A method and system for processing a polymer intermediate
By combining a scraped film evaporator, an evaporation reactor, and a product separation tower, the problem of low utilization rate of unreacted oligomers and intermediates in the preparation of polyglycolic acid was solved, achieving efficient resource recovery and high yield of glycolic acid.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUO NENG YULIN CHEM CO LTD
- Filing Date
- 2026-01-08
- Publication Date
- 2026-06-02
AI Technical Summary
In existing technologies, the utilization rate of unreacted oligomers and intermediates during the preparation of polyglycolic acid is low, leading to material waste and increased production costs. Furthermore, the purification yield of glycolide is insufficient, making it difficult to achieve industrial application.
The process employs a scraped film evaporator and an evaporation reactor for primary and secondary evaporation treatment, combined with a dissolution reactor and a main reactor for dissolution and depolymerization reactions. Finally, the product is separated by distillation in a recovery product separation tower, decomposing it into methanol and methyl glycolate. The recovered solvent is used as washing liquid in the glycolide purification process.
This improved the yield of glycolic acid, reduced the waste of intermediate products, achieved effective recycling of resources, and enhanced the utilization rate and production efficiency of glycolide.
Smart Images
Figure CN122127225A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of chemical technology, and in particular relates to a method and system for processing polymer intermediates. Background Technology
[0002] Polyglycolic acid (PGA) is a synthetic polymer with good biodegradability and biocompatibility. It can be obtained by polymerizing glycolic acid (ester) monomers. However, the polyglycolic acid (PGA) obtained by this method has a very low molecular weight and a dark color, making it difficult to apply in practical applications. Therefore, to realize the industrial application of PGA, the ring-opening polymerization of glycolide is usually used in industry. This process requires the cleavage and cyclization reaction of methyl glycolate oligomers to generate glycolide. However, this cyclization stage has insufficient yield and produces a large amount of unreacted oligomers and intermediates, resulting in significant material waste and increased production costs.
[0003] For the aforementioned unreacted oligomers and intermediates, existing technologies typically employ recrystallization to extract glycolide. However, this purification method yields only 50%-60%, which presents significant limitations. On one hand, some glycolide is carried away by the washing liquid during the washing process, dissolving in the solvent to form a complex mixture with high acid content, making subsequent processing difficult. On the other hand, some glycolide undergoes metamorphic polymerization, forming oligomers that mix with the heterocyclic organic compounds generated in the reaction. These mixtures have high boiling points and are deposited at the bottom of the settling tank as heavy components. Due to excessive acid content, they cannot be returned to the crystallizer for repurification and can only be discharged as waste, further reducing the effective utilization rate of glycolide. Summary of the Invention
[0004] This application discloses a method and system for processing polymer intermediates, aiming to solve the technical problem of low effective utilization rate of unreacted oligomers and intermediates in the existing polyglycolic acid preparation process.
[0005] To achieve the above objectives, the technical solution of this application is: A first aspect of this application provides a method for processing a polymer intermediate, the method comprising: The polymer intermediate is fed into a scraped film evaporator for primary evaporation to obtain the first column bottom component; The first column bottom component is sent to an evaporation reactor for secondary evaporation treatment to obtain the second column bottom component; The second column bottom component is sent to a dissolution reactor containing methyl glycolate for dissolution treatment to obtain the fourth column bottom component; The fourth column bottom component is sent to the main reactor containing methanol for depolymerization reaction to obtain the fifth column bottom component; The components from the bottom of the fifth column are sent to a recovery product separation column for distillation and separation to obtain methanol and methyl glycolate.
[0006] In conjunction with the first aspect, preferably, the first column bottom component is sent to an evaporation reactor for secondary evaporation treatment to obtain a second column top component; The second top component is fed into an evaporative distillation column for high-temperature distillation, including: After the high-temperature distillation process, the third top component and the third bottom component are obtained; the third bottom component is refluxed into the evaporation reactor; the third top component is condensed and then enters the reflux tank.
[0007] Preferably, in conjunction with the first aspect, the method further includes: The first top component of the scraped film evaporator, after pretreatment, is compressed, and the third top component is compressed separately, and then they are both sent into the reflux tank. The material in the reflux tank is discharged and recovered as a light component in one path, and returned to the evaporation distillation column in the other path.
