Method for preparing formyl-2-furoic acid from 5-hydroxymethylfurfural

Abstract

The present invention discloses a method for preparing formyl-2-furoic acid from 5-hydroxymethylfurfural. The specific method is as follows: A certain amount of 5-hydroxymethylfurfural, Anderson-type polyoxometalate, and ternary deep eutectic solvent are placed in a three-necked flask, and the reaction is carried out at a specified temperature and oxygen flux to obtain formyl-2-furoic acid. The process of the present invention has mild reaction conditions and high catalytic activity. Under the conditions of normal pressure and without the addition of external base, formyl-2-furoic acid can be synthesized within 2.5 hours (the yield reaches 98%). At the same time, the process of the present invention is simple to operate, has high selectivity for the product, provides an efficient alkali-free catalytic system for the conversion of biomass resources, and has important significance for the development and utilization of renewable energy.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and specifically relates to a method for preparing formyl-2-furoic acid from 5-hydroxymethylfurfural based on the superoxide radical pathway. Background Art

[0002] In recent years, with the implementation of the national sustainable development strategy, the development of sustainable resource utilization has attracted extensive attention. As the only renewable organic carbon source, the catalytic conversion of biomass has attracted great interest. As one of the biomass derivatives, 5-hydroxymethylfurfural (HMF) is an important platform chemical. By selectively oxidizing the hydroxyl and aldehyde groups on HMF, a series of high-value-added chemicals can be prepared. Among them, 5-formyl-2-furoic acid (FFCA) is a furan compound with both formyl and carboxyl groups, which can be applied to fields such as chemical intermediates and drug synthesis, and has broad application prospects.

[0003] For the oxidation of HMF, traditional methods are carried out using stoichiometric oxidants such as dichromates and permanganates. However, these oxidants are not only expensive but also cause environmental pollution problems. In contrast, the oxidation of HMF using molecular oxygen as the oxidant is more attractive. Currently, it is relatively common to use supported noble metals as catalysts and oxygen as the oxidant to efficiently oxidize HMF to FFCA in the presence of added bases. Antonio Buonerba et al. synthesized a supported gold catalyst AuNPs-sPSB and obtained a 99% yield of FFCA under an O2 pressure of 1.5 Mpa. However, the cost of noble metal catalysts is usually high, which limits their large-scale production. An external base is usually required in their catalytic systems. Hayashi et al. used MnO 2 as the catalyst and obtained a 95% yield of FDCA in the presence of NaHCO 3 . The addition of the base can effectively prevent the aggregation of the oxidation products of HMF on the catalyst surface, thus effectively preventing the decrease in catalyst activity. However, the addition of basic substances will cause serious environmental pollution problems. Therefore, the development of a non-noble metal catalytic system that does not require the addition of an external base has always been expected. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing formyl-2-furoic acid from 5-hydroxymethylfurfural, specifically a method for preparing formyl-2-furoic acid from 5-hydroxymethylfurfural based on the superoxide radical pathway.

[0005] To achieve the conversion from HMF to FFCA, the present invention adopts the following technical solutions:

[0006] A method for preparing formyl-2-furoic acid from 5-hydroxymethylfurfural, comprising the following steps:

[0007] Step 1) Mix 1-butyl-3-methylimidazolium chloride, 4-methylmorpholine-N-oxide and caprolactam in a molar ratio of 1:1-2:1-6, and heat and stir at 60-100 °C until a homogeneous transparent liquid is obtained, which is the deep eutectic solvent;

[0008] Step 2) Add 5-hydroxymethylfurfural and Anderson-type heteropolyacid salt to the deep eutectic solvent prepared in Step 1), and continuously pass oxygen at a flow rate of 20-160 mL / min. After the reaction is complete at 80-150 °C, a mixed liquid containing 5-formyl-2-furoic acid is obtained;

[0009] Among them, the mass ratio of the deep eutectic solvent, Anderson-type heteropolyacid salt to 5-hydroxymethylfurfural is 20-80:0.2-1:1

[0010] Anderson-type heteropolyacid is Na 5 IMo 6 O 24 , (NH 4 ) 4 CrMo 6 O 24 , (NH 4 ) 3 H 6 CoMo 6 O 24 , (NH 4 ) 4 CuMo 6 O 24 , Na 3 H 6 FeMo 6 O 24 , (NH 4 ) 4 NiMo 6 O 24 One of them.

