CN101407445B - Waste polyester material recovery method with ion liquid as reaction medium and catalyst - Google Patents

Abstract

The invention relates to a new method for chemically degrading waste polyester (PET) to generate terephthalic acid and ethylene glycol and realizing recycling of waste PET materials. It is characterized in that ionic liquids such as 1-butyl-3-methylimidazole chloride, 1-allyl-3-methylimidazole chloride and 1-benzyl-3-methylimidazole chloride, which are easy to reuse, are used as Reaction medium functionalized with acids such as 1-methyl-3-(3-sulfopropyl)imidazole hydrogen sulfate, 1-methyl-3-(3-sulfobutyl)imidazole hydrogen sulfate The ionic liquid is used as a catalyst, and the hydrolysis reaction is carried out at 100°C-190°C. After the reaction, water is added to precipitate the precipitate, filtered, and the filtrate is separated by distillation to recover ethylene glycol and ionic liquid. The recovered ionic liquid is directly reused without any treatment. Dissolving the filter cake with sodium hydroxide solution, filtering to remove undegraded PET and other insoluble impurities, adding acid to precipitate the obtained filtrate, filtering and drying to obtain the product terephthalic acid with a yield of over 90%. Compared with the traditional method, the present invention is characterized in that: (1) it overcomes the problems of consuming a large amount of high-concentration inorganic strong acid/strong base and not being able to recycle, which existed in the background technology. (2) Since the ionic liquid with a certain solubility to PET is used as the reaction medium and catalyst, on the one hand, the reaction conditions are eased, and on the other hand, the ionic liquid can be reused, which significantly improves the problems of equipment corrosion and environmental pollution.

Description

Waste polyester material recycling method using ionic liquid as reaction medium and catalyst

technical field

The invention relates to a new method for chemically degrading waste polyester (PET) materials and recovering monomers by using ionic liquid as a reaction medium and a catalyst.

technical background

Polyester (PET) is a polymer material polymerized from terephthalic acid (TPA) or dimethyl terephthalate (DMT) with ethylene glycol (EG). Because of its good physical and chemical properties, it is Widely used in food packaging, fiber, film, film base and electrical insulation materials and other fields. With the rapid increase of PET production and sales, more and more waste PET is produced. Although waste PET does not directly pollute the environment, it will occupy a large amount of space. Because of its strong chemical inertia, it is difficult to degrade under natural conditions, so it will not only have a great impact on the environment, but also cause huge Waste of resources. Therefore, the recycling of waste PET has been paid more and more attention in recent years.

At present, there are mainly two types of recycling methods for waste PET materials. One is physical methods, that is, products with low added value are prepared through melting remolding or pelletizing and remolding. The disadvantage of this method is that it reduces the utilization of waste PET materials. value and a limited number of recycles. The other is the chemical method, that is, waste polyester materials are chemically degraded by means of catalysts or supercritical to generate corresponding monomers or low molecular weight products, so as to realize recycling. Among them, hydrolyzing PET to obtain monomer terephthalic acid and ethylene glycol is a main chemical degradation method. At present, the method is carried out in the presence of a large amount of strong acid, strong base or under supercritical conditions. For example, Pusztaszeri et al. (US4355175) used concentration > 87% concentrated sulfuric acid to catalyze the hydrolysis of PET; Oku et al. (J Appl Polym Sci, 1997, 63:595-601) used solid sodium hydroxide to catalyze the hydrolysis reaction of PET. The disadvantages of these methods are that a large amount of concentrated acid or alkali needs to be applied, the catalyst cannot be reused and recycled, and the equipment is corroded and polluted seriously. Yamamoto (Technology Review, 1997, 20:52-55) carried out the hydrolysis reaction of PET under the supercritical condition of water (350°C, 10-54Mpa). The disadvantage of this method is that it requires high temperature and high pressure, resulting in high energy consumption and harsh conditions. , High requirements on equipment materials, difficult to achieve large-scale operation. Therefore, it is of great significance to introduce new methods to improve the disadvantages of the existing process and realize the chemical recycling of waste PET materials.

Contents of the invention

The invention proposes a new method for hydrolyzing waste PET. This method uses ionic liquids that have a certain solubility in PET and can be recycled and reused as solvents and catalysts to hydrolyze waste PET. On the one hand, the reaction conditions are eased, and on the other hand, the ionic liquids can be reused, which can significantly reduce the three wastes. emission.

