Preparation method and application of a solid acid catalyst for degrading waste PET to produce TPA

Abstract

The present invention belongs to the technical field of recycling of waste resources, and discloses a preparation method and application of a solid acid catalyst for degrading waste PET to TPA. The solid acid catalyst for degrading waste PET to TPA is a heteropolyacid asymmetric double quaternary ammonium salt solid acid catalyst with a phase transfer function. The preparation method is as follows: an asymmetric double quaternary ammonium salt surfactant and a heteropolyacid are subjected to an ion exchange reaction according to a molar ratio of 0.5 to 1.5:1 to obtain the solid acid catalyst for degrading waste PET to TPA; the application is as follows: waste PET, the solid acid catalyst and distilled water are added into a polytetrafluoroethylene or polyphenylene paraffin liner of an autogenous pressure reactor according to a certain mass ratio, and a homogeneous reactor is used to react at 180 to 220 °C for 4 to 24 h. The preparation method of the present invention has a simple process, and the prepared solid acid catalyst has excellent catalytic degradation performance and can also be recycled multiple times, which is environmentally friendly and resource-saving.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling of waste resources, and relates to a preparation method and application of a solid acid catalyst for degrading waste PET to TPA. Background Art

[0002] Since PET waste is difficult to degrade and not easily recycled under normal temperature and pressure, most of the current PET waste is only treated by methods such as incineration, landfill or simple physical recycling and downgrading, but this also causes environmental pollution and waste of petrochemical resources, and increases carbon emissions. With the improvement of people's awareness of environmental safety, how to improve the efficient recycling of resources such as waste textiles has also become a popular research direction.

[0003] Currently, common chemical recycling methods for PET waste include alcoholysis and hydrolysis.

[0004] Alcoholysis mainly includes methanol and ethylene glycol alcoholysis. The former needs to be carried out under high temperature and high pressure, and the reaction conditions are harsh. The latter is a reversible reaction. Although the PET degradation conversion rate is close to 100%, the yield of the product BHET is low, only about 85%.

[0005] Hydrolysis is widely used because of its high conversion rate, short time consumption and few by-products. The generated monomer TPA can be used for re-polymerization to prepare PET with excellent properties, achieving the goal of efficient recycling of polymer resources. According to different media, it can be further divided into acidic, alkaline and neutral hydrolysis. However, in the liquid acid / alkali system, after separating TPA, there will be problems such as how to regenerate the liquid acid / alkali catalyst, the strong corrosion of the reaction process to the equipment, and the treatment of a large amount of strong acid / alkali waste liquid brought by the reaction. Neutral hydrolysis is considered an environmentally friendly green route, but the reaction needs to be carried out in a subcritical water system at high temperature (≥250 ºC) and high pressure, with high energy consumption and high requirements for equipment, which limits the industrial application and promotion.

[0006] In recent years, the use of solid acid catalysts in a neutral hydrolysis system has been proven to be a new green path with low energy consumption, low emissions, low pollution, high performance, and high utilization rate in the acid degradation process of recycling waste PET fibers due to their strong acidity, low corrosion, and easy regeneration. As reported in the literature (Chemical Engineering Journal 2020, 398: 125655), a solid acid catalyst of ZSM-5 zeolite with a Si / Al of 25 was used to degrade 0.1 g of PET bottle chips under microwave assistance with 0.05 g. After degradation at 230 °C for 40 min, the yield of TPA could be close to 100%. However, since the catalyst is solid and the PET waste is also solid, the mass transfer between solids is difficult, resulting in the PET having difficulty in contacting the acidic sites on the catalyst. Therefore, it is necessary to carry out the degradation under high temperature and microwave assistance, and thus large-scale production cannot be achieved.

[0007] Therefore, it is of great significance to develop a preparation method and application of a solid acid catalyst for degrading waste PET to TPA to solve the above problems. Summary of the Invention

[0008] The purpose of the present invention is to solve the problems existing in the prior art and provide a preparation method and application of a solid acid catalyst for degrading waste PET to TPA.

[0009] To achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0010] A preparation method of a solid acid catalyst for degrading waste PET to TPA, in which an asymmetric double quaternary ammonium salt surfactant and a heteropolyacid are subjected to an ion exchange reaction according to a molar ratio of 0.5 - 1.5:1 to obtain a solid acid catalyst for degrading waste PET to TPA. The catalyst is composed of an asymmetric double quaternary ammonium salt cation and a heteropolyacid anion, and has a lipophilic cationic hydrophobic end in structure, which brings the heteropolyacid anion to the interface of the organic phase and the aqueous phase, enabling it to enter the PET organic phase for depolymerization; the cationic hydrophilic end can stabilize the structure of the heteropolyacid anion and improve the recycling performance of the catalyst.

[0011] As a preferred technical scheme:

[0012] The preparation method of a solid acid catalyst for degrading waste PET to TPA as described above includes the following steps:

[0013] (1) Dissolve the asymmetric double quaternary ammonium salt surfactant in ethanol to obtain mixture I;

[0014] (2) Dissolve the heteropolyacid solid powder in water or ethanol to obtain mixture II;

[0015] (3) Slowly add Mixture Ⅰ into Mixture Ⅱ at a rate of 0.5 ml / min to form a flocculent precipitate, and stir evenly at room temperature to obtain Mixture Ⅲ;

[0016] (4) Continuously stir and age Mixture Ⅲ at room temperature for 2 - 6 hours, then wash, centrifuge, and dry it in sequence (first centrifuge and wash 3 times with distilled water, then centrifuge and wash 3 times with ethanol, and finally vacuum dry at 60 ºC for 12 h) to obtain a solid acid catalyst for degrading waste PET to prepare TPA;

[0017] In step (1), the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1 - 1.5:260, and in step (2), the molar ratio of the heteropolyacid solid powder to water or ethanol is 1 - 2:260 - 833.

[0018] For the preparation method of a solid acid catalyst for degrading waste PET to prepare TPA as described above, the preparation method of the asymmetric double quaternary ammonium salt surfactant is as follows: First, mix long-chain monohaloalkane, Solvent A, and tetramethylhexanediamine in a molar ratio of 1:40 - 70:1 - 10, and reflux and heat in a water bath at 45 - 75 ºC with stirring for 5 - 12 h. After filtration, washing with ether, and air drying, an intermediate product is obtained. Then, mix short-chain monohaloalkane, Solvent B, and the intermediate product in a molar ratio of 1 - 3:30 - 55:1, and reflux and heat in an oil bath at 80 - 120 ºC with stirring for 15 - 50 h. Evaporate the solvent and recrystallize with ether to obtain the asymmetric double quaternary ammonium salt surfactant [C m H 2m+1 -N + (CH 3 ) 2 -C 6 H 12 -N + (CH 3 ) 2 -C n H 2n+1 -X 2 (abbreviated as C m-6-n X 2 ), where m = 22, 18, 16, or 12; n = 4 or 6; X is Cl, Br, or I;

[0019] The long-chain monohaloalkane is chlorodocosane, chlorooctadecane, chlorohexadecane, chlorododecane, bromodocosane, bromooctadecane, bromohexadecane, bromododecane, iododocosane, iodoctadecane, iodohexadecane, or iodododecane; the short-chain monohaloalkane is chlorohexane, chlorobutane, bromohexane, bromobutane, iodohexane, or iodobutane.

[0020] A preparation method of a solid acid catalyst for degrading waste PET to produce TPA as described above, wherein solvent A is acetone, dimethyl carbonate, diethyl carbonate or acetonitrile; and solvent B is n-propanol or ethanol.