[0011] Preferably, the reaction temperature in Step 1) is 80 °C and the heating and stirring time is 1 h.

[0012] The present invention proposes a new technical route for preparing 5-formyl-2-furoic acid by coupling a deep eutectic solvent with an Anderson-type heteropolyacid salt. As an efficient catalytic oxidation system, the present invention introduces NMNO into the BmimCl-based DES to synthesize a ternary DES, and after coupling it with POM, it is used for the selective oxidation of HMF to prepare FFCA based on the superoxide radical pathway. Different from the existing coupling catalytic oxidation pathways of deep eutectic solvents and heteropolyacids. Different from the electron transfer between the previous DES and Anderson-type heteropolyacid salts, the Mo 6+ species in the heteropolyacid is reduced to Mo 5+ ( Figure 1 ). The innovation of the present invention different from the prior art lies in realizing selective catalysis through superoxide radicals. That is, under the action of oxygen vacancies, the externally introduced oxygen is activated, and the hydroxyl and aldehyde groups on HMF are oxidized through superoxide radicals to generate the intermediate product HMFCA and further oxidized to generate FFCA. Moreover, the quenching experiment ( Figure 2 ) also confirms that the present invention realizes selective catalysis through the pathway of the reactive oxygen species superoxide radical.

[0013] Beneficial effects

[0014] The present invention provides a new technical route. Different from the electron transfer between the current binary DES and Anderson-type heteropolyacid salts, under the action of the ternary deep eutectic solvent (DES), the Anderson-type heteropolyacid salt catalyst Na 5 IMo 6 O 24 can activate molecular oxygen into superoxide radicals, and realize selective catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid through superoxide radicals.

[0015] In addition, the process route proposed by the present invention can efficiently synthesize FFCA. Under mild conditions, a yield of 98% of FFCA was obtained only after reacting for 2.5 h. The process is simple to operate, the reaction conditions are mild, the oxidation reaction activity is high, and the selectivity is good. It is a green and simple and efficient method for preparing FFCA. Experimental results show that under the optimal reaction conditions, the conversion rate of HMF is 100%, and the yield of FFCA reaches 98%.

[0016] The present invention provides a reference for the activation and utilization of oxygen, and has important significance for the development of efficient catalytic systems. Moreover, the catalytic system used in the present invention does not add alkaline substances and is more environmentally friendly. Description of the drawings

[0017] Figure 1 is the EPR spectrum of the catalyst, the catalyst and the DES mixture.

[0018] Figure 2 Quenching experiment data. Among them, the reaction conditions are: 0.4 mmol HMF, 50 mg IMo 6 , 3 g DES, BmimCl / NMNO / CPL = 1:1:5, oxygen flow rate 140 mL / min, 600 rpm, 130 °C, 2.5 h, 0.4 mmol quencher. Specific implementation manners

[0019] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0020] Example 1

[0021] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0022] (1) 1-Butyl-3-methylimidazolium chloride (BmimCl), 4-methylmorpholine-N-oxide (NMNO) and caprolactam (CPL) are mixed at a molar ratio of 1 / 1 / 1, and heated and stirred at 80 °C for 1 hour to obtain a homogeneous and clear liquid, that is, a deep eutectic solvent (DES).

[0023] (2) 0.4 mmol of HMF is added to 4 g of the DES synthesized in step (1), and then 40 mg of Na 5 IMo 6 O 24 catalyst, and then oxygen is continuously introduced at a flow rate of 140 mL / min, and the HMF oxidation reaction is carried out at 130 °C for 3 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0024] (3) The mixed liquid is diluted with water as a solvent and analyzed by a high performance liquid chromatograph, and the product types are identified using a standard solution. The results are shown in Table 1, showing that the HMF conversion rate is 100%, and the FFCA yield reaches 49%.

[0025] Example 2

[0026] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0027] (1) 1-Butyl-3-methylimidazolium chloride (BmimCl), 4-methylmorpholine-N-oxide (NMNO) and caprolactam (CPL) are mixed at a molar ratio of 1 / 1 / 3, and heated and stirred at 80 °C for 1 hour to obtain a homogeneous and clear liquid, that is, a deep eutectic solvent (DES).

