A photothermal green catalytic synthesis method for 5-hydroxymethylfurfural

Abstract

The present invention provides a 5-hydroxymethylfurfural (HMF) photothermal green synthesis method. Under the radiation of simulated sunlight, a carbon-based solid sulfonic acid is used as a catalyst, the reaction system is heated by photothermal heating, and fructose-based carbohydrates are selectively catalytically dehydrated to generate 5-hydroxymethylfurfural. The present invention uses a black carbon-based solid material containing a sulfonic acid group (-SO3H) active center as a photothermal conversion material and catalyst, and fructose-based carbohydrates are dehydrated by photothermal directional catalysis in a neutral aprotic organic solvent with a boiling point of ≥100°C to generate 5-hydroxymethylfurfural. The carbon-based solid photothermal catalytic material is combined with an organic solvent to construct a "photothermal catalytic material-organic solvent" photothermal green catalytic system, which can achieve selective conversion of fructose structures in carbohydrates, generate HMF with a yield of more than 90%, and the selectivity of HMF can reach ~95%.

Description

Technical Field

[0001] The invention belongs to the technical field of green catalytic synthesis of furan-based chemicals, and particularly relates to a photothermal green catalytic synthesis method of 5-hydroxymethylfurfural. Background Art

[0002] Renewable biomass-based 5-hydroxymethylfurfural (HMF) is a very important platform chemical. Its molecule contains unique active aldehyde (—CHO), hydroxymethyl (—CH2OH) and conjugated double bond (—C=C—C=C—) functional groups. It can be derived into numerous high-value-added chemicals through special chemical reactions (Formula 1). It has become an ideal alternative to petroleum-based chemicals and has great potential to replace traditional fossil energy.

[0003]

[0004] Fructose-based carbohydrates are important raw materials for the production of HMF. The conversion of these raw materials to HMF can be accomplished by heating the reaction system in the presence of an acid catalyst. Traditional heating methods include direct heating and microwave heating. Current heating methods are heavily dependent on fossil energy, necessitating the development of new, green heating methods for the catalytic synthesis of HMF.

[0005] Solar energy is the most fundamental energy source on Earth, with the vast majority of energy coming directly or indirectly from sunlight. Furthermore, solar energy boasts advantages such as wide distribution, environmental friendliness, and safety. It is a clean energy source with broad application prospects and can, to a certain extent, replace traditional fossil fuels.

[0006] Solar energy can be utilized primarily through photothermal conversion and photoelectric conversion. Photothermal conversion is the most traditional mode of utilization, one that has accompanied the history of human society. In recent years, with advancements in solar energy utilization technology and the rapid development of materials science, the clean and efficient conversion of solar energy into thermal energy and its utilization has once again become a hot topic in solar energy utilization research. In the field of photothermal conversion technology, black photothermal conversion materials have attracted widespread attention from scientific researchers due to their broad solar spectrum absorption characteristics, making them more capable of fully utilizing solar energy resources. Therefore, black materials (substances), as solar energy absorbers, can efficiently convert solar energy into thermal energy, making them the preferred choice for preparing photothermal conversion materials.

[0007] Therefore, the development of a new photothermal catalytic system that is green and environmentally friendly, has low dependence on fossil energy, high conversion efficiency, and mild reaction conditions has become an inevitable choice for the green catalytic synthesis of 5-hydroxymethylfurfural. Summary of the Invention

[0008] To address the above-mentioned shortcomings in the prior art, the present invention aims to provide a green photothermal catalytic synthesis method for 5-HMF. This method utilizes a black carbon-based solid material containing sulfonic acid groups (—SO₃H) as the photothermal conversion material and catalyst, combined with a neutral aprotic organic solvent with a boiling point ≥100°C, to construct a novel green catalytic reaction system for the selective conversion of fructose-based carbohydrates to 5-HMF.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a photothermal green catalytic synthesis method for 5-hydroxymethylfurfural, which uses carbon-based solid sulfonic acid as a catalyst under the radiation of simulated sunlight to heat the reaction system by photothermal heating, and selectively catalytically dehydrates fructose-based carbohydrates to generate 5-hydroxymethylfurfural.

