Preparation method of acid-base bifunctional melamine foam and application thereof in catalytic conversion of glucose into hmf

Abstract

The application discloses a preparation method of acid-base bifunctional melamine foam and application of the acid-base bifunctional melamine foam in catalyzing conversion of glucose into HMF, and belongs to the technical field of green catalytic biomass conversion, and comprises the following steps: firstly, the melamine foam is cleaned with different solvents; and then the cleaned melamine foam is reacted with a sultone to obtain an acid-base bifunctional melamine foam catalyst. The acid-base bifunctional melamine foam catalyzes the reaction of converting glucose into 5-hydroxymethylfurfural (HMF), the catalyst shows excellent catalytic activity, has the advantages of short reaction time, high reaction yield, green solvent, good cycle performance and the like. In addition, the catalyst is of a solid porous structure and can be directly applied to filling of an industrial fixed bed, and has good potential industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of green catalytic biomass conversion technology, and relates to a method for catalyzing glucose conversion by using acid-base bifunctional melamine foam and application of the method in catalyzing glucose conversion into HMF. BACKGROUND

[0002] With the driving of global economic growth, world population increase and industrialization, the demand for global fossil fuels is rapidly increasing. In order to reduce the dependence on non-renewable fossil fuels, researchers begin to search for suitable renewable resources to replace fossil fuels. This also triggers a new strategy of converting a series of biomass-derived compounds into fuels and fine chemicals. Biomass resources are the only renewable organic carbon resources in nature, which have the characteristics of low cost, rich resources and sustainability. Lignocellulose is the cheapest and most abundant non-food resource in biomass resources. Lignocellulose is mainly composed of cellulose (40-50%), hemicellulose (25-35%) and lignin (15-20%). Cellulose is easy to hydrolyze to obtain glucose. Hydrolysis of cellulose with the highest content into glucose and then into various high-value chemicals and fuels is an important way for biomass resource utilization and energy utilization.

[0003] 5-hydroxymethylfurfural (HMF) is an important multifunctional platform compound and an important intermediate of various industrial-related chemicals and fuels. Through oxidation, hydrogenation, polymerization, ring-opening and other reactions of the furan ring, aldehyde group and hydroxymethyl group of HMF, HMF can also be converted into various high-value chemical derivatives. For example, levulinic acid (LA), 2,5-dimethylfuran (DMF), 2,5-furandicarboxylic acid (FDCA) and 2,5-furandimethanol (DHMF) and the like. The raw material for preparing HMF is mainly fructose and glucose. Many previous studies show that HMF can be efficiently prepared from fructose. However, fructose has high cost, low yield, and directly competes with the food industry, so its application is limited. Compared with fructose, glucose is the most abundant monosaccharide in nature, which has the advantages of being more inexpensive and having a wider source. Therefore, glucose is an ideal and preferred raw material for producing HMF.

[0004] Existing HMF catalytic preparation methods can be roughly divided into two categories. Homogeneous catalysts are represented by inorganic acids, ionic liquids, metal salts and the like. In this type of catalyst system, although the active centers of the catalysts are uniform and the structures are clear, the catalysts are difficult to separate in the reaction mixture and may be accompanied by side reactions, and the recovery performance of the catalysts is greatly reduced. Therefore, from the industrial point of view of product separation and equipment maintenance, heterogeneous catalysts have more advantages.

[0005] Melamine foam has intrinsic flame retardance, high temperature resistance and thermal stability. The three-dimensional network structure of open-cell type makes it have good sound absorption, heat insulation, light weight and good secondary processing properties, and is often used in the fields of vehicles and rail transportation, aerospace and national defense, cleaning industry, building, etc. The present application uses melamine foam as a carrier to prepare a series of melamine foam-based acid-base bifunctional catalysts, and applies them to catalyze the conversion of glucose to prepare HMF. The preparation method of the catalyst is very simple, the catalytic efficiency is extremely high, can meet various complex reaction conditions, and has excellent softness and stability, so it has great industrial application prospect. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a preparation method of acid-base bifunctional melamine foam and its application in catalyzing the conversion of glucose to HMF; specifically, a method for preparing acid-base bifunctional melamine foam catalyst with simple preparation process, high catalytic activity and good recycling performance to synthesize HMF, thereby solving the problems of non-recyclable small molecule catalysts, environmental pollution and resource waste in the process of synthesizing HMF.

[0007] To solve the above technical problems, the present application adopts the following technical solutions:

[0008] A preparation method of acid-base bifunctional melamine foam, comprising the following steps:

[0009] (1) Melamine foam pretreatment: cut the melamine foam into 1x1x1cm 3 small pieces, then put them into different solvents respectively for refluxing, washing and drying to obtain pretreated melamine foam;

[0010] (2) Preparation of acid-base bifunctional melamine foam: ultrasonic the pretreated melamine foam in a sulfolactone acetonitrile solution, then heat and stir to react, after the reaction is completed, take out and clean with ethanol and water, and dry to obtain acid-base bifunctional melamine foam.