[0028] (2) Add 0.4 mmol of HMF to 4 g of the DES synthesized in step (1), then add 40 mg of Na 5 IMo 6 O 24 catalyst, and then continuously introduce oxygen at a flow rate of 140 mL / min, and carry out the HMF oxidation reaction at 130 °C for 3 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0029] (3) Dilute the mixed solution with water as a solvent and analyze it with a high performance liquid chromatograph. Use a standard solution to identify the product types. The results are shown in Table 1, indicating that the HMF conversion rate is 100% and the FFCA yield reaches 81%.

[0030] Example 3

[0031] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0032] (1) Mix 1-butyl-3-methylimidazolium chloride (BmimCl), 4-methylmorpholine-N-oxide (NMNO) and caprolactam (CPL) in a molar ratio of 1 / 1 / 5, and heat and stir at 80 °C for 1 hour to obtain a homogeneous and clear liquid, that is, a deep eutectic solvent (DES).

[0033] (2) Add 0.4 mmol of HMF to 4 g of the DES synthesized in step (1), then add 40 mg of Na 5 IMo 6 O 24 catalyst, and then continuously introduce oxygen at a flow rate of 140 mL / min, and carry out the HMF oxidation reaction at 130 °C for 3 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0034] (3) Dilute the mixed solution with water as a solvent and analyze it with a high performance liquid chromatograph. Use a standard solution to identify the product types. The results are shown in Table 1, indicating that the HMF conversion rate is 100% and the FFCA yield reaches 98%.

[0035] Example 4

[0036] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0037] (1) Synthesize the deep eutectic solvent (DES) in the same method as in Example 3.

[0038] (2) Add 0.4 mmol of HMF to 4 g of the DES synthesized in step (1), then add 40 mg of Na 5 IMo6 O 24 A catalyst was then continuously introduced with oxygen at a flow rate of 140 mL / min, and the HMF oxidation reaction was carried out at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furancarboxylic acid (FFCA).

[0039] (3) The mixed solution was diluted with water as a solvent and analyzed by a high-performance liquid chromatograph. A standard solution was used to identify the product types. The results are shown in Table 1, indicating that the HMF conversion rate was 100% and the FFCA yield reached 84%.

[0040] Example 5

[0041] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furancarboxylic acid includes the following steps:

[0042] (1) A deep eutectic solvent (DES) was synthesized in the same manner as in Example 3.

[0043] (2) 0.4 mmol of HMF was added to 4 g of the DES synthesized in step (1), and then 40 mg of (NH 4 ) 4 CrMo 6 O 24 A catalyst was then continuously introduced with oxygen at a flow rate of 140 mL / min, and the HMF oxidation reaction was carried out at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furancarboxylic acid (FFCA).

[0044] (3) The mixed solution was diluted with water as a solvent and analyzed by a high-performance liquid chromatograph. A standard solution was used to identify the product types. The results are shown in Table 1, indicating that the HMF conversion rate was 100% and the FFCA yield reached 35%.

[0045] Example 6

[0046] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furancarboxylic acid includes the following steps:

[0047] (1) A deep eutectic solvent (DES) was synthesized in the same manner as in Example 3.

[0048] (2) 0.4 mmol of HMF was added to 4 g of the DES synthesized in step (1), and then 40 mg of (NH 4 ) 3 H 6 CoMo 6 O 24 A catalyst was then continuously introduced with oxygen at a flow rate of 140 mL / min, and the HMF oxidation reaction was carried out at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furancarboxylic acid (FFCA).

[0049] (3) The mixture was diluted with water as the solvent and analyzed by high performance liquid chromatography. The product types were identified using a standard solution. The results are shown in Table 1, indicating that the HMF conversion rate was 100% and the FFCA yield reached 70%.

[0050] Example 7

[0051] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0052] (1) A deep eutectic solvent (DES) was synthesized in the same manner as in Example 3.

[0053] (2) 0.4 mmol of HMF was added to 4 g of the DES synthesized in step (1), and then 40 mg of (NH 4 ) 4 CuMo 6 O 24 catalyst was added. Then, oxygen was continuously introduced at a flow rate of 140 mL / min, and the HMF oxidation reaction was carried out at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0054] (3) The mixture was diluted with water as the solvent and analyzed by high performance liquid chromatography. The product types were identified using a standard solution. The results are shown in Table 1, indicating that the HMF conversion rate was 99% and the FFCA yield reached 49%.

