A method for purifying 1,3,6-hexanetricarbonitrile
By employing acidification, extraction, weak alkali washing, and flash evaporation, the problems of time-consuming and energy-intensive purification of 1,3,6-hexanetrionitrile were solved, resulting in high-purity, low-color, and low-moisture electronic-grade products suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI CHAOWEI TECHNOLOGY CO LTD
- Filing Date
- 2026-04-08
- Publication Date
- 2026-05-29
AI Technical Summary
Existing methods for purifying 1,3,6-hexanetrionitriles are time-consuming, energy-intensive, costly, and generate large amounts of waste, making them unsuitable for industrial production.
The process involves acidification, extraction, weak alkali washing, and flash evaporation. This includes adding a dilute acid solution dropwise to the 1,3,6-hexanetrionitrile synthesis reaction solution, separating the phases, extracting with an organic solvent and washing with water, then washing with a dilute alkali solution, removing the solvent through a scraped film evaporator, and finally performing vacuum flash evaporation.
It has achieved high purity (≥99.5%), low color (≤20 Hazen), low moisture (≤100 ppm), and low acid content (≤50 ppm) of 1,3,6-hexanetrionitrile products, which simplifies operation, reduces energy consumption, reduces by-products, and is suitable for industrial production.
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Figure CN122102950A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of compound purification technology, specifically to the purification of 1,3,6-hexanetrionitrile. Background Technology
[0002] 1,3,6-Hexanetrionitrile (HTCN) is a widely used additive in lithium-ion batteries. Its structural formula is as follows: .
[0003] 1,3,6-Hexanetrionitrile can enhance the electrolyte's resistance to positive electrode oxidation and improve its cycle life under high voltage. However, electronic-grade HTCN products typically have very stringent requirements for purity, color, moisture content, and metal ion content. Generally, electronic-grade HTCN requires a purity >99.5%, a color <50 halons, a moisture content <100 ppm, and a metal ion content <2 ppm.
[0004] Chinese patent application (CN119661401A) discloses a purification method for 1,3,6-hexanetrionitrile. The steps include: first, extracting the crude product using an extractant followed by vacuum thin-film distillation; then, diluting the purified HTCN with a diluent and decolorizing it with activated carbon; finally, subjecting the decolorized HTCN solution to vacuum distillation again to obtain the product. While this method can yield HTCN with relatively high purity, it requires two high-vacuum distillations, which is extremely time-consuming; the need for dilution followed by decolorization not only increases purification costs but also generates more waste throughout the process. Furthermore, the dilution and concentration process significantly increases energy consumption. Therefore, this purification method is costly, energy-intensive, and generates a large amount of waste, making it unsuitable for industrial production.
[0005] Therefore, there is an urgent need to develop a simple and efficient method for purifying HTCN that can ensure the quality of electronic-grade products, making it more suitable for industrial production. Summary of the Invention
[0006] The technical problem to be solved by the present invention is to provide a purification method for 1,3,6-hexanetrionitrile that is simple to operate, has low energy consumption, low by-product yield, high product quality, and is suitable for industrial production.
[0007] To solve the above problems, the technical solution adopted by the present invention is: a method for purifying 1,3,6-hexanetrionitrile, comprising the following steps: 1. Add dilute acid solution dropwise to the synthesis reaction solution of 1,3,6-hexanetrionitrile and stir until the synthesis reaction solution becomes acidic, thus obtaining an acidic reaction solution; 2. Add an organic solvent to the acidic reaction solution, extract, separate the phases and collect the organic phase; wash the organic phase with water at least once and retain the organic phase; 3. Wash the organic phase with dilute alkali solution, separate the phases and take the organic phase. Wash the organic phase with water at least once and retain the organic phase. 4. Remove organic solvents, concentrate for less than or equal to 1 hour, and then flash distill the concentrate under reduced pressure to obtain pure HTCN.
