A method for recovering high purity triphenylphosphine oxide from AVNA production rectification raffinate

Abstract

The application provides a method for recovering high-purity triphenyl phosphine oxide from AVNA production rectification residue, and belongs to the technical field of fine chemical by-product recovery and refining. The method takes AVNA process rectification residue containing triphenyl phosphine oxide as raw material, and realizes efficient recovery and refining of triphenyl phosphine oxide through pretreatment, selective extraction, decolorization and impurity removal, vacuum concentration, segmented temperature control and crystal growth centrifugation and vacuum drying steps. The application promotes the migration of ionic phosphorus-containing components in the residue to the water phase and breaks the emulsion system, and combines with the synergistic optimization of the whole process parameters, so that the product has high purity, high yield and uniform crystal grains, the treatment solvent can be recycled and used, and is suitable for industrial large-scale production.

Description

Technical Field

[0001] This application relates to a method for recovering high-purity triphenylphosphine oxide from distillation residues in AVNA production, belonging to the field of fine chemical by-product recovery and refining technology. Background Technology

[0002] Triphenylphosphine oxide is an important organophosphorus fine chemical product, characterized by strong chemical stability and excellent coordination properties. It is widely used in catalyst synthesis, pharmaceutical intermediates, chemical extraction, and polymer material additives. In the AVNA production process, triphenylphosphine participates in the Wittig reaction as a reactant, transforming into the byproduct triphenylphosphine oxide, which is enriched in the distillation residue. This distillation residue has a complex composition, containing not only triphenylphosphine oxide but also unreacted quaternary phosphine salts, various organic impurities, colloids, pigments, and suspended particulate matter. Furthermore, it exhibits a stable emulsion system, making separation and purification challenging.

[0003] Currently, the main methods for treating this type of distillation residue are simple incineration or hazardous waste disposal. This not only results in a significant waste of the valuable triphenylphosphine oxide resource but also generates a large amount of pollutants, increasing environmental treatment costs. Existing recovery processes mainly include water precipitation-recrystallization routes, acid-base complexation-dissociation routes, and metal ion complexation precipitation routes, but each has its own technical limitations and is difficult to adapt to the complex system of AVNA distillation residue.

[0004] Chinese invention patent application CN109354595A discloses a method for recovering triphenylphosphine oxide from Wittig reactive distillation residue. The method involves adding the distillation residue dropwise to water for water precipitation and crystallization, followed by recrystallization of the crude product using an organic solvent for purification. This method primarily removes impurities through recrystallization, and the examples described show a product purity of approximately 98% and a yield of approximately 80%.

[0005] Chinese invention patent application CN118063508A discloses a method for recovering triphenylphosphine oxide, employing a two-step aqueous phase process: adjusting the pH to 2-5.5 to form a complex precipitate, and then adjusting the pH to 9-11 for dissociation. Water is used as the medium throughout the process, and this route belongs to the aqueous phase acid-base treatment route. Chinese invention patent CN112409409B uses a chemical separation route where metal ion complexing agents such as zinc chloride form a eutectic precipitate with triphenylphosphine oxide. This separation process introduces metal ions, and the product requires additional demetallization treatment. Its examples describe a single-pass recovery rate of approximately 78% and a purity of approximately 92%.

[0006] In summary, the existing recycling processes mainly have the following problems: 1. The AVNA distillation residue contains unreacted quaternary phosphine salts and forms a stable emulsion system. The existing process does not have relevant treatment, resulting in incomplete stratification, large triphenylphosphine entrainment loss, and low recovery rate. 2. Existing impurity removal processes mostly involve single solvent treatment or single decolorization, which cannot simultaneously remove pigments, trace amounts of colloids and suspended impurities. Furthermore, fine activated carbon powder is prone to filter penetration, causing secondary pollution, and the product purity is difficult to consistently meet standards. 3. Existing crystallization processes mostly employ rapid cooling or natural cooling, resulting in a crude crystallization process, uneven crystal size, poor quality, and low purity and yield of the finished product. Summary of the Invention

[0007] To address the aforementioned problems, this application provides a method for recovering high-purity triphenylphosphine oxide from distillation residues in AVNA production. This application achieves simultaneous migration of quaternary phosphine salt plasma-containing phosphorus components into the aqueous phase and dismantling of the emulsion system through pretreatment. Combined with selective treatment using a mixed solvent of toluene and methyl tert-butyl ether, synergistic decolorization using decolorizing agents and filter aids, vacuum concentration using scraped film, and low-speed crystal growth with uniform cooling, the entire process is optimized to produce a high-purity, high-yield, and uniformly sized triphenylphosphine oxide product.

[0008] According to one aspect of this application, a method for recovering high-purity triphenylphosphine oxide from AVNA production distillation residues is provided, comprising the following steps: (1) Pretreatment: Add saturated salt solution to the distillation residue containing triphenylphosphine oxide in the AVNA process, add acidic solution dropwise to adjust the pH value of the system to ≤5, stir and let stand to separate the layers to obtain the organic phase; (2) Selective treatment: Add a mixed solvent of toluene and methyl tert-butyl ether to the organic phase, stir to selectively dissolve triphenylphosphine oxide in the mixed solvent, let stand and separate the lower oily insoluble matter and the residual aqueous phase, and collect the organic liquid containing triphenylphosphine oxide. (3) Decolorization and impurity removal: Add decolorizing agent and filter aid to the organic liquid, reflux at constant temperature for decolorization, and then filter to obtain decolorized liquid; (4) Vacuum concentration: The decolorizing liquid is fed into a scraped film evaporator and the mixed solvent is removed by vacuum distillation to obtain a saturated concentrate of triphenylphosphine oxide. (5) Segmented temperature-controlled crystal growth and centrifugation: The saturated concentrate of triphenylphosphine oxide is cooled at a constant speed and stirred at a low speed. After crystal growth at a constant temperature, the wet triphenylphosphine oxide product is obtained by centrifugation. (6) Vacuum drying: The wet triphenylphosphine oxide is vacuum dried to obtain high-purity triphenylphosphine oxide.