[0008] Preferably, in conjunction with the first aspect, the method further includes: The first portion of the methanol separated by the recovery product separation tower is added as a raw material to the main reactor for depolymerization reaction; the second portion of the methanol separated by the recovery product separation tower is returned to the recovery product separation tower as reflux liquid; and the third portion of the methanol separated by the recovery product separation tower is output as product. A portion of the methyl glycolate separated by the recovery product separation tower is added as a solvent to the dissolution reactor for dissolution, while the other portion is output as product.
[0009] Preferably, in conjunction with the first aspect, the polymer intermediate is glycolide and a solid-phase intermediate dissolved in the washing liquid during the production of polyglycolic acid; The content of glycolide is 60-70%.
[0010] Preferably, in conjunction with the first aspect, the temperature of the scraped film evaporator is 60-80 °C and the pressure is 5-6 kPa(A); and / or, The temperature of the evaporation reactor is 190-200 °C; and / or, The temperature of the evaporative distillation column is 100-110 ℃.
[0011] Preferably, in conjunction with the first aspect, the pressure of the dissolution reactor is 0.5-0.8 MPa, and the temperature is 215-225℃; and / or The main reactor has a pressure of 0.8-1.0 MPa and a temperature of 160-165 ℃; and / or The product recovery separation tower operates under negative pressure at a pressure of 35-40 kPa (A).
[0012] Preferably, in conjunction with the first aspect, when the fifth column bottom component is sent to the recovery product separation column for distillation separation, it includes: The bottom distillate is methyl glycolate with a purity ≥99.2%; the top distillate is methanol with a purity ≥99.5%.
[0013] A second aspect of this application provides a processing system for polymer intermediates, used to implement the processing method for polymer intermediates described in the first aspect, comprising: A scraped film evaporator is used for primary evaporation treatment of polymer intermediates. The scraped film evaporator includes a first column bottom component outlet, which is connected to the feed inlet of the evaporation reactor. An evaporation reactor is connected to the first column bottom component outlet, the evaporation reactor is used to perform secondary evaporation treatment on the first column bottom component, and the evaporation reactor includes a second column bottom component outlet; A dissolving reactor containing methyl glycolate is connected to the outlet of the second column bottom component for dissolving the second column bottom component. The dissolving reactor also includes a fourth column bottom component outlet. The main reactor contains methanol and is connected to the outlet of the fourth column bottom component. The main reactor is used for the depolymerization reaction of the fourth column bottom component and includes an outlet of the fifth column bottom component. A recovery separation tower is connected to the bottom component outlet of the fifth tower. The recovery separation tower is used to perform distillation separation on the bottom component of the fifth tower. The recovery separation tower includes a methanol outlet and a methyl glycolate outlet.
[0014] Preferably, in conjunction with the second aspect, it also includes: An evaporative distillation column is connected to the outlet of the second top component, and the evaporative distillation column is used to perform high-temperature distillation treatment on the second top component; The condenser is connected to the top component outlet of the first column, the top component outlet of the third column, the top outlet of the recovery product separation column, and the bottom outlet of the column, respectively, for condensing each component. A reflux tank, connected to the condenser, is used to receive the components condensed by the condenser and to perform gas-liquid separation on the components; A reboiler, connected to the bottom of the recovery product separation tower, is used to provide heat for the distillation separation of the recovery product separation tower.
[0015] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following: The processing method provided in this application decomposes the product into methanol and methyl glycolate through evaporation, dissolution, and depolymerization reactions. The solvent recovered by the scraped-film evaporator and evaporation reactor can be used as a washing liquid in the glycolide purification process. The evaporated glycolide and heterocyclic organic compounds have high viscosity, making them difficult to transport and directly involved in the reaction. Therefore, methyl glycolate needs to be added for dissolution. By controlling the pressure and temperature of the dissolution reactor, all glycolide and heterocyclic organic compounds can be completely dissolved before being fed into the main reactor containing excess methanol. This increases the residence time and ensures a complete reaction. The resulting mixture flows under pressure into a product recovery separation tower, which operates under negative pressure to thoroughly separate the feed components, separating methyl glycolate from the bottom distillate and methanol from the top distillate. Methanol is added as a raw material to the main reactor for depolymerization, while methyl glycolate is added as a solvent to the dissolution reactor, avoiding waste of intermediate products and indirectly improving the glycolic acid yield, thus turning waste into treasure. Attached Figure Description
[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 A process flow diagram of the polymer intermediate processing system provided in the embodiments of this application. Detailed Implementation
[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0019] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.
[0020] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.