[0008] Furthermore, in the aforementioned method for purifying 1,3,6-hexanetrionitrile, in step one, the pH value of the acidic reaction solution is controlled at 2-3.
[0009] Furthermore, in the aforementioned method for purifying 1,3,6-hexanetrionitrile, in step one, the dilute acid solution is selected from either dilute sulfuric acid or dilute hydrochloric acid. These two dilute acids are commonly used and have low cost.
[0010] Furthermore, in the aforementioned method for purifying 1,3,6-hexanetrionitrile, the concentration of dilute sulfuric acid or dilute hydrochloric acid is 5 wt%~10 wt.%.
[0011] Furthermore, in the aforementioned method for purifying 1,3,6-hexanetrionitrile, in step two, the organic solvent is selected from one or more of methyl acetate, ethyl acetate, dichloroethane, and dichloromethane; the mass ratio of the added organic solvent to the acidic reaction solution is 1~1.1:1.
[0012] Furthermore, in the aforementioned method for purifying 1,3,6-hexanetrionitrile, in step three, the dilute alkaline solution is selected from one of sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution, and potassium bicarbonate solution, and the concentration of the dilute alkaline solution is 3 w.t.%~5 wt%; the mass ratio of the amount of dilute alkaline solution added to the organic phase is 1~1.5:1.
[0013] Furthermore, in the aforementioned method for purifying 1,3,6-hexanetrionitrile, in step four, a scraped-film evaporator is used to remove the organic solvent, the heating temperature is 60~80 ℃, and the pressure is absolute pressure 3000~5000 Pa.
[0014] Furthermore, in the aforementioned method for purifying 1,3,6-hexanetrionitrile, in step four, the heating temperature for the vacuum flash evaporation is 200~230 ℃, the pressure is absolute pressure 50~80 Pa, and the fraction with a boiling point of 170~182 ℃ is collected.
[0015] The advantages of this invention are as follows: The purification method for 1,3,6-hexanetrionitrile (HTCN) described in this invention, through acidification, extraction, weak alkali washing, and flash evaporation, can increase the purity of pure HTCN to over 99.5%, with a color as low as 20 Hazen, water content far below 100 ppm, and acid content far below 50 ppm, thereby obtaining an electronic-grade product. In the first step, acidification converts the amine-type colored impurities in the HTCN synthesis reaction solution, which are easily soluble in organic solvents, into water-soluble ammonium salts. These are then effectively removed by water washing, thus effectively reducing the product's color. Next, a dilute alkali solution is added to wash the organic phase, thereby removing trace amounts of residual acid and effectively reducing the acid value. In the third step, rapid distillation is used to remove the organic solvent, avoiding the increase in color caused by prolonged heating of the HTCN product. This invention avoids the use of decolorizing agents and diluents throughout the entire process. High-quality pure HTCN can be obtained through a single vacuum flash evaporation. This technology has the advantages of low energy consumption, simple operation, low by-product yield, and high product quality, making it suitable for industrial production. Attached Figure Description
[0016] Figure 1 This is the GC chromatogram of the HTCN synthesis reaction solution before purification.
[0017] Figure 2 This is the GC chromatogram of the acidified reaction solution.
[0018] Figure 3 This is the GC chromatogram of the purified HTCN. Detailed Implementation
[0019] The technical solution of the present invention will be further explained and described below with reference to specific embodiments. The following embodiments are merely illustrative examples of this application and are not intended to limit the content of this application. Any improvements or modifications made to the content of the present invention without inventive contribution by those skilled in the art based on the guidance of this specification and their needs shall fall within the protection scope of the present invention.