[0055] Example 8

[0056] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0057] (1) A deep eutectic solvent (DES) was synthesized in the same manner as in Example 3.

[0058] (2) 0.4 mmol of HMF was added to 4 g of the DES synthesized in step (1), and then 40 mg of Na 3 H 6 FeMo 6 O 24 catalyst was added. Then, oxygen was continuously introduced at a flow rate of 140 mL / min, and the HMF oxidation reaction was carried out at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0059] (3) The mixture was diluted with water as the solvent and analyzed by high performance liquid chromatography. The product types were identified using a standard solution. The results are shown in Table 1, indicating that the HMF conversion rate was 100% and the FFCA yield reached 80%.

[0060] Example 9

[0061] The preparation of 5-formyl-2-furoic acid by catalytic oxidation of 5-hydroxymethylfurfural includes the following steps:

[0062] (1) Synthesize the deep eutectic solvent (DES) by the same method as in Example 3.

[0063] (2) Add 0.4 mmol of HMF to 4 g of the DES synthesized in step (1), and then add 40 mg of (NH 4 ) 4 NiMo 6 O 24 catalyst, and then continuously introduce oxygen at a flow rate of 140 mL / min, and carry out the HMF oxidation reaction at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0064] (3) Dilute the mixed solution with water as the solvent, and analyze it with a high performance liquid chromatograph. Use a standard solution to identify the product types. The results are shown in Table 1, showing that the HMF conversion rate is 100%, and the FFCA yield reaches 66%.

[0065] Example 10

[0066] The preparation of 5-formyl-2-furoic acid by catalytic oxidation of 5-hydroxymethylfurfural includes the following steps:

[0067] (1) Synthesize the deep eutectic solvent (DES) by the same method as in Example 3.

[0068] (2) Add 0.4 mmol of HMF to 3 g of the DES synthesized in step (1), and then add 50 mg of Na 5 IMo 6 O 24 catalyst, and then continuously introduce oxygen at a flow rate of 140 mL / min, and carry out the HMF oxidation reaction at 130 °C for 2.5 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0069] (3) Dilute the mixed solution with water as the solvent, and analyze it with a high performance liquid chromatograph. Use a standard solution to identify the product types. The results are shown in Table 1, showing that the HMF conversion rate is 100%, and the FFCA yield reaches 98%.

[0070] Example 11

[0071] The preparation of 5-formyl-2-furoic acid by catalytic oxidation of 5-hydroxymethylfurfural includes the following steps:

[0072] (1) Synthesize the deep eutectic solvent (DES) by the same method as in Example 3.

[0073] (2) Add 0.4 mmol of HMF to 1 g of the DES synthesized in step (1), and then add 50 mg of Na 5 IMo 6 O 24 catalyst, and then continuously introduce oxygen at a flow rate of 140 mL / min, and carry out the HMF oxidation reaction at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0074] (3) Dilute the mixed solution with water as the solvent, and analyze it with a high-performance liquid chromatograph, and use a standard solution to identify the product types. The results are shown in Table 1, showing that the HMF conversion rate is 100%, and the FFCA yield reaches 28%.

[0075] Example 12

[0076] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0077] (1) Synthesize the deep eutectic solvent (DES) by the same method as in Example 3.

[0078] (2) Add 0.4 mmol of HMF to 3 g of the DES synthesized in step (1), and then add 50 mg of Na 5 IMo 6 O 24 catalyst, and then continuously introduce oxygen at a flow rate of 140 mL / min, and carry out the HMF oxidation reaction at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0079] (3) Dilute the mixed solution with water as the solvent, and analyze it with a high-performance liquid chromatograph, and use a standard solution to identify the product types. The results are shown in Table 1, showing that the HMF conversion rate is 100%, and the FFCA yield reaches 97%.

[0080] Example 13

[0081] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0082] (1) Synthesize the deep eutectic solvent (DES) by the same method as in Example 3.

[0083] (2) Add 0.4 mmol of HMF to 5 g of the DES synthesized in step (1), and then add 50 mg of Na 5 IMo 6 O 24A catalyst was then continuously introduced with oxygen at a flow rate of 140 mL / min, and the HMF oxidation reaction was carried out at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0084] (3) The mixed solution was diluted with water as a solvent and analyzed by a high-performance liquid chromatograph. A standard solution was used to identify the product types. The results are shown in Table 1, indicating that the HMF conversion rate was 100% and the FFCA yield reached 83%.

