CN116675603A - Method for catalytic recovery of waste polyester material by acetate ionic liquid - Google Patents

Abstract

The invention discloses a method for recycling waste polyester materials (PET, PC) by high-efficiency catalytic depolymerization of acetate ionic liquid and application of the method in recycling of polyester waste plastics. Belongs to the technology of high-value conversion of waste resources. The method solves the problems of long alcoholysis reaction time, high required temperature and metal residue caused by the metal catalyst of the existing catalyst for catalyzing polyester materials. The acetate ionic liquid catalyst provided by the invention can realize the efficient depolymerization of waste polyester under mild conditions, the conversion rate can reach 100%, and the purity can reach 99%. The method is simple to operate, low in cost and easy to obtain raw materials, environment-friendly in process, low in dosage, easy to separate and reusable, and is an economic and effective method.

Description

A kind of method of acetate ionic liquid catalytic recovery waste polyester material

technical field

The invention relates to a method for catalytic recovery of waste polyester materials by acetate ionic liquid, and the application of the method in alcoholysis recovery of waste polyester waste materials.

Background technique

Over the past 60 years, plastics have accumulated in the natural environment. Emissions of plastic are increasing and will continue to increase even with the most aggressive efforts to reduce plastic waste in the future. Global discharges of plastic waste into rivers, lakes and oceans are estimated to range from 9 to 23 million tonnes per year, with similar discharges into the terrestrial environment at 13 to 25 million tonnes as of 2016. In particular, the production of polyester such as polyester textiles and e-waste continues to increase. However, at the end of their life, more than 80% of post-consumer polyesters end up in landfill without recycling due to lack of effective recycling technologies. This not only causes serious environmental problems, but also leads to a huge waste of precious resources. From the perspective of resource protection and sustainable development, how to recycle waste polyester materials is a great challenge. At the same time, it is necessary to establish a recycling scheme for polyester resources.

Traditional strategies such as landfilling and incineration have high environmental impacts in addition to high costs. Its harsh impact on the environment limits the sustainability of this approach. At present, the recycling of waste plastics mainly includes physical and chemical methods. Physical methods, such as mechanical treatment, yield secondary products, ie corresponding products with degraded properties. This performance degradation is not ideal for the reuse of plastics. Compared with physical methods, chemical recycling has advantages. Some chemical recycling methods have been reported, such as pyrolysis, hydrolysis, ammonolysis, and alcoholysis. Pyrolysis usually requires high temperature and high pressure, high energy loss, and the resulting product has complex components, most of which are compounds that cannot be directly applied. For example, bisphenol A (BPA) can be obtained by hydrolysis, but with low selectivity. Meanwhile, the reaction conditions of this process are harsh, and its important by-product is greenhouse gas (CO ₂ ). In contrast, the alcoholysis of waste plastics can not only obtain valuable polyester monomers, but also chemicals such as alkyl carbonate, ethylene glycol, etc. Therefore, alcoholysis-based chemical recovery shows the absolute necessity of in-depth research.

Regarding the alcoholysis chemical recovery of polyester materials, several organic catalysts have been successfully utilized, especially organic bases, including NaOH, TBD, DBU, and DMAP, etc. Although these catalysts can efficiently degrade polyesters, their thermal stability limits their reuse and wide application. Even the most anticipated TBD needs to be at least 190°C to guarantee high activity recovery of PET. In addition, ionic liquids (ILs), deep eutectic solvents (DESs), as highly anticipated green catalysts and reaction media in recent years, which exhibit enhanced thermal stability, have also been reported to be used in polyester depolymerization to recover corresponding products. . There are still problems such as complex synthesis, high cost, and difficulty in separation and recovery. Heterogeneous catalysts (ZnO-NPs/ _NBu4Cl nanoparticles, _CeO2 nanocrystals, CaO(SrO, BaO)/SBA-15, CaO- _CeO2 /SBA15) overcome the catalyst The separation problem has obvious potential for industrial application. However, there are problems such as high reaction temperature, participation of volatile organic solvents (THF) and transition metals, and difficulty in separating impurities from plastics in this process, resulting in cumbersome post-processing of the product. Most importantly, the reaction system has problems such as high reaction temperature, long time, and large amount of catalyst, which limit the large-scale application of this type of catalyst. Therefore, it is very necessary to provide a catalyst system for recycling waste polyester materials by green alcoholysis under relatively mild, metal-free, and solvent-free conditions, which is rapid, large-scale, and environmentally friendly.

