Preparation and photocatalytic application of lignosulfonic acid-based solid catalyst
In the selective oxidation reaction of 5-hydroxymethylfurfural, the use of lignin sulfonic acid-based solid catalyst and alizarin red S-sensitized metal oxides in synergistic photocatalysis was solved, and a green and efficient catalytic effect was achieved.
Patent Information
- Application Number
- CN202311139674.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-05
- Publication Date
- 2025-03-07
AI Technical Summary
The prior art has disadvantages such as high reaction temperature and pressure, difficulty in separating and recycling of products, and serious reaction contamination in the preparation of 2,5-diformylfuran (DFF) in selective oxidation of 5-hydroxymethylfurfural (HMF).
Sodium lignin sulfonate was used as a support and combined with imidazole ionic liquid through electrostatic action to prepare a lignin sulfonate-based solid catalyst, and it was used in the photocatalytic reaction in concert with the metal oxide sensitized by Alizarin Red S.
It is possible to efficiently oxidize 5-hydroxymethylfurfural to 2,5-diformylfuran under mild photocatalytic conditions, and the catalyst is easy to prepare, recycle and environmentally friendly.
Smart Images
Figure FT_1 
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] The invention belongs to the preparation of solid catalysts, relates to the technical field of preparation of heterogeneous catalysts, and specifically relates to the preparation of a lignin sulfonic acid-based solid catalyst and its photocatalytic application in co-catalyzing the selective oxidation of 5-hydroxymethylfurfural to prepare 2,5-diformylfuran with a sensitized metal oxide. Background Art
[0002] Since the Industrial Revolution, the over-exploitation of traditional fossil energy has not only caused an energy shortage crisis but also caused serious environmental problems. This urgently requires us to seek a renewable alternative energy source. Biomass, as a renewable energy source with abundant total amount, low pollution, low cost and wide application, is an excellent substitute for traditional fossil energy. The development and utilization of renewable biomass resources is an inevitable requirement for the sustainable development of mankind.
[0003] 5-Hydroxymethylfurfural (HMF) is a biomass-based platform compound that can be directly obtained from the dehydration of glucose or fructose. Its unique structure makes it highly chemically active and can be used to catalyze and transform various derivatives through oxidation, hydrogenation, condensation, amination and other reactions. It is the starting substrate for many chemicals. At present, 2,5-diformylfuran (DFF) is mainly produced by the selective oxidation of 5-hydroxymethylfurfural (HMF). However, the presence of active groups in the structure of 5-hydroxymethylfurfural (HMF) can easily produce side reactions. Therefore, it is of great significance to develop a catalyst that can improve the conversion rate and selectivity of 5-hydroxymethylfurfural (HMF).
[0004] At present, in the commonly used method of preparing 2,5-diformylfuran from 5-hydroxymethylfurfural in one pot, although the catalyst has high catalytic activity and thermal stability, it has disadvantages such as high reaction temperature and pressure, difficulty in separating and recovering the product, and serious reaction pollution.
[0005] Based on this problem, the present invention uses sodium lignin sulfonate as a carrier, utilizes a large number of sulfonate groups in its structure to adsorb and fix cationic catalysts, and prepares a lignin sulfonic acid-based solid catalyst, wherein the catalyst carrier sodium lignin sulfonate has the advantages of cheap raw materials, easy availability, and green environmental protection. At the same time, the metal oxide catalyst sensitized by Alizarin Red S can improve the performance of metal absorbance to visible light, and the catalyst is synergistically involved in the photocatalysis of 5-hydroxymethylfurfural (HMF). Compared with the traditional preparation method, the photocatalytic reaction conditions are milder and green and efficient. Summary of the invention
[0006] Purpose of the invention: The present invention provides a method for preparing a low-cost, simple, easy-to-prepare, green and efficient solid catalyst; the catalyst and a sensitized metal oxide can catalyze and oxidize 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) in a green and efficient manner.
