A method for recycling by-products of waste polyester alcoholysis

Abstract

The present invention provides a method for recycling by-products of waste polyester alcoholysis, comprising the following steps: S1) Mix porous boron nitride micropowder, crown ether and water, perform hydrothermal deposition treatment and then freeze-dry to obtain a solid powder material; ball-mill the solid powder material to obtain a porous boron nitride@crown ether hybrid material; S2) Perform an alcoholysis reaction on waste polyester, ethylene glycol and a catalyst potassium carbonate, and add the hybrid material to the obtained reaction solution. The present application also provides a preparation method of the porous boron nitride@crown ether hybrid material. In the method for recycling by-products of waste polyester alcoholysis of the present application, the introduction of the porous boron nitride@crown ether hybrid material combines the strong metal ion adsorption property of porous BN with the selective metal complexation of crown ether, improves the removal rate of potassium ions in the alcoholysis reaction solution, overcomes the molecular chain capping effect caused by potassium ions in the subsequent polymerization process of the depolymerization product, and has important industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of waste polyester recycling, and particularly to a method for recycling by-products of waste polyester alcoholysis. Background Art

[0002] Polyethylene terephthalate (PET), as a thermoplastic polyester material, has been widely used in many fields such as fibers, plastics, and films due to its excellent heat resistance, mechanical properties, chemical stability, electrical insulation, and wear resistance. However, with the continuous expansion of the application scope of PET products and the continuous growth of production capacity, the cumulative amount of waste PET is gradually increasing, which not only causes serious waste of resources but also causes significant environmental pollution. Using chemical recycling technology to depolymerize waste PET into small molecule monomers and preparing high-performance recycled products through subsequent polymerization processes has important economic and practical significance for realizing the circular recycling of waste PET. Among many chemical recycling methods, the glycol alcoholysis method can effectively depolymerize waste PET into bis(2-hydroxyethyl) terephthalate (BHET). This reaction has mild conditions, good safety, and high product yield, making it one of the key technologies for recycling waste PET.

[0003] However, in the glycol alcoholysis process of waste polyester, due to the randomness of the PET molecular chain breakage position and the incomplete depolymerization reaction, and in addition, the product BHET is prone to etherification reaction at high temperature, a series of by-products with low degrees of polymerization will be produced in addition to BHET. In addition, potassium carbonate, as an economical, environmentally friendly, low-toxic, and highly efficient catalyst, has been widely used in the depolymerization reaction. However, due to its property of being easily soluble in the alcohol depolymerization solution, it will remain in the depolymerization by-products in a small amount. When using these depolymerization by-products as raw materials to prepare recycled resins, the potassium ions released by the residual potassium carbonate act as Lewis acids, which will severely inhibit the molecular chain viscosity-increasing reaction. At the same time, the potassium ions will also undergo nucleophilic-electrophilic reactions with the ester groups on the resin molecular chain, inducing molecular chain degradation, seriously affecting the stability of the polymerization reaction and the improvement of the polymer viscosity, making it difficult to recycle a large amount of depolymerization by-products. Although attempts have been made to shield potassium ions by adding metal chelating agents such as crown ethers online, the effect is not ideal, and such metal chelating agents will block the active centers of the polymerization catalyst during the reaction, further reducing the polymerization efficiency.

[0004] Therefore, there is an urgent need to invent a new material and method to achieve the efficient and selective removal of potassium ions during the chemical recycling of waste polyester. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a method for recycling by-products of waste polyester alcoholysis. The method provided by this application can efficiently absorb and shield potassium ions and has a high potassium ion removal rate.

[0006] In view of this, the present application provides a method for recycling by-products of waste polyester alcoholysis, comprising the following steps:

[0007] S1) Mix porous boron nitride micropowder, crown ether and water, perform hydrothermal deposition treatment and then freeze-dry to obtain a solid powder material;

[0008] Ball-mill the solid powder material to obtain a porous boron nitride@crown ether hybrid material;

[0009] S2) Perform alcoholysis reaction on waste polyester, ethylene glycol and catalyst potassium carbonate, and add the hybrid material to the obtained reaction solution to remove potassium ions in the reaction solution.

[0010] Preferably, the preparation method of the porous boron nitride micropowder is specifically as follows:

[0011] Mix a boron source, a nitrogen source, a pore-forming agent and water, heat and then dry to obtain a boron nitride precursor;

[0012] Grind the boron nitride precursor and then calcine it to obtain porous boron nitride micropowder.

