Preparation method of TiO2-SiO2 solid acid catalyst and application thereof in catalyzing alcoholysis reaction of waste polyester

Abstract

The present application relates to the technical field of polyester recycling and green conversion catalysis, and discloses a preparation method of a TiO2-SiO2 solid acid catalyst and application of the TiO2-SiO2 solid acid catalyst in catalyzing alcoholysis of waste polyester, wherein the preparation method comprises the following steps: (1) preparing an aqueous solution containing sodium carbonate and cetyltrimethylammonium bromide; (2) mixing tetraisopropyl titanate and tetraethyl orthosilicate, and then dropping the mixture into the aqueous solution obtained in step (1), and then stirring and reacting at constant temperature to obtain a yellow suspension, and then centrifuging to obtain a solid, and then drying the solid; and (3) calcining the solid obtained in step (2) to obtain the TiO2-SiO2 solid acid catalyst. The TiO2-SiO2 solid acid catalyst can be applied to catalyze alcoholysis of waste polyester to prepare various products, the preparation method of the catalyst is simple, safe and green, the specific surface area of the obtained catalyst is large, the acid strength is high, and the catalyst can be recycled; the alcoholysis reaction condition is mild, and the product yield is high.

Description

Technical Field

[0001] The present invention relates to the technical field of polyester recovery and green conversion catalysis, in particular to a preparation method of a TiO2-SiO2 solid acid catalyst and application of the catalyst in catalyzing alcoholysis of waste polyester. Background Art

[0002] Polyester plastics primarily refer to polyethylene terephthalate (PET). Its high strength, high-temperature resistance, excellent chemical stability, and easy molding make it widely used in packaging, fiber, and construction. In 2020, global PET production exceeded 83 million tons, accounting for approximately 18% of global polymer production, making it the fourth-largest thermoplastic worldwide. Meanwhile, waste PET accounts for 8% by weight or 12% by volume of global solid waste (Ind. Eng. Chem. Res. 2023, 62, 10, 4328-4336). PET is not fully biodegradable in nature, and its slow decomposition produces microplastics and chemicals that are harmful to plants, animals, and the environment. Currently, only 10% of PET products are recycled; the rest is incinerated or landfilled. Therefore, developing recycling technologies for PET is crucial for reducing environmental pollution (ACS Sustainable Chem. Eng, 2023, 11, 10, 4209–4218).

[0003] Currently, the main recycling methods for waste polyester include mechanical recycling, chemical recycling, and energy recovery. Mechanical recycling involves physically crushing and cleaning waste polyester for recycling; chemical recycling involves chemically processing waste polyester into monomer compounds, which are then used to manufacture new polyester products; and energy recovery involves burning waste polyester that is difficult to chemically recycle and utilize as fuel for energy recovery and utilization. Currently, chemical recycling methods mainly include hydrolysis, alcoholysis, and aminolysis, of which alcoholysis is mainly divided into methanol alcoholysis and ethylene glycol alcoholysis. The ethylene glycol alcoholysis method suffers from poor product selectivity, low yield of the product 1,4-dihydroxyethyl terephthalate (BHET), and difficulty in decolorizing and purifying BHET, which has significant limitations for the recovery of waste polyester with color or high impurities. The methanol alcoholysis method is a PET recycling method with important application prospects because its product, dimethyl 1,4-terephthalate (DMT), has a lower boiling point than the product BHET from the ethylene glycol alcoholysis method, has good thermal stability, and is easy to purify.

[0004] Patent application publication number CN112851502A discloses a method for the methanolysis of waste PET polyester using choline and a terephthalic acid-based non-metallic ionic liquid as catalyst. Using choline and a terephthalic acid-based non-metallic ionic liquid for the methanolysis of waste PET polyester avoids the use of metal salt catalysts and the impact of residual metal ions on the depolymerization product, eliminating the need for metal ion removal units in subsequent product processing, simplifying purification steps, and reducing separation costs. However, this ionic liquid has issues such as high production costs, difficulty in recycling, and difficulty in reusing.

