Adiponitrile refining and desalting process
By adding triphenylphosphine oxide to adiponitrile in batches to induce crystallization and using an organic phase transfer agent to separate the metal complex, the problem of high energy consumption in removing inorganic salt impurities in adiponitrile production was solved, achieving efficient and low-cost desalination.
Patent Information
- Application Number
- CN202511851254.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-03-17
AI Technical Summary
Existing methods for removing inorganic salt impurities in adiponitrile production processes are energy-intensive and inefficient, leading to decreased product quality and equipment corrosion, which in turn affects downstream applications.
Triphenylphosphine oxide was used as a metal complexing agent. Adiponitrile was added in batches under an inert atmosphere to induce crystallization. The complex was partitioned by an organic phase transfer agent, and impurities were separated by phase separation.
It achieves efficient removal of metal ions such as zinc, sodium, and copper from adiponitrile, reduces process costs, avoids high energy consumption and pollution, and is suitable for industrial applications.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of chemical synthesis, in particular to a refining and desalting process of adiponitrile. BACKGROUND
[0002] Adiponitrile (ADN) is the most core raw material of nylon 66 (PA66). In the production process of adiponitrile, inorganic salt impurities such as sodium salt (such as NaCl, Na2SO4, etc.), zinc salt (such as ZnCl2, etc.), copper salt, etc. exist, which will have significant negative impact on product quality, process efficiency and downstream application. For example, strong electrolytes such as ZnCl2 may form azeotrope, causing abnormal boiling point during subsequent rectification separation, increasing separation difficulty; moreover, the ionization of salt causes the conductivity of adiponitrile to rise from <1 μS / cm to >50 μS / cm, affecting its electronic grade application (such as lithium battery solvent); if inorganic salt ions enter the product, the impact on the downstream is more serious. Inorganic salts (such as Zn 2+ ) will poison the catalyst (such as Raney nickel) for the preparation of hexamethylenediamine by hydrogenation, causing the reaction activity to decrease by more than 30%, and the byproduct to increase, such as Zn 2+ impurities will terminate the polycondensation reaction, causing the molecular weight distribution (PDI) of nylon 66 to rise from 2.0 to 3.5, and the tensile strength to decrease by 20%; in addition, salt impurities will also block the spinneret during melt spinning, causing the spinning breakage rate to rise from 1% to 5%. Therefore, salt impurities need to be removed in the production process of adiponitrile.
[0003] Traditional adiponitrile desalting processes often rely on physical processes, such as multi-effect evaporation, crystallization-centrifugal separation and electrodialysis method, etc. to remove salt impurities in adiponitrile, but the multi-effect evaporation process has high energy consumption, with steam consumption >3.5 t / t product; crystallization-centrifugal separation will produce salt-containing wastewater (COD >5000 mg / L), with high wastewater treatment cost; and the electrodialysis method has high energy consumption (>200 kWh / t) and short membrane life (<6 months). Therefore, the methods for removing inorganic salt impurities in adiponitrile through physical changes generally have problems such as high energy consumption, adiponitrile entrainment loss and serious pollution. SUMMARY
[0004] In view of the deficiencies in the prior art, the present application discloses a refining and desalting process of adiponitrile to solve the technical problems of high energy consumption and low efficiency in the refining process of adiponitrile in the prior art.
[0005] In order to achieve the above technical purpose, the present application provides a refining and desalting process of adiponitrile, which comprises the following steps: (1) under an inert atmosphere, triphenylphosphine oxide is added to the adiponitrile to be refined in batches to obtain a first material containing a metal complex; (2) adding a phase transfer agent to the first material, so that the metal complex is distributed into the phase transfer agent, and then phase separation is performed to obtain a high-purity adiponitrile product; wherein the phase transfer agent is at least one selected from n-hexane, cyclohexane, petroleum ether, toluene, and dimethyl sulfoxide.
[0006] The research team of the present application found through preliminary experimental exploration that, in the case of a high content of Zn salt in the material to be refined, complexation with triphenylphosphine oxide (TPPO) as a metal ion chelating agent can efficiently obtain a solid-phase precipitate of a metal complex, thereby causing the Zn salt to be separated from the system. However, when the content of Zn salt is low, the efficiency of complexation of TPPO with the Zn salt is low, and the effect of TPPO coordination complexation on removing the Zn salt is not significant.