[0009] Optionally, in step (1), the saturated salt solution is a saturated aqueous solution of sodium chloride or sodium sulfate, and the amount of the saturated salt solution added is 45% to 65% of the mass of the distillation residue; the acidic solution is hydrochloric acid or acetic acid, and the pH value of the system is adjusted to 2 to 5.

[0010] Preferably, the pH value of the system is adjusted to 2.5 to 4, and the pH value is, for example, 2.0, 2.8, 3.0, 3.2, 3.5, 4.0 or 5.0, or a range between any two of the above values.

[0011] Preferably, the amount of saturated salt solution added is 45% to 55% of the mass of the distillation residue, for example, 45%, 50%, 52%, 55%, 60% or 65%, or a range between any two of the above values. As a specific embodiment of this application, the amount of saturated salt solution added is 45%, 50% or 65% of the mass of the distillation residue.

[0012] As one specific embodiment of this application, the pH value of the system is adjusted to 2.0, 3.0 or 5.0.

[0013] Optionally, in step (1), the stirring temperature is 40~80℃, the stirring speed is 200~400r / min, the stirring time is 30~90min, and the settling time is 1~3h.

[0014] Specifically, in step (1), the high ionic strength of the saturated salt solution compresses the double-layer structure of the emulsion droplets, promoting oil-water separation; the acidic conditions combined with the high ionic strength environment alter the state of unreacted quaternary phosphine salts and other ionic phosphorus-containing components, causing them to preferentially migrate to the aqueous phase, thus weakening their stabilizing effect on the emulsion system. These two factors work synergistically to simultaneously achieve the separation of ionic impurities and demulsification, reducing the entrainment loss of triphenylphosphine oxide from the source.

[0015] Optionally, in step (2), the mass ratio of toluene to methyl tert-butyl ether in the mixed solvent is 3~5:1, the mass ratio of the mixed solvent to the distillation residue is 2~3:1, the stirring speed is 300~500 r / min, the stirring time is 40~120 min, and the settling time is 0.5~2 h.

[0016] Preferably, the mass ratio of toluene to methyl tert-butyl ether is 3.5 to 4.5:1, for example, 3:1, 3.5:1, 4:1 or 5:1, or any range between two of the above ratios; As a specific embodiment of this application, the mass ratio of toluene to methyl tert-butyl ether is 3:1, 4:1 or 5:1.

[0017] Specifically, toluene has good solubility for triphenylphosphine oxide, while methyl tert-butyl ether can adjust the polarity and density of the mixed solvent, improving the stratification effect. The two are compounded in a specific ratio, so that triphenylphosphine oxide is fully dissolved in the mixed solvent, while insoluble components such as colloids and high-boiling residues, as well as the residual aqueous phase entrained in step (1), are precipitated and separated, reducing impurity entrainment and achieving the separation of the target product from impurities; the selective treatment can be carried out at 20~40℃ without additional heating.

[0018] Optionally, in step (3), the decolorizing agent is granular activated carbon or powdered activated carbon, and the filter aid is one or both of diatomaceous earth or cellulose filter aid.

[0019] Optionally, in step (3), the amount of the decolorizing agent added is 0.2% to 0.5% of the mass of the distillation residue, the amount of the filter aid added is 0.1% to 0.2% of the mass of the distillation residue; the constant temperature reflux temperature is 40 to 80°C, the reflux decolorization time is 1 to 4 hours, and the filtration adopts a precision negative pressure filtration method.

[0020] Specifically, the decolorizing agent is used to adsorb pigments and trace amounts of colloids in the liquid, while the filter aid forms a porous filter cake layer on the surface of the filter medium to intercept the fine powder of the decolorizing agent and suspended impurities, preventing the fine powder from passing through the filter and causing secondary pollution. The two work together to ensure the clarity of the decolorized liquid.

[0021] Optionally, in step (4), the feed flow rate of the scraped film evaporator is 100~200kg / h, the evaporation temperature is 60~80℃, and the vacuum degree is ≥-97kPa; when the liquid level in the scraped evaporator reaches 400~800mm, the feed is stopped, the circulating pump is started for concentration and distillation, and the circulating feed is stopped when the vacuum degree is ≥-99kPa.

[0022] Specifically, the scraped film evaporation equipment makes the liquid form a uniform film on the heated wall, with a large vaporization area, high heat transfer efficiency, and short heat residence time of the material, which can avoid the changes in trace impurities and solvent residue caused by long-term pot heating; the reduced pressure further lowers the boiling point of the mixed solvent, realizes low-temperature rapid desolvation, and controls the system to the saturated state required for subsequent crystallization, which is connected with the controlled crystallization in step (5).

[0023] Optionally, in step (5), the uniform cooling rate is 0.5~2℃ / min, the temperature is reduced to 0~-5℃, the low-speed stirring speed is 50~150r / min, and the constant temperature crystal growth time is 2~6h.