[0005] Patent application number CN113735705A discloses a method for the methanolysis of waste PET polyester using a polyionic liquid. The polyionic liquid is prepared by mixing zinc acrylate and 1-vinyl-3-ethylimidazole acetate in equal moles, adding acetonitrile and an initiator, stirring the mixture under nitrogen, and then filtering, washing, and vacuum drying to obtain the polyionic liquid PIL-Zn. 2+ .PIL-Zn 2+ The catalyst can achieve 100% PET conversion and 89.06% DMT yield at a catalyst dosage of 2% of polyester, a methanol to PET mass ratio of 3:1, a reaction temperature of 170°C, and a reaction time of 60 minutes. However, the catalyst preparation process uses expensive raw materials and is complex and demanding, making it difficult to manufacture on a large scale.

[0006] Patent application publication number CN110938231A discloses a method for the methanolysis of waste PET using a deep eutectic solvent. The deep eutectic solvent is prepared by mixing urea with one or more of zinc acetate, zinc chloride, zinc sulfate, zinc nitrate, manganese acetate, cobalt acetate, copper acetate, or nickel acetate in a specific molar ratio and stirring at high temperature until a clear solution is obtained. The deep eutectic solvent synthesized from urea / zinc acetate can achieve a 100% PET conversion rate and a 94.32% DMT yield at a 0.5% catalyst dosage, 170°C, and a 60-minute reaction time. However, this catalyst suffers from issues such as residual metal ions in the DMT product and difficulty recovering the catalyst.

[0007] Therefore, there is an urgent need to develop a catalyst that is stable, free of metal ion residues, recyclable and easy to separate and suitable for catalyzing the alcoholysis of polyester under mild conditions. Summary of the Invention

[0008] In order to solve the problems in the prior art such as the high price of ionic liquid catalysts and the difficulty in recovering and separating soluble metal salts that are easily left in the product, the present invention provides a preparation method of a TiO2-SiO2 solid acid catalyst and its application in catalyzing the alcoholysis reaction of waste polyesters.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a TiO2-SiO2 solid acid catalyst for alcoholysis of waste polyester, comprising the following steps:

[0011] (1) preparing an aqueous solution containing sodium carbonate and cetyltrimethylammonium bromide;

[0012] (2) tetraisopropyl titanate and tetraethyl orthosilicate were mixed and added dropwise to the aqueous solution obtained in step (1), stirred at a constant temperature to react to obtain a yellow suspension, centrifuged to obtain a solid, and dried the solid;

[0013] (3) The solid obtained in step (2) is calcined to obtain a TiO2-SiO2 solid acid catalyst.

[0014] The solid acid catalyst described in the present invention is prepared using a mixed hydrolysis method. The specific process involves first mixing tetraisopropyl titanate and tetraethyl orthosilicate in a certain proportion; then dropping the mixed solution into an aqueous solution containing sodium carbonate and cetyltrimethylammonium bromide for hydrolysis. The sodium carbonate acts as a precipitant, which, upon binding with metal ions, precipitates from the aqueous solution; the cetyltrimethylammonium bromide acts as a template; then, the solid precipitate is collected by centrifugation and dried; and finally, the solid is calcined to obtain the TiO2-SiO2 solid acid catalyst. This preparation method is simple, safe, and environmentally friendly.

[0015] The mixed hydrolysis method allows for uniform precipitation of Ti and Si. Only uniform precipitation can form a cross-arrangement of Ti-O-Si-O-Ti-O-Si-O, making the catalyst acidic. This results in high activity and selectivity for the target product in the degradation of waste polyesters (PET, PLA, and PBS). Furthermore, the reaction conditions are mild, there are no metal ion residues, and the catalyst is easily recovered and recyclable. However, if step-by-step hydrolysis and separate precipitation are used, the distribution of Ti and Si in the resulting catalyst is uneven, resulting in no or very weak acidity. Preliminary experiments have shown that catalysts prepared by first precipitating TiO2 and then SiO2, or by first precipitating SiO2 and then TiO2, have poor catalytic activity in the degradation of waste polyesters. In addition, the TiO2-SiO2 sol or solid acid catalyst prepared in the prior art is only suitable for the polycondensation or esterification reaction of polyester, while the TiO2-SiO2 solid acid catalyst in the present invention can be applied to the degradation reaction of polyester. The former is a reaction of molecular weight increase, and the latter is a reaction of long chain cleavage. The two have completely different catalytic reaction mechanisms and do not contain any technical inspiration. The present invention can obtain a TiO2-SiO2 solid acid catalyst with high catalytic activity in polyester alcoholysis through improvement and optimization of the preparation method.