[0021] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.
[0022] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.
[0023] It should be noted that all raw materials and / or reagents in the embodiments of this application were purchased on the market or prepared according to conventional methods known to those skilled in the art.
[0024] In a first aspect, embodiments of this application provide a method for processing a polymer intermediate, the method comprising: The polymer intermediate is fed into a scraped film evaporator for primary evaporation to obtain the first column bottom component; The first column bottom component is sent to an evaporation reactor for secondary evaporation treatment to obtain the second column bottom component; The second column bottom component is sent to a dissolution reactor containing methyl glycolate for dissolution treatment to obtain the fourth column bottom component; The fourth column bottom component is sent to the main reactor containing methanol for depolymerization reaction to obtain the fifth column bottom component; The components from the bottom of the fifth column are sent to a recovery product separation column for distillation and separation to obtain methanol and methyl glycolate.
[0025] In this embodiment, a first-stage layered evaporation process is performed in a scraped-film evaporator to remove most of the solvent. A second-stage high-temperature evaporation process is then performed, where the solvent and other light components are removed through a short period of high-temperature contact. The remaining glycolide and heterocyclic organic compounds are discharged from the bottom of the vessel to participate in the depolymerization reaction. The depolymerization vessel is operated under pressure. First, the glycolide and heterocyclic organic compounds are dissolved by stirring while dissolving to ensure they are fully dissolved in methyl glycolate. This solution is then fed into the main reactor for reaction. Before feeding into the main reactor, excess methanol is added according to the feed rate. The reaction occurs immediately after feeding, and the reaction products are methyl glycolate and methanol. These are then sent to a separation tower for distillation separation based on the different volatility of methanol and methyl glycolate.
[0026] In this embodiment, the polymer intermediates are glycolide dissolved in the washing liquid during the polyglycolic acid (PGA) production process and heterocyclic intermediates precipitated in the settling tank after washing. Glycolide is a component dissolved in the washing liquid used to wash unreacted monomers and residual impurities after the PGA polymerization process. It is mainly composed of incompletely polymerized glycolide and is the core monomer of PGA, with a small amount of low-polymerization linear glycolic acid oligomers also mixed in.
[0027] The heterocyclic intermediates in the settling tank are solid components that are precipitated and separated in the settling tank after the washing process. They are mainly heterocyclic intermediates generated during the reaction, such as derivatives containing ester rings and ether rings. They are formed by the cyclization reaction of glycolic acid monomers or glycolide under high temperature and local high concentration conditions. They also contain some glycolic acid polymers with high degree of polymerization and extremely low solubility, which may be dimers, trimers, tetramers, polymers, etc.
[0028] It should be noted that the depolymerization and transformation of intermediates through alcoholysis follows a reaction mechanism of oligomer / glycolic acid + excess methanol → methyl glycolate + methanol. Specifically, the oligomers (dimers, trimers, tetramers, etc.) in the intermediates are all linear structures with repeating units linked by ester bonds; glycolate is a cyclic dimer. Both possess the cleavable nature of ester bonds, providing the structural basis for the alcoholysis reaction. Methanol acts as the alcoholysis agent, and its hydroxyl groups (-OH) attack the ester bonds (-COO-) in the oligomer or glycolate molecules, resulting in a nucleophilic substitution reaction that breaks the long chain or cyclic structure, generating a single-structure methyl glycolate (an esterification of glycolic acid and methanol). This reaction is reversible; the forward reaction is depolymerization alcoholysis, and the reverse reaction is the polymerization of methyl glycolate. Excess methanol can enhance the forward reaction in two ways: first, it increases the concentration of reactants and accelerates the rate of ester bond breaking; second, excess methanol can inhibit the reverse polymerization reaction and push the reaction equilibrium to completely shift towards the formation of methyl glycolate, ensuring the full conversion of the intermediate.