[0085] Example 14

[0086] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0087] (1) A deep eutectic solvent (DES) was synthesized in the same method as in Example 3.

[0088] (2) 0.4 mmol of HMF was added to 4 g of the DES synthesized in step (1), and then 10 mg of Na 5 IMo 6 O 24 A catalyst was then continuously introduced with oxygen at a flow rate of 140 mL / min, and the HMF oxidation reaction was carried out at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0089] (3) The mixed solution was diluted with water as a solvent and analyzed by a high-performance liquid chromatograph. A standard solution was used to identify the product types. The results are shown in Table 1, indicating that the HMF conversion rate was 100% and the FFCA yield reached 52%.

[0090] Example 15

[0091] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0092] (1) A deep eutectic solvent (DES) was synthesized in the same method as in Example 3.

[0093] (2) 0.4 mmol of HMF was added to 4 g of the DES synthesized in step (1), and then 30 mg of Na 5 IMo 6 O 24 A catalyst was then continuously introduced with oxygen at a flow rate of 140 mL / min, and the HMF oxidation reaction was carried out at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0094] (3) Dilute the mixture with water as the solvent and analyze it using a high-performance liquid chromatograph. Identify the product types using a standard solution. The results are shown in Table 1, indicating that the HMF conversion rate is 100% and the FFCA yield reaches 81%.

[0095] Example 16

[0096] The catalytic oxidation of 5-hydroxymethylfurfural to prepare 5-formyl-2-furoic acid includes the following steps:

[0097] (1) Synthesize the deep eutectic solvent (DES) in the same method as in Example 3.

[0098] (2) Add 0.4 mmol of HMF to 4 g of the DES synthesized in step (1), and then add 50 mg of Na 5 IMo 6 O 24 catalyst. Then continuously introduce oxygen at a flow rate of 140 mL / min and carry out the HMF oxidation reaction at 130 °C for 2 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA).

[0099] (3) Dilute the mixture with water as the solvent and analyze it using a high-performance liquid chromatograph. Identify the product types using a standard solution. The results are shown in Table 1, indicating that the HMF conversion rate is 100% and the FFCA yield reaches 88%.

[0100] Table 1. Reaction results of the catalytic oxidation of HMF to prepare FFCA in Examples 1-16

[0101]

[0102]

[0103] Reaction conditions: 0.4 mmol of HMF, 130 °C, oxygen flow rate of 140 mL / min. B is the abbreviation of 1-butyl-3-methylimidazolium chloride, N is the abbreviation of 4-methylmorpholine-N-oxide, and C is the abbreviation of caprolactam.

[0104] The above experimental data show that: under the new technical route of coupling ternary deep eutectic solvents constructed in the present invention with Anderson-type heteropolyacids for the preparation of 5-formyl-2-furoic acid, within the preferred range, the present invention can effectively achieve high conversion and high yield of 5-formyl-2-furoic acid. Moreover, the catalytic oxidation system of the ternary deep eutectic solvents and Anderson-type heteropolyacids in the present invention is different from the technical route of electron transfer generated by the coupling of the two in the prior art. The present invention realizes the selective catalysis of 5-hydroxymethylfurfural through the superoxide radical path, thereby obtaining the conversion of formyl-2-furoic acid, and the following quenching experiments also verify the above view.

[0105] To verify the types of active species in the reaction process, the present invention verifies the above view through quenching experiments. By adding radical quenchers to the reaction system, if the reaction activity decreases, it indicates that a radical process is involved in the reaction, that is, a certain radical plays a role in the reaction; if the reaction activity remains unchanged, it indicates that the reaction does not involve a radical process, that is, the radical does not play a role in the reaction.

[0106] Hydroxyl radical (OH · ) quenching experiment, including the following steps:

[0107] (1) Synthesize deep eutectic solvent (DES) in the same method as in Example 3.

[0108] (2) Add 0.4 mmol HMF to 3 g of the DES synthesized in step (1), then add 50 mg of Na 5 IMo 6 O 24 catalyst and 0.4 mmol DMSO quencher, and then continuously introduce oxygen at a flow rate of 140 mL / min, and carry out the HMF oxidation reaction at 130 °C for 2.5 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA)

[0109] .