[0007] Based on this finding, the research and development team carried out a large number of researches. In the above technical solution, the combination of the induced crystallization (complexation and precipitation) in step (1) and the organic phase transfer operation in step (2) can promote the complexation reaction equilibrium of the metal salt and TPPO to move in the direction of complex generation, thereby promoting the full complexation and precipitation of the metal impurities. Specifically: in the above technical solution, triphenylphosphine oxide is added to the adiponitrile to be refined in batches in the step (1), which is conducive to the full complexation of each batch of TPPO (avoiding local saturation of TPPO due to one-time addition, and thus the inability to complex with low-concentration metal ions); after the induced crystallization operation in step (1), a specific type of phase transfer agent is added as a "carrier" in step (2), which can further promote the uniform dispersion and rapid transfer of TPPO to the reaction / extraction interface, avoid the aggregation of TPPO in a single phase, and promote the full complexation and precipitation of the metal salt; through the phase transfer effect, the complex can be separated from the complexation reaction system and distributed into the phase transfer agent, and finally separated out of the system with the phase transfer agent, thereby further promoting the reaction equilibrium to move in the direction of complex generation.
[0008] The above technical solution is carried out in an inert atmosphere, which can improve the stability of the process operation and prevent oxidation of the complexing agent during the process. It should be noted that, in the present application, the inert atmosphere refers to a gas environment composed of a gas that does not chemically interact with the reactants, such as a nitrogen atmosphere, or an atmosphere formed by a zero group element gas (such as argon) in the periodic table.
[0009] It should be noted that the present application is not limited to the specific operation of phase separation in step (2), and those skilled in the art can select a method for separating Zn-TPPO from adiponitrile solution as needed, such as static phase separation, centrifugal phase separation, plate and frame filter pressing, etc., and the technical solutions formed thereby are within the scope of the present application. In a further example of the present application, the mass ratio of the adiponitrile to be refined to the triphenyl phosphine oxide is 1:(0.05-0.3). The metal salt impurities in the adiponitrile to be refined include zinc salt, as well as a small amount of sodium salt, copper salt, etc., which are mainly residual catalyst metal components in the upstream preparation process, as well as equipment material metal elements introduced due to equipment corrosion and wear during the process. The content of metal salt impurities in the adiponitrile to be refined is about 1wt%-1.5wt%. By optimizing the mass ratio of the adiponitrile to be refined to the triphenyl phosphine oxide, waste of TPPO can be avoided, process cost can be reduced, and the complexing efficiency of metal salt and TPPO can also be improved. In an optional example of the present application, the mass ratio of the adiponitrile to be refined to the triphenyl phosphine oxide is 1:(0.1-0.2).
[0010] In a further example of the present application, the way of adding triphenyl phosphine oxide in step (1) is explored and optimized.
[0011] Alternatively, the triphenyl phosphine oxide is added to the adiponitrile to be refined in 2-5 batches, and the optimization of the addition batches is beneficial to improve the operability of the process and improve the process efficiency. In an optional example of the present application, the triphenyl phosphine oxide is added to the adiponitrile to be refined in 2-3 batches.
[0012] Alternatively, the triphenyl phosphine oxide is added to the adiponitrile to be refined in equal batches or variable batches. Among them, equal batches refer to an addition method in which the addition amount of TPPO in each batch is the same, and variable batches refer to at least two batches of TPPO with different amounts. Further optionally, when the triphenyl phosphine oxide is added to the adiponitrile to be refined in variable batches, the first addition amount of the triphenyl phosphine oxide is ≤50% of the total amount of the triphenyl phosphine oxide, so that in actual operation, the amount of the first batch of TPPO is relatively small with respect to the metal salt in the adiponitrile to be refined, and the added TPPO can be fully dispersed and fully complexed with the metal salt. Further optionally, the variable batch addition is a batch-by-batch decreasing addition or a batch-by-batch increasing addition.
[0013] Alternatively, step (1) is carried out under stirring, so as to promote the full contact and complexation of TPPO with metal salt impurities in the adiponitrile to be refined; further, the stirring rate can be selected as 100-300 rpm.
[0014] In further examples of the present application, the control conditions of step (1) are explored and optimized.