[0016] Preferably, in step (1), the ratio of sodium carbonate, hexadecyltrimethylammonium bromide and water in the aqueous solution is 0.74-1.84 g:1.52 g:50-150 mL.

[0017] Preferably, in step (2), the molar ratio of tetraisopropyl titanate to tetraethyl orthosilicate is 1:9 to 9:1.

[0018] Preferably, in step (2), the temperature of the constant-temperature hydrolysis reaction is 60-140°C, and the reaction time is 6-12 hours; the temperature of the drying is 60-160°C.

[0019] Preferably, in step (3), the heating rate of the roasting is 2-5°C / min, the roasting temperature is 500-700°C, the roasting holding time is 2-6h, and finally the temperature is naturally lowered to room temperature.

[0020] In a second aspect, the present invention also provides an application of a TiO2-SiO2 solid acid catalyst in catalyzing the alcoholysis of waste polyester.

[0021] Preferably, the application includes the following steps: mixing waste polyester, TiO2-SiO2 solid acid catalyst and alcohol, filling with nitrogen to replace the air, and then heating to 100-220°C, and the reaction time is 0.5-16 hours.

[0022] As the reaction temperature of TiO2-SiO2 solid acid catalyst increases during the catalytic hydrolysis of waste polyester, the catalytic activity and product yield will also increase, but too high a temperature may cause side reactions.

[0023] Preferably, the mass ratio of the TiO2-SiO2 solid acid catalyst to the waste polyester is 1:2 to 1:200; the mass ratio of the alcohol to the waste polyester is 3:1 to 100:1.

[0024] Preferably, the waste polyester includes one or more of polyethylene terephthalate, polylactic acid, and polybutylene succinate. The waste polyester includes scrap powder and granules from PET production enterprises, waste silk fibers from polyester enterprises, or waste plastic bottles or waste plastic packaging boxes.

[0025] When the waste polyester is PET, the preferred TiO2-SiO2 solid acid catalyst is TiO2-SiO2-5 / 5 solid acid catalyst or TiO2-SiO2-3 / 7 solid acid catalyst, the preferred catalytic temperature is 150-170°C, and the reaction time is 2-16h.

[0026] Preferably, the alcohol is methanol, ethanol, isopropanol or ethylene glycol.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The TiO2-SiO2 solid acid catalyst prepared by the present invention can be used to catalyze the alcoholysis of waste polyester (PET, PLA and PBS) with methanol, ethanol or ethylene glycol to prepare various products. The preparation method of the catalyst is simple, safe and green. The obtained catalyst has a large specific surface area, high acid strength and can be recycled. The alcoholysis reaction conditions are mild and the product yield is high, so it has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the Fourier transform infrared spectrum of TiO2-SiO2-5 / 5 solid acid catalyst;

[0030] Figure 2 This is the Raman spectrum of TiO2-SiO2-5 / 5 solid acid catalyst. DETAILED DESCRIPTION

[0031] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0032] The conversion rate of polyester (PET, PLA or PBS) and the yield of degradation products catalyzed by TiO2-SiO2 solid acid catalyst were calculated according to formula (1) (2) respectively:

[0033] Polyester conversion = (W0-W1) / W0×100% (1)

[0034] Molar yield of degradation products = (amount of degradation products) / (theoretical amount of benzene rings in degraded polyester) × 100% (2)

[0035] Where W0 is the initial mass of polyester and W1 is the mass of undegraded polyester.