[0013] Preferably, the boron source includes one or more of boric acid, ammonia borane, metaboric acid, boron chloride, boron oxide, boron sulfide and sodium borohydride; the nitrogen source includes one or more of urea, melamine, sodium azide, dicyandiamide and sodium amide; the pore-forming agent includes one or more of zinc acetate, nickel sulfate, cobalt sulfate, iron sulfate, copper sulfate and zinc sulfate; the mass ratio of the boron source to the nitrogen source is (1.10~2.50):1; the calcination temperature is 500~1500°C and the time is 3~10h; the calcination is carried out in a protective atmosphere, and the protective atmosphere includes one of nitrogen and argon.

[0014] Preferably, the crown ether includes one or more of 18-crown-6, dibenzo-18-crown-6, dibenzo-30-crown-10, 15-crown-5 and cyclohexano-18-crown-6, and the mass ratio of the porous boron nitride micropowder to the crown ether is 10:(3~8).

[0015] Preferably, in step S1), the masses of the grinding beads during the ball-milling process are 2.5g, 10g, 14g, 15g, 55g respectively, and the quantity ratio is (14~16):(9~11):(4~6):(4~6):(2~4); the rotation speed of the ball-milling is 300~500r / min and the time is 10~30h.

[0016] Preferably, in step S2), the waste polyester includes one or more of waste polyester fibers, waste polyester plastics and waste polyester films.

[0017] Preferably, the mass ratio of the waste polyester, the ethylene glycol and the potassium carbonate is 1:(1.5 - 4.0):(0.015 - 0.05), the temperature of the alcoholysis reaction is 150 - 250 °C, and the time is 1.5 - 5 h.

[0018] Preferably, after adding the hybrid material, stirring and secondary filtration are further included, and the stirring rate is 50 - 200 r / min.

[0019] The present application also provides a preparation method of a porous boron nitride@crown ether hybrid material, comprising the following steps:

[0020] Mix the porous boron nitride fine powder, the crown ether and water, and obtain a solid powdery material after freeze-drying;

[0021] Ball-mill the solid powdery material to obtain a porous boron nitride@crown ether hybrid material.

[0022] Preferably, the mass ratio of the porous boron nitride fine powder and the crown ether is 10:(3 - 8).

[0023] The present application provides a method for recycling waste polyester alcoholysis by-products. First, mix the porous boron nitride fine powder, the crown ether and water. After hydrothermal deposition, the crown ether is evenly adsorbed and deposited on the surface layer of the porous boron nitride, and then freeze-dry to stabilize the structure to obtain a solid powdery material. Then ball-mill the solid powdery material to refine the material particles and enhance the interfacial bonding force between the porous boron nitride and the crown ether, obtaining a porous boron nitride@crown ether hybrid material. Then, utilize the unique powdery porous structure of the porous boron nitride@crown ether hybrid material to efficiently adsorb and chelate metal potassium ions after the waste polyester alcoholysis method, so that the potassium ions are effectively shielded and removed, realizing the efficient selective removal of potassium ions in the process of chemically recycling waste polyester. Specific embodiments

[0024] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with the examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0025] In view of the problem that the residual potassium ions in the waste polyester alcoholysis by-products in the prior art affect the recycling of the alcoholysis by-products, the present application provides a method for recycling waste polyester alcoholysis by-products. By introducing a porous boron nitride@crown ether hybrid material, its unique powdery porous structure shows high-efficiency adsorption and chelation ability for metal potassium ions in the process of chemically recycling waste polyester, realizing the efficient removal of potassium ions in the process of recycling waste polyester alcoholysis. Specifically, the embodiments of the present invention disclose a method for recycling waste polyester alcoholysis by-products, comprising the following steps:

[0026] S1) Mix porous boron nitride micropowder, crown ether and water, freeze-dry after hydrothermal deposition treatment to obtain a solid powder material;

[0027] Ball-mill the solid powder material to obtain a porous boron nitride@crown ether hybrid material;

[0028] S2) Perform alcoholysis reaction on waste polyester, ethylene glycol and catalyst potassium carbonate, and add the hybrid material to the obtained reaction solution to remove potassium ions in the reaction solution.

[0029] In this application, first, porous boron nitride micropowder, crown ether and water are mixed, freeze-dried after hydrothermal deposition treatment to obtain a solid powder material; in this process, porous boron nitride micropowder is preferably prepared first, which includes the following steps:

[0030] Mix a boron source, a nitrogen source, a pore-forming agent and water, dry after heating to obtain a boron nitride precursor;

[0031] Grind and calcine the boron nitride precursor to obtain porous boron nitride micropowder.