[0015] The complexation of metal salts in the adiponitrile to be refined with TPPO is an exothermic reaction, so it is understandable that, in order to promote the full complexation of metal impurities, the reaction complexation reaction is made to proceed in the positive direction by reducing the control temperature in step (1). However, the research and development team of the present application accidentally discovered through exploration experiments that, in step (1), appropriately increasing the reaction temperature during the process of adding the TPPO in batches can effectively promote the formation of metal complexes and ultimately improve the removal rate of metal impurities. That is, although the complexation of metal salts in the adiponitrile to be refined with TPPO is an exothermic reaction, appropriately increasing the temperature during the addition of TPPO in step (1) can promote the formation of metal complexes and improve the removal rate of impurities. Based on this discovery, the research and development team speculates that, in the scenario of adding TPPO in batches, appropriately increasing the temperature can accelerate the contact reaction rate of TPPO and metal salts and reduce the incomplete complexation caused by excessively high local concentration; therefore, during the process of adding the first batch of TPPO, the one-time large amount of TPPO can be optionally avoided to create conditions for promoting the reaction by increasing the temperature; in the subsequent industrialization process, it is recommended to monitor the temperature change and metal impurity content of the reaction system throughout the process and dynamically adjust the temperature increase parameters and feeding speed. Based on this discovery, the initial operating temperature of step (1) is optionally 50-65°C, and then the reaction system is gradually increased to 70-90°C. The examples of the present application demonstrate that, by combining the process of adding TPPO in batches with gradually increasing the temperature from the initial operating temperature of 50-65°C to about 70-90°C, the efficiency of metal complexation can be improved.
[0016] Further optionally, the temperature increase rate of the reaction system is 0.5-2°C / min. It should be noted that the specific operation of the present application for increasing the temperature of the reaction system is not limited, and heat exchange, electric heating or other operation methods can be optionally used, and those skilled in the art can select as needed.
[0017] Optionally, in some examples of the present application, the operating temperature of step (1) is 50-90°C, and the process of adding TPPO in batches is controlled within this temperature range, which can effectively realize the coordination complexation of TPPO and metal salts. In optional examples of the present application, the operating temperature of step (1) is 60-80°C.
[0018] Optionally, the reaction system is maintained for 0.5-3h after each batch of TPPO is added, which can promote the complexation of each batch of TPPO with metal impurities in adiponitrile. Further optionally, the process of adding TPPO in batches is carried out under stirring conditions, thereby promoting mass transfer and improving complexation efficiency.
[0019] In a further example of the present application, the phase transfer agent is added in an amount of 15% to 25% of the volume of the adiponitrile to be refined. In an alternative example of the present application, the phase transfer agent is added in an amount of 18% to 22%, preferably 20%, of the volume of the adiponitrile to be refined.
[0020] In a further example of the present application, the phase transfer agent is selected from at least one of n-hexane, cyclohexane, petroleum ether, toluene, preferably at least one of n-hexane, cyclohexane, petroleum ether, and further preferably n-hexane and / or petroleum ether, and again preferably n-hexane.
[0021] In a further example of the present application, the step (2) further comprises gradually reducing the temperature of the reaction system to 5 to 15°C after adding the phase transfer agent to the first material before phase separation, so that the rapid formation and precipitation of the metal complex can be promoted on the basis of the crystallization induced in step (1) by gradually reducing the temperature of the reaction system.
[0022] In a further example of the present application, the cooling rate of the reaction system is 0.5 to 1.5°C / min, and the control of the cooling rate can achieve the regulation of the phase transfer process.
[0023] In a further example of the present application, the process further comprises a step of pretreating the adiponitrile to be refined to remove the solid impurities contained therein. In an alternative example of the present application, the pretreatment is filtration, i.e. filtering out the suspended particles contained in the adiponitrile to be refined by a filtration operation. In an alternative example of the present application, the filtration is performed using a filter with a pore size of 0.2 to 1 μm.
[0024] In a further example of the present application, the process further comprises a solid-liquid separation of the phase transfer agent phase containing the metal complex obtained by phase separation, so that the metal complex can be filtered out; and a recycling of the phase transfer agent obtained by separation, so that the process cost can be reduced. In an alternative example of the present application, the obtained solid phase material is washed with methanol; and the washing liquid is collected and subjected to vacuum distillation, so as to recover triphenylphosphine oxide.