Contents of the invention

Aiming at the problems of long reaction time, high reaction temperature, high catalyst consumption and metal residue brought by the metal catalyst in the alcoholysis of polyester catalyzed by existing catalysts, the invention provides a method for catalyzing and recovering waste polyester materials by acetate ionic liquid.

Technical scheme of the present invention is:

The invention provides a method for catalytic recovery of waste polyester materials by acetate ionic liquid. A certain quality of polyester, acetate ionic liquid, and alcohol compounds are added to the reaction kettle, and the polyester is subjected to alcoholysis reaction at a certain temperature and pressure. After the reaction is completed, it is filtered, rotary evaporated, washed with water, and crystallized. Directly obtain high-purity monomers, such as BPA, dimethyl terephthalate, etc.

Using the above-mentioned acetate ionic liquid as a catalyst to catalyze the alcoholysis of the polyester material can obtain extremely high depolymerization efficiency. Acetate anion has a strong electron-donating effect, can polarize alcoholic hydroxyl groups, and form a high-performance catalytic system, thereby effectively improving the protonation of carbonyl groups on polyester molecules and promoting the breakage of ester bonds. Therefore, the catalyst can greatly accelerate the process of ester bond scission and realize rapid alcoholysis of polyester under mild conditions.

Preferably, the above method specifically includes: after crushing and washing the polyester, removing impurities and drying, adding alcohol and acetate ionic liquid to the polyester in sequence, heating to 50°C to 200°C under stirring, and waiting for the polyester to completely After the dissolution disappears and the solution becomes clear, the reaction ends, and the resulting alcoholysis solution is dried, filtered, and washed to obtain high-purity monomers.

Preferably, the catalyst anion is acetate anion, the cation is 1,8-diazobispiro[5.4.0]undec-7-ene (DBU), 1 5 7-triazidebicyclo(4.4.0) Dec-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD).

Preferably, the PET is derived from polyester and its composite materials, clothes, PET bottles and other solvents, and the PC is derived from optical disks, films, computer casings, medical packaging, and electronic equipment parts.

Preferably, the small alcohol molecules are methanol, ethanol, ethylene glycol, n-propanol, isopropanol, glycerol and 1,2-propanediol.

Preferably, the molar ratio of the amount of the alcohol compound to the polyester is 1-100:1.

Preferably, the solvent is dimethyl carbonate, dichloromethane, tetrahydrofuran, anisole or no solvent is added.

Preferably, the temperature is 50° C. to 200° C., and the depolymerization time is 1 min to 24 h.

Preferably, the gas is nitrogen and argon, or no gas is added.

Preferably, the mass ratio of the amount of the catalyst to the polyester material is 0.0001-0.1:1.

Compared with the prior art, the present invention has the following technical effects: compared with the conventional alcoholysis method for recycling polyester, the method is simpler, greener and more efficient. The simple and easy-to-synthesize acetate ionic liquid is used as the catalyst. The catalyst is low in cost and easy to synthesize. The alcoholysis reaction temperature is low. The depolymerization and recovery of polyester can be carried out under mild conditions. The reaction time is short and the depolymerization rate is fast. Wide applicability, high product purity, easy refining and purification, and obvious economic benefits.

Description of drawings

Fig. 1 is the ¹ HNMR spectrogram of catalyst 1,5,7-triazide bicyclo (4.4.0) dec-5-ene acetate [TBDH] [Ac];

Fig. 2 is the ¹ HNMR spectrogram of product BPA;

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, specific examples are used to illustrate the present invention. It must be pointed out that the examples are applicable to further illustrate the present invention, but should not be construed as limiting the protection scope of the present invention.

Example 1

As shown in Figure 1 and 2,

The specific operation process of this embodiment is:

In a 20 mL autoclave equipped with a magnetic stirrer and a thermometer, add 2 g of PC, 0.5 mmol of 1,5,7-triazidebicyclo(4.4.0)dec-5-ene acetate ([TBDH][OAc]) in sequence , 6mL of methanol, stirred and reacted at 70°C for 8h. After natural cooling to room temperature, the filtrate was evaporated by rotary distillation to remove unreacted methanol and dimethyl carbonate (DMC). Then a pale yellow colloidal liquid was obtained, which was added to an equal volume of ethyl acetate and distilled water, and the layers were separated. The upper organic phase was desolvated to obtain a white solid, and 1.7436 g of BPA was obtained. The lower aqueous phase was treated by vacuum distillation to remove distilled water and dried under vacuum to recover the catalyst. The conversion rate of PC is 100%, and the yield is 97.0%.