[0020] The synthetic route of 1,3,6-hexanetrionitrile (HTCN) mainly includes the following steps: First, adiponitrile is used as a reactant, and after intramolecular isomerization under superbase catalysis, it is purified to prepare high-purity 1-amino-2-cyano-1-cyclopentene crystals; then, 1-amino-2-cyano-1-cyclopentene is reacted with acrylonitrile in the presence of a moderately strong base, a polymerization inhibitor, and a phase transfer catalyst to obtain a synthetic reaction solution containing 1,3,6-hexanetrionitrile; after purification, pure HTCN is obtained. Specific preparation methods can be found in Chinese patent applications CN104387291A, CN117534591A, and CN117779065A. The HTCN synthetic reaction solution to be purified in the following examples is obtained through the above-mentioned pathways. The HTCN synthetic reaction solution has a metal ion content >100 ppm, a color >500 Hazen, and a moisture content >10000 ppm. Example 1.
[0021] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. The GC chromatogram of the HTCN synthesis reaction solution is shown below. Figure 1 As shown, 10 wt% dilute sulfuric acid was slowly added dropwise to the system with stirring. During the addition, the acidity or alkalinity of the system was monitored in real time using an external pH meter. When pH=2, the addition of dilute sulfuric acid was stopped, resulting in an acidic reaction solution. The GC chromatogram of the acidic reaction solution is shown below. Figure 2 As shown. (The sentence is incomplete and requires more context.) Figure 1 and Figure 2 The comparison reveals that after acidification, Figure 1 The impurities at the 2.591 elution time have disappeared.
[0022] S2: Pump 3 kg of ethyl acetate into the extraction washing vessel at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0023] S3: Pump 3 kg of 3 wt% sodium carbonate solution into the reactor at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the reactor, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0024] S4: Transfer the organic phase obtained in the previous step to a scraped-film evaporator, control the heating temperature at 60-80 ℃ and the absolute pressure at 3000-5000 Pa, and rapidly concentrate to obtain crude HTCN. The concentration time should be controlled to be less than or equal to 1 hour to avoid the product's color increasing due to prolonged heating. The scraped-film evaporator has the advantage of short concentration time. Subsequently, transfer the crude HTCN to a flash evaporator for flash evaporation, control the heating temperature at 200-230 ℃ and the pressure at 50-80 Pa, and collect the fraction with a boiling point of 170-182 ℃. The obtained pure HTCN was tested for five indicators: purity, color, moisture, acid value, and metal ion content. The results are shown in Table 1. The GC chromatogram of the pure HTCN is shown in [Table 1]. Figure 3 As shown. Example 2.
[0025] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 5 w.t.% dilute sulfuric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition. Stop adding dilute sulfuric acid when pH = 3 to obtain an acidic reaction solution.
[0026] S2: Pump 3.3 kg of methyl acetate into the extraction washing vessel in one go, stir for 2 hours, and let it stand to separate the phases. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0027] S3: Pump 4.5 kg of 5 wt% sodium bicarbonate solution into the reactor at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the reactor, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0028] S4: Transfer the organic phase obtained in the previous step to a scraped-film evaporator, control the heating temperature at 60-80 ℃ and the absolute pressure at 3000-5000 Pa, and rapidly concentrate to obtain crude HTCN. The concentration time should be controlled to be less than or equal to 1 hour. Subsequently, transfer the crude HTCN to a flash evaporator, control the heating temperature at 200-230 ℃ and the pressure at 50-80 Pa, and collect the fraction with a boiling point of 170-182 ℃. The obtained pure HTCN was tested for five indicators: purity, color, moisture content, acid value, and metal ion content. The results are shown in Table 1. Example 3.
[0029] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 10 w.t.% dilute sulfuric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition. Stop adding dilute sulfuric acid when pH = 2 to obtain an acidic reaction solution.
[0030] S2: Pump 3 kg of dichloroethane into the extraction washing vessel at once, stir for 2 hours, and let it stand to separate the phases. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0031] S3: Pump 3 kg of 3 wt% potassium carbonate solution into the reactor at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the reactor, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0032] S4: Transfer the organic phase obtained in the previous step to a scraped-film evaporator, control the heating temperature at 60-80 ℃ and the absolute pressure at 3000-5000 Pa, and rapidly concentrate to obtain crude HTCN. The concentration time should be controlled to be less than or equal to 1 hour. Subsequently, transfer the crude HTCN to a flash evaporator, control the heating temperature at 200-230 ℃ and the pressure at 50-80 Pa, and collect the fraction with a boiling point of 170-182 ℃. The obtained pure HTCN was tested for five indicators: purity, color, moisture content, acid value, and metal ion content. The results are shown in Table 1. Example 4.