[0036] Example 1

[0037] Preparation of TiO2-SiO2-5 / 5 solid acid catalyst (molar ratio of tetraisopropyl titanate and tetraethyl orthosilicate is 5:5):

[0038] (1) 0.94 g of sodium carbonate, 1.52 g of hexadecyltrimethylammonium bromide, and 100 mL of deionized water were added to a round-bottom flask and stirred at 80 °C for 1 h to obtain a transparent solution.

[0039] (2) A mixture of tetraisopropyl titanate (5.68 g, 0.02 mol) and tetraethyl orthosilicate (5.28 g, 0.02 mol) was added dropwise to the above mixed solution, and the mixture was hydrolyzed at 80°C for 9 h. After cooling, the mixture was centrifuged and the obtained solid product was dried in an oven at 80°C.

[0040] (3) The solid product obtained above was calcined (heating rate 5°C / min, calcined at 550°C for 4h, and then naturally cooled to room temperature) to finally obtain 3.96g of TiO2-SiO2-5 / 5 solid acid catalyst.

[0041] ICP-OES detection showed that the molar ratio of titanium to silicon in the TiO2-SiO2-5 / 5 solid acid catalyst was 1.07.

[0042] like Figure 1 The following is a Fourier transform infrared spectrum of the TiO2-SiO2-5 / 5 solid acid catalyst prepared in Example 1. -1 and 1630cm -1 The absorption peaks at 1095cm correspond to the stretching and bending vibrations of OH. -1 , 950cm -1 and 460cm -1 The absorption peaks correspond to the stretching vibrations of Si-O-Si, Ti-O-Si, and Ti-O. The presence of Ti-O-Si bonds indicates that the titanium and silicon elements are evenly dispersed in the TiO2-SiO2-5 / 5 catalyst.

[0043] like Figure 2 The Raman spectrum of the TiO2-SiO2-5 / 5 solid acid catalyst prepared in Example 1 is shown. There are five representative anatase TiO2 absorption peaks in TiO2-SiO2-5 / 5. Among them, 149 cm -1 、197cm -1 and 628cm -1 The absorption peak at is attributed to E g Model, 399cm -1 and 521cm -1 The absorption peaks at 1g Mode and A 1g / B 1g of Twin Peaks.

[0044] Example 2

[0045] The preparation method was similar to that of Example 1, except that the molar ratios of tetraisopropyl titanate and tetraethyl orthosilicate added were 1:9, 3:7, 5:5, 7:3, and 9:1. The resulting catalysts were labeled TiO2-SiO2-1 / 9, TiO2-SiO2-3 / 7, TiO2-SiO2-5 / 5, TiO2-SiO2-7 / 3, and TiO2-SiO2-9 / 1, respectively.

[0046] Application Example 1

[0047] 0.025 g of the catalysts prepared in Example 1 and Example 2, 1 g of PET solid powder, and 10 mL of methanol were weighed into an autoclave, and the autoclave was placed in an electric heating magnetic stirring device. After the temperature rose to 150°C, stirring was started and timing was started. The reaction time was 2 h.

[0048] After the reaction, the reaction system was cooled to room temperature and the reaction solution was diluted to a 50 mL volumetric flask. The yield of dimethyl 1,4-terephthalate (DMT) was quantitatively analyzed by high-performance liquid chromatography. The remaining solids were separated by centrifugation, dried, and weighed for calculation of the PET conversion. The PET conversion and molar yield of the product DMT for the PET methanolysis reaction using TiO2-SiO2 catalysts synthesized at different molar ratios of tetraisopropyl titanate and tetraethyl orthosilicate are shown in Table 1.