Example 2

The specific operation process of this embodiment is:

In a 20 mL autoclave equipped with a magnetic stirrer and a thermometer, 2 g of PET, 0.5 mmol of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene acetate ([ MTBDH][Ac]), 6mL methanol, stirred at 170°C for 2h. After natural cooling to room temperature, the filtrate was evaporated by rotary distillation to remove unreacted methanol. A light yellow colloidal liquid was then obtained, which was dissolved in equal volumes of ethyl acetate and distilled water, transferred to a separatory funnel, shaken vigorously, and mixed in two stages. Ethyl acetate was removed from the upper organic phase by rotary evaporation to give a white solid, yielding 1.9420 g of dimethyl terephthalate (DMT). The lower aqueous phase was treated by vacuum distillation to remove distilled water and dried under vacuum to recover the catalyst. The conversion rate of PET is 96%, and the yield is 95.5%.

Example 3

The specific operation process of this embodiment is:

In a 20 mL autoclave equipped with a magnetic stirrer and a thermometer, add 0.5 g PC, 0.5 mmol 1,5,7-triazidebicyclo(4.4.0)dec-5-ene acetate ([TBDH][OAc] ), 1 mL of methanol, 2 mL of tetrahydrofuran (THF), and stirred at 70° C. for 30 min. After natural cooling to room temperature, the filtrate was evaporated by rotary distillation to remove solvent, methanol and dimethyl carbonate (DMC). A pale yellow colloidal liquid was then obtained, which was dissolved in equal volumes of ethyl acetate and distilled water, transferred to a separatory funnel, shaken vigorously, and mixed in two stages. Ethyl acetate was removed from the upper organic phase by rotary evaporation to obtain a white solid and 0.4389 g of the product BPA. The lower aqueous phase was treated by vacuum distillation to remove distilled water and dried under vacuum to recover the catalyst. The conversion rate of PC is 100%, and the yield is 97.6%.

Example 4

The specific operation process of this embodiment is:

In a 20 mL autoclave equipped with a magnetic stirrer and a thermometer, 1 g of PET, 0.5 mmol of 1,8-diazobispiro[5.4.0] undec-7-ene acetate ([DBUH][OAc ]), 4mL of ethylene glycol, and stirred at 170°C for 2h. After naturally cooling to room temperature, the reaction solution was diluted with 1 L of distilled water, and the product bishydroxyethyl terephthalate (BHET) was precipitated out. After filtering, washing and drying, a white solid crystal was obtained, which was BHET (0.9865 g, 97.5%). By GC-MS analysis, the selectivity of BHET is greater than 99%.

Example 5

The specific operation process of this embodiment is:

Into a 20 mL autoclave equipped with a magnetic stirrer and a thermometer, 0.5 g PC, 0.5 mmol 1,3-dimethylbenzimidazole acetate, and 1 mL glycerol were sequentially added, and the reaction was stirred at 70° C. for 3 h. After natural cooling to room temperature, the reaction was then cooled to room temperature and then dissolved in diethyl ether and water. First, the organic phase was washed 3 times with water, and the organic phase was dried with _MgSO4 . Ether was then removed by rotary evaporation and washed with excess water to yield a crystalline white solid which was BPA (0.3675 g, 81.78%). The combined aqueous phase was evaporated to recover the heterocycle and catalyst. 4-(Hydroxymethyl)-1,3-dioxo-2-one was purified by flash column chromatography using acetone as eluent.

Example 6

The specific operation process of this embodiment is:

In a 20 mL autoclave equipped with a magnetic stirrer and a thermometer, add 0.5 g PC, 0.5 mmol 1,5,7-triazidebicyclo(4.4.0)dec-5-ene acetate ([TBDH][OAc] ), 2mL of ethylene glycol, stirred and reacted at 160°C for 1h. After natural cooling to room temperature, the reaction was then cooled to room temperature and then dissolved in diethyl ether and water. First, the organic phase was washed 3 times with water, and the organic phase was dried with _MgSO4 . Ether was then removed by rotary evaporation and washed with excess water to yield a crystalline white solid which was BPA (0.4125 g, 91.79%). The combined aqueous phase was evaporated to recover the heterocycle and catalyst. Ethylene carbonate was purified by flash column chromatography using acetone as eluent.

