Acidic ionic liquid catalyst, preparation method and application thereof in degrading waste textiles

Abstract

The present invention provides an acidic ionic liquid catalyst, a preparation method, and an application thereof in degrading waste textiles. The invention relates to the technical field of catalysts. A bissulfonic acid metal-based ionic liquid catalyst with Brønsted-Lewis bis-acidity is designed to solve the problems of traditional catalysts being toxic, difficult to separate, and causing secondary contamination of the product with irremovable color due to residues in the recycling of waste polyester-cotton textiles. The catalyst improves the conversion rate of polyester fibers while separating cotton fibers, thereby achieving considerable economic benefits.

Description

Technical Field

[0001] The present invention relates to the relevant field of catalysts, and in particular to an acidic ionic liquid catalyst, a preparation method and application thereof in degrading waste textiles. Background Art

[0002] Polyester-cotton textiles are blended polyester fibers (polyethylene terephthalate, PET) and cotton fibers (primarily composed of cellulose). They combine the strength and abrasion resistance of polyester fibers with the water and sweat absorption and comfort of cotton fibers. Consequently, they are widely used in clothing, home textiles, and industrial production. However, due to the enormous amount of waste generated after use, incineration and landfill are often used to dispose of used polyester-cotton textiles. Burning waste polyester-cotton textiles produces a large amount of toxic substances, causing air pollution, while landfilling is difficult for natural microbial degradation to occur, resulting in land contamination. Therefore, effective recycling of polyester-cotton textiles is crucial to creating a circular economy.

[0003] Currently, the recycling and reuse of discarded polyester-cotton textiles is divided into physical and chemical methods. The physical method involves disinfecting, sorting, crushing, and spinning waste polyester, while preserving its basic chemical molecular properties. Physical recycling methods involve multiple separation steps and low efficiency, and the separated fibers can only be used to produce low-value-added products. Chemical methods are mainly divided into two categories: one dissolving cotton fibers into oligomers or glucose, and the other depolymerizing polyester fibers into monomeric compounds. Since polyester fiber is the primary component of polyester-cotton textiles, accounting for 60%-90% of the main components, a depolymerization reaction using a catalyst selectively degrades the polyester fibers in polyester-cotton textiles, completely separating the unreacted cotton fibers. The degradation products can be directly used as raw materials for polymer synthesis or converted into other useful chemical intermediates, without any of the drawbacks of other recycling methods. The resulting polymers have the same properties and are more tolerant to contaminants. However, traditional catalysts such as strong inorganic acids and bases, metal acetates, and metal oxides often pose toxicity, are difficult to separate, and leave residues that cause irremovable secondary contamination of the product. Therefore, finding a suitable catalyst for the degradation reaction has long been a research focus and challenge. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to propose an acidic ionic liquid catalyst, a preparation method and its application in degrading waste textiles, so as to alleviate the technical problems existing in the prior art in the recycling of waste polyester-cotton textiles, such as the toxicity of traditional catalysts, the difficulty in separation and the residue causing secondary contamination of the product with color that cannot be removed.

[0005] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0006] The first aspect of the present invention provides an acidic ionic liquid catalyst, the structure of which comprises: a Lewis acidic anion group and Acidic triethylenediamine disulfonic acid cation group; the structural formula is shown below.

[0007]

[0008] Among them, X is Cl, Br, I, and M is Zn, Al, Fe, or Cu.

[0009] In some variations of the first aspect of the present invention, -Lewis bis-acidic bissulfonic acid metal-based ionic liquid catalyst.

[0010] In a second aspect, the present invention further provides a method for preparing an acidic ionic liquid catalyst, which is used to prepare the acidic ionic liquid catalyst described above, and is characterized in that:

[0011] S10. 1,3-propane sultone was added to a triethylenediamine solution with ethyl acetate as a protective solvent at a reaction temperature of 60-90°C for 48 hours. After the reaction was completed, the mixture was filtered under reduced pressure, and the filter cake was washed 3-5 times with ethyl acetate and dried at 60-80°C to obtain intermediate I as a white powder.