[0049] Table 1 Activity of catalysts with different Ti / Si ratios in PET methanolysis

[0050] catalyst PET conversion rate (%) Molar yield of DMT (%) <![CDATA[TiO2-SiO2-1 / 9]]> 71.9 62.1 <![CDATA[TiO2-SiO2-3 / 7]]> 86.8 76.2 <![CDATA[TiO2-SiO2-5 / 5]]> 87.3 79.0 <![CDATA[TiO2-SiO2-7 / 3]]> 76.8 68.6 <![CDATA[TiO2-SiO2-9 / 1]]> 31.1 15.4

[0051] Conclusion: With the increase of titanium-silicon ratio in the catalyst, the activity of the catalyst first increases and then weakens. When the titanium-silicon ratio is 5 / 5, the TiO2-SiO2-5 / 5 catalyst has the best activity for PET alcoholysis, and the molar yield of the product DMT can reach 79.0%.

[0052] Application Example 2

[0053] Weigh 0.025 g of the catalyst prepared in Example 1, 1 g of PET solid powder, and 10 mL of methanol into a high-pressure reactor. Place the high-pressure reactor in an electric heating magnetic stirring device. After the temperature rises to 130-170°C, start stirring and start timing. The reaction time is 2 h.

[0054] After the reaction, the reaction system was cooled to room temperature and the reaction solution was diluted to a 50 mL volumetric flask. The yield of dimethyl 1,4-terephthalate (DMT) was quantitatively analyzed by high-performance liquid chromatography. The remaining solids were separated by centrifugation, dried, and weighed for calculation of the PET conversion. The PET conversion and molar yield of DMT for the PET methanolysis reaction catalyzed by the TiO2-SiO2-5 / 5 catalyst at different reaction temperatures are shown in Table 2.

[0055] Table 2 TiO at different temperatures 2- Activity of SiO2-5 / 5 Catalyst for Methanolysis of PET

[0056] Temperature (℃) PET conversion rate (%) Molar yield of DMT (%) 130 24.5 17.1 140 53.0 41.9 150 87.3 79.0 160 99.5 98.2 170 99.8 98.5

[0057] Conclusion: The reaction temperature has an important effect on the TiO 2-SiO2-5 / 5 catalyst plays a crucial role in the alcoholysis of PET to DMT. As the reaction temperature increases, the molar yield of DMT also increases.

[0058] Application Example 3

[0059] Weigh 0.025 g of the catalyst prepared in Example 1, 1 g of PET solid powder, and 10 mL of methanol into a high-pressure reactor. Place the high-pressure reactor in an electric heating magnetic stirring device. After the temperature rises to 150°C, start stirring and start timing. The reaction time is 0.5 to 4 h.

[0060] After the reaction, the reaction system was cooled to room temperature and the reaction solution was diluted to a 50 mL volumetric flask. The yield of dimethyl 1,4-terephthalate (DMT) was quantitatively analyzed by high-performance liquid chromatography. The remaining solids were separated by centrifugation, dried, and weighed for calculation of the PET conversion. The PET conversion and molar yield of DMT for the PET methanolysis reaction catalyzed by the TiO2-SiO2-5 / 5 catalyst at different reaction times are shown in Table 3.

[0061] Table 3 TiO at different times 2- Activity of SiO2-5 / 5 Catalyst for Methanolysis of PET

[0062] Time (h) PET conversion rate (%) Molar yield of DMT (%) 0.5 59.0 43.8 1 72.7 59.0 2 87.3 79.0 3 96.9 90.9 4 98.3 91.7

[0063] Conclusion: TiO prepared by the present invention 2- The SiO2-5 / 5 catalyst has good initial activity, and the molar yield of DMT gradually increases with the extension of reaction time.

[0064] Application Example 4

[0065] 0.025 g of the catalyst prepared in Example 1, 1 g of PET solid powder, and 10 mL of methanol were weighed into a high-pressure reactor. The high-pressure reactor was placed in an electric heating magnetic stirring device. After the temperature rose to 150°C, stirring was started and timing was started. The reaction time was 2 h.