[0007] In view of the first problem, the present invention prepares a heterogeneous solid catalyst. To this end, the present invention provides the following technical solution:
[0008] The preparation method of lignin sulfonic acid solid catalyst is characterized by: firstly brominating 4-hydroxy-2,2,6,6-tetramethylpiperidinyl oxide (4-OH-TEMPO) with 1,6-dibromoethane, then reacting it with imidazole to obtain imidazole ionic liquid, and then reacting the ionic liquid with sodium lignin sulfonate through electrostatic action to obtain lignin sulfonic acid solid catalyst IS-DTEMPO@LS;
[0009] As a preferred embodiment of the method for preparing the lignin sulfonic acid-based solid catalyst of the present invention, the method comprises:
[0010] Preparation of BrC6-O-TEMPO: 4-OH-TEMPO is dissolved in tetrahydrofuran, and added dropwise to an alkaline mixture of 1,6-dibromohexane and tetrabutylammonium hydrogen sulfate, and stirred for reaction, extracted, washed, dried, and purified to obtain the BrC6-O-TEMPO as a red oily liquid;
[0011] Preparation of imidazolium ionic liquid: Sodium hydride powder with a purity of 60% is added to tetrahydrofuran to form a suspension, and the mixture is stirred in an ice bath until the mixture is cooled, and the tetrahydrofuran solution of imidazole is dripped into the ice bath liquid, and the ice bath liquid is taken out and stirred at room temperature for 2 hours, and under a nitrogen flow, a red oily liquid BrC6-O-TEMPO is dripped and heated to reflux the solvent, and after reflux reaction, it is filtered, washed with tetrahydrofuran, dichloromethane, and ethanol in sequence, and rotary evaporated to obtain a red viscous oil, namely the imidazolium ionic liquid IS-DTEMPO;
[0012] Preparation of TEMPO-loaded lignin sulfonic acid-based material: Dissolve the imidazolium ionic liquid IS-DTEMPO in water, add dropwise into the sodium lignin sulfonate aqueous solution, centrifuge, filter, wash, and dry to obtain the lignin sulfonic acid-based solid catalyst IS-DTEMPO@LS.
[0013] As a preferred embodiment of the preparation method of the sodium lignin sulfonate-based solid catalyst of the present invention, the preparation of the BrC6-O-TEMPO comprises the following steps: dissolving 5-15 mmol 4-OH-TEMPO in 10-20 mL tetrahydrofuran, adding dropwise 20-30 mmol 1,6-dibromohexane, 2-5 mol% tetrabutylammonium hydrogen sulfate and 5-15 mL 50 wt% sodium hydroxide solution into a mixture, stirring for 12-15 h, cooling with ice water, extracting with ethyl acetate, washing with saturated sodium chloride solution, drying with anhydrous sodium sulfate, performing rotary evaporation under reduced pressure, and then purifying with a chromatography column using petroleum ether: ethyl acetate = 8:1 as the eluent, and performing rotary evaporation to obtain a red oily liquid, namely the BrC6-O-TEMPO.
[0014] As a preferred embodiment of the preparation method of the lignin sulfonic acid-based solid catalyst described in the present invention, the preparation of the imidazolium ionic liquid comprises the following steps: taking 10 to 15 mmol of sodium hydride powder with a purity of 60% and adding it to 10 to 20 mL of tetrahydrofuran to form a suspension, placing it in an ice bath and stirring until the mixture is cooled, dropping a mixed solution of 10 to 15 mmol of imidazole and 10 to 20 mL of tetrahydrofuran into the ice bath liquid, taking out the ice bath liquid and placing it at room temperature and stirring for 2 hours, and under a nitrogen flow, dropping a red oily liquid BrC6-O-TEMPO and heating it to solvent reflux, reflux reaction for 5 to 12 hours, filtering, washing with tetrahydrofuran, dichloromethane, and ethanol in sequence, and rotary evaporating to obtain a red viscous oil, namely the imidazolium ionic liquid IS-DTEMPO.
[0015] As a preferred embodiment of the preparation method of the lignin sulfonic acid solid catalyst described in the present invention, the preparation of the TEMPO-loaded lignin sulfonic acid material includes dissolving the imidazolium ionic liquid IS-DTEMPO in 8 to 12 mL of water, adding dropwise into a sodium lignin sulfonate solution dissolved in 80 to 120 mL of water, centrifuging to obtain a waxy solid, washing with a large amount of ethanol, and vacuum drying at 60° C. for 12 to 24 hours to obtain a brown solid, namely, the lignin sulfonic acid solid catalyst IS-DTEMPO@LS.