[0012] S20. A dilute hydrochloric acid solution was slowly added to the aqueous solution of intermediate Ⅰ. The reaction temperature in the first stage was controlled at 20-30 ℃, the reaction time was controlled at 30-60min, the temperature in the second stage was raised to 60-80 ℃, the reaction time was controlled at 6-8h, and after the reaction, the mixture was rotary evaporated and dried in vacuo to obtain intermediate Ⅱ;

[0013] S30. Under N2 protection, add Cl-based Lewis acid metal salt to the molten intermediate II, control the reaction temperature at 60-90 ° C, and control the reaction time at 6-8h to obtain -Lewis bis-acidic bissulfonic acid metal-based ionic liquid catalyst.

[0014] In some modified embodiments of the second aspect of the present invention, the molar ratio of triethylenediamine to sulfonic acid groups in step S10 is 1:2.

[0015] In some modified embodiments of the second aspect of the present invention, the molar ratio of the hydrochloric acid solution to the aqueous solution of intermediate I in step S20 is 2:1.

[0016] In some modified embodiments of the second aspect of the present invention, the molar ratio of the Cl-based Lewis acidic metal salt to the intermediate II in step 30 is 2:1.

[0017] In some variations of the second aspect of the present invention, the complex catalytic performance of the triethylenediamine functionalized cationic group containing a disulfonic acid group and the Lewis acidic metal active site species.

[0018] In some variations of the second aspect of the present invention, the sulfonic acid group is an alkylsulfonic acid.

[0019] In some modified embodiments of the second aspect of the present invention, the solvent of the sulfonic acid group solution is one of ethyl acetate, propyl acetate, butyl acetate, and n-propyl acetate.

[0020] In a third aspect, the present invention provides an application of an acidic ionic liquid catalyst, wherein the acidic ionic liquid catalyst described above is used for the degradation reaction of waste textiles.

[0021] The present invention proposes an acidic ionic liquid catalyst, a preparation method and its application in degrading waste textiles. -Lewis bis-acidic bissulfonic acid metal-based ionic liquid catalyst solves the problems of traditional catalyst toxicity, difficulty in separation, and residual secondary contamination of the product with irremovable color in the recycling of waste polyester-cotton textiles. It improves the conversion rate of polyester fibers while separating cotton fibers, achieving considerable economic benefits.

[0022] (1) Introduction of Lewis acidic metal salts and The acidic functional groups achieve synergistic catalytic effects through the complexation of Z bonds. In the presence of a -Lewis double acid center, by adjusting factors such as the acid strength and the distance of the acid center, it can both provide cations and accept electron pairs. Under their synergistic effect, it polarizes the solvent and reactants and improves their reactivity, thereby better catalyzing the depolymerization reaction of different types of polyesters.

[0023] (2) This catalyst is based on an ionic liquid with zero vapor pressure, and can be used for reactions under vacuum and high pressure conditions. It is non-flammable, non-explosive, and non-oxidizing, and has good thermal and chemical stability.

[0024] (3) The amount of catalyst used is small, the conversion rate of reactants is high, and it is highly efficient, which significantly reduces production costs.

[0025] (4) The catalyst circulation efficiency is high, which can realize the recycling of catalyst while ensuring high selectivity and conversion rate, thus significantly reducing production costs.

[0026] (5) The degradation rate of polyester fiber reached 90.8%, realizing the recycling and reuse of polyester-cotton textiles and breaking through the barriers of existing technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below.

