A method for preparing 5-hydroxymethylfurfural by using waste blended cotton fibers as raw materials

Abstract

The application relates to the chemical technology field and discloses a method for preparing 5-hydroxymethyl furfural from waste blended cotton fibers as raw materials, which comprises the following steps: step 1, pretreating waste blended cotton fiber polyester to prepare pretreated products; step 2, reacting the pretreated products in step 1 with mixed solvents to prepare a primary mixture; step 3, separating insoluble substances and liquid in the primary mixture in step 2, and adding a catalyst into the separated liquid to react to prepare 5-hydroxymethyl furfural; the application adopts the mixed solvents to selectively dissolve the cotton fibers in the waste blended cotton fiber polyester, and the separation efficiency is high; the cotton fibers dissolved in the mixed solvents can be converted into 5-hydroxymethyl furfural under the catalysis of the catalyst, the conversion rate of the cotton fibers is high, the yield of the 5-hydroxymethyl furfural is high, the yield of the 5-hydroxymethyl furfural can reach 48.71% at most, and the conversion rate of the cotton fibers can reach 97.3% at most.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a method for preparing 5-hydroxymethylfurfural using waste blended cotton fibers as raw materials. Background Technology

[0002] Textiles play an important role in our daily lives. A large number of textiles are produced and used every year, resulting in a continuous increase in the amount of waste textiles. The raw materials of textiles mainly include organic polyester fibers and natural fibers. Organic polyester fibers degrade very slowly and cause serious environmental pollution when discarded. Although natural fibers can degrade quickly after being discarded, they also result in resource waste. Therefore, in order to solve the above problems, the technology for reusing waste textiles has attracted much attention in this field.

[0003] 5-Hydroxymethylfurfural (5-HMF) is a key platform compound that can be used to prepare various high-value-added chemicals through reactions such as oxidation, hydrogenation, and amination. Currently, 5-HMF can be obtained by dehydrating various carbohydrate compounds such as fructose, glucose, cellobiose, and oligomers. However, research on one-step conversion of 5-HMF from polysaccharides such as cellulose and coarse cotton is still limited. Furthermore, research on methods combining chemical recycling of waste textiles with efficient conversion into high-value-added platform chemicals is scarce.

[0004] Waste blended cotton fiber polyester is a type of waste textile product, and several technical solutions for recycling and reusing waste blended cotton fiber polyester have been disclosed. For example, patent number CN102199310A discloses a method for recovering cotton components from waste polyester-cotton textiles, which uses an aqueous solution of 4-methylmorpholine-N-oxide to dissolve cotton fibers, followed by solid-liquid separation to obtain a cellulose-containing solution and polyester. However, this method requires a high dissolution temperature and stringent preparation conditions. Publication number CN103304839A discloses a method for recovering polyester components from waste polyester-cotton blended textiles. This method uses a high- and low-efficiency mixed solvent to soak the waste polyester-cotton blended textiles, dissolving the polyester, followed by solid-liquid separation to obtain a polyester-containing solution and cotton fibers. However, this method uses a complex solvent, making subsequent separation and chemical recovery of polyester difficult. Summary of the Invention

[0005] To overcome the problems existing in the prior art, this application provides a method for preparing 5-hydroxymethylfurfural using waste blended cotton fibers as raw materials. In this method, a mixed solvent is used to separate the polyester from the waste blended cotton fibers. The mixed solvent can selectively dissolve the cotton fibers and, under the action of a catalyst, convert the cotton fibers dissolved in the mixed solvent into 5-hydroxymethylfurfural. This method has a high 5-hydroxymethylfurfural yield and cotton fiber conversion rate, and can achieve efficient separation and utilization of waste blended cotton fiber polyester.

[0006] The specific technical solution of this invention is as follows:

[0007] A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers includes the following steps:

[0008] Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material;

[0009] Step 2: React the pretreated material from Step 1 with the mixed solvent to prepare a primary mixture;

[0010] Step 3: Separate the insoluble matter and liquid from the primary mixture in Step 2, and add the catalyst to the separated liquid to react and obtain 5-hydroxymethylfurfural.

[0011] Preferably, the mixed solvent in step 2 includes dimethyl sulfoxide and tetraethylammonium chloride.