[0021] A preparation method of a solid acid catalyst for degrading waste PET to produce TPA as described above, in step (2), the heteropolyacid is phosphotungstic acid (H 3 PW 12 O 40 ), silicotungstic acid (H 4 SiW 12 O 40 ), phosphomolybdic acid (H 3 PMo 12 O 40 ), or silicomolybdic acid (H 4 SiMo 12 O 40 ).

[0022] The present invention also provides an application of the solid acid catalyst prepared by the preparation method described in any one of the above. Waste PET, the solid acid catalyst and distilled water are added to the polytetrafluoroethylene or polyphenylene paraffin liner of an autogenous pressure reactor according to a mass ratio of 1:0.1-0.2:2.5-15, and reacted at 180-220 °C for 4-24 h using a homogeneous reactor.

[0023] As a preferred technical solution:

[0024] An application of a solid acid catalyst for degrading waste PET to produce TPA as described above, wherein the solid acid catalyst is recycled multiple times. When used for the first time, the PET conversion rate is above 99%, and the TPA yield is above 94%; when recycled 6 times, the PET conversion rate is above 96.5%, and the TPA yield is above 90.2%.

[0025] An application of a solid acid catalyst for degrading waste PET to produce TPA as described above, wherein the waste PET is waste PET fiber or PET bottle chips; the waste PET fiber can be uncut, and the PET bottle chips need to be crushed into particles of 2 mm × 2 mm × 2 mm.

[0026] Principle of the invention:

[0027] A solid acid catalyst for degrading waste PET to produce TPA according to the present invention, namely a heteropolyacid asymmetric double quaternary ammonium salt solid acid catalyst, is prepared by an ion exchange reaction of a heteropolyacid and an asymmetric double quaternary ammonium salt in a certain molar ratio and is bonded together by chemical bonds. In the catalyst prepared by the reaction, the heteropolyacid anion provides catalytic activity, and the quaternary ammonium salt cation provides phase transfer ability. Since one end of the double quaternary ammonium salt cation with a longer chain length is a hydrophobic group and has lipophilicity, it can bring the heteropolyacid anion to the solid-liquid interface of the polyester organic phase and the aqueous phase reaction. The heteropolyacid anion enters the organic phase and attacks the surface of the PET macromolecule, and the ester group is attacked and broken into small molecule carboxyl groups and hydroxyl groups, and the generated monomers are quickly separated and enter the aqueous phase. And one end of the double quaternary ammonium salt cation with a shorter chain length shows hydrophilicity and can be tightly combined with the heteropolyacid through ion exchange to stabilize the catalyst structure. After the catalytic reaction is completed, the cations and anions in the catalyst return to their original structures.

[0028] The heteropolyacid asymmetric double quaternary ammonium salt solid acid catalyst has a phase transfer function, strengthens the interfacial mass transfer between solids, can reduce the energy consumption required for the degradation of PET macromolecules, improve the catalytic performance, and at the same time the solid acid catalyst can be recycled multiple times, avoid the discharge of waste liquids such as liquid acids and alkalis, and has no corrosion to equipment, prolonging its service life.

[0029] Beneficial effects:

[0030] (1) The present invention prepares a heteropolyacid double quaternary ammonium salt solid acid catalyst with a phase transfer function, overcomes the mass transfer limitation between macromolecular polymers and solid acid catalysts, effectively improves the catalytic degradation performance, and makes the PET conversion rate reach over 99% and the TPA yield reach over 94%.

[0031] (2) The heteropolyacid double quaternary ammonium salt solid acid catalyst prepared by the present invention has a stable structure and can be recycled multiple times compared with liquid acid catalysts. After the sixth cycle of use, the PET conversion rate can still reach over 96.5%, and at the same time the TPA yield can still be maintained above 90.2%, and there is no discharge of concentrated acid or concentrated alkali waste liquid, which is environmentally friendly; in addition, the entire degradation process has no corrosion to equipment, and only neutral water is used as the solvent, which is environmentally friendly and resource-saving.

[0032] (3) The preparation method of the present invention has a simple process, avoids the discharge of concentrated acid and concentrated alkali waste liquids, significantly reduces environmental pollution, and eliminates the corrosion of equipment, and has environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the molecular formula of the cation C of the asymmetric double quaternary ammonium salt surfactant prepared in Example 1 of the present invention; in the figure, different numbers represent different types of carbon atoms with different chemical environments; 18-6-6 2+ The figure shows different types of carbon atoms with different chemical environments;

[0034] Figure 2 The cation prepared in Example 1 of the present invention is C 18-6-6 2+ of the heteropolyacid double quaternary ammonium salt solid acid catalyst 1 1H NMR spectrum;

[0035] Figure 3 FT-IR spectrum of the solid acid catalyst for degrading waste PET to TPA prepared in Example 1 of the present invention;

[0036] Figure 4 UV absorption standard curve of TPA purified in the present invention at a wavelength of 240 nm;

[0037] Figure 5 Comparison chart of the appearance and purity of TPA purified in the present invention and commercial TPA; In the figure, a is the appearance and purity chart of TPA purified in the present invention, and b is the appearance and purity chart of commercial TPA;

[0038] Figure 6 X-ray diffraction spectra of TPA and commercial TPA obtained after the solid acid catalyst for degrading waste PET to TPA prepared in Example 1 of the present invention is recycled 3 times and 5 times;

[0039] Figure 7 Liquid NMR spectra of the solid acid catalyst for degrading waste PET to TPA prepared in the present invention to generate the product TPA at different cycle times; In the figure, a is the liquid 1 1H NMR spectrum of the solid acid catalyst for degrading waste PET to TPA to generate the product TPA at different cycle times, and b is the liquid 13 13C NMR spectrum;

[0040] Figure 8 Conversion rate of waste PET and TPA yield spectra of the solid acid catalyst for degrading waste PET to TPA prepared in Example 1 of the present invention during the recycling process. Detailed implementation manners

[0041] The present invention will be further described below in conjunction with specific implementation manners. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0042] Example 1

[0043] A preparation method of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0044] (1) Prepare an asymmetric double quaternary ammonium salt surfactant;

[0045] (1.1) Dissolve tetramethylhexanediamine in acetone, then add octadecyl chloride thereto, and reflux and heat in a water bath at 58 °C with stirring for 8 h, then cool to 25 °C, and then filter, wash with ether 3 times, and air-dry to obtain an intermediate product; wherein, the molar ratio of octadecyl chloride, acetone and tetramethylhexanediamine is 1:50:10;

[0046] (1.2) Dissolve the intermediate product in n-propanol, stir evenly, add chlorohexane thereto, and reflux and heat in an oil bath at 105 °C with stirring for 36 h, then evaporate the solvent and recrystallize with ether 3 times to obtain an asymmetric double quaternary ammonium salt surfactant; wherein, the molar ratio of chlorohexane, n-propanol and the intermediate product is 1.25:52.5:1;

[0047] The prepared asymmetric double quaternary ammonium salt surfactant is [C 18 H 37 -N + (CH 3 ) 2 -C 6 H 12 -N + (CH 3 ) 2 -C 6 H 13 -Cl 2 , abbreviated as C 18-6-6 Cl 2 , and the molecular formula of its cation is as Figure 1 shown;

[0048] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0049] (3) Dissolve phosphotungstic acid in distilled water to obtain mixture II; wherein, the molar ratio of phosphotungstic acid to distilled water is 1:833;

[0050] (4) At 25 °C, dropwise add mixture I to mixture II at a speed of 0.5 ml / min under magnetic stirring. A white flocculent precipitate will be formed during the dropping process. After the dropping is completed, mixture III is obtained; wherein, the dropping time is 0.5 h;

[0051] (5) The mixture Ⅲ was continuously stirred and aged at 25 °C for 2 hours, then centrifugally washed 3 times with distilled water first, and then 3 times with ethanol by centrifugation. Finally, it was dried in vacuum at 60 °C for 12 h to obtain a solid acid catalyst for the degradation of waste PET to TPA, whose 1 1H NMR spectrum is as Figure 2 shown, and the types of H and the peak areas correspond one by one to its molecular formula; the FT-IR spectrum of the solid acid catalyst for the degradation of waste PET to TPA is as Figure 3 shown. It can be seen from the figure that the heteropoly acid double quaternary ammonium salt solid acid catalyst has the characteristic peaks of double quaternary ammonium salt, and at the same time retains the complete characteristic structure of heteropoly acid, indicating that a high-purity heteropoly acid double quaternary ammonium salt solid acid catalyst has been successfully prepared.