[0028] Figure 1 A diagram showing the reaction mechanism of the acidic ionic liquid catalyst provided by the present invention in waste textiles;

[0029] Figure 2 Schematic diagram of the synthesis of the acidic ionic liquid catalyst intermediate I provided by the present invention;

[0030] Figure 3 Schematic diagram of the synthesis of the acidic ionic liquid catalyst intermediate II provided by the present invention;

[0031] Figure 4 A schematic diagram of the synthesis of the product catalyst in the method for preparing the acidic ionic liquid catalyst provided by the present invention;

[0032] Figure 5 The infrared spectrum of the catalyst product obtained by using the acidic ionic liquid catalyst provided in the embodiment of the present invention;

[0033] Figure 6 Product catalyst for the application of the acidic ionic liquid catalyst provided in the embodiment of the present invention in the degradation of waste textiles 1 H NMR spectrum;

[0034] Figure 7 This is a schematic diagram of the synthesis of the bissulfonic acid metal-based ionic liquid catalyst, a product of the method for preparing the acidic ionic liquid catalyst provided by the present invention;

[0035] Figure 8 BHET infrared spectrum of the degradation product of the acidic ionic liquid catalyst provided in the embodiment of the present invention when used in the degradation of waste textiles. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0038] The present invention will be further described in detail below through the examples. Through these descriptions, the characteristics and advantages of the present invention will become more clear and distinct.

[0039] like Figure 1-4 The present invention relates to an acidic ionic liquid catalyst, a preparation method and its application in degrading waste polyester-cotton textiles (80% PET-20% cotton). The catalyst is composed of Lewis acidic anion groups and An acidic metal-based ionic liquid catalytic system composed of acidic triethylenediamine disulfonic acid cationic groups enhances its reactivity by adjusting factors such as acid strength and the distance between acidic centers, thereby further improving catalytic efficiency. Furthermore, the disulfonic acid-functionalized triethylenediamine cationic groups can be synthesized and modified with various Lewis acid salts to modify the overall acidity of the catalytic molecule to meet the reaction conditions. This system is used to address issues such as the toxicity of traditional catalysts, the difficulty of separation, and the residual residue that causes irremovable secondary contamination of the product in the recycling of discarded polyester-cotton textiles. Furthermore, it can significantly improve the conversion rate of polyester fiber degradation, resulting in considerable economic benefits.

[0040] The advantage of acidic ionic liquid catalysts lies in the introduction of disulfonic acid groups into the cationic group, which, in synergistic action with the Lewis acidic anionic group, outperforms the catalytic effect of the cationic monosulfonic acid group. The type of metal salt can be varied to achieve different catalytic effects, creating a catalyst system tailored to the specific polyester type.

[0041] The degradation reaction mechanism in this invention is as follows: Under the action of an acidic ionic liquid catalyst, the hydroxyl oxygen in water or alcohol nucleophilically attacks the carbonyl carbon within the PET chain. This attack triggers an elimination reaction, breaking the macromolecular chain and generating different smaller molecules, thus completing the depolymerization reaction.

[0042] An acidic ionic liquid catalyst, the structure of which comprises: a Lewis acidic anion group and Acidic triethylenediamine disulfonic acid cationic group.

[0043] According to the principles of the present invention, the preparation method of the acidic ionic liquid catalyst is mainly divided into two steps. Step 1: Using a disulfonic acid functionalized triethylenediamine cationic group and a Lewis acidic anionic group disulfonic acid metal-based ionic liquid; triethylenediamine is inherently stable and has synthetic reaction sites. By introducing disulfonic acid groups into the cationic group, it provides a catalytic promotion effect; Step 2: Using a dilute HCl solution with a concentration of 1 mol / L, the intermediate I is acidified to obtain the intermediate II. Step 3: Using a Cl-based Lewis acidic metal salt and the intermediate II described in step 2, the acidic ionic liquid catalyst system is prepared. The details are as follows:

[0044] A method for preparing an acidic ionic liquid catalyst,

[0045] (1) 1,3-propane sultone was added to a triethylenediamine solution with ethyl acetate as a protective solvent, the reaction temperature was 60-90°C, the reaction time was 48 hours, after the reaction was completed, the filter cake was filtered under reduced pressure, washed with ethyl acetate 3-5 times, and dried at 60-80°C to obtain a white powder intermediate I;

