A waste polyester degradation and decolorization integrated catalyst, a preparation method and application thereof

Abstract

This invention discloses an integrated catalyst for the degradation and decolorization of waste polyester, its preparation method, and its application. The method includes: the integrated catalyst for the degradation and decolorization of waste polyester can simultaneously perform alcohol decolorization on waste colored polyester. The catalyst is mixed with ethylene glycol, and under the protection of nitrogen and a condenser, the waste colored polyester is added after heating and stirring. Heating is then stopped, at which point the system has completed alcohol decolorization and decolorization. The catalyst is recovered, and boiling water is added, stirred, and then rapidly filtered. The filtrate is refrigerated and allowed to stand, then filtered again to obtain BHET crystals and alcoholysis liquid. The BHET crystals are dried to constant weight, and the alcoholysis liquid is recovered by rotary distillation. This invention enables the simultaneous degradation and decolorization steps in the recycling of waste colored polyester, effectively improving recycling efficiency, reducing processes, and lowering costs.

Description

Technical Field

[0001] This invention belongs to the field of textile technology, specifically relating to an integrated catalyst for the degradation and decolorization of waste polyester, its preparation method, and its application. Background Technology

[0002] Synthetic fibers, primarily polyester (PET), account for over 70% of waste textiles. Because polyester undergoes extensive chemical processing during production to meet wearing and aesthetic requirements, it contains additives such as dyes, pigments, and dispersants, severely limiting its recycling rate to only 5%. The rapidly increasing and non-biodegradable PET not only consumes vast amounts of petroleum resources but is also ubiquitous in the ocean and on land, accumulating even in humans and other organisms, posing a serious threat to the ecological environment.

[0003] Currently, degradation is the main method for recycling waste polyester, including hydrolysis, ammonolysis, and alcoholysis. Among these, ethylene glycol alcoholysis is the most industrially valuable recycling and regeneration method. However, since most waste polyester textiles are colored products, the color of the recycled products is greatly affected by impurities such as dyes and the recycling process. Furthermore, the alcoholysis solution obtained after degradation usually contains some disperse dyes, requiring further decolorization. Current research typically involves degrading and recycling PET, followed by stepwise decolorization of the products and solutions. This approach suffers from problems such as long processing time, low efficiency, and complex processes. As the recycling of waste polyester is still under experimental research, improving the efficiency and effectiveness of degradation and decolorization remains an unsolved problem. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing an integrated catalyst for the degradation and decolorization of waste polyester.

[0007] To solve the above technical problems, the present invention provides the following technical solution: MgFe2O4 and Zn(Ac)2 are added to a solvent, stirred evenly, and then KH560 silane coupling agent is added. After water bath heating and stirring, the mixture is ultrasonically treated to obtain a mixed solution.

[0008] The mixed solution was stirred and evaporated to a thick state, then dried to obtain a solid, which was then ground to obtain an integrated catalyst for the degradation and decolorization of waste polyester.

[0009] In a preferred embodiment of the preparation method described in this invention, the solvent includes at least one of anhydrous ethanol and deionized water.

[0010] As a preferred embodiment of the preparation method described in this invention, the MgFe2O4 is obtained by dissolving MgCl2·6H2O and FeCl3·6H2O in NaOH solution and mixing them, stirring and sonicating until homogeneous, reacting at high temperature, and then filtering, washing, drying and grinding.

[0011] In a preferred embodiment of the preparation method described in this invention, the mass ratio of MgFe2O4, Zn(Ac)2 to solvent is 1:2 to 5:60.

[0012] In a preferred embodiment of the preparation method described in this invention, the mass fraction of the KH560 silane coupling agent is 1.25% to 1.9%.

[0013] In a preferred embodiment of the preparation method described in this invention, the stirring speed is 300-500 r / min and the temperature is 70-80℃.

[0014] Another objective of this invention is to overcome the shortcomings of the prior art and provide an integrated catalyst for the degradation and decolorization of waste polyester.

[0015] Another objective of this invention is to overcome the shortcomings of the prior art and provide an integrated catalyst for the degradation and decolorization of waste polyester in alcohol decolorization.