[0010] Further, the method specifically includes the following steps:

[0011] (1) adding a certain amount of carbon-based solid sulfonic acid to an organic solvent to form a photothermal catalytic dehydration reaction system;

[0012] (2) adding a certain amount of fructose-based carbohydrates to the photothermal reaction system, stirring magnetically, and performing a photothermal catalytic dehydration reaction under the radiation of simulated sunlight;

[0013] The carbon-based solid sulfonic acid is a black carbon-based solid catalytic material containing a sulfonic acid group (—SO3H) active center;

[0014] The organic solvent is one or more neutral aprotic organic solvents.

[0015] Furthermore, the mass fraction of the carbon-based solid sulfonic acid relative to the raw material fructose-based carbohydrate is ≤15%.

[0016] Furthermore, the mass volume ratio of the raw material fructose-based carbohydrate to the organic solvent is (1-50) g:100 mL.

[0017] Furthermore, the fructosyl carbohydrate is a carbohydrate containing a fructose structural unit.

[0018] Furthermore, the carbohydrate is fructose, sucrose or inulin.

[0019] Furthermore, the boiling point of the neutral aprotic organic solvent is ≥100°C.

[0020] Furthermore, the neutral aprotic organic solvent is dimethyl sulfoxide or sulfolane.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention uses a black carbon-based solid material containing a sulfonic acid group (—SO3H) active center as a photothermal conversion material and catalyst to produce 5-hydroxymethylfurfural by photothermal directed catalytic dehydration of fructose-based carbohydrates in a neutral aprotic organic solvent with a boiling point ≥100°C. The carbon-based solid photothermal catalytic material is combined with an organic solvent to construct a "photothermal catalytic material-organic solvent" photothermal green catalytic system, which can achieve selective conversion of fructose structures in carbohydrates, produce HMF with a yield of over 90% and an HMF selectivity of ~95%.

[0023] 2. Compared with the existing preparation methods, the preparation method provided by the present invention has the advantages of low carbon, green, environmental protection, low dependence on fossil energy, mild reaction conditions, wide source of raw materials, easy recycling of catalysts, and high product selectivity, which can accelerate the green industrial production of 5-hydroxymethylfurfural.

[0024] 3. The photothermal green catalytic reaction system of the present invention mainly utilizes the black carbon-based component in the carbon-based solid sulfonic acid to have excellent photothermal conversion ability for sunlight, directly converting sunlight into heat for heating the reaction system. At the same time, the sulfonic acid group (-SO3H) in the carbon-based solid sulfonic acid has a strong catalytic dehydration ability. In the presence of sunlight, the heating and catalytic dehydration reactions of the catalytic reaction system can be carried out simultaneously, thereby accelerating the directional conversion of fructose-based raw materials to 5-hydroxymethylfurfural. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 These are digital camera photos of two carbon-based solid sulfonic acids (C1-SO3H and C2-SO3H);

[0026] Figure 2 The infrared spectra of two carbon-based solid sulfonic acids (C1-SO3H and C2-SO3H);

[0027] Figure 3 It is a photothermal catalytic reaction device;

[0028] Figure 4 This is the relationship between fructose concentration and chromatographic peak area obtained by liquid chromatography standard curve method;

[0029] Figure 5 This is the relationship between HMF concentration and chromatographic peak area obtained by liquid chromatography standard curve method;

[0030] Figure 6 Comparison of the photothermal catalytic effects of C1-SO3H and C2-SO3H (comparison of the results of Example 1 and Example 2, (a): reaction temperature; (b): feedstock conversion rate; (c): HMF yield; (d): HMF selectivity);

[0031] Figure 7 The effect of the amount of carbon-based solid catalyst on the photothermal catalytic efficiency (comparison of the results of Examples 3 and 4 with those of Example 1, (a): reaction temperature; (b): feedstock conversion rate; (c): HMF yield; (d): HMF selectivity);

[0032] Figure 8 The effect of solvent type on photothermal catalytic efficiency (comparison of the results of Example 5 and Example 1: (a): reaction temperature; (b): feedstock conversion; (c): HMF yield; (d): HMF selectivity);