[0046] (2) Slowly adding dilute hydrochloric acid solution to the aqueous solution of intermediate I, the first stage reaction temperature is controlled at 20-30 ° C, the reaction time is controlled at 30-60 min, the second stage temperature is raised to 60-80 ° C, the reaction time is controlled at 6-8 h, after the reaction is completed, the mixture is subjected to rotary evaporation and vacuum drying to obtain intermediate II;

[0047] (3) Under N2 protection, a Cl-based Lewis acidic metal salt is added to the molten intermediate II, the reaction temperature is controlled at 60-90°C, and the reaction time is controlled at 6-8h to obtain an acidic ionic liquid catalyst.

[0048] According to the principles of the present invention, the cationic group in the present invention can be one of triethylenediamine, 1-methylimidazole, 2-methylimidazole, etc., preferably triethylenediamine. The sulfonic acid group can be one of methylsulfonic acid, alkylsulfonic acid, alkylbenzenesulfonic acid, etc., preferably alkylsulfonic acid. The solvent of the sulfonic acid group solution can be one of ethyl acetate, propyl acetate, butyl acetate, n-propyl acetate, etc., preferably ethyl acetate. The Lewis acidic metal salt can be one of ZnCl2, FeCl3, AlCl3, etc., preferably ZnCl2. The above reagents combined with the method of the present invention can also prepare the acidic ionic liquid catalyst proposed by the present invention.

[0049] The invention discloses an application of an acidic ionic liquid catalyst, wherein the catalyst is applied to degradation reaction of polyester-cotton textiles.

[0050] The application method is as follows:

[0051] Under nitrogen protection, 1-5g (preferably 3g) of waste textiles, 10-30g (preferably 27g) of ethylene glycol, and 0.2-1.0g (preferably 0.6g) of a bissulfonic acid-based ionic liquid catalyst are weighed in sequence. The mixture is mixed, and the reaction temperature is controlled at 120-200°C, preferably 190°C, and the reaction time is controlled at 4-10 hours, preferably 6 hours. After the reaction is completed, the reaction liquid is filtered while hot, and the filter cake is washed with distilled water and dried to obtain the mass of cotton and unreacted polyester fiber. Under the action of the bissulfonic acid metal-based ionic liquid catalyst, the hydroxyl oxygen in the water or alcohol nucleophilically attacks the carbonyl carbon in the polyester (PET) chain. After the carbonyl oxygen is attacked, an elimination reaction occurs, breaking the macromolecular chain and generating different small molecules, thus completing the depolymerization reaction.

[0052] Example 1

[0053] The preparation method of the -Lewis bis-acidic bissulfonic acid metal-based ionic liquid catalyst is as follows:

[0054] (1) 1,3-Propane sultone was added to a triethylenediamine solution with ethyl acetate as a protective solvent. The reaction temperature was 80°C and the reaction time was 48 h. After the reaction was completed, the mixture was filtered under reduced pressure. The filter cake was washed with ethyl acetate three times and dried at 60°C to obtain a white powdery intermediate I. The reaction formula is as follows ( Figure 2 ) as shown.

[0055]

[0056] (2) Dissolve an appropriate amount of intermediate I in an appropriate amount of distilled water at room temperature, slowly add dilute hydrochloric acid at a rate of 20-100 ml / s, magnetically stir at room temperature for 1 hour, then heat to 80°C and continue magnetic stirring to react, and condense and reflux under nitrogen protection for 8 hours. After the reaction is completed, the product is rotary evaporated and vacuum dried to obtain a white liquid intermediate II. The reaction formula is as follows ( Figure 3 ) as shown.