[0033] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 10 w.t.% dilute sulfuric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition. Stop adding dilute sulfuric acid when pH = 2 to obtain an acidic reaction solution.
[0034] S2: Pump 3.3 kg of dichloromethane into the extraction washing vessel in one go, stir for 2 hours, and let it stand to separate the phases. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0035] S3: Pump 4.5 kg of 5 wt% potassium bicarbonate solution into the reactor at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the reactor, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0036] S4: Transfer the organic phase obtained in the previous step to a scraped-film evaporator, control the heating temperature at 60-80 ℃ and the absolute pressure at 3000-5000 Pa, and rapidly concentrate to obtain crude HTCN. The concentration time should be controlled to be less than or equal to 1 hour. Subsequently, transfer the crude HTCN to a flash evaporator, control the heating temperature at 200-230 ℃ and the pressure at 50-80 Pa, and collect the fraction with a boiling point of 170-182 ℃. The obtained pure HTCN was tested for five indicators: purity, color, moisture content, acid value, and metal ion content. The results are shown in Table 1. Example 5.
[0037] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 5 w.t.% dilute hydrochloric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition process. Stop adding dilute hydrochloric acid when pH = 3 to obtain an acidic reaction solution.
[0038] S2: Pump 3 kg of ethyl acetate into the extraction washing vessel at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0039] S3: Pump 3 kg of 3 wt% sodium carbonate solution into the reactor at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the reactor, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0040] S4: Transfer the organic phase obtained in the previous step to a scraped-film evaporator, control the heating temperature at 60-80 ℃ and the absolute pressure at 3000-5000 Pa, and rapidly concentrate to obtain crude HTCN. The concentration time should be controlled to be less than or equal to 1 hour. Subsequently, transfer the crude HTCN to a flash evaporator, control the heating temperature at 200-230 ℃ and the pressure at 50-80 Pa, and collect the fraction with a boiling point of 170-182 ℃. The obtained pure HTCN was tested for five indicators: purity, color, moisture content, acid value, and metal ion content. The results are shown in Table 1. Comparative Example 1.
[0041] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 10 w.t.% dilute sulfuric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition. Stop adding dilute sulfuric acid when pH = 2 to obtain an acidic reaction solution.
[0042] S2: Pump 3 kg of ethyl acetate into the extraction washing vessel at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0043] S3: Transfer the organic phase obtained in the previous step to a scraped-film evaporator, control the heating temperature at 60-80 ℃ and the absolute pressure at 3000-5000 Pa, and rapidly concentrate to obtain crude HTCN. The concentration time should be controlled to be less than or equal to 1 hour. Subsequently, transfer the crude HTCN to a flash evaporator, control the heating temperature at 200-230 ℃ and the pressure at 50-80 Pa, and collect the fraction with a boiling point of 170-182 ℃. The obtained pure HTCN was tested for five indicators: purity, color, moisture content, acid value, and metal ion content. The results are shown in Table 1.
[0044] In this embodiment, the organic phase obtained by organic solvent extraction was directly removed by solvent without alkaline washing. The results, shown in Table 1, indicate that the acid value greatly exceeded the standard. Comparative Example 2.
[0045] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 10 w.t.% dilute sulfuric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition process. Stop adding dilute sulfuric acid when pH = 7.
[0046] S2. Pump 3 kg of ethyl acetate into the extraction washing vessel at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0047] S3. Pump 3 kg of 3 wt% sodium carbonate solution into the reactor at once, stir for 2 hours, and allow to stand for phase separation. After discharging the aqueous phase, pump 3 kg of fresh deionized water into the reactor, stir for 2 hours, separate the phases, discharge the aqueous phase, and retain the organic phase.