[0052] An application of a solid acid catalyst for the degradation of waste PET to TPA is as follows:

[0053] (a) Degrading waste PET;

[0054] Waste PET fibers (oil-free semi-dull PET waste filaments, manufacturer: Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the above-prepared solid acid catalyst for the degradation of waste PET to TPA, and distilled water were added to the PTFE liner of an autogenous pressure reactor. Using a homogeneous reactor, it was reacted at 200 °C at a rotation speed of 10 r / min for 12 h, then cooled to room temperature, and the solid was separated by filtration; among them, the mass ratio of waste PET fibers, solid acid catalyst and distilled water is 1:0.1:10;

[0055] (b) TPA purification;

[0056] The solid product obtained in step (a) was dissolved in 1 mol / L NaOH aqueous solution and stirred at 25 °C for 0.5 h. Then, it was centrifuged at a speed of 9000 r / min for 10 minutes by a high-speed centrifuge. After centrifugation, the upper layer was the supernatant, and the lower layer solid was the catalyst and trace impurities. Then, the upper supernatant was taken out, and 1 mol / L dilute sulfuric acid was added thereto under stirring until the solution pH was acidic. Stirring was continued for 1 h until TPA was completely precipitated, and then it was filtered, washed, dried and weighed.

[0057] From the calculation of the mass of TPA and impurities obtained after the above purification, it can be known that the PET conversion rate of the solid acid catalyst for the degradation of waste PET to TPA at the first use is 99.5%, and the TPA yield is 94.3%. The purity of the purified TPA was measured by an ultraviolet-visible spectrophotometer at a wavelength of 240 nm, and the results are as Figure 4 、 Figure 5 shown. It can be seen from the figure that the purity of the TPA purified in the present invention is 99%, which is a pure white powder and has the same purity as commercial TPA;

[0058] (c) Take out the lower-layer solid separated in step (b), wash and dry it in sequence, and after repeating steps (a) to (b) 5 times, the PET conversion rate is 98%, the TPA yield is 91.3%, and the TPA purity is 99% (the PET conversion rate and TPA yield of the solid acid catalyst prepared in this example from the first use to the 6th use are as Figure 8 shown); among them, the catalyst used when repeating steps (a) to (b) 5 times is the product obtained by washing and drying the lower-layer solid separated in the purification process of the previous cycle.

[0059] Compare the crystal structures of the TPA purified after the solid acid catalyst prepared in this example is reused 3 times and 5 times with commercial TPA, as Figure 6 shown, the positions of its XRD diffraction peaks are the same as those of commercial TPA; at the same time, perform 1 H, 13 C liquid nuclear magnetic characterizations on the TPA purified after the solid acid catalyst prepared in this example is recycled 1 time, 3 times, 5 times, and 6 times, and the results are as Figure 7 shown. It can be seen from the figure that the product obtained by the solid acid catalyst recycling to degrade PET is high-purity and high-crystallinity TPA.

[0060] Example 2

[0061] A preparation method of a solid acid catalyst for degrading waste PET to TPA, the steps are as follows:

[0062] (1) Prepare an asymmetric double quaternary ammonium salt surfactant;

[0063] (1.1) Dissolve tetramethylhexanediamine in dimethyl carbonate, then add octadecyl bromide to it, and reflux and heat in a water bath at 60 °C with stirring for 7 h, then cool to 25 °C, and then perform filtration, wash with ether 3 times, and air dry to obtain an intermediate product; among them, the molar ratio of octadecyl bromide, dimethyl carbonate and tetramethylhexanediamine is 1:50:5;

[0064] (1.2) Dissolve the intermediate product in ethanol, stir evenly, add bromohexane, and reflux and heat in an oil bath at 85 °C with stirring for 48 h. Then evaporate the solvent and recrystallize with ether 3 times to obtain an asymmetric double quaternary ammonium salt surfactant; among them, the molar ratio of bromohexane, ethanol and the intermediate product is 1.25:50:1;

[0065] The prepared asymmetric double quaternary ammonium salt surfactant is [C 18 H 37+1 -N + (CH 3 ) 2 -C6 H 12 -N + (CH 3 ) 2 -C 6 H 13 -Br 2 , abbreviated as C 18-6-6 Br 2 ;

[0066] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1.5:260;

[0067] (3) Dissolve phosphomolybdic acid in ethanol to obtain mixture II; wherein, the molar ratio of phosphomolybdic acid to ethanol is 1:260;

[0068] (4) At 25 °C, dropwise add mixture I into mixture II at a speed of 0.5 ml / min under magnetic stirring. White flocculent precipitates will form during the dropping process. After the dropping is completed, mixture III is obtained; wherein, the dropping time is 0.5 h;

[0069] (5) Stir and age mixture III at 25 °C for 2 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it under vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0070] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0071] (a) Degrade waste PET;

[0072] First, crush PET bottle chips (waste mineral water bottles, manufacturer: Nongfu Spring) into particles of 2 mm × 2 mm × 2 mm, then add the granular PET bottle chips, the above-prepared solid acid catalyst for degrading waste PET to produce TPA, and distilled water into the PTFE liner of an autogenous pressure reactor, and use a homogeneous reactor to react at 190 °C at a rotation speed of 10 r / min for 15 h, then cool to room temperature, and filter to separate the solid; wherein, the mass ratio of PET bottle chips, solid acid catalyst, and distilled water is 1:0.125:12.5;

[0073] (b) Purify TPA;

[0074] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 minutes using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid to it under stirring until the solution shows acidic pH. Continue stirring for 1 h. After TPA is completely precipitated, filter, wash, dry and weigh it.

[0075] It can be calculated from the masses of TPA and impurities obtained after the above purification that the PET conversion rate of the solid acid catalyst for degrading waste PET to TPA during the first use is 99.2%, the TPA yield is 94.6%, and the TPA purity is 99%;

[0076] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and then repeat steps (a) - (b) 5 times. The PET conversion rate is 97.4%, the TPA yield is 90.9%, and the TPA purity is 99%; among them, the catalyst used when repeating steps (a) - (b) 5 times is the product obtained after washing and drying the solid on the lower layer separated during the purification process of the previous cycle.