[0025] Alternatively, the obtained solid phase material is washed countercurrently with methanol; optionally, the washing is performed using 2 to 5 times the volume of methanol; optionally, the washing is performed in multiple stages (2 to 3 stages) in series, so as to reduce the consumption of methanol and improve the impurity removal efficiency; and optionally, the washing is performed at room temperature or under slightly heated conditions (40 to 50°C), so as to accelerate the removal of residual solvent TPPO.
[0026] Alternatively, the methanol evaporated during the vacuum distillation is recovered under conditions of 60 to 65°C and -0.08 to -0.09 MPa; and the concentrated TPPO methanol solution is cooled and crystallized to obtain TPPO crystals. The crystallized material is subjected to solid-liquid separation, washed with methanol, and dried to obtain white needle-shaped TPPO crystals.
[0027] Optionally, the residue obtained after the methanol washing is washed with acid to recover the metal salt contained in the residue, thereby realizing resource utilization.
[0028] Compared with the prior art, the present application has the following beneficial effects: the present application realizes induced crystallization by adding TPPO to the adiponitrile to be refined in batches, and then promotes the generation and precipitation of metal complexes by using an organic phase transfer agent, and then the metal ions such as zinc, sodium and copper contained in the adiponitrile can be efficiently removed by phase separation. The adiponitrile refining and desalting process of the present application is simple and efficient, does not consume steam and does not produce three wastes, and has low overall process operation cost, and is suitable for industrialized popularization and application. DETAILED DESCRIPTION
[0029] In order to facilitate the understanding of the present application, the present application will be described more fully below, and the preferred embodiments of the present application are given. However, it should be understood that these embodiments are only used for more detailed description, and should not be understood as limiting the present application in any form, that is, not intended to limit the protection scope of the present application.
[0030] Unless otherwise defined, the technical terms used in the following examples have the same meaning as generally understood by those skilled in the art to which the present application belongs. The test reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; and the experimental methods, unless otherwise specified, are conventional methods.
[0031] In addition, it also needs to be explained that, in the description of the present application, although the steps of the preparation method of the present application are described in a specific order in the present application, these orders are not limiting, and those skilled in the art can perform the steps in different orders without deviating from the basic principles of the present application.
[0032] In addition, the terms "first", "second", etc. are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "multiple" "at least one" is two or more.
[0033] All numerical designations, such as temperature, pressure, time, and the like, include ranges thereof unless otherwise specified. It is to be understood that the numerical designations set forth herein are approximate. It is to be understood that the term "about" is used herein to describe approximations which up to numbers. Also, it is to be understood that, although not always explicitly described, the reagents described herein are merely examples and equivalents are known to those skilled in the art.
[0034] When expressing amounts, concentrations, or other values or parameters of a preferred range, or a range of upper and lower preferred values, it should be understood that the endpoints of the ranges are included in the range, unless specifically indicated otherwise. For example, a range of "1-5" should be interpreted to include both the endpoints, i.e., a range of "1-4", "1-3", "1-2", "1-2 and 4-5", "1-3 and 5", etc. When numeric ranges are described herein, unless otherwise stated, the range is intended to include all integers and fractions within the range.
[0035] Example 1
[0036] A refining desalination process of adiponitrile, comprising the following steps: (1) 800 kg of crude adiponitrile to be refined is heated to 60°C under a nitrogen atmosphere; 40 kg of TPPO is added, and the reaction is stirred at 150 rpm for 40 min; 40 kg of TPPO is further added, and the reaction is continuously stirred for 1 h to obtain a first material containing metal complexes.
[0037] (2) 160 L of n-hexane is added to the first material, and the temperature is slowly reduced to 10°C (reduction rate of 1°C / min). Subsequently, the crystallization residue (containing metal-TPPO complexes) is separated by a plate and frame filter press, and the filtrate (high-purity adiponitrile after refining) is collected in a storage tank. The purity of the adiponitrile to be refined in this example is 93%, and the content of Zn 2+ is 0.8 wt%; after GC detection, the purity of the high-purity adiponitrile reaches 99.82%, and the residual amount of Zn 2+ in the adiponitrile is less than 0.8 ppm. The unit consumption of TPPO in the overall example is 542 kg / t; and the energy consumption is 123 kWh / t.
[0038] In addition, this example can optionally include removing suspended particles by passing through a 1 μm precision filter before the operation of step (1) is performed. In addition, it can optionally include: the filter residue obtained in step (2) is washed countercurrently with 600 L of methanol at 50°C for 3 times to dissolve TPPO. The washed methanol solution is collected and TPPO is recovered by vacuum distillation (80°C, -0.095 MPa); after drying, 75 kg of TPPO is obtained (recovery rate of 94%). The remaining residue (containing ZnCl2) is washed with 5% HCl to recover the metal salt.