[0024] Preferably, the uniform cooling rate is 0.5~1.5℃ / min, for example 0.5, 0.8, 1, 1.5 or 2℃ / min, or a range between any two of the above values; As one specific embodiment of this application, the uniform cooling rate is 0.5, 1, or 2 °C / min.

[0025] Preferably, the isothermal crystal growth time is 3 to 5 hours, for example, 2, 3, 4, 5 or 6 hours, or any range between the two values ​​mentioned above; As one specific embodiment of this application, the isothermal crystal growth time is 2, 4 or 6 hours.

[0026] Specifically, the segmented temperature control includes a uniform cooling stage and a constant-temperature crystal growth stage: the uniform cooling stage cools down at a constant rate, which can avoid explosive nucleation caused by local oversaturation, and low-speed stirring is conducive to uniform crystal growth rather than fine pulverization; after reaching the final crystallization temperature, the constant-temperature crystal growth stage is entered, which promotes the dissolution of small crystals and the growth of large crystals, resulting in crystals with uniform particle size and regular appearance, and reducing the inclusion of impurities in the crystals.

[0027] Optionally, in step (6), the vacuum drying temperature is 60~90℃, the vacuum degree is ≥-0.090MPa, and the drying time is 3~8h.

[0028] Optionally, the obtained triphenylphosphine oxide has a moisture content of ≤0.05%, an HPLC purity of ≥99.7%, and a yield of ≥97%.

[0029] Furthermore, the distillation residue containing triphenylphosphine oxide in the AVNA process contains 50% to 65% triphenylphosphine oxide by mass, and also contains unreacted quaternary phosphine salts, organic impurities, colloids, pigments, and suspended particulate matter.

[0030] Furthermore, the toluene and methyl tert-butyl ether mixed solvent removed by vacuum distillation in step (4) is collected by condensation and directly reused in the selective processing step (2), which can significantly reduce production costs.

[0031] The beneficial effects of this application include, but are not limited to: 1. This application utilizes a synergistic pretreatment process involving saturated salt solution and acid-adjusted pH to promote the migration of unreacted quaternary phosphine salts and other ionic phosphorus-containing components in the AVNA distillation residue to the aqueous phase and effectively break down the stable emulsion system, thereby improving the material stratification state, reducing impurity entrainment, and increasing the yield of triphenylphosphine oxide.

[0032] 2. This application uses a mixed solvent of toluene and methyl tert-butyl ether in a specific ratio for selective treatment, which allows triphenylphosphine oxide to be fully dissolved while separating insoluble impurities and residual aqueous phase, thereby achieving the separation of the target product and impurities, and the preliminary purification effect is stable.

[0033] 3. This application uses a combination of decolorizing agent and filter aid to effectively remove pigments, trace amounts of colloids and suspended impurities from the feed solution, prevent the fine powder of the decolorizing agent from passing through the filter, avoid secondary pollution, ensure the clarity of the feed solution, and lay the foundation for subsequent high-purity crystallization.

[0034] 4. This application adopts a scraped film vacuum evaporation process, which has high solvent removal efficiency and short material heating time. It can avoid changes in trace impurities caused by prolonged autoclave heating, and the mixed solvent can be recycled and reused, reducing production costs and being green and environmentally friendly.

[0035] 5. This application adopts a crystal growth process that combines uniform cooling with low-speed stirring, which can induce uniform and regular crystal precipitation. The crystals have uniform size and good quality, without fine powder or agglomeration. Combined with centrifugation and vacuum drying, the final product has high purity and high yield, meeting the needs of high-end industrial applications. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is the HPLC chromatogram of triphenylphosphine oxide recovered in Example 1 of this application; Figure 2 This is the HPLC chromatogram of triphenylphosphine oxide recovered in Example 2 of this application; Figure 3 This is the HPLC chromatogram of triphenylphosphine oxide recovered in Example 3 of this application; Figure 4 Here is a picture of the triphenylphosphine oxide recovered in Example 1; Figure 5 The image shows the actual triphenylphosphine oxide recovered in Comparative Example 1. Detailed Implementation

[0037] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this application are readily available through conventional means, and unless otherwise specified, they are used in accordance with conventional methods in the art or as per product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this application. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0039] In this application, AVNA is the production process of 7-amino-3-vinyl-3-cephalocyclo-4-carboxylic acid (7-AVCA, CAS No. 79349-82-9), a third-generation cephalosporin nucleus intermediate. This process uses GCLH or GCLE and triphenylphosphine as raw materials, and introduces a vinyl group at the 3-position of the cephalosporin nucleus through a Wittig reaction. During the reaction, triphenylphosphine first forms a quaternary phosphonium salt intermediate, which is then converted into triphenylphosphine oxide after the reaction. The unreacted quaternary phosphonium salt and triphenylphosphine oxide are enriched together in the residue after solvent distillation recovery, which is the distillation residue containing triphenylphosphine oxide in the AVNA process.

[0040] In this application, the yield of triphenylphosphine oxide refers to the mass recovery rate, which is the ratio calculated based on the theoretical mass of triphenylphosphine oxide in the distillation residue and the total mass of the dried product obtained. Yield (%) = Total mass of dried product / (Mass of distillation residue × External standard content of triphenylphosphine oxide in the residue) × 100%; The actual purity of triphenylphosphine oxide in the product is determined separately by HPLC external standard method and labeled separately, and is not included in the above yield.