[0077] Example 3

[0078] A preparation method of a solid acid catalyst for degrading waste PET to TPA is as follows:

[0079] (1) Prepare an asymmetric bisquaternary ammonium salt surfactant;

[0080] (1.1) Dissolve tetramethylhexanediamine in diethyl carbonate, then add iodooctadecane to it, and reflux and heat in a water bath at 75 °C under stirring for 5 h, then cool to 25 °C, and then filter, wash with ether 3 times, and air-dry to obtain an intermediate product; among them, the molar ratio of iodooctadecane, diethyl carbonate and tetramethylhexanediamine is 1:50:3;

[0081] (1.2) Dissolve the intermediate product in ethanol, stir evenly, add iodohexane, and reflux and heat in an oil bath at 80 °C under stirring for 48 h, then evaporate the solvent and recrystallize with ether 3 times to obtain an asymmetric bisquaternary ammonium salt surfactant; among them, the molar ratio of iodohexane, ethanol and the intermediate product is 1.5:50:1;

[0082] The prepared asymmetric bisquaternary ammonium salt surfactant is [C 18 H 37 -N + (CH 3 ) 2 -C 6 H 12 -N+ (CH 3 ) 2 -C 6 H 13 -I 2 , abbreviated as C 18-6-6 I 2 ;

[0083] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; among them, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0084] (3) Dissolve phosphotungstic acid in ethanol to obtain mixture II; among them, the molar ratio of phosphotungstic acid to ethanol is 2:260;

[0085] (4) At 25 °C, under magnetic stirring, add mixture I dropwise to mixture II at a rate of 0.5 ml / min. A white flocculent precipitate will form during the dropping process. After the dropping is completed, mixture III is obtained; among them, the dropping time is 0.5 h;

[0086] (5) Continue to stir and age mixture III at 25 °C for 4 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it under vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to prepare TPA.

[0087] An application of a solid acid catalyst for degrading waste PET to prepare TPA is as follows:

[0088] (a) Degrade waste PET;

[0089] First, crush PET bottle chips (waste mineral water bottles, manufacturer is Nongfu Spring) into particles of 2 mm × 2 mm × 2 mm, then add the particulate PET bottle chips, the above-prepared solid acid catalyst for degrading waste PET to prepare TPA, and distilled water into the PTFE liner of an autogenous pressure reactor. Use a homogeneous reactor to react at 180 °C at a rotation speed of 10 r / min for 24 h, then cool to room temperature, and filter to separate the solid; among them, the mass ratio of PET bottle chips, solid acid catalyst and distilled water is 1:0.125:12.5;

[0090] (b) Purify TPA;

[0091] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid thereto under stirring until the solution shows acidic pH. Continue stirring for 1 h until TPA completely precipitates, then filter, wash, dry and weigh.

[0092] From the calculation of the mass of TPA and impurities obtained after the above purification, it can be known that when the solid acid catalyst for degrading waste PET to prepare TPA is used for the first time, the PET conversion rate is 99.3%, the TPA yield is 94%, and the TPA purity is 99%;

[0093] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and then repeat steps (a) - (b) 5 times. The PET conversion rate is 97.7%, the TPA yield is 90.6%, and the TPA purity is 99%; Among them, when repeating steps (a) - (b) 5 times, the catalyst used is the product obtained after washing and drying the solid on the lower layer separated in the purification process of the previous cycle.

[0094] Example 4

[0095] A preparation method of a solid acid catalyst for degrading waste PET to prepare TPA, the steps are as follows:

[0096] (1) Prepare an asymmetric bisquaternary ammonium salt surfactant;

[0097] (1.1) Dissolve tetramethylhexanediamine in acetone, add dodecyl iodide thereto, and reflux and heat in a water bath at 60 °C under stirring for 8 h, then cool to 25 °C, and then filter, wash with ether 3 times, and air dry to obtain an intermediate product; Among them, the molar ratio of dodecyl iodide, acetone and tetramethylhexanediamine is 1:40:10;

[0098] (1.2) Dissolve the intermediate product in ethanol, stir evenly, add iodobutane, and reflux and heat in an oil bath at 85 °C under stirring for 40 h, then evaporate the solvent and recrystallize with ether 3 times to prepare an asymmetric bisquaternary ammonium salt surfactant; Among them, the molar ratio of iodobutane, ethanol and the intermediate product is 1.5:55:1;

[0099] The prepared asymmetric bisquaternary ammonium salt surfactant is [C 12 H 25 -N + (CH 3 ) 2 -C 6 H 12 -N+ (CH 3 ) 2 -C 4 H 9 -I 2 , abbreviated as CI 12-6-4 I 2 ;

[0100] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; among them, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0101] (3) Dissolve phosphotungstic acid in distilled water to obtain mixture II; among them, the molar ratio of phosphotungstic acid to distilled water is 2:550;

[0102] (4) At 25 °C, drop mixture I into mixture II at a speed of 0.5 ml / min under magnetic stirring. A white flocculent precipitate will be formed during the dropping process. After the dropping is completed, mixture III is obtained; among them, the dropping time is 0.5 h;

[0103] (5) Stir and age mixture III at 25 °C for 4 hours, then first wash it 3 times by centrifugation with distilled water, then wash it 3 times by centrifugation with ethanol, and finally dry it in vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0104] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0105] (a) Degrade waste PET;

[0106] Add waste PET fibers (oil-free semi-dull PET waste filaments, manufacturer is Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the above-prepared solid acid catalyst for degrading waste PET to produce TPA and distilled water into the PTFE liner of an autogenous pressure reactor, and use a homogeneous reactor to react at 200 °C at a rotation speed of 10 r / min for 12 h, then cool to room temperature, and filter to separate the solid; among them, the mass ratio of waste PET fibers, solid acid catalyst and distilled water is 1:0.1:15;

[0107] (b) Purify TPA;

[0108] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid thereto under stirring until the solution shows acidic pH. Continue stirring for 1 h, filter, wash, dry and weigh after TPA completely precipitates.

[0109] It can be calculated from the masses of TPA and impurities obtained after the above purification that the PET conversion rate of the solid acid catalyst for degrading waste PET to TPA is 99.2%, the TPA yield is 94.2%, and the TPA purity is 99% when it is used for the first time;

[0110] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and repeat steps (a) to (b) 5 times. Then the PET conversion rate is 97.6%, the TPA yield is 90.2%, and the TPA purity is 99%; among them, the catalyst used when repeating steps (a) to (b) 5 times is the product obtained after washing and drying the solid on the lower layer separated in the purification process of the previous cycle.

[0111] Example 5

[0112] A preparation method of a solid acid catalyst for degrading waste PET to TPA comprises the following steps:

[0113] (1) Prepare an asymmetric bisquaternary ammonium salt surfactant;

[0114] (1.1) Dissolve tetramethylhexanediamine in acetonitrile, add chlorodocosane thereto, and reflux and heat in a 70 °C water bath under stirring for 10 h, then cool to 25 °C, and then filter, wash with ether 3 times, and air-dry to obtain an intermediate product; among them, the molar ratio of chlorodocosane, acetonitrile and tetramethylhexanediamine is 1:55:7;

[0115] (1.2) Dissolve the intermediate product in n-propanol, stir evenly, add chlorohexane, and reflux and heat in a 100 °C oil bath under stirring for 48 h. Then evaporate the solvent and recrystallize with ether 3 times to prepare an asymmetric bisquaternary ammonium salt surfactant; among them, the molar ratio of chlorohexane, n-propanol and the intermediate product is 1.25:55:1;

[0116] The prepared asymmetric bisquaternary ammonium salt surfactant is [C 22 H 45 -N + (CH 3 ) 2 -C 6 H 12 -N+ (CH 3 ) 2 -C 6 H 13 -Cl 2 , abbreviated as C 22-6-6 Cl 2 ;

[0117] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1.5:260;

[0118] (3) Dissolve phosphotungstic acid in ethanol to obtain mixture II; wherein, the molar ratio of phosphotungstic acid to ethanol is 1:260;

[0119] (4) At 25 °C, dropwise add mixture I into mixture II at a speed of 0.5 ml / min under magnetic stirring. White flocculent precipitate will form during the dropping process. After the dropping is completed, mixture III is obtained; wherein, the dropping time is 0.5 h;

[0120] (5) Stir and age mixture III at 25 °C for 6 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it in vacuum at 60 ºC for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0121] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0122] (a) Degrade waste PET;

[0123] First, crush PET bottle chips (waste mineral water bottles, manufacturer is Nongfu Spring) into particles of 2 mm×2 mm×2 mm, then add the particulate PET bottle chips, the above-prepared solid acid catalyst for degrading waste PET to produce TPA and distilled water into the PTFE liner of an autogenous pressure reactor, and use a homogeneous reactor to react at 200 ºC at a rotation speed of 10 r / min for 12 h, then cool to room temperature, and filter to separate the solid; wherein, the mass ratio of PET bottle chips, solid acid catalyst and distilled water is 1:0.125:10;

[0124] (b) Purify TPA;

[0125] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid to it under stirring until the solution shows acidic pH, continue stirring for 1 h until TPA completely precipitates, then filter, wash, dry and weigh.