[0032] In the above preparation process, the boron source includes one or more of boric acid, ammonia borane, metaboric acid, boron chloride, boron oxide, boron sulfide, and sodium borohydride. Specifically, the boron source is selected from one of boric acid, ammonia borane, metaboric acid, boron chloride, boron oxide, boron sulfide, and sodium borohydride. More specifically, the boron source is selected from boric acid, metaboric acid, boron chloride, boron sulfide, sodium borohydride, or ammonia borane. The nitrogen source includes one or more of urea, melamine, sodium azide, dicyandiamide, and sodium amide. Specifically, the nitrogen source is selected from one of urea, melamine, sodium azide, dicyandiamide, and sodium amide. More specifically, the nitrogen source is selected from urea, melamine, dicyandiamide, or sodium azide. The pore-forming agent includes one or more of zinc acetate, nickel sulfate, cobalt sulfate, iron sulfate, copper sulfate, and zinc sulfate. Specifically, the pore-forming agent is selected from one of zinc acetate, nickel sulfate, cobalt sulfate, iron sulfate, copper sulfate, and zinc sulfate. More specifically, the pore-forming agent is selected from zinc acetate, copper sulfate, iron sulfate, or zinc sulfate. The mass ratio of the boron source to the nitrogen source is (1.10 - 2.50):1. Specifically, the mass ratio of the boron source to the nitrogen source is (1.125 - 2.00):1. More specifically, the mass ratio of the boron source to the nitrogen source is (1.20 - 1.60):1. More specifically, the mass ratio of the boron source to the nitrogen source is (1.24 - 1.36):1. More specifically, the mass ratio of the boron source to the nitrogen source is (1.25 - 1.31):1. The mass ratio of the nitrogen source to the pore-forming agent is (15 - 21):1. Specifically, the mass ratio of the nitrogen source to the pore-forming agent is (18 - 20):1. The heating temperature is 80 - 120°C. Specifically, the heating temperature is 95 - 110°C. The heating is to evaporate the moisture to obtain a white boron nitride (BN) precursor.

[0033] Then, the BN precursor is ground and calcined to obtain porous BN micropowder. In this process, the grinding is a grinding means well-known to those skilled in the art and is not particularly limited here. The calcination temperature is 500 - 1500°C, and the time is 3 - 10 h. The calcination is carried out in a protective atmosphere, and the protective atmosphere includes one of nitrogen and argon. Specifically, the calcination temperature is 700 - 900°C, and the time is 3.5 - 6 h. More specifically, the calcination temperature is 750 - 850°C, and the time is 4 - 5 h.

[0034] Two-dimensional material boron nitride (BN), which consists of nitrogen atoms and boron atoms to form a hexagonal network layer crystal, has rich functional groups and a high specific surface area, can effectively adsorb positively charged metal potassium ions. Further mixing and modification with crown ethers can enhance the reactive sites, greatly improving the adsorption capacity and stability for metal potassium ions. In addition, BN has good chemical inertness and thermal stability, can withstand high-temperature environments without decomposition or chemical changes. At the same time, BN also has high electrical insulation and thermal conductivity. By compounding and filling BN in the regenerated resin matrix, the thermal conductivity and mechanical properties of the resin can be significantly improved.

[0035] After the preparation of porous boron nitride micropowder, it is mixed with crown ether and water, freeze-dried after hydrothermal deposition treatment to obtain a solid powder material; in this process, the crown ether includes one or more of 18-crown-6, dibenzo-18-crown-6, dibenzo-30-crown-10, 15-crown-5, and cyclohexano-18-crown-6. Specifically, the crown ether is selected from one of 18-crown-6, dibenzo-18-crown-6, dibenzo-30-crown-10, 15-crown-5, and cyclohexano-18-crown-6. The mass ratio of the porous boron nitride micropowder to the crown ether is 10:(3 - 8). Specifically, the mass ratio of the porous boron nitride micropowder to the crown ether is 10:(5 - 7); more specifically, the mass ratio of the porous boron nitride micropowder to the crown ether is 10:6. The hydrothermal deposition treatment is used to uniformly adsorb and deposit the crown ether on the surface of porous BN. After the hydrothermal deposition treatment, ultrasonic dispersion is preferably carried out to ensure the preliminary precipitation of the crown ether and the full mixing of each component; the temperature of the hydrothermal deposition treatment is 30 - 40 °C, and the time is 4 - 12 h. More specifically, the time of the hydrothermal deposition treatment is 8 - 10 h. The time of ultrasonic dispersion is 30 - 60 min. Specifically, the time of ultrasonic dispersion is 35 - 50 min. The time of freeze-drying is 25 - 30 h.