[0016] The lignin sulfonic acid solid catalyst prepared by the preparation method, wherein: the lignin sulfonic acid solid catalyst IS-DTEMPO@LS has the structural formula:
[0017]
[0018] In addition, the present invention further provides the application of lignin sulfonic acid-based solid catalyst and sensitized metal oxide in synergistic photocatalysis.
[0019] To this end, the present invention provides the following technical solution: the application of the lignin sulfonic acid solid catalyst and the sensitized metal oxide in synergistic photocatalysis, wherein: the lignin sulfonic acid catalyst and the sensitized metal catalyst jointly photocatalyze the selective oxidation of 5-hydroxymethylfurfural to synthesize 2,5-diformylfuran.
[0020] Among them, the preparation method of the sensitized metal oxide catalyst includes: taking 0.3-0.5 mmol of Alizarin Red S in 10-20 mL of anhydrous ethanol and ultrasonicating for 10-30 minutes to make it evenly dispersed, then taking 1-3 g of metal oxides Cu2O, TiO2, MnO2, MoO3 and placing them in the anhydrous ethanol solution of Alizarin Red S and ultrasonicating for 10-30 minutes to make Alizarin Red S fully contact with the metal oxides Cu2O, TiO2, MnO2, MoO3, and then stirring the mixed solution at room temperature overnight, centrifuging the obtained mixed solution and vacuum drying it for 24 hours to obtain a solid, namely the Alizarin Red S sensitized metal oxide photocatalyst ARS-Cu2O, ARS-TiO2, ARS-MnO2, ARS-MoO3.
[0021] As a preferred application scheme of the catalyst described in the present invention: the application includes weighing 0.2-0.5 mmol of 5-hydroxymethylfurfural, 10-30 mg of lignin sulfonic acid catalyst, 10-15 mg of sensitized metal oxide, and 2-5 mL of solvent into a 15 mL pressure tube, irradiating with an LED lamp for 8-10 hours under normal pressure and oxygen conditions, and after the reaction is completed, removing the catalyst and the solvent to obtain the product 2,5-diformylfuran.
[0022] The invention has the beneficial effects as follows: the invention prepares a lignin sulfonic acid-based solid catalyst, the catalyst carrier raw material source is wide, and it is green and environmentally friendly, and the lignin sulfonic acid-based solid catalyst can be recycled and still maintains high catalytic activity and selectivity during the recycling process. Based on the advantage that the Alizarin Red S-sensitized metal oxide catalyst can improve the visible light absorbance of the metal oxide, the lignin sulfonic acid-based solid catalyst and the Alizarin Red S-sensitized metal oxide catalyst are used as a combined catalyst for photocatalytic preparation of 2,5-diformylfuran. This is a heterogeneous solid catalyst with strong catalytic activity, easy preparation, and green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. The drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:
[0024] Figure 1 It is the reaction formula of the preparation method of the present invention. DETAILED DESCRIPTION
[0025] In order to make the above-mentioned purposes and features of the present invention clear and easy to understand, the specific implementation method of the present invention is described in detail below in conjunction with the embodiments of the specification. The examples given are used to understand the technical scheme and are not limited to the specific embodiments disclosed below. Therefore, those skilled in the art can make similar generalizations without violating the connotation of the present invention.
[0026] The specific steps of the preparation method of the lignin sulfonic acid catalyst are:
[0027] (1) 5-15 mmol 4-OH-TEMPO was dissolved in 10-20 mL tetrahydrofuran, and then added dropwise to a mixture of 20-30 mmol 1,6-dibromohexane, 2-5 mol% tetrabutylammonium hydrogen sulfate and 5-15 mL 50 wt% sodium hydroxide solution, and stirred for 12-15 h. After cooling with ice water, the mixture was extracted with ethyl acetate, washed with saturated sodium chloride solution, dried over anhydrous sodium sulfate, and evaporated under reduced pressure. The mixture was then purified by chromatography using petroleum ether: ethyl acetate = 8:1 as the eluent, and evaporated under reduced pressure to obtain a red oily liquid, namely, the BrC6-O-TEMPO.