[0126] From the calculation of the masses of TPA and impurities obtained after the above purification, it can be known that when the solid acid catalyst for degrading waste PET to prepare TPA is used for the first time, the PET conversion rate is 99.3%, the TPA yield is 94.1%, and the TPA purity is 99%;

[0127] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and then repeat steps (a) - (b) 5 times. The PET conversion rate is 96.8%, the TPA yield is 91.2%, and the TPA purity is 99%; Among them, when repeating steps (a) - (b) 5 times, the catalyst used is the product obtained after washing and drying the solid on the lower layer separated in the purification process of the previous cycle.

[0128] Example 6

[0129] A preparation method of a solid acid catalyst for degrading waste PET to prepare TPA, the steps are as follows:

[0130] (1) Prepare an asymmetric double quaternary ammonium salt surfactant;

[0131] (1.1) Dissolve tetramethylhexanediamine in dimethyl carbonate, then add docosyl bromide to it, and reflux and heat in a water bath at 70 °C under stirring for 7 h, then cool to 25 °C, and then filter, wash with ether 3 times, and air dry to obtain an intermediate product; Among them, the molar ratio of docosyl bromide, dimethyl carbonate and tetramethylhexanediamine is 1:70:1;

[0132] (1.2) Dissolve the intermediate product in ethanol, stir evenly, add hexyl bromide, and reflux and heat in an oil bath at 80 °C under stirring for 48 h, then evaporate the solvent and recrystallize with ether 3 times to prepare an asymmetric double quaternary ammonium salt surfactant; Among them, the molar ratio of hexyl bromide, ethanol and the intermediate product is 3:50:1;

[0133] The prepared asymmetric double quaternary ammonium salt surfactant is [C 22 H 45 -N + (CH 3 ) 2 -C 6 H 12 -N+ (CH 3 ) 2 -C 6 H 13 -Br 2 , abbreviated as C 22-6-6 Br 2 ;

[0134] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0135] (3) Dissolve phosphotungstic acid in distilled water to obtain mixture II; wherein, the molar ratio of phosphotungstic acid to distilled water is 2:550;

[0136] (4) At 25 °C, dropwise add mixture I into mixture II at a rate of 0.5 ml / min under magnetic stirring. White flocculent precipitates will form during the dropping process. After the dropping is completed, mixture III is obtained; wherein, the dropping time is 0.5 h;

[0137] (5) Stir and age mixture III at 25 °C for 6 hours, then first wash it centrifugally with distilled water 3 times, then wash it centrifugally with ethanol 3 times, and finally dry it under vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0138] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0139] (a) Degrade waste PET;

[0140] Add waste PET fibers (oil-free semi-dull PET waste filaments, manufacturer: Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the above-prepared solid acid catalyst for degrading waste PET to produce TPA, and distilled water into the parylene liner of an autogenous pressure reactor. Use a homogeneous reactor to react at 205 °C at a rotation speed of 10 r / min for 10 h, then cool to room temperature, and filter to separate the solid; wherein, the mass ratio of waste PET fibers, solid acid catalyst and distilled water is 1:0.1:7.5;

[0141] (b) Purify TPA;

[0142] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid to it under stirring until the solution shows acidic pH, continue stirring for 1 h until TPA completely precipitates, then filter, wash, dry and weigh it.

[0143] It can be calculated from the masses of TPA and impurities obtained after the above purification that the PET conversion rate of the solid acid catalyst for degrading waste PET to TPA during the first use is 99.4%, the TPA yield is 94%, and the TPA purity is 99%;

[0144] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and then repeat steps (a) to (b) 5 times. The PET conversion rate is 97.4%, the TPA yield is 91.2%, and the TPA purity is 99%; among them, the catalyst used when repeating steps (a) to (b) 5 times is the product obtained after washing and drying the solid on the lower layer separated during the purification process of the previous cycle.

[0145] Example 7

[0146] A preparation method of a solid acid catalyst for degrading waste PET to TPA, the steps are as follows:

[0147] (1) Prepare an asymmetric bisquaternary ammonium salt surfactant;

[0148] (1.1) Dissolve tetramethylhexanediamine in acetone, then add cetyl chloride to it, and reflux and heat in a water bath at 45 °C for 12 h under stirring, then cool to 25 °C, and then filter, wash with ether 3 times, and air-dry to obtain an intermediate product; among them, the molar ratio of cetyl chloride, acetone and tetramethylhexanediamine is 1:50:10;

[0149] (1.2) Dissolve the intermediate product in ethanol, stir evenly, add chlorobutane, and reflux and heat in an oil bath at 80 °C for 50 h under stirring, then evaporate the solvent and recrystallize with ether 3 times to obtain an asymmetric bisquaternary ammonium salt surfactant; among them, the molar ratio of chlorobutane, ethanol and the intermediate product is 2:40:1;

[0150] The prepared asymmetric bisquaternary ammonium salt surfactant is [C 16 H 33 -N + (CH 3 ) 2 -C 6 H 12 -N +(CH 3 ) 2 -C 4 H 9 -Cl 2 , abbreviated as C 16-6-4 Cl 2 ;

[0151] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0152] (3) Dissolve silicotungstic acid in ethanol to obtain mixture II; wherein, the molar ratio of silicotungstic acid to ethanol is 1:260;

[0153] (4) At 25 °C, dropwise add mixture I into mixture II at a speed of 0.5 ml / min under magnetic stirring. A white flocculent precipitate will form during the dropping process. After the dropping is completed, mixture III is obtained; wherein, the dropping time is 0.5 h;

[0154] (5) Stir and age mixture III at 25 °C for 2 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it under vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0155] Application of a solid acid catalyst for degrading waste PET to produce TPA, the steps are as follows:

[0156] (a) Degrade waste PET;

[0157] Add waste PET fibers (oil-free semi-dull PET waste silk, manufacturer: Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the above-prepared solid acid catalyst for degrading waste PET to produce TPA, and distilled water into the PTFE liner of an autogenous pressure reactor. Use a homogeneous reactor to react at 220 °C at a rotation speed of 10 r / min for 4 h, then cool to room temperature, and filter to separate the solid; wherein, the mass ratio of waste PET fibers, solid acid catalyst and distilled water is 1:0.125:5;

[0158] (b) Purify TPA;

[0159] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 minutes using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid thereto under stirring until the solution shows acidic pH, continue stirring for 1 h. After TPA is completely precipitated, filter, wash, dry and weigh it.

[0160] It can be calculated from the masses of TPA and impurities obtained after the above purification that when the solid acid catalyst for degrading waste PET to prepare TPA is used for the first time, the PET conversion rate is 99%, the TPA yield is 94.1%, and the TPA purity is 99%;

[0161] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and after repeating steps (a) to (b) 5 times, the PET conversion rate is 96.5%, the TPA yield is 90.2%, and the TPA purity is 99%; among them, when repeating steps (a) to (b) 5 times, the catalyst used is the product obtained after washing and drying the solid on the lower layer separated in the purification process of the previous cycle.