[0036] According to the present invention, then the solid powder material is ball-milled. While refining the material particles, the interfacial bonding force between porous BN and crown ether is enhanced, and a porous BN@crown ether hybrid material is successfully prepared. During the ball-milling process, the masses of the grinding beads are 2.5 g, 10 g, 14 g, 15 g, and 55 g respectively, and the quantity ratio is (14 - 16):(9 - 11):(4 - 6):(4 - 6):(2 - 4). Specifically, the quantity ratio of the grinding beads for ball-milling is 15:10:5:5:3 to make the ball-milling more sufficient. The rotation speed of the ball-milling is 300 - 500 r / min, and the time is 10 - 30 h. Specifically, the rotation speed of the ball-milling is 400 - 450 r / min, and the time is 15 - 20 h.

[0037] This application then conducts alcoholysis reaction on waste polyester, ethylene glycol and catalyst potassium carbonate, and then adds the above-mentioned hybrid material to the obtained reaction solution to remove potassium ions in the reaction solution; during this process, the waste polyester is a waste polyester material well-known to those skilled in the art, and this application has no special restrictions on its source and composition. For example, the waste polyester includes one or more of waste polyester fibers, waste polyester plastics and waste polyester films. Specifically, the waste polyester is selected from one of waste polyester fibers, waste polyester plastics and waste polyester films. The mass ratio of the waste polyester, the ethylene glycol and the potassium carbonate is 1:(1.5 - 4.0):(0.015 - 0.05). Specifically, the mass ratio of the waste polyester, the ethylene glycol and the potassium carbonate is 1:(2 - 3):(0.025 - 0.03). More specifically, the mass ratio of the waste polyester, the ethylene glycol and the potassium carbonate is 1:(2.3 - 2.5):(0.025 - 0.03). The temperature of the alcoholysis reaction is 150 - 250 °C and the time is 1.5 - 5 h. Specifically, the temperature of the alcoholysis reaction is 175 - 215 °C and the time is 2 - 3.5 h. More specifically, the temperature of the alcoholysis reaction is 197 - 205 °C and the time is 2.5 - 3 h. Then, the hybrid material is added to the obtained reaction solution. The self-assembled porous BN@crown ether hybrid material, with its unique powdery porous structure, exhibits high-efficiency adsorption and chelation ability for metal potassium ions during the chemical recycling process of waste polyester, showing excellent shielding and removal performance; during the above process, it is preferably stirred and filtered twice to remove potassium ions in the alcoholysis reaction solution; the stirring rate is 50 - 200 r / min. Specifically, the stirring rate is 80 - 150 r / min.

[0038] Furthermore, this application also provides a preparation method of a porous boron nitride@crown ether hybrid material, which includes the following steps:

[0039] Mix porous boron nitride micropowder, crown ether and water, and obtain a solid powdery material after freeze-drying;

[0040] Ball-mill the solid powdery material to obtain a porous boron nitride@crown ether hybrid material.

[0041] The preparation of the above-mentioned porous boron nitride@crown ether hybrid material has been described in detail in the above content, and will not be elaborated here.

[0042] The porous boron nitride in the porous boron nitride@crown ether hybrid material prepared by this application has large pore diameters, which is more conducive to the high-efficiency adsorption of metal potassium ions.

[0043] The present invention provides a method for recycling by-products of waste polyester alcoholysis. Through the design of a porous boron nitride @ crown ether hybrid material composite structure, the strong metal ion adsorption property of porous BN is successfully combined with the selective ion complexation of crown ether to form an efficient adsorption and shielding system for potassium ions. The self-assembled porous BN @ crown ether hybrid material prepared has a good shielding effect on potassium ions during the chemical recycling process of waste polyester. This technology can effectively relieve the molecular chain capping effect that potassium carbonate may cause during the polymerization process of the later depolymerization products, and avoid the occurrence of side reactions such as nucleophilic-electrophilic reactions in the subsequent polycondensation stage, thereby effectively improving the overall polymerization reaction efficiency and product quality.

[0044] To further understand the present invention, the following examples are used to illustrate in detail the method for recycling by-products of waste polyester alcoholysis provided by the present invention. The protection scope of the present invention is not limited by the following examples.

[0045] Example 1

[0046] (1) Dissolve 2.43 g of boric acid, 1.85 g of urea and 0.10 g of zinc acetate in ultrapure water, stir and evaporate the water at 95 °C to obtain a white solid BN precursor. After the precursor is ground, it is heated to 800 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined for 4 h to obtain porous BN micropowder.