[0033] Figure 9 The effect of raw material concentration on photothermal catalytic efficiency (comparison of the results of Examples 6 and 7 with those of Example 1, (a): reaction temperature; (b): raw material conversion rate; (c): HMF yield; (d): HMF selectivity);

[0034] Figure 10 The results of raw material expansion (comparison of the results of Examples 8 and 9 with those of Example 1 (a): reaction temperature; (b): HMF yield) DETAILED DESCRIPTION

[0035] The method of the present invention is described in detail below with reference to specific examples. 5-Hydroxymethylfurfural in the present invention can be abbreviated as HMF.

[0036] 1. A photothermal green catalytic synthesis method for 5-hydroxymethylfurfural

[0037] Example 1

[0038] A photothermal green catalytic synthesis method of 5-hydroxymethylfurfural, comprising the following steps:

[0039] 1) The carbon-based solid sulfonic acid (C1-SO3H) used in this example was prepared by reacting glucose with p-toluenesulfonic acid (TsOH).

[0040] The specific method is as follows: 4.0g of glucose was mixed with 6.0g of p-toluenesulfonic acid and 5.0g of anhydrous sodium sulfate, ground and transferred to a 100mL hydrothermal reactor, and reacted and aged at 180℃ for 48h. After the reaction, the black material was collected from the reactor and washed with hot water until no sulfate was detected in the filtrate (Ba 2+ Finally, dry in a vacuum drying oven at 100 ° C for 24 h to obtain carbon-based solid sulfonic acid C1-SO3H (2.8825 g), grind to a certain mesh size and set aside (see Figure 1 ). Its structure was characterized by FT-IR spectroscopy (see Figure 2), while acid-base titration determined the C1-SO3H acid content to be 1.5521 mmol / g. Elemental analysis determined the sulfonic acid content to be 1.2425 mmol / g.

[0041] 2) 1.0 g of carbon-based solid sulfonic acid C1-SO3H with a particle size of 60-80 mesh and 9.0 g of fructose (50 mmol) were added to a 250 mL quartz reactor. 100 mL of dimethyl sulfoxide (DMSO) was then added as solvent. The reactor was covered with a quartz cover and magnetically stirred. After the raw materials dissolved, the light source was turned on and the timing was started to examine the performance of C1-SO3H in photothermal catalysis of fructose dehydration to form HMF (see the photothermal reaction apparatus for details). Figure 3 During the reaction, the temperature of the reaction system was measured every 10 min using a thermometer to monitor the temperature change of the reaction system in real time. At the same time, a sample (0.1 mL) was taken every 10 min using a pipette and the volume was adjusted to 100 mL with deionized water. Finally, the concentrations of the raw materials and products in the reaction system were measured using high-performance liquid chromatography (HPLC), and the raw material conversion rate and the yield of the target product were calculated to monitor the reaction progress.

[0042] Example 2

[0043] A photothermal green catalytic synthesis method of 5-hydroxymethylfurfural, comprising the following steps:

[0044] 1) The carbon-based solid sulfonic acid (C2-SO3H) used in this example was prepared by reacting glucose with 1,4-butane sultone. The specific method is as follows: 4.0g of glucose and 15.0g of 1,4-butane sultone were placed in a hydrothermal reactor and reacted at 180°C for 48h. After the reaction, the black material was collected and washed with hot water until no sulfate was detected in the filtrate (Ba 2+ Finally, dry in a vacuum drying oven at 100 ° C for 24 h to obtain carbon-based solid sulfonic acid C2-SO3H (2.6781 g), grind to a certain mesh size and set aside (see Figure 1 ). Its structure was characterized by FT-IR spectroscopy (see Figure 2 ), and the acid-base titration method measured the C2-SO3H acid content to be 1.1645 mmol / g. Elemental analysis calculated the sulfonic acid group content to be 1.0341 mmol / g.