[0162] Example 8

[0163] A preparation method of a solid acid catalyst for degrading waste PET to prepare TPA, the steps are as follows:

[0164] (1) Prepare an asymmetric bisquaternary ammonium salt surfactant;

[0165] (1.1) Dissolve tetramethylhexanediamine in acetone, add dodecyl bromide thereto, and reflux and heat in a water bath at 60 °C under stirring for 10 h, then cool to 25 °C, and then filter, wash with ether 3 times, and air dry to obtain an intermediate product; among them, the molar ratio of dodecyl bromide, acetone and tetramethylhexanediamine is 1:50:10;

[0166] (1.2) Dissolve the intermediate product in n-propanol, stir evenly, add butyl bromide, and reflux and heat in an oil bath at 120 °C under stirring for 15 h, then evaporate the solvent and recrystallize with ether 3 times to prepare an asymmetric bisquaternary ammonium salt surfactant; among them, the molar ratio of butyl bromide, n-propanol and the intermediate product is 1:30:1;

[0167] The prepared asymmetric bisquaternary ammonium salt surfactant is [C 12 H 25 -N + (CH 3 ) 2 -C 6 H 12 -N+ (CH 3 ) 2 -C 4 H 9 -Br 2 , abbreviated as C 12-6-4 Br 2 ;

[0168] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0169] (3) Dissolve silicomolybdic acid in distilled water to obtain mixture II; wherein, the molar ratio of silicomolybdic acid to distilled water is 2:833;

[0170] (4) At 25 °C, dropwise add mixture I into mixture II at a speed of 0.5 ml / min under magnetic stirring. White flocculent precipitate will be formed during the dropping process. After the dropping is completed, mixture III is obtained; wherein, the dropping time is 0.5 h;

[0171] (5) Stir and age mixture III at 25 °C for 2 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it under vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0172] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0173] (a) Degrade waste PET;

[0174] Add waste PET fiber (oil-free semi-dull PET waste silk, manufacturer is Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the solid acid catalyst for degrading waste PET to produce TPA prepared above, and distilled water into the parylene liner of a self-pressure reactor. After reacting at 210 °C for 8 h at a rotation speed of 10 r / min using a homogeneous reactor, cool it to room temperature, and filter and separate the solid; wherein, the mass ratio of waste PET fiber, solid acid catalyst and distilled water is 1:0.1:10;

[0175] (b) Purify TPA;

[0176] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid to it under stirring until the solution shows acidic pH, continue stirring for 1 h until TPA completely precipitates, then filter, wash, dry and weigh.

[0177] It can be calculated from the masses of TPA and impurities obtained after the above purification that when the solid acid catalyst for degrading waste PET to prepare TPA is used for the first time, the PET conversion rate is 99.4%, the TPA yield is 94.5%, and the TPA purity is 99%;

[0178] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and then repeat steps (a) - (b) 5 times. After that, the PET conversion rate is 97.2%, the TPA yield is 90.9%, and the TPA purity is 99%; Among them, when repeating steps (a) - (b) 5 times, the catalyst used is the product obtained after washing and drying the solid on the lower layer separated in the purification process of the previous cycle.

[0179] Example 9

[0180] A preparation method of a solid acid catalyst for degrading waste PET to prepare TPA, the steps are as follows:

[0181] (1) Prepare an asymmetric bisquaternary ammonium salt surfactant;

[0182] (1.1) Dissolve tetramethylhexanediamine in dimethyl carbonate, then add dodecyl chloride to it, and reflux and heat in a water bath at 65 °C under stirring for 8 h, then cool to 25 °C, and then filter, wash with ether 3 times, and air-dry to obtain an intermediate product; Among them, the molar ratio of dodecyl chloride, dimethyl carbonate and tetramethylhexanediamine is 1:40:5;

[0183] (1.2) Dissolve the intermediate product in n-propanol, stir evenly, add chlorohexane, and reflux and heat in an oil bath at 108 °C under stirring for 36 h, then evaporate the solvent and recrystallize with ether 3 times to obtain an asymmetric bisquaternary ammonium salt surfactant; Among them, the molar ratio of chlorohexane, n-propanol and the intermediate product is 1.25:30:1;

[0184] The prepared asymmetric bisquaternary ammonium salt surfactant is [C 12 H 25 -N + (CH 3 ) 2 -C 6 H 12-N + (CH 3 ) 2 -C 6 H 13 -Cl 2 , abbreviated as C 12-6-6 Cl 2 ;

[0185] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1.25:260;

[0186] (3) Dissolve phosphotungstic acid in distilled water to obtain mixture II; wherein, the molar ratio of phosphotungstic acid to distilled water is 2:833;

[0187] (4) At 25 °C, dropwise add mixture I into mixture II at a speed of 0.5 ml / min under magnetic stirring. White flocculent precipitates will form during the dropping process. After the dropping is completed, mixture III is obtained; wherein, the dropping time is 0.5 h;

[0188] (5) Stir and age mixture III at 25 °C for 2 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it in vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0189] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0190] (a) Degrade waste PET;

[0191] Add waste PET fibers (oil-free semi-dull PET waste filaments, manufacturer is Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the above-prepared solid acid catalyst for degrading waste PET to produce TPA, and distilled water into the PTFE liner of an autogenous pressure reactor. Use a homogeneous reactor to react at 200 °C at a rotation speed of 10 r / min for 12 h, then cool to room temperature, and filter to separate the solid; wherein, the mass ratio of waste PET fibers, solid acid catalyst and distilled water is 1:0.15:10;

[0192] (b) Purify TPA;

[0193] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid to it under stirring until the solution shows an acidic pH. Continue stirring for 1 h. After TPA is completely precipitated, filter, wash, dry and weigh it.

[0194] From the calculation of the masses of TPA and impurities obtained after the above purification, it can be known that when the solid acid catalyst for degrading waste PET to produce TPA is used for the first time, the PET conversion rate is 99.4%, the TPA yield is 94.4%, and the TPA purity is 99%;

[0195] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and then repeat steps (a) - (b) 5 times. The PET conversion rate is 97.4%, the TPA yield is 90.7%, and the TPA purity is 99%; Among them, when repeating steps (a) - (b) 5 times, the catalyst used is the product obtained after washing and drying the solid on the lower layer separated in the purification process of the previous cycle.