[0012] This application provides a method for preparing 5-hydroxymethylfurfural (5-HMF) from waste blended cotton fibers. The method employs a mixed solvent to separate cotton fibers and organic polyester from the waste blended cotton fiber polyester, and then uses a catalyst to synthesize 5-HMF from the separated cotton fibers. The mixed solvent is a mixture of dimethyl sulfoxide and tetraethylammonium chloride. This solvent, when mixed with the blended cotton fiber polyester, can selectively dissolve the cotton fibers, efficiently separating them from the polyester. Furthermore, since only cotton fibers are dissolved in the mixed solvent, the dissolved cotton fibers can be directly converted into 5-HMF. This application uses Lewis acid as a catalyst to convert the cotton fibers dissolved in the mixed solvent into 5-HMF. This method enables the efficient utilization of cotton fibers from waste blended cotton fiber polyester.

[0013] Preferably, the mass ratio of dimethyl sulfoxide to tetraethylammonium chloride is 2 to 5:1.

[0014] Preferably, the reaction conditions in step 2 include: nitrogen atmosphere, heating and stirring to dissolve, the heating and stirring temperature being 80-90°C, and the heating and stirring time being 5-10 min.

[0015]

[0012] Preferably, the reaction steps in step 3 include: adding the catalyst to the separated liquid, heating and stirring to prepare a reaction solution, cooling and diluting the reaction solution and separating it to obtain unconverted cotton fibers and crude product, and extracting, removing impurities and purifying the crude product to obtain 5-hydroxymethylfurfural.

[0016] Preferably, the dilution conditions are as follows: the diluent is distilled water, and the amount of diluent used is 5-25%.

[0017] Preferably, the catalyst is an inorganic metal salt, which includes one or more of AlCl3, CrCl3, SnCl4 and CuCl2.

[0018] Preferably, the amount of catalyst used is 5-50 mol%.

[0019] Preferably, the pretreatment conditions in step 1 include: washing, bleaching, and pulverizing waste blended cotton fiber polyester to prepare a pretreated material with a size of 4–20 cm. 2 .

[0020] Preferably, the cotton content of the waste polyester-cotton blended fabric in step 1 is 10-65%.

[0021] Compared with the prior art, this application has the following technical effects:

[0022] (1) This application uses a mixed solvent to selectively dissolve the cotton fibers in the waste blended cotton fiber polyester, resulting in high separation efficiency;

[0023] (2) The cotton fibers dissolved in the mixed solvent can be converted into 5-hydroxymethylfurfural under the catalysis of the catalyst. The conversion rate of cotton fibers is high and the yield of 5-hydroxymethylfurfural is high. Detailed Implementation

[0024] The present invention will be further described below with reference to embodiments.

[0025] Example 1: (Mixed solvent mass ratio is 2:1)

[0026] A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers includes the following steps:

[0027] Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material; after washing and bleaching, the waste blended cotton fiber polyester (cotton fiber to PET mass ratio of 35:65) is crushed into pieces with a size of 4-20cm. 2 Pre-treated materials;

[0028] Step 2: React the pretreated material from Step 1 with the mixed solvent to prepare a primary mixture. The reaction conditions include: mixing 4.58 mL of methyl sulfoxide with 2.5 g of tetraethylammonium chloride (the mass ratio of tetramethyl sulfoxide to tetraethylammonium chloride is 2:1), stirring at 90 °C until completely dissolved to prepare a mixed solvent, adding the pretreated material to the mixed solvent, and heating and stirring under a nitrogen atmosphere to prepare a primary mixture. The dissolution time is 5 min.

[0029] Step 3: The insoluble matter and liquid in the primary mixture from Step 2 are separated by centrifugation. The separated liquid is transferred to a tubular reactor, diluted, and a catalyst is added to prepare a reaction solution. The diluent is 15% distilled water, the catalyst is 35 mol% AlCl3, and the reaction temperature is 130℃. After the reaction is completed, distilled water is added to the reaction solution to dilute it to 30 ml. The unconverted cotton fibers and supernatant are separated by centrifugation. The supernatant is injected into the extraction tank to transfer a large amount of product to the organic phase. The extraction temperature is less than 50℃, and the volume ratio of extractant to solvent is 5:1. The extracted mixture is passed through a decanter to achieve efficient water-oil separation. The separated aqueous phase is passed through a purification unit, neutralized with an appropriate amount of alkali, and a small amount of levulinic acid and formic acid produced by the side reaction are precipitated. The precipitate and humic acid are then removed by filtration and adsorption, and recycled with fresh raw materials. The separated organic phase is subjected to multi-stage vacuum distillation to recover part of the extractant to obtain 5-hydroxymethylfurfural.