Example 7

The specific operation process of this embodiment is:

In a 20 mL autoclave equipped with a magnetic stirrer and a thermometer, add 2 g of PET, 0.25 mmol of 1,5,7-triazidebicyclo(4.4.0)dec-5-ene acetate ([TBDH][OAc]) in sequence , 0.25mmol 1,3-dimethylbenzimidazole acetate, 6mL ethylene glycol, stirred and reacted at 160°C for 1h. After naturally cooling to room temperature, the reaction solution was diluted with 1 L of distilled water, and the product bishydroxyethyl terephthalate (BHET) was precipitated out. After filtering, washing and drying, a white solid crystal was obtained, which was BHET (1.9560 g, 96.0%). By GC-MS analysis, the selectivity of BHET is greater than 99%.

Example 8

The specific operation process of this embodiment is:

In a 10L autoclave equipped with a mechanical stirrer, 1kg of polyester foam (PET), 10mmol of 1,5,7-triazidebicyclo(4.4.0)dec-5-ene acetate ([TBDH][ OAc]), 4L methanol, and stirred at 190°C for 3h. After naturally cooling to room temperature, methanol was removed by distillation to obtain a mixed liquid of ethylene glycol and DMT. After adding an equal volume of distilled water to the mixture, DMT was obtained by filtration as white crystals with a yield of 98%. The lower aqueous phase was treated by vacuum distillation to remove distilled water and ethylene glycol and dried under vacuum to recover the catalyst.

Example 9

The operation process of this embodiment is the same as that of Example 2, except that the catalyst is changed to the recovered catalyst, and the experiment is repeated 5 times. The results of repeated catalyst reuse are shown in Table 1.

Table 1 Reuse results of [TBDH][OAc]

Raw materials used in the present invention, equipment, if not specified, are commonly used raw materials in this area, equipment; Method used in the present invention, if not specified, are conventional methods in this area.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any way. All simple modifications, changes and equivalent transformations made to the above embodiments according to the technical essence of the present invention belong to the technical solution of the present invention. scope of protection.

Claims (9)

1. A method for recovering waste polyester material by acetate ionic liquid catalysis is characterized in that waste polyester is taken as a raw material, acetate ionic liquid is taken as a catalyst, and the waste polyester is alcoholyzed into a monomer capable of being polymerized again at 50-200 ℃.

2. The method for catalytic recovery of waste polyester material by acetate ionic liquid according to claim 1, wherein: adding acetate ionic liquid and alcohol compound into waste polyester, adding solvent, stirring and heating until the waste polyester completely disappears and the solution becomes clear, filtering and cleaning the obtained reaction liquid, crystallizing and drying to obtain high-purity monomer.

3. A process for the catalytic recovery of waste polyester material from acetate ionic liquids as claimed in claim 2 wherein: the structure of the acetate ionic liquid is shown as follows:

anions:

cation:

organic bases of formula (I): the nitrogen-containing polycyclic organic matter is selected from six-membered bicyclic guanidine, diazabicycloalkane and diazabicycloalkene compounds;

(II) imidazole and derivatives thereof:

R ₁ ，R ₂ ，R ₃ ，R ₄ is hydrogen atom, halogen atom, hydroxyl, alkyl, alkenyl, alkynyl, alkoxy, aryloxy, aryl, amino, independently of each other.

4. A process for the catalytic recovery of waste polyester material, according to claim 2, wherein the alcohol compound is selected from the group consisting of compounds of the general formula:

r represents a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an aryl group, or an amino group.

5. A process for the catalytic recovery of waste polyester material from acetate ionic liquid according to claim 4, wherein: the molar ratio of the alcohol compound to the polyester is 1-1000:1.

6. The method for catalytic recovery of waste polyester material by acetate ionic liquid according to claim 2, wherein the solvent is anisole, dimethyl carbonate, methylene chloride, chloroform, tetrahydrofuran or 2-methyl-tetrahydrofuran or no solvent is added.

7. The method for catalytic recovery of waste polyester material by acetate ionic liquid according to claim 2, wherein the temperature is heated to 50-200 ℃ and the depolymerization time is 1 min-100 h.

8. The method for catalytic recovery of waste polyester material by acetate ionic liquid according to claim 2, wherein the mass ratio of catalyst to polyester is 0.00001-0.1:1.

9. The method for catalytic recovery of waste polyester material by acetate ionic liquid according to claim 2, wherein the polyester is PET or PC material.