[0039] Comparative Example 1 This comparative example shows a desalination process of adiponitrile to be refined. The process and parameter control in this comparative example are the same as those in Example 1, except that 80 kg of TPPO is added at one time in step (1) of this comparative example. The specific process steps are as follows: (1) Under nitrogen atmosphere, 800 kg of crude adiponitrile to be refined was heated to 60°C and kept at this temperature; 80 kg of TPPO was added at one time, and the reaction was stirred at 150 rpm for 100 min (consistent with the total reaction time of Example 1) to obtain a first material containing metal complexes.
[0040] (2) 160 L of n-hexane was added to the first material, and the temperature was slowly lowered to 10°C (cooling rate of 1°C / min). Then the crystallization residue (filter residue containing metal-TPPO complexes) was separated by a plate and frame filter press, and the filtrate (refined adiponitrile) was collected in a storage tank.
[0041] The purity of the crude adiponitrile to be refined in this comparative example was 93%, and the content of Zn 2+ was 0.8 wt%; GC detection showed that the purity of high-purity adiponitrile reached 99.25%, and ICP-MS detection showed that the residual amount of Zn 2+ in adiponitrile was 12.5 ppm. The unit consumption of TPPO in the overall comparative example was 680 kg / t; the energy consumption was 125 kWh / t.
[0042] Example 2
[0043] A refining and desalting process for adiponitrile, the specific reaction steps are as follows: (1) Under nitrogen atmosphere, 1000 kg of crude adiponitrile to be refined (purity 92.5%, Zn 2+ content 0.75 wt%) was heated to 65°C and kept at this temperature; 30 kg of TPPO was added for the first time, and the reaction was stirred at 180 rpm for 30 min; 35 kg of TPPO was added for the second time, and the temperature was raised to 70°C for continued stirring for 40 min; 35 kg of TPPO was added for the third time, and the reaction was stirred at 70°C for 50 min to obtain a first material containing metal complexes.
[0044] (2) 200 L of n-hexane was added to the first material, and the temperature was slowly lowered to 8°C at a cooling rate of 0.8°C / min. Then the crystallization residue (filter residue containing metal-TPPO complexes) was separated by a plate and frame filter press (filtration accuracy 0.8 μm), and the filtrate was collected in an inert gas protected storage tank.
[0045] (3) The filter residue was washed countercurrently with 750 L of methanol at 55°C for 4 times, and the washing liquid was collected; TPPO was recovered by vacuum distillation (85°C, -0.098 MPa), and then weighed after drying; the remaining residue was washed with 8% HCl solution to recover the metal salt.
[0046] GC detection showed that the purity of refined adiponitrile reached 99.88%, which was 7.38 percentage points higher than that of the crude product. ICP-MS detection showed that the content of Zn 2+The residual amount was reduced to 0.5 ppm, and the removal rate of metal salt was calculated as 94.7%. The TPPO unit consumption was 520 kg / t, which was reduced by 4.1% compared with Example 1; the total energy consumption of the reaction and separation process was 118 kWh / t, which was further optimized. 92 kg of TPPO was recovered, with a recovery rate of 92%; the metal salt recovery rate after pickling reached 88%, realizing resource recycling.
[0047] In this embodiment, three batches of TPPO were added in stages, and a gradient temperature rise strategy of 65-70°C was used. On the one hand, this avoids incomplete complexation caused by excessively high local reactant concentration, and on the other hand, it strengthens the reaction kinetics by moderate heating, improving the combination efficiency of TPPO and metal ions; combined with the cooling operation, the crystallization and separation of metal complexes can be further promoted.
[0048] Example 3
[0049] A kind of adiponitrile refining salt removal process, the specific reaction steps are as follows: (1) In a nitrogen atmosphere, 800 kg of crude adiponitrile to be refined (purity 93%, Zn 2+ content 0.8 wt%) was first heated to 55°C and kept; 40 kg of TPPO was added, and the reaction was stirred at 150 rpm for 40 min; then the temperature of the system was raised to 62°C at a rate of 2°C / min, 40 kg of TPPO was added, and the reaction was continued for 1 h, to obtain a first material containing metal complexes.