[0066] After the reaction, the reaction system was cooled to room temperature, the reaction solution was fixed to volume in a 50 mL volumetric flask, and the yield of dimethyl 1,4-terephthalate (DMT) was quantitatively analyzed by high performance liquid chromatography. The remaining solid matter was centrifuged, dried, and weighed for calculation of the PET conversion rate. The recovered solid was calculated to supplement PET to 1 g for the next recycling reaction. The PET conversion rate and molar yield of DMT for the recycled TiO2-SiO2-5 / 5 catalyst catalyzed PET methanolysis reaction are shown in Table 4.

[0067] Table 4TiO 2-Reusable activity of SiO2-5 / 5 catalyst in PET methanolysis

[0068]

[0069]

[0070] Conclusion: TiO prepared by the present invention 2- The SiO2-5 / 5 catalyst has good cyclic stability, and the catalyst activity does not decrease significantly after 5 cycles.

[0071] Application Example 5

[0072] Weigh 0.025 g of the catalyst prepared in Example 1, and the raw materials of waste polyester are 1 g of a domestic brand of mineral water bottle (380 ml specification) (sliced ​​into fragments with a side length of 5 mm) or 1 g of waste silk from a polyester enterprise (shredded to a length of less than 5 mm); then add 10 mL of methanol to the autoclave, place the autoclave in an electric heating magnetic stirring device, start stirring after the temperature rises to 160 ° C and start timing, and the reaction time is 3 h.

[0073] After the reaction, the reaction system was cooled to room temperature and the reaction solution was diluted to a 50 mL volumetric flask. The yield of dimethyl 1,4-terephthalate (DMT) was quantitatively analyzed by high-performance liquid chromatography. The remaining solids were separated by centrifugation, dried, and weighed for calculation of the PET conversion. The PET conversion and molar yield of DMT for different PET methanolysis reactions catalyzed by the TiO2-SiO2-5 / 5 catalyst are shown in Table 5.

[0074] Table 5 Methanolysis activity of TiO2-SiO2-5 / 5 catalyst on waste PET products

[0075] PET material PET conversion rate (%) Molar yield of DMT (%) Sliced ​​PET plastic bottles 99.1 97.0 Shredded PET fiber material 99.2 97.6

[0076] Conclusion: TiO prepared by the present invention 2- SiO2-5 / 5 catalyst has very good catalytic activity for methanolysis of PET waste and plastic bottles made of PET.

[0077] Application Example 6

[0078] 0.025 g of the catalyst prepared in Example 1, 1 g of PET solid powder, and 10 mL of ethanol were weighed into an autoclave. The autoclave was placed in an electric heating magnetic stirring device. After the temperature rose to 160°C, stirring was started and timing was started. The reaction time was 4 h.

[0079] After the reaction was completed, the reaction system was cooled to room temperature and the reaction solution was diluted to volume in a 50 mL volumetric flask. The yield of diethyl 1,4-terephthalate was quantitatively analyzed by high-performance liquid chromatography. The remaining solid material was separated by centrifugation, dried, and weighed for calculation of the PET conversion. The reaction results showed a PET conversion of 98.7% and a molar yield of diethyl 1,4-terephthalate of 96.6%.

[0080] Conclusion: TiO prepared by the present invention 2- SiO2-5 / 5 catalyst has good catalytic activity for the alcoholysis of PET in ethanol.

[0081] Application Example 7

[0082] 0.025 g of the catalyst prepared in Example 1, 1 g of PET solid powder, and 10 mL of ethylene glycol were weighed into an autoclave. The autoclave was placed in an electric heating magnetic stirring device. After the temperature rose to 190°C, stirring was started and timing was started. The reaction time was 5 h.

[0083] After the reaction was completed, the reaction system was cooled to room temperature and the reaction solution was diluted to volume in a 50 mL volumetric flask. The yield of 1,4-dihydroxyethyl terephthalate was quantitatively analyzed by high-performance liquid chromatography. The remaining solid material was separated by centrifugation, dried, and weighed to calculate the PET conversion rate. The reaction results showed a PET conversion rate of 99.4% and a molar yield of 1,4-dihydroxyethyl terephthalate of 90.2%.

[0084] Conclusion: TiO prepared by the present invention 2- SiO2-5 / 5 catalyst has good catalytic activity for the alcoholysis of PET in ethylene glycol.