[0011] Further, in step (1), the solvent is ethanol, cyclohexane, distilled water or acetone; the mass-volume ratio of melamine foam to solvent is 1:30-1:100 g / mL, and the refluxing time is 4-10 h.

[0012] Further, in step (2), the sulfolactone is 1,3-propane sulfolactone or 1,4-butane sulfolactone.

[0013] Further, in step (2), the concentration of the sulfolactone acetonitrile solution is 0.1-1 mol / L.

[0014] Further, in step (2), the mass-volume ratio of pretreated melamine foam to sulfolactone acetonitrile solution is 1:30-1:100 g / mL, and the ultrasonic treatment time is 10-50 min.

[0015] Furthermore, in step (2), the temperature is raised to 40-82°C and stirred for 10-72 hours.

[0016] Furthermore, the acid-base bifunctional melamine foam catalyst prepared by the method of the present invention is applied in the catalytic conversion of glucose to HMF.

[0017] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0018] This invention prepares an acid-base bifunctional melamine foam for catalytic conversion of glucose to HMF. The catalyst has a simple preparation process, excellent catalytic effect, is easy to separate, and has good recyclability. It effectively solves the problems of existing small-molecule catalysts, such as non-recyclability, environmental pollution, and high cost. Attached Figure Description

[0019] Figure 1 A schematic diagram of the preparation route for an example of acid-base bifunctional melamine foam.

[0020] Figure 2 Schematic diagram of catalytic conversion of glucose to prepare HMF. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and not for limiting the scope of the invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention. Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Where the manufacturers of reagents or instruments are not specified, they are all commercially available conventional reagent products.

[0022] The following examples illustrate the preparation route of an acid-base bifunctional melamine foam. Figure 1 As shown.

[0023] Example 1

[0024] The preparation method of the acid-base bifunctional melamine foam catalyst in this embodiment is as follows:

[0025] (1) Cut 2g of melamine foam into 1×1×1cm pieces. 3 Small pieces of melamine foam were added to a round-bottom flask containing 60 mL of cyclohexane and refluxed for 4 hours. The melamine foam was then removed and placed in a round-bottom flask containing 60 mL of ethanol and refluxed for 4 hours. After rinsing and drying, the pretreated melamine foam was obtained.

[0026] (2) Preparation of acid-base bifunctional melamine foam: 1 g of melamine foam was added to 30 mL of 0.1 mol / L 1,3-propane sultone acetonitrile solution, and after ultrasonic treatment for 10 min, it was stirred at 40°C for 10 h. Finally, the foam was taken out and washed clean with ethanol and water, and after drying, acid-base bifunctional melamine foam MF-NSO3H was obtained.

[0027] Example 2

[0028] The preparation method of the acid-base bifunctional melamine foam catalyst in this example is as follows:

[0029] (1) 2 g of melamine foam was cut into 1 × 1 × 1 cm 3 small pieces, and after reflux stirring in a round-bottom flask containing 100 mL of acetone for 6 h, the foam was taken out and placed in a round-bottom flask containing 60 mL of ethanol for reflux stirring for 6 h. The pretreated melamine foam obtained after washing and drying.

[0030] (2) Preparation of acid-base bifunctional melamine foam: 1 g of melamine foam was added to 50 mL of 0.5 mol / L 1,3-propane sultone acetonitrile solution, and after ultrasonic treatment for 20 min, it was stirred at 60°C for 20 h. Finally, the foam was taken out and washed clean with ethanol and water, and after drying, acid-base bifunctional melamine foam MF-NSO3H was obtained.

[0031] Example 3

[0032] The preparation method of the acid-base bifunctional melamine foam catalyst in this example is as follows:

[0033] (1) 2 g of melamine foam was cut into 1 × 1 × 1 cm 3 small pieces, and after reflux stirring in a round-bottom flask containing 150 mL of cyclohexane for 8 h, the foam was taken out and placed in a round-bottom flask containing 150 mL of distilled water for reflux stirring for 8 h. The pretreated melamine foam obtained after washing and drying.

[0034] (2) Preparation of acid-base bifunctional melamine foam: 1 g of melamine foam was added to 80 mL of 0.8 mol / L 1,4-butane sultone acetonitrile solution, and after ultrasonic treatment for 30 min, it was stirred at 70°C for 48 h. Finally, the foam was taken out and washed clean with ethanol and water, and after drying, acid-base bifunctional melamine foam MF-NSO3H was obtained.