The purpose of the present invention is to provide a new method for hydrolyzing waste PET, which overcomes the shortcomings of traditional methods such as consumption of a large amount of inorganic strong acid or strong alkali, serious equipment corrosion and environmental pollution, inability to recycle catalysts, and harsh reaction conditions. The present invention solves these problems through the following scheme, using a solvent-based ionic liquid with certain solvent properties for PET as the reaction medium, using an acid-functionalized catalyst-type ionic liquid as a catalyst, and performing a hydrolysis reaction on waste PET under a certain pressure and temperature . After the reaction, add water to precipitate the precipitate, filter, and distill the filtrate to separate and recover ethylene glycol and ionic liquid, and the recovered ionic liquid is directly reused without any treatment. Dissolve the filter cake with sodium hydroxide solution, filter to remove undegraded PET and other insoluble impurities, add acid to the obtained filtrate to precipitate, filter and dry to obtain the product terephthalic acid.

The solvent-based ionic liquid described in the method of the present invention has the following general structural formula:

Among them, R is C ₂ ~ C ₁₂ alkyl or alkenyl, Y is HSO ₄ , CF ₃ SO ₃ , p-CH ₃ C ₆ H ₄ SO ₃ etc., X is Cl, Br, BF ₄ , PF ₆ , CF ₃ COO, HSO ₄ etc.

The most commonly used are 1-butyl-3-methylimidazole chloride, 1-ethyl-3-methylimidazole bromide, 1-octyl-3-methylimidazole chloride, 1-allyl chloride -3-methylimidazole, 1-benzyl-3-methylimidazole chloride, 1-dodecyl-3-methylimidazole bromide, 1-ethyl-3-methylpyridine bromide, N- Methylpyrrolidone methanesulfonate, N-methylpyrrolidone p-toluenesulfonate, N-methylpyrrolidone bisulfate or their complexes, etc.

The catalyst-type ionic liquid described in the inventive method has the following general structural formula:

Among them, n=3~4, R ₁ is C ₁ ~C ₃ alkyl, R ₂ is C ₁ ~C ₄ alkyl, X is HSO ₄ , H ₂ PO ₄ , CF ₃ SO ₃ , p-CH ₃ C ₆ H ₄ SO ₃ etc.

The most commonly used are 1-methyl-3-(3-sulfopropyl)imidazole p-toluenesulfonate, 1-methyl-3-(3-sulfobutyl)imidazole bisulfate, N- (3-sulfopropyl)pyridine hydrogensulfate, N-(3-sulfobutyl)pyridine hydrogensulfate, 3-sulfopropyltriethylammonium hydrogensulfate or its compound, etc. .

Under the reaction conditions, the ionic liquid used has a certain dissolution effect on PET and water, which can promote the hydrolysis reaction, resulting in a significant improvement in the amount of catalyst and reaction temperature. The reaction temperature described in the method of the present invention is generally at 100-190°C, and the amount of the catalyst-type ionic liquid is generally 1%-9% of the PET amount

The reaction principle involved in the present invention is as follows:

This method is realized through the following steps:

The solvent-type ionic liquid, water, catalyst-type ionic liquid and waste PET are added into the reaction kettle according to a certain ratio, and stirred and reacted at a certain temperature for a certain period of time. After the reaction, add water to precipitate the precipitate, filter, and distill the filtrate to separate and recover ethylene glycol and ionic liquid, and the recovered ionic liquid is directly reused without any treatment. Dissolve the filter cake with sodium hydroxide solution, filter to remove undegraded PET and other insoluble impurities, add acid to the obtained filtrate to precipitate, filter and dry to obtain the product terephthalic acid.

Compared with the traditional method, the present invention is characterized in that: (1) It overcomes the problems of consuming a large amount of high-concentration inorganic strong acid/strong alkali and not being able to recycle, which existed in the background technology. (2) Since the ionic liquid with certain solubility to PET is used as the reaction medium and catalyst, on the one hand, the reaction conditions are eased, and on the other hand, the ionic liquid can be reused, which significantly improves the problems of equipment corrosion and environmental pollution.

Description of drawings

A schematic diagram of the technical route of the method of the present invention.