[0030] Example 2: (Mixed solvent mass ratio is 4:1)

[0031] A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers includes the following steps:

[0032] Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material; after washing and bleaching, the waste blended cotton fiber polyester (cotton fiber to PET mass ratio of 35:65) is crushed into pieces with a size of 4-20cm. 2 Pre-treated materials;

[0033] Step 2: React the pretreated material from Step 1 with the mixed solvent to prepare a primary mixture. The reaction conditions include: mixing 4.58 mL of methyl sulfoxide with 1.25 g of tetraethylammonium chloride (the mass ratio of tetramethyl sulfoxide to tetraethylammonium chloride is 4:1), stirring at 90 °C until completely dissolved to prepare a mixed solvent, adding the pretreated material to the mixed solvent, and heating and stirring under a nitrogen atmosphere to prepare a primary mixture. The dissolution time is 5 min.

[0034] Step 3: The insoluble matter and liquid in the primary mixture from Step 2 are separated by centrifugation. The separated liquid is transferred to a tubular reactor, diluted, and a catalyst is added to prepare a reaction solution. The diluent is 15% distilled water, the catalyst is 35 mol% AlCl3, and the reaction temperature is 130℃. After the reaction is completed, distilled water is added to the reaction solution to dilute it to 30 ml. The unconverted cotton fibers and supernatant are separated by centrifugation. The supernatant is injected into the extraction tank to transfer a large amount of product to the organic phase. The extraction temperature is less than 50℃, and the volume ratio of extractant to solvent is 5:1. The extracted mixture is passed through a decanter to achieve efficient water-oil separation. The separated aqueous phase is passed through a purification unit, neutralized with an appropriate amount of alkali, and a small amount of levulinic acid and formic acid produced by the side reaction are precipitated. The precipitate and humic acid are then removed by filtration and adsorption, and recycled with fresh raw materials. The separated organic phase is subjected to multi-stage vacuum distillation to recover part of the extractant to obtain 5-hydroxymethylfurfural.

[0035] Example 3: (Catalyst is CrCl3)

[0036] A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers includes the following steps:

[0037] Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material; after washing and bleaching, the waste blended cotton fiber polyester (cotton fiber to PET mass ratio of 35:65) is crushed into pieces with a size of 4-20cm. 2 Pre-treated materials;

[0038] Step 2: React the pretreated material from Step 1 with the mixed solvent to prepare a primary mixture. The reaction conditions include: mixing 4.58 mL of methyl sulfoxide with 2.5 g of tetraethylammonium chloride (the mass ratio of tetramethyl sulfoxide to tetraethylammonium chloride is 2:1), stirring at 90 °C until completely dissolved to prepare a mixed solvent, adding the pretreated material to the mixed solvent, and heating and stirring under a nitrogen atmosphere to prepare a primary mixture. The dissolution time is 5 min.

[0039] Step 3: The insoluble matter and liquid in the primary mixture from Step 2 are separated by centrifugation. The separated liquid is transferred to a tubular reactor, diluted, and a catalyst is added to prepare a reaction solution. The diluent is 15% distilled water, the catalyst is 35 mol% CrCl3, and the reaction temperature is 130℃. After the reaction is completed, distilled water is added to the reaction solution to dilute it to 30 ml. The unconverted cotton fibers and supernatant are separated by centrifugation. The supernatant is injected into the extraction tank to transfer a large amount of product to the organic phase. The extraction temperature is less than 50℃, and the volume ratio of extractant to solvent is 5:1. The extracted mixture is passed through a decanter to achieve efficient water-oil separation. The separated aqueous phase is passed through a purification unit, neutralized with an appropriate amount of alkali, and a small amount of levulinic acid and formic acid produced by the side reaction are precipitated. The precipitate and humic acid are then removed by filtration and adsorption, and recycled with fresh raw materials. The separated organic phase is subjected to multi-stage vacuum distillation to recover part of the extractant to obtain 5-hydroxymethylfurfural.

[0040] Example 4: (Catalyst: SnCl4)

[0041] A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers includes the following steps:

[0042] Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material; after washing and bleaching, the waste blended cotton fiber polyester (cotton fiber to PET mass ratio of 35:65) is crushed into pieces with a size of 4-20cm. 2 Pre-treated materials;

[0043] Step 2: React the pretreated material from Step 1 with the mixed solvent to prepare a primary mixture. The reaction conditions include: mixing 4.58 mL of methyl sulfoxide with 2.5 g of tetraethylammonium chloride (the mass ratio of tetramethyl sulfoxide to tetraethylammonium chloride is 2:1), stirring at 90 °C until completely dissolved to prepare a mixed solvent, adding the pretreated material to the mixed solvent, and heating and stirring under a nitrogen atmosphere to prepare a primary mixture. The dissolution time is 5 min.