[0016] As a preferred embodiment of the preparation method described in this invention, the integrated catalyst for the degradation and decolorization of waste polyester can perform alcohol decolorization on waste colored polyester, allowing alcohol decolorization to occur simultaneously. After mixing the integrated catalyst for the degradation and decolorization of waste polyester with ethylene glycol, waste colored polyester is added under the protection of nitrogen and a condenser. The mixture is heated and stirred, and then the heating is stopped. At this point, the system has completed alcohol decolorization and decolorization. The catalyst is recovered, and boiling water is added and stirred before rapid filtration. The filtrate is refrigerated and allowed to stand, and then filtered again to obtain BHET crystals and alcoholysis liquid. The BHET crystals are dried to constant weight, and the alcoholysis liquid is recovered by rotary distillation.

[0017] As a preferred embodiment of the preparation method described in this invention, the mass ratio of ethylene glycol, waste colored polyester and waste polyester degradation and decolorization integrated catalyst is 250:50:(0.5~1.5); after heating, waste colored polyester is added, heated and stirred, and then heating is stopped, wherein the heating temperature is 196℃ and the stirring time is 2~4h.

[0018] Beneficial effects of this invention:

[0019] (1) This invention overcomes the shortcomings of low efficiency and complex processes in the chemical degradation and decolorization of waste polyester textiles in the prior art, and provides a method for integrated research on polyester degradation and decolorization and the preparation of a catalyst. It can simultaneously carry out the degradation and decolorization steps in the recycling of waste colored polyester, effectively improving recycling efficiency, reducing the number of processes, simplifying operation, and reducing costs.

[0020] (2) Based on the research on improving the degradation and decolorization efficiency of waste colored polyester, this invention attempts to conduct integrated research on degradation and decolorization, and prepares a catalyst that can effectively shorten the time and improve the degradation and decolorization efficiency of waste colored polyester. The prepared composite catalyst has a certain magnetic properties and can be magnetically attracted and recycled, effectively saving costs, protecting the environment and saving resources.

[0021] (3) This invention replaces the traditional adsorption decolorization method and effectively improves the decolorization effect. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0023] Figure 1 This is a scanning electron microscope image of the MgFe2O4 powder prepared in Example 1 of the present invention.

[0024] Figure 2 The image shows a scanning electron microscope (SEM) image of the Zn(Ac)2-MgFe2O4 composite catalyst 1 prepared in Example 2 of this invention (where the left image is at 100 μm magnification and the right image is at 30 μm magnification).

[0025] Figure 3 The image shows a scanning electron microscope (SEM) image of the Zn(Ac)2-MgFe2O4 composite catalyst 8 prepared in Comparative Example 6 of this invention. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0028] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0030] Colored polyester fabric: Suzhou Dexianji Textile Co., Ltd., available in the general market;

[0031] Ethylene glycol: Shanghai Titan Technology Co., Ltd., commercially available;

[0032] Zn(Ac)2: Shanghai Mairui Biochemical Technology Co., Ltd., commercially available;

[0033] MgCl2·6H2O: Shanghai Mairui Biochemical Technology Co., Ltd.;

[0034] FeCl3·6H2O: Sinopharm Chemical Reagent Co., Ltd., commercially available;

[0035] NaOH: Available from Sinopharm Chemical Reagent Co., Ltd., commonly sold in the market;

[0036] Anhydrous ethanol: Available from Navigation Titan Technology Co., Ltd., commercially available.

[0037] Nitrogen: Wuxi Xinxi Instrument Technology Co., Ltd.

[0038] Silane coupling agent KH560: Suzhou Great Pharmaceutical Technology Co., Ltd., commercially available.

[0039] Example 1

[0040] 1. Preparation of MgFe2O4 nanoparticles:

[0041] (1) Prepare a 1 mol / L NaOH solution. Take 5 mmol MgCl2·6H2O and 10 mmol FeCl3·6H2O (molar ratio of 1:2) and dissolve them in 30 mL of 1 mol / L NaOH solution respectively. Then mix the two suspensions into a 250 mL Erlenmeyer flask, stir magnetically for 30 min, and sonicate for 30 min (ultrasonic power of 200 W, ultrasonic frequency of 40 kHz).

[0042] (2) After the ultrasound is completed, pour the well mixed liquid into a 100 mL polytetrafluoroethylene inner liner, place it in the reaction vessel, and place it at 180 °C for 24 hours.

[0043] (3) After the reaction is completed, the product is taken out and cooled to room temperature. The product in the inner liner is vacuum filtered and washed with distilled water and anhydrous ethanol 3-5 times each to remove impurity ions and excess water from the surface of the product. Finally, the solid product obtained by vacuum filtration is placed in a vacuum drying oven at 60°C and dried. The product is ground with a mortar and pestle to obtain the final product MgFe2O4 nanoparticles.