[0057]

[0058] (3) Under N2 protection, 0.01 mol of intermediate II was heated until completely melted, and then 0.02 mol of ZnCl2 was added. The mixture was stirred and heated, and then the temperature was raised to 90°C, and magnetic stirring was continued and the reaction was refluxed under condensation for 6 hours. After the reaction was completed, the mixture was subjected to rotary evaporation and vacuum drying at 60°C for 24 hours to obtain a bissulfonic acid metal-based ionic liquid catalyst, as follows ( Figure 4 ) as shown.

[0059]

[0060] The structural formula of the bissulfonic acid metal-based ionic liquid catalyst of Example 1 is as follows:

[0061]

[0062] The infrared spectrum of the bissulfonic acid metal-based ionic liquid catalyst of Example 1 is 1 H NMR spectrum is shown as ( Figure 5 、 Figure 6 ) as shown.

[0063] The general formula for preparing the bissulfonic acid metal-based ionic liquid catalyst of Example 1 is as follows ( Figure 7 ) as shown:

[0064]

[0065] Example 2

[0066] Add 3.0g of polyester-cotton textile and 27g of ethylene glycol to a three-necked flask, take 0.6g of the acidic catalyst prepared in Example 1 (2% of the raw material dosage), and heat the reactor to 190℃ for 6h of heat preservation. After the reaction is completed, filter the reaction solution while hot, wash the filter cake with distilled water and dry it to obtain the mass of cotton and unreacted polyester fiber. Add about 400ml of distilled water to the filtrate, heat and stir to dissolve, filter and remove the insoluble oligomers in the filtrate, concentrate the filtrate to 100ml by rotary evaporation, and place it in a refrigerator at 3℃ for 8 hours. The degradation product BHET crystallizes and precipitates. After filtration, vacuum dry at 60℃ and weigh to obtain the product BHET. The filtrate is distilled at 120℃ under reduced pressure to remove water and ethylene glycol to recover the ionic liquid catalyst. The infrared spectrum of the degradation product BHET is as follows ( Figure 8 ), the calculated yield of the degradation product BHET was 76.62%.

[0067] Example 3

[0068] Under the same conditions as in Example 2, the monoacidic [DA-2PS][Cl]2 was used to replace the bissulfonic acid metal-based ionic liquid catalyst of the present invention. When the reaction time, temperature and other conditions were not changed, the BHET yield was calculated to be 15.23%.

[0069] Example 4

[0070] Under the same conditions as in Example 2, the monoacidic ZnCl2 was used to replace the bissulfonic acid metal-based ionic liquid catalyst of the present invention. When the reaction time, temperature and other conditions were not changed, the BHET yield was calculated to be 30.14%.

[0071] Example 5

[0072] Under the same conditions as in Example 2, without adding any catalyst, and without changing the reaction time, temperature and other conditions, the BHET yield was calculated to be 0%.

[0073] Comparison 1: Compared with implementation case 2, only the reaction time was changed to 3h;

[0074] Comparison 2: Compared with implementation case 2, only the amount of catalyst was changed, and the catalyst accounted for 10%.

[0075] The catalytic performances of Examples 2 to 5 and Comparative 1 and Comparative 2 are compared, as shown in Table 1.

[0076] Table 1 Comparison of catalytic performance of ionic liquids

[0077] project Example 2 Example 3 Example 4 Example 5 Comparison 1 Comparison 2 reactant ratio 1:09 1:09 1:09 1:09 1:09 1:09 Catalyst ratio 20％ 20％ 20％ 0％ 20％ 10％ Reaction temperature 190℃ 190℃ 190℃ 190℃ 190℃ 190℃ Reaction time 6h 6h 6h 6h 3h 6h BHET yield 76.62％ 15.23％ 30.14％ 0％ 26.23％ 42.12％

[0078] As can be seen from Table 1, the yield of BHET obtained by degrading polyester PET using the acidic ionic liquid catalyst of the present invention can reach 76.62%.

[0079] The present invention only selected the catalyst of Example 1 for comparison test. According to the principle of the present invention, other acidic ionic liquid catalysts also have the effect of degrading polyester-cotton textiles.