[0047] (2) Uniformly disperse porous BN micropowder and 18-crown-6 in ultrapure water according to a mass ratio of 10:6. Place the mixed solution in a shaker at 30 °C and perform oscillation deposition treatment for 4 h. After the oscillation deposition is completed, ultrasonically disperse the mixed dispersion for 40 min, and then freeze-dry for 30 h. Place the obtained solid product in a ball mill and ball mill at a rotation speed of 400 r / min for 15 h to obtain a porous BN @ 18-crown-6 hybrid material.

[0048] The powdery porous BN @ 18-crown-6 hybrid material prepared by the above method is directly used for potassium ion shielding in the depolymerization solution of waste polyester fiber, and the process is as follows:

[0049] Put waste polyester, ethylene glycol and catalyst potassium carbonate into the depolymerization reactor according to a mass ratio of 1:2.5:0.025, carry out alcoholysis reaction at 197 °C for 2.5 h. After the reaction is completed, stop heating, filter the depolymerization solution with an industrial filter screen, remove the filter residue to obtain the final reaction solution, and then add the porous BN @ 18-crown-6 hybrid material to the reaction solution. After stirring and secondary filtration, measure the residual content of potassium ions in the reaction solution.

[0050] Example 2

[0051] (1) 2.52 g of boric acid, 1.85 g of melamine and 0.10 g of zinc acetate were mixed and dissolved in ultrapure water. The water was evaporated by stirring at 85 °C to obtain a white solid BN precursor. After grinding the precursor, it was heated to 750 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined for 3 h to obtain porous BN micropowder;

[0052] (2) Porous BN micropowder and dibenzo-18-crown-6 were uniformly dispersed in ultrapure water according to a mass ratio of 10:5. The mixed solution was placed in a shaker at 30 °C and subjected to oscillatory deposition treatment for 4 h. After the oscillatory deposition was completed, the mixed dispersion was ultrasonically dispersed for 35 min, and then freeze-dried for 25 h. The obtained solid product was placed in a ball mill and ball-milled at a rotation speed of 450 r / min for 20 h to obtain a porous BN@dibenzo-18-crown-6 hybrid material.

[0053] The powdery porous BN@dibenzo-18-crown-6 hybrid material prepared by the above method was directly used for potassium ion shielding in the depolymerization solution of waste polyester fibers, and the process was as follows:

[0054] Waste polyester, ethylene glycol and potassium carbonate catalyst were added to the depolymerization reactor according to a mass ratio of 1:2:0.025. The alcoholysis reaction was carried out at 200 °C for 2 h. After the reaction was completed, heating was stopped, and the depolymerization solution was filtered through an industrial filter to remove the filter residue to obtain the final reaction solution. Subsequently, the porous BN@dibenzo-18-crown-6 hybrid material was added to the reaction solution, and after stirring and secondary filtration, the residual content of potassium ions in the reaction solution was measured.

[0055] Example 3

[0056] (1) 2.48 g of boric acid, 2.0 g of urea and 0.10 g of zinc acetate were mixed and dissolved in ultrapure water. The water was evaporated by stirring at 90 °C to obtain a white solid BN precursor. After grinding the precursor, it was heated to 850 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined for 3.5 h to obtain porous BN micropowder;

[0057] (2) Porous BN micropowder and 18-crown-6 were uniformly dispersed in ultrapure water according to a mass ratio of 10:5. The mixed solution was placed in a shaker at 30 °C and subjected to oscillatory deposition treatment for 8 h. After the oscillatory deposition was completed, the mixed dispersion was ultrasonically dispersed for 45 min, and then freeze-dried for 25 h. The obtained solid product was placed in a ball mill and ball-milled at a rotation speed of 450 r / min for 20 h to obtain a porous BN / 18-crown-6 hybrid material.

[0058] The powdery porous BN / 18-crown-6 hybrid material prepared by the above method was directly used for potassium ion shielding in the depolymerization solution of waste polyester fibers, and the process was as follows:

[0059] Waste polyester, ethylene glycol, and potassium carbonate catalyst were added to the depolymerization reactor at a mass ratio of 1:2:0.03, and the alcoholysis reaction was carried out at 205 °C for 2 h. After the reaction ended, heating was stopped, and the depolymerized solution was filtered using an industrial filter screen. After removing the filter residue, the final reaction solution was obtained. Subsequently, the porous BN / 18-crown-6 hybrid material was added to the reaction solution, and after stirring and secondary filtration, the residual potassium ion content in the reaction solution was measured.

[0060] Example 4

[0061] (1) 2.50 g of boric acid, 2.0 g of urea, and 0.10 g of zinc acetate were mixed and dissolved in ultrapure water. The water was evaporated by stirring at 95 °C to obtain a white solid BN precursor; after the precursor was ground, it was heated to 900 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined at a constant temperature for 3.5 h to obtain porous BN micropowder.