[0110] (3) Dilute the mixed liquid with water as the solvent and analyze it with a high performance liquid chromatograph, and use a standard solution to identify the product types. The results are shown in Figure 2 , showing that the HMF conversion rate is 100% and the FFCA yield reaches 98%.

[0111] Comparing the results of this example with those in Example 10, the results show that: when other reaction conditions are kept unchanged, when DMSO (hydroxyl radical scavenger) is added to the system, the reaction activity does not change significantly.

[0112] Hydroxyl radical (OH ·)The quenching experiment shows that the reaction system coupling the ternary eutectic solvent and Anderson-type heteropolyacid salt of the present invention does not involve the hydroxyl radical process.

[0113] Superoxide radical (O 2 ·— ) quenching experiment

[0114] Superoxide radical (O 2 ·— ) quenching experiment, including the following steps:

[0115] (1) Synthesize the eutectic solvent (DES) by the same method as in Example 3.

[0116] (2) Add 0.4 mmol of HMF to 3 g of the DES synthesized in step (1), then add 50 mg of Na 5 IMo 6 O 24 catalyst and 0.4 mmol of BQ quencher, and then continuously introduce oxygen at a flow rate of 140 mL / min, and carry out the HMF oxidation reaction at 130 °C for 2.5 h to obtain a mixed liquid containing 5-formyl-2-furoic acid (FFCA)

[0117] of the mixed liquid.

[0118] (3) Dilute the mixed liquid with water as the solvent and analyze it with a high-performance liquid chromatograph, and use a standard solution to identify the product types. The results are shown in Figure 2 , showing that the HMF conversion rate is 100% and the FFCA yield reaches 28%.

[0119] Compared with the experiment in Example 10, the experimental results show that: when other reaction conditions are kept unchanged, when BQ (superoxide radical scavenger) is added to the system, the FFCA yield drops from 98% to 28%. When BQ is not added to the reaction, the presence of superoxide radicals in the system can efficiently oxidize HMF to FFCA. After adding BQ to the reaction, since the superoxide radicals in the system are captured, the reaction activity drops significantly.

[0120] Superoxide radical (O 2 ·— ) quenching experiment shows that: the reaction system coupling the ternary eutectic solvent and Anderson-type heteropolyacid salt of the present invention involves the superoxide radical process, and the superoxide radical is the active oxygen path in the reaction. The present invention realizes the catalytic oxidation of HMF through the superoxide radical.

[0121] That is, through the quenching experiment, it is shown and verified that: the catalytic oxidation system coupling the ternary eutectic solvent and Anderson-type heteropolyacid salt of the present invention is different from the prior art Mo 6+The species is reduced to Mo 5+ For the catalytic oxidation route of HMF achieved by triggering oxygen vacancies in heteropolyacids, the present invention realizes the selective catalysis of 5-hydroxymethylfurfural through the superoxide radical path, thereby obtaining the conversion of formyl-2-furoic acid.

[0122] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

Method for preparing formyl-2-furoic acid from 5-hydroxymethylfurfural characterized in that it comprises the following steps: Step 1) Mix 1-butyl-3-methylimidazolium chloride, 4-methylmorpholine-N-oxide and caprolactam according to a molar ratio of 1:1-2:1-6, and heat and stir at 60-100 °C until a homogeneous and transparent liquid is obtained, which is the deep eutectic solvent; Step 2) Add 5-hydroxymethylfurfural and Anderson-type heteropolyacid salt into the deep eutectic solvent prepared in Step 1), where the mass ratio of the deep eutectic solvent, Anderson-type heteropolyacid salt to 5-hydroxymethylfurfural is 20-80:0.2-1:1, and the Anderson-type heteropolyacid is Na 5 IMo 6 O 24 , (NH 4 ) 4 CrMo 6 O 24 , (NH 4 ) 3 H 6 CoMo 6 O 24 , (NH 4 ) 4 CuMo 6 O 24 , Na 3 H 6 FeMo 6 O 24 , (NH 4 ) 4 NiMo 6 O 24 and one of the following And continuously introduce oxygen at a flow rate of 20-160 mL / min. After the reaction is complete at 80-150 °C, a mixed liquid containing 5-formyl-2-furoic acid is obtained.

2. The method according to claim 1, characterized in that the reaction temperature in Step 1) is 80 °C.

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