[0196] Example 10

[0197] A preparation method of a solid acid catalyst for degrading waste PET to produce TPA, the steps are as follows:

[0198] (1) Prepare an asymmetric bisquaternary ammonium salt surfactant;

[0199] (1.1) Dissolve tetramethylhexanediamine in acetone, then add hexadecyl bromide to it, and reflux and heat in a water bath at 55 °C for 9 h under stirring, then cool to 25 °C, and then filter, wash with ether 3 times, and air-dry to obtain an intermediate product; Among them, the molar ratio of hexadecyl bromide, acetone and tetramethylhexanediamine is 1:60:10;

[0200] (1.2) Dissolve the intermediate product in ethanol, stir evenly, add bromohexane, and reflux and heat in an oil bath at 80 °C for 50 h under stirring. Then evaporate the solvent and recrystallize with ether 3 times to obtain an asymmetric bisquaternary ammonium salt surfactant; Among them, the molar ratio of bromohexane, ethanol and the intermediate product is 1.5:40:1;

[0201] The prepared asymmetric bisquaternary ammonium salt surfactant is [C 16 H 33 -N + (CH 3 ) 2 -C 6 H 12 -N+ (CH 3 ) 2 -C 6 H 13 -Br 2 , abbreviated as C 16-6-6 Br 2 ;

[0202] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0203] (3) Dissolve phosphotungstic acid in distilled water to obtain mixture II; wherein, the molar ratio of phosphotungstic acid to distilled water is 2:550;

[0204] (4) At 25 °C, dropwise add mixture I into mixture II at a rate of 0.5 ml / min under magnetic stirring. A white flocculent precipitate will be formed during the dropping process. After the dropping is completed, mixture III is obtained; wherein, the dropping time is 0.5 h;

[0205] (5) Stir and age mixture III at 25 °C for 2 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it in vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0206] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0207] (a) Degrade waste PET;

[0208] Add waste PET fibers (oil-free semi-dull PET waste filaments, manufacturer: Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the above-prepared solid acid catalyst for degrading waste PET to produce TPA, and distilled water into the PTFE liner of an autogenous pressure reactor. React at 200 °C for 12 h at a rotation speed of 10 r / min using a homogeneous reactor, then cool to room temperature, and filter to separate the solid; wherein, the mass ratio of waste PET fibers, solid acid catalyst, and distilled water is 1:0.1:2.5;

[0209] (b) Purify TPA;

[0210] The solid product obtained in step (a) was dissolved in 1 mol / L aqueous NaOH solution, stirred at 25 °C for 0.5 h, and then centrifuged at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant was on the upper layer and the solid on the lower layer was the catalyst and trace impurities. Subsequently, the supernatant on the upper layer was taken out, and 1 mol / L dilute sulfuric acid was added thereto under stirring until the solution showed acidic pH. Stirring was continued for 1 h. After TPA was completely precipitated, it was filtered, washed, dried and weighed.

[0211] From the calculation of the mass of TPA and impurities obtained after the above purification, it can be known that when the solid acid catalyst for degrading waste PET to prepare TPA was used for the first time, the PET conversion rate was 99.6%, the TPA yield was 94.5%, and the TPA purity was 99%;

[0212] (c) The solid on the lower layer separated in step (b) was taken out, washed and dried in sequence, and after repeating steps (a) to (b) 5 times, the PET conversion rate was 97.8%, the TPA yield was 91%, and the TPA purity was 99%; Among them, when repeating steps (a) to (b) 5 times, the catalyst used was the product obtained after washing and drying the solid on the lower layer separated in the purification process of the previous cycle.

[0213] Example 11

[0214] A preparation method of a solid acid catalyst for degrading waste PET to prepare TPA, the steps are as follows:

[0215] (1) Prepare an asymmetric bisquaternary ammonium salt surfactant;

[0216] (1.1) Tetramethylhexanediamine was dissolved in diethyl carbonate, and then 1-iododocosane was added thereto, and it was refluxed and heated in a water bath at 75 °C for 6 h under stirring and then cooled to 25 °C. Then, filtration, washing with ether 3 times, and air drying were carried out in sequence to obtain an intermediate product; among them, the molar ratio of 1-iododocosane, diethyl carbonate and tetramethylhexanediamine was 1:50:5;

[0217] (1.2) The intermediate product was dissolved in n-propanol, stirred evenly, and then iodobutane was added, and it was refluxed and heated in an oil bath at 110 °C for 32 h under stirring. Subsequently, the solvent was evaporated to dryness and recrystallized with ether 3 times to prepare an asymmetric bisquaternary ammonium salt surfactant; among them, the molar ratio of iodobutane, n-propanol and the intermediate product was 2:50:1;

[0218] The prepared asymmetric bisquaternary ammonium salt surfactant is [C 22 H 45 -N + (CH 3 ) 2 -C 6 H 12 -N+ (CH 3 ) 2 -C 4 H 9 -I 2 , abbreviated as C 22-6-4 I 2 ;

[0219] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; wherein, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0220] (3) Dissolve phosphotungstic acid in distilled water to obtain mixture II; wherein, the molar ratio of phosphotungstic acid to distilled water is 2:833;

[0221] (4) At 25 °C, under magnetic stirring, slowly add mixture I to mixture II at a rate of 0.5 ml / min. A white flocculent precipitate will form during the addition process. After the addition is completed, mixture III is obtained; wherein, the addition time is 0.5 h;

[0222] (5) Stir and age mixture III at 25 °C for 2 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it in vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0223] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0224] (a) Degrade waste PET;

[0225] Add waste PET fibers (oil-free semi-dull PET waste silk, manufacturer: Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the above-prepared solid acid catalyst for degrading waste PET to produce TPA, and distilled water into the PTFE liner of an autogenous pressure reactor. Use a homogeneous reactor to react at 200 °C at a rotation speed of 10 r / min for 12 h, then cool to room temperature, and filter to separate the solid; wherein, the mass ratio of waste PET fibers, solid acid catalyst and distilled water is 1:0.2:10;

[0226] (b) Purify TPA;

[0227] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid to it under stirring until the solution shows acidic pH, continue stirring for 1 h until TPA completely precipitates, then filter, wash, dry and weigh it.

[0228] From the calculation of the mass of TPA and impurities obtained after the above purification, it can be known that when the solid acid catalyst for degrading waste PET to prepare TPA is used for the first time, the PET conversion rate is 99.3%, the TPA yield is 94.3%, and the TPA purity is 99%;

[0229] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and then repeat steps (a) - (b) 5 times. The PET conversion rate is 97.2%, the TPA yield is 90.5%, and the TPA purity is 99%; Among them, when repeating steps (a) - (b) 5 times, the catalyst used is the product after washing and drying of the solid on the lower layer separated in the purification process of the previous cycle.

[0230] Example 12

[0231] A preparation method of a solid acid catalyst for degrading waste PET to prepare TPA, the steps are as follows:

[0232] (1) Prepare an asymmetric double quaternary ammonium salt surfactant;

[0233] (1.1) Dissolve tetramethylhexanediamine in acetonitrile, then add hexadecyl iodide to it, and reflux and heat in a water bath at 60 °C under stirring for 12 h, then cool to 25 °C, and then filter, wash with ether 3 times, and air dry to obtain an intermediate product; Among them, the molar ratio of hexadecyl iodide, acetonitrile and tetramethylhexanediamine is 1:70:10;

[0234] (1.2) Dissolve the intermediate product in n-propanol, stir evenly, add iodohexane, and reflux and heat in an oil bath at 105 °C under stirring for 40 h, then evaporate the solvent and recrystallize with ether 3 times to prepare an asymmetric double quaternary ammonium salt surfactant; Among them, the molar ratio of iodohexane, n-propanol and the intermediate product is 2.5:55:1;

[0235] The prepared asymmetric double quaternary ammonium salt surfactant is [C 16 H 33 -N + (CH 3 ) 2 -C 6 H 12 -N+ (CH 3 ) 2 -C 6 H 13 -I 2 , abbreviated as CI 16-6-6 I 2 ;

[0236] (2) Dissolve the asymmetric double quaternary ammonium salt surfactant prepared in step (1) in ethanol and stir evenly to obtain mixture I; among them, the molar ratio of the asymmetric double quaternary ammonium salt surfactant to ethanol is 1:260;

[0237] (3) Dissolve phosphotungstic acid in distilled water to obtain mixture II; among them, the molar ratio of phosphotungstic acid to distilled water is 2:550;

[0238] (4) At 25 °C, drop mixture I into mixture II at a speed of 0.5 ml / min under magnetic stirring. A white flocculent precipitate will form during the dropping process. After the dropping is completed, mixture III is obtained; among them, the dropping time is 0.5 h;

[0239] (5) Stir and age mixture III at 25 °C for 2 hours, then first centrifuge and wash it 3 times with distilled water, then centrifuge and wash it 3 times with ethanol, and finally dry it under vacuum at 60 °C for 12 h to obtain a solid acid catalyst for degrading waste PET to produce TPA.