[0062] (2) The porous BN micropowder and 18-crown-6 were uniformly dispersed in ultrapure water at a mass ratio of 10:7. The mixed solution was placed in a shaker at 30 °C and subjected to oscillatory deposition treatment for 10 h. After the oscillatory deposition was completed, the mixed dispersion was ultrasonically dispersed for 50 min, and then freeze-dried for 25 h. The obtained solid product was placed in a ball mill and ball-milled at a rotation speed of 500 r / min for 20 h to obtain the porous BN@18-crown-6 hybrid material.

[0063] The powdered porous BN@18-crown-6 hybrid material prepared by the above method was directly used for potassium ion shielding in the waste polyester fiber depolymerized solution, and the process was as follows:

[0064] Waste polyester, ethylene glycol, and potassium carbonate catalyst were added to the depolymerization reactor at a mass ratio of 1:2.3:0.03, and the alcoholysis reaction was carried out at 198 °C for 2.5 h. After the reaction ended, heating was stopped, and the depolymerized solution was filtered using an industrial filter screen. After removing the filter residue, the final reaction solution was obtained. Subsequently, the porous BN@18-crown-6 hybrid material was added to the reaction solution, and after stirring and secondary filtration, the residual potassium ion content in the reaction solution was measured.

[0065] Example 5

[0066] (1) 2.50 g of boron chloride, 2.0 g of dicyandiamide, and 0.10 g of copper sulfate were mixed and dissolved in ultrapure water. The water was evaporated by stirring at 95 °C to obtain a white solid BN precursor; after the precursor was ground, it was heated to 800 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined at a constant temperature for 5 h to obtain porous BN micropowder.

[0067] (2) Porous BN micropowder and dibenzo-30-crown-10 were uniformly dispersed in ultrapure water at a mass ratio of 10:6. The mixed solution was placed in a shaker at 30 °C and subjected to oscillatory deposition treatment for 10 h. After the oscillatory deposition was completed, the mixed dispersion was ultrasonically dispersed for 50 min, and then freeze-dried for 30 h. The obtained solid product was placed in a ball mill and ball-milled at a rotation speed of 450 r / min for 25 h to obtain a porous BN@dibenzo-30-crown-10 hybrid material.

[0068] The powdered porous BN@dibenzo-30-crown-10 hybrid material prepared by the above method was directly used for potassium ion shielding in the depolymerization solution of waste polyester fibers. The process is as follows:

[0069] Waste polyester, ethylene glycol, and potassium carbonate as a catalyst were added to a depolymerization reactor at a mass ratio of 1:2:0.025. An alcoholysis reaction was carried out at 198 °C for 3 h. After the reaction ended, heating was stopped, and the depolymerization solution was filtered using an industrial filter screen. After removing the filter residue, the final reaction solution was obtained. Subsequently, the porous BN@dibenzo-30-crown-10 hybrid material was added to the reaction solution, and after stirring and secondary filtration, the residual content of potassium ions in the reaction solution was measured.

[0070] Example 6

[0071] (1) 2.50 g of boron sulfide, 2.1 g of urea, and 0.10 g of copper sulfate were mixed and dissolved in ultrapure water, and the water was evaporated by stirring at 95 °C to obtain a white solid BN precursor; after the precursor was ground, it was heated to 850 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined for 5 h to obtain porous BN micropowder;

[0072] (2) Porous BN micropowder and 15-crown-5 were uniformly dispersed in ultrapure water at a mass ratio of 10:5. The mixed solution was placed in a shaker at 30 °C and subjected to oscillatory deposition treatment for 12 h. After the oscillatory deposition was completed, the mixed dispersion was ultrasonically dispersed for 60 min, and then freeze-dried for 30 h. The obtained solid product was placed in a ball mill and ball-milled at a rotation speed of 450 r / min for 25 h to obtain a porous BN@15-crown-5 hybrid material.

[0073] The powdered porous BN@15-crown-5 hybrid material prepared by the above method was directly used for potassium ion shielding in the depolymerization solution of waste polyester fibers. The process is as follows:

[0074] Waste polyester, ethylene glycol, and potassium carbonate catalyst were put into a depolymerization reactor according to a mass ratio of 1:2:0.025, and an alcoholysis reaction was carried out at 198 °C for 3 h. After the reaction ended, heating was stopped, and the depolymerized solution was filtered using an industrial filter screen. After removing the filter residue, the final reaction solution was obtained. Subsequently, the porous BN@15-crown-5 hybrid material was added to the reaction solution, and after stirring and secondary filtration, the residual potassium ion content in the reaction solution was measured.