[0028] (2) 10-15 mmol of 60% pure sodium hydride powder was added to 10-20 mL of tetrahydrofuran to form a suspension, and the mixture was placed in an ice bath and stirred until the mixture was cooled. A mixed solution of 10-15 mmol of imidazole and 10-20 mL of tetrahydrofuran was dripped into the ice bath liquid. The ice bath liquid was taken out and stirred at room temperature for 2 hours. Under a nitrogen flow, a red oily liquid BrC6-O-TEMPO was added dropwise and heated to reflux the solvent. After reflux reaction for 5-12 hours, the mixture was filtered, washed with tetrahydrofuran, dichloromethane, and ethanol in turn, and rotary evaporated to obtain a red viscous oil, namely the imidazole ionic liquid IS-DTEMPO.
[0029] (3) The imidazolium ionic liquid IS-DTEMPO was dissolved in 8-12 mL of water, and the solution was added dropwise into a sodium lignin sulfonate solution dissolved in 80-120 mL of water. The waxy solid was obtained by centrifugation, filtered, washed with a large amount of ethanol, and dried under vacuum at 60° C. for 12-24 h to obtain a brown solid lignin sulfonic acid catalyst IS-DTEMPO@LS.
[0030] One application mode of the catalyst of the present invention is as follows:
[0031] Weigh 0.2-0.5 mmol of 5-hydroxymethylfurfural, 10-30 mg of lignin sulfonic acid catalyst, 10-15 mg of sensitized metal oxide, and 2-5 mL of solvent into a 15 mL pressure tube. Irradiate with an LED lamp for 8-10 hours under normal pressure and oxygen conditions. After the reaction is completed, remove the catalyst and the solvent to obtain the product 2,5-diformylfuran.
[0032] Embodiment 1:
[0033] Preparation of lignin sulfonic acid-based solid catalyst IS-DTEMPO@LS:
[0034] Preparation of BrC6-O-TEMPO: 10 mmol of 4-OH-TEMPO was dissolved in 10 mL of tetrahydrofuran, and then added dropwise to a mixture of 30 mmol of 1,6-dibromohexane, 4 mol% of tetrabutylammonium hydrogen sulfate and 10 mL of a 50 wt% sodium hydroxide solution, and stirred for 12 h. After cooling with ice water, the mixture was extracted with ethyl acetate, washed with a saturated sodium chloride solution, dried over anhydrous sodium sulfate, and evaporated under reduced pressure. The mixture was then purified by chromatography using petroleum ether: ethyl acetate = 8:1 as the eluent, and evaporated to obtain a red oily liquid, namely the BrC6-O-TEMPO.
[0035] Preparation of imidazolium ionic liquid: 10 mmol of 60% pure sodium hydride powder is added to 10 mL of tetrahydrofuran to form a suspension, and the mixture is placed in an ice bath and stirred until the mixture is cooled. A mixed solution of 10 mmol of imidazole and 10 mL of tetrahydrofuran is dripped into the ice bath liquid, and the ice bath liquid is taken out and stirred at room temperature for 2 h. Under a nitrogen flow, a red oily liquid BrC6-O-TEMPO is added dropwise, heated to solvent reflux for 7 h, and then filtered. The mixture is washed with tetrahydrofuran, dichloromethane, and ethanol in sequence, and rotary evaporated to obtain a red viscous oil, namely the imidazolium ionic liquid IS-DTEMPO.
[0036] Preparation of TEMPO-loaded lignin sulfonate-based materials: Dissolve the imidazolium ionic liquid IS-DTEMPO in 10 mL of water and add it dropwise into 100 mL of sodium lignin sulfonate aqueous solution. After standing for a period of time, centrifuge to obtain a waxy solid, filter, wash with a large amount of ethanol, and vacuum dry at 60°C for 15 h to obtain a brown solid, namely the lignin sulfonate-based solid catalyst IS-DTEMPO@LS.