[0044] 2. Preparation of catalyst for the degradation and decolorization of waste polyester:

[0045] (4) After stirring MgFe2O4 and Zn(Ac)2 with anhydrous ethanol in a mass ratio of 1:3:60, a mixed solution is obtained. Then, 1.5% (for the mixed solution) of KH560 silane coupling agent is added to obtain a solution.

[0046] (5) After the solution obtained in step (4) is heated in a water bath at 80°C and stirred for 30 min, it is then subjected to ultrasonic treatment for 15 min (frequency 100 kHz).

[0047] (6) Place the well-mixed solution on an 80°C constant temperature magnetic stirrer, evaporate it to a thick state, and then transfer it to an oven at 60°C to dry. Grind the solid to obtain waste polyester degradation and decolorization catalyst 1.

[0048] Example 2

[0049] The difference from Example 1 is that the mass fraction of KH560 silane coupling agent in step (4) is 1.25%, and waste polyester degradation and decolorization catalyst 2 is obtained.

[0050] Comparative Example 1

[0051] The difference from Example 1 is that Zn(Ac)2 is not added in step (4), and waste polyester degradation and decolorization catalyst 3 is obtained.

[0052] Comparative Example 2

[0053] The difference from Example 1 is that MgFe2O4 is not added in step (4), and waste polyester degradation and decolorization catalyst 4 is obtained.

[0054] Comparative Example 3

[0055] The difference from Example 1 is that step (4) is not performed, and the mass ratio of MgFe2O4 to Zn(Ac)2 is 1:1, so that waste polyester degradation and decolorization catalyst 5 is obtained.

[0056] Comparative Example 4

[0057] The difference from Example 1 is that step (4) is not performed, and the mass ratio of MgFe2O4 to Zn(Ac)2 is 0.5:3, so that waste polyester degradation and decolorization catalyst 6 is obtained.

[0058] Comparative Example 5

[0059] The difference from Example 1 is that step (4) is not performed, and the mass ratio of MgFe2O4 to Zn(Ac)2 is 1.5:3, so that waste polyester degradation and decolorization catalyst 7 is obtained.

[0060] Comparative Example 6

[0061] The difference from Example 1 is that the mass fraction of KH560 silane coupling agent in step (4) is 1%, and waste polyester degradation and decolorization catalyst 8 is obtained.

[0062] Example 3

[0063] (1) Prepare ethylene glycol, waste colored polyester and waste polyester degradation and decolorization catalyst 1 prepared in Example 1 with a mass ratio of 75:15:0.2.

[0064] (2) Add ethylene glycol and waste polyester degradation and decolorization catalyst 1 into a four-necked flask and place it in an oil bath for fixation. Connect nitrogen gas and condenser tube to the four-necked flask and plug the remaining necks with glass stoppers.

[0065] (3) When the temperature rises to 196°C, add waste colored polyester and heat and stir for 3 hours until completely dissolved.

[0066] (4) Stop heating and stirring, recover the catalyst by magnetic attraction, add 300ml of boiling water and stir, then quickly filter to remove insoluble matter. Place the alcoholysis liquid in a refrigerator at 4℃ and refrigerate for 24h. Filter to obtain crystallized BHET and alcoholysis liquid. Place the crystals in an oven at 60℃ to dry and weigh.

[0067] Example 4

[0068] The difference from Example 6 is that the waste polyester degradation and decolorization catalyst 2 is used in step (1).

[0069] Comparative Example 7

[0070] The difference from Example 6 is that the waste polyester degradation and decolorization catalyst 3 is used in step (1).

[0071] Comparative Example 8

[0072] The difference from Example 6 is that the waste polyester degradation and decolorization catalyst 4 is used in step (1).

[0073] Comparative Example 9

[0074] The difference from Example 6 is that the waste polyester degradation and decolorization catalyst 5 is used in step (1).

[0075] Comparative Example 10

[0076] The difference from Example 6 is that the waste polyester degradation and decolorization catalyst 6 is used in step (1).

[0077] Comparative Example 11

[0078] The difference from Example 6 is that the waste polyester degradation and decolorization catalyst 7 is used in step (1).

[0079] Comparative Example 12

[0080] The difference from Example 6 is that the waste polyester degradation and decolorization catalyst is not used in step (1).