[0080] The catalytic performance of the catalysts without adding any catalyst, traditional catalysts Zn(OAc)2 and ZnCl2, bissulfonic acid non-metallic ionic liquid catalyst [DA-2PS][Cl]2, imidazolesulfonic acid bisacid type ionic liquid catalysts [HO3S-(CH2)4-mim]Cl-ZnCl2, [HO3S-(CH2)3-mim]Cl-ZnCl2, and acidic ionic liquid catalyst [DA-2PS][FeCl3]2 synthesized by the method of the present invention were compared, as shown in Table 2 for details.

[0081] Table 2 Comparison of catalytic performance between ionic liquid catalysts and traditional catalysts

[0082] serial number Catalyst type PET alcoholysis rate BHET yield 1 - 0 0 2 <![CDATA[Zn(OAc)2]]> 66.06％ 52.12％ 3 <![CDATA[ZnCl2]]> 60.12％ 30.14％ 4 <![CDATA[[DA-2PS][Cl]2]]> 28.90％ 15.23％ 5 <![CDATA[[HO3S-(CH2)4-mim]Cl-ZnCl2]]> 85.68％ 70.50％ 6 <![CDATA[[HO3S-(CH2)3-mim]Cl-ZnCl2]]> 87.20％ 72.21％ 7 <![CDATA[[DA-2PS][ZnCl3]2]]> 90.80％ 76.62％

[0083] As can be seen from Table 2, by comparing the catalytic performance of the ionic liquid catalyst with that of the traditional catalyst, the present invention found that the acidic ionic liquid catalyst designed and synthesized by the present invention had a polyester fiber degradation rate of 90.8%, achieving actual economic benefits for the recycling and reuse of waste polyester-cotton textiles and breaking through the barriers of the prior art.

[0084] It should be noted that the method used in this embodiment is applied to textiles other than polyester.

[0085] The present invention has been described above with reference to preferred embodiments, but these embodiments are merely exemplary and serve only as illustrations. On this basis, various replacements and improvements can be made to the present invention, all of which fall within the scope of protection of the present invention.

[0086] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. Application of an acidic ionic liquid catalyst in the degradation of waste textiles, the catalyst structure is shown below: 。 2. A method for preparing the acidic ionic liquid catalyst for use as claimed in claim 1, characterized in that: S10. 1,3-propane sultone was added to a triethylenediamine solution with ethyl acetate as a protective solvent at a reaction temperature of 60-90°C for 48 hours. After the reaction was completed, the mixture was filtered under reduced pressure, and the filter cake was washed 3-5 times with ethyl acetate and dried at 60-80°C to obtain intermediate I as a white powder. Intermediate Ⅰ, the reaction formula is as follows: ； S20. A dilute hydrochloric acid solution was slowly added to the aqueous solution of intermediate Ⅰ. The reaction temperature in the first stage was controlled at 20-30 ℃, the reaction time was controlled at 30-60min, the temperature in the second stage was raised to 60-80 ℃, the reaction time was controlled at 6-8h, and after the reaction, the mixture was rotary evaporated and dried in vacuo to obtain intermediate Ⅱ; Intermediate II, the reaction formula is as follows: ； S30. Under N2 protection, ZnCl2 is added to the molten intermediate II, the reaction temperature is controlled at 60-90°C, and the reaction time is controlled at 6-8h to obtain an acidic ionic liquid catalyst.

3. The method for preparing the acidic ionic liquid catalyst according to claim 2, wherein: In step S10, the molar ratio of triethylenediamine to sulfonic acid groups is 1:

2.

4. The method for preparing the acidic ionic liquid catalyst according to claim 2, wherein: In step S20, the molar ratio of the hydrochloric acid solution to the aqueous solution of intermediate I is 2:

1.

5. The method for preparing the acidic ionic liquid catalyst according to claim 2, wherein: The molar ratio of ZnCl2 to intermediate II in step 30 is 2:1.

Images