[0037] The solid is a lignin sulfonic acid-based catalyst IS-DTEMPO@LS, and its structural formula is:
[0038]
[0039] Embodiment 2:
[0040] Preparation of sensitized metal oxide catalysts:
[0041] Preparation of ARS-Cu2O: 0.3 mmol of Alizarin Red S was added to 20 mL of anhydrous ethanol, and ultrasonicated for 20 min to make it evenly dispersed. 2.5 g of Cu2O was placed in the anhydrous ethanol solution of Alizarin Red S, and ultrasonicated for 20 min to make Alizarin Red S and Cu2O fully contact. The mixed solution was then stirred at room temperature overnight. The obtained mixed solution was centrifuged and vacuum dried for 24 h to obtain a solid, namely the ARS-Cu2O.
[0042] Preparation of ARS-TiO2: Add 0.3 mmol of Alizarin Red S to 20 mL of anhydrous ethanol, and ultrasonicate for 20 min to make it evenly dispersed. Take 1.4 g of TiO2 and put it into the anhydrous ethanol solution of Alizarin Red S. Continue ultrasonicating for 20 min to make Alizarin Red S and TiO2 fully contact. Then stir the mixed solution at room temperature overnight. The obtained mixed solution can be centrifuged and vacuum dried for 24 h to obtain a solid, namely the ARS-TiO2.
[0043] Preparation of ARS-MnO2: Add 0.3 mmol of Alizarin Red S to 20 mL of anhydrous ethanol, and ultrasonicate for 20 min to make it evenly dispersed. Take 1.5 g of MnO2 and put it into the anhydrous ethanol solution of Alizarin Red S. Continue ultrasonicating for 20 min to make Alizarin Red S and MnO2 fully contact. Then stir the mixed solution at room temperature overnight. The obtained mixed solution can be centrifuged and vacuum dried for 24 h to obtain a solid, namely the ARS-MnO2.
[0044] Preparation of ARS-MoO3: Add 0.3 mmol of Alizarin Red S to 20 mL of anhydrous ethanol, and perform ultrasonic treatment for 20 min to make it evenly dispersed. Take 2.5 g of MoO3 and place it in the anhydrous ethanol solution of Alizarin Red S. Continue ultrasonic treatment for 20 min to make Alizarin Red S and MoO3 fully contact. Then stir the mixed solution at room temperature overnight. Centrifuge the obtained mixed solution and vacuum dry it for 24 h to obtain a solid, namely the ARS-MoO3.
[0045] Embodiment 3:
[0046] Application of sodium lignin sulfonate solid catalyst and sensitized metal oxide synergistic photocatalytic preparation of 2,5-diformylfuran:
[0047] 30 mg of IS-DTEMPO@LS solid catalyst, 10 mg of sensitized metal oxide ARS-Cu2O, 0.2 mmol of 5-hydroxymethylfurfural, and 2 mL of solvent were weighed and added to a 15 mL pressure tube, irradiated with a 380-435 nm LED light for 10 h, and reacted under normal pressure oxygen conditions. After the reaction was completed, the product was cooled to room temperature and analyzed by high performance liquid chromatography to obtain the product 2,5-diformylfuran, and the conversion rate of HMF and the selectivity of DFF were calculated. The types of solvents added are shown in Table 1.
[0048] Table 1 Effect of adding different solvents on the conversion of HMF and the selectivity of DFF
[0049]
[0050] Embodiment 4:
[0051] Application of sodium lignin sulfonate solid catalyst and sensitized metal oxide synergistic photocatalytic preparation of 2,5-diformylfuran:
[0052] 30 mg of IS-DTEMPO@LS solid catalyst, 10 mg of sensitized metal oxide ARS-Cu2O, 0.2 mmol of 5-hydroxymethylfurfural, and 2 mL of acetonitrile were weighed and added to a 15 mL pressure tube, irradiated with LED light for 10 h, and reacted under normal pressure oxygen conditions. After the reaction was completed, the product was cooled to room temperature and analyzed by high performance liquid chromatography to obtain the product 2,5-diformylfuran, and the conversion rate of HMF and the selectivity of DFF were calculated. The LED wavelength range used is shown in Table 2.