[0035] Example 4

[0036] The preparation method of the acid-base bifunctional melamine foam catalyst in this example is as follows:

[0037] (1) 2 g of melamine foam was cut into 1 × 1 × 1 cm 3The melamine foam was pretreated by refluxing in acetone for 10 h and then in distilled water for 10 h. The pretreated melamine foam was washed and dried to obtain the pretreated melamine foam.

[0038] (2) Preparation of the acid-base bifunctional melamine foam: 1 g of melamine foam was added into 100 mL of 1 mol / L 1,4-butane sultone acetonitrile solution, and then ultrasonic treatment was performed for 50 min, followed by stirring at 82°C for 72 h. Finally, the melamine foam was taken out and washed with ethanol and water, and then dried to obtain the acid-base bifunctional melamine foam MF-NSO3H.

[0039] Example 5

[0040] The acid-base bifunctional melamine foam catalyst prepared in the above example was applied to catalyze the reaction of glucose into HMF, and the following scheme was used:

[0041] 50 mg of glucose, 50 mg of melamine foam catalyst and 5 mL of distilled water were mixed uniformly in a certain proportion, and then stirred at 130°C for 2 h under nitrogen protection. After the reaction was completed, the reaction system was cooled to room temperature, and the reaction yield was determined by high performance liquid chromatography. The experimental results are shown in Tables 1 and 2. The schematic diagram of the preparation of HMF by catalyzing glucose is shown in Figure 2 .

[0042] Comparative Example 1

[0043] The homogeneous ammonium sulfate was applied to catalyze the reaction of glucose into HMF, and the following scheme was used:

[0044] 50 mg of glucose, 50 mg of ammonium sulfate and 5 mL of distilled water were mixed uniformly in a certain proportion, and then stirred at 130°C for 2 h under nitrogen protection. After the reaction was completed, the reaction system was cooled to room temperature, and the reaction yield was determined by high performance liquid chromatography. The experimental results are shown in Tables 1 and 2. The schematic diagram of the preparation of HMF by catalyzing glucose is shown in Figure 2 .

[0045] Table 1 Activity evaluation of the acid-base bifunctional melamine foam catalyst for glucose conversion reaction

[0046]

[0047]

[0048] Table 2 Recycling results of the acid-base bifunctional melamine foam catalyst in Example 3

[0049] Cycles 1 2 3 4 5 6 7 8 Yield (%) 75 74 74 75 74 73 73 73

[0050] According to the results of the above Table 1 and Table 2, it can be seen that the acid-base bifunctional melamine foam in the embodiment 3 of the present application can efficiently catalyze the conversion of glucose into HMF at a lower temperature, and the yield reaches 75%, and the reaction yield does not decrease obviously after the catalyst is recycled for 8 times, which indicates that the recycling effect is excellent, the pollution can be reduced, the use cost is reduced, and the green chemistry requirement is met.

[0051] The basic principles and main features of the present application and the advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an acid-base bifunctional melamine foam, characterized in that, Includes the following steps: (1) Pretreatment of melamine foam: Cut melamine foam into 1×1×1cm pieces 3 Small pieces were then placed in different solvents and refluxed, rinsed and dried to obtain pretreated melamine foam. (2) Preparation of acid-base bifunctional melamine foam: The pretreated melamine foam was added to an acetonitrile solution of sulfonyl lactone and sonicated. Then it was heated and stirred to carry out the reaction. After the reaction was completed, it was taken out and cleaned with ethanol and water. After drying, the acid-base bifunctional melamine foam was obtained.

2. The method for preparing acid-base bifunctional melamine foam according to claim 1, characterized in that: In step (1), the solvent is ethanol, cyclohexane, distilled water or acetone; the mass-to-volume ratio of melamine foam to solvent is 1:30-1:100 g / mL, and the reflux time is 4-10 h.

3. The method for preparing acid-base bifunctional melamine foam according to claim 1, characterized in that: In step (2), the sulfonyl lactone is 1,3-propanesulfonyl lactone or 1,4-butanesulfonyl lactone.

4. The method for preparing acid-base bifunctional melamine foam according to claim 1, characterized in that: In step (2), the concentration of acetonitrile solution of sulfonyl lactone is 0.1-1 mol / L.

5. The method for preparing acid-base bifunctional melamine foam according to claim 1, characterized in that: In step (2), the mass-to-volume ratio of pretreated melamine foam to sulfonyl lactone acetonitrile solution is 1:30-1:100 g / mL, and the ultrasonic treatment time is 10-50 min.

6. The method for preparing acid-base bifunctional melamine foam according to claim 1, characterized in that: In step (2), heat to 40-82℃ and stir for 10-72 hours.

7. The application of the acid-base bifunctional melamine foam catalyst prepared by any one of claims 1-6 in the catalytic conversion of glucose to HMF.

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