[0081] Morphological performance testing:

[0082] The MgFe2O4 and Zn(Ac)2-MgFe2O4 composite catalyst 1 prepared in Example 1 were examined by scanning electron microscopy. The testing standard was in accordance with the national standard GB / T 33834-2017, and the testing instrument was a Japanese SU1510 scanning electron microscope with a voltage of 5.00 kV. The results are as follows. Figure 1 (MgFe2O4) Figure 2 (Zn(Ac)2-MgFe2O4 composite catalyst 1) is shown in the figure. MgFe2O4 appears as dispersed particles with uneven size distribution. This is because MgFe2O4 easily absorbs water vapor from the air, causing inter-particle agglomeration. Therefore, some particles will form agglomerates, resulting in larger particles.

[0083] The Zn(Ac)2-MgFe2O4 composite catalyst 1 in the figure has a relatively smooth surface and is generally spherical. (See magnified view.) Figure 2 (Right) A coating effect can be observed, and the dispersion effect is good. This is because MgFe2O4 is a magnetic particle, and the addition of the coupling agent weakens the electrostatic interaction between MgFe2O4 particles, resulting in an increase in the dispersion of MgFe2O4 particles.

[0084] The Zn(Ac)2-MgFe2O4 composite catalyst 8 prepared in Comparative Example 6 was examined by scanning electron microscopy, and the results were as follows: Figure 3 As shown in the figure, the composite catalyst was dispersed, but not very uniformly, and the effect was mediocre, with agglomeration still being obvious.

[0085] Alcohololysis effect test:

[0086] The PET degradation rate and BHET yield were calculated for Examples 3-4 and Comparative Examples 7-12, according to the formula: PET degradation rate (%) = (mass of input PET - mass of unreacted PET) / mass of input PET

[0087] BHET yield (%) = (mass of BHET produced * PET repeating unit (192 g / mol)) / (mass of PET input * molecular weight of BHET (254 g / mol))

[0088] The calculations were performed, and the results are shown in Table 1:

[0089] Table 1:

[0090] PET degradation rate (%) BHET Yield (%) Example 3 100 79.6 Example 4 98.8 77.3 Comparative Example 7 40.6 15.1 Comparative Example 8 98.2 66.9 Comparative Example 9 86.8 58.2 Comparative Example 10 98.6 61.8 Comparative Example 11 97.2 53.5 Comparative Example 12 32.3 14.6

[0091] As shown in Table 1, Example 3 of the present invention exhibits a good PET degradation rate and a high BHET yield (79.6%). When the amount of MgFe2O4 added to the composite catalyst is 0 (Comparative Example 8), the PET degradation rate is close to that of Example 3, but the BHET yield is lower than that of Example 3. When the amount of Zn(Ac)2 added to the composite catalyst is 0 (Comparative Example 7), the polyester alcoholysis effect is poor, with low PET degradation rate and BHET yield. At the end of the reaction, a large amount of polyester fabric remains un-alcoholized. This is because the oxygen atom of the alkoxy group in the Zn(Ac)2 ester bond contains a lone pair of electrons, which can form an unstable intermediate complex with zinc having empty orbitals. This increases the positive charge on the carbonyl carbon atom, making it easier for the lone pair of electrons on the oxygen atom in ethylene glycol to undergo a nucleophilic reaction with the carbon atom to form a bond, while the CO bond breaks, thereby accelerating the reaction process.

[0092] When no catalyst was added in Comparative Example 12, the degradation effect of the product was weak. As the amount of catalyst (as a percentage of the PET mass) continued to increase, the hydroxyl value of the alcoholysis product also increased significantly, and the average molecular weight decreased accordingly. However, when the amount added reached a certain value, further increasing the amount did not change the hydroxyl value and average molecular weight of the alcoholysis product.

[0093] As can be seen from Comparative Examples 8-10 in Table 1, when preparing composite catalysts, changing the ratio of Zn(Ac)2 to MgFe2O4 can affect the experimental alcoholysis effect, and when the amount added is unstable, it may produce an antagonistic effect.