[0041] The main raw materials used in this application are all commercially available conventional industrial-grade products, with the following specific specifications: the distillation residue from the AVNA process was provided by Shandong Prodebang Pharmaceutical Co., Ltd., with a triphenylphosphine oxide content of 50%~65%; sodium chloride was industrial-grade, with a purity ≥99.0%; sodium sulfate was industrial-grade, with a purity ≥98.0%; hydrochloric acid was industrial-grade, with a mass fraction of 30%~36%; acetic acid was industrial-grade, with a purity ≥99.0%; toluene was industrial-grade, with a purity ≥99.5%; methyl tert-butyl ether was industrial-grade, with a purity ≥99.0%; granular activated carbon was coal-based columnar activated carbon, with an iodine adsorption value ≥800mg / g; powdered activated carbon was wood-based powdered activated carbon, with a methylene blue adsorption value ≥180mL / g; diatomaceous earth filter aid was industrial-grade, with a SiO2 content ≥88%; and cellulose filter aid was industrial-grade, with a fiber length of 20~100μm.

[0042] Main experimental equipment: scraped film evaporator (BM2.0 type, evaporation area 0.2m²), precision negative pressure filter (GLJ-500 type), crystallization kettle (500L, with jacket temperature control and stirring), vacuum drying oven (DZF-6090 type), high performance liquid chromatograph (Agilent 1260 type), Karl Fischer moisture analyzer (Metrohm 870 type).

[0043] Example 1 This embodiment provides a method for recovering high-purity triphenylphosphine oxide from AVNA production distillation residue, comprising the following steps: (1) Pretreatment: Take 1000 kg of AVNA process distillation residue (triphenylphosphine oxide external standard content is 58.62%), add 450 kg of saturated sodium chloride solution, and slowly add 31% hydrochloric acid by mass while stirring to adjust the pH of the system to 3.0. Set the stirring temperature to 50℃ and the speed to 350 r / min, and continue stirring for 45 min to promote the migration of quaternary phosphine salt and other ionic phosphorus-containing components to the aqueous phase and demulsify. After stirring, let stand for 2 h, separate and remove the lower aqueous phase after separation. (2) Selective treatment: Add 2500 kg of mixed solvent (toluene to methyl tert-butyl ether mass ratio of 4:1, mixed solvent to distillation residue mass ratio of about 2.5:1) to the obtained organic phase, control the material temperature at 30℃, set the stirring speed at 500 r / min, and stir at constant temperature for 120 min to selectively dissolve triphenylphosphine oxide; after completion, let stand for 2 h, separate and remove the lower layer of insoluble residue and residual aqueous phase, and collect the organic liquid containing triphenylphosphine oxide; (3) Decolorization and impurity removal: Add 4 kg of granular activated carbon and 1 kg of diatomaceous earth filter aid to the organic liquid (the addition amounts are 0.4% and 0.1% of the mass of the distillation residue, respectively), heat to 45°C, and decolorize by constant temperature reflux for 3 hours; after decolorization, use precision negative pressure filtration to obtain a colorless, clear and transparent decolorized liquid. (4) Vacuum concentration: The decolorized liquid is fed into the scraped film evaporator, and the feed flow rate is controlled at 200 kg / h, the evaporation temperature at 75℃ and the vacuum degree at ≥-97 kPa. When the liquid level in the scraped evaporator reaches 400 mm, the feed is stopped and the circulating pump is started for concentration and distillation. When the vacuum degree is ≥-99 kPa, the circulating feed is stopped to obtain a saturated concentrate of triphenylphosphine oxide. The removed mixed solvent is collected by condensation and recycled. (5) Segmented temperature-controlled crystal growth centrifugation: The saturated concentrate is transferred into the crystallization vessel while hot. The segmented temperature control is divided into a uniform cooling stage and a constant temperature crystal growth stage: When the material temperature drops to 50℃, the uniform cooling stage is entered, and the temperature is lowered at a rate of 0.5℃ / min. The stirring speed is 150r / min throughout the process. When the material temperature drops to -3℃, the constant temperature crystal growth stage is entered, and the temperature is kept for crystal growth for 3h. After the crystal growth is completed, centrifugation is performed to obtain pure white triphenylphosphine oxide wet product. (6) Vacuum drying: The wet product was placed in a vacuum drying oven, the drying temperature was set to 70℃ and the vacuum degree to -0.095MPa, and the product was dried for 5 hours. After cooling, the product was discharged to obtain 570.4 kg of high-purity triphenylphosphine oxide product.

[0044] Example 2 This embodiment provides a method for recovering high-purity triphenylphosphine oxide from AVNA production distillation residue, which differs from Example 1 in that: In step (1), 650 kg of saturated sodium chloride solution was added, the pH of the system was adjusted to 5.0, the stirring temperature was 60℃, the stirring speed was 300 r / min, and the stirring time was 60 min; In step (2), add 2000 kg of mixed solvent (toluene to methyl tert-butyl ether in a mass ratio of 3:1), stir at 400 r / min for 80 min, and let stand for 1 h; In step (3), 2 kg of granular activated carbon and 1 kg of diatomaceous earth filter aid are added, and the mixture is heated to 60°C and refluxed for 2 hours for decolorization. In step (4), the feed flow rate is 150 kg / h, the evaporation temperature is 60°C, and the bottom liquid level is 800 mm. In step (5), the cooling rate is 1℃ / min, the stirring speed is 100r / min, and the temperature is kept constant for 4h after cooling to 0℃. In step (6), the drying temperature is 90℃, the vacuum degree is -0.090MPa, and the drying time is 5h.

[0045] The external standard content of triphenylphosphine oxide in the distillation residue of the AVNA process was 56.84%, and the feed amount was 1000 kg, yielding 553.6 kg of high-purity triphenylphosphine oxide product. The specifications of other raw materials and process parameters were exactly the same as in Example 1.