[0045] 2) 1.0 g of carbon-based solid sulfonic acid C2-SO3H (60-80 mesh particle size) and 9.0 g of fructose (50 mmol) were added to a 250 mL quartz reactor. 100 mL of dimethyl sulfoxide (DMSO) was then added as solvent. The reactor was covered with a quartz cover slip and magnetically stirred. Subsequent experimental procedures were the same as in Example 1.

[0046] Example 3

[0047] 1) The carbon-based solid sulfonic acid used in this example is C1-SO3H, with an amount of 0.50 g. Its preparation method is shown in Example 1.

[0048] 2) 0.50 g of carbon-based solid sulfonic acid C1-SO3H (60-80 mesh particle size) and 9.0 g of fructose (50 mmol) were added to a 250 mL quartz reactor. 100 mL of dimethyl sulfoxide (DMSO) was then added as solvent. The reactor was covered with a quartz cover slip and magnetically stirred. Subsequent experimental procedures were the same as in Example 1.

[0049] Example 4

[0050] 1) The carbon-based solid sulfonic acid used in this example is C1-SO3H, with an amount of 1.25 g. Its preparation method is shown in Example 1.

[0051] 2) 1.25 g of carbon-based solid sulfonic acid C1-SO3H (60-80 mesh particle size) and 9.0 g of fructose (50 mmol) were added to a 250 mL quartz reactor. 100 mL of dimethyl sulfoxide (DMSO) was then added as solvent. The reactor was covered with a quartz cover slip and magnetically stirred. Subsequent experimental procedures were the same as in Example 1.

[0052] Example 5

[0053] 1) The carbon-based solid sulfonic acid used in this example is 1.0 g of C1-SO3H, and the solvent is sulfolane.

[0054] 2) 1.0 g of carbon-based solid sulfonic acid C1-SO3H with a particle size of 60-80 mesh and 9.0 g of fructose (50 mmol) were added to a 250 mL quartz reactor. 100 mL of sulfolane was then added as the solvent. The reactor was covered with a quartz cover slip and magnetically stirred. Subsequent experimental procedures were the same as in Example 1.

[0055] Example 6

[0056] 1) The carbon-based solid sulfonic acid used in this example is 1.0 g C1-SO3H, and the amount of fructose used is 4.5 g (25 mmol).

[0057] 2) 1.0 g of carbon-based solid sulfonic acid C1-SO3H (60-80 mesh particle size) and 4.5 g of fructose (25 mmol) were added to a 250 mL quartz reactor. 100 mL of dimethyl sulfoxide (DMSO) was then added as solvent. The reactor was covered with a quartz cover slip and magnetically stirred. Subsequent experimental procedures were the same as in Example 1.

[0058] Example 7

[0059] 1) The carbon-based solid sulfonic acid used in this example is 1.0 g C1-SO3H, and the amount of fructose used is 13.5 g (75 mmol).

[0060] 2) 1.0 g of carbon-based solid sulfonic acid C1-SO3H (60-80 mesh particle size) and 13.5 g of fructose (75 mmol) were added to a 250 mL quartz reactor. 100 mL of dimethyl sulfoxide (DMSO) was then added as solvent. The reactor was covered with a quartz cover slip and magnetically stirred. Subsequent experimental procedures were the same as in Example 1.

[0061] Example 8

[0062] 1) The carbon-based solid sulfonic acid used in this example is 1.0 g C1-SO3H, and the raw material is 17.1 g (50 mmol) of sucrose.

[0063] 2) 1.0 g of carbon-based solid sulfonic acid C1-SO3H (60-80 mesh particle size) and 17.1 g of sucrose (50 mmol) were added to a 250 mL quartz reactor. 100 mL of dimethyl sulfoxide (DMSO) was then added as solvent. The reactor was covered with a quartz cover slip and magnetically stirred. Subsequent experimental procedures were the same as in Example 1.

[0064] Example 9

[0065] 1) The carbon-based solid sulfonic acid used in this example is 1.0 g of C1-SO3H, and the raw material is 8.1 g of inulin (50 mmol of fructose structural units).