[0044] Step 3: The insoluble matter and liquid in the primary mixture from Step 2 are separated by centrifugation. The separated liquid is transferred to a tubular reactor, diluted, and a catalyst is added to prepare a reaction solution. The diluent is 15% distilled water, and the catalyst is 35 mol% SnCl4. The reaction temperature is 130℃. After the reaction is complete, distilled water is added to the reaction solution to dilute it to 30 ml. Unconverted cotton fibers and supernatant are separated by centrifugation. The supernatant is injected into an extraction tank to transfer a large amount of product to the organic phase. The extraction temperature is less than 50℃, and the volume ratio of extractant to solvent is 5:1. The extracted mixture is passed through a decanter to achieve efficient water-oil separation. The separated aqueous phase is processed by a purification unit, where a suitable amount of alkali is used to neutralize and precipitate the small amount of levulinic acid and formic acid produced by the side reaction. The precipitate and humic acid are then removed by filtration and adsorption, and the product is recycled with fresh raw materials. The separated organic phase is processed by multi-stage vacuum distillation to recover part of the extractant and obtain 5-hydroxymethylfurfural (HMF). The HMF yield is 28.35%, and the cotton fiber conversion rate is 59.5%.

[0045] Example 5: (Catalyst: CuCl2)

[0046] A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers includes the following steps:

[0047] Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material; after washing and bleaching, the waste blended cotton fiber polyester (cotton fiber to PET mass ratio of 35:65) is crushed into pieces with a size of 4-20cm. 2 Pre-treated materials;

[0048] Step 2: React the pretreated material from Step 1 with the mixed solvent to prepare a primary mixture. The reaction conditions include: mixing 4.58 mL of methyl sulfoxide with 2.5 g of tetraethylammonium chloride (the mass ratio of tetramethyl sulfoxide to tetraethylammonium chloride is 2:1), stirring at 90 °C until completely dissolved to prepare a mixed solvent, adding the pretreated material to the mixed solvent, and heating and stirring under a nitrogen atmosphere to prepare a primary mixture. The dissolution time is 5 min.

[0049] Step 3: The insoluble matter and liquid in the primary mixture from Step 2 are separated by centrifugation. The separated liquid is transferred to a tubular reactor, diluted, and a catalyst is added to prepare a reaction solution. The diluent is 15% distilled water, and the catalyst is 35 mol% CuCl2. The reaction temperature is 130℃. After the reaction is complete, distilled water is added to the reaction solution to dilute it to 30 ml. Unconverted cotton fibers and supernatant are separated by centrifugation. The supernatant is injected into an extraction tank to transfer a large amount of product to the organic phase. The extraction temperature is less than 50℃, and the volume ratio of extractant to solvent is 5:1. The extracted mixture is passed through a decanter to achieve efficient water-oil separation. The separated aqueous phase is processed by a purification unit, where a suitable amount of alkali is used to neutralize and precipitate the small amount of levulinic acid and formic acid produced by the side reaction. The precipitate and humic acid are then removed by filtration and adsorption, and the product is recycled with fresh raw materials. The separated organic phase is subjected to multi-stage vacuum distillation to recover part of the extractant and obtain 5-hydroxymethylfurfural (HMF). The HMF yield is 22.19%, and the cotton fiber conversion rate is 76.42%.

[0050] Example 6: (Diluent content is 5%)

[0051] A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers includes the following steps:

[0052] Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material; after washing and bleaching, the waste blended cotton fiber polyester (cotton fiber to PET mass ratio of 35:65) is crushed into pieces with a size of 4-20cm. 2 Pre-treated materials;

[0053] Step 2: React the pretreated material from Step 1 with the mixed solvent to prepare a primary mixture. The reaction conditions include: mixing 4.58 mL of methyl sulfoxide with 2.5 g of tetraethylammonium chloride (the mass ratio of tetramethyl sulfoxide to tetraethylammonium chloride is 2:1), stirring at 90 °C until completely dissolved to prepare a mixed solvent, adding the pretreated material to the mixed solvent, and heating and stirring under a nitrogen atmosphere to prepare a primary mixture. The dissolution time is 5 min.