[0046] Example 3 This embodiment provides a method for recovering high-purity triphenylphosphine oxide from AVNA production distillation residue, which differs from Example 1 in that: In step (1), 500 kg of saturated sodium chloride solution was added, the pH of the system was adjusted to 2.0, the stirring temperature was 80℃, the stirring speed was 400 r / min, and the stirring time was 90 min; In step (2), add 2850 kg of mixed solvent (toluene to methyl tert-butyl ether in a mass ratio of 5:1), stir at 400 r / min for 90 min, and let stand for 1 h; In step (3), 2 kg of powdered activated carbon and 1 kg of cellulose filter aid are added, and the mixture is heated to 80°C and refluxed for 3 hours for decolorization. In step (4), the feed flow rate is 100 kg / h, the evaporation temperature is 80°C, and the liquid level in the bottom of the tower is 620 mm, at which point the feed is stopped. In step (5), the cooling rate is 2℃ / min, the stirring speed is 50r / min, and the temperature is kept constant for 6h after cooling to -5℃; In step (6), the drying temperature is 80℃, the vacuum degree is -0.095MPa, and the drying time is 6h.

[0047] The external standard content of triphenylphosphine oxide in the distillation residue of the AVNA process was 55.47%, and the feed amount was 1000 kg, yielding 538.1 kg of high-purity triphenylphosphine oxide product. The specifications of other raw materials and process parameters were exactly the same as in Example 1.

[0048] Example 4 This embodiment provides a method for recovering high-purity triphenylphosphine oxide from AVNA production distillation residue, which differs from Example 1 in that: In step (1), saturated sodium sulfate solution is used instead of saturated sodium chloride solution, with an addition amount of 550 kg. The pH value of the system is adjusted to 4.0, the stirring temperature is 55℃, the stirring speed is 350 r / min, and the stirring time is 60 min. In step (2), the mass ratio of the mixed solvent to toluene to methyl tert-butyl ether is 4:1, the mass ratio of the mixed solvent to the distillation residue is 2.5:1, the stirring speed is 450 r / min, and the stirring time is 90 min; In step (3), 3 kg of granular activated carbon and 2 kg of diatomaceous earth filter aid (the amount of filter aid added is 0.2% of the mass of the distillation residue) are added, and the temperature is raised to 55℃ and refluxed for decolorization for 2.5 h; In step (5), the cooling rate is 1℃ / min, the stirring speed is 100r / min, and the temperature is kept constant for 4 hours after cooling to -2℃.

[0049] The external standard content of triphenylphosphine oxide in the distillation residue of the AVNA process was 57.20%, and the feed amount was 1000 kg, yielding 555.4 kg of high-purity triphenylphosphine oxide product. The specifications of other raw materials and process parameters were exactly the same as in Example 1.

[0050] Example 5 This embodiment provides a method for recovering high-purity triphenylphosphine oxide from AVNA production distillation residue, which differs from Example 1 in that: In step (1), acetic acid was used to replace hydrochloric acid to adjust the pH of the system to 3.5, 500 kg of saturated sodium chloride solution was added, and the stirring temperature was 60℃, the speed was 300 r / min, and the stirring time was 75 min. In step (2), the mass ratio of the mixed solvent to toluene to methyl tert-butyl ether is 5:1, the mass ratio of the mixed solvent to the distillation residue is 3:1, the stirring speed is 400 r / min, and the stirring time is 100 min; In step (3), 5 kg of granular activated carbon and 1 kg of diatomaceous earth filter aid were added (the amount of decolorizing agent added was 0.5% of the mass of the distillation residue), and the remaining decolorization parameters were exactly the same as in Example 1; In step (4), the feed flow rate is 150 kg / h, the evaporation temperature is 70°C, and the liquid level in the bottom of the tower is 600 mm, at which point the feed is stopped. In step (5), the cooling rate is 1.5℃ / min, the stirring speed is 80r / min, and the temperature is kept constant for 5h after cooling to -4℃; In step (6), the drying temperature is 75℃, the vacuum degree is -0.092MPa, and the drying time is 6h.

[0051] The external standard content of triphenylphosphine oxide in the distillation residue of the AVNA process was 56.50%, and the feed amount was 1000 kg, yielding 549.2 kg of high-purity triphenylphosphine oxide product. The specifications of other raw materials and process parameters were exactly the same as in Example 1.

[0052] Example 6 This embodiment provides a method for recovering high-purity triphenylphosphine oxide from AVNA production distillation residue, which differs from Example 1 in that: In step (1), 600 kg of saturated sodium chloride solution was added, the pH of the system was adjusted to 2.8, the stirring temperature was 65℃, the stirring speed was 350 r / min, and the stirring time was 50 min; In step (2), the mass ratio of the mixed solvent to toluene to methyl tert-butyl ether is 3.5:1, the mass ratio of the mixed solvent to the distillation residue is 2.5:1, the stirring speed is 450 r / min, and the stirring time is 80 min; In step (3), powdered activated carbon and cellulose filter aid are combined, with 3 kg of activated carbon and 1.2 kg of cellulose filter aid added, and the mixture is heated to 65°C and refluxed for 2 hours for decolorization. In step (4), the feed flow rate is 180 kg / h, the evaporation temperature is 72°C, and the bottom liquid level is 550 mm. In step (5), the cooling rate is 1.5℃ / min, the stirring speed is 120r / min, and the temperature is kept constant for 2 hours after cooling to -3℃.