[0048] S4. The organic phase obtained in the previous step was transferred to a scraped-film evaporator, and the heating temperature was controlled at 60-80 °C and the absolute pressure at 3000-5000 Pa. The HTCN crude product was then rapidly concentrated. Subsequently, the HTCN crude product was transferred to a flash evaporator, and the heating temperature was controlled at 200-230 °C and the pressure at 50-80 Pa. The fractions with boiling points of 170-182 °C were collected, and the results are shown in Table 1.
[0049] In this embodiment, the pH of the HTCN synthesis reaction solution was adjusted to 7, i.e., no acidification treatment was performed. Table 1 shows that the flash evaporation process failed due to paraffinic impurities clogging the condenser. These paraffinic impurities are... Figure 1 Impurities with a peak elution time at position 2.591.
[0050] Comparative Example 3.
[0051] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 10 w.t.% dilute sulfuric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition. Stop adding dilute sulfuric acid when pH = 2 to obtain an acidic reaction solution.
[0052] S2: Pump 3 kg of ethyl acetate into the extraction washing vessel at one time, stir for 2 hours, let stand for phase separation, release the aqueous phase, retain the organic phase, and do not wash with water again.
[0053] S3: Pump 3 kg of 3 wt% sodium carbonate solution into the reactor at one time, stir for 2 hours, let stand for phase separation, release the aqueous phase, retain the organic phase, and do not wash the organic phase with deionized water again.
[0054] S4. Transfer the organic phase obtained in the previous step to a scraped-film evaporator, control the heating temperature at 60-80 ℃ and the absolute pressure at 3000-5000 Pa, and rapidly concentrate to obtain crude HTCN. The concentration time should be controlled to be less than or equal to 1 hour. Subsequently, transfer the crude HTCN to a flash evaporator, control the heating temperature at 200-230 ℃ and the pressure at 50-80 Pa, and collect the fraction with a boiling point of 170-182 ℃. The obtained pure HTCN was tested for five indicators: purity, color, moisture content, acid value, and metal ion content. The results are shown in Table 1.
[0055] In this embodiment, no water washing was performed after the second extraction step and the third alkaline washing step, and the results in Table 1 show that the color of the product exceeded the standard. Comparative Example 4.
[0056] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 10 w.t.% dilute sulfuric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition. Stop adding dilute sulfuric acid when pH = 0 to obtain an acidic reaction solution.
[0057] S2: Pump 3 kg of ethyl acetate into the extraction washing vessel at once, stir for 2 hours, let stand for phase separation, release the aqueous phase, then pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phase, release the aqueous phase, and retain the organic phase.
[0058] S3: Pump 3 kg of 3 wt% sodium carbonate solution into the reactor at one time, stir for 2 hours, let stand for phase separation, release the aqueous phase, then pump 3 kg of fresh deionized water into the reactor, stir for 2 hours, separate the phase, release the aqueous phase, and retain the organic phase.
[0059] S4: Transfer the organic phase obtained in the previous step to a scraped-film evaporator, control the heating temperature at 60-80 ℃ and the absolute pressure at 3000-5000 Pa, and rapidly concentrate to obtain crude HTCN. The concentration time should be controlled to be less than or equal to 1 hour. Subsequently, transfer the crude HTCN to a flash evaporator, control the heating temperature at 200-230 ℃ and the pressure at 50-80 Pa, and collect the fraction with a boiling point of 170-182 ℃. The obtained pure HTCN was tested for five indicators: purity, color, moisture content, acid value, and metal ion content. The results are shown in Table 1.
[0060] In this embodiment, the pH value of the HTCN synthesis reaction solution was adjusted to 0 in the first step, that is, the degree of acidification was increased. As shown in Table 1, the product yield was lower than that in Example 1. Comparative Example 5.