[0054] Step 3: The insoluble matter and liquid in the primary mixture from Step 2 are separated by centrifugation. The separated liquid is transferred to a tubular reactor, diluted, and a catalyst is added to prepare a reaction solution. The diluent is 5% distilled water, the catalyst is 35 mol% AlCl3, and the reaction temperature is 130℃. After the reaction is completed, distilled water is added to the reaction solution to dilute it to 30 ml. The unconverted cotton fibers and supernatant are separated by centrifugation. The supernatant is injected into the extraction tank to transfer a large amount of product to the organic phase. The extraction temperature is less than 50℃, and the volume ratio of extractant to solvent is 5:1. The extracted mixture is passed through a decanter to achieve efficient water-oil separation. The separated aqueous phase is passed through a purification unit, neutralized with an appropriate amount of alkali, and a small amount of levulinic acid and formic acid produced by the side reaction are precipitated. The precipitate and humic acid are then removed by filtration and adsorption, and recycled with fresh raw materials. The separated organic phase is subjected to multi-stage vacuum distillation to recover part of the extractant to obtain 5-hydroxymethylfurfural.

[0055] Example 7: (Diluent content is 25%)

[0056] A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers includes the following steps:

[0057] Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material; after washing and bleaching, the waste blended cotton fiber polyester (cotton fiber to PET mass ratio of 35:65) is crushed into pieces with a size of 4-20cm. 2 Pre-treated materials;

[0058] Step 2: React the pretreated material from Step 1 with the mixed solvent to prepare a primary mixture. The reaction conditions include: mixing 4.58 mL of methyl sulfoxide with 2.5 g of tetraethylammonium chloride (the mass ratio of tetramethyl sulfoxide to tetraethylammonium chloride is 2:1), stirring at 90 °C until completely dissolved to prepare a mixed solvent, adding the pretreated material to the mixed solvent, and heating and stirring under a nitrogen atmosphere to prepare a primary mixture. The dissolution time is 5 min.

[0059] Step 3: The insoluble matter and liquid in the primary mixture from Step 2 are separated by centrifugation. The separated liquid is transferred to a tubular reactor, diluted, and a catalyst is added to prepare a reaction solution. The diluent is 15% distilled water, the catalyst is 35 mol% AlCl3, and the reaction temperature is 130℃. After the reaction is completed, distilled water is added to the reaction solution to dilute it to 30 ml. The unconverted cotton fibers and supernatant are separated by centrifugation. The supernatant is injected into the extraction tank to transfer a large amount of product to the organic phase. The extraction temperature is less than 50℃, and the volume ratio of extractant to solvent is 5:1. The extracted mixture is passed through a decanter to achieve efficient water-oil separation. The separated aqueous phase is passed through a purification unit, neutralized with an appropriate amount of alkali, and a small amount of levulinic acid and formic acid produced by the side reaction are precipitated. The precipitate and humic acid are then removed by filtration and adsorption, and recycled with fresh raw materials. The separated organic phase is subjected to multi-stage vacuum distillation to recover part of the extractant to obtain 5-hydroxymethylfurfural.

[0060] Comparative Example 1: (Too high a proportion of mixed solvent)

[0061] Compared with Example 1, the mass ratio of dimethyl sulfoxide to tetraethylammonium chloride in the mixed solvent of Comparative Example 1 was 5:1, and all other conditions were the same as in Example 1.

[0062] Comparative Example 2: (The proportion of mixed solvents is too low)

[0063] Compared with Example 1, the mass ratio of dimethyl sulfoxide to tetraethylammonium chloride in the mixed solvent of Comparative Example 1 was 1:1, and all other conditions were the same as in Example 1.

[0064] Example of detection:

[0065] The yield of 5-hydroxymethylfurfural and the yield of cellulose obtained in Examples 1-7 and Comparative Examples 1-2 were tested. The yield of 5-hydroxymethylfurfural was determined by high performance liquid chromatography (HPLC) to measure the mass fraction of 5-hydroxymethylfurfural in the reaction solution and calculate the total yield Y of 5-hydroxymethylfurfural. The formula for calculating the yield Y of 5-hydroxymethylfurfural is as follows: Y = [(m H *M c ) / (m F *ω c *M H As shown in the formula: m*100%. H For the mass of 5-hydroxymethylfurfural, m F For the quality of the feed blending, ω c M represents the mass fraction of cotton fiber in the raw material, where Mc is the relative molecular mass of the cotton fiber. H The relative molecular mass of 5-hydroxymethylfurfural;

[0066] Test method for cotton fiber conversion rate: The conversion rate of cotton fiber is the ratio of the mass of unconverted cotton fiber to the cotton fiber content in the mixed solvent;

[0067] The cotton fiber content in the solutions of Examples 1, 2, Comparative Example 1 and Comparative Example 2 was detected, and the cotton fiber dissolution rate under different mixed solvent mass ratios was calculated.