[0053] The external standard content of triphenylphosphine oxide in the distillation residue of the AVNA process was 57.80%, and the feed amount was 1000 kg, yielding 561.8 kg of high-purity triphenylphosphine oxide product. The specifications of other raw materials and process parameters were exactly the same as in Example 1.

[0054] Example 7 This embodiment provides a method for recovering high-purity triphenylphosphine oxide from AVNA production distillation residue, which differs from Example 1 in that: In step (1), 520 kg of saturated sodium chloride solution was added, the pH of the system was adjusted to 3.2, the stirring temperature was 40℃, the stirring speed was 320 r / min, and the stirring time was 55 min; In step (2), the mass ratio of the mixed solvent to toluene to methyl tert-butyl ether is 4:1, the mass ratio of the mixed solvent to the distillation residue is 2.8:1, the stirring speed is 480 r / min, and the stirring time is 100 min; In step (3), 3.5 kg of granular activated carbon and 1.2 kg of diatomaceous earth filter aid were added, and the mixture was heated to 40°C and refluxed for 3 hours for decolorization. In step (4), the feed flow rate is 160 kg / h, the evaporation temperature is 73°C, and the bottom liquid level is 500 mm. In step (5), the cooling rate is 0.8℃ / min, the stirring speed is 130r / min, and the temperature is kept constant for 4 hours after cooling to -3℃. In step (6), the drying temperature is 60℃, the vacuum degree is -0.094MPa, and the drying time is 5.5h.

[0055] The external standard content of triphenylphosphine oxide in the distillation residue of the AVNA process was 58.00%, and the feed amount was 1000 kg, yielding 563.8 kg of high-purity triphenylphosphine oxide product. The specifications of other raw materials and process parameters were exactly the same as in Example 1.

[0056] Comparative Example 1 This comparative example uses traditional direct leaching and natural cooling crystallization processes to treat the same AVNA distillation residue, without setting up a salt-dissolving acid-adjusting pretreatment step, a filter aid synergistic decolorization step, or a uniform cooling and constant temperature crystal growth step.

[0057] The specific steps are as follows: Take 1000 kg of the same batch of AVNA process distillation residue (triphenylphosphine oxide external standard content is 58.62%) as in Example 1, add 2500 kg of toluene directly, stir at 500 r / min for 120 min to dissolve, let stand, and take the upper organic phase; add 4 kg of granular activated carbon, reflux at 45℃ for 3 h for decolorization, and then filter with ordinary filter paper; concentrate the filtrate to saturation by atmospheric distillation, and then cool naturally to room temperature (cooling rate is about 5℃ / min), without a isothermal crystallization stage, centrifuge, and then vacuum dry at 70℃ for 5 h. 425.0 kg of triphenylphosphine oxide product is obtained. The specifications of the remaining raw materials are the same as in Example 1.

[0058] Comparative Example 2 The difference between this comparative example and Example 1 is as follows: In step (1), no saturated salt solution is added, only hydrochloric acid is added dropwise to adjust the pH of the system to 3.0. The other pretreatment parameters (stirring temperature 50℃, speed 350r / min, stirring time 45min, standing for 2h) are exactly the same as in Example 1. All process parameters in steps (2) to (6) are exactly the same as in Example 1.

[0059] The AVNA process distillation residue used was from the same batch as in Example 1 (triphenylphosphine oxide external standard content was 58.62%), with a feed amount of 1000 kg, yielding 515.9 kg of finished triphenylphosphine oxide.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: In step (2), toluene was used as the treatment solvent, without the addition of methyl tert-butyl ether. The solvent volume was 2500 kg, and the other treatment parameters (stirring speed 500 r / min, stirring time 120 min, standing time 2 h) were exactly the same as in Example 1. All process parameters in steps (1), (3) to (6) are exactly the same as in Example 1.

[0061] The AVNA process distillation residue used was from the same batch as in Example 1 (triphenylphosphine oxide external standard content was 58.62%), with a feed amount of 1000 kg, yielding 539.3 kg of finished triphenylphosphine oxide.

[0062] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: In step (3), no filter aid is added, only 4 kg of granular activated carbon is added for decolorization. The other decolorization parameters (heating to 45°C, constant temperature reflux decolorization for 3 hours, and precision negative pressure filtration) are exactly the same as in Example 1. All process parameters in steps (1), (2), (4) to (6) are exactly the same as in Example 1.

[0063] The AVNA process distillation residue used was from the same batch as in Example 1 (triphenylphosphine oxide external standard content was 58.62%), with a feed amount of 1000 kg, yielding 556.9 kg of finished triphenylphosphine oxide.

[0064] Comparative Example 5 The difference between this comparative example and Example 1 is as follows: In step (5), the traditional rapid cooling crystallization process is adopted, the cooling rate is 5℃ / min, no constant temperature crystal growth stage is set, and centrifugation is performed immediately after cooling to -3℃, with a stirring speed of 150r / min. All process parameters in steps (1) to (4) and (6) are exactly the same as in Example 1.

[0065] The AVNA process distillation residue used was from the same batch as in Example 1 (triphenylphosphine oxide external standard content was 58.62%), with a feed amount of 1000 kg, yielding 527.6 kg of finished triphenylphosphine oxide.