[0061] S1: Pour 3 kg of crude 1,3,6-hexanetrionitrile into the extraction vessel, and slowly pour in 1.5 kg of anhydrous ethanol while stirring. After the anhydrous ethanol has been added, continue stirring for 30–60 min. Let it stand for 30–60 min, and then extract the ethanol layer. Repeat the above steps three times and collect the lower layer of 1,3,6-hexanetrionitrile.
[0062] S2: The extracted 1,3,6-hexanetrionitrile is slowly fed into the thin-film distillation column of a wiped-film molecular distillation apparatus. The main heating temperature is set to 190℃, the distillation column temperature to 200℃, the wiper rotation speed to 280 r / min, and the vacuum degree to 20 Pa. The light components are discarded, and the remaining 1,3,6-hexanetrionitrile is collected. The remaining 1,3,6-hexanetrionitrile is slowly fed into the thin-film distillation column. The main heating temperature is set to 280℃, the distillation column temperature to 210℃, the vacuum degree to 20 Pa, and the wiper rotation speed to 280 r / min. The heavy components are discarded, and the remaining 1,3,6-hexanetrionitrile is collected.
[0063] S3: Add 5 times the volume of ethyl acetate to the distilled 1,3,6-hexanetrionitrile, stir well, add 1% activated carbon, stir for 30-60 min, and then filter through a plate and frame filter and a 0.22μm precision filter system.
[0064] S4: The filtered 1,3,6-hexanetrionitrile was forced into the distillation column. The column temperature was set to 70℃, and the vacuum was controlled between 0.08 and 0.1 MPa. When no ethyl acetate liquid flowed out, the temperature was adjusted to 50℃, the nitrogen valve at the bottom of the column was opened, the nitrogen pressure was set to 0.2 MPa, and the vacuum valve at the top of the column was opened. Distillation was continued for 2 hours using a bottom-feed and top-evacuation method to obtain the target product. The obtained 1,3,6-hexanetrionitrile was then tested for five indicators: purity, color, moisture content, acid value, and metal ion content. The results are shown in Table 1.
[0065] This embodiment uses the purification method mentioned in the background art. The second step requires two distillations, the third step requires the addition of ethyl acetate for dilution, and then the fourth step is concentration. The whole process is time-consuming and energy-intensive, but the yield is low and the acid value of the product is also high. Comparative Example 6.
[0066] S1: Transfer 3 kg of HTCN synthesis reaction solution to an extraction and washing vessel. Slowly add 10 w.t.% dilute sulfuric acid to the system while stirring. Monitor the acidity and alkalinity of the system in real time with an external pH meter during the addition. Stop adding dilute sulfuric acid when pH = 2 to obtain an acidic reaction solution.
[0067] S2: Pump 3 kg of ethyl acetate into the extraction washing vessel at once, stir for 2 hours, let stand for phase separation, release the aqueous phase, then pump 3 kg of fresh deionized water into the vessel, stir for 2 hours, separate the phase, release the aqueous phase, and retain the organic phase.
[0068] S3: Pump 3 kg of 3 wt% sodium carbonate solution into the reactor at one time, stir for 2 hours, let stand for phase separation, release the aqueous phase, then pump 3 kg of fresh deionized water into the reactor, stir for 2 hours, separate the phase, release the aqueous phase, and retain the organic phase.
[0069] S4: The organic phase obtained in the previous step was transferred to a batch distillation apparatus, and the heating temperature was controlled at 60-80 ℃ and the absolute pressure at 3000-5000 Pa. After continuous concentration for 8 hours, crude HTCN was obtained. Subsequently, the crude HTCN was transferred to a flash distillation apparatus, and the heating temperature was controlled at 200-230 ℃ and the pressure at 50-80 Pa. The fraction with a boiling point of 170-182 ℃ was collected. The purity, color, moisture content, acid value, and metal ion content of the obtained pure HTCN were tested, and the results are shown in Table 1.
[0070] In this embodiment, the distillation time for removing the solvent in the fourth step is relatively long, requiring 8 hours. The results are shown in Table 1, with a significant increase in color.
