acrylonitrile is 7wt%, the cathode used is Pb, the anode is carbon steel, and the current density is 1000 A / m 2 .

[0070] Comparative Example 3

[0071] The electrolyte used contains 5wt% of EDTA sodium salt, 10wt% of sodium dihydrogen phosphate, and 1wt% of borax, 2wt% of modified quaternary ammonium salt shown in formula (B). The pH of the electrolyte is adjusted to 8 by adding NaOH. The concentration of acrylonitrile is 7wt%, the cathode used is Pb, the anode is carbon steel, and the current density is 1000 A / m 2 .

[0072] Table 1

[0073]

[0074]

[0075] From the results of Table 1, it can be seen that the examples used in the present application have significantly better effects.

[0076] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details, nor limit the present application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the present specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application. The present application is limited only by the claims and their full scope and equivalents.

Claims

1. An electrolyte for the electrolytic production of adiponitrile from propylene nitrile, characterized in that The electrolyte comprises acrylonitrile, modified quaternary ammonium salt and water, wherein the modified quaternary ammonium salt comprises functional groups represented by formula (a), formula (b) and formula (c) simultaneously. The functional group represented by formula (a) is and / or ; The functional group represented by the formula (b) is ; The functional group represented by the formula (c) is ; wherein R1to R9in formula (a) are each an alkyl group having a carbon number of 0 to 6; R 10 ~R 12 in formula (b) are each an alkyl group having a carbon number of 1 to 6; and formula (c) is an alkyl group having a carbon number of n, n = 1 to 20; The structure of the modified quaternary ammonium salt comprises one functional group represented by formula (a), one functional group represented by formula (b) and one functional group represented by formula (c); and the functional group represented by formula (a) or (b) can only be connected with the functional group represented by formula (c); The anion of the modified quaternary ammonium salt is one or more of hydroxide, hydrogen sulfate, dihydrogen phosphate, acetate and nitrate; and the content of the modified quaternary ammonium salt is 0.1-10wt%.

2. The electrolyte according to claim 1, characterized in that, R1~R9 in the functional group shown in formula (a) are respectively carbon number 0~4; R 10 ~R 12 in formula (b) are respectively carbon number 1~4; n in the functional group shown in formula (c) is 4~6.

3. The electrolyte of claim 1, wherein The content of the modified quaternary ammonium salt is 0.5-5wt%.

4. The electrolyte of claim 1, wherein The electrolyte further comprises 0.1-10wt% of EDTA or its sodium salt or potassium salt, and 0.01-5wt% of borax.

5. The electrolyte of claim 1, wherein The electrolyte further comprises 1-20wt% of 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 of claim 1, wherein The content of the acrylonitrile is 3-7wt%.

7. A process for the electrolytic production of adiponitrile from acrylonitrile, characterized in that The electrolyte of any one of claims 1-6 is used for electrolysis reaction.

8. The method of claim 7, wherein, The cathode of the electrolysis reaction is Cd or Pb or alloy thereof, and the anode is carbon steel or stainless steel.

9. The method of claim 7, wherein, The reaction temperature of the electrolysis reaction is 30-70℃, and the current density is 200-5000 A / m 2 .

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