[0029] In this embodiment, dichloromethane, with a boiling point of 39.8 °C, is used as the solvent. It is a good solvent for glycolide, capable of washing and dissolving both heterocyclic organic compounds and glycolide itself, leading to some glycolide loss and a lower glycolide yield. Through evaporation, dissolution, and depolymerization reactions, it is ultimately decomposed into methyl glycolate, which serves as a raw material for PGA production, avoiding waste of intermediate products and indirectly improving the glycolic acid yield. The dichloromethane solvent recovered through the scraped-film evaporator and evaporation reactor can be used as a washing liquid in the glycolide purification process. The evaporated glycolide and heterocyclic organic compounds have high viscosity, making them difficult to transport and directly participate in the reaction. Therefore, they need to be dissolved by adding methyl glycolate, which has a higher boiling point. The dissolution reactor pressure is controlled at 0.5-0.8 MPa and the temperature at 215-225 ℃. Under these operating conditions, the glycolide and heterocyclic organic compounds can be completely dissolved. The solution is then fed into a main reactor containing excess methanol, with the pressure controlled at 0.8-1.0 MPa and the temperature at 160-165 ℃. By increasing the residence time, the reaction is fully realized. The reaction mixture flows by pressure into a recovery product separation tower. The recovery product separation tower operates under negative pressure, with the pressure controlled at 35-40 kPa(A). The reboiler in the tower bottom is heated by 1.0 MPa steam. The tower internals use structured packing to increase the heat and mass transfer area, thus thoroughly separating the mixed feed components. High-purity methyl glycolate is separated from the bottom effluent, and high-purity methanol is separated from the top effluent.
[0030] It should be noted that the polymer intermediates in this application are dissolved by adding dichloroethane before entering the scraped-film evaporator. Dichloroethane can both wash and dissolve heterocyclic organic compounds in glycolide and dissolve glycolide itself, resulting in some glycolide loss and a lower glycolide yield. The dichloroethane solvent recovered through the scraped-film evaporator and evaporation reactor can be used as a washing liquid in the glycolide purification process.
[0031] It should be noted that the solvent with a high concentration of glycolide is fed into a scraped-film evaporator. The scraped-film evaporator uses 0.2 MPa, 120 °C steam for stratified heating, primarily to distill off the lighter solvent components from the material. The preferred temperature of the scraped-film evaporator is 60-80 °C to prevent glycolide from being carried into the lighter components at the top of the column, affecting the purity of the recovered solvent. The scraped-film evaporator has three heating layers: a lower layer at 75-80 °C, a middle layer at 70-75 °C, and an upper layer at 60-65 °C. Under the action of the distributor and scraper in the scraped-film evaporator, the lighter solvent components in the feed are distilled off first. After condensation, they enter the reflux tank of the evaporative distillation column, where they mix with the reflux liquid. Part of this mixture is returned to the evaporative distillation column as reflux liquid, and the other part is returned to the glycolide purification unit for washing as recovered solvent. The heavier components at the bottom of the scraped-film evaporator are pressurized by the column bottom pump and sent to the evaporation reactor.
[0032] It should be noted that the evaporation reactor uses a heat transfer oil jacket for heating, with a preferred temperature of 190-200 ℃ and a pressure of atmospheric pressure. Higher temperatures and shorter residence times allow for the instantaneous high-temperature evaporation of the solvent in the heavy components. An evaporative distillation column is set at the top, with a top pressure of 35-45 kPa(A), a top temperature of 100-110 ℃, and a bottom temperature of 40-50 ℃. After the evaporated light vapor component enters the evaporative distillation column, it exchanges heat and mass with the reflux liquid on the trays, increasing the purity of the solvent at the top. The heavy components at the bottom return to the evaporative distillation column under gravity. The solvent with higher purity at the top is condensed in the condenser and enters the reflux tank, where it mixes with the vapor phase condenser from the top of the scraped film evaporator. Part of this mixture is returned to the distillation column as reflux liquid, and the other part is sent out as solvent. Under the instantaneous high temperature in the evaporation reactor, the light vapor solvent is almost completely evaporated, increasing the concentration of the remaining heavy components at the bottom. These components are then pressurized by a melt pump and sent to the dissolution reactor.
[0033] It should be noted that the function of the dissolving reactor is to dissolve the heavy components from the bottom of the evaporation reactor. The dissolving solution is methyl glycolate. Under pressure, all the heavy organic components dissolve. The temperature of the dissolving reactor is controlled at 0.5-0.8 MPa and 215-225 °C. The dissolved oligomer mixture flows into the main reactor by gravity. The temperature of the main reactor is controlled at 160-165 °C and 0.8-1.0 MPa, with a residence time of 3 h. In the main reactor, the oligomer mixture undergoes a depolymerization reaction, and the reaction products are methyl glycolate monomers and methanol.