[0094] Decolorization performance test:

[0095] Using a UV spectrophotometer, with Comparative Example 8 as the control group requiring decolorization treatment, the UV absorption spectrum of the alcoholysis solution was measured and analyzed. Referring to the alcoholysis solution, ethylene glycol and deionized water were selected as solvents (ethylene glycol:deionized water volume = 1:4). The alcoholysis solution was brought to a constant volume, and a dye absorbance standard curve was established. Based on qualitative analysis, the regression equation for the standard curve was obtained by self-fitting: C = 131.6591*A + 0.3062, r = 0.999432. The absorbance values ​​of the alcoholysis solutions obtained in Examples 3-4 and Comparative Examples 9-11 were measured using a UV spectrophotometer. The dye concentration was obtained from the standard curve, and the decolorization rate was calculated. The formula for calculating the decolorization rate is as follows:

[0096] ω Dye decolorization rate (%) = [Initial dye concentration in the alcoholysis solution (μg / mL) - Dye concentration at any time (μg / mL)] / Initial dye concentration in the alcoholysis solution (μg / mL)

[0097] The calculation results are shown in Table 2:

[0098]

[0099] Conclusion: As shown in Table 2, Example 3 of the present invention has good decolorization performance, and the recovered catalyst can still achieve decolorization effect after repeated recycling. When the mass fraction of KH560 silane coupling agent is changed when preparing the composite catalyst (Example 4), it can be seen that the decolorization effect in the first cycle is close to that of Example 3, but the decolorization effect is significantly weakened in the second cycle. This is because the silane coupling agent, as an intermediate binding agent, contains both organic and inorganic groups, which can enable chemical bonding at the interface of inorganic and organic materials. When the alkoxy group at one end hydrolyzes, it generates hydroxyl groups, which undergo a condensation reaction with the hydroxyl groups on the surface of MgFe2O4 particles to form an -O-Si-R structure. The epoxy group at the other end reacts with Zn(Ac)2 to combine the two together. Changing the amount of silane coupling agent will affect the binding effect between the two.

[0100] As can be seen from Comparative Examples 9-11 in Table 2, changing the ratio of Zn(Ac)2 to MgFe2O4 can affect the experimental decolorization effect, and when the amount added is unstable, it may produce an antagonistic effect.

[0101] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing an integrated catalyst for the degradation and decolorization of waste polyester, characterized in that: include, MgFe2O4 and Zn(Ac)2 were added to a solvent and stirred until homogeneous. Then, KH560 silane coupling agent was added, and the mixture was heated and stirred in a water bath before ultrasonic treatment to obtain a mixed solution. The mixed solution was stirred and evaporated to a thick state, then dried to obtain a solid. The solid was then ground to obtain an integrated catalyst for the degradation and decolorization of waste polyester. The mass ratio of MgFe2O4, Zn(Ac)2 to solvent is 1:2~5:60; The amount of KH560 silane coupling agent used is 1.25% to 1.9% of the total mass of the mixed solution of MgFe2O4, Zn(Ac)2 and solvent.

2. The preparation method according to claim 1, characterized in that: The solvent includes at least one of anhydrous ethanol and deionized water.

3. The preparation method according to claim 1, characterized in that: The MgFe2O4 is obtained by dissolving MgCl2·6H2O and FeCl3·6H2O in NaOH solution and mixing them, stirring and sonicating until homogeneous, reacting at high temperature, and then filtering, washing, drying and grinding.

4. The preparation method according to claim 1, characterized in that: The stirring speed is 300~500 r / min and the temperature is 70~80℃.

5. The integrated catalyst for the degradation and decolorization of waste polyester prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the integrated catalyst for the degradation and decolorization of waste polyester as described in claim 5 in alcohol decolorization.

7. The application as described in claim 6, characterized in that: The integrated catalyst for the degradation and decolorization of waste polyester can perform alcohol decolorization on waste colored polyester, allowing alcohol decolorization to occur simultaneously. After mixing the integrated catalyst for the degradation and decolorization of waste polyester with ethylene glycol, waste colored polyester is added under the protection of nitrogen and a condenser. After heating and stirring, the system is stopped. At this point, the alcohol decolorization and decolorization have been completed. The catalyst is recovered, and boiling water is added and stirred before rapid filtration. The filtrate is refrigerated and allowed to stand, then filtered again to obtain BHET crystals and alcoholysis liquid. The BHET crystals are dried to constant weight, and the alcoholysis liquid is recovered by rotary distillation.

8. The application as described in claim 7, characterized in that: The mass ratio of ethylene glycol, waste colored polyester and waste polyester degradation and decolorization integrated catalyst is 250:50:(0.5~1.5); after heating, waste colored polyester is added, heated and stirred, and then heating is stopped. The heating temperature is 196℃ and the stirring time is 2~4h.

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