[0066] Experimental Example 1. Testing methods and reference standards (1) Determination of the purity of triphenylphosphine oxide: High performance liquid chromatography (HPLC) was used. The chromatographic column was an Agilent ZORBAX Eclipse XDB-C18 (4.6 mm × 250 mm, 5 μm), the mobile phase was methanol-water (70:30 v / v), the flow rate was 1.0 mL / min, the detection wavelength was 254 nm, the column temperature was 30 ℃, the injection volume was 20 μL, and the external standard method was used for quantification. The external standard content of triphenylphosphine oxide in the distillation residue of the raw material was determined under the same chromatographic conditions. The sample pretreatment was as follows: a quantitative amount of distillation residue was weighed, dissolved in methanol and quantitatively diluted, filtered through a 0.45 μm organic phase filter membrane, and injected for quantification by external standard method.

[0067] The HPLC chromatograms of the triphenylphosphine oxide products obtained in Examples 1-3 are shown below. Figure 1 , Figure 2 , Figure 3 As shown.

[0068] Determination of triphenylphosphine oxide content in the lower oily insoluble matter obtained after separation: Accurately weigh the oily insoluble matter, add methanol for ultrasonic extraction to fully transfer the triphenylphosphine oxide into the methanol phase, quantitatively transfer and make up to volume, filter through a 0.45 μm organic phase filter membrane, and detect under the above chromatographic conditions. Calculate using the external standard method; w (%) = c × V × D / (m × 10⁻⁶). 6 The concentration of TPPO in the test solution is calculated as c × 100%, where c is the concentration of TPPO in the test solution (μg / mL), V is the volume of the final solution (mL), D is the dilution factor (1 for undiluted solutions), and m is the sample weight (g). The percentage of the measured mass of triphenylphosphine oxide to the total mass of the weighed oily insoluble substance is taken as the mass fraction of triphenylphosphine oxide in the oily insoluble substance.

[0069] (2) Moisture determination: Refer to GB / T 6283-2008 "Determination of moisture content in chemical products by Karl Fischer method (general method)" and use a Karl Fischer moisture analyzer, with anhydrous methanol as solvent and Karl Fischer reagent as titrant.

[0070] (3) Yield calculation: The yield of triphenylphosphine oxide referred to in this application is based on the theoretical mass of triphenylphosphine oxide in the distillation residue and the total mass of the dried product obtained. Yield (%) = total mass of dried product / (mass of distillation residue × external standard content of triphenylphosphine oxide in the residue) × 100%; the actual purity of triphenylphosphine oxide in the product is determined separately by HPLC external standard method and labeled separately.

[0071] (4) Product appearance: Visually observe the color, shape and uniformity of the crystals under natural light, and record whether there are yellowing, clumping, fine powder or other phenomena.

[0072] The appearance of the triphenylphosphine oxide product obtained in Example 1 is as follows: Figure 4As shown, it is white and has uniform crystals; the product obtained in Comparative Example 1 has the following appearance. Figure 5 As shown, there is yellowing and clumping.

[0073] 2. Experimental Results and Data Table 1. Mass fraction of triphenylphosphine oxide in the oily insoluble matter after selective treatment

[0074] Results analysis: The mass fraction of triphenylphosphine oxide in the oily insoluble matter after extraction with a mixed solvent of toluene and methyl tert-butyl ether was only 0.09%~0.13%, indicating that triphenylphosphine oxide was fully dissolved in the mixed solvent and was lost very little with the oily insoluble matter.

[0075] The performance test results of each embodiment and comparative example are shown in Table 2 below: Table 2 Performance test results of each embodiment and comparative example

[0076] In summary, by adopting the full-process technology defined in this application, including pretreatment, selective treatment, decolorization and impurity removal, vacuum concentration, and segmented temperature-controlled crystal growth, the triphenylphosphine oxide products obtained in each embodiment have an HPLC purity of not less than 99.7%, a yield of not less than 97.0%, a moisture content of not more than 0.05%, a pure white appearance, uniform crystal size, and excellent and stable overall performance.

[0077] Comparative Example 1 employed a traditional direct dissolution and natural cooling crystallization process, without the salt-dissolution and acid-adjustment pretreatment, filter aid-assisted decolorization, and segmented temperature-controlled crystal growth steps. Its HPLC purity was 4.5% lower than Example 1, and its yield was 24.8% lower. The product was slightly yellowish and had uneven crystal size. The reasons for this are: the lack of pretreatment resulted in ineffective separation of quaternary phosphine salt and other ionic components, failure to break down the emulsion system, incomplete stratification, and severe impurity entrainment; the absence of a filter aid led to the permeation of fine activated carbon powder; and rapid natural cooling caused explosive nucleation, uneven crystal size, and impurity inclusion, all contributing to a significant decrease in purity and yield.

[0078] Comparative Example 2 omitted the addition of saturated salt solution and only used acid to adjust the pH for pretreatment. Its HPLC purity was 2.1% lower than that of Example 1, and its yield was 9.3% lower than that of Example 1. The product also exhibited clumping. The reason for this is that the lack of the high ionic strength demulsification effect of saturated salt solution meant that acid adjustment alone could not fully break down the stable emulsion system of the AVNA residue. This resulted in a blurred oil-water interface, water and water-soluble impurities trapped in the organic phase, which affected subsequent processing and crystallization, significantly reducing the yield and making the product prone to clumping.

[0079] Comparative Example 3 used toluene as the processing solvent without adding methyl tert-butyl ether for compounding. Its HPLC purity was 1.2% lower than that of Example 1, and its yield was 5.3% lower. The reasons for this are as follows: Toluene alone has insufficient polarity and density adjustment capabilities, resulting in a decreased selective dissolution ability for triphenylphosphine oxide. Some colloidal substances and polar impurities dissolved into the organic phase along with the triphenylphosphine oxide, leading to an increased burden on subsequent purification and a decrease in product purity. At the same time, the layering speed of the toluene-only system was slower and the layering was incomplete, causing some triphenylphosphine oxide to be lost with the lower insoluble matter and residual water, resulting in a decrease in yield.