[0034] It should be noted that the reaction products from the main reactor, after passing through the feed cooler, enter the recovery product separation tower under pressure. The main function of the recovery product separation tower is to distill and separate the reaction products from the main reactor into methanol and methyl glycolate with higher purity, which are then sent to the tank area for storage. The recovery product separation tower is heated by steam at 1.0 MPa and 158 °C.
[0035] It should be noted that the scraped-film evaporator uses pipeline feeding, with the feed in a liquid state containing glycolide and heterocyclic organic compounds. After pretreatment in the scraped-film evaporator, the viscosity of the material gradually increases. It is then pumped into the evaporation reactor, where the high temperature effectively evaporates most of the solvent, leaving a slurry with high viscosity. This slurry is then pumped into the dissolution reactor, where methyl glycolate is added for dissolution, resulting in a lower viscosity. Depending on the equipment layout, the material can flow by gravity to the main reactor, where a depolymerization reaction occurs, producing methyl glycolate monomer and methanol. Under pressure in the main reactor, the product flows by gravity to the recovery product separation tower. To increase the mass and heat transfer area of the separation tower, a packed tower is used to separate the product into higher purity methyl glycolate and methanol, which are then stored in tank areas.
[0036] It should be noted that this application uses methyl glycolate for dissolution without introducing new components, which facilitates subsequent separation.
[0037] It should be noted that the polymer intermediates mainly consist of various oligomers, glycolide, and solvents. First, the solvent is dissolved and removed from the mixture. Because the solvent is a light component with a low boiling point and high partial pressure, it must be completely removed beforehand. This application uses a scraped-film evaporator and an evaporation reactor for this removal, and the removed solvent is recycled. After the solvent is completely removed, the remaining heavy components have high boiling points and high viscosity. To facilitate transport and dispersion in the reaction, they need to be dissolved and diluted before entering the main reactor. This application uses methyl glycolate for dissolution because methyl glycolate is also a reaction product. Therefore, to avoid introducing a third component, methyl glycolate is used as the solvent. The solvent is then sent to the main reactor for the reaction. An excess of methanol is added to the main reactor for the reaction; the methanol must be in excess. The reaction product enters a recovery product separation tower for methanol and methyl glycolate distillation separation. Methanol is recycled to participate in the main reactor reaction, and methyl glycolate is sent to the tank farm as a recovered product.
[0038] A second aspect of this application provides a processing system for polymer intermediates, used to implement the processing method for polymer intermediates described in the first aspect, comprising: A scraped-film evaporator is used for primary evaporation of polymer intermediates. The scraped-film evaporator includes a first reboiler component outlet connected to the feed inlet of the evaporation reactor; an evaporation reactor connected to the first reboiler component outlet for secondary evaporation of the first reboiler component, the evaporation reactor including a second reboiler component outlet; an evaporative distillation column connected to the second top component outlet for high-temperature distillation of the second top component; a dissolution reactor containing methyl glycolate connected to the second reboiler component outlet for dissolving the second reboiler component, the dissolution reactor including a fourth reboiler component outlet; a main reactor containing methanol connected to the fourth reboiler component outlet for depolymerization of the fourth reboiler component, the main reactor including a fifth reboiler component outlet; and a recovery separation column connected to the fifth reboiler component outlet for distillation separation of the fifth reboiler component, the recovery separation column including a methanol outlet and a methyl glycolate outlet. A condenser is connected to the top component outlet of the first column, the top component outlet of the third column, the top outlet of the recovery product separation column, and the bottom outlet of the column, respectively, for condensing each component; a reflux tank is connected to the condenser to receive the components condensed by the condenser and to perform gas-liquid separation of the components; a reboiler is connected to the bottom of the recovery product separation column to provide heat for the distillation separation of the recovery product separation column.
[0039] The processing method of this application will be illustrated below through application examples.
[0040] Example 1 For a detailed description of the process of the embodiments of this application, please refer to [link / reference]. Figure 1 The process flow diagram of the polymer intermediate processing method provided in this application embodiment is illustrated in this example, which takes an annual processing capacity of 100,000 tons of mixed feedstock as an example. The method specifically includes the following steps: S101: The upstream mixed feed is dissolved in dichloromethane and then fed into the scraped film evaporator (70 ℃, 5 KPa (A)) at a rate of 12 t / h, 0.7 MPa (A), 40 ℃.