[0066] 2) 1.0 g of 60-80 mesh carbon-based solid sulfonic acid C1-SO3H and 8.1 g (50 mmol fructose building blocks) were added to a 250 mL quartz reactor. 100 mL of dimethyl sulfoxide (DMSO) was then added as solvent. The reactor was covered with a quartz cover slip and magnetically stirred. Subsequent experimental procedures were the same as in Example 1.

[0067] 2. Sample Analysis

[0068] 0.1 mL of the reaction solution was added to a 100 mL volumetric flask and brought to volume with deionized water. The solution was filtered through a 0.22 μm microporous membrane and analyzed using a high-performance liquid chromatograph (HPLC, Agilent 1200) with external standard quantification. Fructose conversion was analyzed using an HPX-87H column (300 × 7.8 mm, 5 μm) with a 5 mM H₂SO₄ solution as the mobile phase at a flow rate of 0.6 mL / min, the column temperature maintained at 65°C, and a differential index detector (RID). HMF yield was analyzed using a C₁8 reversed-phase column (250 × 4.6 mm, 5 μm) with a 1:4 volume ratio of CH₃OH / H₂O as the mobile phase at a flow rate of 0.6 mL / min, the column temperature maintained at 30°C, and an ultraviolet (UV) detector (UV) at a wavelength of 284 nm.

[0069] When using the external standard method to quantify fructose and products, it is necessary to first establish a corresponding standard curve, which is established by the peak area of ​​different concentrations of fructose, HMF and other standards during HPLC analysis (such as Figure 4 and Figure 5 ).

[0070] During the sample analysis process, the raw material conversion rate (Conv., mol%) and HMF yield (Y) can be calculated based on the size of the peak area corresponding to the sample to be tested and combined with the standard curve. HMF , mol%) and the corresponding selectivity (S HMF , mol%). The calculation formula is as shown in 1-3.

[0071]

[0072] Where M RF M F are the moles of fructose remaining in the reaction system and the fructose added at the beginning of the reaction; M HMF is the number of moles of HMF produced during the reaction.

[0073] Table 1 shows the reaction time when HMF selectivity reaches the maximum value, the conversion rate of raw materials and the HMF yield of Examples 1 to 9

[0074]

[0075] Among them: the raw material used in Example 8 is sucrose, whose molecule contains 1 molecule of fructose and 1 molecule of glucose structural unit. During the photothermal catalytic conversion process, the fructose structural unit can be catalytically dehydrated to form HMF. Therefore, the yield and selectivity of HMF are calculated based on the fructose structural unit in the sucrose molecule; the raw material used in Example 9 is inulin (a fructan), and during the photothermal reaction, the fructose structural unit of inulin is catalytically depolymerized to form fructose, and then further catalytically dehydrated to form HMF. The conversion of inulin is a gradual depolymerization process, so the conversion rate and HMF selectivity of inulin cannot be calculated in this example. The HMF yield can only be calculated based on the amount of HMF generated and the number of fructose structural units in inulin.

[0076] from Figure 1 It can be seen that the two carbon-based solid sulfonic acids (C1-SO3H and C2-SO3H) prepared by carbonization of glucose and sulfonation reagent are black and have typical photothermal conversion function. The molecular structure of the prepared carbon-based solid sulfonic acid was characterized by infrared spectroscopy ( Figure 2 ), the results showed that both C1-SO3H and C2-SO3H contained sulfonic acid groups (-SO3H). -1 The characteristic peaks of 2800~2900cm -1 The characteristic peaks of 1167cm are respectively attributed to the C=C and CH stretching vibrations in solid sulfonic acid, confirming the carbon-based properties of C1-SO3H and C2-SO3H. -1 and 1039cm -1 The characteristic peaks belong to the symmetric stretching vibration of O=S=O in the sulfonic acid group (—SO3H) and the sulfonic acid radical (—SO3 － ) stretching vibration. In addition, Figure 2 Medium 1700cm -1 and 3400cm -1 The characteristic peaks of the ions are derived from the vibration absorption of C=O and OH, and are located at 2300-2700 cm -1 The presence of distinct absorption bands indicates the presence of carboxyl (—COOH) structures in the carbon-based solid sulfonic acid. This result is consistent with the evolution of these groups during the preparation of carbon-based materials using glucose as a raw material. Infrared spectroscopy confirms the carbon-based solid sulfonic acid properties of C1-SO3H and C2-SO3H, indicating their potential as solid acid catalysts.