[0075] Example 7

[0076] (1) 2.50 g of sodium borohydride, 1.5 g of sodium azide, and 0.10 g of ferric sulfate were mixed and dissolved in ultrapure water, and the water was evaporated by stirring at 90 °C to obtain a white solid BN precursor; after the precursor was ground, it was heated to 700 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined at a constant temperature for 5 h to obtain porous BN micropowder;

[0077] (2) Porous BN micropowder and cyclohexane-18-crown-6 were uniformly dispersed in ultrapure water according to a mass ratio of 10:8, and the mixed solution was placed in a shaker at 30 °C and subjected to oscillatory deposition treatment for 10 h. After the oscillatory deposition was completed, the mixed dispersion was ultrasonically dispersed for 60 min, and then freeze-dried for 25 h. The obtained solid product was placed in a ball mill and ball-milled at a rotation speed of 420 r / min for 20 h to obtain a porous BN@cyclohexane-18-crown-6 hybrid material.

[0078] The powdery porous BN@cyclohexane-18-crown-6 hybrid material prepared by the above method was directly used for potassium ion shielding in the waste polyester fiber depolymerized solution, and the process was as follows:

[0079] Waste polyester, ethylene glycol, and potassium carbonate catalyst were put into a depolymerization reactor according to a mass ratio of 1:2:0.03, and an alcoholysis reaction was carried out at 197 °C for 2.5 h. After the reaction ended, heating was stopped, and the depolymerized solution was filtered using an industrial filter screen. After removing the filter residue, the final reaction solution was obtained. Subsequently, the porous BN@cyclohexane-18-crown-6 hybrid material was added to the reaction solution, and after stirring and secondary filtration, the residual potassium ion content in the reaction solution was measured.

[0080] Example 8

[0081] (1) 2.25 g of ammonia borane, 2.0 g of urea, and 0.10 g of zinc sulfate were mixed and dissolved in ultrapure water, and the water was evaporated by stirring at 90 °C to obtain a white solid BN precursor. After the precursor was ground, it was heated to 800 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and calcined at a constant temperature for 5 h to obtain porous BN micropowder;

[0082] (2) Uniformly disperse porous BN micropowder and 18-crown-6 in ultrapure water according to the mass ratio of 10:8. Place the mixed solution in a shaker at 30 °C and perform oscillating deposition treatment for 10 h. After the oscillating deposition is completed, ultrasonically disperse the mixed dispersion for 60 min, and then freeze-dry for 25 h. Place the obtained solid product in a ball mill and ball mill at a rotation speed of 420 r / min for 20 h to obtain a porous BN@18-crown-6 hybrid material.

[0083] Directly use the powdered porous BN@18-crown-6 hybrid material prepared by the above method for potassium ion shielding in the depolymerization solution of waste polyester fiber. The process is as follows:

[0084] Put waste polyester, ethylene glycol, and catalyst potassium carbonate into the depolymerization reactor according to the mass ratio of 1:3:0.03, and carry out alcoholysis reaction at 197 °C for 3.5 h. After the reaction is completed, stop heating, filter the depolymerization solution with an industrial filter screen, remove the filter residue to obtain the final reaction solution, and then add the porous BN@18-crown-6 hybrid material to the reaction solution. Measure the residual content of potassium ions in the reaction solution after stirring and secondary filtration.

[0085] Comparative Example 1

[0086] Dissolve 2.43 g of boric acid, 1.85 g of urea, and 0.10 g of zinc acetate in ultrapure water, stir and evaporate the water at 95 °C to obtain a white solid BN precursor. After the precursor is ground, heat it to 800 °C at a heating rate of 5 °C / min in a nitrogen atmosphere and keep it calcined for 4 h to obtain porous BN micropowder;

[0087] Directly use the porous BN micropowder prepared by the above method for potassium ion shielding in the alcoholysis depolymerization solution of waste polyester fiber. The process is as follows:

[0088] Put waste polyester, ethylene glycol, and catalyst potassium carbonate into the depolymerization reactor according to the mass ratio of 1:2.5:0.025, and carry out alcoholysis reaction at 197 °C for 2.5 h. After the reaction is completed, stop heating, filter the depolymerization solution with an industrial filter screen, remove the filter residue to obtain the final reaction solution, and then add the porous BN micropowder to the reaction solution. Measure the residual content of potassium ions in the reaction solution after stirring and secondary filtration.