[0041] S102: The top component enters the reflux tank 1 after passing through condenser 1, while the bottom component, pressurized by pump 1, enters the evaporation reactor (100 ℃, 40 KPa) for a residence time of 60 min, undergoing high-temperature evaporation. The more volatile component (i.e., the second top component) is discharged from the top of the evaporation reactor and sent to the evaporative distillation column; the less volatile component (i.e., the second bottom component) is discharged from the bottom of the evaporation reactor and sent to the dissolution reactor via pump 3. The light component at the top of the evaporative distillation column enters condenser 2 and also the reflux tank, and after being pumped by pump 2, it enters the evaporative distillation column.
[0042] S103: Methyl glycolate (purity ≥99.0%) is added to the dissolving reactor in advance, and the amount added is twice the mass of the second column bottom component; the operating parameters of the dissolving reactor are set as follows: stirring speed 200 r / min, operating pressure 0.6 MPa, heating temperature 220 ℃, and heat transfer oil is used for heating; the second column bottom component stays in the dissolving reactor for 90 min, and after being fully dissolved, a mixture (i.e., the fourth column bottom component) is obtained and sent to the main reactor.
[0043] S104: Methanol (purity ≥99.5%) is continuously fed into the main reactor. The methanol feed rate is controlled at a methanol-to-total ester molar ratio of 10:1 to ensure excess methanol and inhibit reverse polymerization. The operating parameters of the main reactor are set as follows: stirring speed 150 r / min, operating pressure 0.9 MPa, and reaction temperature 162 ℃ maintained by a steam heating jacket. The fourth column bottom component stays in the main reactor for 120 min and undergoes a depolymerization reaction. The reaction process is: oligomer / glycolic acid + excess methanol → methyl glycolate + methanol, which is essentially the reverse reaction of methyl glycolate polymerization. After the reaction is completed, the fifth column bottom component is obtained and sent to the recovery product separation tower after being depressurized to 0.3 MPa.
[0044] S105: The recovery product separation tower operates under negative pressure. Operating parameters are set as follows: bottom temperature 120℃ (heated by reboilers 1 and 2), top temperature 65℃, and operating pressure 38 kPa(A). The bottom components of the fifth tower undergo distillation separation within the packed bed. Top distillate: The main component is methanol. After condensation in top condenser 4 to 40℃, it enters reflux tank 2. The first portion is returned to the tower as reflux liquid via pump 4. The second portion is fed to the main reactor as methanol feed, recycled as raw material for the depolymerization reaction. The third portion is collected as qualified product at a rate of 18 t / h, with a methanol purity ≥99.5%. Bottom distillate: The main component is methyl glycolate. After cooling to 80℃ in bottom condenser 3, it is collected at a rate of 22 t / h, with a methyl glycolate purity ≥99.2%. A portion is added as a solvent to the dissolution reactor for dissolution, and the other portion is output as product.
[0045] This embodiment operated continuously for 72 hours, processing 900 tons of polymer intermediate raw materials, ultimately producing 300 tons of qualified methanol and 1200 tons of methyl glycolate. The total conversion rate of glycolide and oligomers in the polymer intermediates reached 98.5%, the methanol recycling rate reached 92%, and the purity of the methyl glycolate product met the requirements for industrial applications (≥99.0%). Compared with traditional processing methods, this significantly improved resource recovery and utilization. It should be noted that methanol participates in the reaction as a reactant. The recovery product separation tower separates the excess methanol remaining after the reaction. This portion of methanol needs to be recycled back to the main reactor to continue participating in the reaction; any insufficient amount needs to be supplemented with fresh methanol. A portion of the separated methyl glycolate product is sent to the dissolving tank for dissolution. This portion of methyl glycolate does not participate in the reaction; theoretically, the inflow and outflow are balanced, so the amount collected from the bottom of the tower is the recovered product.
[0046] Therefore, the processing method provided in this application decomposes methanol and methyl glycolate through evaporation, dissolution, and depolymerization reactions. The generated methanol is added as a raw material to the main reactor for depolymerization, and methyl glycolate is added as a solvent to the dissolution reactor, thus avoiding waste of intermediate products, indirectly improving the yield of glycolic acid, and turning waste into treasure.
[0047] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.
[0048] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.
Claims
1. A method for processing polymer intermediates, characterized in that, The method includes: The polymer intermediate is fed into a scraped film evaporator for primary evaporation to obtain the first column bottom component; The first column bottom component is sent to an evaporation reactor for secondary evaporation treatment to obtain the second column bottom component; The second column bottom component is sent to a dissolution reactor containing methyl glycolate for dissolution treatment to obtain the fourth column bottom component; The fourth column bottom component is sent to the main reactor containing methanol for depolymerization reaction to obtain the fifth column bottom component; The components from the bottom of the fifth column are sent to a recovery product separation column for distillation and separation to obtain methanol and methyl glycolate.