Specific implementation method

The method of the present invention will be further described below in conjunction with the examples, but the present invention is not limited.

Example 1: Put 15.0g of waste PET into an autoclave, add 15.0g of water, 1.5g of 1-methyl-3-(3-sulfonic acid propyl) imidazole bisulfate, 30g of 1-butyl chloride -3-Methylimidazole, after the addition, stir and react at 190°C for 1.5h. After cooling down to room temperature, add a certain amount of water to precipitate a precipitate, filter, distill and separate the filtrate to recover ethylene glycol and ionic liquid, and dilute the filter cake with hydrogen Sodium oxide solution was dissolved, and then filtered to remove undegraded PET and other insoluble impurities, and the obtained filtrate was added with acid to precipitate, filtered and dried to obtain 11.90 g of terephthalic acid. The degradation rate of PET is 99.1%, and the yield of terephthalic acid is 91.8%.

Example 2: The experimental conditions and steps are the same as in Example 1, except that 1-butyl-3-methylimidazole chloride is changed to 1-ethyl-3-methylimidazole bromide to obtain 11.93 g of terephthalic acid product . The degradation rate of PET is 99%, and the yield of terephthalic acid is 92.0%.

Example 3: The experimental conditions and steps are the same as in Example 1, except that 1-butyl-3-methylimidazole chloride is changed to 1-ethyl-3-picoline bromide to obtain 11.87 g of terephthalic acid product . The degradation rate of PET is 98.2%, and the yield of terephthalic acid is 91.5%.

Example 4: The experimental conditions and steps are the same as in Example 1, except that 1-methyl-3-(3-sulfonic acid propyl) imidazole hydrogen sulfate is changed to 1-methyl-3-(3-sulfonic acid group Butyl)imidazole bisulfate, the reaction temperature was changed to 170°C to obtain 11.84g of terephthalic acid product. The degradation rate of PET is 99%, and the yield of terephthalic acid is 91.3%.

Example 5: The experimental conditions and steps are the same as in Example 1, except that 1-methyl-3-(3-sulfopropyl) imidazole hydrogen sulfate is changed to N-(3-sulfopropyl) pyridinesulfuric acid hydrogen salt to obtain 11.80 g of terephthalic acid product. The degradation rate of PET is 99.2%, and the yield of terephthalic acid is 91.0%.

Examples 6-13: The experimental conditions and steps were the same as in Example 1, except that the ionic liquid was changed to the ionic liquid recovered in Example 1, and eight repeated use experiments were carried out. The results of repeated reuse of ionic liquids are shown in Table 1.

Table 1 Repeated reuse results of ionic liquids

Comparative example: the experimental conditions and steps are the same as in Example 1, except that 1-butyl-3-methylimidazole chloride is changed to water. Hydrolysis hardly occurred and no terephthalic acid product was obtained.

Claims (3)

1. the method for terephthalic acid and terepthaloyl moietie is reclaimed in a useless polyester hydrolysis; Be about to useless polyester, solvent-borne type ionic liquid, catalyst type ionic liquid and water and add in the reaction kettle, at a certain temperature, the stirring reaction certain hour; After reaction finishes; Add elutriation and go out deposition, filter, filtrating is reclaimed terepthaloyl moietie and ionic liquid through fractionation by distillation; The ionic liquid that reclaims is without any processing direct reuse; Filter cake is dissolved, removes by filter undegradable useless polyester and other insoluble impurities with sodium hydroxide solution, gained filtrating is added acid out go out deposition, through filtration, the dry product terephthalic acid that gets; The solvent-borne type ionic liquid that is wherein adopted is chlorination 1-butyl-3-Methylimidazole, bromination 1-ethyl-3-Methylimidazole or bromination 1-ethyl-3-picoline, and the catalyst type ionic liquid that is adopted is 1-methyl-3-(3-sulfonic group propyl group) imidazole bisulfate, 1-methyl-3-(3-sulfonic group butyl) imidazole bisulfate or N-(3-sulfonic group propyl group) pyridine hydrosulfate.

2. method according to claim 1, wherein hydrolysising reacting temperature is 100 ℃-190 ℃.

3. method according to claim 1, wherein catalyst type ionic liquid consumption is the 1%-9% of useless polyester amount in the hydrolysis reaction.

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