[0050] (2) 200 L of n-hexane was added to the first material, and the temperature was slowly lowered to 8°C at a rate of 0.8°C / min. Then the crystalline residue (filter residue containing metal-TPPO complex) was separated by a plate and frame filter press (filtering precision 0.8 μm), the reaction vessel outlet was connected to the filter press inlet, and the feeding pressure was controlled at 0.2-0.3 MPa, the crystalline residue (containing metal-TPPO complex) was separated, and the filtrate was collected in an inert gas protected tank.
[0051] After GC detection, the purity of refined adiponitrile reached 99.85%, which was increased by 6.85 percentage points compared with the crude product. Through ICP-MS detection, the Zn 2+ content in adiponitrile was reduced to 0.6 ppm, the TPPO unit consumption was 533 kg / t, the total energy consumption of the reaction and separation process was 120 kWh / t, and good economic efficiency was maintained. After drying, 77 kg of TPPO was obtained (recovery rate 96.2%), and the efficiency of recovering metal salt from the remaining residue after pickling was simultaneously improved to 90%.
[0052] In this embodiment, the amount of TPPO in three batches was adjusted in step (1) (25:25:20) to control the appropriate temperature rise gradient, and the high Zn 2+The content of crude adiponitrile can still maintain excellent removal effect, which proves the flexibility and reliability of the multi-batch feeding process of the application.
[0053] Example 4
[0054] This embodiment is based on the process framework of Example 1. In this embodiment, TPPO is recycled and used for 5 times. By optimizing the recovery and purification process, the complexing activity of TPPO is stable during the recycling process. The specific experimental steps are as follows: (1) First complexation reaction (Cycle 1): same as steps (1)-(2) of Example 1, that is, 800 kg of crude adiponitrile (purity 93%, Zn 2+ 0.8wt%), 80 kg of fresh TPPO was added in two batches at 60°C, after reaction, 160 L of n-hexane was added to cool to 10°C, and then filtered, and the filtrate and residue were collected.
[0055] (2) TPPO recovery and purification: the residue (containing metal-TPPO complex) obtained by each pressure filtration was washed with 600 L of methanol at 50°C for 3 times countercurrently, and the washing liquid was collected; the washing liquid was distilled under reduced pressure (80°C, -0.095 MPa) to remove methanol, and the crude recovered TPPO was obtained; 5wt% of activated carbon (based on the mass of the crude recovered TPPO) was added to the crude recovered TPPO, and the mixture was stirred at 60°C for 30 min to decolorize, then filtered to remove the activated carbon, and the refined recovered TPPO (purity ≥98.5%) was obtained.
[0056] (3) Recycle complexation reaction (Cycle 2-Cycle 5): the refined recovered TPPO from the previous batch was used in each cycle, and the process parameters were the same as those in the first reaction: 800 kg of crude adiponitrile of the same specification, 80 kg of recovered TPPO was added in two batches at 60°C, and the stirring reaction time and crystallization separation conditions were the same as those in Example 1, and the results are shown in Table 1.
[0057] Table 1
[0058] As can be verified from the table, by using the recovery and purification process of "methanol washing-reduced pressure distillation-activated carbon decolorization", the metal impurities and organic by-products in TPPO are effectively removed, so that the recovered TPPO still maintains a high complexing activity in 5 cycles. From the test results, after 5 cycles, the purity of adiponitrile is still 99.78%, the residual amount of Zn 2+ is only 1.2 ppm, the removal rate of metal salt reaches 92.5%, and the TPPO consumption is controlled within 552 kg / t, which reflects the process stability of TPPO recycling.
[0059] Example 5 In this embodiment, the type of phase transfer agent is optimized through a small-scale experiment. The specific steps include: (1) Add 100 mL of ADN raw material containing Zn 2+ to a three-necked flask, start stirring (400 rpm), and heat to 60°C for 10 min to make the system temperature uniform; then, according to the molar ratio of ADN to TPPO of 1:0.1, weigh the corresponding amount of TPPO (about 1.32 g) as the first batch of feed into the reaction system, and stir at 60°C for 30 min, during which the stirring speed is kept stable; then, add the remaining 50% of TPPO (about 1.32 g), and continue to stir at 60°C for 1 h to further promote the complexation reaction of TPPO with the residual Zn 2+ in the system.