[0085] Application Example 8

[0086] Weigh 0.025 g of the catalyst prepared in Example 1, 1 g of polylactic acid (PLA) solid particles, and 10 mL of methanol into a high-pressure reactor. Place the high-pressure reactor in an electric heating magnetic stirring device. After the temperature rises to 140°C, start stirring and start timing. The reaction time is 4 h.

[0087] After the reaction was completed, the reaction system was cooled to room temperature, benzyl alcohol as an internal standard was added, and the yield of methyl lactate was quantitatively analyzed by gas chromatography (GC). The reaction result showed that the molar yield of methyl lactate was 88.0%.

[0088] Conclusion: TiO prepared by the present invention 2- SiO2-5 / 5 catalyst has good catalytic activity for the alcoholysis of PLA in methanol.

[0089] Application Example 9

[0090] Weigh 0.025 g of the catalyst prepared in Example 1, 1 g of polybutylene succinate (PBS) solid particles, and 10 mL of methanol into a high-pressure reactor. Place the high-pressure reactor in an electric heating magnetic stirring device. After the temperature rises to 140°C, start stirring and start timing. The reaction time is 5 h.

[0091] After the reaction was completed, the reaction system was cooled to room temperature, benzyl alcohol as an internal standard was added, and the yield of dimethyl succinate was quantitatively analyzed by gas chromatography (GC). The reaction result showed that the molar yield of dimethyl succinate was 98.9%.

[0092] Conclusion: TiO prepared by the present invention 2- SiO2-5 / 5 catalyst has good catalytic activity for the alcoholysis of PBS in methanol.

[0093] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for catalyzing the alcoholysis of waste polyesters, characterized in that: The steps include: (1) preparing an aqueous solution containing sodium carbonate and cetyltrimethylammonium bromide; (2) Tetraisopropyl titanate and tetraethyl orthosilicate were mixed and then added dropwise to the aqueous solution obtained in step (1), wherein the molar ratio of tetraisopropyl titanate to tetraethyl orthosilicate was 1:9 to 9:1, and the mixture was stirred at a constant temperature to obtain a yellow suspension, which was centrifuged to obtain a solid, and the solid was dried; (3) The solid obtained in step (2) is calcined to obtain a TiO2-SiO2 solid acid catalyst; the waste polyester, the TiO2-SiO2 solid acid catalyst and alcohol are mixed to carry out an alcoholysis reaction.

2. The method according to claim 1, wherein In step (1), the ratio of sodium carbonate, hexadecyltrimethylammonium bromide and water in the aqueous solution is 0.74-1.84 g:1.52 g:50-150 mL.

3. The method according to claim 1, wherein: In step (2), the molar ratio of tetraisopropyl titanate to tetraethyl orthosilicate is 5:

5.

4. The method according to claim 1 or 3, wherein In step (2), the temperature of the constant temperature hydrolysis reaction is 60~140℃, and the reaction time is 6~12 hours; the temperature of the drying is 60~160℃.

5. The method according to claim 1, wherein In step (3), the heating rate of the roasting is 2-5 °C / min, the roasting temperature is 500-700 °C, the roasting holding time is 2-6 h, and finally the temperature is naturally lowered to room temperature.

6. The method according to claim 1, wherein The method comprises the following steps: mixing waste polyester, TiO2-SiO2 solid acid catalyst and alcohol, introducing nitrogen to replace air, then heating to 100-220°C, and reacting for 0.5-16 hours.

7. The method according to claim 6, wherein: The mass ratio of the TiO2-SiO2 solid acid catalyst to the waste polyester is 1:2-1:200; the mass ratio of the alcohol to the waste polyester is 3:1-100:

1.

8. The method according to any one of claims 1 to 7, characterized in that: The waste polyester includes one or more of polyethylene terephthalate, polylactic acid and polybutylene succinate.

9. The method according to claim 6 or 7, wherein: The alcohol is methanol, ethanol, isopropanol or ethylene glycol.

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