[0071] The test results of each index of Examples 1-5 and Comparative Examples 1-6 are shown in Table 1.
[0072] Table 1: .
[0073] Based on the experimental results of Examples 1-5 and Comparative Examples 1-6 above, it is found that the purification method of 1,3,6-hexanetrionitrile (HTCN) described in this invention, through acidification, extraction, weak alkali washing, and flash evaporation, can increase the purity of pure HTCN to over 99.5%, with a color as low as 20 Hazen, water content far below 100 ppm, acid content far below 50 ppm, and extremely low metal ion content, thereby obtaining an electronic-grade product. In the first step of this application, the acidification treatment converts the amine-type colored impurities in the HTCN synthesis reaction solution, which are easily soluble in organic solvents, into ammonium salts that are easily soluble in water. These impurities can then be effectively removed by water washing, thus effectively reducing the product's color. Next, a dilute alkali solution is added to wash the organic phase, thereby removing trace amounts of residual acid and effectively reducing the acid value. In the third step, rapid distillation is used to remove the organic solvent, avoiding the increase in color caused by prolonged heating of the HTCN product. This invention avoids the use of decolorizing agents and diluents throughout the entire process. High-quality pure HTCN can be obtained through a single vacuum flash evaporation. This technology has the advantages of low energy consumption, simple operation, low by-product yield, and high product quality, making it suitable for industrial production.
Claims
1. A method for purifying 1,3,6-hexanetrionitrile, characterized in that: Includes the following steps:
1. Add dilute acid solution dropwise to the synthesis reaction solution of 1,3,6-hexanetrionitrile and stir until the synthesis reaction solution becomes acidic to obtain an acidic reaction solution; 2. Add an organic solvent to the acidic reaction solution, extract, separate the phases and collect the organic phase; wash the organic phase with water at least once and retain the organic phase; 3. Wash the organic phase with dilute alkali solution, separate the phases and take the organic phase. Wash the organic phase with water at least once and retain the organic phase.
4. Remove organic solvents, concentrate for less than or equal to 1 hour, and then flash distill the concentrate under reduced pressure to obtain pure HTCN.
2. The method for purifying 1,3,6-hexanetrionitrile according to claim 1, characterized in that: In step one, the pH value of the acidic reaction solution is controlled at 2-3.
3. The method for purifying 1,3,6-hexanetrionitrile according to claim 1, characterized in that: In step one, the dilute acid solution is selected from either dilute sulfuric acid or dilute hydrochloric acid.
4. The purification method for 1,3,6-hexanetrionitrile according to claim 3, characterized in that: The concentration of dilute sulfuric acid or dilute hydrochloric acid is 5 wt%~10 wt%.
5. The method for purifying 1,3,6-hexanetrionitrile according to claim 1, characterized in that: In step two, the organic solvent is selected from one or more of methyl acetate, ethyl acetate, dichloroethane, and dichloromethane; the mass ratio of the added organic solvent to the acidic reaction solution is 1~1.1:
1.
6. The method for purifying 1,3,6-hexanetrionitrile according to claim 1, characterized in that: In step three, the dilute alkaline solution is selected from one of sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution, and potassium bicarbonate solution, and the concentration of the dilute alkaline solution is 3 w.t.%~5 wt%; the mass ratio of the added dilute alkaline solution to the organic phase is 1~1.5:
1.
7. The method for purifying 1,3,6-hexanetrionitrile according to claim 1, characterized in that: In step four, a scraped film evaporator is used to remove the organic solvent, with a heating temperature of 60~80 ℃ and a pressure of 3000~5000 Pa absolute.
8. The method for purifying 1,3,6-hexanetrionitrile according to claim 1, characterized in that: In step four, the heating temperature for the reduced pressure flash evaporation is 200~230 ℃, the pressure is absolute pressure of 50~80 Pa, and the fraction with a boiling point of 170~182 ℃ is collected.