2. The method for processing polymer intermediates according to claim 1, characterized in that, The first column bottom component is sent to an evaporation reactor for secondary evaporation treatment to obtain the second column top component; The second top component is fed into an evaporative distillation column for high-temperature distillation, including: After the high-temperature distillation process, the third top component and the third bottom component are obtained; the third bottom component is refluxed into the evaporation reactor; the third top component is condensed and then enters the reflux tank.
3. The method for processing polymer intermediates according to claim 2, characterized in that, The method further includes: After the first top component of the scraped film evaporator is pretreated and the third top component is condensed, they are both fed into the reflux tank. The material in the reflux tank is discharged and recovered as a light component in one path, and returned to the evaporation distillation column in the other path.
4. The method for processing polymer intermediates according to claim 1, characterized in that, The method further includes: The first portion of the methanol separated by the recovery product separation tower is added as a raw material to the main reactor for depolymerization reaction; the second portion of the methanol separated by the recovery product separation tower is returned to the recovery product separation tower as reflux liquid; and the third portion of the methanol separated by the recovery product separation tower is output as product. A portion of the methyl glycolate separated by the recovery product separation tower is added as a solvent to the dissolution reactor for dissolution, while the other portion is output as product.
5. The method for processing polymer intermediates according to claim 1, characterized in that, The polymer intermediate is glycolide and solid-phase intermediate dissolved in the washing liquid during the production of polyglycolic acid; The content of glycolide is 60-70%.
6. The method for processing polymer intermediates according to claim 1, characterized in that, The temperature of the scraped film evaporator is 60-80℃, and the pressure is 5-6 kPa(A); and / or, The temperature of the evaporation reactor is 190-200 °C; and / or, The temperature of the evaporative distillation column is 100-110 ℃.
7. The method for processing polymer intermediates according to claim 1, characterized in that, The pressure of the dissolution reactor is 0.5-0.8 MPa, and the temperature is 215-225 ℃; and / or The main reactor has a pressure of 0.8-1.0 MPa and a temperature of 160-165 ℃; and / or The product recovery separation tower operates under negative pressure at a pressure of 35-40 kPa (A).
8. The method for processing polymer intermediates according to claim 1, characterized in that, When the fifth column bottom component is sent to the recovery product separation column for distillation separation, the following steps are included: The bottom distillate is methyl glycolate with a purity ≥99.2%; the top distillate is methanol with a purity ≥99.5%.
9. A processing system for polymer intermediates, characterized in that, The system is used to implement the method for processing the polymer intermediate according to any one of claims 1-8, comprising: A scraped film evaporator is used for primary evaporation treatment of polymer intermediates. The scraped film evaporator includes a first column bottom component outlet, which is connected to the feed inlet of the evaporation reactor. An evaporation reactor is connected to the first column bottom component outlet, the evaporation reactor is used to perform secondary evaporation treatment on the first column bottom component, and the evaporation reactor includes a second column bottom component outlet; A dissolving reactor containing methyl glycolate is connected to the outlet of the second column bottom component for dissolving the second column bottom component. The dissolving reactor also includes a fourth column bottom component outlet. The main reactor contains methanol and is connected to the outlet of the fourth column bottom component. The main reactor is used for the depolymerization reaction of the fourth column bottom component and includes an outlet of the fifth column bottom component. A recovery separation tower is connected to the bottom component outlet of the fifth tower. The recovery separation tower is used to perform distillation separation on the bottom component of the fifth tower. The recovery separation tower includes a methanol outlet and a methyl glycolate outlet.
10. The processing system for polymer intermediates according to claim 9, characterized in that, Also includes: An evaporative distillation column is connected to the outlet of the second top component, and the evaporative distillation column is used to perform high-temperature distillation treatment on the second top component; The condenser is connected to the top component outlet of the first column, the top component outlet of the third column, the top outlet of the recovery product separation column, and the bottom outlet of the column, respectively, for condensing each component. A reflux tank, connected to the condenser, is used to receive the components condensed by the condenser and to perform gas-liquid separation on the components; A reboiler, connected to the bottom of the recovery product separation tower, is used to provide heat for the distillation separation of the recovery product separation tower.