[0053] Table 2 Effect of different wavelengths on HMF conversion and DFF selectivity
[0054]
[0055]
[0056] Embodiment 5:
[0057] Application of sodium lignin sulfonate solid catalyst and sensitized metal oxide synergistic photocatalytic preparation of 2,5-diformylfuran:
[0058] 30 mg of IS-DTEMPO@LS solid catalyst, 10 mg of sensitized metal oxide, 0.2 mmol of 5-hydroxymethylfurfural, and 2 mL of acetonitrile were weighed and added to a 15 mL pressure tube, irradiated with a 380-435 nm LED light for 10 h, and reacted under normal pressure oxygen conditions. After the reaction was completed, the product was cooled to room temperature and analyzed by high performance liquid chromatography to obtain the product 2,5-diformylfuran, and the conversion rate of HMF and the selectivity of DFF were calculated. The types of co-catalysts added are shown in Table 3.
[0059] Table 3 Effect of adding different co-catalysts on the conversion of HMF and the selectivity of DFF
[0060]
[0061] Embodiment 6:
[0062] Application of sodium lignin sulfonate solid catalyst and sensitized metal oxide synergistic photocatalytic preparation of 2,5-diformylfuran:
[0063] Weigh IS-DTEMPO@LS solid catalyst, 10 mg of sensitized metal oxide, 0.2 mmol of 5-hydroxymethylfurfural, and 2 mL of acetonitrile into a 15 mL pressure tube, irradiate with a 380-435 nm LED light for 10 h, and react under normal pressure oxygen conditions. After the reaction is completed, the product is cooled to room temperature and analyzed by high performance liquid chromatography to obtain the product 2,5-diformylfuran, and the conversion rate of HMF and the selectivity of DFF are calculated. The types of co-catalysts added are shown in Table 4.
[0064] Table 4 Effect of the amount of lignin sulfonic acid solid catalyst on the conversion rate of HMF and the selectivity of DFF
[0065]
[0066] It should be clear that the preparation method and application described in the above embodiments are only technical solutions of the present invention and are not limitations. Any modifications, equivalent substitutions, improvements, etc. made without departing from the principle of the technical solution of the present invention should be included in the protection scope of the present invention.
Claims
1. A preparation of a lignin sulfonic acid solid catalyst and its photocatalytic application in the selective oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran in cooperation with a sensitized metal oxide, characterized in that: include, The preparation method of the lignin sulfonic acid solid catalyst is as follows: firstly brominating 4-hydroxy-2,2,6,6-tetramethylpiperidinyl oxide (4-OH-TEMPO) with 1,6-dibromoethane, then reacting the bromination with imidazole to obtain an imidazole ionic liquid, and then reacting the ionic liquid with sodium lignin sulfonate through electrostatic action to obtain a lignin sulfonic acid solid catalyst IS-DTEMPO@LS; The preparation method of the sensitized metal oxide catalyst is as follows: dissolving Alizarin Red S in anhydrous ethanol and ultrasonicating, then taking a solution of metal oxides Cu2O, TiO2, MnO2, MoO3 and ultrasonicating, and then stirring the mixture at room temperature, centrifuging, and drying to obtain sensitized metal oxides ARS-Cu2O, ARS-TiO2, ARS-MnO2, ARS-MoO3, etc.; The IS-DTEMPO@LS and sensitized metal oxides synergistically catalyze the selective oxidation of 5-hydroxymethylfurfural to prepare 2,5-diformylfuran using photocatalytic applications: 5-hydroxymethylfurfural, lignin sulfonic acid-based solid catalyst and sensitized metal oxide (ARS-Cu2O, ARS-TiO2, ARS-MnO2, ARS-MoO3, etc.) are placed in a solvent, and reacted under normal pressure oxygen conditions using LED light. After the reaction is completed, the catalyst is filtered out, and the filtrate is distilled under reduced pressure to remove the solvent to obtain the product 2,5-diformylfuran.