[0077] As shown in Table 1, the constructed carbon-based solid sulfonic acid has good photothermal catalytic activity. Under the irradiation of simulated sunlight, both C1-SO3H and C2-SO3H showed good catalytic activity in DMSO. With fructose as the raw material, the selectivity of generating HMF reached more than 95%. It can be considered that the fructose raw material can be converted in a targeted manner under the conditions of the photothermal catalytic reaction ( Figure 6 ).from Figure 6 As can be seen from a, the temperature of the reaction system shows a rapid upward trend with the extension of the illumination time. When the illumination time reaches 1.0h, the temperature of the reaction system reaches above 110℃, indicating that the added C1-SO3H and C2-SO3H have good photothermal conversion performance; if the illumination time is further extended, the temperature of the reaction system remains unchanged at 114℃. Figure 6 As can be seen from the data bd, when the reaction system reaches a certain temperature, the fructose dehydration reaction initiates and is rapidly converted to HMF. With the continued increase in reaction temperature (or the extension of illumination time), the fructose conversion rate, HMF yield, and selectivity all increase. The highest fructose conversion rate reaches over 98%, and the maximum HMF yield and selectivity are both above 95%, indicating that C1-SO3H and C2-SO3H also have good catalytic activity for fructose dehydration. Overall, C1-SO3H and C2-SO3H have excellent photothermal conversion capabilities and acid catalytic activity, and can be used as catalytic materials for the green and efficient photothermal dehydration of fructose-based carbohydrates to produce HMF.

[0078] The amount of catalyst used has a great influence on the photocatalytic efficiency of the reaction system ( Figure 7 ). Figure 7 It can be seen that with the increase of the amount of catalyst, the photothermal efficiency of the reaction system also shows an upward trend; when 0.50g C1-SO3H is used as the catalyst (Example 3), the photothermal conversion efficiency of the reaction system is significantly lower than that of 1.0g C1-SO3H (Example 1) and 1.25g C1-SO3H (Example 4), and the final photothermal temperature (102°C) is also much lower than that of Example 1 (114°C) and Example 4 (115°C). In addition, the amount of catalyst also has a great influence on the photothermal catalytic dehydration conversion efficiency of fructose ( Figure 7 bd). The reaction system with high catalyst dosage has high photothermal conversion efficiency. At the same time, the number of catalytic active centers in the catalyst is large (Example 4), which can realize the rapid photothermal catalytic dehydration reaction of fructose ( Figure 7 b); However, in the reaction system with high catalyst dosage, the probability of side reactions is higher and the yield of HMF is ( Figure 7 c) and selectivity ( Figure 7 d) is too low. For example, when 0.50g C1-SO3H is used as a catalyst (Example 3), the photothermal catalytic conversion efficiency of fructose is lower than that of 1.0g C1-SO3H (Example 1), the maximum yield of HMF is 85.1%, the selectivity is 90.4%, and the fructose conversion rate is only 94.2%. The time to reach the optimal HMF yield is 120min (Example 3) ( Figure 7However, when the catalyst dosage was 1.25 g (Example 4), the conversion rate of fructose increased, but the yield (85.9%) and selectivity (86.5%) of HMF were much lower than those in Example 1 ( Figure 7 c,d).

[0079] The effect of solvent on the photothermal catalytic dehydration efficiency of fructose is also quite obvious ( Figure 8 DMSO is a common universal solvent with good solubility for carbohydrates such as fructose. It can also stabilize the HMF produced in the reaction system. Therefore, when DMSO is used as the solvent (Example 1), the yield of HMF is much higher than that of the photothermal catalytic system using sulfolane as the solvent (Example 5). Figure 8 As can be seen in a, in the presence of the photothermal catalytic material C1-SO3H, the reaction system can be quickly heated by light, and the maximum temperature of the reaction system can reach 114 ° C. However, through the analysis of the photothermal catalytic dehydration conversion efficiency of fructose in different solvent systems, it was found that when sulfolane was used as the solvent, the dehydration conversion efficiency of fructose was low ( Figure 8 bd), the possible reason is that the solubility of fructose in sulfolane solvent is much lower than that in DMSO solvent system, which leads to the contact efficiency between fructose and catalyst being much lower than that in DMSO system, resulting in low fructose conversion efficiency.