[0240] An application of a solid acid catalyst for degrading waste PET to produce TPA is as follows:

[0241] (a) Degrade waste PET;

[0242] Add waste PET fiber (oil-free semi-dull PET waste silk, manufacturer is Tongkun Group Co., Ltd., TiO 2 content is 0.225%), the above-prepared solid acid catalyst for degrading waste PET to produce TPA, and distilled water into the PTFE liner of the autogenous pressure reactor. Use a homogeneous reactor to react at 200 °C at a rotation speed of 10 r / min for 12 h, then cool to room temperature, and filter and separate the solid; among them, the mass ratio of waste PET fiber, solid acid catalyst and distilled water is 1:0.1:10;

[0243] (b) Purify TPA;

[0244] Dissolve the solid product obtained in step (a) in 1 mol / L aqueous NaOH solution, stir at 25 °C for 0.5 h, then centrifuge at 9000 rpm for 10 min using a high-speed centrifuge. After centrifugation, the supernatant is on the upper layer and the solid on the lower layer is the catalyst and trace impurities. Then take out the supernatant on the upper layer, and add 1 mol / L dilute sulfuric acid thereto under stirring until the solution shows an acidic pH. Continue stirring for 1 h. After TPA is completely precipitated, filter, wash, dry and weigh it.

[0245] From the calculation of the mass of TPA and impurities obtained after the above purification, it can be known that when the solid acid catalyst for degrading waste PET to prepare TPA is used for the first time, the PET conversion rate is 99.1%, the TPA yield is 94.2%, and the TPA purity is 99%.

[0246] (c) Take out the solid on the lower layer separated in step (b), wash and dry it in sequence, and then repeat steps (a) to (b) 5 times. The PET conversion rate is 97%, the TPA yield is 90.3%, and the TPA purity is 99%. Among them, the catalyst used when repeating steps (a) to (b) 5 times is the product obtained by washing and drying the solid on the lower layer separated in the purification process of the previous cycle.

[0247] Comparative Example 1

[0248] An application of a solid acid catalyst for degrading waste PET to prepare TPA is basically the same as that in Example 1, except that: the solid acid catalyst for degrading waste PET to prepare TPA in step (a) is replaced with phosphotungstic acid of the same mass.

[0249] In step (b), phosphotungstic acid is used as the catalyst. When used for the first time, the PET conversion rate is 97% and the TPA yield is 91.3%; however, phosphotungstic acid cannot be recovered and cannot be recycled.

[0250] Comparing Comparative Example 1 with Example 1, it can be seen that when phosphotungstic acid is used as the catalyst in Comparative Example 1, the PET conversion rate and TPA yield when used for the first time will decrease and it cannot be recycled. This is because compared with the heteropolyacid asymmetric double quaternary ammonium salt solid acid catalyst prepared in Example 1, phosphotungstic acid is soluble in water and generates H +It is evenly distributed in water and has no phase transfer catalytic function. However, the heteropolyacid asymmetric double quaternary ammonium salt solid acid catalyst has a phase transfer function. The hydrophobic end of the quaternary ammonium cation is lipophilic and can bring the heteropolyacid anion to the solid-liquid interface of the polyester organic phase and the aqueous phase reaction, which is conducive to the entry of the heteropolyacid anion into the organic phase to attack the surface of the PET macromolecule. Therefore, the PET conversion rate and the TPA yield are lower when phosphotungstic acid is used as the catalyst compared with the solid acid catalyst. In addition, due to the fact that phosphotungstic acid is highly soluble in water, after the degradation reaction, phosphotungstic acid will dissolve in the aqueous solution (including ethylene glycol and trace impurities), making it difficult to recover and recycle at room temperature.

Claims

1. A method for preparing a solid acid catalyst for degrading waste PET to produce TPA, characterized in that: An asymmetric diquaternary ammonium salt surfactant and a heteropoly acid are subjected to an ion exchange reaction at a molar ratio of 0.5 to 1.5:1 to prepare a solid acid catalyst for degrading waste PET to prepare TPA, which specifically comprises the following steps: (1) dissolving an asymmetric diquaternary ammonium salt surfactant in ethanol to obtain a mixture I; (2) dissolving the heteropoly acid solid powder in water or ethanol to obtain a mixture II; (3) Add mixture I to mixture II dropwise at a rate of 0.5 ml / min to generate a flocculent precipitate, and stir evenly at room temperature to obtain mixture III; (4) stirring and aging the mixture III at room temperature for 2 to 6 hours, and then washing, centrifuging, and drying in sequence to obtain a solid acid catalyst for degrading waste PET to produce TPA; The molar ratio of the asymmetric diquaternary ammonium salt surfactant to ethanol in step (1) is 1-1.5:260, and the molar ratio of the heteropolyacid solid powder to water or ethanol in step (2) is 1-2:260-833; The preparation method of an asymmetric diquaternary ammonium salt surfactant comprises the following steps: firstly, a long-chain alkyl halide, a solvent A and tetramethylhexanediamine are mixed in a molar ratio of 1:40-70:5-10, heated under reflux in a water bath at 45-75° C. for 5-12 hours under stirring, and air-dried to obtain an intermediate product; then, a short-chain alkyl halide, a solvent B and the intermediate product are mixed in a molar ratio of 1-3:30-55:1, heated under reflux at 80-120° C. for 15-50 hours under stirring, the solvent is evaporated and recrystallized from ether to obtain an asymmetric diquaternary ammonium salt surfactant [C m H 2m+1 -N + (CH3)2-C6H 12 -N + (CH3)2-C n H 2n+1 ]-X2, wherein m=22, 18, 16, or 12; n=4 or 6; X is Cl, Br, or I; The long-chain monohaloalkane is chlorodocosanane, chlorooctadecane, chlorohexadecane, chlorododecane, bromodocosanane, bromooctadecane, bromohexadecane, bromododecane, iododocosanane, iodooctadecane, iodohexadecane or iodododecane; the short-chain monohaloalkane is hexyl chloride, chlorobutyl, hexyl bromide, bromobutyl, hexyl iodide or iodobutyl; The process of using the solid acid catalyst to degrade waste PET to prepare TPA is as follows: waste PET, the solid acid catalyst and distilled water are added into the polytetrafluoroethylene or para-polyphenyl lining of an autoclave in a mass ratio of 1:0.1-0.2:2.5-15, and a homogeneous reactor is used to react at 180-220° C. for 4-24 hours; The solid acid catalyst is recycled for multiple times, and the PET conversion rate is more than 99% and the TPA yield is more than 94% when it is used for the first time; the PET conversion rate is more than 96.5% and the TPA yield is more than 90.2% when it is recycled for 6 times.

2. The method for preparing a solid acid catalyst for degrading waste PET to produce TPA according to claim 1, characterized in that: Solvent A is acetone, dimethyl carbonate, diethyl carbonate or acetonitrile; solvent B is n-propanol or ethanol.

3. The method for preparing a solid acid catalyst for degrading waste PET to produce TPA according to claim 1, characterized in that: In step (2), the heteropoly acid is phosphotungstic acid, silicotungstic acid, phosphomolybdic acid or silicomolybdic acid.

4. The method for preparing a solid acid catalyst for degrading waste PET to produce TPA according to claim 1, characterized in that: Waste PET refers to waste PET fibers or PET bottle flakes.

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