[0068] The yield of 5-hydroxymethylfurfural, the conversion rate of cotton fibers, and the solubility of cotton fibers are shown in Table 1.

[0069] Table 1. Yield of 5-hydroxymethylfurfural and conversion rate of cotton fiber

[0070] 5-Hydroxymethylfurfural yield (%) Cotton fiber conversion rate (%) Cotton fiber solubility (%) Example 1 48.71 97.3 100 Example 2 33.78 91.0 85 Example 3 39.66 86.2 100 Example 4 28.35 59.5 100 Example 5 22.19 76.42 100 Example 6 46.32 93.7 100 Example 7 36.82 87.4 100 Comparative Example 1 - - 0 Comparative Example 2 43.15 90.5 100

[0071] As shown in Table 1, the method provided in this application can selectively and efficiently separate cotton fibers from waste blended cotton polyester and convert the cotton fibers into 5-hydroxymethylfurfural (HMF). The yield of HMF can reach up to 48.71%, and the conversion rate of cotton fibers can reach up to 97.3%. Furthermore, the results of Examples 1, 2, Comparative Example 1, and 2 show that the mass ratio of dimethyl sulfoxide (DMSO) to tetraethylammonium chloride (TEC) in the mixed solvent significantly increases the solubility of cotton fibers. When the mass ratio of DMSO to TEC in the mixed solvent in Example 1 is 2:1, the solubility of cotton fibers can reach 100%. When the mass ratio of DMSO to TEC in the mixed solvent in Comparative Example 2 is 1:1, the cotton fibers can be completely dissolved, but the solution viscosity is too high, which is not conducive to the subsequent efficient conversion of cotton fibers into HMF. When the mass ratio of dimethyl sulfoxide to tetraethylammonium chloride in the mixed solvent in Example 2 is 4:1, the solubility of cotton fibers is only 1%. When the mass ratio of dimethyl sulfoxide to tetraethylammonium chloride in the mixed solvent in Comparative Example 1 is 5:1, the cotton fibers do not dissolve at all. In this application, the cotton fibers can only be completely dissolved when the mass ratio of the mixed solvent reaches 2:1.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing 5-hydroxymethylfurfural from waste blended cotton fibers, characterized in that, Includes the following steps: Step 1: Pre-treat waste blended cotton fiber polyester to make pre-treated material; Step 2: React the pretreated material from Step 1 with a mixed solvent to prepare a primary mixture, wherein the mixed solvent is dimethyl sulfoxide and tetraethylammonium chloride, and the mass ratio of dimethyl sulfoxide to tetraethylammonium chloride is 2:1; Step 3: Separate the insoluble matter and liquid from the primary mixture in Step 2, and add the catalyst to the separated liquid to react and obtain 5-hydroxymethylfurfural. The catalyst is one of AlCl3 and CrCl3.

2. The preparation method according to claim 1, characterized in that, The reaction conditions described in step 2 include: nitrogen atmosphere, heating and stirring to dissolve, the heating and stirring temperature being 80~90℃, and the heating and stirring time being 5~10 min.

3. The preparation method according to claim 2, characterized in that, The temperature for heating and stirring to dissolve was 90℃, and the heating and stirring time was 5 min.

4. The preparation method according to claim 1, characterized in that, The reaction steps described in step 3 include: adding the catalyst to the separated liquid, heating and stirring to prepare a reaction solution, cooling and diluting the reaction solution and separating it to obtain unconverted cotton fibers and crude product, and extracting, removing impurities and purifying the crude product to obtain 5-hydroxymethylfurfural.

5. The preparation method according to claim 4, characterized in that, The dilution conditions are as follows: the diluent is distilled water, and the amount of diluent used is 5-25%.

6. The preparation method according to claim 1, characterized in that, The amount of catalyst used is 5~50 mol%.

7. The preparation method according to claim 1, characterized in that, The pretreatment conditions described in step 1 include: washing, bleaching, and pulverizing waste blended cotton fibers into polyester to prepare a pretreated material with a length of 4-20 cm. 2 .

8. The preparation method according to claim 1, characterized in that, The cotton content of the waste blended cotton fiber polyester mentioned in step 1 is 10-65%.