[0080] The substrate concentration is also a key issue to be investigated in this photothermal catalytic system ( Figure 9 ).from Figure 9 As can be seen from Figure a, the fructose concentration has little effect on the photothermal conversion efficiency of the reaction system. As the illumination time increases, the temperature change pattern of the reaction system is close, and the final reaction temperature is maintained at 114°C. However, the fructose concentration has a greater impact on the conversion efficiency of its photothermal catalytic dehydration to prepare HMF. Fructose can undergo rapid dehydration reaction at low concentrations (Example 6) and high concentrations (Example 7) ( Figure 9 b), but the efficiency of generating HMF varies greatly ( Figure 9 c, d). When the fructose addition level was low, the photothermal conversion efficiency to HMF was significantly higher than in a reaction system with a higher fructose concentration. With increasing fructose concentration, both the HMF yield and selectivity decreased, indicating that a reaction system with a high fructose concentration produces a large number of byproducts, hindering the targeted conversion of fructose to HMF. However, lower fructose concentrations also affect HMF production. Overall, the fructose concentration in Example 1 was relatively appropriate, with both the HMF yield and selectivity exceeding 95%, indicating targeted conversion of fructose to HMF.

[0081] In addition, this photothermal catalytic system also has certain substrate applicability. The fructose structural unit contained in the raw material can be efficiently converted into HMF ( Figure 10 ).from Figure 10 As can be seen in a, the type of raw materials does not affect the photothermal conversion efficiency of the reaction system. However, the efficiency of dehydration conversion to HMF of raw materials with different structures is significantly different ( Figure 10 b). For example, when sucrose (containing one molecule of fructose and one molecule of glucose) is used as the raw material, the HMF yield can reach 73.7% (Example 8); when fructan (inulin) is used as the raw material, the HMF yield can still reach 40.9% (Example 9), but both are lower than the reaction system using fructose directly as the raw material (95.2%, Example 1). This shows that this photothermal catalytic system can also catalyze the hydrolysis and dehydration of sucrose, fructan, and other substances to form HMF. However, due to the limited contact between the carbon-based solid sulfonic acid catalyst and the fructan substrate, the HMF yield is relatively low. Overall, the constructed green photothermal catalytic reaction system has certain raw material applicability.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A photothermal green catalytic synthesis method of 5-hydroxymethylfurfural, characterized in that: Under the radiation of simulated sunlight, a carbon-based solid sulfonic acid is used as a catalyst, the reaction system is heated by photothermal heating, and fructose-based carbohydrates are selectively catalytically dehydrated in dimethyl sulfoxide, an organic solvent, to produce 5-hydroxymethylfurfural, wherein the carbon group of the carbon-based solid sulfonic acid is glucose, the fructose-based carbohydrate is fructose, and the mass fraction of the carbon-based solid sulfonic acid relative to the raw material fructose-based carbohydrate is ≤15%.

2. The 5-hydroxymethylfurfural photothermal green catalytic synthesis method according to claim 1, characterized in that The specific steps include: (1) adding a certain amount of carbon-based solid sulfonic acid to an organic solvent to form a photothermal catalytic dehydration reaction system; (2) adding a certain amount of fructose-based carbohydrates to the photothermal reaction system, stirring magnetically, and performing a photothermal catalytic dehydration reaction under the radiation of simulated sunlight; The carbon-based solid sulfonic acid is a black carbon-based solid catalytic material containing a sulfonic acid active center.

3. The 5-hydroxymethylfurfural photothermal green catalytic synthesis method according to claim 1, characterized in that: The mass volume ratio of the raw material fructose-based carbohydrate to the organic solvent is (1-50) g:100 mL.

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