2. The method for preparing a lignin sulfonic acid-based solid catalyst according to claim 1, characterized in that: include, Preparation of BrC6-O-TEMPO: 4-OH-TEMPO is dissolved in tetrahydrofuran, and added dropwise to an alkaline mixture of 1,6-dibromohexane and tetrabutylammonium hydrogen sulfate, and stirred for reaction, extracted, washed, dried, and purified to obtain the BrC6-O-TEMPO as a red oily liquid; Preparation of imidazolium ionic liquid: Sodium hydride powder with a purity of 60% is added to tetrahydrofuran to form a suspension, and the suspension is placed in an ice bath and stirred until the solution is cooled. The tetrahydrofuran solution of imidazole is dripped into the ice bath solution, and the ice bath solution is taken out and stirred at room temperature for 2 hours. BrC6-O-TEMPO is dripped under nitrogen flow and heated to reflux the solvent. After reacting for a period of time, the suspension is filtered, and the suspension is washed with tetrahydrofuran, dichloromethane, and ethanol in turn, and rotary evaporated. The filtrate is rotary evaporated to obtain a red viscous oil, which is the imidazolium ionic liquid IS-DTEMPO; Preparation of TEMPO-loaded lignin sulfonic acid solid catalyst: dissolve the imidazolium ionic liquid IS-DTEMPO in water, add dropwise into a sodium lignin sulfonate aqueous solution, centrifuge, filter, wash, and dry to obtain the lignin sulfonic acid solid catalyst IS-DTEMPO@LS.
3. The method for preparing a lignin sulfonic acid-based solid catalyst as claimed in claim 2, characterized in that: The preparation of the BrC6-O-TEMPO comprises the following steps: dissolving 5-15 mmol 4-OH-TEMPO in 10-20 mL THF, adding dropwise into a mixture of 20-30 mmol 1,6-dibromohexane, 2-5 mol% tetrabutylammonium hydrogen sulfate and 5-15 mL 50 wt% sodium hydroxide solution, stirring for 12-15 hours, cooling in an ice-water bath, extracting with ethyl acetate, washing with saturated sodium chloride solution, drying with anhydrous sodium sulfate, and purifying by chromatography with petroleum ether: ethyl acetate = 8:1 as eluent after rotary evaporation, and rotary evaporation to obtain a red oily liquid, namely the BrC6-O-TEMPO.
4. The method for preparing the lignin sulfonic acid solid catalyst according to claim 2, characterized in that: The preparation of the imidazolium ionic liquid comprises the following steps: taking 10 to 15 mmol of sodium hydride powder with a purity of 60% and adding it to 10 to 20 mL of tetrahydrofuran to form a suspension, placing the suspension in an ice bath and stirring until the solution is cooled, and continuing to dropwise add 10 to 15 mmol of imidazole in an ice water bath, taking out the mixture from the ice bath and placing it at room temperature and stirring it for 2 hours, and under a nitrogen flow, dropwise adding a red oily liquid BrC6-O-TEMPO and heating it to solvent reflux, refluxing for 5 to 12 hours, filtering, washing with tetrahydrofuran, dichloromethane, and ethanol in sequence, and rotary evaporating to obtain a red viscous oil, namely the imidazolium ionic liquid IS-DTEMPO.
5. The method for preparing the lignin sulfonic acid solid catalyst according to claim 2, characterized in that: The preparation of the TEMPO-loaded lignin sulfonic acid-based material includes dissolving an imidazole ionic liquid in 8 to 12 mL of water, adding the solution dropwise to a sodium lignin sulfonate solution dissolved in 80 to 120 mL of water, centrifuging to obtain a waxy solid, filtering, washing with a large amount of ethanol, and vacuum drying at 60° C. for 12 to 24 hours to obtain a brown solid, namely, a lignin sulfonic acid-based solid catalyst IS-DTEMPO@LS.
6. The lignin sulfonic acid solid catalyst prepared as claimed in claims 1 to 6 is characterized in that: the structural formula of the lignin sulfonic acid solid catalyst IS-DTEMPO@LS is:
7. The use according to claim 1, characterized in that: The application comprises the steps of weighing 0.2-0.5 mmol of 5-hydroxymethylfurfural (HMF), 10-30 mg of lignin sulfonic acid-based solid catalyst (IS-DTEMPO@LS), 10-15 mg of sensitized metal oxide catalyst (ARS-Cu2O, ARS-TiO2, ARS-MnO2, ARS-MoO3), and 2-5 mL of solvent (acetonitrile, methanol, dichloromethane, deionized water), adding the mixture into a 15 mL pressure tube, and irradiating the mixture with an LFD lamp for 8-10 hours under normal pressure and oxygen conditions. After the reaction is completed, the catalyst and the solvent are removed to obtain the product 2,5-diformylfuran.