[0060] (2) Slowly cool the material obtained in step (1) to 10°C by adding different types of phase transfer solvents (the amount of phase transfer solvent is 20% of the volume of ADN); then, stand for 15 min to separate the phases, and the upper layer is the refined ADN phase, and the lower layer is the TPPO-Zn 2+ complex precipitate; separate the two phases by centrifugation (6000 rpm for 8 min), take the upper layer of ADN clear liquid, and detect the residual amount of Zn 2+ by ICP-MS.
[0061] The specific types of phase transfer agents and the refining results are shown in Table 2.
[0062] Table 2
[0063] Based on Table 1, it can be confirmed that the phase transfer agent described in the present application can be selected from at least one of n-hexane, cyclohexane, petroleum ether, toluene, and dimethyl sulfoxide. In combination with the stripping efficiency and separation time, the phase transfer agent described in the present application can be further selected from at least one of n-hexane, cyclohexane, petroleum ether, and toluene, preferably at least one of n-hexane, cyclohexane, and petroleum ether. Considering that n-hexane has a large difference in density with adiponitrile, and has the advantages of low toxicity, single composition, and high stability, the phase transfer agent described in the present application is preferably n-hexane.
[0064] It should be noted that the above content is a further detailed description of the present application in combination with specific embodiments, and the specific implementation of the present application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, a number of simple improvements can be made without departing from the concept of the present application, and all of them should be regarded as falling within the scope of protection of the present application.
Claims
1. An adiponitrile finishing desalting process characterized by, The process comprises the following steps: (1) under inert atmosphere, adding triphenyl phosphine oxide into the adiponitrile to be refined in batches to obtain a first material containing metal complex; (2) adding phase transfer agent into the first material to make the metal complex distribute into the phase transfer agent, and then separating the phases to obtain high-purity adiponitrile product; wherein the phase transfer agent is selected from at least one of n-hexane, cyclohexane, petroleum ether, toluene, dimethyl sulfoxide.
2. The adiponitrile finishing desalting process of claim 1, wherein, The mass ratio of the adiponitrile to be refined to the triphenyl phosphine oxide is 1:(0.05-0.3), preferably 1:(0.1-0.2).
3. The adiponitrile finishing desalting process of claim 1, wherein, The triphenyl phosphine oxide is added into the adiponitrile to be refined in 2-5 times; Preferably, the triphenyl phosphine oxide is added into the adiponitrile to be refined in equal or variable batches; Further preferably, when the triphenyl phosphine oxide is added into the adiponitrile to be refined in variable batches, the first addition amount of the triphenyl phosphine oxide is ≤50% of the total amount of the triphenyl phosphine oxide.
4. The adiponitrile finishing desalting process of claim 1, wherein, The initial operation temperature of step (1) is 50-65℃, and then the reaction system is gradually heated to 70-90℃; Preferably, the heating rate of the reaction system is 0.5-2℃ / min.
5. The adiponitrile finishing desalting process of claim 1, wherein, The operation temperature of step (1) is 50-90℃, preferably 60-80℃.
6. The adiponitrile finishing desalting process of claim 1, wherein, After each batch of the triphenyl phosphine oxide is added, the reaction system is maintained for 0.5-3h.
7. The adiponitrile finishing desalting process of claim 1, wherein, The addition amount of the phase transfer agent is 15%-25% of the volume of the adiponitrile to be refined, preferably 18%-22%; And / or, the phase transfer agent is selected from at least one of n-hexane, cyclohexane, petroleum ether, toluene; preferably at least one of n-hexane, cyclohexane, petroleum ether.
8. The adiponitrile finishing desalting process of claim 1, wherein, In step (2), the temperature of the reaction system is gradually reduced to 5-15℃ after the phase transfer agent is added into the first material before the phase separation; Preferably, the cooling rate of the reaction system is 0.5-1.5℃ / min.
9. The adiponitrile finishing desalting process of claim 1, wherein, The process further comprises a step of pretreating the adiponitrile to be refined to remove solid impurities contained therein; Preferably, the pretreatment is filtration; Further preferably, the filtration is performed using a filter with a pore size of 0.2-1μm.
10. The adiponitrile finishing desalting process of claim 1, wherein, The process further comprises solid-liquid separation of the phase transfer agent phase containing metal complex obtained after the phase separation, and recycling the separated phase transfer agent; Preferably, the solid material obtained after washing with methanol is washed with acid, and the metal salt is recovered.