[0080] Comparative Example 4 omitted the addition of filter aid and used only activated carbon for decolorization. Its HPLC purity was 0.9% lower than that of Example 1, its yield was 2.3% lower than that of Example 1, and the product appearance was slightly cloudy. The reason for this is that without the porous filter cake layer formed on the surface of the filter medium by the filter aid, the fine powder and trace suspended impurities of the granular activated carbon could not be effectively intercepted. Some of the fine powder passed through the filter and entered the decolorization solution, mixing into the product during the subsequent concentration and crystallization process, resulting in a decrease in product purity and a slightly cloudy appearance. At the same time, the fine powder that passed through the filter may have blocked the crystal faces, affecting crystal growth and indirectly causing a slight decrease in yield.

[0081] Comparative Example 5 used a traditional rapid cooling crystallization process (cooling rate 5℃ / min) without a constant-temperature crystal growth stage. Its HPLC purity was 1.7% lower than Example 1, and its yield was 7.3% lower, with finer crystals. The reasons for this are: rapid cooling caused a sharp increase in local supersaturation in the system, triggering explosive nucleation and producing a large number of fine crystals; the fine crystals have a large specific surface area, resulting in more surface-adsorbed impurities, and the mother liquor easily gets trapped between the crystals, leading to a decrease in product purity; without a constant-temperature crystal growth stage, small crystals cannot be transformed into large crystals through the Ostwald ripening mechanism, resulting in a wide crystal size distribution, poor quality, and easy loss of fine crystals during centrifugation, causing a significant decrease in yield.

[0082] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for recovering high-purity triphenylphosphine oxide from distillation residues in AVNA production, characterized in that, Includes the following steps: (1) Pretreatment: Add saturated salt solution to the distillation residue containing triphenylphosphine oxide in the AVNA process, add acidic solution dropwise to adjust the pH value of the system to ≤5, stir and let stand to separate the layers to obtain the organic phase; (2) Selective extraction: Add a mixed solvent of toluene and methyl tert-butyl ether to the organic phase, stir to selectively dissolve triphenylphosphine oxide in the mixed solvent, let stand and separate the lower oily insoluble matter and the residual aqueous phase, and collect the organic liquid containing triphenylphosphine oxide. (3) Decolorization and impurity removal: Add decolorizing agent and filter aid to the organic liquid, reflux at constant temperature for decolorization, and then filter to obtain decolorized liquid; (4) Vacuum concentration: The decolorizing liquid is fed into a scraped film evaporator and the mixed solvent is removed by vacuum distillation to obtain a saturated concentrate of triphenylphosphine oxide. (5) Segmented temperature-controlled crystal growth and centrifugation: The saturated concentrate of triphenylphosphine oxide is cooled at a constant speed and stirred at a low speed. After crystal growth at a constant temperature, the wet triphenylphosphine oxide product is obtained by centrifugation. (6) Vacuum drying: The wet triphenylphosphine oxide is vacuum dried to obtain high-purity triphenylphosphine oxide.

2. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, In step (1), the saturated salt solution is a saturated aqueous solution of sodium chloride or sodium sulfate, and the amount of saturated salt solution added is 45% to 65% of the mass of the distillation residue; The acidic solution is hydrochloric acid or acetic acid, and the pH of the system is adjusted to 2-5.

3. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, In step (1), the stirring temperature is 40~80℃, the stirring speed is 200~400r / min, the stirring time is 30~90min, and the settling time is 1~3h.

4. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, In step (2), the mass ratio of toluene to methyl tert-butyl ether in the mixed solvent is 3~5:1, and the mass ratio of the mixed solvent to the distillation residue is 2~3:1; The stirring speed is 300~500 r / min, the stirring time is 40~120 min, and the settling time is 0.5~2 h.

5. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, In step (3), the decolorizing agent is granular activated carbon or powdered activated carbon, and the filter aid is one or both of diatomaceous earth or cellulose filter aid.

6. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, In step (3), the amount of decolorizing agent added is 0.2% to 0.5% of the mass of the distillation residue, and the amount of filter aid added is 0.1% to 0.2% of the mass of the distillation residue. The constant temperature reflux temperature is 40~80℃, the reflux decolorization time is 1~4h, and the filtration adopts a precision negative pressure filtration method.

7. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, In step (4), the feed flow rate of the scraped film evaporator is 100~200kg / h, the evaporation temperature is 60~80℃, and the vacuum degree is ≥-97kPa; When the liquid level in the scraped evaporator reaches 400~800mm, stop feeding and start the circulating pump for concentration and distillation. Stop circulating feeding when the vacuum degree is ≥-99kPa.

8. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, In step (5), the uniform cooling rate is 0.5~2℃ / min, the temperature is reduced to 0~-5℃, the low-speed stirring speed is 50~150r / min, and the constant temperature crystal growth time is 2~6h.

9. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, In step (6), the vacuum drying temperature is 60~90℃, the vacuum degree is ≥-0.090MPa, and the drying time is 3~8h.

10. The method for recovering high-purity triphenylphosphine oxide according to claim 1, characterized in that, The obtained triphenylphosphine oxide had a moisture content of ≤0.05%, an HPLC purity of ≥99.7%, and a yield of ≥97.0%.

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