[0089] Comparative Example 2

[0090] Put waste polyester, ethylene glycol, and catalyst potassium carbonate into the depolymerization reactor according to the mass ratio of 1:2.5:0.025, and carry out alcoholysis reaction at 197 °C for 2.5 h. After the reaction is completed, stop heating, filter the depolymerization solution with an industrial filter screen, remove the filter residue to obtain the final reaction solution, and then add 18-crown-6 to the reaction solution. Measure the residual content of potassium ions in the reaction solution after stirring and secondary filtration.

[0091] The potassium ion removal rates in the depolymerization solutions of the above examples and comparative examples are shown in Table 1 as follows:

[0092] Table 1 Data table of potassium ion removal rate in depolymerization solution

[0093]

[0094] As can be seen from Table 1, by analyzing the results of Examples 1 to 8, through adjusting the boron source, nitrogen source and pore-forming agent during the preparation of porous BN for self-assembly with crown ether, the prepared hybrid material has achieved good effects on shielding potassium ions during the alcoholysis of waste polyester.

[0095] The results of Comparative Example 1 and Comparative Example 2 show that under the same depolymerization conditions of waste polyester, adding porous BN micropowder or 18-crown-6 alone has a poor shielding effect on potassium ions in the reaction solution. It can be seen that there is an obvious synergistic effect between porous BN and crown ether in shielding potassium ion pairs in the present invention.

[0096] The description of the above examples is only used to help understand the method and its core idea of the present invention. It should be pointed out that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0097] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recycling by-products of waste polyester alcoholysis, comprising the following steps: S1) Mix porous boron nitride micropowder, crown ether and water, perform hydrothermal deposition treatment and then freeze-dry to obtain a solid powder material; Ball-mill the solid powder material to obtain a porous boron nitride@crown ether hybrid material; S2) Perform an alcoholysis reaction on waste polyester, ethylene glycol and catalyst potassium carbonate, and add the hybrid material to the obtained reaction solution to remove potassium ions in the reaction solution.

2. The reuse method according to claim 1, wherein The specific preparation method of the porous boron nitride micropowder is as follows: Mix a boron source, a nitrogen source, a pore-forming agent and water, heat and then dry to obtain a boron nitride precursor; Grind the boron nitride precursor and then calcine it to obtain porous boron nitride micropowder.

3. The reuse method according to claim 2, wherein The boron source includes one or more of boric acid, ammonia borane, metaboric acid, boron chloride, boron oxide, boron sulfide and sodium borohydride; the nitrogen source includes one or more of urea, melamine, sodium azide, dicyandiamide and sodium amide; the pore-forming agent includes one or more of zinc acetate, nickel sulfate, cobalt sulfate, iron sulfate, copper sulfate and zinc sulfate; the mass ratio of the boron source to the nitrogen source is (1.10~2.50):1; the calcination temperature is 500~1500 °C and the time is 3~10 h; the calcination is carried out in a protective atmosphere, and the protective atmosphere includes one of nitrogen and argon.

4. The reuse method according to claim 1, wherein The crown ether includes one or more of 18-crown-6, dibenzo-18-crown-6, dibenzo-30-crown-10, 15-crown-5 and cyclohexano-18-crown-6, and the mass ratio of the porous boron nitride micropowder to the crown ether is 10:(3~8).

5. The reuse method according to claim 1, wherein, In step S1), during the ball-milling process, the masses of the grinding beads are 2.5 g, 10 g, 14 g, 15 g, 55 g respectively, and the quantity ratio is (14~16):(9~11):(4~6):(4~6):(2~4); the rotation speed of the ball-milling is 300~500 r / min and the time is 10~30 h.

6. The reuse method according to claim 1, characterized in that, In step S2), the waste polyester includes one or more of waste polyester fibers and waste polyester plastics.

7. The reuse method according to claim 1, characterized in that The mass ratio of the waste polyester, the ethylene glycol and the potassium carbonate is 1:(1.5~4.0):(0.015~0.05), the temperature of the alcoholysis reaction is 150~250 °C and the time is 1.5~5 h.

8. The reuse method according to claim 1, wherein After adding the hybrid material, it further includes stirring and secondary filtration, and the stirring rate is 50~200 r / min.

9. A method for preparing a porous boron nitride@crown ether hybrid material, comprising the following steps: Mix porous boron nitride micropowder, crown ether and water, perform hydrothermal deposition treatment and then freeze-dry to obtain a solid powder material; Ball-mill the solid powder material to obtain a porous boron nitride@crown ether hybrid material.

10. The preparation method according to claim 9, characterized in that, The mass ratio of the porous boron nitride micropowder to the crown ether is 10:(3~8).

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